Luis Cutz
info
Please Note
<p>This page displays the records of the person named above and is not linked to a unique person identifier. This record may need to be merged to a profile.</p>
20 records found
1
Carbon capture and storage (CCS) requires captured CO2 to be purified and dried (i.e. conditioned) before it can be compressed or liquefied for transport, yet the adsorption dryers that remove water are routinely represented in process models as simplified separators with a fixed removal efficiency. Their regeneration energy, a contributor to the conditioning penalty that this study sets out to quantify, is left uncharacterised, because systematic dynamic data for commercial desiccants under CO2-conditioning conditions are largely absent from the open literature. This gap prevents reliable process design and, in particular, hides where the energy-optimal operating window of the dryer actually lies.
This thesis characterises two commercial adsorbents, silica gel and zeolite 4A, and integrates validated dryer models into complete conditioning chains that deliver a liquid or supercritical CO2 end product. Zeolite 4A is the industrial standard for this duty and, by virtue of its stronger affinity for water, is expected to outperform silica gel; it does so, however, at the cost of more demanding regeneration conditions, whereas silica gel regenerates at much lower temperatures and can potentially draw on low-grade waste heat. This raises the central question of whether, over the long run and at cyclic steady state, the milder regeneration requirements of silica gel make it the more efficient choice, or whether zeolite 4A retains its advantage.
Breakthrough experiments were carried out on a mixSorb L dynamic sorption analyser at pressures up to 10 bar across adsorption and regeneration temperatures, with a dedicated CO2-carrier run to bound competitive adsorption. Toth and dual-site Langmuir isotherms and LDF mass-transfer coefficients were fitted to the data in Python and validated in a cyclic bed model in Aspen Adsorption, which was then implemented in Aspen Plus flowsheets of three transport routes: subcritical liquefaction at 16 bar, low-pressure ship transport at 8 bar, and supercritical pipeline transport at 150 bar.
The results give explicit design rules: adsorb cold and at pressure, treat the dryer as a polishing step on a stream already dried by compression with intercooling, and regenerate hot with a minimal purge. Measuring the true working capacity and kinetics shows standard literature practice to be heavily oversized: a 2% purge suffices where 10% is customary, cutting dryer-loop energy fivefold, from 1.6 to 0.3 kWh/t, in the 16 bar case. At the process scale, the transport route dominates: roughly 30 kWh/t separates the chains, against 4 kWh/t or less between sorbents within a chain. Silica gel proves a genuine alternative to molecular sieves: where it can occupy the same downstream position as the zeolite, it matches its specific energy consumption while regenerating at less than half the temperature, so low-grade waste heat suffices. Its penalties in the other two routes are mechanical, set by the pressure tolerance of the pellet batch rather than by thermodynamics, which suggests a pressure-qualified grade would reduce the material choice to cost rather than energy. ...
This thesis characterises two commercial adsorbents, silica gel and zeolite 4A, and integrates validated dryer models into complete conditioning chains that deliver a liquid or supercritical CO2 end product. Zeolite 4A is the industrial standard for this duty and, by virtue of its stronger affinity for water, is expected to outperform silica gel; it does so, however, at the cost of more demanding regeneration conditions, whereas silica gel regenerates at much lower temperatures and can potentially draw on low-grade waste heat. This raises the central question of whether, over the long run and at cyclic steady state, the milder regeneration requirements of silica gel make it the more efficient choice, or whether zeolite 4A retains its advantage.
Breakthrough experiments were carried out on a mixSorb L dynamic sorption analyser at pressures up to 10 bar across adsorption and regeneration temperatures, with a dedicated CO2-carrier run to bound competitive adsorption. Toth and dual-site Langmuir isotherms and LDF mass-transfer coefficients were fitted to the data in Python and validated in a cyclic bed model in Aspen Adsorption, which was then implemented in Aspen Plus flowsheets of three transport routes: subcritical liquefaction at 16 bar, low-pressure ship transport at 8 bar, and supercritical pipeline transport at 150 bar.
The results give explicit design rules: adsorb cold and at pressure, treat the dryer as a polishing step on a stream already dried by compression with intercooling, and regenerate hot with a minimal purge. Measuring the true working capacity and kinetics shows standard literature practice to be heavily oversized: a 2% purge suffices where 10% is customary, cutting dryer-loop energy fivefold, from 1.6 to 0.3 kWh/t, in the 16 bar case. At the process scale, the transport route dominates: roughly 30 kWh/t separates the chains, against 4 kWh/t or less between sorbents within a chain. Silica gel proves a genuine alternative to molecular sieves: where it can occupy the same downstream position as the zeolite, it matches its specific energy consumption while regenerating at less than half the temperature, so low-grade waste heat suffices. Its penalties in the other two routes are mechanical, set by the pressure tolerance of the pellet batch rather than by thermodynamics, which suggests a pressure-qualified grade would reduce the material choice to cost rather than energy. ...
Carbon capture and storage (CCS) requires captured CO2 to be purified and dried (i.e. conditioned) before it can be compressed or liquefied for transport, yet the adsorption dryers that remove water are routinely represented in process models as simplified separators with a fixed removal efficiency. Their regeneration energy, a contributor to the conditioning penalty that this study sets out to quantify, is left uncharacterised, because systematic dynamic data for commercial desiccants under CO2-conditioning conditions are largely absent from the open literature. This gap prevents reliable process design and, in particular, hides where the energy-optimal operating window of the dryer actually lies.
This thesis characterises two commercial adsorbents, silica gel and zeolite 4A, and integrates validated dryer models into complete conditioning chains that deliver a liquid or supercritical CO2 end product. Zeolite 4A is the industrial standard for this duty and, by virtue of its stronger affinity for water, is expected to outperform silica gel; it does so, however, at the cost of more demanding regeneration conditions, whereas silica gel regenerates at much lower temperatures and can potentially draw on low-grade waste heat. This raises the central question of whether, over the long run and at cyclic steady state, the milder regeneration requirements of silica gel make it the more efficient choice, or whether zeolite 4A retains its advantage.
Breakthrough experiments were carried out on a mixSorb L dynamic sorption analyser at pressures up to 10 bar across adsorption and regeneration temperatures, with a dedicated CO2-carrier run to bound competitive adsorption. Toth and dual-site Langmuir isotherms and LDF mass-transfer coefficients were fitted to the data in Python and validated in a cyclic bed model in Aspen Adsorption, which was then implemented in Aspen Plus flowsheets of three transport routes: subcritical liquefaction at 16 bar, low-pressure ship transport at 8 bar, and supercritical pipeline transport at 150 bar.
The results give explicit design rules: adsorb cold and at pressure, treat the dryer as a polishing step on a stream already dried by compression with intercooling, and regenerate hot with a minimal purge. Measuring the true working capacity and kinetics shows standard literature practice to be heavily oversized: a 2% purge suffices where 10% is customary, cutting dryer-loop energy fivefold, from 1.6 to 0.3 kWh/t, in the 16 bar case. At the process scale, the transport route dominates: roughly 30 kWh/t separates the chains, against 4 kWh/t or less between sorbents within a chain. Silica gel proves a genuine alternative to molecular sieves: where it can occupy the same downstream position as the zeolite, it matches its specific energy consumption while regenerating at less than half the temperature, so low-grade waste heat suffices. Its penalties in the other two routes are mechanical, set by the pressure tolerance of the pellet batch rather than by thermodynamics, which suggests a pressure-qualified grade would reduce the material choice to cost rather than energy.
This thesis characterises two commercial adsorbents, silica gel and zeolite 4A, and integrates validated dryer models into complete conditioning chains that deliver a liquid or supercritical CO2 end product. Zeolite 4A is the industrial standard for this duty and, by virtue of its stronger affinity for water, is expected to outperform silica gel; it does so, however, at the cost of more demanding regeneration conditions, whereas silica gel regenerates at much lower temperatures and can potentially draw on low-grade waste heat. This raises the central question of whether, over the long run and at cyclic steady state, the milder regeneration requirements of silica gel make it the more efficient choice, or whether zeolite 4A retains its advantage.
Breakthrough experiments were carried out on a mixSorb L dynamic sorption analyser at pressures up to 10 bar across adsorption and regeneration temperatures, with a dedicated CO2-carrier run to bound competitive adsorption. Toth and dual-site Langmuir isotherms and LDF mass-transfer coefficients were fitted to the data in Python and validated in a cyclic bed model in Aspen Adsorption, which was then implemented in Aspen Plus flowsheets of three transport routes: subcritical liquefaction at 16 bar, low-pressure ship transport at 8 bar, and supercritical pipeline transport at 150 bar.
The results give explicit design rules: adsorb cold and at pressure, treat the dryer as a polishing step on a stream already dried by compression with intercooling, and regenerate hot with a minimal purge. Measuring the true working capacity and kinetics shows standard literature practice to be heavily oversized: a 2% purge suffices where 10% is customary, cutting dryer-loop energy fivefold, from 1.6 to 0.3 kWh/t, in the 16 bar case. At the process scale, the transport route dominates: roughly 30 kWh/t separates the chains, against 4 kWh/t or less between sorbents within a chain. Silica gel proves a genuine alternative to molecular sieves: where it can occupy the same downstream position as the zeolite, it matches its specific energy consumption while regenerating at less than half the temperature, so low-grade waste heat suffices. Its penalties in the other two routes are mechanical, set by the pressure tolerance of the pellet batch rather than by thermodynamics, which suggests a pressure-qualified grade would reduce the material choice to cost rather than energy.
Catalytic Solvothermal Liquefaction of Polyolefin Plastic Waste in Ghana
Technical Characterisation and Stakeholder Analysis for Chemical Recycling Feasibility
Global plastic production exceeds 460 million tonnes per year, with polyolefins constituting the dominant fraction of post-consumer waste. In Ghana, plastics account for approximately 17 % of municipal solid waste, yet the formal recycling rate remains around 10 %. Clogged waterways, overflowing landfills and open burning are visible consequences of a system overwhelmed by growing consumption and insufficient infrastructure. Polyolefins are particularly challenging to recycle because they resist degradation under the mild conditions of conventional hydrothermal liquefaction, while supercritical water processing requires pressures exceeding 22 MPa, limiting deployment in low-resource contexts. Solvothermal liquefaction (STL) with an organic solvent and a heterogeneous catalyst offers a potentially lower-severity alternative, but its feasibility for polyolefin-rich waste streams remains poorly understood, particularly in low- and middle-income country settings.
This thesis investigates the technical and socio-technical feasibility of catalytic STL for polyolefin plastic waste in Ghana through two complementary studies. The technical study comprised two experimental campaigns on a mixed polyolefin feedstock (50 wt% PP, 30 wt% HDPE, 20 wt% LDPE) sourced from
Accra in Ghana: a subcritical campaign using decanoic acid as solvent with ZSM-5 as catalyst (335–345 °C), and a supercritical campaign using both water and decanoic acid at 455 °C. The socio-technical study conducted 14 stakeholder interviews in Ghana, mapped the plastic waste value chain and identified conditions under which chemical recycling could feasibly be integrated into the existing system.
The subcritical STL campaign with decanoic acid proved technically infeasible in its current form. Visual inspection and analytical characterisation revealed that the original plastic morphology was fully disrupted. No pieces retaining the feedstock structure were recovered from either the solid or the liquid phase,
which both appeared homogeneous, suggesting physical interaction between the polyolefins and the solvent. The nature of this interaction could not be determined from the available evidence. Critically, the solvent could not be separated from the organic phase, making a mass balance impossible and preventing any quantitative assessment of product yields.
The supercritical campaign with water demonstrated effective conversion, achieving an oil yield of 54.01 wt% at 455 °C and 60 min, with o-xylene and mesitylene as the dominant products. The catalyst markedly promoted monomer formation in the gas phase, increasing the combined ethane and ethylene fraction from 19.90 to 29.05 wt% and propylene from 9.80 to 12.76 wt%, opening a pathway toward plastic-to-plastic recycling. In contrast, the supercritical experiments with decanoic acid as solvent showed that at 455 °C, decanoic acid decomposes rather than acting as a stable reaction medium. To confirm this, a decanoic acid blank experiment without plastic was conducted. Ultra-high resolution APCI-FT-Orbitrap MS analysis, evaluated through a heteroatom class histogram, Van Krevelen diagram, DBE versus carbon number plot and KNM versus O/C ratio plot, showed that the decanoic
acid experiment with plastic was virtually indistinguishable from the blank across all four representations, confirming that the oil phase is governed by solvent decomposition products rather than plastic conversion.
The field research identified six structural complexities shaping Ghana’s plastic waste management system and concluded that existing policy frameworks, including the NPAP roadmap, provide a foundation for chemical recycling deployment but require translation into binding legislation, explicit chemical
recycling targets and dedicated financing. A phased Plastic-to-Fuel followed by Plastic-to-Polymer deployment strategy is proposed, leveraging Ghana’s position as a net fuel importer and the growing volumes of otherwise unrecoverable mixed plastic waste. The proposed deployment strategy positions chemical recycling as complementary to, rather than competitive with, mechanical recycling, forming a
cascading system that maximises resource recovery across the full waste stream. ...
This thesis investigates the technical and socio-technical feasibility of catalytic STL for polyolefin plastic waste in Ghana through two complementary studies. The technical study comprised two experimental campaigns on a mixed polyolefin feedstock (50 wt% PP, 30 wt% HDPE, 20 wt% LDPE) sourced from
Accra in Ghana: a subcritical campaign using decanoic acid as solvent with ZSM-5 as catalyst (335–345 °C), and a supercritical campaign using both water and decanoic acid at 455 °C. The socio-technical study conducted 14 stakeholder interviews in Ghana, mapped the plastic waste value chain and identified conditions under which chemical recycling could feasibly be integrated into the existing system.
The subcritical STL campaign with decanoic acid proved technically infeasible in its current form. Visual inspection and analytical characterisation revealed that the original plastic morphology was fully disrupted. No pieces retaining the feedstock structure were recovered from either the solid or the liquid phase,
which both appeared homogeneous, suggesting physical interaction between the polyolefins and the solvent. The nature of this interaction could not be determined from the available evidence. Critically, the solvent could not be separated from the organic phase, making a mass balance impossible and preventing any quantitative assessment of product yields.
The supercritical campaign with water demonstrated effective conversion, achieving an oil yield of 54.01 wt% at 455 °C and 60 min, with o-xylene and mesitylene as the dominant products. The catalyst markedly promoted monomer formation in the gas phase, increasing the combined ethane and ethylene fraction from 19.90 to 29.05 wt% and propylene from 9.80 to 12.76 wt%, opening a pathway toward plastic-to-plastic recycling. In contrast, the supercritical experiments with decanoic acid as solvent showed that at 455 °C, decanoic acid decomposes rather than acting as a stable reaction medium. To confirm this, a decanoic acid blank experiment without plastic was conducted. Ultra-high resolution APCI-FT-Orbitrap MS analysis, evaluated through a heteroatom class histogram, Van Krevelen diagram, DBE versus carbon number plot and KNM versus O/C ratio plot, showed that the decanoic
acid experiment with plastic was virtually indistinguishable from the blank across all four representations, confirming that the oil phase is governed by solvent decomposition products rather than plastic conversion.
The field research identified six structural complexities shaping Ghana’s plastic waste management system and concluded that existing policy frameworks, including the NPAP roadmap, provide a foundation for chemical recycling deployment but require translation into binding legislation, explicit chemical
recycling targets and dedicated financing. A phased Plastic-to-Fuel followed by Plastic-to-Polymer deployment strategy is proposed, leveraging Ghana’s position as a net fuel importer and the growing volumes of otherwise unrecoverable mixed plastic waste. The proposed deployment strategy positions chemical recycling as complementary to, rather than competitive with, mechanical recycling, forming a
cascading system that maximises resource recovery across the full waste stream. ...
Global plastic production exceeds 460 million tonnes per year, with polyolefins constituting the dominant fraction of post-consumer waste. In Ghana, plastics account for approximately 17 % of municipal solid waste, yet the formal recycling rate remains around 10 %. Clogged waterways, overflowing landfills and open burning are visible consequences of a system overwhelmed by growing consumption and insufficient infrastructure. Polyolefins are particularly challenging to recycle because they resist degradation under the mild conditions of conventional hydrothermal liquefaction, while supercritical water processing requires pressures exceeding 22 MPa, limiting deployment in low-resource contexts. Solvothermal liquefaction (STL) with an organic solvent and a heterogeneous catalyst offers a potentially lower-severity alternative, but its feasibility for polyolefin-rich waste streams remains poorly understood, particularly in low- and middle-income country settings.
This thesis investigates the technical and socio-technical feasibility of catalytic STL for polyolefin plastic waste in Ghana through two complementary studies. The technical study comprised two experimental campaigns on a mixed polyolefin feedstock (50 wt% PP, 30 wt% HDPE, 20 wt% LDPE) sourced from
Accra in Ghana: a subcritical campaign using decanoic acid as solvent with ZSM-5 as catalyst (335–345 °C), and a supercritical campaign using both water and decanoic acid at 455 °C. The socio-technical study conducted 14 stakeholder interviews in Ghana, mapped the plastic waste value chain and identified conditions under which chemical recycling could feasibly be integrated into the existing system.
The subcritical STL campaign with decanoic acid proved technically infeasible in its current form. Visual inspection and analytical characterisation revealed that the original plastic morphology was fully disrupted. No pieces retaining the feedstock structure were recovered from either the solid or the liquid phase,
which both appeared homogeneous, suggesting physical interaction between the polyolefins and the solvent. The nature of this interaction could not be determined from the available evidence. Critically, the solvent could not be separated from the organic phase, making a mass balance impossible and preventing any quantitative assessment of product yields.
The supercritical campaign with water demonstrated effective conversion, achieving an oil yield of 54.01 wt% at 455 °C and 60 min, with o-xylene and mesitylene as the dominant products. The catalyst markedly promoted monomer formation in the gas phase, increasing the combined ethane and ethylene fraction from 19.90 to 29.05 wt% and propylene from 9.80 to 12.76 wt%, opening a pathway toward plastic-to-plastic recycling. In contrast, the supercritical experiments with decanoic acid as solvent showed that at 455 °C, decanoic acid decomposes rather than acting as a stable reaction medium. To confirm this, a decanoic acid blank experiment without plastic was conducted. Ultra-high resolution APCI-FT-Orbitrap MS analysis, evaluated through a heteroatom class histogram, Van Krevelen diagram, DBE versus carbon number plot and KNM versus O/C ratio plot, showed that the decanoic
acid experiment with plastic was virtually indistinguishable from the blank across all four representations, confirming that the oil phase is governed by solvent decomposition products rather than plastic conversion.
The field research identified six structural complexities shaping Ghana’s plastic waste management system and concluded that existing policy frameworks, including the NPAP roadmap, provide a foundation for chemical recycling deployment but require translation into binding legislation, explicit chemical
recycling targets and dedicated financing. A phased Plastic-to-Fuel followed by Plastic-to-Polymer deployment strategy is proposed, leveraging Ghana’s position as a net fuel importer and the growing volumes of otherwise unrecoverable mixed plastic waste. The proposed deployment strategy positions chemical recycling as complementary to, rather than competitive with, mechanical recycling, forming a
cascading system that maximises resource recovery across the full waste stream.
This thesis investigates the technical and socio-technical feasibility of catalytic STL for polyolefin plastic waste in Ghana through two complementary studies. The technical study comprised two experimental campaigns on a mixed polyolefin feedstock (50 wt% PP, 30 wt% HDPE, 20 wt% LDPE) sourced from
Accra in Ghana: a subcritical campaign using decanoic acid as solvent with ZSM-5 as catalyst (335–345 °C), and a supercritical campaign using both water and decanoic acid at 455 °C. The socio-technical study conducted 14 stakeholder interviews in Ghana, mapped the plastic waste value chain and identified conditions under which chemical recycling could feasibly be integrated into the existing system.
The subcritical STL campaign with decanoic acid proved technically infeasible in its current form. Visual inspection and analytical characterisation revealed that the original plastic morphology was fully disrupted. No pieces retaining the feedstock structure were recovered from either the solid or the liquid phase,
which both appeared homogeneous, suggesting physical interaction between the polyolefins and the solvent. The nature of this interaction could not be determined from the available evidence. Critically, the solvent could not be separated from the organic phase, making a mass balance impossible and preventing any quantitative assessment of product yields.
The supercritical campaign with water demonstrated effective conversion, achieving an oil yield of 54.01 wt% at 455 °C and 60 min, with o-xylene and mesitylene as the dominant products. The catalyst markedly promoted monomer formation in the gas phase, increasing the combined ethane and ethylene fraction from 19.90 to 29.05 wt% and propylene from 9.80 to 12.76 wt%, opening a pathway toward plastic-to-plastic recycling. In contrast, the supercritical experiments with decanoic acid as solvent showed that at 455 °C, decanoic acid decomposes rather than acting as a stable reaction medium. To confirm this, a decanoic acid blank experiment without plastic was conducted. Ultra-high resolution APCI-FT-Orbitrap MS analysis, evaluated through a heteroatom class histogram, Van Krevelen diagram, DBE versus carbon number plot and KNM versus O/C ratio plot, showed that the decanoic
acid experiment with plastic was virtually indistinguishable from the blank across all four representations, confirming that the oil phase is governed by solvent decomposition products rather than plastic conversion.
The field research identified six structural complexities shaping Ghana’s plastic waste management system and concluded that existing policy frameworks, including the NPAP roadmap, provide a foundation for chemical recycling deployment but require translation into binding legislation, explicit chemical
recycling targets and dedicated financing. A phased Plastic-to-Fuel followed by Plastic-to-Polymer deployment strategy is proposed, leveraging Ghana’s position as a net fuel importer and the growing volumes of otherwise unrecoverable mixed plastic waste. The proposed deployment strategy positions chemical recycling as complementary to, rather than competitive with, mechanical recycling, forming a
cascading system that maximises resource recovery across the full waste stream.
This study investigates sustainable recycling methods for cardiac ablation catheters, which contain precious-metal electrodes classified as critical raw materials. Recycling these devices is challenging due to their complex material composition and the presence of highly resistant polymers such as PEEK. The research evaluates different recycling methods and identifies hydrothermal liquefaction (HTL) as the most promising approach for polymer removal. HTL was selected because it can remove resistant polymers while minimizing hazardous emissions and preserving the valuable metal electrodes. Experimental testing focused on optimizing solvent systems and operating conditions for effective removal of PEEK. Results show that HTL successfully removes resistant polymers and enables recovery of physically intact precious-metal electrodes from Johnson & Johnson’s ThermoCool SmartTouch catheter tips. Surface analysis using scanning electron microscopy and elemental mapping revealed limited contamination after polymer removal. Additionally, ultrasonic cleaning significantly improved electrode cleanliness. Overall, the findings suggest that combining HTL with ultrasonic cleaning is a promising method for recycling cardiac catheter tips. Further work is needed to validate electrode quality, optimize residue removal, and assess large-scale implementation for practical reuse. ...
This study investigates sustainable recycling methods for cardiac ablation catheters, which contain precious-metal electrodes classified as critical raw materials. Recycling these devices is challenging due to their complex material composition and the presence of highly resistant polymers such as PEEK.
The research evaluates different recycling methods and identifies hydrothermal liquefaction (HTL) as the most promising approach for polymer removal. HTL was selected because it can remove resistant polymers while minimizing hazardous emissions and preserving the valuable metal electrodes. Experimental testing focused on optimizing solvent systems and operating conditions for effective removal of PEEK.
Results show that HTL successfully removes resistant polymers and enables recovery of physically intact precious-metal electrodes from Johnson & Johnson’s ThermoCool SmartTouch catheter tips. Surface analysis using scanning electron microscopy and elemental mapping revealed limited contamination after polymer removal. Additionally, ultrasonic cleaning significantly improved electrode cleanliness.
Overall, the findings suggest that combining HTL with ultrasonic cleaning is a promising method for recycling cardiac catheter tips. Further work is needed to validate electrode quality, optimize residue removal, and assess large-scale implementation for practical reuse.
Recycling of Vitrimer Resins and Composites
Recycling of Vitrimer Resins and Composites using sub-critical Hydrothermal Liquefaction
Vitrimer resins have been increasingly considered for circular materials design due to their dynamic covalent networks, yet end-of-life processes remain insufficiently established. In this work, sub-critical hydrothermal liquefaction (HTL) in water was investigated as a chemical recycling pathway for a disulfide-based vitrimer (VR-RD) formulated from EP600 Part A (epoxy), 4-aminophenyl disulfide, and a cardanol-based diluent (LITE 513DF). Batch experiments were performed in Parr autoclave reactor (Model 4560, 300 mL) at a resin-to-water mass ratio of 1:17 under nitrogen. A matrix of conditions was assessed at 310 °C and 340 °C for 35 and 60 minutes, with the 300 mL reactor stirred at 150 rpm. Product streams were separated into gas, aqueous, crude oil, and char; the crude oil was further fractionated by distillation into light, intermediate, and heavy cuts.
Effective depolymerization of the vitrimer network was observed across all runs. Lower temperature and shorter residence time favored liquid formation, whereas higher severity promoted secondary conversion. The most favorable liquid production was obtained at 310 °C for 35 minutes, yielding the highest crude fraction (43.5\% of feed) and a light cut of 11.1\%. At 310 °C for 60 minutes, a reduction in crude oil and an increase in gas were observed, consistent with over-cracking. At 340 °C, liquid yields were diminished and solid/gaseous products increased.
Characterization of products was used to elucidate depolymerization pathways and product quality. Gas chromatography–mass spectrometry (GC–MS) of the light fractions confirmed the presence of aniline, indicating recovery of moieties associated with the epoxy precursor; the 310 °C-60 minutes case exhibited the highest relative aniline abundance (≈44\% within the light fraction). Inductively coupled plasma–optical emission spectroscopy (ICP-OES) of aqueous phases indicated sulfate, consistent with disulfide bond cleavage, and measurable chloride, which displayed contrasting trends with time and temperature. Thermogravimetric analysis (TGA) showed that most chars and heavy fractions possessed reduced thermal stability compared with the parent VR-RD, whereas the char obtained at 310 °C for 60 minutes exhibited a comparable onset temperature, suggesting partial retention or restructuring of thermally stable motifs. The fractionation protocol defined light as <120 °C vapor, intermediate as 120–350 °C vapor (noted as largely lost during handling), and heavy as non-vaporized residue (>350 °C), providing a practical basis for subsequent compositional analysis.
Overall, sub-critical HTL in water was demonstrated as a viable option for chemical recycling of disulfide-based vitrimers. Process severity was shown to govern the balance between depolymerization and secondary conversion, with 310 °C for 35 minutes identified as optimal for maximizing desirable liquids while minimizing over-cracking. These findings provide actionable guidance for scale-up and for coupling HTL with targeted product upgrading.
...
Effective depolymerization of the vitrimer network was observed across all runs. Lower temperature and shorter residence time favored liquid formation, whereas higher severity promoted secondary conversion. The most favorable liquid production was obtained at 310 °C for 35 minutes, yielding the highest crude fraction (43.5\% of feed) and a light cut of 11.1\%. At 310 °C for 60 minutes, a reduction in crude oil and an increase in gas were observed, consistent with over-cracking. At 340 °C, liquid yields were diminished and solid/gaseous products increased.
Characterization of products was used to elucidate depolymerization pathways and product quality. Gas chromatography–mass spectrometry (GC–MS) of the light fractions confirmed the presence of aniline, indicating recovery of moieties associated with the epoxy precursor; the 310 °C-60 minutes case exhibited the highest relative aniline abundance (≈44\% within the light fraction). Inductively coupled plasma–optical emission spectroscopy (ICP-OES) of aqueous phases indicated sulfate, consistent with disulfide bond cleavage, and measurable chloride, which displayed contrasting trends with time and temperature. Thermogravimetric analysis (TGA) showed that most chars and heavy fractions possessed reduced thermal stability compared with the parent VR-RD, whereas the char obtained at 310 °C for 60 minutes exhibited a comparable onset temperature, suggesting partial retention or restructuring of thermally stable motifs. The fractionation protocol defined light as <120 °C vapor, intermediate as 120–350 °C vapor (noted as largely lost during handling), and heavy as non-vaporized residue (>350 °C), providing a practical basis for subsequent compositional analysis.
Overall, sub-critical HTL in water was demonstrated as a viable option for chemical recycling of disulfide-based vitrimers. Process severity was shown to govern the balance between depolymerization and secondary conversion, with 310 °C for 35 minutes identified as optimal for maximizing desirable liquids while minimizing over-cracking. These findings provide actionable guidance for scale-up and for coupling HTL with targeted product upgrading.
...
Vitrimer resins have been increasingly considered for circular materials design due to their dynamic covalent networks, yet end-of-life processes remain insufficiently established. In this work, sub-critical hydrothermal liquefaction (HTL) in water was investigated as a chemical recycling pathway for a disulfide-based vitrimer (VR-RD) formulated from EP600 Part A (epoxy), 4-aminophenyl disulfide, and a cardanol-based diluent (LITE 513DF). Batch experiments were performed in Parr autoclave reactor (Model 4560, 300 mL) at a resin-to-water mass ratio of 1:17 under nitrogen. A matrix of conditions was assessed at 310 °C and 340 °C for 35 and 60 minutes, with the 300 mL reactor stirred at 150 rpm. Product streams were separated into gas, aqueous, crude oil, and char; the crude oil was further fractionated by distillation into light, intermediate, and heavy cuts.
Effective depolymerization of the vitrimer network was observed across all runs. Lower temperature and shorter residence time favored liquid formation, whereas higher severity promoted secondary conversion. The most favorable liquid production was obtained at 310 °C for 35 minutes, yielding the highest crude fraction (43.5\% of feed) and a light cut of 11.1\%. At 310 °C for 60 minutes, a reduction in crude oil and an increase in gas were observed, consistent with over-cracking. At 340 °C, liquid yields were diminished and solid/gaseous products increased.
Characterization of products was used to elucidate depolymerization pathways and product quality. Gas chromatography–mass spectrometry (GC–MS) of the light fractions confirmed the presence of aniline, indicating recovery of moieties associated with the epoxy precursor; the 310 °C-60 minutes case exhibited the highest relative aniline abundance (≈44\% within the light fraction). Inductively coupled plasma–optical emission spectroscopy (ICP-OES) of aqueous phases indicated sulfate, consistent with disulfide bond cleavage, and measurable chloride, which displayed contrasting trends with time and temperature. Thermogravimetric analysis (TGA) showed that most chars and heavy fractions possessed reduced thermal stability compared with the parent VR-RD, whereas the char obtained at 310 °C for 60 minutes exhibited a comparable onset temperature, suggesting partial retention or restructuring of thermally stable motifs. The fractionation protocol defined light as <120 °C vapor, intermediate as 120–350 °C vapor (noted as largely lost during handling), and heavy as non-vaporized residue (>350 °C), providing a practical basis for subsequent compositional analysis.
Overall, sub-critical HTL in water was demonstrated as a viable option for chemical recycling of disulfide-based vitrimers. Process severity was shown to govern the balance between depolymerization and secondary conversion, with 310 °C for 35 minutes identified as optimal for maximizing desirable liquids while minimizing over-cracking. These findings provide actionable guidance for scale-up and for coupling HTL with targeted product upgrading.
Effective depolymerization of the vitrimer network was observed across all runs. Lower temperature and shorter residence time favored liquid formation, whereas higher severity promoted secondary conversion. The most favorable liquid production was obtained at 310 °C for 35 minutes, yielding the highest crude fraction (43.5\% of feed) and a light cut of 11.1\%. At 310 °C for 60 minutes, a reduction in crude oil and an increase in gas were observed, consistent with over-cracking. At 340 °C, liquid yields were diminished and solid/gaseous products increased.
Characterization of products was used to elucidate depolymerization pathways and product quality. Gas chromatography–mass spectrometry (GC–MS) of the light fractions confirmed the presence of aniline, indicating recovery of moieties associated with the epoxy precursor; the 310 °C-60 minutes case exhibited the highest relative aniline abundance (≈44\% within the light fraction). Inductively coupled plasma–optical emission spectroscopy (ICP-OES) of aqueous phases indicated sulfate, consistent with disulfide bond cleavage, and measurable chloride, which displayed contrasting trends with time and temperature. Thermogravimetric analysis (TGA) showed that most chars and heavy fractions possessed reduced thermal stability compared with the parent VR-RD, whereas the char obtained at 310 °C for 60 minutes exhibited a comparable onset temperature, suggesting partial retention or restructuring of thermally stable motifs. The fractionation protocol defined light as <120 °C vapor, intermediate as 120–350 °C vapor (noted as largely lost during handling), and heavy as non-vaporized residue (>350 °C), providing a practical basis for subsequent compositional analysis.
Overall, sub-critical HTL in water was demonstrated as a viable option for chemical recycling of disulfide-based vitrimers. Process severity was shown to govern the balance between depolymerization and secondary conversion, with 310 °C for 35 minutes identified as optimal for maximizing desirable liquids while minimizing over-cracking. These findings provide actionable guidance for scale-up and for coupling HTL with targeted product upgrading.
Sediment Ripening with Biochar
Assessing the effect of biochar content and particle size on the biophysicochemical ripening processes of sediments
The growing demand for sustainable construction materials has prompted interest in reusing dredged sediments as an alternative to traditional raw materials in dike construction. Before they can be reused, sediments must undergo the lengthy ripening process, during which they are transformed into stable soil. Accelerating this transformation could significantly improve the feasibility of sediment reuse. This study investigates whether biochar amendment can enhance the biophysicochemical ripening of dredged sediments, focusing on the influence of biochar application rate and particle size.
Dredged material from the port of Hamburg, Germany, that was dewatered and processed at the METHA plant, was mixed with biochar produced by Bio Energy Netherlands from the gasification of wood waste at 800-1000°C for 90-120 minutes. The mixtures contained biochar with varying application rates (2%, 4%, 6%) and particle sizes (<2 mm, 2-5 mm, >5 mm). Over the course of 15 weeks of field ripening, the sediment-biochar mixtures were exposed to natural weather conditions and turned weekly. Biochar amendment introduced additional porosity which increased water holding capacity by 33-72% compared to the control after 15 weeks of ripening, resulting in values of 24-72% DW. The oven-dried COLE, ranged from of 2.2 to 5.4% which represents a decrease of up to 54% relative to the unamended sediments. This improvement can be attributed to the non-plastic behavior of biochar and explains the decreasing shrinkage observed with an increasing application rate. Increasing particle size was correlated to decreasing shrinkage (p <0.05) which could be due to the interrupting effect of coarse biochar particles on tensile load propagation in the rods. A qualitative assessment of the structure development of the experimental variants suggests an acceleration of structure formation with higher biochar application rate and larger particle size when combined with weekly turning. This resulted in a faster breakdown of the dense and platy METHA material into smaller and more aerated aggregates. Overall, the physical ripening of the dredged material was improved with the addition of biochar at increasing application rates and particle size, which promoted a faster stabilization of sediment aggregates and enhanced physical properties beneficial for construction applications.
The occurrence of sulfur oxidation, the main chemical ripening reaction, was evidenced by a loss in the total sulfur content of samples and an increasing electrical conductivity during dry periods. The pH was expected to decrease as a result of the release of protons from this reaction, however this was not observed. Instead, increasing biochar application rates was correlated to a higher pH (p <0.05) and was evidence of the material's buffering capacity which can be attributed to its high functional group and mineral content. The total sulfur content reduced on average by 5% and 22% in the amended samples and the control, and this smaller decrease compared to the control could be explained either by a slower chemical ripening in amended sediments or by measurement limitations. Furthermore, the evolution of electrical conductivity over the 15 weeks of field ripening evidenced the accumulation of chemical reaction products in dry periods.
The influence of biochar on sediment physical and chemical properties, including the increased pore structure, water holding capacity, aeration and buffering capacity, all contributed to creating conditions favorable to microbial activity. A priming effect of biochar application could be observed in the first six weeks of ripening, with high respiration rates, high decomposition rates, and decreasing stabilization of organic matter. In this period, total organic carbon content decreased on average by 30\% in amended samples, compared to only 6% in the control. At the same time, nitrogen content decreased on average by 13% in the samples with biochar, further confirming the high microbial activity. This was followed by a period of decreasing microbial activity until the end of the experiment, which was marked by 14-32% lower respiratory carbon release of the amended samples compared to the control, decreasing decomposition rates and increasing stabilization of organic matter. Thus, biochar application accelerated the decomposition of labile carbon and enhanced the biological stabilization of organic matter in sediments.
These findings suggest that biochar amendment can significantly improve sediment ripening processes and can result in a material with properties desirable for dike construction. ...
Dredged material from the port of Hamburg, Germany, that was dewatered and processed at the METHA plant, was mixed with biochar produced by Bio Energy Netherlands from the gasification of wood waste at 800-1000°C for 90-120 minutes. The mixtures contained biochar with varying application rates (2%, 4%, 6%) and particle sizes (<2 mm, 2-5 mm, >5 mm). Over the course of 15 weeks of field ripening, the sediment-biochar mixtures were exposed to natural weather conditions and turned weekly. Biochar amendment introduced additional porosity which increased water holding capacity by 33-72% compared to the control after 15 weeks of ripening, resulting in values of 24-72% DW. The oven-dried COLE, ranged from of 2.2 to 5.4% which represents a decrease of up to 54% relative to the unamended sediments. This improvement can be attributed to the non-plastic behavior of biochar and explains the decreasing shrinkage observed with an increasing application rate. Increasing particle size was correlated to decreasing shrinkage (p <0.05) which could be due to the interrupting effect of coarse biochar particles on tensile load propagation in the rods. A qualitative assessment of the structure development of the experimental variants suggests an acceleration of structure formation with higher biochar application rate and larger particle size when combined with weekly turning. This resulted in a faster breakdown of the dense and platy METHA material into smaller and more aerated aggregates. Overall, the physical ripening of the dredged material was improved with the addition of biochar at increasing application rates and particle size, which promoted a faster stabilization of sediment aggregates and enhanced physical properties beneficial for construction applications.
The occurrence of sulfur oxidation, the main chemical ripening reaction, was evidenced by a loss in the total sulfur content of samples and an increasing electrical conductivity during dry periods. The pH was expected to decrease as a result of the release of protons from this reaction, however this was not observed. Instead, increasing biochar application rates was correlated to a higher pH (p <0.05) and was evidence of the material's buffering capacity which can be attributed to its high functional group and mineral content. The total sulfur content reduced on average by 5% and 22% in the amended samples and the control, and this smaller decrease compared to the control could be explained either by a slower chemical ripening in amended sediments or by measurement limitations. Furthermore, the evolution of electrical conductivity over the 15 weeks of field ripening evidenced the accumulation of chemical reaction products in dry periods.
The influence of biochar on sediment physical and chemical properties, including the increased pore structure, water holding capacity, aeration and buffering capacity, all contributed to creating conditions favorable to microbial activity. A priming effect of biochar application could be observed in the first six weeks of ripening, with high respiration rates, high decomposition rates, and decreasing stabilization of organic matter. In this period, total organic carbon content decreased on average by 30\% in amended samples, compared to only 6% in the control. At the same time, nitrogen content decreased on average by 13% in the samples with biochar, further confirming the high microbial activity. This was followed by a period of decreasing microbial activity until the end of the experiment, which was marked by 14-32% lower respiratory carbon release of the amended samples compared to the control, decreasing decomposition rates and increasing stabilization of organic matter. Thus, biochar application accelerated the decomposition of labile carbon and enhanced the biological stabilization of organic matter in sediments.
These findings suggest that biochar amendment can significantly improve sediment ripening processes and can result in a material with properties desirable for dike construction. ...
The growing demand for sustainable construction materials has prompted interest in reusing dredged sediments as an alternative to traditional raw materials in dike construction. Before they can be reused, sediments must undergo the lengthy ripening process, during which they are transformed into stable soil. Accelerating this transformation could significantly improve the feasibility of sediment reuse. This study investigates whether biochar amendment can enhance the biophysicochemical ripening of dredged sediments, focusing on the influence of biochar application rate and particle size.
Dredged material from the port of Hamburg, Germany, that was dewatered and processed at the METHA plant, was mixed with biochar produced by Bio Energy Netherlands from the gasification of wood waste at 800-1000°C for 90-120 minutes. The mixtures contained biochar with varying application rates (2%, 4%, 6%) and particle sizes (<2 mm, 2-5 mm, >5 mm). Over the course of 15 weeks of field ripening, the sediment-biochar mixtures were exposed to natural weather conditions and turned weekly. Biochar amendment introduced additional porosity which increased water holding capacity by 33-72% compared to the control after 15 weeks of ripening, resulting in values of 24-72% DW. The oven-dried COLE, ranged from of 2.2 to 5.4% which represents a decrease of up to 54% relative to the unamended sediments. This improvement can be attributed to the non-plastic behavior of biochar and explains the decreasing shrinkage observed with an increasing application rate. Increasing particle size was correlated to decreasing shrinkage (p <0.05) which could be due to the interrupting effect of coarse biochar particles on tensile load propagation in the rods. A qualitative assessment of the structure development of the experimental variants suggests an acceleration of structure formation with higher biochar application rate and larger particle size when combined with weekly turning. This resulted in a faster breakdown of the dense and platy METHA material into smaller and more aerated aggregates. Overall, the physical ripening of the dredged material was improved with the addition of biochar at increasing application rates and particle size, which promoted a faster stabilization of sediment aggregates and enhanced physical properties beneficial for construction applications.
The occurrence of sulfur oxidation, the main chemical ripening reaction, was evidenced by a loss in the total sulfur content of samples and an increasing electrical conductivity during dry periods. The pH was expected to decrease as a result of the release of protons from this reaction, however this was not observed. Instead, increasing biochar application rates was correlated to a higher pH (p <0.05) and was evidence of the material's buffering capacity which can be attributed to its high functional group and mineral content. The total sulfur content reduced on average by 5% and 22% in the amended samples and the control, and this smaller decrease compared to the control could be explained either by a slower chemical ripening in amended sediments or by measurement limitations. Furthermore, the evolution of electrical conductivity over the 15 weeks of field ripening evidenced the accumulation of chemical reaction products in dry periods.
The influence of biochar on sediment physical and chemical properties, including the increased pore structure, water holding capacity, aeration and buffering capacity, all contributed to creating conditions favorable to microbial activity. A priming effect of biochar application could be observed in the first six weeks of ripening, with high respiration rates, high decomposition rates, and decreasing stabilization of organic matter. In this period, total organic carbon content decreased on average by 30\% in amended samples, compared to only 6% in the control. At the same time, nitrogen content decreased on average by 13% in the samples with biochar, further confirming the high microbial activity. This was followed by a period of decreasing microbial activity until the end of the experiment, which was marked by 14-32% lower respiratory carbon release of the amended samples compared to the control, decreasing decomposition rates and increasing stabilization of organic matter. Thus, biochar application accelerated the decomposition of labile carbon and enhanced the biological stabilization of organic matter in sediments.
These findings suggest that biochar amendment can significantly improve sediment ripening processes and can result in a material with properties desirable for dike construction.
Dredged material from the port of Hamburg, Germany, that was dewatered and processed at the METHA plant, was mixed with biochar produced by Bio Energy Netherlands from the gasification of wood waste at 800-1000°C for 90-120 minutes. The mixtures contained biochar with varying application rates (2%, 4%, 6%) and particle sizes (<2 mm, 2-5 mm, >5 mm). Over the course of 15 weeks of field ripening, the sediment-biochar mixtures were exposed to natural weather conditions and turned weekly. Biochar amendment introduced additional porosity which increased water holding capacity by 33-72% compared to the control after 15 weeks of ripening, resulting in values of 24-72% DW. The oven-dried COLE, ranged from of 2.2 to 5.4% which represents a decrease of up to 54% relative to the unamended sediments. This improvement can be attributed to the non-plastic behavior of biochar and explains the decreasing shrinkage observed with an increasing application rate. Increasing particle size was correlated to decreasing shrinkage (p <0.05) which could be due to the interrupting effect of coarse biochar particles on tensile load propagation in the rods. A qualitative assessment of the structure development of the experimental variants suggests an acceleration of structure formation with higher biochar application rate and larger particle size when combined with weekly turning. This resulted in a faster breakdown of the dense and platy METHA material into smaller and more aerated aggregates. Overall, the physical ripening of the dredged material was improved with the addition of biochar at increasing application rates and particle size, which promoted a faster stabilization of sediment aggregates and enhanced physical properties beneficial for construction applications.
The occurrence of sulfur oxidation, the main chemical ripening reaction, was evidenced by a loss in the total sulfur content of samples and an increasing electrical conductivity during dry periods. The pH was expected to decrease as a result of the release of protons from this reaction, however this was not observed. Instead, increasing biochar application rates was correlated to a higher pH (p <0.05) and was evidence of the material's buffering capacity which can be attributed to its high functional group and mineral content. The total sulfur content reduced on average by 5% and 22% in the amended samples and the control, and this smaller decrease compared to the control could be explained either by a slower chemical ripening in amended sediments or by measurement limitations. Furthermore, the evolution of electrical conductivity over the 15 weeks of field ripening evidenced the accumulation of chemical reaction products in dry periods.
The influence of biochar on sediment physical and chemical properties, including the increased pore structure, water holding capacity, aeration and buffering capacity, all contributed to creating conditions favorable to microbial activity. A priming effect of biochar application could be observed in the first six weeks of ripening, with high respiration rates, high decomposition rates, and decreasing stabilization of organic matter. In this period, total organic carbon content decreased on average by 30\% in amended samples, compared to only 6% in the control. At the same time, nitrogen content decreased on average by 13% in the samples with biochar, further confirming the high microbial activity. This was followed by a period of decreasing microbial activity until the end of the experiment, which was marked by 14-32% lower respiratory carbon release of the amended samples compared to the control, decreasing decomposition rates and increasing stabilization of organic matter. Thus, biochar application accelerated the decomposition of labile carbon and enhanced the biological stabilization of organic matter in sediments.
These findings suggest that biochar amendment can significantly improve sediment ripening processes and can result in a material with properties desirable for dike construction.
The rapidly growing global demand for heating and cooling is largely met by greenhouse gas-emitting sources and will place increasing strain on future power grids. To meet growing demand and diversify energy sources, novel technologies and sustainable materials are essential. Adsorption heat transformation presents a promising solution for heating, cooling, and heat storage by harnessing sustainable low-temperature or waste heat. This work explores the use of salt hydrates as thermochemical materials and general adsorbents, overcoming their stability challenges by embedding them within porous biochar derived from waste streams. Biochars based on residual wood and chestnut shells were obtained as by-products from two gasification plants and chemically activated with KHCO3 and urea to enhance its pore properties. This treatment significantly increased the specific surface area and pore volume of the chestnut shelland woodbased biochars to 1576 ± 91 m²/g and 0.505 ± 0.01 cm³/g, and 1356 ± 101 m²/g and 0.622 ± 0.05 cm³/g, respectively. The wood-based biochar retained structural features of the original biomass and exhibited pronounced mesoporosity, whereas the chestnut shell-derived biochar predominantly displayed micropores. This structure seems to influence the vacuum impregnation with 80wt.% K2CO3 hydrate, as the structure of wood is still visible and salt is deposited in the nanopores, while chestnut shell biochar appeared coated with a salt layer, determined by SEM/EDS. The resulting composites (subscript ‘ad’) underwent multiple hydration–dehydration cycles to evaluate the stability of the salt hydrates within the carbon support. Initial testing revealed that water uptake and adsorption kinetics improved with cycling, with the wood-based composite showing superior kinetics. This performance is attributed to enhanced vapor transport facilitated by its mesoporous network and large-scale channels inherited from the wood precursor. Long-term cycling of the wood biochar-K2CO3 composite demonstrated stable water uptake of 275 ± 5 kgH2O/kgad over ten cycles, corresponding to a specific water loading of approximately 2.8 molH2O/molK2CO3 . This exceeds the equilibrium uptake of pure K2CO3, indicating altered equilibrium phases due to salt confinement in nanopores. Solution formation was found to significantly influence theoretical power output and energy density of the wood-based composite. Experimental data showed a specific maximum power output exceeding 1 kW/kgK2CO3 for at least ten cycles, and a theoretical energy density of about 1.63 GJ/m³, surpassing that of the pure salt. These findings suggest strong potential for domestic thermochemical energy storage. However, investigation of such systems in residential settings revealed major challenges, including limited efficiency and the availability of more efficient alternatives. In addition to heat storage, the potential for adsorption-based refrigeration was investigated. A composite of wood-based biochar impregnated with 80wt.% CaCl2 hydrate showed enhanced hydration performance, with a maximum water uptake of 1.12 kgH2O/kgad, resulting in a substantial specific cooling effect of up to 2736 kJ/kgad. However, salt solution leakage during hydration was observed, which may limit its use in packed-bed configurations. While the K2CO3 composite delivered a lower overall cooling effect, it demonstrated high specific cooling power, exceeding 550 W/kgad at short cycle times, due to its rapid reaction kinetics. Overall, porous biochar proves to be a promising support matrix for salt hydrates, enabling stable and reversible hydration reactions. The versatility of salt types offers potential not only for novel thermal energy storage systems but also for enhancing existing technologies such as adsorption refrigeration and desalination, particularly by utilizing sustainable low-temperature or waste heat sources
...
The rapidly growing global demand for heating and cooling is largely met by greenhouse gas-emitting sources and will place increasing strain on future power grids. To meet growing demand and diversify energy sources, novel technologies and sustainable materials are essential. Adsorption heat transformation presents a promising solution for heating, cooling, and heat storage by harnessing sustainable low-temperature or waste heat. This work explores the use of salt hydrates as thermochemical materials and general adsorbents, overcoming their stability challenges by embedding them within porous biochar derived from waste streams. Biochars based on residual wood and chestnut shells were obtained as by-products from two gasification plants and chemically activated with KHCO3 and urea to enhance its pore properties. This treatment significantly increased the specific surface area and pore volume of the chestnut shelland woodbased biochars to 1576 ± 91 m²/g and 0.505 ± 0.01 cm³/g, and 1356 ± 101 m²/g and 0.622 ± 0.05 cm³/g, respectively. The wood-based biochar retained structural features of the original biomass and exhibited pronounced mesoporosity, whereas the chestnut shell-derived biochar predominantly displayed micropores. This structure seems to influence the vacuum impregnation with 80wt.% K2CO3 hydrate, as the structure of wood is still visible and salt is deposited in the nanopores, while chestnut shell biochar appeared coated with a salt layer, determined by SEM/EDS. The resulting composites (subscript ‘ad’) underwent multiple hydration–dehydration cycles to evaluate the stability of the salt hydrates within the carbon support. Initial testing revealed that water uptake and adsorption kinetics improved with cycling, with the wood-based composite showing superior kinetics. This performance is attributed to enhanced vapor transport facilitated by its mesoporous network and large-scale channels inherited from the wood precursor. Long-term cycling of the wood biochar-K2CO3 composite demonstrated stable water uptake of 275 ± 5 kgH2O/kgad over ten cycles, corresponding to a specific water loading of approximately 2.8 molH2O/molK2CO3 . This exceeds the equilibrium uptake of pure K2CO3, indicating altered equilibrium phases due to salt confinement in nanopores. Solution formation was found to significantly influence theoretical power output and energy density of the wood-based composite. Experimental data showed a specific maximum power output exceeding 1 kW/kgK2CO3 for at least ten cycles, and a theoretical energy density of about 1.63 GJ/m³, surpassing that of the pure salt. These findings suggest strong potential for domestic thermochemical energy storage. However, investigation of such systems in residential settings revealed major challenges, including limited efficiency and the availability of more efficient alternatives. In addition to heat storage, the potential for adsorption-based refrigeration was investigated. A composite of wood-based biochar impregnated with 80wt.% CaCl2 hydrate showed enhanced hydration performance, with a maximum water uptake of 1.12 kgH2O/kgad, resulting in a substantial specific cooling effect of up to 2736 kJ/kgad. However, salt solution leakage during hydration was observed, which may limit its use in packed-bed configurations. While the K2CO3 composite delivered a lower overall cooling effect, it demonstrated high specific cooling power, exceeding 550 W/kgad at short cycle times, due to its rapid reaction kinetics. Overall, porous biochar proves to be a promising support matrix for salt hydrates, enabling stable and reversible hydration reactions. The versatility of salt types offers potential not only for novel thermal energy storage systems but also for enhancing existing technologies such as adsorption refrigeration and desalination, particularly by utilizing sustainable low-temperature or waste heat sources
The present work investigates the valorization of wine industry residues through the production of advanced biofuels, focusing on grape pomace as a representative lignocellulosic feedstock. The study aims to assess the technical and economic feasibility of converting this residue into liquid fuels via hydrothermal liquefaction (HTL)and to compareits performance against the bioethanol basedpathway currently implemented by Destilerías y Biorefinerías Zambrana, S.A. in the Basque Country.
...
The present work investigates the valorization of wine industry residues through the production of advanced biofuels, focusing on grape pomace as a representative lignocellulosic feedstock. The study aims to assess the technical and economic feasibility of converting this residue into liquid fuels via hydrothermal liquefaction (HTL)and to compareits performance against the bioethanol basedpathway currently implemented by Destilerías y Biorefinerías Zambrana, S.A. in the Basque Country.
Master thesis
(2025)
-
S. de Blocq van Scheltinga, T. Horeman, Luis Cutz , B.J. van Straten, J.C. Diehl
background: To decrease health care’s emissions, the reacquiring of rare earth metals from a complex single use medical device was researched. For a complex single use device (SUD), a cardiac catheter was used, which has electrodes in its tip made of platinum, iridium and palladium. methods: A patent study was done to gain insight into the design and assembly of the catheters, which resulted in the identification of the plastics present. Depending on the electrode type, polyether etherketone (PEEK) or polyamide 12 (PA12) were dominant plastics surrounding the electrode. 5 concepts were developed, all involving a chemical or thermal treatment, which were assessed on their ability to structurally remove these plastics. The treatments used were: nitric acid treatment, sulphuric acid treatment, pyrolysis treatment, toluene treatment and phenol treatment. Treatment removal ability and the purity of the acquired electrodes, were assessed through the use of mass fractions and SEM analyses. Practical aspects, which will be relevant for scale up, such as risk indications, waste created and costs were briefly assessed as well. results: The only treatment that was able to structurally remove all plastics without compromising electrode’s purity, was the sulphuric acid treatment. It is in line with literature that sulphuric acid is the only agent able to structurally remove PEEK at room temperature. Pyrolysis could remove the plastics, but the electrodes were charred. Nitric acid and phenol could only dissolve PA12 but left PEEK structurally present, whereas toluene left all plastics structurally present. conclusion: Reacquiring the electrodes chemically is possible through the use of sulphuric acid. If the spent sulphuric acid can be regenerated, this would be a great benefit since no constant replenishment of acid is required. Pyrolysis could also be investigated further, but a separate cleaning step would be required.
...
background: To decrease health care’s emissions, the reacquiring of rare earth metals from a complex single use medical device was researched. For a complex single use device (SUD), a cardiac catheter was used, which has electrodes in its tip made of platinum, iridium and palladium. methods: A patent study was done to gain insight into the design and assembly of the catheters, which resulted in the identification of the plastics present. Depending on the electrode type, polyether etherketone (PEEK) or polyamide 12 (PA12) were dominant plastics surrounding the electrode. 5 concepts were developed, all involving a chemical or thermal treatment, which were assessed on their ability to structurally remove these plastics. The treatments used were: nitric acid treatment, sulphuric acid treatment, pyrolysis treatment, toluene treatment and phenol treatment. Treatment removal ability and the purity of the acquired electrodes, were assessed through the use of mass fractions and SEM analyses. Practical aspects, which will be relevant for scale up, such as risk indications, waste created and costs were briefly assessed as well. results: The only treatment that was able to structurally remove all plastics without compromising electrode’s purity, was the sulphuric acid treatment. It is in line with literature that sulphuric acid is the only agent able to structurally remove PEEK at room temperature. Pyrolysis could remove the plastics, but the electrodes were charred. Nitric acid and phenol could only dissolve PA12 but left PEEK structurally present, whereas toluene left all plastics structurally present. conclusion: Reacquiring the electrodes chemically is possible through the use of sulphuric acid. If the spent sulphuric acid can be regenerated, this would be a great benefit since no constant replenishment of acid is required. Pyrolysis could also be investigated further, but a separate cleaning step would be required.
This research investigates the co-liquefaction of Arundo donax and PET plastic to assess their potential as feedstocks for producing bio-oil suitable for bio-pavement applications. The study demonstrates the feasibility of using an invasive species like Arundo donax combined with plastic waste for hydrothermal liquefaction (HTL) to generate bio-oil. The experimental design varied three critical parameters— temperature, residence time, and biomass-to-plastic ratio—to optimize oil yield and gross calorific value (GCV). By employing Response Surface Methodology (RSM) and a Rotatable Central Composite Design (RCCD), the study achieved robust statistical modeling, enabling the identification of optimal conditions across 15 experimental runs and two blank experiments. The results indicated that the char produced from both biomass and PET dominated the product distribution, albeit due to different decomposition mechanisms. PET decomposition primarily yielded solid terephthalic acid (TPA), while biomass char resulted from incomplete lignin and cellulose breakdown. The highest oil yield was obtained under severe conditions, highlighting the significant impact of process parameters on product distribution. Analytical techniques such as FTIR and GC-MS revealed the presence of diverse functional groups and confirmed the decomposition of PET into its monomers. XRD and XRF analyses further characterized the char, identifying key structural components and elemental composition. Statistical analysis showed a significant quadratic relationship between oil yield and GCV, with minimal prediction error, indicating the model’s reliability. The optimized bio-oil exhibited a higher benzene content, suggesting enhanced decarboxylation of PET, which was supported by FTIR data. Rheological testing demonstrated the potential of the bio-oil as a rejuvenator for bio-pavements, with bio-char showing promising properties as a filler. Rheological testing using Dynamic Shear Rheometry (DSR) was conducted to evaluate the bio-oil’s potential as a rejuvenator in bio-pavements. The DSR tests revealed that the bio-rejuvenators effectively reduced the stiffness of aged materials, restoring some of the original flexibility and viscous properties lost due to aging. While the oil derived from pure biomass performed slightly better in this regard, the co-liquefied oil still showed promise, particularly in applications requiring a balance between flexibility and stiffness. Additionally, when bio-char was used as a filler in mastic formulations, it exhibited superior stiffness and rutting resistance compared to conventional fillers, although it was less effective in resisting fatigue cracking. Despite the bio-oil’s lower GCV compared to traditional fuels, the process offers a promising pathway toward sustainable energy production. Continued optimization, particularly of the biomass-to-PET ratio and process conditions, could further enhance the fuel properties of the bio-oil, making it a viable alternative for energy and material applications.
...
This research investigates the co-liquefaction of Arundo donax and PET plastic to assess their potential as feedstocks for producing bio-oil suitable for bio-pavement applications. The study demonstrates the feasibility of using an invasive species like Arundo donax combined with plastic waste for hydrothermal liquefaction (HTL) to generate bio-oil. The experimental design varied three critical parameters— temperature, residence time, and biomass-to-plastic ratio—to optimize oil yield and gross calorific value (GCV). By employing Response Surface Methodology (RSM) and a Rotatable Central Composite Design (RCCD), the study achieved robust statistical modeling, enabling the identification of optimal conditions across 15 experimental runs and two blank experiments. The results indicated that the char produced from both biomass and PET dominated the product distribution, albeit due to different decomposition mechanisms. PET decomposition primarily yielded solid terephthalic acid (TPA), while biomass char resulted from incomplete lignin and cellulose breakdown. The highest oil yield was obtained under severe conditions, highlighting the significant impact of process parameters on product distribution. Analytical techniques such as FTIR and GC-MS revealed the presence of diverse functional groups and confirmed the decomposition of PET into its monomers. XRD and XRF analyses further characterized the char, identifying key structural components and elemental composition. Statistical analysis showed a significant quadratic relationship between oil yield and GCV, with minimal prediction error, indicating the model’s reliability. The optimized bio-oil exhibited a higher benzene content, suggesting enhanced decarboxylation of PET, which was supported by FTIR data. Rheological testing demonstrated the potential of the bio-oil as a rejuvenator for bio-pavements, with bio-char showing promising properties as a filler. Rheological testing using Dynamic Shear Rheometry (DSR) was conducted to evaluate the bio-oil’s potential as a rejuvenator in bio-pavements. The DSR tests revealed that the bio-rejuvenators effectively reduced the stiffness of aged materials, restoring some of the original flexibility and viscous properties lost due to aging. While the oil derived from pure biomass performed slightly better in this regard, the co-liquefied oil still showed promise, particularly in applications requiring a balance between flexibility and stiffness. Additionally, when bio-char was used as a filler in mastic formulations, it exhibited superior stiffness and rutting resistance compared to conventional fillers, although it was less effective in resisting fatigue cracking. Despite the bio-oil’s lower GCV compared to traditional fuels, the process offers a promising pathway toward sustainable energy production. Continued optimization, particularly of the biomass-to-PET ratio and process conditions, could further enhance the fuel properties of the bio-oil, making it a viable alternative for energy and material applications.
The increasing accumulation of biomass and plastic waste presents significant environmental challenges, necessitating the development of effective recycling technologies. Hydrothermal liquefaction (HTL) emerges as a promising solution, converting these wastes into valuable hydrocarbons, platform chemicals and materials under mild temperature and pressure in the presence of water. Compared to conventional methods such as pyrolysis and incineration, HTL offers several advantages, including higher efficiency, reduced emissions, and the ability to process wet feedstocks without prior drying. Despite its potential, the current state of HTL
technology predominantly involves batch-scale studies, with limited continuous pilot-scale and commercial-scale implementations. Research at TU Delft has significantly contributed to this field, conducting numerous batch experiments with various feedstocks and catalysts. To bridge the gap between laboratory research and industrial application, scaling up to a continuous pilot scale plant is essential. This thesis presents the design of a pilot-scale continuous HTL system for biomass and plastic. This design addresses the major challenges associated with scale-up, providing a blueprint for future advancements in sustainable waste management and resource recovery.
The design process began with identifying three major challenges in continuous HTL: high-pressure solid-liquid slurry pumping, lower heating rates leading to ash formation and reduced yield, and the need for a robust separation system for gas, liquid, and solid phases. The first step involved establishing the basis of design, including selecting the primary feedstock, thermophysical properties, and required solid particle size. A block flow diagram was then developed to define the battery limits. The continuous pilot-scale HTL system was divided into three main sections: feed introduction, reactor, and product separation. All potential options and equipment were evaluated, and the most suitable ones were chosen. Various equipment manufacturers were consulted to understand the suitability and cost implications. Based on the selected equipment, a process flow sheet was generated, followed by detailed sizing of all equipment and finalizing the process and instrumentation diagram. Finally, a cost analysis was conducted to determine the capital expenditure and operational expenditure of the designed plant.
During the design process, it was observed that only one commercially available pump could achieve the required pressure. However, the cost of this pump was extremely high. To address this, a dual piston pump system was developed, effectively pressurizing slurries to the required process pressure (200 bar). This system uses two asynchronously operated hydraulic power pistons and measures the slurry flow rate based on the position of the piston, eliminating the need for flow indicators or control valves. Additionally, a heating system consisting of a tubular preheater and an induction heater was proposed, capable of heating the slurry at a rate of 4°C/s. The separation system was designed with a solid filter, flash tank, and gravity settler to extract bio-crude oil or plastic oil as the final product. Economic analysis showed that operational costs are around 18-21.5% of the capital cost per year, with feed introduction and reactor costs accounting for 85% of the total capital cost. Overall, two design alternatives were developed during the thesis, addressing all identified major challenges. These alternatives provide cost-effective solutions for parametric studies of the HTL process.
...
technology predominantly involves batch-scale studies, with limited continuous pilot-scale and commercial-scale implementations. Research at TU Delft has significantly contributed to this field, conducting numerous batch experiments with various feedstocks and catalysts. To bridge the gap between laboratory research and industrial application, scaling up to a continuous pilot scale plant is essential. This thesis presents the design of a pilot-scale continuous HTL system for biomass and plastic. This design addresses the major challenges associated with scale-up, providing a blueprint for future advancements in sustainable waste management and resource recovery.
The design process began with identifying three major challenges in continuous HTL: high-pressure solid-liquid slurry pumping, lower heating rates leading to ash formation and reduced yield, and the need for a robust separation system for gas, liquid, and solid phases. The first step involved establishing the basis of design, including selecting the primary feedstock, thermophysical properties, and required solid particle size. A block flow diagram was then developed to define the battery limits. The continuous pilot-scale HTL system was divided into three main sections: feed introduction, reactor, and product separation. All potential options and equipment were evaluated, and the most suitable ones were chosen. Various equipment manufacturers were consulted to understand the suitability and cost implications. Based on the selected equipment, a process flow sheet was generated, followed by detailed sizing of all equipment and finalizing the process and instrumentation diagram. Finally, a cost analysis was conducted to determine the capital expenditure and operational expenditure of the designed plant.
During the design process, it was observed that only one commercially available pump could achieve the required pressure. However, the cost of this pump was extremely high. To address this, a dual piston pump system was developed, effectively pressurizing slurries to the required process pressure (200 bar). This system uses two asynchronously operated hydraulic power pistons and measures the slurry flow rate based on the position of the piston, eliminating the need for flow indicators or control valves. Additionally, a heating system consisting of a tubular preheater and an induction heater was proposed, capable of heating the slurry at a rate of 4°C/s. The separation system was designed with a solid filter, flash tank, and gravity settler to extract bio-crude oil or plastic oil as the final product. Economic analysis showed that operational costs are around 18-21.5% of the capital cost per year, with feed introduction and reactor costs accounting for 85% of the total capital cost. Overall, two design alternatives were developed during the thesis, addressing all identified major challenges. These alternatives provide cost-effective solutions for parametric studies of the HTL process.
...
The increasing accumulation of biomass and plastic waste presents significant environmental challenges, necessitating the development of effective recycling technologies. Hydrothermal liquefaction (HTL) emerges as a promising solution, converting these wastes into valuable hydrocarbons, platform chemicals and materials under mild temperature and pressure in the presence of water. Compared to conventional methods such as pyrolysis and incineration, HTL offers several advantages, including higher efficiency, reduced emissions, and the ability to process wet feedstocks without prior drying. Despite its potential, the current state of HTL
technology predominantly involves batch-scale studies, with limited continuous pilot-scale and commercial-scale implementations. Research at TU Delft has significantly contributed to this field, conducting numerous batch experiments with various feedstocks and catalysts. To bridge the gap between laboratory research and industrial application, scaling up to a continuous pilot scale plant is essential. This thesis presents the design of a pilot-scale continuous HTL system for biomass and plastic. This design addresses the major challenges associated with scale-up, providing a blueprint for future advancements in sustainable waste management and resource recovery.
The design process began with identifying three major challenges in continuous HTL: high-pressure solid-liquid slurry pumping, lower heating rates leading to ash formation and reduced yield, and the need for a robust separation system for gas, liquid, and solid phases. The first step involved establishing the basis of design, including selecting the primary feedstock, thermophysical properties, and required solid particle size. A block flow diagram was then developed to define the battery limits. The continuous pilot-scale HTL system was divided into three main sections: feed introduction, reactor, and product separation. All potential options and equipment were evaluated, and the most suitable ones were chosen. Various equipment manufacturers were consulted to understand the suitability and cost implications. Based on the selected equipment, a process flow sheet was generated, followed by detailed sizing of all equipment and finalizing the process and instrumentation diagram. Finally, a cost analysis was conducted to determine the capital expenditure and operational expenditure of the designed plant.
During the design process, it was observed that only one commercially available pump could achieve the required pressure. However, the cost of this pump was extremely high. To address this, a dual piston pump system was developed, effectively pressurizing slurries to the required process pressure (200 bar). This system uses two asynchronously operated hydraulic power pistons and measures the slurry flow rate based on the position of the piston, eliminating the need for flow indicators or control valves. Additionally, a heating system consisting of a tubular preheater and an induction heater was proposed, capable of heating the slurry at a rate of 4°C/s. The separation system was designed with a solid filter, flash tank, and gravity settler to extract bio-crude oil or plastic oil as the final product. Economic analysis showed that operational costs are around 18-21.5% of the capital cost per year, with feed introduction and reactor costs accounting for 85% of the total capital cost. Overall, two design alternatives were developed during the thesis, addressing all identified major challenges. These alternatives provide cost-effective solutions for parametric studies of the HTL process.
technology predominantly involves batch-scale studies, with limited continuous pilot-scale and commercial-scale implementations. Research at TU Delft has significantly contributed to this field, conducting numerous batch experiments with various feedstocks and catalysts. To bridge the gap between laboratory research and industrial application, scaling up to a continuous pilot scale plant is essential. This thesis presents the design of a pilot-scale continuous HTL system for biomass and plastic. This design addresses the major challenges associated with scale-up, providing a blueprint for future advancements in sustainable waste management and resource recovery.
The design process began with identifying three major challenges in continuous HTL: high-pressure solid-liquid slurry pumping, lower heating rates leading to ash formation and reduced yield, and the need for a robust separation system for gas, liquid, and solid phases. The first step involved establishing the basis of design, including selecting the primary feedstock, thermophysical properties, and required solid particle size. A block flow diagram was then developed to define the battery limits. The continuous pilot-scale HTL system was divided into three main sections: feed introduction, reactor, and product separation. All potential options and equipment were evaluated, and the most suitable ones were chosen. Various equipment manufacturers were consulted to understand the suitability and cost implications. Based on the selected equipment, a process flow sheet was generated, followed by detailed sizing of all equipment and finalizing the process and instrumentation diagram. Finally, a cost analysis was conducted to determine the capital expenditure and operational expenditure of the designed plant.
During the design process, it was observed that only one commercially available pump could achieve the required pressure. However, the cost of this pump was extremely high. To address this, a dual piston pump system was developed, effectively pressurizing slurries to the required process pressure (200 bar). This system uses two asynchronously operated hydraulic power pistons and measures the slurry flow rate based on the position of the piston, eliminating the need for flow indicators or control valves. Additionally, a heating system consisting of a tubular preheater and an induction heater was proposed, capable of heating the slurry at a rate of 4°C/s. The separation system was designed with a solid filter, flash tank, and gravity settler to extract bio-crude oil or plastic oil as the final product. Economic analysis showed that operational costs are around 18-21.5% of the capital cost per year, with feed introduction and reactor costs accounting for 85% of the total capital cost. Overall, two design alternatives were developed during the thesis, addressing all identified major challenges. These alternatives provide cost-effective solutions for parametric studies of the HTL process.
As policies and technological advancements accelerate the energy transition, more resources are required to develop sustainable pathways for end-of-life solar modules. Chemical delamination is an attractive option for solar recycling as it has the potential to separate the layers of a module and recover the cell intact. In this work, four primary testing factors were considered to optimize the process: solvent, temperature and residence time with the goal to reduce the reliance on fossil fuel based solvents, improve the reliability of cell material recovery and to attempt to recover cell materials intact. A preliminary solvent screening found three sustainable solvents that could replace current fossil fuel based recommendations. A subsequent optimization under atmospheric conditions found that 60% of the encapsulating EVA could be removed in 3 hours at 160°C. Additionally, this process was observed to be scalable. This research offers a baseline result for chemical delamination that can be built upon to advance the technical and economic viability of this solar recycling method.
...
As policies and technological advancements accelerate the energy transition, more resources are required to develop sustainable pathways for end-of-life solar modules. Chemical delamination is an attractive option for solar recycling as it has the potential to separate the layers of a module and recover the cell intact. In this work, four primary testing factors were considered to optimize the process: solvent, temperature and residence time with the goal to reduce the reliance on fossil fuel based solvents, improve the reliability of cell material recovery and to attempt to recover cell materials intact. A preliminary solvent screening found three sustainable solvents that could replace current fossil fuel based recommendations. A subsequent optimization under atmospheric conditions found that 60% of the encapsulating EVA could be removed in 3 hours at 160°C. Additionally, this process was observed to be scalable. This research offers a baseline result for chemical delamination that can be built upon to advance the technical and economic viability of this solar recycling method.
In Europe, 20.7 Mt of Polystyrene (PS) was produced in the year 2021, mostly consisting of packaging, insulation, and food utensils. Like many other kinds of plastics, they take hundreds of years to naturally degrade in the environment. To prevent the buildup of plastics in our environment, recycling technology will have to be employed. Current recycling technologies can be divided into three categories: organic, mechanical and chemical recycling. Organic recycling involves the use of biological organisms or enzymes to breakdown plastic into useful materials. Mechanical recycling technologies include processes such as dissolution and conventional mechanical recycling. Among chemical recycling, baseline technology includes
pyrolysis that involves higher temperatures (>500°C) which produces char, gasses, and complex oils. Hydrothermal Liquefaction (HTL) of PS has shown promising results in tackling the problem plastic waste buildup in the environment. This process utilizes water as solvent and subjecting it to mild temperatures and pressures to produce less complex oils that contain building blocks such as monomeric compounds and high value chemicals (HVC). These compounds can then be used as platform chemicals or as source to manufacture new materials, as well as closing the loop on PS waste.
This thesis focuses on the use of catalysis to increase the selectivity for PS conversion through HTL to increase the yields of monomeric compounds and high-value chemicals (HVCs) at lower temperatures (<370°C) than current approaches. In this work, different catalysts were screened and the best performing catalyst was used to optimize the HTL process. The HTL process was optimized using a design-ofexperience (DOE) approach for the following process conditions: temperature (330-350°C), catalyst loading (0-15%) and reaction time (30-60 minutes). The analytical techniques used to characterize the quality of oil as well as determine the amount of chemicals present are: Bomb Calorimetry, Ultimate analysis (CHN-analysis), Gas Chromatography-Mass Spectrometry with Flame Ionization Detection (GCMS-FID)
and Two-Dimensional Gas Chromatography with Flame Ionization Detection (GCxGC-FID).
Results from a screening campaign indicated high yields of oil (90 wt%). Following this, a simple distillation was conducted to separate the lighter fraction from the heavier ones within 90 wt%. Ultimate analysis of the compounds showed high C,H,and N ratios similar to what was found in literature. Bomb calorimetry of the PS-Crude oil product showed of 40 MJ/kg, indicating that oil product is comparable to what is found in literature. GCMS-FID indicated that 17 wt% of styrene was produced from this process,
along with 5.5 wt% of alpha-methyl styrene and other HVCs. The rest of the oil consists of heavy fractions (C-20) which could be go through another upgrading process.
After the screening campaign MgO was chosen as a catalyst to increase the yield of styrene. The yield of oil remain high with 80-90 wt% yield of oil in most cases. Aqueous phase and gas yields remain low (<5 wt%), while char can vary but also remains quite low (<10 wt%). Analysis of Bomb calorimetry showed similar results to screening with an average of 38 MJ/kg. CHNO also showed similar ratios of C,H, and N ratios. When looking at the GCMS-FID and GCxGC-FID, the amount of styrene remained at a maximum of 16-17 wt% with no significant increase. However, results of the research also showed that catalyst does have effect in increasing yield of styrene. Optimization for oil was conducted and optimum point for oil production is at 340°C, 34 minutes and 8% catalyst loading. The research will contribute to the growing body of research into processes for plastic waste valorization and offers more insight into catalytic
hydrothermal liquefaction as well as experimental methodology to separate the oils into its components. ...
pyrolysis that involves higher temperatures (>500°C) which produces char, gasses, and complex oils. Hydrothermal Liquefaction (HTL) of PS has shown promising results in tackling the problem plastic waste buildup in the environment. This process utilizes water as solvent and subjecting it to mild temperatures and pressures to produce less complex oils that contain building blocks such as monomeric compounds and high value chemicals (HVC). These compounds can then be used as platform chemicals or as source to manufacture new materials, as well as closing the loop on PS waste.
This thesis focuses on the use of catalysis to increase the selectivity for PS conversion through HTL to increase the yields of monomeric compounds and high-value chemicals (HVCs) at lower temperatures (<370°C) than current approaches. In this work, different catalysts were screened and the best performing catalyst was used to optimize the HTL process. The HTL process was optimized using a design-ofexperience (DOE) approach for the following process conditions: temperature (330-350°C), catalyst loading (0-15%) and reaction time (30-60 minutes). The analytical techniques used to characterize the quality of oil as well as determine the amount of chemicals present are: Bomb Calorimetry, Ultimate analysis (CHN-analysis), Gas Chromatography-Mass Spectrometry with Flame Ionization Detection (GCMS-FID)
and Two-Dimensional Gas Chromatography with Flame Ionization Detection (GCxGC-FID).
Results from a screening campaign indicated high yields of oil (90 wt%). Following this, a simple distillation was conducted to separate the lighter fraction from the heavier ones within 90 wt%. Ultimate analysis of the compounds showed high C,H,and N ratios similar to what was found in literature. Bomb calorimetry of the PS-Crude oil product showed of 40 MJ/kg, indicating that oil product is comparable to what is found in literature. GCMS-FID indicated that 17 wt% of styrene was produced from this process,
along with 5.5 wt% of alpha-methyl styrene and other HVCs. The rest of the oil consists of heavy fractions (C-20) which could be go through another upgrading process.
After the screening campaign MgO was chosen as a catalyst to increase the yield of styrene. The yield of oil remain high with 80-90 wt% yield of oil in most cases. Aqueous phase and gas yields remain low (<5 wt%), while char can vary but also remains quite low (<10 wt%). Analysis of Bomb calorimetry showed similar results to screening with an average of 38 MJ/kg. CHNO also showed similar ratios of C,H, and N ratios. When looking at the GCMS-FID and GCxGC-FID, the amount of styrene remained at a maximum of 16-17 wt% with no significant increase. However, results of the research also showed that catalyst does have effect in increasing yield of styrene. Optimization for oil was conducted and optimum point for oil production is at 340°C, 34 minutes and 8% catalyst loading. The research will contribute to the growing body of research into processes for plastic waste valorization and offers more insight into catalytic
hydrothermal liquefaction as well as experimental methodology to separate the oils into its components. ...
In Europe, 20.7 Mt of Polystyrene (PS) was produced in the year 2021, mostly consisting of packaging, insulation, and food utensils. Like many other kinds of plastics, they take hundreds of years to naturally degrade in the environment. To prevent the buildup of plastics in our environment, recycling technology will have to be employed. Current recycling technologies can be divided into three categories: organic, mechanical and chemical recycling. Organic recycling involves the use of biological organisms or enzymes to breakdown plastic into useful materials. Mechanical recycling technologies include processes such as dissolution and conventional mechanical recycling. Among chemical recycling, baseline technology includes
pyrolysis that involves higher temperatures (>500°C) which produces char, gasses, and complex oils. Hydrothermal Liquefaction (HTL) of PS has shown promising results in tackling the problem plastic waste buildup in the environment. This process utilizes water as solvent and subjecting it to mild temperatures and pressures to produce less complex oils that contain building blocks such as monomeric compounds and high value chemicals (HVC). These compounds can then be used as platform chemicals or as source to manufacture new materials, as well as closing the loop on PS waste.
This thesis focuses on the use of catalysis to increase the selectivity for PS conversion through HTL to increase the yields of monomeric compounds and high-value chemicals (HVCs) at lower temperatures (<370°C) than current approaches. In this work, different catalysts were screened and the best performing catalyst was used to optimize the HTL process. The HTL process was optimized using a design-ofexperience (DOE) approach for the following process conditions: temperature (330-350°C), catalyst loading (0-15%) and reaction time (30-60 minutes). The analytical techniques used to characterize the quality of oil as well as determine the amount of chemicals present are: Bomb Calorimetry, Ultimate analysis (CHN-analysis), Gas Chromatography-Mass Spectrometry with Flame Ionization Detection (GCMS-FID)
and Two-Dimensional Gas Chromatography with Flame Ionization Detection (GCxGC-FID).
Results from a screening campaign indicated high yields of oil (90 wt%). Following this, a simple distillation was conducted to separate the lighter fraction from the heavier ones within 90 wt%. Ultimate analysis of the compounds showed high C,H,and N ratios similar to what was found in literature. Bomb calorimetry of the PS-Crude oil product showed of 40 MJ/kg, indicating that oil product is comparable to what is found in literature. GCMS-FID indicated that 17 wt% of styrene was produced from this process,
along with 5.5 wt% of alpha-methyl styrene and other HVCs. The rest of the oil consists of heavy fractions (C-20) which could be go through another upgrading process.
After the screening campaign MgO was chosen as a catalyst to increase the yield of styrene. The yield of oil remain high with 80-90 wt% yield of oil in most cases. Aqueous phase and gas yields remain low (<5 wt%), while char can vary but also remains quite low (<10 wt%). Analysis of Bomb calorimetry showed similar results to screening with an average of 38 MJ/kg. CHNO also showed similar ratios of C,H, and N ratios. When looking at the GCMS-FID and GCxGC-FID, the amount of styrene remained at a maximum of 16-17 wt% with no significant increase. However, results of the research also showed that catalyst does have effect in increasing yield of styrene. Optimization for oil was conducted and optimum point for oil production is at 340°C, 34 minutes and 8% catalyst loading. The research will contribute to the growing body of research into processes for plastic waste valorization and offers more insight into catalytic
hydrothermal liquefaction as well as experimental methodology to separate the oils into its components.
pyrolysis that involves higher temperatures (>500°C) which produces char, gasses, and complex oils. Hydrothermal Liquefaction (HTL) of PS has shown promising results in tackling the problem plastic waste buildup in the environment. This process utilizes water as solvent and subjecting it to mild temperatures and pressures to produce less complex oils that contain building blocks such as monomeric compounds and high value chemicals (HVC). These compounds can then be used as platform chemicals or as source to manufacture new materials, as well as closing the loop on PS waste.
This thesis focuses on the use of catalysis to increase the selectivity for PS conversion through HTL to increase the yields of monomeric compounds and high-value chemicals (HVCs) at lower temperatures (<370°C) than current approaches. In this work, different catalysts were screened and the best performing catalyst was used to optimize the HTL process. The HTL process was optimized using a design-ofexperience (DOE) approach for the following process conditions: temperature (330-350°C), catalyst loading (0-15%) and reaction time (30-60 minutes). The analytical techniques used to characterize the quality of oil as well as determine the amount of chemicals present are: Bomb Calorimetry, Ultimate analysis (CHN-analysis), Gas Chromatography-Mass Spectrometry with Flame Ionization Detection (GCMS-FID)
and Two-Dimensional Gas Chromatography with Flame Ionization Detection (GCxGC-FID).
Results from a screening campaign indicated high yields of oil (90 wt%). Following this, a simple distillation was conducted to separate the lighter fraction from the heavier ones within 90 wt%. Ultimate analysis of the compounds showed high C,H,and N ratios similar to what was found in literature. Bomb calorimetry of the PS-Crude oil product showed of 40 MJ/kg, indicating that oil product is comparable to what is found in literature. GCMS-FID indicated that 17 wt% of styrene was produced from this process,
along with 5.5 wt% of alpha-methyl styrene and other HVCs. The rest of the oil consists of heavy fractions (C-20) which could be go through another upgrading process.
After the screening campaign MgO was chosen as a catalyst to increase the yield of styrene. The yield of oil remain high with 80-90 wt% yield of oil in most cases. Aqueous phase and gas yields remain low (<5 wt%), while char can vary but also remains quite low (<10 wt%). Analysis of Bomb calorimetry showed similar results to screening with an average of 38 MJ/kg. CHNO also showed similar ratios of C,H, and N ratios. When looking at the GCMS-FID and GCxGC-FID, the amount of styrene remained at a maximum of 16-17 wt% with no significant increase. However, results of the research also showed that catalyst does have effect in increasing yield of styrene. Optimization for oil was conducted and optimum point for oil production is at 340°C, 34 minutes and 8% catalyst loading. The research will contribute to the growing body of research into processes for plastic waste valorization and offers more insight into catalytic
hydrothermal liquefaction as well as experimental methodology to separate the oils into its components.
Hydrochar from Fischer-Topsch biosludge
Is there an application for Fischer-Tropsch biosludge hydrochar produced via hydrothermal carbonization
Master thesis
(2023)
-
L.D. van der Loos, W. de Jong, M.K. de Kreuk, L.L. Cutz IJchajchal, J.A. Pavez Jara, Georg Stockinger, R.E.F. Lindeboom
Improving circularity and reducing greenhouse gas emissions can be achieved by utilizing secondary streams like Fischer-Tropsch biosludge, which is typically disposed of in landfills. Biochar, which has accumulated increased interest recently, has significant potential for decreasing carbon emissions and can be created from biosludge. This master thesis was set up as an opportunity-based research project to understand the utilization of Fischer-Tropsch biosludge by the hydrothermal carbonisation process and characterise its product phases; biochar, aqueous phase and gaseous phase. A central composite surface response design was used to conduct experiments to analyse the impact of temperature and time on the characteristics of the phases. Three different levels of the factors have been used. The high ash content and low surface area of the biochar made it difficult to determine a specific use case for the biochar. Yet, the aqueous phase has low ash and possible potential for biogas creation by anaerobic digestion. The gas phase is quantitatively not of significance. Stockpiling the biochar could sequestrate carbon credits and more research can be conducted to find a post- or pre-treatment to improve the biochar for a social-economically benefiting application.
...
...
Improving circularity and reducing greenhouse gas emissions can be achieved by utilizing secondary streams like Fischer-Tropsch biosludge, which is typically disposed of in landfills. Biochar, which has accumulated increased interest recently, has significant potential for decreasing carbon emissions and can be created from biosludge. This master thesis was set up as an opportunity-based research project to understand the utilization of Fischer-Tropsch biosludge by the hydrothermal carbonisation process and characterise its product phases; biochar, aqueous phase and gaseous phase. A central composite surface response design was used to conduct experiments to analyse the impact of temperature and time on the characteristics of the phases. Three different levels of the factors have been used. The high ash content and low surface area of the biochar made it difficult to determine a specific use case for the biochar. Yet, the aqueous phase has low ash and possible potential for biogas creation by anaerobic digestion. The gas phase is quantitatively not of significance. Stockpiling the biochar could sequestrate carbon credits and more research can be conducted to find a post- or pre-treatment to improve the biochar for a social-economically benefiting application.
Master thesis
(2023)
-
N. RAMACHANDRAN, Siddhant Kumar, Luis Cutz , S.T. Abrahami, Michiel de Rapper
Pressurized liquid Tin finds application in the generation of Extreme Ultra-Violet light for semiconductor lithography. In order to improve the throughput of the lithography systems, tin must be pressurized to higher levels, and in turn, new pressurization methods are needed.
A phase change tin pump is an innovative system that pressurizes and pumps liquid Tin by harnessing the expansion and contraction during phase changes, without the need for any moving parts. The pump needs to pressurize liquid tin up to 2000 bars, with a pumping capacity of 4 ml/hr. Since this system relies heavily on control over the temperatures of tin, this study is set up to address the thermal constraints in the system by investigating three aspects of temperature distribution in the system.
Firstly, the heaters in the pump are placed at discrete locations, but the working volume is continuous. Thus, it is challenging to define a temperature control function that can facilitate uniform melting and continuous flow of tin. The relation between rate of heat input to the pump and the rate of heat transfer in tin is estimated using an analytical model. From the analytical model, it is found that heating rates of the order of 0.1 K/s are required in order to melt tin in a reasonably uniform fashion over a zone length of 5 mm.
Secondly, the number of heaters are limited, and it is hard to achieve precise control over the temperature of tin at any given location. In order to establish a good basic control, the free design parameters are optimized so that a steady state gradient of 50 K is achieved between solid (200°C) and liquid (250°C) tin in the working volume. This is done by evaluating the thermal profile of the system for different combinations of the design variables, using Finite Element Analysis. The two objectives of this optimization problem (maximum temperature gain and minimum crosstalk) are seen to have contrasting requirements of the design variables. An optimal combination of the variables is found such that a gradient of 50 K is possible, but with a little trade-off on both the objectives.
Thirdly, a direct measurement of temperature of tin inside the pump is not feasible, and tin temperatures are estimated analytically. The accuracy of estimation is impacted by changes in local temperatures due to the non-linear properties of tin like absorption/release of latent heat, pressure-dependent melting point. The effect of non-linear tin properties on local temperature distribution is studied by setting up a finite difference model. It is seen that the absorption of latent heat during melting of tin results in a temperature that is 12 K lower than what would have been without the effect of latent heat. ...
A phase change tin pump is an innovative system that pressurizes and pumps liquid Tin by harnessing the expansion and contraction during phase changes, without the need for any moving parts. The pump needs to pressurize liquid tin up to 2000 bars, with a pumping capacity of 4 ml/hr. Since this system relies heavily on control over the temperatures of tin, this study is set up to address the thermal constraints in the system by investigating three aspects of temperature distribution in the system.
Firstly, the heaters in the pump are placed at discrete locations, but the working volume is continuous. Thus, it is challenging to define a temperature control function that can facilitate uniform melting and continuous flow of tin. The relation between rate of heat input to the pump and the rate of heat transfer in tin is estimated using an analytical model. From the analytical model, it is found that heating rates of the order of 0.1 K/s are required in order to melt tin in a reasonably uniform fashion over a zone length of 5 mm.
Secondly, the number of heaters are limited, and it is hard to achieve precise control over the temperature of tin at any given location. In order to establish a good basic control, the free design parameters are optimized so that a steady state gradient of 50 K is achieved between solid (200°C) and liquid (250°C) tin in the working volume. This is done by evaluating the thermal profile of the system for different combinations of the design variables, using Finite Element Analysis. The two objectives of this optimization problem (maximum temperature gain and minimum crosstalk) are seen to have contrasting requirements of the design variables. An optimal combination of the variables is found such that a gradient of 50 K is possible, but with a little trade-off on both the objectives.
Thirdly, a direct measurement of temperature of tin inside the pump is not feasible, and tin temperatures are estimated analytically. The accuracy of estimation is impacted by changes in local temperatures due to the non-linear properties of tin like absorption/release of latent heat, pressure-dependent melting point. The effect of non-linear tin properties on local temperature distribution is studied by setting up a finite difference model. It is seen that the absorption of latent heat during melting of tin results in a temperature that is 12 K lower than what would have been without the effect of latent heat. ...
Pressurized liquid Tin finds application in the generation of Extreme Ultra-Violet light for semiconductor lithography. In order to improve the throughput of the lithography systems, tin must be pressurized to higher levels, and in turn, new pressurization methods are needed.
A phase change tin pump is an innovative system that pressurizes and pumps liquid Tin by harnessing the expansion and contraction during phase changes, without the need for any moving parts. The pump needs to pressurize liquid tin up to 2000 bars, with a pumping capacity of 4 ml/hr. Since this system relies heavily on control over the temperatures of tin, this study is set up to address the thermal constraints in the system by investigating three aspects of temperature distribution in the system.
Firstly, the heaters in the pump are placed at discrete locations, but the working volume is continuous. Thus, it is challenging to define a temperature control function that can facilitate uniform melting and continuous flow of tin. The relation between rate of heat input to the pump and the rate of heat transfer in tin is estimated using an analytical model. From the analytical model, it is found that heating rates of the order of 0.1 K/s are required in order to melt tin in a reasonably uniform fashion over a zone length of 5 mm.
Secondly, the number of heaters are limited, and it is hard to achieve precise control over the temperature of tin at any given location. In order to establish a good basic control, the free design parameters are optimized so that a steady state gradient of 50 K is achieved between solid (200°C) and liquid (250°C) tin in the working volume. This is done by evaluating the thermal profile of the system for different combinations of the design variables, using Finite Element Analysis. The two objectives of this optimization problem (maximum temperature gain and minimum crosstalk) are seen to have contrasting requirements of the design variables. An optimal combination of the variables is found such that a gradient of 50 K is possible, but with a little trade-off on both the objectives.
Thirdly, a direct measurement of temperature of tin inside the pump is not feasible, and tin temperatures are estimated analytically. The accuracy of estimation is impacted by changes in local temperatures due to the non-linear properties of tin like absorption/release of latent heat, pressure-dependent melting point. The effect of non-linear tin properties on local temperature distribution is studied by setting up a finite difference model. It is seen that the absorption of latent heat during melting of tin results in a temperature that is 12 K lower than what would have been without the effect of latent heat.
A phase change tin pump is an innovative system that pressurizes and pumps liquid Tin by harnessing the expansion and contraction during phase changes, without the need for any moving parts. The pump needs to pressurize liquid tin up to 2000 bars, with a pumping capacity of 4 ml/hr. Since this system relies heavily on control over the temperatures of tin, this study is set up to address the thermal constraints in the system by investigating three aspects of temperature distribution in the system.
Firstly, the heaters in the pump are placed at discrete locations, but the working volume is continuous. Thus, it is challenging to define a temperature control function that can facilitate uniform melting and continuous flow of tin. The relation between rate of heat input to the pump and the rate of heat transfer in tin is estimated using an analytical model. From the analytical model, it is found that heating rates of the order of 0.1 K/s are required in order to melt tin in a reasonably uniform fashion over a zone length of 5 mm.
Secondly, the number of heaters are limited, and it is hard to achieve precise control over the temperature of tin at any given location. In order to establish a good basic control, the free design parameters are optimized so that a steady state gradient of 50 K is achieved between solid (200°C) and liquid (250°C) tin in the working volume. This is done by evaluating the thermal profile of the system for different combinations of the design variables, using Finite Element Analysis. The two objectives of this optimization problem (maximum temperature gain and minimum crosstalk) are seen to have contrasting requirements of the design variables. An optimal combination of the variables is found such that a gradient of 50 K is possible, but with a little trade-off on both the objectives.
Thirdly, a direct measurement of temperature of tin inside the pump is not feasible, and tin temperatures are estimated analytically. The accuracy of estimation is impacted by changes in local temperatures due to the non-linear properties of tin like absorption/release of latent heat, pressure-dependent melting point. The effect of non-linear tin properties on local temperature distribution is studied by setting up a finite difference model. It is seen that the absorption of latent heat during melting of tin results in a temperature that is 12 K lower than what would have been without the effect of latent heat.
Renewable H2 via Pressure Swing Adsorption from waste gasification
A techno-economic analysis
This work deals with the techno-economic assessment of Hydrogen production from waste-derived syngas coming from a large-scale gasifier. This research was developed for the purpose of converting nonrecyclable waste using a patented gasification technology to meet the demand for cleaner fuels, reducing global carbon emissions in line with the concept of a circular economy. A market analysis is conducted to identify the primary drivers and building blocks involved in the development of a Waste to Hydrogen scheme within the European context. Subsequently, a process route is designed and successfully implemented within Aspen Tech software to treat the raw syngas from the HTW gasifier, featuring a syngas adjustment and purification unit, a Pressure Swing Adsorption system, and a Combined Heat and Power unit. The system design achieves a Hydrogen recovery of 63% and purity around 99.5 vol%. The Hydrogen’s quality aligns with the requirements for use in refineries, ammonia and methanol production, and for various heat-related applications. The economic analysis demonstrated the profitability of the plant, with a return on investment at a rate of 9.7 %. The levelized cost of Hydrogen at 7.35 €/kg substantiates the competitiveness of the Waste to Hydrogen model in comparison to steam methane reforming and electrolysis routes. The project’s results offer a promising outlook for future research, indicating a sustainable approach to waste management and a viable pathway for reducing carbon emissions in the industry and transportation sectors.
...
This work deals with the techno-economic assessment of Hydrogen production from waste-derived syngas coming from a large-scale gasifier. This research was developed for the purpose of converting nonrecyclable waste using a patented gasification technology to meet the demand for cleaner fuels, reducing global carbon emissions in line with the concept of a circular economy. A market analysis is conducted to identify the primary drivers and building blocks involved in the development of a Waste to Hydrogen scheme within the European context. Subsequently, a process route is designed and successfully implemented within Aspen Tech software to treat the raw syngas from the HTW gasifier, featuring a syngas adjustment and purification unit, a Pressure Swing Adsorption system, and a Combined Heat and Power unit. The system design achieves a Hydrogen recovery of 63% and purity around 99.5 vol%. The Hydrogen’s quality aligns with the requirements for use in refineries, ammonia and methanol production, and for various heat-related applications. The economic analysis demonstrated the profitability of the plant, with a return on investment at a rate of 9.7 %. The levelized cost of Hydrogen at 7.35 €/kg substantiates the competitiveness of the Waste to Hydrogen model in comparison to steam methane reforming and electrolysis routes. The project’s results offer a promising outlook for future research, indicating a sustainable approach to waste management and a viable pathway for reducing carbon emissions in the industry and transportation sectors.
Coffee farmers and producers in Kerala (India) face a serious obstacle in their pursuit of a self-sustaining coffee processing technology and fuel deficiency. Research indicates that coffee, as one of the largest industries, generates a huge amount of waste, namely Spent Coffee Grounds (SCGs). This study aims to evaluate the feasibility and efficiency of converting SCG into biochar using a solar-assisted biomass torrefying technique, while keeping frugal or "jugaad" innovation in mind. To torrefy the feedstock, it was intended to use the available SK14 solar cooker in conjunction with a prototype reactor unit. Based on previous research on torrefying coffee waste, this study asks: Can the biomass torrefied using the SK 14 cooker be utilized as fuel? In this context: Solar biomass torrefaction is an endothermic process of converting the feedstock in an inert environment at low temperatures of 200-300 °C provided by concentrated solar energy in order to produce a high yield of solid biochar.
Based on the literature research, it was important to characterize the SK14 cooker, the feedstock, and to understand the operating principles of the chosen reactor, namely Evacuated Tube Vacuum Collectors (EVCs). Since the design of the reactor and cooker were interdependent, COMSOL was used to simulate the heat distribution profile and temperature profile of the reactor model. Literature and simulation results were used to construct a prototype reactor, and torrefaction tests were conducted in Hyderabad (India). SCG was effectively torrefied to generate biochar at 240 °C and 260 °C, as evidenced by high heating values of 26 MJ/kg (21% increase) and 26.3 MJ/kg (22.50% increase), respectively compared to the raw material. The results show that the current system can be utilized as a small-scale solar biomass torrefier, creating biochar that can be used as a fuel. However, the reactor's non-homogeneous heating rate and poor heat retention severely hampered its applicability. Further study is required to find other features and aspects that might not only improve the design and efficacy of the torrefier, but also facilitate its implementation for coffee producers in Kerala.
...
Based on the literature research, it was important to characterize the SK14 cooker, the feedstock, and to understand the operating principles of the chosen reactor, namely Evacuated Tube Vacuum Collectors (EVCs). Since the design of the reactor and cooker were interdependent, COMSOL was used to simulate the heat distribution profile and temperature profile of the reactor model. Literature and simulation results were used to construct a prototype reactor, and torrefaction tests were conducted in Hyderabad (India). SCG was effectively torrefied to generate biochar at 240 °C and 260 °C, as evidenced by high heating values of 26 MJ/kg (21% increase) and 26.3 MJ/kg (22.50% increase), respectively compared to the raw material. The results show that the current system can be utilized as a small-scale solar biomass torrefier, creating biochar that can be used as a fuel. However, the reactor's non-homogeneous heating rate and poor heat retention severely hampered its applicability. Further study is required to find other features and aspects that might not only improve the design and efficacy of the torrefier, but also facilitate its implementation for coffee producers in Kerala.
...
Coffee farmers and producers in Kerala (India) face a serious obstacle in their pursuit of a self-sustaining coffee processing technology and fuel deficiency. Research indicates that coffee, as one of the largest industries, generates a huge amount of waste, namely Spent Coffee Grounds (SCGs). This study aims to evaluate the feasibility and efficiency of converting SCG into biochar using a solar-assisted biomass torrefying technique, while keeping frugal or "jugaad" innovation in mind. To torrefy the feedstock, it was intended to use the available SK14 solar cooker in conjunction with a prototype reactor unit. Based on previous research on torrefying coffee waste, this study asks: Can the biomass torrefied using the SK 14 cooker be utilized as fuel? In this context: Solar biomass torrefaction is an endothermic process of converting the feedstock in an inert environment at low temperatures of 200-300 °C provided by concentrated solar energy in order to produce a high yield of solid biochar.
Based on the literature research, it was important to characterize the SK14 cooker, the feedstock, and to understand the operating principles of the chosen reactor, namely Evacuated Tube Vacuum Collectors (EVCs). Since the design of the reactor and cooker were interdependent, COMSOL was used to simulate the heat distribution profile and temperature profile of the reactor model. Literature and simulation results were used to construct a prototype reactor, and torrefaction tests were conducted in Hyderabad (India). SCG was effectively torrefied to generate biochar at 240 °C and 260 °C, as evidenced by high heating values of 26 MJ/kg (21% increase) and 26.3 MJ/kg (22.50% increase), respectively compared to the raw material. The results show that the current system can be utilized as a small-scale solar biomass torrefier, creating biochar that can be used as a fuel. However, the reactor's non-homogeneous heating rate and poor heat retention severely hampered its applicability. Further study is required to find other features and aspects that might not only improve the design and efficacy of the torrefier, but also facilitate its implementation for coffee producers in Kerala.
Based on the literature research, it was important to characterize the SK14 cooker, the feedstock, and to understand the operating principles of the chosen reactor, namely Evacuated Tube Vacuum Collectors (EVCs). Since the design of the reactor and cooker were interdependent, COMSOL was used to simulate the heat distribution profile and temperature profile of the reactor model. Literature and simulation results were used to construct a prototype reactor, and torrefaction tests were conducted in Hyderabad (India). SCG was effectively torrefied to generate biochar at 240 °C and 260 °C, as evidenced by high heating values of 26 MJ/kg (21% increase) and 26.3 MJ/kg (22.50% increase), respectively compared to the raw material. The results show that the current system can be utilized as a small-scale solar biomass torrefier, creating biochar that can be used as a fuel. However, the reactor's non-homogeneous heating rate and poor heat retention severely hampered its applicability. Further study is required to find other features and aspects that might not only improve the design and efficacy of the torrefier, but also facilitate its implementation for coffee producers in Kerala.
Biochar for horticultural and agricultural applications using high temperature torrefaction technology
Biochar for horticultural and agricultural applications using high temperature torrefaction technology
Master thesis
(2021)
-
P. Ravi, D.J.E.M. Roeakerts, L.L. Cutz IJchajchal, R.E.F. Lindeboom, L. Botto
Biochar for horticultural and agricultural applications using high temperature torrefaction technology
Pradeep Ravi
Supervisors: Prof Dr. D.J.E.M Roekaerts, ir.Bart de Vries, Dr. Luis Cutz, Dr.Lorenzo Botto & Dr.Ralph Lindeboom
Biomass currently accounts for less than 10 percentage of the world’s renewable energy production. Currently the major global sustainability issue stems from the sourcing of virgin wood chips from dense forests for pellet production. An alternative is to use residual biomass from agriculture or forestry, which is produced in large volumes, to produce different products that range from biofuels to chemicals via thermochemical conversion technologies. Among thermochemical technologies, torrefaction is a promising route to produce solid biofuel known as biochar. With an increasing potential for biomass production coupled with an increased scrutiny on the use of biomass as a green fuel, the need for alternative clean applications for the biochar is critical.
The aim of this study is to investigate new and novel agricultural residues or other waste streams to produce biochar using high temperature (350 °C) torrefaction technology. The obtained biochar is evaluated experimentally to determine the best feedstocks out of the ones that are selected from a performance and cost point of view for horticultural applications.
.
This research aims to provide a clear and useful analytical tool which will benefit the scientific community to select suitable biomass materials based on material properties and end applications. The efficacy for the various torrefied biomass feedstocks on the soil and its stability are tested. Overall, about 50 different biomass feedstocks were identified and evaluated based on past performances from literature. The top 10 best performing feedstocks were sourced and subjected to various physical and chemical characterization tests with a specific focus on soil remediation. The selected materials were torrefied in a fixed bed pilot reactor Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy (SEM-EDS), Brunauer–Emmett–Teller (BET) and pH measurements. Ultimately the feedstocks were scored and ranked from best to worst performing biochar for soil remediation and sequestration-based applications. The results of this project indicate potential for biochar production from woody, grassy and other processed materials that could help to remove the dependence on evergreen forests and wood chips. The system proposed in this work could also yield negative emissions since the feedstocks are residual flows and the biochar is going to be used in the soil.
...
Biochar for horticultural and agricultural applications using high temperature torrefaction technology
Pradeep Ravi
Supervisors: Prof Dr. D.J.E.M Roekaerts, ir.Bart de Vries, Dr. Luis Cutz, Dr.Lorenzo Botto & Dr.Ralph Lindeboom
Biomass currently accounts for less than 10 percentage of the world’s renewable energy production. Currently the major global sustainability issue stems from the sourcing of virgin wood chips from dense forests for pellet production. An alternative is to use residual biomass from agriculture or forestry, which is produced in large volumes, to produce different products that range from biofuels to chemicals via thermochemical conversion technologies. Among thermochemical technologies, torrefaction is a promising route to produce solid biofuel known as biochar. With an increasing potential for biomass production coupled with an increased scrutiny on the use of biomass as a green fuel, the need for alternative clean applications for the biochar is critical.
The aim of this study is to investigate new and novel agricultural residues or other waste streams to produce biochar using high temperature (350 °C) torrefaction technology. The obtained biochar is evaluated experimentally to determine the best feedstocks out of the ones that are selected from a performance and cost point of view for horticultural applications.
.
This research aims to provide a clear and useful analytical tool which will benefit the scientific community to select suitable biomass materials based on material properties and end applications. The efficacy for the various torrefied biomass feedstocks on the soil and its stability are tested. Overall, about 50 different biomass feedstocks were identified and evaluated based on past performances from literature. The top 10 best performing feedstocks were sourced and subjected to various physical and chemical characterization tests with a specific focus on soil remediation. The selected materials were torrefied in a fixed bed pilot reactor Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy (SEM-EDS), Brunauer–Emmett–Teller (BET) and pH measurements. Ultimately the feedstocks were scored and ranked from best to worst performing biochar for soil remediation and sequestration-based applications. The results of this project indicate potential for biochar production from woody, grassy and other processed materials that could help to remove the dependence on evergreen forests and wood chips. The system proposed in this work could also yield negative emissions since the feedstocks are residual flows and the biochar is going to be used in the soil.
Master thesis
(2021)
-
S.S. Sridar Sandeep, W. de Jong, L.L. Cutz IJchajchal, E.L.V. Goetheer, L. Botto
The last decade has seen an increase in the world wide energy demand, it was recorded as the highest spike encountered in the energy demand over a decade. On analyzing the main sources which were able to satisfy this overwhelming demand it was found that the majority was still from non-renewable sources or fossil fuels such as coal, oil and natural gas. The aftermath of the continued use of these fossil fuels are already well known, one can argue that there has still not been a serious attempt to phase out these non-renewable sources even though the concerns regarding the harmful emissions being released with their continued use are subject of numerous discussions and studies. It is paramount that the share of renewable energy technologies in the overall energy mix needs to be increased,various options must be explored such that it is possible to substitute these renewable energy sources in place of fossil fuels particularly in energy and emission intensive industries without a comprise in meeting their energy demand. Refuse derived fuel (RDF), which is the combustible fraction that has been separated from municipal solid waste (MSW) has gained attention due to it being seen as an alternative to convectional fossil fuels as well as a method of sustainable waste management and disposal. The reason for their use as an alternative fuel is mainly attributed to their physical and chemical characteristic such as their low moisture content, high grindability and calorific value. However, the challenges faced in their application as a substitute fuel or feedstock is attributed mainly to the high variability in the properties of the RDF material that is being supplied to the relevant industries. Therefore a standardization in its properties needs to be carried out particularly with regards to their moisture content and calorific value in order to promote their application. Torrefaction, also referred to as mild pyrolysis is a thermal treatment method that usually is carried out in temperature ranges of 200-300°C and residence times of 30-60 min in the absence of oxygen. The material that is being subject to this treatment method partly decomposes to release volatiles,and the left over solid product has been reported to undergone a modification its physical and chemical characteristics when compared to the initial solid material. From a chemical point of view the final solid product is reported to have an increase in the carbon content and decrease in the hydrogen and oxygen content which leads to a higher calorific value than the original material. Several experimental studies have been conducted for the torrefaction of RDF with aim of improving and standardizing the calorific value and have yielded promising results. However there has not yet been a work that has focused on the torrefaction of RDF on large scale, that takes into account the process design and economics associated with their production. The aim of this thesis was to carry out a techno-economic evaluation into the torrefaction of refuse derived fuel. An initial composition of raw RDF was selected from literature which has a high moisture content and low calorific value. The raw material is then subject to several process such as drying, torrefaction, grinding and pellitization with the aim producing torrefied RDF pellets. These process were simulated and optimized through Aspen Plus in order to obtain a better understanding of the influence of process parameters such as moisture content, drying temperature, torrefaction temperature and residence time on the final product as well as to select the optimum route for their production. Economic evaluation was also carried out to determine if the implementation of such a project is feasible. This was done on the basis of certain economic or profitability indicators. Results from simulations show that the optimum torrefaction conditions were 250°C and residence time of 30 min, which resulted in the final torrefied RDF having an increased calorific value. The economic analysis provides positive results particularly when moving towards a higher processing capacity of initial raw RDF. Finally, the effect of substitution of the torrefied RDF in a cement plant was also evaluated and has shown that significant savings can be achieved through the reduction in fossil fuel consumption and carbon dioxide emissions.
...
The last decade has seen an increase in the world wide energy demand, it was recorded as the highest spike encountered in the energy demand over a decade. On analyzing the main sources which were able to satisfy this overwhelming demand it was found that the majority was still from non-renewable sources or fossil fuels such as coal, oil and natural gas. The aftermath of the continued use of these fossil fuels are already well known, one can argue that there has still not been a serious attempt to phase out these non-renewable sources even though the concerns regarding the harmful emissions being released with their continued use are subject of numerous discussions and studies. It is paramount that the share of renewable energy technologies in the overall energy mix needs to be increased,various options must be explored such that it is possible to substitute these renewable energy sources in place of fossil fuels particularly in energy and emission intensive industries without a comprise in meeting their energy demand. Refuse derived fuel (RDF), which is the combustible fraction that has been separated from municipal solid waste (MSW) has gained attention due to it being seen as an alternative to convectional fossil fuels as well as a method of sustainable waste management and disposal. The reason for their use as an alternative fuel is mainly attributed to their physical and chemical characteristic such as their low moisture content, high grindability and calorific value. However, the challenges faced in their application as a substitute fuel or feedstock is attributed mainly to the high variability in the properties of the RDF material that is being supplied to the relevant industries. Therefore a standardization in its properties needs to be carried out particularly with regards to their moisture content and calorific value in order to promote their application. Torrefaction, also referred to as mild pyrolysis is a thermal treatment method that usually is carried out in temperature ranges of 200-300°C and residence times of 30-60 min in the absence of oxygen. The material that is being subject to this treatment method partly decomposes to release volatiles,and the left over solid product has been reported to undergone a modification its physical and chemical characteristics when compared to the initial solid material. From a chemical point of view the final solid product is reported to have an increase in the carbon content and decrease in the hydrogen and oxygen content which leads to a higher calorific value than the original material. Several experimental studies have been conducted for the torrefaction of RDF with aim of improving and standardizing the calorific value and have yielded promising results. However there has not yet been a work that has focused on the torrefaction of RDF on large scale, that takes into account the process design and economics associated with their production. The aim of this thesis was to carry out a techno-economic evaluation into the torrefaction of refuse derived fuel. An initial composition of raw RDF was selected from literature which has a high moisture content and low calorific value. The raw material is then subject to several process such as drying, torrefaction, grinding and pellitization with the aim producing torrefied RDF pellets. These process were simulated and optimized through Aspen Plus in order to obtain a better understanding of the influence of process parameters such as moisture content, drying temperature, torrefaction temperature and residence time on the final product as well as to select the optimum route for their production. Economic evaluation was also carried out to determine if the implementation of such a project is feasible. This was done on the basis of certain economic or profitability indicators. Results from simulations show that the optimum torrefaction conditions were 250°C and residence time of 30 min, which resulted in the final torrefied RDF having an increased calorific value. The economic analysis provides positive results particularly when moving towards a higher processing capacity of initial raw RDF. Finally, the effect of substitution of the torrefied RDF in a cement plant was also evaluated and has shown that significant savings can be achieved through the reduction in fossil fuel consumption and carbon dioxide emissions.
Master thesis
(2021)
-
C. Zamora Roman, W. de Jong, L.L. Cutz IJchajchal, H. Gilvari, H.B. Eral, R.M. Stikkelman
The Dutch government program “ A circular economy in the Netherlands by 2050“ prioritizes the 100% recycling of plastics used in the country by 2050 to reduce the consumption of fossil resources and increase the value of the plastic waste, which is currently incinerated or exported in its majority [1]. This objective can be facilitated by including chemical recycling techniques to recover valuable chemicals such as syngas (H2/CO) and monomers (ethylene/propylene) from plastic waste [2]. Among the chemical recycling techniques, gasification is a mature technology with the highest flexibility on the feedstock composition, allowing to treat complex mixtures as plastic waste [3]. In this framework, the project “Towards improved the circularity of polyolefin-based packaging” evaluates the technology readiness level of gasification for recycling a plastic waste mixture representative of the packaging sector (39.6% of the European plastics demand in 2019 [4]), to increase the knowledge of polyolefins waste (PW) gasification to contribute in closing the plastics loop [5]. The Process and Energy Department of TU Delft is part of this project and is responsible for gasifying a polyolefins waste mixture representative of the packaging sector (PW-DKR350) in a novel Indirectly Heated Bubbling Fluidized Bed Steam Reformer (IHBFBSR) [6]. This thesis focuses on developing a kinetic model of the IHBFBSR, which describes the bed hydrodynamics according to the two-phase theory (TPM) in Aspen plus as a complementary tool for the validation of the experimental work and narrow down the number of laboratory tests by identifying the gasification parameters (temperature, ER and SF ratios) that optimizes the following key performance indicators: carbon conversion efficiency (CCE), cold gas efficiency (CGE), product gas yield (GY) and tar yield (TY). This document describes the development of the TPM-IHBFBSR model. It starts with a literature review of the most-used modelling approaches for carbonaceous materials. Next, it describes the upgrading strategies applied, according to the equilibrium and kinetic approaches, emphasizing in the hydrodynamic models and simulation settings. Through this part were identified the optimal gasification parameters: 680°C<T<800°C, ER=0.15 and SF=2. Finally, the comparison of the TPM-IHBFBSR model and its previous versions against two validation cases found in the literature, highlights the advantage of having developed an adaptable model to a particular PW mixture, making possible to continue improving it
...
The Dutch government program “ A circular economy in the Netherlands by 2050“ prioritizes the 100% recycling of plastics used in the country by 2050 to reduce the consumption of fossil resources and increase the value of the plastic waste, which is currently incinerated or exported in its majority [1]. This objective can be facilitated by including chemical recycling techniques to recover valuable chemicals such as syngas (H2/CO) and monomers (ethylene/propylene) from plastic waste [2]. Among the chemical recycling techniques, gasification is a mature technology with the highest flexibility on the feedstock composition, allowing to treat complex mixtures as plastic waste [3]. In this framework, the project “Towards improved the circularity of polyolefin-based packaging” evaluates the technology readiness level of gasification for recycling a plastic waste mixture representative of the packaging sector (39.6% of the European plastics demand in 2019 [4]), to increase the knowledge of polyolefins waste (PW) gasification to contribute in closing the plastics loop [5]. The Process and Energy Department of TU Delft is part of this project and is responsible for gasifying a polyolefins waste mixture representative of the packaging sector (PW-DKR350) in a novel Indirectly Heated Bubbling Fluidized Bed Steam Reformer (IHBFBSR) [6]. This thesis focuses on developing a kinetic model of the IHBFBSR, which describes the bed hydrodynamics according to the two-phase theory (TPM) in Aspen plus as a complementary tool for the validation of the experimental work and narrow down the number of laboratory tests by identifying the gasification parameters (temperature, ER and SF ratios) that optimizes the following key performance indicators: carbon conversion efficiency (CCE), cold gas efficiency (CGE), product gas yield (GY) and tar yield (TY). This document describes the development of the TPM-IHBFBSR model. It starts with a literature review of the most-used modelling approaches for carbonaceous materials. Next, it describes the upgrading strategies applied, according to the equilibrium and kinetic approaches, emphasizing in the hydrodynamic models and simulation settings. Through this part were identified the optimal gasification parameters: 680°C<T<800°C, ER=0.15 and SF=2. Finally, the comparison of the TPM-IHBFBSR model and its previous versions against two validation cases found in the literature, highlights the advantage of having developed an adaptable model to a particular PW mixture, making possible to continue improving it
Pretreatment and densification processes such as torrefaction coupled with pelletization have proven to be valuable techniques to convert biomass to solid biofuels. Presently, waste streams from the torrefaction process in the form of volatiles are usually combusted to generate heat required for the torrefaction process. Nevertheless, the chemical characteristics of the torrefaction gas combined with recent technologies have opened new alternatives that could be used for further valorization of volatiles in other ways than combustion. The aim of this Thesis was to find alternative pathways other than straight up combustion of volatiles to valorize the volatiles released during torrefaction of biomass. Two types of biomass were investigated: corn stalk and sugarcane bagasse. Four different configurations for valorization were developed for their prospects of valorization: (1) valorization via straight up combustion, (2) chemical looping combustion, (3) chemical looping steam reforming and (4) a combination of chemical looping combustion and straight up combustion. A model based on experimental data was build in Aspen Plus to simulate the drying, torrefaction and valorization for a torrefaction plant with a capacity of 100 kton/year. The results were analysed in terms of process efficiency and economics. Results indicate that chemical looping combustion of all volatiles is the most attractive option of valorization, both in terms of efficiency and economics. The gross LHV efficiency for this option is 92 % for corn stalk and 84 % for sugarcane bagasse. The production costs in these scenarios are €208/ton for torrefied corn stalk pellets and €180/ton for torrefied sugarcane bagasse pellets. The capital investment required for the torrefaction plant for this configuration is €527/kW installed for corn stalk and €650/kW installed for sugarcane bagasse.
...
Pretreatment and densification processes such as torrefaction coupled with pelletization have proven to be valuable techniques to convert biomass to solid biofuels. Presently, waste streams from the torrefaction process in the form of volatiles are usually combusted to generate heat required for the torrefaction process. Nevertheless, the chemical characteristics of the torrefaction gas combined with recent technologies have opened new alternatives that could be used for further valorization of volatiles in other ways than combustion. The aim of this Thesis was to find alternative pathways other than straight up combustion of volatiles to valorize the volatiles released during torrefaction of biomass. Two types of biomass were investigated: corn stalk and sugarcane bagasse. Four different configurations for valorization were developed for their prospects of valorization: (1) valorization via straight up combustion, (2) chemical looping combustion, (3) chemical looping steam reforming and (4) a combination of chemical looping combustion and straight up combustion. A model based on experimental data was build in Aspen Plus to simulate the drying, torrefaction and valorization for a torrefaction plant with a capacity of 100 kton/year. The results were analysed in terms of process efficiency and economics. Results indicate that chemical looping combustion of all volatiles is the most attractive option of valorization, both in terms of efficiency and economics. The gross LHV efficiency for this option is 92 % for corn stalk and 84 % for sugarcane bagasse. The production costs in these scenarios are €208/ton for torrefied corn stalk pellets and €180/ton for torrefied sugarcane bagasse pellets. The capital investment required for the torrefaction plant for this configuration is €527/kW installed for corn stalk and €650/kW installed for sugarcane bagasse.