Exploring the design and performance of an Arctic heat exchanger system employing a Rankine cycle for Arctic Thermal Energy Conversion (ATEC). The system harnesses the temperature difference between sub-zero Arctic air and near-freezing seawater to power water pumps for ice thickening, aiming to sustain ice layers and mitigate climate change impacts. The research focuses on selecting the optimal working fluid through thermodynamic analysis and designing Rankine cycle heat exchangers by determining the heat loads and operating pressures. Several heat exchanger designs are developed using Python calculations, with additional designs through simulations in Aspen EDR. The air-cooled condenser is first compared with the specifications of a V-type commercial heat exchanger because they are smaller than the horizontal type that is only available in Aspen EDR. The design of an evaporator that uses sea water with discussion of impossibility of implementing it under water and using a plate heat exchanger instead after comparison with a shell and tube heat exchanger. Both are analyzed for size, cost, and frosting is discussed that it is not an issue that would affect the project. The study aims to provide a scalable, economically viable renewable energy solution for Arctic communities, potentially reducing reliance on fossil fuels and addressing environmental challenges, with the final design going through a levelized cost of electricity analysis to find out if it is viable to sell the electricity. ... Read more

Mosquitoes of the species Aedes Aegypti exhibit a particularly distinctive figure-eight shaped wingtip trajectory, which includes a vertical component of motion (characterized by deviation angle) that is hypothesized to influence aerodynamic force generation through interactions with the wing’s own wake, referred to as wake capture. While standard quasi-steady (QS) aerodynamic numerical models can effectively predict the forces generated by translational, rotational, coupling and added mass effects during wing motion, they do not capture the additional forces arising from wake interaction.

This study aims to leverage this known limitation of quasi-steady models, to investigate the influence of deviation angle on wake capture forces during hovering flight. Aerodynamic forces were measured using a robotic flapping-wing apparatus programmed to replicate biologically plausible kinematics of a mosquito, across a range of deviation angles (0° - 6°) (including an outlier at 7.5°). By subtracting forces predicted by a validated quasi-steady model from the experimentally measured forces, the residual unsteady component associated with wake capture was isolated and quantitatively analyzed.

The results of this study demonstrated that wake capture forces play a beneficial aerodynamic role in the mid-to-high deviation angle range, specifically between approximately 4° and 6°. Within this interval, the wake capture lift and drag forces exhibit relatively elevated mean values, and the experimentally observed lift-to-drag ratio surpasses quasi-steady predictions, indicating enhanced aerodynamic efficiency. Correspondingly, power utilization increases, and flapping efficiency peaks near 5° to 6°, collectively highlighting an optimal regime where unsteady wake interactions benefit aerodynamic performance. This favorable trend could be attributed to the pronounced out-of-plane wing motion at these deviation angles, which intensifies three-dimensional wake structures and possibly promotes more effective wing-wake vortex interactions that augment lift and overall flapping efficiency.

In spite of the high uncertainty in the force sensor readings, this study successfully established a kinematically accurate, high-fidelity setup for examining the influence of deviation angle on wake capture phenomena. The elevated noise from the inbuilt force sensor and structural vibration in the wing assembly were identified as the primary limitations, which could only be fully resolved through hardware replacement beyond the present scope. Nevertheless, the findings provide novel insights into the role of deviation angle in shaping wake capture forces, with both scientific implications for advancing flapping-wing micro air vehicle (FWMAV) design and societal relevance given the connection between mosquito flight and public health. ... Read more

Understanding and controlling primary nucleation remains one of the central challenges in crystallization. Nucleation governs the physicochemical, optical, and mechanical properties of the resulting crystals. In this thesis, we investigate a novel pathway for inducing nucleation in supersaturated solutions using the hydrodynamic interaction of laser-induced tandem thermocavitation bubbles confined inside a microcapillary. When two cavitation bubbles are generated in antiphase, their asymmetric pressure fields give rise to micron-scale liquid microjets with velocities far exceeding those produced by single-bubble events. These jets penetrate the primary bubble interface, causing localized evaporation, strong solute redistribution, and transient supersaturation spikes. Using supersaturated aqueous potassium permanganate (KMnO₄) as a model system, we demonstrate that crystallization occurs exclusively under tandem-bubble conditions that produce a high-velocity piercing jet, whereas single-bubble cavitation—even at twice the laser energy—fails to nucleate crystals. The results reveal a clear correlation between jet velocity and nucleation probability, highlighting shear-driven solute transport and microjet-induced evaporation as the dominant mechanisms triggering nucleation. This work establishes microjet-mediated crystallization as a physically grounded and a relatively more energy-efficient alternative to conventional non-photochemical laser-induced nucleation mechanisms, with potential applications in controlled crystallization, microfluidic processing and pharmaceutical manufacturing. ... Read more

Inkjet printing is a technology that has been widely studied and implemented. The liquids that are used for inkjet printing can vary. There is the traditional ink which can be found in almost every household printer. But it is also possible to use inkjet printing to deposit drugs, proteins and nanoparticles on substrates. Inkjet printing has the ability to precisely deposit picoliters of liquid onto the substrate. Thus, reducing cost and waste when the material being used is expensive and/or of limited quantity. This project works with a LP50 PIXDRO inkjet printer. Another interest that gained traction in the scientific community are the stimuli-responsive microgels. These microgels are able to change their dimensions depending on the external stimuli and if this stimuli is removed from the microgel, it changes back to its original shape, thus it is a reversible process. This project uses a suspension of the stimuli-responsive microgel; poly(N-isopropylacrylamide)-coacrylic acid (pNIPAm). This microgel is responsive to temperature and pH. To deposit the pNIPAm suspension on the substrate, inkjet technology will be used. The printability of the pNIPAm will be determined by characterizing the physical and rheological properties. Such as the density, surface tension, viscosity and particle size of the pNIPAm beads. These properties will be compared to the ideal liquid requirements given by the print cartridge that will be used, a Fuijifilm Dimatix. To influence the surface tension three surfactants will be tested. These surfactants are Triton X-114 (TRT), Sodium dodecyl sulphate (SDS) and Hexadecyltrimethylammonium bromide (CTAB). Based on the results the and comparison to the requirements the surfactant Triton X-114 is chosen because it lowers the surface tension the most. While it has minimal to no affect on the pNIPAm particles. The next phase of the project is testing the printability of the pNIPAm. This is done by adjusting the waveform on the LP50 PIXDRO inkjet printer. As a result it is indeed possible to deposit pNIPAm on a substrate with an inkjet printer. After this step a SEM is used to investigate if the printed pNIPAm particles will form a monolithic layer. This monolithic layer is important when it comes to having a functional etalon. The pNIPAm particles form indeed a monolithic layer on the substrate. The last step is to see if there is a peak shift in the wavelength when the temperature is increased. The microgel based etalons that used an inkjet printer to deposit the micrgol show a peak shift. Therefore, it can be concluded that it is possible to use an inkjet printer to deposit pNIPAm on a substrate and that the pNIPAm particles behave according to literature. All the results of this project show that using an inkjet printer is a viable alternative for fabricating microgel based etalons. ... Read more

The percentage of electric vehicles (EVs) in the automotive sector is expected to quadruple by 2040, causing concern regarding the material supply required for the production of lithium-ion batteries. Currently, a substantial part of these materials, such as cobalt and lithium, are subject to non-circular economies, have a substantial environmental impact and are mined in countries with unstable political situations.
Up until now, numerous companies have attempted to resolve these issues through the use of pyro- and hydrometallurgical recycling methods. However, they are yet to meet the mandated recycling goals put in place by the European Commission. This enhances the urgency for the development of a novel, efficient and scalable technology for the recovery of valuable material from spent lithium-ion batteries.
In order to achieve such a development, this study proposes to incorporate Bipolar Membrane Electrodialysis into the standard hydrometallurgical recycling approach. During the course of this research, a prototype of this technology was realized and used to investigate its effectiveness. For practical reasons, the research focused exclusively on the metal and acid recovery from leached LCO cathode material.
Within the subsequent experimental phase of this research a critical issue was identified. Namely, the tendency of divalent cobalt ions to precipitate in non-acidic media. The resolution to this issue required the incorporation of Donnan dialysis into the built BPMED setup, which was used to adjust the acidity of the solutions within the different electrolytic compartments.
Ultimately, this approach led to the respectively recovery of 14 and 22 percent of the lithium and cobalt initially present in the feed solution. Simultaneously, the study recovered a significant amount of the starting leaching agent in the form of 0.6 M nitric acid. Whilst additional optimizations are required to improve the recovery efficiencies, the study successfully demonstrates a proof of concept of the proposed solution.
... Read more

As the global energy transition accelerates, transitioning away from fossil fuels has become critical to assist the mitigation of climate change. Hydrogen, with its dual role as both an energy carrier and fuel, holds great potential for this transition. However, its large-scale production, particularly for industries like chemicals and transportation, still relies heavily on fossil fuels, posing a challenge for sustainable development.

This research focuses on advancing green hydrogen production, specifically through alkaline water electrolysis, a technology associated with zero greenhouse gas emissions. A key aspect of this work is addressing a gap in large-scale electrolysis modeling, with an emphasis on a modular system design. Modularity, as opposed to traditional single-unit scaling, offers improved operational flexibility and safety. This approach is especially relevant when electrolysis systems are powered by renewable energy sources, another critical component of the energy transition.

This thesis presents an investigation into the performance optimization of a modular alkaline water electrolysis system, designed to handle fluctuating renewable energy inputs. A physics-based numerical model was developed in Python, to simulate a large-scale AWE system composed of multiple modular units, capturing critical parameters such as temperature evolution, gas purity, and energy losses. The model was built progressively, starting from the cell level, incorporating a thermal model for temperature development and a mass transfer model for gas purity estimation. These combined elements formed a robust tool for simulating and optimizing the performance of modular electrolysis systems.

After validating the model against existing numerical and experimental data at the cell level, it demonstrated a strong ability to accurately capture the behavior of a single-cell system across all modeled parameters, including cell potential, temperature, and gas impurities. The differences between the simulated values and experimental data were minimal, further confirming the model's accuracy and reliability. This validation provided confidence in the model's predictive capabilities and laid the foundation for extending it for a larger modular system.

Following this, a scaling analysis was conducted to evaluate the model's performance when applied to a modular system. The simulations were carried out under both steady and varying power inputs, reflecting realistic operational conditions, particularly when coupled with renewable energy sources. The results highlighted the model's capacity to predict temperature evolution and gas impurity levels in such a scaled system. These findings indicated that the model not only captured the thermal and mass transfer behavior but also provided valuable insights into the effect of system scaling on overall performance and safety.

The outcomes of this research demonstrate that the developed model could act as a valuable tool for optimizing the performance of modular alkaline water electrolysis systems. The model successfully predicts the thermal behavior, gas purity, and energy losses across a range of operational conditions, including fluctuating power inputs typical of renewable energy sources. By enabling the fine-tuning of operational parameters prior to system deployment, this model provides a significant advantage in designing safe, efficient, and scalable hydrogen production systems. Future work could extend the model's capabilities by incorporating additional factors such as degradation mechanisms and detailed component-level interactions, ensuring even more robust predictions over long-term operation. ... Read more

For the first time, we present data on the actual growth rate, supersaturation, viscosity, and growth mechanism that lead to spherulitic growth. So far, fundamental questions regarding the growth conditions, mechanisms, and the necessity of a viscous growth medium have remained unresolved. Surprisingly, we observed a sol-gel transition in evaporating silica-free sulfate mixtures, followed by the growth
of sodium sulfate spherulites. We characterized the spherulites’ morphological evolution and chemical/structural composition using various microscopy techniques and Raman Spectroscopy. The study reveals that faceted crystals, during their morphological evolution, can transiently exhibit a spherulitic morphology before attaining their final shape. We demonstrate that adding bivalent ions to sulfate solutions can create the conditions required for the spherulitic growth of the crystal phase. We show how to obtain perfectly developed spherulites through an in-depth experimental investigation of ion concentrations, evaporation rate, and geometric constraints. Moreover, quantifying the growth conditions enables a precise understanding and facilitates a comprehensive discussion on a general approach for
cultivating spherulites through solvent evaporation that is imperative for innovative purposes.
... Read more

In an effort to make water electrolysis more efficient and simple, flow-through electrolyzers eliminate the need for a gas-separating membrane between the electrodes. However, replacing the membrane with a forced flow field brings new challenges and considerations. In this research, the design of a flow-through electrolyzer is optimized for minimum voltage losses due to bubble formation, pressure drop, and electrolytic resistance. These parameters are all influenced by the potassium hydroxide concentration, the inter-electrode gap and the feed flow rate. The effect on the power dissipation of a flow-through electrolyzer is analytically modelled and validated using experiments, where the design variables are varied.

Additionally, the effect on the resistance in the electrolyte of keeping the gasses dissolved in the electrolyte is studied using IV curves of degassed electrolyte. The gasses in the electrolyte were purged with a vacuum chamber. This degassed electrolyte showed a reduction in overpotential of 150 mV at max. However, this reduction in overpotential was outweighed by the energy requirements to degas the electrolyte. Besides degassing, the effect of suppressing bubble formation by different flow rates was investigated. It was found that there was no noticeable reduction in overpotential between the state where bubbles are suppressed and bubbles were formed.

In addition to the effect of keeping the gasses dissolved, an analytical model was constructed to describe the necessary flow rates to mitigate the electrical resistance due to bubbles in the electrolyte. In the analytical model, solubility plays a big role in determining the necessary flow rate, as solubility is related to the emergence of bubbles. Contrarily, experiments showed the effect of solubility was found to be rather low. By varying the gap width, it was shown that the shear rate at the wall is a better indicator for bubble removal and therefore reduction in resistance due to bubbles.

Furthermore, the shape of the discharge channel was changed to promote uniform flow across the electrodes. The uniform flow should make the product removal at every part of the electrolyzer equal, such that there are no stagnant zones where gas accumulation could build up. This new discharge channel shape was analysed using COMSOL Multiphysics by comparing it with a conventional straight discharge channel. The variable discharge channel outperformed the straight discharge channel in creating a uniform flow across the electrodes for Euler numbers bigger than 10, meaning that the inertial forces are negligible compared to the pressure drop. During experiments, the electrolyzer with a variable discharge channel was tested. This electrolyzer configuration did not perform as well as expected from the theory and simulations, having a higher pressure drop and electric resistance than the conventional electrolyzer. The reason why the variable discharge channel performed poorly was inconclusive.

Lastly, the performance of the various variables was evaluated using the total power dissipation as a function of the current density. This took both the pressure drop across the system and the electrical power consumption of the electrolyzer into account. It was found that using a high electrolyte of 6M potassium hydroxide (KOH) together with a small inter-electrode gap gave the lowest energy dissipation per kg produced hydrogen gas. However, increasing the KOH concentration increases the viscosity and thereby the pressure drop. The theoretical optimum for KOH concentration was calculated to be 5M for this flow-through electrolyzer. ... Read more

Fresh water is a scarce source. Demand for freshwater is greater than supply, due to the increasing industrialisation of countries and the low natural supply of freshwater sources such as rivers and lakes. Contamination of these natural freshwater sources by industrial wastewater adds to the freshwater deficit. Throughout history, technologies have been developed to increase the supply of fresh water by desalinating other water sources into fresh water. Reverse osmosis is the most widely used desalination technology for seawater desalination, but the energy transition calls for electric-based technologies that can desalinate water using renewable energy sources. Capacitive deionisation is a relatively new desalination technology that uses electrical energy to desalinate brackish water. The capacitive deionisation cell is an electrochemical cell in which the feed water flows between two electrodes. When electricity is applied to these electrodes, ions in the water are attracted to move towards the porous electrodes where they are adsorbed within the electrical double layer. Unfortunately, the capacitive deionisation system has some challenges: it is a batch-system, has a low freshwater production and it has not been built for large-scale production. Avsalt AB, a Swedish company, has developed a new capacitive deionisation architecture to address these challenges, called the multichannel capacitive deionisation system (MC-CDI). This system consists of two capacitive porous electrodes and several membrane-like electrodes between them, referred to as capacitive membrane electrodes (CMEs). To maximise the performance of the multichannel deionisation system, the performance of the capacitive membrane electrodes should be enhanced. Therefore, the aim of his thesis is to optimise the physical properties of the capacitive membrane electrodes that affect the performance of the capacitive membrane electrodes and to gain a better understanding of how the microscopic properties of the CMEs should be carefully tailored to improve the performance.
To address these questions we can turn to Electrochemical Impedance Spectroscopy (EIS). EIS is a non-invasive measurement technique that may be regarded as a much more sophisticated resistance measurement compared to, for example, a multimeter. In contrast to the latter device, EIS measures the impedance, which is a combination of the resistance and the reactance, at a wide range of frequencies. The frequency dependency of the measured impedance can be used to find a so-called equivalent electrical circuit model (EECM). For EIS measurements on electrochemical cells, such as batteries, fuel cells, and electrolysers, the EECM elucidates the different electrochemical processes that occur at different timescales and impedance plots are used to analyse and compare these electrochemical processes. EIS has been successfully used to analyse the electrochemical processes within CDI electrodes and ion exchange membranes, but capacitive membrane electrodes used in an MC-CDI system have never been studied with an accurate and fast measurement technique such as EIS. Because CMEs do not have a solid support structure, in contrast to most CDI electrodes, ions are free to migrate through the electrodes. Therefore, the alternating current that is needed in EIS measurements can be applied on an external set of electrodes, while the response alternating voltage can be picked up at the CMEs. This 4-point impedance measurement configuration enables precise determination of the ionic resistance and capacitance of the electrode material. Therefore, an electrochemical impedance spectroscopy setup is built to determine the performance indicators of the CMEs and to gain a better understanding of the electrochemical processes taking place at the interface of the CMEs. The resulting Nyquist and Bode plots are used to analyse the ion diffusion and capacitive behaviour of the electrodes. To enable the analysis, first, an equivalent electrical circuit is determined for these freestanding electrodes. It was found that the CME can be represented by the Transmission-line model, which in the equivalent electrical circuit takes the form of a junction of three complex impedances. From the values of the electrochemical parameters, the performance indicators of the CME, membrane conductivity and permselectivity, were evaluated.
The CME meter presents itself as an accurate measurement system to quickly evaluate the performance indicators of the CME, with the aim of efficiently searching for the CME that will show the best performance within the MC-CDI system, without placing it within the MC-CDI system. Further research should be conducted to investigate the extent to which EIS could be used to estimate the permselectivity of the CME and whether the total measurement time to predict permselectivity is still short enough to propose EIS as an alternative measurement technique. ... Read more

Nitrogen emissions contribute significantly to climate change, especially in the Netherlands around Natura-2000 areas, and one of the main contributors is manure. However, not only does manure usually have high nitrogen emissions, a lot of it is in the form of ammonia, which in itself is very energy-intensive to create. Therefore MEZT developed a solution to extract ammonia from manure, reducing both nitrogen emissions and emissions from ammonia production. However, what to do with this ammonia after it is extracted was still unknown. Thus, the research question was as follows: Within the context of farms and MEZT's BPMED process, what is the best ammonia recycling process and usage, and is it financially feasible?

To answer this, first, all major potential uses for ammonia were identified, after which many uses were discarded immediately due to logical and fairly obvious reasons. Then, the remaining ammonia uses, consisting of mostly fertilizers, fuel cells, and selling it as a wholesale substance, were investigated further. For this, a scoring matrix was made based on a farmer's needs, and all technologies were scored on nine criteria (maturity/feasibility, process profitability, initial costs, reliability/maintenance, ease of use, environmental impact, safety, scalability/compactness).

From this scoring matrix, there were three clear top choices: selling as wholesale, ammonium sulphate, and enriched biochar. Since the stream to sell ammonia as a wholesale can be taken from either of the two other processes, a clear choice still had to be made between ammonium sulphate and biochar. After also investigating the effect of manure disposal costs, upcoming RENURE regulations, grant and subsidy differences, the legality of using both substances, and the combination of using it with other streams of the MEZT process, ammonium sulphate came out as the best solution.

With this in mind, the final process was designed. Here the potassium stream was also considered and included as it was part of the ammonia stream. The final process is a flexible solution of making ammonium sulphate, potassium sulphate, their (raw) mineral concentrates and aqueous ammonia. This allows for the most flexibility depending on a farmer's needs, while having minimal additional costs and the ability to 'cut out' unwanted parts/processes.

Afterwards, an economic evaluation was made. First, precise equipment and operational costs and revenues were estimated, after which it was combined with the overall MEZT solution train to form the final costing and revenues. From this it was determined that the additional parts to process ammonia was relatively cheap compared to the BPMED unit, but nonetheless the entire process was shown to be at least cost-neutral for reducing manure emissions and in many cases even lucrative for a farmer to implement.

In the end, due to the new and broad nature of this topic, it was at times difficult to make very accurate estimations (especially for the costing as data is not always available), but multiple sources/methods were always checked and the final choice and financial evaluation was deemed reliable. With this, the conclusion and recommendation was given to proceed with the development of the MEZT solution train to work towards a greener and sustainable future. ... Read more

In the effort against climate change the company ZEF has as its target to make methanol (CH3OH) out of atmospheric CO2; a process which can be seen as power-to-fuel and/or power-to-x. In light of the developmental cycle within ZEF a new reactor with an increased size and enhanced mass manufacturability is required. The reactor contains three main components: reactor bed, condenser and heat exchanger. The heat exchanger design has been shown to be highly efficient as well as the underlying design philosophy [1]. However, an exact in depth evaluation of the condenser performance has not been performed yet. Furthermore, in light of reactor optimisation, an investigation on the reactor bed design for the use case of ZEF is seen as necessary. The condenser plays a dual role in the reactor: it acts as the separation mechanism of products from the recycle stream and as vital factor in generating mass flow. Due to the current modelling architecture/philosophy of ZEF computationally simple descriptions of condensation phenomena are desired. A method based on linear relations for the latent heat release is developed. In combination with a PT-flash plug-in for MatLab this allows for modelling of heat effects and liquid-gas separation due to condensation. According to literature local heat transfer of condensation is significantly hampered com- pared to ideal Nusselt Film Condensation theory. The reason for this degradation is the presence of Non-Condensable Gasses which will limit the heat flux of the condensing species to the condenser surface. A sub model is used to evaluate whether this effect is significant. A combined model and experimental approach is used for evaluation of these models. The reactor bed is the generation site of the methanol and in previous work it has been found there might be limiting effects in this bed [1]. Evaluation of literature on the causes indicates that mass transfer and temperature limitations are likely the cause. Furthermore literature suggests that the reactor bed might be able to attain a higher Space Time Yield. A set of models are made to describe the mass and heat transport of the reactor bed. These are based on 1-D heat transfer correlations, a linearized Thiele modulus, and the Bussche & Froment kinetic model. Furthermore, the reactor bed and condensation models are integrated into an existing overall model. This enables the simulation of synergy between these processes. A new reactor bed design is made based on these models which should increase the Space Time Yield, and is subject to experimental validation. For the experimental validation a new reactor was designed and build based upon the new models developed. Characterisation experiments indicate satisfactory qualitative behaviour of the condensation modelling. Quantitatively deviations are observed which are expected to be due the over prediction of methanol formation by the reactor bed models. The reactor bed model deviations are mainly attributed to a lower than predicted mass flow rate, and adverse flow fields in the reactor bed. A new reactor bed design is proposed which should significantly reduce the adverse flow field effects while increasing thermal performance. The reactor bed design used allows for a decrease in catalyst size without causing a significant decrease in mass flow rate. An increase of a factor 1.25 for the Space Time Yield compared to the previous design has been observed during experiments. Insulation performance is satisfactory with the insulation performing within 20 W as modelled. Thermal efficiency has decreased by a factor 1.8 and is attributed to the under performance of the reactor bed. Furthermore, the control of the reactor has been evaluated in terms of mass flow rate measurements, the prevention of the stalling of flow, and control. A new mass flow rate measurements device based on differential pressure, a new feed injection design, and further development of control have been experimentally validated. Designs for each of these subjects have been found to be satisfactory. Furthermore, it was found that reactor bed geometry also has an effect on the control of the reactor.    ... Read more

The unprecedented rise in CO2 concentration in the atmosphere, and the accompanying rise in global temperature, has created the need for the development of environmentally friendly sources of energy. A very promising line of research focuses in the development of Carbon Capture and Utilisation (CCU) technologies; through which carbon-neutral liquid fuels could be synthesized. A great example of such technologies can be found in Zero Emission Fuels (ZEF), a dutch start-up currently developing a microplant capable of producing methanol from solar energy and ambient air. ZEF’s process involves the capture of CO2 and H2O directly from ambient air, the splitting of the captured H2O into its constituent
elements through electrolysis, and the synthesis of methanol from H2 and CO2. The entire process is powered by solar energy, which makes ZEF’s methanol a carbon-neutral liquid fuel.

This thesis focuses in the capture of CO2 and H2O from ambient air, a process known as Direct Air Capture (DAC). ZEF’s DAC unit differs from industry standards by using a novel continuous chemical absorption process through the flow of an amine based sorbent between its absorption and regeneration systems, instead of using a conventional batch process through a supported sorbent. The work of this thesis pertains the build and experimental characterization of ZEF’s first full scale DAC prototype, referred to as the 10X DAC prototype.

The built prototype, a fully functional DAC unit working in a continuous process, was experimentally characterized in terms of its performance and energy efficiency for the environmental conditions of the Dutch summer (i.e. hot and wet conditions). The absorption process was found to be limited by the capture of CO2 when compared to the H2O capture process, and to be liquid side limited; which aligned with literature sources where CO2 capture is defined as diffusion limited in the liquid side. Overall, the 10X DAC absorption column has the capacity of capturing 0.52 kgCO2/m3·hr; which is higher than the reported capture capacity of a very well established company like Carbon Engineering. In the
regeneration process, residence times in the stripper column as low as six minutes were enough for the sorbent to reach vapour liquid equilibrium (VLE) loadings for a regeneration temperature of 120◦C. The overall 10X DAC process is capable of producing 0.21 kgCO2/hr with an energy demand of up to 33MJ/kgCO2; which is up to 6 times higher than the reported most energy efficient DAC unit in industry. Furthermore, the H2O:CO2 product ratio was found to vary significantly, with a dependence to absolute humidity in the environment.

Through the experimental results of the characterization process, a chemical absorption model was developed which, assuming a liquid side diffusion limited process, considers the effects of the selected sorbent’s characteristics and the environmental conditions in the absorption process. Through this model, and the use of previous developed regeneration models, a DAC cycle is presented through which the effects of varying dynamic conditions (i.e. absolute humidity and ambient air temperature) were determined. Overall, it was noticed that the performance of the absorption process was negatively affected by higher temperatures, while the regeneration process remained unaffected by temperature
changes. Absolute humidity variations affected the H2O loading of the sorbent, which then affected the performance of the regeneration process; lower H2O loadings in the rich sorbent translated to higher CO2 lean loadings after regeneration. Furthermore, it was determined that the current sorbent in ZEF’s process favors cold and humid environments.

Finally, through the learnings and findings from both experiments and the developed absorption model, an optimized 10X DAC design is presented which focuses in meeting the CO2 production and energy demand requirements established by ZEF for its process. ... Read more

Prilling is the industrial process in which thin jets of a molten substance break up into drops and the subsequent solidification of the droplets into solids due to cooling when they fall down in the prilling tower. Prilling is widely used for efficient production of a variety of materials such as, e.g., fertilizer grains, laundry detergent, and substances for drugs and foods.
While in most prilling applications the jet can be considered as a pure liquid, in some cases the molten substance may contain suspended particles. The present study is motivated by prilling of fertilizers composed of Urea or Ammonium Nitrate (AN) containing polyhalite particles. To date, the effects of suspended particles on jet breakup, drop formation and crystallization are not well-understood. In the first part of this report a literature review is given on prilling and the current understanding of the effect of suspended particles on this. It has been found in literature that a large concentration of suspended particles will increase the viscosity of the suspension but also promote breakup of the jet. Besides, the size of the particles also influences the viscosity and jet breakup, resulting in a decrease in the amount of smaller formed secondary droplets at larger suspended particle sizes, hence increasing monodispersity. The objectives of this MSc research project are to assess under what conditions high-quality fertilizer grains can be optimally prilled from polyhalite suspensions in molten urea or ammonium nitrate. An experimental setup was designed to assess how molten liquid jets of Urea or AN with suspended polyhalite particles can be optimally prilled for producing high-quality fertilizer grains. This design consists of melting and mixing the batch of materials, from where it will pump the particulate suspension through a vertical tube with a screw pump to a nozzle. Here, a jet will be formed. This will breakup into droplets, which will fall in an oil batch to increase cooling and hence fasten the solidification process. Unfortunately, the current design was always dripping and not able to form a jet due clogging and the formation of hard lumps, which decreased the flow rate. The droplets were however collected and analyzed. It was found in this thesis that a larger concentration of P4 particles in urea will increase the viscosity. When the particles are grinded more, the viscosity increased as well, however a direct relationship between particle size and viscosity has yet to be determined. The particles were also unequally distributed over the prills, because P4 tends to stick together. To obtain the best quality prills, it is recommended to use relatively large P4 particles in combination with larger nozzles of >1mm to decrease the desired prilling force and prevent clogging. Also melting ... Read more

This interdisciplinary thesis gives a simulational approach for the production of basic chemicals in a renewable manner, while simultaneously managing uncertainty inherent in the development of novel and innovative technologies. The simulational approach focuses on the capture of CO2 and subsequent conversion into methanol using Aspen Plus. CO2 is captured by chemical absorption into MEA. The CO2 rich stream is mixed with hydrogen and converted into methanol. The flowsheet is finalized by integrating recycle streams and upgrading of the product. The e-Refinery institute is used as a case study in order to research the managing of uncertainty in the development of these innovative technologies. The concept shared vision is the focus point in the collaboration and a conceptual design of a virtual platform has been developed in order to aid in the development of a shared vision within interdisciplinary research institutes.
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Water scarcity is an increasing problem around the world due to growing population and more frequent weather extremities. Desalination, the process in which salt water is converted into freshwater, is a sensible option to expand the drinking water supply by accessing the vast salt water resources on Earth. Capacitive deionization (CDI) is a novel desalination technology that is based on separating salt ions from aqueous solutions in an electrical double layer. An electrostatic potential difference is applied between two high surface area electrodes, the two oppositely charged electrodes attract and adsorb salt ions onto the electrode surface, as such producing a purified stream of water. In time, the electrodes become saturated with ions. To regenerate the electrodes the applied potential is removed or reversed, producing a concentrated stream of water. For brackish water, this new fundamental method of desalination has advantages over conventional desalination technologies. CDI can be operated with minimal energy requirement in ambient pressures and temperatures, delivering easy operable systems. This thesis investigates manufacturing of activated carbon electrodes purposed for multi-channel CDI. Current CDI systems operate by desalinating one channel and concentrating the same channel periodically. Multi-channel CDI operates a charging scheme, utilizing more than two electrodes, to desalinate one channel into another channel, circumventing the need to separate desalinated water from concentrated water downstream. Due to the different mode of separation are currently available CDI electrodes not tailored to, or not usable at all, in multi-channel CDI.In this project six successful different types of electrodes have been manufactured by dip coating. The coating compositions applied are 80:10:10, 70:10:20 and 40:40:20 using activated carbon powder (ACP), carbon black and PVDF binder respectively. The in-house build electrodes are analyzed with cyclic voltammetry, desalination measurements and a surface and pore size analyzer. Two-dimensional electrosorption simulations are performed to explore the effect of electrode resistance, micropore porosity and electrode thickness. The dip coated electrodes resulted in permeable smooth uniform electrodes. The electrodes with the most amount of ACP displayed largest capacitance and salt adsorption capacity. Electrosorption modelling shows that thin, highly electrical conductive electrodes are desired in multi-channel CDI operation. ... Read more

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 ... Read more

The purpose of this study was to create a theoretical model for the distillation of synthetic crude oil (syncrude) into straight-run naphtha, kerosene and gas oil fractions, at a scale of 235 ktfeed/year. To that end, a process model was created that receives the output of a Co-LTFT process as raw feed. The raw feed was prefractionated to remove the majority of the unreacted syngas, inert gases, light hydrocarbons (C1-C4) and water. The remaining stream was syncrude, primarily composed of alkanes and 1-alkenes in the C5-50 range.
A Base Case was designed in ASPEN plus, with a distillation unit with two steam strippers and three pumparounds. The goal was to receive the syncrude and separate naphtha, kerosene and gas oil cuts, with least 90% purity and recovery of the components. The Fenske-Underwood-Gilliland method was used to estimate the number of stages and reflux ratio of the column, and the Kirkbride method was used to find an initial estimate for the feed stage. The TBP curves of the cuts were compared with similar cuts from literature and found to be similar.
The Base Case underwent a sensitivity analysis in order to ascertain the effect of different design and process parameters on the separation quality and utility consumption. The parameters that were tested are cold condensate temperature, feed stage, condenser duty, feed temperature and stripping steam flow rate to the ADU. According to the sensitivity analysis results, for optimal separation between the syncrude and the other gases in the raw feed, the gases must be purged at a temperature of -70°C. Furthermore, the optimal configuration for the distillation of the given syncrude into naphtha, kerosene and gas oil fractions with at least 90% purity and recovery is as follows: The ADU has 40 equilibrium stages and a condenser duty of approximately -5.7 MW. The feed must be heated to 310°C and enter the column at stage 37. The stripping steam flow rate must be around 1.3 kg/s.
Five alternative processes were modelled as well, with similar inputs to the column model, and the results of the distillate separation quality and utility consumption were documented as well. The alterations of the alternative cases include replacing the stripping steam with a reboiler in one of the strippers, adding a stripper from where an additional product was drawn, concentrating the pumparound duty on the condenser, using a vacuum distillation unit to fractionate the residue of the atmospheric distillation unit, and employing a heat integration network.
The most important conclusions are listed. Firstly, the side strippers must use low pressure stripping steam instead of reboilers. Next, the minimum number of products must be drawn off in order to minimize utility consumption at a given separation quality. Furthermore, heat integration can save up to 50% in total utility consumption (heat and cooling water). It is recommended that further research, including a cost estimation, is conducted on refineries that produce on-specification final products.
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The dwindling of natural resources, mainly fossil fuels, and the alarming increase in the global average temperatures, are the biggest concerns of the engineering and scientific community of 21st century. Studies have found that known reserves of oil and natural gas will last another 50 years. Coal will last another 110 years, which points towards dire consequences. The experience will not be that of a car slowly running out of gas, but rather like driving off a cliff, since we innately depend on these resources. The realization of these concerns has lead to a rise in the investments all over the globe for Sustainability. The right questions are now being asked. How can we fulfill our demands without compromising the demands of our future generations? One of the keen areas of interest is the conversion of power into fuel. Synthesis of hydrocarbons from sequestrated carbon can produce carbon-neutral fuels that can replace some of the conventional fossil fuels. Methanol has been actively wiping the floor with the research community due to its simplicity of production and less toxic nature. While there are quite a lot of ways of producing methanol, very few of them are carbon neutral. Zero Emission Fuels B.V. has embarked on a venture to produce methanol by a totally carbon neutral process. They begin by capturing carbon dioxide and water from air and splitting the water into hydrogen and oxygen using solar power. Carbon dioxide and hydrogen are then combined in a reactor to form methanol, making a truly carbon-neutral process. They aim to make fuel consumption, a completely circular process while keeping it economic. An experimental characterization of ZEF’s methanol reactor under varying pressures and H2/CO2compositions was done. The new reactor design focuses on heating the feed gases before catalyst bed, more heat integration, reliable sensor data, and the ability to mix gases in desired compositions. Methanol yield, quality, energy efficiency, reactor inlet and outlet temperatures, power requirements were experimentally determined in a transient analysis. It was seen that the reactor produces 4.84 mmol/gcat /hr of methanol at 50 Bar and reactor wall temperature of 250◦C with H2 : CO2 = 3:1 mol% feed gas. The catalyst exhibited partial deactivation during night after shutdown. Contrary to expectation, the reactor produced more methanol at lower pressure. The production was reported at 5.96 mmol/gcat /hr at 35 Bar. Although, only 4.36 mmol/gcat /hr at 25 Bar. Moreover, the pressure reduction caused the natural circulation to slow down, and increase the inlet temperature from 208◦C at 50 Bar to 234◦C at 35 Bar, which is the reason for the observed increase in yield. It can be concluded that the reactor yield under these conditions is limited by kinetics and not thermodynamics. The reduced mass flow rate allowed the reactor to consume less power and show higher energy efficiency. It increased from 34.7% at 50 Bar to 43.2% at 35 Bar. The rate of pressure decline in the reactor was correlated with the methanol yield using gas law by accounting for non-ideality with the compressibility factor. The predicted yield was seen to be in good agreement with experimentally determined. The methanol yield of the reactor with variable feed gas composition was obtained for 50 Bar and 250◦C reactor wall temperature and seen to decrease on either side of the ideal composition. It was concluded that the yield becomes both stoichiometrically and kinetically limited.
It is recommended that similar experiments be done at increasing temperatures and equilibrium yield be determined experimentally. Additionally, the reactor needs to be operated with varying compositions and higher reactor wall temperatures at constant pressure, to obtain the operating line for maximum production of reactor. ... Read more

The phenomenon of lateral migration of neutrally buoyant rigid spheres is studied experimentally for Poiseuille Flow. The study relied on the particle migration technique to capture the distribution of particles radial position at different flow parameters. In this thesis, the varying experimental parameters are flow Reynolds number and particle concentration. These two parameters have been reported to have an opposing effect on the migration. Reynolds number is varying at Re=200-1200 and the particle concentration at φ = 0.05-0.5% . The results reveal that an increase in Reynolds number and particle concentration causes the migration to develop at a longer distance from the inlet. The migration is said to be developed when the particles have migrated to the region between the tube-axis and tube-wall. An increase in particle concentration shows a similar effect with the Reynolds number on the migration which the migration develop at a longer distance. An interesting result occurred at high particle concentration, at which the significance of the Reynolds number in altering the migration is decreasing. The study is also conducted to the secondary phenomena following the migration, the generation of inner annulus and the formation of trains of particles. It is shown that the variation of Reynolds number and particle concentration are significantly affected these secondary phenomena. ... Read more