Assessment Of Current And Future Yield Of Lignocellulosic Biomass As A Feedstock For Modelling a Steam Gasifier followed by Hydrogen and Synthetic Natural Gas Production

Abstract

With issues such as climate change and global warming worsening with each passing day, sustainability has become more important now then ever. The world needs to employ sustainable means of energy in order to overcome the global challenges we are faced with and mitigate the damage already done. Energy from biomass in the form of biofuels is one of the answers to our problem. Biomass is a carbon neutral fuel, and the biofuels produced from treating biomass have the advantage of being readily used in the current energy infrastructure. Lignocellulosic biomass feedstocks are a type of biomass that are available from a variety of sources and do not compete with the food chain. Gasification is a type of thermochemical method for treating biomass, by heating the biomass at temperatures greater than 700°C in the presence of one or more gasifying agents such as air or steam. Gasification of biomass produces a high calorific value gas called syngas which is composed of CO, H2, CO2 and CH4. This syngas has a lot of applications, and can be further processed to form various biofuels. The aim of this study was to determine the various sources of lignocellulosic biomass available in the European Union, and to estimate their current and future (2050) production potential, in order to meet some of the energy demands of the EU. This study also dealt with creating a kinetic model in ASPEN Plus of a steam gasifier after the Indirectly Heated Bubbling Fluidized Bed Steam Reformer at TU Delft. The model was validated with experimental results obtained fromthe setup at TU Delft, and evaluated its efficiency. Furthermore, two case studies were undertaken, each to model a process to produce a biofuel, in a biorefinery context. The two kinetic models made were for the production of Synthetic Natural Gas and Hydrogen, both of which have a number of applications in the European context. Finally, a sensitivity analysis was also performed to study the effect of various parameters on each of the models. The results from the model indicated that the model was validated by the experimental results fairly well, with a maximum relative error of 18% for the primary components. Also, the final product streams from the SNG and the Hydrogen models, were composed of a majority of the desired fuel, and can be used for any desired application once the Nitrogen is removed from them, which was not implemented in the model. Each of the two models have their own merits and demerits, but purely from a process standpoint, it was determined that the SNG model was more attractive as a process due to better efficiency (34.6% for SNG model compared to 20.5% for the Hydrogen model) and lower heat requirements. In the end, the main conclusions of the thesis were drawn and compiled in the form of five research questions, and some recommendations for future work was suggested.