Perspectives on gasification systems to produce energy carriers and other chemicals with low CO2 emissions : techno‐economic system analysis on current and advanced flexible thermo‐chemical conversion of fossil fuels and biomass

Abstract

To prevent dangerous climate change, the emissions of anthropogenic greenhouse gasses (GHG) need to be reduced. Two key mitigation options to reduce GHG involve a transition from the current fossil-fuel based infrastructure towards one based on renewable and the implementation of CO2 capture, transport and storage (CCS). Gasification facilities could be attractive for both of these options. Gasification is a relatively new technology where carbonaceous feedstocks (including coal and biomass), can be converted into electricity or chemicals (including transportation fuels). During this conversion process, a syngas stream with a high CO2 partial pressure is obtained, making CCS attractive at this location as it reduces the energy consumption and costs of capturing the CO2. Furthermore, during chemical production CO2is often already removed to improve the overall conversion efficiency of the facility, reducing the penalty due to CCS even further. However, at current market conditions, gasification facilities are economically unattractive. There are, however, large fluctuations in these market prices. Exploiting these variations could improve the economics of the facilities. These economics are also expected to improve as a result of technological learning, especially concerning the gasification of solid feedstocks. This thesis aims to determine the techno-economic potential of commercial scale gasification systems producing energy carriers and other chemicals with low CO2 emissions and to assess how and when flexibility improves the overall performance of these gasification systems. This was done by developing chemical simulation models on a component level. The flexibility has been studied by changing the feedstock (coal, biomass pellets and torrefied biomass pellets) and product (electricity, FT-liquids, methanol and urea). The future performance of gasification facilities was assessed using a combination of an engineering study and trend analysis. The results show that flexibility in feedstock of up to 50%, and in production of up to 60%, is technically possible with only minor reductions in overall conversion efficiency. The economic analysis indicates that an attractive strategy for exploiting variations in market prices is to adjust production between electricity and FT-liquids, following the daily variation of the electricity price. Gasification facilities that use this kind of flexibility are not only more profitable than their static counterparts; they are also less vulnerable to large changes in market conditions. Results also show that there is a large potential in improving the performance of current facilities as a result of technological learning. The combination of new technologies, such as ion transfer membranes and warm gas cleaning, and improved operating experience, could decrease production costs of electricity or transportation fuels by around 30%. Summarising, this research points out a large potential for (flexible) gasification facilities which apply CCS, allowing gasification to play a role in decarbonising both the energy and transportation sectors and, therefore, make a valuable contribution in the transition from a fossil-based energy infrastructure towards one based on renewables. Although the potential for technological learning is considerable, this will not be achieved without R&D as well as new gasification facilities.