System studies of different CO2 mitigation options in the oil refining industry: Post-combustion CO2 capture and biomass gasification

Sammanfattning: To reach the objective endorsed by the EU Council for reducing EU greenhouse gas (GHG) emissions by 80-90% compared to 1990 levels by 2050, extensive cuts are necessary in all sectors. The oil refining sector is a major energy user and thus a major GHG emitter. The overall aim of the work presented in this thesis is to analyse the potential for reductions in GHG emissions in the oil refining industry. The focus is on the implementation of three development routes at case refineries: Large-scale biomass gasification, to hydrogen or Fischer-Tropsch fuel, as well as post-combustion CO2 capture and storage (CCS). The analysis has been conducted both at the aggregated level; investigating the potential for on-site CO2 mitigation for the EU refining sector, and at the case study level; focusing on three development routes and including global reduction in GHG emission as well as economic performance. The findings indicate that the potential for reduction in CO2 by the available short-term mitigation options in the oil refining industry are relatively limited. The potential for CO2 capture varies depending on the targeted CO2 emission point source, the CO2 capture technology considered and whether CCS is assumed to be limited to areas with large point sources of CO2 emissions or not. Further, implementing a post-combustion CO2 capture process at a refinery could be profitable for future conditions characterized by a high charge for CO2 emissions. The cost for post-combustion CO2 capture at a refinery is significantly reduced if excess heat from the refining process is used with or without the aid of a heat pump. From a global perspective heat supply by a natural gas combined cycle can also be an interesting option. The potential for global GHG mitigation for the implementation of large-scale biomass gasification for production of hydrogen or Fischer-Tropsch fuel at a refinery is significantly increased with the possibility to capture the clean CO2 stream generated in the biomass gasification process. Fischer-Tropsch fuel production could be an economically interesting option for a refinery, presupposing economic support for renewable fuel production. Finally, it is important to consider uncertainties in the future energy market. In a comparison between Fischer-Tropsch and post-combustion CO2 capture, the most profitable option depends on the assumptions on the future energy market. All the studied development routes lead to reductions in GHG emissions. However, as biomass should be considered a limited resource it is reasonable to assume that the biomass will be used in applications with highest efficiency. In this thesis it is shown that, in most cases, large-scale biomass gasification at a refinery results in lower potential for GHG emission reduction compared to using biomass in coal condensing power plants.