2015

Hannula, Ilkka

The objective of this compilation dissertation is to examine and compare the technical and economic feasibility of selected large-scale plant configurations capable of producing synthetic fuels or chemicals from renewable feedstocks. The evaluation of technical performance is based on mass and energy flows calculated with ASPEN Plusr simulation software. The investment costs and the sensitivity of overall economics to different price assumptions are investigated with a spreadsheet based tool. The production of synthetic fuels from CO2, water and electricity is an emerging process alternative, whose feasibility against gasification-based production is evaluated in detail. Three basic production routes are considered: (1) production from biomass residues via gasification; (2) from CO2 and electricity via water electrolysis; (3) from biomass and electricity via a hybrid process combining elements from gasification and electrolysis. Process designs are developed based on technologies that are either commercially available or at least successfully demonstrated on a pre-commercial scale. The following gasoline equivalent production cost estimates were calculated for plants co-producing fuels and district heat: 0.6-1.2 /Lgeq (18-37 /GJ) for synthetic natural gas, 0.7-1.3 / Lgeq (21-40 /GJ) for methanol and 0.7-1.5 /Lgeq (23-48 /GJ) for gasoline. For a given end-product, the lowest costs are associated with thermochemical plant configurations, followed by hybrid and then by electrochemical plants. Production costs of gasification-based configurations can be further reduced by five per cent, if filtration temperature can be successfully elevated from its present 550 °C level to the target of 850 °C. The results of this thesis can be used to guide future process development work towards configurations identified as best candidates for near-term deployment at scale. The results can also be used by the industry and the government to make rational decisions about development projects and policy measures that will help renewable fuel technologies to reach a self-sustaining growth path.