CO_2 implications of coal-to-liquids (CTL) plants

摘要

In this study, plant-level techno-economic models are developed and applied to systematically evaluate the performance, emissions and costs of a much broader range of coal-to-liquids (CTL) plant designs than have previously been studied. These includetwo plant configurations (a liquids-only plant similar to current commercial technology, and a co-production plant producing both liquids and electricity), two types of coal gasification systems (slurry-feed and dry-feed gasifiers), and three types of coal feedstock (bituminous, sub-bituminous and lignite). For all twelve designs, the additional cost of carbon dioxide capture and storage (CCS) and the effects of a price or tax on plant-level CO_2 emissions, as well as the option of sale of CO_2 for enhanced oil recovery (EOR), also are studied. The potential of the co-production configuration to reduce overall CO_2 emissions by displacing conventional pulverized coal power plants is also investigated. The economic feasibility of CCS depends strongly on the CO_2 price/tax and electricity selling price. In general for liquids-only plants, CCS is the more economical option than paying even the “low” CO_2 tax of $20/tonne for the non-CCS cases. For co-production plants, a higher CO_2 tax is required tomake CCS feasible because of the foregone revenues from electricity sales (due to CCS energy requirements). EOR options generally have the lowest cost of liquids produced, in the range of $45-$l 00/barrel, across all cases. Co-production is more efficient than the separate production of liquids and power, and this difference in efficiency increases with the addition of CCS. This advantage can be utilized to achieve a net reduction in overall CO_2 emissions.