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Modeling and Analysis of an Indirect Coal Biomass to Liquids Plant Integrated with a Combined Cycle Plant and CO2 Capture and Storage

Jiang, Yuan, Bhattacharyya, Debangsu
Energy & Fuels 2015 v.29 no.8 pp. 5434-5451
biomass, carbon, carbon dioxide, coal, feedstocks, gasoline, models, power generation, steam, synthesis gas
A model of an indirect coal biomass to liquids (CBTL) plant integrated with CO₂ capture and storage (CCS) and a combined cycle plant has been developed in Aspen Plus 7.3.2. In the CBTL plant, syngas produced in the gasifier is sent to a water-gas shift (WGS) reactor to obtain the desired H₂/CO ratio in the syngas for Fischer–Tropsch (FT) synthesis. The product upgrading section is configured to satisfy the desired product specifications. CO₂ generated in the syngas and syncrude production units are captured by different CO₂ capture technologies. Fuel gas and steam generated in the plant are used as either utilities or sent to the combined cycle plant for power generation. The CBTL plant includes a novel integrated hydrotreating unit, which has the potential to reduce both operating and capital costs of the product upgrading section, in comparison to conventional separate hydrotreating units for gasoline and diesel. Impacts of a number of key input and operational variables, such as the steam/carbon ratio in the autothermal reformer (ATR) inlet, H₂/CO ratio in the FT inlet, extent of carbon capture in the CCS unit, biomass/coal ratio, and biomass type in the feedstock, are evaluated in this paper. It is observed that the thermal efficiency can be increased by decreasing the biomass/coal ratio, increasing the H₂/CO ratio in the FT inlet stream, and/or decreasing the extent of CCS. The thermal and carbon efficiencies of the base case are about 46.6 and 36.4%, respectively, which are slightly higher than the data reported in the literature for a similar product yield and extent of CO₂ capture.