385589 Techno-Economic Analysis of a Novel Indirect Coal-Biomass to Liquids (CBTL) Plant Integrated with a Combined Cycle Plant and CO2 Capture and Storage (CCS)
The indirect coal to liquids plant using the Fischer-Tropsch (FT) synthesis is technically feasible, but is plagued with high CO2 emission in comparison to the petroleum-based fuels. Addition of moderate amount of biomass to the feed and inclusion of CO2 capture and storage (CCS) processes can reduce its environmental footprint, but at the cost of higher capital investment and larger operational penalty. Techno-economic optimization can be very valuable tool for improving the overall economics of the coal-biomass to liquids (CBTL) plant with CCS. With this motivation, a high-fidelity process model of a novel indirect coal-biomass to liquids (CBTL) plant integrated with a combined cycle plant and CCS is developed and then used for techno-economic analysis where the impact of a number of feasible technologies on the plant economics is evaluated.
In the CBTL plant with CCS, the syngas is first produced by gasification from coal and biomass, is then shifted to obtain the desired H2/CO ratio, and is finally converted to syncrude in the FT reactor after removing a significant portion of CO2 using a physical solvent. An autothermal reformer is used to increase the fuel yield by converting light hydrocarbons to syngas. The process flowsheet includes a novel integrated hydrotreater in comparison to the conventional multiple hydrotreaters. It has been observed that the integrated hydrotreater not only reduces the operational penalty, but also reduces the capital investment significantly. On-spec gasoline and diesel are then produced from the product upgrading section. The excess light gases and the available heat from the CBTL plant is used in a combined cycle plant to produce steam and electricity.
The process model of the base case is built and validated in Aspen Plus while the economic analysis is performed using Aspen Process Economic Analyzer (APEA). All the key equipment items are designed and their capital costs are estimated. The equipment items for which the cost cannot be estimated in APEA, cost correlations are obtained from the open literature or derived using the data available in the open literature. The outside battery limit (OSBL) section is designed based on the utilities requirement in the plant and then integrated with the inside battery limit (ISBL) units for economic analysis. Impacts of a number of technologies including various CO2 capture technologies on the various economic matrices such as net present value (NPV), payout date, and internal rate of return (IRR) are studied. The study shows that the techno-economic optimization of the indirect CBTL plant can substantially improve the plant economics without violating the operational constraints and environmental emission limits while satisfying the desired fuel specifications.
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