Modeling the advanced flash stripper for CO2 capture using 5 m piperazine
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Amine scrubbing is the most mature technology for post-combustion CO2 capture. Several studies have demonstrated that the advanced flash stripper (AFS) consumes less energy among stripper alternatives. This thesis seeks to demonstrate the AFS energy performance and cost over a wide range of CO2 loading. Solvent models based on experimental results have been created by previous researchers and are available for simulation and process modeling in Aspen Plus®. In collaboration with Membrane Technology and Research Inc., various hybrid amine/membrane configurations were studied to minimize the total CO2 capture cost. CO2 in the flue gas is enriched by membranes from 12% to 18 and 23% for coal-fired power plant, and from 6% to 12~18% for natural gas combined cycle power plant (NGCC). The CO2 loading covers the range of flue gas CO2 from coal-fired power plants and NGCC. For each configuration, the cold and warm rich bypasses are optimized to minimize the energy cost. The cost optimization is also demonstrated on 5 m PZ, 5 m MDEA/5 m PZ, and 2 m PZ/3 m HMPD. The most cost-effective solvent varies with the flue gas CO2. When applied to a coal-fired power plant, hybrid parallel amine/membrane designs with 99% and 95% CO2 removal cost less than hybrid series with 60% CO2 removal. The equivalent work of the parallel configuration with 99% CO2 removal using 5 m MDEA/5 m PZ (32.3 kJ/mol CO2) is less than using 5 m PZ (34.0 kJ/mol CO2). The equivalent work with 95% CO2 removal (Case 19) using 5 m MDEA/5 m PZ (32.5 kJ/mol CO2) is less than using 5 m PZ (33.3 kJ/mol CO2). The capital cost with 99% CO2 removal using 5 m MDEA/5 m PZ ($70.5MM) is more than using 5 m PZ ($67.5MM). The capital cost with 95% CO2 removal using 5 m MDEA/5 m PZ ($73.5MM) is less than using 5 m PZ ($79.5MM). The total annual cost with 95% CO2 removal using 2 m PZ/3 m HMPD ($38.7/tonne CO2) is less than using 5 m PZ ($41.5/tonne CO2). When applied to NGCC, the cost of amine scrubbing is reduced by increasing absorber inlet CO2 by membranes. However, this is offset by the membrane cost. As absorber inlet CO2 increases from 6% to 18%, the operating cost decreases from $18.8 to $15.4/tonne CO2, while total regeneration cost decreases from $35.6 to $33.1/tonne CO2.