Demonstration Project for Post Combustion CO2 Capture Process (Third Generation, Energy Saving and Compact) for Coal-Fired Power Plant

Chemical absorption/stripping technologies continue to focus on solvent development efforts to obtain solvents with high reaction kinetics for CO2 capture with relatively lower regeneration energy compared to benchmark MEA. While considerable progress has been made, one major challenge that still pertains is that the energy savings from these alternative solvents generally correlates with lower reaction rates for CO2 capture. The low reaction rates will necessitate the need for larger absorption towers, which will result in higher direct capital costs and could counter-balance the savings from operational cost (low energy consumption for solvent regeneration). The relatively low CO2 partial pressure (1.7-2.3 psia) in flue gas from utility boilers constitutes a major limitation via the driving force needed for these solvents to obtain the desired capture using smaller absorption columns. An approach to boost the driving force that reduces column sizes and consequently offsets the capital cost will be ideal. The use of membranes to boost the CO2 concentration to approximately 6-8 psia and the driving force has been identified as a technology approach to provide the synergistic benefits to overcome this limitation with a solvent-alone approach. Membrane-alone technology for CO2 capture also continues to be developed but one of the major hurdles is selectivity, scalability and economic feasibility for a full process considering the large volume of contaminated flue gas from power plants. Compared to existing technologies, the hybrid technology proposed here has several advantages that stem from leveraging the synergistic benefits of some of the isolated approaches currently being pursued. First, the use of membranes for the initial enrichment of the flue gas will provide an increased driving force for high CO2 capture in the absorber. Second, the increased driving force for CO2 capture makes the process amenable to a versatile suite of potential solvents in addition to the proposed advanced thermally stable piperazine (PZ) solvent that can capture 90% CO2 with significant reduction in capital investment of the absorber. The enhanced CO2 absorption in the solvent from the pre-concentration will result in high rich carbon loadings which will consequently lower steam requirements for vaporization.