Economic Analysis of CO_2 Separation from Coal-fired Flue Gas by Chemical Absorption and Membrane absorption Technologies in China

摘要

Two typical CO_2 chemical absorption processes using MEA and aqueous ammonia (AA) solutions to act as absorbents and one novel process using hollow fiber membrane contactors (HFMCs) to act as absorber and MEA as absorbent were analyzed in this study to find out what CO_2 capture process may be more suitable for China. An ultra supercritical PC power plant with 840-MWe-gross-output was selected as the reference case without CO_2 capture. Economic results show that when membrane price is set at RMB 50/m~2 and lifetime is 5 years, CAPEX of MEA, HFMC and AA cases are increased by about 90.12%, 85.4% and 68%, respectively, compared to reference case. And the corresponding cost of avoided is RMB 305.1/tCO_2, RMB 266.45/tCO_2 and RMB 206.02/tCO_2, respectively. The seemingly positive results imply that AA-based chemical absorption process should be the best for China nowadays. In addition, prospect of HFMC process in the future was also considered based on the increasing anxiety of NH_3 slip for AA process. If membrane price can be reduced to less than RMB 20/m~2 and new solvents with ～3 GJ/tCO_2 total regeneration heat requirement can be adopted in the future, HFMC may replace the AA-based method to capture CO_2. Additionally, economic results also show that the development of new solvents only considering the reduction of heat of CO_2 absorption may be not sufficient in terms of the reduction of CO_2 avoided cost. That is because CO_2 avoided cost can only be reduced by about 8% even the heat of CO_2 absorption can be reduced by about 60%. Finally, effects of coal price, improvements of reference case and CO_2 capture system on the cost of CO_2 avoided were also investigated.