中空纖維管快速變溫吸附應用於燃煤火力發電廠燃燒後碳捕捉程序

Abstract

燃燒後碳捕捉是減少燃煤電廠二氧化碳排放的有效方法之一。其最大的挑戰是降低能耗，此研究將探討新型的中空纖維快速變溫吸附系統應用於捕捉燃煤發電廠排出的二氧化碳。此方法相較其他吸附系統可以有效地縮短操作時間，並且有應用低階能量的潛力。 研究中採用一系列平行雙塔操作來連續捕捉一個550 MW燃煤發電廠煙道氣中的二氧化碳，並以捕捉率、純度和能耗來探討主要操作變數對系統的影響，其中包括進氣體積流量，棄置時間，脫附溫度等關鍵操作變數。研究發現進氣體積流量顯著影響捕捉率，較小的流量會提高捕捉率。而棄置時間則是與捕捉的二氧化碳純度息息相關，放棄時間愈長純度會愈高。研究發現以一組雙塔中空纖維RTSA來模擬，當入口氣體體積流量為0.12 m3/s時，放棄時間為7秒，脫附溫度為120°C，二氧化碳之純度和捕獲率皆可超過90％。 本研究考慮使用從低壓渦輪機中所抽取之蒸汽作為雙塔真空快速溫變吸附（DC-vRTSA）所需熱源的可能性，計算對燃煤電廠發電效率和蒸汽流量的影響及經濟分析。DC-vRTSA在120°C到55°C的脫附溫度下分別減少了8.2%到1.9%的燃煤電廠發電效率。在經濟分析方面，結果顯示最佳的年總成本與捕捉成本在脫附溫度為60°C時分別為61.52 百萬美金及每噸二氧化碳19.20美金。

Post-combustion carbon capture is one of the feasible methods to reduce emission of carbon dioxide (CO2) from coal-fired power plants. The biggest challenge in this technology is reduction of energy consumption. This work proposes a hollow fiber based rapid temperature swing adsorption (RTSA) method for capturing CO2 from typical coal-fired power plants. The proposed RTSA approach can shorten the operating time and using low-grade energy for regeneration of adsorption elements. In this study, the tank-in-series model is used to simulate the RTSA process including adsorption and desorption periods. A series of parallel operation dual-columns is used to capture the CO2 continuously from the flue gas of a typical 550 MW power plant. Main operating variables including inlet gas volume flow rate, abandon time, desorption temperature on key performance factors such as discharged gas purity, capture ratio of CO2, and energy consumption per unit CO2, etc., are investigated for reducing the energy consumption. This study found that the inlet gas volume flow rate will significantly affect the capture ratio, where smaller gas volume flow rate is beneficial to increase capture ratio. The abandon time obviously affects the purity of the captured CO2, where the longer abandon time leads to higher purity. Desorption temperature affects both the capture ratio and purity of captured CO2. The higher the desorption temperature, the higher the purity and capture ratio. For one typical basic unit with dual-column hollow fibers, the study found that when the inlet gas volume flow rate is 0.12 m3/s, the abandon time is 7 s, and the desorption temperature is 120 °C, both the CO2 purity and the capture ratio can exceed 90 %. With considering the possibility of using extracted steam from a low-pressure turbine as the heating source for the dual column vacuum RTSA (DC-vRTSA), the impact on the efficiency and stream data of typical coal-fired power plants are calculated. The DC-vRTSA at 120°C-55°C will reduce the efficiency of the coal-fired power plant by 8.2 % to 1.9 %, respectively. The economic analysis of the DC-vRTSA (120°C-55°C desorption temperature) used in the coal-fired power plant has been estimated. The best total annual cost and CO2 capture costs of these processes located at 60°C desorption temperature process, is 61.52 million US dollars and 19.20 US dollars per tons of captured CO2.