Selective Capture of CO_2 from Boiler Flue Gases by a Novel CO_2 'Molecular Basket' Adsorbent

摘要

Flue gas is one of main CO_2 emission sources. CO_2 capture from flue gas is a major step for control of CO_2 emissions. However, the cost for the current absorption process is considerably high. Recently, a novel CO_2 "molecular basket" adsorbent was developed in our laboratory, which shows a high CO_2 adsorption capacity and a high CO_2 selectivity, with CO_2/N_2 ratio 100. In this paper, the selective capture of CO_2 from boiler flue gas by this novel CO_2 "molecular basket" adsorbent is reported. Two types of flue gases, i.e., coal-fired flue gas and natural gas-fired flue gas were used. The influence of moisture, N_2, O_2, CO, NO_x and SO_2 on the selective capture of CO_2 from flue gases were investigated. Moisture had a promoting effect on the CO_2 adsorption. When the moisture content in the flue gas was 10 percent, the CO_2 adsorption capacity was approx 30 percent higher than that under the dry flue gas condition. This is a major advantage, because conventional solid adsorbent would require pre-separation of moisture before CO_2 separation. The adsorbent hardly adsorbed any N_2, O_2 or CO. The selectivity of CO_2/NO_x was 2.5 for gas-fired flue gas and the selectivity of CO_2/SO_2 and CO_2/NO_x were 10.7 and 2.86, respectively for coal-fired flue gas. The results showed that CO_2 can be selectively separated from the flue gases by using this novel CO_2 "molecular basket" adsorbent. However, very little NO_x and SO_2 desorbed after adsorption indicating the need for pre-removal of NO_x and SO_2 from the flue gas mixture before capture of CO_2 by the novel CO_2 "molecular basket" adsorbent.