It is expected that integrated carbon capture and conversion (iCCC) will reduce the overall cost of carbon capture & conversionby leveraging the CO2 conversion process to simultaneously regenerate CO2-rich solutions. To assess the feasibility of coupling biomethanation and carbon capture, the absorption performance of a slightly alkaline absorbent (pH = 10) prepared with 4.2 g/ L NaHCO3, 6 g/ LNa2CO3 and a microbial nutrient solution for CO2 in simulated flue gas in a packed column was investigated. Second, the CO2-rich solution was subjected to a five-cycle regeneration experiment using the biomethanation process in anaerobic bottles. The results show that inthe flow-through mode, when the gas flow rate of packed column is≤ 1.0 L/ min, with the increase of liquid flow rate, CO2 removal ratesof all experimental groups gradually increase and can be stabilized above 80%, and the liquid flow rate of this packed column is suitable tobe ≤ 0.9 L/ min. Overall volumetric mass transfer coefficients of the packed column at different gas flow rates (0.4-1.2 L/ min) are generally stable between 17- 19 mol/ ( h·kPa·m3 ). As a result of CO2 absorption, NaHCO3 in the absorption solution increases andNa2CO3 decreases, with a ratio between 1.2 and 1.9. Under the condition that the CO2 removal rate is greater than 80%, the slightly alkaline absorbent can be recycled 6 times at a gas flow rate of 0.6 L/ min and liquid flow rate of 0.7 L/ min. The utilization rate of the active component CO2-3 reaches 89.5%, and the total inorganic carbon(TIC) of the formed CO2 -rich solution is 0.127 mol/ L at a pH of8.82, creating an environment conducive to the growth of biomethanation microorganisms. The results of the cyclic experiments on the bioregeneration of the CO2-rich solution reveal that the absorbed CO2 of the absorbent is basically stable in the range of 69.6-78.6 mmol/ Lafter each regeneration and the CH4 production is reproducible during the regeneration process. As a result of the regeneration experiment,alkali-resistant bacteria at the phylum level, such as Firmicutes and Actinobacteriota, are somewhat enriched. Approximately 99% of archaeal genera are dominated by hydrogenotrophic methanogens before and after regeneration, but the slightly alkaline environment duringregeneration results in a 19.5% decrease in the relative abundance of Methanobrevibacter and a 18.7% increase in the relative abundanceof unclassified_f_Methanobacteriaceae, respectively. In conclusion, the above experimental results indicate the feasibility of biomethanation combined with carbon capture.
China Coal Science and Industry Group Co., Ltd
Coal Science Research Institute Co., Ltd
Coal Industry Clean Coal Engineering
Technology Research Center
XIE Qiang
YU Chang
SHI Yixiang
ZHAO Yongchun
DUAN Linbo
CAO Jingpei
ZENG Jie
Monthly
1006-6772
11-3676/TD