Performance of tidal hydrogenotrophic methanation and its feasibility for regenerating CO2-loaded solutions
To counteract global warming and reach the"double carbon"target,carbon capture,conversion,and utilization(CCCU)is a crucial technical strategy.One of the most recognizable carbon capture techniques,chemical absorption requires a lot of energy to regenerate CO2-loaded solutions.Bio-regeneration of CO2-loaded solutions using hydrogenotrophic methanation was proposed here for reducing carbon capture costs.In this method,a solution with a pH of 10 was prepared with Na2CO3 and microbial nutrient solutions as CO2 absorbents,and hydrogenotrophic methanation was used to convert CO2 to CH4 so that the solution could be regenerated and the absorbent reused.Initially,a tidal hydrogenotrophic methanation reactor was developed in order to increase the rate of CO2 bioconversion.Its viability for bio-regeneration of CO2-loaded solutions was determined after examining its startup performance.The results showed that on day 33,the gas residence time(GRT)of the tidal hydrogenotrophic methanation reactor had reached 23 minutes and the CH4 content at the reactor outlet was about 95％ ,indicating a CO2 conversion rate about 10 times higher than that of the conventional trickling bed and fixed bed.During the start-up phase,pH and alkalinity were essentially stable,there was no obvious accumulation of organic acids,and the average total organic acid concentration ranged from 0.2 to 2.3 mmol/L.In the subsequent 5 cycles of CO2-loaded solution bio-regeneration experiments,the regenerated absorbent's mean CO2 uptake was 55 mmol/L with a standard deviation of 1.1 mmol/L.The pH of the regenerated absorbent remained stable at 9.53±0.05,indicating that a CO2-loaded solution based on hydrogenotrophic methanation could effectively recycle absorbent.In the reactor,the relative abundance of the alkali-tolerant bacterial genera Proteiniborus and Acinetobacter and the archaeon Methanobacterium increased after the CO2-loaded solution bio-regeneration experiment.Results indicate that microorganisms have progressively adapted to weakly alkaline environments by reorganizing their communities to conduct metabolic processes such as CO2 methanation.
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