潮汐式嗜氢型甲烷化性能及其用于CO_(2)富液再生可行性

Performance of tidal hydrogenotrophic methanation and its feasibility for regenerating CO_(2)-loaded solutions

碳捕集与转化利用是应对气候变暖、实现“双碳”目标的重要技术手段之一。化学吸收法是目前发展成熟的碳捕集技术之一,但面临CO_(2)富液再生能耗高的问题。为降低碳捕集成本,提出了一种基于嗜氢型甲烷化的CO_(2)富液生物再生方法,即以Na_(2)CO_(3)和微生物营养液配制pH为10的溶液作为CO_(2)吸收剂,同时利用嗜氢型甲烷化过程将吸收富液中的CO_(2)转化为CH_(4),实现CO_(2)富液再生和吸收剂循环利用。为提高CO_(2)生物转化速率,构建了一种潮汐式嗜氢型甲烷化反应器,在完成该反应器启动阶段运行性能研究的基础上,考察了该反应器用于CO_(2)富液生物再生的可行性。结果表明:潮汐式嗜氢型甲烷化反应器在第33天时的气体停留时间(Gas Residence Time,GRT)达到23 min,反应器出口CH_(4)体积分数为95%左右,CO_(2)转化速率是常规滴流床和固定床的10倍左右;启动阶段的pH、碱度基本保持稳定,未出现明显的有机酸积累现象,有机酸总浓度平均值为0.2~2.3 mmol/L。在随后5个周期的CO_(2)富液生物再生试验中,再生后吸收剂的CO_(2)吸收量平均值为55 mmol/L,标准差为1.1 mmol/L,再生后吸收剂的pH稳定在9.53±0.05,说明基于嗜氢型甲烷化的CO_(2)富液生物再生可基本实现吸收剂的循环利用;CO_(2)富液生物再生试验结束后,反应器内耐碱性细菌属Proteiniborus、Acinetobacter以及古菌属Methanobacterium的相对丰度增加,说明微生物通过群落结构调整逐步适应在弱碱性条件下开展CO_(2)甲烷化等代谢活动。

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 CO_(2)-loaded solutions.Bio-regeneration of CO_(2)-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 Na_(2)CO_(3) and microbial nutrient solutions as CO_(2) absorbents,and hydrogenotrophic methanation was used to convert CO_(2) to CH_(4) 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 CO_(2) bioconversion.Its viability for bio-regeneration of CO_(2)-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 CH_(4) content at the reactor outlet was about 95%,indicating a CO_(2) 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 CO_(2)-loaded solution bio-regeneration experiments,the regenerated absorbent’s mean CO_(2) 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 CO_(2)-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 CO_(2)-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 CO_(2) methanation.