Abstract A process to upgrade a biogas product to biomethane has been investigated. Recycling of an absorbent is important for low-cost upgrading of biogas by chemical absorption. This study investigated the alkaline recovery of absorbent solution by thermal decomposition at various temperatures (75, 85 and 95 °C) and various vacuum levels (0.2, 0.4 and 0.6 bar). During heating, CO2 and H2S were released from the absorbent solution, which increased the pH. The highest pH 10.58 was reached for NaHCO3 solution from initial pH 8.86 when treated at 95 °C and 0.6 bar vacuum level (gauge pressure). The mass fraction of CO32− in the solution increased from 0.06 to 0.78. Experiments on H2S removal from NaHS solution gave the highest pH 10.38 at 95 °C and 0.6 bar vacuum pressure. Moreover, the performance of the recovered alkaline solution was tested in biogas absorption. The results show that CO2 and H2S removal efficiencies of alkaline solution before and after recovery were similar, at 80 and 99 % respectively. This study demonstrated that thermal decomposition has high potential for recovering the alkaline used absorbent, for recirculation back into the absorption process.

中文翻译：

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将沼气升级为生物甲烷：通过热分解碱回收吸收溶液

摘要 研究了一种将沼气产品升级为生物甲烷的工艺。吸收剂的回收对于通过化学吸收进行沼气的低成本升级很重要。该研究调查了在不同温度（75、85 和 95 °C）和不同真空度（0.2、0.4 和 0.6 巴）下通过热分解对吸收剂溶液的碱回收。在加热过程中，CO2 和 H2S 从吸收剂溶液中释放出来，从而增加了 pH 值。当在 95 °C 和 0.6 bar 真空水平（表压）下处理时，NaHCO3 溶液从初始 pH 值 8.86 达到最高 pH 值 10.58。溶液中 CO32− 的质量分数从 0.06 增加到 0.78。从 NaHS 溶液中去除 H2S 的实验在 95 °C 和 0.6 bar 真空压力下给出了最高的 pH 值 10.38。而且，对回收的碱性溶液在沼气吸收方面的性能进行了测试。结果表明，回收前后碱性溶液的CO2和H2S去除效率相似，分别为80%和99%。该研究表明，热分解具有很高的回收碱性吸收剂的潜力，可将其再循环回吸收过程。