Abstract:

The carbon dioxide (CO₂) capture technology using traditional absorbent of organic amine aqueous solution from flue gas is well-established and has significant potential for large-scale application. However, the post-absorption solution exhibits corrosive properties, which can severely reduce the service life of equipment and pipelines. Non-aqueous absorbents containing amines not only have the same advantages of faster CO₂ absorption rate and higher capacity as the traditional organic amine aqueous solution, but also have a minimal corrosivity toward metal equipment. But in fact, water vapor absorbed during the CO₂ capture process from flue gas can alter corrosion characteristics of non-aqueous absorbent. Thus, this study investigated the influence of varying water content in the monoethanolamine-N,N-dimethylformamide (MEA-DMF) non-aqueous absorbent on the corrosion behavior of carbon steel during CO₂ capture process from flue gas, and proposed effective corrosion inhibition strategies. The results showed that MEA-DMF non-aqueous absorbent was non-corrosive to carbon steel. With the number of absorption-desorption cycles increased, the water content in the absorbent gradually rose, leading to the enhancement of corrosion towards carbon steel. EDS analysis confirmed that the corrosion mechanism was consistent with that of wet CO₂ and amine solution. Additionally, the corrosiveness intensified with increasing temperature and CO₂ load once water was present in the absorbent. In order to alleviate the corrosiveness, it was necessary to reducing the water content or adding >0.2g/L 2-mercaptobenzimidazole (MBI) corrosion inhibitor in absorbent, which could greatly mitigate the corrosivity of the MEA-DMF absorbent towards carbon steel during the wet flue gas CO₂ capture process.

Key words: flue gas CO₂ capture, non-aqueous absorbent, water content, corrosiveness, corrosion inhibitor

摘要：

传统的有机胺水溶液吸收法捕集烟气CO₂技术成熟，极具大规模应用前景，但吸收CO₂后溶液具有腐蚀性，会严重影响设备、管线寿命。基于胺法的非水吸收剂具有有机胺水溶液吸收CO₂的速率高、容量大等优点，且对金属设备腐蚀性极低。但非水吸收剂捕集烟气CO₂过程中伴随吸收的水蒸气会引起金属腐蚀特性的变化。本文针对单乙醇胺-N,N-二甲基甲酰胺（MEA-DMF）非水吸收剂研究其捕集烟气CO₂过程中吸收剂内含水量变化对金属腐蚀特性的影响，并提出缓蚀的方法。研究结果表明，MEA-DMF非水吸收剂对碳钢没有腐蚀性；随着吸收-解吸循环次数的增加，吸收剂内的水含量逐渐增加，对碳钢的腐蚀性随之增加；能量色散X射线谱（EDS）分析表明其腐蚀机理与湿CO₂和胺溶液腐蚀机理一致；吸收剂内含水后，随着温度和负载的增加腐蚀性随之增加；降低吸收剂使用过程中的含水量或添加大于0.2g/L的2-巯基苯并咪唑（MBI）缓蚀剂，均可极大地降低MEA-DMF吸收剂捕集湿烟气CO₂过程对金属的腐蚀性。

关键词: 烟气CO₂捕集, 非水吸收剂, 含水量, 腐蚀性, 缓蚀剂