靖边气田天然气脱硫装置腐蚀行为研究

CORROSION PERFORMANCE STUDY ON NATURAL GAS DESULFURIZATION UNIT IN THE JINGBIAN GASFIELD

靖边气田天然气采用湿法脱硫工艺,脱硫剂为醇胺溶液,设备及管线在运行过程中存在均匀腐蚀和局部腐蚀现象。为分析腐蚀原因,确定腐蚀程度,分别从气相腐蚀、液相腐蚀、电偶腐蚀三方面开展了实验与分析工作,分析了MDEA富液中降解产物的成分,研究了主要降解产物对20#碳钢腐蚀速率的影响。通过新配脱硫贫液的高压模拟实验与现场连续两年的富液腐蚀速率测试结果对比分析,发现低浓度降解产物对碳钢腐蚀速率影响程度较小。根据在役压力容器内不同金属材质的面积比例,测试了电偶腐蚀对富液腐蚀速率的影响程度,实验发现在用材料1Cr18Ni9Ti不锈钢和20#碳钢构成的电偶对设备腐蚀程度贡献额小,天然气脱硫设备内腐蚀程度属于弱腐蚀范围。

The wet treatment method is adopted for natural gas sweetening with hydramine solution as the desulfurizer in the Jingbian Gasfield, where uniform and local corrosion occur now and then to the working equipments and pipelines. In order to determine both causes and degree of the corrosion, experimental study and analysis were carried out from three aspects respectively, i. e. vapour corrosion, liquid corrosion, and bimetallic corrosion. In this case of study, it classified the ingredients of degradation products in MDEA rich solution, and investigated on the effects of the main degradation products on the corrosion rate of 20# carbon steel. Compared high-pressure modeling experiments for newly-formulated lean solution to testing and analysis on the corrosion rate of rich solution from two continual years' field application, it was found that the low-concentration degradation products have less effects on the corrosion rate of carbon steel. On the other hand, bimetallic corrosion was also tested on the effects of the corrosion rate of rich solution according to different area ratio of different metals inside the in-service pressure vessels. The result shows that the galvanic made by 1Cr18Ni9Ti stainless steel and 20# carbon steel has little effect on the corrosion rate of the equipments, which proves that the corrosion degree is rather low inside the equipments of natural gas desulfurization units.