天然气三甘醇脱水装置重沸器烟管腐蚀特性研究

Study on corrosion failure characteristics of reboiler smoke pipe in nature gas triethylene glycol dehydration unit

以重庆南川某脱水站为研究对象,对现场重沸器烟管进行了宏观形貌、金相、微观形貌及腐蚀产物分析,探究了烟管腐蚀失效机理,并提出了防治措施。结果表明:烟管外壁失效是由Cl^(-)引起的点腐蚀,同时弯管段叠加了空泡腐蚀。造成烟管外壁点腐蚀的主要原因是天然气中的Cl^(-)等盐类腐蚀介质进入了三甘醇溶液;造成烟管外壁空泡腐蚀的主要原因是重沸器罐内的三甘醇溶液在运行过程中曾出现过酸性变质或起泡变质失效,现场运行作业未能及时发现消除。烟管管体材料为20G普通碳钢,耐Cl^(-)点腐蚀和空泡腐蚀的能力较差,是造成腐蚀失效事故的次要原因。

Taking a dehydration station in Nanchuan of Chongqing as the research object,the macroscopic morphology,metallographic,microscopic morphology and corrosion product analyses were conducted on the field reboiler smoke pipe,the corrosion failure mechanism of the smoke pipe was explored,and prevention measures were proposed.The results showed that the failure of the outer wall of the smoke pipe was due to pitting corrosion caused by Cl^(-),and at the same time,the curved section was superimposed with the cavitation corrosion.The main reason for the corrosion of the outer wall of the smoke pipe was that salt corrosion media such as Cl^(-)in natural gas entered the triethylene glycol solution.The main reason for the cavitation corrosion on the outer wall of the smoke pipe was that the triethylene glycol solution in the reboiler tank had experienced acidic deterioration or foaming deterioration during the operation,and the on-site operation didn′t timely identify and eliminate such failure.The material of the smoke pipe body was 20G ordinary carbon steel,which had poor resistance to Cl^(-)pitting and cavitation corrosion,and it was the secondary reason causing corrosion failure accidents.