加氢精制装置高压换热器泄漏原因分析

Leakage analysis for a high pressure heat exchangerin hydrorefining unit

从工艺操作及设计条件方面对中国石油化工股份有限公司石家庄炼化分公司2号加氢精制装置高压换热器E1103在装置运行期间发生两次泄漏的原因进行了分析。核算结果表明:开工期间注水量在3 t/h左右,低于7. 7 t/h,说明开工期间在换热器管束内形成了NH4Cl结晶;失效分析报告表明:换热管材质合格,换热管失效原因为铵盐与水反应形成腐蚀介质,产生腐蚀。综上分析泄漏原因:工艺反应中生成的NH4Cl或NH4HS结晶铵盐在原设计注水条件下不能完全溶解在水中,在装置运行期间造成铵盐冲刷腐蚀;停工期间换热器长期存放于有水环境中,铵盐造成垢下腐蚀的点蚀。最后从注水量、换热器线速、停工过程中优化操作以及停工后对换热器进行保护性处理等方面提出了解决措施,从而保证换热器长周期运行。

The leakings of two times on the high-pressure heat exchanger E1103 in 2#hydrorefining unitof SINOPEC Shijiazhuang Refining & Chemical Co.,Ltd. and leaking conditions are analyzed. The results ofanalysis show that,the water injection at the beginning of start-up is about 3 t/h which is lower than 7. 7 t/h,showing that the NH4 HS crystals are formed in the heat exchanger tubes during the start-up. The failure analy-sis report shows that,the heat exchanger tubes’ metallurgy meet the specifications,and the tube failure iscaused by the corrosion from the corrosive media from the reaction of amine salts and water. The causes of cor-rosion are: the NH4 Cl or NH4 HS crystal salts in the process reaction can not be completely dissolved in thewater under the original water injection conditions,and therefore amine salts erosion will occur during the unitoperation;During the shutdown for maintenance,the heat exchangers are in the long-term water conditionsand the under pit corrosion will occur. The effective solutions countermeasures are recommended in respect ofwater injection rate,space velocity of heat exchanger flow,optimization of unit shutdown procedures and pro-tection of heat exchangers after unit shutdown. The long-term operation of the heat exchangers has beenensured.