制氢装置酸性水汽提塔开裂分析

制氢装置酸性水汽提塔投用3年后装置停工大检修时发现塔壁出现多处裂纹,通过酸性水汽提塔取样件分析,母材化学成分满足标准对0Cr18Ni9的要求;试块塔内外壁渗透检测判断裂纹是从外壁向内壁扩展,局部已穿透,裂纹有明显分枝现象;微观形貌观察/EDS能谱分析裂纹从外壁起裂,垂直于壁厚方向向内壁扩展,金相观察裂纹均为穿晶树枝状扩展特征;保温材料中Cl-检测Cl-质量分数为0.005。综合分析为保温材料中的Cl-在保温层下浓缩,最终导致氯离子应力腐蚀现象的发生。因此,酸性水汽提塔外壁裂纹系奥氏体不锈钢保温层下氯离子应力腐蚀开裂导致。

Study on Causes of Cracking of Sour Water Stripping Tower for Hydrogen Generation Plant

Cracks were found on the tower shell in the scheduled overhaul of stripping tower of hydrogen generation plant after 3 years＇ operation.To locate the root causes of cracking,the base metal of stripping tower was sampled and analyzed,and whose chemical compositions were found to meet the specifications for 0Cr18Ni9 steel.The testing of both internal and external walls concluded that the cracks propagated from external wall to the internal wall.Some cracks penetrated the shell and some had branch cracks.The micro morphology/EDS analysis found that the cracks developed from external wall and propagated vertically to the internal wall in the direction of wall thickness.The metallographic analysis found the cracks had transgranular characteristics.The mass concentration of Cl-in insulation material was tested and found to be 0.005.As the Cl-concentrated in the insulation layer,the Cl-stress corrosion finally occurred.Therefore,the cracks on the external wall of sour water stripping tower were caused by Cl-stress corrosion cracking under the insulation of austenitic steel.