煤化工酚氨回收器0Cr18Ni9不锈钢换热管断裂原因分析及对策  

Analysis and Countermeasures on Fracture Causes of 0Cr18Ni9 Stainless Steel Heat Exchange Tubes of Phenol Ammonia Reclaimer in Coal Chemical Plants

作　　者：曹海平[1] CAO Hai-ping(Datang International Chemical Technology Research Institute Co., Ltd., Beijing 100062,China)

机构地区：[1]大唐国际化工技术研究院有限公司,北京100062

出　　处：《化肥设计》2019年第2期46-50,共5页Chemical Fertilizer Design

摘　　要：针对某煤化工企业使用0Cr18Ni9不锈钢换热管发生腐蚀断裂的现象,利用光学显微镜(OM)、扫描电子显微镜(SEM)、能谱分析仪(EDS)、X射线衍射仪(XRD)等技术手段,对腐蚀开裂的换热管进行了金相组织、元素成分、力学性能、显微硬度、物相组成等的分析。水质监测结果发现,循环冷却水中Cl-离子浓度远超过国标含量小于25mg/L的要求,最高达到了2066mg/L;腐蚀产物成分分析证实了Cl元素的存在;衍射分析中发现了FeCl2相的存在;裂纹扩展前沿微观组织分析表明,裂纹扩展路径穿过奥氏体不锈钢晶粒内部进行,属于穿晶型应力腐蚀开裂(IG-SCC)。损坏位置位于换热器入口折流板附近,其他位置未见损坏。经过综合分析,指出不锈钢换热管腐蚀开裂的原因是由氯离子引发的应力腐蚀开裂,同时温度梯度也影响腐蚀的发展,并在循环水氯离子浓度控制、换热管材质、介质流速设计方面给出了换热器设计防腐蚀建议。Against corrosion and cracking occurring to 0Cr18Ni9stainless steel heat exchange tubes in coal chemical enterprises, optical microscope (OM), scanning electron microscope (SEM), energy spectrum analyzer (EDS), X-ray diffraction (XRD), and other technical means are used to conduct analysis on the microstructure, element composition, mechanical properties, microhardness and phase composition of the heat exchange tubes which has been corroded and cracked. Water quality monitoring showed that the concentration of Cl - ions in the circulating cooling water far exceeded the international standard (-below 25 mg/L), and the highest value reached 2066 mg/L. The corrosion product composition analysis confirmed the existence of Cl element. Diffraction analysis showed the presence of FeCl 2 phase. The microstructure analysis of crack propagation front shows that the crack propagation path passes through the grain of austenitic stainless steel, which belongs to the transgranular stress corrosion cracking (IG-SCC). The damage happens near the baffle plate at the inlet of the heat exchanger. No damage is found in other positions. Comprehensive analysis shows that the corrosion cracking of stainless steel heat exchanger is caused by the stress corrosion cracking due to chloride ion, and the temperature gradient also affects the development of corrosion. The paper also puts forward anti-corrosion suggestions for heat exchanger from the perspective of chloride ion concentration control of circulation water, material of heat exchange tube and medium flow rate.

关 键 词：失效分析 应力腐蚀裂纹 煤气化 不锈钢 

分 类 号：TQ051.5[化学工程]