烟气余热回收器管束连接泄漏失效分析

LEAKAGE FAILURE ANALYSIS OF TUBE BUNDLE CONNECTION OF FLUE GAS WASTE HEAT RECOVERY DEVICE

某公司的废热锅炉烟气余热回收器在使用过程中管板与管束连接处发生漏水,为了确定漏水的原因,以便采取有效对策,对余热回收器失效原因进行分析。首先通过Ansys仿真软件计算了余热回收器在工作工况下应力水平,得到应力最大点位于管板处,并且管板和换热管连接处应力值较大。而后对管束泄漏取样部位进行宏观腐蚀形态分析、金相微观组织分析、显微硬度测试、腐蚀微观形貌扫描电镜(Scanning Electron Microscope,SEM)分析及腐蚀产物EDS(Energy Dispersive X-Ray spectroscopy)微区成分分析。结果表明,该换热器在高温下管束和管板的缝隙处发生碱浓缩,并且该处存在焊接裂纹,最终导致管板和管束焊缝处发生碱应力腐蚀开裂。

Leakage occurred on a company′s waste heat recovery unit after short-term operation of it.In order to determine the cause of the leak and take effective countermeasures,the reasons for the failure of the waste heat recovery device were analyzed.Firstly,the stress level of the waste heat recovery device under working condition was calculated by Ansys simulation software,and the maximum stress point was found at the tube sheet,and the stress value at the joint of tube sheet and heat exchange tube was larger.Then,macro-corrosion morphology analysis,metallographic microstructure analysis,micro-hardness test,scanning electron microscope(SEM) analysis of corrosion micro-morphology and EDS micro-area composition analysis of corrosion products were carried out on the sampling site of tube bundle leakage.The results show that,because of high temperature,increasing alkali concentration occurs at the crack of tube bundle.And welding cracks exist there,which eventually leads to alkali stress corrosion cracking at the weld of tube sheet and tube bundle.