再生塔重沸器管束换热管腐蚀分析

简要描述了制氢装置再生塔底重沸器运行工况,通过现场检查换热管腐蚀形貌,以及对工艺介质的组成、管束的材质分析、泄漏点的腐蚀产物分析、试样的金相分析,明确了再生塔底重沸器由于装置长周期运行,水分的蒸发造成苯菲尔溶液中微量的Cl-浓度不断浓缩,形成Cl-在管板和换热管中间的缝隙富集,导致缝隙与壳体内溶液形成浓度差,从而形成缝隙腐蚀,缝隙腐蚀形成的点蚀造成再生塔底重沸器的泄漏。针对上述腐蚀分析原因,从技术及管理角度制定相应的整改措施。为消除缝隙的存在,通过技术实验,对比了管束加工制作方式的差异,指明管束制作应根据生产实际需要选择合适的加工工艺。

Analysis of Corrosion of Reboiler Tubes in Regeneration Tower

The operating conditions of the bottom reboiler in a hydrogen plant are briefed.Through field examination of topographic form of heat exchanger tubes,analysis of process media compositions,tube metallurgy and corrosion product at the leaking points and well as metallographic analysis of samples,it is concluded that the leaking of regeneration tower bottom reboiler is the result of pitting corrosion from crevice corrosion because of the concentration difference between the solution in crevice and the solution in shell resulted from continuous increased concentration of Cl-in Benfield solution with water vaporization and accumulation of Cl-in the crevice between tube sheet and tube.The preventive measures are purposed in respect of technology and management.It is pointed out that appropriate manufacturing process should be selected for the tubes based upon the actual operation requirements.