羟胺肟化装置汽提塔再沸器泄漏原因分析及改进措施

Reason analysis and improvement measures for reboiler leakage of stripper in hydroxylamine oximation unit

针对羟胺肟化装置的汽提塔再沸器频繁出现换热管泄漏的情况,分析了再沸器换热管的腐蚀现象、金相显微组织、设备运行操作、进料组分和安装高度等,提出了改进方法并进行实施。结果表明:汽提塔再沸器换热管内壁有明显的点蚀、坑蚀及穿孔情况,被腐蚀穿孔部位主要集中区域在气液分界处;腐蚀处附近未发现夹杂物等明显冶金组织缺陷;设备运行操作正常;进料组分中不存在氯离子腐蚀;塔内控制液位低于再沸器上管板的高度。提出的相应措施为:将再沸器安装高度整体下移400 mm,确保汽提塔液位精准控制在40%;将再沸器的换热器分成上下两部分结构,有利于维修时拆装方便;换热管材质依然选择304L不锈钢。经过改进后的再沸器自2018年10月投入使用以来其运行稳定,未发生列管泄漏事故。

Aiming at the frequent leakage of heat exchange tube of stripper reboiler of hydroxylamine oximation unit,the corrosion phenomenon,metallographic microstructure,equipment operation,feed composition and installation height of reboiler heat exchange tube were analyzed,and the improvement measures were put forward and implemented.The results showed that obvious pitting corrosion,pitting corrosion and perforation were observed on the inner wall of the heat exchange tube of the stripper reboiler,and the corrosion perforation mainly occurred at the gas-liquid boundary;no obvious metallurgical defects such as inclusions were found near the corrosion site;the equipment operated normally;no chloride corrosion occurred in the feed components;and the control liquid level in the tower was lower than the height of the tube sheet on the reboiler.The corresponding measures were proposed as follows:the installation height of reboiler was reduced by 400 mm to ensure that the liquid level of stripper was accurately controlled at 40%;the heat exchanger of reboiler was divided into upper and lower parts,which was convenient for disassembly and assembly during maintenance;304L stainless steel was still selected for heat exchange tube.The improved reboiler has been running stably without any tube leakage accident since it was put into use in October 2018.