【作者】 李玲；

【导师】 旷亚非； 李德刚；

【作者基本信息】 湖南大学 ， 化学工程， 2004， 硕士

【摘要】 本文以己内酰胺装置中不锈钢换热器为研究背景，运用不锈钢腐蚀研究理论及成果对三台典型的不锈钢换热设备的失效形式进行了腐蚀分析与对策研究。 E6608气体冷却器失效形式属于典型的不锈钢局部腐蚀，既有冲刷腐蚀、晶间腐蚀、又有高温酸性环境下的过氧化腐蚀。选择四种金属材料（2RE10、C₄、Zr-702、304L）和一种非金属材料（聚四氟乙烯塑料）进行现场挂片和实验研究，结果表明：2RE10不锈钢的抗过钝化腐蚀能力要比304L不锈钢强，同时2RE10不锈钢的耐晶间腐蚀性能也明显优于304L不锈钢。对E6608设备防护设施的研究结果表明：在设备壳程高温气体入口处设置锆材内套筒（含防冲挡板）及锆折流板，入口硝酸喷嘴采用钛材转阀结构及管束上部安装防冲假管，可明显减缓局部冲刷腐蚀和过氧化腐蚀；改进设备的焊接结构设计和优化焊接制造工艺，同样可遏止不锈钢本体材料的晶间腐蚀倾向。氧化和冲刷腐蚀是影响E6608气体冷却器使用寿命的主要原因，寻求耐蚀性和耐冲刷性能均佳的金属材料，是延长E6608使用寿命的有效途径。 E6805气体加热器腐蚀失效研究表明：恶劣复杂的腐蚀体系是引起设备腐蚀失效的主要原因，要消除奥氏体不锈钢在高温氮氧化合物混合气体介质下的应力腐蚀，最好选用含碳量不低于0.04％的高铬镍钢，以保证其材料的高温抗蚀性及热强性；此外，合理的结构设计和优化工艺操作环境也是控制应力腐蚀与其它局部腐蚀的有效手段。设计改进后的新设备已连续高负荷运行四年，且经受了多次开停车非正常工况下的运行考验，达到了延长设备使用寿命的目的，应用效果显著。 E3008低变再沸器管束腐蚀失效的主要原因是电化学腐蚀和应力腐蚀，以及设备设计结构不合理和制造加工工艺，引起了热壁汽蚀和缝隙腐蚀，工艺措施不到位也是造成腐蚀的人为原因。通过对20钢、渗铝20钢、18-8、304、316L五种材料进行性能对比试验，五种不同材料的传热面腐蚀试验结果表明：在与介质完全接触时，304不锈钢的耐腐蚀性能最好；在有露点腐蚀的环境中，304不锈钢的抗腐蚀性能同样优于所试验的其它各钢种；在有汽液两相存在的部位，304不锈钢的耐腐蚀性能最好，优于其他各试验钢种。综合研究结果：推荐采用304不锈钢作为E3008再沸器管束材料；同时改进结构设计，避免产生危害较大的局部腐蚀，在设备投用时，进行严格的钒化处理，也是防止再沸器腐蚀失效的有效措施。更多还原

【Abstract】 The corrosion behavior and protective methods of three typical stainless steel heat exchangers in hexanolactam apparatus were studied in this paper.The corrosion type of E6608 gas cooler included eroding corrosion, intercrystalline corrosion and overoxidation corrosion in acidic high temperature environment. The in-situ hung-sample corrosion behaviors of four metallic materials(2REl0 C4 Zr-702 304L) and a non-metallic material (PTFE) were investigated. The results showed that the anti-overpassivity ability and anti-inter crystalline corrosion ability of 2RE10 were higher than those of 304L. Meanwhile, the eroding corrosion and overoxidation corrosion of E6608 can be inhibited obviously by installing Zr inner-cannula and Zr barrier at the high temperature gas entrance of the appartus, installing anti-concussion solid tube at the upper tube bundle and Ti rotational valve at the HNO3 muzzle entrance. Additionally, the intercrystalline corrosion of stainless steel could also be inhibited by using better welding process.The eroding corrosion of E6608 was the main factor that affected the life of the apparatus. The effective measure of prolonging the life of E6608 was seeking a suitable metallic material which has good performance of anti-corrosion as well as anti-eroding corrosion.The research results of E6805 also showed that the corrosion invalidation of the apparatus was caused by complicated corrosion system.The high Cr-Ni steel,which has good anti-corrosion performance and high strength at high temperture should be chosed to eliminate the stress corrosion of austenitic stainless steel in the mixed gases of nitrogen-oxygen compound at high temperture. In addition, the reasonable design of structure and the optimal process were effective means controlling the stress corrosion and other local corrosion. The improved new apparatus has run normally for four years and no corrosion was observed.The primary reasons of E3008 invalidation were electrochemical corrosion and stress corrosion. The unreasonable design of structure and manufacturing process resulted in heat-wall corrosion and crack corrosion.The corrosion behavior of the heat exchange surface of five materials(20 s teel,infiltrating-aluminium 20 steel, 18-8 stainless steel, 304 stainless steel ,316 L stainless steel) were investigated. The results showed that 304 stainless steel had theIIbest anti-corrosion performance when the corrosion medium contacted with the material totally. The 304 stainless steel also exhibited the best anti-corrosion performance in the environment of dew point corrosion and at the gas/liquid interface. Consequently, 304 stainless steel can be used as the tube bundle material of E3008 re-boiling implement. Simultaneously, strict treatment with V2O5 and more reasonable structure were the effective measures which prevented the E3008 from corrosion invalidation.更多还原