【作者】 朱晓航；

【导师】 李宁；

【作者基本信息】 哈尔滨工业大学 ， 化学工程与技术， 2010， 硕士

【摘要】 硫磺和硫化氢联合制备硫酸装置是巴陵石化己内酰胺生产中重要设备。硫酸装置平稳、安全的运行状态不仅能保障工厂生产计划顺利完成,同时也是公司经济效益最大化的必要保证。本文从现场出发,调查硫酸装置的设计资料以及设备服役条件,勘察腐蚀设备形貌以及采集腐蚀设备腐蚀样品。采用XRD、EDS、SEM以及化学分析等方法对现场采集腐蚀产品进行分析,借助热力学软件Factsage的计算结果,结合国内外硫酸设备腐蚀与防护的最新研究进展,对设备腐蚀原因与腐蚀机制进行全面分析。硫酸制备装置发生腐蚀设备有:物料入口设备以及各级换热器等,其中以E304热管省煤器腐蚀情况最为严重。物料入口设备下料口产生腐蚀主要原因有:沉降设备表面硫磺粉尘,水蒸气结露,设备未涂覆保护涂层以及具有腐蚀性工业大气。通过软件模拟研究,结合模拟实验结果,确定其主要为大气腐蚀,导致设备氧化腐蚀。E301高温换热器膨胀节遭受的是,未燃尽硫磺蒸汽与膨胀节发生硫化腐蚀后,设备表面硫化物连同停工过程中产生的冷凝酸共同造成的连多硫酸应力腐蚀;E303中温换热器主要遭受服役环境中烟气的化学腐蚀以及未燃尽硫磺硫腐蚀;E304则因设备服役温度低于烟气露点,导致造成硫酸露点腐蚀。导致换热器腐蚀根本原因是工艺控制不良造成的,同时设备的选材以及构造等方面也给设备腐蚀埋下隐患。模拟实验对硫酸装置采用设备用钢:Q235、20#钢、316L、16MnR以及ND钢进行了电化学测试、浸泡腐蚀实验、电偶腐蚀实验、大气腐蚀实验等方法,得到了各种钢材在硫酸中耐蚀性数据,通过浸泡实验以及电化学测试,发现当硫酸浓度低于60mass%时,金属腐蚀速度随温度、浓度增大而增大。合金钢316L以及ND钢耐蚀性优于普通低碳钢Q235以及20#钢。实验发现,316L在20℃硫酸中具有优异耐蚀性;合金钢ND钢在60℃硫酸中耐蚀性较316L好;Q235在各类测试中其耐蚀性均优于20#钢。本文首次对ND钢与20#钢、316L与Q235接触产生的电偶腐蚀实验进行研究,此项研究在国内外仍未见报道。实验发现电偶腐蚀不仅会使得ND钢与316L耐蚀性降低,同时也会造成Q235与20#钢腐蚀加剧。实验表明,电偶腐蚀必然加速至少一种钢材腐蚀速率。实验进一步研究了材料在硫酸装置服役环境中腐蚀机理,同时为设备建造提供了选材依据。针对硫酸设备腐蚀关键因素,提出切实可行的防腐对策与建议。对未发生腐蚀设备依据现场环境、软件计算以及文献报道等进行腐蚀预测,并提出了相关防腐措施。最后本文展望了相应防腐措施,以及有关研究方向。更多还原

【Abstract】 Sulfuric acid manufacture device using sulphur and hydrogen sulfide is important to Petro China Yue Yang branch caprolactam production equipment. Smooth and safe running of sulfuric acid device can not only ensure the completion of the production plan, but also ensure the maximum economic benefits of the company.With the assistance of research team in the plant, the design data of the sulfuric acid plant, working conditions of the devices, and the corrosion products from the equiments have been investigated and collected.Using XRD, EDS, SEM and chemical analysis, corrosion products collected on the spot are analysed. With the calculation results of the thermodynamics software Factsage, and the analysis of the corrosion products, the causes leading to the corrosion of the sulfuric acid equipments havd been discussed in this paper. With the benefits of the latest researches on the corrosion mechanisms of equipments corrosion and analysis of the real cases, key factors to the corrosion of the equipments have been found and protective measurements are put forward in anti-corrosion suggestions. Mile steel Q235 and 20#, alloy 316L and ND steel have been tested by the electrochemical tests, immersion corrosion test, galvanic corrosion test in order to get the datas of corrosion resistance of the steels. Further studies in the corrosion mechanisms of steels in sulfuric acid have been taken, providing selection of the steels in equipment construction in the future.Corrosion happens in all of the equipments of the sulfuric acid including sulphur filler, heat exchangers and et al. The corrosion of E304 heat pipe economizer is the most severe.The main causes leading to corrosion of the sulphur filler has been found. First, the equipment is coverd by the sulphur dust on the surface. Second, Liquid membrane is formed, when vapor condensed into water. Third, the device is not coated with any protective coatings and exposed to industrial air. Through software simulation study and comparing with different types of experiment results, the main cause of the corrosion of the suphur filler was the atmospheric corrosion.E301 Superheater expansion joint is subjected to the sulphur corrosion by sulfur steam and produced sulfide at high temperature. Afterwards the sulfide reacted with sulfuric acid and caused sulfide cracking corrosion. Chemical corrosion happened in E303 medium temperature superheater by its working conditions. E304 heat pipe economizer is subjected to dew point corrosion caused by sulfuric acid by the inappropriate selection of equipment constructive steel, the unreasonable design of the equipment and the poor control of the production process. By immersion and electrochemical tests, it is found that when sulfuric acid concentration is lower than 60wt%, the corrosion rate of the metal increases with risen of temperature and concentration. ND steel and 316L have better corrosion resistance than carbon steel Q235 and 20 # steel. It was found that at 20℃, 316L has excellent corrosion resistance in all different concentrations of sulfuric acids. ND steel has better corrosion resistance than 316L in sulfuric acid at 60℃. in all kinds of tests, Q235 is superior to 20 # steel in corrosion resistance. But when ND steel, 316L attach to general structural steel such as 20# and Q235A in sulfuric acid, the galvanic corrosion will lower the corrosion resistance of the alloy steel, and increase the corrosion rate of the alloy steel, indicating that galvanic corrosion does weaken the corrosion resistance of all the tested steels.Against the mechanisms of the corrosion and causes of the corrosion, Anti-corrosion measurements are put forward in this paper. A Further look in relating research has been proposed in the end of this article.更多还原