蒸发汽堤塔塔顶真空系统的腐蚀原因分析及对策

Corrosion Analysis of Vacuum Evaporation Tower and Countermeasures

调查白土精制装置蒸发塔真空系统的运行状况,发现真空系统塔顶馏出油线、塔顶冷却器、馏油罐出现严重的腐蚀。冷却器不锈钢管束前后出现腐蚀穿孔3次,堵管12根,冷却器壳体上部有均匀褐色垢,垢厚约1 mm。通过分析,查明了白土装置蒸发汽提塔真空系统腐蚀的原因和腐蚀介质的来源。从腐蚀调查看来,白土本身成酸性,且含有硫酸根、氯离子等杂质,这些物质在白土精制过程中,会由加工处理的油品带出,并溶于水中,形成低浓度的硫酸、盐酸的混合水溶液是导致蒸发塔顶真空系统严重腐蚀的根源。为了降低腐蚀对设备的危害,从设备和工艺方面进行了防护:增加涂料防护、材质升级;变更工艺流程和注入缓释剂等。工业应用效果说明,这些措施很好地解决了影响装置安全生产的设备腐蚀问题。

The investigation of the vacuum system operation of evaporation tower in the clay refining unit found serious corrosion in the overhead distillate oil line, overhead cooler and oil drum. The stainless steel tubes failed 3 times, 12 tubes were plugged and uniform fouling about 1 mm thick was deposited on the shell of the overhead cooler. The detailed field investigation of corrosion, corrosion detection and corrosion analysis have identified the causes of corrosion in the vacuum condensing system of evaporation tower and sources of corrosive media. The clay is acidic and contains impurities such as sulfate radicals and chloride ions, etc. All these impurities will be brought out with oil effluent in the white clay refining process and be dissolved in the water, forming the mixture of low - concentration sulfuric acid and hydrofluoric acid. This leads to serious overhead corrosion of vacuum evaporation tower. To reduce the corrosion damage to equipment, anti - corrosion coatings and anti - corrosion measures are proposed in respect of upgrading the material of equipment, improvement of process and injection of corrosion inhibitor, etc. The commercial operation has shown that these measures are very effective in the control of equipment corrosion in the unit.