Analysis Of The Causes And Countermeasures To The Corrosion Mechanism Of Low-temperature Methanol Wash Device Low Alloy Steel

The purification unit of the synthetic ammonia installation in the First Fertelizer Plant had been introduced into China from German.The materials of equipments were composed of carbon steel such as10Nil4、TTST35N. The features of the process fluids were high pressure, low temperature, inflammable, flammable and noxious. The purification unit had been in motion under the circumstances of high pressure, low temperature and high sulphur for twenty years since1985. The wall thickness of pipelines was thin according to the design of German standard. Recently, the high-pressure process pipeline and appliance and fittings were leaked verb many times along with the aging of the unit, which had posed great threats to high load of the unit, long-periodic safe in operation, the life safety of the operators and maintainers.At the same time, the environment was polluted to some extent and the safety, environmental protection and high-benefit developing of the enterprise had been brought adverse impact. Improving the fatal and potential safety hazard of equipments and pipelines was the most important task which might be an oncoming train.The paper made a summary, carried on field research, collected parameters of apparatus and inquired information and drawing on account of leakage of equipments which had happened recently. Referring to the technical papers concerning the metallic corrosion of the low alloy steel in the Rectisol unit, the paper made a comprehensive analysis of the running conditions of quipments and pipelines in the Rectisol unit and arrived at a conclusion that the low alloy steel had produced internal corrosion under the circumstance of a humid hydrogen sulphide and oxygen in the low alloy steel was unpolarizing which had made quipments and pipelines corrosion cracking in the Rectisol unit. Solutions were brought forward in the end.By putting the solutions into effect, the original materials of equipments were upgraded and localized production.After four hundred and eighty nine potential safety hazards had been eliminated, the high-pressure process pipeline and appliance and fittings were never leaked verb up to the present.