The Study On The Simulation And Retrofit Of The Rectisol Process Of A Plant

Ammonia industry has developed over100years of history up to now. As an important basic chemical industry, its yield of products is in the first place of various chemical products. The main raw materials of ammonia synthesis include heavy oil, coal, natural gas, naphtha etc., among which using natural gas for the ammonia synthesis equipment has lower investment, energy consumption and cost. As a result, natural gas is used as raw material for most ammonia synthesis equipments in the world. However, with the large consumption and rising price of oil, coal-to-ammonia process has aroused great attention and developed rapidly. Especially for China, the energy reserve of which is that the resources of oil and gas are far less than coal. Thus, using coal as raw material instead of oil and natural gas has become an important development direction and strategy of ammonia synthesis industry.With the constantly improvement of Rectisol technology of Linde Company and Lurgi Company, Rectisol process is widely used in the large synthetic ammonia plant as an energy-saving gas purification technology. Due to the changing of conditions and aging of the equipments in actual production, a variety of Rectisol processes are faced with problems of revamp and optimization. This work is involved to the revamp of coal replacing oil Rectisol process aiming at increasing production by adding a stream of feed gas. With the help of common chemical simulation software, after analyzing the original Rectisol process, a revamping scheme is proposed according to the conditions of the plant and the requirements of the process, which is as follows:(1) A new purification system is added:new absorption tower C208.(2) The old system is revamped:water removal of feed gas, the revamp of absorption system and medium flash system, a new added stripping tower C207, etc., all of which are purposed to decrease the temperature of circulating methanol so that a portion of poor methanol can be used in the new purification system. Therefore, the potential of original process is developed by the revamp of the old system.In this work, the whole process of original Rectisol is simulated by the common chemical simulation software. The simulation result and design data meet well, which verify the reliability of the process simulation and can provide guidance for engineering design. On this basis, the simulation of revamping process is conducted and the results of key streams can meet the technical index. By using the original equipments mostly, this revamping scheme can meet the goal of increasing production, which costs low investment and is easy to operate. The revamp scheme has been adopted by the plant and completed in a short term. Meanwhile, the design methods and measures used in the scheme can provide effective reference for other similar production expansion problems of Rectisol process.