The Design Of Low-pressure Rectisol Process With Sulphur-free Feed Gas

Generally speaking, acid gases refer to sulfur oxides, nitrogen oxides, hydrogen sulfide, carbon dioxide and some other gases generated in the process of coal or natural gas conversion. In the technologies of ammonia synthesis and synthetic fuels, main raw materials include natural gas, coal, acetylene off-gas, etc. In the chemical production processes using the above raw materials, different kinds and concentrations of acid gases usually exist, which will always decrease the activity of catalysts or even worse, i.e., by inactivate them. Consequently, it is necessary to remove these acid gas components and, at the same time, recycle those useful gases before raw materials entering into the process of synthesis, to guarantee the condition of raw materials to meet the relative criterion.Presently, domestic techniques to remove acid gases include the alcohol-amine method, NHD method, rectisol and membrane separation. Among these techniques, rectisol process is comparatively mature and has been widely used in China, especially in the long run stable chemical production process. As a physical absorption method, methanol is selected as the absorbing solvent because of its advantage of great solubility of acid gases and is used to acid gas removal in the purification process of feed gas under low temperature.Chemical simulation softwares are mainly applied in the optimization of chemical process and design of new devices. With the rapid progress of the escalation of simulation softwares and the advances of technologies, some steady-state simulation results are accurate enough to test the first production line. Besides, as the chemical technologies and chemical simulation softwares are becoming more and more mature, quite a lot process simulation results can be directly used in the design of industrial devices and are able to be optimized according to the actual demands. This avoids the waste of time and resources in the process of lab and pilot tests.In this paper, the rectisol process of the feed gas (acetylene tail gas) with a low pressure of 1.9MPa is designed. Based on the strong simulation function and integrated physical prope rty database of Aspen Plus software, the whole process simulation is completed using PSRK p hysical property. An optimal designed process has obtained by deleting some unnecessary uni ts. This new rectisol process ensures the removal of some impurities in the feed gas like CO2 at a low pressure without increasing the equipment investment and utilities and expands the application field of the rectisol process.