Development Of Unshifted-gas Rectisol Process

Rectisol process has played an important role in coal chemical purification since 1950 s,due to its high selectivity,high purification and low energy consumption.By taking advantage of methanol's property,this physical absorption method not only removes impurity gases(like CO2,H2 S,COS),but also recovers recyclable gases(like H2,CO,CH4),and this is of great application value.Meanwhile,the development of rectisol processes to fulfill the requirements of various feed-gas situations also makes remarkable progress.The present work targets at developing a rectisol process with unshifted-gas as feed gas,which only has half of the CO2 content of the ordinary feed-gas.As the desorption of CO2 from methanol is the chief source of refrigeration capacity,the feature of unshifted-gas,i.e.,its low CO2 content,always leads to an over-high temperature of the rectisol system when applied in regular rectisol process.Thus,regular rectisol process can't satisfy its low-temperature requirements,which in turn always ends up with impure product and high energy consumption.To solve this problem,we developed two sets of rectisol processes based on one-step rectisol technology by using Aspen Plus software.Firstly,PSRK was selected as property method,which was appropriate renovated to meet the practical situations,with suitable simulative models chosen.Secondly,two sets of rectisol processes were developed,where in process I the C3H6 compression refrigeration was included,whereas in process II the CO2/NH3 cascade compression refrigeration was incorporated,respectively.Through the analysis of parameters by sensitivity analysis method and design spec method,it's found that both processes satisfied the technical requirements.Thirdly,for each process,the refrigeration system with different refrigerants was simulated,with its heat exchanger networks matched based upon refrigerant performance coefficient.Lastly,a comparison of the rectisol processes' purification and energy consumption was come out.Two feasible unshifted-gas rectisol processes,for the first time,were developed by principle analysis and process simulation.Different from the ordinary methods which focus on the optimization of certain devices structure,this work employed different refrigerants to make sure of the relatively low-temperature running circumstance of the system.It's also found that process II achieves higher purification and lower energy consumption than process I by comparison.The two rectisol processes we developed both succeed in overcoming the limitations ofspecial feed gas,which provide not only theoretical guiding,but also solid fundamental base for industrial application with broad prospect.