The Simulation And Development Of A Revamped Rectisol Process For Increase Of A Plant

Rectisol process,which uses methanol as an absorbent,absorbs selectively acid gases such as CO₂ and H₂S under low temperature and high pressure conditions.Later,CO₂ and H₂S are desorbed successively from rich methanol to other processes,and methanol is used circularly.The process is widely used in many fields such as coal to methanol,coal to synthetic natural gas and coal to synthetic ammonia on account of its strong absorption、excellent selectivity and high purification.According to the statistics,Rectisol process is the most widely used among numerous methods of desulfurization of decarburization。A factory puts forward a plan of production expansion and transformation,which BGL gas volume will be increased by 20%on the premise of using the original device as far as possible and ensuring the component content of main streams to meet the standard.To achieve this objective,the actual working condition of the original rectisol process is simulated by using Aspen Plus on the basis of the property method PSRK firstly.The simulation results of main streams match well to the actual operation data,so the original flow is well restored.Later,a revamping scheme based on above is proposed as follows:two heat exchagers are added to precool feed gas.A nitrogen stripping tower is also added to strip the dissolved acid gas contained in the methanol in the absorber,with both the temperature and the content of CO₂ in the methanol are reduced,which leads to an obviously increasing absorption capacity of methanol.The methanol striped is transported to the absorber by adding a feed pump.Meanwhile,the optimal parameters are determined by sensitivity analysis,i.e.,300kmol/h feed flow of N₂,7 theoretical stages and 0.020 of split ratio.After the reform above,the product streams conform to process requirements and the goal of expanding production by 20%is achieved.Finally,the preliminary design of the newly added equipment is done,which provides a reference for the equipment selection.The original equipments are remained rationally and less equipment is added,which the reformation is completed in a relatively short time。The energy consumption did not change significantly as the methanol circulation keeps constant.The work provides guidance for the actual expansion revamp of the plant.