Study On The Influence And Elimination Of Sulfide And Methane In Rectisol Process

Rectisol is a method of mature and effective physical adsorption from acidic gas.The origin is about around the 1950s.This process takes advantage of the large difference in solubility between acid gas and effective gas in low-temperature methanol solution,and uses low-temperature methanol as a solvent to deeply remove sulfide and carbon dioxide in the gas.It is mainly composed of absorption,relief,regeneration,and recycling systems.Compared with other physical solvents,methanol has higher selectivity for acid components,requires less solvents,and the required operating costs are lower,so it is widely used in the field of gas purification.During the operation of a factory rectisol process,there are problems such as sulfide,methane,and carbon monoxide in carbon dioxide emissions in the operation of carbon dioxide emissions.As a result,the gas content in the carbon dioxide product gas of the plant does not meet the process requirements and contains too much sulfide and methane gas.The original process flow needs to be reformed to eliminate the influence of methanol and discharged impurities.First,the Aspen Plus software was used to simulate the actual working conditions of the plant’s rectisol process based on the PSRK physical property method.The obtained simulated values were in good agreement with the actual production data of the plant,verifying the reliability of the simulation process.Analyze the existing relevant problems of the plant,add sulfur-free methanol flash tank,flash steam compressor,flash steam inlet and outlet heat exchanger and lean methanol/semi lean liquid heat exchanger on the basis of the original process flow,and determine the optimal parameters of the revamped unit through sensitivity analysis.After the transformation,the temperature of the lean methanol liquid is-51.01℃,and the temperature of the methanol semi-lean liquid is-45.57℃,which reduces the methanol circulation in the system,reduces the system temperature,and restores the original design capacity.The mole fraction of CO₂ in the carbon dioxide exhaust gas increased to 98.17%,the mole fraction of CH₄ was reduced to 0.49%,the mole fraction of H₂S was reduced to 70 ppm,and the mole fraction of CO was reduced to 0.09%,all meeting the process requirements and reducing the waste of effective gas.Finally,Aspen Energy Analyzer is used to analyze and optimize the heat exchange network of the transformed process.The design and transformation scheme effectively solves the problem of excessive effective gas component methane and acid gas component hydrogen sulfide in carbon dioxide product gas,matches the temperature of methanol liquid and methanol semi-lean liquid with the process design value,increases the purification capacity of the absorption tower,and lays a foundation for the subsequent reduction of methanol solution circulation.The reconstruction plan in this paper adds less equipment and investment,retains the original equipment and does not make major changes to the relevant pipelines.The reconstruction scheme is simple and easy to implement,which ensures the integrity of the original process to a certain extent.It provides some guidance for the actual production transformation of the factory.