EOR Natural Gas CO₂Seperation Process Simulation Study

As the characteristics of complex and mutable component of EOR natural gas,there’s no separation mode has been constituted to be consulted. In this paper, theseparation mode is formulated based on the deeply analysis of the characteristics of EORnatural gas and the separation process. The MDEA+MEA chemical process, low tempturefractionation process and membrane separation process is designed. The simulation ofchemical process and fractionation process is taken out with ASPEN to analyze theinteration between the process parameters, specifications of the products and separationprecess energy cost.Considering the characteristics of high and mutable CO2content, high heavyhydrocarbon content, instability flow of EOR natural gas, the characteristics, adaptiveworking condition, energy consumption and separation cost of different technology isanalyzed to formulate the separation mode. For the small-scaled, high CO2contentcondition, the membrane separation process is recommended; For the larger-scaledcondition, as the CO2content rises, MDEA mixed amine process, PSA, membraneprocess and fractionation process is suggested differentiate. The MDEA+MEA process,fractionation process and membrane process is designed aims at specific conditions,which conclude the process design, process parameters calculation and the mainequipment design.The simulation of MDEA+MEA process is taken out with Aspen Plus. The influenceof the absorption tower packing height, lean solution temperature, absorbing pressure andCO2content in lean solution on the lean solution flow rate and the influence of absorbingpressure, desorption pressure and CO2content in lean solution on the heat duty of therebioler is analyzed to draw the conclusion: The lean solution flowrate drops as thepacking height increases, lean solution temperature decreases, absorbing pressureincreases and CO2content of lean solution decreases. Within a certain range, thedesorption energy consumption drops as the absorbing pressure increases and CO2 content of lean solution decreases. As the desorption pressure increases, the desorptionenergy consumption decreases firstly and then increases. The optimized parameters of thesystem is: the absorber inlet lean solution temperature is40℃, the absorbing pressure is2.5~4.0MPa, the desorption pressure is0.12MPa and the CO2content in lean solution is0.1mol/mol.The material specifications, temperature distribution and mass distribution of thefractionating tower and stripper is analyzed by taking out the simulation of thefractionation process with HYSYS. The influence of the reboiler temperature, condensingtemperature, on-stream pressure of the fractionating tower and CO2content in feed gas onCO2purity, recovery and system energy consumption is analyzed to draw the conclusion:Within a certain range, as the demanded CO2purity and recovery rises, the reboilertemperature rises, condensing temperature drops and the system cooling energyconsumption rises. The bottom of the energy consumption is at the pressure of3.1MPaand the compressor power increases as an approximately linear relation with theon-stream pressure rises. As the CO2content in the feed gas drops, the highest CO2puritydrops and the cooling energy consumption increases.