EOR Associated Gas Cryogenic Separation CO 2 Recovery Process Improvement Research

With the exploitation of old oilfields,some of them use CO₂-EOR to increase production.The equipment investment and operation cost of conventional CO₂ recovery process is quite high,but the product recovery rate is low.It is necessary to carry on the research to inventa high efficiency process.Based on the study of the traditional Ryan/Holmes process,this paper puts forward an integrated separation process with low-temperature separation and Selexol,which possesses a certain reference value for the research of CO₂ recoveryof EOR associated gas in China.First of all,The CO₂ content and components changes of EOR associated gas in Shengli Oilfield has been analyzed in order to compare the principle,characteristics and application range of chemical absorption,physical absorption,Ryan/Holmes low temperature separation process,membrane separation and integrated separation process.From the process characteristics,unit product energy consumption,production costs and so on,the integrated separation process isdetermined to be the research direction in this paper.Based on the study of the formation mechanism of CO₂-CH₄ system,it is found that the prediction accuracy of Aspen HYSYS is higher and the PR equation is more suitable.At the same time,the refrigeration method available for CO₂ gas was analyzed,and the method of preventing the formation of frozen plug was put forward.The formation mechanism of the azeotrope of CO₂-C2H6 system was studied.It was found that we can not change the operating conditions to achieve azeotropic separation.The greater the amount of additive added,the heavier the composition,the better the separation effect.The results show that liquid-liquid extraction and stripping can effectively separate the azeotrope.By studying the effect of C2H6 on the performance of the solvent,it is found that the Selexol is improved but the performance of activated MDEA is reduced.Through the analysis of Ryan/Homles three-tower and the four-tower process,the key parameters are analyzed and optimized,and the traditional process can achieve a high CO₂,CH₄ recovery and product yield,but the comprehensive energy consumption is too high and the traditional low temperature separation process was improved by the side line extraction,increasing the dosage of demethanizer,the use of multi-point feed and increasing the intermediate reboiler.By analyzing reasons of the high energy consumption of traditional low temperature separation process,the multi-stage supercharging module,CO₂ gas TEG dehydration process module,low temperature separation pretreatment process module and improved solvent absorption process module were designed and studied.The results show that the low-temperature separation + Selexol process is 36.76%lower than the comprehensive energy consumption of the four-tower process,and the yield is greatly improved by 3 times compared with the traditional process,and the low-temperature separation + Selexol process is determined by the separation process performance,energy consumption and production cost to be the best EOR associated gas treatment process.Finally,through an example study of the Wasson Denver CO₂ recovery unit,it was found that the comprehensive energy consumption decreased by 9.47%,the amount of CO₂ was increased by 13.3 t/d and the methane,LPG and light hydrocarbon production improve.The integrated separation process could not be used with LNG liquefaction device,the adaptability has improved.It is proved that the low temperature separation + Selexol process is proved to be good process performance and excellent development prospect.