Study On The Solubility Of Carbon Dioxide In Hydrocarbons At High Pressures And Temperatures

The phase equilibrium data of CO₂-hydrocarbon mixtures provide basic data for the design and processes of carbon dioxide flooding,coal liquefaction,and supercritical extraction.In particular,carbon dioxide flooding technology has received extensive attention.Carbon dioxide flooding technology can bury carbon dioxide to reduce the greenhouse effect and increase the crude oil recovery rate.At present,a lot of phase equilibrium data of CO₂-hydrocarbon binary mixtures have been measured and the multicomponent phase equilibrium data are scarce,so the phase equilibrium data that have been measured are still unable to meet the requirements of carbon dioxide flooding technology.It is of great significance to use the existing binary phase equilibrium data to develop the equation of states in order to accurately calculate the phase equilibrium data of binary and multicomponent mixtures by interpolating or extrapolating the equation of states for the development and application of carbon dioxide flooding technology.A large number of phase equilibrium data of CO₂-hydrocarbon mixtures were collected,including 36 CO₂-hygrocarbon binary mixtures,a total of 6600 data and six ternary mixtures a total of 247 data.Qualitative and quantitative analysis about the solubility of carbon dioxide in hydrocarbons was performed using solubility data reported in the literatures.In addition,the apparatus was designed to measure the phase equilibrium data at high temperatures and pressures using visual synthesis method,it was tested and phase equilibrium data of CO₂-n-hexane binary mixture were measured using this apparatus and compared with the experimental data in the literature to verify the feasibility of the apparatus.The phase equilibrium data of CO₂-n-hexane-n-tetradecane ternary mixture was determined by this apparatus and was calculated by models in this research.In order to calculate the phase equilibrium data easily and improve the calculation accuracy of models,the PR-BM EOS and PR EOS and the model PRMHV2 were improved in this paper.The phase equilibrium data were calculated by the improved models and many sets of interaction parameters were obtained.The results calculated by the improved models are compared with the results calculated by the models such as PPR78,PSRK,PR-LCVM-UNIFAC in the literatures.The results show that the model PR-BM EOS,PR EOS and PR-MHV2-NRTL perform better than these group contribution models and can be interpolated and extrapolated to calculate phase equilibrium data at other temperatures and pressures.Finally,phase equilibrium data of four ternary mixtures CO₂-n-butane-n-decane,CO₂-n-hexane-n-decane,CO₂-n-octane-n-decane and CO₂-n-hexane-n-tetradecane were selected to verify accuracy of the improved model for calculating the phase equilibrium data of the multicomponent mixtures.The results show that the improved models calculate the ternary phase equilibrium data accurately.It is feasible to use the binary interaction parameters to calculate phase equilibrium data of the ternary mixtures.