The Hydrate Method Captures CO₂ Thermodynamic Model And Kinetic Experiment Research

At present,the greenhouse effect has become one of the most serious environmental problems facing mankind.As the main greenhouse gas,CO2 has caused more than 60%of the global greenhouse effect.According to statistics,75%of CO2 comes from the combustion of fossil fuels,but the demand for fossil fuels in various countries is increasing.Therefore,CO2 capture is the main measure to deal with greenhouse effect.The main CO2 capture processes are post-combustion capture,pre-combustion capture and oxy-fuel combustion.Commonly used CO2 separation techniques include adsorption,absorption,membrane separation and so on.Recently,as a new separation method,hydrate based separation method(HBGS)has become a hot topic for its advantages of low energy consumption and simple operation.To the current research on HBGS,thermodynamic model is not accurate enough,and there is no systematic dynamic data.Therefore this paper established the thermodynamic model for post-combustion CO2 capture and pre-combustion CO2 capture by HBGS to obtain better calculation accuracy,and studied effects of thermodynamic and kinetic accelerator.To the thermodynamic model for post-combustion CO2 capture,firstly on the base of vdW-P hydrate phase equilibrium model,developed a thermodynamic model for post-combustion CO2 capture combined DA equation and PR equation.The model used two correlation coefficient Cc,Kc,w to describe the association effect between CO2 and H2O molecules.Phase equilibrium data of CO2+H2O system was used to fit the value Cc,Kc,w.And the solubility data of CO2+H2O and N2+H2O systems was used to fit the binary interaction parameters of PR equation,verifying its accuracy by comparing calculated value and experimental value.Calculate the phase equilibrium condition of CO2+N2 mixture with different initial concentrations at different temperatures by fitted model and the reported model without association effect between CO2 and H2O molecules and compared with experimental value.It was found that the new fitting model had a better accuracy.Aiming at the thermodynamic model for pre-combustion CO2 capture,the solubility data of H2+H2O system was used to fit the binary interaction parameters of PR equation,verifying its accuracy by comparing calculated value and experimental value.Calculate the phase equilibrium condition of CO2+H2 mixture with different initial concentrations at different temperatures by fitted model and the reported model without the association effect between CO2 and H2O molecules and compared with experimental value.It was found that the new fitting model had a better accuracy.A stirred-kettle hydrate production experimental device was used to study effects of dynamic accelerator SDS(twelve sodium dodecyl sulfate)and thermodynamic accelerator THF(tetrahydrofuran)on CO2 capture from flue gas by HGBS.Effects of different concentrations of SDS and THF on the separation effect were studied.On this basis,effects of different initial pressures and different reaction temperatures on the separation efficiency were studied.The results showed that both SDS and THF can increase the CO2 recovery,but simultaneously reduce the separation factor.Under experimental conditions,more appropriate concentrations of SDS and THF were 0.01wt%～0.05wt%and 0.5mol%～2mol%,respectively.The initial pressure increase can effectively shorten the hydration induction time,increase the gas storage density,CO2 recovery and separation factor.Reducing the temperature can effectively improve the separation efficiency.