Study On The Performance Of Hydrate-based Carbon Dioxide And Methane Separation By Adding Tert-butanol Or 1,1-Dichloro-1-fluoroethane

The hydrate-based gas separation method is a new separation technology with the advantages of simple operation,no pollution,small footprint,etc,which has been proven to be useful for CO₂/CH₄ mixure separation.However,there are still many problems in this technique,such as harsh operating conditions and poor separation efficiency.For the requirements of mild separation operating conditions and high separation efficiency of hydrate-based CO₂/CH₄ mixture separation technology,tert-butanol（tBA）and1,1-Dichloro-1-fluoroethane（HCFC-141b）were used as hydrate-based CO₂/CH₄ separation promoters in this paper.The effects of tBA or HCFC-141b on the phase equilibrium conditions of CO₂/CH₄ hydrate were measured,and the operation conditions and separation efficiency of hydrate-based CO₂/CH₄ mixture separation with the presence of tBA or HCFC-141b were investigated.Firstly,the hydrate phase equilibrium conditions of CH₄,33.00 mol%CO₂/CH₄ and50.00 mol%CO₂/CH₄ with the presence of single tBA and HCFC-141b were determined by isochoric pressure-search method.The measured phase equilibrium temperature range in the presence of tBA was 276.8²87.9 K,and the pressure range was 1.98⁷.74 MPa.With the presence of HCFC-141b,the measured phase equilibrium temperature range was 283.0²94.2 K and the pressure range was 0.10¹.62 MPa.The results showed that both tBA and HCFC-141b had a promotion effect on the formation of CH₄ and CO₂/CH₄ hydrate,but the promotion effect of tBA was weaker than that of HCFC-141b.Next,the effect of single HCFC-141b and tBA on the hydrate-based CO₂/CH₄ mixture separation was studied,and the separation mechanism was analyzed.The results showed that with the presence of tBA,the CH₄ concentration in gas phase increased from 67.00 mol%to89.02 mol%with solution injection pressure-recovery method,and the separation factor was9.34.For 50.00 mol%CO₂/CH₄ mixture,the concentration of CH₄ in hydrate phase reached71.00 mol%with a gas injection pressure-recovery method,and the separation factor was 2.33.With the presence of HCFC-141b,the CH₄ concentration in gas phase was up to 98.01 mol%for the 33.00 mol%CO₂/CH₄ mixture,and the maximum separation factor was 61.38,which was about 4 times that when using TBAB as an additive;the maximum space velocity of reactor was 14.45 h^-1,which was about 3.9 times that when using TBAB.For the 50.00 mol%CO₂/CH₄ mixture,the CH₄ concentration in the gas phase was increased to 92.76 mol%,and the maximum separation factor was 29.18,which was about 7.1 times that when using THF as a promoter.The space velocity of reactor was 19.55 h^-1,which was about 7.5 times that when using THF.The results of this study indicated that HCFC-141b could be used as an additive for hydrate-based CO₂/CH₄ mixture separation to efficiently and rapidly separate CO₂/CH₄ under mild conditions,providing a good theoretical guidance for the industrial application of hydrate-based CO₂/CH₄ mixture separation technology.