Basic Study On Gas Separation Technology Based On The Formation Of TBAB Semiclathrate

Hydrate-based gas separation technology has been widely concerned because of its mild operating conditions,simple technological process and low cost and environmental working medium.Hydrate additive tetrabutyl ammonium bromide?TBAB?as a kind of less volatile quaternary ammonium salt can form semiclahrate with specified gas molecules within the scope of the moderate temperature and pressure is the most widely used thermodynamic promoter.There are a lot of studies using TBAB in the literature on hydration separation,but most of them are experimental studies,and the research on model of hydration separation process is still relatively rare.At present,most hydration separation experiments are still carried out in the phase equilibrium reactor,which has certain limitations and cannot reflect continuous industrial process.However,few reports have been reported on the hydration separation under continuous flow condition,and the reactor type adopted is relatively limited,and the separation performance is not satisfactory.The above problems need to be solved urgently in order to make the hydrate separation technology closer to industrialization.In view of the above problems,this paper has developed flash models for predicting the separation performance and studied the continuous separation using two types of reactors.The specific contents are as follows:?1?The thermodynamic model of TBAB semiclathrate is the basis of the calculation of hydration separation process.In this paper,thermodynamic model is developed.The Patel-Teja equation of state?PT EOS?combined with a Debye-Hückel electrostatic term is chosen to describe the fugacity of TBAB in aqueous solution and calculated gas solubility in aqueous phase.The Chen-Guo hydrate model is extended to calculate the fugacity of TBAB in semiclathrate phase.?2?Phase equilibrium experiments for CO₂+TBAB system are conducted.The influence of TBAB concentration,pressure and temperature upon the hydrate formation process and GSCH is systematically investigated.To quantitatively describe the gas consumption ability of semiclathrate slurry,a new concept,i.e.,the apparent liquid phase,is introduced.A algorithm coupled with modified Patel-Teja equation of state and Chen-Guo hydrate model is developed to conduct vapor-liquid-semiclathrate multiphase flash calculation for TBAB containing systems at constant temperature and pressure.?3?Phase equilibrium experiments for CO₂+TBAB system are conducted in the presence of acid gas solvent dimethyl sulfoxide?DMSO?and propylene carbonate?PC?.The results show that the addition of DMSO and PC improves the pressure for the formation of TBAB hydrate.When the addition amount is high,the induction time of hydrate will be increased and the rate of hydrate formation will be reduced.?4?Equilibrium separation experiments for CO₂+N₂+TBAB and CO₂+H₂+TBAB system are conducted.The influence of initial gas liquid ratio,pressure and temperature upon separation performance is systematically investigated.A new algorithm for flash calculation at constant volume and temperature is developed through the“pressure transferred”method.The separation performance can be predicted using this model.And the calculation results are satisfactory.?5?A tubular hydration reactor is designed and built in this paper.A venturi tube is used as gas-liquid mixer.Stable continuous separation has been realized in the form of gas-liquid co-current contact.The experimental results show that for flue gas,the concentration of CO₂ can be increased to more than 95%,and the recovery rate of CO₂is 38.99%after 4 stage separation.For IGCC fuel gas,the CO₂ concentration can be increased to 76.70-88.88%after one stage separation,indicating a good industrial application prospect.?6?Based on the thermodynamic model of TBAB semiclathrate,a kinetic model for TBAB hydrate formation is established using the fugacity difference as driving force of hydration reaction.Based on the assumption of plug flow in tubular reactor,the micro elements model for continuous separation is established.The calculation results are satisfactory.?7?The conditions to form the CH₄+H₂+TBAB hydrate are measured.Single-stage equilibrium separation experiments toward CH₄+H₂ mixture are conducted.The influence of initial pressure,temperature,and initial gas liquid volume ratio are systematically optimized.The continuous separation experiments of CH₄+H₂ binary mixture and hydrogenation plant off-gas are conducted using a set of laboratory-scale continuous stirred reactor according to the optimized conditions,in which the effects of pressure and liquid flow rate upon continuous separation were further studied.The experimental results that the H₂ concentration in the unhydrated gas?the recovered gas?is up to 90 mol%indicate the efficiency to recover H₂ using continuous hydrate separation,which lays the foundation for further industrial application.