Research On Natural Gas Dehydration Process Using [EMIM][DEP] As Dehydrant

Natural gas has been favored for its clean and efficient advantages.However,using triethylene glycol(TEG)as dehydrating solvent has many defects in the natural gas purification process.The ionic liquid has the potential to become a new type of dehydrating solvent due to its extremely low vapor pressure and good stability.In this paper,the ionic liquid [EMIM][DEP] was used as the dehydrant of natural gas dehydration process,and compared with TEG in dehydrating effect,lean solution regeneration heat load,and solvent loss.Firstly,the HYSPR and NRTL models were selected as the physical method of TEG and [EMIM][DEP] natural gas dehydration processes in the Aspen software,respectively.In the NRTL model,enthalpy of gas and liquid phase is calculated by user models.For the above two dehydration processes and their physical property models,the average relative error between simulated values and literature values is less than 4%.Then,the influence of main parameters was simulated in the natural gas dehydration process with conventional TEG regeneration.The simulation results show that increasing regeneration temperature and circulation flow rate of TEG lean solution and the number of absorption tower plate can reduce the water content of dry gas significantly,but at the same time,increase the lean solution regeneration heat load and TEG loss.When the purity of lean TEG solution obtained by conventional TEG regeneration can’t meet dew point requirement of the natural gas,stripping regeneration is required.In this paper,dry gas at the outlet of absorption tower is selected as the stripping gas,and a simulation study was conducted.The study shows that using stripping gas can reduce the water content of dry gas and TEG loss significantly and the lean solution regeneration heat load slightly.Finally,the influence of main parameters was simulated in the [EMIM][DEP] natural gas dehydration process,and the [EMIM][DEP] process was compared with two TEG ones.The influence of lean solution regeneration temperature and absorption tower plate number were consistent with the TEG process.However,the influence of lean solution circulation flow rate on the water content of dry gas is far weaker than that of the TEG lean solution,due to the extremely low vapor pressure of [EMIM][DEP] lean solution,and the water content decreases slightly as it increases.Based on the simulation study of [EMIM][DEP] natural gas dehydration,the TEG and [EMIM][DEP] dehydration processes were compared.The following results were obtained.When [EMIM][DEP] is applied to the dehydration of natural gas,its dehydration effect is close to or even better than that of TEG,and its lean solution regeneration heat load is lower significantly,with almost no absorbent loss.Compared with the TEG process,[EMIM][DEP] process is simpler because the regeneration of its lean solution only needs one flash tank.Compared with stripping gas TEG regeneration process,the amount of dry gas loss in the [EMIM][DEP] process is significantly lower.In addition,the viscosity of [EMIM][DEP] lean solution during absorption is close to that of TEG lean solution.Therefore,in summary,ionic liquid [EMIM][DEP] is a potential alternative to TEG.