A Computational Simulation Study For Techno-Economic Analysis Of Different Techniques For Natural Gas Dehydration

Natural gas(NG)is among the most used fossil fuels in industrial and domestic sectors.When extracted,it often contains water vapors,which result in the formation of hydrates,causing clogging of the pipes and valves.Furthermore,water vapors in NG can also lead to corrosion of pipelines when there is acid gas,such as H2S and CO2,existing in the NG.Hence,NG must be dehydrated before its supply to transmission lines.Several methods are available in the literature for dehydration of NG.Among them,the solvent absorption method is the most mature method.However,the conventional triethylene glycol(TEG)solvent absorption method is quite expensive and involves extensive energy consumptions and TEG loss.Therefore,the improvement of this method is the need of time.In this work,improvements of the solvent absorption method are made by introducing stripping gas process modification and ionic liquids(IL)as a new alternative solvent.Techno-economic analysis of the process has been done with the aid of Aspen HYSYS process simulation software and Aspen Process Economic Analyzer(APEA)software.This work is divided into two parts.In the first part,a techno-economic comparison of conventional NG dehydration method(CDM)has been made with a new stripping gas method(SGM).Process simulation models of both methods are developed on Aspen HYSYS.After technical and economic evaluation,SGM is proved to more feasible for NG dehydration compared to CDM.For the fixed output of dry gas,SGM can achieve 46%lower solvent rate and 42%lower reboiler duty,hence decreasing the energy consumptions involved in the process.Furthermore,economic evaluation of CDM and SGM revealed that with SGM,10%reduction in total annual operating cost and 9%reduction in total annual cost can be achieved.These results prove SGM to be technically and economically more suitable for NG dehydration.In the second part,instead of applying different process modifications,new alternative solvent,i.e.,IL EMIMNTf2,has been introduced for the absorption of water.Like the first part,the simulation model of the IL NG dehydration process is developed by Aspen HYSYS,and economic evaluations are done by APEA software.A techno-economic comparison is established between conventional TEG NG dehydration process and IL NG dehydration process.Results of the analysis reveal that,for the fixed output of dry gas,the IL process can give 56%lower solvent rate,45%lower reboiler duty,93%lower NG loss,and almost zero solvent loss compared to TEG process.Moreover,compared to the TEG process,the IL process has 12.5%lower total operating cost per annum and 9.3%lower total annual cost of the process.Hence,EMIMNTf2 is a suitable replacement of TEG for NG dehydration as it can improve the process from the technical and economic aspects.