Biogas purification via sII hydrates in the presence of THF and DMSO solutions using MD simulations

Abstract

Biogas is the result of the biological degradation of organic waste and consists mainly of a mixture of different gases, including CH4 and CO2. Both gases, if they could be separated from the mixture, can be used in different industrial applications, but above all it is of particular interest to investigate alternatives that allow enriching in CH4 the biogas and thus increasing its calorific value. In this work the main objectives are to study the formation of gas hydrates as a means of purification of biogas via Molecular Dynamics simulations, analyzing the effect of adding two promoters on the thermodynamic conditions of the formation of gas hydrates and the degree of purification of the gaseous mixture. The main results obtained indicate that the ratio CH4/CO2, for the sII hydrates, is increased from 1.06 when only the promoter THF is used to 1.34 when the two promoters THF (tetrahydrofuran) and DMSO (dimethyl sulfoxide) are used for the thermodynamic conditions analyzed. The fraction of CH4 in the gas region changes from 0.6% mol to 0.66% mol when sII hydrates are formed in the presence of the analyzed promoters. Additionally, the results of the MD simulations coincide in the experimental tendency to displace the coexistence curve to higher temperature conditions with the use of the promoters.