The hydrate-based gas separation of hydrogen and ethylene from fluid catalytic cracking dry gas in presence of Poly (sodium 4-styrenesulfonate)

Abstract

The effects of the influential factors (initial promoter concentration in liquid phase, initial ratio of the volumes of gas to liquid (IFL) and temperature) on the hydrate-based gas separation (HBGS) and their relationships with the conversion rate of the water into hydrate (RHW) were experimentally investigated. Poly (sodium 4-styrenesulfonate) (PSS) was first-time used in HBGS. After one-stage HBGS, hydrogen can be concentrated from 26.0 mol% to more than 45.9 mol% in the residual gas and ethylene can be concentrated from 52.0 mol% to more than 72.6 mol% in the dissociated gas. PSS had low foaming ability, it effectively decreased the gas–liquid interfacial tension and had little effect on the thermodynamic equilibrium hydrate formation condition. PSS had little effect on the separation performance when RHW was about 13% whereas it significantly improved the separation performance when RHW was higher than 59%, the optimum PSS concentration was 0.2 mass%. In the separation in presence of PSS, the increase in IFL did not cause a decrease in the separation performance until IFL increased to more than 300 NL/L. The positive effect of decreasing temperature on HBGS decreased with the increase in RHW, and it disappeared in the HBGS using pure water when RHW was higher than 57.0% whereas it still existed in the HBGS using PSS solution when RHW was 67.8%. An innovative model was established to predict the equilibrium hydrate formation pressure, and the average relative deviation was 2.6%, with the maximum relative deviation being 5.5%.