Hydrate-Based Separation for Industrial Gas Mixtures

Abstract

The removal of acidic gases and impurities from gas mixtures is a critical operation in the oil and gas industry. Several separation techniques, e.g., cryogenic fractionation, polymeric membranes, zeolites, and metal–organic frameworks, are employed to treat gas mixtures depending upon the nature of separation and contaminants present in the gas mixtures. However, removing N2, H2, H2S, and CO2 contents from industrial gas mixtures is a challenging step due to economic factors, high energy consumption, and effective separation. Hydrate-based separation for selective gas removal is a promising and efficient separation technique over a range of temperatures, pressures, and acidic gas contents. The enclathration of CO2, H2, N2, H2S, and other natural gas constituents effectively removes acidic gases and other contaminants from process gas streams. This work presents a novel process design to remove acidic gases and other contaminants from industrial waste gases and natural gas mixtures to achieve the desired selectivity in gas mixtures. Multi-phase equilibria calculations were also performed for various binary and ternary gas mixtures (e.g., CO2 + CH4, H2S + CH4, CO2 + N2, CH4 + CO2 + H2S, and CO2 + H2S + N2) over a range of compositions and T, P conditions. The former calculations established the suitable region in terms of temperature and pressure for adequate separations. To determine the optimal process conditions (T & P) for efficient separation, fractional cage occupancy and gas mole fraction in each phase were also computed. A detailed analysis of the hydrate-based separation shows that the number of stages necessary for desired separation efficiency depends on the nature of the gas mixture and hydrate stability.