Hydrate formation in i-butane- n-butane or a butene isomer water system at a given temperature

Abstract

In this study- it was first confirmed experimentally that of the four-carbon hydrocarbons, only i-butane seems to be able to form solid hydrate by itself in coexistence with an aqueous phase. Then similar experiments with i-butanef-based binary mixtures with each of these hydrocarbons were carried out at a fixed temperature of -0.7°C. The results show that the relationships between the composition of the mixture used and the equilibrium total pressure can be found approximately by a proposed theoretical consideration. Thus, the mixtures with less than 73.8% i-butane can not form a hydrate at -0.7°C with 1.6% NaCl aqueous solution, and this limiting ratio increases with increasing temperature. For example, the following values are obtained: 84.1%, at 0.0°C and 69.5%, at -1.0°C. The mixtures containing more than the above ratios could form a solid hydrate, whose quantity was proportional to the excess of the i-butane used. Although to justify the above theory, it will be necessary to conduct further studies with propane instead of i-butane at this and/or at other temperatures, it suggests a suitable composition for the secondary refrigerant applied in the direct contact freezing process for the desalination of sea water, from the point of view of the operating pressure and the prevention of hydrate formation.