Hydrate phase equilibrium of H-2/CH4/CO2 ternary gas mixtures and cage occupancy percentage of hydrogen molecules

摘要

Hydrogen, methane, and carbon dioxide are co-existence in many cases such as vent gas from the steam reforming of hydrocarbons. For the purpose of H-2 recovery and/or CO2 sequestration via separation technology based on hydrate, the hydrate phase equilibrium of four groups of H-2/CH4/CO2 ternary gas mixtures in pure water system were determined using the isothermal pressure-search method in a temperature range of (274.7-284.5) K. During modeling hydrate formation conditions, there is little difference with experimental data no matter whether H-2 works as a hydrate former or not. Hydrogen can be regarded as a kind of diluent gas for convenience when presetting the operation conditions. To meet the mass balance of each gas species, the cage occupancy percentages of hydrogen in hydrate have been evaluated. The result illustrates that the occupancy percentage of hydrogen molecules ranges from 0.3 to 2.3 percent in small cage and (2.16-13.6) x 10(-7) percent in large cage, which deduces that H-2 molecules are indeed trapped in hydrate solid. (C) 2015 Elsevier B.V. All rights reserved.