Study On Hydrate-Based Carbon Dioxide Separation From Simulated Fuel Gas

Hydrate based gas separation is one of the potential methods of carbon dioxide capture from fuel gases (CO2/H2) for integrated coal gasification combined cycle (IGCC) power plant. In this study, an experimental platform was built up to study the hydrate formation and dissociation processes, and the influences of porous properties, tetrahydrofuran (THF) concentration, sodium dodecyl sulfate (SDS) concentration on hydrate phase equilibria, gas consumption and gas separation are experimentally investigated. The magnetic resonance imaging (MRI) plantform was also used to study the hydrate formation processes when the gas mixture was in the flow. This work can provide a theory basis and fundamental information for the hydrate based CO2separation process.The phase equilibria data of the hydrate with the additives mixture (1,2,3and4mol%tetrahydrofuran (THF), with1000mg/L sodium dodecyl sulphate) were gotten in the paper. An increasing THF concentration increases the driving force for hydrate formation and decreases the hydrate induction time. The presence of THF results in a drastic decrease of the hydrate phase equilibrium pressure. Higher THF concentrations correspond to lower hydrate phase equilibrium pressures. When the THF concentration is1mol%, the structural transition (s-II to s-I) caused the’"pseudo-retrograde" behaviour.With the increase of glass beads size, the hydrate phase equilibrium conditions moves to moderate directions, the gas consumption gets bigger and the CO2recovery gets larger. The hydrate phase equilibrium conditions get harder, and the gas separation effects become better in silica gel. The presence of THF moderates the hydrate formation conditions by forming structure II hydrates. When the THF concentration is3mol%, the gas separation effect is the best. Change of the SDS concentration does not influence the hydrate phase equilibria. The hydrate phase equilibrium pressure increases with the rise of initial pressure. When driving force increases, the gas consumption gets larger, but the gas separation effect gets worse.When the gas mixture was in the flow, hydrates formed or dissociated rapidly with pressurization or depressurization. Hydrate blockage often appeared in the cycles which should be avoided for industrial utilization. Hydrates formed firstly near the axis and the dissociation process near the axis took place finally. The formation and dissociation distribution was not homogeneous, a large amount of gas consumed and discharged in the process and caused the increase and descrease of the MI. The separation effect when in the BZ-01glass beads is the best of all; the CO2concentration and hydrate saturation both increased with the increase of pressure; the flow rates didn’t have remarkable impact on the final result.