CO2 Separation from Natural Gas Through Hydrate Formation

Abstract

Presently, the major factor hindering the monetization of high carbon dioxide gas field is the high capital cost for the Acid Gas Removal System (AGRS). Several technologies have been evaluated by the industry so far including the membrane system and phase separation system such as cryogenic distillation. Based on the previous studies on Integrated Coal Gassification Combined Cycle (IGCC), a new model of carbon dioxide removal through the formation of carbon dioxide hydrate is proposed. The concept capitalized on the difference in the phase equilibria of carbon dioxide and the rest of the gas making up natural gas component such as methane, nitrogen and butane. Using this concept, the operating parameters are chosen to be in region of thermodynamic equilibrium of carbon dioxide, while at the same being in the hydrate dissociation region of other gas components by varying the pressure and temperature. The selectivity of carbon dioxide as the main guest molecule for the hydrate encapsulation is further promoted via the optimization of thermodynamic and kinetic properties, including the solubility of carbon dioxide in water and increasing carbon dioxide hydrate formation rate via the optimization of hydrodynamic properties. These variables are assessed in the continuous bench scale where hydrate slurries are formed in the tank reactor, and upon separation from the unreacted gas, is dissociated as the carbon dioxide rich stream. The performance indicator of the system is the amount of the carbon dioxide captured in the outlet stream compared to the feed gas. The paper discussed the separation system and its trending with operating parameters.