Two-Stage Clathrate Hydrate/Membrane Process for Precombustion Capture of Carbon Dioxide and Hydrogen

A hybrid process for the capture of CO2 and H2 from a treated fuel gas mixture is presented. It consists of two hydrate crystallization stages operating at 273.7 K and 3.8 and 3.5 MPa, respectively. The CO2-lean stream from the first stage is directed to a membrane separation unit whereas the CO2-rich one is directed to the second hydrate stage. These operating pressures at the crystalli- zation stages are possible by adding 2.5% by mole propane. Propane enables the reduction in the hydrate formation pressure and thus reduces the cost associated with the compression of the fuel gas. The two hydrate stages would operate at 7.5 and 3.5 MPa without adding propane. This work provides the relevant kinetic data, as well as the separation efficiency and recoveries achieved.