Hydrogen separation from the H-2/N-2 mixture by using a single and multi-stage inorganic membrane

The separation characteristics of hydrogen from a gas mixture were investig ated by using a single and two-stage inorganic membrane. Three palladium im pregnated membranes were prepared by using the sol-gel, hydrolysis, and soa king-and-vapor deposition (SVD) techniques. A two-stage gas separation syst em without a recycling stream was constructed to see how much the hydrogen separation factor would be increased. Numerical simulation for the separati on system was conducted to predict the separation behavior for the multi-st age separation system and to determine the optimal operating conditions at which the highest separation factor is obtained. Gas separation through eac h prepared membrane was achieved mainly by Knudsen diffusion. The real sepa ration factor for the H-2/N-2 mixture was increased with the pressure diffe rence and temperature for a single stage, respectively. For the two-stage s eparation system, there was a maximum point at which the highest separation factor was obtained and the real hydrogen separation factor for H-2/N-2 mi xture was increased about 40 % compared with a single stage separation. The numerical simulation for the single and two-stage separation system was in a good agreement with the experimental results. By numerical simulation fo r the three-stage separation system, which has a recycle stream and three m embranes that have the same permeability and hydrogen selectivity near to t he Knudsen value, it is clear that the hydrogen separation factors for H-2/ N-2 mixture are increased from 1.8 to 3.65 and hydrogen can be concentrated up to about 80 %. The separation factors increased with increasing recycle ratio. Optimal operating conditions exist at which the maximum real separa tion factor for the gas mixture can be obtained for three-stage gas separat ion and they can be predicted successfully by numerical simulation.