Hydrogen recovery captures the hydrogen from refinery gas streams coming from the hydrotreaters and hydrocracker.

There are three common methods for hydrogen recovery:

• Cryogenic hydrogen recovery - the gas mixture is cooled to the point that the non-hydrogen components drop out as a liquid, allowing separation from the hydrogen

• Pressure swing adsorption (PSA) - the gas mixture is passed through a molecular sieve solid adsorbant, which adsorbs the hydrocarbon and allows the hydrogen to pass through.

• Membrane diffusion - the gas mixture is separated by using pressure to force the hydrogen through a membrane that is hydrogen permeable but not permeable to large hydrocarbons