Refinery gas upgrading via partial condensation and PSA
A process and system for recovering valuable by-products (e.g., hydrogen) from refinery gas streams. For hydrogen-only recovery, the invention comprises a partial condensation step to upgrade the refinery fuel gas to a minimum of 60% hydrogen, which is further purified in a pressure swing adsorption process. When configured to recover hydrogen, methane-rich gas and raw LPG (methane depleted gas containing C2 hydrocarbons and heavier), the invention comprises two partial condensation steps where the feed is cooled in the first step to allow separation of ethane and heavier hydrocarbons, and the resulting vapor is cooled to a lower temperature in a second step for hydrogen recovery.
1. A process for recovering high purity hydrogen from a feed gas containing less than 50 mole % hydrogen comprising the steps of:
a) cooling a feed gas in one or more heat exchangers and producing a partially condensed feed gas;
b) separating the partially condensed feed gas to produce a hydrogen-rich stream and a hydrocarbon-rich stream;
c) generating refrigeration by Joule-Thomson expansion of the hydrocarbon-rich stream and producing a colder hydrocarbon-rich stream;
d) recovering refrigeration from the colder hydrocarbon-rich stream to cool the feed gas in step (a);
e) recovering refrigeration from the hydrogen-rich stream to cool the feed gas in step (a);
f) recovering a gas stream containing at least 60 mole % hydrogen from the hydrogen-rich stream; and
g) feeding the gas stream containing at least 60 mole % hydrogen to a pressure swing adsorption (PSA) system and recovering high purity hydrogen product with or without feeding an external hydrogen-containing stream to the PSA system.
2. The process of claim 1 , wherein in step (g), a low pressure tailgas comprising methane, residual hydrogen and other non-readily condensable compounds leaves the PSA system.
3. The process of claim 1 , wherein the feed gas contains between 30-50 mole % hydrogen.
4. The process of claim 3 , wherein the feed gas is at a temperature of about 100° F. and 50-120 psia.
5. The process of claim 1 , wherein the high purity hydrogen product contains at least 99 mole % hydrogen.