Process for maximizing hydrogen recovery
The process can be used in any hydrocarbon process in which it is desirable to recover hydrogen. The process can include catalytically reforming a hydrocarbon feed, a paraffin dehydrogenation to produce light olefins or a synthesis gas generating process. There is an effluent stream having hydrogen and hydrocarbons that is first sent to an adsorption zone to produce a pure hydrogen stream and a tail gas stream. The tail gas stream is then sent across a feed side of a membrane having the feed side and a permeate side. The membrane that is selected is selective for hydrogen over one or more C1-C6 hydrocarbons and light ends including CO, CO2, N2 and O2, and withdrawing from the permeate side a permeate stream enriched in hydrogen compared with a residue stream withdrawn from the feed side. The permeate stream is then recycled to be sent through the adsorption zone.
1. A process for recovery of hydrogen, comprising:
A) obtaining a stream comprising hydrogen, hydrocarbons, carbon monoxide, carbon dioxide, oxygen and nitrogen from a reaction zone;
B) sending said stream through an adsorption zone to produce a hydrogen stream and a tail gas stream;
C) compressing the tail gas stream to at least 467 psig and passing at least a portion of the compressed tail gas stream across a feed side of a membrane having the feed side and a permeate side, and being selective for hydrogen over one or more C1-C6 hydrocarbons, carbon monoxide, carbon dioxide, oxygen and nitrogen, wherein the membrane rejects at least about 79% by mole methane of said stream obtained from the reaction zone;
D) withdrawing from the permeate side a permeate stream enriched in hydrogen compared with a residue stream withdrawn from the feed side, wherein said residue stream is sent to a product recovery section of an upstream process for additional recovery of feed and product; and
E) recycling said permeate stream into said stream from said reaction zone.
2. The process according to claim 1 , wherein the permeate stream comprises no more than about 8 percent, by mole, of nitrogen and no more than about 0.3 percent, by mole, of carbon monoxide.
3. The process according to claim 1 , wherein the permeate stream comprises no more than about 100 ppm, by mole, of nitrogen and no more than about 100 ppm, by mole, of carbon monoxide.
4. The process according to claim 1 , wherein the permeate stream comprises no more than about 20 ppm, by mole, of nitrogen and no more than about 40 ppm, by mole, of carbon monoxide.
5. The process according to claim 1 , wherein an amount of hydrogen by mole percent in the permeate stream is substantially the same as said stream from said reaction zone.
6. The process according to claim 5 , wherein the amount of hydrogen composition in the permeate stream is within about 15%, by mole, of the said stream from said reaction zone.
7. The process according to claim 5 , wherein the amount of hydrogen composition in the permeate stream is within about 2%, by mole, of the said stream from said reaction zone.
8. The process according to claim 5 , wherein the amount of hydrogen composition in the permeate stream is within about 1%, by mole, of the said stream from said reaction zone.
9. The process according to claim 1 , wherein the membrane comprises a hollow fiber membrane.
10. The process according to claim 1 , wherein the membrane comprises a spiral wound membrane.
11. The process according to claim 1 , wherein the permeate comprises from about 60 to 97%, by mole, hydrogen.
12. The process according to claim 1 , wherein the permeate comprises at least about 98%, by mole, hydrogen.
13. The process according to claim 9 , wherein the hollow fiber membrane comprises at least one polymer selected from the group consisting of polyimide, cellulose acetate, cellulose triacetate, and polysulfone.