Method for the continuous production of a gaseous hydrogen stream
A process for the production of a hydrogen gas stream having a CO content of less than 1 ppm having a production cycle comprising two phases: phase 1 includes a) purifying a synthesis gas in a PSA unit, b) recovering a hydrogen gas stream comprising a CO content of greater than 1 ppm, c) purifying the gas stream by adsorption in a TSA unit, and recovery a hydrogen gas stream exhibiting a CO content of less than 1 ppm, and phase 2 includes e) purifying the synthesis gas in a PSA unit, f) recovering a hydrogen gas stream having a CO content of less than 1 ppm, where throughout steps e) and f), the TSA unit is bypassed by the hydrogen gas stream and is regenerated.
1. A process for the production of a hydrogen gas stream comprising a CO content of less than 1 ppm derived from synthesis gas feed gas, the method comprising a production cycle comprising two phases:
a first phase comprising the following successive steps:
a) purifying a synthesis gas feed by adsorption in a PSA unit,
b) recovering, at the outlet of the PSA unit a hydrogen gas stream comprising a CO content of greater than 1 ppm,
c) purifying the gas stream recovered in step b) by adsorption in a TSA unit, and
d) recovery at the outlet of the TSA unit a hydrogen gas stream comprising a CO content of less than 1 ppm, and
a second phase comprising the following successive steps:
e) purifying the synthesis gas by adsorption in the PSA unit,
f) recovering at the outlet of the PSA unit a hydrogen gas stream comprising a CO content of less than 1 ppm,
wherein, throughout steps e) and f), the TSA unit is bypassed by the hydrogen gas stream and is regenerated.
2. The process as claimed in claim 1 , wherein, during the second phase, the TSA unit is bypassed by means of a bypass line.
3. The process as claimed in claim 1 , wherein the TSA unit comprises a single adsorber.
4. The process as claimed in claim 3 , wherein the single adsorber comprises an active material which will chemisorb at least a part of the CO.
5. The process as claimed in claim 4 , wherein the active material comprises nickel and/or copper.
6. The process as claimed in claim 1 , wherein the PSA unit comprises at least two adsorbers which each follow, in staggered fashion during the first phase, a pressure cycle comprising adsorption, depressurization and repressurization stages.
7. The process as claimed in claim 6 , wherein a pressure cycle carried out during the second phase exhibits a shorter duration than the duration of the pressure cycle carried out during the first phase.
8. The process as claimed in claim 6 , wherein:
the pressure cycle during the first phase and a pressure cycle during the second phase exhibit an identical duration and
a depressurization of the pressure cycle carried out during the second phase is carried out at a lower pressure than the pressure of the depressurization carried out during the first phase.
9. The process as claimed in claim 1 , wherein the PSA unit comprises at least one adsorber comprising a layer of alumina, a layer of activated carbon and a layer of molecular sieve.
10. The process as claimed in claim 1 , wherein the duration of the first phase is greater than 10 times the duration of the second phase.