Water gas shift process
High-pressure steam supply in hydrogen production process is made more efficient by water gas shift process which comprises, in alternating sequence: (a) a reaction stage wherein a feed gas comprising CO and H 2 O is fed into a water gas shift reactor containing a sorbent material capable of adsorbing H 2 O and CO 2 and wherein a product gas issuing from the reactor is collected, (b) a regeneration stage wherein CO 2 is removed from the reactor, (c) a loading stage, wherein H 2 O is fed into the reactor; wherein said feed gas mixture has a molar ratio of H 2 O to CO below 1.2, and the loading stage is performed at a lower pressure than the pressure of the reaction stage.
1. A water gas shift process comprising:
(a) feeding a feed gas comprising CO and H 2 O into a water gas shift reactor containing a sorbent material capable of adsorbing H 2 O and CO 2 and collecting a product gas issuing from the reactor,
(b) removing CO 2 from the reactor, and
(c) feeding H 2 O into the reactor, wherein:
step (c) coincides with or follows step (b);
step (c) is performed at a pressure of less than ⅔ of the pressure of step (a),
all the steps are performed in alternating sequence, and
the feed gas mixture has a molar ratio of H 2 O to CO of below 1.2.
2. The process according to claim 1 , wherein step (a) is performed at a pressure between 4 and 80 bar.
3. The process according to claim 2 , wherein step (a) is performed at a pressure between 10 and 40 bar.
4. The process according to claim 1 , wherein step (b) is performed at a pressure less than half of that of step (a).
5. The process according to claim 1 , wherein step (b) is performed at a pressure between 0 and 4 bar.
6. The process according to claim 1 , wherein step (b) and step (c) are performed simultaneously using a gas containing at least 50 vol. % of steam, after depressurisation.
7. The process according to claim 1 , wherein the step (c) is performed following step (b), and step (c) is performed at a pressure which is higher than the pressure of step (b).
8. The process according to claim 7 , wherein step (b) is performed using a gas containing less than 50 vol. % of steam.
9. The process according to claim 1 , wherein step (a) is performed at an average reactor temperature of between 300 and 500° C.
10. The process according to claim 1 , wherein the adsorbent comprises an alkali-promoted alumina.
11. The process according to claim 1 , wherein the adsorbent comprises calcium oxide and/or magnesium oxide and/or zinc oxide.
12. The process according to claim 10 , wherein the adsorbent has an atomic ratio of (Mg+Ca+Zn) to Al of between 0.25 and 1.5, and an atomic ratio of alkali metal to Al of between 0.1 and 1.0.
13. The process according to claim 10 , wherein the adsorbent has an atomic ratio of (Mg+Ca+Zn) to Al of between 0.4 and 1.0, and an atomic ratio of alkali metal to Al of between 0.25 and 0.75.
14. The process according to claim 1 , wherein the feed gas further comprises between 100 and 10,000 ppm of H 2 S.
15. The process according to claim 1 , further comprising, between steps (a) and (b), feeding a purging gas comprising CO 2 into the reactor.
16. The process according to claim 1 , wherein the feed gas mixture has a molar ratio of H 2 O to CO of 0-0.75, and a CO concentration in the feed gas of at least 10%.
17. The process according to claim 1 , wherein the feed gas issues from a preceding water gas shift reaction.
18. The process according to claim 1 , wherein the product gas is used for combustion, and the feed gas mixture has a molar ratio of H 2 O to CO of 0.5-1.2.
19. The process according to claim 1 , wherein the product gas is used for producing chemicals, and the feed gas mixture has a molar ratio of H 2 O to CO of below 0.8.
20. A water gas shift process comprising: (a) reacting a feed gas comprising CO and H 2 O in a water gas shift reactor containing a sorbent material capable of adsorbing H 2 O and CO 2 and collecting a product gas issuing from the reactor, (b) removing CO 2 from the reactor, and (c) loading H 2 O into the reactor, wherein the loading step follows the removing step; all of the steps are performed in alternating sequence, the loading step is performed at a pressure of less than ⅔ of that of the reaction step, and the feed gas mixture has a molar ratio of H 2 O to CO 0-2.0.