Process for removing and recovering H
A process for altering the composition of a feed gas containing H 2 S equivalents is disclosed. The process comprises (a) contacting the feed gas with a solid adsorbent at a temperature of 250-500° C., to obtain a loaded adsorbent, (b) purging the loaded adsorbent with a purge gas comprising steam, thus producing a product stream which typically contains substantially equal levels of CO 2 and H 2 S. The process further comprises a step (c) of regenerating the purged adsorbent by removal of water. The adsorbent comprises alumina and one or more alkali metals, such as potassium oxides, hydroxide or the like.
1. A process for altering the composition of a gas comprising H 2 S equivalents and CO2, comprising the steps of:
(a) contacting a feed gas containing H 2 S equivalents, CO 2 and optionally H 2 O, wherein the molar ratio of H 2 O to H 2 S equivalents is within the range of 0-(5+X), with a solid adsorbent at a temperature of 250-500° C., to obtain a loaded adsorbent and a first product gas;
(b) contacting the loaded adsorbent with a purge gas containing H 2 O, to obtain a second product gas; and
(c) regenerating the adsorbent after step (b) by removal of H 2 O,
wherein the process is performed in cycles of steps (a) to (c), and wherein the feed gas and/or the purge gas contains a reducing agent and the adsorbent comprises alumina and one or more alkali metals, and wherein X is defined as:
X
=
∑
n
i
⨯
[
H
2
S
equivalent
]
i
[
H
2
S
equivalents
]
wherein [H 2 S equivalents] indicates the total concentration of H 2 S equivalents, [H 2 S equivalent] i indicates the concentration of a particular H 2 S equivalent i and n i indicates the amount of water molecules n consumed when said H 2 S equivalent i is converted to H 2 S.
2. The process according to claim 1 , wherein the H 2 S equivalents comprise H 2 S, COS and/or CS 2 .
3. The process according to claim 1 , wherein the molar ratio of H 2 S equivalents to CO 2 in the feed gas is below 1.
4. The process according to claim 1 , wherein the molar ratio of H 2 S equivalents to CO 2 in the feed gas is in the range of 0.001-0.1.
5. The process according to claim 1 , wherein the feed gas contains 0.1-20% H 2 as the reducing agent.
6. The process according to claim 1 , wherein the adsorbent further comprises one or more divalent metals.
7. The process according to claim 1 , wherein the divalent metals are oxides, hydroxides, carbonates, sulphides and/or hydrosulphides.
8. The process according to claim 1 , wherein the adsorbent further comprises MgO.
9. The process according to claim 5 , wherein the alkali metal is K and the adsorbent is K-promoted alumina, or is based on a K-promoted hydrotalcite.
10. The process according to claim 1 , wherein the process is continued with step (a) after the regeneration of step (c).
11. The process according to claim 1 , wherein step (b) is performed counter-currently with respect to step (a).
12. The process according to claim 1 , wherein the purge gas comprises at least 75% H 2 O.
13. The process according to claim 1 , wherein the first product gas contains less than 10 ppm of H 2 S equivalents, and/or the first product gas contains less than 0.1 times the level of H 2 S equivalents of the feed gas, and/or the first product gas has a molar ratio of H 2 S equivalents to CO 2 of less than 0.005.
14. The process according to claim 1 , wherein the second product gas has a molar ratio of H 2 S equivalents to CO 2 of at least 0.5.
15. The process according to claim 1 , wherein the feed gas is an optionally pre-dried syngas further containing H 2 and CO.
16. The process according to claim 1 , wherein the feed gas is an optionally pre-treated Claus tail gas further containing N 2 .
17. The process according to claim 1 , wherein the second product gas is subjected, optionally after pre-drying, to a Claus process to obtain elemental sulphur and a tail gas comprising H 2 S equivalents and CO 2 , and the tail gas is used as feed gas in step (a), optionally after pre-drying.
18. A method for the production of elemental sulphur comprising subjecting a H 2 S-enriched gas to a Claus process, wherein the H 2 S-enriched gas is obtained in step (b) of a process for altering the composition of a gas comprising H 2 S equivalents and CO 2 , comprising the steps of:
(a) contacting a feed gas containing H 2 S equivalents, CO 2 and optionally H 2 O, wherein the molar ratio of H 2 O to H 2 S equivalents is within the range of 0-(5+X), with a solid adsorbent at a temperature of 250-500° C., to obtain a loaded adsorbent and a first product gas;
(b) contacting the loaded adsorbent with a purge gas containing H 2 O, to obtain a second product gas; and
(c) regenerating the adsorbent after step (b) by removal of H 2 O,
wherein the process is performed in cycles of steps (a) to (c), and wherein the feed gas and/or the purge gas contains a reducing agent and the adsorbent comprises alumina and one or more alkali metals, and wherein X is defined as:
X
=
∑
n
i
⨯
[
H
2
S
equivalent
]
i
[
H
2
S
equivalents
]
wherein [H 2 S equivalents] indicates the total concentration of H 2 S equivalents, [H 2 S equivalent] i indicates the concentration of a particular H 2 S equivalent i and n i indicates the amount of water molecules n consumed when said H 2 S equivalent i is converted to H 2 S.
19. The process according to claim 3 , wherein the molar ratio of H 2 S equivalents to CO 2 in the feed gas is in the range of 0.001-0.1.
20. The process according to claim 6 , wherein the divalent metals are in the form of oxides, hydroxides, carbonates, sulphides and/or hydrosulphides.
21. The process according to claim 20 , wherein the adsorbent further comprises MgO.