Chemistry of inorganic compounds – Modifying or removing component of normally gaseous mixture – Carbon dioxide or hydrogen sulfide component
Patent
1987-06-03
1989-12-26
Stoll, Robert L.
Chemistry of inorganic compounds
Modifying or removing component of normally gaseous mixture
Carbon dioxide or hydrogen sulfide component
423223, 423228, 423229, 423242, 423243, 423563, 423645, 55 48, 55 68, 55 73, 55 93, C01B 1716
Patent
active
048897000
DESCRIPTION:
BRIEF SUMMARY
The invention pertains to a process for selective extraction of H.sub.2 S from an H.sub.2 S-containing gas. It also refers to a device for realizing this process.
Selective extraction of H.sub.2 S from an H.sub.2 S-containing gas is usually used to eliminate the majority, or almost the entirety, of the H.sub.2 S present in the said gas, to produce a desulfured gas with an H.sub.2 S content below an imposed threshold and/or to generate a stream of acid gas which is rich in H.sub.2 S and includes as low as possible a quantity of other acid compounds such as CO.sub.2, with such a stream of acid gas being usable as a source of H.sub.2 S for the production of sulfur according to the Claus process of controlled H.sub.2 S oxidation or also for the synthesis of thioorganic compounds.
Such selective extraction of H.sub.2 S is normally accomplished by washing the gas under treatment by means of an absorbent liquid which can be regenerated by heat and is selective for H.sub.2 S, i.e., an absorbent liquid which, on the one hand, is capable of retaining gaseous acid compounds such as H.sub.2 S and CO.sub.2 and returning practically the totality of these acid compounds by heating, and on the other hand, possesses an absorptive capacity which is distinctly greater with regard to H.sub.2 S than to other acid compounds, particularly CO.sub.2. The absorbent liquid fixes the gaseous acid compounds by simple physical dissolution and/or by dissolution after formation of a thermally unstable salt or complex by reaction between the said gaseous acid compounds and a basic compound, for example, an amine or alkanolamine, contained in the absorbent liquid.
In practice, the gas under treatment, which contains H.sub.2 S and possibly other gaseous acid compounds such as CO.sub.2, is brought into contact, in an absorption zone, with the selected absorbent liquid, circulating in countercurrent, so as to produce a gas with a reduced level of H.sub.2 S which is drawn off from the top of the absorption zone, and tapping from the bottom of the said zone a stream of absorbent liquid charged with H.sub.2 S and containing as little CO.sub.2 and other gaseous acid compounds as possible. The said stream of absorbent liquid is then introduced into a regeneration zone in which it is subjected to conditions of temperature and pressure such as to produce almost complete release of the absorbed gaseous acid compounds, which are taken off from the top of the regeneration zone in the form of a gaseous acid effluent rich in H.sub.2 S, and to produce at the bottom of the regeneration zone a regenerated absorbent liquid practically free of dissolved gaseous acid compounds, which is tapped and reused as the absorbent liquid in the absorption zone.
When the gaseous acid effluent rich in H.sub.2 S drawn off from the top of the regeneration zone does not contain a sufficient level of H.sub.2 S to allow the said effluent to be used in the application envisaged, especially manufacture of sulfur by controlled oxidation of H.sub.2 S or synthesis of thioorganic compounds, the operations are repeated, i.e., the gaseous acid effluent is treated in a second absorption zone with an absorbent liquid which is also selective for H.sub.2 S and regeneratable by heating, to produce a stream of absorbent liquid highly charged with H.sub.2 S, which is conveyed to a second regeneration zone to be regenerated as indicated above, producing a gaseous acid effluent with a higher concentration of H.sub.2 S than the gaseous acid effluent emerging from the first treatment.
Such a method of operation presents the disadvantage, among others, of requiring the use of very high-volume installations to produce a gaseous acid effluent sufficiently rich in H.sub.2 S to be usable in the applications, cited above, for which it is designed, and for this reason it is very expensive.
The present invention proposes to remedy this disadvantage by offering a process for selective extraction of H.sub.2 S from an H.sub.2 S-containing gas which makes it possible to produce a gaseous acid effluent highl
REFERENCES:
patent: 4129425 (1978-12-01), Stephenson et al.
patent: 4293531 (1981-10-01), Field et al.
patent: 4519991 (1985-05-01), Oliveau et al.
Elgue Jean
Oliveau Olivier
Peytavy Jean-Louis
Societe Nationale Elf Aquitaine (Production)
Stoll Robert L.
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