Claims
- 1. In a process for the recovery of sulfur from a hydrogen sulfide containing gas comprising the steps of:
- partially oxidizing hydrogen sulfide in a gaseous stream with oxygen in an oxidation stage to produce SO.sub.2 and non-oxidized H.sub.2 S;
- reacting the product gases of said partial oxidation stage further in at least two catalytic stages, in accordance with the equation:
- 2H.sub.2 S+SO.sub.2 .revreaction.2H.sub.2 O+3/n S.sub.n,
- wherein the H.sub.2 S concentration in the gas leaving the last of said at least two catalytic stages is controlled to have a value ranging between 0.8 and 3% by volume by employing at least one: of the following steps a and b:
- a) reducing the quantity of combustion or oxidation air passed to said oxidation stage;
- b) causing a portion of the hydrogen sulfide containing feedstock gas to by-pass the oxidation stage and to be added to the gas flowing to one of said at least two catalytic stages;
- following by selectively oxidizing H.sub.2 S in the gas stream leaving the last of said at least two catalytic stages to sulfur, employing for this purpose a catalytic stage including a selective oxidation catalyst which is substantially insensitive to the presence of water vapor in the gas stream, is ineffective in promoting establishment of the equilibrium
- 2H.sub.2 S+SO.sub.2 .revreaction.2H.sub.2 O+3/n S.sub.n,
- and is effective to promote oxidation of H.sub.2 S to sulfur in the presence of water vapor;
- the improvement comprising subsequently introducing the gas stream leaving said catalytic stage including said selective oxidation catalyst into the lower end of an inclined tube or plate heat exchanger, said heat exchanger being inclined from the horizontal plane by an angle greater than 45.degree., a tube or plate of said heat exchanger having an inner wall, said inner wall of said heat exchanger tube or plate being maintained, throughout the entire length of the heat exchanger, at a temperature below the solidification point of sulfur and above the dew point of water in the gas stream by flow of a coolant;
- cooling the upwardly flowing gas stream in the heat exchanger, so as to establish a deposited layer of solid sulfur on the gas stream side of said inner wall;
- continuing to cool said upwardly flowing gas stream by said flow of said coolant so that, after said solid elemental sulfur layer is established on said inner wall, elemental sulfur condenses as a liquid onto said solid sulfur layer; and
- collecting said condensed liquid elemental sulfur from said heat exchanger by gravity flow while said gas leaving said catalytic stage including said selective oxidation catalyst passes through said heat exchanger, said introducing, continuing to cool and collecting steps being carried out in a continuous mode.
- 2. The process of claim 1, wherein the H.sub.2 S concentration in the gas leaving the last of said at least two catalytic stages is maintained at a value of between 1 and 3% by volume.
- 3. The process of claim 1, wherein the quantity of combustion or partial oxidation air passed to the oxidation stage is about 86-98.5% of the stoichiometric quantity of air required for optimum conversion of the supplied quantity of hydrogen sulfide to sulfur.
- 4. The process of claim 1, wherein about 1.5-14% of the available quantity of H.sub.2 S containing gas is caused to by-pass the partial oxidation stage and to be added to the gas flowing to one of said at least two catalytic stages.
- 5. The process of claim 1, wherein, with an oxidation efficiency to sulfur of 80-85% for the selective oxidation catalyst, an H.sub.2 S concentration of 0.8-1.7% by volume is selected in the gas coming from the last of said at least two catalytic stages.
- 6. The process of claim 5, wherein, with an oxidation efficiency to sulfur of 85-90% for the selective oxidation catalyst, an H.sub.2 S concentration of 1.0-2% by volume is selected in the gas coming from the last of said at least two catalytic stages.
- 7. The process of claim 5, wherein, with an oxidation efficiency to sulfur of 90-95% for the selective oxidation catalyst, an H.sub.2 S concentration of 1.4-2.4% by volume is selected in the gas coming from the last of said at least two catalytic stages.
- 8. The process of claim 5, wherein said selective oxidation catalyst includes a carrier of which, under the reaction conditions applied, the surface exposed to the gaseous phase does not exhibit alkaline properties, said carrier having a catalytically active material applied thereto or formed thereon, the specific area of the selective oxidation catalyst being less than 20 m.sup.2 /g catalyst, and less than 10% of the total pore volume having a pore radius of between 5 and 500 .ANG..
- 9. The process of claim 8, wherein less than 2% of the total pore volume of said selective oxidation catalyst are pores having a pore radius of between 5 and 500 .ANG..
- 10. The process of claim 8, wherein said selective oxidation catalyst has a specific area less than 10 m.sup.2 /g catalyst.
- 11. The process of claim 8, wherein the carrier material employed in the selective oxidation catalyst is alpha-alumina or hydrothermally sintered silica.
- 12. The process of claim 8, wherein the catalytically active material is present on the carrier of the selective oxidation catalyst in a proportion of 0.1-10% by weight calculated on the total mass of the catalyst.
- 13. The process of claim 8, wherein the catalytically active material employed in the selective oxidation catalyst is a metal oxide, a mixed oxide of a plurality of metals, or a mixture of metal oxides.
- 14. The process of claim 13, wherein the catalytically active material is iron oxide or a mixed oxide of iron and chromium.
- 15. The process of claim 1, wherein the step of selectively oxidizing takes place in a liquid, and with an oxidation efficiency to sulfur of 90-100% in the liquid employed for selective oxidation, an H.sub.2 S concentration of 2-4% by volume is selected in the gas coming from the last of said at least two catalytic stages.
- 16. The process of claim 1, wherein in said step of selectively oxidizing, an excess of oxygen over that required for said selective oxidation step is employed, said excess of oxygen being sufficient to result in an overall excess of oxygen being employed in said process.
- 17. The process of claim 1, wherein the gas introduced in the heat exchanger is cooled to a temperature between the water dew point and 120.degree. C.
- 18. The process of claim 1, wherein it is ensured that the inner wall of the heat exchanger has a temperature which is at least 2.degree. C. above the condensation temperature of the water.
- 19. The process of claim 1, wherein the inner wall of the heat exchanger has a temperature of at most 95.5.degree. C.
- 20. The process of claim 1, wherein the gas to be introduced in the heat exchanger has a temperature between 120.degree. C. and 300.degree. C.
- 21. The process of claim 1, wherein a tube or plate-shaped heat exchanger is used.
- 22. The process of claim 21, wherein the tube or plate-shaped heat exchanger is disposed vertically.
- 23. The process of claim 1, wherein a heat exchanger is used of which the walls have an absolute roughness of less than 0.05 mm.
- 24. The process of claim 1, wherein the catalytic stage and the heat exchanger are combined in one device.
- 25. The process of claim 1, wherein the gas is cooled in said heat exchanger by cocurrent flow of a coolant.
- 26. The process of claim 1, wherein the gas is cooled in said heat exchanger by countercurrent flow of a coolant.
Priority Claims (1)
Number |
Date |
Country |
Kind |
9302081 |
Nov 1993 |
NLX |
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Parent Case Info
This application is continuation of application Ser. No. 08/756,395, now abandoned filed Nov. 27, 1996, which is a continuation of application Ser. No. 08/459,268, filed Jun. 2, 1995, abandoned which is a continuation-in-part of application Ser. No. 08/343,655, filed Nov. 22, 1994 abandoned.
US Referenced Citations (7)
Foreign Referenced Citations (4)
Number |
Date |
Country |
2572952 |
May 1986 |
FRX |
1083790 |
Jun 1960 |
DEX |
80-61393 |
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JPX |
51-45008 |
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JPX |
Non-Patent Literature Citations (1)
Entry |
Paskall, Howard C. Sulfuacondensor Function and Problem Arears, Western Research Amsterdam 1981. |
Continuations (2)
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Number |
Date |
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Parent |
756395 |
Nov 1996 |
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Parent |
459268 |
Jun 1995 |
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Continuation in Parts (1)
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Number |
Date |
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Parent |
343655 |
Nov 1994 |
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