CA1057934A - Process for the production of sulfur from sulfur dioxide extracted from gas streams - Google Patents
Process for the production of sulfur from sulfur dioxide extracted from gas streamsInfo
- Publication number
- CA1057934A CA1057934A CA251,021A CA251021A CA1057934A CA 1057934 A CA1057934 A CA 1057934A CA 251021 A CA251021 A CA 251021A CA 1057934 A CA1057934 A CA 1057934A
- Authority
- CA
- Canada
- Prior art keywords
- sulfur dioxide
- sulfur
- hydrogen sulfide
- zone
- absorbent
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- RAHZWNYVWXNFOC-UHFFFAOYSA-N Sulphur dioxide Chemical compound O=S=O RAHZWNYVWXNFOC-UHFFFAOYSA-N 0.000 title claims abstract description 264
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 title claims abstract description 54
- 239000011593 sulfur Substances 0.000 title claims abstract description 42
- 229910052717 sulfur Inorganic materials 0.000 title claims abstract description 42
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 26
- 238000000034 method Methods 0.000 title claims description 33
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 claims abstract description 50
- 238000010521 absorption reaction Methods 0.000 claims abstract description 50
- 229910000037 hydrogen sulfide Inorganic materials 0.000 claims abstract description 50
- 239000007789 gas Substances 0.000 claims abstract description 44
- 238000006243 chemical reaction Methods 0.000 claims abstract description 20
- 239000002250 absorbent Substances 0.000 claims description 35
- 230000002745 absorbent Effects 0.000 claims description 35
- 239000003054 catalyst Substances 0.000 claims description 16
- 239000001257 hydrogen Substances 0.000 claims description 16
- 229910052739 hydrogen Inorganic materials 0.000 claims description 16
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 14
- 229910052751 metal Inorganic materials 0.000 claims description 11
- 239000002184 metal Substances 0.000 claims description 11
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 9
- 230000000737 periodic effect Effects 0.000 claims description 8
- 229910052761 rare earth metal Inorganic materials 0.000 claims description 6
- 150000002910 rare earth metals Chemical class 0.000 claims description 6
- KRKNYBCHXYNGOX-UHFFFAOYSA-K Citrate Chemical compound [O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O KRKNYBCHXYNGOX-UHFFFAOYSA-K 0.000 claims description 5
- -1 alkali metal citrate Chemical class 0.000 claims description 5
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims description 4
- 239000008346 aqueous phase Substances 0.000 claims description 4
- 229910017052 cobalt Inorganic materials 0.000 claims description 4
- 239000010941 cobalt Substances 0.000 claims description 4
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 4
- 229910052750 molybdenum Inorganic materials 0.000 claims description 4
- 239000011733 molybdenum Substances 0.000 claims description 4
- 229910052783 alkali metal Inorganic materials 0.000 claims description 3
- 235000010269 sulphur dioxide Nutrition 0.000 claims 32
- 239000004291 sulphur dioxide Substances 0.000 claims 1
- 239000006096 absorbing agent Substances 0.000 abstract description 7
- 230000015572 biosynthetic process Effects 0.000 abstract description 3
- 239000000243 solution Substances 0.000 description 36
- QGJOPFRUJISHPQ-UHFFFAOYSA-N Carbon disulfide Chemical compound S=C=S QGJOPFRUJISHPQ-UHFFFAOYSA-N 0.000 description 15
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 10
- 230000003197 catalytic effect Effects 0.000 description 9
- JJWKPURADFRFRB-UHFFFAOYSA-N carbonyl sulfide Chemical compound O=C=S JJWKPURADFRFRB-UHFFFAOYSA-N 0.000 description 8
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 6
- 150000002739 metals Chemical class 0.000 description 6
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 6
- 239000000047 product Substances 0.000 description 6
- 239000007864 aqueous solution Substances 0.000 description 5
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 4
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 4
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 4
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 4
- 229910002091 carbon monoxide Inorganic materials 0.000 description 4
- 239000000377 silicon dioxide Substances 0.000 description 4
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 3
- 230000007797 corrosion Effects 0.000 description 3
- 238000005260 corrosion Methods 0.000 description 3
- 238000005984 hydrogenation reaction Methods 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 2
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 229910052770 Uranium Inorganic materials 0.000 description 2
- GJEAMHAFPYZYDE-UHFFFAOYSA-N [C].[S] Chemical class [C].[S] GJEAMHAFPYZYDE-UHFFFAOYSA-N 0.000 description 2
- 150000004982 aromatic amines Chemical class 0.000 description 2
- 125000004429 atom Chemical group 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 229910002092 carbon dioxide Inorganic materials 0.000 description 2
- 239000001569 carbon dioxide Substances 0.000 description 2
- 238000006555 catalytic reaction Methods 0.000 description 2
- 239000003638 chemical reducing agent Substances 0.000 description 2
- 229910052804 chromium Inorganic materials 0.000 description 2
- 239000011651 chromium Substances 0.000 description 2
- KYYSIVCCYWZZLR-UHFFFAOYSA-N cobalt(2+);dioxido(dioxo)molybdenum Chemical compound [Co+2].[O-][Mo]([O-])(=O)=O KYYSIVCCYWZZLR-UHFFFAOYSA-N 0.000 description 2
- 238000002485 combustion reaction Methods 0.000 description 2
- 239000000446 fuel Substances 0.000 description 2
- 159000000011 group IA salts Chemical class 0.000 description 2
- 150000002431 hydrogen Chemical class 0.000 description 2
- 238000006460 hydrolysis reaction Methods 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- 150000007522 mineralic acids Chemical class 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 229910052759 nickel Inorganic materials 0.000 description 2
- 150000007524 organic acids Chemical class 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 230000008929 regeneration Effects 0.000 description 2
- 238000011069 regeneration method Methods 0.000 description 2
- NLJMYIDDQXHKNR-UHFFFAOYSA-K sodium citrate Chemical compound O.O.[Na+].[Na+].[Na+].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O NLJMYIDDQXHKNR-UHFFFAOYSA-K 0.000 description 2
- 239000001509 sodium citrate Substances 0.000 description 2
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 2
- 229910052721 tungsten Inorganic materials 0.000 description 2
- 239000010937 tungsten Substances 0.000 description 2
- JFALSRSLKYAFGM-UHFFFAOYSA-N uranium(0) Chemical compound [U] JFALSRSLKYAFGM-UHFFFAOYSA-N 0.000 description 2
- 229910052720 vanadium Inorganic materials 0.000 description 2
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 2
- 239000010457 zeolite Substances 0.000 description 2
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- 241000286904 Leptothecata Species 0.000 description 1
- 241001072332 Monia Species 0.000 description 1
- LSNNMFCWUKXFEE-UHFFFAOYSA-N Sulfurous acid Chemical class OS(O)=O LSNNMFCWUKXFEE-UHFFFAOYSA-N 0.000 description 1
- 241000949391 Thorea Species 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 239000001273 butane Substances 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- 239000002826 coolant Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 238000004134 energy conservation Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- XDAHMMVFVQFOIY-UHFFFAOYSA-N methanedithione;sulfane Chemical compound S.S=C=S XDAHMMVFVQFOIY-UHFFFAOYSA-N 0.000 description 1
- 238000005065 mining Methods 0.000 description 1
- IJDNQMDRQITEOD-UHFFFAOYSA-N n-butane Chemical compound CCCC IJDNQMDRQITEOD-UHFFFAOYSA-N 0.000 description 1
- OFBQJSOFQDEBGM-UHFFFAOYSA-N n-pentane Natural products CCCCC OFBQJSOFQDEBGM-UHFFFAOYSA-N 0.000 description 1
- 235000005985 organic acids Nutrition 0.000 description 1
- 239000001294 propane Substances 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000004071 soot Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 241000894007 species Species 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- ZCUFMDLYAMJYST-UHFFFAOYSA-N thorium dioxide Chemical compound O=[Th]=O ZCUFMDLYAMJYST-UHFFFAOYSA-N 0.000 description 1
- 239000002918 waste heat Substances 0.000 description 1
Landscapes
- Treating Waste Gases (AREA)
Abstract
Abstract of the Invention A sulfur dioxide containing gas stream is purified by passage through an absorber containing an aqueous absorption solution for sulfur dioxide. Sulfur dioxide-laden aqueous absorption solution is continuously removed from the absorber.
Approximately one-third is passed to a sulfur production zone.
The balance of the solution is passed to a sulfur dioxide stripping zone where the sulfur dioxide is separated from the absorption solution which is returned to the absorber. The extracted sulfur dioxide is catalytically hydrogenated to hydrogen sulfide which is passed to the sulfur production zone for reaction with sulfur dioxide to form elemental sulfur.
After the formation of elemental sulfur, the balance of the aqueous absorption solution essentially free of sulfur dioxide is returned to the absorber.
Approximately one-third is passed to a sulfur production zone.
The balance of the solution is passed to a sulfur dioxide stripping zone where the sulfur dioxide is separated from the absorption solution which is returned to the absorber. The extracted sulfur dioxide is catalytically hydrogenated to hydrogen sulfide which is passed to the sulfur production zone for reaction with sulfur dioxide to form elemental sulfur.
After the formation of elemental sulfur, the balance of the aqueous absorption solution essentially free of sulfur dioxide is returned to the absorber.
Description
`` lOS793~
IMPROVED PROCESS FOR THE PRODUCTION OF SULFUR
FROM SULFUR DIOXIDE EXTRACTED FROM GAS STREAMS
. ........ . .. _ ,. __.__.. __ _.. ... _ .. , . _ Back~round of the Invention The present invention i8 related to processes which utilize heat regenerable liquids for the removal of sulfur dioxide from gas streams and to the production of elemental sulfur from sulfur dioxide extracted from gas streams.
Many processes employ aqueous solutions of ammonia, alkaline salts of organic and inorganic acids, and aromatic amines as absorbents for the extraction of sulfur dioxide from gas streams. These solutions are readily stripped of sulfur dioxide ~pon the application of heat and therefore regenerated for reuse. The ~tripped sulfur dioxlde is proc-ssed for the . -1--lU5793~
¦ production of liquid sulfur dioxide, sulfuric acid or elemental I sulfur.
¦ To produce elemental sulfur from the recovered sulfur ¦ dioxide, it is expedient to react the sulfur dioxide with hydrogen 5 ¦ sulfide by the Claus reaction. This requires two moles of ¦ hydrogen sulfide for each mole of sulfur dioxide.
¦ In a situation where a source of hydrogen sulfide is not ¦ available as, for example, in a power plant where sulfur ¦ dioxide must be removed from stack exhaust gases, hydrogen 10 ¦ sulfide has to be generated if sulfur is to be produced.
¦ This may be accomplished by converting two thirds of the ¦ stripped sulfur dioxide to hydrogen sulfide and reacting the ¦ balance with the formed hydrogen sulfide over an alumina ¦ catalyst in the catalytic zone of a typical Claus plant.
15 ¦ Another possibility, which has been proposed for the ¦ regeneration step of the Citrate process, is to produce hydrogen ¦ sulfide by reduction of elemental sulfur generated in the ¦ process for reaction with sulfur dioxide dissolved in the I citrate solution.
201 Known methods of producing hydrogen sulfide from elemental sulfur have been described, for instance, in "Canadian Mining l and Metallurgical Bulletin", October 1957, p. 614 and follow-¦ ing, and '~ining Engineering", January 1970, p. 75 and follow-I ing.
25¦ The former process involves non-catalytic direct reaction of hydrogen with sulfur to form hydrogen sulfide at temperatures from 820 to 1000F. An admitted deficiency in the process is ¦ that the reaction products, i.e., a mixture of unreacted I sulfur and hydrogen sulfide, are highly corrosive. Type 316 301 stainless steel, for instance, suffers severe corrosion. In iO579 34 1 addition, hydrogcn of hi~h purity is required for the process and this is expensive.
The process described in the latter publication involves two conversion stages. In the first, sulfur is reacted with a S hydrocarbon, such as methane, at a temperature from 600 to 700C
over a catalyst to form a mixture of hydrogen sulfide and carbon disulfide. The gas stream is passed to a second stage where, at a temperature of 200 to 300C, the carbon disulfide reacts with water to form hydrogen suifide and carbon dioxide.
This process also sufers from severe corrosion problems and the net gas stream can contain considerable quantities of carbon-sulfur compounds such as carbonyl sulfide and carbon disulfide.
As it pertains to the operation of the Citrate process, it would be necessary to convert two thirds of the formed sulfur to hydrogen sulfide for reaction with sulfur dioxide in the liquid phase at ambient temperature. This is an expensive operation from an energy conservation standpoint since two-thirds of the product must always be recycled back in the form of hydrogen sulfide. Further, the proposed means to generate hydrogen sulfide from the formed sulfur leaves much to be desired due to the corrosion and pOllution problems attendant to the generation of hydrogen sulfide from the elemental sulfur.
l(lS7~4 l Summary of the Invention In accordance with the present invention there is provided a process for the production of sulfur from sulfur dioxide contained in gas streams which comprises: -(a~ passing a sulfur dioxide containing gas stream through a sulfur dioxide absorption zone containing an aqueous absorbent for sulfur dioxide to form a sulfur dioxide rich absorbent and a sulfur dioxide lean gaseous stream;
(b) separating the sulfur dioxide rich absorbent from the absorption zone;
(c) passing about one-third of the sulfur dioxide rich absorbent to a sulfur production zone;
(d) passing the balance of the sulfur dioxide rich absorbent to a sulfur dioxide stripping zone to separate sulfur dioxide from the absorbent to form a sulfur dioxide lean absorbent for recycle to the absorption zone;
(e~ catalytically hydrogenating the sulfur dioxide separated from the sulfur dioxide rich absorbent in the stripping zone in the presence of a source of hydrogen to hydrogen sulfide at a temperature from about 300 to about lOQ0F in the presence of a catalyst consisting of at least one supported metal selected from Group Va, VIa, VIII and the Rare Earth Series of the Periodic Table;
(f) passing the formed hydrogen sulfide to the sulfur production zone where sulfur is formed from the introduced hydrogen sulfide and sulfur dioxide.
Also in accordance with the invention there is provided a process for the production of sulfur from sulfur dioxide contained in gas streams which comprises:
10~7~34 1 (a) passing a sulfur dioxide containing gas stream through a sulfur dioxide absorption zone containing an aqueous absorbent for sulfur dioxide to form a sulfur dioxide rich absorbent and sulfur dioxide lean gaseous stream;
(b) separating the sulfur dioxide rich absorbent from the absorption zone; ~- ;
~c) stripping sulfur dioxide from about two thirds of the sulfur dioxide rich absorbent to form a sulfur dioxide lean absorbent for recycle to the absorption zone;
(d~ catalytically hydrogenating the sulfur dioxide, separated from the sulfur dioxide rich absorbent by stripping in the presence of a source of hydrogen to hydrogen sulfide at a temperature from about 300 to about 1000F in the presence of a catalyst consisting of at least one supported metal selected from Group Va, VIa, VIII and the Rare Earth Series of the Periodic Table;
'~ (el combining the formed hydrogen sulfide and the balance of the sulfur dioxide rich absorbent solution in a sulfur production zone where sulfur is formed by an aqueous phase,reaction between hydrogen sulfide and sulfur dioxide to yield a sulfur dioxide lean absorption solution for recycle to the absorption zone.
Thus, according to the present invention there is provided an improvement to processes where sulfur is to be formed from the ~ulfur dioxide extracted from gas streams by an aqueous sulfur dioxide ab.sorption ~olution, such as the Citrate process ~:~ ~ ~
1~57~ ~
l which employs a buffered aqueous solution of an alkali metal citrate, such as sodium citrate, as the absorbent solution.
In accordance with the practice of the present invention a gas stream containing sulfur dioxide is passed through an absorption zone where sulfur dioxide is extracted by an aqueous sulfur dioxide ab~orption solution. Aqueous absorption solution laden with sulfur dioxide is continuously separated from the absorption zone and split. Approximately two thirds of the sulfur dioxide rich absorption solution is passed to a sulfur dioxide stripping zone where sulfur dioxide is separated from the aqueous solution. The sulfur dioxide lean absorption solution is recycled back to the absorption zone.
The sulfur dioxide separated from the absorption solution is then catalytically hydrogenated in the presence of a source of lS hydrogen to hydrogen sulfide. This is preferably accomplished l by forming a reducing gas stream by the combustion of a i carbonaceous fuel such as methane, in the presence of a source of oxygen, typically air, in a reducing gas generator. This forms a gas stream containing as the principal reductants hydrogen and carbon monoxide. The gaseous products from the reducing gas generator are combined with the sulfur dioxide gas and passed to catalytic conversion zone 42 where at a temperature from about 300 to about 1000F, preferably from abo~
500 to about 800F, the sulfur dioxide reacts with the hydrogen present and the hydrogen formed as a consequence of the reaction of carbon monoxide with water to yield hydrogen sulfide. The cata~ysts employed are those containing the metals o Group Va, VIa, VIII and the Rare Earth series of the Periodic Table as defined by Mendeleef and published as the "Periodic Chart of the Atoms" by W. N. Welch Manufacturing Company. The metals are preferably supported on conventional 1~579 3~
supports such as silica, alumina, alumina-silica, and the zeolites. Alumina is preferred. The preferred catalysts are those containing one or more of the metals cobalt, molybdenum, iron, chromium, vanadium, thoria, nickel, tungsten and uranium. A cobalt-molybdate catalyst where the support is alumina is particularly preferred.
In addition to causing the hydrogenation of sulfur dioxide to hydrogen sulfide at the temperatures employed, the catalyst serves to hydrolyze any carbonyl sulfide and carbon disulfide which may be present or formed to hydrogen sulfide.
The water required for the hydrogenation and hydrolysis reactionS may be provided in the stripped sulfur dioxide gas stream. The hydrogen sulfide gas stream after cooling to remove any water present, is combined with the aqueous 15 solution containing the balance of sulfur dioxide where,in the aqueous phase,the hydrogen sulfide reacts with the sulfur dioxide to form elemental sulfur. The elemental sulfur is collected as product, a gas stream now free of sulfur species vented to the atmosphere and the aqueous absorption solution 20 recycled back to the absorption zone.
In the practice of the process of this invention all of the sulfur dioxide removed from the gas stream in the absorption zone leaves the process as elemental sulfur and no recycle of product sulfur is required for the production of hydrogen sulfide.
An additional advantage of the process is that by using sulfur dioxide stripped from two thirds of the absorption solution as the source of hydrogen sulfide, the proper stoichiometry ~ill always be maintained in the sulfur dioxide production zone regardless of solution loading. This enables ready control over the system and prevents unreacted hydrogen sulfide or sulfur dioxidc from being vcnted to the atmosphere.
iO ~'79 ~4 1 The Drawinp, The attached drawing depicts a flow diagr~m for carrying out the preferred process of the present invention.
Description According to the present invention there is provided a process for the production of sulfur from sulfur dioxide absorbed in aqueous absorption solutions. Typical of the absorption solutions are aqueous solutions of a~monia, alkaline salts of inorganic and organic acids and certain aromatic amines which are capable of absorbing sulfur dioxide ! at ambient temperature and releasing the absorbed sulfur dioxide upon the application of heat. The preferred absorbent is an aqueous solution of an alkali metal citrate such as sodium citrate.
With reference to the Drawing, the sulfur dioxide containing gas is passed through sulfur dioxide absorption zone 10, where it is brought into counter current contact with a lean sulfur dioxide absorption solution entering absorption tower 10 in line 12 after being cooled in heat exchanger 14 to maximize the absorption capacity of the solution. The gas stream free of sulfur dioxide is vented to the atmosphere.
The sulfur dioxide-rich absorption solution is withdrawn from the base of absorption tower 10 in line 16 and split. About two thirds of the solution is passed by line 18 after under-going indirect heat exchange with recycled lean solution in heat exchanger 20 to a sulfur dioxide stripping tower 24. In sulfur dioxide stripper 24 the aqueous absorption solution is heated to a temperature which w~ll enable the solution to effectively desorb the contained sulfur dioxide. The heat 1~57~ ~ ~
I required to heat the solution may be provided by indirect heat supplied through reboiler 26.
The lean sulfur dioxide absorption solution is passed by line 28 through heat exchanger 40 and by pump 30 through heat exchanger 14 and back to absorption tower 10.
The sulfur dioxide separated from the absorption solution is passed by line 32 through cooler 34 which enables water vapor and droplets of vaporized absorption solution to cool and coalesce in condenser 36 for recycle by pump 38 back to stripping tower 24.
The sulfur dioxide gas stream which is substantially free of absorption solution but which still contains some water, is passed by line 40 to catalytic converter 42.
Simultaneously there is formed a reducing gas in generator 44. The reducing gas is formed by the partial combustion of a carbonaceous fuel such as methane, propane, butane and the like, in the presence of a source of oxygen, typically air.
Steam may be introduced to suppress the formation of soot and carbon-sulfur compounds. The gas stream exiting reducing gas generator 44 comprises as principal reductants, hydrogen and carbon monoxide which serves as a hydrogen doner as it will react with the water in catalysis zone 42 to generate hydrogen for reaction with sulfur dioxide.
The streams are combined and passed by line 46 to catalytic generator 42. Catalytic generator 42 contains one or more beds of a catalyst capable of hydrogenating the sulfur dioxide to hydrogen sulfide. Preerably, the catalyst is also capable of causing hydrolysis of any carbonyl sulfide and carbon disulfide which may be present or formed in the gas stream to hydrogen sulfide and carbon dioxide.
lU57934 1 Conversion of the sulfur dioxide to hydrogen sulfide occurs at a temperature of from about 300 to about 1000F, preferably from about 500 to about 800F. The catalysts employed are those containing the metals of Group Va, VIa, VIII and the Rare Earth Series of the Periodic Table as defined by ; Mendeleef and published as the "Periodic Chart of the Atoms"
by W. N. Welch Manufacturing Company. The metals are prefer-ably supported on conventional supports such as silica, alumina, alumina-silica, and the zeolites. Alumina is preferred.
The most preferred catalysts are those which contain one or more of the metals cobalt, molybdenum, iron, chromium, ; vanadium, thorea, nickel, tungsten and uranium. A cobalt-molybdate catalyst where the support is alumina is particularly preferred.
Reaction in catalytic con~erter 42 is highly exothermic.
To maintain the temperature within the prescribed range, an external coolant can be employed to absorb the heat of reaction. In the alternative, as shown, there may be injected water as a fine spray into the catalysis zone to ~uench the reaction and absorb the heat of reaction. Introduced water also serves to hydrolYze any carbonyl sulfide and carbon disulfide present to hydrogen sulfide and to react with carbon monoxide present in the effluent from the reducing gas generator to form hydxogen for reaction with the sulfur dioxide. Another alternative is recycling of a portion of the effluent gas from reactor 56. Under the temperature conditions employed, complete conversion of the ~ulfur dioxide to hydrogen sulfide ls realized.
The hydrogen sulfide gas stream from catalytic converter 42 is passed in line 48 to waste heat generator 50 where heat is generated in the form of steam for use in heating the solution undergoing sulfur dioxide stripping in stripper I ~S 7~ ~9~
1 ¦ tower 24, or alternately the hot &aS stream may be passed ¦ through reboiler 26. The gas stream is then passed to contact ¦ cooler 52 where the water present is removed.
¦ Since hydrogenation of sulfur dioxide in converter 42 5 ¦ is complete, the condensate is free o corrosive polythionic ¦ and sulfurous acids.
¦ The hydrogen sulfide gas stream i8 then passed by I line 54 to sulfur production zone 56 where it is brought ¦ into contact with the balance of the sulfur dioxide rich ?
10 ¦ absorption solution from absorber 109 which is passed to ¦ sulfur production zone 56 by line 58.
¦ In sulfur production zone 56, hydrogen sulfide and ¦ sulfur dioxide react in the aqueous phase to form elemental ¦ sulfur which is withdrawn as product, typically as a slurry.
lS ¦ Gases presént which are essentially free of sulfur dioxide ¦ and hydrogen sulfide are vented to the atmosphere. Upon ¦ formation of sulfur, the absorption solution which is rendered l lean, is pumped by pump 60 through line 62 back for recycle ¦ to absorption tower 10.
201 In the practice of this invention, all sulfur dioxide ; removed from the gas stream in the absorber leaves the plant as elemental sulfur and no recycle of product sulfur is required. An additional advantage of the improved process is the fact that by using the sulfur dioxide stripped from two-thirds of the absorbent solution as the source of hydrogen sulfide to react with sulfur dioxide contained in the remain-ing one-third of the solution, the proper stoichiometry will always be maintained in the reaction tank, regardless of solution loading. This feature permits easy control of the system and prevents unreacted hydrogen sulfide or sulfur dioxide to the atmosphere.
1~57~ 3 4 l The improved process, with moclifications, can be applied to other processes embodying thermal regeneration (and stripping of sulfur dioxide) of a solvent. For example, the rich solution from the bottom of the absorber can be split into two streams, in the ratio of 2:1, and stripped in two separate strippers. The sulfur dioxide obtained from the larger stream can be catalytically converted to hydrogen sulfide as described above. The hydrogen sulfide rich gas, without being cooled, is then combined with the sulfur dioxide stripped from the smaller liquid stream in a suLfur production zone and the mixed gases fed to one or more catalytic Claus stages of the sulfur production zone.
Since~ the source of the hydrogen sulfide and sulfur dioxide is the rich absorbent and the control of the split of the rich solution at a ratio of 2:1 is quite simple, the ratio of hydrogen sulfide to sulfur dioxide entering the Claus stages will always be near optimum resulting in maximum conversion ~.-of elemental sulfur.
: i -,
IMPROVED PROCESS FOR THE PRODUCTION OF SULFUR
FROM SULFUR DIOXIDE EXTRACTED FROM GAS STREAMS
. ........ . .. _ ,. __.__.. __ _.. ... _ .. , . _ Back~round of the Invention The present invention i8 related to processes which utilize heat regenerable liquids for the removal of sulfur dioxide from gas streams and to the production of elemental sulfur from sulfur dioxide extracted from gas streams.
Many processes employ aqueous solutions of ammonia, alkaline salts of organic and inorganic acids, and aromatic amines as absorbents for the extraction of sulfur dioxide from gas streams. These solutions are readily stripped of sulfur dioxide ~pon the application of heat and therefore regenerated for reuse. The ~tripped sulfur dioxlde is proc-ssed for the . -1--lU5793~
¦ production of liquid sulfur dioxide, sulfuric acid or elemental I sulfur.
¦ To produce elemental sulfur from the recovered sulfur ¦ dioxide, it is expedient to react the sulfur dioxide with hydrogen 5 ¦ sulfide by the Claus reaction. This requires two moles of ¦ hydrogen sulfide for each mole of sulfur dioxide.
¦ In a situation where a source of hydrogen sulfide is not ¦ available as, for example, in a power plant where sulfur ¦ dioxide must be removed from stack exhaust gases, hydrogen 10 ¦ sulfide has to be generated if sulfur is to be produced.
¦ This may be accomplished by converting two thirds of the ¦ stripped sulfur dioxide to hydrogen sulfide and reacting the ¦ balance with the formed hydrogen sulfide over an alumina ¦ catalyst in the catalytic zone of a typical Claus plant.
15 ¦ Another possibility, which has been proposed for the ¦ regeneration step of the Citrate process, is to produce hydrogen ¦ sulfide by reduction of elemental sulfur generated in the ¦ process for reaction with sulfur dioxide dissolved in the I citrate solution.
201 Known methods of producing hydrogen sulfide from elemental sulfur have been described, for instance, in "Canadian Mining l and Metallurgical Bulletin", October 1957, p. 614 and follow-¦ ing, and '~ining Engineering", January 1970, p. 75 and follow-I ing.
25¦ The former process involves non-catalytic direct reaction of hydrogen with sulfur to form hydrogen sulfide at temperatures from 820 to 1000F. An admitted deficiency in the process is ¦ that the reaction products, i.e., a mixture of unreacted I sulfur and hydrogen sulfide, are highly corrosive. Type 316 301 stainless steel, for instance, suffers severe corrosion. In iO579 34 1 addition, hydrogcn of hi~h purity is required for the process and this is expensive.
The process described in the latter publication involves two conversion stages. In the first, sulfur is reacted with a S hydrocarbon, such as methane, at a temperature from 600 to 700C
over a catalyst to form a mixture of hydrogen sulfide and carbon disulfide. The gas stream is passed to a second stage where, at a temperature of 200 to 300C, the carbon disulfide reacts with water to form hydrogen suifide and carbon dioxide.
This process also sufers from severe corrosion problems and the net gas stream can contain considerable quantities of carbon-sulfur compounds such as carbonyl sulfide and carbon disulfide.
As it pertains to the operation of the Citrate process, it would be necessary to convert two thirds of the formed sulfur to hydrogen sulfide for reaction with sulfur dioxide in the liquid phase at ambient temperature. This is an expensive operation from an energy conservation standpoint since two-thirds of the product must always be recycled back in the form of hydrogen sulfide. Further, the proposed means to generate hydrogen sulfide from the formed sulfur leaves much to be desired due to the corrosion and pOllution problems attendant to the generation of hydrogen sulfide from the elemental sulfur.
l(lS7~4 l Summary of the Invention In accordance with the present invention there is provided a process for the production of sulfur from sulfur dioxide contained in gas streams which comprises: -(a~ passing a sulfur dioxide containing gas stream through a sulfur dioxide absorption zone containing an aqueous absorbent for sulfur dioxide to form a sulfur dioxide rich absorbent and a sulfur dioxide lean gaseous stream;
(b) separating the sulfur dioxide rich absorbent from the absorption zone;
(c) passing about one-third of the sulfur dioxide rich absorbent to a sulfur production zone;
(d) passing the balance of the sulfur dioxide rich absorbent to a sulfur dioxide stripping zone to separate sulfur dioxide from the absorbent to form a sulfur dioxide lean absorbent for recycle to the absorption zone;
(e~ catalytically hydrogenating the sulfur dioxide separated from the sulfur dioxide rich absorbent in the stripping zone in the presence of a source of hydrogen to hydrogen sulfide at a temperature from about 300 to about lOQ0F in the presence of a catalyst consisting of at least one supported metal selected from Group Va, VIa, VIII and the Rare Earth Series of the Periodic Table;
(f) passing the formed hydrogen sulfide to the sulfur production zone where sulfur is formed from the introduced hydrogen sulfide and sulfur dioxide.
Also in accordance with the invention there is provided a process for the production of sulfur from sulfur dioxide contained in gas streams which comprises:
10~7~34 1 (a) passing a sulfur dioxide containing gas stream through a sulfur dioxide absorption zone containing an aqueous absorbent for sulfur dioxide to form a sulfur dioxide rich absorbent and sulfur dioxide lean gaseous stream;
(b) separating the sulfur dioxide rich absorbent from the absorption zone; ~- ;
~c) stripping sulfur dioxide from about two thirds of the sulfur dioxide rich absorbent to form a sulfur dioxide lean absorbent for recycle to the absorption zone;
(d~ catalytically hydrogenating the sulfur dioxide, separated from the sulfur dioxide rich absorbent by stripping in the presence of a source of hydrogen to hydrogen sulfide at a temperature from about 300 to about 1000F in the presence of a catalyst consisting of at least one supported metal selected from Group Va, VIa, VIII and the Rare Earth Series of the Periodic Table;
'~ (el combining the formed hydrogen sulfide and the balance of the sulfur dioxide rich absorbent solution in a sulfur production zone where sulfur is formed by an aqueous phase,reaction between hydrogen sulfide and sulfur dioxide to yield a sulfur dioxide lean absorption solution for recycle to the absorption zone.
Thus, according to the present invention there is provided an improvement to processes where sulfur is to be formed from the ~ulfur dioxide extracted from gas streams by an aqueous sulfur dioxide ab.sorption ~olution, such as the Citrate process ~:~ ~ ~
1~57~ ~
l which employs a buffered aqueous solution of an alkali metal citrate, such as sodium citrate, as the absorbent solution.
In accordance with the practice of the present invention a gas stream containing sulfur dioxide is passed through an absorption zone where sulfur dioxide is extracted by an aqueous sulfur dioxide ab~orption solution. Aqueous absorption solution laden with sulfur dioxide is continuously separated from the absorption zone and split. Approximately two thirds of the sulfur dioxide rich absorption solution is passed to a sulfur dioxide stripping zone where sulfur dioxide is separated from the aqueous solution. The sulfur dioxide lean absorption solution is recycled back to the absorption zone.
The sulfur dioxide separated from the absorption solution is then catalytically hydrogenated in the presence of a source of lS hydrogen to hydrogen sulfide. This is preferably accomplished l by forming a reducing gas stream by the combustion of a i carbonaceous fuel such as methane, in the presence of a source of oxygen, typically air, in a reducing gas generator. This forms a gas stream containing as the principal reductants hydrogen and carbon monoxide. The gaseous products from the reducing gas generator are combined with the sulfur dioxide gas and passed to catalytic conversion zone 42 where at a temperature from about 300 to about 1000F, preferably from abo~
500 to about 800F, the sulfur dioxide reacts with the hydrogen present and the hydrogen formed as a consequence of the reaction of carbon monoxide with water to yield hydrogen sulfide. The cata~ysts employed are those containing the metals o Group Va, VIa, VIII and the Rare Earth series of the Periodic Table as defined by Mendeleef and published as the "Periodic Chart of the Atoms" by W. N. Welch Manufacturing Company. The metals are preferably supported on conventional 1~579 3~
supports such as silica, alumina, alumina-silica, and the zeolites. Alumina is preferred. The preferred catalysts are those containing one or more of the metals cobalt, molybdenum, iron, chromium, vanadium, thoria, nickel, tungsten and uranium. A cobalt-molybdate catalyst where the support is alumina is particularly preferred.
In addition to causing the hydrogenation of sulfur dioxide to hydrogen sulfide at the temperatures employed, the catalyst serves to hydrolyze any carbonyl sulfide and carbon disulfide which may be present or formed to hydrogen sulfide.
The water required for the hydrogenation and hydrolysis reactionS may be provided in the stripped sulfur dioxide gas stream. The hydrogen sulfide gas stream after cooling to remove any water present, is combined with the aqueous 15 solution containing the balance of sulfur dioxide where,in the aqueous phase,the hydrogen sulfide reacts with the sulfur dioxide to form elemental sulfur. The elemental sulfur is collected as product, a gas stream now free of sulfur species vented to the atmosphere and the aqueous absorption solution 20 recycled back to the absorption zone.
In the practice of the process of this invention all of the sulfur dioxide removed from the gas stream in the absorption zone leaves the process as elemental sulfur and no recycle of product sulfur is required for the production of hydrogen sulfide.
An additional advantage of the process is that by using sulfur dioxide stripped from two thirds of the absorption solution as the source of hydrogen sulfide, the proper stoichiometry ~ill always be maintained in the sulfur dioxide production zone regardless of solution loading. This enables ready control over the system and prevents unreacted hydrogen sulfide or sulfur dioxidc from being vcnted to the atmosphere.
iO ~'79 ~4 1 The Drawinp, The attached drawing depicts a flow diagr~m for carrying out the preferred process of the present invention.
Description According to the present invention there is provided a process for the production of sulfur from sulfur dioxide absorbed in aqueous absorption solutions. Typical of the absorption solutions are aqueous solutions of a~monia, alkaline salts of inorganic and organic acids and certain aromatic amines which are capable of absorbing sulfur dioxide ! at ambient temperature and releasing the absorbed sulfur dioxide upon the application of heat. The preferred absorbent is an aqueous solution of an alkali metal citrate such as sodium citrate.
With reference to the Drawing, the sulfur dioxide containing gas is passed through sulfur dioxide absorption zone 10, where it is brought into counter current contact with a lean sulfur dioxide absorption solution entering absorption tower 10 in line 12 after being cooled in heat exchanger 14 to maximize the absorption capacity of the solution. The gas stream free of sulfur dioxide is vented to the atmosphere.
The sulfur dioxide-rich absorption solution is withdrawn from the base of absorption tower 10 in line 16 and split. About two thirds of the solution is passed by line 18 after under-going indirect heat exchange with recycled lean solution in heat exchanger 20 to a sulfur dioxide stripping tower 24. In sulfur dioxide stripper 24 the aqueous absorption solution is heated to a temperature which w~ll enable the solution to effectively desorb the contained sulfur dioxide. The heat 1~57~ ~ ~
I required to heat the solution may be provided by indirect heat supplied through reboiler 26.
The lean sulfur dioxide absorption solution is passed by line 28 through heat exchanger 40 and by pump 30 through heat exchanger 14 and back to absorption tower 10.
The sulfur dioxide separated from the absorption solution is passed by line 32 through cooler 34 which enables water vapor and droplets of vaporized absorption solution to cool and coalesce in condenser 36 for recycle by pump 38 back to stripping tower 24.
The sulfur dioxide gas stream which is substantially free of absorption solution but which still contains some water, is passed by line 40 to catalytic converter 42.
Simultaneously there is formed a reducing gas in generator 44. The reducing gas is formed by the partial combustion of a carbonaceous fuel such as methane, propane, butane and the like, in the presence of a source of oxygen, typically air.
Steam may be introduced to suppress the formation of soot and carbon-sulfur compounds. The gas stream exiting reducing gas generator 44 comprises as principal reductants, hydrogen and carbon monoxide which serves as a hydrogen doner as it will react with the water in catalysis zone 42 to generate hydrogen for reaction with sulfur dioxide.
The streams are combined and passed by line 46 to catalytic generator 42. Catalytic generator 42 contains one or more beds of a catalyst capable of hydrogenating the sulfur dioxide to hydrogen sulfide. Preerably, the catalyst is also capable of causing hydrolysis of any carbonyl sulfide and carbon disulfide which may be present or formed in the gas stream to hydrogen sulfide and carbon dioxide.
lU57934 1 Conversion of the sulfur dioxide to hydrogen sulfide occurs at a temperature of from about 300 to about 1000F, preferably from about 500 to about 800F. The catalysts employed are those containing the metals of Group Va, VIa, VIII and the Rare Earth Series of the Periodic Table as defined by ; Mendeleef and published as the "Periodic Chart of the Atoms"
by W. N. Welch Manufacturing Company. The metals are prefer-ably supported on conventional supports such as silica, alumina, alumina-silica, and the zeolites. Alumina is preferred.
The most preferred catalysts are those which contain one or more of the metals cobalt, molybdenum, iron, chromium, ; vanadium, thorea, nickel, tungsten and uranium. A cobalt-molybdate catalyst where the support is alumina is particularly preferred.
Reaction in catalytic con~erter 42 is highly exothermic.
To maintain the temperature within the prescribed range, an external coolant can be employed to absorb the heat of reaction. In the alternative, as shown, there may be injected water as a fine spray into the catalysis zone to ~uench the reaction and absorb the heat of reaction. Introduced water also serves to hydrolYze any carbonyl sulfide and carbon disulfide present to hydrogen sulfide and to react with carbon monoxide present in the effluent from the reducing gas generator to form hydxogen for reaction with the sulfur dioxide. Another alternative is recycling of a portion of the effluent gas from reactor 56. Under the temperature conditions employed, complete conversion of the ~ulfur dioxide to hydrogen sulfide ls realized.
The hydrogen sulfide gas stream from catalytic converter 42 is passed in line 48 to waste heat generator 50 where heat is generated in the form of steam for use in heating the solution undergoing sulfur dioxide stripping in stripper I ~S 7~ ~9~
1 ¦ tower 24, or alternately the hot &aS stream may be passed ¦ through reboiler 26. The gas stream is then passed to contact ¦ cooler 52 where the water present is removed.
¦ Since hydrogenation of sulfur dioxide in converter 42 5 ¦ is complete, the condensate is free o corrosive polythionic ¦ and sulfurous acids.
¦ The hydrogen sulfide gas stream i8 then passed by I line 54 to sulfur production zone 56 where it is brought ¦ into contact with the balance of the sulfur dioxide rich ?
10 ¦ absorption solution from absorber 109 which is passed to ¦ sulfur production zone 56 by line 58.
¦ In sulfur production zone 56, hydrogen sulfide and ¦ sulfur dioxide react in the aqueous phase to form elemental ¦ sulfur which is withdrawn as product, typically as a slurry.
lS ¦ Gases presént which are essentially free of sulfur dioxide ¦ and hydrogen sulfide are vented to the atmosphere. Upon ¦ formation of sulfur, the absorption solution which is rendered l lean, is pumped by pump 60 through line 62 back for recycle ¦ to absorption tower 10.
201 In the practice of this invention, all sulfur dioxide ; removed from the gas stream in the absorber leaves the plant as elemental sulfur and no recycle of product sulfur is required. An additional advantage of the improved process is the fact that by using the sulfur dioxide stripped from two-thirds of the absorbent solution as the source of hydrogen sulfide to react with sulfur dioxide contained in the remain-ing one-third of the solution, the proper stoichiometry will always be maintained in the reaction tank, regardless of solution loading. This feature permits easy control of the system and prevents unreacted hydrogen sulfide or sulfur dioxide to the atmosphere.
1~57~ 3 4 l The improved process, with moclifications, can be applied to other processes embodying thermal regeneration (and stripping of sulfur dioxide) of a solvent. For example, the rich solution from the bottom of the absorber can be split into two streams, in the ratio of 2:1, and stripped in two separate strippers. The sulfur dioxide obtained from the larger stream can be catalytically converted to hydrogen sulfide as described above. The hydrogen sulfide rich gas, without being cooled, is then combined with the sulfur dioxide stripped from the smaller liquid stream in a suLfur production zone and the mixed gases fed to one or more catalytic Claus stages of the sulfur production zone.
Since~ the source of the hydrogen sulfide and sulfur dioxide is the rich absorbent and the control of the split of the rich solution at a ratio of 2:1 is quite simple, the ratio of hydrogen sulfide to sulfur dioxide entering the Claus stages will always be near optimum resulting in maximum conversion ~.-of elemental sulfur.
: i -,
Claims (8)
1. A process for the production of sulfur from sulfur dioxide contained in gas streams which comprises:
(a) passing a sulfur dioxide containing gas stream through a sulfur dioxide absorption zone containing an aqueous absorbent for sulfur dioxide to form a sulfur dioxide rich absorbent and a sulfur dioxide to lean gaseous stream;
(b) separating the sulfur dioxide rich absorbent from the absorption zone;
(c) passing about one-third of the sulfur dioxide rich absorbent to a sulfur production zone;
(d) passing the balance of the sulfur dioxide rich absorbent to a sulfur dioxide stripping zone to separate sulfur dioxide from the absorbent to form a sulfur dioxide lean absorbent for recycle to the absorption zone;
(e) catalytically hydrogenating the sulfur dioxide separated from the sulphur dioxide rich absorbent in the stripping zone in the presence of a source of hydrogen to hydrogen sulfide at a temperature from about 300 to about 1000°F
in the presence of a catalyst consisting of at least one supported metal selected from Group Va, VIa, VIII and the Rare Earth Series of the Periodic Table;
(f) passing the formed hydrogen sulfide to the sulfur production zone where sulfur is formed from the introduced hydrogen sulfide and sulfur dioxide.
(a) passing a sulfur dioxide containing gas stream through a sulfur dioxide absorption zone containing an aqueous absorbent for sulfur dioxide to form a sulfur dioxide rich absorbent and a sulfur dioxide to lean gaseous stream;
(b) separating the sulfur dioxide rich absorbent from the absorption zone;
(c) passing about one-third of the sulfur dioxide rich absorbent to a sulfur production zone;
(d) passing the balance of the sulfur dioxide rich absorbent to a sulfur dioxide stripping zone to separate sulfur dioxide from the absorbent to form a sulfur dioxide lean absorbent for recycle to the absorption zone;
(e) catalytically hydrogenating the sulfur dioxide separated from the sulphur dioxide rich absorbent in the stripping zone in the presence of a source of hydrogen to hydrogen sulfide at a temperature from about 300 to about 1000°F
in the presence of a catalyst consisting of at least one supported metal selected from Group Va, VIa, VIII and the Rare Earth Series of the Periodic Table;
(f) passing the formed hydrogen sulfide to the sulfur production zone where sulfur is formed from the introduced hydrogen sulfide and sulfur dioxide.
2. A process as claimed in claim 1 in which the sulfur dioxide is hydrogenated to hydrogen sulfide at a temperature from about 500 to about 800°F.
3. A process as claimed in claim 1 in which the catalyst consists of cobalt and molybdenum deposited on alumina.
4. A process as claimed in claim 1 in which the aqueous absorption solution is an aqueous metal citrate solution.
5. A process for the production of sulfur from sulfur dioxide contained in gas streams which comprises:
(a) passing a sulfur dioxide containing gas stream through a sulfur dioxide absorption zone containing an aqueous absorbent for sulfur dioxide to form a sulfur dioxide rich absorbent and sulfur dioxide lean gaseous stream;
(b) separating the sulfur dioxide rich absorbent from the absorption zone;
(c) stripping sulfur dioxide from about two thirds of the sulfur dioxide rich absorbent to form a sulfur dioxide lean absorbent for recycle to the absorption zone;
(d) catalytically hydrogenating the sulfur dioxide, separated from the sulfur dioxide rich absorbent by stripping, in the presence of a source of hydrogen to hydrogen sulfide at a temperature from about 300 to about 1000°F in the presence of a catalyst consisting of at least one supported metal selected from group Va, VIa, VIII and the Rare Earth Series of the Periodic Table;
(e) combining the formed hydrogen sulfide and the balance of the sulfur dioxide rich absorbent solution in a sulfur production zone where sulfur is formed by an aqueous phase reaction between hydrogen sulfide and sulfur dioxide to yield a sulfur dioxide lean absorption solution for recycle to the absorption zone.
(a) passing a sulfur dioxide containing gas stream through a sulfur dioxide absorption zone containing an aqueous absorbent for sulfur dioxide to form a sulfur dioxide rich absorbent and sulfur dioxide lean gaseous stream;
(b) separating the sulfur dioxide rich absorbent from the absorption zone;
(c) stripping sulfur dioxide from about two thirds of the sulfur dioxide rich absorbent to form a sulfur dioxide lean absorbent for recycle to the absorption zone;
(d) catalytically hydrogenating the sulfur dioxide, separated from the sulfur dioxide rich absorbent by stripping, in the presence of a source of hydrogen to hydrogen sulfide at a temperature from about 300 to about 1000°F in the presence of a catalyst consisting of at least one supported metal selected from group Va, VIa, VIII and the Rare Earth Series of the Periodic Table;
(e) combining the formed hydrogen sulfide and the balance of the sulfur dioxide rich absorbent solution in a sulfur production zone where sulfur is formed by an aqueous phase reaction between hydrogen sulfide and sulfur dioxide to yield a sulfur dioxide lean absorption solution for recycle to the absorption zone.
6. A process as claimed in claim 5 in which the sulfur dioxide is hydrogenated to hydrogen sulfide at a temperature from about 500 to about 800°F.
7. A process as claimed in claim 5 in which the catalyst consists of cobalt and molybdenum deposited on alumina.
8. A process as claimed in claim 5 in which the aqueous absorption solution is an aqueous alkali metal citrate solution.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
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CA251,021A CA1057934A (en) | 1976-04-26 | 1976-04-26 | Process for the production of sulfur from sulfur dioxide extracted from gas streams |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
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CA251,021A CA1057934A (en) | 1976-04-26 | 1976-04-26 | Process for the production of sulfur from sulfur dioxide extracted from gas streams |
Publications (1)
Publication Number | Publication Date |
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CA1057934A true CA1057934A (en) | 1979-07-10 |
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CA251,021A Expired CA1057934A (en) | 1976-04-26 | 1976-04-26 | Process for the production of sulfur from sulfur dioxide extracted from gas streams |
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1976
- 1976-04-26 CA CA251,021A patent/CA1057934A/en not_active Expired
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