CA1146873A - Process for improving a gas containing a minor amount of sulfur dioxide impurity and producing a hydrogen sulfide-rich gas - Google Patents
Process for improving a gas containing a minor amount of sulfur dioxide impurity and producing a hydrogen sulfide-rich gasInfo
- Publication number
- CA1146873A CA1146873A CA000359213A CA359213A CA1146873A CA 1146873 A CA1146873 A CA 1146873A CA 000359213 A CA000359213 A CA 000359213A CA 359213 A CA359213 A CA 359213A CA 1146873 A CA1146873 A CA 1146873A
- Authority
- CA
- Canada
- Prior art keywords
- gas
- range
- sulfur
- adsorbate
- sulfur dioxide
- 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 61
- 239000007789 gas Substances 0.000 title claims abstract description 55
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 title claims abstract description 13
- 229910000037 hydrogen sulfide Inorganic materials 0.000 title claims abstract description 13
- 238000000034 method Methods 0.000 title claims abstract description 11
- 239000012535 impurity Substances 0.000 title claims abstract description 9
- 239000011593 sulfur Substances 0.000 claims abstract description 25
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 25
- 239000003463 adsorbent Substances 0.000 claims abstract description 22
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims abstract description 20
- 239000002156 adsorbate Substances 0.000 claims abstract description 20
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims abstract description 16
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims abstract description 10
- 229910002091 carbon monoxide Inorganic materials 0.000 claims abstract description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 9
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 claims abstract description 6
- 239000011734 sodium Substances 0.000 claims abstract description 6
- 239000002131 composite material Substances 0.000 claims abstract description 4
- 229910052720 vanadium Inorganic materials 0.000 claims description 10
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 claims description 10
- GNTDGMZSJNCJKK-UHFFFAOYSA-N divanadium pentaoxide Chemical compound O=[V](=O)O[V](=O)=O GNTDGMZSJNCJKK-UHFFFAOYSA-N 0.000 claims description 6
- 239000003245 coal Substances 0.000 claims description 5
- 229910052708 sodium Inorganic materials 0.000 claims description 5
- 239000000571 coke Substances 0.000 claims description 4
- 239000000446 fuel Substances 0.000 claims description 4
- KKCBUQHMOMHUOY-UHFFFAOYSA-N Na2O Inorganic materials [O-2].[Na+].[Na+] KKCBUQHMOMHUOY-UHFFFAOYSA-N 0.000 claims description 3
- LSGOVYNHVSXFFJ-UHFFFAOYSA-N vanadate(3-) Chemical class [O-][V]([O-])([O-])=O LSGOVYNHVSXFFJ-UHFFFAOYSA-N 0.000 claims description 3
- 238000001354 calcination Methods 0.000 claims description 2
- 239000000567 combustion gas Substances 0.000 claims description 2
- 239000007921 spray Substances 0.000 claims description 2
- 239000002912 waste gas Substances 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims 3
- 230000001590 oxidative effect Effects 0.000 claims 1
- 229910001948 sodium oxide Inorganic materials 0.000 abstract description 2
- XHCLAFWTIXFWPH-UHFFFAOYSA-N [O-2].[O-2].[O-2].[O-2].[O-2].[V+5].[V+5] Chemical class [O-2].[O-2].[O-2].[O-2].[O-2].[V+5].[V+5] XHCLAFWTIXFWPH-UHFFFAOYSA-N 0.000 abstract 1
- 229910001935 vanadium oxide Inorganic materials 0.000 abstract 1
- 229940044609 sulfur dioxide Drugs 0.000 description 22
- 235000010269 sulphur dioxide Nutrition 0.000 description 22
- 229960005349 sulfur Drugs 0.000 description 16
- 235000001508 sulfur Nutrition 0.000 description 14
- 239000003546 flue gas Substances 0.000 description 7
- 229940045605 vanadium Drugs 0.000 description 7
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 6
- IHIXIJGXTJIKRB-UHFFFAOYSA-N trisodium vanadate Chemical compound [Na+].[Na+].[Na+].[O-][V]([O-])([O-])=O IHIXIJGXTJIKRB-UHFFFAOYSA-N 0.000 description 5
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 4
- 230000001172 regenerating effect Effects 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 239000011148 porous material Substances 0.000 description 3
- 230000008929 regeneration Effects 0.000 description 3
- 238000011069 regeneration method Methods 0.000 description 3
- 238000001179 sorption measurement Methods 0.000 description 3
- 241000518994 Conta Species 0.000 description 2
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 2
- SMDHCQAYESWHAE-UHFFFAOYSA-N benfluralin Chemical compound CCCCN(CC)C1=C([N+]([O-])=O)C=C(C(F)(F)F)C=C1[N+]([O-])=O SMDHCQAYESWHAE-UHFFFAOYSA-N 0.000 description 2
- 229910002092 carbon dioxide Inorganic materials 0.000 description 2
- 239000001569 carbon dioxide Substances 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000002485 combustion reaction Methods 0.000 description 2
- 238000005470 impregnation Methods 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 229910052698 phosphorus Inorganic materials 0.000 description 2
- 239000011574 phosphorus Substances 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 229910000166 zirconium phosphate Inorganic materials 0.000 description 2
- 229910019142 PO4 Inorganic materials 0.000 description 1
- 239000007983 Tris buffer Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000009089 cytolysis Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 239000000295 fuel oil Substances 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- 239000003701 inert diluent Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- JCXJVPUVTGWSNB-UHFFFAOYSA-N nitrogen dioxide Inorganic materials O=[N]=O JCXJVPUVTGWSNB-UHFFFAOYSA-N 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000006722 reduction reaction Methods 0.000 description 1
- 239000001488 sodium phosphate Substances 0.000 description 1
- 239000002594 sorbent Substances 0.000 description 1
- RYFMWSXOAZQYPI-UHFFFAOYSA-K trisodium phosphate Chemical compound [Na+].[Na+].[Na+].[O-]P([O-])([O-])=O RYFMWSXOAZQYPI-UHFFFAOYSA-K 0.000 description 1
- 229910000406 trisodium phosphate Inorganic materials 0.000 description 1
- 235000019801 trisodium phosphate Nutrition 0.000 description 1
- 238000013022 venting Methods 0.000 description 1
- 239000003039 volatile agent Substances 0.000 description 1
Landscapes
- Solid-Sorbent Or Filter-Aiding Compositions (AREA)
- Treating Waste Gases (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A process is provided for adsorbing sulfur dioxide impurity from an impure gas and producing a hydrogen sulfide-rich gas. In the process, a first adsorbate containing oxidized sulfur is produced by contacting the im-pure gas with an adsorbent comprising a composite of an alumina support and sodium and vanadium oxides. A second adsorbate obtaining reduced sulfur is produced by contacting said first adsorbate with carbon monoxide. A gas rich in hydrogen sulfide is then produced by contacting said second adsorb-ate with water vapor at a temperature in the range 120°C to 815°C.
A process is provided for adsorbing sulfur dioxide impurity from an impure gas and producing a hydrogen sulfide-rich gas. In the process, a first adsorbate containing oxidized sulfur is produced by contacting the im-pure gas with an adsorbent comprising a composite of an alumina support and sodium and vanadium oxides. A second adsorbate obtaining reduced sulfur is produced by contacting said first adsorbate with carbon monoxide. A gas rich in hydrogen sulfide is then produced by contacting said second adsorb-ate with water vapor at a temperature in the range 120°C to 815°C.
Description
1~46~73 BACKGR~UND OF THE INVEN$IoN
-This invention relates to a process for adsorbing sulfur dioxide impurity fram a gas. Mbre particularly, it relates to improving an i~pure gas and producing a hydrogen sulfide-rich gas.
Even as a minor component in a gas, sulfur dioxide is an obnoxious and harmful impurity. Its effective nemoval from a gasecus mix~ure which normally must be vented to the atmDsphere is a ODntinuing problem. m ere is a need for an efficient and economic means for removing sulfur dioxide im-purity from a gas, especially for a regenerative adsorbent system wherein oxidized sulfur is converted to reduced sulfur suitable for use as feed to a Claus sulfur plant and the like. m e present invention prDvides an effect-ive solution to the pnDblem.
SUMMARY OF THE INVENTIoN
. .
A process is provided for improving a gas conta m ing sulfur dioxide impurity which comprises:
(1) producing (i) an adsorbate oontaining oxidized sulfur and (ii) a first effluent gas having, relative to said feed gas, a reduced sulfur dioxide content by contacting said feed gas with an adsorbent under sulfur dioxide adsorbing oonditions, said adsorbent comprising a oomposite of .sodium and vanadium as oxides or vanadate salts and an alumina support;
-This invention relates to a process for adsorbing sulfur dioxide impurity fram a gas. Mbre particularly, it relates to improving an i~pure gas and producing a hydrogen sulfide-rich gas.
Even as a minor component in a gas, sulfur dioxide is an obnoxious and harmful impurity. Its effective nemoval from a gasecus mix~ure which normally must be vented to the atmDsphere is a ODntinuing problem. m ere is a need for an efficient and economic means for removing sulfur dioxide im-purity from a gas, especially for a regenerative adsorbent system wherein oxidized sulfur is converted to reduced sulfur suitable for use as feed to a Claus sulfur plant and the like. m e present invention prDvides an effect-ive solution to the pnDblem.
SUMMARY OF THE INVENTIoN
. .
A process is provided for improving a gas conta m ing sulfur dioxide impurity which comprises:
(1) producing (i) an adsorbate oontaining oxidized sulfur and (ii) a first effluent gas having, relative to said feed gas, a reduced sulfur dioxide content by contacting said feed gas with an adsorbent under sulfur dioxide adsorbing oonditions, said adsorbent comprising a oomposite of .sodium and vanadium as oxides or vanadate salts and an alumina support;
(2) producing an adsorbate containing reduced sulfur by contacting said oxidized sulfur-c~ltaining adsorbate at a temperature in the range of about 370 to 815C with a gas oonsisting essentially of carbon monoxide; and
(3) producing a second effluent gas rich in hydrogen sulfide by oon-tacting said reduoe d-sulfur-containing adsorbate with water vapor at a temperature in the range of about 90 to 815 & .
A major aspect of the present invention was a surprising discovery.
m us, it was found that so long as a reducing-gas stream oomprising carbon mDnoxide having no substantial oontent of water vapor was contacted with an adsorbate containing oxidized sulfur, the effluent gas cantaining residual ~, b'~ c~
carbon monoxide contained little or no hydrogen sulfide and an adsorbate con-taining redu oe d sulfur was produ oe d. A yet further aspect was the discovery that a hydrogen sulfide-rich effluent gas stream was produoe d when the adsorbate containing redu oe d sulfur was contacted with a gas rich in water vapor. These discoveries provide a two-fold advantage. First, the effluent gas during an oxidized-sulfur reducing step is not conta D ated with hydrogen sulfide and may be conveniently disposed of, for example, by camr busting. Second, a hydrogen sulfide-rich gas stream without contaminating am~unts of carbon monoxide is produ oe d. Such a stream is especially suit-able, for example, as feed for a Claus plant or the like.
By "sulfur dioxide adsorbing canditions" as used herein is meant contacting at (1) a temperature in the range of from about 90C to 345C, (2) a pressure in the range of from about 0.8 to 5 atmospheres, and (3) a space velocity, volume of gas per bulk volume of adsorbent per haur, in the range of from about 500 to 40,000. Preferred sulfur dioxide adsorbing conditions include contacting at (1) a temperature in the range 120 to 260 &, (2) a pressure in the range 1 to 1.5 atmospheres, and (3) a V/V/Hr in the range 1000 to 20,000.
EMEODIMENT
The Figure is a schematic process flow diagram representing a pre-ferred enlxxl~ment of the invention. A sulfur-containing coal or coke fuel is delivered by any suitable means, for example a conveyor system via 1 to boiler unit 2, wherein the fuel is typically combusted and steam, an effluent combustion or flue gas containing sulfur dioxide impurity and residual ash are produ oe d. Via lines 3 and 4 the ash and flue gas, the latter at a temperature of about 150C, are withdrawn from unit 2.
Because the sulfur dioxide content of the flue gas ex oe eds a per-missible level, for example about 75 ppmw, the flue gas must be desulfurized.
To this end, via line 4 the flue gas is passed to adsorber unit 5 wherein it is contacted with a sulfur dioxide adsorbent at (1) a temperature of about ~'146873 150 &, (2) a pressure of about 1.03 atm~spheres, and (3) a space velocity of about 10,000 V/V/Hr. me resulting adsorption of sulfur dioxide, for conven-ience, may be represented as follaws: -(1) Adsorbent-O + SO2 -> Adsorbent-O.S02 m e adsorbent in unit 5 is a moving bed of a aowposite of sodium vanadate disposed upon porous alumina having (1) a weight ratio of vanadium to alumina of about 1 to 20, (2) a mol ratio of sodium to vanadium of about 3 to 1, (3) a surface area of about 150 m2/g, and (4) a particle size of about 0.6 cm. m is ~A~rbent is conveniently and typically prepared by im-pregnating a oommercially available alumina with an aqueous solutian of sodium ortho vanadate followed by drying.
Via line 6, treated flue gas is withdrawn from unit 5 and vented to the atmDsphere. m e sulfur dioxide content of the treated gas is deter-mined by means of a aanventional monitoring unit, which is not shown.
Regenerated adsorbent is added via line 18 and spent adsorbent is withdrawn via line 6 at a rate sufficient to maintain the sulfur dioxide content of the flue gas below a predetermined level, for example, 75 ppmw.
For the regeneration, the spent adsorbent (adsorbate containing axidized sulfur, e.g., +4 and/or +6 sulfur) is withdrawn from w t 5 and pa~s d via line 6 to redu oe r unit 7 wherein at a temperature of about 480 &
it is aanverted to an adsorbate aontaining reduced (-2) sulfur in a reaction which may oanvenientl~ be represented as follcws:
(2) ~dsorbent-O.S02 + 3CO -> Adsorkent-S + 3CO2 This canversion is achieved by introducing a suitable hot gas stream aontain-ing carbon man~xi,de via line 8 into reduaer 7 into aontact with the spent ad-sorbent. The effluent gas stream contains carbon monoxide and tra oe s of sulfur-cantaining gases. In order to clean it up for venting, this stream is ccmbusted in unit 2.
m e carbon moncxide stream required for the regeneration is ob-~46873 tained by typical partial oxidation of calcined coal or coke which is intro-duoe d to gasifier 11 via line 12 for disposal, together with ash from line 3 produoe d in unit 2 for disposal via l;ne 13.
The adsorbate containing redu oe d sulfur resulting from the reduc-tion carried out in redu oe r 7 is withdrawn via line 14 and passed to hydrolyzer 15, where m it is contacted with low-pressure steam intrcduoe d via line 16. A rapid reaction ensues upon the contacting in which a hydrogen sulfide-rich gas is generated. The reaCtiQn may conveniently be summarized as follows:
(3) Adsorbent-S + H20 -> Adsorbent-O + H2S
Via line 17, this gas is withdrawn from hydrolyzer 15 for use as desired, for exa~ple as feed to a Claus plant or the like, and via line 18, regene-rated adsorbent is recycled to adsorber 5.
Feed Gas Gases in general which have in the past normally been vented to the atmosphere and which contain sulfur dioxide as an impurity (usually less than a~out 5 vDlume per oe nt thereof is sulfur dioxide) are satisfactory feed-stocks for the prooess of the invention and are oontemplated for such use.
Preferred feedstocks are effluent gases (waste gas) resulting from combusting (or calcining) a ql~lfur-contaln m g fuel, for exa~ple coal, fuel oil, re-finery residue, ooke and the like. Representative such gases 11~68'73 include off-gas streams, steam boiler combustion, incinerator and the like industrial gaseous effluent streams containing sul-fur dioxide impurity. Typically, such gases have a sulfur diox-ide content in the 100 ppmw to 5 volume percent range.
Adsorbent Adsorbents satisfactory and contemplated for use herein include composites comprising a minor fraction of sodium and vana-dium as oxides and/or vanadate salts, and a major fraction of a porous support, preferably containing at least 80 weight percent of alumina, and more preferably alumina. Typical adsorbents are described in United States Patents 3,501,897 and 3,816,597.
The relative portions of the components of the adsorbent composite may vary. In general, better results are achieved when the weight ratio of vanadium support is in the range 1 to 50-10, preferably 1 to 40-lS, and more preferably 1 to 20, and the molar ratios of sodium oxide to vanadium pentoxide is in the range 1:2 to 12:1, preferably 1:1 to 6:1, and more preferably 3 to 1, respectively.
The support must be porous and should have a surface area of at least 20 m /g and usually is in the range 20 to 400 m /g.
Conditions satisfactory, in general, and contemplated for use in the reducing step herein, include a temperature in the range of from about 370C to 650C, preferably 425C to 540C, more preferably about 480C.
A gas, in general, comprising carbon monoxide and inert diluents, such as nitrogen, carbon dioxide and the like, is satis-factory and contemplated for use in the reducing step herein. It may also contain a minor amount, for example below about 1 volume.
1~46873 per oe nt, of water vapor, although a substantially (less than 500 ppmw) anhydrous gas is preferred. A representative and preferred reducing gas is one produced by a typical partial oxidation of calcined coal or coke; an-other is a gas containing about 30 volume percent of carbon monoxide and the balan oe being nitrogen and carbon dioxide.
Hydr~lysis Step Conditions satisfactory, in general, and contemplated for use in the hydrolysis step herein, include (1) a temperature in the range of fram about 120 to 815C, preferably 150 to 540 &, and more preferably 150 & to 480 & (for example resulting from quenching or cooling the adsorbate contain-ing redu oe d sulfur to about 150 &), (2) a pressure in the range of fram about atmospheric to 10 atmospheres, preferably at or below that of a typical low-pxessure steam, and (3) use of a water spray or, preferably, low-pressure steam.
EXAMPLES
The follcwing examples are provided for the further description of the invention, there being no intent therein to limit the scope of the inven-tion.
Examples 1-6 In the following examples, the carrier was a porous alumLna having (1) a surface area of about 200 m /g; (2) pore volume of about 0.6 cc per gram, of which about 75% of the pore volume was provided by pores in the 80-to 150-Angstrom-diameter range; and (3) a 24- to 42-mesh particle size. In each example, the adsorbent was prepared by the impregnation method using concentration of aqueous sodium ortho-vanadate or a mixture of sodium ortho-vanadate and tris~A;um phosphate. In each case, the wet or impregnated carrier was dried by maintaining it at 150C and finally any remaining volatiles were remDved by maintaining the dried adsorbent at 482 & and in a stream of nitrogen gas until, for practical purposes, oonstant weight was reached.
- ~1468~73 In a standard test, each adsorbent in a fixed bed was subjected to alternate adsorbing and regenerating cycles until its capacity (defined as SO2-loading when the effluent stream reaches a sulfur dioxide content of 0.05 volume percent) had leveled out.
In the adsorbing cycle of the test, the sulfur dioxide-containing gas used had the following composition:
Cbmponent %, Volume S2 0.2 o~2 12 N2 Balan oe m e conditions for the adsorbing cycle included a te~perature of lS0 & and a spa oe velocity of 5000 V/V/Hr 1.
In the regenerating cycle, the spent bed was nalntained at 482 &
and a regenerating gas oonsisting of 10 volume peroe nt CO in nitrogen was passed through the bed for l to 2 hours. The redu oe d adsorbeni was then con-tacted with the same water vapor containing gas used in the adsorption cycle.
Evolution of H2S was virtually complete in less than 12 m;inutes.
The test results are listed in the Table below.
TABLE
Example Vanadium, A~ded Component Capacity, No. Wt. ~ Kind Wt Wt. % SO~
1 5 None - 6.0 2 5 P 1.1 9.7 3 5 P 2.2 8.3
A major aspect of the present invention was a surprising discovery.
m us, it was found that so long as a reducing-gas stream oomprising carbon mDnoxide having no substantial oontent of water vapor was contacted with an adsorbate containing oxidized sulfur, the effluent gas cantaining residual ~, b'~ c~
carbon monoxide contained little or no hydrogen sulfide and an adsorbate con-taining redu oe d sulfur was produ oe d. A yet further aspect was the discovery that a hydrogen sulfide-rich effluent gas stream was produoe d when the adsorbate containing redu oe d sulfur was contacted with a gas rich in water vapor. These discoveries provide a two-fold advantage. First, the effluent gas during an oxidized-sulfur reducing step is not conta D ated with hydrogen sulfide and may be conveniently disposed of, for example, by camr busting. Second, a hydrogen sulfide-rich gas stream without contaminating am~unts of carbon monoxide is produ oe d. Such a stream is especially suit-able, for example, as feed for a Claus plant or the like.
By "sulfur dioxide adsorbing canditions" as used herein is meant contacting at (1) a temperature in the range of from about 90C to 345C, (2) a pressure in the range of from about 0.8 to 5 atmospheres, and (3) a space velocity, volume of gas per bulk volume of adsorbent per haur, in the range of from about 500 to 40,000. Preferred sulfur dioxide adsorbing conditions include contacting at (1) a temperature in the range 120 to 260 &, (2) a pressure in the range 1 to 1.5 atmospheres, and (3) a V/V/Hr in the range 1000 to 20,000.
EMEODIMENT
The Figure is a schematic process flow diagram representing a pre-ferred enlxxl~ment of the invention. A sulfur-containing coal or coke fuel is delivered by any suitable means, for example a conveyor system via 1 to boiler unit 2, wherein the fuel is typically combusted and steam, an effluent combustion or flue gas containing sulfur dioxide impurity and residual ash are produ oe d. Via lines 3 and 4 the ash and flue gas, the latter at a temperature of about 150C, are withdrawn from unit 2.
Because the sulfur dioxide content of the flue gas ex oe eds a per-missible level, for example about 75 ppmw, the flue gas must be desulfurized.
To this end, via line 4 the flue gas is passed to adsorber unit 5 wherein it is contacted with a sulfur dioxide adsorbent at (1) a temperature of about ~'146873 150 &, (2) a pressure of about 1.03 atm~spheres, and (3) a space velocity of about 10,000 V/V/Hr. me resulting adsorption of sulfur dioxide, for conven-ience, may be represented as follaws: -(1) Adsorbent-O + SO2 -> Adsorbent-O.S02 m e adsorbent in unit 5 is a moving bed of a aowposite of sodium vanadate disposed upon porous alumina having (1) a weight ratio of vanadium to alumina of about 1 to 20, (2) a mol ratio of sodium to vanadium of about 3 to 1, (3) a surface area of about 150 m2/g, and (4) a particle size of about 0.6 cm. m is ~A~rbent is conveniently and typically prepared by im-pregnating a oommercially available alumina with an aqueous solutian of sodium ortho vanadate followed by drying.
Via line 6, treated flue gas is withdrawn from unit 5 and vented to the atmDsphere. m e sulfur dioxide content of the treated gas is deter-mined by means of a aanventional monitoring unit, which is not shown.
Regenerated adsorbent is added via line 18 and spent adsorbent is withdrawn via line 6 at a rate sufficient to maintain the sulfur dioxide content of the flue gas below a predetermined level, for example, 75 ppmw.
For the regeneration, the spent adsorbent (adsorbate containing axidized sulfur, e.g., +4 and/or +6 sulfur) is withdrawn from w t 5 and pa~s d via line 6 to redu oe r unit 7 wherein at a temperature of about 480 &
it is aanverted to an adsorbate aontaining reduced (-2) sulfur in a reaction which may oanvenientl~ be represented as follcws:
(2) ~dsorbent-O.S02 + 3CO -> Adsorkent-S + 3CO2 This canversion is achieved by introducing a suitable hot gas stream aontain-ing carbon man~xi,de via line 8 into reduaer 7 into aontact with the spent ad-sorbent. The effluent gas stream contains carbon monoxide and tra oe s of sulfur-cantaining gases. In order to clean it up for venting, this stream is ccmbusted in unit 2.
m e carbon moncxide stream required for the regeneration is ob-~46873 tained by typical partial oxidation of calcined coal or coke which is intro-duoe d to gasifier 11 via line 12 for disposal, together with ash from line 3 produoe d in unit 2 for disposal via l;ne 13.
The adsorbate containing redu oe d sulfur resulting from the reduc-tion carried out in redu oe r 7 is withdrawn via line 14 and passed to hydrolyzer 15, where m it is contacted with low-pressure steam intrcduoe d via line 16. A rapid reaction ensues upon the contacting in which a hydrogen sulfide-rich gas is generated. The reaCtiQn may conveniently be summarized as follows:
(3) Adsorbent-S + H20 -> Adsorbent-O + H2S
Via line 17, this gas is withdrawn from hydrolyzer 15 for use as desired, for exa~ple as feed to a Claus plant or the like, and via line 18, regene-rated adsorbent is recycled to adsorber 5.
Feed Gas Gases in general which have in the past normally been vented to the atmosphere and which contain sulfur dioxide as an impurity (usually less than a~out 5 vDlume per oe nt thereof is sulfur dioxide) are satisfactory feed-stocks for the prooess of the invention and are oontemplated for such use.
Preferred feedstocks are effluent gases (waste gas) resulting from combusting (or calcining) a ql~lfur-contaln m g fuel, for exa~ple coal, fuel oil, re-finery residue, ooke and the like. Representative such gases 11~68'73 include off-gas streams, steam boiler combustion, incinerator and the like industrial gaseous effluent streams containing sul-fur dioxide impurity. Typically, such gases have a sulfur diox-ide content in the 100 ppmw to 5 volume percent range.
Adsorbent Adsorbents satisfactory and contemplated for use herein include composites comprising a minor fraction of sodium and vana-dium as oxides and/or vanadate salts, and a major fraction of a porous support, preferably containing at least 80 weight percent of alumina, and more preferably alumina. Typical adsorbents are described in United States Patents 3,501,897 and 3,816,597.
The relative portions of the components of the adsorbent composite may vary. In general, better results are achieved when the weight ratio of vanadium support is in the range 1 to 50-10, preferably 1 to 40-lS, and more preferably 1 to 20, and the molar ratios of sodium oxide to vanadium pentoxide is in the range 1:2 to 12:1, preferably 1:1 to 6:1, and more preferably 3 to 1, respectively.
The support must be porous and should have a surface area of at least 20 m /g and usually is in the range 20 to 400 m /g.
Conditions satisfactory, in general, and contemplated for use in the reducing step herein, include a temperature in the range of from about 370C to 650C, preferably 425C to 540C, more preferably about 480C.
A gas, in general, comprising carbon monoxide and inert diluents, such as nitrogen, carbon dioxide and the like, is satis-factory and contemplated for use in the reducing step herein. It may also contain a minor amount, for example below about 1 volume.
1~46873 per oe nt, of water vapor, although a substantially (less than 500 ppmw) anhydrous gas is preferred. A representative and preferred reducing gas is one produced by a typical partial oxidation of calcined coal or coke; an-other is a gas containing about 30 volume percent of carbon monoxide and the balan oe being nitrogen and carbon dioxide.
Hydr~lysis Step Conditions satisfactory, in general, and contemplated for use in the hydrolysis step herein, include (1) a temperature in the range of fram about 120 to 815C, preferably 150 to 540 &, and more preferably 150 & to 480 & (for example resulting from quenching or cooling the adsorbate contain-ing redu oe d sulfur to about 150 &), (2) a pressure in the range of fram about atmospheric to 10 atmospheres, preferably at or below that of a typical low-pxessure steam, and (3) use of a water spray or, preferably, low-pressure steam.
EXAMPLES
The follcwing examples are provided for the further description of the invention, there being no intent therein to limit the scope of the inven-tion.
Examples 1-6 In the following examples, the carrier was a porous alumLna having (1) a surface area of about 200 m /g; (2) pore volume of about 0.6 cc per gram, of which about 75% of the pore volume was provided by pores in the 80-to 150-Angstrom-diameter range; and (3) a 24- to 42-mesh particle size. In each example, the adsorbent was prepared by the impregnation method using concentration of aqueous sodium ortho-vanadate or a mixture of sodium ortho-vanadate and tris~A;um phosphate. In each case, the wet or impregnated carrier was dried by maintaining it at 150C and finally any remaining volatiles were remDved by maintaining the dried adsorbent at 482 & and in a stream of nitrogen gas until, for practical purposes, oonstant weight was reached.
- ~1468~73 In a standard test, each adsorbent in a fixed bed was subjected to alternate adsorbing and regenerating cycles until its capacity (defined as SO2-loading when the effluent stream reaches a sulfur dioxide content of 0.05 volume percent) had leveled out.
In the adsorbing cycle of the test, the sulfur dioxide-containing gas used had the following composition:
Cbmponent %, Volume S2 0.2 o~2 12 N2 Balan oe m e conditions for the adsorbing cycle included a te~perature of lS0 & and a spa oe velocity of 5000 V/V/Hr 1.
In the regenerating cycle, the spent bed was nalntained at 482 &
and a regenerating gas oonsisting of 10 volume peroe nt CO in nitrogen was passed through the bed for l to 2 hours. The redu oe d adsorbeni was then con-tacted with the same water vapor containing gas used in the adsorption cycle.
Evolution of H2S was virtually complete in less than 12 m;inutes.
The test results are listed in the Table below.
TABLE
Example Vanadium, A~ded Component Capacity, No. Wt. ~ Kind Wt Wt. % SO~
1 5 None - 6.0 2 5 P 1.1 9.7 3 5 P 2.2 8.3
4 5 P* 2.0 3.0 P* 1.0 3.4 *Phosphorus in the form of aqueous trisodium phosphate added separately to alumina carrier and calcined prior to impregnation using sodium vanadate solution.
These data demanstrate that the ~ tion of an aIkali metal salt of an oxyacid of phosphorus enhances the sulfur dioxide capacity of sulfur dioxide adsorbents comprising a porous alumina carrier and an aIkaline earth salt of an oxyacid of vanadium, for example sodium phosphovanadate.
These data also demanstrate that significant capacities for S02 adsorption are maintained when using the regeneration prccedure described herein.
These data demanstrate that the ~ tion of an aIkali metal salt of an oxyacid of phosphorus enhances the sulfur dioxide capacity of sulfur dioxide adsorbents comprising a porous alumina carrier and an aIkaline earth salt of an oxyacid of vanadium, for example sodium phosphovanadate.
These data also demanstrate that significant capacities for S02 adsorption are maintained when using the regeneration prccedure described herein.
Claims (4)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for improving a gas containing sulfur dioxide impurity comprising:
(1) producing (i) an adsorbate containing oxidized sulfur and (ii) a first effluent gas having, relative to said feed gas, a reduced sulfur dioxide content by contacting said feed gas with an adsorbent under sulfur dioxide adsorbing conditions, said adsorbent comprising a composite of sodium and vanadium as oxides or vanadate salts and a porous support contain-ing at least 80 weight percent-alumina;
(2) producing an adsorbate containing reduced sulfur by contacting said oxidized sulfur-containing adsorbate at a temperature in the range of about 370° to 815° with a gas consisting essentially of carbon monoxide;
and (3) producing a second effluent gas rich in hydrogen sulfide by con-tacting said reduced-sulfur-containing adsorbate with a water vapor contain-ing gas at a temperature in the range of about 90° to 815°C.
(1) producing (i) an adsorbate containing oxidized sulfur and (ii) a first effluent gas having, relative to said feed gas, a reduced sulfur dioxide content by contacting said feed gas with an adsorbent under sulfur dioxide adsorbing conditions, said adsorbent comprising a composite of sodium and vanadium as oxides or vanadate salts and a porous support contain-ing at least 80 weight percent-alumina;
(2) producing an adsorbate containing reduced sulfur by contacting said oxidized sulfur-containing adsorbate at a temperature in the range of about 370° to 815° with a gas consisting essentially of carbon monoxide;
and (3) producing a second effluent gas rich in hydrogen sulfide by con-tacting said reduced-sulfur-containing adsorbate with a water vapor contain-ing gas at a temperature in the range of about 90° to 815°C.
2. A process as in Claim 1 wherein said impure gas is a waste gas re-sulting from calcining or combusting a sulfur-containing fuel.
3. A process as in Claim 1 wherein (I) said sulfur dioxide adsorbing conditions include (1) a temperature in the range of from about 120° to 260°C, (2) a pressure in the range of from about 1 to 1.5 atmospheres, and (3) a space velocity in the range of from about 1000 to 20,000; (II) said adsorbent has (1) a weight ratio of vanadium to support in the range of from about 1 to 50-10, (2) a mol ratio of Na2O to V2O5 in the range of from about 1:2 to 12:1, and (3) a surface area in the range of from about 20 to 400 m2/gram; (III) said production of reduced-sulfur-containing absorbate is carried out at a temperature in the range of from about 370° to 650°C using a substantially anhydrous reducing gas comprising carbon monoxide; and (IV) said production of said second effluent gas is carried out (1) at a temperature in the range of from about 120° to 650°C. (2) at a pressure of from about 1 to 10 atmospheres, and (3) using a water spray or low-pressure steam.
4. A process as in claim 3 wherein (1) said impure gas is a combustion gas, (2) said range of weight ratio of vanadium to support is 1 to 40-15, (3) said range of molar ratio of Na2O to V2O5 is 1:1: to 6:1, (41 said reducing gas is produced by partially oxidizing calcined coal or coke, (5) said second effluent production temperature range is 120°C to 480°C, and (6) said contacting of said reduced-sulfur-containing adsorbate is carried out using low-pressure steam.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000359213A CA1146873A (en) | 1980-08-28 | 1980-08-28 | Process for improving a gas containing a minor amount of sulfur dioxide impurity and producing a hydrogen sulfide-rich gas |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000359213A CA1146873A (en) | 1980-08-28 | 1980-08-28 | Process for improving a gas containing a minor amount of sulfur dioxide impurity and producing a hydrogen sulfide-rich gas |
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| Publication Number | Publication Date |
|---|---|
| CA1146873A true CA1146873A (en) | 1983-05-24 |
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| CA000359213A Expired CA1146873A (en) | 1980-08-28 | 1980-08-28 | Process for improving a gas containing a minor amount of sulfur dioxide impurity and producing a hydrogen sulfide-rich gas |
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| Country | Link |
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| CA (1) | CA1146873A (en) |
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1980
- 1980-08-28 CA CA000359213A patent/CA1146873A/en not_active Expired
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