CA1136384A - Regeneration of spent so.sub.2-so.sub.3 sorbents with h.sub.2s at moderate temperature - Google Patents
Regeneration of spent so.sub.2-so.sub.3 sorbents with h.sub.2s at moderate temperatureInfo
- Publication number
- CA1136384A CA1136384A CA000339103A CA339103A CA1136384A CA 1136384 A CA1136384 A CA 1136384A CA 000339103 A CA000339103 A CA 000339103A CA 339103 A CA339103 A CA 339103A CA 1136384 A CA1136384 A CA 1136384A
- Authority
- CA
- Canada
- Prior art keywords
- cerium oxide
- gas
- regenerating
- spent
- sub
- 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
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/46—Removing components of defined structure
- B01D53/48—Sulfur compounds
- B01D53/50—Sulfur oxides
- B01D53/508—Sulfur oxides by treating the gases with solids
Abstract
ABSTRACT OF THE DISCLOSURE
A process for desulfurizing an effluent waste gas stream comprising adsorbing sulfur oxides by a cerium oxide sorbent, at a temperature of from 300-700°C in the presence of sufficient oxygen to convert any SO2 in said gas to SO3 and thereafter regenerating the spent cerium oxide sorbent, said process charact-erized in that said spent cerium oxide sorbent is regenerated by contacting said spent cerium oxide sorbent with an H2S containing reducing-regenerating gas comprising from 0.5 to 100.0 volume percent H2S with the balance comprising a non-regenerating gas, at a temperature of from 300-700°C at a convenient flow rate.
A process for desulfurizing an effluent waste gas stream comprising adsorbing sulfur oxides by a cerium oxide sorbent, at a temperature of from 300-700°C in the presence of sufficient oxygen to convert any SO2 in said gas to SO3 and thereafter regenerating the spent cerium oxide sorbent, said process charact-erized in that said spent cerium oxide sorbent is regenerated by contacting said spent cerium oxide sorbent with an H2S containing reducing-regenerating gas comprising from 0.5 to 100.0 volume percent H2S with the balance comprising a non-regenerating gas, at a temperature of from 300-700°C at a convenient flow rate.
Description
i3i~
BRIEF DISCLOSURE '~
The metal oxides CeO2, either supported or unsupported, used to remove sulfur oxides from waste gas effluent streams by conversion into cerium sulfate and/or cerium oxysulfate, is re~
generated to the starting cerium oxide by means of a reducing regenerating atmosphere consisting essentially of H2S as the re ducing component at a concentration of from 0.5 to 100 vol. ~, preferably 1-70 vol. ~, most preferably 5-70 vol. ~, the balance comprising non-regenerating non-reactive and inert gases such as helium, argon, CO2, nitrogen, water vapor, etc. at a temperature of from 3~0-700 C, preferably 350-700C, most preferably 450-600 C
in the presence of sufficient oxygen to convert any SO2 in said gas to SO3, (in the SO2 removal step) the reducing-regenerating atmosphere passing at any convenient rate, such as from 50 to 50,000 V/V/Hr, preferably 100 to 50,000 V/V/Hr, most preferably 100-20,000 V/V/Hr.
Regeneration is typically conducted on the cerium oxide sorbent which has been converted to cerium sulfate, and/or oxy-sulfate to the extent of 10 to 100 mole ~, preferably 10-70 mole %.
Regenera~ion of the cerium-sulfur oxide compounds to the cerium oxide is accompanied by the liberation of SO2 which is conveniently used with additional H2S in a Claus plant for conversion to ele-mental sulfur.
DISCLOSURE
Metal oxides selected from the group consisting of CeO~, copper oxides, iron oxides, preferably CeO2, either supported or unsupported, which have been used as a sorbent to scrub suIfur oxides (i~e. SO2, SO3, etc.) from waste gas effluent streams and are :~ -2-. .
~136i;~
thereby converted to the metal sulfate, and/or metal oxysulfate ~for use of CeO2 see U.S. Patent ~,001,375).
-2a-: `
, ..
are regenerated to the metal oxide by means of a reduc-ing regenerating a~mosphere consisting essentially of H2S
as the reducing-regenerating component present at from 0.5 to 100 vol. %, most preferably 5 - 70 vol. %, the balance co~prising nonregenerating inert gases such as helium, neon, argon, C02, nitrogen, wa~er vapor, etc. a~d mixtures thereof, at a temperature ~rom 300-700C, preferably 3S0-700C, most preferably 450-600C, the reducing-regenerating atmosphere ~ stream passing through the sorbent at any convenient rate, such as ~rom 50 to 50,000 V/V/Hr, preferably 100 to 50,000 V~V/Hr., most-preferably 100 to 20,000 Vlv!Hr~ This regeneration proce-dure can be practiced on either a cyclic or continuous basis.
The regeneration procedure of the instant invention is utilized in flue gas desulfurization processes in which the flue gas is contacted with a sorbent comprising cerium oxide in elther the ~3 or the ~4 oxidation state. Preferably, the ceriumoxide is supported on an inert support. The support LS preferably an inorganic refractory oxide, for example, various aluminas, silica, etc. The support can be of various shapes, such as pellets, extrudates, Raschig rings, saddles or monoliths, e.g. honeycombs. The most preferred support is ~ -alumina, especially in the shape of Raschig rings:
The support will have a surface area of from lcm2/c to 300 m2/~, oreferably from 100 m2!8 to 200 m2!g, The cerium oxide is co~bined with the support at from 1 to 40 wt. ~/0 of said support. Pree~rably, the sorbent will comprise .rom
BRIEF DISCLOSURE '~
The metal oxides CeO2, either supported or unsupported, used to remove sulfur oxides from waste gas effluent streams by conversion into cerium sulfate and/or cerium oxysulfate, is re~
generated to the starting cerium oxide by means of a reducing regenerating atmosphere consisting essentially of H2S as the re ducing component at a concentration of from 0.5 to 100 vol. ~, preferably 1-70 vol. ~, most preferably 5-70 vol. ~, the balance comprising non-regenerating non-reactive and inert gases such as helium, argon, CO2, nitrogen, water vapor, etc. at a temperature of from 3~0-700 C, preferably 350-700C, most preferably 450-600 C
in the presence of sufficient oxygen to convert any SO2 in said gas to SO3, (in the SO2 removal step) the reducing-regenerating atmosphere passing at any convenient rate, such as from 50 to 50,000 V/V/Hr, preferably 100 to 50,000 V/V/Hr, most preferably 100-20,000 V/V/Hr.
Regeneration is typically conducted on the cerium oxide sorbent which has been converted to cerium sulfate, and/or oxy-sulfate to the extent of 10 to 100 mole ~, preferably 10-70 mole %.
Regenera~ion of the cerium-sulfur oxide compounds to the cerium oxide is accompanied by the liberation of SO2 which is conveniently used with additional H2S in a Claus plant for conversion to ele-mental sulfur.
DISCLOSURE
Metal oxides selected from the group consisting of CeO~, copper oxides, iron oxides, preferably CeO2, either supported or unsupported, which have been used as a sorbent to scrub suIfur oxides (i~e. SO2, SO3, etc.) from waste gas effluent streams and are :~ -2-. .
~136i;~
thereby converted to the metal sulfate, and/or metal oxysulfate ~for use of CeO2 see U.S. Patent ~,001,375).
-2a-: `
, ..
are regenerated to the metal oxide by means of a reduc-ing regenerating a~mosphere consisting essentially of H2S
as the reducing-regenerating component present at from 0.5 to 100 vol. %, most preferably 5 - 70 vol. %, the balance co~prising nonregenerating inert gases such as helium, neon, argon, C02, nitrogen, wa~er vapor, etc. a~d mixtures thereof, at a temperature ~rom 300-700C, preferably 3S0-700C, most preferably 450-600C, the reducing-regenerating atmosphere ~ stream passing through the sorbent at any convenient rate, such as ~rom 50 to 50,000 V/V/Hr, preferably 100 to 50,000 V~V/Hr., most-preferably 100 to 20,000 Vlv!Hr~ This regeneration proce-dure can be practiced on either a cyclic or continuous basis.
The regeneration procedure of the instant invention is utilized in flue gas desulfurization processes in which the flue gas is contacted with a sorbent comprising cerium oxide in elther the ~3 or the ~4 oxidation state. Preferably, the ceriumoxide is supported on an inert support. The support LS preferably an inorganic refractory oxide, for example, various aluminas, silica, etc. The support can be of various shapes, such as pellets, extrudates, Raschig rings, saddles or monoliths, e.g. honeycombs. The most preferred support is ~ -alumina, especially in the shape of Raschig rings:
The support will have a surface area of from lcm2/c to 300 m2/~, oreferably from 100 m2!8 to 200 m2!g, The cerium oxide is co~bined with the support at from 1 to 40 wt. ~/0 of said support. Pree~rably, the sorbent will comprise .rom
2 to 20 wt. ~ cerium oxlde.
- 4 ~
In the ~ollowing discussion CeO2 will be used as the specific example, it being understood that e~uivalent arguments and descriptions are available and operable for other metal oxide sor~ents unless specifically indicated other-wise . T~e sup30rted cerium oxide sorbent may be prepared by methods known Ln the art for preparing supported catalysts fo~
use in petroleum processes, e.g. re~ormingl hydsocrac~ing, etc.
For example, an aqueous s~lution of a cerium oxide precursor may be impregnated onto an alumina support. The ~m~regnated support may be subsequen~ly separated from excess solution, dried ae a temperature o~ ~ro~ abou~ 20 to llO~C and calclned at a te~perature of rom ab~ut 300C ~o 600C. ~uring the drying and/or the calcin~ng step, the supported catalyst may be contacted with air or 2 to convert the cerium oxide prec~rsor co~pound on the support into the oxide.
An alter~ative approach to the preparation o~ a ceri~m oxide impregnated support which olaces the CeO2 on the outer surface of a porous support involves prefilling of the pores wieh an inert liquid as described in U.S. Patent 2,746,936, For convenie~ce, the catalyst i5 imp~egnated with an aque~us solution of t~e ceriu~.o~ide precursor. However, or~anic solvents may be utilized provided the cexi-nm oxide?recursor is soluble eherein. Precursors of the preferred sor~er.t, ceriu~
o~ide, tdhich are soluble in aqueous solutions, include ce ic am~onium ~itraee, cerous nitrate, basic ceric ~itrate, cerous acetate, ecc. For other m~tal oxides, similar metal salts may be utiliz~d.
I The waste gas effLuent stream scr~boed is typically a ..~, ,~
: .
~3~3 1 gas, preferably a flue gas, which comprises from 0 01 to 2.0%
2 by volume (100 ppm to 20,000 ppm) sulfur oxides. T'nis waste
- 4 ~
In the ~ollowing discussion CeO2 will be used as the specific example, it being understood that e~uivalent arguments and descriptions are available and operable for other metal oxide sor~ents unless specifically indicated other-wise . T~e sup30rted cerium oxide sorbent may be prepared by methods known Ln the art for preparing supported catalysts fo~
use in petroleum processes, e.g. re~ormingl hydsocrac~ing, etc.
For example, an aqueous s~lution of a cerium oxide precursor may be impregnated onto an alumina support. The ~m~regnated support may be subsequen~ly separated from excess solution, dried ae a temperature o~ ~ro~ abou~ 20 to llO~C and calclned at a te~perature of rom ab~ut 300C ~o 600C. ~uring the drying and/or the calcin~ng step, the supported catalyst may be contacted with air or 2 to convert the cerium oxide prec~rsor co~pound on the support into the oxide.
An alter~ative approach to the preparation o~ a ceri~m oxide impregnated support which olaces the CeO2 on the outer surface of a porous support involves prefilling of the pores wieh an inert liquid as described in U.S. Patent 2,746,936, For convenie~ce, the catalyst i5 imp~egnated with an aque~us solution of t~e ceriu~.o~ide precursor. However, or~anic solvents may be utilized provided the cexi-nm oxide?recursor is soluble eherein. Precursors of the preferred sor~er.t, ceriu~
o~ide, tdhich are soluble in aqueous solutions, include ce ic am~onium ~itraee, cerous nitrate, basic ceric ~itrate, cerous acetate, ecc. For other m~tal oxides, similar metal salts may be utiliz~d.
I The waste gas effLuent stream scr~boed is typically a ..~, ,~
: .
~3~3 1 gas, preferably a flue gas, which comprises from 0 01 to 2.0%
2 by volume (100 ppm to 20,000 ppm) sulfur oxides. T'nis waste
3 gas stream is contacted with th~ sorbent described above
4 Addi~ionally, the waste gas stream contains 2 su~ficient to convert all S02 to S03 and may also comprise ~2~ C02, C0, H~O~
6 N0X, etc. It should be noted that none o~ these additional 7 co~ponants w;~ll interfere with t:he scrubbing o~ tbe gas stream.
8 In practice, at least a stoichiometric quantity o~ oxygen in the 9 waste gas is needed to per~it the absorption o~ S02 on CeO2 to form the sulfate Or oxysulfate. During the initial contacting 11 step, the temperatu~e is maintained at from 300C to 700C, 12 most pre~erably from 450C to 600C. The pressure is not 13 critical. For convenience, whatever pressure is ob~ained at 14 the flow and temperatures utilized will be acceptable. The ~low of the flue gas through the initial contacting zone, i.e 16 the zo~e in which the sorbent is contained, ~ay vary from 50 17 to 50,000, preferably f~om 500 to 50,000, and most preferabl~
18 from 500-20,000 V/V/~r. In the initial contacting zone, the lg catalyst may be present in the form of pellets, extrudates, etc. After a certain time, depending on the above contacting 21 condi~ions, the cerium oxide will be conver~ed subs~antially 22 to cerium sulfate and/or cerium oxysulfate.
23 When the conversion of the cerlum 24 oxide to the corresponding sulfate or oxysulfate reaches ~ lQ-100%, preferably 10~70r/~ of capacity, the sorbent is regenera~ed 26 by the prOC9Ss of the instant invention utilizing an H2S con-77 taini~g gas wherein the reducing-regeneratlng agent consists 28 essentially of the H2S present at a concentration o_ f~o~ 0.;
29 to lC0 vol. %, preferably, 1-70 vol ~/" most preferably S~
., .
' ~ '` ' .
`.` '.
~31~i3~4~
1 70 vol %, the balance of the stream being nonregenerative, 2 nonreactive inert gas such as nitrogen, helium~ argon, neon, 3 water vapor, C02, etc. The ceri~m sulfate, and/or oxysulfate 4 is converted substantially to cerium oxide while the sul~ur is removed as sulfur dioxide from the sorbent.
6 When dealing with the cerium~system for example, 7 if reaction of the spent cerium sorbent with H2S goes too far 8 and begins to convert the regenerated cerium oxide to the 9 sulfide, a treatment with air, air/steam mixture, or steam alone can be used to restore the sorbent to full capacity.
11 Preferably the atmosphere is steam. The temperature at which 12 this final s~ep is performed (if it is necessary) ranges from 13 300-700C, preferably, 400-700C, most preferably 450 to 600C.
14 This step converts any sulfide bac~ to the oxide with only small amounts of sulfate formation. The reaction of cerium 16 sulfide with oxygen to ~ive almost quantitatively the oxide 17 is unique for cerium among the lanthanide sulfides which 18 generally burn to give oxysulfates.
19 Cerium oxysulfates have the general formula:
CeO2_y(SO4)y where 0 C y ' 2.
21 The overall general regeneration reaction is:
22 CeO2_y(S04)y ~ Y3 H2S -> CeO2 + 4Y S02 + Y H20 23 so tha~ the overall method is to sequester S02 from a flue 24 gas and recover it as concentrated S02 as follo~s;
S0~ + 2 2 + 3 H2S~ 4 S02 ~ 1 H20 26 Any S03 present in the flue gas will also be re~oved.
27 The S02 thus formed can be reacted with additional 28 H2S over the amount needed to regenerate the sorben~ to for~
29 elemental sulfur by the Claus reaction:
- .
;3~9~
l S2 + 2~T2S --~ 3S + 2H20 2 which can be made to procePd in the same or a separate 3 reactor from the CeO2 containing vessel. Note that a mole 4 of H2S is able to reduce three times as much sulfate as a mole of hydrogen, a major advantage o~ this method of regen-6 eration over the prior art.
7 Alternatively, the S2 thus formed ma~J then be fed 8 to a separate Claus plant for conversion to elemental sulfur 9 In the Claus plant H2S is mixed with the SO2 to bring the H2S:SO2 mole ratio to 2:1 prior to the catalytic converter.
11 One advantageous method of regenerating the spent 12 metal oxide sorbent is to pass an excess of H2S-containing 13 gas over it, that is, in an amount in excess of the volume 14 of H2S needed to just regenerate the sorbent so that H2S/SO2 mixture is produced, which can be fed directly to the Claus 16 plant. Indeed, some of the 2H2S + SO2 Claus reaction takes 17 place over the metal oxide sorbent resulting in the production 18 of some elemental sulfur in the sorbent vessel.
19 As previously stated, this regeneration procedure can be practiced in either a cyclic or continuous manner.
21 When operated in a cyclie manner the scrubber-regenerator 22 ccmprises multibed units, wherein a gas mixture containing 23 sulfur oxides is passed through one or more fixed beds of sup-24 ported cerium oxide. ~hile these beds are scrubbing sulfur oxides, the other beds of the unit are being ~egenerated with 26 an H2S containing gas as described. The roles o~ the scrubber 27 and regenerator are reversed when both have completed their 28 task. Purging with a gas stream such as steam, between these 29 two steps may be advantageous both to prevent explosive conditions :
, ... . .
.-' ~ ~' .
~13~3~3~
.
as well as for converting any cerium sulfide which may have ~ormed in the regeneration step to cerium oxide.
In another embodiment of the instant invention, ~he catalyst is continuously removed and regenerated. For example, see the apparatus described in U.S. Patent No 3,989,798 As stated above, ~he cerium oxide is preferably sup-ported on an inert support material to most economically use the cerium o~ide. However, unsupported cerium o.~ide may be used provided adequate surface areàs are obtained. Preferably the unsupported cerium oxide should have a sur~ace area of at least 10 m2/g, preferably ~rcm 20 m2/g to 50 m2/g. Such un-supported cerium oxide is regenerated by the same H2S pro-cedure as is supported cerium oxide.
EXAl'ilPIES
A 5.5 g (8.2 cc) sample of 20~/~ CeO2 supported on extruded ~ -A1203 is held in place by quartz wool within a vertical quartz tube (rVl" dia.). A gas blend containing 3700 ppm S02, 5% 2 and balance Ar is passed upward through the heated sample at 4000-5000 V/V/Hr. during the SO2 scrubbing mode. The S02 content of the exit gas is analyzed using an electrochemical method containing a Faristor which is cali-brated to read L00% at 5000 ppm S02. ~uring regeneration, a 1% H2S in ~e regeneration gas i~s run through the bed at r-1000 ~/VIhr and the exit gas is bubbled through Pb(M03)2 solutions.
.~ white precipitate (PbS0~) indicates S0~ while a black pre-cipitate ~PbS) indicates H2S in the gas stream and sio~nals the end of a regeneration.
A number of S02 scrubbings, H2S regenerations, , .
.. . .
.
~L36384 1 and optional burns w ere carr ied ou t un der 2 the condi~ions described above. Typically, duri~g the SO2 3 scrubbing, the SO2 content in the exit gas as a function of 4 time ~as as follows: 500!ppm/20 mi.n; 1000 ppm/40 min; 1500 ppm/
65 min; and 2000 ppm/95 min. The regeneration at 500-600C with 6 1% H2S~He too~ about 1 hr. '~efore breakthrough of H2S. The for-7 mation of cerium oxysulfate, oxide, and sulfide ~ere all moni-8 tored by removing a small sa~ple of extrudate at appropriate 9 times and examining the product by X-ray diffraction.
When a dry or we t H2S containing gas is used for the regen-11 eration, prolonged treatment of the spent sorbent may first 12 convert it to the oxide, followed by further conversion to 13 the sulfide, CeS2. It was also shown tha~ the resultant sul-14 fide can be converted back to the oxide by passing an oxygen and/or steam containing gas over it a~ 300-700C.
16 The present inven~ion is particularly well suited 17 for the removal of SO2 from gases in an installation where 18 stoichiometrically adequate amounts of H2S are also available 19 from other operations. Typical examples æe as follows:
(a) Claus plant tail gas cleanup.
21 (b) So2!sO3 removal from refinery flue gases.
22 (c) So2!SO3 removal from flue gases in coal gasi-23 fication or liquefaction plant, tar sand refineries, and the 24 like where H2S is available as a byproduct - : , : ..
~ . . ;
: : .
6 N0X, etc. It should be noted that none o~ these additional 7 co~ponants w;~ll interfere with t:he scrubbing o~ tbe gas stream.
8 In practice, at least a stoichiometric quantity o~ oxygen in the 9 waste gas is needed to per~it the absorption o~ S02 on CeO2 to form the sulfate Or oxysulfate. During the initial contacting 11 step, the temperatu~e is maintained at from 300C to 700C, 12 most pre~erably from 450C to 600C. The pressure is not 13 critical. For convenience, whatever pressure is ob~ained at 14 the flow and temperatures utilized will be acceptable. The ~low of the flue gas through the initial contacting zone, i.e 16 the zo~e in which the sorbent is contained, ~ay vary from 50 17 to 50,000, preferably f~om 500 to 50,000, and most preferabl~
18 from 500-20,000 V/V/~r. In the initial contacting zone, the lg catalyst may be present in the form of pellets, extrudates, etc. After a certain time, depending on the above contacting 21 condi~ions, the cerium oxide will be conver~ed subs~antially 22 to cerium sulfate and/or cerium oxysulfate.
23 When the conversion of the cerlum 24 oxide to the corresponding sulfate or oxysulfate reaches ~ lQ-100%, preferably 10~70r/~ of capacity, the sorbent is regenera~ed 26 by the prOC9Ss of the instant invention utilizing an H2S con-77 taini~g gas wherein the reducing-regeneratlng agent consists 28 essentially of the H2S present at a concentration o_ f~o~ 0.;
29 to lC0 vol. %, preferably, 1-70 vol ~/" most preferably S~
., .
' ~ '` ' .
`.` '.
~31~i3~4~
1 70 vol %, the balance of the stream being nonregenerative, 2 nonreactive inert gas such as nitrogen, helium~ argon, neon, 3 water vapor, C02, etc. The ceri~m sulfate, and/or oxysulfate 4 is converted substantially to cerium oxide while the sul~ur is removed as sulfur dioxide from the sorbent.
6 When dealing with the cerium~system for example, 7 if reaction of the spent cerium sorbent with H2S goes too far 8 and begins to convert the regenerated cerium oxide to the 9 sulfide, a treatment with air, air/steam mixture, or steam alone can be used to restore the sorbent to full capacity.
11 Preferably the atmosphere is steam. The temperature at which 12 this final s~ep is performed (if it is necessary) ranges from 13 300-700C, preferably, 400-700C, most preferably 450 to 600C.
14 This step converts any sulfide bac~ to the oxide with only small amounts of sulfate formation. The reaction of cerium 16 sulfide with oxygen to ~ive almost quantitatively the oxide 17 is unique for cerium among the lanthanide sulfides which 18 generally burn to give oxysulfates.
19 Cerium oxysulfates have the general formula:
CeO2_y(SO4)y where 0 C y ' 2.
21 The overall general regeneration reaction is:
22 CeO2_y(S04)y ~ Y3 H2S -> CeO2 + 4Y S02 + Y H20 23 so tha~ the overall method is to sequester S02 from a flue 24 gas and recover it as concentrated S02 as follo~s;
S0~ + 2 2 + 3 H2S~ 4 S02 ~ 1 H20 26 Any S03 present in the flue gas will also be re~oved.
27 The S02 thus formed can be reacted with additional 28 H2S over the amount needed to regenerate the sorben~ to for~
29 elemental sulfur by the Claus reaction:
- .
;3~9~
l S2 + 2~T2S --~ 3S + 2H20 2 which can be made to procePd in the same or a separate 3 reactor from the CeO2 containing vessel. Note that a mole 4 of H2S is able to reduce three times as much sulfate as a mole of hydrogen, a major advantage o~ this method of regen-6 eration over the prior art.
7 Alternatively, the S2 thus formed ma~J then be fed 8 to a separate Claus plant for conversion to elemental sulfur 9 In the Claus plant H2S is mixed with the SO2 to bring the H2S:SO2 mole ratio to 2:1 prior to the catalytic converter.
11 One advantageous method of regenerating the spent 12 metal oxide sorbent is to pass an excess of H2S-containing 13 gas over it, that is, in an amount in excess of the volume 14 of H2S needed to just regenerate the sorbent so that H2S/SO2 mixture is produced, which can be fed directly to the Claus 16 plant. Indeed, some of the 2H2S + SO2 Claus reaction takes 17 place over the metal oxide sorbent resulting in the production 18 of some elemental sulfur in the sorbent vessel.
19 As previously stated, this regeneration procedure can be practiced in either a cyclic or continuous manner.
21 When operated in a cyclie manner the scrubber-regenerator 22 ccmprises multibed units, wherein a gas mixture containing 23 sulfur oxides is passed through one or more fixed beds of sup-24 ported cerium oxide. ~hile these beds are scrubbing sulfur oxides, the other beds of the unit are being ~egenerated with 26 an H2S containing gas as described. The roles o~ the scrubber 27 and regenerator are reversed when both have completed their 28 task. Purging with a gas stream such as steam, between these 29 two steps may be advantageous both to prevent explosive conditions :
, ... . .
.-' ~ ~' .
~13~3~3~
.
as well as for converting any cerium sulfide which may have ~ormed in the regeneration step to cerium oxide.
In another embodiment of the instant invention, ~he catalyst is continuously removed and regenerated. For example, see the apparatus described in U.S. Patent No 3,989,798 As stated above, ~he cerium oxide is preferably sup-ported on an inert support material to most economically use the cerium o~ide. However, unsupported cerium o.~ide may be used provided adequate surface areàs are obtained. Preferably the unsupported cerium oxide should have a sur~ace area of at least 10 m2/g, preferably ~rcm 20 m2/g to 50 m2/g. Such un-supported cerium oxide is regenerated by the same H2S pro-cedure as is supported cerium oxide.
EXAl'ilPIES
A 5.5 g (8.2 cc) sample of 20~/~ CeO2 supported on extruded ~ -A1203 is held in place by quartz wool within a vertical quartz tube (rVl" dia.). A gas blend containing 3700 ppm S02, 5% 2 and balance Ar is passed upward through the heated sample at 4000-5000 V/V/Hr. during the SO2 scrubbing mode. The S02 content of the exit gas is analyzed using an electrochemical method containing a Faristor which is cali-brated to read L00% at 5000 ppm S02. ~uring regeneration, a 1% H2S in ~e regeneration gas i~s run through the bed at r-1000 ~/VIhr and the exit gas is bubbled through Pb(M03)2 solutions.
.~ white precipitate (PbS0~) indicates S0~ while a black pre-cipitate ~PbS) indicates H2S in the gas stream and sio~nals the end of a regeneration.
A number of S02 scrubbings, H2S regenerations, , .
.. . .
.
~L36384 1 and optional burns w ere carr ied ou t un der 2 the condi~ions described above. Typically, duri~g the SO2 3 scrubbing, the SO2 content in the exit gas as a function of 4 time ~as as follows: 500!ppm/20 mi.n; 1000 ppm/40 min; 1500 ppm/
65 min; and 2000 ppm/95 min. The regeneration at 500-600C with 6 1% H2S~He too~ about 1 hr. '~efore breakthrough of H2S. The for-7 mation of cerium oxysulfate, oxide, and sulfide ~ere all moni-8 tored by removing a small sa~ple of extrudate at appropriate 9 times and examining the product by X-ray diffraction.
When a dry or we t H2S containing gas is used for the regen-11 eration, prolonged treatment of the spent sorbent may first 12 convert it to the oxide, followed by further conversion to 13 the sulfide, CeS2. It was also shown tha~ the resultant sul-14 fide can be converted back to the oxide by passing an oxygen and/or steam containing gas over it a~ 300-700C.
16 The present inven~ion is particularly well suited 17 for the removal of SO2 from gases in an installation where 18 stoichiometrically adequate amounts of H2S are also available 19 from other operations. Typical examples æe as follows:
(a) Claus plant tail gas cleanup.
21 (b) So2!sO3 removal from refinery flue gases.
22 (c) So2!SO3 removal from flue gases in coal gasi-23 fication or liquefaction plant, tar sand refineries, and the 24 like where H2S is available as a byproduct - : , : ..
~ . . ;
: : .
Claims (6)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for desulfurizing an effluent waste gas stream comprising adsorbing sulfur oxides by a cerium oxide sor-bent, at a temperature of from 300-700°C., in the presence of sufficient oxygen to convert any SO2 in said gas to SO3 and there-after regenerating the spent cerium oxide sorbent, said process characterized in that said spent cerium oxide sorbent is re-generated by contacting said spent cerium oxide sorbent with an H2S containing reducing-regenerating gas comprising from 0.5 to 100.0 volume percent H2S with the balance comprising a non-re-generating gas, at a temperature of from 300-700°C. at a convenient flow rate.
2. The process of claim 1 wherein the H2S containing reducing-regenerating gas flow rate ranges from 50 to 50,000 V/V/Hr.
3. A process according to claim 2 wherein the H2S
concentration in said reducing-regenerating gas ranges from about 1-70 volume percent.
concentration in said reducing-regenerating gas ranges from about 1-70 volume percent.
4. A process according to claim 3 wherein said non-regenerating gas is helium, CO2, N2, Ar, water vapor or mixtures thereof.
5. The process of claim 4 wherein said cerium oxide is exposed, as a final regeneration step, to steam, air or steam/
air mixtures to convert any CeS2 to CeO2 and wherein said exposure is conducted at a temperature of from 300-700°C.
air mixtures to convert any CeS2 to CeO2 and wherein said exposure is conducted at a temperature of from 300-700°C.
6. A process according to any of one of claims 4 or 5 wherein said cerium oxide sorbent is supported on an inert support.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US95755778A | 1978-11-03 | 1978-11-03 | |
| US957,557 | 1978-11-03 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1136384A true CA1136384A (en) | 1982-11-30 |
Family
ID=25499758
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000339103A Expired CA1136384A (en) | 1978-11-03 | 1979-11-02 | Regeneration of spent so.sub.2-so.sub.3 sorbents with h.sub.2s at moderate temperature |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPS5570324A (en) |
| CA (1) | CA1136384A (en) |
| DE (1) | DE2944754A1 (en) |
| NL (1) | NL7908098A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6960548B2 (en) * | 2000-06-02 | 2005-11-01 | Institute Francais Du Petrole | Method for regenerating used absorbents derived from treatment of thermal generator fumes |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL7906181A (en) * | 1979-08-14 | 1981-02-17 | Shell Int Research | PROCESS FOR THE SIMULTANEOUS REMOVAL OF NITROGEN OXIDES AND SULFUR OXIDES FROM A GAS FLOW. |
| FR2587236B1 (en) * | 1985-09-13 | 1987-11-13 | Inst Francais Du Petrole | PROCESS FOR THE REMOVAL OF SULFUR OXIDES FROM A GAS BY MEANS OF AN ABSORPTION MASS REGENERABLE BY REACTION WITH HYDROGEN SULFIDE |
| FR2587237B1 (en) * | 1985-09-13 | 1988-01-08 | Inst Francais Du Petrole | PROCESS FOR THE REMOVAL OF SULFUR OXIDES FROM A GAS BY MEANS OF AN ABSORPTION MASS REGENERABLE BY REACTION WITH ELEMENTAL SULFUR |
| FR2608458B1 (en) * | 1986-12-23 | 1989-03-10 | Rhone Poulenc Chimie | CATALYST BASED ON CERIUM OXIDE AND METHOD FOR THE TREATMENT OF INDUSTRIAL GASES CONTAINING SULFUR COMPOUNDS |
-
1979
- 1979-11-02 JP JP14271279A patent/JPS5570324A/en active Pending
- 1979-11-02 CA CA000339103A patent/CA1136384A/en not_active Expired
- 1979-11-03 DE DE19792944754 patent/DE2944754A1/en not_active Withdrawn
- 1979-11-05 NL NL7908098A patent/NL7908098A/en not_active Application Discontinuation
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6960548B2 (en) * | 2000-06-02 | 2005-11-01 | Institute Francais Du Petrole | Method for regenerating used absorbents derived from treatment of thermal generator fumes |
| US7678344B2 (en) | 2000-06-02 | 2010-03-16 | Institut Francais Du Petrole | Process and device intended for regeneration of used absorbents from thermal generator fumes treatment |
Also Published As
| Publication number | Publication date |
|---|---|
| DE2944754A1 (en) | 1980-05-14 |
| NL7908098A (en) | 1980-05-07 |
| JPS5570324A (en) | 1980-05-27 |
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| MKEX | Expiry |