CA1099491A - Process for removing chlorine ions from the wet flue- gas processing system - Google Patents
Process for removing chlorine ions from the wet flue- gas processing systemInfo
- Publication number
- CA1099491A CA1099491A CA290,427A CA290427A CA1099491A CA 1099491 A CA1099491 A CA 1099491A CA 290427 A CA290427 A CA 290427A CA 1099491 A CA1099491 A CA 1099491A
- Authority
- CA
- Canada
- Prior art keywords
- processing system
- chlorine ions
- washing tower
- solids
- washing
- 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
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
- B01D53/68—Halogens or halogen compounds
-
- 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
- B01D53/501—Sulfur oxides by treating the gases with a solution or a suspension of an alkali or earth-alkali or ammonium compound
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Biomedical Technology (AREA)
- Environmental & Geological Engineering (AREA)
- Analytical Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Treating Waste Gases (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A process for removing chlorine ions from a wet flue-gas processing system comprising the sequence of steps of bringing a flue-gas containing sulfur dioxide in contact with a magnesium oxide slurry, separating solids from a part of the slurry, drying and calcining the solids to regenerate and reuse the magnesium oxide and washing the gas formed during the drying and calcining step with water in a washing tower. According to the process of this invention, the accumulation of the chlorine ions in the processing system is sufficiently prevented, and thus the corro-sion of the apparatus is efficiently avoided.
A process for removing chlorine ions from a wet flue-gas processing system comprising the sequence of steps of bringing a flue-gas containing sulfur dioxide in contact with a magnesium oxide slurry, separating solids from a part of the slurry, drying and calcining the solids to regenerate and reuse the magnesium oxide and washing the gas formed during the drying and calcining step with water in a washing tower. According to the process of this invention, the accumulation of the chlorine ions in the processing system is sufficiently prevented, and thus the corro-sion of the apparatus is efficiently avoided.
Description
1(~99491 1. Field of the Invention .
The present invention relates to a process for removing chlorine ions from a wet flue-gas processing system.
The present invention relates to a process for removing chlorine ions from a wet flue-gas processing system.
2. Description of the Prior Art For a wet flue-gas processing system, various proce-dures have hitherto been employed to completely avoid the formation of waste water in order to prevent pollution. These procedures, however, suffer from the disadvantage in that small amounts of chlorine contained in industrlal water, heavy fuel oil, the reagents employed, and the like is concentrated and accumulated in the circulating absorption solution during the processing.
When the chlorine concentration in the circulating absorption solution reaches 4,000 to 6,000 ppm, stress corrosion cracking, pitching corrosion, etc., of stainless steel, of which an absorp-tion tower and the like are principally made, Therefore, it has long been desired to effectively remove chlorine ions, In the past, in order to remove the disadvantages due to the accumulation of chlorine ions, a part or the whole of the circulating absorption solution has been withdrawn from the pro-cessing system when the chlorine ion concentration reaches a predetermined level~
This procedure, however, has the disadvantages in that it is difficult to regenerate the circulating absorption solution withdrawn and when abandoned, secondary pollution results.
In addition, economic disadvantages take place in that fresh absorption solution must be added in an amount correspond- ;
ing to that of the absorption solution withdrawn, and in that .
large amounts of dissolved salts are contained in the absorption solution withdrawn and therefore lost.
, 1~9~4~1 1 SUMMARY OF THE INVE~ITION
In accordance with the present invention, we haveprovided a process for treating a flue-gas by a nearly closed system while maintaining the chlorine ion concentration in the system below a predetermined level.
BRIEF DESCRIPTION OF THE DRAWING
Figure 1 is a flow diagram showing an embodiment of the process of the present invention.
DETAILED DESCRIPTION OF THE INVENTIO~
Processing of a flue-gas containing sulfur dioxide by the wet processing system is shown in Fig. 1. Referring to the flow diagram shown in Fig. 1, an absorption slurry containing magnesium compounds such as magnesium oxide, magnesium sulfite, magnesium sulfate and the like are brought in contact with the flue-gas in absorption tower 1 to absorb the sulfur dioxide therein. For example, these reactions are as follows:
MgO + SO2 + 3H2O > MgS03.3H2o MgSO3 + S02 + H2O > Mg(HS03)2 Mg(HSO3)2 + MgO + 5H2O ~ 2MgS3 3H2 MgO + SO3 + 7H2O - - > MgS04.7H2o -MgSO3 + 1/2 2 + 7H20 ~ MgSO4.7H2O
The reaction products and the absorption agents are separated with centrifugal separator 2 or the like, and the mother liquor is returned to the absorption step for reuse. The solids (wet cake) separated are dried in dryer 3 and then calcined in cal- -cining unit 4 to recover sulfur dioxide and at the same time, to regenerate the magnesium compounds. These magnesium compounds are reused as absorption agents. The recovered gas containing sulfur dioxide is dedusted in washing tower 6, and it is then used as a feed for production of byproducts, such as sulfur or `` 1~99491 1 sulfuric acid. The solution withdrawn from the washing tower is returned to the circulating absorption system. In the Figure, 5 is a tank, 7 is a neutralizing vessel, 8 is a filter and 9 is an air exposure processing vessel.
In the above flue-gas processing system, the chlorine ions not only circulate through the circulating absorption system together with other components, but a part of the chlorine ions circulate the following course: absorption system -~
solid-liquid separating step --- drying step - -~
calcining step- --~ washing step- ~ absorption system.
We have recognized that the solids obtained in the centrifugal separator by the solid-liquid separation (wet cake) usually contain from 5 to 30~ by weight water and that the chlorine ions contained in this water are liberated as hydrogen chloride to the gàs formed at the dry-calcination step and at ; least about 90~ thereof is finally trapped in the solution at the washing tower. The amount of the chlorine trapped exceeds the amount of chlorine ions formed in all the steps. Thus it has been found that the accumulation of chlorine ions in the absorption system can be effectively prevented by discharging a part of the solution withdrawn from the above washing tower out of the processing system. The present invention is based upon these findings.
The present invention provides a process for removing chlorine ions from the wet flue-gas processing system comprising the steps of bringing a flue-gas containing sulfur dioxide in contact with a circulating absorption slurry containing a magne- -sium compound (absorption step), separating solids from a part of the circulating absorption slurry (solid-liquid separation step), drying and calcining the solids to regenerate and reuse 1~994~
1 the magnesium compound (dry-calcination step) and washing the gas formed at the dry-calcination step with water in a washing tower (washing step), which comprises taking at least a part of the solution withdrawn from the washing tower out of the processing system and controlling the water content of the solids to be fed to the dry-calcination step and the amount of the solution with-drawn from the washing tower to be taken out of the processing system, whereby the accumulation of the chlorine ions in the pro-cessing system is sufficiently prevented.
~ Since the solution withdrawn from washing tower 6, as described above, contains a large amount of chlorine ions, it is possible to prevent the accumulation of the chlorine ions in the processing system and to maintain its concentration below a certain level by taking a part or the whole of the solution with-drawn from the washing tower out of the processing system.
The amount of the solution withdrawn from the process-ing system is controlled taking into account the relation between the desired chlorine ion concentration of the absorption solution and the water content of the wet cake. For example, where the water content of the wet cake is 15% by weight, if the whole of the solution withdrawn from the washing tower is taken out of the processing system, the chlorine ion concentration in the absorp- ;
tion system is maintained at about 340 ppm. If the amount of the solution withdrawn from the processing system is controlled to about 11%, the chlorine ion concentration in the absorption sys-tem is as high as 3,000 ppm.
If the chlorine ion concentration in the absorption system is maintained below about 3,000 ppm, it is possible to prevent troubles such as corrosion of the absorption tower and the like, and thus stable operation is possible for a long period of time.
.
1~99491 1 In accordance with the present invention, if the water content of the wet cake to be fed to the dryer is above 2% by weight, it is possible to maintain the chlorine ion concentration in the absorption system below 3,000 ppm by taking a certain amount of the solution withdrawn from the washing tower out of the processing system. The amount of the solution withdrawn from the processing system is made inversely proportional to the water content of the solids to be fed to the regeneration processing.
That is to say, the amount of the solution withdrawn to be taken out of the processing system can be lowered by increasing the water content of the wet cake. Therefore, it is possible to transfer a part of the circulation absorption slurry directly to the dryer without passing it through the centrifugal separator.
The removal of the solution withdrawn from the washing tower of the processing system can be carried out either continu-ously or discontinuously. Also, by increasing the chlorine ion concentration of the solution withdrawn from the washing tower by temporarily increasing the water content of the wet cake, the amount of the solution to be taken out of the processing system can be decreased.
The solution withdrawn from the washing tower which has been taken out of the processing system generally has a pH of from 1.5 to 3.5, a slurry concentration of from 0 to 3 percent by weight, a total SO3 concentration including the dissolved SO2 gas of from 5 to 8 percent by weight and a COD concentration in supernatant liquid of from 700 to 1500 ppm. By neutralizing this solution with an alkali reagent and, if necessary, adding a flocculating agent, followed by filtration or standing to sepa-. rate solid and liquid, the solution thus separated is reduced in its ~olid content of from about 10 to about 20 ppm, its total ~ -5-1~399491 1 SO3 concentration of from about 2000 to about 3000 ppm and its COD concentration of from about 25 to about 30 ppm. Further, the total SO3 concentration of the solution can be reduced to from about 20 to about 100 ppm by subjecting the solution to an air exposure processing, and thus it is possible to abandon the solution without causing any socondary pollution. As alkali reagents being employed for neutralization, it is possible to use magnesium oxide slurry of the flue-gas processing as shown in Fig. 1, and the solids separated are again returned to the flue-gas processing step. In carrying out the present invention, temperatures at which the drying and calcination steps are carried out, and operation conditions under which all the steps are effected, can be set as in usual operations. For example, the drying step is usually carried out at from 200 to 250C
and the calcination step is carried out usually at from 500 to 1,O00C.
~ ` .
When the chlorine concentration in the circulating absorption solution reaches 4,000 to 6,000 ppm, stress corrosion cracking, pitching corrosion, etc., of stainless steel, of which an absorp-tion tower and the like are principally made, Therefore, it has long been desired to effectively remove chlorine ions, In the past, in order to remove the disadvantages due to the accumulation of chlorine ions, a part or the whole of the circulating absorption solution has been withdrawn from the pro-cessing system when the chlorine ion concentration reaches a predetermined level~
This procedure, however, has the disadvantages in that it is difficult to regenerate the circulating absorption solution withdrawn and when abandoned, secondary pollution results.
In addition, economic disadvantages take place in that fresh absorption solution must be added in an amount correspond- ;
ing to that of the absorption solution withdrawn, and in that .
large amounts of dissolved salts are contained in the absorption solution withdrawn and therefore lost.
, 1~9~4~1 1 SUMMARY OF THE INVE~ITION
In accordance with the present invention, we haveprovided a process for treating a flue-gas by a nearly closed system while maintaining the chlorine ion concentration in the system below a predetermined level.
BRIEF DESCRIPTION OF THE DRAWING
Figure 1 is a flow diagram showing an embodiment of the process of the present invention.
DETAILED DESCRIPTION OF THE INVENTIO~
Processing of a flue-gas containing sulfur dioxide by the wet processing system is shown in Fig. 1. Referring to the flow diagram shown in Fig. 1, an absorption slurry containing magnesium compounds such as magnesium oxide, magnesium sulfite, magnesium sulfate and the like are brought in contact with the flue-gas in absorption tower 1 to absorb the sulfur dioxide therein. For example, these reactions are as follows:
MgO + SO2 + 3H2O > MgS03.3H2o MgSO3 + S02 + H2O > Mg(HS03)2 Mg(HSO3)2 + MgO + 5H2O ~ 2MgS3 3H2 MgO + SO3 + 7H2O - - > MgS04.7H2o -MgSO3 + 1/2 2 + 7H20 ~ MgSO4.7H2O
The reaction products and the absorption agents are separated with centrifugal separator 2 or the like, and the mother liquor is returned to the absorption step for reuse. The solids (wet cake) separated are dried in dryer 3 and then calcined in cal- -cining unit 4 to recover sulfur dioxide and at the same time, to regenerate the magnesium compounds. These magnesium compounds are reused as absorption agents. The recovered gas containing sulfur dioxide is dedusted in washing tower 6, and it is then used as a feed for production of byproducts, such as sulfur or `` 1~99491 1 sulfuric acid. The solution withdrawn from the washing tower is returned to the circulating absorption system. In the Figure, 5 is a tank, 7 is a neutralizing vessel, 8 is a filter and 9 is an air exposure processing vessel.
In the above flue-gas processing system, the chlorine ions not only circulate through the circulating absorption system together with other components, but a part of the chlorine ions circulate the following course: absorption system -~
solid-liquid separating step --- drying step - -~
calcining step- --~ washing step- ~ absorption system.
We have recognized that the solids obtained in the centrifugal separator by the solid-liquid separation (wet cake) usually contain from 5 to 30~ by weight water and that the chlorine ions contained in this water are liberated as hydrogen chloride to the gàs formed at the dry-calcination step and at ; least about 90~ thereof is finally trapped in the solution at the washing tower. The amount of the chlorine trapped exceeds the amount of chlorine ions formed in all the steps. Thus it has been found that the accumulation of chlorine ions in the absorption system can be effectively prevented by discharging a part of the solution withdrawn from the above washing tower out of the processing system. The present invention is based upon these findings.
The present invention provides a process for removing chlorine ions from the wet flue-gas processing system comprising the steps of bringing a flue-gas containing sulfur dioxide in contact with a circulating absorption slurry containing a magne- -sium compound (absorption step), separating solids from a part of the circulating absorption slurry (solid-liquid separation step), drying and calcining the solids to regenerate and reuse 1~994~
1 the magnesium compound (dry-calcination step) and washing the gas formed at the dry-calcination step with water in a washing tower (washing step), which comprises taking at least a part of the solution withdrawn from the washing tower out of the processing system and controlling the water content of the solids to be fed to the dry-calcination step and the amount of the solution with-drawn from the washing tower to be taken out of the processing system, whereby the accumulation of the chlorine ions in the pro-cessing system is sufficiently prevented.
~ Since the solution withdrawn from washing tower 6, as described above, contains a large amount of chlorine ions, it is possible to prevent the accumulation of the chlorine ions in the processing system and to maintain its concentration below a certain level by taking a part or the whole of the solution with-drawn from the washing tower out of the processing system.
The amount of the solution withdrawn from the process-ing system is controlled taking into account the relation between the desired chlorine ion concentration of the absorption solution and the water content of the wet cake. For example, where the water content of the wet cake is 15% by weight, if the whole of the solution withdrawn from the washing tower is taken out of the processing system, the chlorine ion concentration in the absorp- ;
tion system is maintained at about 340 ppm. If the amount of the solution withdrawn from the processing system is controlled to about 11%, the chlorine ion concentration in the absorption sys-tem is as high as 3,000 ppm.
If the chlorine ion concentration in the absorption system is maintained below about 3,000 ppm, it is possible to prevent troubles such as corrosion of the absorption tower and the like, and thus stable operation is possible for a long period of time.
.
1~99491 1 In accordance with the present invention, if the water content of the wet cake to be fed to the dryer is above 2% by weight, it is possible to maintain the chlorine ion concentration in the absorption system below 3,000 ppm by taking a certain amount of the solution withdrawn from the washing tower out of the processing system. The amount of the solution withdrawn from the processing system is made inversely proportional to the water content of the solids to be fed to the regeneration processing.
That is to say, the amount of the solution withdrawn to be taken out of the processing system can be lowered by increasing the water content of the wet cake. Therefore, it is possible to transfer a part of the circulation absorption slurry directly to the dryer without passing it through the centrifugal separator.
The removal of the solution withdrawn from the washing tower of the processing system can be carried out either continu-ously or discontinuously. Also, by increasing the chlorine ion concentration of the solution withdrawn from the washing tower by temporarily increasing the water content of the wet cake, the amount of the solution to be taken out of the processing system can be decreased.
The solution withdrawn from the washing tower which has been taken out of the processing system generally has a pH of from 1.5 to 3.5, a slurry concentration of from 0 to 3 percent by weight, a total SO3 concentration including the dissolved SO2 gas of from 5 to 8 percent by weight and a COD concentration in supernatant liquid of from 700 to 1500 ppm. By neutralizing this solution with an alkali reagent and, if necessary, adding a flocculating agent, followed by filtration or standing to sepa-. rate solid and liquid, the solution thus separated is reduced in its ~olid content of from about 10 to about 20 ppm, its total ~ -5-1~399491 1 SO3 concentration of from about 2000 to about 3000 ppm and its COD concentration of from about 25 to about 30 ppm. Further, the total SO3 concentration of the solution can be reduced to from about 20 to about 100 ppm by subjecting the solution to an air exposure processing, and thus it is possible to abandon the solution without causing any socondary pollution. As alkali reagents being employed for neutralization, it is possible to use magnesium oxide slurry of the flue-gas processing as shown in Fig. 1, and the solids separated are again returned to the flue-gas processing step. In carrying out the present invention, temperatures at which the drying and calcination steps are carried out, and operation conditions under which all the steps are effected, can be set as in usual operations. For example, the drying step is usually carried out at from 200 to 250C
and the calcination step is carried out usually at from 500 to 1,O00C.
~ ` .
Claims (2)
1. In a process for removing chlorine ions from a wet flue-gas processing system comprising the sequence of steps of bringing a flue-gas containing sulfur dioxide in contact with a circulating absorption slurry containing a magnesium oxide (absorption step), separating solids from a part of the circula-ting absorption slurry (solid-liquid separation step), drying and calcining the solids to regenerate and reuse the magnesium oxide (dry-calcination step) and washing the gas formed during the dry-ing and calcining step with water in a washing tower (washing step), the improvement which comprises taking at least a part of the solution withdrawn from the washing tower out of the process-ing system and controlling the water content of the solids fed to said drying and calcining step and the amount of the solution withdrawn from the washing tower out of the processing system so that the amount of the solution withdrawn from the washing tower out of the processing system is inversely proportional to the water content of the solids fed to the drying and calcining step whereby accumulation of the chlorine ions in the processing system is sufficiently prevented.
2. The process according to claim 1 wherein the chlorine ion concentration in the processing system is maintained below about 3,000 ppm.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP136374/1976 | 1976-11-15 | ||
| JP51136374A JPS6048220B2 (en) | 1976-11-15 | 1976-11-15 | Method for removing chlorine ions from wet flue gas treatment process |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1099491A true CA1099491A (en) | 1981-04-21 |
Family
ID=15173660
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA290,427A Expired CA1099491A (en) | 1976-11-15 | 1977-11-08 | Process for removing chlorine ions from the wet flue- gas processing system |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS6048220B2 (en) |
| CA (1) | CA1099491A (en) |
| DE (1) | DE2750768C2 (en) |
| GB (1) | GB1560038A (en) |
| NL (1) | NL168424C (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AT377542B (en) * | 1981-06-24 | 1985-03-25 | Procter & Gamble | TEXTILE FINISHING AGENT |
| JPS6058230A (en) * | 1983-09-09 | 1985-04-04 | Babcock Hitachi Kk | Waste gas desulfurization and apparatus thereof |
| AT388882B (en) * | 1987-07-29 | 1989-09-11 | Andritz Ag Maschf | METHOD FOR THE PURIFICATION OF EXHAUST GASES FROM COMBUSTION PLANTS CONTAINING SALTIC ACID AND SULFUR DIOXIDE, IN PARTICULAR MUSEUM COMBUSTION PLANTS |
| EP2921214B1 (en) | 2010-02-25 | 2018-10-24 | Alfa Laval Corporate AB | Exhaust gas and gas scrubber fluid cleaning equipment and method |
| DK2402288T3 (en) * | 2010-07-02 | 2017-02-06 | Alfa Laval Corp Ab | GAS SCRUBBER FLUID CLEANING EQUIPMENT |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2109096C3 (en) * | 1971-02-25 | 1980-02-14 | Envirotech Corp., Menlo Park, Calif. (V.St.A.) | Process for removing sulfur dioxide with entrained particulate matter from exhaust gases |
| US3727105A (en) * | 1971-06-24 | 1973-04-10 | Anthony S Mfg Co | Fail-safe power cut-out device |
-
1976
- 1976-11-15 JP JP51136374A patent/JPS6048220B2/en not_active Expired
-
1977
- 1977-11-08 CA CA290,427A patent/CA1099491A/en not_active Expired
- 1977-11-11 NL NL7712413A patent/NL168424C/en not_active IP Right Cessation
- 1977-11-12 DE DE19772750768 patent/DE2750768C2/en not_active Expired
- 1977-11-14 GB GB4725977A patent/GB1560038A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| GB1560038A (en) | 1980-01-30 |
| NL168424C (en) | 1982-04-16 |
| DE2750768A1 (en) | 1978-05-24 |
| DE2750768C2 (en) | 1983-03-03 |
| NL168424B (en) | 1981-11-16 |
| JPS6048220B2 (en) | 1985-10-25 |
| JPS5361567A (en) | 1978-06-02 |
| NL7712413A (en) | 1978-05-17 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |