CA1115464A - Method for carbonation of green liquor by means of concentrated carbon dioxide gas in a mixing reactor and for the separation of concentrated hydrogen sulphide only in process steps after carbonation for the preparation of alkali carbonate - Google Patents
Method for carbonation of green liquor by means of concentrated carbon dioxide gas in a mixing reactor and for the separation of concentrated hydrogen sulphide only in process steps after carbonation for the preparation of alkali carbonateInfo
- Publication number
- CA1115464A CA1115464A CA299,099A CA299099A CA1115464A CA 1115464 A CA1115464 A CA 1115464A CA 299099 A CA299099 A CA 299099A CA 1115464 A CA1115464 A CA 1115464A
- Authority
- CA
- Canada
- Prior art keywords
- carbonation
- green liquor
- hydrogen sulphide
- carbon dioxide
- solution
- 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
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 title claims abstract description 34
- 238000000034 method Methods 0.000 title claims abstract description 30
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 title claims abstract description 29
- 229910002092 carbon dioxide Inorganic materials 0.000 title claims abstract description 19
- 239000001569 carbon dioxide Substances 0.000 title claims abstract description 17
- 239000007789 gas Substances 0.000 title claims abstract description 16
- 238000000926 separation method Methods 0.000 title claims abstract description 10
- 238000002156 mixing Methods 0.000 title abstract description 4
- 239000003513 alkali Substances 0.000 title description 10
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 title description 5
- 238000002360 preparation method Methods 0.000 title description 2
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims abstract description 7
- 239000005864 Sulphur Substances 0.000 claims abstract description 7
- BVKZGUZCCUSVTD-UHFFFAOYSA-M Bicarbonate Chemical compound OC([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-M 0.000 claims description 6
- 239000013078 crystal Substances 0.000 claims description 5
- UIIMBOGNXHQVGW-UHFFFAOYSA-M Sodium bicarbonate Chemical compound [Na+].OC([O-])=O UIIMBOGNXHQVGW-UHFFFAOYSA-M 0.000 claims 6
- 229910000030 sodium bicarbonate Inorganic materials 0.000 claims 3
- 235000017557 sodium bicarbonate Nutrition 0.000 claims 3
- 238000005054 agglomeration Methods 0.000 claims 1
- 230000002776 aggregation Effects 0.000 claims 1
- 239000007788 liquid Substances 0.000 claims 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 abstract description 2
- 238000006243 chemical reaction Methods 0.000 description 9
- 239000000203 mixture Substances 0.000 description 4
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 3
- RAHZWNYVWXNFOC-UHFFFAOYSA-N Sulphur dioxide Chemical compound O=S=O RAHZWNYVWXNFOC-UHFFFAOYSA-N 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 238000003795 desorption Methods 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- 229910052783 alkali metal Inorganic materials 0.000 description 1
- 150000001340 alkali metals Chemical group 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- 238000006757 chemical reactions by type Methods 0.000 description 1
- 230000002860 competitive effect Effects 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 235000019988 mead Nutrition 0.000 description 1
- 239000004291 sulphur dioxide Substances 0.000 description 1
- 235000010269 sulphur dioxide Nutrition 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Landscapes
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
The present invention provides a method for carbona-tion of green liquor by means of a concentrated carbon dioxide gas, of more than 50 per cent by volume, under elevated pressure and for separation of sulphur from the above solution as hydro-gen sulphide, whereby the hydrogen sulphide is not removed from the solution in the carbonating apparatus but only in the process steps following the carbonation, characterized in that the carbonation is performed in a mixing reactor under a pressure that is higher than the summed-up total counter-pressure of the component pressures of the carbon dioxide and hydrogen sulphide in the green liquor solution and the component pressure of water vapour.
The present invention provides a method for carbona-tion of green liquor by means of a concentrated carbon dioxide gas, of more than 50 per cent by volume, under elevated pressure and for separation of sulphur from the above solution as hydro-gen sulphide, whereby the hydrogen sulphide is not removed from the solution in the carbonating apparatus but only in the process steps following the carbonation, characterized in that the carbonation is performed in a mixing reactor under a pressure that is higher than the summed-up total counter-pressure of the component pressures of the carbon dioxide and hydrogen sulphide in the green liquor solution and the component pressure of water vapour.
Description
lli54t~
Rauma-Repola Oy : .
Method for carbonation of green liquor by means of concentrated carbon dioxide gas in a mixing reactor and for the separation of concentrated hydrogen sulphide only in process steps after carbonation for the preparation of alkali carbonate ' The subject of the present invention is a method for the carbonation of green liquor and for the separation of sulphur from the solution mentioned above as hydrogen sulphide.
In the method in accordance with the present invention, the sulphur is 'separated as hydrogen sulphide out of the clarified ;~ 10 green liquor obtained from burning of the waste liquor produced in the production of pulp so that the green liquor is first precarbonated by means of gas containing carbon dioxide and thereupon carbonated by means of concentrated carbon dioxide gas, whereby alkali bicarbonate is produced in the solution . to be carbonated. Hereupon the carbonated green liquor is passed into the apparatus for separation of hydrogen sulphide, , .~.
wherein alkali bicarbonate and alkali bisulphide react and liberate hydrogen sulphide.
. .
Several methods are known for the separation of sulphur from an alkali sulphide solution or from an alkali sulphide solution that contains alkali carbonate, as hydrogen sulphide.
Among these methods should be mentioned the Sivola process, the Mead method, the Stora pro¢ess, and the Tampella process.
The method in accordance with the present invention is mainly characterized by what is stated in claim 1.
The method in accordance with the present invention is the following:
Green liquor clarified and precarbonated in a known way is carbonated by means of concentrated carbon dioxide gas of more than 50 per cent by volume in a mixing reactor under a pressure that is higher than the total counter-pressure of the solution. The obtained bicarbonate-containing solution that c~ntains bisulphide and carbonate is passed into a known apparatus for the separation of hydrogen sulphide, in which part of the bicarbonate reacts with bisulphide and a desired quantity of the total sulphur in the solution leaves the solution as hydrogen sulphide.
The method in accordance with the present invention is more specifically the following:
The following reactions take place in the carbonation of green liquor:
(Me = alkali metal) Me2C03 + C2 ~ H20 ~ 2 MeHC03 (1) MeHS ~ MeH;C03 ~ Me2C03 + H2S (2) According to the above reaction equations, when the green liquor is carbonated, when C02 is absorbed, at the same time desorption of H2S tends to take place. When carbonation of the green liquor is performed in known absorption columns by means of concentrated carbon dioxide, the conversion of carbon dioxide to the carbonation reactions is poor and the gas leaving the apparatuses is a mixture of carbon dioxide and hydrogen sulphide, and this is detrimental in view of the .
- 3 li~5464 known further treatment of the gas, burning of the hydrogen sulphide and recovery of the sulphur dioxide.
The principle of the present invention is to perform carbon-ation of green liquor with no liberation of hydrogen sulphide taking place at the same time.
When green liquor is Garbonated, the component pressure of hydrogen sulphide as well as the component pressure of carbon dioxide are increased together with the degree of carbonation.
In order to aecelerate absorption of carbon dioxide and to prevent desorption of hydrogen sulphide, a pressure must be used in the carbonator that is higher than the summed-up total counter-pressure of the component pressures of the carbon dioxide and hydrogen sulphide in the green liquor solution and the component pressure of water vapour. The further the carbonation is extended, the higher shall the pressure in the carbonator be made. In the procedure in accordance with the present invention, the carbonation can be performed either in one carbonator or in several subsequent carbonators. When several carbonators are used in series, their operating pressures can be staggered, whereby savings are obtained in expenses of compressing C02 as well as in purchase expenses affected by the structural pressures of the carbonators.
In the method in accordance with the present invention, the ! . ~
carbonation is performed by means of concentrated carbon dioxide gas of more than 50 per cent by volume in carbonators of the mixing-reactor type.
The carbonation reactor is a continuous stirred tank reactor, or a back-mix reactor with a steady-state continuous flow of feed, and product streams. The feed of gaseous carbon dioxide and the incoming green liquor are very carefully mixed to form a dispersion of small bubbles in green liquor, which makes the reaction rate signifieantly high because of large area of contact surface. The composition of mixture inside the reactor vessel is practically uniform with high gas hold-up and large amount of very small crystals of product bicarbonate.
, .
- 4 11~54fi4 The carbon dioxide gas is dispersed in the carbonators into small bubbles in the green liquor so that a dispersion is formed in which the proportion of gas by volume is 10 to 50 per cent. By means of this method, the mass~transfer area can be made as large as possible and the total mass trans-fer coefficient of the carbonator can be made even 20 to 40 . .
fold as compared, e.g., with the carbonating towers of "passette"
construction used in the Sivola recovery process.l) The very high total mass tran;sfer coefficient of the carbonator makes the carbonators belonging to the method in accordance with the invention so small that, despite their nature of pressure vessel, they are economically competitive as compared with conventional known carbonators.
- The operating temperature of the carbonator,is 0 to 100C.
When a carbonation temperature of 50 to 100C is used, according to the solubility data, a great part of the reaction product MeHC03 of reaction (1) remains uncrystallised in the solution. Owing to the high speed of the carbonation in accordance with the invention, the proportion of MeHC03 in excess of the solubility is not crystallised well, but a very high number of Grystal nuclei are produced and the crystal size remains very small.
Small crystal size is advantageous in the process step following the carbonation, in which the hydrogen sulphide is separated from the solution in a known way. When hydrogen sulphide is removed from the solution, the reaction (2) can proceed from the le~t to the right. The rate of dissolution of MeHC03 (s), i.e. of crystalline MeHC03, i8 proportional t~ the pha~e limit area between the crystals and the solution.
The carbonation in accordance with the method of the invention can be performed without cooling, in which case,the reaction heat liberated owing to the exothermic nature of the carbonation reaction (1) is bound t~ the process flow and is utilized in the next process step, of endothermic reaction type, separation of hydrogen sulphide.
1) The construction of said previously known towers is described, e.g., in the book by Hou, T-P, Manufacture of Soda, Reinhold, New York 1942, pp. 134, 170, 246.
- 5 - 1~154fi4 By means of the method in accordance with the invention, it is possible, from green liquor, to prepare an alkali carbonate solution whose alkali sulphide content is of ~he desired magnitude, by connecting one or se~eral carbonation and hydrogen-sulphide separation steps one after the other.
.
' .
~ ~ ;
.
Rauma-Repola Oy : .
Method for carbonation of green liquor by means of concentrated carbon dioxide gas in a mixing reactor and for the separation of concentrated hydrogen sulphide only in process steps after carbonation for the preparation of alkali carbonate ' The subject of the present invention is a method for the carbonation of green liquor and for the separation of sulphur from the solution mentioned above as hydrogen sulphide.
In the method in accordance with the present invention, the sulphur is 'separated as hydrogen sulphide out of the clarified ;~ 10 green liquor obtained from burning of the waste liquor produced in the production of pulp so that the green liquor is first precarbonated by means of gas containing carbon dioxide and thereupon carbonated by means of concentrated carbon dioxide gas, whereby alkali bicarbonate is produced in the solution . to be carbonated. Hereupon the carbonated green liquor is passed into the apparatus for separation of hydrogen sulphide, , .~.
wherein alkali bicarbonate and alkali bisulphide react and liberate hydrogen sulphide.
. .
Several methods are known for the separation of sulphur from an alkali sulphide solution or from an alkali sulphide solution that contains alkali carbonate, as hydrogen sulphide.
Among these methods should be mentioned the Sivola process, the Mead method, the Stora pro¢ess, and the Tampella process.
The method in accordance with the present invention is mainly characterized by what is stated in claim 1.
The method in accordance with the present invention is the following:
Green liquor clarified and precarbonated in a known way is carbonated by means of concentrated carbon dioxide gas of more than 50 per cent by volume in a mixing reactor under a pressure that is higher than the total counter-pressure of the solution. The obtained bicarbonate-containing solution that c~ntains bisulphide and carbonate is passed into a known apparatus for the separation of hydrogen sulphide, in which part of the bicarbonate reacts with bisulphide and a desired quantity of the total sulphur in the solution leaves the solution as hydrogen sulphide.
The method in accordance with the present invention is more specifically the following:
The following reactions take place in the carbonation of green liquor:
(Me = alkali metal) Me2C03 + C2 ~ H20 ~ 2 MeHC03 (1) MeHS ~ MeH;C03 ~ Me2C03 + H2S (2) According to the above reaction equations, when the green liquor is carbonated, when C02 is absorbed, at the same time desorption of H2S tends to take place. When carbonation of the green liquor is performed in known absorption columns by means of concentrated carbon dioxide, the conversion of carbon dioxide to the carbonation reactions is poor and the gas leaving the apparatuses is a mixture of carbon dioxide and hydrogen sulphide, and this is detrimental in view of the .
- 3 li~5464 known further treatment of the gas, burning of the hydrogen sulphide and recovery of the sulphur dioxide.
The principle of the present invention is to perform carbon-ation of green liquor with no liberation of hydrogen sulphide taking place at the same time.
When green liquor is Garbonated, the component pressure of hydrogen sulphide as well as the component pressure of carbon dioxide are increased together with the degree of carbonation.
In order to aecelerate absorption of carbon dioxide and to prevent desorption of hydrogen sulphide, a pressure must be used in the carbonator that is higher than the summed-up total counter-pressure of the component pressures of the carbon dioxide and hydrogen sulphide in the green liquor solution and the component pressure of water vapour. The further the carbonation is extended, the higher shall the pressure in the carbonator be made. In the procedure in accordance with the present invention, the carbonation can be performed either in one carbonator or in several subsequent carbonators. When several carbonators are used in series, their operating pressures can be staggered, whereby savings are obtained in expenses of compressing C02 as well as in purchase expenses affected by the structural pressures of the carbonators.
In the method in accordance with the present invention, the ! . ~
carbonation is performed by means of concentrated carbon dioxide gas of more than 50 per cent by volume in carbonators of the mixing-reactor type.
The carbonation reactor is a continuous stirred tank reactor, or a back-mix reactor with a steady-state continuous flow of feed, and product streams. The feed of gaseous carbon dioxide and the incoming green liquor are very carefully mixed to form a dispersion of small bubbles in green liquor, which makes the reaction rate signifieantly high because of large area of contact surface. The composition of mixture inside the reactor vessel is practically uniform with high gas hold-up and large amount of very small crystals of product bicarbonate.
, .
- 4 11~54fi4 The carbon dioxide gas is dispersed in the carbonators into small bubbles in the green liquor so that a dispersion is formed in which the proportion of gas by volume is 10 to 50 per cent. By means of this method, the mass~transfer area can be made as large as possible and the total mass trans-fer coefficient of the carbonator can be made even 20 to 40 . .
fold as compared, e.g., with the carbonating towers of "passette"
construction used in the Sivola recovery process.l) The very high total mass tran;sfer coefficient of the carbonator makes the carbonators belonging to the method in accordance with the invention so small that, despite their nature of pressure vessel, they are economically competitive as compared with conventional known carbonators.
- The operating temperature of the carbonator,is 0 to 100C.
When a carbonation temperature of 50 to 100C is used, according to the solubility data, a great part of the reaction product MeHC03 of reaction (1) remains uncrystallised in the solution. Owing to the high speed of the carbonation in accordance with the invention, the proportion of MeHC03 in excess of the solubility is not crystallised well, but a very high number of Grystal nuclei are produced and the crystal size remains very small.
Small crystal size is advantageous in the process step following the carbonation, in which the hydrogen sulphide is separated from the solution in a known way. When hydrogen sulphide is removed from the solution, the reaction (2) can proceed from the le~t to the right. The rate of dissolution of MeHC03 (s), i.e. of crystalline MeHC03, i8 proportional t~ the pha~e limit area between the crystals and the solution.
The carbonation in accordance with the method of the invention can be performed without cooling, in which case,the reaction heat liberated owing to the exothermic nature of the carbonation reaction (1) is bound t~ the process flow and is utilized in the next process step, of endothermic reaction type, separation of hydrogen sulphide.
1) The construction of said previously known towers is described, e.g., in the book by Hou, T-P, Manufacture of Soda, Reinhold, New York 1942, pp. 134, 170, 246.
- 5 - 1~154fi4 By means of the method in accordance with the invention, it is possible, from green liquor, to prepare an alkali carbonate solution whose alkali sulphide content is of ~he desired magnitude, by connecting one or se~eral carbonation and hydrogen-sulphide separation steps one after the other.
.
' .
~ ~ ;
.
Claims (5)
1. A method of carbonating green liquor and removing sulphur therefrom in the form of hydrogen sulphide comprising:
(a) carbonating the green liquid to form sodium bicarbonate by contacting said green liquor in a carbonation zone with a gas comprising greater than about 50 percent by volume of carbon dioxide to achieve a sodium bicarbonate concentration in said liquor in excess of the solubility limit of said sodium bicarbonate in said liquor, the pressure in said carbonation zone being greater than the sum of the partial pressures of the gases in solution in said green liquor, while maintaining a gas hold-up of from about 10 to 50 percent by volume, said green liquor being sufficiently agitated during said contacting to prevent the agglomeration of bicarbonate crystals which form during said carbonation, and no hydrogen sulphide being removed from the solution in the carbonation zone;
(b) passing said green liquor which is carbonated in said carbonation zone to a hydrogen sulphide separation zone; and (c) removing sulphur from said carbonated green liquor as hydrogen sulphide.
(a) carbonating the green liquid to form sodium bicarbonate by contacting said green liquor in a carbonation zone with a gas comprising greater than about 50 percent by volume of carbon dioxide to achieve a sodium bicarbonate concentration in said liquor in excess of the solubility limit of said sodium bicarbonate in said liquor, the pressure in said carbonation zone being greater than the sum of the partial pressures of the gases in solution in said green liquor, while maintaining a gas hold-up of from about 10 to 50 percent by volume, said green liquor being sufficiently agitated during said contacting to prevent the agglomeration of bicarbonate crystals which form during said carbonation, and no hydrogen sulphide being removed from the solution in the carbonation zone;
(b) passing said green liquor which is carbonated in said carbonation zone to a hydrogen sulphide separation zone; and (c) removing sulphur from said carbonated green liquor as hydrogen sulphide.
2. The method according to claim 1, wherein the green liquor to be carbonated has first been clarified and pre-carbonated in known ways.
3. The method of claim 1 wherein the carbonation of step (a) occurs at a temperature of 50 to 100°C.
4. The method of claim 3 wherein the carbonation of step (a) occurs at a temperature of 60 to 80°C.
5. The method of claim 4 wherein the gas hold up ranges from 25 to 35 percent by volume.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA299,099A CA1115464A (en) | 1978-03-16 | 1978-03-16 | Method for carbonation of green liquor by means of concentrated carbon dioxide gas in a mixing reactor and for the separation of concentrated hydrogen sulphide only in process steps after carbonation for the preparation of alkali carbonate |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA299,099A CA1115464A (en) | 1978-03-16 | 1978-03-16 | Method for carbonation of green liquor by means of concentrated carbon dioxide gas in a mixing reactor and for the separation of concentrated hydrogen sulphide only in process steps after carbonation for the preparation of alkali carbonate |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1115464A true CA1115464A (en) | 1982-01-05 |
Family
ID=4111014
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA299,099A Expired CA1115464A (en) | 1978-03-16 | 1978-03-16 | Method for carbonation of green liquor by means of concentrated carbon dioxide gas in a mixing reactor and for the separation of concentrated hydrogen sulphide only in process steps after carbonation for the preparation of alkali carbonate |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1115464A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2013040747A1 (en) * | 2011-09-19 | 2013-03-28 | 北京沃特玛德环境技术股份有限公司 | Method for comprehensively utilizing solid waste during soda recovery in papermaking industry |
-
1978
- 1978-03-16 CA CA299,099A patent/CA1115464A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2013040747A1 (en) * | 2011-09-19 | 2013-03-28 | 北京沃特玛德环境技术股份有限公司 | Method for comprehensively utilizing solid waste during soda recovery in papermaking industry |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry | ||
| MKEX | Expiry |
Effective date: 19990105 |