CA1241534A - Method for preparing compositions which can be used in the production of sodium dithionite; and the use of such compositions - Google Patents
Method for preparing compositions which can be used in the production of sodium dithionite; and the use of such compositionsInfo
- Publication number
- CA1241534A CA1241534A CA000481106A CA481106A CA1241534A CA 1241534 A CA1241534 A CA 1241534A CA 000481106 A CA000481106 A CA 000481106A CA 481106 A CA481106 A CA 481106A CA 1241534 A CA1241534 A CA 1241534A
- Authority
- CA
- Canada
- Prior art keywords
- sulphur dioxide
- sodium
- ratio
- sodium oxide
- mixture
- 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
- 239000000203 mixture Substances 0.000 title claims abstract description 26
- JVBXVOWTABLYPX-UHFFFAOYSA-L sodium dithionite Chemical compound [Na+].[Na+].[O-]S(=O)S([O-])=O JVBXVOWTABLYPX-UHFFFAOYSA-L 0.000 title claims abstract description 10
- 238000000034 method Methods 0.000 title claims description 18
- 238000004519 manufacturing process Methods 0.000 title abstract description 8
- RAHZWNYVWXNFOC-UHFFFAOYSA-N Sulphur dioxide Chemical compound O=S=O RAHZWNYVWXNFOC-UHFFFAOYSA-N 0.000 claims abstract description 142
- 239000004291 sulphur dioxide Substances 0.000 claims abstract description 53
- 235000010269 sulphur dioxide Nutrition 0.000 claims abstract description 53
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims abstract description 33
- KKCBUQHMOMHUOY-UHFFFAOYSA-N sodium oxide Chemical compound [O-2].[Na+].[Na+] KKCBUQHMOMHUOY-UHFFFAOYSA-N 0.000 claims abstract description 21
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 20
- 239000007788 liquid Substances 0.000 claims abstract description 16
- 229910001948 sodium oxide Inorganic materials 0.000 claims abstract description 14
- 239000007864 aqueous solution Substances 0.000 claims abstract description 10
- 230000003134 recirculating effect Effects 0.000 claims abstract description 9
- GRWZHXKQBITJKP-UHFFFAOYSA-L dithionite(2-) Chemical compound [O-]S(=O)S([O-])=O GRWZHXKQBITJKP-UHFFFAOYSA-L 0.000 claims abstract description 8
- 239000011369 resultant mixture Substances 0.000 claims abstract description 4
- 239000003638 chemical reducing agent Substances 0.000 claims description 8
- 238000002360 preparation method Methods 0.000 claims description 4
- 238000007865 diluting Methods 0.000 claims description 3
- 238000011144 upstream manufacturing Methods 0.000 claims description 3
- 239000000243 solution Substances 0.000 description 20
- WQDSRJBTLILEEK-UHFFFAOYSA-N sulfurous acid Chemical compound OS(O)=O.OS(O)=O WQDSRJBTLILEEK-UHFFFAOYSA-N 0.000 description 7
- 239000007789 gas Substances 0.000 description 6
- 229940124024 weight reducing agent Drugs 0.000 description 6
- 238000003860 storage Methods 0.000 description 5
- 239000003546 flue gas Substances 0.000 description 4
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 3
- 239000012279 sodium borohydride Substances 0.000 description 3
- 229910000033 sodium borohydride Inorganic materials 0.000 description 3
- VYKVQJFOZDGJLN-UHFFFAOYSA-M sodium hydrogen sulfite sulfurous acid Chemical compound [Na+].OS(O)=O.OS([O-])=O VYKVQJFOZDGJLN-UHFFFAOYSA-M 0.000 description 3
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 239000001117 sulphuric acid Substances 0.000 description 2
- 235000011149 sulphuric acid Nutrition 0.000 description 2
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 239000005864 Sulphur Substances 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- XQIMLPCOVYNASM-UHFFFAOYSA-N borole Chemical compound B1C=CC=C1 XQIMLPCOVYNASM-UHFFFAOYSA-N 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- 239000008139 complexing agent Substances 0.000 description 1
- 238000009833 condensation Methods 0.000 description 1
- 230000005494 condensation Effects 0.000 description 1
- 239000000356 contaminant Substances 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 125000004435 hydrogen atom Chemical class [H]* 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000000047 product Substances 0.000 description 1
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- Treating Waste Gases (AREA)
Abstract
ABSTRACT
There is provided a method for producing compositions which can be used for preparing sodium dithionite, in which sulphur dioxide is brought into contact with a recirculating aqueous solution of sodium hydroxide and previously absorbed sulphur dioxide to a ratio of sulphur dioxide and the sum of sulphur dioxide and sodium oxide of 0.61-0.66, whereafter the resultant mixture is pressurized and liquid sulphur dioxide introduced therein to a ratio between sulphur dioxide and the sum of sulphur dioxide and sodium oxide of 0.75-0.81,and the water content is adjusted to a concentration of sulphur dioxide + sodium oxide of 10-13 percent by weight. The invention also relates to the use of the prepared composition for the manufacture of dithionite.
There is provided a method for producing compositions which can be used for preparing sodium dithionite, in which sulphur dioxide is brought into contact with a recirculating aqueous solution of sodium hydroxide and previously absorbed sulphur dioxide to a ratio of sulphur dioxide and the sum of sulphur dioxide and sodium oxide of 0.61-0.66, whereafter the resultant mixture is pressurized and liquid sulphur dioxide introduced therein to a ratio between sulphur dioxide and the sum of sulphur dioxide and sodium oxide of 0.75-0.81,and the water content is adjusted to a concentration of sulphur dioxide + sodium oxide of 10-13 percent by weight. The invention also relates to the use of the prepared composition for the manufacture of dithionite.
Description
SK-5~
A Method For Preparing Compositions WhiCh Can se Used In The Production Of Sodium Dithionite; And The Use Of Such Compositons The present invention relates to a method of preparing compositions which can be used in the production of sodium dithionite; and the use of such compositions.
According to one known method for preparing sodium dithionite, 40-50 percent by weight aqueous solution of sodium hydroxide, liquid sulphur dioxide and water are mixed with the reducingagent mixture comprising 12 percent by weight sodium borohydride, 40 percent by weight sodium hydroxide and 48 percent by weight water in a conduit system, in which the mixture is circulated in order to conduct away the high quantity of heat of reaction generated.Because of the number of components to be mixed together, it is necessary to make several adjustments.In addition, liquid sulphur dioxide is difficult to handle.
Consequently an object of the present invention is to proYide a method for producing compositions which can be used in the production of sodium dithionite and which facilitate the work of the manufacturer of the dithionite, by reducing the number of components which need be handled, and therewith - 20 reducing the number of adjustments which need be made, and by reducing cooling requirements.
This is achieved in accordance with the present invention by means of a method which comprises wringing sulphur dioxide into contact with.a recirculating aqueous solution of sodium hydroxide and previously absorbed sulphur dioxide to a ratio between sulphur dioxide and the sum of sulphur dioxide and sodium oxide(SO2~(S02 Na2o)) of 0.61-0.66,preferably 0.63-0.65, and subsequently pressurizing the resultant mixture and introducing liquid sulphur dioxide thereinto to a ratio between sulphur dioxide and the sum of sulphur dioxide and I, .
~L~41~34 sodium oxide of 0.75-0.81, preferably about 0.78, and adjusting the water content to a concentration of sulphur dioxide + sodium oxide of 10-13 percent by weight, preferably about 12 percent by weight.
In the first part stage of the method according to the invention, in which sulphur dioxide is brought into contact with a recirculating aqueous solution of sodium hydroxide and previously absorbed sulphur dioxide, sulphur dioxide is preferably introduced in the form of a preferably dry sulphur dioxide-containing flue gas obtained in the manufacture of sulphuric acid.Flue gases obtained from plants which combust sulphur-containing fuels can also be used, provided that measures are taken to prevent condensation of the water when handling the gas with the recirculating aqueous solution of r 15 sodium hydroxide and sulphur dioxide.The sulphur dioxide containing gas is preferably brought into contact with the aforesaid recirculating aqueous solution in a conventional scrubber plant.
This part method stage is preferably carried out cont-inuously at approximately atmospheric pressure, a part of thesolution being removed from circulation and replaced with an aqueous solution of sodium hydroxide, although the part stage can also be carried out intermittently.The method is controlled in both alternatives in a manner such that the resultant mixture exhibits a ratio between sulphur dioxide and the sum of sulphur dioxide and sodium oxide of 0.61-0.66, preferably 0.63-Q.65.
In the second part method stage, the mixture obtained in the first part stage is tranferred to a pressurized space or chamber, for example a space standing under a pressure in the order of 2.5 bars or more, preferably in the form of a section or part of a recirculation loop defined upstream by a recirculation pump and downstream by a constriction, in which space liquid sulphur dioxide is introduced into the mixture to a ratio S02/(SO2 + Na2O) of 0.75-0.81, ?refera~ly -I about 0.78, and the water content being adjusted to a concen-tration of sulphur dioxide + sodium oxide of 10-13 percent by wieght, preferably about 12 percent by . .
. . , 3 ~L2~.S3~L
weight,so as to obtain aproduct in the form of a solution which can be stored at atmospheric pressure.
The invention also relates to the use of a composition prepared in accordance with the method according to the invention for preparing dithionite by reduction.In use the composition is mixed with a reducing agent mixture of preferably the aforementioned conventional kind and is optionally recir-culated in a conduit system, optionally while diluting the mixture by adding ~ater.If desired,the mixture can be diluted with water prior to circulation, instead of during circulation, or the end product itself can be diluted.
The invention will now be described in more detail with reference to a plant illustrated schematically in the accom-panying drawing and intended for the preparation of sodium dithionite in accordance with the invention.
In the drawing the references 1 and 2 identify respectively a road tanker and a tank trailer.The tank of the road tanker 1 is adapted to contain liquid sulphur dioxide and the tank trailer 2 to accommodate a sodium sulphite-bisulphite solution 20 in a ratio SO2~(SO2 + Na2Ol in the order of 0.61-0.65 and a concentration in the order of, for example, 40 percent by weight.The total concentration of sulphur dioxide + sodium oxide in the combined contents of the tanks of the tanker 1 and the tank trailer 2 is suitably about 50 percent by weight.
The reference 3 identifies a tank having an internal prevailing pressure of approximately atmospheric pressure and forming part of a recirculation system comprising a circulation pump 4, a conduit 5 extending from the tank 3 to the suction side of the pump 4, and a conduit 6 which extends between the 3Q the pressure side of the pump 4 and the tank 3 and which incorporates a closure YalYe 7, a restriction 8, and a conduit part 4 of enlarged crossection.The tank of the road tanker 1 can be connected to the conduit part 9 by means of a conduit l incorporating a pump 10, while the trailer tank 2 can be connected to the conduit 5 by means of a conduit ~3 incorpo-rating a pump 12.The refernce ~4 identifies a water-supply conduit which branches into three conduits 15,16,17, of which the conduit 15 supplies water to the conduit 5 for diluting a sulphite-bisulphite solution conveyed through the conduit 13.
4 ~2~534 The flows through the inlet conduits 11,13,14 and in the recirculation systems 3-9 are adjusted with the aid of control means not shown, and by adjusting the constriction 8, so as to maintain in the conduit part9 a pressure in the order of, for example, 2.5 bars while emptying the road tanker and the tank trailer 2.This avoids in a favourable manner the need of providing conventional, expensive pressure vessels.With the aid of the hitherto described arrangement there is prepared and supplied to the tank 3 a sodium sulphite-bisulphite solution having a ratio SO2/(SO2 + Na2O) of 0.75-0.81, and a concent-ration (10-13 percent by weight) which enables it to be stored at atmospheric pressure.
The pressure side of the pump 4 can be connected to a storage tank 20 by means of a conduit 19 provided with a closure valve 18, the pressure prevailing in the storage tank also being approximately atmospheric pressure.Gas departing from the upper part of the tank 20 is led-off subsequent to being washed in a scrubber 21 or the like with water supplied throughthe conduit 17.This water, with sulphur dioxide dis-solved therein, is supplied to the tank 3 through a conduit 22.Gas collected in the upper part of the tank 3 is sprayed with water passed through the conduit 16, while undissolved gases are conducted to the upper part of the tank 20 through a gas conduit 23.
For the purpose of preparing sodium dithionite, solution from the tank 2 is combined with a conventional reducing~aqe~t comprising substantially an aqueous solution of sodium boro-hydride and sodium hydroxide.This is effected in a recirculation circuit incorporating a circulation pump 24, a vessel 25, a conduit-26 extending between the bottom of the vessel 25 and the suction side of the pump 24, and a conduit 27 which extends between the pressure side of the pump 24 and the vessel 25 and in which there is arrranged a heat exchanger 28 for cooling the circulating liquid to a desired temperature level.The sodium sulphite-bisulphite solution is supplied to the conduit 27 through a conduit 30 which incorporates a pump 29, while the solution of reducing agent is supplied to the conduit 27 from a storage tank 3~ through a conduit 33 incorporating a pump 32.Prepared sodium dithionite solution departs through a 5 ~4~J3~
spillway 34 arranged in the vessel 25 and is conducted to a storage tank 35 through a conduit 36, optionally after being diluted with water entering through a conduit 37.Prepared dithionite solution is conveyed to consumer sites from the tank 35 through a conduit 39 incorporating a pump 38.
In order to avoid yield losses due to hydrogen formation in the recirculation circuit 24-28, it has been found highly suitable to charge the solution of the reducing agent, and advantageously also the sulphite-bisulphite solution, to the liquid circulating in the circuit 24-28, substantially iso-kinetically, i.e. the supplied solute s are introduced into the conduit 27 in a direction and at a flow rate which coin-cides substantially with the flow direction and flow rate of the recirculated solution.To this end, the conduits 30 and 33 discharge into the conduit 27 through nozzles 41 directed downstream, as eYident from the part 40 of said conduit 27 shown in axial section,wherewith each conduit 30 or 33 can be branched in the manner indicated, each branch being provided with a nozzle 41 and an adjustable valve 42.The solution 20 leaving the circulation systems 24-28 through the conduit 36 can be admixed, for example, with a complexing agent for separating undesirable metal contaminants, and also with pH-regulating additives.
Example Sulphite-bisulphite solution obtained from a flue gas scrubber adapted for sulphur-dioxide containing flue gas derived from a sulphuric acid plant hazing a sulphite bisulphite concen-tration in percent Na2O + SO2 = 39 and a ratio SO2~(SO2 +
Na2OI of 0.63-0.65 was used together with liquid sulphur dioxide and water to produce a composition suitable for the preparation of dithionite.
In this respect 4680 kg of liquid sulphur dioxide were charged to a pressurized space and added with 22,000 kg 39 %-sulphite-bisulphite solution,having a ratio SO~(SO2 + Na2O) 35 of Q.64,and 7q,320 kg water, which gaYe SO2~(SO2 + Na2O) =
0.775 and a concentration of ~2 %.
The solution was passed to a storage tank in which a pressure equal to atmospheric pressure was maintained and then used directly for preparing dithionite, it being necessary 6 ~L24~534 only to add a reducing agent mixture,for example a reducing agent retailed by Ventron Corporation, Mass. USA; under the registered trade mark BOROL (R) containing approximately 12 percent by weight NaBH4 , 40 percent by weight NaOH and 48 percent by weight H2O.The outgoing dithionite solution was diluted with water to a concentration of 3 % by weight.
Example 2 Example 1 was repeated but with the ratio SO2~(SO2 + Na2o) of the sulphite-bisulphite solution equal to 0.65; and this time 4333 kg of liquid sulphur dioxide and 76,775 kg water were added, so as to obtain the same factor of 0.775.
Example 3 Example 1 was repeated and the same sulphite-bisulphite solution as that in Example 1 was used, although with the desire to obtain a product having a ratio of SO2~(SO2 + Na2O~
= 0.790 kg.CcnseqUently 5741 kg of liquid sulphur dioxide and 85,684 kg water were added to the 20,000 kg sulphite-bisulphite solution in this example.
A Method For Preparing Compositions WhiCh Can se Used In The Production Of Sodium Dithionite; And The Use Of Such Compositons The present invention relates to a method of preparing compositions which can be used in the production of sodium dithionite; and the use of such compositions.
According to one known method for preparing sodium dithionite, 40-50 percent by weight aqueous solution of sodium hydroxide, liquid sulphur dioxide and water are mixed with the reducingagent mixture comprising 12 percent by weight sodium borohydride, 40 percent by weight sodium hydroxide and 48 percent by weight water in a conduit system, in which the mixture is circulated in order to conduct away the high quantity of heat of reaction generated.Because of the number of components to be mixed together, it is necessary to make several adjustments.In addition, liquid sulphur dioxide is difficult to handle.
Consequently an object of the present invention is to proYide a method for producing compositions which can be used in the production of sodium dithionite and which facilitate the work of the manufacturer of the dithionite, by reducing the number of components which need be handled, and therewith - 20 reducing the number of adjustments which need be made, and by reducing cooling requirements.
This is achieved in accordance with the present invention by means of a method which comprises wringing sulphur dioxide into contact with.a recirculating aqueous solution of sodium hydroxide and previously absorbed sulphur dioxide to a ratio between sulphur dioxide and the sum of sulphur dioxide and sodium oxide(SO2~(S02 Na2o)) of 0.61-0.66,preferably 0.63-0.65, and subsequently pressurizing the resultant mixture and introducing liquid sulphur dioxide thereinto to a ratio between sulphur dioxide and the sum of sulphur dioxide and I, .
~L~41~34 sodium oxide of 0.75-0.81, preferably about 0.78, and adjusting the water content to a concentration of sulphur dioxide + sodium oxide of 10-13 percent by weight, preferably about 12 percent by weight.
In the first part stage of the method according to the invention, in which sulphur dioxide is brought into contact with a recirculating aqueous solution of sodium hydroxide and previously absorbed sulphur dioxide, sulphur dioxide is preferably introduced in the form of a preferably dry sulphur dioxide-containing flue gas obtained in the manufacture of sulphuric acid.Flue gases obtained from plants which combust sulphur-containing fuels can also be used, provided that measures are taken to prevent condensation of the water when handling the gas with the recirculating aqueous solution of r 15 sodium hydroxide and sulphur dioxide.The sulphur dioxide containing gas is preferably brought into contact with the aforesaid recirculating aqueous solution in a conventional scrubber plant.
This part method stage is preferably carried out cont-inuously at approximately atmospheric pressure, a part of thesolution being removed from circulation and replaced with an aqueous solution of sodium hydroxide, although the part stage can also be carried out intermittently.The method is controlled in both alternatives in a manner such that the resultant mixture exhibits a ratio between sulphur dioxide and the sum of sulphur dioxide and sodium oxide of 0.61-0.66, preferably 0.63-Q.65.
In the second part method stage, the mixture obtained in the first part stage is tranferred to a pressurized space or chamber, for example a space standing under a pressure in the order of 2.5 bars or more, preferably in the form of a section or part of a recirculation loop defined upstream by a recirculation pump and downstream by a constriction, in which space liquid sulphur dioxide is introduced into the mixture to a ratio S02/(SO2 + Na2O) of 0.75-0.81, ?refera~ly -I about 0.78, and the water content being adjusted to a concen-tration of sulphur dioxide + sodium oxide of 10-13 percent by wieght, preferably about 12 percent by . .
. . , 3 ~L2~.S3~L
weight,so as to obtain aproduct in the form of a solution which can be stored at atmospheric pressure.
The invention also relates to the use of a composition prepared in accordance with the method according to the invention for preparing dithionite by reduction.In use the composition is mixed with a reducing agent mixture of preferably the aforementioned conventional kind and is optionally recir-culated in a conduit system, optionally while diluting the mixture by adding ~ater.If desired,the mixture can be diluted with water prior to circulation, instead of during circulation, or the end product itself can be diluted.
The invention will now be described in more detail with reference to a plant illustrated schematically in the accom-panying drawing and intended for the preparation of sodium dithionite in accordance with the invention.
In the drawing the references 1 and 2 identify respectively a road tanker and a tank trailer.The tank of the road tanker 1 is adapted to contain liquid sulphur dioxide and the tank trailer 2 to accommodate a sodium sulphite-bisulphite solution 20 in a ratio SO2~(SO2 + Na2Ol in the order of 0.61-0.65 and a concentration in the order of, for example, 40 percent by weight.The total concentration of sulphur dioxide + sodium oxide in the combined contents of the tanks of the tanker 1 and the tank trailer 2 is suitably about 50 percent by weight.
The reference 3 identifies a tank having an internal prevailing pressure of approximately atmospheric pressure and forming part of a recirculation system comprising a circulation pump 4, a conduit 5 extending from the tank 3 to the suction side of the pump 4, and a conduit 6 which extends between the 3Q the pressure side of the pump 4 and the tank 3 and which incorporates a closure YalYe 7, a restriction 8, and a conduit part 4 of enlarged crossection.The tank of the road tanker 1 can be connected to the conduit part 9 by means of a conduit l incorporating a pump 10, while the trailer tank 2 can be connected to the conduit 5 by means of a conduit ~3 incorpo-rating a pump 12.The refernce ~4 identifies a water-supply conduit which branches into three conduits 15,16,17, of which the conduit 15 supplies water to the conduit 5 for diluting a sulphite-bisulphite solution conveyed through the conduit 13.
4 ~2~534 The flows through the inlet conduits 11,13,14 and in the recirculation systems 3-9 are adjusted with the aid of control means not shown, and by adjusting the constriction 8, so as to maintain in the conduit part9 a pressure in the order of, for example, 2.5 bars while emptying the road tanker and the tank trailer 2.This avoids in a favourable manner the need of providing conventional, expensive pressure vessels.With the aid of the hitherto described arrangement there is prepared and supplied to the tank 3 a sodium sulphite-bisulphite solution having a ratio SO2/(SO2 + Na2O) of 0.75-0.81, and a concent-ration (10-13 percent by weight) which enables it to be stored at atmospheric pressure.
The pressure side of the pump 4 can be connected to a storage tank 20 by means of a conduit 19 provided with a closure valve 18, the pressure prevailing in the storage tank also being approximately atmospheric pressure.Gas departing from the upper part of the tank 20 is led-off subsequent to being washed in a scrubber 21 or the like with water supplied throughthe conduit 17.This water, with sulphur dioxide dis-solved therein, is supplied to the tank 3 through a conduit 22.Gas collected in the upper part of the tank 3 is sprayed with water passed through the conduit 16, while undissolved gases are conducted to the upper part of the tank 20 through a gas conduit 23.
For the purpose of preparing sodium dithionite, solution from the tank 2 is combined with a conventional reducing~aqe~t comprising substantially an aqueous solution of sodium boro-hydride and sodium hydroxide.This is effected in a recirculation circuit incorporating a circulation pump 24, a vessel 25, a conduit-26 extending between the bottom of the vessel 25 and the suction side of the pump 24, and a conduit 27 which extends between the pressure side of the pump 24 and the vessel 25 and in which there is arrranged a heat exchanger 28 for cooling the circulating liquid to a desired temperature level.The sodium sulphite-bisulphite solution is supplied to the conduit 27 through a conduit 30 which incorporates a pump 29, while the solution of reducing agent is supplied to the conduit 27 from a storage tank 3~ through a conduit 33 incorporating a pump 32.Prepared sodium dithionite solution departs through a 5 ~4~J3~
spillway 34 arranged in the vessel 25 and is conducted to a storage tank 35 through a conduit 36, optionally after being diluted with water entering through a conduit 37.Prepared dithionite solution is conveyed to consumer sites from the tank 35 through a conduit 39 incorporating a pump 38.
In order to avoid yield losses due to hydrogen formation in the recirculation circuit 24-28, it has been found highly suitable to charge the solution of the reducing agent, and advantageously also the sulphite-bisulphite solution, to the liquid circulating in the circuit 24-28, substantially iso-kinetically, i.e. the supplied solute s are introduced into the conduit 27 in a direction and at a flow rate which coin-cides substantially with the flow direction and flow rate of the recirculated solution.To this end, the conduits 30 and 33 discharge into the conduit 27 through nozzles 41 directed downstream, as eYident from the part 40 of said conduit 27 shown in axial section,wherewith each conduit 30 or 33 can be branched in the manner indicated, each branch being provided with a nozzle 41 and an adjustable valve 42.The solution 20 leaving the circulation systems 24-28 through the conduit 36 can be admixed, for example, with a complexing agent for separating undesirable metal contaminants, and also with pH-regulating additives.
Example Sulphite-bisulphite solution obtained from a flue gas scrubber adapted for sulphur-dioxide containing flue gas derived from a sulphuric acid plant hazing a sulphite bisulphite concen-tration in percent Na2O + SO2 = 39 and a ratio SO2~(SO2 +
Na2OI of 0.63-0.65 was used together with liquid sulphur dioxide and water to produce a composition suitable for the preparation of dithionite.
In this respect 4680 kg of liquid sulphur dioxide were charged to a pressurized space and added with 22,000 kg 39 %-sulphite-bisulphite solution,having a ratio SO~(SO2 + Na2O) 35 of Q.64,and 7q,320 kg water, which gaYe SO2~(SO2 + Na2O) =
0.775 and a concentration of ~2 %.
The solution was passed to a storage tank in which a pressure equal to atmospheric pressure was maintained and then used directly for preparing dithionite, it being necessary 6 ~L24~534 only to add a reducing agent mixture,for example a reducing agent retailed by Ventron Corporation, Mass. USA; under the registered trade mark BOROL (R) containing approximately 12 percent by weight NaBH4 , 40 percent by weight NaOH and 48 percent by weight H2O.The outgoing dithionite solution was diluted with water to a concentration of 3 % by weight.
Example 2 Example 1 was repeated but with the ratio SO2~(SO2 + Na2o) of the sulphite-bisulphite solution equal to 0.65; and this time 4333 kg of liquid sulphur dioxide and 76,775 kg water were added, so as to obtain the same factor of 0.775.
Example 3 Example 1 was repeated and the same sulphite-bisulphite solution as that in Example 1 was used, although with the desire to obtain a product having a ratio of SO2~(SO2 + Na2O~
= 0.790 kg.CcnseqUently 5741 kg of liquid sulphur dioxide and 85,684 kg water were added to the 20,000 kg sulphite-bisulphite solution in this example.
Claims (7)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method for preparing compositions capable of being used in the preparation of sodium dithionite, which method comprises bringing sulphur dioxide into contact with a re-circulating aqueous solution of sodium hydroxide and pre-viously absorbed sulphur dioxide to a ratio between sulphur dioxide and the sum of sulphur dioxide and sodium oxide of 0.61-0.66, pressurizing the resultant mixture and introducing liquid sulphur dioxide thereinto to a ratio between sulphur dioxide and the sum of sulphur dioxide and sodium oxide of 0.75-0.81, and adjusting the water content to a concentration of SO2 + Na2O of 10-13 percent by weight.
2. A method according to claim 1, wherein liquid sulphur dioxide is supplied to the mixture in a pressurized part of a recirculation loop defined upstream by a recirculating pump and downstream by a constriction.
3. A method according to claim 1, wherein sulphur dioxide is added to the recirculating aqueous solution of sodium hydroxide and previously absorbed sulphur dioxide to a ratio between sulphur dioxide and the sum of sulphur dioxide and sodium oxide of 0.63-0.65 prior to pressurizing the system.
4. A method according to claim 1, wherein the liquid sulphur dioxide is introduced into the pressurized mixture to a ratio between sulphur dioxide and the sum of sulphur dioxide and sodium oxide of about 0.78.
5. A method according to claim 1, wherein the water content is adjusted to a concentration of sulphur dioxide and sodium oxide of about 12 percent by weight.
6. A method according to claim 1, which for the preparation of dithionite comprises the additional step of introducing isokinetically the composition formed and a reducing agent into a mixture of said composition and said reducing agent recirculating in a circuit.
7. A method according to claim 2, wherein liquid sulphur dioxide and diluting water are supplied to the mixture in a pressurized part of a recirculation loop defined upstream by a recirculating pump and downstream by a constriction.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000481106A CA1241534A (en) | 1985-05-08 | 1985-05-08 | Method for preparing compositions which can be used in the production of sodium dithionite; and the use of such compositions |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000481106A CA1241534A (en) | 1985-05-08 | 1985-05-08 | Method for preparing compositions which can be used in the production of sodium dithionite; and the use of such compositions |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1241534A true CA1241534A (en) | 1988-09-06 |
Family
ID=4130458
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000481106A Expired CA1241534A (en) | 1985-05-08 | 1985-05-08 | Method for preparing compositions which can be used in the production of sodium dithionite; and the use of such compositions |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1241534A (en) |
-
1985
- 1985-05-08 CA CA000481106A patent/CA1241534A/en not_active Expired
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