WO2016013027A2 - A novel process for recovery of calcium hypochlorite - Google Patents
A novel process for recovery of calcium hypochlorite Download PDFInfo
- Publication number
- WO2016013027A2 WO2016013027A2 PCT/IN2015/000303 IN2015000303W WO2016013027A2 WO 2016013027 A2 WO2016013027 A2 WO 2016013027A2 IN 2015000303 W IN2015000303 W IN 2015000303W WO 2016013027 A2 WO2016013027 A2 WO 2016013027A2
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- WO
- WIPO (PCT)
- Prior art keywords
- calcium hypochlorite
- sodium chloride
- slurry
- high strength
- waste water
- Prior art date
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Classifications
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D3/00—Halides of sodium, potassium or alkali metals in general
- C01D3/04—Chlorides
- C01D3/06—Preparation by working up brines; seawater or spent lyes
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B11/00—Oxides or oxyacids of halogens; Salts thereof
- C01B11/04—Hypochlorous acid
- C01B11/06—Hypochlorites
- C01B11/064—Hypochlorites of alkaline-earth metals
Abstract
The present invention provides a novel process to recover a high strength Calcium Hypochlorite from aqueous waste water stream by selective crystallization of sodium chloride and calcium hypochlorite by changing process parameters such as pressure, temperature, mixing etc. The main advantage of the present invention is related to production process for recovery of Calcium Hypochlorite from the mother water stream/ aqueous waste water stream generated from Calcium Hypochlorite production process thus improving the overall yield of the production process.
Description
A NOVEL PROCESS FOR RECOVERY OF CALCIUM HYPOCHLORITE
FIELD OF THE INVENTION
The present invention relates to the manufacturing of high strength calcium hypochlorite and more specifically a novel process for recovery of high strength calcium hypochlorite by selective crystallization of sodium chloride and calcium hypochlorite from the mother water stream/aqueous waste water stream.
BACKGROUND OF THE INVENTION
Calcium hypochlorite has been widely produced by chlorination of calcium hydroxide and sodium hydroxide with chlorine gas. In the course of manufacturing of calcium hypochlorite, lime is reacted with chlorine in presence of caustic soda. After the completion of reaction, part of the calcium hypochlorite generated remains in the precipitated form and part of the same remains in the dissolved form along with sodium chloride. The precipitated Calcium Hypochlorite is filtered and sent for drying. The dissolved Calcium Chlorite remains with Sodium Chloride in the mother water/ aqueous waste water stream. Only small portion of this mother water is recycled to the original process and rest of the mother water is either sold as by-product or treated in the effluent treatment plant. Thus the yield of the Calcium Hypochlorite is low as the same is lost with the mother water.
US1931622 discloses a process for removing water from calcium hypochlorite which comprises adding to a calcium hypochlorite solution a substance imparting to the solution a slight but lasting alkaline reaction and atomizing the resulting product in heated dry air. The process involves spray drying/dispersing of Calcium Hypochlorite in presence of Calcium Hydroxide in hot air. Thus water is completely evaporated for recovery of Calcium Hypochlorite.
US4348372 discloses calcium chloride hydrates are recovered from calcium hypochlorite process effluents comprised of an aqueous solution of calcium chloride, calcium hypochlorite, and calcium chlorate in a process which comprises acidifying the effluent with a chlorine-containing compound selected from the group consisting of chlorine, hydrochloric acid and hydrogen chloride to form an acidic aqueous solution of calcium chloride having
l
reduced concentrations of calcium hypochlorite. Water is evaporated from the acidic aqueous solution to produce a concentrated acidic aqueous solution containing at least 45 percent by weight of calcium chloride. The concentrated acidic aqueous solution of calcium chloride is fed to a crystallizer to form crystals of a calcium chloride hydrate. The calcium chloride hydrate crystals are separated from mother liquor and recovered. The process is used to produce calcium chloride hexahydrate, calcium chloride tetrahydrate or calcium chloride dehydrate.
US 4367209 discloses a process for producing neutral calcium hypochlorite which comprises reacting an aqueous slurry of lime containing insoluble impurities with chlorine to form a first slurry of dibasic calcium hypochlorite crystals and insoluble impurities. The insoluble impurities are separated from the first slurry by employing separation means for classifying solids with respect to particle size. Dibasic calcium hypochlorite crystals are then separated and admixed with an alkali metal hypochlorite and recycle dibasic calcium hypochlorite crystals to form mixing zone slurry. This slurry is reacted with chlorine to form a paste of neutral calcium hypochlorite. The paste is separated into a cake of neutral calcium hypochlorite and paste liquor and the cake of neutral calcium hypochlorite recovered. The paste liquor is reacted with lime to form second slurry of dibasic calcium hypochlorite crystals which are separated from their mother liquor and returned to the mixing zone as recycle dibasic calcium hypochlorite. The above patent explains the process for production of Calcium hypochlorite from impure Lime. Equipment like classifiers/hydro cyclone are used for separation of impurities (insoluble impurities introduced in the process by Lime) & Dibasic Calcium Hypochlorite. The patents details out the process where even low quality/impure lime can also be used for production of Calcium Hypochlorite.
US3950499 discloses a continuous cyclic process for production of calcium hypochlorite wherein an aqueous solution saturated with calcium hypochlorite and sodium chloride is chlorinated by using chlorine gas to produce sodium chloride crystals and an aqueous chlorinated reaction mixture, the formed sodium chloride crystals being then separated from said aqueous chlorinated reaction mixture. First sodium hydroxide is added to the foregoing aqueous solution which solution also contains calcium hypochlorite and sodium chloride in the crystal phase. Then calcium hydroxide and sodium hydroxide is further added to the aqueous chlorinated reaction mixture remaining after separation of said crystals therefrom. This mixture containing calcium hydroxide and sodium hydroxide is again chlorinated with
chlorine gas to produce a slurry containing mainly sodium chloride crystals, calcium hypochlorite crystals and a mother liquor saturated with calcium hypochlorite and sodium chloride. The obtained slurry is divided into a first slurry [I] having mainly calcium hypochlorite crystals, sodium chloride crystals and mother liquor saturated with calcium hypochlorite and sodium chloride, and a second slurry [II] containing calcium hypochlorite crystals with a small amount of sodium chloride crystals and mother liquor saturated with calcium hypochlorite and sodium chloride. The second slurry [II] is then treated so as to remove the calcium hypochlorite crystals with a small amount of sodium chloride crystals thus forming a third phase mother liquor [III] saturated with calcium hypochlorite and sodium chloride. This third phase mother liquor [III] and the first slurry [I] is then recycled to the first step, i.e., the aforesaid aqueous , solution with saturated calcium hypochlorite and sodium chloride containing a small amount of calcium hypochlorite crystals and sodium chloride crystals.
US4089935 discloses the process for recovery of Calcium Hypochlorite from the filter media used or filtration of Calcium Hypochlorite slurry.
Therefore, there is need to provide a process in which a high yield/strength calcium hypochlorite can be produced.
OBJECT OF THE INVENTION
The present invention seeks to redress the problems faced in the existing state of the art. The primary object of the present invention is to provide an innovative process for recovery of high strength Calcium Hypochlorite by selective crystallization of sodium chloride and calcium hypochlorite from the mother water stream/ aqueous waste water stream.
Another object of the present invention is to provide a process for producing an overall high yield Calcium Hypochlorite.
Another object of the present invention is to provide a process for recovery of Calcium hypochlorite of highest purity having a concentration of at least 70 %, most preferably at least 75%.
Another object of the present invention is to eliminate the need for treatment of mother water stream in effluent treatment facility during the course of manufacturing of high strength Calcium Hypochlorite.
Another object of the present invention is to provide a process of recovery of sodium chloride along with the production of high strength Calcium Hypochlorite.
SUMMARY OF THE PRESENT INVENTION
The present invention provides a novel process to recover a high strength Calcium Hypochlorite from mother water stream/ aqueous waste water stream by selective crystallization of sodium chloride and calcium hypochlorite by changing process parameters such as pressure, temperature, mixing etc. The by-product sodium chloride can then be reused and employed for other purposes.
During the process the mother water stream is concentrated by currently know technologies such as water evaporation, dewatering or by membrane technology.
The process deals with recovery of High purity Calcium Hypochlorite from the aqueous waste water generated during the course of manufacturing Calcium Hypochlorite. The steps involved in the process are:
1 . Evaporation of water from the aqueous solution under reduced pressure condition;
2. Separation of Calcium Hypochlorite and Sodium Chloride from the slurry by
a. crystallization of sodium chloride from said slurry:
b. filtration of concentrated slurry containing precipitated sodium chloride;
c. selective crystallization of filtrate to obtain high strength calcium hypochlorite;
3. Washing and drying of Calcium Hypochlorite to get high strength Calcium Hypochlorite.
The main advantage of the present invention is related to production process for recovery of Calcium Hypochlorite from the mother water stream generated from Calcium Hypochlorite production process thus improving the overall yield of the production process.
BRIEF DESCRIPTION OF DRAWINGS
The detailed description is described with reference to the accompanying figure. In the figure the left-most digit of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to reference like features and components.
Figure 1 illustrates a flow chart showing the process of selective crystallization of sodium chloride and calcium hypochlorite from the mother water stream.
DETAILED DESCRIPTION
Exemplary embodiments now will be described with reference to the accompanying drawings. The disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey its scope to those skilled in the art. The terminology used in the detailed description of the particular exemplary embodiments illustrated in the accompanying drawings is not intended to be limiting. In the drawings, like numbers refer to like elements.
The specification may refer to "an", "one" or "some" embodiment(s) in several locations. This does not necessarily imply that each such reference is to the same embodiment(s), or that the feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments.
The figures depict a simplified structure only showing some elements and functional entities, all being logical units whose implementation may differ from what is shown. The connections shown are logical connections; the actual physical connections may be different.
The present invention deals with the innovative process to recover high strength Calcium Hypochlorite by selective crystallization of Sodium Chloride followed by selective crystallization of Calcium Hypochlorite. The mother water stream/ aqueous waste water stream is concentrated by currently known technologies such as water evaporation,
dewatering or by membrane technology. During the concentration process, Sodium Chloride starts crystallizing out. The crystallization can be carried out in a conventional crystallizer such as stirred vessel or special crystallizers such as Oslo type crystallizer. The concentrated slurry containing precipitated Sodium Chloride is then filtered. After filtration, some water is recovered and separated out from the process. The filtration can be carried out using commercial available solid liquid separators working in batch/continuous mode. The filtrate is then subjected to selective crystallization of high strength Calcium Hypochlorite by changing process parameters such as pressure, temperature, and mixing etc. The crystallization slurry is filtered to obtain High strength Calcium Hypochlorite which is then dried. The part of the crystallization filtrate is purged out from the system and remaining filtrate is mixed with the mother water stream prior to concentration and recycled back.
One embodiment of the present invention as shown in Figure-1, it describes the process of selective crystallization of sodium chloride and calcium hypochlorite to obtain recovered high strength calcium hypochlorite according to one embodiment of the present invention.
The mother stream/ aqueous waste water stream mixed with recycled stream and subjected to Sodium Chloride concentration. Small amount of water is recovered after concentration process. Concentrated stream is then filtered to obtain Sodium Chloride wet cake.
The filtrate thus obtained is subjected to high strength Calcium hypochlorite selective crystallization process by changing process parameters such as pressure, temperature, and mixing etc. The crystallized slurry is then filtered to obtain wet cake of high strength Calcium hypochlorite which is finally dried to obtain high strength Calcium hypochlorite.
In one embodiment, the present invention relates to a process for recovery of high strength calcium hypochlorite from aqueous waste water solution generated during manufacturing of calcium hypochlorite, the process comprises the steps of: evaporating water from the aqueous waste water to obtain concentrated slurry; separating Calcium Hypochlorite and Sodium Chloride from said slurry by
process comprising steps of:-
• crystallization of sodium chloride from said slurry:
• filtration of concentrated slurry containing precipitated sodium chloride;
• selective crystallization of filtrate to obtain high strength
calcium hypochlorite; washing and drying of Calcium Hypochlorite to get wet high strength Calcium
Hypochlorite.
The aqueous waste water generated during manufacturing of calcium hypochlorite is subject to evaporation which is done at reduced pressure and is carried out using equipment like classifiers/hydro cyclone. The selective crystallization is carried out by changing process parameters including but not limited to pressure, temperature, mixing. Following it a crystallized filtrate is purged out from the system. Thereafter, the remaining filtrate is recycled into aqueous waste water solution. The crystallization is carried out in stirred vessel or Oslotype crystallizer. The filtration is carried out using solid -liquid separators working in continuous mode.
In specific embodiments of the invention the aqueous waste water stream from which Calcium Hypochlorite, is to be recovered comprises less than 8% Calcium hypochlorite, preferably less than 10 %, more preferably less than 20% Calcium hypochlorite.
In specific embodiments, during the evaporative concentration, the aqueous waste water stream is fully concentrated to fonn slurry. In further specific embodiments the aqueous stream is mixed with recycled filtrate aqueous stream, wherein the recycled filtrate stream is mixed with the aqueous waste water stream in a ratio in the range of about 0.2 to about 5.
In specific embodiments the mixture of aqueous stream and the recycled filtrate is evaporated upto 30%, more preferably up to 35% to prepare a slurry of about 20 % liquids, more preferably, 25% liquids.
Example 1
In one of the example, 1000 gm of Mother water containing Calcium Hypochlorite (8.8%), Sodium Chloride ( 17.7%) & Calcium Chloride (4.8%) is charged in the round bottom flask. The flask is kept in a water bath & attached to a flash distillation assembly containing double
surface condenser, water receiver. The entire assembly is connected to a vacuum pump. Liquid temperature is measured using thermometer.
The water bath is heated to 60 deg C & vacuum is applied. The pressure inside the assembly is maintained at 20 Torr. Water from the solution is evaporated under reduced pressure, condensed & collected in a water receiver. After collection of 315 gm of distilled water the evaporation is stopped. The slurry obtained is transferred to a cylindrical vessel having provision for mixing the content. 700 gm of clear liquid obtained from previous experiment which is saturated with respect to Calcium Hypochlorite & Sodium Chloride is added to the slurry. The resultant slurry is stirred for 10 min. After completion of mixing time the stirring is stopped & slurry is allowed to stand for 10 min. The upper layer containing suspended particles is decanted & filtered to get wet cake of Calcium Hypochlorite. The filtrate obtained is again charged in the mixing vessel & similar steps are repeated till no cake is obtained after filtration. During this filtration process 98 gm of Wet cake of Calcium Hypochlorite is obtained. The wet cake thus obtained is washed with saturated solution of Calcium Hypochloite with 1 : 1 ratio in two stages. The washed wet cake of Calcium Hypochlorite is dried under reduced pressure to obtain Calcium Hypochlorite with 75% purity.
The final slurry is filtered to get 121 gm of Sodium Chloride having purity of 90%.
Example 2
In a non-limiting embodiment, 100 grams per litre of mother water/aqueous waste water is mixed with the recycled stream and subjected to sodium chloride ( NaCl ) concentration to recover 40 grams per litre of water. Then concentrated stream is filtered to obtain 12 grams per litre of NaCl wet cake. After filtration, the filtrate thus obtained is subjected to high strength Calcium Hypochlorite crystallization. After crystallization, the crystallization slurry is filtered to obtain 6.5 percent of High Strength Calcium Hypochlorite wet cake. Thereafter, a part of the filtrate is purged and rest is recycled back for further use.
Advantages of the present invention
The main advantage of the present invention is related to production process for recovery of Calcium Hypochlorite from the mother water stream generated from Calcium Hypochlorite production process thus improving the overall yield of the production process.
Another advantage is eliminating the need for treatment of mother water stream in effluent treatment facility.
Another advantage of the process of recovery of High strength of Calcium Hypochlorite thus increases in overall yield of the Calcium Hypochlorite. The process also recovers of Sodium Chloride.
The present invention is limited to production process of manufacturing of calcium hypochlorite. The invention is related to recovery of calcium hypochlorite from the mother water stream by selective crystallization. Hence complete recovery of calcium hypochlorite is not possible as small portion of Calcium Hypochlorite is lost with the filtrate.
Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternate embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that such modifications can be made without departing from the spirit or scope of the present invention as defined.
Claims
im:
A process for recovery of high strength calcium hypochlorite from aqueous waste water solution generated during manufacturing of calcium hypochlorite, the process comprises the steps of :
evaporating water from the aqueous waste water to obtain concentrated slurry; separating Calcium Hypochlorite and Sodium Chloride from said slurry by
process comprising steps of :- a. crystallization of sodium chloride from said slurry:
b. filtration of concentrated slurry containing precipitated sodium chloride;
c. selective crystallization of filtrate to obtain high strength calcium
hypochlorite;
washing and drying of Calcium Hypochlorite to get wet high strength Calcium
Hypochlorite.
The process as claimed in claim 1, wherein evaporation is done at reduced pressure.
The process as claimed in claim 1 , wherein the reduced pressure is 20 Torr.
The process as claimed in claim 1 , wherein evaporation is carried out using equipment like classifiers/hydro cyclone.
The process as claimed in claim 1 , wherein selective crystallization is carried out by changing process parameters including but not limited to pressure, temperature, mixing.
The process as claimed in claim 1„ wherein a crystallized filtrate is purged out from the system.
The process as claimed in claim 1 , wherein the remaining filtrate is recycled into aqueous waste water solution.
The process as claimed in claim 1 , wherein crystallization is carried out in stirred vessel or Oslotype crystallizer.
The process as claimed in claim 1 , wherein the filtration is carried out using solid liquid separators working in continuous mode.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| IN2396MU2014 | 2014-07-24 | ||
| IN2396/MUM/2014 | 2014-07-24 |
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| Publication Number | Publication Date |
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| WO2016013027A2 true WO2016013027A2 (en) | 2016-01-28 |
| WO2016013027A3 WO2016013027A3 (en) | 2016-03-17 |
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| PCT/IN2015/000303 WO2016013027A2 (en) | 2014-07-24 | 2015-07-29 | A novel process for recovery of calcium hypochlorite |
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Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4196184A (en) * | 1972-05-30 | 1980-04-01 | Olin Corporation | Lime recovery process |
| US3895099A (en) * | 1972-05-30 | 1975-07-15 | Olin Corp | Process for manufacture of calcium hydrochlorite |
| US4468377A (en) * | 1983-03-07 | 1984-08-28 | Olin Corporation | Continuous process for the manufacture of calcium hypochlorite |
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| WO2016013027A3 (en) | 2016-03-17 |
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