CA2959113A1 - Method for removing sodium from chloride solutions - Google Patents
Method for removing sodium from chloride solutions Download PDFInfo
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- CA2959113A1 CA2959113A1 CA2959113A CA2959113A CA2959113A1 CA 2959113 A1 CA2959113 A1 CA 2959113A1 CA 2959113 A CA2959113 A CA 2959113A CA 2959113 A CA2959113 A CA 2959113A CA 2959113 A1 CA2959113 A1 CA 2959113A1
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- Prior art keywords
- stream
- sodium
- solution
- chloride
- process stream
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- 238000000034 method Methods 0.000 title claims abstract description 87
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 title claims abstract description 55
- 239000011734 sodium Substances 0.000 title claims abstract description 55
- 229910052708 sodium Inorganic materials 0.000 title claims abstract description 55
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 title claims description 12
- 238000009854 hydrometallurgy Methods 0.000 claims abstract description 41
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims abstract description 38
- 238000001704 evaporation Methods 0.000 claims abstract description 28
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 23
- 239000011780 sodium chloride Substances 0.000 claims abstract description 19
- 150000003385 sodium Chemical class 0.000 claims abstract description 14
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 claims abstract description 10
- TWRXJAOTZQYOKJ-UHFFFAOYSA-L Magnesium chloride Chemical compound [Mg+2].[Cl-].[Cl-] TWRXJAOTZQYOKJ-UHFFFAOYSA-L 0.000 claims abstract description 6
- 239000002002 slurry Substances 0.000 claims abstract description 6
- 235000019270 ammonium chloride Nutrition 0.000 claims abstract description 5
- 229910021586 Nickel(II) chloride Inorganic materials 0.000 claims abstract description 3
- GVPFVAHMJGGAJG-UHFFFAOYSA-L cobalt dichloride Chemical compound [Cl-].[Cl-].[Co+2] GVPFVAHMJGGAJG-UHFFFAOYSA-L 0.000 claims abstract description 3
- ORTQZVOHEJQUHG-UHFFFAOYSA-L copper(II) chloride Chemical compound Cl[Cu]Cl ORTQZVOHEJQUHG-UHFFFAOYSA-L 0.000 claims abstract description 3
- 229910001629 magnesium chloride Inorganic materials 0.000 claims abstract description 3
- QMMRZOWCJAIUJA-UHFFFAOYSA-L nickel dichloride Chemical compound Cl[Ni]Cl QMMRZOWCJAIUJA-UHFFFAOYSA-L 0.000 claims abstract description 3
- 239000000243 solution Substances 0.000 claims description 56
- 235000002639 sodium chloride Nutrition 0.000 claims description 41
- 238000002425 crystallisation Methods 0.000 claims description 27
- 230000008025 crystallization Effects 0.000 claims description 27
- 230000008020 evaporation Effects 0.000 claims description 25
- 150000003839 salts Chemical class 0.000 claims description 23
- 229920006395 saturated elastomer Polymers 0.000 claims description 9
- 239000012047 saturated solution Substances 0.000 claims description 8
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 claims description 4
- 239000001110 calcium chloride Substances 0.000 claims description 4
- 229910001628 calcium chloride Inorganic materials 0.000 claims description 4
- 235000011148 calcium chloride Nutrition 0.000 claims description 4
- 238000001556 precipitation Methods 0.000 claims description 4
- 230000008929 regeneration Effects 0.000 claims description 4
- 238000011069 regeneration method Methods 0.000 claims description 4
- 238000000638 solvent extraction Methods 0.000 claims description 4
- 238000006386 neutralization reaction Methods 0.000 claims description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 claims 1
- 230000008569 process Effects 0.000 description 54
- 229960002668 sodium chloride Drugs 0.000 description 17
- 239000012141 concentrate Substances 0.000 description 10
- 238000002386 leaching Methods 0.000 description 9
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 8
- 229910052751 metal Inorganic materials 0.000 description 8
- 239000002184 metal Substances 0.000 description 8
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 6
- 239000000047 product Substances 0.000 description 6
- 230000001419 dependent effect Effects 0.000 description 5
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 4
- 239000013078 crystal Substances 0.000 description 4
- 239000012535 impurity Substances 0.000 description 4
- 229910052759 nickel Inorganic materials 0.000 description 4
- 229910021529 ammonia Inorganic materials 0.000 description 3
- 150000002739 metals Chemical class 0.000 description 3
- 238000011084 recovery Methods 0.000 description 3
- 238000010923 batch production Methods 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 239000011575 calcium Substances 0.000 description 1
- 150000001805 chlorine compounds Chemical class 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 230000003455 independent Effects 0.000 description 1
- 239000012452 mother liquor Substances 0.000 description 1
- 239000011591 potassium Substances 0.000 description 1
- 229910052700 potassium Inorganic materials 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
- C22B3/20—Treatment or purification of solutions, e.g. obtained by leaching
- C22B3/22—Treatment or purification of solutions, e.g. obtained by leaching by physical processes, e.g. by filtration, by magnetic means, or by thermal decomposition
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
- C22B3/20—Treatment or purification of solutions, e.g. obtained by leaching
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B1/00—Preliminary treatment of ores or scrap
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D1/00—Evaporating
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D9/00—Crystallisation
- B01D9/0018—Evaporation of components of the mixture to be separated
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B23/00—Obtaining nickel or cobalt
- C22B23/04—Obtaining nickel or cobalt by wet processes
- C22B23/0407—Leaching processes
- C22B23/0446—Leaching processes with an ammoniacal liquor or with a hydroxide of an alkali or alkaline-earth metal
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Geology (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Environmental & Geological Engineering (AREA)
- Materials Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Geochemistry & Mineralogy (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Crystallography & Structural Chemistry (AREA)
- Manufacture And Refinement Of Metals (AREA)
Abstract
The present invention provides a method for removing sodium from a hydrometallurgical process stream comprising ammonium chloride, nickel chloride, copper chloride, cobalt chloride, and/or magnesium chloride,comprising the steps of:(a) withdrawing a bleed stream of hydrometallurgical process liquors and/or slurries from the hydrometallurgical process steam; (b) evaporating water from the bleed stream to obtain a saturated sodium containing solution; (c) crystallizing a part of the sodium chloride comprised in the saturated sodium containing solution from the said solution to obtain a sodium depleted solution; and (d) returning the sodium depleted solution to the hydrometallurgical process stream.
Description
METHOD FOR REMOVING SODIUM FROM CHLORIDE SOLUTIONS
FIELD OF THE INVENTION
The present invention relates to a method for removing sodium from chloride containing solutions in a hydrometallurgical metal recovery processes.
More specifically the invention relates to removal of sodium from hydrometal-lurgical process solutions resulting from chloride based leaching of nickel con-taining ores and/or concentrates.
BACKGROUND OF THE INVENTION
In chloride based leaching of ores and/or concentrates, in particular of nickel containing ores and/or concentrates, the leaching solution is typically recirculated within the process. This leads to build-up of elements such as so-dium and potassium. Sodium is typically present in the solution as sodium chloride. In low concentrations, i.e. less than about 10 g/L, this is not a prob-lem. However, the sodium will make the solution more concentrated and even-tually more solution is needed to leach same amount of metals if sodium is not removed.
Traditional way to remove impurities such as sodium is to take out a small bleed stream from the process. In concentrated chloride solutions this is not an economical option since the solution needs to be treated and the chlo-rides need to be replaced.
The invention is based on the fact that the sodium chloride crystal-lizes before the other salts present in the solution for example calcium chloride or ammonium chloride.
BRIEF DESCRIPTION OF THE INVENTION
An object of the present invention is thus to provide a method so as to alleviate the above disadvantages. The objects of the invention are achieved by a method, which is characterized by what is stated in the inde-pendent claims. The preferred embodiments of the invention are disclosed in the dependent claims.
The invention based on the realization that sodium can be removed from the hydrometallurgical process streams simultaneously to adjusting the wa-ter content of the process stream. Accordingly taking out only the impurity that needs to be removed the volume of the bleed stream can be minimized and the process can be made more economical and usually more environmental friendly.
FIELD OF THE INVENTION
The present invention relates to a method for removing sodium from chloride containing solutions in a hydrometallurgical metal recovery processes.
More specifically the invention relates to removal of sodium from hydrometal-lurgical process solutions resulting from chloride based leaching of nickel con-taining ores and/or concentrates.
BACKGROUND OF THE INVENTION
In chloride based leaching of ores and/or concentrates, in particular of nickel containing ores and/or concentrates, the leaching solution is typically recirculated within the process. This leads to build-up of elements such as so-dium and potassium. Sodium is typically present in the solution as sodium chloride. In low concentrations, i.e. less than about 10 g/L, this is not a prob-lem. However, the sodium will make the solution more concentrated and even-tually more solution is needed to leach same amount of metals if sodium is not removed.
Traditional way to remove impurities such as sodium is to take out a small bleed stream from the process. In concentrated chloride solutions this is not an economical option since the solution needs to be treated and the chlo-rides need to be replaced.
The invention is based on the fact that the sodium chloride crystal-lizes before the other salts present in the solution for example calcium chloride or ammonium chloride.
BRIEF DESCRIPTION OF THE INVENTION
An object of the present invention is thus to provide a method so as to alleviate the above disadvantages. The objects of the invention are achieved by a method, which is characterized by what is stated in the inde-pendent claims. The preferred embodiments of the invention are disclosed in the dependent claims.
The invention based on the realization that sodium can be removed from the hydrometallurgical process streams simultaneously to adjusting the wa-ter content of the process stream. Accordingly taking out only the impurity that needs to be removed the volume of the bleed stream can be minimized and the process can be made more economical and usually more environmental friendly.
2 Since the sodium input to the process is usually quite small and process can tolerate some sodium, all sodium is not needed to be removed from the process stream. This enables crystallization from the bleed stream instead of the main process stream. This means smaller equipment and lower investment cost. Since the water is needed to be evaporated due to the closed solution circulation in the process the saturated solution can be produced for the crystallization when the evaporation is also put to the bleed stream. Crys-tallization from the saturated solution is easier since it starts immediately when more water is evaporated or temperature is lowered.
lo Sodium chloride can be taken with this invention as almost pure product since some sodium is left to the depleted sodium solution. Sodium chloride is the first salt that crystallizes from the solution and therefore amount of solid impurities in the sodium chloride product is small. To further purify so-dium chloride product it can be washed.
BRIEF DESCRIPTION OF THE DRAWINGS
In the following the invention will be described in greater detail by means of preferred embodiments with reference to the attached drawings, in which Figure 1 is a flow diagram illustrating an embodiment of the method of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a method for removing sodium from a chloride-based hydrometallurgical process stream comprising the steps of:
(a) withdrawing a bleed stream of hydrometallurgical process liquors and/or slurries from the chloride-based hydrometallurgical process stream;
(b) evaporating water from the bleed stream to obtain a saturated sodium containing solution;
(c) crystallizing a part of the sodium chloride comprised in the satu-rated sodium containing solution from the said solution to obtain a sodium de-pleted solution; and (d) returning the sodium depleted solution to the process stream.
The method of the present invention is suitable for treating any hy-drometallurgical process streams resulting from leaching of metal containing ores and/or concentrates with chloride based leaching solutions, such as a concentrated CaCl2 based solution. The said hydrometallurgical process
lo Sodium chloride can be taken with this invention as almost pure product since some sodium is left to the depleted sodium solution. Sodium chloride is the first salt that crystallizes from the solution and therefore amount of solid impurities in the sodium chloride product is small. To further purify so-dium chloride product it can be washed.
BRIEF DESCRIPTION OF THE DRAWINGS
In the following the invention will be described in greater detail by means of preferred embodiments with reference to the attached drawings, in which Figure 1 is a flow diagram illustrating an embodiment of the method of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a method for removing sodium from a chloride-based hydrometallurgical process stream comprising the steps of:
(a) withdrawing a bleed stream of hydrometallurgical process liquors and/or slurries from the chloride-based hydrometallurgical process stream;
(b) evaporating water from the bleed stream to obtain a saturated sodium containing solution;
(c) crystallizing a part of the sodium chloride comprised in the satu-rated sodium containing solution from the said solution to obtain a sodium de-pleted solution; and (d) returning the sodium depleted solution to the process stream.
The method of the present invention is suitable for treating any hy-drometallurgical process streams resulting from leaching of metal containing ores and/or concentrates with chloride based leaching solutions, such as a concentrated CaCl2 based solution. The said hydrometallurgical process
3 stream further comprises ammonium chloride, nickel chloride, copper chloride, cobalt chloride, and/or magnesium chloride. Typically the said hydrometallurgi-cal process stream comprises ammonium chloride. The hydrometallurgical process stream typically comprises significant amounts of sodium. In particular the hydrometallurgical process stream comprises 1 to 50 g/L, more particularly 5 to 25 g/L, sodium. Further preferably the hydrometallurgical process stream comprises 10 to 100 g/L Ca and/or 0.1 to 10 g/L NH4-.
The method of the present invention is particularly suitable for treatment of leaching solution resulting from leaching of nickel containing ore and/or concentrate. The term "concentrate" as used herein refers to any prod-uct generally produced from metal containing ore for concentrating the desired metal(s) in the product and/or removing impurities from the mined ore for fur-ther treatment of the product for the recovery of one or more of said metal(s).
Such concentrate can be produced by any suitable methods known to a per-son skilled in the art.
Preferably the method of the present invention provides for removal of at least 30%, more preferably at least 50%, typically 30 to 90%, more typi-cally 60 to 80%, of sodium comprised in the hydrometallurgical process stream before the withdrawal of the bleed stream. Typically the sodium depleted solu-tion returned into the main process stream, i.e. the hydrometallurgical process stream, comprises less than 4 wt%, preferably less than 2 wt%, sodium. In some cases where evaporation need of the process is big the sodium concen-tration is higher in the main process stream after the evaporation and sodium removal than before those process steps due to the decreased total amount of the process stream.
Figure 1 shows an example of a process flow of the method of the present invention. Referring to Figure 1, a bleed stream 2 is withdrawn from a hydrometallurgical process stream 1. The bleed stream can be withdrawn at any process stage after leaching of the ore and/or concentrate. Preferably the bleed stream is withdrawn at a process stage where the concentration of any valuable metals in the said process stream is as low as possible to prevent loss said valuable metals during the removal of sodium. Advantageously the bleed stream is withdrawn after a process stage whereby the acid concentra-tion of the said process stream is under 5 g/L. Such process stages include precipitation, solvent extraction and neutralization stages. In nickel leaching such process stages are in particularly iron precipitation, solvent extraction
The method of the present invention is particularly suitable for treatment of leaching solution resulting from leaching of nickel containing ore and/or concentrate. The term "concentrate" as used herein refers to any prod-uct generally produced from metal containing ore for concentrating the desired metal(s) in the product and/or removing impurities from the mined ore for fur-ther treatment of the product for the recovery of one or more of said metal(s).
Such concentrate can be produced by any suitable methods known to a per-son skilled in the art.
Preferably the method of the present invention provides for removal of at least 30%, more preferably at least 50%, typically 30 to 90%, more typi-cally 60 to 80%, of sodium comprised in the hydrometallurgical process stream before the withdrawal of the bleed stream. Typically the sodium depleted solu-tion returned into the main process stream, i.e. the hydrometallurgical process stream, comprises less than 4 wt%, preferably less than 2 wt%, sodium. In some cases where evaporation need of the process is big the sodium concen-tration is higher in the main process stream after the evaporation and sodium removal than before those process steps due to the decreased total amount of the process stream.
Figure 1 shows an example of a process flow of the method of the present invention. Referring to Figure 1, a bleed stream 2 is withdrawn from a hydrometallurgical process stream 1. The bleed stream can be withdrawn at any process stage after leaching of the ore and/or concentrate. Preferably the bleed stream is withdrawn at a process stage where the concentration of any valuable metals in the said process stream is as low as possible to prevent loss said valuable metals during the removal of sodium. Advantageously the bleed stream is withdrawn after a process stage whereby the acid concentra-tion of the said process stream is under 5 g/L. Such process stages include precipitation, solvent extraction and neutralization stages. In nickel leaching such process stages are in particularly iron precipitation, solvent extraction
4 and/or ammonia regeneration. Suitable locations for the withdrawal include after iron precipitation, after one of the solvent extraction stages, and/or after regeneration of ammonia. In a preferred aspect of the present invention the bleed stream is withdrawn after regeneration of ammonia.
The volume of the bleed stream is dependent of the amount of water that needs to be removed from the process stream to maintain water balance. If water balance is taken care in other parts of the process the bleed stream is dependent of the amount of sodium needed to be removed, but typically the wa-ter balance determine the bleed stream amount. The amount of bleed stream can be calculated from the amount of water needed to be removed from the process at this stage, from the salt concentration of the process stream and the salt concentration of the saturated sodium containing solution, e.g. a solution containing 50 g/L CaCl2 and 5 g/L NaCI has a salt concentration of 55 g/L. Un-less otherwise denoted, the term "salt concentration" as used herein and hereaf-ter refers to the amount of all dissolved salts in the particular stream. The salt concentration of a solution is dependent on temperature and the nature of salts in the said solution. The process stream typically comprises 5 to 35 wt%
salts, more typically 10 to 30 wt% of the total weight of the said stream. The saturated sodium containing solution typically contains 35 to 70 wt% of salts more typically 40 to 65 wt% of the total weight of the saturated solution. Typically a variation of 10%, more typically 5%, is tolerated for the amount of required bleed stream.
If the salt concentration in the process solution, evaporation need or salt con-centration the saturated sodium containing solution changes, also the amount of bleed stream will change. Examples how the amount of the bleed stream can be calculated are presented in examples 1 and 2.
The bleed stream is preferably withdrawn continuously from the hy-drometallurgical process stream i.e. as a continuous bleed stream of the hy-drometallurgical process stream. The continuous operation of sodium chloride crystallization enables smaller equipment and more even sodium concentration in the process. The other option is to withdraw a continuous bleed stream for evaporation of water in step (b) and operate the crystallization of sodium chlo-ride in step (c) as a batch process.
The bleed stream 2 is then subjected to evaporation 10 in the evap-oration step (b) to remove water 11 from the bleed stream and to concentrate sodium in the bleed stream. This results in a saturated or nearly saturated so-dium containing solution 3 which is subjected to crystallization 20 in the crystal-lization step (c). The term "saturated or nearly saturated" as used in context of the saturated sodium containing solution refers to the fact that further evapora-tion of water from the solution would cause crystallization of sodium chloride thus enabling the crystallization of the same in the next step.
The volume of the bleed stream is dependent of the amount of water that needs to be removed from the process stream to maintain water balance. If water balance is taken care in other parts of the process the bleed stream is dependent of the amount of sodium needed to be removed, but typically the wa-ter balance determine the bleed stream amount. The amount of bleed stream can be calculated from the amount of water needed to be removed from the process at this stage, from the salt concentration of the process stream and the salt concentration of the saturated sodium containing solution, e.g. a solution containing 50 g/L CaCl2 and 5 g/L NaCI has a salt concentration of 55 g/L. Un-less otherwise denoted, the term "salt concentration" as used herein and hereaf-ter refers to the amount of all dissolved salts in the particular stream. The salt concentration of a solution is dependent on temperature and the nature of salts in the said solution. The process stream typically comprises 5 to 35 wt%
salts, more typically 10 to 30 wt% of the total weight of the said stream. The saturated sodium containing solution typically contains 35 to 70 wt% of salts more typically 40 to 65 wt% of the total weight of the saturated solution. Typically a variation of 10%, more typically 5%, is tolerated for the amount of required bleed stream.
If the salt concentration in the process solution, evaporation need or salt con-centration the saturated sodium containing solution changes, also the amount of bleed stream will change. Examples how the amount of the bleed stream can be calculated are presented in examples 1 and 2.
The bleed stream is preferably withdrawn continuously from the hy-drometallurgical process stream i.e. as a continuous bleed stream of the hy-drometallurgical process stream. The continuous operation of sodium chloride crystallization enables smaller equipment and more even sodium concentration in the process. The other option is to withdraw a continuous bleed stream for evaporation of water in step (b) and operate the crystallization of sodium chlo-ride in step (c) as a batch process.
The bleed stream 2 is then subjected to evaporation 10 in the evap-oration step (b) to remove water 11 from the bleed stream and to concentrate sodium in the bleed stream. This results in a saturated or nearly saturated so-dium containing solution 3 which is subjected to crystallization 20 in the crystal-lization step (c). The term "saturated or nearly saturated" as used in context of the saturated sodium containing solution refers to the fact that further evapora-tion of water from the solution would cause crystallization of sodium chloride thus enabling the crystallization of the same in the next step.
5 The evaporation step (b) 10 is typically performed in a multi stage evaporation equipment. In a multi stage evaporation the first evaporation step is typically performed atmospherically or near atmospherically. Further evapo-ration step(s) are typically performed under reduced pressure. Advantageously steam formed in the first evaporation stage is utilized for indirect heating of the further evaporation step(s).
Depending on the process sodium balance, a part of the saturated or nearly saturated sodium containing solution 3 can be fed back to the main process between evaporation of the water and crystallization of the sodium chloride as a concentrated stream 5. Thus in an embodiment of the present invention a part of the saturated sodium containing solution (3) obtained in step (b) is returned to the hydrometallurgical process stream before crystalliza-tion step (c). Alternatively or additionally part of a partly concentrated sodium containing solution i.e. part of the bleed stream being concentrated in step (b) can be returned to the hydrometallurgical process stream before it is saturated or nearly saturated. This is possible when a multi stage evaporation equipment is utilized and/or the evaporation step is otherwise performed in multiple sub-steps. In the above mentioned embodiments the bleed stream of hydrometal-lurgical process liquors and/or slurries withdrawn from the chloride-based hy-drometallurgical process stream may be 100% of the hydrometallurgical pro-cess stream.
The concentrated stream 5 is preferably returned continuously to the hydrometallurgical process stream 1. The amount of such concentrated stream is dependent on the sodium amount in the stream, sodium removal need in the process and the amount of sodium at the concentrated stream af-ter crystallization, stream 4. For example if the sodium amount in the stream is 100 kg/h and sodium is needed to be removed from the process 50 kg/h and the stream 4 after crystallization contains 10 kg/h sodium, 40% of the stream is fed back to the main process stream in stream 5. Typically the variation of stream split percentage value is 10%, more typically 5%.
Depending on the process sodium balance, a part of the saturated or nearly saturated sodium containing solution 3 can be fed back to the main process between evaporation of the water and crystallization of the sodium chloride as a concentrated stream 5. Thus in an embodiment of the present invention a part of the saturated sodium containing solution (3) obtained in step (b) is returned to the hydrometallurgical process stream before crystalliza-tion step (c). Alternatively or additionally part of a partly concentrated sodium containing solution i.e. part of the bleed stream being concentrated in step (b) can be returned to the hydrometallurgical process stream before it is saturated or nearly saturated. This is possible when a multi stage evaporation equipment is utilized and/or the evaporation step is otherwise performed in multiple sub-steps. In the above mentioned embodiments the bleed stream of hydrometal-lurgical process liquors and/or slurries withdrawn from the chloride-based hy-drometallurgical process stream may be 100% of the hydrometallurgical pro-cess stream.
The concentrated stream 5 is preferably returned continuously to the hydrometallurgical process stream 1. The amount of such concentrated stream is dependent on the sodium amount in the stream, sodium removal need in the process and the amount of sodium at the concentrated stream af-ter crystallization, stream 4. For example if the sodium amount in the stream is 100 kg/h and sodium is needed to be removed from the process 50 kg/h and the stream 4 after crystallization contains 10 kg/h sodium, 40% of the stream is fed back to the main process stream in stream 5. Typically the variation of stream split percentage value is 10%, more typically 5%.
6 The saturated sodium containing solution 3 is then fed to crystalliza-tion step (c) 20 to remove sodium as sodium chloride 22 from the saturated sodium containing solution. Crystallization can be achieved by evaporation of water thus causing the sodium chloride to crystallize from the saturated solu-tion or decreasing the temperature to cause the sodium chloride to crystallize.
In evaporation crystallization option the evaporated water is removed from the process with stream 21. Typically crystallization in step (c) 20 is achieved in a separate crystallization device. Alternatively crystallization step (c) 20 can be achieved in the same equipment as the evaporation step (b) 10. Further, part of the evaporation step can be achieved in a first evaporation equipment to concentrate the stream and the final saturation and the crystallization step is achieved in an another equipment.
Typically a slurry comprising sodium chloride crystals is obtained from the crystallization step. The slurry is then mostly dried in a centrifuge to obtain mostly dry or dry crystals. The dried crystals may then be washed with water to remove remaining mother liquor and to further purify the crystals.
The washing solution is preferably recirculated to the crystallization step (c) to im-prove the recovery of sodium chloride.
Preferably at least 30 wt%, preferably from 30 to 100 wt%, more preferably from 50 to 95 wt%, of the sodium chloride contained in the originally withdrawn bleed stream is crystallized. Removal of sodium chloride in step (c) results in a sodium depleted solution 4 that is returned to the process stream to keep the salts in the process in a closed circulation.
The sodium depleted solution 4 is returned to the hydrometallurgical process stream 1 typically at the same process stage where the bleed stream 2 was withdrawn from the process stream 1. This enables continuation of the following process steps in a conventional manner.
The sodium depleted solution 4 is preferably returned to the hydro-metallurgical process stream i.e. as a continuous sodium depleted stream. This enables a steady salt concentration in the main process stream. Even if the crystallization is operated as a batch process a continuous stream of sodium depleted solution to the process stream is needed since big differences in the salt concentrations in other parts of the process make it difficult to operate the process. The hydrometallurgical process stream 1 typically contains from 1 to 50 g/L, more typically 5 to 25 g/L sodium after the sodium depleted solution is mixed with the said process stream.
In evaporation crystallization option the evaporated water is removed from the process with stream 21. Typically crystallization in step (c) 20 is achieved in a separate crystallization device. Alternatively crystallization step (c) 20 can be achieved in the same equipment as the evaporation step (b) 10. Further, part of the evaporation step can be achieved in a first evaporation equipment to concentrate the stream and the final saturation and the crystallization step is achieved in an another equipment.
Typically a slurry comprising sodium chloride crystals is obtained from the crystallization step. The slurry is then mostly dried in a centrifuge to obtain mostly dry or dry crystals. The dried crystals may then be washed with water to remove remaining mother liquor and to further purify the crystals.
The washing solution is preferably recirculated to the crystallization step (c) to im-prove the recovery of sodium chloride.
Preferably at least 30 wt%, preferably from 30 to 100 wt%, more preferably from 50 to 95 wt%, of the sodium chloride contained in the originally withdrawn bleed stream is crystallized. Removal of sodium chloride in step (c) results in a sodium depleted solution 4 that is returned to the process stream to keep the salts in the process in a closed circulation.
The sodium depleted solution 4 is returned to the hydrometallurgical process stream 1 typically at the same process stage where the bleed stream 2 was withdrawn from the process stream 1. This enables continuation of the following process steps in a conventional manner.
The sodium depleted solution 4 is preferably returned to the hydro-metallurgical process stream i.e. as a continuous sodium depleted stream. This enables a steady salt concentration in the main process stream. Even if the crystallization is operated as a batch process a continuous stream of sodium depleted solution to the process stream is needed since big differences in the salt concentrations in other parts of the process make it difficult to operate the process. The hydrometallurgical process stream 1 typically contains from 1 to 50 g/L, more typically 5 to 25 g/L sodium after the sodium depleted solution is mixed with the said process stream.
7 EXAMPLES
Example 1 50 t/h water is removed from a 100 t/h process solution. The flow of the needed bleed stream amount is calculated followingly: The process solu-tion comprises 20 wt% of salts. 60 wt% of salts in the saturated solution is used. The 100 t/h process solution flow then contains 20 t/h salts, 80 t/h water and produced saturated solution contains 20 t/h salts and 13.3 t/h water.
Therefore in the bleed stream is 50 t/h + 13.3 t/h = 63.3 t/h water. This means that water needed to be put to the bleed stream is 63.3 t/h / 80 t/h = 0.791 times the water in the initial process stream.
Example 2 When process stream is 100 t/h, water evaporation need is 10 t/h, salt concentration of the process solution is 25 wt% and saturated solution salt concentration is 60 wt%, the amount of bleed stream is 33.3%.
It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The in-vention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.
Example 1 50 t/h water is removed from a 100 t/h process solution. The flow of the needed bleed stream amount is calculated followingly: The process solu-tion comprises 20 wt% of salts. 60 wt% of salts in the saturated solution is used. The 100 t/h process solution flow then contains 20 t/h salts, 80 t/h water and produced saturated solution contains 20 t/h salts and 13.3 t/h water.
Therefore in the bleed stream is 50 t/h + 13.3 t/h = 63.3 t/h water. This means that water needed to be put to the bleed stream is 63.3 t/h / 80 t/h = 0.791 times the water in the initial process stream.
Example 2 When process stream is 100 t/h, water evaporation need is 10 t/h, salt concentration of the process solution is 25 wt% and saturated solution salt concentration is 60 wt%, the amount of bleed stream is 33.3%.
It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The in-vention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.
Claims (18)
1. A method for removing sodium from a hydrometallurgical process stream (1) comprising ammonium chloride, nickel chloride, copper chloride, cobalt chloride, and/or magnesium chloride, comprising the steps of:
(a) withdrawing a bleed stream (2) of hydrometallurgical process liquors and/or slurries from the hydrometallurgical process steam (1);
(b) evaporating water (11) from the bleed stream (2) to obtain a sat-urated sodium containing solution (3);
(c) crystallizing a part of the sodium chloride (22) comprised in the saturated sodium containing solution (3) from the said solution to obtain a so-dium depleted solution (4); and (d) returning the sodium depleted solution (4) to the hydrometallur-gical process stream.
(a) withdrawing a bleed stream (2) of hydrometallurgical process liquors and/or slurries from the hydrometallurgical process steam (1);
(b) evaporating water (11) from the bleed stream (2) to obtain a sat-urated sodium containing solution (3);
(c) crystallizing a part of the sodium chloride (22) comprised in the saturated sodium containing solution (3) from the said solution to obtain a so-dium depleted solution (4); and (d) returning the sodium depleted solution (4) to the hydrometallur-gical process stream.
2. The method as claimed in claim 1, wherein the bleed stream (2) comprises less than 5 g/L HCI.
3. The method as claimed in claim 1 or 2, wherein the hydrometal-lurgical process stream (1) is a concentrated CaCl2 based solution.
4. The method as claimed in any one of claims 1 to 3, wherein the hydrometallurgical process stream (1) comprises 10 to 100 g/L Ca.
5. The method as claimed in any one of claims 1 to 4, wherein the hydrometallurgical process stream comprises (1) 0.1 to 10 g/L NH4-.
6. The method as claimed in any one of claims 1 to 5, wherein the hydrometallurgical process stream (1) comprises 1 to 50 g/L, more particularly to 25 g/L, sodium.
7. The method as claimed in any one of claims 1 to 6, wherein the bleed stream (2) is withdrawn after a precipitation, solvent extraction and/or neutralization stage.
8. The method as claimed in claim 7, wherein the bleed stream (2) is withdrawn after regeneration of ammonium.
9. The method as claimed in any of claims 1 to 8, wherein at least 30%, preferably from 30 to 100%, more preferably from 50 to 95% of the sodi-um chloride comprised in the hydrometallurgical process stream (1) is crystal-lized.
10. The method as claimed in any one of claims 1 to 9, wherein the bleed stream (2) is withdrawn continuously from the hydrometallurgical pro-cess stream.
11. The method as claimed in any one of claims 1 to 10, wherein the sodium depleted stream (4) is returned continuously back to the hydrometal-lurgical process stream.
12. The method as claimed in any one of claims 1 to 11, wherein the saturated sodium containing solution (3) comprises 35 to 70 wt% of salts, pref-erably 40 to 65 wt% of the total weight of the saturated solution.
13. The method as claimed in any one of claims 1 to 12, wherein the hydrometallurgical process stream after returning of sodium depleted solution (4) to the hydrometallurgical process stream contains from 1 to 50 g/L, typically to 25 g/L, sodium.
14. The method as claimed in any one of claims 1 to 13, wherein crystallization in step (c) is achieved in a separate crystallization device.
15. The method as claimed in any one of claims 1 to 13, wherein in crystallization in step (c) is achieved the same equipment as the evaporation step (b).
16. The method as claimed in any one of claims 1 to 15, wherein a part of the saturated sodium containing solution (3) obtained in step (b) is re-turned to the hydrometallurgical process stream before crystallization step (c).
17. The method as claimed in any one of claims 1 to 16, wherein a part of the bleed stream concentrated in step (b) is returned to the hydrometal-lurgical process stream before it is saturated or nearly saturated.
18. The method as claimed in claim 16 or 17, wherein the bleed stream in step (a) is 100% of the hydrometallurgical process stream.
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US3655333A (en) * | 1970-05-04 | 1972-04-11 | Dow Chemical Co | Process for producing anhydrous sodium chloride and purified saturated brine |
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ATE148425T1 (en) * | 1990-12-28 | 1997-02-15 | Akzo Nobel Nv | METHOD FOR PRODUCING SODIUM CHLORIDE |
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