CN112591770B - Production process and device for purifying and separating potassium sulfate from dilute brine - Google Patents
Production process and device for purifying and separating potassium sulfate from dilute brine Download PDFInfo
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- CN112591770B CN112591770B CN202011072923.XA CN202011072923A CN112591770B CN 112591770 B CN112591770 B CN 112591770B CN 202011072923 A CN202011072923 A CN 202011072923A CN 112591770 B CN112591770 B CN 112591770B
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- nanofiltration
- membrane
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- potassium chloride
- brine
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- 239000012267 brine Substances 0.000 title claims abstract description 79
- HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical compound O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 title claims abstract description 79
- OTYBMLCTZGSZBG-UHFFFAOYSA-L potassium sulfate Chemical compound [K+].[K+].[O-]S([O-])(=O)=O OTYBMLCTZGSZBG-UHFFFAOYSA-L 0.000 title claims abstract description 62
- 229910052939 potassium sulfate Inorganic materials 0.000 title claims abstract description 62
- 235000011151 potassium sulphates Nutrition 0.000 title claims abstract description 62
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 9
- WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical compound [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 claims abstract description 141
- 238000001728 nano-filtration Methods 0.000 claims abstract description 87
- 239000001103 potassium chloride Substances 0.000 claims abstract description 67
- 235000011164 potassium chloride Nutrition 0.000 claims abstract description 66
- 238000000034 method Methods 0.000 claims abstract description 52
- 239000000243 solution Substances 0.000 claims abstract description 48
- 150000003839 salts Chemical class 0.000 claims abstract description 46
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 40
- 230000008569 process Effects 0.000 claims abstract description 31
- 238000001704 evaporation Methods 0.000 claims abstract description 15
- 238000010790 dilution Methods 0.000 claims abstract description 10
- 239000012895 dilution Substances 0.000 claims abstract description 10
- 239000012528 membrane Substances 0.000 claims description 149
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 63
- 239000012510 hollow fiber Substances 0.000 claims description 55
- 230000004907 flux Effects 0.000 claims description 36
- 239000007788 liquid Substances 0.000 claims description 33
- 238000000926 separation method Methods 0.000 claims description 33
- 239000012466 permeate Substances 0.000 claims description 30
- 238000011282 treatment Methods 0.000 claims description 26
- 239000011777 magnesium Substances 0.000 claims description 24
- VKJKEPKFPUWCAS-UHFFFAOYSA-M potassium chlorate Chemical compound [K+].[O-]Cl(=O)=O VKJKEPKFPUWCAS-UHFFFAOYSA-M 0.000 claims description 17
- 238000002425 crystallisation Methods 0.000 claims description 13
- 230000008025 crystallization Effects 0.000 claims description 13
- 230000008020 evaporation Effects 0.000 claims description 12
- 239000013049 sediment Substances 0.000 claims description 12
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims description 9
- 150000002500 ions Chemical class 0.000 claims description 9
- 229910052749 magnesium Inorganic materials 0.000 claims description 9
- 238000010979 pH adjustment Methods 0.000 claims description 9
- 238000007789 sealing Methods 0.000 claims description 9
- 239000004952 Polyamide Substances 0.000 claims description 8
- 229920002647 polyamide Polymers 0.000 claims description 8
- 238000003491 array Methods 0.000 claims description 6
- 230000000903 blocking effect Effects 0.000 claims description 6
- 238000005259 measurement Methods 0.000 claims description 6
- 239000012141 concentrate Substances 0.000 claims description 5
- 239000000463 material Substances 0.000 claims description 4
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims description 3
- 239000000460 chlorine Substances 0.000 claims description 3
- 229910052801 chlorine Inorganic materials 0.000 claims description 3
- 239000003292 glue Substances 0.000 claims description 3
- 239000012452 mother liquor Substances 0.000 claims description 3
- 230000009467 reduction Effects 0.000 claims description 3
- 239000004642 Polyimide Substances 0.000 claims description 2
- 229920002301 cellulose acetate Polymers 0.000 claims description 2
- 229920002492 poly(sulfone) Polymers 0.000 claims description 2
- 229920002239 polyacrylonitrile Polymers 0.000 claims description 2
- 229920001721 polyimide Polymers 0.000 claims description 2
- 229920000642 polymer Polymers 0.000 claims description 2
- 229920003055 poly(ester-imide) Polymers 0.000 claims 1
- 238000005868 electrolysis reaction Methods 0.000 abstract description 11
- 239000000126 substance Substances 0.000 abstract description 9
- 239000003513 alkali Substances 0.000 abstract description 3
- 235000011121 sodium hydroxide Nutrition 0.000 description 20
- 239000011575 calcium Substances 0.000 description 16
- 239000013078 crystal Substances 0.000 description 15
- 238000001914 filtration Methods 0.000 description 15
- 238000001816 cooling Methods 0.000 description 13
- 239000011148 porous material Substances 0.000 description 12
- 239000011734 sodium Substances 0.000 description 12
- 239000002244 precipitate Substances 0.000 description 10
- 238000001556 precipitation Methods 0.000 description 9
- 239000008367 deionised water Substances 0.000 description 8
- 229910021641 deionized water Inorganic materials 0.000 description 8
- 238000001035 drying Methods 0.000 description 8
- 238000002156 mixing Methods 0.000 description 7
- 239000002994 raw material Substances 0.000 description 7
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 6
- 239000000919 ceramic Substances 0.000 description 6
- 239000012043 crude product Substances 0.000 description 6
- 238000006298 dechlorination reaction Methods 0.000 description 6
- 239000012530 fluid Substances 0.000 description 6
- 238000001471 micro-filtration Methods 0.000 description 6
- 230000000149 penetrating effect Effects 0.000 description 6
- 238000003860 storage Methods 0.000 description 6
- 239000000047 product Substances 0.000 description 5
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 4
- 238000001514 detection method Methods 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 229910017053 inorganic salt Inorganic materials 0.000 description 4
- 239000002245 particle Substances 0.000 description 4
- 238000007670 refining Methods 0.000 description 4
- 229910001425 magnesium ion Inorganic materials 0.000 description 3
- 229940072033 potash Drugs 0.000 description 3
- BWHMMNNQKKPAPP-UHFFFAOYSA-L potassium carbonate Substances [K+].[K+].[O-]C([O-])=O BWHMMNNQKKPAPP-UHFFFAOYSA-L 0.000 description 3
- 235000015320 potassium carbonate Nutrition 0.000 description 3
- 238000000746 purification Methods 0.000 description 3
- 230000008439 repair process Effects 0.000 description 3
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 2
- JLVVSXFLKOJNIY-UHFFFAOYSA-N Magnesium ion Chemical compound [Mg+2] JLVVSXFLKOJNIY-UHFFFAOYSA-N 0.000 description 2
- 239000006227 byproduct Substances 0.000 description 2
- 229910001424 calcium ion Inorganic materials 0.000 description 2
- 238000007865 diluting Methods 0.000 description 2
- 230000014759 maintenance of location Effects 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000002861 polymer material Substances 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- 229910002651 NO3 Inorganic materials 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- ZFXVRMSLJDYJCH-UHFFFAOYSA-N calcium magnesium Chemical compound [Mg].[Ca] ZFXVRMSLJDYJCH-UHFFFAOYSA-N 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 229920000728 polyester Polymers 0.000 description 1
- 239000001120 potassium sulphate Substances 0.000 description 1
- 238000001953 recrystallisation Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- -1 salt ions Chemical class 0.000 description 1
- 239000000565 sealant Substances 0.000 description 1
- 159000000000 sodium salts Chemical class 0.000 description 1
- 239000000725 suspension Substances 0.000 description 1
- 229920002554 vinyl polymer Polymers 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D5/00—Sulfates or sulfites of sodium, potassium or alkali metals in general
- C01D5/16—Purification
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
- C02F1/442—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by nanofiltration
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Organic Chemistry (AREA)
- Materials Engineering (AREA)
- Inorganic Chemistry (AREA)
- Nanotechnology (AREA)
- Life Sciences & Earth Sciences (AREA)
- Hydrology & Water Resources (AREA)
- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
Abstract
The invention relates to a production process and a device for purifying and separating potassium sulfate from dilute brine, belonging to the technical field of chlor-alkali chemical industry. The method comprises the following steps: step a, potassium chloride brine is subjected to first nanofiltration, and monovalent and divalent salts are separated; step b, after the concentrated solution obtained in the first nanofiltration process is diluted by water, carrying out second nanofiltration, and separating monovalent and divalent salts; and c, evaporating and crystallizing the concentrated solution obtained by the second nanofiltration to obtain analytically pure potassium sulfate. In one embodiment, in said step b, the dilution factor is 3-8. The method can reuse the light brine generated in the potassium chloride electrolysis process, effectively separate the potassium sulfate from the potassium chloride, and can prepare an analytically pure-grade potassium sulfate product.
Description
Technical Field
The invention relates to a production process and a device for purifying and separating potassium sulfate from dilute brine, belonging to the technical field of chlor-alkali chemical industry.
Background
The potassium chloride brine is an aqueous solution containing potassium chloride, potassium sulfate and possibly potassium chlorate, and the most typical potassium chloride brine system is provided with a brine refining system required in the process of preparing refined potassium chloride and potassium hydroxide, wherein the refined potassium chloride mainly uses industrial crystalline potassium chloride to produce ultrapure potassium chloride, medical grade potassium chloride, food grade potassium chloride, edible potassium chloride required for producing low sodium salt and the like through dissolution, refining and recrystallization, and the refining process mainly removes impurities such as calcium magnesium ions, sulfate ions and the like; the potassium chloride brine refining system for producing the ionic membrane potash is low-concentration potassium chloride brine produced by electrolyzing potassium chloride brine, commonly called dilute brine, wherein: the concentrations of the individual components are as follows: 120-220 g/l of potassium chloride, 3-13 g/l of potassium sulfate and 2-20 g/l of potassium chlorate.
However, how to use the potassium chloride brine and the byproducts after electrolysis is a problem in industrial processes.
Disclosure of Invention
The purpose of the invention is that: the production of analytically pure grade potassium sulphate is carried out using the weak brine produced after electrolysis in a potash plant.
The technical proposal is as follows:
the production process of potassium sulfate comprises the following steps:
step a, potassium chloride brine is subjected to first nanofiltration, and monovalent and divalent salts are separated;
step b, after the concentrated solution obtained in the first nanofiltration process is diluted by water, carrying out second nanofiltration, and separating monovalent and divalent salts;
and c, evaporating and crystallizing the concentrated solution obtained by the second nanofiltration to obtain analytically pure potassium sulfate.
In one embodiment, in said step b, the dilution factor is 3-8.
In one embodiment, in the step a, the light salt water of potassium chloride contains 120-220 g/l potassium chloride, 3-13 g/l potassium sulfate and 2-20 g/l potassium chlorate.
In one embodiment, the potassium chloride brine is further subjected to a treatment of pH adjustment, temperature reduction or free chlorine removal prior to said step a.
In one embodiment, the nanofiltration membrane used in the first nanofiltration and/or the second nanofiltration may be made of a polymer material such as cellulose acetate polymer, polyamide, sulfonated polysulfone, polyacrylonitrile, polyester, polyimide or vinyl polymer.
In one embodiment, in step a, the permeate obtained in the first nanofiltration comprises: 120-220 g/L potassium sulfate: 0.05-1 g/L, 2-20 g/L potassium chlorate; the concentrated solution contains: 120-220 g/l of potassium chloride, 25-50g/l of potassium sulfate and 2-20 g/l of potassium chlorate; in the first nanofiltration process, the operating pressure is 0.8-3.0MPa.
In one embodiment, in step b, the concentrate obtained in the second nanofiltration comprises: potassium chloride solution, 0.01-2 g/L potassium sulfate: 25-50 g/L; in the second nanofiltration process, the operating pressure is 0.5-3.0MPa.
In one embodiment, in the step c, an MVR evaporator is used in the evaporative crystallization process.
In one embodiment, the stepsIn step c, after the evaporation process, 0.1 to 0.3wt% NH is added to the crystallization mother liquor 4 HCO 3 。
In one embodiment, the permeate obtained in the first nanofiltration and/or the second nanofiltration is used for the salt dissolving process of dissolving crude potassium chloride salt, and after the suspension of the dissolved potassium chloride brine is removed by a first solid-liquid separation membrane, na is added 2 CO 3 And NaOH to remove Ca from brine 2+ And Mg (magnesium) 2+ The ions are converted into sediment, and the sediment is filtered by a second solid-liquid separation membrane and then is sent into an electrolytic tank for electrolytic treatment.
In one embodiment, the first solid-liquid separation membrane is filled with hollow fiber membrane filaments.
In one embodiment, the method further comprises the step of detecting and repairing the breakage of the hollow fiber membrane filaments, and comprises the following steps:
step 1, the section of a hollow fiber membrane component is rectangular, and hollow fiber membranes are filled in the hollow fiber membrane component; the rectangle is provided with a long side and a short side;
step 2, closing one short side by using a plugging belt, blocking membrane holes of a hollow fiber membrane covered by the plugging belt, and measuring water flux;
step 3, removing the plugging band 16, then moving the plugging band along the long side direction, sequentially closing all other areas, and measuring the water flux after each closing; obtaining flux arrays after traversing long sides;
step 4, sealing one long side by using a sealing strip, blocking membrane holes of the hollow fiber membrane covered by the sealing strip, and measuring water flux;
step 5, removing the plugging band, then moving the plugging band along the long side direction, sequentially closing all other areas, and measuring the water flux after each closing; obtaining flux arrays after traversing long sides;
step 6, finding out one data with water flux obviously smaller than other values in the flux array after traversing the long side, and recording the position of the long side of the plugging band under the measurement condition corresponding to the data; finding out data with water flux obviously smaller than other values in the flux array after traversing the short side, and recording the position of the short side of the plugging band under the measurement condition corresponding to the data; the positions on the long sides and the positions on the short sides are used as coordinate values on the rectangle, and the membrane holes of the hollow fiber membranes on the coordinate values are blocked by glue.
The apparatus for producing potassium sulfate includes:
a raw material liquid storage tank for storing a potassium chloride solution;
the first nanofiltration membrane is connected with the raw material liquid storage tank and is used for carrying out nanofiltration separation on the raw material liquid to obtain monovalent and divalent inorganic salt treatment;
the second nanofiltration membrane is connected to the concentrated solution side of the first nanofiltration membrane and is used for carrying out nanofiltration separation on monovalent and divalent inorganic salt treatment on the concentrated solution obtained in the first nanofiltration membrane;
the water adding port is connected with the feeding port of the second nanofiltration membrane and is used for diluting the feed liquid entering the second nanofiltration membrane;
and the evaporation crystallizer is connected to the concentrated solution side of the second nanofiltration membrane and is used for performing evaporation crystallization treatment on the concentrated solution obtained in the second nanofiltration membrane to obtain refined potassium sulfate.
In one embodiment, the method further comprises: and the salt dissolving tank is used for dissolving potassium chloride salt through permeate liquid obtained from the first nanofiltration membrane and the second nanofiltration membrane.
In one embodiment, the method further comprises: the first solid-liquid separation membrane is connected with the salt dissolving tank and is used for filtering the dissolved potassium chloride solution to remove suspended matters.
In one embodiment, the method further comprises: a precipitation tank connected to the permeation side of the first solid-liquid separation membrane for converting calcium and magnesium ions in the permeate obtained in the first solid-liquid separation membrane 8 into precipitates.
In one embodiment, the method further comprises: na (Na) 2 CO 3 The inlet and NaOH inlet are respectively connected with the precipitation tank for respectively adding Na into the precipitation tank 2 CO 3 And NaOH.
In one embodiment, the method further comprises: and the second solid-liquid separation membrane is connected with the precipitation tank and is used for removing generated precipitate.
In one embodiment, the method further comprises: and an electrolytic tank connected to the permeation side of the second solid-liquid separation membrane and used for carrying out electrolytic treatment on the permeation liquid of the second solid-liquid separation membrane.
In one embodiment, NH is also arranged on the pipeline connected with the evaporation crystallizer at the concentrate side of the second nanofiltration membrane 4 HCO 3 And (5) an inlet.
Advantageous effects
The method can reuse the light brine generated in the alkali chloride electrolysis process, effectively separate the potassium sulfate from the potassium chloride, and can prepare an analytically pure-grade potassium sulfate product. The main advantages of the above method include: 1. the method adopts water dilution-nanofiltration treatment, realizes the deep separation of potassium sulfate and potassium chloride, and ensures that the prepared potassium sulfate product has higher purity; 2. during crystallization, by NH 4 HCO 3 The charge property of the surface of the crystallization nucleus is changed by adding the potassium sulfate, so that the prepared potassium sulfate crystal particles are larger and the yield is higher; 3. the permeate liquid in nanofiltration separation is deeply utilized again, and is used in the salt dissolving process of crude potassium chloride salt, so that the reutilization of byproducts is realized; 4. in the salt dissolving process, a filter membrane is adopted to filter suspended matters and precipitates, the purity of the purified brine is high, and the damage of the filter membrane is easy to detect and repair.
Drawings
FIG. 1 is a process flow diagram of the present invention;
FIG. 2 is a diagram of an apparatus of the present invention;
FIG. 3 is a diagram of a hollow fiber membrane detection process;
FIG. 4 is a diagram of a hollow fiber membrane detection process;
FIG. 5 is an SEM photograph of potassium sulfate crystals;
FIG. 6 is a graph showing the particle size distribution of potassium sulfate crystals.
1, a raw material liquid storage tank; 2. a first nanofiltration membrane; 3. a water inlet; 4. second sodiumA filter membrane; 5. an evaporative crystallizer; 6. NH (NH) 4 HCO 3 An inlet; 7. a salt dissolving tank; 8. a first solid-liquid separation membrane; 9. a precipitation tank; 10. na (Na) 2 CO 3 An inlet; 11. a NaOH inlet; 12. a second solid-liquid separation membrane; 13. an electrolytic cell; 14. a hollow fiber membrane module; 15. a hollow fiber membrane; 16. a plugging band.
Detailed Description
The material to be treated in the invention is dilute brine produced by electrolysis in potash factories, mainly comprising potassium chloride and potassium sulfate, and the main components of the dilute brine comprise: 120-220 g/l of potassium chloride, 3-13 g/l of potassium sulfate and 2-20 g/l of potassium chlorate. Before separation and purification, it is necessary to carry out treatments of pH adjustment, temperature reduction and free chlorine removal.
In the step of the invention, firstly, the potassium chloride brine is subjected to salt separation treatment by adopting a first nanofiltration membrane, and low-sulfate salt brine and sulfate-rich brine can be obtained due to the higher retention rate of the nanofiltration membrane on divalent salt ions, wherein the main components in the low-sulfate salt brine comprise: 120-220 g/L potassium sulfate: 0.05-1 g/L and 2-20 g/L of potassium chlorate. The main components in the sulfate-rich brine include: 120-220 g/l of potassium chloride, 25-50g/l of potassium sulfate and 2-20 g/l of potassium chlorate;
for the obtained sulfate-rich brine, the enrichment of potassium sulfate is realized, and in the process of the invention, the innovation point is that the secondary nanofiltration is carried out on the brine by adding deionized water, so that the purity of the potassium sulfate can be further improved, and the refined potassium sulfate is obtained; if the above-mentioned dilution step is not used, the crystallization process yields potassium chloride after direct secondary concentration and evaporation, and potassium sulfate cannot be obtained. The method comprises the following specific steps: deionized water (the total water amount is about 3-8 times of the materials) is added through continuous mixing, and after the mixture enters a membrane purification system, the treated materials contain the following contents: potassium chloride solution, 0.01-2 g/L potassium sulfate: 25-50 g/L; in the step, the enrichment of potassium sulfate is further realized, and the separation from potassium chloride is realized.
After the refined potassium sulfate brine is obtained, the refined potassium sulfate brine can be further concentrated by MVR evaporation, and the concentration is 2.2-4.4 times, and then obtaining analytically pure potassium sulfate by a cooling crystallization mode. During crystallization, NH is added in an auxiliary way 4 HCO 3 The charge of the surface of the crystal nucleus can be regulated, the crystal nucleus can grow greatly, the yield and the grain diameter of crystal grains can be improved, the addition amount can be 0.1-0.3wt% of the crystallization mother liquor, and NH can be added through the subsequent grain drying process 4 CO 3 The product is removed easily in the subsequent crystal drying process, and the product quality is not affected.
In the purification step and the nanofiltration membrane separation step, low-sulfate high-potassium chloride brine can be obtained and sent into a low-nitrate brine storage tank, and can be further used for a salt dissolving section to be recycled. The salt dissolving process may be to dissolve potassium chloride salt to obtain potassium chloride salt water, filtering the salt water to eliminate suspended matter, and adding Na separately 2 CO 3 And NaOH to remove Ca from brine 2+ And Mg (magnesium) 2+ After the ions are converted into precipitates, the precipitates are removed by a filtering membrane, so as to obtain refined potassium chloride brine, and the refined potassium chloride brine is applied to the technical process of ionic membrane caustic soda.
In the above steps, the hollow fiber membrane module is mainly used for removing suspended particles in the chemical brine, and in order to further prevent the breakage of the hollow fiber membrane made of polymer material from causing the damage of the whole set of equipment, the following detection and repair steps are adopted:
step 1, the section of the hollow fiber membrane module 14 is rectangular, and hollow fiber membranes 15 are filled in the hollow fiber membrane module; the rectangle is provided with a long side and a short side;
as shown in fig. 3: step 2, closing one short side by using a plugging band 16, blocking membrane holes of a hollow fiber membrane 15 covered by the plugging band 16, and measuring water flux;
step 3, removing the plugging band 16, then moving the plugging band 16 along the long side direction, sequentially closing all other areas, and measuring the water flux after each closing; obtaining flux arrays after traversing long sides;
as shown in fig. 4: step 4, sealing one long side by using a sealing strip 16, blocking membrane holes of the hollow fiber membrane 15 covered by the sealing strip 16, and measuring water flux;
step 5, removing the plugging band 16, then moving the plugging band 16 along the long side direction, sequentially closing all other areas, and measuring the water flux after each closing; obtaining flux arrays after traversing long sides;
step 6, finding out one data with water flux obviously smaller than other values in the flux array after traversing the long side, and recording the position of the long side of the plugging band 16 under the measurement condition corresponding to the data; finding out data with water flux obviously smaller than other values in the flux array after traversing the short sides, and recording the position of the plugging band 16 on the short sides under the measurement condition corresponding to the data; the positions on the long sides and the positions on the short sides are used as coordinate values on the rectangle, and the membrane holes of the hollow fiber membranes on the coordinate values are blocked by glue.
With the above-described detection and repair means, since the hollow fiber membranes inside are randomly distributed when the hollow fiber membrane module 14 is packed, it is considered that the number of hollow fiber membranes within the set area range is approximately equal. If one of the hollow fiber membranes is broken, the flux is obviously increased when the filtering process is carried out, and for the whole membrane assembly shift, the number of the hollow fiber membranes is very large, so that the fact of which hollow fiber membrane is broken cannot be confirmed; therefore, after plugging a strip-shaped area along the long edge sequentially by using the plugging belt, when filtering is performed (the plugging belt is positioned on the water inlet side of the hollow fiber membrane assembly in the filtering process), the hollow fiber membrane under the area does not have a filtering function any more, if the just broken hollow fiber membrane is positioned in the plugged area, the flux data under the plugging condition can be obviously smaller than the flux data under other conditions, and the values have obvious differences (when under other plugging conditions, the just broken hollow fiber membrane is not in a plugging state and has a filtering function again, so that the flux of the whole hollow fiber membrane is obviously increased); therefore, a position which is obviously smaller than other values in the flux array when the long sides are blocked in sequence can be obtained respectively, and a position which is obviously smaller than other values in the flux array when the short sides are blocked in sequence can also be obtained, wherein the two positions respectively correspond to the position coordinates of the long sides and the short sides, so that the position where the hollow fiber membrane breaks is convenient for the coordinate value to cross, and then the pore canal of the hollow fiber membrane at the position is blocked by using sealant, so that when the hollow fiber membrane is filtered again, the broken hollow fiber membrane does not have water pressure any more, and the whole assembly is recovered to work normally without being scrapped.
The production integrated apparatus of potassium sulfate used in the present invention is shown in fig. 2, comprising:
a raw material liquid storage tank 1 for storing a potassium chloride solution;
the first nanofiltration membrane 2 is connected with the raw material liquid storage tank 1 and is used for carrying out nanofiltration separation on the raw material liquid to obtain monovalent and divalent inorganic salt treatment;
the second nanofiltration membrane 4 is connected to the concentrated solution side of the first nanofiltration membrane 2 and is used for carrying out nanofiltration separation on monovalent and divalent inorganic salt treatment on the concentrated solution obtained in the first nanofiltration membrane 2;
a water inlet 3 connected to the feed inlet of the second nanofiltration membrane 4 for diluting the feed liquid entering the second nanofiltration membrane 4;
and an evaporation crystallizer 5 connected to the concentrated solution side of the second nanofiltration membrane 4, and used for performing evaporation crystallization treatment on the concentrated solution obtained in the second nanofiltration membrane 4 to obtain refined potassium sulfate.
In one embodiment, the method further comprises: the salt dissolving tank 7 is connected with the permeation side of the first nanofiltration membrane 2 and the second nanofiltration membrane 4, and the salt dissolving tank 7 is used for dissolving potassium chloride salt through the permeate obtained from the first nanofiltration membrane 2 and the second nanofiltration membrane 4.
In one embodiment, the method further comprises: the first solid-liquid separation membrane 8 is connected to the salt dissolving tank 7 and is used for filtering the dissolved potassium chloride solution to remove suspended matters.
In one embodiment, the method further comprises: a precipitation tank 9 connected to the permeate side of the first solid-liquid separation membrane 8 for converting calcium and magnesium ions in the permeate obtained in the first solid-liquid separation membrane 8 into precipitates.
In one embodiment, the method further comprises: na (Na) 2 CO 3 An inlet 10 and an NaOH inlet 11 connected to the precipitation tank 9 for adding Na to the precipitation tank 9 2 CO 3 And NaOH.
In one embodiment, the method further comprises: a second solid-liquid separation membrane 12 connected to the precipitation tank 9 for removing the generated precipitate.
In one embodiment, the method further comprises: an electrolytic tank 13 connected to the permeate side of the second solid-liquid separation membrane 12 for performing electrolytic treatment on the permeate of the second solid-liquid separation membrane 12.
In one embodiment, NH is also provided on the line connecting the concentrate side of the second nanofiltration membrane 4 with the evaporative crystallizer 5 4 CO 3 And (5) an inlet.
Example 1
After pH adjustment, dechlorination and cooling treatment are carried out on the dilute brine after the electrolysis of the potassium chloride, 180g/L of potassium chloride, 4.4g/L of potassium sulfate and 1.2g/L of potassium chlorate are contained, a nanofiltration membrane is adopted for separating divalent salt (the operation pressure is 1.5 MPa), and the nanofiltration membrane is made of polyamide, so that a first concentrated solution and a first penetrating fluid are obtained; continuously adding 4 times deionized water into the first concentrated solution for dilution, and separating divalent salt through a second nanofiltration membrane (the operation pressure is 1.2 MPa) to obtain a second concentrated solution and a second permeate; and concentrating the second concentrated solution by MVR, cooling, crystallizing, and drying the crystals to obtain analytically pure potassium sulfate.
Mixing the first and second permeate, adding into salt dissolving tank containing potassium chloride crude product for dissolving salt, filtering with hollow fiber membrane with average pore diameter of 0.45um to remove suspended substances, and adding Na into the permeate of the hollow fiber membrane 2 CO 3 And NaOH, na 2 CO 3 Is added in an amount ratio of Ca in the completely precipitated brine 2+ 0.15g/L more NaOH is added than the Mg in the completely precipitated brine 2+ The amount of Ca in the brine is 0.05g/L more 2+ And Mg (magnesium) 2+ Converting the ions into precipitate and averagingFiltering the precipitate with ceramic micro-filtration membrane with aperture of 50nm to obtain refined brine, and sending into an electrolytic tank for electrolytic treatment.
Example 2
After pH adjustment, dechlorination and cooling treatment are carried out on the dilute brine after the electrolysis of the potassium chloride, 160g/L of potassium chloride, 3.2g/L of potassium sulfate and 0.3g/L of potassium chlorate are contained, a nanofiltration membrane is adopted for separating divalent salt (the operation pressure is 1.2 MPa), and the nanofiltration membrane is made of polyamide, so that a first concentrated solution and a first penetrating fluid are obtained; continuously adding 5 times deionized water into the first concentrated solution for dilution, and then separating divalent salt through a second nanofiltration membrane (the operation pressure is 1.0 MPa) to obtain a second concentrated solution and a second permeate; and concentrating the second concentrated solution by MVR, cooling, crystallizing, and drying the crystals to obtain analytically pure potassium sulfate.
Mixing the first and second permeate, adding into salt dissolving tank containing potassium chloride crude product for dissolving salt, filtering with hollow fiber membrane with average pore diameter of 0.45um to remove suspended substances, and adding Na into the permeate of the hollow fiber membrane 2 CO 3 And NaOH, na 2 CO 3 Is added in an amount ratio of Ca in the completely precipitated brine 2+ 0.20g/L more NaOH is added than the Mg in the completely precipitated brine 2+ The amount of Ca in the brine is 0.10g/L more 2+ And Mg (magnesium) 2+ The ions are converted into sediment, and then the sediment is filtered by a ceramic microfiltration membrane with the average pore diameter of 50nm to obtain refined brine, and the refined brine is sent into an electrolytic tank for electrolytic treatment.
Example 3
After pH adjustment, dechlorination and cooling treatment are carried out on the dilute brine after the electrolysis of the potassium chloride, 140g/L of potassium chloride, 7.6g/L of potassium sulfate and 2.3g/L of potassium chlorate are contained, a nanofiltration membrane is adopted for separating divalent salt (the operation pressure is 1.8 MPa), and the nanofiltration membrane is made of polyamide, so that a first concentrated solution and a first penetrating fluid are obtained; continuously adding 8 times deionized water into the first concentrated solution for dilution, and separating divalent salt through a second nanofiltration membrane (the operation pressure is 1.5 MPa) to obtain a second concentrated solution and a second permeate; and concentrating the second concentrated solution by MVR, cooling, crystallizing, and drying the crystals to obtain analytically pure potassium sulfate.
Mixing the first and second permeate, adding into salt dissolving tank containing potassium chloride crude product for dissolving salt, filtering with hollow fiber membrane with average pore diameter of 0.45um to remove suspended substances, and adding Na into the permeate of the hollow fiber membrane 2 CO 3 And NaOH, na 2 CO 3 Is added in an amount ratio of Ca in the completely precipitated brine 2+ 0.05g/L more NaOH is added than the Mg in the completely precipitated brine 2+ The amount of Ca in the brine is 0.10g/L more 2+ And Mg (magnesium) 2+ The ions are converted into sediment, and then the sediment is filtered by a ceramic microfiltration membrane with the average pore diameter of 50nm to obtain refined brine, and the refined brine is sent into an electrolytic tank for electrolytic treatment.
Example 4
The differences from example 1 are: adding 0.1-0.3wt% NH into concentrated brine after MVR evaporation 4 HCO 3 ；
After pH adjustment, dechlorination and cooling treatment are carried out on the dilute brine after the electrolysis of the potassium chloride, 180g/L of potassium chloride, 4.4g/L of potassium sulfate and 1.2g/L of potassium chlorate are contained, a nanofiltration membrane is adopted for separating divalent salt (the operation pressure is 1.5 MPa), and the nanofiltration membrane is made of polyamide, so that a first concentrated solution and a first penetrating fluid are obtained; continuously adding 4 times deionized water into the first concentrated solution for dilution, and separating divalent salt through a second nanofiltration membrane (the operation pressure is 1.2 MPa) to obtain a second concentrated solution and a second permeate; concentrating the second concentrated solution with MVR, adding 0.1-0.3wt% NH 4 HCO 3 Cooling, crystallizing, and drying the crystals to obtain analytically pure potassium sulfate.
Mixing the first and second permeate, adding into salt dissolving tank containing potassium chloride crude product for dissolving salt, filtering with hollow fiber membrane with average pore diameter of 0.45um to remove suspended substances, and adding Na into the permeate of the hollow fiber membrane 2 CO 3 And NaOH, na 2 CO 3 Is added in an amount ratio of Ca in the completely precipitated brine 2+ 0.15g/L more NaOH is added than the Mg in the completely precipitated brine 2+ The amount of Ca in the brine is 0.05g/L more 2+ And Mg (magnesium) 2+ Conversion of ions to precipitateFiltering the precipitate with ceramic micro-filtration membrane with average pore size of 50nm to obtain refined brine, and delivering into an electrolytic tank for electrolytic treatment.
Example 5
The differences from example 2 are: adding 0.1-0.3wt% NH into concentrated brine after MVR evaporation 4 HCO 3 ；
After pH adjustment, dechlorination and cooling treatment are carried out on the dilute brine after the electrolysis of the potassium chloride, 160g/L of potassium chloride, 3.2g/L of potassium sulfate and 0.3g/L of potassium chlorate are contained, a nanofiltration membrane is adopted for separating divalent salt (the operation pressure is 1.2 MPa), and the nanofiltration membrane is made of polyamide, so that a first concentrated solution and a first penetrating fluid are obtained; continuously adding 5 times deionized water into the first concentrated solution for dilution, and then separating divalent salt through a second nanofiltration membrane (the operation pressure is 1.0 MPa) to obtain a second concentrated solution and a second permeate; concentrating the second concentrated solution with MVR, adding 0.1-0.3wt% NH 4 HCO 3 Cooling, crystallizing, and drying the crystals to obtain analytically pure potassium sulfate.
Mixing the first and second permeate, adding into salt dissolving tank containing potassium chloride crude product for dissolving salt, filtering with hollow fiber membrane with average pore diameter of 0.45um to remove suspended substances, and adding Na into the permeate of the hollow fiber membrane 2 CO 3 And NaOH, na 2 CO 3 Is added in an amount ratio of Ca in the completely precipitated brine 2+ 0.20g/L more NaOH is added than the Mg in the completely precipitated brine 2+ The amount of Ca in the brine is 0.10g/L more 2+ And Mg (magnesium) 2+ The ions are converted into sediment, and then the sediment is filtered by a ceramic microfiltration membrane with the average pore diameter of 50nm to obtain refined brine, and the refined brine is sent into an electrolytic tank for electrolytic treatment.
Example 6
The differences from example 3 are: adding 0.1-0.3wt% NH into concentrated brine after MVR evaporation 4 HCO 3 ；
After pH adjustment, dechlorination and cooling treatment of the dilute brine after potassium chloride electrolysis, 140g/L of potassium chloride, 7.6g/L of potassium sulfate and 2.3g/L of potassium chlorate are contained, and nanofiltration membrane is adopted for separation of divalent salt (operating pressure is 1.8 MPa)The nanofiltration membrane is made of polyamide, so as to obtain a first concentrated solution and a first penetrating fluid; continuously adding 8 times deionized water into the first concentrated solution for dilution, and separating divalent salt through a second nanofiltration membrane (the operation pressure is 1.5 MPa) to obtain a second concentrated solution and a second permeate; concentrating the second concentrated solution with MVR, adding 0.1-0.3wt% NH 4 HCO 3 Cooling, crystallizing, and drying the crystals to obtain analytically pure potassium sulfate.
Mixing the first and second permeate, adding into salt dissolving tank containing potassium chloride crude product for dissolving salt, filtering with hollow fiber membrane with average pore diameter of 0.45um to remove suspended substances, and adding Na into the permeate of the hollow fiber membrane 2 CO 3 And NaOH, na 2 CO 3 Is added in an amount ratio of Ca in the completely precipitated brine 2+ 0.05g/L more NaOH is added than the Mg in the completely precipitated brine 2+ The amount of Ca in the brine is 0.10g/L more 2+ And Mg (magnesium) 2+ The ions are converted into sediment, and then the sediment is filtered by a ceramic microfiltration membrane with the average pore diameter of 50nm to obtain refined brine, and the refined brine is sent into an electrolytic tank for electrolytic treatment.
The operational data obtained from the above procedure are shown below:
as can be seen from comparison of the operation results of example 1 and comparative example 1 in the above table, the concentration of the first nanofiltration process was further diluted and then the second nanofiltration process was carried out, so that the concentration of KCl and K contained in the mixture was effectively reduced 2 SO 4 KCl rejection in concentrate of (C) is reduced and K is reduced 2 SO 4 The retention rate of the nano-filtration membrane is improved, so that the separation degree of a divalent salt on the surface of the nano-filtration membrane is higher, the residual monovalent salt in the first nano-filtration concentrated solution can penetrate through the nano-filtration membrane more, and the finally obtained K is improved 2 SO 4 Is a pure product of (a).
As shown in FIG. 5, SEM photograph of recovered potassium sulfate prepared in example 4 shows the particle size fractions of potassium sulfate crystal grains in examples 1 and 4The layout is shown in FIG. 6, from which it can be seen that by using NH during crystallization 4 HCO 3 The grain diameter of the obtained crystal is larger, which is beneficial to the subsequent centrifugal separation operation and leads the yield to be higher.
Claims (6)
1. The production process of potassium sulfate is characterized by comprising the following steps:
step a, potassium chloride brine is subjected to first nanofiltration, and monovalent and divalent salts are separated;
step b, after the concentrated solution obtained in the first nanofiltration process is diluted by water, carrying out second nanofiltration, and separating monovalent and divalent salts;
step c, evaporating and crystallizing the concentrated solution obtained by the second nanofiltration to obtain analytically pure potassium sulfate; in the step c, after the evaporation process, 0.1 to 0.3 weight percent of NH is required to be added into the crystallization mother liquor 4 HCO 3 。
2. The process according to claim 1, wherein in step b, the dilution factor is 3-8 times; in the step a, the potassium chloride brine contains 120-220 g/l of potassium chloride, 3-13 g/l of potassium sulfate and 2-20 g/l of potassium chlorate.
3. The process according to claim 1, wherein the potassium chloride brine is subjected to pH adjustment, temperature reduction or free chlorine removal prior to step a.
4. The process according to claim 1, wherein the nanofiltration membrane used in the first nanofiltration and/or the second nanofiltration is made of a material selected from the group consisting of cellulose acetate polymer, polyamide, sulfonated polysulfone, polyacrylonitrile, polyester and polyimide;
in step a, the permeate obtained in the first nanofiltration contains: 120-220 g/L potassium sulfate: 0.05-1 g/L, 2-20 g/L potassium chlorate; the concentrated solution contains: 120-220 g/l of potassium chloride, 25-50g/l of potassium sulfate and 2-20 g/l of potassium chlorate;
in step b, the concentrate obtained in the second nanofiltration contains: potassium chloride solution, 0.01-2 g/L potassium sulfate: 25-50 g/L.
5. The process according to claim 1, wherein in step c, an MVR evaporator is used for the evaporative crystallization; dissolving potassium chloride salt in the permeate liquid obtained in the first nanofiltration and/or the second nanofiltration to obtain potassium chloride salt water, removing suspended matters by using a first solid-liquid separation membrane, and adding Na 2 CO 3 And NaOH to remove Ca from brine 2+ And Mg (magnesium) 2+ The ions are converted into sediment, and the sediment is filtered by a second solid-liquid separation membrane and then is sent into an electrolytic tank for electrolytic treatment.
6. The process for producing potassium sulfate according to claim 1, wherein the first solid-liquid separation membrane is filled with hollow fiber membrane filaments; the method also comprises the steps of detecting and repairing the breakage of the hollow fiber membrane wire, and comprises the following steps: step 1, the section of a hollow fiber membrane module (14) adopted is rectangular, and hollow fiber membranes (15) are filled in the hollow fiber membrane module; the rectangle is provided with a long side and a short side; step 2, closing one short side by using a plugging belt (16), blocking membrane holes of a hollow fiber membrane (15) covered by the plugging belt (16), and measuring water flux; step 3, removing the plugging band (16), then moving the plugging band (16) along the long side direction, sequentially closing all other areas, and measuring the water flux after each closing; obtaining flux arrays after traversing long sides; step 4, sealing one long side by using a sealing strip (16), blocking membrane holes of a hollow fiber membrane (15) covered by the sealing strip (16), and measuring water flux; step 5, removing the plugging band (16), then moving the plugging band (16) along the long side direction, sequentially closing all other areas, and measuring the water flux after each closing; obtaining flux arrays after traversing long sides; step 6, finding out one data with water flux obviously smaller than other values in the flux array after traversing the long side, and recording the position of the long side of the plugging band (16) under the measurement condition corresponding to the data; finding out data with water flux obviously smaller than other values in the flux array after traversing the short sides, and recording the position of the short sides of the plugging band (16) under the measurement condition corresponding to the data; the positions on the long sides and the positions on the short sides are used as coordinate values on the rectangle, and the membrane holes of the hollow fiber membranes on the coordinate values are blocked by glue.
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