CN117623339A - Method for preparing chlor-alkali by treating wastewater with purified graphite tail gas - Google Patents
Method for preparing chlor-alkali by treating wastewater with purified graphite tail gas Download PDFInfo
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- CN117623339A CN117623339A CN202311592135.7A CN202311592135A CN117623339A CN 117623339 A CN117623339 A CN 117623339A CN 202311592135 A CN202311592135 A CN 202311592135A CN 117623339 A CN117623339 A CN 117623339A
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- 239000002351 wastewater Substances 0.000 title claims abstract description 41
- 239000003513 alkali Substances 0.000 title claims abstract description 36
- 238000000034 method Methods 0.000 title claims abstract description 30
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 28
- 229910002804 graphite Inorganic materials 0.000 title claims abstract description 28
- 239000010439 graphite Substances 0.000 title claims abstract description 28
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims abstract description 56
- 239000011780 sodium chloride Substances 0.000 claims abstract description 28
- 239000012267 brine Substances 0.000 claims abstract description 25
- HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical compound O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 claims abstract description 25
- 150000003839 salts Chemical class 0.000 claims abstract description 23
- 238000001728 nano-filtration Methods 0.000 claims abstract description 18
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 claims abstract description 12
- 239000011259 mixed solution Substances 0.000 claims abstract description 12
- 238000001704 evaporation Methods 0.000 claims abstract description 11
- 230000008020 evaporation Effects 0.000 claims abstract description 11
- 238000001223 reverse osmosis Methods 0.000 claims abstract description 10
- 239000002253 acid Substances 0.000 claims abstract description 5
- 238000000108 ultra-filtration Methods 0.000 claims abstract description 5
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 15
- OTYBMLCTZGSZBG-UHFFFAOYSA-L potassium sulfate Chemical compound [K+].[K+].[O-]S([O-])(=O)=O OTYBMLCTZGSZBG-UHFFFAOYSA-L 0.000 claims description 14
- 229910052939 potassium sulfate Inorganic materials 0.000 claims description 14
- 235000011151 potassium sulphates Nutrition 0.000 claims description 14
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 14
- 238000002425 crystallisation Methods 0.000 claims description 13
- 230000008025 crystallization Effects 0.000 claims description 13
- WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical compound [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 claims description 12
- 150000002500 ions Chemical class 0.000 claims description 12
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 10
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 10
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 8
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 8
- 229910052804 chromium Inorganic materials 0.000 claims description 8
- 239000011651 chromium Substances 0.000 claims description 8
- 239000010936 titanium Substances 0.000 claims description 8
- 229910052719 titanium Inorganic materials 0.000 claims description 8
- 229910052720 vanadium Inorganic materials 0.000 claims description 8
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 claims description 8
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims description 7
- 229910052801 chlorine Inorganic materials 0.000 claims description 7
- 239000000460 chlorine Substances 0.000 claims description 7
- 239000001103 potassium chloride Substances 0.000 claims description 6
- 235000011164 potassium chloride Nutrition 0.000 claims description 6
- 230000008014 freezing Effects 0.000 claims description 5
- 238000007710 freezing Methods 0.000 claims description 5
- 229960002089 ferrous chloride Drugs 0.000 claims description 4
- 239000011790 ferrous sulphate Substances 0.000 claims description 4
- 235000003891 ferrous sulphate Nutrition 0.000 claims description 4
- NMCUIPGRVMDVDB-UHFFFAOYSA-L iron dichloride Chemical compound Cl[Fe]Cl NMCUIPGRVMDVDB-UHFFFAOYSA-L 0.000 claims description 4
- 229910000359 iron(II) sulfate Inorganic materials 0.000 claims description 4
- 239000002994 raw material Substances 0.000 abstract description 11
- 238000004064 recycling Methods 0.000 abstract description 7
- 238000004065 wastewater treatment Methods 0.000 abstract description 4
- 238000005660 chlorination reaction Methods 0.000 abstract description 3
- 238000005265 energy consumption Methods 0.000 abstract description 2
- 238000000746 purification Methods 0.000 abstract description 2
- 239000007789 gas Substances 0.000 description 15
- 238000004519 manufacturing process Methods 0.000 description 8
- 239000000126 substance Substances 0.000 description 5
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 4
- 238000000354 decomposition reaction Methods 0.000 description 4
- 208000028659 discharge Diseases 0.000 description 4
- 239000003337 fertilizer Substances 0.000 description 4
- 239000002699 waste material Substances 0.000 description 3
- 239000005708 Sodium hypochlorite Substances 0.000 description 2
- RAHZWNYVWXNFOC-UHFFFAOYSA-N Sulphur dioxide Chemical compound O=S=O RAHZWNYVWXNFOC-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000003912 environmental pollution Methods 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 229910000029 sodium carbonate Inorganic materials 0.000 description 2
- SUKJFIGYRHOWBL-UHFFFAOYSA-N sodium hypochlorite Chemical compound [Na+].Cl[O-] SUKJFIGYRHOWBL-UHFFFAOYSA-N 0.000 description 2
- 239000002912 waste gas Substances 0.000 description 2
- BZSXEZOLBIJVQK-UHFFFAOYSA-N 2-methylsulfonylbenzoic acid Chemical compound CS(=O)(=O)C1=CC=CC=C1C(O)=O BZSXEZOLBIJVQK-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 238000005189 flocculation Methods 0.000 description 1
- 230000016615 flocculation Effects 0.000 description 1
- 239000002920 hazardous waste Substances 0.000 description 1
- 229910017053 inorganic salt Inorganic materials 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910001510 metal chloride Inorganic materials 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 239000010802 sludge Substances 0.000 description 1
- 238000003900 soil pollution Methods 0.000 description 1
- 239000002910 solid waste Substances 0.000 description 1
- 238000005406 washing Methods 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
- C01D3/00—Halides of sodium, potassium or alkali metals in general
- C01D3/04—Chlorides
- C01D3/06—Preparation by working up brines; seawater or spent lyes
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- 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
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F9/00—Multistage treatment of water, waste water or sewage
-
- 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
- C02F1/02—Treatment of water, waste water, or sewage by heating
- C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
-
- 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
- C02F1/441—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by reverse osmosis
-
- 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
-
- 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
- C02F1/444—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by ultrafiltration or microfiltration
-
- 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
- C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
- C02F1/5236—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents
- C02F1/5245—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents using basic salts, e.g. of aluminium and iron
-
- 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
- C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
-
- 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
- C02F1/70—Treatment of water, waste water, or sewage by reduction
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/18—Nature of the water, waste water, sewage or sludge to be treated from the purification of gaseous effluents
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Inorganic Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Hydrology & Water Resources (AREA)
- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
- Treatment Of Water By Oxidation Or Reduction (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
Abstract
The invention discloses a method for preparing chlor-alkali by treating wastewater by utilizing purified graphite tail gas, which comprises the following steps: adding acid into tail gas treatment wastewater of graphite purification by a chlorination method, adjusting the pH value to 3-6, adding soluble ferrous salt, adding alkali to adjust the pH value of the mixed solution to 7-9, performing ultrafiltration and/or multistage reverse osmosis treatment on the mixed solution, separating sodium chloride brine by nanofiltration, further separating, purifying and concentrating, and directly delivering chlor-alkali corporate salt as a raw material for use, recycling sodium chloride in the wastewater, simultaneously saving energy consumption of sodium chloride evaporation and wastewater treatment cost.
Description
Technical Field
The invention belongs to the technical field of wastewater treatment, and particularly relates to a method for preparing chlor-alkali by treating wastewater by utilizing purified graphite tail gas.
Background
The waste gas from graphite purification mainly contains chlorine, sulfur dioxide, metal chloride and other pollutants, and waste water is produced by the waste gas treatment through the absorption of an alkaline washing tower. The waste brine produced by the process of chloridizing roasting and purifying graphite contains sodium chloride, sodium hypochlorite, sodium carbonate, sodium chlorate, vanadium, titanium, chromium and other impurities, and the waste water can produce environmental pollution if directly discharged. The main substances of the waste brine are sodium chloride and sodium carbonate, wherein the content of the sodium chloride is about 150g/L, and the waste brine can be recycled in a chlor-alkali plant after removing metal impurities such as vanadium, titanium, chromium and the like and sodium hypochlorite, so that the raw material cost of the chlor-alkali plant can be reduced, and the environmental pollution problem caused by wastewater discharge can be reduced.
At present, many domestic enterprises mainly adopt reclaimed water recycling or evaporation crystallization to obtain mixed salt, concentrate the waste water, recycle the water, discharge strong brine, or treat hazardous waste in the form of sludge, salt mud and mixed salt, and the solid waste causes secondary soil pollution or water body pollution at the same time of zero water discharge. Although there are methods related to recycling waste water in the prior art, it is generally aimed at treating a specific problem in waste water, and there is no method related to recycling all water and salts of different prices in waste water.
Disclosure of Invention
The invention aims to solve the technical problems that: the method for preparing chlor-alkali by treating wastewater by utilizing purified graphite tail gas is provided, so that the technical aim that water and salt in the wastewater can be fully recycled and the wastewater treatment cost is reduced is fulfilled.
In order to achieve the above purpose, the invention adopts the following technical scheme: the method for preparing chlor-alkali by treating wastewater by utilizing purified graphite tail gas comprises the following steps:
s1: adjusting the pH value of the purified graphite tail gas treatment wastewater to 3-6 by using acid, adding soluble ferrous salt, and then adding alkali to adjust the pH value of the mixed solution to 7-9;
s2: subjecting the mixed solution to ultrafiltration and/or multistage reverse osmosis treatment; then the monovalent salt and the high-valence salt are separated by nanofiltration;
s3: the monovalent salt separated by nanofiltration is further separated, converted and concentrated to prepare sodium chloride strong brine, and the brine can be used for chlor-alkali primary brine and is normally produced by a common chlor-alkali production process;
s4: adding potassium chloride into the mixed brine containing the high valence ions and the monovalent ions, which is separated by nanofiltration, and then obtaining potassium sulfate and sodium chloride respectively through freezing crystallization and high-temperature evaporation crystallization.
The beneficial effects of the technical scheme adopted by the invention are as follows: the sodium chloride brine separated by nanofiltration is further separated, purified and concentrated and then directly sent to chlor-alkali company salt to be used as a raw material, so that the energy consumption of sodium chloride evaporation is saved while the sodium chloride in the wastewater is recycled. The mixed brine containing high valence ions and monovalent ions, which is obtained by nanofiltration separation, is sent to a high valence salt conversion device, potassium chloride is added for double decomposition reaction to generate potassium sulfate and sodium chloride, and the potassium sulfate and the sodium chloride are separated by low-temperature evaporation crystallization and high-temperature evaporation crystallization. The produced potassium sulfate is used as a raw material for producing chemical fertilizers, and the separated sodium chloride is sent to chlor-alkali company to be used as a raw material.
Based on the technical scheme, the invention can also be improved as follows:
further, the acid is hydrochloric acid or sulfuric acid.
Further, the soluble ferrous salt is ferrous sulfate and/or ferrous chloride, and the proportioning relation between the soluble ferrous salt and the purified graphite tail gas treatment wastewater is 10kg:1m 3 。
Further, the base is sodium hydroxide.
Further, the concentration in step S3 is high pressure reverse osmosis concentration.
Further, the free chlorine content of the residual water after the treatment in steps S3 and S4 is less than 2ppb, and the contents of vanadium, titanium and chromium elements are all less than 15ppb.
The beneficial effects of the invention are as follows:
1. by adopting the method of adding soluble ferrous salt for reduction and flocculation, free chlorine and vanadium, titanium and chromium in the tail gas treatment wastewater of the chloridizing and purifying graphite can be treated in one step, and the treatment process is simplified.
2. The method can solve the problem of wastewater generated in the treatment of the tail gas of the purified graphite by the chlorination process, is applied to the production of chlor-alkali, and can effectively reduce the treatment cost of the wastewater generated in the treatment of the tail gas of the purified graphite by the chlorination process.
3. The invention can realize the recycling and zero discharge treatment of materials in the wastewater, the wastewater is treated by the method of the invention, the evaporation loss of the system and the water carried away by the materials are removed by about 2%, the residual water is completely recovered, the water recycling rate is more than 98%, the inorganic salt recycling rate is more than 80%, the environment is protected, and the wastewater treatment cost is saved.
Detailed Description
The following description of the specific embodiments of the present invention is provided to facilitate understanding of the present invention by those skilled in the art, and the examples are not intended to be limiting, and the reagents or apparatus used are not intended to be limiting, and are conventional products available for commercial purchase. It should be understood that the invention is not limited to the specific embodiments, but is capable of numerous modifications within the spirit and scope of the invention as hereinafter defined and defined by the appended claims as will be apparent to those skilled in the art all falling within the true spirit and scope of the invention as hereinafter claimed.
Example 1:
a method for preparing chlor-alkali by treating wastewater with purified graphite tail gas comprises the following steps:
s1: adjusting the pH value of the purified graphite tail gas treatment wastewater to 5.5 by using hydrochloric acid or sulfuric acid, adding 10kg of ferrous chloride into each cubic meter of wastewater, and then adding sodium hydroxide to adjust the pH value of the mixed solution to 7.3;
s2: subjecting the mixed solution to ultrafiltration treatment; then the monovalent salt and the high-valence salt are separated by nanofiltration;
s3: the monovalent salt separated by nanofiltration is further separated and converted, and then concentrated by high-pressure reverse osmosis to prepare sodium chloride strong brine, wherein the brine can be used as chlor-alkali primary brine and is normally produced by a common chlor-alkali production process;
s4: adding potassium chloride into the mixed brine containing high valence ions and monovalent ions, which is separated by nanofiltration, to perform double decomposition reaction to generate potassium sulfate and sodium chloride, and then respectively obtaining the potassium sulfate and the sodium chloride by freezing crystallization and high-temperature evaporation crystallization, wherein the produced potassium sulfate is used as a raw material for producing chemical fertilizers, and the separated sodium chloride is used as a chlor-alkali production raw material.
The free chlorine content of the residual water after the treatment in steps S3 and S4 was 1ppb, the vanadium content was 3ppb, the titanium content was 10ppb, and the chromium content was 1ppb.
Example 2:
a method for preparing chlor-alkali by treating wastewater with purified graphite tail gas comprises the following steps:
s1: adjusting the pH value of the purified graphite tail gas treatment wastewater to 3 by using hydrochloric acid or sulfuric acid, adding 10kg of ferrous sulfate into each cubic meter of wastewater, and then adding sodium hydroxide to adjust the pH value of the mixed solution to 9;
s2: subjecting the mixed solution to multistage reverse osmosis treatment; then the monovalent salt and the high-valence salt are separated by nanofiltration;
s3: the monovalent salt separated by nanofiltration is further separated and converted, and then concentrated by high-pressure reverse osmosis to prepare sodium chloride strong brine, wherein the brine can be used as chlor-alkali primary brine and is normally produced by a common chlor-alkali production process;
s4: adding potassium chloride into the mixed brine containing high valence ions and monovalent ions, which is separated by nanofiltration, to perform double decomposition reaction to generate potassium sulfate and sodium chloride, and then respectively obtaining the potassium sulfate and the sodium chloride by freezing crystallization and high-temperature evaporation crystallization, wherein the produced potassium sulfate is used as a raw material for producing chemical fertilizers, and the separated sodium chloride is used as a chlor-alkali production raw material.
The free chlorine content of the residual water after the treatment in steps S3 and S4 was 2ppb, the vanadium content was 1ppb, the titanium content was 15ppb, and chromium was not detected.
Example 3:
a method for preparing chlor-alkali by treating wastewater with purified graphite tail gas comprises the following steps:
s1: adjusting the pH value of the purified graphite tail gas treatment wastewater to 6 by using hydrochloric acid or sulfuric acid, and adding 10kg of ferrous sulfate and ferrous chloride into each cubic meter of wastewater to 1:1, then adding sodium hydroxide to adjust the pH value of the mixed solution to 7;
s2: subjecting the mixed solution to ultrafiltration and multistage reverse osmosis treatment; then the monovalent salt and the high-valence salt are separated by nanofiltration;
s3: the monovalent salt separated by nanofiltration is further separated and converted, and then concentrated by high-pressure reverse osmosis to prepare sodium chloride strong brine, wherein the brine can be used as chlor-alkali primary brine and is normally produced by a common chlor-alkali production process;
s4: adding potassium chloride into the mixed brine containing high valence ions and monovalent ions, which is separated by nanofiltration, to perform double decomposition reaction to generate potassium sulfate and sodium chloride, and then respectively obtaining the potassium sulfate and the sodium chloride by freezing crystallization and high-temperature evaporation crystallization, wherein the produced potassium sulfate is used as a raw material for producing chemical fertilizers, and the separated sodium chloride is used as a chlor-alkali production raw material.
The free chlorine, vanadium and chromium elements of the residual water after the treatment in steps S3 and S4 were not detected, and the titanium content was 2ppb.
Claims (6)
1. The method for preparing chlor-alkali by treating wastewater by utilizing purified graphite tail gas is characterized by comprising the following steps of:
s1: adjusting the pH value of the purified graphite tail gas treatment wastewater to 3-6 by using acid, adding soluble ferrous salt, and then adding alkali to adjust the pH value of the mixed solution to 7-9;
s2: subjecting the mixed solution to ultrafiltration and/or multistage reverse osmosis treatment; then the monovalent salt and the high-valence salt are separated by nanofiltration;
s3: the monovalent salt separated by nanofiltration is further separated and converted, and concentrated to prepare sodium chloride concentrated brine;
s4: adding potassium chloride into the mixed brine containing the high valence ions and the monovalent ions, which is separated by nanofiltration, and then obtaining potassium sulfate and sodium chloride respectively through freezing crystallization and high-temperature evaporation crystallization.
2. The method for preparing chlor-alkali by treating wastewater by utilizing purified graphite tail gas according to claim 1, wherein the method comprises the following steps: the acid is hydrochloric acid or sulfuric acid.
3. The method for preparing chlor-alkali by treating wastewater by utilizing purified graphite tail gas according to claim 1, wherein the method comprises the following steps: the soluble ferrous salt is ferrous sulfate and/or ferrous chloride, and the proportioning relation between the soluble ferrous salt and the purified graphite tail gas treatment wastewater is 10kg:1m 3 。
4. The method for preparing chlor-alkali by treating wastewater by utilizing purified graphite tail gas according to claim 1, wherein the method comprises the following steps: the alkali is sodium hydroxide.
5. The method for preparing chlor-alkali by treating wastewater by utilizing purified graphite tail gas according to claim 1, wherein the method comprises the following steps: the concentration in the step S3 is high-pressure reverse osmosis concentration.
6. The method for preparing chlor-alkali by treating wastewater by utilizing purified graphite tail gas according to claim 1, wherein the method comprises the following steps: the free chlorine content of the residual water after the treatment in the steps S3 and S4 is lower than 2ppb, and the contents of vanadium, titanium and chromium elements are all lower than 15ppb.
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| CN202311592135.7A CN117623339A (en) | 2023-11-27 | 2023-11-27 | Method for preparing chlor-alkali by treating wastewater with purified graphite tail gas |
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