CN114956126A - Method for recycling mother solution in sodium method iron phosphate production process - Google Patents
Method for recycling mother solution in sodium method iron phosphate production process Download PDFInfo
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- CN114956126A CN114956126A CN202210705112.1A CN202210705112A CN114956126A CN 114956126 A CN114956126 A CN 114956126A CN 202210705112 A CN202210705112 A CN 202210705112A CN 114956126 A CN114956126 A CN 114956126A
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- sodium
- sodium sulfate
- mother liquor
- iron phosphate
- filtrate
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- 238000000034 method Methods 0.000 title claims abstract description 70
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical compound [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 title claims abstract description 64
- 229910000398 iron phosphate Inorganic materials 0.000 title claims abstract description 61
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 43
- 238000004064 recycling Methods 0.000 title claims abstract description 28
- 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 description 10
- 239000011734 sodium Substances 0.000 title claims description 10
- 229910052708 sodium Inorganic materials 0.000 title claims description 10
- 239000010413 mother solution Substances 0.000 title claims 2
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 claims abstract description 127
- 229910052938 sodium sulfate Inorganic materials 0.000 claims abstract description 126
- 235000011152 sodium sulphate Nutrition 0.000 claims abstract description 126
- 239000000706 filtrate Substances 0.000 claims abstract description 100
- 239000012452 mother liquor Substances 0.000 claims abstract description 68
- 235000003891 ferrous sulphate Nutrition 0.000 claims abstract description 35
- 239000011790 ferrous sulphate Substances 0.000 claims abstract description 35
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 claims abstract description 35
- 229910000359 iron(II) sulfate Inorganic materials 0.000 claims abstract description 35
- 239000013078 crystal Substances 0.000 claims abstract description 20
- 238000006243 chemical reaction Methods 0.000 claims abstract description 14
- 239000000126 substance Substances 0.000 claims abstract description 3
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims description 50
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 38
- 238000002425 crystallisation Methods 0.000 claims description 35
- 230000008025 crystallization Effects 0.000 claims description 35
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims description 25
- 239000012535 impurity Substances 0.000 claims description 24
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims description 22
- 239000012065 filter cake Substances 0.000 claims description 17
- 238000000746 purification Methods 0.000 claims description 17
- 229910000162 sodium phosphate Inorganic materials 0.000 claims description 16
- 239000001488 sodium phosphate Substances 0.000 claims description 16
- RYFMWSXOAZQYPI-UHFFFAOYSA-K trisodium phosphate Chemical compound [Na+].[Na+].[Na+].[O-]P([O-])([O-])=O RYFMWSXOAZQYPI-UHFFFAOYSA-K 0.000 claims description 16
- 238000001914 filtration Methods 0.000 claims description 13
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 claims description 13
- 229910019142 PO4 Inorganic materials 0.000 claims description 11
- 239000010452 phosphate Substances 0.000 claims description 11
- 235000017550 sodium carbonate Nutrition 0.000 claims description 11
- 229910000029 sodium carbonate Inorganic materials 0.000 claims description 11
- 239000003814 drug Substances 0.000 claims description 5
- 239000005955 Ferric phosphate Substances 0.000 claims description 3
- 229940032958 ferric phosphate Drugs 0.000 claims description 3
- 229910000399 iron(III) phosphate Inorganic materials 0.000 claims description 3
- 239000000243 solution Substances 0.000 claims 1
- 238000001704 evaporation Methods 0.000 abstract description 16
- 230000008020 evaporation Effects 0.000 abstract description 15
- 238000000926 separation method Methods 0.000 abstract description 7
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 abstract description 6
- 229910052698 phosphorus Inorganic materials 0.000 abstract description 6
- 239000011574 phosphorus Substances 0.000 abstract description 6
- 239000000047 product Substances 0.000 abstract description 6
- 230000000694 effects Effects 0.000 abstract description 5
- 230000007613 environmental effect Effects 0.000 abstract description 3
- 239000000376 reactant Substances 0.000 abstract description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 17
- 235000011008 sodium phosphates Nutrition 0.000 description 14
- 238000005406 washing Methods 0.000 description 10
- 239000003513 alkali Substances 0.000 description 9
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 9
- 239000001301 oxygen Substances 0.000 description 9
- 229910052760 oxygen Inorganic materials 0.000 description 9
- 239000002244 precipitate Substances 0.000 description 9
- BNIILDVGGAEEIG-UHFFFAOYSA-L disodium hydrogen phosphate Chemical compound [Na+].[Na+].OP([O-])([O-])=O BNIILDVGGAEEIG-UHFFFAOYSA-L 0.000 description 8
- 229910000403 monosodium phosphate Inorganic materials 0.000 description 8
- 235000019799 monosodium phosphate Nutrition 0.000 description 8
- 238000003825 pressing Methods 0.000 description 8
- AJPJDKMHJJGVTQ-UHFFFAOYSA-M sodium dihydrogen phosphate Chemical compound [Na+].OP(O)([O-])=O AJPJDKMHJJGVTQ-UHFFFAOYSA-M 0.000 description 8
- 239000007787 solid Substances 0.000 description 8
- 239000012528 membrane Substances 0.000 description 7
- 150000003839 salts Chemical class 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 3
- 229910001385 heavy metal Inorganic materials 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- 150000001768 cations Chemical class 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- 230000007704 transition Effects 0.000 description 2
- 238000003889 chemical engineering Methods 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 229940116007 ferrous phosphate Drugs 0.000 description 1
- 230000008014 freezing Effects 0.000 description 1
- 238000007710 freezing Methods 0.000 description 1
- -1 heavy metals Chemical class 0.000 description 1
- 229910000155 iron(II) phosphate Inorganic materials 0.000 description 1
- SDEKDNPYZOERBP-UHFFFAOYSA-H iron(ii) phosphate Chemical compound [Fe+2].[Fe+2].[Fe+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O SDEKDNPYZOERBP-UHFFFAOYSA-H 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000010446 mirabilite Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000011268 retreatment Methods 0.000 description 1
- RSIJVJUOQBWMIM-UHFFFAOYSA-L sodium sulfate decahydrate Chemical compound O.O.O.O.O.O.O.O.O.O.[Na+].[Na+].[O-]S([O-])(=O)=O RSIJVJUOQBWMIM-UHFFFAOYSA-L 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 1
- 238000004065 wastewater treatment Methods 0.000 description 1
Images
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
- C01D5/02—Preparation of sulfates from alkali metal salts and sulfuric acid or bisulfates; Preparation of bisulfates
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B25/00—Phosphorus; Compounds thereof
- C01B25/16—Oxyacids of phosphorus; Salts thereof
- C01B25/26—Phosphates
- C01B25/37—Phosphates of heavy metals
- C01B25/375—Phosphates of heavy metals of iron
-
- 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
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
-
- 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
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/10—Process efficiency
Abstract
The invention belongs to the technical field of chemical industry, and relates to a method for recycling mother liquor in the production process of sodium-method iron phosphate. Because of the homoionic effect, especially at low temperatures, the solubility and solubility product of ferrous sulfate is greater than that of sodium sulfate, and more sodium sulfate can be precipitated. And (3) feeding the formed filtrate containing the ferrous sulfate into an iron phosphate reaction kettle to be used as a reactant for generating iron phosphate. The invention realizes the separation of the sodium sulfate crystals by utilizing the solubility characteristics of ferrous sulfate and sodium sulfate, greatly reduces the investment scale of an evaporation system, simultaneously reduces the operation cost of the evaporation system, and even can cancel the evaporation system. Meanwhile, the phosphorus source in the filtrate is recovered, so that great benefits can be brought, and the environmental protection treatment cost can be saved.
Description
Technical Field
The invention belongs to the technical field of chemical engineering, and relates to a method for recycling mother liquor in a sodium method iron phosphate production process.
Background
The traditional sodium method iron phosphate production process is that ferrous sulfate reacts with excessive phosphoric acid and oxygen, then alkali is added to adjust the PH value, iron phosphate precipitate, sodium sulfate and sodium phosphate solution are generated, the iron phosphate is washed, dried and calcined to obtain a product, and the filtrate enters waste water treatment. The process flow is shown in the attached figure 1.
In the traditional production process, filtrate and filter cake washing liquor produced by the filter press mainly contain sodium sulfate, sodium phosphate and a small amount of excessive phosphoric acid, most of the filtrate needs to be evaporated to separate sodium sulfate and impurities in the traditional production process, for example, in the Chinese invention patent application CN113072048A, MVR evaporation is carried out on secondary mother liquor or the secondary mother liquor is discharged into a salt pan to be subjected to salt drying to obtain high-purity sodium sulfate, the MVR evaporation energy consumption is high, the investment is large, and the salt pan salt drying efficiency is low. At the same time valuable raw materials cannot be recovered.
For example, in the chinese patent application CN113402089A, a pretreatment system is first used to remove phosphate ions, heavy metal ions and suspended matters in the oxidation mother liquor, and the concentration of the suspended matters in the pretreated effluent is controlled to be less than or equal to 0.1 mg/L; then, concentrating the sodium sulfate concentration in the pretreated effluent from 7.4-14% to 16-20% by using a membrane concentration system, and simultaneously obtaining produced water with the sodium sulfate concentration being less than or equal to 0.09%, and recycling; finally, a freezing crystallization system is utilized to centrifugally separate 99 percent of mirabilite (sodium sulfate decahydrate), and the centrifugally separated mother liquor returns to a pretreatment system for retreatment; thereby realizing the aim of recycling the oxidation mother liquor in the sodium method ferric phosphate production.
Although the recovery method avoids MVR evaporation with high energy consumption, a membrane concentration system is required to be used for concentrating the mother liquor before crystallization, the efficiency is low, the membrane concentration system also increases the recovery cost of the mother liquor, and the removal of phosphate ions in the mother liquor increases the disposal cost and loses valuable phosphate which can be used as a raw material.
Disclosure of Invention
The invention overcomes the defects and provides a method for recycling mother liquor in the production process of sodium-method iron phosphate. In order to separate more sodium sulfate, a small amount of ferrous sulfate can be added in the process of sodium sulfate crystallization, and because of the isoionic product effect, the solubility of the ferrous sulfate is much higher than that of the sodium sulfate, the ferrous sulfate is added, which is more beneficial to sodium sulfate crystallization and separation.
The invention adopts the following technical scheme:
a method for recycling mother liquor in the production process of sodium-method iron phosphate comprises the steps of purifying filtrate, adding sulfuric acid into the filtrate to convert sodium phosphate into sodium sulfate and phosphoric acid, and then cooling to separate the sodium sulfate crystals.
Sulfuric acid is added without impurity components, and after the mother liquor is acidified by the sulfuric acid, the mother liquor only contains sodium sulfate and phosphoric acid so as to prevent sodium phosphate from being contained in the mother liquor, otherwise, the sodium phosphate can firstly react with ferrous sulfate to generate solid ferrous phosphate which is not beneficial to oxidation reaction.
Preferably, in order to separate more sodium sulfate, ferrous sulfate may be added to the mother liquor, and the solubility and solubility product of ferrous sulfate is larger than that of sodium sulfate, especially at low temperature, due to the homoionic effect, so that more sodium sulfate can be separated out.
And (3) sending the formed filtrate containing phosphoric acid and ferrous sulfate into an iron phosphate reaction kettle to be used as a reactant for generating iron phosphate.
According to the scheme, the sodium phosphate is converted into the sodium sulfate by using the sulfuric acid, the concentration of the sodium sulfate in the filtrate is increased, the ferrous sulfate is added into the filtrate, the crystallization and separation of the sodium sulfate are realized by using the solubility characteristics of the ferrous sulfate and the sodium sulfate, and the crystallization and separation of the sodium sulfate are not realized by depending on evaporation water, so that the evaporation capacity is greatly reduced, the investment scale of an evaporation system is greatly reduced, the operation cost of the evaporation system is reduced, and the evaporation system can be even cancelled.
Preferably, the addition amount of the sulfuric acid is 0.2mol/L-1 mol/L.
Preferably, the amount of the ferrous sulfate added is 0.5mol/L-1.5 mol/L. Specifically, the method comprises the following steps:
s1: and (3) conveying the filtrate produced by the filter press from the mother liquor in the production process of the sodium-method iron phosphate to a purification tank, adding a medicament to purify and remove impurities in the filtrate, and selecting the medicament without new components brought to the system, such as soda ash and the like, according to different impurity costs.
S2: purifying and filtering, separating out a system after impurities form a filter cake, adding sulfuric acid into filtrate to convert all phosphate into sodium sulfate and phosphoric acid, and feeding the filtrate into a sodium sulfate crystallization tank, wherein the filtrate contains a large amount of sodium sulfate and a small amount of sodium dihydrogen phosphate or sodium monohydrogen phosphate or sodium phosphate;
s3: adding a small amount of ferrous sulfate into the mother liquor, and reducing the crystallization temperature to the temperature required by the crystallization of sodium sulfate to separate out the sodium sulfate crystals.
S4: separating sodium sulfate crystal by a separator, and sending filtrate into an iron phosphate reaction kettle for reaction.
Preferably, the temperature is reduced to 0-30 deg.C, preferably 10-15 deg.C.
Preferably, the chemical used in step S-1 is soda ash, pH is adjusted to about 8, cations such as heavy metals and transition elements are removed, PAM is flocculated, and impurities are removed by filtration.
By implementing the technical scheme, the invention has the following beneficial effects:
1. the invention realizes the crystal separation of sodium sulfate by utilizing the solubility characteristics of ferrous sulfate and sodium sulfate, rather than separating the sodium sulfate crystal by evaporating water, thereby greatly reducing the evaporation capacity, greatly reducing the investment scale of an evaporation system, simultaneously reducing the operation cost of the evaporation system and even canceling the evaporation system.
2. The invention recycles the filtrate of the filter press after purification treatment, can effectively recover the residual phosphorus source in the filtrate and the washing liquid, improves the yield, reduces the environmental pollution and saves the cost. Can completely realize the clean production target with zero emission.
Drawings
FIG. 1 is a flow chart of a sodium method ferric phosphate production process in the prior art;
FIG. 2 is a graph showing the relationship between the solubility of ferrous sulfate and sodium sulfate at different temperatures;
FIG. 3 is a flow chart of a sodium-method iron phosphate production process in an embodiment of the invention;
FIG. 4 is a table showing the effect analysis of the invention for saving phosphorus source and environmental protection treatment.
Detailed Description
The invention is explained in further detail below with reference to the figures and the embodiments.
It should be noted that the following embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art will understand that: the technical solutions described in the foregoing embodiments can be modified, or some technical features can be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
A method for recycling mother liquor in the production process of sodium-method iron phosphate comprises the following steps:
s1-filtration of mother liquor
Mother liquor generated in the production process of the sodium-method iron phosphate is separated by a filter press or other filter pressing equipment to obtain filtrate and filter residue, the filtrate is sent to a purification tank, a medicament (such as sodium carbonate) is added, the pH is adjusted to about 8, and various impurities (cations such as heavy metals, transition elements and the like) and PAM in the filtrate are flocculated and purified and removed.
S2-refiltering
Purifying, filtering again, separating out the system with impurities forming filter cake, adding sulfuric acid into the filtrate to convert all phosphate into sodium sulfate and phosphoric acid, and feeding the filtrate into sodium sulfate crystallizing tank. Sulfuric acid is added in an amount of 0.2mol/L to 1 mol/L.
S3 sodium sulfate crystal
The crystallization temperature is reduced to the temperature required by the crystallization of sodium sulfate, so that most of sodium sulfate is crystallized and separated out. In order to fully and thoroughly crystallize the sodium sulfate, ferrous sulfate is selectively added into the obtained filtrate, and the ferrous sulfate is added according to the amount of 0.5-1.5 mol/L on the principle that the ferrous sulfate is not precipitated.
S4-separation of sodium sulfate crystal
And (3) centrifugally separating sodium sulfate crystals, feeding the filtrate into an iron phosphate reaction kettle, adding excessive phosphoric acid and oxygen, and adjusting the pH value with alkali to react to generate iron phosphate precipitate and a sodium sulfate solution.
The invention realizes the separation of sodium sulfate crystal by utilizing the solubility characteristics of two sulfates of ferrous sulfate and sodium sulfate, adds a small amount of ferrous sulfate before low-temperature crystallization, and can separate out more sodium sulfate due to the same ion effect, particularly at low temperature, the product of the solubility and the solubility of the ferrous sulfate is larger than that of the sodium sulfate.
The relationship between the solubility of ferrous sulfate and sodium sulfate at different temperatures is shown in figure 2, and at any temperature, the product of the solubility and the solubility of ferrous sulfate is larger than that of sodium sulfate, which can be realized by the scheme of the application.
Example 1
A method for recycling mother liquor in the production process of sodium-method iron phosphate comprises the following steps:
s1: separating mother liquor generated in the production process of the sodium-method iron phosphate by a filter press or other filter pressing equipment to obtain filtrate and filter residue, sending the filtrate to a purification tank, adding soda ash, and adjusting the pH value to about 8 to purify and remove various impurities in the filtrate.
S2: after purification, filtering again, separating out the system by forming a filter cake by impurities, wherein the filtrate contains a large amount of sodium sulfate and a trace amount of sodium dihydrogen phosphate or sodium monohydrogen phosphate or sodium phosphate, adding sulfuric acid into the filtrate according to the amount of 1 mol/L. All the phosphate is converted into sodium sulfate and phosphoric acid, and the filtrate is sent to a sodium sulfate crystallization tank.
S3: the crystallization temperature was lowered to 15 ℃ to crystallize out most of the sodium sulfate. The filtrate in this step also includes wash water for the filter cake of steps S1 and S2. The washing water can be directly used, or can be concentrated firstly, and after concentration, the washing water which meets the discharge requirement can be directly discharged and does not meet the requirement through detection, and then is crystallized in the step.
S4: and (4) centrifugally separating sodium sulfate crystals to obtain solid sodium sulfate, feeding the filtrate into an iron phosphate reaction kettle, adding excessive phosphoric acid and oxygen, adjusting the pH value with alkali to react to generate iron phosphate precipitate and mother liquor containing sodium sulfate, and allowing the mother liquor to enter step S1, and circulating the steps.
Sodium sulfate in the filtrate filtered in the step S4 was detected, and the sodium sulfate content was 9.2%.
Example 2
A method for recycling mother liquor in the production process of sodium-method iron phosphate is disclosed, referring to the attached figure 3, and comprises the following steps:
s1: separating mother liquor generated in the production process of the sodium-method iron phosphate by a filter press or other filter pressing equipment to obtain filtrate and filter residue, sending the filtrate to a purification tank, adding soda ash, and adjusting the pH value to about 8 to purify and remove various impurities in the filtrate.
S2: after purification, filtering again, separating out the system by forming a filter cake by impurities, wherein the filtrate contains a large amount of sodium sulfate and a trace amount of sodium dihydrogen phosphate or sodium monohydrogen phosphate or sodium phosphate, adding sulfuric acid into the filtrate according to the amount of 1 mol/L. All the phosphate is converted into sodium sulfate and phosphoric acid, and the filtrate is sent to a sodium sulfate crystallization tank.
S3: ferrous sulfate was added to the obtained filtrate in an amount of 1.0 mol/L. The crystallization temperature was lowered to 15 ℃ to crystallize out most of the sodium sulfate. The filtrate in this step also includes wash water for the filter cake of steps S1 and S2. The washing water can be directly used, or can be concentrated firstly, and after concentration, the washing water which meets the discharge requirement can be directly discharged and does not meet the requirement through detection, and then is crystallized in the step.
S4: and (4) centrifugally separating sodium sulfate crystals to obtain solid sodium sulfate, feeding the filtrate into an iron phosphate reaction kettle, adding excessive phosphoric acid and oxygen, adjusting the pH value with alkali to react to generate iron phosphate precipitate and mother liquor containing sodium sulfate, and allowing the mother liquor to enter step S1, and circulating the steps.
Sodium sulfate in the filtrate filtered in the step S4 is detected, and the content of the sodium sulfate is below 5%.
Example 3
A method for recycling mother liquor in the production process of sodium-method iron phosphate comprises the following steps:
s1: separating mother liquor generated in the production process of the sodium-method iron phosphate by a filter press or other filter pressing equipment to obtain filtrate and filter residue, sending the filtrate to a purification tank, adding soda ash, and adjusting the pH value to about 8 to purify and remove various impurities in the filtrate.
S2: after purification, filtration is carried out again, impurities form a filter cake and are separated out of the system, at the moment, the filtrate contains a large amount of sodium sulfate and a trace amount of sodium dihydrogen phosphate or sodium monohydrogen phosphate or sodium phosphate, sulfuric acid is added into the filtrate according to the amount of 0.5 mol/L. All the phosphate is converted into sodium sulfate and phosphoric acid, and the filtrate is sent to a sodium sulfate crystallization tank.
S3: ferrous sulfate was added to the obtained filtrate in an amount of 0.6 mol/L. The crystallization temperature was lowered to 22 ℃ to crystallize out most of the sodium sulfate. The filtrate in this step also includes wash water for the filter cake of steps S1 and S2. The washing water can be directly used, or can be concentrated by a membrane and then crystallized in the step.
S4: and (4) centrifugally separating sodium sulfate crystals to obtain solid sodium sulfate, feeding the filtrate into an iron phosphate reaction kettle, adding excessive phosphoric acid and oxygen, adjusting the pH value with alkali to react to generate iron phosphate precipitate and mother liquor containing sodium sulfate, and allowing the mother liquor to enter step S1, and circulating the steps.
Sodium sulfate in the filtrate filtered in the step S4 is detected, and the content of the sodium sulfate is below 5%.
Example 4
A method for recycling mother liquor in the production process of sodium-method iron phosphate comprises the following steps:
s1: separating mother liquor generated in the production process of the sodium-method iron phosphate by using a filter press or other filter pressing equipment to obtain filtrate and filter residue, conveying the filtrate to a purification tank, adding sodium carbonate, and adjusting the pH value to about 8 to purify and remove various impurities in the filtrate.
S2: after purification, filtration is carried out again, impurities form a filter cake and are separated out of the system, at the moment, the filtrate contains a large amount of sodium sulfate and a trace amount of sodium dihydrogen phosphate or sodium monohydrogen phosphate or sodium phosphate, sulfuric acid is added into the filtrate according to the amount of 0.5 mol/L. All the phosphate is converted into sodium sulfate and phosphoric acid, and the filtrate is sent to a sodium sulfate crystallization tank.
S3: ferrous sulfate was added to the obtained filtrate in an amount of 1.3 mol/L. The crystallization temperature was lowered to 10 ℃ to crystallize out most of the sodium sulfate. The filtrate in this step also includes wash water for the filter cake of steps S1 and S2. The washing water can be directly used, or can be concentrated by a membrane and then crystallized in the step.
S4: and (4) centrifugally separating sodium sulfate crystals to obtain solid sodium sulfate, feeding the filtrate into an iron phosphate reaction kettle, adding excessive phosphoric acid and oxygen, adjusting the pH value with alkali to react to generate iron phosphate precipitate and mother liquor containing sodium sulfate, and allowing the mother liquor to enter step S1, and circulating the steps.
Sodium sulfate in the filtrate filtered in the step S4 is detected, and the content of the sodium sulfate is below 5%.
Example 5
A method for recycling mother liquor in the production process of sodium-method iron phosphate comprises the following steps:
s1: separating mother liquor generated in the production process of the sodium-method iron phosphate by a filter press or other filter pressing equipment to obtain filtrate and filter residue, sending the filtrate to a purification tank, adding soda ash, and adjusting the pH value to about 8 to purify and remove various impurities in the filtrate.
S2: after purification, filtration is carried out again, impurities form a filter cake and are separated out of the system, at the moment, the filtrate contains a large amount of sodium sulfate and a trace amount of sodium dihydrogen phosphate or sodium monohydrogen phosphate or sodium phosphate, sulfuric acid is added into the filtrate according to the amount of 0.5 mol/L. All the phosphate is converted into sodium sulfate and phosphoric acid, and the filtrate is sent to a sodium sulfate crystallization tank.
S3: ferrous sulfate was added to the obtained filtrate in an amount of 0.7 mol/L. The crystallization temperature was lowered to 0 ℃ to crystallize out most of the sodium sulfate. The filtrate in this step also includes wash water for the filter cake of steps S1 and S2. The washing water can be directly used, or can be concentrated by a membrane and then crystallized in the step.
S4: and (4) centrifugally separating sodium sulfate crystals to obtain solid sodium sulfate, feeding the filtrate into an iron phosphate reaction kettle, adding excessive phosphoric acid and oxygen, adjusting the pH value with alkali to react to generate iron phosphate precipitate and mother liquor containing sodium sulfate, and allowing the mother liquor to enter step S1, and circulating the steps.
Sodium sulfate in the filtrate filtered in the step S4 is detected, and the content of sodium sulfate is below 2%.
In the scheme of the embodiment, all phosphate is converted into sodium sulfate and phosphoric acid by adding sulfuric acid, a phosphorus source in the mother liquor is recovered, the phosphorus source is saved, and the environmental protection treatment benefit analysis is shown in a table of attached figure 4.
Example 6
A method for recycling mother liquor in the production process of sodium-method iron phosphate comprises the following steps:
s1: separating mother liquor generated in the production process of the sodium-method iron phosphate by a filter press or other filter pressing equipment to obtain filtrate and filter residue, sending the filtrate to a purification tank, adding soda ash, and adjusting the pH value to about 8 to purify and remove various impurities in the filtrate.
S2: after purification, filtering again, separating out the system by forming a filter cake by impurities, wherein the filtrate contains a large amount of sodium sulfate and a trace amount of sodium dihydrogen phosphate or sodium monohydrogen phosphate or sodium phosphate, and sending the filtrate into a sodium sulfate crystallization tank.
S3: ferrous sulfate was added to the obtained filtrate in an amount of 0.7 mol/L. The crystallization temperature was lowered to 0 ℃ to crystallize out most of the sodium sulfate. The filtrate in this step also includes wash water for the filter cake of steps S1 and S2. The washing water can be directly used, or can be concentrated by a membrane and then crystallized in the step.
S4: and (4) centrifugally separating sodium sulfate crystals to obtain solid sodium sulfate, feeding the filtrate into an iron phosphate reaction kettle, adding excessive phosphoric acid and oxygen, adjusting the pH value with alkali to react to generate iron phosphate precipitate and mother liquor containing sodium sulfate, and allowing the mother liquor to enter step S1, and circulating the steps.
Sodium sulfate in the filtrate filtered in the step S4 is detected, and the content of sodium sulfate is below 2%. However, in this scheme, the phosphorus source is not recovered.
Comparative example 1
A method for recycling mother liquor in the production process of sodium-method iron phosphate comprises the following steps:
s1: mother liquor generated in the production process of the sodium-method iron phosphate is separated by a filter press or other filter pressing equipment to obtain filtrate and filter residue, the filtrate is sent to a purification tank, and a medicament (such as soda ash) is added to purify and remove various impurities in the filtrate.
S2: purifying, filtering again, separating out the impurities to form a filter cake, sending the filtrate into a sodium sulfate crystallization tank, adding sulfuric acid into the filtrate according to the amount of 0.5mol/L, wherein the filtrate contains a large amount of sodium sulfate and a trace amount of sodium dihydrogen phosphate or sodium monohydrogen phosphate or sodium phosphate. All the phosphate is converted into sodium sulfate and phosphoric acid, and the filtrate is sent to a sodium sulfate crystallization tank.
S3: the crystallization temperature was lowered to 10 ℃ to crystallize out most of the sodium sulfate.
S4: and (4) centrifugally separating sodium sulfate crystals to obtain solid sodium sulfate, feeding the filtrate into an iron phosphate reaction kettle, adding excessive phosphoric acid and oxygen, adjusting the pH value with alkali to react to generate iron phosphate precipitate and mother liquor containing sodium sulfate, and allowing the mother liquor to enter step S1, and circulating the steps.
Sodium sulfate in the filtrate filtered in the step S4 was detected, and the content of sodium sulfate was 9.5%.
Claims (12)
1. A method for recycling mother liquor in the production process of sodium-method iron phosphate is characterized in that sulfuric acid is added into filtrate obtained after mother liquor filtration to convert sodium phosphate into sodium sulfate and phosphoric acid, and then the temperature is reduced to separate the sodium sulfate crystals.
2. The method for recycling the mother liquor in the production process of the sodium-method iron phosphate as claimed in claim 1, wherein ferrous sulfate is added into the mother liquor before the sodium sulfate is crystallized at low temperature.
3. The method for recycling the mother liquor in the production process of the sodium-method iron phosphate as claimed in claim 1, wherein the addition amount of the ferrous sulfate is 0.5mol/L-1.5 mol/L.
4. The method for recycling the mother liquor in the production process of the sodium-method iron phosphate, according to claim 1, is characterized in that the addition amount of the sulfuric acid is 0.2-1 mol/L.
5. The method for recycling the mother liquor in the production process of iron phosphate by sodium method according to claim 1, characterized in that the crystallization temperature is 0-30 ℃.
6. The method for recycling the mother liquor in the production process of iron phosphate by sodium method according to claim 5, characterized in that the crystallization temperature is 10-15 ℃.
7. The recycling method of the mother liquor in the production process of the sodium-method iron phosphate as claimed in claim 1, is characterized by comprising the following steps:
s1: sending filtrate produced by a filter press from mother liquor in the production process of the sodium-method iron phosphate to a purification tank, and adding a medicament to purify and remove impurities in the filtrate;
s2: purifying and filtering, separating out a system after impurities form a filter cake, adding sulfuric acid into filtrate to convert all phosphate into sodium sulfate and phosphoric acid, sending the filtrate into a sodium sulfate crystallization tank, and sending the filtrate into the sodium sulfate crystallization tank;
s3: adding a small amount of ferrous sulfate into the mother solution, and reducing the crystallization temperature to the temperature required by the crystallization of sodium sulfate to separate out the sodium sulfate crystals;
s4: separating sodium sulfate crystal by a separator, and sending the filtrate into an iron phosphate reaction kettle for reaction.
8. The method for recycling the mother liquor in the production process of the sodium-method iron phosphate as claimed in claim 1, wherein the chemical used in the step S-1 is soda ash.
9. A method for recycling mother liquor in the production process of ferric phosphate by a sodium method is characterized in that ferrous sulfate is added into the mother liquor before the solution temperature is reduced to the temperature required by sodium sulfate crystallization.
10. The method for recycling the mother liquor in the production process of iron phosphate by sodium method according to claim 9, wherein the addition amount of the ferrous sulfate is 0.5-1.5 mol/L.
11. The method for recycling the mother liquor in the production process of iron phosphate by sodium method according to claim 9, characterized in that the crystallization temperature is 0-30 ℃.
12. The method for recycling the mother liquor in the production process of the sodium-method iron phosphate as claimed in claim 9, wherein sulfuric acid is added into the filtrate obtained after the mother liquor is filtered, so that the sodium phosphate is converted into sodium sulfate and phosphoric acid, and then the temperature is reduced, so that the sodium sulfate is crystallized and separated.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116462169A (en) * | 2023-05-22 | 2023-07-21 | 甘肃睿思科新材料有限公司 | Method for preparing battery grade lithium dihydrogen phosphate by recycling all elements of waste lithium iron phosphate |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AU2429177A (en) * | 1977-04-14 | 1978-10-19 | Yi-Hung Fang Albert | Recovering phosphate from waste in aluminum bright dipping |
| JPH038490A (en) * | 1989-06-07 | 1991-01-16 | Kurita Water Ind Ltd | Treatment of phosphate-contatining waste water |
| CN113402089A (en) * | 2021-07-08 | 2021-09-17 | 江苏卓博环保科技有限公司 | Recycling treatment device and method for oxidation mother liquor in sodium-method iron phosphate production |
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2022
- 2022-06-21 CN CN202210705112.1A patent/CN114956126A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AU2429177A (en) * | 1977-04-14 | 1978-10-19 | Yi-Hung Fang Albert | Recovering phosphate from waste in aluminum bright dipping |
| JPH038490A (en) * | 1989-06-07 | 1991-01-16 | Kurita Water Ind Ltd | Treatment of phosphate-contatining waste water |
| CN113402089A (en) * | 2021-07-08 | 2021-09-17 | 江苏卓博环保科技有限公司 | Recycling treatment device and method for oxidation mother liquor in sodium-method iron phosphate production |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116462169A (en) * | 2023-05-22 | 2023-07-21 | 甘肃睿思科新材料有限公司 | Method for preparing battery grade lithium dihydrogen phosphate by recycling all elements of waste lithium iron phosphate |
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