Iron phosphate production wastewater treatment method and system

Abstract

The invention relates to the technical field of water treatment, in particular to an iron phosphate production wastewater treatment method and system. The method comprises the following steps: carrying out first desalination on iron phosphate production wastewater to obtain first concentrated water and first fresh water; combining the first concentrated water with the mother solution to obtain a first combined solution, carrying out second desalination on the first fresh water under a first pH condition to obtain second fresh water, and recovering the second fresh water; removing a first type of impurities from the first combined liquid under a second pH condition to obtain first produced water and first sludge; carrying out third desalination on the first produced water under an acidic condition to obtain third concentrated water and third fresh water; sending the third concentrated water to MVR evaporation crystallization recovery, and carrying out fourth desalination on the third fresh water to obtain fourth fresh water; the fourth fresh water and the first fresh water are combined for desalination, or the fourth fresh water is subjected to second desalination under the first pH condition. Therefore, the problems that the TDS content is low and the water amount is large when the ammonium-process ferric phosphate production wastewater enters the MVR are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and in particular to a method and system for treating wastewater from iron phosphate production. Background Art

[0002] In recent years, with the rapid development of the new energy vehicle market, iron phosphate, as an important component of the positive electrode material of lithium-ion batteries, has continued to grow in market demand. As one of the world's largest new energy vehicle markets, China's iron phosphate market is also showing a booming development trend. At present, there are six main iron phosphate production processes: sodium method, ammonium method, iron powder, fertilizer phosphoric acid, red iron oxide, and calcium hydrogen phosphate. The more mainstream iron phosphate production routes are the ammonium method, also known as the industrial ammonium method (ferrous sulfate + monoammonium phosphate) and the sodium method, also known as the phosphoric acid method (phosphoric acid + liquid alkali + ferrous sulfate). They are mainly composed of iron phosphates on the sub-iron line. The preparation process requires ammonia water or sodium hydroxide to adjust the pH value. According to the use of different pH regulators, it is divided into sodium method and ammonium method. The ammonium method uses ammonia water, and the sodium method uses sodium hydroxide.

[0003] The wastewater from the production of ammonia ferric sulfate mainly contains ammonium, sulfate, phosphate, magnesium ions, etc., among which sulfate and ammonium account for the largest proportion. At present, the conventional treatment process for the wastewater from the production of ammonia ferric sulfate adopts lime precipitation + MVR crystallization. The lime precipitation method can simultaneously generate calcium sulfate and calcium phosphate precipitation to remove sulfate and phosphate, but the amount of mixed sludge is large, which is not easy to recycle and form new solid waste. In addition, the TDS content of the sewage entering the MVR is low (usually 70,000-90,000 mg / L) and the water volume is large, resulting in a large scale of supporting MVR, high construction cost, large land area, and expensive operating costs, which brings huge cost pressure to enterprises. Summary of the invention

[0004] In order to solve the problem of low TDS content and large water volume of ammonium process ferric phosphate production wastewater when entering MVR, the present invention provides a method and system for treating ferric phosphate production wastewater.

[0005] According to a first aspect of the present invention, the present invention provides a method for treating wastewater from iron phosphate production, comprising the following steps:

[0006] The first concentrated water and the first fresh water are obtained by first desalting the wastewater produced by the iron phosphate production;

[0007] The first concentrated water is combined with the mother liquor to obtain a first combined liquid, the pH of the first fresh water is increased to a pH value that meets the requirements of the reused water under the first pH condition, the first fresh water is subjected to a second desalination to obtain second fresh water, and the second fresh water is recovered;

[0008] The first combined liquid is subjected to a second pH condition to remove the first type of impurities to obtain the first produced water and the first sludge;

[0009] The pH of the first produced water under the second pH condition is reduced under the acidic condition, and the first produced water after the pH is reduced is subjected to the third desalination to obtain the third concentrated water and the third fresh water;

[0010] The third concentrated water is sent to MVR for evaporation and crystallization recovery, and the third fresh water is subjected to the fourth desalination to obtain the fourth fresh water;

[0011] The fourth fresh water is combined with the first fresh water for desalination, or the fourth fresh water is subjected to a second desalination under the first pH condition;

[0012] The first type of impurities include ammonium, magnesium, phosphorus or suspended matter;

[0013] The pH value of the first pH condition is less than or equal to the pH value of the second pH condition.

[0014] According to one embodiment of the present invention, the process of removing the first type of impurities includes:

[0015] Ammonia water is provided to increase the pH of the first concentrated water to 6.5-7, and first sludge containing first-class impurities and first produced water from which the first-class impurities are removed are obtained through flocculation separation.

[0016] According to one embodiment of the present invention, the process of performing the third desalination comprises:

[0017] Sulfur-containing acid is provided to reduce the pH of the first produced water to 4-5, and a third concentrated water containing salt compounds is obtained through reverse osmosis separation, and a third fresh water is separated from the salt compounds.

[0018] According to one embodiment of the present invention, the process of performing the second desalination comprises:

[0019] Ammonia water is provided to increase the pH of the first fresh water and / or the fourth fresh water to 6-7, and second fresh water with salt compounds removed is obtained by reverse osmosis separation, wherein the TDS of the second fresh water is ≤10.

[0020] According to one embodiment of the present invention, the process of performing the first desalination comprises:

[0021] After removing the second impurities from the wastewater produced by iron phosphate production, the second produced water and the second sludge are obtained;

[0022] The second produced water is separated by ultrafiltration and reverse osmosis to obtain first concentrated water containing salt compounds and first fresh water with the salt compounds removed.

[0023] According to one embodiment of the present invention, the amount of the third concentrated water sent to the MVR evaporation crystallization is less than or equal to 31.6% of the sum of the inflow of ferric phosphate production wastewater and the inflow of mother liquor.

[0024] According to a second aspect of the present invention, the present invention provides a system for treating wastewater from iron phosphate production, comprising:

[0025] A first impurity removal system, a second impurity removal system, a first desalination system, a second desalination system, a third desalination system, a fourth desalination system and an MVR system;

[0026] The first impurity removal system includes an impurity removal reaction tank and a first integrated flocculation reaction precipitation water purifier;

[0027] The second impurity removal system includes a second integrated flocculation reaction precipitation water purifier;

[0028] The first desalination system includes a wash water UF membrane system and a wash water RO membrane system;

[0029] The second desalination system includes a first pH adjustment tank, a primary clean water RO membrane system and a secondary clean water RO membrane system;

[0030] The third desalination system includes a second pH adjustment tank, a mother liquor UF membrane system, and a primary mother liquor RO membrane system;

[0031] The fourth desalination system includes a secondary mother liquor RO membrane system;

[0032] The liquid outlet of the second integrated flocculation reaction precipitation water purifier is connected to the liquid inlet of the wash water UF membrane system, the fresh water outlet of the wash water UF membrane system is connected to the liquid inlet of the wash water RO membrane system, the fresh liquid outlet of the wash water RO membrane system is connected to the liquid inlet of the first pH regulating tank, the concentrated liquid outlet of the wash water RO membrane system is connected to the liquid inlet of the impurity removal reaction tank, the liquid outlet of the impurity removal reaction tank is connected to the liquid inlet of the first integrated flocculation reaction precipitation water purifier, the liquid outlet of the first integrated flocculation reaction precipitation water purifier is connected to the liquid inlet of the second pH regulating tank, and the liquid outlet of the second pH regulating tank is connected to The liquid inlet of the mother liquor UF membrane system is connected, the dilute liquid outlet of the mother liquor UF membrane system is connected to the liquid inlet of the first-level mother liquor RO membrane system, the concentrated liquid outlet of the first-level mother liquor RO membrane system is connected to the liquid inlet of the MVR system, the dilute liquid outlet of the first-level mother liquor RO membrane system is connected to the liquid inlet of the second-level mother liquor RO membrane system, the dilute liquid outlet of the second-level mother liquor RO membrane system is connected to the liquid inlet of the first pH regulating tank, the liquid outlet of the first pH regulating tank is connected to the liquid inlet of the first-level clean water RO membrane system, and the dilute liquid outlet of the first-level clean water RO membrane system is connected to the liquid inlet of the second-level clean water RO membrane system.

[0033] According to one embodiment of the present invention, the impurity removal reaction tank is equipped with a first alkali adding device, the water inlet pipe of the first integrated flocculation reaction precipitation water purifier is equipped with a flocculant adding device, the first pH adjustment tank is equipped with a second alkali adding device, and the second pH adjustment tank is equipped with an acid adding device.

[0034] According to one embodiment of the present invention, the membrane elements of the UF membrane system and the RO membrane system are special anti-pollution, acid-resistant and alkali-resistant membranes.

[0035] According to one embodiment of the present invention, a sludge filter press system is included, wherein the sludge inlet is connected to the sludge outlets of the first integrated flocculation reaction sedimentation water purifier and the second integrated flocculation reaction sedimentation water purifier.

[0036] In order to solve the problem of low TDS content and large water volume of ammonium ferric phosphate production wastewater entering MVR, the present invention has the following advantages:

[0037] 1. The present invention combines the concentrated water after desalination and concentration of ferric phosphate production wastewater with the mother liquor, removes impurities and performs reverse osmosis membrane desalination and concentration treatment, thereby greatly improving the TDS content of MVR influent, achieving a significant wastewater reduction effect, effectively reducing the construction cost and operation cost of the enterprise, and achieving effective complementarity between environmental protection and economy.

[0038] 2. The ferric phosphate treatment method of the present invention is simple, the pH adjustment times are few, the TDS content of the concentrated water sent to the MVR crystallization evaporation is high, and the water quality TDS of the final recycled water is ≤10 mg / L, which greatly improves the purity of the recycled water, and the recycled water of ferric phosphate wastewater can be applied to multiple different water use fields.

[0039] 3. The present invention not only improves the water quality standard by adding ammonia water to remove impurities and adjust pH without introducing new ions, but also increases the recovery rate of fresh water, so that the recovery rate of fresh water reaches more than 96%. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 The present invention shows a flow chart of wastewater treatment from iron phosphate production;

[0041] Figure 2 A schematic diagram of a system for treating wastewater from iron phosphate production according to the present invention is shown.

[0042] 01-the second integrated flocculation reaction sedimentation water purifier; 02-wash water UF membrane system; 03-wash water RO membrane system; 04-impurity removal reaction tank; 05-the first integrated flocculation reaction sedimentation water purifier; 06-the second pH adjustment tank; 07-mother liquor UF membrane system; 08-first mother liquor RO membrane system; 09-MVR system; 10-second mother liquor RO membrane system; 11-first pH adjustment tank; 12-first clean water RO membrane system; 13-second clean water RO membrane system. DETAILED DESCRIPTION

[0043] The present disclosure will now be discussed with reference to several exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and thus implement the present disclosure, rather than implying any limitation on the scope of the present disclosure.

[0044] As used herein, the term "including" and its variants are to be interpreted as open-ended terms meaning "including but not limited to". The term "based on" is to be interpreted as "based at least in part on". The terms "one embodiment" and "an embodiment" are to be interpreted as "at least one embodiment". The term "another embodiment" is to be interpreted as "at least one other embodiment". The orientation or position relationship indicated by the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "vertical", "horizontal", "lateral", "longitudinal" and the like is based on the orientation or position relationship shown in the accompanying drawings. These terms are mainly for better describing the present application and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation. In addition, in addition to being used to indicate an orientation or position relationship, some of the above terms may also be used to indicate other meanings, such as the term "upper" may also be used to indicate a certain dependency or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to the specific circumstances. In addition, the terms "install", "set", "provided with", "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection, or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be an internal connection between two devices, elements or components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to the specific circumstances. In addition, the terms "first", "second", etc. are mainly used to distinguish different devices, elements or components (the specific types and structures may be the same or different), and are not used to indicate or imply the relative importance and quantity of the indicated devices, elements or components. Unless otherwise specified, "plurality" means two or more.

[0045] According to the first aspect of the present invention, this embodiment discloses a method for treating wastewater from iron phosphate production, such as Figure 1 As shown, the following steps are included:

[0046] The first concentrated water and the first fresh water are obtained by first desalting the wastewater produced by the iron phosphate production;

[0047] The first concentrated water is combined with the mother liquor to obtain a first combined liquid, the pH of the first fresh water is increased to a pH value that meets the requirements of the reused water under the first pH condition, the first fresh water is subjected to a second desalination to obtain second fresh water, and the second fresh water is recovered;

[0048] The first combined liquid is subjected to a second pH condition to remove the first type of impurities to obtain the first produced water and the first sludge;

[0049] The pH of the first produced water under the second pH condition is reduced under the acidic condition, and the first produced water after the pH is reduced is subjected to the third desalination to obtain the third concentrated water and the third fresh water;

[0050] The third concentrated water is sent to MVR for evaporation and crystallization recovery, and the third fresh water is subjected to the fourth desalination to obtain the fourth fresh water;

[0051] The fourth fresh water is combined with the first fresh water for desalination, or the fourth fresh water is subjected to a second desalination under the first pH condition;

[0052] The first type of impurities include ammonium, magnesium, phosphorus or suspended matter;

[0053] The pH value of the first pH condition is less than or equal to the pH value of the second pH condition.

[0054] In this embodiment, since the wastewater from the production of iron phosphate is acidic, in order to meet the pH requirements of the recycled water, the pH of the water after desalting the wastewater from the production of iron phosphate is increased under the first pH condition to meet the pH requirement of 6-7 for the production of iron phosphate. At the same time, since the fourth fresh water is obtained by desalting the acidic third fresh water obtained by the first produced water under acidic conditions, the pH of the fourth fresh water is also increased by setting the first pH condition, and the second fresh water meets the inlet pH requirements for water treatment by the membrane system by setting the first pH condition. By setting the second pH condition, the ammonium radical, magnesium ion, and phosphate radical in the first combined liquid react to form magnesium ammonium phosphate precipitate, effectively removing magnesium ions and phosphate ions, and providing favorable conditions for MVR evaporation and crystallization to obtain ammonium sulfate. By setting the acidic condition, the third concentrated water and the third fresh water also meet the inlet pH requirements for water treatment by the membrane system and the MVR system. Among the first type of impurities, ammonium is ammonium radical, magnesium is magnesium ion, and phosphorus is phosphate radical. The water quality of the second fresh water is TDS≤10mg / L, pH6-7, Mg 2+ 0mg / L, Ca 2+ 0mg / L, Mn2+ 0mg / L, NH 4+ ≤2.4mg / L,

[0055] According to one embodiment of the present invention, the process of removing the first type of impurities includes:

[0056] Ammonia water is provided to increase the pH of the first concentrated water to 6.5-7, and first sludge containing first-class impurities and first produced water from which the first-class impurities are removed are obtained through flocculation separation.

[0057] In this embodiment, by removing the first impurity after adding ammonia water, no new ions are introduced, the purity of water quality is guaranteed, and there is no influence on the subsequent MVR crystal salt.

[0058] Preferably, a PAM flocculant is also provided during the process of removing the first type of impurities to further increase the flocculation effect. Preferably, the amount of flocculant added is 3-5 ppm.

[0059] According to one embodiment of the present invention, the process of performing the third desalination comprises:

[0060] Sulfur-containing acid is provided to reduce the pH of the first produced water to 4-5, and a third concentrated water containing salt compounds is obtained through reverse osmosis separation, and a third fresh water is separated from the salt compounds.

[0061] Preferably, the sulfur-containing acid is sulfuric acid. By adding sulfuric acid to adjust the pH of the first produced water, the dosing in this example does not introduce new ions, further ensuring the purity of the water quality and having no effect on the MVR crystal salt.

[0062] According to one embodiment of the present invention, the process of performing the second desalination comprises:

[0063] Ammonia water is provided to increase the pH of the first fresh water and / or the fourth fresh water to 6-7, and second fresh water with salt compounds removed is obtained by reverse osmosis separation, wherein the TDS of the second fresh water is ≤10.

[0064] According to one embodiment of the present invention, the process of performing the first desalination comprises:

[0065] After removing the second impurities from the wastewater produced by iron phosphate production, the second produced water and the second sludge are obtained;

[0066] The second produced water is separated by ultrafiltration and reverse osmosis to obtain first concentrated water containing salt compounds and first fresh water with the salt compounds removed.

[0067] According to one embodiment of the present invention, the amount of the third concentrated water sent to the MVR evaporation crystallization is less than or equal to 31.6% of the sum of the inflow of ferric phosphate production wastewater and the inflow of mother liquor.

[0068] According to the second aspect of the present invention, this embodiment discloses a system for treating wastewater from iron phosphate production, such as Figure 2 As shown, including:

[0069] A first impurity removal system, a second impurity removal system, a first desalination system, a second desalination system, a third desalination system, a fourth desalination system and an MVR system 09;

[0070] The first impurity removal system includes an impurity removal reaction tank 04 and a first integrated flocculation reaction precipitation water purifier 05;

[0071] The second impurity removal system includes a second integrated flocculation reaction precipitation water purifier 01;

[0072] The first desalination system includes a wash water UF membrane system 02 and a wash water RO membrane system 03;

[0073] The second desalination system includes a first pH adjustment tank 11, a primary clean water RO membrane system 12 and a secondary clean water RO membrane system 13;

[0074] The third desalination system includes a second pH adjustment tank 06, a mother liquor UF membrane system 07, and a primary mother liquor RO membrane system 08;

[0075] The fourth desalination system includes a secondary mother liquor RO membrane system 10;

[0076] The liquid outlet of the second integrated flocculation reaction precipitation water purifier 01 is connected to the liquid inlet of the wash water UF membrane system 02, the fresh water outlet of the wash water UF membrane system 02 is connected to the liquid inlet of the wash water RO membrane system 03, the fresh liquid outlet of the wash water RO membrane system 03 is connected to the liquid inlet of the first pH regulating tank 11, the concentrated liquid outlet of the wash water RO membrane system 03 is connected to the liquid inlet of the impurity removal reaction tank 04, the liquid outlet of the impurity removal reaction tank 04 is connected to the liquid inlet of the first integrated flocculation reaction precipitation water purifier 05, the liquid outlet of the first integrated flocculation reaction precipitation water purifier 05 is connected to the liquid inlet of the second pH regulating tank 06, and the liquid outlet of the second pH regulating tank 06 is connected to The liquid inlet of the mother liquor UF membrane system 07 is connected, the dilute liquid outlet of the mother liquor UF membrane system 07 is connected to the liquid inlet of the primary mother liquor RO membrane system 08, the concentrated liquid outlet of the primary mother liquor RO membrane system 08 is connected to the liquid inlet of the MVR system 09, the dilute liquid outlet of the primary mother liquor RO membrane system 08 is connected to the liquid inlet of the secondary mother liquor RO membrane system 10, the dilute liquid outlet of the secondary mother liquor RO membrane system 10 is connected to the liquid inlet of the first pH regulating tank 11, the liquid outlet of the first pH regulating tank 11 is connected to the liquid inlet of the primary clean water RO membrane system 12, and the dilute liquid outlet of the primary clean water RO membrane system 12 is connected to the liquid inlet of the secondary clean water RO membrane system 13.

[0077] When carrying out this embodiment, the liquid inlet of the second integrated flocculation reaction precipitation water purifier 01 is connected to the iron phosphate production wastewater supply port, the liquid outlet of the second integrated flocculation reaction precipitation water purifier 01 is connected to the liquid inlet of the wash water UF membrane system 02, the fresh water inlet of the wash water UF membrane system 02 is connected to the liquid inlet of the wash water RO membrane system 03, the concentrated water outlet of the wash water UF membrane system 02 is connected to the liquid inlet of the second integrated flocculation reaction precipitation water purifier 01, the fresh liquid outlet of the wash water RO membrane system 03 is connected to the liquid inlet of the first pH regulating tank 11, and the wash water UF membrane system 03 is connected to the liquid inlet of the second integrated flocculation reaction precipitation water purifier 01. The concentrated liquid outlet of the water RO membrane system 03 is connected to the liquid inlet of the impurity removal reaction tank 04, and the liquid inlet of the impurity removal reaction tank 04 is connected to the mother liquid supply port, the liquid outlet of the impurity removal reaction tank 04 is connected to the liquid inlet of the first integrated flocculation reaction precipitation water purifier 05, the liquid outlet of the first integrated flocculation reaction precipitation water purifier 05 is connected to the liquid inlet of the second pH adjustment tank 06, the liquid outlet of the second pH adjustment tank 06 is connected to the liquid inlet of the mother liquid UF membrane system 07, and the dilute liquid outlet of the mother liquid UF membrane system 07 is connected to the primary mother liquid RO membrane system 08. The concentrated liquid outlet of the mother liquor UF membrane system 07 is connected to the liquid inlet of the impurity removal reaction tank 04, the concentrated liquid outlet of the primary mother liquor RO membrane system 08 is connected to the liquid inlet of the MVR system 09, the condensed water outlet of the MVR system 09 is connected to the liquid inlet of the first pH regulating tank 11, the dilute liquid outlet of the primary mother liquor RO membrane system 08 is connected to the liquid inlet of the secondary mother liquor RO membrane system 10, the dilute liquid outlet of the secondary mother liquor RO membrane system 10 is connected to the liquid inlet of the first pH regulating tank 11, and the concentrated liquid of the secondary mother liquor RO membrane system 10 is connected to the liquid inlet of the first pH regulating tank 11. The outlet is connected to the liquid inlet of the wash water UF membrane system 02, the liquid outlet of the first pH adjusting tank 11 is connected to the liquid inlet of the first-level clean water RO membrane system 12, the dilute liquid outlet of the first-level clean water RO membrane system 12 is connected to the liquid inlet of the second-level clean water RO membrane system 13, the concentrated liquid outlet of the first-level clean water RO membrane system 12 is connected to the liquid inlet of the second-level mother liquid RO membrane system 10, the concentrated water outlet of the second-level clean water RO membrane system 13 is connected to the liquid inlet of the first pH adjusting tank 11, and the fresh water outlet of the second-level clean water RO membrane system 13 is connected to the recycled water supply end.

[0078] In this embodiment, through the setting of the second integrated flocculation reaction sedimentation water purifier 01, UF membrane system, and RO membrane system, the concentrated water obtained by treating the iron phosphate production wastewater is combined with the mother liquor, and the TDS of the concentrated water after pH adjustment and then passing through the first integrated flocculation reaction sedimentation water purifier 05, UF membrane system, and RO membrane system is increased, and the amount of concentrated water sent to the MVR is reduced. The setting of the iron phosphate production wastewater system in this embodiment can achieve the requirement of zero sewage discharge and improve complete resource utilization.

[0079] Preferably, the pore size of the UF membrane is 0.001-0.01 μm, and the pore size of the RO membrane is 0.0001-0.0005 μm.

[0080] Preferably, the integrated flocculation reaction sedimentation water purifier includes a cyclone reaction zone, a suspension clarification zone, an inclined tube sedimentation zone and a sludge concentration zone, and the sludge concentration zone is provided with quartz sand and manganese sand, so as to have a dual filtering effect and increase the filtering effect. It also provides favorable water treatment conditions for the normal and stable operation of the membrane elements of the subsequent membrane system, and prolongs the cleaning cycle and life of the membrane system.

[0081] According to one embodiment of the present invention, the impurity removal reaction tank 04 is equipped with a first alkali adding device, the water inlet pipe of the first integrated flocculation reaction precipitation water purifier 05 is equipped with a flocculant adding device, the first pH adjustment tank 11 is equipped with a second alkali adding device, and the second pH adjustment tank 06 is equipped with an acid adding device.

[0082] In this embodiment, it is convenient to supply medicine.

[0083] According to one embodiment of the present invention, the membrane elements of the UF membrane system and the RO membrane system are special anti-pollution, acid-resistant and alkali-resistant membranes.

[0084] In this embodiment, the service life of the membrane system is extended.

[0085] According to one embodiment of the present invention, a sludge filter press system is included, wherein the sludge inlet is connected to the sludge outlets of the first integrated flocculation reaction sedimentation water purifier 05 and the second integrated flocculation reaction sedimentation water purifier 01 .

[0086] In this embodiment, it is convenient to further recover the sludge produced by the first integrated flocculation reaction sedimentation water purifier 05 and the second integrated flocculation reaction sedimentation water purifier 01 .

[0087] Example 1

[0088] The method for treating wastewater from ammonium ferric phosphate production comprises the following steps:

[0089] Provide ammonium ferric phosphate production wastewater, the water quality of the wash water is TDS ≥ 32000, pH 2-4, turbidity ≤ 500NTU.

[0090] The iron phosphate production wastewater is sent to the second integrated flocculation reaction sedimentation water purifier 01, and the first produced water and the sludge containing impurities are obtained by removing the larger suspended matter and other impurities in the water. The first produced water is desalted and concentrated by the wash water UF membrane system 02 to remove the suspended matter, colloidal macromolecular organic matter and the like in the water to obtain the wash water UF membrane concentrated water and the wash water UF membrane fresh water. The wash water UF membrane concentrated water is returned to the second integrated flocculation reaction sedimentation water purifier 01, and the wash water UF membrane fresh water is desalted and concentrated by the wash water RO membrane system 03 to obtain the first Concentrated water and first fresh water, the first fresh water reacts with ammonia water in the first pH regulating tank 11, after the pH of the first fresh water is increased, the first fresh water is concentrated through the desalination membrane of the primary clean water RO membrane system 12 to obtain primary clean water RO membrane concentrated water and primary clean water RO membrane fresh water, the primary clean water RO membrane fresh water is desalted and concentrated through the secondary clean water RO membrane system 13 to obtain second concentrated water and second fresh water, the second concentrated water returns to the primary clean water RO membrane system 12, the second fresh water meets the production water standard, and the second fresh water is recovered as production water.

[0091] The second concentrated water and the mother liquor are combined in the impurity removal reaction tank 04 to obtain a first combined liquid. Ammonia water is added to the impurity removal reaction tank 04, the pH of the first combined liquid is increased, and the ammonium ions, magnesium ions and phosphate ions in the first combined liquid react to form magnesium ammonium phosphate precipitate. The combined liquid is then sent to the first integrated flocculation reaction precipitation water purifier 05. The first integrated flocculation reaction precipitation water purifier 05 removes impurities such as larger suspended solids and magnesium ammonium phosphate precipitate in the water to obtain second produced water and second sludge. The second produced water reacts with sulfuric acid in the second desalination, the pH of the second produced water is reduced, and the second produced water The water is desalted and concentrated by the mother liquor UF membrane system 07 to further remove impurities such as suspended matter, colloids, and macromolecular organic matter in the water to obtain mother liquor UF membrane concentrated water and mother liquor UF membrane fresh water. The mother liquor UF membrane concentrated water is returned to the impurity removal reaction tank 04. The mother liquor UF membrane fresh water is desalted and concentrated by the primary mother liquor RO membrane system 08 to obtain third concentrated water and third fresh water. The third concentrated water is sent to the MVR system 09. The MVR system 09 evaporates and crystallizes the third concentrated water to obtain ammonium sulfate. The MVR evaporated condensate is sent to the first pH adjustment tank 11 for subsequent recovery. The ammonium sulfate is used as a fertilizer raw material. The third fresh water is desalted and concentrated by the secondary mother liquor RO membrane system 10 to obtain the fourth concentrated water and the fourth fresh water. The fourth concentrated water is returned to the wash water UF membrane system 02. The fourth fresh water is combined with the first fresh water to obtain a second combined liquid. The second combined liquid is reacted with ammonia water in the first pH adjustment tank 11 and then subjected to desalination and concentration by the primary clean water RO membrane system 12 and the secondary clean water RO membrane system 13 in sequence to obtain the second fresh water. The second fresh water is recovered, wherein the primary clean water RO membrane concentrated water is returned to the secondary mother liquor RO membrane system 10 for desalination and concentration.

[0092] The first sludge and the second sludge are subjected to subsequent magnesium ammonium phosphate recovery treatment through the sludge filter press system, the sludge water generated by the first sludge is returned to the first integrated flocculation reaction sedimentation water purifier 05, and the sludge water generated by the second sludge is returned to the second integrated flocculation reaction sedimentation water purifier 01.

[0093] The water quality in each step of Example 1 is shown in Table 1 and Table 2:

[0094] Table 1 Comparison of water quality before and after treatment of ferric phosphate production wastewater (I)

[0095]

[0096]

[0097] Table 2 Comparison of water quality before and after treatment of ferric phosphate production wastewater (II)

[0098]

[0099] Note: The data of the first combined solution and the second combined solution are the data after adding the drug.

[0100] As can be seen from Table 1, the first concentrated water and mother liquor are treated by pretreatment and membrane system concentration, and the concentrated liquid is sent to MVR for crystallization and evaporation. The evaporated condensate is then returned to the clean water reverse osmosis system for treatment, achieving true zero emission and effectively reducing the environmental burden of the production site. The present invention not only improves the water quality standard by adding ammonia water to remove impurities and adjust the pH, but also increases the recovery rate of fresh water without introducing new ions, so that the fresh water recovery rate reaches more than 96%, greatly reducing the scale of water intake for enterprises. The first concentrated water and mother liquor are treated by an integrated flocculation reaction precipitation water purifier and concentrated by a membrane system. The amount of concentrated water sent to the MVR is 31.6% of the sum of the washing water inlet and the mother liquor inlet, so that the scale of the back-end MVR is effectively controlled. Compared with the traditional process, the MVR scale reduces the amount of water processed by 68.4%, reducing the investment cost and operating cost of the subsequent process. The investment cost of the MVR section is calculated based on the water inlet, which is equivalent to 490,000 yuan / m 3 The operating cost is calculated based on the water intake, which is equivalent to 32 yuan / m 3 ), the method for treating wastewater from the production of ferrous phosphate not only saves a lot of expenses for enterprises, but also actively responds to the national policy of energy conservation and emission reduction. The third fresh water meets the enterprise's requirements for recycled water, and the third concentrated water TDS ≥ 185000 mg / L can effectively improve the evaporation efficiency of MVR. Compared with conventional treatment processes, the energy consumption per ton of water treatment in the present invention is reduced by 45%-50%.

[0101] The present invention combines the concentrated water after desalination and concentration of ferric phosphate production wastewater with the mother liquor, removes impurities and performs reverse osmosis membrane desalination and concentration treatment, greatly improving the TDS content of MVR inlet water (production wash water TDS 32000mg / L, production mother liquor TDS 96000mg / L, and the final membrane concentration into the MVR concentrated water TDS ≥ 185000mg / L), and the wastewater reduction effect is significant (production wash water + mother liquor total 600m 3 / h, external MVR concentrated water 190m 3 / h), effectively reducing the construction and operation costs of enterprises and achieving effective complementarity between environmental protection and economy.

[0102] Those skilled in the art will appreciate that the above-mentioned embodiments are specific examples for implementing the present disclosure, and in actual applications, various changes may be made thereto in form and detail without departing from the scope of the present disclosure.

Claims

1. A method for treating wastewater from ferric phosphate production, characterized in that: include: The first concentrated water and the first fresh water are obtained by first desalting the wastewater produced by the iron phosphate production; The first concentrated water is combined with the mother liquor to obtain a first combined liquid, the pH of the first fresh water is increased to a pH value that meets the requirements of the reused water under the first pH condition, the first fresh water is subjected to a second desalination to obtain second fresh water, and the second fresh water is recovered; The first combined liquid is subjected to a second pH condition to remove the first type of impurities to obtain the first produced water and the first sludge; The pH of the first produced water under the second pH condition is reduced under the acidic condition, and the first produced water after the pH is reduced is subjected to the third desalination to obtain the third concentrated water and the third fresh water; The third concentrated water is sent to MVR for evaporation and crystallization recovery, and the third fresh water is subjected to the fourth desalination to obtain the fourth fresh water; The fourth fresh water is combined with the first fresh water for desalination, or the fourth fresh water is subjected to a second desalination under the first pH condition; The first type of impurities include ammonium, magnesium, phosphorus or suspended matter; The pH value of the first pH condition is less than or equal to the pH value of the second pH condition, and the pH value of the first pH condition is greater than the pH value of the acidic condition.

2. A method for treating wastewater from iron phosphate production according to claim 1, characterized in that: The process of removing the first type of impurities comprises: Ammonia water is provided to increase the pH of the first concentrated water to 6.5-7, and first sludge containing first-class impurities and first produced water from which the first-class impurities are removed are obtained through flocculation separation.

3. A method for treating wastewater from iron phosphate production according to claim 1, characterized in that: The process of carrying out the third desalination comprises: Sulfur-containing acid is provided to reduce the pH of the first produced water to 4-5, and a third concentrated water containing salt compounds is obtained through reverse osmosis separation, and a third fresh water is separated from the salt compounds.

4. The method for treating wastewater from ferric phosphate production according to claim 1, characterized in that: The process of performing the second desalination comprises: Ammonia water is provided to increase the pH of the first fresh water and / or the fourth fresh water to 6-7, and second fresh water with salt compounds removed is obtained by reverse osmosis separation, wherein the TDS of the second fresh water is ≤10.

5. The method for treating wastewater from ferric phosphate production according to claim 1, characterized in that: The process of performing the first desalination comprises: After removing the second impurities from the wastewater produced by iron phosphate production, the second produced water and the second sludge are obtained; The second produced water is separated by ultrafiltration and reverse osmosis to obtain first concentrated water containing salt compounds and first fresh water with the salt compounds removed.

6. The method for treating wastewater from ferric phosphate production according to claim 1, characterized in that: The amount of the third concentrated water sent to the MVR evaporation crystallization is less than or equal to 31.6% of the sum of the inflow of ferric phosphate production wastewater and the inflow of mother liquor.

7. A system for treating wastewater from iron phosphate production, characterized in that: include: A first impurity removal system, a second impurity removal system, a first desalination system, a second desalination system, a third desalination system, a fourth desalination system and an MVR system; The first impurity removal system includes an impurity removal reaction tank and a first integrated flocculation reaction precipitation water purifier; The second impurity removal system includes a second integrated flocculation reaction precipitation water purifier; The first desalination system includes a wash water UF membrane system and a wash water RO membrane system; The second desalination system includes a first pH adjustment tank, a primary clean water RO membrane system and a secondary clean water RO membrane system; The third desalination system includes a second pH adjustment tank, a mother liquor UF membrane system, and a primary mother liquor RO membrane system; The fourth desalination system includes a secondary mother liquor RO membrane system; The liquid outlet of the second integrated flocculation reaction precipitation water purifier is connected to the liquid inlet of the wash water UF membrane system, the fresh water outlet of the wash water UF membrane system is connected to the liquid inlet of the wash water RO membrane system, the fresh liquid outlet of the wash water RO membrane system is connected to the liquid inlet of the first pH regulating tank, the concentrated liquid outlet of the wash water RO membrane system is connected to the liquid inlet of the impurity removal reaction tank, the liquid outlet of the impurity removal reaction tank is connected to the liquid inlet of the first integrated flocculation reaction precipitation water purifier, the liquid outlet of the first integrated flocculation reaction precipitation water purifier is connected to the liquid inlet of the second pH regulating tank, and the liquid outlet of the second pH regulating tank is connected to The liquid inlet of the mother liquor UF membrane system is connected, the dilute liquid outlet of the mother liquor UF membrane system is connected to the liquid inlet of the first-level mother liquor RO membrane system, the concentrated liquid outlet of the first-level mother liquor RO membrane system is connected to the liquid inlet of the MVR system, the dilute liquid outlet of the first-level mother liquor RO membrane system is connected to the liquid inlet of the second-level mother liquor RO membrane system, the dilute liquid outlet of the second-level mother liquor RO membrane system is connected to the liquid inlet of the first pH regulating tank, the liquid outlet of the first pH regulating tank is connected to the liquid inlet of the first-level clean water RO membrane system, and the dilute liquid outlet of the first-level clean water RO membrane system is connected to the liquid inlet of the second-level clean water RO membrane system.

8. A ferric phosphate production wastewater treatment system according to claim 7, characterized in that: The impurity removal reaction tank is equipped with a first alkali adding device, the water inlet pipe of the first integrated flocculation reaction precipitation water purifier is equipped with a flocculant adding device, the first pH adjustment tank is equipped with a second alkali adding device, and the second pH adjustment tank is equipped with an acid adding device.

9. A ferric phosphate production wastewater treatment system according to claim 7, characterized in that: The membrane elements of the UF membrane system and the RO membrane system are special anti-pollution, acid-resistant and alkali-resistant membranes.

10. A ferric phosphate production wastewater treatment system according to claim 7, characterized in that: It comprises a sludge filter press system, wherein the sludge inlet is connected to the sludge outlets of the first integrated flocculation reaction sedimentation water purifier and the second integrated flocculation reaction sedimentation water purifier.

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