A cyclic concentration device and its application

Abstract

The present invention provides a cyclic concentration device, which includes a stirring tank, a cyclic concentration tank and a cross-flow filtration membrane mechanism. The feed inlet of the cyclic concentration tank is connected to the discharge outlet of the stirring tank. The discharge outlet of the cyclic concentration tank is respectively connected to the feed inlet of the cross-flow filtration membrane mechanism and the feed inlet of the stirring tank. The discharge outlet of the cross-flow filtration membrane mechanism is connected to the cyclic feed inlet of the cyclic concentration tank. The present invention can be used for the pretreatment of iron phosphate mother liquor, shortening the process flow, reducing the floor area and lowering the equipment failure rate. The present invention can also be used for the cleaning of iron phosphate products. The washing water is completely mixed with the iron phosphate products or intermediate products, in full contact, thoroughly cleaned, and an iron phosphate slurry with impurity ions meeting the requirements is obtained, which can save water consumption, achieve full-automatic operation, save labor, and is simple to operate. The present invention realizes that one set of equipment has two uses, reducing the production cost.

Description

Technical Field

[0001] The present invention relates to the technical field of battery production, and particularly relates to a circulating concentration device and its application. Background Art

[0002] Lithium iron phosphate is an important cathode material for batteries. With the rapid development of the electric vehicle industry, the market demand for lithium iron phosphate has gradually increased. Ferric phosphate, as one of the precursors for the synthesis of lithium iron phosphate, its quality has an important impact on the performance of lithium iron phosphate.

[0003] A typical production process of ferric phosphate is as follows: a reaction kettle is used for the reaction of ferrous sulfate solution, hydrogen peroxide, and monoammonium phosphate solution to obtain a precipitate, and the precipitate is washed to remove impurities to obtain ferric phosphate precipitate; the washed ferric phosphate is re-slurried and aged, then washed again, and dried to obtain the product ferric phosphate.

[0004] In this process, it is necessary to press the ferric phosphate reaction slurry to discharge the reaction mother liquor, and the formed filter cake is washed twice. Therefore, a large amount of mother liquor and rinsing water will be discharged during the production process of ferric phosphate. The mother liquor and washing water contain phosphate radicals, hydrogen ions, and metal ions such as manganese, magnesium, calcium, iron, and aluminum.

[0005] After these mother liquor and rinsing water are discharged into the wastewater treatment section, a pretreatment process of adding medicine + neutralization stirring tank reaction + high-density clarifier + filter + ultrafiltration is adopted. The ultrafiltration produced water after that enters the reverse osmosis process, and the reverse osmosis produced water is further treated and then returned to the ferric phosphate production process to wash the product.

[0006] The current pretreatment process route of adding medicine + neutralization stirring tank reaction + high-density clarifier + filter + ultrafiltration commonly used for the pretreatment of ferric phosphate production mother liquor and washing water has the following disadvantages:

[0007] 1. The mixing efficiency of the stirring tank reaction is low, requiring a larger reaction volume and a higher ammonia water dosage;

[0008] 2. The mother liquor and washing water directly react with ammonia water, and there is no coagulation nucleus in the reaction system, resulting in tiny particles of manganese phosphate, magnesium ammonium phosphate, ferric phosphate, and calcium phosphate being formed, with poor precipitation effect, and the formed slurry having poor fluidity, which easily causes blockage of the high-density clarifier;

[0009] 3. The water treatment load of the high-density clarifier and filter is small, resulting in a large floor area for the water treatment structures.

[0010] Meanwhile, during the production process of iron phosphate, the iron phosphate needs to be washed twice. The washing effect has an important impact on the purity and quality of the iron phosphate product. Currently, the filtration and washing of iron phosphate are usually carried out using a plate and frame filter press. The iron phosphate slurry is filtered using the plate and frame filter press, and then pure water is injected into the filter plate to wash the filter cake. The main problems existing in the current washing method are as follows:

[0011] 1. When using a plate and frame filter press to wash the filter cake, due to problems such as intermediate short-circuit or uneven cleaning water flow, the iron product may not be washed thoroughly. After the existing iron phosphate filter cake is washed, there will still be a small amount of impurities in the filter cake, which affects the quality of iron phosphate;

[0012] 2. The washing operation using a plate and frame filter press is complex, and there are problems such as intermittent operation and high labor intensity of operation.

[0013] 3. When using a plate and frame filter press for washing, there are problems such as product loss caused by the penetration of iron phosphate particles through the filter and an increase in the turbidity of the rinsing wastewater.

[0014] 4. The particle size of the iron phosphate product particles generally ranges from a few hundred nanometers to a few micrometers. These fine particles are in a compacted state in the plate and frame filter press, making it difficult to clean. To meet the cleaning standards, a large amount of high-temperature pure water must be used, and the corresponding amount of washing water to be treated is also very high, increasing the production cost of iron phosphate.

[0015] 5. The manual operation is complex, and re-slurrying filtration and manual plate discharging are required during the two washing processes.

[0016] Currently, two different sets of equipment are required for the pretreatment of the iron phosphate production mother liquor and washing water and the cleaning of the iron phosphate product, increasing the production cost. Summary of the Invention

[0017] The present invention aims to solve at least one of the technical problems in the related art to a certain extent. For this reason, an embodiment of the present invention provides a circulating concentration device and its application, which can be used for the pretreatment of the iron phosphate production mother liquor and washing water, and can also be used for the cleaning of the iron phosphate product, reducing the production cost.

[0018] An embodiment of the first aspect of the present invention provides a circulating concentration device, comprising: a stirring tank, a circulating concentration tank and a cross-flow filtration membrane mechanism. The stirring tank has a first feed inlet, a second feed inlet and a discharge outlet, and a first stirring device is provided in the stirring tank; the circulating concentration tank has a feed inlet, a circulating feed inlet and a discharge outlet, the first feed inlet of the circulating concentration tank is connected to the discharge outlet of the stirring tank, and a second stirring device is provided in the circulating concentration tank; the cross-flow filtration membrane mechanism has a feed inlet, a water outlet and a discharge outlet, the discharge outlet of the circulating concentration tank is respectively connected to the feed inlet of the cross-flow filtration membrane mechanism and the feed inlet of the stirring tank, a concentrated liquid discharge valve is connected to the circulating concentration tank, and the discharge outlet of the cross-flow filtration membrane mechanism is connected to the circulating feed inlet of the circulating concentration tank.

[0019] In some embodiments, the cross-flow filtration membrane mechanism includes a microfiltration membrane.

[0020] In some embodiments, the feed inlet of the stirring tank is connected to a lift pump through a pipeline, and an impeller for mixing materials is provided inside the lift pump.

[0021] In some embodiments, the discharge outlet of the circulating concentration tank is connected to a concentrated liquid circulation pump.

[0022] In some embodiments, the discharge outlet of the circulating concentration tank is connected to the feed inlet of the stirring tank through a first pipeline, the discharge outlet of the circulating concentration tank is connected to the feed inlet of the cross-flow filtration membrane mechanism through a second pipeline, a first regulating valve is connected to the first pipeline, a second regulating valve is connected to the second pipeline, and a concentrated liquid discharge valve is connected to the circulating concentration tank.

[0023] In some embodiments, an aeration device is provided in the circulating concentration tank.

[0024] In some embodiments, the circulating concentration device further includes a backwashing device, and the backwashing device performs backwashing on the filtration membrane in the cross-flow filtration membrane mechanism.

[0025] In some embodiments, the circulating concentration device further includes a chemical cleaning device, and the chemical cleaning device performs chemical cleaning on the filtration membrane in the cross-flow filtration membrane mechanism.

[0026] An embodiment of the second aspect of the present invention provides an application of the above-mentioned circulating concentration device in the pretreatment of iron phosphate mother liquor, comprising the following steps:

[0027] After the iron phosphate mother liquor and ammonia water are mixed by a lift pump, they are introduced into a stirring tank for reaction to generate a reaction feed liquid; the reaction feed liquid is introduced into a circulating concentration tank and mixed with the concentrated liquid filtered by a cross-flow filtration membrane mechanism to form a reaction feed liquid circulating concentrated liquid; a part of the reaction feed liquid circulating concentrated liquid is returned to the lift pump, mixed with the iron phosphate mother liquor and ammonia water, and then jointly introduced into the stirring tank. The remaining part of the reaction feed liquid circulating concentrated liquid is introduced into the cross-flow filtration membrane mechanism for circulating concentration. The fresh water in the reaction feed liquid circulating concentrated liquid is discharged and introduced into a reverse osmosis system. After the reverse osmosis product water is further treated, it is recycled to the iron phosphate production system for flushing the iron phosphate product; the reaction feed liquid circulating concentrated liquid after filtering out part of the water returns to the circulating concentration tank again, is mixed with the feed liquid, and circulates reciprocally. The concentration of the reaction feed liquid circulating concentrated liquid of the iron phosphate mother liquor is gradually increased. When it is increased to a certain concentration, part of it is discharged from the circulating concentration tank.

[0028] The third aspect embodiment of the present invention proposes an application of the above-mentioned circulating concentration device in the cleaning of iron phosphate products, including the following steps:

[0029] The iron phosphate product or intermediate product to be cleaned and the washing water are introduced into a circulating concentration tank for stirring washing and aeration washing to form a circulating water washing slurry; the circulating water washing slurry is introduced into a cross-flow filtration membrane mechanism for circulating filtration, and part of the washing water and soluble impurities in the circulating water washing slurry are discharged; the circulating water washing slurry after filtering out part of the washing water and soluble impurities returns to the circulating concentration tank again, is mixed with the washing water newly added to the circulating concentration tank, and circulates reciprocally until the conductivity of the discharged washing water is lower than the set value, then the cleaning is completed, and the cleaned iron phosphate product or intermediate product is discharged to the subsequent process section. Description of the Drawings

[0030] The above-mentioned and / or additional aspects and advantages of the present invention will become obvious and easy to understand from the following description of the embodiments in conjunction with the drawings.

[0031] Wherein:

[0032] Figure 1 is a schematic structural diagram of the circulating concentration device according to the embodiment of the present invention;

[0033] Reference numerals:

[0034] 1, lift pump; 2, stirring tank; 3, circulating concentration tank; 4, concentrated liquid circulating pump; 5, cross-flow filtration membrane mechanism; 6, first regulating valve; 7, second regulating valve; 8, concentrated liquid discharge valve. Detailed Embodiments

[0035] Embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the accompanying drawings. The embodiments described below by referring to the accompanying drawings are exemplary and are intended to explain the present invention, and should not be construed as a limitation of the present invention.

[0036] The circulating concentration device and its application in the embodiments of the present invention will be described below with reference to the accompanying drawings.

[0037] As Figure 1 shown, an embodiment of the first aspect of the present invention provides a circulating concentration device, including: a stirring tank 2, a circulating concentration tank 3 and a cross-flow filtration membrane mechanism 5. The stirring tank 2 has a feed inlet and a discharge outlet, and a first stirring device is provided in the stirring tank 2; the circulating concentration tank 3 has a first feed inlet, a second feed inlet, a circulating feed inlet and a discharge outlet. The first feed inlet of the circulating concentration tank 3 is connected to the discharge outlet of the stirring tank 2. The second feed inlet of the circulating concentration tank 3 is used to introduce the iron phosphate product or intermediate product to be cleaned and washing water. A second stirring device is provided in the circulating concentration tank 3; the cross-flow filtration membrane mechanism 5 has a feed inlet, a water outlet and a discharge outlet. The discharge outlet of the circulating concentration tank 3 is respectively connected to the feed inlet of the cross-flow filtration membrane mechanism 5 and the feed inlet of the stirring tank 2. A concentrated liquid discharge valve 8 is connected to the circulating concentration tank 3, and the discharge outlet of the cross-flow filtration membrane mechanism 5 is connected to the circulating feed inlet of the circulating concentration tank 3.

[0038] The circulating concentration device of the embodiments of the present invention can be used not only for the pretreatment of iron phosphate mother liquor, but also for the cleaning of iron phosphate slurry, to obtain an iron phosphate slurry with impurity ions meeting the requirements, realizing that one set of equipment has two uses and reducing production costs.

[0039] The circulating concentration device of the embodiments of the present invention is not limited to the above two uses, and can also be widely applied in the chemical field, the biological medicine field, etc.

[0040] The concentrated liquid discharge valve 8 is used to discharge the iron phosphate product or intermediate product after the cleaning is completed and the iron phosphate mother liquor (or washing water) after the pretreatment is completed to the subsequent process section. When the slurry in the circulating concentration tank 3 is concentrated to a certain extent, the concentrated liquid discharge valve 8 is opened to discharge part of the slurry. The opening degree of the concentrated liquid discharge valve 8 can also be adjusted according to the operating conditions to realize the continuous discharge of the concentrated slurry in the circulating concentration tank 3 at a certain ratio.

[0041] Further, the stirring tank 2 and the circulating concentration tank 3 are combined and arranged, so that the material after reaction or cleaning in the stirring tank 2 can quickly enter the circulating concentration tank 3 for circulating concentration treatment, improving the efficiency.

[0042] Further, the stirring tank 2 and the circulating concentration tank 3 are separated by a partition, and an overflow port is opened on the partition for feeding the slurry in the stirring tank 2 into the circulating concentration tank 3 in an overflow manner.

[0043] Further, a temperature regulating device is provided in the stirring tank 2 to regulate the reaction temperature and the cleaning temperature.

[0044] Further, the water discharged from the water outlet of the cross-flow filtration membrane mechanism 5 is the qualified product water of this system and enters the subsequent reverse osmosis section.

[0045] In some embodiments, the cross-flow filtration membrane mechanism 5 includes a microfiltration membrane.

[0046] Further, the microfiltration membrane can be a high-temperature resistant microfiltration membrane, which can withstand materials to be filtered at a relatively high temperature.

[0047] Further, the microfiltration membrane can be a tubular microfiltration membrane. Using the cross-flow filtration membrane mechanism 5 with tubular membranes to replace the plate-and-frame filter press system to clean the iron phosphate slurry, the washing water is completely mixed with the slurry and in full contact, not only with good cleaning effect, but also water consumption can be saved.

[0048] In some embodiments, the feed inlet of the stirring tank 2 is connected to the lift pump 1 through a pipeline, and the internal impeller of the lift pump 1 can be used for mixing materials.

[0049] Further, the feed inlet of the stirring tank 2 is connected to a liquid inlet pipeline, the mother liquor (or washing water) enters the stirring tank 2 through the liquid inlet pipeline, the lift pump 1 is connected to the liquid inlet pipeline, and a concentrated liquid return port and a chemical addition port are provided on the liquid inlet pipeline for adding the reaction feed liquid circulating concentrated liquid and ammonia water. Both the concentrated liquid return port and the chemical addition port are located upstream of the lift pump 1.

[0050] Further, the other end of the liquid inlet pipe is connected to a storage tank for storing the mother liquor or washing water.

[0051] In some embodiments, the discharge port of the circulating concentration tank 3 is connected to the concentrated liquid circulating pump 4. By setting the concentrated liquid circulating pump 4, the reaction feed liquid circulating concentrated liquid in the circulating concentration tank 3 can be quickly sent to the cross-flow filtration membrane mechanism 5 and the stirring tank 2.

[0052] When the circulating concentration device of the embodiment of the present invention is used for the pretreatment of the iron phosphate mother liquor, the concentrated liquid circulating pump 4 first sends a part of the concentrated liquid into the lift pump 1, mixes efficiently with the iron phosphate mother liquor (or washing water) and ammonia water, and then enters the stirring tank 2.

[0053] In some embodiments, the discharge port of the circulating concentration tank 3 is connected to the feed inlet of the stirring tank 2 through a first pipeline, and the discharge port of the circulating concentration tank 3 is connected to the feed inlet of the cross-flow filtration membrane mechanism 5 through a second pipeline. A first regulating valve 6 is connected to the first pipeline, and a second regulating valve 7 is connected to the second pipeline. The flow rate of the reaction feed liquid circulating concentrated liquid entering the cross-flow filtration membrane mechanism 5 and the stirring tank 2 can be adjusted.

[0054] The first regulating valve 6 and the second regulating valve 7 can be selectively opened and closed or their flow rates adjusted according to the actual situation. When the circulating concentration device of the embodiment of the present invention is used for cleaning the iron phosphate slurry, since the circulating washing slurry discharged from the circulating concentration tank 3 does not need to flow back to the stirring tank 2, the first regulating valve 6 can be selectively closed.

[0055] Furthermore, a drain pipe is connected through a tee at a position on the second pipeline close to the concentrated liquid circulating pump 4, and a concentrated liquid discharge valve 8 is connected to the drain pipe. When it is necessary to discharge the iron phosphate product or intermediate product after the cleaning is completed, the first regulating valve 6 and the second regulating valve 7 are closed, and the concentrated liquid discharge valve 8 is opened.

[0056] In some embodiments, an aeration device is provided in the circulating concentration tank 3. During the iron phosphate slurry cleaning operation, the hydraulic shear action between the washing water and the iron phosphate product can be increased without consuming washing water, thereby improving the flushing effect. The aeration device can be selectively used.

[0057] Furthermore, the aeration device is provided at the bottom of the circulating concentration tank 3. Aerating from the bottom of the circulating concentration tank 3 can improve the flushing effect.

[0058] In some embodiments, the circulating concentration device further includes a backwashing device, and the backwashing device performs backwashing on the filter membrane in the cross-flow filtration membrane mechanism 5.

[0059] Furthermore, the backwashing device includes a backwashing water tank and a backwashing water pump. The backwashing water tank is connected to the cross-flow filtration membrane mechanism 5 through a pipeline, and the backwashing water pump is provided on this pipeline, and can perform backwashing on the filter membrane regularly to relieve the fouling of the membrane system.

[0060] In some embodiments, the circulating concentration device further includes a chemical cleaning device, and the chemical cleaning device performs chemical cleaning on the filter membrane in the cross-flow filtration membrane mechanism 5. When the filter membrane is fouled, the chemical cleaning device can be enabled to perform chemical cleaning on the filter membrane.

[0061] Furthermore, the chemical cleaning device includes a chemical agent barrel and a circulation pump. The chemical agent barrel is connected to the cross-flow filtration membrane mechanism 5 through a circulation pipeline, and the circulation pump is provided on this pipeline, and performs chemical cleaning on the filter membrane through the circulating flow of the chemical agent.

[0062] A second aspect embodiment of the present invention proposes an application of the above-mentioned circulating concentration device in the pretreatment of iron phosphate mother liquor, including the following steps:

[0063] After the iron phosphate mother liquor and ammonia water are mixed by the lift pump 1, they are introduced into the stirring tank 2 for reaction to generate a reaction stock solution, and the stock solution contains solid suspended matters; the stock solution is introduced into the circulating concentration tank 3 and mixed with the concentrated solution filtered by the cross-flow filtration membrane mechanism 5 to form a reaction stock solution circulating concentrated solution; a part of the reaction stock solution circulating concentrated solution is returned to the lift pump 1, mixed with the iron phosphate mother liquor and ammonia water, and then jointly introduced into the stirring tank 2, and the remaining part of the reaction stock solution circulating concentrated solution is introduced into the cross-flow filtration membrane mechanism 5 for circulating concentration. The fresh water in the reaction stock solution circulating concentrated solution is discharged and introduced into the reverse osmosis system. After the reverse osmosis product water is further treated, the fresh water is introduced into the iron phosphate production system for washing the iron phosphate product; the reaction stock solution circulating concentrated solution after filtering out part of the water returns to the circulating concentration tank 3 again and is mixed with the newly introduced reaction stock solution, and circulates reciprocally. The concentration of the reaction stock solution circulating concentrated solution of the iron phosphate mother liquor is gradually increased, and when it is increased to a certain concentration, part of it is discharged from the circulating concentration tank 3.

[0064] Mix the iron phosphate mother liquor (or washing water) to be treated with ammonia water in the lift pump 1. Through the stirring action of the impeller, it is fully mixed with the refluxed concentrated solution, which can improve the mixing efficiency of the materials, make the reaction more complete, reduce the dosage of ammonia water medicament. At the same time, manganese phosphate, magnesium ammonium phosphate, iron phosphate, calcium phosphate, etc. generated by the reaction of the iron phosphate mother liquor (or washing water) and ammonia water can be fully combined with the high-concentration and high-specific-surface-area solid suspended matters in the reaction stock solution circulating concentrated solution, attach and grow on the existing solid particles to form larger solid particles, which can improve the solid-liquid separation efficiency.

[0065] By using the circulating concentration device in the pretreatment method of the iron phosphate mother liquor, it can replace the traditional iron phosphate wastewater pretreatment method, shorten the process flow, reduce the floor area, and reduce the equipment failure rate.

[0066] Furthermore, the cross-flow filtration membrane mechanism 5 includes a microfiltration membrane. Part of the water in the reaction stock solution circulating concentrated solution permeates through the microfiltration membrane to form product water, and the solid suspended matters cannot permeate through the microfiltration membrane and are retained in the reaction stock solution circulating concentrated solution and returned to the circulating concentration tank 3. By using the microfiltration membrane for solid-liquid separation, the separation efficiency can be improved, the quality of the product water can be improved, so that the product water can be used in the reverse osmosis process, and the water resources can be recycled. Using cross-flow filtration with the microfiltration membrane does not require the addition of PAM medicament, reducing the adverse impact of the PAM medicament on the subsequent reverse osmosis membrane.

[0067] The third aspect of the embodiments of the present invention proposes an application of the above-mentioned circulating concentration device in the cleaning of iron phosphate products, including the following steps:

[0068] (1) Introduce the iron phosphate product or intermediate product to be cleaned and the washing water into the circulating concentration tank 3 for stirring washing and aeration washing. The iron phosphate slurry in a loose state repeatedly contacts the washing water, and the surface impurities are carried away by the washing water.

[0069] (2) The circulating water-washed slurry is passed into the cross-flow filtration membrane mechanism 5 for circulating filtration, and part of the washing water and soluble impurities in the circulating water-washed slurry are discharged.

[0070] (3) The circulating water-washed slurry from which part of the washing water and soluble impurities have been filtered out returns to the circulating concentration tank 3 again, mixes with the washing water newly added to the circulating concentration tank 3, and circulates reciprocally until the conductivity of the discharged washing water is lower than the set value, then the cleaning is completed. The concentrated liquid discharge valve 8 is opened, and the washed iron phosphate product or intermediate product is discharged to the subsequent process section through the concentrated liquid circulating pump 4.

[0071] The circulating concentration device is used for the cleaning of the iron phosphate slurry, enabling the washing water and the slurry to be fully mixed and in full contact, with thorough cleaning and water consumption saved. The washed slurry is in a mixed liquid state rather than a filter cake. For the entire process of iron phosphate production, the repulping process can be omitted, saving equipment investment. There is no need for manual plate discharging, achieving full-automatic operation, saving labor, and being simple to operate.

[0072] Further, the washing water is deionized water.

[0073] In the description of the present invention, it should be understood that the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features.

[0074] In the present invention, unless otherwise clearly defined and limited, terms such as "connected" and "connected to" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection, an electrical connection, or communicable with each other; it may be directly connected, or indirectly connected through an intermediate medium, and may be the internal communication of two elements or the interaction relationship between two elements, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0075] In the present invention, terms such as "some embodiments" mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment of the present invention. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments and the features of different embodiments described in this specification.

[0076] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A cyclic concentration device, characterized in that, Including: A stirring tank, the stirring tank having a feed inlet and a discharge outlet, and a first stirring device being provided inside the stirring tank; A circulating concentration tank, the circulating concentration tank having a first feed inlet, a second feed inlet, a circulating feed inlet and a discharge outlet, the first feed inlet of the circulating concentration tank being connected to the discharge outlet of the stirring tank, and a second stirring device being provided inside the circulating concentration tank; A cross-flow filtration membrane mechanism, the cross-flow filtration membrane mechanism having a feed inlet, a water outlet and a discharge outlet, the discharge outlet of the circulating concentration tank being respectively connected to the feed inlet of the cross-flow filtration membrane mechanism and the feed inlet of the stirring tank, the circulating concentration tank being connected with a concentrated liquid discharge valve, and the discharge outlet of the cross-flow filtration membrane mechanism being connected to the circulating feed inlet of the circulating concentration tank; The discharge outlet of the circulating concentration tank is connected to the feed inlet of the stirring tank through a first pipeline, the discharge outlet of the circulating concentration tank is connected to the feed inlet of the cross-flow filtration membrane mechanism through a second pipeline, a first regulating valve is connected to the first pipeline, and a second regulating valve is connected to the second pipeline.

2. The circulating concentration device according to claim 1, wherein The cross-flow filtration membrane mechanism includes a microfiltration membrane.

3. The circulating concentration device according to claim 1, wherein The feed inlet of the stirring tank is connected to a lift pump through a pipeline, and an impeller for mixing materials is provided inside the lift pump.

4. The cyclic concentration device according to claim 1, characterized in that, The discharge outlet of the circulating concentration tank is connected to a concentrated liquid circulation pump.

5. The circulating concentration device according to claim 1, wherein An aeration device is provided inside the circulating concentration tank.

6. The circulating concentration device according to claim 1, wherein It further includes a backwashing device, and the backwashing device performs backwashing on the filtration membrane in the cross-flow filtration membrane mechanism.

7. The circulating concentration device according to claim 1, wherein It further includes a chemical cleaning device, and the chemical cleaning device performs chemical cleaning on the filtration membrane in the cross-flow filtration membrane mechanism.

8. Use of the circulation concentration device according to any one of claims 1-7 in the pretreatment of iron phosphate mother liquor, characterized in that, Including the following steps: After the iron phosphate mother liquor and ammonia water are mixed by the lift pump, they are introduced into the stirring tank for reaction to generate a reaction material liquid; The reaction material liquid is introduced into the circulating concentration tank and mixed with the concentrated liquid filtered by the cross-flow filtration membrane mechanism to form a reaction material liquid circulating concentrated liquid; Part of the reaction material liquid circulating concentrated liquid is returned to the lift pump, mixed with the iron phosphate mother liquor and ammonia water, and then jointly introduced into the stirring tank. The remaining part of the reaction material liquid circulating concentrated liquid is introduced into the cross-flow filtration membrane mechanism for circulating concentration. The fresh water in the reaction material liquid circulating concentrated liquid is discharged and introduced into a reverse osmosis system. After the reverse osmosis produced water is further treated, the fresh water is introduced into the iron phosphate production system for rinsing the iron phosphate product; The reaction material liquid circulating concentrated liquid after filtering out part of the water returns to the circulating concentration tank again, is mixed with the newly introduced reaction material liquid, and circulates reciprocally. The concentration of the reaction material liquid circulating concentrated liquid of the iron phosphate mother liquor is gradually increased. When it is increased to a certain concentration, part of it is discharged from the circulating concentration tank.

9. Use of the cyclic concentration device according to any one of claims 1-7 in the cleaning of iron phosphate products, characterized in that, Including the following steps: The iron phosphate product or intermediate product to be cleaned and the washing water are introduced into the circulating concentration tank for stirring washing and aeration washing to form a circulating water washing slurry; The circulating water washing slurry is introduced into the cross-flow filtration membrane mechanism for circulating filtration, and part of the washing water and soluble impurities in the circulating water washing slurry are discharged; The recycled washing slurry that filters out part of the washing water and soluble impurities returns to the aforementioned recycling and concentration tank again, mixes with the washing water newly added to the recycling and concentration tank, and circulates reciprocally until the conductivity of the discharged washing water is lower than the set value, then the cleaning is completed, and the washed iron phosphate product or intermediate product is discharged to the subsequent process section.

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