Preparation process and system of ferric phosphate by kettle-type external circulation mixing and agitation

Abstract

To provide a preparation process of ferric phosphate with a low impurity content, high yield, and a fast reaction rate, and a system thereof.SOLUTION: Disclosed is a preparation process of ferric phosphate by kettle type external circulation mixing and agitating including a step of adding an iron salt solution, a monoammonium phosphate solution, and a protective agent to a reaction pot, allowing the obtained mixed liquid for preliminary reaction at 90 to 100°C, then, after the preliminary reaction, conducting a kettle type external circulation reaction at 85 to 90°C.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to the technical field of ferric phosphate, and in particular to a process and system for preparing ferric phosphate using a kettle-type external circulation mixing and stirring method. [Background technology]

[0002] Ferric phosphate can be prepared by one-step and two-step methods. The one-step method involves the precipitation and transformation of ferric phosphate in the same reaction, i.e., first producing a yellow ferric phosphate precipitate, which is then converted to pink-white ferric phosphate at a high temperature of 90°C or higher. The two-step method mainly involves filtering the yellow ferric phosphate precipitate produced in the first reaction, then transferring it to another reaction, adding a certain concentration of dilute phosphoric acid, and then converting it to pink-white ferric phosphate at a high temperature of 90°C or higher. The ferric phosphate produced by the two-step method has low impurity content, especially the sulfur content, which can be reduced to several tens of ppm, but it requires low reaction efficiency and is not suitable for industrial production.

[0003] The one-step method has a simple reaction process, but has the disadvantage that the purity of the obtained ferric phosphate is low.

[0004] For this purpose, a process and system for preparing ferric phosphate using a kettle-type external circulation mixing and stirring is provided. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention provides a kettle-type external circulation mixing and stirring process for preparing ferric phosphate and its system.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions.

[0007] The preparation process of iron(III) phosphate by kettle type external circulation mixing and agitation is as follows: The method includes the steps of adding an iron salt solution, a monoammonium phosphate solution, and a protective agent to a reaction kettle, pre-reacting the resulting mixture at 90-100°C, and then carrying out a kettle-type external circulation reaction at 85-90°C after the pre-reaction.

[0008] Furthermore, the preliminary reaction time is 1.5 to 2 hours.

[0009] Furthermore, the circulation reaction time is 2 to 3 hours.

[0010] In addition, the feed port of the reaction vessel is equipped with a feed distributor, through which the contact area of ​​the materials in the feed can be enlarged, so that the reaction can be more complete.

[0011] Further, a circulation line is provided in the reaction vessel, and a circulation pump is provided in the circulation line, and the mixed liquid is transported from the reaction vessel to the circulation pipe by the circulation pump, and the mixed liquid is transported from the circulation pipe to the reaction vessel to form a circulation, thereby carrying out a kettle-type external circulation reaction.

[0012] Furthermore, one end of the circulation line is connected to the bottom of the reaction vessel, and the other end of the circulation line is connected to the top of the reaction vessel, and the mixed liquid in the reaction vessel is discharged from the bottom of the reaction vessel by a circulation pump, and the material liquid is supplied from the top of the reaction vessel to the circulation process in the reaction vessel.

[0013] In addition, the kettle external circulation pump is a ceramic dispersion pump, which has a certain dispersion effect, can disperse materials in the kettle, and improve the reaction speed.

[0014] In addition, the reactor is made of steel-lined PE material, and is equipped with a double heating coil inside, which, combined with the upper and lower thermometers, can uniformly control the temperature of the materials and keep the reaction conditions constant. A cooling coil is installed on the outside, which is used for heat exchange of the materials at the end of the reaction, thereby improving the production efficiency.

[0015] Furthermore, the stirring speed of the stirring paddle in the reaction vessel is 800 to 900 r / min, and the material liquid transport speed of the circulation pump is 50 m3 / h.

[0016] Furthermore, the stirring paddle in the reaction vessel is a mixing direction stirring paddle.

[0017] Furthermore, the reaction vessel is a reaction vessel having a sloping bottom.

[0018] Additionally, the protective agent is hydrogen peroxide.

[0019] In the present application, a flow baffle is provided in the reaction vessel, and when the mixing direction stirring paddle is used for stirring, the reaction liquid collides with the flow baffle in a stirred state to form a backflow, and the backflowing reaction liquid and the reaction liquid that collides with the flow baffle form turbulent flows, which speeds up the mixing and contact of the raw materials in the reaction liquid and promotes the reaction.

[0020] After the preliminary reaction, a portion of the ferric phosphate precipitates and accumulates on the inclined bottom of the reaction vessel. This can be discharged from a discharge port provided at the bottom of the reaction vessel (provided at the bottom of the surface facing the circulating raw material outlet), thereby promoting the progress of stirring.

[0021] During the circulation reaction, the circulation pump promotes mixing of the liquid materials at the bottom and upper layers of the reaction vessel, so that the raw materials that have not yet come into contact and reacted can be brought into sufficient contact with each other, thereby promoting the progress of the reaction.

[0022] The system for preparing iron(III) phosphate by kettle-type external circulation mixing and stirring includes a controller for executing the process for preparing iron(III) phosphate by kettle-type external circulation mixing and stirring described above. Effect of the Invention

[0023] The present invention has the following beneficial effects: The process of the present application has a fast reaction rate, prepares ferric phosphate, has a high yield of ferric phosphate, and has a low content of impurities in ferric phosphate. [Brief description of the drawings]

[0024] The invention will now be further described with reference to the figures and examples. [Figure 1] FIG. 1 is a schematic diagram showing a reaction vessel and a circulation line involved in the circulation process of the present invention. [Diagram 2] FIG. 1 is a schematic diagram showing a reaction vessel involved in the circulating process of the present invention. [Diagram 3] FIG. 2 is a schematic diagram showing the internal structure of a reaction vessel involved in the circulation process of the present invention. [Explanation of symbols]

[0025] 1. Reaction vessel 2 Circulation Line 3 Circulation pump 11 Stirring paddle 12 Spoilers 13 Circulating material outlet 14 Circulating material inlet 15 Jacket 111 Upper Branch Paddle 112 Middle Branch Paddle 113 Lower Branch Paddle DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] In order to facilitate understanding by those skilled in the art, the present invention will be further described below with reference to examples, but the contents mentioned in the embodiments are not intended to limit the present invention.

[0027] The term "and / or" as used herein includes all combinations of one or more associated examples. The terms used herein are used only for the purpose of describing specific examples and are not intended to limit the present invention. As used herein, the singular forms "a", "one", "a kind" and "the" also include the plural forms unless the context clearly indicates otherwise. Furthermore, when "comprising" is used herein, it is to be understood that the term includes a particular feature, integer, step, operation, element and / or composition, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, compositions and / or combinations thereof.

[0028] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by a person of ordinary skill in the art to which the present invention belongs. Furthermore, unless otherwise clearly defined, it is to be understood that terms as defined in commonly used dictionaries should be interpreted in a manner consistent with the meaning in the context of the relevant art, and not in an idealized or overly formal sense.

[0029] The exemplary invention described herein may appropriately lack one or more element limitations, and is not specifically limited herein. Thus, terms such as "comprise", "include", "contain", etc., are to be understood broadly and without limitation. Furthermore, the terminology used herein is for the purpose of explanation, not limitation, and these terminology expressions without equivalent characteristics are used to describe their partial characteristics without specific intention, and various modifications can be made within the scope of the present invention according to the claims. Thus, although the present invention has specifically disclosed the preferred embodiment and optional features, modifications disclosed herein to embody the variations of the present invention can be recorded by those skilled in the art, and such modifications and variations will be considered to be within the scope of the present invention.

[0030] The raw materials or reagents used in the examples and comparative examples of the present invention are all purchased from mainstream manufacturers in the market, and if the manufacturer is not indicated or the concentration is not indicated, they are routinely available in analytically pure grade and are not particularly limited as long as they serve the intended purpose. The equipment used in the examples, such as the reaction kettle and the circulation pump, are all purchased from mainstream manufacturers in the market, and are not particularly limited as long as they serve the intended purpose. In the examples, if no specific techniques or conditions are indicated, they shall follow the techniques and conditions described in the literature or product specifications in the field.

[0031] In the present application, the structure of the reaction vessel 1 is specifically as follows: the reaction vessel 1 has a sloping bottom. The sloping angle is 10-30 degrees, which facilitates the removal and discharge of the produced ferric phosphate, the volume of the reaction vessel is 10-100 cubic meters, an inlet, an observation window and a motor position are provided at the top, and a mixing direction stirring paddle 11 is provided in the reaction vessel, and the mixing direction stirring paddle 11 has three different directional branch paddles, namely, upper, middle and lower, where the upper branch paddle 111 is distributed downward at an angle of 35-45 degrees, the middle branch paddle 112 is distributed upward at an angle of 15-20 degrees, and the lower branch paddle 113 is distributed upward at an angle of 15-20 degrees. A spoiler 12 is further provided in the reaction kettle. The spoiler 12 is specifically a trapezoidal block provided on the inner wall of the reaction kettle. The thickness can be set according to actual needs. Generally, it is the same as the main rod thickness of the stirring paddle. The bottom of the spoiler is parallel to the bottom of the stirring paddle, and the top of the spoiler is higher than the upper branch paddle of the stirring paddle.

[0032] A circulating material outlet 13 is provided at the bottom of the reaction vessel, and the circulating material outlet 13 is connected to a circulation line 2, to which a circulation pump 3 is provided. A circulating material inlet 14 is provided at the top of the reaction vessel, and the circulating material inlet 14 is connected to the circulation line 2. The material liquid in the reaction vessel 1 is circulated through the circulation line 2 under the transport of the circulation pump 3.

[0033] A jacket or coil is provided on the outside of the reaction vessel, and the reaction vessel can be heated by passing steam through it, or cooled by passing ice water or cold water through it.

[0034] In this application, the preparation process in the reaction vessel is as follows: iron salt solution: ferrous sulfate is dissolved in water in an iron pool, pumped to a precipitation tank for precipitation, filtered to obtain ferrous sulfate filtrate, and the ferrous sulfate filtrate is prepared into an iron salt solution of a certain concentration.

[0035] In the present application, the amount of iron salt solution charged is 750 kg, the weight content of ferrous sulfate heptahydrate in the iron salt solution is 21.7%, the amount of monoammonium phosphate solution charged is 445 kg, the weight content of monoammonium phosphate in the monoammonium phosphate solution is 19.6%, the amount of ammonia water charged is 49 kg, the concentration is 20%, and the amount of hydrogen peroxide charged is 60 kg.

[0036] Example 1 The process for preparing iron(III) phosphate by kettle-type external circulation mixing and stirring includes the following steps: Add iron salt solution, monoammonium phosphate solution, ammonia water, and hydrogen peroxide into the reaction kettle, and perform pre-reaction of the resulting mixture at 90°C for 1.5 hours. After the pre-reaction, perform kettle-type external circulation reaction at 85°C for 2 hours. The stirring speed of the mixing direction stirring paddle is 800 r / min, and the material liquid transport speed of the circulation pump is 50 m 3 / h.

[0037] Example 2 Add iron salt solution, monoammonium phosphate solution, ammonia water, and hydrogen peroxide into the reaction kettle, and perform pre-reaction of the resulting mixture at 90°C for 2 hours. After the pre-reaction, perform kettle-type external circulation reaction at 90°C for 3 hours. The stirring speed of the mixing direction stirring paddle is 900 r / min, and the material liquid transport speed of the circulation pump is 50 m 3 / h. The reactor volume is 80m 3 It is.

[0038] Example 3 Add iron salt solution, monoammonium phosphate solution, ammonia water, and hydrogen peroxide into the reaction kettle, and perform pre-reaction of the resulting mixture at 95°C for 1.8h. After the pre-reaction, perform kettle-type external circulation reaction at 88°C for 2.5h. The stirring speed of the mixing direction stirring paddle is 850 r / min, and the material liquid transport speed of the circulation pump is 50 m 3 / h. The reactor volume is 80m 3 It is.

[0039] Comparative Example 1 In this comparative example, no circulation reaction was performed (i.e., no circulation line or circulation pump was installed outside the reaction vessel), and the mixture was pre-reacted at 90°C for 1.5 hours, and then reacted at 85°C for 2 hours. The other conditions were the same as in Example 1.

[0040] Comparative Example 2 In this comparative example, the circulation reaction is not performed (i.e., the circulation line and the circulation pump are not provided outside the reaction vessel), and the stirring speed of the mixing direction stirring paddle is 850 r / min. The other conditions are the same as those of Example 1.

[0041] Comparative Example 3 In this comparative example, the circulation reaction is not performed (i.e., the circulation line and the circulation pump are not provided outside the reaction vessel), and the stirring speed of the mixing direction stirring paddle is set to 1200 r / min. The other conditions are the same as those of Example 1.

[0042] Regarding the above Examples 1-3 and Comparative Examples 1-3, after the reaction, the reaction material liquid is post-treated: after the reaction is completed, the reaction material liquid is filtered and washed multiple times, the filter residue is sent to a slurry tank and pure water is added to perform high-speed dispersion washing, and then press-filtered again to obtain an iron(II) phosphate filter cake: after the iron(II) phosphate filter cake is washed and passed, the filter cake is sent to a flash dryer to obtain iron phosphate dihydrate, the moisture content before drying is about 45%, and the moisture content after drying is 1%, and the iron phosphate dihydrate after flash drying is fired in a rotary kiln to obtain anhydrous iron(II) phosphate.

[0043] The physical indicators and chemical compositions of the ferric phosphates prepared in Example 1 and Comparative Examples 1 to 3 were detected, and the results are summarized in Table 1 below.

[0044] [Table 1]

[0045] As can be seen from Table 1, the weight of the iron(II) phosphate obtained in Example 1 was 1.4 times that of the iron(II) phosphate obtained in Comparative Example 1. The detection of the reacted material solution in Comparative Example 1 revealed that there was a large amount of unreacted iron salt solution. From the ratio of the impurity phase in Example 1 and Comparative Examples 1 to 3, it can be seen that the overall impurity content in Example 1 is low, and the corresponding purity is improved. The particle diameter is smaller than that in Comparative Examples 1 to 3, and the particles are distributed relatively uniformly. In the later stage of the lithium iron phosphate battery, the impurity content in Example 1 is low, and the impurity content in Comparative Example 1 is low. + Shorten the diffusion path.

[0046] As can be seen from Comparative Examples 1 to 3, when the circulation pump is not activated, the stirring speed is too slow and the reaction of the material is incomplete. By correspondingly increasing the stirring speed, the vibration density can be improved to a certain extent, but the specific surface area will be reduced to a certain extent, and the porosity will also be reduced, resulting in the late Li + The mosaic and desorption speed are disadvantageous, and the present application has conducted comparative tests focusing on this difference. In Example 1, the particle size obtained by adding the extra-kettle circulation reaction is relatively uniform and better, and while ensuring its high vibration density, it also takes into account the specific surface area, improving the energy density and electrochemical activity of the material.

[0047] The system for preparing iron(III) phosphate by external circulation mixing and stirring in a kettle includes a controller for executing the above-mentioned process for preparing iron(III) phosphate by external circulation mixing and stirring in a kettle. It is understood by those skilled in the art that all or part of the flow in the above-mentioned embodiment method can be implemented by hardware associated with existing controller (computer program) instructions, and the computer program is stored in a non-volatile computer-readable storage medium, and when the computer program is executed, it can constitute the flow of the embodiment of each of the above-mentioned methods. Here, any implementation of memory, storage, database or other medium used in each embodiment provided by the present application may include non-volatile and / or volatile memory. The non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. The volatile memory may include random access memory (RAM) or external cache memory. By way of example and not limitation, RAM is available in various forms such as Static RAM (SRAM), Dynamic RAM (DRAM), Synchronous DRAM (SDRAM), Double Data Rate SDRAM (DDRSDRAM), Enhanced SDRAM (ESDRAM), Synchronous Link DRAM (SLDRAM), Memory Bus (Rambus) Direct RAM (RDRAM), Direct Memory Bus Dynamic RAM (DRDRAM), and Memory Bus Dynamic RAM (RDRAM).

[0048] The above examples are preferred embodiments of the present invention, in addition to which the present invention can be implemented in other ways, and all obvious substitutions without departing from the concept of the present invention are included within the protection scope of the present invention.

Claims

1. A process for preparing iron(III) phosphate by kettle-type external circulation mixing and stirring, comprising the steps of adding an iron salt solution, a monoammonium phosphate solution and a protective agent into a reaction kettle, pre-reacting the resulting mixed solution at 90-100°C, and carrying out a kettle-type external circulation reaction at 85-90°C after the pre-reaction, wherein the protective agent is hydrogen peroxide.

2. The preparation process of iron(III) phosphate by kettle type external circulation mixing and stirring according to claim 1, wherein the pre-reaction time is 1.5-2h.

3. The process for preparing iron(III) phosphate by external circulation mixing and stirring according to claim 1, wherein the circulation reaction time is 2-3h.

4. 2. The process for preparing iron(III) phosphate by kettle-type external circulation mixing and stirring according to claim 1, wherein the reaction kettle is provided with a circulation line, the circulation line is provided with a circulation pump, the mixed liquid reaction kettle is transported to the circulation pipe by the circulation pump, and the mixed liquid is transported from the circulation pipe to the reaction kettle to form a circulation, and a kettle-type external circulation reaction is carried out.

5. 5. The process for preparing iron(III) phosphate by external circulation mixing and stirring according to claim 4, wherein one end of the circulation line is connected to the bottom of the reaction kettle and the other end of the circulation line is connected to the top of the reaction kettle, and a circulation pump is used to make the mixed liquid in the reaction kettle flow out from the bottom of the reaction kettle and to supply the material liquid from the top of the reaction kettle to the circulation process in the reaction kettle.

6. The stirring speed of the stirring paddle in the reaction vessel is 800 to 900 r / min, and the material liquid transport speed of the circulation pump is 50 m ３ 5. The process for preparing iron(III) phosphate by kettle-type external circulation mixing and stirring according to claim 4, wherein the mixing rate is 1000 / h.

7. The process for preparing iron(III) phosphate by kettle type external circulation mixing and stirring as claimed in claim 6, wherein the stirring paddle in the reaction kettle is a mixing direction stirring paddle.

8. The process for preparing iron(III) phosphate by external circulation mixing and stirring as claimed in claim 1, wherein the reaction kettle is a reaction kettle with a sloping bottom.

9. 2. A system for preparing iron(III) phosphate by external circulation mixing and stirring in a kettle type, comprising: a controller for executing the process for preparing iron(III) phosphate by external circulation mixing and stirring in a kettle type according to claim 1.

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