Method and device for continuously synthesizing iron phosphate

Abstract

The invention relates to the technical field of iron phosphate preparation, and discloses a method and device for continuously synthesizing iron phosphate, and the method comprises the following steps: 1) respectively adding iron powder and dilute sulphuric acid into a first continuous tubular reactor; 2) respectively pumping the ferrous sulfate solution and the phosphate solution into a second continuous tubular reactor; 3) continuously feeding the slurry into a crystal transformation aging kettle; 4) continuously conveying the aged slurry into a horizontal screw centrifuge for solid-liquid separation; 5) continuously conveying solids obtained by solid-liquid separation in the step 4) to a re-pulping tank, adding pure water, re-pulping and washing; 6) continuously conveying a filter cake to flash evaporation drying and high-temperature calcination, and then crushing, packaging and demagnetizing to obtain an iron phosphate product; according to the invention, the quality stability is ensured, the product production cycle is shortened, and the product quality stability is improved; the problem that a large amount of hydrogen escapes from a traditional kettle type reaction kettle to cause safety risks is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of iron phosphate preparation, and in particular to a method and device for continuously synthesizing iron phosphate. Background Art

[0002] At present, the production of iron phosphate, especially the synthesis reaction section, has always been carried out by the batch method. There are problems in preparing iron phosphate by the batch method, such as unstable production process control between batches leading to poor product quality consistency, a large number of reaction kettles in production equipment, large floor area, high labor cost, and high equipment failure rate due to frequent start-up and shutdown of equipment. To reduce costs, the mainstream process for the production of iron phosphate in the industry at present is the "ammonium method process", which uses by-product ferrous sulfate from titanium dioxide as the iron source and phosphorus source (phosphoric acid or phosphate) and hydrogen peroxide as the main raw materials. Among them, according to the characteristics of the process flow, it is divided into the "one-step method" and the "two-step method". Due to the high impurity content of ferrous sulfate, in order to ensure that the quality of the iron phosphate product meets the customer's index requirements, most enterprises adopt the two-step method process. Compared with the "one-step method" process, this process removes the impurities brought in by the ferrous sulfate raw material by increasing the washing of the iron phosphate filter cake during the synthesis process to control the impurity content of the product. However, compared with the "one-step method" process, this process will cause an increase in the amount of washing water used and the load of intermediate water treatment, resulting in an increase in investment and operating costs.

[0003] At present, although there are already methods for continuously synthesizing iron phosphate, most of the ferrous phosphate in its raw materials still uses by-product ferrous sulfate from titanium dioxide as the iron source and phosphorus source. In order to reduce the subsequent impurity treatment processes and costs, ferrous sulfate is also prepared from dilute sulfuric acid and iron powder. However, the conventional method for preparing ferrous sulfate usually carries out the iron melting reaction in an iron melting kettle. The reaction rate of dilute sulfuric acid and iron powder is relatively fast. Using a traditional kettle-type reaction kettle, the process control is relatively difficult, and the concentration of iron ions in the iron melting liquid fluctuates greatly. Once the concentration range of the iron melting liquid fluctuates greatly, it is necessary to adaptively adjust the concentration of phosphate before the oxidation reaction. For large-scale industrial production enterprises, not only does the process take a long time, but the concentration of phosphate needs to be readjusted during the production process of different batches, which may ultimately lead to unstable product performance. Summary of the Invention

[0004] The purpose of the present invention is to provide a method and device for continuously synthesizing iron phosphate, so as to solve the problems of complex process control and unstable product performance existing in the process of preparing iron phosphate with dilute sulfuric acid and iron powder as raw materials in the prior art.

[0005] The solution of the present invention is as follows:

[0006] A method for continuously synthesizing iron phosphate, comprising the following steps:

[0007] 1) Pump iron powder and dilute sulfuric acid into the first continuous tubular reactor respectively, and carry out iron conversion continuously for 5 min to 15 min at a temperature of 60 °C to 80 °C. The obtained iron-converted liquid is continuously output after filtration to obtain a ferrous sulfate solution;

[0008] 2) Pump the ferrous sulfate solution and the phosphate solution into the second continuous tubular reactor respectively, and simultaneously add an oxidant to react to obtain a slurry; control the temperature at 50 °C to 60 °C and the residence time at 5 min to 20 min;

[0009] 3) Continuously send the slurry to a crystal conversion aging kettle for high-temperature crystal conversion reaction to obtain an aged slurry; control the temperature at 85 °C to 92 °C and the residence time at 60 min to 90 min;

[0010] 4) Continuously transport the aged slurry to a horizontal screw centrifuge for solid-liquid separation;

[0011] 5) Continuously send the solid matter separated by solid-liquid separation in step 4) to a re-slurrying tank to add pure water for re-slurrying and washing, and continuously send the re-slurried slurry to a horizontal screw centrifuge for solid-liquid separation;

[0012] 6) Continuously send the filter cake separated in step 5) to flash drying, high-temperature calcination, and then through crushing, packaging, and demagnetization to obtain a ferric phosphate product.

[0013] As a preferred technical solution, in step 1), the purity of the iron powder ≥ 98%, the particle size of the iron powder is 80 mesh to 120 mesh; the concentration of the dilute sulfuric acid is 10% to 30%.

[0014] As a preferred technical solution, the continuously output ferrous sulfate solution in step 1) is continuously sent to an adjustment tank, and water is added in the adjustment tank to adjust the Fe 2+ concentration in the ferrous sulfate solution to 4.0% to 5.0%.

[0015] As a preferred technical solution, the phosphate solution is adjusted with water to adjust the PO4 3- concentration to 18% to 21%, and ammonia water is added to adjust the pH to 3.5 to 4.5.

[0016] As a preferred technical solution, steps 4) and 5) are cycled until the conductivity of the washing water for re-slurrying and washing

[0017] ≤ 2000 μs / cm.

[0018] The present invention also discloses a device for continuously synthesizing ferric phosphate, including a first continuous tubular reactor, a filter, an adjustment tank, a second continuous tubular reactor, a crystal conversion aging kettle, a horizontal screw centrifuge, and a re-slurrying tank that are sequentially connected through pipelines.

[0019] As a preferred technical solution, the first continuous tubular reactor is a tubular microreactor. An exhaust pipe is provided on the tubular microreactor, and an inlet pipe is connected to the exhaust pipe; the inlet pipe is used to introduce air or inert gas into the exhaust pipe.

[0020] Advantages of the present invention:

[0021] 1. Since the raw material purity of iron powder and dilute sulfuric acid solution is high, reacting iron powder with sulfuric acid can obtain a ferrous sulfate solution with low impurity content, solving the problem of high impurity content in by-product ferrous sulfate from titanium dioxide production; at the same time, during the iron melting process, using a tubular microreactor as the first continuous tubular reactor realizes continuous iron melting, that is, while ensuring a reduction in the impurity content of ferrous sulfate itself, it can also stabilize the fluctuation range of the concentration, reduce the repeated adjustment of the concentration of the subsequent phosphate solution, thereby further ensuring the stability of the quality of the iron phosphate product, shortening the product production cycle, and improving the stability of the product quality;

[0022] 2. Since the explosion limit of hydrogen is relatively wide (4% - 75%), there is a certain safety risk caused by a large amount of hydrogen escaping during the iron melting process. In the present invention, a tubular microreactor is used for iron melting, and the hydrogen generated during the process is collected through the exhaust pipe, and fresh air or inert gas is introduced for concentration dilution to make its concentration lower than 4% of the lower explosion limit, and then discharged safely in a unified manner, solving the problem of safety risks caused by a large amount of hydrogen escaping from traditional batch reactors.

[0023] 3. The present invention uses a horizontal screw centrifuge to replace the traditional plate and frame filter press for solid-liquid separation and washing of the iron phosphate slurry, fundamentally solving the problem that the current plate and frame filter press can only perform single-plate intermittent operation and cannot achieve continuous filtration and washing operations; in the present invention, the horizontal screw centrifuge and the re-slurry tank are combined to achieve continuous filtration and continuous washing, improving the product performance while ensuring the product performance and stability. Using a horizontal screw centrifuge can reduce the influence of uncontrollable human factors on the product performance, and at the same time improve the processing efficiency; at the same time, the horizontal screw centrifuge has a small floor area and a high degree of automation, solving the disadvantages of the traditional plate and frame filter press that requires manual cake unloading operation and high manual labor intensity.

[0024] 4. After the iron phosphate slurry is obtained through reaction in the second continuous tubular reactor in the present invention, it is continuously fed into a high-temperature crystal conversion kettle for high-temperature crystal conversion, and the crystal form is converted at a high temperature of 85°C to 92°C. The purpose of crystal conversion is to convert the amorphous iron phosphate obtained from the low-temperature reaction into iron phosphate dihydrate under high temperature, a crystal conversion agent, and suitable pH conditions. Temperature is an important influencing factor for whether amorphous iron phosphate can achieve crystal conversion. To ensure the effect of crystal conversion, the temperature needs to be maintained within 85°C to 92°C; if the temperature is lower than 85°C, the high-temperature conditions required for crystal conversion cannot be reached, and the successful crystal conversion of amorphous iron phosphate cannot be achieved; if the temperature is higher than 92°C, there will be problems such as excessive energy consumption and increased production costs; at the same time, in the high-temperature crystal conversion kettle of the present invention, iron phosphate slurries of different batches are mixed and then continuously conveyed out, and mixing is carried out therein to reduce the fluctuation of product quality between batches and improve the stability of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is the process flow diagram of the method for continuously synthesizing iron phosphate in the present invention;

[0026] Figure 2 is the structural schematic diagram of the first continuous tubular reactor in Example 2 of the present invention;

[0027] Figure 3 is the 50,000-fold scanning electron microscope picture of the LXHC-004 iron phosphate product prepared in the example of the present invention;

[0028] Figure 4 is the 20,000-fold scanning electron microscope picture of the LXHC-004 iron phosphate product prepared in the example of the present invention;

[0029] Figure 5 is the XRD characterization result of the LXHC-004 iron phosphate product prepared in the example of the present invention;

[0030] 1 - Dilute sulfuric acid inlet; 2 - Iron powder inlet; 3 - Hydrogen gas outlet; 4 - Ferrous sulfate solution outlet. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] In order to make the technical means, creative features, achieved purposes, and functions of the present invention easy to understand, the present invention will be further described below in conjunction with specific embodiments.

[0032] Example 1:

[0033] A method for continuously synthesizing iron phosphate includes the following steps:

[0034] 1) Using iron powder with a purity ≥ 98% and a particle size of 100 mesh and dilute sulfuric acid with a concentration of 20% as raw materials, they are respectively pumped into the first continuous tubular reactor. The molar ratio of Fe:H₂SO₄ is 1.05:1. Continuously react iron for 8 minutes at a temperature of 65 °C. The resulting iron reacted solution is continuously output after filtration to obtain a ferrous sulfate solution.

[0035] 2) Dilute the ferrous sulfate solution prepared in step 1) with water until the Fe 2+ concentration is 4.5% and the PO₄ 3- concentration is 18.5% and the pH is 4.0 (adjust the pH value by adding ammonia water). The phosphate solution is separately pumped into the second continuous tubular reactor. The P:Fe molar ratio is 1.15:1, and an oxidant hydrogen peroxide is added for reaction. Control the temperature at 52 °C and the residence time at 15 minutes.

[0036] 3) Continuously send the slurry obtained from the second continuous tubular reactor in step 2) to a crystal conversion aging kettle for high-temperature crystal conversion reaction. Control the temperature at 85 °C and the residence time at 60 minutes.

[0037] 4) Continuously transport the aging slurry in step 3) to a horizontal spiral centrifuge for solid-liquid separation.

[0038] 5) Continuously send the separated filter cake in step 4) to a re-slurry tank to add pure water for re-slurrying and washing. After re-slurrying, the solid content is 15%. The slurried slurry is continuously sent to a horizontal spiral centrifuge for solid-liquid separation, and the operation is repeated until the conductivity of the washing water ≤ 2000 μs / cm.

[0039] 6) Continuously send the filter cake in step 5) to flash drying, high-temperature calcination, and then through crushing, packaging, and demagnetization to obtain a ferric phosphate product.

[0040] Example 2:

[0041] As Figure 2 shown, a device for continuously synthesizing ferric phosphate is applicable to the method for continuously synthesizing ferric phosphate in Example 1. It includes a first continuous tubular reactor, a filter, an adjustment tank, a second continuous tubular reactor, a crystal conversion aging kettle, a horizontal spiral centrifuge, and a re-slurry tank that are sequentially connected through pipelines. The first continuous tubular reactor is a tubular micro-reactor, and the tubular micro-reactor is provided with an exhaust pipe. An inlet pipe is connected to the exhaust pipe. The inlet pipe is used to introduce air or inert gas into the exhaust pipe.

[0042] Example 3:

[0043] Using the first continuous tubular reactor in Example 2 and the method in Example 1 to prepare ferrous sulfate, the obtained ferrous sulfate is subjected to physical and chemical analysis and compared with the solutions obtained by dissolving and removing impurities from ferrous sulfate by-products of traditional iron reaction processes and titanium dioxide production. The results are shown in Table 1 below.

[0044] Among them, the conditions of the traditional iron melting process are as follows: with the molar ratio of Fe:H2SO4 being 1.05:1, iron powder and a dilute sulfuric acid solution with a concentration of 20% are placed in a reaction kettle, and continuous iron melting is carried out at a temperature of 45°C for 90 minutes.

[0045] Ferrous sulfate solution by-produced from titanium dioxide: Take a certain amount of ferrous sulfate solid, dissolve it in water to prepare a solution with a concentration of Fe 2+ of 5.5%, add ammonia water to adjust the pH value to 5, and filter the clear liquid obtained after reacting for 30 minutes.

[0046] Table 1 Comparison of the main content and impurity content of ferrous sulfate solutions obtained by different iron melting processes

[0047]

[0048] As can be seen from Table 1, when continuous iron melting is carried out using the first continuous tubular reactor, the main content of Fe in the obtained iron-melted ferrous sulfate solution is stable, and the content is between 5.50% and 5.60%, which is basically consistent with the theoretical calculated value. However, for the ferrous solution obtained by traditional kettle iron melting and impurity removal of ferrous sulfate by-produced from titanium dioxide, due to the occurrence of oxidation side reactions during the iron melting process, the Fe 2+ concentration in the solution is low. In terms of impurity content control: the impurity content of the iron-melted ferrous sulfate solution obtained from the reaction of iron powder and dilute sulfuric acid is significantly lower than that of the iron-melted solution obtained by using ferrous sulfate by-produced from titanium dioxide as raw material after impurity removal treatment. In particular, the impurities of Mg, Mn, Zn, Al, and Ca have decreased significantly. Mg has decreased from the original 1200 - 1300 ppm to ≤10 ppm, Mn has decreased from the original 280 - 300 ppm to ≤50 ppm, Zn has decreased from the original 8 - 10 ppm to ≤2 ppm, and Al has decreased from the original 8 - 10 ppm to ≤1 ppm, achieving the purpose of obtaining a raw material of ferrous sulfate solution with high purity and low impurity content.

[0049] Example 3

[0050] A method for continuously synthesizing iron phosphate, comprising the following steps:

[0051] 1) Using iron powder with a purity ≥98% and a particle size of 100 mesh and dilute sulfuric acid with a concentration of 12% as raw materials, respectively pump them into the first continuous tubular reactor, with the molar ratio of Fe:H2SO4 being 1.1:1; carry out continuous iron melting at a temperature of 70°C for 10 minutes, and the obtained iron-melted liquid is continuously output after filtration to obtain a ferrous sulfate solution;

[0052] 2) Dilute the ferrous sulfate solution prepared in step 1) with water to a concentration of Fe 2+ of 4.5% and PO4 3-A phosphate solution with a concentration of 20.5% and a pH of 4.0 (adjusted with ammonia water) is pumped into the second continuous tubular reactor in batches. The P:Fe molar ratio is 1.2:1, and an oxidant, hydrogen peroxide, is added for reaction. The temperature is controlled at 55 °C, and the residence time is 15 min.

[0053] 3) Continuously send the slurry obtained in the second continuous tubular reactor in step 2) to a crystal conversion aging kettle for high-temperature crystal conversion reaction. Control the temperature at 87 °C and the residence time at 65 min.

[0054] 4) Continuously transport the aged slurry in step 3) to a horizontal screw centrifuge for solid-liquid separation.

[0055] 5) Continuously send the separated filter cake in step 4) to a re-slurrying tank to be re-slurried and washed with pure water. The solid content after re-slurrying is 12%. The slurried slurry is continuously sent to a horizontal screw centrifuge for solid-liquid separation, and the operation is repeated until the conductivity of the washing water ≤ 2000 μs / cm.

[0056] 6) Continuously send the filter cake in step 5) to flash drying, high-temperature calcination, and then obtain iron phosphate products after crushing, packaging, and demagnetization.

[0057] Example 4

[0058] A method for continuously synthesizing iron phosphate, comprising the following steps:

[0059] 1) Using iron powder with a purity ≥ 98% and a particle size of 100 mesh and dilute sulfuric acid with a concentration of 25% as raw materials, pump them into the first continuous tubular reactor in batches. The Fe:H2SO4 molar ratio is 1.2:1. Continuously dissolve iron for 6 min at a temperature of 75 °C. The obtained iron-dissolved solution is continuously output after filtration to obtain a ferrous sulfate solution.

[0060] 2) Dilute the ferrous sulfate solution prepared in step 1) with water to Fe 2+ with a concentration of 4.5% and PO4 3- A phosphate solution with a concentration of 20% and a pH of 4.2 (adjusted with ammonia water) is pumped into the second continuous tubular reactor in batches. The P:Fe molar ratio is 1.5:1, and an oxidant, hydrogen peroxide, is added for reaction. The temperature is controlled at 58 °C, and the residence time is 12 min.

[0061] 3) Continuously send the slurry obtained in the second continuous tubular reactor in step 2) to a crystal conversion aging kettle for high-temperature crystal conversion reaction. Control the temperature at 90 °C and the residence time at 60 min.

[0062] 4) Continuously transport the aged slurry in step 3) to a horizontal screw centrifuge for solid-liquid separation.

[0063] 5) Continuously feed the separated filter cake in step 4) into a repulping tank, add pure water for repulping and washing. After repulping, the solid content is 10%. Continuously feed the slurried material after repulping into a horizontal scroll centrifuge for solid-liquid separation, and repeat the operation until the conductivity of the washing water ≤ 2000 μs / cm;

[0064] 6) Continuously feed the filter cake in step 5) into flash drying, high-temperature calcination, and then obtain iron phosphate products after crushing, packaging, and demagnetization.

[0065] Comparative Example 1:

[0066] Take the Fe obtained by impurity removal of by-product ferrous sulfate from titanium dioxide 2+ Ferrous sulfate solution with a concentration of 4.5%. Add the phosphate solution with a pH adjusted to 4.5 by ammonia water and a PO4 3- Concentration of 18.5% to the ferrous sulfate solution, control the reaction temperature at 52 °C, and the reaction residence time at 15 min; Raise the reaction temperature of the synthetic slurry to 85 °C for high-temperature crystal transformation reaction, and the residence time is 60 min; Wash the aged slurry through a plate and frame online until the conductivity of the washing water ≤ 2000 μs / cm for solid-liquid separation; Continuously feed the obtained filter cake into flash drying, high-temperature calcination, and then obtain iron phosphate products after crushing, packaging, and demagnetization.

[0067] Comparative Example 2:

[0068] Take the Fe obtained by impurity removal of by-product ferrous sulfate from titanium dioxide 2+ Ferrous sulfate solution with a concentration of 4.5%. Add the phosphate solution with a pH adjusted to 8.0 by ammonia water and a PO4 3 - Concentration of 18.5% to the ferrous sulfate solution, control the reaction temperature at 52 °C, and the reaction residence time at 15 min; Filter and wash the obtained synthetic reaction slurry until the conductivity of the washing water ≤ 5000 μs / cm; Add water to the obtained filter cake to adjust the slurry solid content to 15%, and send it to a crystal transformation aging kettle for high-temperature crystal transformation reaction; Control the temperature at 85 °C and the residence time at 60 min; Wash the aged slurry through a plate and frame online until the conductivity of the washing water ≤ 2000 μs / cm for solid-liquid separation; Continuously feed the obtained filter cake into flash drying, high-temperature calcination, and then obtain iron phosphate products after crushing, packaging, and demagnetization.

[0069] Use the device for continuous synthesis of iron phosphate in Example 2 and the method for continuous synthesis of iron phosphate in Example 1 to prepare iron phosphate, conduct physical and chemical analysis on the obtained iron phosphate, and compare it with the iron phosphate products synthesized by the traditional "one-step method" and "two-step method" processes used in Comparative Example 1 and Comparative Example 2. The results are shown in Table 2 below.

[0070] Table 2 Comparison of iron phosphate products synthesized by continuous sulfuric acid dissolution of ferrous sulfate "one-step method" and "two-step method" processes

[0071]

[0072] As can be seen from Table 2, when the ferrous sulfate solution obtained by continuous iron melting in a microreactor is used as the iron source raw material, and the ammonium method "one-step" process is adopted to synthesize iron phosphate, the physical and chemical indexes and impurity contents of the obtained product are significantly better than those of the iron phosphate product synthesized by the ammonium method "one-step" process using by-product ferrous sulfate of titanium dioxide as the raw material, and are also better than those of the iron phosphate product synthesized by the ammonium method "two-step" process using by-product ferrous sulfate of titanium dioxide as the raw material.

[0073] In addition, from Figure 3 , Figure 4 it can be seen that when the ferrous sulfate obtained by continuous iron melting of iron powder and sulfuric acid is used as the iron source raw material, the micro-morphology of the iron phosphate product obtained according to the ammonium method "one-step" process with the phosphorus source and the oxidant is in good consistency. The primary particle size is evenly distributed, and there are certain pores between the particles, which is consistent with the micro-morphology of the mainstream ammonium method "two-step" process iron phosphate product in the market.

[0074] From Figure 5 it can be seen that when the ferrous sulfate obtained by continuous iron melting of iron powder and sulfuric acid is used as the iron source raw material, the iron phosphate product obtained according to the ammonium method "one-step" process with the phosphorus source and the oxidant has no miscellaneous peaks, and corresponds one by one to the characteristic peaks of the iron phosphate standard card, and the characteristic peaks are obvious; the crystallinity is 84.5%, which is consistent with the crystallinity of the mainstream ammonium method "two-step" process iron phosphate product in the market.

[0075] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for continuously synthesizing ferric phosphate, characterized in that: The following steps are involved: 1) adding iron powder and dilute sulfuric acid into a first continuous tubular reactor respectively, and continuously ferricizing at a temperature of 60° C. to 80° C. for 5 to 15 minutes, and the obtained ferric sulphate solution is filtered and continuously output to obtain a ferrous sulfate solution; 2) pumping the ferrous sulfate solution and the phosphate solution into a second continuous tubular reactor respectively, and adding an oxidant to react to obtain a slurry; controlling the temperature to 50° C. to 60° C. and the residence time to 5 min to 20 min; 3) continuously sending the slurry to a crystallization aging kettle for high-temperature crystallization reaction to obtain aged slurry; controlling the temperature to 85° C. to 92° C. and the residence time to 60 min to 90 min; 4) continuously conveying the aged slurry to a horizontal screw centrifuge for solid-liquid separation; 5) The solid separated from the solid and liquid in step 4) is continuously sent to a re-slurry tank to be re-slurried and washed with pure water, and the re-slurry is continuously sent to a horizontal screw centrifuge for solid-liquid separation; 6) The filter cake separated in step 5) is continuously sent to flash drying, high-temperature calcination, and then crushed, packaged and demagnetized to obtain the iron phosphate product.

2. A method for continuously synthesizing ferric phosphate according to claim 1, characterized in that: In the step 1), the purity of the iron powder is ≥98%, the particle size of the iron powder is 80-120 meshes; and the concentration of the dilute sulfuric acid is 10%-30%.

3. A method for continuously synthesizing ferric phosphate according to claim 1, characterized in that: The ferrous sulfate solution continuously output in step 1) is continuously sent to the regulating tank, and water is added to the regulating tank to adjust the Fe content of the ferrous sulfate solution. 2+ The concentration is 4.0%~5.0%.

4. A method for continuously synthesizing ferric phosphate according to claim 1, characterized in that: The phosphate solution is added with water to adjust PO4 3- The concentration is 18% to 21%, and ammonia water is added to adjust the pH to 3.5 to 4.

5.

5. A method for continuously synthesizing ferric phosphate according to claim 1, characterized in that: The steps 4) and 5) are repeated until the conductivity of the washing water of the repulping washing is ≤2000 μs / cm.

6. A device for continuously synthesizing ferric phosphate, characterized in that: The invention comprises a first continuous tubular reactor, a filter, an adjusting tank, a second continuous tubular reactor, a crystallization aging kettle, a horizontal screw centrifuge and a re-slurry tank which are sequentially connected through pipelines.

7. The device for continuous synthesis of ferric phosphate according to claim 6, characterized in that: The first continuous tubular reactor is a tubular microreactor, and an exhaust pipe is arranged on the tubular microreactor, and an air inlet pipe is connected to the exhaust pipe; the air inlet pipe is used to introduce air or inert gas into the exhaust pipe.

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