A continuous iron dissolution method for iron phosphate preparation

Abstract

The application discloses a continuous iron dissolving method for preparing iron phosphate, and comprises the following steps: S1, acid solution is added into a dynamic tubular reactor for pre-washing, and the flow of the acid solution is calibrated, and iron powder is added into the dynamic tubular reactor according to a reducing parameter; S2, a displacement reaction occurs in the dynamic tubular reactor, and the dynamic tubular reactor is in a closed and slightly negative pressure environment; acid mist and by-product hydrogen overflowing from the dynamic tubular reactor are pumped into a gas-liquid separator, and then the hydrogen is pumped into a hydrogen storage tank; S3, the iron phosphate solution obtained through the reaction of the dynamic tubular reactor is filtered through a bag filter through the gas-liquid separator, and then the iron phosphate solution is sampled and analyzed to obtain a clear iron dissolving solution. The application can accurately control the addition amount of raw materials, so that the iron powder is fully reacted in the reactor without residual iron powder, and the continuous iron dissolving process is realized. The safety problem caused by the high hydrogen concentration in the environment due to hydrogen production in the iron dissolving process is effectively solved.

Description

Technical Field

[0001] This invention relates to the field of lithium iron phosphate precursor technology, and more particularly to a continuous iron dissolution method for the preparation of lithium iron phosphate. Background Technology

[0002] Iron phosphate is an important precursor for the preparation of lithium iron phosphate, a cathode material for batteries. It can also be used in catalysts, coatings and ceramics. Currently, the clean and energy-saving preparation method of iron phosphate involves reacting pure iron with phosphoric acid or sulfuric acid to form an iron salt solution (Fe(H2PO4)2 or FeSO4), followed by oxidation precipitation, washing and calcination to obtain a high-purity iron phosphate product.

[0003] Traditional industrial iron melting processes are all batch-type batch production. After a single batch of iron melting is completed, the solution needs to be transferred and the iron concentration adjusted again. The iron melting efficiency is low, and the iron melting time is as long as 6-14 hours. Due to the difficulty in accurately controlling the feed amount of solvent acid and solid iron, as well as the iron melting rate, the solid iron reaction is incomplete, and solid iron residues remain in the iron melting solution. This leads to the problems of large amounts of iron slag accumulation and difficulty in accurately controlling the concentration of the iron melting solution. At the same time, the existing iron melting process generates a large amount of by-product hydrogen gas that cannot be effectively collected. The high hydrogen concentration in the plant can easily cause safety hazards.

[0004] Existing iron-dissolving methods utilize equipment such as the automated iron-dissolving system disclosed in CN202220764032.9 for iron phosphate production. This system uses the iron-dissolving device body, filter box, and rotating plate to filter the solution after iron dissolution. By removing iron residue, it mitigates the impact of residue on the iron content of the molten iron solution, increases the concentration of the solution after iron dissolution, and prevents residual iron solids from remaining undissolved. However, this system cannot improve iron-dissolving efficiency and cannot accurately control the added raw materials, nor can it maintain a consistent molar ratio of iron powder to acid in different batches of iron-dissolving solutions, affecting the quality of each batch of product. This results in inconsistent iron and phosphorus content in the molten iron solutions obtained from different batches, impacting the quality of different batches of product.

[0005] A dynamic tubular reactor is a type of mixing reactor. For example, the method for preparing 1-nitroanthraquinone using a dynamic tubular reactor disclosed in CN 202111639721.3 includes a mixing zone, a mass transfer zone, and a delayed reaction zone located inside the reactor body; a heat exchanger is connected to the reactor body. Using this reactor under these process parameters ensures that the raw materials for preparing 1-nitroanthraquinone are heated and mixed uniformly during the reaction, preventing agglomeration and blockage, and improving reaction efficiency. However, existing dynamic tubular reactors cannot effectively control the amount of solid powder entering the reaction stage; furthermore, no specific solution is proposed for collecting the byproduct hydrogen. Summary of the Invention

[0006] This invention provides a continuous iron-dissolving method for the preparation of iron phosphate to solve the problems mentioned in the background art.

[0007] The solution of the present invention is:

[0008] A continuous iron-dissolving method for the preparation of ferric phosphate includes the following steps:

[0009] S1. The acid solution is added to the dynamic tubular reactor for washing. After the acid solution reaches the overflow height of the dynamic tubular reactor and the temperature fluctuation in the middle section of the dynamic tubular reactor is constant, the acid solution flow rate is calibrated, and iron powder is added to the dynamic tubular reactor according to the feed reduction parameters.

[0010] S2. A displacement reaction occurs inside the dynamic tubular reactor, which is in a closed environment with slight negative pressure. The acid mist and byproduct hydrogen overflowing from the dynamic tubular reactor are pumped to a gas-liquid separator, and then the hydrogen is sent to a hydrogen storage tank.

[0011] S3. The molten iron obtained from the reaction in the dynamic tubular reactor is filtered through a bag filter via a gas-liquid separator, and then a sample is taken for analysis of the iron-to-phosphorus ratio of the molten iron to obtain a clear molten iron solution.

[0012] As a preferred technical solution, the iron powder has a purity greater than 99.90% and a loose bulk density of 2.84–3.42 g / cm³. 3 The iron powder is either reduced iron powder or water-atomized iron powder; the iron powder is reduced iron powder, and the fluidity of the reduced iron powder is within 20-31s; the iron powder used is water-atomized iron powder, and the fluidity of the water-atomized iron powder is within the range of 20-50s.

[0013] As a preferred technical solution, the inverse temperature of the dynamic tubular reactor is controlled at 65-90℃; the residence time of the iron powder and the acid solution in the dynamic tubular reactor is 30-120 min; and the rotation speed of the dynamic tubular reactor is 250 r / min-350 r / min.

[0014] As a preferred technical solution, the acid solution is phosphoric acid, the concentration of the phosphoric acid is 20-40%, the phosphoric acid is added to the dynamic tubular reactor by a high-pressure constant flow pump at a flow rate of A mL / min, and the iron powder is collected into the dynamic tubular reactor by a solid feeder at a flow rate of B g / min, the ratio of A to B is 12.5-22.5.

[0015] As a preferred technical solution, the acid solution is sulfuric acid, the concentration of the sulfuric acid is 10-30%, the sulfuric acid is added to the dynamic tubular reactor by a horizontal flow pump at a flow rate of C mL / min, and the iron powder is collected in the guide channel and flows into the dynamic tubular reactor by a solid feeder at a flow rate of D g / min, and the ratio of C to D is 11.7-15.3.

[0016] As a preferred technical solution, the acid solution is nitric acid, which is added to the dynamic tubular reactor by a horizontal flow pump at a flow rate of E mL / min. Iron powder is collected in the guide channel by a solid feeder at a flow rate of F g / min and then flows into the dynamic tubular reactor. The ratio of E to F is 10.0 to 23.0.

[0017] This invention also discloses an apparatus for a continuous iron-dissolving method in the preparation of iron phosphate, characterized in that it includes a solid feeder, a pump, a feeding cylinder, a dynamic tubular reactor, a gas-liquid separator, a hydrogen storage tank, a fume extraction hood, and a blower. The solid feeder is connected to the dynamic tubular reactor via the feeding cylinder. The pump is connected to the side wall of the feeding cylinder via a pipe. The outlet of the dynamic tubular reactor is connected to the gas-liquid separator via a pipe. The outlet of the gas-liquid separator is connected to the hydrogen storage tank via the blower. The outlet of the gas-liquid separator is connected to a filter. A fume extraction hood is provided at the gas overflow point of the dynamic tubular reactor, and the gas supply pipe of the fume extraction hood is connected to the outlet of the dynamic tubular reactor via a pipe connection.

[0018] As a preferred technical solution, the exhaust port of the dynamic tubular reactor is connected to the exhaust hood; the filter is a bag filter; the solid feeder contains iron powder; and the feed pipe of the pump is connected to the acid solution storage equipment and the nitrogen gas pipeline.

[0019] As a preferred technical solution, the two ends of the feeding cylinder are respectively connected to the outlet of the solid feeder and the inlet of the dynamic tubular reactor. A connecting pipe is provided around the side of the feeding cylinder. One end of the connecting pipe inside the feeding cylinder is connected to the tail end of the spray tip. The other end of the connecting pipe outside the feeding cylinder is connected to the liquid outlet of the pump through a pipe.

[0020] As a preferred technical solution, the outer diameter of the dynamic tubular reactor is 50-450cm, the inner diameter of the dynamic tubular reactor is 35-400cm, and the length of the dynamic tubular reactor is 1.5-10m.

[0021] The above-mentioned technical solution is used in a continuous molten iron method for the preparation of iron phosphate. S1: An acid solution is added to a dynamic tubular reactor for washing. After the acid solution reaches the overflow height of the dynamic tubular reactor and the temperature fluctuation in the middle section of the reactor becomes constant, the acid solution flow rate is calibrated, and iron powder is added to the dynamic tubular reactor according to the feed reduction parameters. S2: A displacement reaction occurs inside the dynamic tubular reactor, which is in a closed environment with slight negative pressure. The acid mist and byproduct hydrogen overflowing from the dynamic tubular reactor are pumped to a gas-liquid separator, and then the hydrogen is sent to a hydrogen storage tank. S3: The molten iron obtained from the reaction in the dynamic tubular reactor is filtered through a bag filter via the gas-liquid separator. Samples are taken for analysis of the iron-to-phosphorus ratio of the molten iron to obtain a clear molten iron solution.

[0022] Advantages of this invention:

[0023] 1) A solid feeder is used to push iron powder with a purity greater than 99.90% into a dynamic tubular reactor to mix and react with phosphoric acid (or sulfuric acid, nitric acid). By precisely controlling the molar ratio of iron powder and phosphoric acid (or sulfuric acid, nitric acid), the iron and phosphorus content in the molten iron solution can be precisely controlled, thereby improving the quality of each batch of products. Using this method for feeding and reaction, the amount of raw materials added can be precisely controlled, thus ensuring that there is no iron powder residue after the iron powder has fully reacted in the reactor, realizing a continuous iron molten iron process.

[0024] 2) The continuous iron dissolving method for the preparation of iron phosphate provided in this application can realize automated feeding of solid-liquid reaction, continuous operation of the whole process, and reduce the general iron dissolving time in large-scale industrial production to 50 minutes to 2 hours. At the same time, the hydrogen produced by the reaction can be continuously and effectively collected in a closed tubular reactor, effectively solving the safety problem caused by excessively high concentration of hydrogen in the environment due to iron dissolving.

[0025] 3) The continuous iron-dissolving apparatus for the preparation of iron phosphate provided in this application employs a liquid diversion and continuous flushing method at the inlet to prevent solid powder (iron powder) from clumping and sticking to the wall at the inlet due to acid vapor, effectively improving the accuracy and precision of solid powder feeding. Simultaneously, the outlet of the dynamic tubular reactor is positioned directly above the reactor main pipe to allow hydrogen gas in the liquid flow to escape. Both the inlet and outlet of the entire system are sealed and subjected to slight negative pressure treatment. The overflowing acid mist and hydrogen gas are extracted from the liquid at a certain speed, and then further separated by condensation before the gas is collected. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the reaction system structure of the equipment used in the continuous iron dissolving method for the preparation of iron phosphate according to the present invention;

[0027] Figure 2This is a schematic diagram of the closed tubular reactor structure used in the embodiments of the present invention;

[0028] Figure 3 This is a flowchart of the continuous iron dissolving method for preparing iron phosphate in an embodiment of the present invention;

[0029] Figure 4 This is a top view of the feeding cylinder structure in an embodiment of the present invention;

[0030] Figure 5 This is a schematic diagram of the three-dimensional structure of the feeding cylinder in an embodiment of the present invention;

[0031] 1-Iron powder; 2-Solid feeder; 3-Feeding cylinder; 31-Cylinder body; 311-Connecting pipe; 312-Spray nozzle; 4-High-pressure constant flow pump; 5-Dynamic tubular reactor; 50-Reaction chamber; 51-Stirring shaft; 52-Jacketed chamber; 6-Hydrogen storage tank; 7-Bag filter; 21-Fan; 22-Gas-liquid separator; 23-Escape hood; 8-Acid solution; 9-Nitrogen. Detailed Implementation

[0032] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific embodiments.

[0033] Example 1

[0034] The steps include the following (using phosphoric acid as an example for acid solutions):

[0035] 1) Pretreatment of raw materials and dynamic tubular reaction system:

[0036] Weigh out industrial-grade refined phosphoric acid, prepare a 20% acid solution with demineralized water, pump it into the dynamic tube inverter through a high-pressure constant flow pump, rinse the inner cavity of the tube inverter, and calibrate the flow rate. Weigh out a sufficient amount of iron powder into the solid transmission feeding system, fix the iron powder to flush the bearing plate, and calibrate and adjust the iron powder feeding parameters. The purity of the acid and iron powder used is greater than 99.90%.

[0037] 2) Continuous preparation

[0038] Start the dynamic tubular reactor system, set the temperature to 80℃, and the reactor rotation speed to 250 r / min. Pump the acid solution into the dynamic tubular reactor system for rinsing using a high-pressure constant flow pump, setting the flow rate to 30 mL / min. Once the acid solution reaches the overflow port height and the temperature fluctuation in the middle section of the reactor becomes constant, turn on the solid feeder, control the iron powder flow rate at 2 g / min, and adjust the angle of the diverted acid solution to flush the iron powder carrier plate, ensuring that all iron powder enters the feed port of the dynamic tubular reactor evenly.

[0039] Iron powder undergoes a displacement reaction with acid in a dynamic tubular reactor to generate molten iron. Solid iron powder is then flushed into the tubular reactor using either acid solution or nitrogen gas until the reaction is complete, yielding the molten iron. Using acid solution or nitrogen gas to flush the iron powder into the tubular reactor avoids clogging of the feed inlet and inaccurate iron powder metering caused by the iron powder sticking to the reactor walls after becoming damp.

[0040] In a closed and slightly negative pressure environment, the acid mist and byproduct hydrogen generated at the inlet are extracted and fed into the solid feeder. The flow rate of the acid solution or nitrogen flow is adjusted according to the amount of acid mist and byproduct hydrogen.

[0041] The outer diameter of the dynamic tubular reactor used is 50-450 cm, the inner diameter is 35-400 cm, and the length is 1.5-10 m.

[0042] The iron powder used has a purity greater than 99.90%; the loose density of the iron powder used is 3.14 g / cm³. 3 The iron powder used was reduced iron powder with a flowability within 21 seconds.

[0043] The temperature of the dynamic tubular reactor is controlled at 65–90℃; the residence time of the acid solution in the dynamic tubular reactor is 30–120 min. The rotational speed of the dynamic tubular reactor is 250 r / min–350 r / min.

[0044] Phosphoric acid is added to the dynamic tubular reactor via a constant flow pump at a flow rate of A mL / min, and iron powder is collected into the dynamic tubular reactor via a solid feeder at a flow rate of B g / min. The ratio of A to B is 12.5 to 22.5.

[0045] The acid solution used is refined phosphoric acid with a concentration of 30%.

[0046] The reaction system used in the iron melting reaction is as follows: Figure 1 , Figure 2 , Figure 3 and 4As shown, iron powder enters the dynamic tubular reactor 5 through the solid feeder 2, and the acid solution used in the reaction enters the dynamic tubular reactor 5 through the high-pressure constant flow pump 4 for the iron melting reaction. The liquid inlet pipe of the high-pressure constant flow pump 4 is connected to the nitrogen gas pipeline. The iron melting liquid after the reaction enters the bag filter 7, and the filtrate is then used for clearing. The feed port of the dynamic tubular reactor 5 is connected to the feed pipe of the high-pressure constant flow pump 4 through a pipeline to realize the recovery of acid mist and hydrogen. At the same time, the hydrogen discharged from the outlet is recovered through the hydrogen storage tank 6 connected to the outlet pipe of the dynamic tubular reactor 5. This avoids production safety accidents caused by excessive hydrogen concentration in the production environment. After the reaction starts, the exhaust port on the feed side is connected to the suction hood. After the exhaust pipe touches the outlet, the gas is separated by the gas-liquid separator, and then the gas is drawn into the hydrogen storage tank 6 by the terminal fan 21. Then, the acid mist overflowing from the feed port of the dynamic tubular reactor 5 and the by-product hydrogen are blown into the dynamic tubular reactor 5. Because acid or nitrogen is used to purge the iron powder adhering to the wall at the feed inlet, some acid mist and by-product hydrogen will be carried into the dynamic tubular reactor 5 and flow out with the reaction liquid.

[0047] Dynamic tubular reactors, such as Figure 2 , Figure 3 and Figure 5 As shown, the dynamic tubular reactor 5 is connected to the solid feeder 2 via the feeding cylinder 3; the high-pressure constant flow pump 4 is connected to a connecting pipe opened on the upper side wall of the feeding cylinder 3; the solid feeder 2 is connected to the cylinder body of the feeding cylinder 3, and the dynamic tubular reactor 5 is connected to the other end of the cylinder body of the feeding cylinder 3. This allows large volumes of solid iron powder to enter the dynamic tubular reactor 5 through the cylinder body 31 of the feeding cylinder 3, while the acid solution is sprayed into the dynamic tubular reactor through the spray nozzles 312 on the side wall of the feeding cylinder 3. This simultaneous feeding and spraying washes away the iron powder, preventing it from adhering to the dynamic tubular reactor 5 and enabling accurate control of the feed amount of the reaction raw materials.

[0048] A connecting pipe 311 is installed on the side wall of the cylinder 31 to connect the inner and outer walls of the cylinder 31, so that the acid solution can flow out inward; a spray tip 312 is provided on the opening of the connecting pipe 311 on the inner wall of the cylinder 31 to enhance the scouring intensity of the acid solution and achieve effective washing of iron powder.

[0049] See the internal structure of dynamic tubular reactor 5. Figure 2 The reaction chamber 50 is internally configured, and a stirring shaft 51 is installed in the reaction chamber 50. The stirring shaft is equipped with an auger agitator, which agitates the materials in the horizontal reaction chamber. A jacketed chamber 52 is installed outside the reaction chamber 50 to control the temperature inside the reaction chamber 51.

[0050] 3) Product post-processing:

[0051] The molten iron from the outlet of the dynamic tubular reactor 5 is passed through a bag filter 7 to remove a small amount of iron residue. The clarified filtrate is packaged separately for later use, and a sample is taken for analysis to determine the iron-to-phosphorus ratio of the molten iron. Hydrogen is collected from the inlet, vent, and outlet of the dynamic tubular reactor 5.

[0052] Example 2

[0053] The difference from Example 1 is that the outer diameter of the dynamic tubular reactor is 50 cm, the inner diameter is 35 cm, and the length is 1.5 m. The raw material is iron powder with a loose density of 2.84 g / cm³. 3 .

[0054] The temperature of the tube reactor in the dynamic tubular reactor is controlled at 65℃; the residence time of the acid solution in the dynamic tubular reactor is 30 min.

[0055] The rotational speed of the dynamic tubular reactor is 250 r / min. Phosphoric acid is added to the dynamic tubular reactor via a constant flow pump at a flow rate of A mL / min, and iron powder is collected into the dynamic tubular reactor via a solid feeder at a flow rate of B g / min. The ratio of A to B is 12.5.

[0056] The acid solution is purified phosphoric acid with a concentration of 20%.

[0057] The fluidity of the reduced iron powder is within 20 seconds.

[0058] Example 3

[0059] The difference from Example 1 is that the outer diameter of the dynamic tubular reactor is 450 cm, the inner diameter is 400 cm, and the length is 10 m. The raw material is iron powder with a loose density of 3.42 g / cm³. 3 .

[0060] The temperature of the tube reactor in the dynamic tubular reactor is controlled at 90℃; the residence time of the acid solution in the dynamic tubular reactor is 120 min.

[0061] The rotational speed of the dynamic tubular reactor is 350 r / min. Phosphoric acid is added to the dynamic tubular reactor via a constant flow pump at a flow rate of A mL / min, and iron powder is collected into the dynamic tubular reactor via a solid feeder at a flow rate of B g / min. The ratio of A to B is 22.5.

[0062] The acid solution is purified phosphoric acid with a concentration of 40%.

[0063] The fluidity of the reduced iron powder is within 31 seconds.

[0064] Example 4

[0065] The difference from Example 1 is that the concentration of industrial-grade sulfuric acid is 30%. The iron powder used is water-atomized iron powder, and the flowability of the water-atomized iron powder is within 20 seconds.

[0066] Example 5

[0067] The difference from Example 1 is that the iron powder used is water-atomized iron powder, and the flowability of the water-atomized iron powder is within 50 seconds. The concentration of industrial-grade sulfuric acid is 10%.

[0068] The iron melting reaction process in Examples 1-5 was monitored, and no solid iron residue was observed in the resulting ferromolten iron. The reaction times were 50 minutes, 60 minutes, 70 minutes, 90 minutes, and 120 minutes, respectively. The method in Example 1 was repeated three times, and the iron-to-phosphorus ratio (molar ratio) in the resulting ferromolten iron was measured in each reaction.

[0069] See Table 1 below:

[0070]

[0071] Note: The iron-phosphorus ratio may not be completely consistent with the same feed amount but different reaction times, possibly due to inconsistencies in the evaporation of acid solution in the tube reaction chamber and analytical errors.

[0072] As shown in the table above, the iron-to-phosphorus ratio in the molten iron obtained by repeating the reaction multiple times using this method remains basically uniform, indicating that the quality of the reactants is uniform when the reaction is repeated multiple times using this method, and the quality of each batch of products is improved. The above describes and illustrates the basic principles, main features, and advantages of this invention. Those skilled in the art should understand that this invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this invention. Various changes and modifications can be made to this invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of this invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A continuous iron-dissolving method for the preparation of ferric phosphate, characterized in that, Includes the following steps: S1. The acid solution is added to the dynamic tubular reactor for washing. After the acid solution reaches the overflow height of the dynamic tubular reactor and the temperature fluctuation in the middle section of the dynamic tubular reactor is constant, the acid solution flow rate is calibrated, and iron powder is added to the dynamic tubular reactor according to the feed reduction parameters. S2. A displacement reaction occurs inside the dynamic tubular reactor, which is in a closed environment with slight negative pressure. The acid mist and byproduct hydrogen overflowing from the dynamic tubular reactor are pumped to a gas-liquid separator, and then the hydrogen is sent to a hydrogen storage tank. S3. The molten iron obtained from the reaction in the dynamic tubular reactor is filtered through the gas-liquid separator and then sampled and sent for analysis of the iron-to-phosphorus ratio of the molten iron to obtain a clear molten iron solution. The iron powder has a purity greater than 99.90%; its loose density is 2.84–3.42 g / cm³. 3 The residence time of the iron powder and the acid solution in the dynamic tubular reactor is 30 to 120 minutes; the rotational speed of the dynamic tubular reactor is 250 r / min to 350 r / min. The equipment used in the continuous iron-dissolving method for preparing ferric phosphate includes a solid feeder, a pump, a feeding cylinder, a dynamic tubular reactor, a gas-liquid separator, a hydrogen storage tank, a fume extraction hood, and a blower. The solid feeder is connected to the dynamic tubular reactor via the feeding cylinder. The pump is connected to the side wall of the feeding cylinder via a pipe. The outlet of the dynamic tubular reactor is connected to the gas-liquid separator via a pipe. The outlet of the gas-liquid separator is connected to the hydrogen storage tank via the blower. The outlet of the gas-liquid separator is connected to a filter. A fume extraction hood is provided at the gas overflow point of the dynamic tubular reactor, and the gas supply pipe of the fume extraction hood is connected to the outlet pipe of the dynamic tubular reactor. The two ends of the feeding cylinder are connected to the outlet of the solid feeder and the inlet of the dynamic tubular reactor, respectively. A connecting pipe is provided around the side of the feeding cylinder. One end of the connecting pipe inside the feeding cylinder is connected to the tail end of the spray nozzle. The other end of the connecting pipe outside the feeding cylinder is connected to the liquid outlet of the pump through a pipe.

2. The continuous iron-dissolving method for preparing ferric phosphate as described in claim 1, characterized in that: The iron powder is either reduced iron powder or water-atomized iron powder; the iron powder is reduced iron powder with a flowability of 20-31s; the iron powder used is water-atomized iron powder with a flowability of 20-50s.

3. The continuous iron-dissolving method for preparing ferric phosphate as described in claim 1, characterized in that: The reaction temperature of the dynamic tubular reactor is controlled between 65 and 90°C.

4. The continuous iron-dissolving method for preparing ferric phosphate as described in claim 1, characterized in that: The acid solution is phosphoric acid, and the concentration of the phosphoric acid is 20-40%. The phosphoric acid is added to the dynamic tubular reactor at a flow rate of A mL / min by a high-pressure constant flow pump. Iron powder is collected into the dynamic tubular reactor at a flow rate of B g / min by a solid feeder. The ratio of A to B is 12.5-22.

5.

5. The continuous iron-dissolving method for preparing ferric phosphate as described in claim 1, characterized in that: The acid solution is sulfuric acid, and the concentration of the sulfuric acid is 10-30%. The sulfuric acid is added to the dynamic tubular reactor by a horizontal flow pump at a flow rate of C mL / min. The iron powder is collected in the guide channel and flows into the dynamic tubular reactor by a solid feeder at a flow rate of D g / min. The ratio of C to D is 11.7-15.

3.

6. The continuous iron-dissolving method for preparing ferric phosphate as described in claim 1, characterized in that: The acid solution is nitric acid, which is added to the dynamic tubular reactor by a horizontal flow pump at a flow rate of E mL / min. Iron powder is collected in the guide channel by a solid feeder at a flow rate of F g / min and then flows into the dynamic tubular reactor. The ratio of E to F is 10.0 to 23.

0.

7. The continuous iron-dissolving method for preparing ferric phosphate as described in claim 1, characterized in that: The vent of the dynamic tubular reactor is connected to the exhaust hood; the filter is a bag filter; the solid feeder contains iron powder; and the pump's feed pipe is connected to the acid solution storage equipment and the nitrogen gas supply line.

8. The continuous iron-dissolving method for preparing iron phosphate as described in claim 1, wherein the outer diameter of the dynamic tubular reactor is 50-450 cm, the inner diameter of the dynamic tubular reactor is 35-400 cm, and the length of the dynamic tubular reactor is 1.5-10 m.

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