Method for preparing iron phosphate and byproduct fertilizer by using ammonium phosphate

Abstract

The invention discloses a method for preparing iron phosphate and a byproduct fertilizer by using ammonium phosphate, a granulation device for producing the byproduct fertilizer comprises a shell with an accommodating space, and the accommodating space of the shell is sequentially divided into a granulation cavity, a material screening cavity and a material temporary storage cavity from top to bottom; an air blowing assembly is arranged between the granulation cavity and the material screening cavity, a vibrating screen capable of vertically moving in a reciprocating mode is arranged between the material screening cavity and the material temporary storage cavity, the material temporary storage cavity is communicated with a discharging pipe, and an end cover is further detachably arranged at the upper end of the shell; the end cover is provided with a plurality of material spraying devices used for spraying fused materials into the shell, and the end cover is further communicated with an exhaust pipe. The blowing assembly comprises a plurality of distribution pipes which are arranged in a staggered mode and communicated with one another, the upper ends of the distribution pipes are communicated with a plurality of air blowing pipes, and one sides of the distribution pipes are further communicated with air inlet pipes. The method not only improves the removal rate of acid insoluble substances in the phosphate concentrate, but also improves the quality of the nitrophosphate fertilizer prepared from the by-product.

Description

Method for preparing ferric phosphate and by-product fertilizer using ammonium phosphate Technical Field

[0001] The present invention relates to the technical field of ferric phosphate production, and in particular to a method for preparing ferric phosphate and by-product fertilizer by using ammonium phosphate. Background Art

[0002] In the process of preparing iron phosphate from phosphate concentrate, the phosphate concentrate needs to be acid-lyzed to remove acid-insoluble matter therein. However, the existing acid hydrolysis method has the problem of low removal rate of acid-insoluble matter. The residual acid-insoluble matter not only affects the quality of subsequent iron phosphate, but also affects the quality of nitric phosphate fertilizer produced as a by-product of the preparation of iron phosphate. Therefore, there is an urgent need to develop a method that can effectively improve the removal rate of acid-insoluble matter in phosphate concentrate.

[0003] Summary of the Invention

[0004] Based on the technical problems existing in the background technology, the present invention proposes a method for preparing iron phosphate and by-product fertilizer using ammonium phosphate.

[0005] The present invention proposes a method for preparing ferric phosphate using ammonium phosphate, the method steps are as follows:

[0006] S11: decomposing the phosphate concentrate with nitric acid, adding a defoaming agent to defoam during the decomposition process, and removing acid-insoluble matter by filtration after decomposition to obtain a first solution;

[0007] S12: adding sulfuric acid to the first solution in S11 to carry out a reaction, and filtering to remove the calcium sulfate precipitate after the reaction to obtain a crude phosphoric acid solution;

[0008] S13: adding ammonia to the crude phosphoric acid solution in S12 for neutralization reaction, and filtering to obtain precipitate A and a second solution after the reaction is completed;

[0009] S14: Add an iron source to the second solution in S13 to react. After the reaction is completed, filter to obtain a precipitate B of iron phosphate and a by-product, the third solution.

[0010] Preferably, the concentration of the nitric acid solution in S11 is 55-65%, and the mass ratio of the nitric acid to the phosphate concentrate is 1.2-1.4:1.

[0011] Preferably, the defoaming agent in S11 is composed of polysiloxane, polyoxyethylene alcohol, and lauryl alcohol polyoxyethylene ether in a mass ratio of 1:0.5-1.5:0.5-1.5.

[0012] Preferably, the concentration of sulfuric acid in S12 is 98%, and the amount of sulfuric acid is 90-96% of the theoretical amount of calcium in the frozen mother liquor.

[0013] Preferably, the amount of ammonia added in S13 is 105-110% of the theoretical amount of ammonia required to form ammonium phosphate in the crude phosphoric acid solution, and the reaction pH is 7-8.

[0014] Preferably, the iron source in S14 is one or more of iron powder, iron oxide, ferrous oxide or ferric nitrate; and the amount of the iron source added is 90-95% of the theoretical amount required for complete reaction with the phosphoric acid in the second solution.

[0015] The above-mentioned method proposed by the present invention uses the by-product of preparing iron phosphate from ammonium phosphate to prepare fertilizer, and the method steps are as follows: the precipitate A in S13 and the by-product third solution in S14 are mixed and concentrated and then melted, and the melted material is granulated by a granulating device to obtain nitrophosphate fertilizer.

[0016] Preferably, the granulation device includes a shell having a accommodating space, and the accommodating space of the shell is divided into a granulation chamber, a screening chamber and a material temporary storage chamber from top to bottom. A blowing assembly is provided between the granulation chamber and the screening chamber, and a vibrating screen that can be vertically moved back and forth is provided between the screening chamber and the material temporary storage chamber. The material temporary storage chamber is connected to a discharge pipe, and the upper end of the shell is also detachably provided with an end cover, and the end cover is provided with a number of spraying devices for spraying molten material into the shell, and the end cover is also connected to an exhaust pipe.

[0017] Preferably, the blowing assembly includes a plurality of distribution pipes that are staggered and interconnected, the upper ends of the distribution pipes are connected to a plurality of blower pipes, and one side of the distribution pipes is also connected to an air inlet pipe.

[0018] Preferably, the lower end of the vibrating screen is connected to a vibrating telescopic rod for driving the vibrating screen to move back and forth, and a telescopic isolation sleeve is provided on the outer side of the vibrating telescopic rod. The two ends of the telescopic isolation sleeve are respectively connected to the bottom of the shell and the lower end of the vibrating screen; the telescopic isolation sleeve includes a reference sleeve and a sliding sleeve slidably connected to it, and a spring is also provided between the reference sleeve and the sliding sleeve.

[0019] Beneficial technical effects of the present invention:

[0020] (1) The present invention adds a defoaming agent during the acid hydrolysis of phosphate concentrate to reduce the generation of foam. The defoaming agent composed of polysiloxane, polyoxyethylene alcohol, and lauryl alcohol polyoxyethylene ether not only has a certain synergistic effect in defoaming, but also can improve the removal rate of acid-insoluble matter, thereby ensuring the quality of subsequently prepared iron phosphate and nitric phosphate fertilizer.

[0021] (2) The present invention prepares nitrophosphate fertilizer by mixing the phosphate of the impurity metal (precipitate A) with a mixed solution of ammonium nitrate and ammonium phosphate produced by preparing ferric phosphate (third solution), thereby achieving full reuse of the by-products of preparing ferric phosphate.

[0022] (3) In the granulation device of the present invention, an upward airflow is generated by the blowing component, which acts on the material in a falling state, causing the material to rotate while falling, thereby making the prepared fertilizer particles more uniform and the surface smoother; the vibrating screen arranged in the shell can realize the screening of the material to obtain nitric acid phosphate fertilizer that meets the particle size requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG1 is a flow chart of a method for preparing ferric phosphate and by-product fertilizer using ammonium phosphate proposed by the present invention.

[0024] FIG2 is a schematic structural diagram of the granulation device proposed in the present invention.

[0025] FIG3 is a partial AA enlarged view of the granulation device proposed by the present invention.

[0026] FIG4 is a schematic structural diagram of the air blowing assembly proposed in the present invention.

[0027] In the figure: 1-shell, 2-end cover, 3-exhaust pipe, 4-spraying device, 5-granulating chamber, 6-blowing assembly, 7-vibrating screen, 8-telescopic isolation sleeve, 9-vibrating telescopic rod, 10-discharge pipe, 11-material temporary storage chamber, 12-screen chamber, 13-inlet pipe, 14-reference sleeve, 15-spring, 16-sliding sleeve, 17-distribution pipe, 18-blast pipe. DETAILED DESCRIPTION

[0028] The composition of the phosphate concentrate used in the examples of the present invention was measured, and the results are shown in Table 1.

[0029] Table 1 Weight composition of the main components in phosphate concentrate

[0030] Example 1

[0031] The present invention proposes a method for preparing ferric phosphate using ammonium phosphate, the method steps are as follows:

[0032] S11: decomposing the phosphate concentrate by nitric acid, adding a defoaming agent for defoaming during the decomposition process, and removing acid-insoluble matter by filtration after decomposition to obtain a first solution; the concentration of the nitric acid solution is 60%, and the mass ratio of the nitric acid to the phosphate concentrate is 1.3:1; the defoaming agent is composed of polysiloxane, polyoxyethylene alcohol, and lauryl alcohol polyoxyethylene ether in a mass ratio of 1:1:1, and the amount of the defoaming agent added is 1% of the mass of the phosphate concentrate.

[0033] S12: adding sulfuric acid to the first solution in S11 to carry out a reaction. After the reaction is completed, the calcium sulfate precipitate is removed by filtration to obtain a crude phosphoric acid solution; the concentration of the sulfuric acid is 98%, and the amount of the sulfuric acid is 93% of the theoretical amount of calcium in the frozen mother liquor.

[0034] S13: adding ammonia to the crude phosphoric acid solution in S12 for neutralization reaction. After the reaction is completed, precipitate A and a second solution are obtained by filtration. The amount of ammonia added is 108% of the theoretical amount of ammonia required to form ammonium phosphate in the crude phosphoric acid solution. The reaction pH is 7.5.

[0035] S14: Add an iron source to the second solution in S13 to react. After the reaction is completed, filter to obtain a precipitate B of ferric phosphate and a third solution as a by-product. The iron source is ferrous oxide. The amount of the iron source added is 92% of the theoretical amount required for complete reaction with the phosphoric acid in the second solution.

[0036] Example 2

[0037] The present invention proposes a method for preparing ferric phosphate using ammonium phosphate, the method steps are as follows:

[0038] S11: decomposing the phosphate concentrate with nitric acid, adding a defoaming agent to defoam during the decomposition process, and removing acid-insoluble matter by filtration after decomposition to obtain a first solution; the concentration of the nitric acid solution is 55%, and the mass ratio of the nitric acid to the phosphate concentrate is 1.2:1; the defoaming agent is composed of polysiloxane, polyoxyethylene alcohol, and lauryl alcohol polyoxyethylene ether in a mass ratio of 1:0.5:0.5, and the amount of the defoaming agent added is 1% of the mass of the phosphate concentrate

[0039] S12: adding sulfuric acid to the first solution in S11 to carry out a reaction. After the reaction is completed, the calcium sulfate precipitate is removed by filtration to obtain a crude phosphoric acid solution; the concentration of the sulfuric acid is 98%, and the amount of the sulfuric acid is 90% of the theoretical amount of calcium in the frozen mother liquor.

[0040] S13: adding ammonia to the crude phosphoric acid solution in S12 for neutralization reaction. After the reaction is completed, precipitate A and a second solution are obtained by filtration. The amount of ammonia added is 105% of the theoretical amount of ammonia required to form ammonium phosphate in the crude phosphoric acid solution. The reaction pH is 7.

[0041] S14: Add an iron source to the second solution in S13 to react. After the reaction is completed, filter to obtain a precipitate B of ferric phosphate and a third solution as a by-product. The iron source is ferric nitrate. The amount of the iron source added is 90% of the theoretical amount required for complete reaction with the phosphoric acid in the second solution.

[0042] Example 3

[0043] The present invention proposes a method for preparing ferric phosphate using ammonium phosphate, the method steps are as follows:

[0044] S11: decomposing the phosphate concentrate by nitric acid, adding a defoaming agent for defoaming during the decomposition process, and removing acid-insoluble matter by filtration after decomposition to obtain a first solution; the concentration of the nitric acid solution is 65%, and the mass ratio of the nitric acid to the phosphate concentrate is 1.4:1; the defoaming agent is composed of polysiloxane, polyoxyethylene alcohol, and lauryl alcohol polyoxyethylene ether in a mass ratio of 1:1.5:1.5, and the amount of the defoaming agent added is 1% of the mass of the phosphate concentrate.

[0045] S12: adding sulfuric acid to the first solution in S11 to carry out a reaction. After the reaction is completed, the calcium sulfate precipitate is removed by filtration to obtain a crude phosphoric acid solution; the concentration of the sulfuric acid is 98%, and the amount of the sulfuric acid is 96% of the theoretical amount of calcium in the frozen mother liquor.

[0046] S13: adding ammonia to the crude phosphoric acid solution in S12 for neutralization reaction. After the reaction is completed, precipitate A and a second solution are obtained by filtration. The amount of ammonia added is 110% of the theoretical amount of ammonia required to form ammonium phosphate in the crude phosphoric acid solution. The reaction pH is 8.

[0047] S14: Add an iron source to the second solution in S13 to react. After the reaction is completed, filter to obtain a precipitate B of ferric phosphate and a third solution as a by-product. The iron source is a mixture of iron powder and iron oxide. The amount of the iron source added is 95% of the theoretical amount required for complete reaction with the phosphoric acid in the second solution.

[0048] Example 4

[0049] The above-mentioned method proposed by the present invention uses the by-product of preparing iron phosphate from ammonium phosphate to prepare fertilizer, and the method steps are as follows: the precipitate A in S13 and the by-product third solution in S14 are mixed and concentrated and then melted, and the melted material is granulated by a granulating device to obtain nitrophosphate fertilizer.

[0050] 2-4 , the granulation device of the present invention includes a shell 1 having a accommodating space, the accommodating space of the shell 1 is divided into a granulation chamber 5, a screening chamber 12 and a material temporary storage chamber 11 from top to bottom, a blowing assembly 6 is provided between the granulation chamber 5 and the screening chamber 12, a vibrating screen 7 that can be vertically moved back and forth is provided between the screening chamber 12 and the material temporary storage chamber 11, the material temporary storage chamber 11 is connected to a discharge pipe 10, the upper end of the shell 1 is also detachably provided with an end cover 2, the end cover 2 is provided with a number of spraying devices 4 for spraying molten material into the shell 1, for the spraying device, the atomization of the material can be achieved by using existing technology, the end cover 2 is also connected to an exhaust pipe 3, and the exhaust pipe can also be connected to an exhaust gas treatment device to reduce environmental pollution.

[0051] Specifically, the blowing assembly 6 includes a plurality of distribution pipes 17 that are staggered and interconnected. The upper ends of the distribution pipes 17 are connected to a plurality of blast pipes 18. One side of the distribution pipes 17 is also connected to an air inlet pipe 13. The gas introduced into the air inlet pipe is an inert gas.

[0052] In addition, the lower end of the vibrating screen 7 is connected to a vibrating telescopic rod 9 for driving the vibrating screen 7 to move back and forth. A telescopic isolation sleeve 8 is provided on the outer side of the vibrating telescopic rod 9. The two ends of the telescopic isolation sleeve 8 are respectively connected to the bottom of the shell 1 and the lower end of the vibrating screen 7; the telescopic isolation sleeve 8 includes a reference sleeve 14 and a sliding sleeve 16 slidably connected to it, and a spring 15 is also provided between the reference sleeve 14 and the sliding sleeve 16.

[0053] In the granulation device of the present invention, an upward airflow is generated by the blowing component 6, which acts on the material in a falling state, causing the material to rotate while falling, thereby making the prepared fertilizer particles more uniform and having a smoother surface; the vibrating screen 7 provided in the shell 1 can realize material screening to obtain nitrophosphate fertilizer that meets the particle size requirements.

[0054] Comparative Example 1

[0055] The present invention proposes a method for preparing ferric phosphate using ammonium phosphate, the method steps are as follows:

[0056] S11: decomposing the phosphate concentrate by nitric acid, adding a defoaming agent for defoaming during the decomposition process, and removing acid-insoluble matter by filtration after decomposition to obtain a first solution; the concentration of the nitric acid solution is 60%, and the mass ratio of the nitric acid to the phosphate concentrate is 1.3:1; the defoaming agent is composed of polysiloxane and polyoxyethylene alcohol in a mass ratio of 1:1, and the amount of the defoaming agent added is 1% of the mass of the phosphate concentrate.

[0057] S12: adding sulfuric acid to the first solution in S11 to carry out a reaction. After the reaction is completed, the calcium sulfate precipitate is removed by filtration to obtain a crude phosphoric acid solution; the concentration of the sulfuric acid is 98%, and the amount of the sulfuric acid is 93% of the theoretical amount of calcium in the frozen mother liquor.

[0058] S13: adding ammonia to the crude phosphoric acid solution in S12 for neutralization reaction. After the reaction is completed, precipitate A and a second solution are obtained by filtration. The amount of ammonia added is 108% of the theoretical amount of ammonia required to form ammonium phosphate in the crude phosphoric acid solution. The reaction pH is 7.5.

[0059] S14: Add an iron source to the second solution in S13 to react. After the reaction is completed, filter to obtain a precipitate B of ferric phosphate and a third solution as a by-product. The iron source is ferrous oxide. The amount of the iron source added is 92% of the theoretical amount required for complete reaction with the phosphoric acid in the second solution.

[0060] Comparative Example 2

[0061] The present invention proposes a method for preparing ferric phosphate using ammonium phosphate, the method steps are as follows:

[0062] S11: decomposing the phosphate concentrate by nitric acid, adding a defoaming agent for defoaming during the decomposition process, and removing acid-insoluble matter by filtration after decomposition to obtain a first solution; the concentration of the nitric acid solution is 60%, and the mass ratio of the nitric acid to the phosphate concentrate is 1.3:1; the defoaming agent is composed of polysiloxane and lauryl alcohol polyoxyethylene ether in a mass ratio of 1:1, and the amount of the defoaming agent added is 1% of the mass of the phosphate concentrate.

[0063] S12: adding sulfuric acid to the first solution in S11 to carry out a reaction. After the reaction is completed, the calcium sulfate precipitate is removed by filtration to obtain a crude phosphoric acid solution; the concentration of the sulfuric acid is 98%, and the amount of the sulfuric acid is 93% of the theoretical amount of calcium in the frozen mother liquor.

[0064] S13: adding ammonia to the crude phosphoric acid solution in S12 for neutralization reaction. After the reaction is completed, precipitate A and a second solution are obtained by filtration. The amount of ammonia added is 108% of the theoretical amount of ammonia required to form ammonium phosphate in the crude phosphoric acid solution. The reaction pH is 7.5.

[0065] S14: Add an iron source to the second solution in S13 to react. After the reaction is completed, filter to obtain a precipitate B of ferric phosphate and a third solution as a by-product. The iron source is ferrous oxide. The amount of the iron source added is 92% of the theoretical amount required for complete reaction with the phosphoric acid in the second solution.

[0066] Comparative Example 3

[0067] The present invention proposes a method for preparing ferric phosphate using ammonium phosphate, the method steps are as follows:

[0068] S11: decomposing the phosphate concentrate by nitric acid, adding a defoaming agent for defoaming during the decomposition process, and removing acid-insoluble matter by filtration after decomposition to obtain a first solution; the concentration of the nitric acid solution is 60%, and the mass ratio of the nitric acid to the phosphate concentrate is 1.3:1; the defoaming agent is composed of polyoxyethylene alcohol and lauryl alcohol polyoxyethylene ether in a mass ratio of 1:1, and the amount of the defoaming agent added is 1% of the mass of the phosphate concentrate.

[0069] S12: adding sulfuric acid to the first solution in S11 to carry out a reaction. After the reaction is completed, the calcium sulfate precipitate is removed by filtration to obtain a crude phosphoric acid solution; the concentration of the sulfuric acid is 98%, and the amount of the sulfuric acid is 93% of the theoretical amount of calcium in the frozen mother liquor.

[0070] S13: adding ammonia to the crude phosphoric acid solution in S12 for neutralization reaction. After the reaction is completed, precipitate A and a second solution are obtained by filtration. The amount of ammonia added is 108% of the theoretical amount of ammonia required to form ammonium phosphate in the crude phosphoric acid solution. The reaction pH is 7.5.

[0071] S14: Add an iron source to the second solution in S13 to react. After the reaction is completed, filter to obtain a precipitate B of ferric phosphate and a third solution as a by-product. The iron source is ferrous oxide. The amount of the iron source added is 92% of the theoretical amount required for complete reaction with the phosphoric acid in the second solution.

[0072] Comparative Example 4

[0073] The present invention proposes a method for preparing ferric phosphate using ammonium phosphate, the method steps are as follows:

[0074] S11: decomposing the phosphate concentrate with nitric acid, and removing acid-insoluble matter by filtration after decomposition to obtain a first solution; the concentration of the nitric acid solution is 60%, and the mass ratio of the nitric acid to the phosphate concentrate is 1.3:1.

[0075] S12: adding sulfuric acid to the first solution in S11 to carry out a reaction. After the reaction is completed, the calcium sulfate precipitate is removed by filtration to obtain a crude phosphoric acid solution; the concentration of the sulfuric acid is 98%, and the amount of the sulfuric acid is 93% of the theoretical amount of calcium in the frozen mother liquor.

[0076] S13: adding ammonia to the crude phosphoric acid solution in S12 for neutralization reaction. After the reaction is completed, precipitate A and a second solution are obtained by filtration. The amount of ammonia added is 108% of the theoretical amount of ammonia required to form ammonium phosphate in the crude phosphoric acid solution. The reaction pH is 7.5.

[0077] S14: Add an iron source to the second solution in S13 to react. After the reaction is completed, filter to obtain a precipitate B of ferric phosphate and a third solution as a by-product. The iron source is ferrous oxide. The amount of the iron source added is 92% of the theoretical amount required for complete reaction with the phosphoric acid in the second solution.

[0078] From the test results of Example 1 and Comparative Examples 1-3, it can be seen that the defoaming effect of the defoaming agent of Example 1 is significantly better than the defoaming effect of Comparative Examples 1-3, which shows that the defoaming agent of the present invention has a certain synergistic effect in eliminating foam during the acid hydrolysis process.

[0079] In addition, it was determined that the mass of acid-insoluble matter in 1000 g of phosphate concentrate after acid hydrolysis using the scheme of Example 1 was 68.71 g, while the mass of acid-insoluble matter in 1000 g of phosphate concentrate after acid hydrolysis using the scheme of Comparative Example 4 was as high as 87.48 g, indicating that the defoaming agent added in the present invention not only has a defoaming effect, but also can improve the removal rate of acid-insoluble matter, thereby ensuring the quality of the subsequently prepared iron phosphate and nitrophosphate fertilizers.

[0080] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing ferric phosphate using ammonium phosphate, characterized in that: The steps are as follows: S11: decomposing the phosphate concentrate with nitric acid, adding a defoaming agent to defoam during the decomposition process, and removing acid-insoluble matter by filtration after decomposition to obtain a first solution; S12: adding sulfuric acid to the first solution in S11 to carry out a reaction, and filtering to remove the calcium sulfate precipitate after the reaction to obtain a crude phosphoric acid solution; S13: adding ammonia to the crude phosphoric acid solution in S12 for neutralization reaction, and filtering to obtain precipitate A and a second solution after the reaction is completed; S14: Add an iron source to the second solution in S13 to react. After the reaction is completed, filter to obtain a precipitate B of iron phosphate and a by-product, the third solution.

2. The method for preparing ferric phosphate using ammonium phosphate according to claim 1, wherein: The concentration of the nitric acid solution in S11 is 55-65%, and the mass ratio of the nitric acid to the phosphate concentrate is 1.2-1.4:

1.

3. The method for preparing ferric phosphate using ammonium phosphate according to claim 1, wherein: The defoaming agent in S11 is composed of polysiloxane, polyoxyethylene alcohol, and lauryl alcohol polyoxyethylene ether in a mass ratio of 1:0.5-1.5:0.5-1.

5.

4. The method for preparing ferric phosphate using ammonium phosphate according to claim 1, wherein: The concentration of sulfuric acid in the S12 is 98%, and the amount of sulfuric acid is 90-96% of the theoretical amount of calcium in the frozen mother liquor.

5. The method for preparing ferric phosphate using ammonium phosphate according to claim 1, wherein: The amount of ammonia added in S13 is 105-110% of the theoretical value of ammonia required to form ammonium phosphate in the crude phosphoric acid solution, and the reaction pH is 7-8.

6. The method for preparing ferric phosphate using ammonium phosphate according to claim 1, wherein: The iron source in S14 is one or more of iron powder, ferric oxide, ferrous oxide or ferric nitrate; the amount of the iron source added is 90-95% of the theoretical amount required for complete reaction with the phosphoric acid in the second solution.

7. A method for preparing fertilizer using a by-product of preparing ferric phosphate using ammonium phosphate according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: mixing and concentrating the precipitate A in S13 and the third by-product solution in S14, and then melting the mixture; and granulating the melted material by a granulating device to obtain nitrophosphate fertilizer.

8. The method for preparing fertilizer using a by-product of preparing ferric phosphate using ammonium phosphate according to claim 7, characterized in that: The granulation device includes a shell with a accommodating space, and the accommodating space of the shell is divided into a granulation chamber, a screening chamber and a material temporary storage chamber from top to bottom. A blowing component is provided between the granulation chamber and the screening chamber, and a vibrating screen that can be vertically moved back and forth is provided between the screening chamber and the material temporary storage chamber. The material temporary storage chamber is connected to a discharge pipe, and an end cover is detachably provided at the upper end of the shell. A plurality of spraying devices for spraying molten material into the shell are provided on the end cover, and the end cover is also connected to an exhaust pipe.

9. The method for preparing fertilizer using a by-product of preparing ferric phosphate using ammonium phosphate according to claim 8, characterized in that: The blowing assembly includes a plurality of distribution pipes that are arranged in a staggered manner and are interconnected. The upper ends of the distribution pipes are connected to a plurality of blast pipes, and one side of the distribution pipes is also connected to an air inlet pipe.

10. The method for preparing fertilizer using a by-product of preparing ferric phosphate using ammonium phosphate according to claim 8, characterized in that: The lower end of the vibrating screen is connected to a vibrating telescopic rod for driving the vibrating screen to move back and forth. A telescopic isolation sleeve is provided on the outer side of the vibrating telescopic rod. The two ends of the telescopic isolation sleeve are respectively connected to the bottom of the shell and the lower end of the vibrating screen; the telescopic isolation sleeve includes a reference sleeve and a sliding sleeve slidably connected to the reference sleeve, and a spring is also provided between the reference sleeve and the sliding sleeve.

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