Preparation method and preparation reactor of ammonium polyphosphate

Abstract

The invention discloses a preparation method and a preparation reactor of ammonium polyphosphate, and the preparation method of ammonium polyphosphate comprises the following steps: step 1, mixing three raw materials of diammonium hydrogen phosphate, phosphorus pentoxide and urea to obtain a uniformly mixed powdery material; step 2, granulating the powdery material prepared in the step 1 by adopting a dry granulation method; 3, the granules prepared in the step 2 are pressurized and heated in a wet ammonia atmosphere until the granules are in a fully molten state, then heating and pressurizing are stopped, the granules are cooled and then smashed, the ammonium polyphosphate product with the high polymerization degree is obtained, the production efficiency is high, and the polymerization degree of the prepared ammonium polyphosphate is high.

Description

Technical Field

[0001] The invention belongs to the technical field of ammonium polyphosphate preparation, in particular to a method for preparing ammonium polyphosphate and a preparation reactor. Background Art

[0002] Ammonium phosphate (APP) is often used as a flame retardant due to its excellent flame retardant properties. APP is not composed of a single molecule, but a chain polymer formed by the condensation of many phosphoric acid molecules, in which phosphorus atoms and oxygen atoms are connected to each other by covalent bonds. There are six types of ammonium polyphosphate, APP-Ⅰ to APP-Ⅵ6, of which II and V have more application scenarios, such as fertilizers and flame retardants. At present, the main methods for preparing ammonium polyphosphate are as follows: phosphoric acid-urea method, ammonium phosphate dehydration polymerization method, ammonium phosphate and phosphorus pentoxide polymerization method, and phosphorus pentoxide, ammonia, and water vapor gas phase polymerization method. The phosphoric acid-urea method uses urea as an ammonia source and condensation agent, mixes it with phosphoric acid and heats it, so that the reactants maintain a sufficient ammonia concentration in the gas phase to promote the dehydration condensation reaction of ammonium polyphosphate. The ammonium phosphate dehydration polymerization method uses the dehydration condensation reaction of ammonium phosphate (such as diammonium phosphate) and urea to generate ammonium polyphosphate at high temperature. The ammonium phosphate and phosphorus pentoxide polymerization method is that ammonium phosphate reacts with phosphorus pentoxide in an ammonia environment to generate long-chain, high-polymerization degree ammonium polyphosphate. The phosphorus pentoxide, ammonia, and water vapor gas phase polymerization method is that phosphorus pentoxide reacts with ammonia and water vapor at high temperature to generate ammonium metaphosphate, which is then polymerized into APP. These traditional methods have been used in industry for many years, the process is relatively mature, the operators are experienced, the process flow is simple and highly repeatable, and they are suitable for standardized production.

[0003] However, most traditional preparation methods rely on external heating, which leads to uneven temperature distribution in the reactor, prone to local overheating or cooling problems, affecting the degree of polymerization and product quality of ammonium polyphosphate. In addition, the water control effect in the traditional process is poor, and the introduction and discharge of water are difficult to control, which easily leads to side reactions or reduces the degree of polymerization of the product. Summary of the invention

[0004] In order to solve the above technical problems, one of the objects of the present invention is to provide a method for preparing ammonium polyphosphate with a simple preparation method and capable of producing a high degree of polymerization.

[0005] In order to achieve the above object, the technical scheme of the present invention is as follows: A method for preparing ammonium polyphosphate comprises the following steps:

[0006] Step 1: Mixing three raw materials, namely, diammonium hydrogen phosphate, phosphorus pentoxide and urea, to obtain a uniformly mixed powdery material;

[0007] Step 2: granulating the powdery material obtained in step 1 by a dry granulation method;

[0008] Step 3: The pellets obtained in step 2 are pressurized and heated in a wet ammonia atmosphere until they are fully molten, and then the heating and pressurization are stopped, and after cooling, they are pulverized to obtain an ammonium polyphosphate product with a high degree of polymerization.

[0009] The beneficial effects of the above technical solution are: by using wet ammonia as a heat-carrying gas, the temperature of the reaction system can be adjusted, the pressure of the reaction system can be adjusted, and the water participating in the reaction can be entrained at the same time, so that the amount of water added to the entire reaction system, the reaction temperature and the reaction pressure are all flexibly controllable; and the three raw materials are granulated, so that when the materials are reacted in the later stage, there are gaps between the pellets to facilitate the flow of wet ammonia for mass transfer and heat transfer, and at the same time, the ammonia released by the urea in the pellets during the reaction can participate in the polymerization reaction under the internal pressure of the pellets, which is overall beneficial to improving the degree of polymerization of ammonium polyphosphate.

[0010] In step 1 of the above technical solution, diammonium hydrogen phosphate, phosphorus pentoxide and urea are mixed in a molar ratio of 1:0.9-1.2:0.3.

[0011] The beneficial effect of the above technical solution is that as the phosphorus pentoxide increases in the ratio, the degree of polymerization generally shows an upward trend, and the lower the phosphorus pentoxide content, the less complete the chain growth reaction in the polymerization reaction.

[0012] In the dry granulation in step 2 of the above technical solution, a tablet press with a pressure of 10-13KN is used to press the powdery granules into flake granules with a diameter of 5-7mm and a thickness of 3mm.

[0013] The beneficial effect of the above technical solution is that the pellets are prepared into the above specifications, so that the overall fluidity of the pellets is enhanced, the ammonia generated by the internal reaction of the pellets has a good penetration effect from the inside to the outside, and the heat transfer effect of the entire reaction system is better.

[0014] In step 3 of the above technical solution, the reaction temperature is 245-260° C. and the reaction pressure is 7-9 MPa.

[0015] The beneficial effect of the above technical solution is that the influence of selecting this temperature and pressure is mainly because the ammonia pressure has a significant effect on the polymerization degree of the product, especially when the reaction pressure decreases, the average polymerization degree decreases, because the higher the pressure, the more it will inhibit the migration of free ammonia in the solid phase to the phase interface and the diffusion in the gas phase, prolonging the residence time in the solid phase and increasing the chance of amination reaction.

[0016] A second object of the present invention is to provide an ammonium polyphosphate preparation reactor that can perform step 3 in the above preparation method.

[0017] In order to achieve the above-mentioned purpose, the technical scheme of the present invention is as follows: an ammonium polyphosphate preparation reactor, which is used to perform the steps of the preparation method as described above, comprising a reaction part and a recovery part connected to each other, the pellets are added into the reaction part, and hot wet ammonia is continuously introduced into the reaction part, and the recovery part is used to recover the residual ammonia in the tail gas discharged from the reaction part.

[0018] The beneficial effect of the above technical solution is that the pellets can react in the reaction section under the action of hot wet ammonia and eventually form a molten polymer, and the reaction section will eventually discharge tail gas containing a large amount of ammonia, at which time the ammonia in the tail gas can be recovered and utilized by the recovery section.

[0019] The above technical solution also includes a fan disposed at the connection between the reaction part and the recovery part, which is used to draw the tail gas discharged from the reaction part into the recovery part.

[0020] The beneficial effect of the above technical solution is that the fan can provide driving force for the airflow in the reaction part, thereby preventing ammonia from overflowing from the reaction part and causing environmental pollution.

[0021] The recovery part in the above technical solution is used to contain phosphoric acid to react with the residual ammonia in the reaction part to generate diammonium hydrogen phosphate.

[0022] The beneficial effect of the above technical solution is that the diammonium hydrogen phosphate obtained in the recovery unit can be used as one of the raw materials for pellets.

[0023] The reaction part in the above technical solution includes a kettle body and a reaction tube, two partitions are horizontally arranged in the kettle body to divide the kettle body into a first chamber, a second chamber and a third chamber distributed in sequence in an upper and lower order, the lower end of the third chamber is trumpet-shaped to form a slurry outlet, a wet ammonia inlet connected to the second chamber is arranged on the side wall of the kettle body, a tail gas outlet connected to the first chamber is arranged at the upper end of the kettle body, and the tail gas outlet is connected to the recovery part, the reaction tube is vertically arranged in the kettle body, and its upper end passes through the kettle body to form a feeding port, the lower end of the reaction tube passes through the partition to be located in the second chamber, the side wall of the reaction tube is provided with an air outlet connected to the first chamber, the side wall of the reaction tube is provided with an air inlet connected to the second chamber, a valve is arranged at the slurry outlet, and a grid plate is arranged at the lower end of the reaction tube.

[0024] The beneficial effects of the above technical solution are: its structure is simple, so that the heat-carrying wet ammonia can be passed into the reaction tube through the air inlet and flow in the opposite direction to the pellets in the reaction tube, thereby heating and pressurizing the pellets and creating an ammonia atmosphere at the same time. In addition, the pellets are placed in the vertical tube, so that the mass transfer and heat transfer between the pellets are more uniform.

[0025] In the above technical solution, there are multiple reaction tubes.

[0026] The beneficial effect of the above technical solution is that it can improve the utilization rate of heat in wet ammonia and also improve production efficiency.

[0027] The recovery unit described in the above technical solution is an ammonia absorption tower.

[0028] The beneficial effect of the above technical solution is that it has a good absorption effect on ammonia. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of the structure of the reactor for preparing ammonium polyphosphate according to the present invention;

[0030] Figure 2 2 is a cross-sectional view of a reaction portion in an embodiment of the present invention.

[0031] In the figure: 1. reaction part; 11. kettle body; 111. first chamber; 112. second chamber; 113. third chamber; 114. slurry outlet; 115. wet ammonia inlet; 116. tail gas outlet; 117. valve; 118. pressure regulating valve; 12. reaction tube; 121. air outlet; 122. air inlet; 123. grille plate; 13. partition; 14. cover; 2. recovery part; 3. fan. DETAILED DESCRIPTION

[0032] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention. The present invention is described in more detail by way of example with reference to the accompanying drawings in the following paragraphs. The advantages and features of the present invention will become clearer according to the following description and claims. It should be noted that the drawings are all in a very simplified form and are not in precise proportions, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0033] The embodiment of the present invention provides a method for preparing ammonium polyphosphate, comprising the following steps:

[0034] Step 1: Mixing three raw materials, namely, diammonium hydrogen phosphate, phosphorus pentoxide and urea, to obtain a uniformly mixed powdery material;

[0035] Step 2: granulating the powdery material obtained in step 1 by a dry granulation method;

[0036] Step 3: The pellets obtained in step 2 are pressurized and heated in a wet ammonia atmosphere until they are in a fully molten state, and then the heating and pressurization are stopped, and after cooling, they are crushed to obtain a high degree of polymerization ammonium polyphosphate product. By using wet ammonia as a heat-carrying gas, the temperature of the reaction system can be adjusted, and the pressure of the reaction system can be adjusted. At the same time, the water involved in the reaction can be entrained, so that the amount of water added to the entire reaction system, the reaction temperature and the reaction pressure are all flexible and controllable; and the three raw materials are granulated, so that when the materials react in the later stage, there are gaps between the pellets to facilitate the flow of wet ammonia for mass transfer and heat transfer, and at the same time, the ammonia released by the urea in the pellets during the reaction can participate in the polymerization reaction under the internal pressure of the pellets, which is beneficial to improve the degree of polymerization of ammonium polyphosphate as a whole.

[0037] In this embodiment, the moisture content of the wet ammonia can be 0.1-5wt% (it can be any value among 0.1wt%, 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt% and 5wt% or the corresponding range between any two values). Preferably, the moisture content of the wet ammonia is 1.5wt%.

[0038] In the step 1 of the technical scheme, diammonium hydrogen phosphate, phosphorus pentoxide and urea are mixed in a molar ratio of 1:0.9-1.2 (specifically, it can be any value among 0.9, 1, 1.1 and 1.2 or a range corresponding to any two values):0.3. In the above ratio, as the phosphorus pentoxide increases, the degree of polymerization generally shows an upward trend. The lower the phosphorus pentoxide content, the less complete the chain growth reaction in the polymerization reaction.

[0039] Reaction principle: CO(NH2)2+H2O→CO2↑+2NH3↑ Reaction formula 1;

[0040] (NH4)2HPO4+P2O5+NH3→3 / n(NH4PO3)n Reaction formula 2;

[0041] The water in reaction formula 1 of this embodiment comes from wet ammonia, and the ammonia gas generated in reaction formula 1 diffuses inside the pellets and participates in reaction formula 2. Of course, part of the ammonia gas in reaction formula 2 also comes from wet ammonia.

[0042] In the dry granulation in step 2 of the technical scheme (dry granulation is selected because the raw material is hygroscopic), a tablet press machine with a pressure of 10-13KN (which can be any value among 10KN, 11KN, 12KN, 13KN or a range corresponding to any two values) is used to press the powdery granules into flaky granules with a diameter of 5-7mm (which can be any value among 5mm, 6mm and 7mm or a range corresponding to any two values) and a thickness of 3mm. The granules are prepared into the above specifications, so that the overall fluidity of the granules is enhanced, the ammonia generated by the internal reaction of the granules has a good penetration effect from the inside to the outside, and the heat transfer effect of the entire reaction system is better.

[0043] The reaction temperature in step 3 of the above technical scheme is 245-260°C (any value among 245°C, 250°C, 255°C and 260°C or the corresponding range between any two values), and the reaction pressure is 7-9Mpa (any value among 7 Mpa, 8Mpa and 9Mpa or the corresponding range between any two values). The influence of selecting this temperature and pressure is mainly because the ammonia pressure has a significant effect on the polymerization degree of the product, especially when the reaction pressure decreases, the average polymerization degree decreases, because the higher the pressure, the more it will inhibit the migration of free ammonia in the solid phase to the phase interface and the diffusion in the gas phase, prolonging the residence time in the solid phase and increasing the chance of amination reaction.

[0044] In addition, this embodiment also provides an ammonium polyphosphate preparation reactor, which is used to perform step 3 of the preparation method as described above, including a reaction unit 1 and a recovery unit 2 that are connected to each other, the pellets are added to the reaction unit 1, and hot wet ammonia is continuously introduced into the reaction unit 1, and the recovery unit 2 is used to recover the residual ammonia in the tail gas discharged from the reaction unit 1, so that the pellets can react in the reaction unit under the action of hot wet ammonia and finally form a molten polymer, and the reaction unit will eventually discharge tail gas containing a large amount of ammonia, at this time the ammonia in the tail gas can be recovered and utilized by the recovery unit.

[0045] The above technical solution also includes a fan 3 placed at the connection between the reaction part 1 and the recovery part 2, which is used to suck the exhaust gas discharged from the reaction part 1 into the recovery part 2. In this way, the fan can provide driving force for the airflow in the reaction part, thereby avoiding the overflow of ammonia from the reaction part and causing environmental pollution.

[0046] The recovery part 2 in the above technical solution is used to contain phosphoric acid to react with the residual ammonia in the reaction part 1 to form diammonium hydrogen phosphate, so that the diammonium hydrogen phosphate obtained in the recovery part can be used as one of the raw materials of the pellets.

[0047] The reaction part 1 in the above technical solution includes a kettle body 11 and a reaction tube 12, two baffles 13 are horizontally arranged in the kettle body 11 to divide the kettle body 11 into a first chamber 111, a second chamber 112 and a third chamber 113 which are sequentially distributed in the upper and lower order, the lower end of the third chamber 113 is trumpet-shaped to form a slurry outlet 114, a wet ammonia inlet 115 communicating with the second chamber 112 is arranged on the side wall of the kettle body 11 (a pressure regulating valve 118 may be arranged at the wet ammonia inlet 115), an exhaust gas outlet 116 communicating with the first chamber 111 is arranged at the upper end of the kettle body 11, and the exhaust gas outlet 116 is communicated with the recovery part 2, the reaction tube 12 is vertically arranged in the kettle body 11, and its upper end passes through the recovery part 2. A feeding port is formed in the kettle body 11, the lower end of the reaction tube 12 passes through the partition 13 to be located in the second chamber 112, the side wall of the reaction tube 12 is provided with an air outlet 121 connected to the first chamber 111, the side wall of the reaction tube 12 is provided with an air inlet 122 connected to the second chamber 112, a valve 117 is provided at the slurry outlet 114, and a grid plate 123 is provided at the lower end of the reaction tube 12, which has a simple structure, so that the heat-carrying wet ammonia can pass into the reaction tube through the air inlet and flow in the opposite direction to the pellets in the reaction tube, thereby heating and pressurizing the pellets and creating an ammonia atmosphere at the same time. In addition, the pellets are placed in the vertical pipe, which makes the mass transfer and heat transfer between the pellets more uniform.

[0048] In the above technical solution, a plurality of reaction tubes 12 are provided, which can improve the utilization rate of heat in wet ammonia and also improve production efficiency.

[0049] The recovery part 2 in the above technical solution is an ammonia absorption tower, which has a good absorption effect on ammonia.

[0050] In this embodiment, the tail gas components are mainly ammonia, carbon dioxide and water vapor, among which carbon dioxide is directly discharged and ammonia is absorbed using phosphoric acid. The principle is: 2NH3+H3PO4→(NH4)2HPO4. The absorbed diammonium hydrogen phosphate can be recycled as a raw material.

[0051] The upper end of the reaction tube in this embodiment can be sealed with a cover after the addition is completed, so as to prevent the pellets from absorbing moisture in the air and causing an increase in the amount of water in the entire reaction system.

[0052] The present embodiment ensures the uniform distribution of temperature in the reaction system by adopting heat-carrying ammonia to carry out thermal polymerization reaction, and significantly improves the reaction efficiency and the polymerization degree of ammonium polyphosphate. The closed design of the dry granulation process and the reaction tube can realize effective water control, reduce the adverse effect of moisture on the reaction, and improve the polymerization degree and quality of the product. In addition, the reaction tube is used as a reactor, which optimizes gas flow and heat conduction, and enhances the controllability and efficiency of the reaction. The tail gas is absorbed by phosphoric acid, and the recycling of ammonia and ammonium phosphate is realized, which reduces production costs and complies with environmental protection policies. The advantages of the present invention in terms of reaction efficiency, water control effect, process control, resource utilization, equipment design, product performance and cost-effectiveness are all obvious, and have significant industrial application value and market competitiveness.

[0053] In this embodiment, the grid plate can be located below the air inlet, and the holes on the grid plate are smaller than the particle size of the pellets (i.e., the pellets will not fall through the holes of the grid plate). In this embodiment, multiple air inlet holes and air outlet holes can be set on the reaction tube.

[0054] Example 1

[0055] The present embodiment provides a method for preparing ammonium polyphosphate, comprising the following steps: Step 1: mixing diammonium hydrogen phosphate, phosphorus pentoxide and urea in a molar ratio of 1:0.9:0.3 to obtain a uniformly mixed powdery material;

[0056] Step 2: Put the evenly mixed powdered material into a tablet press, and use a mold with a pressure of 10KN and a mold diameter of 5mm to perform dry granulation to obtain flake particles with a diameter of 5mm and a thickness of 3mm;

[0057] Step S3: Place the flaky particles into a reaction tube, introduce heat-carrying wet ammonia (water content 1.5wt%) at a temperature of 255°C, adjust the pressure to 9MPa, control the reaction until the material is completely melted, collect the molten material, and after cooling, crush it to obtain the ammonium polyphosphate product.

[0058] Example 2

[0059] Same as Example 1, except that the molar ratio of the raw materials in step 1 is 1:1.0:0.3.

[0060] Example 3

[0061] Same as Example 1, except that the molar ratio of the raw materials in step 1 is 1:1.1:0.3; and the pressure for flattening the base in step 2 is 11 KN.

[0062] Example 4

[0063] Same as Example 3, except that the molar ratio of the raw materials in step 1 is 1:1.2:0.3; and the pressure of the tablet press in step 2 is 12 KN.

[0064] Example 5

[0065] Same as Example 4, except that the diameter of the abrasive tool in step 2 is 7 mm, and flaky particles with a diameter of 7 mm and a thickness of 3 mm are obtained; and the reaction pressure in step 3 is 9 MPa.

[0066] Example 6

[0067] Same as Example 5, except that the reaction pressure in step 3 is 8 MPa.

[0068] Example 7

[0069] Same as Example 5, except that the reaction pressure in step 3 is 7 MPa.

[0070] Example 8

[0071] Same as Example 4, except that the pressure of the tablet press in step 2 is 13 KN, and the reaction pressure in step 3 is 9 MPa.

[0072] The ammonium polyphosphate products obtained in Examples 1 to 8 were tested for P2O5 content, N content, pH, water-insoluble matter and other indicators in accordance with industrial ammonium polyphosphate HG / T 2770-2020, and the average degree of polymerization of the products was determined by end group titration, and the main crystal structure of the products was detected by XRD. The results are shown in the following table:

[0073] Table of analysis results of ammonium polyphosphate obtained from Example 1 to Example 8

[0074] <![CDATA[w(P2O5) / %]]> w(N) / % Average degree of polymerization Example 1 71.2 14.2 705 Example 2 71.8 14.6 735 Example 3 72.1 14.7 760 Example 4 72.7 14.9 805 Example 5 72.5 14.8 775 Example 6 72.0 14.6 745 Example 7 71.7 14.5 720 Example 8 72.9 14.9 800

[0075] As can be seen from the above table, the final ammonium polyphosphate product has a high average degree of polymerization. The selection of the ratio and the size of the granulating mold is extremely important. As the proportion of phosphorus pentoxide added increases, the degree of polymerization generally shows an upward trend. This is because when the content of phosphorus pentoxide is low, the chain extension reaction in the polymerization reaction is not complete. Compared with 7mm, the particle size of 5mm is smaller, which enhances the penetration and heat transfer effect of ammonia. Therefore, the fluidity is better during polymerization, the heating is more uniform, and the smaller the volume, the greater the partial pressure of ammonia, which is conducive to the polymerization reaction. The ammonia pressure has a significant effect on the degree of polymerization of the product. The reaction pressure decreases and the average degree of polymerization decreases because the higher the pressure, the more it will inhibit the migration of free ammonia in the solid phase to the phase interface and the diffusion in the gas phase, prolonging the residence time in the solid phase and increasing the chance of amination reaction.

[0076] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any ordinary technician in the industry can smoothly implement the present invention as shown in the drawings and described above. However, any equivalent changes, modifications and evolutions made by technicians familiar with the profession without departing from the scope of the technical solution of the present invention using the technical content disclosed above are all equivalent embodiments of the present invention. At the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing ammonium polyphosphate, characterized in that: The steps include: Step 1: Mixing three raw materials, namely, diammonium hydrogen phosphate, phosphorus pentoxide and urea, to obtain a uniformly mixed powdery material; Step 2: granulating the powdery material obtained in step 1 by a dry granulation method; Step 3: The pellets obtained in step 2 are pressurized and heated in a wet ammonia atmosphere until they are fully molten, and then the heating and pressurization are stopped, and after cooling, they are pulverized to obtain an ammonium polyphosphate product with a high degree of polymerization.

2. The method for preparing ammonium polyphosphate according to claim 1, characterized in that: In the step 1, diammonium hydrogen phosphate, phosphorus pentoxide and urea are mixed in a molar ratio of 1:0.9-1.2:0.

3.

3. The method for preparing ammonium polyphosphate according to claim 1, characterized in that: In the step 2, the dry granulation is performed by using a tablet press with a pressure of 10-13 KN to press the powdery granules into flake granules with a diameter of 5-7 mm and a thickness of 3 mm.

4. The method for preparing ammonium polyphosphate according to claim 1, characterized in that: In step 3, the reaction temperature is 245-260° C., and the reaction pressure is 7-9 MPa.

5. An ammonium polyphosphate preparation reactor, which is used to perform step 3 of the preparation method according to any one of claims 1 to 4, characterized in that: The invention comprises a reaction part (1) and a recovery part (2) which are connected to each other. The pellets are added into the reaction part (1), and hot wet ammonia is continuously introduced into the reaction part (1). The recovery part (2) is used to recover the residual ammonia in the tail gas discharged from the reaction part (1).

6. The ammonium polyphosphate preparation reactor according to claim 5, characterized in that: It also includes a fan (3) disposed at the connection between the reaction part (1) and the recovery part (2), and used for sucking the tail gas discharged from the reaction part (1) into the recovery part (2).

7. The ammonium polyphosphate preparation reactor according to claim 5, characterized in that: The recovery section (2) is used to store phosphoric acid to react with residual ammonia in the reaction section (1) to generate diammonium hydrogen phosphate.

8. The ammonium polyphosphate preparation reactor according to claim 5, characterized in that: The reaction part (1) comprises a kettle body (11) and a reaction tube (12); two partitions (13) are horizontally arranged in the kettle body (11) to divide the kettle body (11) into a first chamber (111), a second chamber (112) and a third chamber (113) which are sequentially arranged in an up-down order; the lower end of the third chamber (113) is trumpet-shaped to form a slurry outlet (114); a wet ammonia inlet (115) which is in communication with the second chamber (112) is arranged on the side wall of the kettle body (11); an exhaust gas outlet (116) which is in communication with the first chamber (111) is arranged at the upper end of the kettle body (11); the exhaust gas outlet (116) is in communication with the third chamber (113); The reaction tube (12) is vertically arranged in the kettle body (11), and its upper end passes through the kettle body (11) to form a feeding port. The lower end of the reaction tube (12) passes through the partition (13) to be located in the second chamber (112). The side wall of the reaction tube (12) is provided with an air outlet (121) communicating with the first chamber (111). The side wall of the reaction tube (12) is provided with an air inlet (122) communicating with the second chamber (112). A valve (117) is provided at the slurry outlet (114), and a grid plate (123) is provided at the lower end of the reaction tube (12).

9. The ammonium polyphosphate preparation reactor according to claim 8, characterized in that: A plurality of reaction tubes (12) are provided.

10. The ammonium polyphosphate preparation reactor according to claim 5, characterized in that: The recovery part (2) is an ammonia absorption tower.

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