A system for preparing disodium hydrogen phosphate using sodium pyrophosphate containing metal impurities

Abstract

This utility model discloses a system for preparing disodium hydrogen phosphate from sodium pyrophosphate containing metallic impurities, belonging to the field of waste treatment technology. Crude sodium pyrophosphate is added to a dissolving vessel, followed by demineralized water, to fully dissolve the sodium pyrophosphate and form a solution. Hydrogen peroxide is added to the dissolving vessel, oxidizing low-valence iron and manganese ions to higher valence states. Ethylenediaminetetraacetic acid (EDTA) is added to the dissolving vessel, forming stable complexes with the oxidized high-valence iron and manganese ions, thus separating the impurity ions from the sodium pyrophosphate solution. Precipitation separation is then performed. The filtrate flows into a hydrolysis vessel, where demineralized water and sulfuric acid are added to the dissolving vessel. Hydrolysis occurs in the hydrolysis vessel, hydrolyzing the sodium pyrophosphate into disodium hydrogen phosphate. After hydrolysis, crystallization is performed in a crystallizer to precipitate disodium hydrogen phosphate. The crystallized solution is then separated and dried in an oven to obtain the final disodium hydrogen phosphate product.

Description

Technical Field

[0001] This utility model belongs to the field of waste treatment technology, specifically relating to a system for preparing disodium hydrogen phosphate using sodium pyrophosphate containing metallic impurities. Background Technology

[0002] Glyphosate mother liquor treatment is an industry-wide challenge. Whether produced via the glycine process or the IDA process, the mother liquor is characterized by high COD, high TP, high salt content, complex composition, and difficulty in degradation, making treatment very difficult and costly. Currently, the mainstream mother liquor treatment process uses oxidation methods to degrade the mother liquor and recover phosphorus, including incineration, high-temperature oxidation, medium-temperature oxidation, and low-temperature oxidation. Membrane separation technology or evaporation concentration is also used during the mother liquor treatment process to recover sodium chloride and phosphate. For example: membrane separation recovers sodium chloride, glyphosate, and other substances; evaporation concentration recovers glyphosate and sodium chloride; concentrated mother liquor undergoes targeted conversion to recover sodium pyrophosphate; catalytic oxidation of the mother liquor recovers phosphate, and so on. Each method has its advantages and disadvantages, and major glyphosate manufacturers employ different treatment processes, with most companies combining several of these processes to treat the glyphosate mother liquor. Currently, companies such as Xingfa Group, Xin'an Chemical, and Shandong Runfeng all have facilities for the targeted conversion of concentrated mother liquor to produce sodium pyrophosphate. The crude sodium pyrophosphate obtained has a main content of 40-70%, and the sodium chloride content ranges from 3-35% depending on the processing technology of each company. It also contains impurities such as sodium carbonate, sodium bicarbonate, sodium sulfite, sodium bisulfite, and organophosphates. For this route, whether membrane treatment desalination or evaporation concentration desalination process, the final crude sodium pyrophosphate contains high levels of sodium chloride. The product has many impurities, poor color, off-odor, low main content, and poor quality, resulting in low market price and limited application. Further purification is needed to improve the main content and quality.

[0003] Some companies refine crude sodium pyrophosphate to obtain sodium pyrophosphate, but the production process suffers from problems such as slow dissolution of crude sodium pyrophosphate, high viscosity of the solution, small processing capacity, large wastewater volume, high cost, and poor product quality. The phosphate product also exhibits high levels of residual sodium chloride and organophosphates, resulting in poor quality. For example, CN206915770U describes a system for purifying phosphorus resources after deep treatment of glyphosate mother liquor. CN1068098llA describes a method for preparing sodium pyrophosphate using crude sodium pyrophosphate, and CN106882781A describes a decolorization method for directly refining and extracting sodium pyrophosphate during the purification of crude sodium pyrophosphate to produce sodium pyrophosphate. These methods also suffer from the same problems in processing crude sodium pyrophosphate, including slow dissolution, high viscosity of the solution, small processing capacity, and high sodium chloride content in the sodium pyrophosphate product. Therefore, it is necessary to develop new process methods tailored to the characteristics of the materials.

[0004] Chinese patent CN109399593A, published on March 1, 2019, discloses a method for purifying crude sodium pyrophosphate to produce disodium hydrogen phosphate and sodium chloride. The method involves mixing crude sodium pyrophosphate and water in a hydrolysis reactor at a mass ratio of 1:0.5. Phosphoric acid is added dropwise to control the pH of the mixture within the range of 1.0-8.8. After adding an oxidizing agent, the mixture is stirred at 70-120°C for 5-60 minutes to dissolve and hydrolyze the crude sodium pyrophosphate. The crude sodium pyrophosphate is a crude product obtained by incinerating glyphosate mother liquor and diglyphosate mother liquor wastewater, with sodium pyrophosphate and sodium chloride as its main components. The main components are sodium pyrophosphate and sodium chloride, with a sodium pyrophosphate content of 40-85%, a sodium chloride content of 3-35%, and a total organic carbon content of 0.1-0. 3%, also contains sodium carbonate, sodium bicarbonate, sodium sulfite, sodium bisulfite, and organophosphorus impurities, with an aqueous solution pH of 9.5-10.55; Sodium chloride product recovery: The slurry in the hydrolysis vessel described in step (1) is discharged hot and filtered to obtain sodium chloride product and filtrate; Disodium hydrogen phosphate recovery: The filtrate described in step (2) is cooled and mixed with alkali in a mixer, wherein the alkali is one or a combination of sodium hydroxide, sodium carbonate, and sodium bicarbonate, and the pH of the mixed solution is controlled in the range of 8-10 to generate disodium hydrogen phosphate. After filtering out impurities, it is sent to the crystallization vessel. After the slurry is cooled to 70-85℃, water and disodium hydrogen phosphate crystals are added to the crystallization vessel, and the temperature is controlled at 0-30℃ for 2-8 hours to precipitate disodium hydrogen phosphate dodecahydrate. The fully crystallized slurry is filtered and separated to obtain disodium hydrogen phosphate dodecahydrate product. The disodium hydrogen phosphate dodecahydrate product obtained by this patent has low purity and is ineffective in removing the metal impurities. Utility Model Content

[0005] The purpose of this invention is to solve the problems of existing technologies and provide a system for preparing disodium hydrogen phosphate using sodium pyrophosphate containing metallic impurities. Crude sodium pyrophosphate is added to a dissolving vessel through a crude sodium pyrophosphate inlet pipe, and demineralized water is added to the dissolving vessel through a first water inlet pipe, allowing the sodium pyrophosphate to fully dissolve and form a solution. Subsequently, hydrogen peroxide is added to the dissolving vessel through a hydrogen peroxide inlet pipe, oxidizing low-valence iron and manganese ions to higher valence states. Ethylenediaminetetraacetic acid (EDTA) is added to the dissolving vessel through an EDTA inlet pipe, where ETA forms stable complexes with the oxidized high-valence iron and manganese ions, thereby achieving the desired dissolution. The process involves separating the ions from the sodium pyrophosphate solution; then, the solution is discharged through a first feed pipe into a first filter for precipitation separation; the filtrate flows into a hydrolysis reactor through a first connecting pipe, demineralized water is added to a dissolving reactor through a second inlet pipe, and sulfuric acid is added to the hydrolysis reactor through a sulfuric acid inlet pipe. Hydrolysis occurs in the hydrolysis reactor, hydrolyzing the sodium pyrophosphate into disodium hydrogen phosphate. After hydrolysis, the solution is discharged into a crystallizer through a second feed pipe, where crystallization occurs, precipitating the disodium hydrogen phosphate. The crystallized solution is then separated from the ions through a second filter and dried in an oven to obtain the final disodium hydrogen phosphate product. This invention enables the preparation of high-purity disodium hydrogen phosphate from sodium pyrophosphate containing metallic impurities.

[0006] This utility model is achieved through the following technical solution:

[0007] A system for preparing disodium hydrogen phosphate from sodium pyrophosphate containing metallic impurities includes a dissolving vessel and a hydrolysis vessel. The dissolving vessel is equipped with a crude sodium pyrophosphate inlet pipe, a first water inlet pipe, a hydrogen peroxide inlet pipe, an ethylenediaminetetraacetic acid inlet pipe, and a first feed pipe. The first feed pipe is connected to a first filter, which is connected to the hydrolysis vessel via a first connecting pipe. The hydrolysis vessel is equipped with a second water inlet pipe, a sulfuric acid inlet pipe, and a second feed pipe. The second feed pipe is connected to a crystallizer, which is connected to a second filter via a second connecting pipe. The second filter is connected to an oven.

[0008] Preferably, the dissolving vessel is equipped with a first stirring device.

[0009] Preferably, the hydrolysis vessel is equipped with a second stirring device.

[0010] Preferably, the dissolving vessel is provided with a first temperature control unit, which includes a first temperature sensor and a first heat exchange jacket on the dissolving vessel. The first heat exchange jacket is provided with a first heat exchange inlet pipe and a first heat exchange outlet pipe, and the first heat exchange inlet pipe is provided with a first heat exchange valve.

[0011] Preferably, the hydrolysis vessel is provided with a second temperature control unit, the second temperature control unit includes a second temperature sensor and a second heat exchange jacket provided on the hydrolysis vessel, the second heat exchange jacket is provided with a second heat exchange inlet pipe and a second heat exchange outlet pipe, and the second heat exchange inlet pipe is provided with a second heat exchange valve.

[0012] Preferably, the sodium pyrophosphate crude product inlet pipe, the first water inlet pipe, the hydrogen peroxide inlet pipe, the ethylenediaminetetraacetic acid inlet pipe, the first feed pipe, the second water inlet pipe, the sulfuric acid inlet pipe, and the second feed pipe are all equipped with switch valves.

[0013] Preferably, flow meters are installed on the crude sodium pyrophosphate inlet pipe, the first water inlet pipe, the hydrogen peroxide inlet pipe, the ethylenediaminetetraacetic acid inlet pipe, the second water inlet pipe, and the sulfuric acid inlet pipe.

[0014] Preferably, the ethylenediaminetetraacetic acid (EDTA) inlet pipe is connected to the EDTA feed pump and the EDTA storage tank.

[0015] Preferably, the hydrogen peroxide inlet pipe is connected to the hydrogen peroxide feed pump and the hydrogen peroxide storage tank.

[0016] Compared with the prior art, this utility model has the following advantages and beneficial effects:

[0017] I. This utility model provides a system for preparing disodium hydrogen phosphate from sodium pyrophosphate containing metallic impurities. Crude sodium pyrophosphate is added to a dissolving vessel through a crude sodium pyrophosphate inlet pipe, and demineralized water is added to the dissolving vessel through a first water inlet pipe, allowing the sodium pyrophosphate to fully dissolve and form a solution. Subsequently, hydrogen peroxide is added to the dissolving vessel through a hydrogen peroxide inlet pipe, oxidizing low-valence iron and manganese ions to high-valence states. Ethylenediaminetetraacetic acid (EDTA) is added to the dissolving vessel through an EDTA inlet pipe, where ETA forms stable complexes with the oxidized high-valence iron and manganese ions, thereby achieving the reaction of impurity ions with pyrophosphate. The sodium pyrophosphate solution is separated; then discharged through the first feed pipe into the first filter for precipitation separation; the filtrate flows into the hydrolysis kettle through the first connecting pipe, the demineralized water is added to the dissolving kettle through the second inlet pipe, and sulfuric acid is added to the hydrolysis kettle through the sulfuric acid inlet pipe. Hydrolysis occurs in the hydrolysis kettle, hydrolyzing the sodium pyrophosphate into disodium hydrogen phosphate; after hydrolysis, the solution is discharged into the crystallizer through the second feed pipe, where crystallization occurs to precipitate disodium hydrogen phosphate. The crystallized solution is then separated by the second filter and dried in an oven to obtain the final disodium hydrogen phosphate product. This invention can prepare high-purity disodium hydrogen phosphate from sodium pyrophosphate containing metallic impurities.

[0018] II. The present invention provides a system for preparing disodium hydrogen phosphate from sodium pyrophosphate containing metal impurities. The first temperature control unit facilitates the adjustment of the temperature inside the dissolving vessel, resulting in more thorough dissolution of crude sodium pyrophosphate and better precipitation of metal impurities.

[0019] III. The present invention provides a system for preparing disodium hydrogen phosphate using sodium pyrophosphate containing metallic impurities. The setting of the second temperature control unit facilitates the adjustment of the temperature inside the hydrolysis vessel, resulting in better hydrolysis effect of sodium pyrophosphate.

[0020] IV. The present invention provides a system for preparing disodium hydrogen phosphate using sodium pyrophosphate containing metallic impurities. The setting of the switching valve and flow meter facilitates material feeding and unloading.

[0021] V. The present invention provides a system for preparing disodium hydrogen phosphate from sodium pyrophosphate containing metal impurities. The configuration of the ethylenediaminetetraacetic acid (EDTA) feed pump, EDTA storage tank, hydrogen peroxide feed pump, and hydrogen peroxide storage tank enables precise feeding of EDTA and hydrogen peroxide, and can effectively remove metal impurities. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of this utility model;

[0023] Figure 2 This is a schematic diagram of the structure of Embodiment 2 of this utility model.

[0024] The components include: 1. Dissolving vessel; 2. Hydrolysis vessel; 3. Crude sodium pyrophosphate inlet pipe; 4. First water inlet pipe; 5. Hydrogen peroxide inlet pipe; 6. Ethylenediaminetetraacetic acid inlet pipe; 7. First feed pipe; 8. First filter; 9. First connecting pipe; 10. Second water inlet pipe; 11. Sulfuric acid inlet pipe; 12. Second feed pipe; 13. Crystallizer; 14. Second connecting pipe; 15. Second filter; 16. Drying oven; 17. First stirring device; 18. Second stirring device; 19. 20. First temperature sensor; 21. First heat exchange jacket; 22. First heat exchange inlet pipe; 23. First heat exchange outlet pipe; 24. First heat exchange valve; 25. Second temperature sensor; 26. Second heat exchange jacket; 27. Second heat exchange inlet pipe; 28. Second heat exchange outlet pipe; 29. ​​Second heat exchange valve; 20. Switch valve; 31. Flow meter; 32. Ethylenediaminetetraacetic acid (EDTA) feed pump; 33. ETA storage tank; 34. Hydrogen peroxide feed pump; 35. Hydrogen peroxide storage tank. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to the embodiments, but the implementation of the present invention is not limited thereto.

[0026] Example 1

[0027] like Figure 1As shown, this embodiment provides a system for preparing disodium hydrogen phosphate from sodium pyrophosphate containing metallic impurities. The system includes a dissolving vessel 1 and a hydrolysis vessel 2. The dissolving vessel 1 is equipped with a crude sodium pyrophosphate inlet pipe 3, a first water inlet pipe 4, a hydrogen peroxide inlet pipe 5, an ethylenediaminetetraacetic acid (EDTA) inlet pipe 6, and a first feed pipe 7. The first feed pipe 7 is connected to a first filter 8, which is connected to the hydrolysis vessel 2 via a first connecting pipe 9. The hydrolysis vessel 2 is equipped with a second water inlet pipe 10, a sulfuric acid inlet pipe 11, and a second feed pipe 12. The second feed pipe 12 is connected to a crystallizer 13, which is connected to a second filter 15 via a second connecting pipe 14. The second filter 15 is connected to an oven 16. Both the first filter 8 and the second feed pipe 12 are plate and frame filters.

[0028] Example 2

[0029] like Figure 2 As shown, this embodiment provides a system for preparing disodium hydrogen phosphate from sodium pyrophosphate containing metallic impurities. The system includes a dissolving vessel 1 and a hydrolysis vessel 2. The dissolving vessel 1 is equipped with a crude sodium pyrophosphate inlet pipe 3, a first water inlet pipe 4, a hydrogen peroxide inlet pipe 5, an ethylenediaminetetraacetic acid (EDTA) inlet pipe 6, and a first feed pipe 7. The first feed pipe 7 is connected to a first filter 8, which is connected to the hydrolysis vessel 2 via a first connecting pipe 9. The hydrolysis vessel 2 is equipped with a second water inlet pipe 10, a sulfuric acid inlet pipe 11, and a second feed pipe 12. The second feed pipe 12 is connected to a crystallizer 13, which is connected to a second filter 15 via a second connecting pipe 14. The second filter 15 is connected to an oven 16. Both the first filter 8 and the second feed pipe 12 are plate and frame filters.

[0030] The dissolving vessel 1 is equipped with a first stirring device 17.

[0031] The hydrolysis vessel 2 is equipped with a second stirring device 18. Both the first stirring device 17 and the second stirring device 18 are existing technologies and will not be described in detail here.

[0032] The dissolving vessel 1 is provided with a first temperature control unit, which includes a first temperature sensor 19 and a first heat exchange jacket 20. The first heat exchange jacket 20 is provided with a first heat exchange inlet pipe 21 and a first heat exchange outlet pipe 22. The first heat exchange inlet pipe 21 is provided with a first heat exchange valve 23.

[0033] The hydrolysis vessel 2 is provided with a second temperature control unit, which includes a second temperature sensor 24 and a second heat exchange jacket 25. The second heat exchange jacket 25 is provided with a second heat exchange inlet pipe 26 and a second heat exchange outlet pipe 27. The second heat exchange inlet pipe 26 is provided with a second heat exchange valve 28.

[0034] Among them, the sodium pyrophosphate crude product inlet pipe 3, the first water inlet pipe 4, the hydrogen peroxide inlet pipe 5, the ethylenediaminetetraacetic acid inlet pipe 6, the first feed pipe 7, the second water inlet pipe 10, the sulfuric acid inlet pipe 11, and the second feed pipe 12 are all equipped with switch valves 29.

[0035] Flow meters 30 are installed on the crude sodium pyrophosphate inlet pipe 3, the first water inlet pipe 4, the hydrogen peroxide inlet pipe 5, the ethylenediaminetetraacetic acid inlet pipe 6, the second water inlet pipe 10, and the sulfuric acid inlet pipe 11.

[0036] The ethylenediaminetetraacetic acid (EDTA) inlet pipe 6 is connected to the EDTA feed pump 31 and the EDTA storage tank 32.

[0037] The hydrogen peroxide inlet pipe 5 is connected to the hydrogen peroxide feed pump 33 and the hydrogen peroxide storage tank 34.

[0038] In this process, a 30% hydrogen peroxide solution is added to the hydrogen peroxide inlet pipe 5, with the addition amount being 0.5-1% of the crude sodium pyrophosphate mass. Oxidized to , Oxidized to The molar ratio of ethylenediaminetetraacetic acid (EDTA) to the oxidized metal ions is 1:1 to 1:1.2, forming a stable complex (such as...). and Solid-liquid separation is achieved through filtration. Hydrolysis reaction conditions: sulfuric acid concentration (e.g., 98% concentrated sulfuric acid), hydrolysis temperature (80-100℃), time (30-60min); reaction formula: Na3PO4 + H2SO4 → NaH2PO4 + Na2SO4.

[0039] Compared with the prior art, this utility model has the following advantages and beneficial effects:

[0040] I. This utility model provides a system for preparing disodium hydrogen phosphate from sodium pyrophosphate containing metallic impurities. Crude sodium pyrophosphate is added to a dissolving vessel 1 through a crude sodium pyrophosphate inlet pipe 3. Demineralized water is added to the dissolving vessel 1 through a first water inlet pipe 4, allowing the sodium pyrophosphate to fully dissolve and form a solution. Subsequently, hydrogen peroxide is added to the dissolving vessel 1 through a hydrogen peroxide inlet pipe 5, oxidizing low-valence iron and manganese ions to high-valence states. Ethylenediaminetetraacetic acid (EDTA) is added to the dissolving vessel 1 through an ETA inlet pipe 6, forming stable complexes with the oxidized high-valence iron and manganese ions, thereby achieving the reaction of impurity ions with the sodium pyrophosphate solution. The solution is separated; then discharged through the first feed pipe 7 into the first filter 8 for precipitation separation; the filtrate flows into the hydrolysis kettle 2 through the first connecting pipe 9, the demineralized water is added to the dissolving kettle 1 through the second inlet pipe 10, and the sulfuric acid is added to the hydrolysis kettle 2 through the sulfuric acid inlet pipe 11. Hydrolysis occurs in the hydrolysis kettle 2, hydrolyzing sodium pyrophosphate into disodium hydrogen phosphate; after hydrolysis, the solution is discharged into the crystallizer 13 through the second feed pipe 12, where crystallization occurs to precipitate disodium hydrogen phosphate. The crystallized solution is then separated by the second filter and dried in the oven 16 to obtain the final disodium hydrogen phosphate product. This invention can prepare high-purity disodium hydrogen phosphate from sodium pyrophosphate containing metallic impurities.

[0041] II. The present invention provides a system for preparing disodium hydrogen phosphate from sodium pyrophosphate containing metal impurities. The first temperature control unit facilitates the adjustment of the temperature inside the dissolving vessel 1, resulting in more thorough dissolution of crude sodium pyrophosphate and better precipitation of metal impurities.

[0042] III. The present invention provides a system for preparing disodium hydrogen phosphate using sodium pyrophosphate containing metal impurities. The setting of the second temperature control unit facilitates the adjustment of the temperature inside the hydrolysis vessel 2, resulting in better hydrolysis effect of sodium pyrophosphate.

[0043] IV. The present invention provides a system for preparing disodium hydrogen phosphate using sodium pyrophosphate containing metallic impurities. The setting of the switching valve 29 and the flow meter 30 facilitates material feeding and unloading.

[0044] V. The present invention provides a system for preparing disodium hydrogen phosphate from sodium pyrophosphate containing metal impurities. The arrangement of the ethylenediaminetetraacetic acid feed pump 31, the ethylenediaminetetraacetic acid storage tank 32, the hydrogen peroxide feed pump 33, and the hydrogen peroxide storage tank 34 enables precise feeding of ethylenediaminetetraacetic acid and hydrogen peroxide, and can effectively remove metal impurities.

[0045] The above description is merely a preferred embodiment of the present utility model and is not intended to limit the present utility model in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present utility model shall fall within the protection scope of the present utility model.

Claims

1. A system for preparing disodium hydrogen phosphate using sodium pyrophosphate containing metal impurities, characterized by: The apparatus includes a dissolving vessel (1) and a hydrolysis vessel (2). The dissolving vessel (1) is provided with a crude sodium pyrophosphate inlet pipe (3), a first water inlet pipe (4), a hydrogen peroxide inlet pipe (5), an ethylenediaminetetraacetic acid inlet pipe (6), and a first feed pipe (7). The first feed pipe (7) is connected to a first filter (8), which is connected to the hydrolysis vessel (2) via a first connecting pipe (9). The hydrolysis vessel (2) is provided with a second water inlet pipe (10), a sulfuric acid inlet pipe (11), and a second feed pipe (12). The second feed pipe (12) is connected to a crystallizer (13), which is connected to a second filter (15) via a second connecting pipe (14). The second filter (15) is connected to an oven (16).

2. The system for preparing disodium hydrogen phosphate using sodium pyrophosphate containing metal impurities according to claim 1, characterized in that: The dissolving vessel (1) is equipped with a first stirring device (17).

3. The system for preparing disodium hydrogen phosphate using sodium pyrophosphate containing metal impurities according to claim 1, characterized in that: The hydrolysis vessel (2) is equipped with a second stirring device (18).

4. The system for preparing disodium hydrogen phosphate using sodium pyrophosphate containing metal impurities according to claim 1, characterized in that: The dissolving vessel (1) is provided with a first temperature control unit. The first temperature control unit includes a first temperature sensor (19) provided on the dissolving vessel (1) and a first heat exchange jacket (20) provided on the dissolving vessel (1). The first heat exchange jacket (20) is provided with a first heat exchange inlet pipe (21) and a first heat exchange outlet pipe (22). The first heat exchange inlet pipe (21) is provided with a first heat exchange valve (23).

5. The system for preparing disodium hydrogen phosphate using sodium pyrophosphate containing metal impurities according to claim 1, characterized in that: The hydrolysis vessel (2) is provided with a second temperature control unit. The second temperature control unit includes a second temperature sensor (24) provided on the hydrolysis vessel (2) and a second heat exchange jacket (25) provided on the hydrolysis vessel (2). The second heat exchange jacket (25) is provided with a second heat exchange inlet pipe (26) and a second heat exchange outlet pipe (27). The second heat exchange inlet pipe (26) is provided with a second heat exchange valve (28).

6. The system for preparing disodium hydrogen phosphate using sodium pyrophosphate containing metal impurities according to claim 1, characterized in that: Switch valves (29) are installed on the crude sodium pyrophosphate inlet pipe (3), the first water inlet pipe (4), the hydrogen peroxide inlet pipe (5), the ethylenediaminetetraacetic acid inlet pipe (6), the first feed pipe (7), the second water inlet pipe (10), the sulfuric acid inlet pipe (11), and the second feed pipe (12).

7. The system for preparing disodium hydrogen phosphate using sodium pyrophosphate containing metal impurities according to claim 6, characterized in that: Flow meters (30) are installed on the crude sodium pyrophosphate inlet pipe (3), the first water inlet pipe (4), the hydrogen peroxide inlet pipe (5), the ethylenediaminetetraacetic acid inlet pipe (6), the second water inlet pipe (10), and the sulfuric acid inlet pipe (11).

8. The system for preparing disodium hydrogen phosphate using sodium pyrophosphate containing metal impurities according to claim 1, characterized in that: The ethylenediaminetetraacetic acid inlet pipe (6) is connected to the ethylenediaminetetraacetic acid feed pump (31) and the ethylenediaminetetraacetic acid storage tank (32).

9. The system for preparing disodium hydrogen phosphate using sodium pyrophosphate containing metal impurities according to claim 1, characterized in that: The hydrogen peroxide inlet pipe (5) is connected to the hydrogen peroxide feed pump (33) and the hydrogen peroxide storage tank (34).

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