Green and energy-saving production method of food-grade diammonium hydrogen phosphate

Abstract

The invention belongs to the technical field of production of diammonium hydrogen phosphate, and provides a green and energy-saving production method of food-grade diammonium hydrogen phosphate. The production method comprises the following steps: (1) combusting high-purity yellow phosphorus in clean and dry air to generate gaseous P2O5; spraying and absorbing the gaseous P2O5 by using ultrapure water to generate a phosphoric acid solution; the method comprises the following steps: sequentially adding P2O5 and H2O2 into a phosphoric acid solution, stirring for reaction, and sequentially filtering and adsorbing to obtain a food-grade phosphoric acid raw material; (2) preparing a food-grade phosphoric acid raw material into a phosphoric acid solution with the concentration of 85% by adopting ultrapure water, reacting with liquid ammonia, and cooling to obtain a neutralization solution; and (3) separating and dehydrating the neutralization solution to obtain wet crystals, and drying the wet crystals to obtain the food-grade diammonium hydrogen phosphate finished product. According to the production method, the phosphoric acid raw material is subjected to deep purification, graded drying and waste heat utilization, high-purity and low-energy-consumption production is achieved, the impurity content meets the food-grade standard, and remarkable economic benefits and environmental protection advantages are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of diammonium hydrogen phosphate production, and specifically relates to a production method of food-grade diammonium hydrogen phosphate with green energy saving. Background Art

[0002] Food-grade diammonium hydrogen phosphate is the main raw material for preparing food additives, and its production has extremely high requirements for raw material purity and process safety. In recent years, with the continuous growth of the market demand in the food industry, the demand for food-grade diammonium hydrogen phosphate has gradually increased.

[0003] In traditional production methods, wet-process phosphoric acid or thermal-process phosphoric acid is mostly used as the phosphoric acid raw material. Wet-process phosphoric acid needs to go through a complex purification process to remove impurities such as heavy metals and fluorides, with a long process and high cost; although thermal-process phosphoric acid has a relatively high purity, there is still a risk of impurity residue in raw material preparation and subsequent treatment. In addition, the existing drying process mostly uses a single drying device, making it difficult to accurately control the product moisture. Moreover, traditional production methods have high energy consumption and do not conform to the concept of green production.

[0004] Therefore, the diammonium hydrogen phosphate products prepared by traditional methods have problems such as low main component content, high heavy metal content, high energy consumption, and small production scale. Summary of the Invention

[0005] Aiming at the above deficiencies in the prior art, the purpose of the present invention is to provide a production method of food-grade diammonium hydrogen phosphate with green energy saving. This production method realizes high-purity and low-energy consumption production through deep purification, staged drying and waste heat utilization of the phosphoric acid raw material, and the impurity content meets the food-grade standard, with significant economic benefits and environmental protection advantages.

[0006] To achieve the above purpose, the solution adopted by the present invention is:

[0007] A production method of food-grade diammonium hydrogen phosphate with green energy saving includes: (1) burning yellow phosphorus with a purity of greater than or equal to 99.99% in clean and dry air to generate gaseous P2O5; after spraying and absorbing the gaseous P2O5 with ultrapure water at a temperature of 40 - 50°C, a phosphoric acid solution with a concentration of 85% is generated; adding P2O5 and 30% H2O2 in sequence to the phosphoric acid solution, stirring and reacting at 60 - 80°C for 1 - 2 hours, and then performing filtration and adsorption in sequence to obtain a food-grade phosphoric acid raw material; (2) configuring the food-grade phosphoric acid raw material with ultrapure water into a phosphoric acid solution with a concentration of 85%, then reacting with liquid ammonia, stopping adding ammonia when the pH reaches 7.6 - 8.2, and cooling to below 26°C to obtain a neutralization solution; (3) separating and dehydrating the neutralization solution to obtain wet crystals, and drying the wet crystals to obtain a food-grade diammonium hydrogen phosphate finished product.

[0008] Further, in a preferred embodiment of the present invention, in step (1), the addition amount of P2O5 is 0.1%-0.3% of the mass of the phosphoric acid solution.

[0009] Further, in a preferred embodiment of the present invention, in step (1), the addition amount of H2O2 is 0.5%-1% of the mass of the phosphoric acid solution.

[0010] Further, in a preferred embodiment of the present invention, in step (1), the preparation of ultrapure water includes: distilled water passes through a reverse osmosis water treatment system, a resin softening device, a quartz sand filter, an ion exchange column and a precision filter in sequence, then polyacrylamide is added at 0.5-2 mg / L and stirred for 10-15 min, and then ozone is introduced at 1-3 mg / L and contacted for 10-20 min to obtain ultrapure water with a conductivity ≤ 0.05 μS / cm.

[0011] Further, in a preferred embodiment of the present invention, in step (3), the drying includes: the wet crystals enter the first vibrating fluidized bed and the second vibrating fluidized bed in sequence: the first vibrating fluidized bed: hot air drying is adopted, the hot air temperature is set at 80-90 °C, the wind speed is 1.5-2.0 m / s, and the residence time is 5-10 min; the second vibrating fluidized bed: cold air drying is adopted, the cold air temperature is set at 20-30 °C, the wind speed is 0.5-1.0 m / s, and the residence time is 15-20 min.

[0012] Further, in a preferred embodiment of the present invention, in step (3), the hot air of the first vibrating fluidized bed comes from: converting the waste heat generated in step (2) into steam and then converting it into hot air through a heat exchanger.

[0013] Further, in a preferred embodiment of the present invention, in step (3), the mother liquor generated after separation and dehydration is concentrated and then returned to step (2) for recycling.

[0014] Further, in a preferred embodiment of the present invention, in step (3), the heat source required for concentrating the mother liquor comes from: converting the waste heat generated in step (2) into steam for heating.

[0015] The beneficial effects of the production method of food-grade diammonium hydrogen phosphate with green energy conservation provided by the present invention are:

[0016] (1) The production method of food-grade diammonium hydrogen phosphate with green energy conservation provided by the present invention deeply purifies the phosphoric acid raw material: on the one hand, distilled water passes through a reverse osmosis water treatment system, a resin softening device, a quartz sand filter, an ion exchange column and a precision filter, and then after adding a flocculant polyacrylamide and a bactericide ozone treatment, ultrapure water is obtained, which is used as the absorption water for the preparation of food-grade phosphoric acid, avoiding the introduction of impurities such as heavy metals and salts in water; on the other hand, refined high-purity yellow phosphorus is burned in clean and dry air to generate gaseous phosphorus pentoxide (P2O5), which is sprayed and absorbed by the above ultrapure water, and then P2O5 and hydrogen peroxide (H2O2) are added for arsenic and heavy metal treatment to achieve deep purification, ensuring the high purity of the phosphoric acid raw material from the source and significantly reducing the impurity content.

[0017] The above method reduces many chemical and physical method purification processes using industrial phosphoric acid as the raw material, and solves the problems of high viscosity of concentrated phosphoric acid, difficult filtration and inability to rectify and purify phosphoric acid.

[0018] The reverse osmosis water treatment system can operate continuously, the quality of the product water is stable, there is no need for acid-base regeneration, there will be no shutdown due to regeneration, it saves backwashing and cleaning water, produces ultrapure water with high yield, has no regeneration sewage, and does not require sewage treatment facilities.

[0019] (2) The production method of food-grade diammonium hydrogen phosphate with green energy conservation provided by the present invention realizes the gradient removal of moisture through the design of two vibrating fluidized beds: in the drying stage of wet crystals, two vibrating fluidized beds are used to achieve the fractional drying of diammonium hydrogen phosphate products, meeting the moisture requirements of battery grade (≤0.2%). Among them, the first vibrating fluidized bed uses hot air for rapid drying to improve efficiency and remove a large amount of moisture in the product; the second vibrating fluidized bed uses cold air for slow drying, thus avoiding product caking caused by too fast drying.

[0020] (3) The production method of food-grade diammonium hydrogen phosphate with green energy conservation provided by the present invention can play a significant role in energy conservation and environmental protection: the waste heat generated by the thermal phosphoric acid production line is converted into steam, which is used in the processes of mother liquor evaporation and product drying in the production of diammonium hydrogen phosphate, completely replacing the past coal-fired energy supply, reducing coal consumption, reducing waste gas emissions (after achieving a production volume of 5000 tons per year, it can save 2500 tons of coal per year, reduce carbon dioxide emissions by 6500 tons, reduce sulfur dioxide emissions by 60 tons, and reduce nitrogen oxide emissions by 17.5 tons), and at the same time reducing the production cost of the product (reducing the unit production cost by about 300 yuan), meeting the national production requirements for energy conservation and emission reduction. At the same time, the excess steam is sold to other enterprises in the park, promoting the construction and development of the circular economy in the park. Detailed implementation mode

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. For those not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are followed. For reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0022] The features and performance of the present invention will be further described in detail below in conjunction with the embodiments.

[0023] Embodiment 1

[0024] This embodiment provides a production method of food-grade diammonium hydrogen phosphate with green energy conservation, including:

[0025] (1) Burning yellow phosphorus with a purity of greater than or equal to 99.99% in clean and dry air to generate gaseous P2O5; after the gaseous P2O5 is spray-absorbed by ultrapure water at a temperature of 45°C, a phosphoric acid solution with a concentration of 85% is generated; P2O5 (the addition amount of P2O5 is 0.2% of the mass of the phosphoric acid solution) and H2O2 with a concentration of 30% (the addition amount of H2O2 is 0.8% of the mass of the phosphoric acid solution) are sequentially added to the phosphoric acid solution, and the mixture is stirred and reacted at 70°C for 1.5 h. After filtration and adsorption in sequence, a food-grade phosphoric acid raw material is obtained;

[0026] The preparation of ultrapure water includes: distilled water sequentially passes through a reverse osmosis water treatment system (Thermo Scientific RO, RO 24LPH), a resin softening device (LWRH softening resin tank of Lingwo Environment), a quartz sand filter (Mingheta Environmental Protection Technology, Φ350×1760×1.5), an ion exchange column (Dionex TM IonPac TM AS11) and a precision filter (Honeywell, pre-filter PFF61M12-EC), and then polyacrylamide is added at 1.2 mg / L and stirred for 12 min, and then ozone is introduced at 2 mg / L and contacted for 15 min to obtain ultrapure water with a conductivity ≤ 0.05 μS / cm.

[0027] (2) The food-grade phosphoric acid raw material is configured into a phosphoric acid solution with a concentration of 85% using ultrapure water, and then reacted with liquid ammonia. When the pH reaches 8.0, the addition of ammonia is stopped, and it is cooled to below 26°C to obtain a neutralized solution;

[0028] After converting the waste heat generated in step (2) into steam, a part is used as the heat source required for the mother liquor concentration in step (3), and a part is converted into hot air through a heat exchanger and supplied to the first vibrating fluidized bed in step (3). If there is excess steam, it can be sold to other enterprises in the park.

[0029] (3) After separating and dehydrating the neutralized liquid, mother liquor and wet crystals are obtained. The mother liquor is concentrated and then recycled to step (2); the wet crystals are dried to obtain food-grade diammonium hydrogen phosphate finished products. Drying includes: the wet crystals enter a vibrating fluidized bed, and hot air drying is adopted. The hot air temperature is set at 85°C, the wind speed is 1.8 m / s, and the residence time is 25 min.

[0030] Example 2

[0031] This example provides a production method of food-grade diammonium hydrogen phosphate with green energy saving. The difference from Example 1 is as follows: Step (1): Yellow phosphorus with a purity of greater than or equal to 99.99% is burned in clean and dry air to generate gaseous P2O5; the gaseous P2O5 is sprayed and absorbed by ultrapure water at a temperature of 40°C to generate a phosphoric acid solution with a concentration of 85%; P2O5 (the addition amount of P2O5 is 0.1% of the mass of the phosphoric acid solution) and 30% H2O2 (the addition amount of H2O2 is 0.5% of the mass of the phosphoric acid solution) are sequentially added to the phosphoric acid solution, and the mixture is stirred and reacted at 60°C for 2 h. After filtration and adsorption in sequence, food-grade phosphoric acid raw materials are obtained.

[0032] Example 3

[0033] This example provides a production method of food-grade diammonium hydrogen phosphate with green energy saving. The difference from Example 1 is as follows: Step (1): Yellow phosphorus with a purity of greater than or equal to 99.99% is burned in clean and dry air to generate gaseous P2O5; the gaseous P2O5 is sprayed and absorbed by ultrapure water at a temperature of 50°C to generate a phosphoric acid solution with a concentration of 85%; P2O5 (the addition amount of P2O5 is 0.3% of the mass of the phosphoric acid solution) and 30% H2O2 (the addition amount of H2O2 is 1% of the mass of the phosphoric acid solution) are sequentially added to the phosphoric acid solution, and the mixture is stirred and reacted at 80°C for 1 h. After filtration and adsorption in sequence, food-grade phosphoric acid raw materials are obtained.

[0034] Example 4

[0035] This example provides a production method of food-grade diammonium hydrogen phosphate with green energy saving. The difference from Example 1 is as follows: The preparation of ultrapure water includes: distilled water passes through a reverse osmosis water treatment system, a resin softening device, a quartz sand filter, an ion exchange column, and a precision filter in sequence, then polyacrylamide is added at 0.5 mg / L and stirred for 15 min, and then ozone is introduced at 1 mg / L and contacted for 20 min to obtain ultrapure water with a conductivity ≤ 0.05 μS / cm.

[0036] Example 5

[0037] This embodiment provides a method for producing food-grade diammonium hydrogen phosphate with green energy conservation. The difference from Embodiment 1 is that the preparation of ultrapure water includes: distilled water passes through a reverse osmosis water treatment system, a resin softening device, a quartz sand filter, an ion exchange column, and a precision filter in sequence, then polyacrylamide is added at 2 mg / L and stirred for 10 min, and then ozone is introduced at 3 mg / L and contacted for 10 min to obtain ultrapure water with a conductivity ≤ 0.05 μS / cm.

[0038] Example 6

[0039] This embodiment provides a method for producing food-grade diammonium hydrogen phosphate with green energy conservation. The difference from Embodiment 1 is that in step (3) drying, the wet crystals enter a first vibrating fluidized bed and a second vibrating fluidized bed in sequence: First vibrating fluidized bed: Hot air drying is adopted, the hot air temperature is set at 85 °C, the wind speed is 1.8 m / s, and the residence time is 8 min; Second vibrating fluidized bed: Cold air drying is adopted, the cold air temperature is set at 25 °C, the wind speed is 0.8 m / s, and the residence time is 18 min.

[0040] Example 7

[0041] This embodiment provides a method for producing food-grade diammonium hydrogen phosphate with green energy conservation. The difference from Embodiment 1 is that in step (3) drying, the wet crystals enter a first vibrating fluidized bed and a second vibrating fluidized bed in sequence: First vibrating fluidized bed: Hot air drying is adopted, the hot air temperature is set at 80 °C, the wind speed is 2.0 m / s, and the residence time is 10 min; Second vibrating fluidized bed: Cold air drying is adopted, the cold air temperature is set at 20 °C, the wind speed is 1.0 m / s, and the residence time is 15 min.

[0042] Example 8

[0043] This embodiment provides a method for producing food-grade diammonium hydrogen phosphate with green energy conservation. The difference from Embodiment 1 is that in step (3) drying, the wet crystals enter a first vibrating fluidized bed and a second vibrating fluidized bed in sequence: First vibrating fluidized bed: Hot air drying is adopted, the hot air temperature is set at 90 °C, the wind speed is 1.5 m / s, and the residence time is 5 min; Second vibrating fluidized bed: Cold air drying is adopted, the cold air temperature is set at 30 °C, the wind speed is 0.5 m / s, and the residence time is 20 min.

[0044] Comparative Example 1

[0045] This comparative example provides a method for producing diammonium hydrogen phosphate, including:

[0046] (1) Phosphoric acid is configured into a phosphoric acid solution with a concentration of 85% using distilled water, and then reacted with liquid ammonia. When the pH reaches 8.0, ammonia addition is stopped, and it is cooled to below 26 °C to obtain a neutralization solution;

[0047] (2) After separating and dehydrating the neutralized solution, wet crystals are obtained; the wet crystals enter a vibrating fluidized bed: hot air drying is adopted, the hot air temperature is set at 85 °C, the wind speed is 1.8 m / s, and the residence time is 25 min.

[0048] Comparative Example 2

[0049] This comparative example provides a production method of food-grade diammonium hydrogen phosphate with green energy conservation. The difference from Example 1 is that: in steps (1) and (2), distilled water is used for both.

[0050] Comparative Example 3

[0051] This comparative example provides a production method of food-grade diammonium hydrogen phosphate with green energy conservation. The difference from Example 1 is that: (1) Yellow phosphorus with a purity of greater than or equal to 99.99% is burned in clean and dry air to generate gaseous P2O5; the gaseous P2O5 is spray-absorbed with ultrapure water at a temperature of 35 °C to generate a phosphoric acid solution with a concentration of 70%; P2O5 (the addition amount of P2O5 is 0.4% of the mass of the phosphoric acid solution) and 30% H2O2 (the addition amount of H2O2 is 1.2% of the mass of the phosphoric acid solution) are sequentially added to the phosphoric acid solution, and the mixture is stirred and reacted at 50 °C for 2.5 h. After filtration and adsorption in sequence, a food-grade phosphoric acid raw material is obtained.

[0052] Comparative Example 4

[0053] This comparative example provides a production method of food-grade diammonium hydrogen phosphate with green energy conservation. The difference from Example 1 is that the preparation of ultrapure water includes: distilled water passes through a reverse osmosis water treatment system, a resin softening device, a quartz sand filter, an ion exchange column and a precision filter in sequence, and then polyacrylamide is added at 0.5 mg / L and stirred for 15 min, and then ozone is introduced at 1 mg / L and contacted for 20 min to obtain ultrapure water with a conductivity ≤ 0.05 μS / cm.

[0054] Comparative Example 5

[0055] This comparative example provides a production method of food-grade diammonium hydrogen phosphate with green energy conservation. The difference from Example 1 is that the drying in step (3) includes: the wet crystals enter the first vibrating fluidized bed and the second vibrating fluidized bed in sequence: the first vibrating fluidized bed: hot air drying is adopted, the hot air temperature is set at 100 °C, the wind speed is 1.0 m / s, and the residence time is 3 min; the second vibrating fluidized bed: cold air drying is adopted, the cold air temperature is set at 10 °C, the wind speed is 2.0 m / s, and the residence time is 25 min.

[0056] Experimental Example 1

[0057] Experimental method: The following indicators of diammonium hydrogen phosphate provided in Examples 1-8 and Comparative Examples 1-5 were detected, and the detection results are shown in Table 1:

[0058] Main content (calculated as (NH4)2HPO4): It was determined according to the regulations in GB 1886.331-2021 "National Food Safety Standard Food Additive Diammonium Hydrogen Phosphate".

[0059] Moisture: It was determined according to GB / T 10209.3-2010 "Determination of Monoammonium Phosphate and Diammonium Phosphate - Part 3: Moisture".

[0060] Phosphorus pentoxide (calculated as P2O5): It was determined according to GB / T 10209.2-2010 "Determination of Monoammonium Phosphate and Diammonium Phosphate - Part 2: Phosphorus Content".

[0061] Nitrogen (calculated as N): The Kjeldahl method was used, and it was determined according to GB / T 10209.1-2008 "Determination of Monoammonium Phosphate and Diammonium Phosphate - Part 1: Total Nitrogen Content".

[0062] Sulfide (calculated as SO4): It was determined according to the colorimetric method for sulfide and other related methods in GB / T 5009.74-2016 "Determination of Heavy Metals in Food Additives".

[0063] Fluoride (calculated as F): It was determined according to the method specified in GB / T 5009.18.

[0064] Heavy metals (calculated as Pb): It was determined according to the method specified in GB / T 5009.74.

[0065] Arsenic (calculated as As): It was determined according to the method specified in GB 5009.11.

[0066] Table 1

[0067] Group <![CDATA[(NH4)2HPO4]]> Moisture <![CDATA[P2O5]]> N <![CDATA[SO4]]> F Pb As Example 1 99.54％ 0.32％ 53.3％ 21.0％ 0.0013％ 0.00085％ 0.00005％ 0.00014％ Example 2 99.46％ 0.32％ 53.2％ 21.0％ 0.0013％ 0.00088％ 0.00005％ 0.00015％ Example 3 99.48％ 0.33％ 53.1％ 21.0％ 0.0012％ 0.00092％ 0.00006％ 0.00015％ Example 4 99.52％ 0.31％ 53.3％ 21.0％ 0.0014％ 0.00087％ 0.00005％ 0.00014％ Example 5 99.50％ 0.31％ 53.2％ 21.0％ 0.0013％ 0.00094％ 0.00005％ 0.00013％ Example 6 99.76％ 0.08％ 53.5％ 21.2％ 0.0011％ 0.00080％ 0.00004％ 0.00012％ Example 7 99.68％ 0.12％ 53.5％ 21.1％ 0.0012％ 0.00082％ 0.00004％ 0.00012％ Example 8 99.66％ 0.14％ 53.4％ 21.0％ 0.0012％ 0.00081％ 0.00004％ 0.00013％ Comparative Example 1 97.22％ 0.38％ 49.8％ 19.8％ 0.12％ 0.00920％ 0.00052％ 0.00131％ Comparative Example 2 98.12％ 0.32％ 52.4％ 20.2％ 0.0821％ 0.00411％ 0.00034％ 0.00082％ Comparative Example 3 98.88％ 0.33％ 52.8％ 20.6％ 0.0522％ 0.00640％ 0.00041％ 0.00098％ Comparative Example 4 98.64％ 0.31％ 52.5％ 20.4％ 0.0666％ 0.00580％ 0.00038％ 0.00088％ Comparative Example 5 99.14％ 0.18％ 53.0％ 20.8％ 0.0065％ 0.00122％ 0.00012％ 0.00052％

[0068] As can be seen from the data in Table 1, the diammonium hydrogen phosphate products prepared by using the green and energy-saving production method of food-grade diammonium hydrogen phosphate provided in Examples 1-8 of this application have excellent product quality, good stability, extremely high purity and extremely low impurity content, and each content index far exceeds the standard requirements of GB1886.331-2021 "Food-grade Diammonium Phosphate".

[0069] In summary, the green and energy-saving production method of food-grade diammonium hydrogen phosphate provided by the present invention is adopted. This production method realizes high-purity and low-energy consumption production through deep purification, staged drying and waste heat utilization of phosphoric acid raw materials, and the impurity content meets the food-grade standard, with significant economic benefits and environmental protection advantages.

[0070] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A production method of food-grade diammonium hydrogen phosphate with green energy conservation, characterized in that: Including: (1) Burning yellow phosphorus with a purity of greater than or equal to 99.99% in clean and dry air to generate gaseous P2O5; after spraying and absorbing the gaseous P2O5 with ultrapure water at a temperature of 40 - 50°C, a phosphoric acid solution with a concentration of 85% is generated; successively adding P2O5 and 30% H2O2 to the phosphoric acid solution, stirring and reacting at 60 - 80°C for 1 - 2 h, and then successively filtering and adsorbing to obtain a food-grade phosphoric acid raw material; (2) Configuring the food-grade phosphoric acid raw material with the ultrapure water into a phosphoric acid solution with a concentration of 85%, then reacting with liquid ammonia, stopping adding ammonia when the pH reaches 7.6 - 8.2, and cooling to below 26°C to obtain a neutralized solution; (3) Separating and dehydrating the neutralized solution to obtain wet crystals, and drying the wet crystals to obtain the finished product of food-grade diammonium hydrogen phosphate.

2. The production method of food-grade diammonium hydrogen phosphate with green energy conservation according to claim 1, characterized in that: In step (1), the addition amount of the P2O5 is 0.1% - 0.3% of the mass of the phosphoric acid solution.

3. The production method of food-grade diammonium hydrogen phosphate with green energy conservation according to claim 1, characterized in that: In step (1), the addition amount of the H2O2 is 0.5% - 1% of the mass of the phosphoric acid solution.

4. The production method of food-grade diammonium hydrogen phosphate with green energy saving according to claim 1, characterized in that: In step (1), the preparation of the ultrapure water includes: successively passing distilled water through a reverse osmosis water treatment system, a resin softening device, a quartz sand filter, an ion exchange column, and a precision filter, then adding polyacrylamide at 0.5 - 2 mg / L and stirring for 10 - 15 min, and then passing ozone at 1 - 3 mg / L and contacting for 10 - 20 min to obtain the ultrapure water with a conductivity ≤ 0.05 μS / cm.

5. The production method of food-grade diammonium hydrogen phosphate with green energy conservation according to claim 1, characterized in that: In step (3), the drying includes: the wet crystals successively enter the first vibrating fluidized bed and the second vibrating fluidized bed: for the first vibrating fluidized bed: drying with hot air, the hot air temperature is set at 80 - 90°C, the wind speed is 1.5 - 2.0 m / s, and the residence time is 5 - 10 min; for the second vibrating fluidized bed: drying with cold air, the cold air temperature is set at 20 - 30°C, the wind speed is 0.5 - 1.0 m / s, and the residence time is 15 - 20 min.

6. The production method of food-grade diammonium hydrogen phosphate with green energy conservation according to claim 5, characterized in that: In step (3), the hot air of the first vibrating fluidized bed comes from: converting the waste heat generated in step (2) into steam and then converting it into the hot air through a heat exchanger.

7. The production method of food-grade diammonium hydrogen phosphate with green energy conservation according to claim 1, characterized in that: In step (3), the mother liquor generated after separation and dehydration is concentrated and then returned to step (2) for recycling.

8. The production method of food-grade diammonium hydrogen phosphate with green energy conservation according to claim 7, characterized in that: In step (3), the heat source required for concentrating the mother liquor comes from: converting the waste heat generated in step (2) into steam for heating.