Method for preparing nitrophosphate fertilizer from phosphate byproduct white fertilizer

Abstract

The invention relates to the technical field of nitrophosphate fertilizers, in particular to a method for preparing a nitrophosphate fertilizer from a phosphate byproduct white fertilizer. The invention discloses a method for preparing a nitrophosphate fertilizer from a phosphate by-product white fertilizer, which comprises the following steps: mixing the phosphate by-product white fertilizer with a shunting mother solution to obtain white fertilizer slurry; adding a nitrogen source and a potassium source into the white fertilizer slurry, and mixing and dissolving to obtain nitro compound fertilizer slurry; spraying granulation and drying are conducted on the nitro compound fertilizer slurry in a drying granulator, the temperature of a drying inlet of the drying granulator is controlled to be 270-350 DEG C in the drying process, the moisture of granulated materials is dried to be smaller than 1%, and the nitrophosphate fertilizer is obtained after granulation is completed. The method provided by the invention solves the problems of massive accumulation and low utilization efficiency of the byproduct white fertilizer in the phosphate industry, and improves the additional value of the white fertilizer.

Description

Technical Field

[0001] The present application relates to the technical field of nitrophosphate fertilizers, and in particular to a method for preparing nitrophosphate fertilizers from phosphate by-product white fertilizer. Background Art

[0002] In the production process of the phosphate industry, especially when producing fine phosphate products (such as industrial-grade MAP, i.e. monoammonium phosphate), a by-product - white fertilizer is produced. White fertilizer contains a large amount of phosphate rock impurities, which are regarded as unfavorable factors in the production process of phosphoric acid and fine phosphate. Due to their large enrichment, they often restrict the continuous development of downstream processes. However, these so-called "impurities" contain medium-amount nutrients and trace nutrients required by a variety of crops and cash crops, such as calcium, magnesium, iron, etc., which makes white fertilizer have the potential to be converted into high-end fertilizer products.

[0003] At present, a common practice for the utilization of phosphate byproduct white fertilizer is to mix a small amount of white fertilizer into the neutralization system of the nitrophosphate fertilizer plant for neutralization, thereby producing nitrogen-phosphorus fertilizer. Although this method can solve the problem of the outlet of white fertilizer to a certain extent, due to the relatively large amount of byproducts produced by the phosphate plant, this doping method cannot digest all the byproducts, resulting in most of the white fertilizer still cannot be effectively utilized and is piled up on site, which not only takes up space but also brings environmental pressure.

[0004] In addition, the industry has also noticed the potential value of "impurities" in white fertilizers, and tried to convert them into slow-release or controlled-release fertilizer products that are more acceptable in the market. This idea can not only increase the value of "crude phosphorus", but also achieve "salt-fertilizer combination, fertilizer-salt complementarity", and is regarded as an effective way to improve the overall economic benefits of fine phosphate plants. However, there are still some problems with the current conversion technology, such as complex processes, low efficiency, and high production costs, which have limited the progress of high-end utilization of white fertilizers.

[0005] In summary, there are many problems in the current utilization of phosphate by-product white fertilizer. To this end, the present application provides a method for preparing nitrophosphate fertilizer from phosphate by-product white fertilizer. Summary of the invention

[0006] In order to overcome the shortcomings of the prior art, the present application provides a method for preparing nitrophosphate fertilizer from phosphate by-product white fertilizer, which comprises mixing the phosphate by-product white fertilizer with the split mother liquor, subsequently adding a nitrogen source and a potassium source to form a nitro-compound fertilizer slurry, and spraying granulating and drying in a drying granulator to finally prepare nitrophosphate fertilizer, thereby solving the problems of large accumulation and low utilization efficiency of by-product white fertilizer in the phosphate industry and increasing the added value of the white fertilizer.

[0007] The technical solution adopted by this application to solve its technical problem is: In a first aspect, the present application provides a method for preparing nitrophosphate fertilizer from phosphate by-product white fertilizer, comprising the following steps: mixing the phosphate byproduct white fertilizer with the split mother liquor to obtain a white fertilizer slurry; Adding a nitrogen source and a potassium source to the white fertilizer slurry, mixing and dissolving them, and obtaining a nitro compound fertilizer slurry; The nitro compound fertilizer slurry is sprayed granulated and dried in a drying granulator. During the drying process, the drying inlet temperature of the drying granulator is controlled at 270-350° C., and the moisture content of the granulated material is dried to less than 1%. After the granulation is completed, nitrophosphate fertilizer is obtained.

[0008] In one or more technical solutions, the phosphate byproduct white fertilizer comprises the following components in percentage by weight: N total: 9.00%-10.00% P2O5: 35.00%-50.00% Water-soluble phosphorus: 20.00%-25.00% H2O: 1.00%-2.00% Ca: 0.50%-1.00% Mg: 1.50%-2.00% Other impurities: remainder; The split mother liquor comprises the following components in percentage by weight: N total: 7.00%-7.50% P2O5: 15.00%-20.00% Water-soluble phosphorus: 15.00%-20.00% H2O: 35.00%-40.00% Fe: 0.00%-0.05% Ca: 0.00%-0.50% Mg: 0.00%-0.50% SO42-: 1.00%-1.50% F: 0.00%-0.20% Other impurities: remainder.

[0009] In one or more technical solutions, the potassium source is one or both of potassium sulfate and potassium nitrate.

[0010] In one or more technical solutions, the nitrogen source is one or both of ammonium nitrate and ammonium sulfate.

[0011] In one or more technical solutions, the nitro compound fertilizer slurry includes the following raw materials in parts by weight: 20-50 parts of white fertilizer, 10-30 parts of split mother liquor, 30-40 parts of nitrogen source, and 29-50 parts of potassium source.

[0012] In one or more technical solutions, the weight content of water in the nitro compound fertilizer slurry is 10%-15%. During the spray granulation process, the temperature of the spray feed is 85-100°C.

[0013] In one or more technical solutions, the drying air outlet temperature during the drying process is controlled at 95-100°C.

[0014] In one or more technical solutions, the hot air pipe of the drying and granulating machine is connected to the heating assembly, and the exhaust pipe of the drying and granulating machine is connected to the dust collector; The feed pipe of the drying granulator is connected to the concentrator, and the discharge pipe of the drying granulator is connected to the conveyor; white fertilizer slurry, nitrogen source and potassium source are added into the concentrator, mixed and dissolved to obtain nitro compound fertilizer slurry.

[0015] In a second aspect, the present application provides nitrophosphate fertilizer, including the nitrophosphate fertilizer prepared by the method described in the first aspect.

[0016] The beneficial effects of this application are: The method described in the present application is to mix the phosphate byproduct white fertilizer with the split mother liquor, then add nitrogen source and potassium source to form nitro compound fertilizer slurry, and spray granulate and dry in a drying granulator to finally prepare nitrophosphate fertilizer, thereby solving the problem of large amount of accumulation and low utilization efficiency of byproduct white fertilizer in the phosphate industry and improving the added value of white fertilizer.

[0017] The method described in the present application produces high-quality nitrophosphate fertilizer, simplifies the production process, reduces production costs, and improves economic benefits. In addition, the method also reduces environmental pressure and realizes the recycling of resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present application is further described below in conjunction with the accompanying drawings and embodiments.

[0019] Figure 1 is a schematic structural diagram of the drying device described in the present application; Figure 2 It is a structural schematic diagram of the drying granulator described in the present application; Figure 3 This application Figure 2 Enlarged view of point A in the middle.

[0020] Among them: 1. Drying granulator; 2. Dust collector; 3. Concentrator; 4. Conveyor; 5. Hot air furnace; 6. Air heater; 7. Blower; 8. Dehumidifier; 9. Cyclone separator; 101. Rotating drum; 102. Feed box; 103. Discharge box; 104. Nozzle; 1021. Feed box; 1022. Feed pipe; 1023. Hot air pipe; 1031. Discharge box; 1032. Discharge pipe; 1033. Exhaust pipe. DETAILED DESCRIPTION

[0021] The following will clearly and completely describe the concept, specific structure and technical effects of the present application in combination with the embodiments and drawings, so as to fully understand the purpose, characteristics and effects of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of them. Based on the embodiments of the present application, other embodiments obtained by technicians in this field without creative work are all within the scope of protection of the present application. In addition, all the connection / connection relationships involved in the patent do not simply refer to the direct connection of components, but refer to the formation of a better connection structure by adding or reducing connection accessories according to the specific implementation situation. The various technical features created in this application can be combined interactively without conflicting with each other.

[0022] Terminology explanation: Phosphate byproduct white fertilizer usually refers to the byproduct produced in the process of phosphate production. This byproduct is enriched with many impurities in phosphate ore. Although it is not good for the production of phosphoric acid and fine phosphate, the medium and trace nutrients contained in it are particularly beneficial to crops and cash crops.

[0023] Split mother liquor refers to a liquid containing a certain concentration of phosphoric acid, ammonium salts and other impurities separated from the phosphate purification or crystallization section during the phosphate production process. This liquid is usually produced as a by-product and has certain economic value in subsequent treatment and utilization.

[0024] Specifically, the phosphate byproduct white fertilizer includes the following components in percentage by weight: N total: 9.00%-10.00% P2O5: 35.00%-50.00% Water-soluble phosphorus: 20.00%-25.00% H2O: 1.00%-2.00% Ca: 0.50%-1.00% Mg: 1.50%-2.00% Other impurities: remainder; Specifically, the split mother liquor includes the following components in percentage by weight: N total: 7.00%-7.50% P2O5: 15.00%-20.00% Water-soluble phosphorus: 15.00%-20.00% H2O: 35.00%-40.00% Fe: 0.00%-0.05% Ca: 0.00%-0.50% Mg: 0.00%-0.50% SO4 2- :1.00%-1.50% F: 0.00%-0.20% Other impurities: remainder.

[0025] The present application provides a method for preparing nitrophosphate fertilizer from phosphate by-product white fertilizer, comprising the following steps: In such Figure 1 In the concentrator of the drying device shown, the phosphate byproduct white fertilizer is mixed with the split mother liquor to obtain a white fertilizer slurry; Adding a nitrogen source and a potassium source to the white fertilizer slurry, mixing and dissolving them, and obtaining a nitro compound fertilizer slurry; The nitro compound fertilizer slurry is concentrated and then transported to Figure 2 The drying granulator shown in the figure; the nitro compound fertilizer slurry is sprayed granulated and dried in the drying granulator. During the drying process, the drying inlet temperature of the drying granulator is controlled at 270-350°C, and the moisture content of the granulated material is dried to <1%. After the granulation is completed, nitrophosphate fertilizer is obtained.

[0026] In one or more embodiments, the nitro-compound fertilizer slurry includes the following raw materials in parts by weight: 20-50 parts of white fertilizer, 10-30 parts of split mother liquor, 30-40 parts of nitrogen source, and 29-50 parts of potassium source.

[0027] Specifically, the potassium source is one or both of potassium sulfate and potassium nitrate.

[0028] Specifically, the nitrogen source is one or both of ammonium nitrate and ammonium sulfate.

[0029] In one or more embodiments, the weight content of water in the nitro-compound fertilizer slurry is 10%-15%; during the spraying granulation process, the temperature of the spraying feed is 85-100°C.

[0030] Specifically, the moisture content is controlled at 10%-15%, and the nitro-compound fertilizer slurry has good fluidity and can pass through pipes and nozzles smoothly to avoid blockage; the temperature of the spraying feed is 85-100℃, which can control the viscosity of the slurry and avoid the slurry being too thin due to too high temperature or too thick due to too low temperature, thereby affecting the granulation effect.

[0031] In one or more embodiments, during the drying process, the drying inlet temperature of the drying granulator is controlled at 270-350° C., the drying outlet temperature is controlled at 95-100° C., and the moisture content of the granulated material is dried to less than 1%.

[0032] In one or more embodiments, the hot air pipe of the drying and granulating machine is connected to the heating assembly, and the exhaust pipe of the drying and granulating machine is connected to the dust collector; The feed pipe of the drying granulator is connected to the concentrator, and the discharge pipe of the drying granulator is connected to the conveyor; white fertilizer slurry, nitrogen source and potassium source are added into the concentrator, mixed and dissolved to obtain nitro compound fertilizer slurry.

[0033] Specifically, the drying device includes a drying granulator 1, the hot air pipe 1023 of the drying granulator 1 is connected to the heating component, and the exhaust pipe 1033 of the drying granulator 1 is connected to the dust collector 2; the feed pipe 1022 of the drying granulator 1 is connected to the concentrator 3, and the discharge pipe 1032 of the drying granulator 1 is connected to the conveyor 4.

[0034] The heating assembly includes a hot air furnace 5, which is connected to the hot air pipe 1023 of the drying granulator 1; the heating assembly also includes an air heater 6 connected to the hot air furnace 5 and a blower 7 connected to the air heater 6. In a specific embodiment, an air heater is used to heat the steam to 160°C once, and then the hot air furnace is connected in series to heat the air for a second time, so that the inlet temperature of the drying cylinder is increased to a control range of 270°C-350°C, ensuring the efficiency and stability of the drying process. The operating parameters of the hot air furnace can be adjusted through the control cabinet and connected to the control system of the central control through an optical fiber cable, which is convenient for the operator to monitor and adjust in real time to ensure the safety and efficiency of the drying process.

[0035] Specifically, the drying granulator 1 includes a rotating drum 101, a feed box 102, a discharge box 103 and a nozzle 104. The feed box and the discharge box 103 are respectively arranged at the two ends of the rotating drum 101, and the nozzle 104 is arranged on the side of the feed box away from the rotating drum 101; the feed box includes a feed box body 1021, a feed pipe 1022, and a hot air pipe 1023. The feed pipe 1022 passes through the feed box body 1021, and one end is placed on the side of the feed box away from the rotating drum 101, and the other end of the feed pipe 1022 is placed in the rotating drum 101; the hot air pipe 1023 is fixedly connected to the feed box body 1021, and is located on the side of the feed box body 1021 away from the rotating drum 101. The discharge box includes a discharge box body 1031 , a discharge pipe 1032 , and an exhaust pipe 1033 . The discharge pipe 1032 is disposed at the bottom of the tail end of the discharge box body 1031 ; the exhaust pipe 1033 is installed on a side of the discharge box body 1031 away from the drum 101 .

[0036] Specifically, the feed box 1021 is fixedly installed at the front end of the drying granulator, and maintains a certain distance from the drum 101 to ensure that the slurry can smoothly enter the drum. One end of the feed pipe 1022 is connected to the concentrator 3, and the other end passes through the feed box 1021 and extends to the inside of the drum 101. The design of the feed pipe 1022 ensures the uniform distribution of the slurry. The hot air pipe 1023 is fixedly connected to the feed box 1021 and is located on the side of the feed box 1021 away from the drum 101. The hot air pipe 1023 is connected to the hot air furnace 5 through a pipeline to ensure that the high-temperature hot air can be smoothly transmitted to the feed box.

[0037] Therefore, by designing the feed pipe 1022 to pass through the feed box 1021, and placing one end of the feed box on the side away from the drum 101, and the other end in the drum 101, it is ensured that the slurry can be evenly distributed before entering the drum. At the same time, the high-temperature hot air introduced by the hot air pipe 1023 preheats the slurry in the feed box, increases the contact area between the slurry and the hot air, and significantly improves the water removal efficiency. The discharge box 1031 is fixedly installed at the rear end of the drying granulator, and maintains a certain distance from the drum 101 to ensure that the dried particles can smoothly enter the discharge box 1031. The discharge pipe 1032 is placed at the bottom of the tail end of the discharge box 1031 to ensure that the material can be discharged smoothly. The discharge pipe 1032 is fixedly connected to the discharge box 1031 and is connected to the conveyor 4 through a flange or other connector. The exhaust pipe 1033 is installed on the side of the discharge box 1031 away from the drum 101 to ensure that the hot and humid gas can be effectively discharged. The exhaust pipe 1033 is fixedly connected to the discharge box 1031 , and is connected to the cyclone separator 9 through a pipeline, and is finally connected to the bag dust collector 2 .

[0038] Therefore, in the drying device described in the present application, the high-temperature hot air generated by the hot air furnace is preheated by the air heater and conveyed by the blower, and after the excess moisture is removed by the dehumidifier, it is introduced into the rotating drum of the drying granulator through the hot air pipe, directly contacts and turns the material to improve the drying efficiency. The hot and humid gas generated during the drying process is discharged through the exhaust pipe and enters the cyclone separator for preliminary particle separation. The gas is then introduced into the bag dust collector for further purification to ensure that the exhaust gas meets environmental protection standards. The dried material is discharged from the discharge box through the discharge pipe and transported to the designated location by the conveyor.

[0039] Example 1 A method for preparing nitrophosphate fertilizer from phosphate by-product white fertilizer comprises the following steps: The phosphate byproduct white fertilizer is mixed with the split mother liquor in a concentrator to obtain a white fertilizer slurry; a nitrogen source and a potassium source are added to the white fertilizer slurry, mixed and dissolved to obtain a nitro compound fertilizer slurry, and concentrated or diluted to control the weight content of water in the nitro compound fertilizer slurry to be 10%-12%; the nitro compound fertilizer slurry comprises the following raw materials in parts by weight: 20 parts of white fertilizer, 10 parts of split mother liquor, 30 parts of ammonium nitrate, and 50 parts of potassium sulfate.

[0040] After concentration, the nitro-compound fertilizer slurry is transferred to a drying granulator; the nitro-compound fertilizer slurry is subjected to spray granulation and drying in the drying granulator, and the temperature of the spray feed during the spray granulation process is 85°C; during the drying process, the drying inlet temperature of the drying granulator is controlled at 270-290°C, and the drying outlet temperature is controlled at 95-100°C, and the moisture content of the granulated material is dried to <1%. After granulation, nitrophosphate fertilizer is obtained.

[0041] Example 2 A method for preparing nitrophosphate fertilizer from phosphate by-product white fertilizer comprises the following steps: The phosphate byproduct white fertilizer is mixed with the split mother liquor in a concentrator to obtain a white fertilizer slurry; a nitrogen source and a potassium source are added to the white fertilizer slurry, mixed and dissolved to obtain a nitro compound fertilizer slurry, and concentrated or diluted to control the weight content of water in the nitro compound fertilizer slurry to be 13%-15%; the nitro compound fertilizer slurry comprises the following raw materials in parts by weight: 50 parts of white fertilizer, 30 parts of split mother liquor, 40 parts of ammonium nitrate, and 29 parts of potassium sulfate.

[0042] After concentration, the nitrocompound fertilizer slurry is transferred to a drying granulator; the nitrocompound fertilizer slurry is subjected to spray granulation and drying in the drying granulator, and the temperature of the spray feed during the spray granulation process is 100°C; during the drying process, the drying inlet temperature of the drying granulator is controlled at 320-350°C, and the drying outlet temperature is controlled at 95-100°C, and the moisture content of the granulated material is dried to <1%, and nitrophosphate fertilizer is obtained after granulation.

[0043] Example 3 A method for preparing nitrophosphate fertilizer from phosphate by-product white fertilizer comprises the following steps: The phosphate byproduct white fertilizer is mixed with the split mother liquor in a concentrator to obtain a white fertilizer slurry; a nitrogen source and a potassium source are added to the white fertilizer slurry, mixed and dissolved to obtain a nitro-compound fertilizer slurry, and concentrated or diluted to control the weight content of water in the nitro-compound fertilizer slurry to be 12%-13%; the nitro-compound fertilizer slurry includes the following raw materials in parts by weight: 31 parts of white fertilizer, 26 parts of split mother liquor, 35 parts of ammonium nitrate, 2 parts of ammonium sulfate, and 35 parts of potassium sulfate.

[0044] After concentration, the nitrocompound fertilizer slurry is transferred to a drying granulator; the nitrocompound fertilizer slurry is subjected to spray granulation and drying in the drying granulator, and the temperature of the spray feed during the spray granulation process is 90°C; during the drying process, the drying inlet temperature of the drying granulator is controlled at 300-320°C, and the drying outlet temperature is controlled at 95-100°C, and the moisture content of the granulated material is dried to <1%, and nitrophosphate fertilizer is obtained after granulation.

[0045] Example 4 A method for preparing nitrophosphate fertilizer from phosphate by-product white fertilizer comprises the following steps: The phosphate byproduct white fertilizer is mixed with the split mother liquor in a concentrator to obtain a white fertilizer slurry; a nitrogen source and a potassium source are added to the white fertilizer slurry, mixed and dissolved to obtain a nitro-compound fertilizer slurry, and concentrated or diluted to control the weight content of water in the nitro-compound fertilizer slurry to 14%; the nitro-compound fertilizer slurry comprises the following raw materials in parts by weight: 20 parts of white fertilizer, 10 parts of split mother liquor, 10 parts of ammonium nitrate, 20 parts of ammonium sulfate, and 40 parts of potassium sulfate.

[0046] After concentration, the nitro-compound fertilizer slurry is transferred to a drying granulator; the nitro-compound fertilizer slurry is subjected to spray granulation and drying in the drying granulator, and the temperature of the spray feed during the spray granulation process is 88°C; during the drying process, the drying inlet temperature of the drying granulator is controlled at 280-285°C, and the drying outlet temperature is controlled at 95-100°C, and the moisture content of the granulated material is dried to <1%. After granulation, nitrophosphate fertilizer is obtained.

[0047] Comparative Example 1 A method for preparing nitrophosphate fertilizer from phosphate by-product white fertilizer comprises the following steps: The phosphate byproduct white fertilizer is mixed with the split mother liquor in a concentrator to obtain white fertilizer slurry; a nitrogen source and a potassium source are added to the white fertilizer slurry, mixed and dissolved to obtain a nitro compound fertilizer slurry, and concentrated or diluted to control the weight content of water in the nitro compound fertilizer slurry to be 7%-8%; the nitro compound fertilizer slurry comprises the following raw materials in parts by weight: 20 parts of white fertilizer, 10 parts of split mother liquor, 30 parts of ammonium nitrate, and 50 parts of potassium sulfate.

[0048] After concentration, the nitro-compound fertilizer slurry is transferred to a drying granulator; the nitro-compound fertilizer slurry is subjected to spray granulation and drying in the drying granulator, and the temperature of the spray feed during the spray granulation process is 85°C; during the drying process, the drying inlet temperature of the drying granulator is controlled at 270-290°C, and the drying outlet temperature is controlled at 95-100°C, and the moisture content of the granulated material is dried to <1%. After granulation, nitrophosphate fertilizer is obtained.

[0049] Comparative Example 2 A method for preparing nitrophosphate fertilizer from phosphate by-product white fertilizer comprises the following steps: The phosphate byproduct white fertilizer is mixed with the split mother liquor in a concentrator to obtain a white fertilizer slurry; a nitrogen source and a potassium source are added to the white fertilizer slurry, mixed and dissolved to obtain a nitro compound fertilizer slurry, and concentrated or diluted to control the weight content of water in the nitro compound fertilizer slurry to be 10%-12%; the nitro compound fertilizer slurry comprises the following raw materials in parts by weight: 20 parts of white fertilizer, 10 parts of split mother liquor, 30 parts of ammonium nitrate, and 50 parts of potassium sulfate.

[0050] After concentration, the nitro-compound fertilizer slurry is transferred to a drying granulator; the nitro-compound fertilizer slurry is subjected to spray granulation and drying in the drying granulator, and the temperature of the spray feed during the spray granulation process is 85°C; during the drying process, the drying inlet temperature of the drying granulator is controlled at 250-260°C, and the drying outlet temperature is controlled at 90-93°C, and the moisture content of the granulated material is dried to <1%. After granulation, nitrophosphate fertilizer is obtained.

[0051] Comparative Example 3 A method for preparing nitrophosphate fertilizer from phosphate by-product white fertilizer comprises the following steps: The phosphate byproduct white fertilizer is mixed with the split mother liquor in a concentrator to obtain a white fertilizer slurry; a nitrogen source and a potassium source are added to the white fertilizer slurry, mixed and dissolved to obtain a nitro compound fertilizer slurry, and concentrated or diluted to control the weight content of water in the nitro compound fertilizer slurry to be 10%-12%; the nitro compound fertilizer slurry comprises the following raw materials in parts by weight: 20 parts of white fertilizer, 10 parts of split mother liquor, 30 parts of ammonium nitrate, and 50 parts of potassium sulfate.

[0052] After concentration, the nitro-compound fertilizer slurry is transferred to a drying granulator; the nitro-compound fertilizer slurry is subjected to spray granulation and drying in the drying granulator, and the temperature of the spray feed during the spray granulation process is 105°C; during the drying process, the drying inlet temperature of the drying granulator is controlled at 270-290°C, and the drying outlet temperature is controlled at 95-100°C, and the moisture content of the granulated material is dried to <1%. After granulation, nitrophosphate fertilizer is obtained.

[0053] Comparative Example 4 A method for preparing nitrophosphate fertilizer from phosphate by-product white fertilizer comprises the following steps: The phosphate byproduct white fertilizer is mixed and dissolved with the nitrogen source and the potassium source in the concentrator to obtain a nitro compound fertilizer slurry, which is then concentrated or diluted so that the weight content of water in the nitro compound fertilizer slurry is controlled at 10%-12%; the nitro compound fertilizer slurry includes the following raw materials in parts by weight: 20 parts of white fertilizer, 30 parts of ammonium nitrate, and 50 parts of potassium sulfate.

[0054] After concentration, the nitro-compound fertilizer slurry is transferred to a drying granulator; the nitro-compound fertilizer slurry is subjected to spray granulation and drying in the drying granulator, and the temperature of the spray feed during the spray granulation process is 85°C; during the drying process, the drying inlet temperature of the drying granulator is controlled at 270-290°C, and the drying outlet temperature is controlled at 95-100°C, and the moisture content of the granulated material is dried to <1%. After granulation, nitrophosphate fertilizer is obtained.

[0055] The specific compositions of the white fertilizer and split mother liquor in the embodiments and comparative examples are shown in Tables 1 and 2 below.

[0056] Table 1 Composition of white fertilizer

[0057] Table 2 Composition of split mother liquor

[0058] The nitrophosphate fertilizers prepared in Examples 1-4 and Comparative Examples 1-4 were subjected to the following performance tests, and the relevant results are summarized in Table 3; Hygroscopicity: Use constant temperature and humidity chamber method and test in accordance with GB / T 10510-2023 "Nitrophosphate Fertilizer, Nitrophosphate Potassium Fertilizer"; Compressive strength: Use a particle strength tester to test in accordance with GB / T 10510-2023 "Nitrophosphate fertilizer, nitrate-phosphate-potassium fertilizer"; Particle size and uniformity: Tested in accordance with GB / T 10510-2023 "Nitrophosphate Fertilizer, Nitrophosphate Potassium Fertilizer".

[0059] Table 3

[0060] Table 4

[0061] As can be seen from Table 3, the nitrophosphate fertilizers prepared in Examples 1-4 have lower hygroscopicity, higher compressive strength, and better particle size and uniformity. These characteristics indicate that: Low hygroscopicity: A low hygroscopicity value means that the fertilizer is less likely to absorb moisture from the air during storage and transportation, thereby reducing the possibility of caking and improving product stability and ease of use.

[0062] High compressive strength: Higher compressive strength means that the fertilizer particles are more solid and are not easy to break into powder during packaging, transportation and field use, thus ensuring the fertilization effect.

[0063] Good particle size and uniformity: A high proportion of particles can pass through a sieve of 1-4.75 mm, which helps ensure that the fertilizer can be evenly distributed in the soil, improve nutrient utilization, and is suitable for the operating requirements of mechanized sowing or fertilization equipment.

[0064] As can be seen from Table 4, the chemical composition characteristics of the nitrophosphate fertilizers prepared in Examples 1-4, such as the moderate to abundant contents of major nutrient elements such as nitrogen, phosphorus, and potassium, meet the needs of crop growth. At the same time, the pH value is within an appropriate range and will not cause adverse effects on the soil. In addition, the lower Cl- (chloride ion) content also helps to reduce potential damage to sensitive crops.

[0065] Therefore, in this application, the moisture content in the nitro-compound fertilizer slurry is adjusted to an appropriate range (10%-15%) before spray granulation, which not only ensures fluidity but also avoids agglomeration caused by excessive humidity; the drying inlet temperature is set at 270-350°C, and the air outlet temperature is controlled at 95-100°C. Such temperature control measures effectively remove excess moisture without destroying the fertilizer structure.

[0066] The white fertilizer, split mother liquor, nitrogen source and potassium source are mixed in a certain proportion, which not only makes full use of the useful components in the by-product white fertilizer, but also optimizes the chemical composition of the final product to meet high quality standards.

[0067] It can be seen from Table 3 that compared with Example 1, the nitrophosphate fertilizers prepared in Comparative Examples 1-4 exhibit higher hygroscopicity, lower compressive strength, and poorer particle size and uniformity. The specific reasons are as follows: High hygroscopicity: The hygroscopicity of Comparative Examples 1-4 is significantly higher than that of Example 1, which may be due to the failure to fully remove moisture during the drying process or the improper setting of process parameters resulting in more moisture adsorbed on the fertilizer surface.

[0068] Low compressive strength: The compressive strength of Comparative Examples 1-4 is generally lower than that of Example 1, which may be due to inappropriate material viscosity during spray granulation (such as too high or too low temperature), resulting in insufficient strength of the particle structure; in addition, if the heat treatment during the drying process is insufficient, it may also affect the formation of crystals inside the particles, thereby weakening the particle strength.

[0069] Poor particle size and uniformity: The particle size distribution of Comparative Examples 1-4 is not as uniform as that of Example 1. This may be due to the fact that key process parameters such as the spraying feed temperature and the drying inlet temperature deviate from the optimal range, resulting in different particle sizes and affecting the quality of the final product.

[0070] As can be seen from Table 4, the chemical compositions of Comparative Examples 1-4 are similar to those of Example 1, but there are differences in some aspects, such as: Moisture content: Although the H2O% is not much different between the comparative example and the example, considering the significant difference in hygroscopicity, it is shown that the comparative example product is more likely to absorb moisture from the environment.

[0071] pH value: The pH of the comparative example is slightly lower than that of Example 1, which may be due to the difference in production process resulting in a change in the ratio of acid and base substances in the finished product.

[0072] The differences between Comparative Examples 1-4 and Example 1 are mainly attributed to the following factors: Improper moisture control: The moisture content of the nitro compound fertilizer slurry in Comparative Example 1 is 7%-8%, which is far below the recommended range (10%-15%). Too little moisture may cause poor material fluidity, increase the difficulty of spray granulation, and easily cause internal stress concentration of the particles, reducing the compressive strength. At the same time, too low moisture will also affect the roundness of the particles, thereby affecting the uniformity of the particle size.

[0073] Insufficient drying temperature: Comparative Example 2 sets a lower drying inlet temperature (250-260°C) and drying outlet temperature (90-93°C), which may lead to incomplete evaporation of water, resulting in a high moisture content in the product, thereby increasing hygroscopicity and reducing compressive strength.

[0074] The spraying temperature is too high: the spraying feed temperature of comparative example 3 is set at 105°C, which exceeds the recommended range of 85-100°C. Too high a temperature may make the material viscosity too low, resulting in poor spraying effect and affecting the quality of particle forming.

[0075] No split mother liquor was added: Comparative Example 4 did not use split mother liquor, which means that a part of the important components that help adjust the chemical composition of the fertilizer is missing. This may affect the ratio of P2O5 and other trace elements, and thus affect the overall performance of the fertilizer.

[0076] The above is a specific description of the preferred implementation of the present application, but the invention of the present application is not limited to the described embodiments. Technical personnel familiar with the field can also make various equivalent modifications or substitutions without violating the spirit of the present application. These equivalent modifications or substitutions are all included in the scope defined by the claims of the present application.

Claims

1. A method for preparing nitrophosphate fertilizer from phosphate by-product white fertilizer, characterized in that: The following steps are involved: mixing the phosphate byproduct white fertilizer with the split mother liquor to obtain a white fertilizer slurry; Adding a nitrogen source and a potassium source to the white fertilizer slurry, mixing and dissolving them, and obtaining a nitro compound fertilizer slurry; The nitro compound fertilizer slurry is sprayed granulated and dried in a drying granulator. During the drying process, the drying inlet temperature of the drying granulator is controlled at 270-350° C., and the moisture content of the granulated material is dried to less than 1%. After the granulation is completed, nitrophosphate fertilizer is obtained.

2. The method according to claim 1, characterized in that The phosphate byproduct white fertilizer comprises the following components in percentage by weight: N total: 9.00%-10.00% P2O5: 35.00%-50.00% Water-soluble phosphorus: 20.00%-25.00% H2O: 1.00%-2.00% Ca: 0.50%-1.00% Mg: 1.50%-2.00% Other impurities: remainder; The split mother liquor comprises the following components in percentage by weight: N total: 7.00%-7.50% P2O5: 15.00%-20.00% Water-soluble phosphorus: 15.00%-20.00% H2O: 35.00%-40.00% Fe: 0.00%-0.05% Ca: 0.00%-0.50% Mg: 0.00%-0.50% SO4 2- :1.00%-1.50% F：0.00%-0.20% Other impurities: remainder.

3. The method according to claim 1, characterized in that The potassium source is one or both of potassium sulfate and potassium nitrate.

4. The method according to claim 1, characterized in that: The nitrogen source is one or both of ammonium nitrate and ammonium sulfate.

5. The method according to claim 1, characterized in that The nitro compound fertilizer slurry comprises the following raw materials in parts by weight: 20-50 parts of white fertilizer, 10-30 parts of split mother liquor, 30-40 parts of nitrogen source, and 29-50 parts of potassium source.

6. The method according to claim 1, characterized in that The weight content of water in the nitro compound fertilizer slurry is 10%-15%.

7. The method according to claim 1, characterized in that During the spray granulation process, the temperature of the spray feed is 85-100°C.

8. The method according to claim 1, characterized in that The drying air outlet temperature during the drying process is controlled at 95-100°C.

9. The method according to claim 1, characterized in that: The hot air pipe of the drying and granulating machine is connected to the heating assembly, and the exhaust pipe of the drying and granulating machine is connected to the dust collector; The feed pipe of the drying granulator is connected to the concentrator, and the discharge pipe of the drying granulator is connected to the conveyor; white fertilizer slurry, nitrogen source and potassium source are added into the concentrator, mixed and dissolved to obtain nitro compound fertilizer slurry.

10. Nitrophosphate fertilizer, characterized in that The invention relates to nitrophosphate fertilizer prepared by the method according to any one of claims 1 to 9.

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