A zinc and boron element-containing compound phosphorus fertilizer and a preparation method thereof

Abstract

The application discloses a kind of zinc, boron element composite phosphorus fertilizer and its preparation method, for reducing the generation of precipitate, reduce the loss of effective nutrients.The application includes: zinc boric acid is premixed with raffinate according to preset weight ratio in acid mixing tank, the pH value in the acid mixing tank is controlled to be 5.5-6.5;The mixture in the acid mixing tank is pumped into tubular reactor and reacted with liquid ammonia, to obtain reaction slurry, the temperature in the tubular reactor is between 120-150 DEG C during reaction, the pressure is between 0.5-0.7MPa;Reaction slurry is sprayed into granulator to granulate, after granulation, drying, screening, cooling, obtain zinc, boron element phosphorus ammonium product.

Description

Technical Field

[0001] This application relates to the field of fertilizer manufacturing technology, and in particular to a zinc- and boron-containing compound phosphate fertilizer and its preparation method. Background Technology

[0002] Zinc is one of the essential micronutrients for crop growth, participating in crop growth, development, and metabolic processes. Zinc deficiency in crops can lead to symptoms such as stunted growth, yellow spot disease, or chlorosis, reducing crop quality and lowering the nutritional content of agricultural products. Therefore, it is necessary to supplement crops with zinc appropriately.

[0003] To meet the crop's need for zinc, some zinc-containing ammonium phosphate products have appeared on the market. Ammonium phosphate is a compound fertilizer containing phosphorus and nitrogen, which are essential for crop growth. Adding zinc to ammonium phosphate creates zinc-containing ammonium phosphate products, which aim to achieve the synergistic supply of multiple nutrients such as nitrogen, phosphorus, and zinc, improve the overall fertilizer efficiency, and reduce the number of fertilizations and labor intensity.

[0004] In traditional processes for producing zinc-containing ammonium phosphate, zinc reacts with phosphoric acid to easily form Zn3(PO4)2 precipitate. Because Zn3(PO4)2 has extremely low solubility (<0.1 g / L), once this precipitate forms, zinc exists in the fertilizer as a poorly soluble compound, making it unavailable for crop absorption. Simultaneously, the precipitation reduces the effective phosphorus content, leading to nutrient loss, decreased fertilizer efficiency, and increased agricultural production costs. Summary of the Invention

[0005] To address the aforementioned technical problems, this application provides a zinc- and boron-containing compound phosphate fertilizer and its preparation method, which can reduce the formation of precipitates and the loss of effective nutrients.

[0006] The technical solution provided in this application is described below:

[0007] The first aspect of this application provides a method for preparing a zinc- and boron-containing compound phosphate fertilizer, comprising: Zinc boric acid and residual raffinate are premixed in an acid mixing tank at a preset weight ratio, and the pH value in the acid mixing tank is controlled to be 5.5-6.5. The mixture in the acid mixing tank is pumped into a tubular reactor to react with liquid ammonia to obtain a reaction slurry. During the reaction, the temperature inside the tubular reactor is between 120-150℃ and the pressure is between 0.5-0.7MPa. The reaction slurry is sprayed into a granulator for granulation. After granulation, it is dried, sieved, and cooled to obtain a phosphate fertilizer product containing zinc and boron.

[0008] Optionally, prior to the step of premixing zinc boric acid and residual raffinate in an acid mixing tank at a preset weight ratio, the preparation method further includes: Zinc boric acid is transferred from the storage container to the mixing tank using a self-priming pump, and then stirred at a speed of 200-300 r / min in the mixing tank.

[0009] Optionally, the weight ratio of zinc boric acid to residual acid in the acid mixing tank is 5-9‰.

[0010] Optionally, the zinc boric acid contains ≥2.5 g / L of zinc and ≥4 g / L of boron.

[0011] Optionally, the step of controlling the pH value in the acid preparation tank to 5.5-6.5 includes: An online pH sensor is used to monitor the pH value of the mixture in the acid mixing tank in real time, and an automatic acid addition system is used to maintain the pH within the range of 5.5-6.5.

[0012] Optionally, during the drying process, the inlet flue gas temperature is controlled at 450-590℃, and the moisture content of the outlet material is ≤1.5%.

[0013] Optionally, the step of spraying the reaction slurry into a granulator for granulation includes: The ammonia pressure inside the granulator is collected by a real-time ammonia pressure sensor, and the amount of ammonia is dynamically compensated to the granulator through a directional ammonia replenishment nozzle in the latter half of the granulator based on the ammonia pressure.

[0014] Optionally, the step of pumping the mixture in the acid preparation tank into the tubular reactor to react with liquid ammonia includes: The molar ratio of amino acids in the tubular reactor is monitored and adjusted in real time.

[0015] Optionally, the step of real-time monitoring and adjusting the amino acid molar ratio in the tubular reactor includes: The amino acid molar ratio is adjusted in real time by the APC intelligent control system so that the fluctuation range of the amino acid molar ratio is ≤±2%.

[0016] The second aspect of this application provides a zinc- and boron-containing compound phosphate fertilizer, prepared by the first aspect and any optional preparation method thereof, comprising: Total nutrients consisting of nitrogen and phosphorus ≥ 57%; Zinc content ≥80mg / kg; Boron content ≥30mg / kg; Nucleotide content ≥500mg / kg.

[0017] As can be seen from the above technical solutions, this application has the following beneficial effects: This application first premixes zinc boric acid and residual raffinate in an acid mixing tank at a preset weight ratio. Then, the mixed material is pumped into a tubular reactor to react with liquid ammonia to obtain a reaction slurry. Finally, the reaction slurry is sprayed into a granulator for granulation. After drying, sieving, and cooling, a phosphate ammonium product containing zinc boric acid is obtained. The phosphate ammonium product obtained by this preparation method contains zinc and boron elements. In the preparation process, zinc boric acid and residual raffinate are premixed, and a stable complex is formed in the mixture. The complex has high solubility in an acidic environment and is not easy to precipitate, thereby reducing the formation of precipitate Zn3(PO4)2. Therefore, it reduces the loss of effective nutrients and improves the fertilizer efficiency. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of a method for preparing a zinc- and boron-containing compound phosphate fertilizer according to this application; Figure 2 This is another schematic diagram of a method for preparing a zinc- and boron-containing compound phosphate fertilizer according to this application. Detailed Implementation

[0020] Traditional techniques directly react zinc with phosphoric acid, easily forming Zn3(PO4)2 precipitate with extremely low solubility. This results in the new element existing in a poorly soluble form in the fertilizer, causing nutrient loss. To address this drawback, this application proposes a zinc- and boron-containing compound phosphate fertilizer and its preparation method. The method involves pre-mixing zinc boric acid and residual raffinate in a pre-mixed acid bath at a predetermined weight ratio, adjusting the pH of the pre-mixing to between 5.5 and 6.5. This pre-mixing generates a relatively stable complex. The complex has high solubility in an acidic environment and is less likely to precipitate, thus reducing the formation of Zn3(PO4)2 precipitate. This reduces the loss of available nutrients and improves fertilizer efficiency.

[0021] It should be noted that the method for preparing a zinc- and boron-containing compound phosphate fertilizer provided in this application can be applied to terminals, systems, and servers. For ease of explanation, the following detailed description will focus on a system as the implementing entity.

[0022] Please see Figure 1 The first aspect of this application provides an embodiment of a method for preparing a zinc- and boron-containing compound phosphate fertilizer, the embodiment comprising: 101. Premix zinc boric acid and residual raffinate in an acid mixing tank at a preset weight ratio, and control the pH value in the acid mixing tank to be 5.5-6.5.

[0023] Zinc boric acid is a raw material that provides two key nutrients, zinc and boron; raffinate is a byproduct produced during phosphoric acid extraction and contains a certain amount of phosphorus. Adding raffinate as a raw material not only achieves comprehensive resource utilization and reduces waste emissions, but also provides phosphorus nutrition for compound fertilizers.

[0024] In solution, zinc boric acid will partially dissociate to release zinc ions (Zn²⁺). + ) and borate ions (B4O7²) - Phosphoric acid is a tribasic acid that dissociates into hydrogen ions (H+) in aqueous solution. + ) and phosphate ions (PO4³ - HPO4² - H2PO4 - When zinc boric acid is mixed with residual raffinate, zinc ions may interact weakly with phosphate ions, but under suitable pH conditions (pH between 5.5 and 6.5), this interaction will not lead to zinc precipitation.

[0025] Mixing zinc boric acid and residual raffinate in a preset weight ratio is to precisely control the content ratio of nutrients such as zinc, boron, and phosphorus in compound fertilizer, so as to meet the nutrient requirements of different crops at different growth stages.

[0026] Zinc boric acid and residual raffinate are premixed in an acid mixing tank equipped with a stirring device to ensure that the zinc boric acid and residual raffinate are fully and evenly mixed, thus ensuring that the subsequent reaction can proceed smoothly and avoiding problems such as incomplete reaction or uneven product composition caused by uneven mixing of raw materials.

[0027] During the mixing process, the pH value in the acid preparation tank is controlled between 5.5 and 6.5. Within this pH range, the direct reaction between zinc and phosphoric acid to form insoluble Zn3(PO4)2 precipitate can be effectively reduced. At this pH, zinc exists in the solution in a relatively stable ionic or complex form, thereby improving the availability of zinc in subsequent reactions and the final product. If the pH value is too low (below 5.5), the acidity is too strong and may accelerate certain side reactions; if the pH value is too high (above 6.5), it can easily lead to the formation of zinc precipitate, reducing zinc utilization.

[0028] 102. The mixture in the acid preparation tank is pumped into a tubular reactor to react with liquid ammonia to obtain a reaction slurry. During the reaction, the temperature in the tubular reactor is between 120-150℃ and the pressure is between 0.5-0.7MPa.

[0029] The acid mixing tank and the feed inlet of the tubular reactor are connected by an acid mixing pipe, which is equipped with a pump. The pump is used to draw the mixture from the acid mixing tank and transport it to the tubular reactor. Zinc boric acid and residual raffinate are mixed to form a mixture.

[0030] The feed inlet of the tubular reactor is also connected to the liquid ammonia supply equipment, and the discharge outlet of the tubular reactor is connected to the granulator. Within a temperature range of 120-150℃, the chemical reaction between zinc boric acid, residual raffinate, and liquid ammonia can proceed rapidly and completely, thus shortening the reaction time and improving production efficiency. The reaction temperature can be controlled externally using heating or cooling devices to meet the reaction requirements. Specifically, when the reaction temperature is too low, a heating jacket is installed outside the tubular reactor, and heating media such as steam or heat transfer oil are circulated to provide heat for the reaction and raise the reaction temperature. When the reaction temperature is too high, cooling media such as cooling water can be circulated to absorb the heat generated by the reaction and lower the reaction temperature.

[0031] Pressure affects the solubility of gases in liquids. Liquid ammonia is a gas, and under higher pressures, it dissolves better in mixtures, increasing the contact opportunities between reactants and thus improving the homogeneity and completeness of the reaction. Under a pressure environment of 0.5-0.7 MPa, liquid ammonia dissolves better in mixtures, reacting fully with zinc boric acid and residual raffinate, thereby improving reaction efficiency.

[0032] After reacting in a tubular reactor, zinc boric acid, residual acid and liquid ammonia undergo a chemical reaction to generate compounds containing nutrients such as zinc, boron, phosphorus and nitrogen. These compounds exist in the form of a slurry, i.e., the reaction slurry.

[0033] 103. The reaction slurry is sprayed into a granulator for granulation. After granulation, it is dried, sieved, and cooled to obtain a zinc and boron-containing ammonium phosphate product.

[0034] The reaction slurry is sprayed into the granulator through a nozzle or other means. Inside the granulator, the reaction slurry is formed into granular fertilizer with a certain particle size and strength through rotation, rolling or spraying.

[0035] During the drying process, moisture in the fertilizer granules is removed by ventilation or heating.

[0036] During the screening process, screening equipment is used to classify the dried granules according to different particle sizes, removing oversized or undersized particles. This ensures that the fertilizer granules leaving the factory meet the particle size requirements, while granules that do not meet the requirements can be reworked and re-granulated, thereby ensuring a uniform particle size distribution and improving product quality.

[0037] Fertilizer granules exposed to high temperatures are prone to clumping due to heat buildup during storage, affecting their usability. Therefore, fertilizer granules need to be cooled, and this process should be carried out using ventilation.

[0038] In this embodiment, zinc boric acid and residual raffinate are first premixed in an acid mixing tank at a preset weight ratio. Then, the mixed material is pumped into a tubular reactor to react with liquid ammonia to obtain a reaction slurry. Finally, the reaction slurry is sprayed into a granulator for granulation. After drying, sieving, and cooling, a phosphate ammonium product containing zinc boric acid is obtained. The phosphate ammonium product obtained by this preparation method contains zinc and boron elements. In the preparation process, zinc boric acid and residual raffinate are premixed, and a stable complex is formed in the mixture. The complex has high solubility in an acidic environment and is not easy to precipitate, thereby reducing the formation of precipitate Zn3(PO4)2. Therefore, the loss of effective nutrients is reduced and the fertilizer efficiency is improved.

[0039] Please see Figure 2 This application provides another embodiment of a method for preparing a zinc- and boron-containing compound phosphate fertilizer, which includes: 201. Transfer zinc boric acid from the storage container to the mixing tank using a self-priming pump, and stir the mixture in the mixing tank at a speed of 200-300 r / min.

[0040] The storage container and the mixing tank are connected by a pipe, and a self-priming pump is installed on this pipe. When the self-priming pump is started, it transfers the zinc boric acid from the storage container to the mixing tank. The mixing tank is equipped with a stirring device, which stirs the zinc boric acid in the mixing tank when it is activated.

[0041] Zinc boric acid (ZnB(OH)4) is a liquid, but zinc and boron elements are prone to local concentration gradients when left to stand, leading to stratification or precipitation (e.g., Zn²⁺). + (Potentially forming Zn(OH)2 colloid). The shear force of 200-300 r / min during stirring breaks up particle agglomeration, ensuring a uniform distribution of zinc and boron ions in the liquid phase. This reduces the risk of Zn3(PO4)2 precipitation due to excessively high local concentrations when subsequently mixed with residual raffinate.

[0042] The mixing tank and the acid preparation tank are connected by a pipeline. After the zinc boric acid is fully stirred in the mixing tank, it is pumped into the acid preparation tank to mix with the residual raffinate.

[0043] In an optional embodiment, when mixing zinc boric acid with residual raffinate, the weight ratio of zinc boric acid to residual raffinate in the acid mixing tank needs to be controlled to be 5-9‰.

[0044] In this embodiment, both zinc boric acid and raffinate have certain acidity or alkalinity, and their mixing ratio directly affects the pH of the mixed acid solution. When the weight ratio of zinc boric acid to raffinate varies within the range of 5-9‰, the pH of the mixed acid solution will fluctuate within a relatively stable range.

[0045] Zinc boric acid is an important raw material for providing zinc and boron, and its ratio with residual raffinate directly affects the zinc and boron content in compound fertilizers. A weight ratio of 5-9‰ ensures that the zinc and boron content in the compound fertilizer meets product standards and satisfies the needs of crop growth.

[0046] After zinc boric acid is pumped into the acid mixing tank by a metering pump, residual raffinate acid is added at a ratio of 5-9‰ (for example, 1 ton of residual raffinate acid is mixed with 5-9 kg of zinc boric acid) and stirred. The stirring time is set according to the time requirements, such as 1 minute, 10 minutes, etc.

[0047] It should be noted that the acid concentration of the residual acid selected in this application is ≥44%.

[0048] In an optional embodiment, the zinc boric acid contains ≥2.5 g / L of zinc and ≥4 g / L of boron.

[0049] In this embodiment, by designing a zinc boric acid solution with zinc ≥2.5g / L and boron ≥4g / L, the prepared fertilizer product has a zinc content ≥80mg / kg, a boron content ≥30mg / kg, a nucleotide content ≥700mg / kg, and a total nutrient content (N+P2O5) ≥57%. This provides a relatively sufficient source of zinc and boron nutrients for zinc-boron compound fertilizer, meets the basic needs of different crops for these two micronutrients at different growth stages, and helps to improve crop yield and quality.

[0050] In an optional embodiment, when the pH value in the acid mixing tank is controlled to be 5.5-6.5, an online pH sensor is used to monitor the pH value of the mixture in the acid mixing tank in real time, and an automatic acid addition system is used to maintain the pH value within the range of 5.5-6.5.

[0051] An online pH sensor is installed in the acid mixing tank, using a glass electrode as the sensing element. The potential of the glass electrode has a specific functional relationship with the hydrogen ion concentration (i.e., pH value) in the acid mixing tank solution. When the glass electrode is immersed in the solution to be tested, hydrogen ions in the solution exchange and adsorb on the glass electrode surface, generating a potential difference. By measuring this potential difference and combining it with the potential of the reference electrode, the pH value of the solution can be calculated.

[0052] The automatic acid dosing system consists of an acid storage tank, an acid dosing pump, a flow meter, and a control system. The acid storage tank stores the acid (phosphoric acid or residual raffinate) needed to adjust the pH value; the acid dosing pump draws the acid from the storage tank and delivers it to the acid mixing tank; the flow meter measures the flow rate of the added acid; and the control system compares the signal from the online pH sensor with the set pH range, then issues control commands to adjust the speed of the acid dosing pump, thereby achieving automatic control of the amount of acid added.

[0053] When the online pH sensor detects that the pH value of the mixture in the acid mixing tank is higher than the set range (6.5), the control system will issue a command to start the acid adding pump or increase the speed of the acid adding pump to add acid to the acid mixing tank. As acid is added, the pH value of the mixture gradually decreases. When the pH value drops to the set range (5.5), the control system will issue a command to stop the acid adding pump or reduce the speed of the acid adding pump, stop adding acid or reduce the amount of acid added, thereby maintaining the pH value of the mixture in the acid mixing tank within the range of 5.5-6.5.

[0054] In an optional embodiment, during the drying process after granulation, the inlet flue gas temperature is controlled at 450-590°C, and the moisture content of the outlet material is ≤1.5%.

[0055] The temperature of the inlet flue gas affects the heat transfer efficiency of the drying process. Higher temperatures accelerate heat transfer, causing moisture in the material to evaporate more quickly, thus increasing the drying rate. A temperature range of 450-590℃ ensures a sufficient drying rate while avoiding equipment damage and energy waste caused by excessively high temperatures. Simultaneously, controlling the moisture content of the outlet material to ≤1.5% ensures that the material meets drying requirements, reduces subsequent processing time and costs, and improves overall production efficiency.

[0056] The drying process is carried out using a rotary dryer or a spray drying tower.

[0057] In an optional embodiment, when the reaction slurry is sprayed into the granulator for granulation, the ammonia pressure inside the granulator is collected by a real-time ammonia pressure sensor, and the amount of ammonia is dynamically compensated to the granulator through a directional ammonia replenishment nozzle in the latter half of the granulator based on the ammonia pressure.

[0058] The real-time ammonia pressure sensor is installed inside the granulator and is used to collect ammonia pressure data inside the granulator in real time.

[0059] The reaction intensity and ammonia demand vary at different locations within the granulator. The first half of the granulator primarily involves the initial reaction of the slurry and the initial stage of particle formation, while the reaction progresses further in the second half, potentially leading to insufficient ammonia supply. Real-time ammonia pressure data is collected from within the granulator using a real-time ammonia pressure sensor, allowing for timely monitoring of ammonia pressure changes. Based on this real-time data, directional ammonia supply nozzles are used to dynamically compensate for ammonia levels in the second half of the granulator, precisely controlling the ammonia supply and ensuring the sufficiency and stability of the reaction throughout the granulation process, thereby obtaining uniform and compliant granular products.

[0060] In this embodiment, the system calculates the amount of ammonia needed based on the degree of ammonia pressure deviation and the actual situation in the ammonia replenishment area, and sends a control signal to the directional ammonia replenishment nozzle. The directional ammonia replenishment nozzle, according to the control signal, injects ammonia into the designated location of the granulator at an appropriate pressure and flow rate.

[0061] In an optional embodiment, the amino acid molar ratio in the tubular reactor is monitored and adjusted in real time as the mixture in the acid preparation tank is pumped into the tubular reactor to react with liquid ammonia.

[0062] The molar ratio of amino acids (the ratio of the amount of acid to ammonia) is one of the core factors affecting reaction efficiency and product quality. An inappropriate molar ratio may lead to incomplete reactions, producing unreacted raw materials, and reducing product purity and yield. Excessive deviation in the molar ratio may also trigger side reactions, generating unwanted impurities and affecting product performance and applications.

[0063] In this embodiment, the molar ratio of amino acids in the tubular reactor is adjusted in real time to keep it within a stable range. For example, if the molar ratio is set to 2±0.04, the molar ratio of amino acids in the tubular reactor is adjusted in real time to be between 1.96 and 2.04.

[0064] Real-time monitoring can be achieved using online analytical instruments, such as infrared spectrometers and gas chromatographs, to analyze the material composition at the inlet and outlet of the tubular reactor and obtain concentration data for acids and ammonia. This data is used to calculate the amino acid molar ratio. Simultaneously, temperature and pressure sensors are used to monitor the temperature and pressure inside the tubular reactor in real time.

[0065] During real-time adjustment, the current amino acid molar ratio is first calculated based on the real-time monitoring data and compared with the previously set amino acid molar ratio. If there is a deviation, the opening of the liquid ammonia flow regulating valve is automatically adjusted to change the flow rate of liquid ammonia entering the tubular reactor, so that the amino acid molar ratio gradually approaches the target value.

[0066] In an optional embodiment, while monitoring and adjusting the amino acid molar ratio in the tubular reactor in real time, the amino acid molar ratio is adjusted in real time by the APC intelligent control system so that the fluctuation range of the amino acid molar ratio is ≤±2%.

[0067] The APC (Advanced Process Control) intelligent control system has powerful data processing capabilities and intelligent control algorithms, enabling it to make adjustment decisions quickly and accurately based on real-time data, thereby achieving precise control of the amino acid molar ratio.

[0068] Based on the aforementioned real-time monitoring data (including temperature, pressure, acid concentration, ammonia concentration, etc.), and with the help of the APC intelligent control system, the fluctuation range of the amino acid molar ratio can be controlled within ≤±2%, ensuring that the reaction always proceeds under optimal conditions, improving product quality stability, production efficiency, and reducing production costs and energy consumption.

[0069] In the traditional preparation method, concentrated acid is used as a total nutrient regulator, combined with zinc boric acid to produce compound phosphate fertilizer. The average nucleotide content of the product is stable at 506.8 mg / kg, which meets the standard requirement of ≥500 mg / kg. At this time, 7‰ zinc boric acid needs to be added.

[0070] Unlike traditional preparation methods, this method utilizes residual raffinate acid instead of concentrated slag acid. The residual raffinate acid is premixed with zinc boric acid as a raw material for compound phosphate fertilizer production. Since the residual raffinate acid itself contains nucleotides, adding 7‰ zinc boric acid increases the nucleotide content of the prepared compound phosphate fertilizer to 741.6 mg / kg, exceeding the standard requirement (500 mg / kg). Therefore, while meeting the standard requirement (500 mg / kg), the amount of zinc boric acid can be reduced during preparation. In this method, only 5‰ zinc boric acid needs to be added. Based on 5‰ zinc boric acid, a compound phosphate fertilizer meeting the standard requirement (nucleotide content ≥ 500 mg / kg) can be prepared, thereby further reducing production costs.

[0071] The second aspect of this application discloses an embodiment of a zinc- and boron-containing compound phosphate fertilizer, which includes: Total nutrients consisting of nitrogen and phosphorus ≥ 57%; Zinc content ≥80mg / kg; Boron content ≥30mg / kg; Nucleotide content ≥500mg / kg.

[0072] In this embodiment, the moisture content of the compound phosphate fertilizer is ≤1.5%, and the nucleotides are derived from raffinate and zinc boric acid. Raffinate contains 3000 mg / kg of nucleotides, and zinc boric acid itself contains about 8% nucleotides.

[0073] It should be noted that the above description of the disclosed embodiments enables those skilled in the art to implement or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a zinc- and boron-containing compound phosphate fertilizer, characterized in that, include: Zinc boric acid and residual raffinate are premixed in an acid mixing tank at a preset weight ratio, and the pH value in the acid mixing tank is controlled to be 5.5-6.

5. The mixture in the acid mixing tank is pumped into a tubular reactor to react with liquid ammonia to obtain a reaction slurry. During the reaction, the temperature inside the tubular reactor is between 120-150℃ and the pressure is between 0.5-0.7MPa. The reaction slurry is sprayed into a granulator for granulation. After granulation, it is dried, sieved, and cooled to obtain a phosphate fertilizer product containing zinc and boron.

2. The preparation method according to claim 1, characterized in that, Before the step of premixing zinc boric acid and residual raffinate in an acid mixing tank at a preset weight ratio, the preparation method further includes: Zinc boric acid is transferred from the storage container to the mixing tank using a self-priming pump, and then stirred at a speed of 200-300 r / min in the mixing tank.

3. The preparation method according to claim 1 or 2, characterized in that, The weight ratio of zinc boric acid to residual acid in the acid mixing tank is 5-9‰.

4. The preparation method according to claim 1 or 2, characterized in that, The zinc boric acid contains ≥2.5 g / L of zinc and ≥4 g / L of boron.

5. The preparation method according to claim 1 or 2, characterized in that, The step of controlling the pH value in the acid preparation tank to be 5.5-6.5 includes: An online pH sensor is used to monitor the pH value of the mixture in the acid mixing tank in real time, and an automatic acid addition system is used to maintain the pH within the range of 5.5-6.

5.

6. The preparation method according to claim 1 or 2, characterized in that, During the drying process, the inlet flue gas temperature is controlled at 450-590℃, and the moisture content of the outlet material is ≤1.5%.

7. The preparation method according to claim 1 or 2, characterized in that, The step of spraying the reaction slurry into the granulator for granulation includes: The ammonia pressure inside the granulator is collected by a real-time ammonia pressure sensor, and the amount of ammonia is dynamically compensated to the granulator through a directional ammonia replenishment nozzle in the latter half of the granulator based on the ammonia pressure.

8. The preparation method according to claim 1 or 2, characterized in that, The step of pumping the mixture in the acid preparation tank into the tubular reactor to react with liquid ammonia includes: The molar ratio of amino acids in the tubular reactor is monitored and adjusted in real time.

9. The preparation method according to claim 8, characterized in that, The step of real-time monitoring and adjustment of the amino acid molar ratio in the tubular reactor includes: The amino acid molar ratio is adjusted in real time by the APC intelligent control system so that the fluctuation range of the amino acid molar ratio is ≤±2%.

10. A zinc- and boron-containing compound phosphate fertilizer, prepared by any one of the preparation methods according to claims 1 to 9, characterized in that, include Total nutrients consisting of nitrogen and phosphorus ≥ 57%; Zinc content ≥80mg / kg; Boron content ≥30mg / kg; Nucleotide content ≥500mg / kg.

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