Preparation process of functional fertilizer containing combined phosphate

Abstract

The invention relates to a preparation process of a functional fertilizer containing combined phosphate. The process comprises the following steps: concentrating an acidolysis neutralization solution to obtain NP concentrated slurry; the NP concentrated slurry is introduced into a polymerization tank to be heated and polymerized at the temperature of 160-190 DEG C, and polymerized slurry is prepared; overflowing the polymerized slurry into a first-stage mixing tank, adding phosphite and nano zinc oxide into the first-stage mixing tank, and heating and stirring for 3-8 minutes at the temperature of 130-150 DEG C; overflowing slurry prepared by reaction in the primary mixing tank into a secondary mixing tank, adding biostimulant substances and medium trace elements into the secondary mixing tank, and heating and stirring for 2-5 minutes at the temperature of 100-120 DEG C; the slurry prepared in the second-stage mixing tank is granulated, dried, wrapped and screened to prepare the functional fertilizer containing the combined phosphate, the functional fertilizer prepared in the invention contains three phosphorus forms of orthophosphate, phosphite and polyphosphate at the same time, the phosphate in different forms has complementary functions, the absorption and transfer speed of phosphorus is increased, and the long-acting slow release property of the phosphate is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of fertilizers, and in particular to a preparation process of a functional fertilizer containing combined phosphates. Background Art

[0002] At present, the phosphorus source of phosphorus-containing compound fertilizers or water-soluble fertilizers is mostly in the form of orthophosphate, mainly in the form of H2PO4 - or HPO4 2- This type of +5-valent phosphorus can only be transported upward in a single channel in the xylem of the crop body. The transport speed is slow and it is easily adsorbed and fixed by the soil, resulting in a very low utilization rate of phosphorus in the current season, causing a serious waste of the already severely scarce phosphorus resources, which is not in line with the concept of sustainable development of low-carbon agriculture.

[0003] Phosphites are alkali metal salts of phosphoric acid. These salts are highly soluble and easily and rapidly absorbed by plants. They have significant selectivity and systemic translocation. As a functional fertilizer, phosphites have been widely used abroad, but less studied in my country. The trivalent phosphorus in phosphites has a bidirectional transport function and can be transported in both the xylem and phloem of crops, which can accelerate the absorption and utilization of nutrients by crops. In addition, a large number of studies at home and abroad have confirmed that phosphites can induce plants to produce defensins and PR proteins, stimulate crops to activate defense mechanisms, reduce the invasion of pathogens on plants, and improve the resistance of crops to abiotic stress.

[0004] However, although phosphite contains a large amount of phosphorus, the functional group of phosphorus is a stable dibasic acid group with strong binding force between elements. The process of conversion into orthophosphate group under the action of soil microorganisms is very slow, which is not conducive to plant absorption, utilization and conversion. This causes phosphite to lose its functional advantages and results in a waste of phosphorus resources. Summary of the invention

[0005] The present invention provides a functional fertilizer containing combined phosphate and a preparation process thereof, so as to solve the technical problem in the prior art that phosphorus element is slowly transported and easily adsorbed and fixed by soil, resulting in very low utilization rate of phosphorus in the current season.

[0006] In order to solve the above technical problems, a preparation process of a functional fertilizer containing combined phosphates is provided, the process comprising:

[0007] S1: Concentrating the acid hydrolysis neutralization liquid to obtain NP concentrated slurry;

[0008] S2: passing the concentrated NP slurry into a polymerization tank and heating and polymerizing at a temperature of 160-190° C. to obtain a polymerization slurry;

[0009] S3: overflow the polymer slurry into a primary mixing tank, add phosphite and nano zinc oxide into the primary mixing tank, and heat and stir at 130-150° C. for 3-8 minutes;

[0010] S4: overflow the slurry obtained by the reaction in the primary mixing tank to the secondary mixing tank, add biostimulant substances and trace elements to the secondary mixing tank, and heat and stir at a temperature of 100-120° C. for 2-5 minutes;

[0011] S5: Granulate, dry, package and screen the slurry obtained in the secondary mixing tank to obtain a functional fertilizer containing combined phosphate.

[0012] Among them, in the step S1, the acid solution is obtained by decomposing the phosphate rock with nitric acid, and the acid-base neutralization solution is obtained after neutralization with ammonia. The acid-base neutralization solution is pumped into the NP evaporator, and the NP concentrated slurry is obtained by reaction at 150-170° C. and a negative pressure of 0.005-0.02 MPa.

[0013] Wherein, the amount of the NP concentrated slurry entering the polymerization tank in step S2 is 15-30 t / h, and the polymerization reaction time is 1.0-1.5 h.

[0014] Wherein, the phosphite in step S3 is an alkali metal phosphite.

[0015] Wherein, the phosphite in step S3 is one or more of potassium phosphite, sodium phosphite, ammonium phosphite, and potassium dihydrogen phosphite.

[0016] Wherein, the weight ratio of the phosphite in step S3 to the functional fertilizer is 1.0-5.0%.

[0017] Wherein, the average particle size of the nano zinc oxide in step S3 is 50-100 nm, and the weight proportion of the nano zinc oxide in the functional fertilizer is 0.1-0.5%.

[0018] Wherein, the biostimulant substance in step S4 includes one or more of amino acids, fulvic acid, polyglutamic acid, monosaccharides, polysaccharides, and glycopeptides, and the weight ratio of the biostimulant substance to the functional fertilizer is 0.5-2.0%.

[0019] Wherein, the trace elements in step S4 are one or more of manganese sulfate, boric acid, ferrous sulfate and copper sulfate, and the trace elements account for 0.5-1.5% of the weight of the functional fertilizer.

[0020] The slurry obtained in the secondary mixing tank in step S5 is granulated, dried, wrapped and screened, and the granulation methods include biaxial granulation, drum granulation, drum fluidized bed granulation and spray granulation, and the screening particle size is 2.0 to 4.0 mm.

[0021] The beneficial effects of the present invention are:

[0022] The functional fertilizer prepared by the preparation process of the functional fertilizer containing combined phosphates of the present invention contains three phosphorus forms of orthophosphate, phosphite and polyphosphate at the same time. Phosphite partially replaces orthophosphate to form a combined phosphate functional complementary system, thereby increasing the absorption and transportation speed of phosphorus. Meanwhile, polyphosphate ensures its long-term slow release. Phosphite can induce crops to produce defensins, thereby enhancing their disease prevention and antibacterial effects and reducing crop disease infection. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] By reading the detailed description below with reference to the accompanying drawings, the above and other purposes, features and advantages of the exemplary embodiments of the present disclosure will become readily understood. In the accompanying drawings, several embodiments of the present disclosure are shown in an exemplary and non-limiting manner, and the same or corresponding reference numerals represent the same or corresponding parts, wherein:

[0024] Figure 1 It is a sample diagram of functional fertilizers according to different embodiments of the present application;

[0025] Figure 2 This is a trend chart showing the change of chlorophyll content of Shanghai green treated with different test examples of this application as the growth cycle changes;

[0026] Figure 3 is a trend chart of the height of Shanghai green treated with different test examples of this application as the plant changes with the growth cycle;

[0027] Figure 4 These are pictures of the roots of Shanghai green treated in different test examples of this application;

[0028] Figure 5 It is a growth diagram of Shanghai green treated by different test examples of this application;

[0029] Figure 6 These are pictures of green beans processed in different test examples of this application. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present disclosure to clearly and completely describe the technical solutions in the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present disclosure.

[0031] The specific embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.

[0032] Example 1

[0033] This embodiment is used to produce a functional fertilizer containing a combined phosphate with a weight proportion of 1% of trivalent phosphite. The process includes:

[0034] S1: Concentrating the acid hydrolysis neutralization liquid to obtain NP concentrated slurry;

[0035] It should be noted that in step S1, phosphate rock is decomposed by nitric acid to obtain an acid solution, which is neutralized with ammonia to obtain an acid-base neutralized solution, and the acid-base neutralized solution is pumped into the NP evaporator to obtain NP concentrated slurry through reaction at 150-170°C and a negative pressure of 0.005-0.02MPa.

[0036] In this embodiment, the heating temperature is 160° C. and the negative pressure is 0.01 MPa.

[0037] S2: passing the concentrated NP slurry into a polymerization tank and heating and polymerizing at a temperature of 160-190° C. to obtain a polymerization slurry;

[0038] In the step S2, the amount of the NP concentrated slurry entering the polymerization tank is 15-30 t / h, and the polymerization reaction time is 1.0-1.5 h.

[0039] In this embodiment, the amount of the NP concentrated slurry entering the polymerization tank is 20 t / h, the temperature is 170° C., and the polymerization reaction time is 1.0 h.

[0040] S3: overflow the polymer slurry into a primary mixing tank, add phosphite and nano zinc oxide into the primary mixing tank, and heat and stir at 130-150° C. for 3-8 minutes;

[0041] The phosphite in step S3 is an alkali metal phosphite, and the phosphite is one or more of potassium phosphite, sodium phosphite, ammonium phosphite, and potassium dihydrogen phosphite. The average particle size of the nano zinc oxide is 50-100 nm, and the weight proportion of the nano zinc oxide in the functional fertilizer is 0.1-0.5%.

[0042] The phosphite in the present invention is itself an effective chelating agent, which can synergize with biostimulant substances rich in functional groups such as hydroxyl and carboxyl groups to chelate metal cations such as Ca, Zn, Fe, Mn, Cu, Mo, etc. from multiple dimensions to improve the nutrient effectiveness of trace elements.

[0043] In the present invention, nano zinc oxide is added and free electrons and holes can be generated under light, thereby leading to the generation of hydroxyl radicals and promoting the photocatalytic oxidation of +3-valent phosphorus to +5-valent phosphorus, thereby solving the technical problem that phosphite cannot be absorbed and utilized as a phosphorus source by crops due to its slow oxidation process. At the same time, zinc ions are supplemented, which can enhance the photosynthesis performance of crops, participate in the synthesis of various enzymes in crops, and play an important role in the metabolism of crops.

[0044] In this embodiment, the phosphite is potassium phosphite, the weight ratio of the potassium phosphite to the functional fertilizer is 1%, the weight ratio of the nano zinc oxide to the functional fertilizer is 0.2%, the heating temperature is 140°C, and the stirring is performed for 5 minutes. It should be noted that the weight ratio of the functional fertilizer described in the present invention can also be expressed as the weight ratio of the raw material input.

[0045] S4: overflow the slurry obtained by the reaction in the primary mixing tank to the secondary mixing tank, add biostimulant substances and trace elements to the secondary mixing tank, and heat and stir at a temperature of 100-120° C. for 2-5 minutes;

[0046] The biostimulant substance includes one or more of amino acids, fulvic acid, polyglutamic acid, monosaccharides, polysaccharides, and glycopeptides, and the weight proportion of the biostimulant substance in the functional fertilizer is 0.5-2.0%. The trace elements are one or more of manganese sulfate, boric acid, ferrous sulfate, and copper sulfate, and the trace elements account for 0.5-1.5% of the weight proportion of the functional fertilizer. In this embodiment, the biostimulant substance is amino acid, and the amino acid accounts for 1.0% of the weight proportion of the functional fertilizer. The trace elements are manganese sulfate and ferrous sulfate, and the weight proportion of manganese sulfate and ferrous sulfate in the functional fertilizer is 1%, wherein the weight proportion of manganese sulfate and ferrous sulfate in the functional fertilizer is 0.5%, respectively, and heated and stirred at 110°C for 3 minutes.

[0047] The biostimulant substances added in the present invention can promote the synthesis of phosphorus transport protein, improve the transportation and metabolism of phosphite in crops, and reduce the excessive accumulation of phosphite in plants.

[0048] S5: Granulate, dry, package and screen the slurry obtained in the secondary mixing tank to obtain a functional fertilizer containing combined phosphate.

[0049] Granulation methods include biaxial granulation, drum granulation, roller fluidized bed granulation, and spray granulation. This embodiment adopts spray granulation. The functional fertilizer particles obtained after granulation are further sieved, wherein the sieved particle size is 2.0 to 4.0 mm.

[0050] The functional fertilizer prepared by the preparation process of the functional fertilizer containing combined phosphates of the present invention contains three phosphorus forms of orthophosphate, phosphite and polyphosphate at the same time. Phosphite partially replaces orthophosphate to form a combined phosphate functional complementary system, thereby increasing the absorption and transportation speed of phosphorus. Meanwhile, polyphosphate ensures its long-term slow release. Phosphite can induce crops to produce defensins, thereby enhancing their disease prevention and antibacterial effects and reducing crop disease infection.

[0051] Example 2

[0052] This embodiment is used to manufacture a functional fertilizer containing a combined phosphate with a weight ratio of 3% of trivalent phosphite, and its process parameters are consistent with those of Example 1. The process includes:

[0053] S1: The acid hydrolysis neutralization liquid is concentrated to obtain NP concentrated slurry.

[0054] S2: The concentrated NP slurry is introduced into a polymerization tank and heated at 170° C. to obtain a polymerization slurry. The polymerization reaction time is 1.0 h.

[0055] S3: overflow the polymer slurry into a primary mixing tank, add potassium phosphite and nano zinc oxide into the primary mixing tank, wherein the weight ratio of potassium phosphite to the functional fertilizer is 3%, and the weight ratio of nano zinc oxide to the functional fertilizer is 0.2%, and heat and stir at 140°C for 5 minutes.

[0056] S4: overflow the slurry obtained by the reaction in the primary mixing tank to the secondary mixing tank, add amino acids, manganese sulfate and ferrous sulfate to the secondary mixing tank, wherein the weight proportions of amino acids, manganese sulfate and ferrous sulfate to the functional fertilizer are 1%, 0.5% and 0.5%, respectively, and heat and stir at 110°C for 3 minutes.

[0057] S5: Granulate, dry, package and screen the slurry obtained in the secondary mixing tank to obtain a functional fertilizer containing combined phosphate.

[0058] Example 3

[0059] This embodiment is used to manufacture a functional fertilizer containing a combined phosphate with a weight ratio of 5% of trivalent phosphite, and its process parameters are consistent with those of Example 1. The process includes:

[0060] S1: The acid hydrolysis neutralization liquid is concentrated to obtain NP concentrated slurry.

[0061] S2: The concentrated NP slurry is introduced into a polymerization tank and heated at 170° C. to obtain a polymerization slurry. The polymerization reaction time is 1.0 h.

[0062] S3: overflow the polymer slurry into a primary mixing tank, add potassium phosphite and nano zinc oxide into the primary mixing tank, wherein the weight ratio of potassium phosphite to the functional fertilizer is 5%, and the weight ratio of nano zinc oxide to the functional fertilizer is 0.2%, and heat and stir at 140°C for 5 minutes.

[0063] S4: overflow the slurry obtained by the reaction in the primary mixing tank to the secondary mixing tank, add amino acids, manganese sulfate and ferrous sulfate to the secondary mixing tank, wherein the weight proportions of amino acids, manganese sulfate and ferrous sulfate to the functional fertilizer are 1%, 0.5% and 0.5%, respectively, and heat and stir at 110° C. for 3 minutes.

[0064] S5: Granulate, dry, package and screen the slurry obtained in the secondary mixing tank to obtain a functional fertilizer containing combined phosphate.

[0065] Comparative Example 1

[0066] This comparative example is used to manufacture a functional fertilizer that does not contain +3-valent phosphite. The phosphate fertilizers in the functional fertilizer are all positive pentavalent phosphates, and the process parameters are consistent with those in Example 1. The process includes:

[0067] S1: The acid hydrolysis neutralization liquid is concentrated to obtain NP concentrated slurry.

[0068] S2: The concentrated NP slurry is introduced into a polymerization tank and heated at 170° C. to obtain a polymerization slurry. The polymerization reaction time is 1.0 h.

[0069] S3: overflow the polymer slurry into a primary mixing tank, add nano zinc oxide into the primary mixing tank, the nano zinc oxide accounts for 0.2% of the weight of the functional fertilizer, and heat and stir at 140° C. for 5 minutes.

[0070] S4: overflow the slurry obtained by the reaction in the primary mixing tank to the secondary mixing tank, add amino acids, manganese sulfate and ferrous sulfate to the secondary mixing tank, wherein the weight proportions of amino acids, manganese sulfate and ferrous sulfate to the functional fertilizer are 1%, 0.5% and 0.5%, respectively, and heat and stir at 110° C. for 3 minutes.

[0071] S5: Granulate, dry, package and screen the slurry obtained in the secondary mixing tank to obtain a functional fertilizer containing combined phosphate.

[0072] Specific test examples

[0073] Furthermore, the present application further verifies the effect of functional fertilizers containing combined phosphates on crop growth through experiments, using Shanghai green as the experimental object, and mainly studies its growth traits (including plant height, chlorophyll value), root system and yield differences.

[0074] In this test, the compound fertilizer used is 21-8-8 compound fertilizer. It should be noted that the numbers and letters marked on the compound fertilizer product packaging bag indicate the nutrient type and nutrient content of the compound fertilizer [usually marked in the order of nitrogen (N) - phosphorus pentoxide (P2O5) - potassium oxide (K2O)]. Taking 17-7-17 compound fertilizer as an example, the nitrogen (N) content of the compound fertilizer product is 21%, the phosphorus pentoxide (P2O5) content is 8%, and the potassium oxide (K2O) content is 8%. Regarding the conversion of nutrient content and raw material ratio, the conversion method in the compound fertilizer industry is adopted, and no specific explanation is given here.

[0075] In the present invention, Excel 2007 and SPSS10.0 software were further used for statistical analysis and drawing, and Duncan's new multivariate test method was used for variance analysis and difference significance test (α=0.05).

[0076] First, the present application prepares functional fertilizers containing combined phosphates with different contents of components through Examples 1-3 and Comparative Example 1. The pictures of the functional fertilizers used in different test examples are shown in Figure 1 , Figure 1 (a) is a compound fertilizer prepared by the production process of comparative example 1, which does not contain trivalent phosphite, (b) is a compound fertilizer prepared by the production process of Example 1, containing 1% trivalent phosphite, (c) is a compound fertilizer prepared by the production process of Example 2, containing 3% trivalent phosphite, (d) is a compound fertilizer prepared by the production process of Example 3, containing 5% trivalent phosphite. This application further adopts a parallel test method to apply it to the planting process of Shanghai Qing, and the content of trivalent phosphate in each test example is shown in Table 1.

[0077] Table 1: Content of trivalent phosphite in the functional fertilizers of each test example

[0078]

[0079] It should be noted that Test Example 1 is a blank control group, the phosphate fertilizer in Test Example 2 is pentavalent phosphate and does not contain trivalent phosphite, and the contents of trivalent phosphite in Test Examples 3-5 are 1%, 3%, and 5%, respectively.

[0080] In this experiment, Shanghai Qing was planted in potted plants. The soil used in the experiment was garden soil. After air-drying, impurities such as stones and plant residues were removed. After sieving and mixing, 7 kg of garden soil was placed in each pot. Each test case was repeated 3 times, with a total of 15 potted plants, and 3 plants were planted in each pot. The specific experimental fertilization treatment details are shown in Table 2.

[0081] Table 2: Details of fertilization for Shanghai green in each test case

[0082]

[0083]

[0084] The specific test items for Shanghai green are as follows: (1) determination of chlorophyll value and plant height, which are measured before and 3-7 days after fertilization; (2) root weight test, which involves harvesting the roots of each test case, measuring the root weight, and taking photos for record; (3) measurement of Shanghai green yield, which involves harvesting the plant parts above the ground, and taking photos for record.

[0085] The effects of the treatments in each test example of this application on Shanghai green chlorophyll are shown in Table 3.

[0086] Table 3: Effects of each test case treatment on Shanghai green chlorophyll

[0087]

[0088] As can be seen from Table 3, before the first fertilization, the chlorophyll values ​​of the Shanghai Qingzhong in Experimental Examples 1 and 2 were relatively high. Five days after the first fertilization, the chlorophyll value in Experimental Example 3 was the highest. Seven days after the second fertilization and before harvest, the chlorophyll value in Experimental Example 4 was the highest.

[0089] Further references Figure 2 The chlorophyll values ​​in test cases 3, 4, and 5 were all improved compared with those in test case 1, and the gain effect of test case 4 was the best. As the amount of trivalent phosphite added increased, the chlorophyll value increased less, showing a negative correlation trend.

[0090] Furthermore, the present application tested the effects of different test case treatments on the plant height of Shanghai Green, and the specific results are shown in Table 4.

[0091] Table 4: Effects of each test case treatment on plant height of Shanghai green (cm / plant)

[0092]

[0093] It can be seen from Table 4 that before the first fertilization, the plant height of Test Example 4 was relatively high. Under the fertilization conditions, the plant heights of Test Examples 3, 4, and 5 were all improved compared with Test Example 2. The gain effect of Test Example 3 was the best. Figure 3 As shown, with the increase of trivalent phosphite added, the plant height value increased less, showing a negative correlation trend.

[0094] See also Figure 4 , Figure 4 These are pictures of the roots of Shanghai green trees processed in different test cases. Figure 4From top to bottom are pictures of the roots of Shanghai green in Test Examples 1 to 5. After treatment with functional fertilizer, the root weight of Shanghai green in Test Example 3 was the highest, with an average root weight of 0.35g, followed by Test Example 4, with an average root weight of 0.33g. The average root weight of Shanghai green treated with competing fertilizer was 0.30g. The root weights of Test Examples 3 and 4 were 15.38% and 9.89% higher than those of Test Example 2, respectively.

[0095] Furthermore, the present application also tested the effects of different test case treatments on the yield of Shanghai green, and the specific test results are shown in Table 5.

[0096] Table 5: Effects of each test case treatment on the yield of Shanghai green

[0097]

[0098]

[0099] As can be seen from Table 5, after fertilization treatment, the yield of Shanghai Qing in Test Example 3 was the highest, followed by Test Example 4, which increased by 11.20% and 10.60% respectively compared with the Shanghai Qing treated with the competitive fertilizer in Test Example 2. At the same time, with the increase of trivalent phosphite, the yield increase decreased. For pictures of the growth of Shanghai Qing in different test cases, please refer to Figure 5 , Figure 5 From left to right in the figure are the growth pictures of Shanghai Qing in Experimental Examples 1 to 5.

[0100] The present invention further tests the effects of different valence phosphate combinations to form a combined phosphate system on green bean planting through parallel experiments. For the results of green beans, please refer to Figure 6 , Figure 6 From left to right in the figure are pictures of green beans in Experimental Examples 1 to 5. In the cultivation of green beans, with the increase of trivalent phosphite, the yield increase decreases, and the best content is 1% trivalent phosphite.

[0101] The functional fertilizer containing combined phosphates of the present invention forms a combined phosphate system by combining phosphates of different valence states, and contains three phosphorus forms of orthophosphate, phosphite and polyphosphate. Phosphite partially replaces orthophosphate, and the functions of phosphates of different forms are complementary, thereby increasing the transport speed of phosphorus and ensuring its long-term slow release. At the same time, phosphite can induce crops to produce defensins, enhance their disease prevention and antibacterial effects, protect and strengthen roots, and reduce crop disease infection.

[0102] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present invention.

[0103] Finally, it should be noted that, in the present invention, the terms "include", "comprises" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, or article including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, or article. In the absence of further restrictions, an element defined by the sentence "includes a ..." does not exclude the existence of other identical elements in the process, method, or article including the element.

[0104] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A process for preparing a functional fertilizer containing combined phosphates, characterized in that: The process comprises: S1: Concentrating the acid hydrolysis neutralization liquid to obtain NP concentrated slurry; S2: passing the concentrated NP slurry into a polymerization tank and heating and polymerizing at a temperature of 160-190° C. to obtain a polymerization slurry; S3: overflow the polymer slurry into a primary mixing tank, add phosphite and nano zinc oxide into the primary mixing tank, and heat and stir at 130-150° C. for 3-8 minutes; S4: overflow the slurry obtained by the reaction in the primary mixing tank to the secondary mixing tank, add biostimulant substances and trace elements to the secondary mixing tank, and heat and stir at a temperature of 100-120° C. for 2-5 minutes; S5: Granulate, dry, package and screen the slurry obtained in the secondary mixing tank to obtain a functional fertilizer containing combined phosphate.

2. The process for preparing the functional fertilizer containing combined phosphate according to claim 1, characterized in that: In the step S1, phosphate rock is decomposed by nitric acid to obtain an acid solution, which is neutralized with ammonia to obtain an acid-base neutralized solution, and the acid-base neutralized solution is pumped into the NP evaporator to obtain NP concentrated slurry through reaction at 150-170° C. and a negative pressure of 0.005-0.02 MPa.

3. The process for preparing the functional fertilizer containing combined phosphate according to claim 1, characterized in that: In the step S2, the amount of the NP concentrated slurry entering the polymerization tank is 15-30 t / h, and the polymerization reaction time is 1.0-1.5 h.

4. The process for preparing the functional fertilizer containing combined phosphate according to claim 1, characterized in that: The phosphite in step S3 is an alkali metal phosphite.

5. The process for preparing the functional fertilizer containing combined phosphate according to claim 4, characterized in that: The phosphite in step S3 is one or more of potassium phosphite, sodium phosphite, ammonium phosphite, and potassium dihydrogen phosphite.

6. The process for preparing the functional fertilizer containing combined phosphate according to claim 1, characterized in that: In the step S3, the weight ratio of the phosphite to the functional fertilizer is 1.0-5.0%.

7. The process for preparing the functional fertilizer containing combined phosphate according to claim 1, characterized in that: The average particle size of the nano zinc oxide in step S3 is 50-100 nm, and the weight proportion of the nano zinc oxide in the functional fertilizer is 0.1-0.5%.

8. The process for preparing the functional fertilizer containing combined phosphate according to claim 1, characterized in that: The biostimulant substance in step S4 includes one or more of amino acids, fulvic acid, polyglutamic acid, monosaccharides, polysaccharides, and glycopeptides, and the weight ratio of the biostimulant substance to the functional fertilizer is 0.5-2.0%.

9. The process for preparing the functional fertilizer containing combined phosphate according to claim 1, characterized in that: The trace elements in step S4 are one or more of manganese sulfate, boric acid, ferrous sulfate and copper sulfate, and the trace elements account for 0.5-1.5% of the weight of the functional fertilizer.

10. The process for preparing the functional fertilizer containing combined phosphate according to claim 1, characterized in that: The slurry obtained in the secondary mixing tank in step S5 is granulated, dried, wrapped and screened. The granulation methods include biaxial granulation, drum granulation, roller fluidized bed granulation and spray granulation. The screening particle size is 2.0-4.0 mm.

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