Zinc-containing diammonium phosphate and preparation method thereof, and fertilizer containing zinc-containing diammonium phosphate

Abstract

The present invention belongs to the technical field of phosphate fertilizer production, and specifically relates to a zinc-containing diammonium phosphate, a preparation method thereof, and a fertilizer containing zinc-containing diammonium phosphate. Zinc-containing diammonium phosphate is prepared by coating elemental sulfur on the outer layer of solid zinc fertilizer to obtain a sulfur-containing zinc mixed slurry, which is then sprayed onto the diammonium phosphate for granulation to obtain the zinc-containing diammonium phosphate. The amount of solid zinc fertilizer added accounts for 30 to 100% of the total mass of elemental sulfur; and the amount of sulfur-containing zinc mixed slurry added is 1 to 10% based on the total weight of the zinc-containing diammonium phosphate. This preparation method avoids direct contact and antagonistic reactions between phosphate and zinc ions, prevents degradation of phosphorus and zinc nutrients, and maintains a good ratio of water-soluble zinc content and water-soluble phosphorus content.

Description

Technical Field

[0001] The invention belongs to the technical field of phosphate fertilizer production, and particularly relates to zinc-containing diammonium phosphate and a preparation method thereof, and fertilizers containing zinc-containing diammonium phosphate. Technical Background

[0002] Zinc deficiency in my country's soils accounts for over 50% of the country's total arable land. Zinc deficiency has become a major factor limiting crop yield and quality improvement, particularly on calcareous soils in northern my country. Diammonium phosphate (DAP) is the primary and most commonly used phosphate fertilizer in my country. To supplement zinc nutrition and upgrade traditional phosphate fertilizers, the addition of zinc to DAP has become a common practice within the industry. Patents CN106431563A and CN110590479A report on methods for adding zinc fertilizer by feeding solid zinc oxide into a granulator via a return hopper. Patent CN101723733B describes a method for adding zinc fertilizer by metering zinc oxide into a trench, flushing it through a washing solution into an underground trough to create a mixed solution. The mixed solution is then pumped into a pre-neutralization tank and a tubular reaction feed trough to produce a zinc-containing DAP slurry. Finally, the zinc-containing DAP slurry is pumped into a granulator for spray granulation. Patent CN103787723A describes a method for adding zinc sulfate to a pre-neutralizer for granulation. Patent CN101967070A reports a method for producing a phosphate-ammonium compound fertilizer containing sulfur, zinc, manganese and boron by adding a tailings slurry containing zinc, manganese and boron to a fast ammonia reactor and then granulating it. However, a large number of studies at home and abroad have shown that the extent to which zinc fertilizer can exert its agronomic effect is linearly correlated with the water solubility of the zinc fertilizer. The higher the proportion of water-soluble zinc content, the better the agronomic benefit. In the report of the above patent, whether the zinc fertilizer is directly added to the granulator, flushed into the underground tank by washing liquid, added to the pre-neutralizer, or the zinc-containing tailings are added to the fast ammonia reactor, the zinc fertilizer is in direct contact with the phosphate ions in the phosphate fertilizer or phosphoric acid to generate insoluble (slightly) substances such as zinc phosphate and zinc ammonium phosphate; at the same time, the proportion of the water-soluble content of phosphorus will be reduced to a certain extent. Adding chelated zinc can effectively avoid the precipitation reaction of zinc and phosphate, but the price of chelated zinc fertilizer is much higher than that of ordinary zinc fertilizer. When the amount added is slightly increased, the investment cost of fertilizer manufacturers and consumers will be greatly increased. In addition, amino acid chelated zinc can also be added to fertilizers. However, during the granulation process, especially in the front section of the dryer, the temperature is high, which can easily lead to the decomposition and carbonization of amino acids, and the loss of their original properties. Therefore, adding chelated zinc to fertilizers is not the best choice. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for preparing zinc-containing diammonium phosphate in response to the shortcomings of existing zinc fertilizer addition technology for diammonium phosphate products and the high cost of adding chelated zinc, thereby solving the problems of low water-soluble zinc content, low agronomic effect and high cost of adding chelated zinc caused by adding ordinary zinc fertilizer to diammonium phosphate products.

[0004] The purpose of the present invention is achieved through the following technical solutions.

[0005] Unless otherwise specified, all percentages used in the present invention are by mass.

[0006] The invention provides a preparation method of zinc-containing diammonium phosphate, which comprises the following steps: wrapping elemental sulfur on the outer layer of solid zinc fertilizer to obtain sulfur-containing zinc mixed slurry, and then spraying the sulfur-containing zinc mixed slurry onto diammonium phosphate for granulation to obtain zinc-containing diammonium phosphate.

[0007] As a preferred embodiment of the present invention, the added amount of the solid zinc fertilizer accounts for 30 to 100% of the total mass of the elemental sulfur.

[0008] As a preferred embodiment of the present invention, the addition amount of the sulfur-zinc mixed slurry is 1-10% based on the total weight of the zinc-containing diammonium phosphate.

[0009] As a preferred embodiment of the present invention, the elemental sulfur is sulfur. Modified sulfur in the prior art can also be selected, such as micro-powdered sulfur with a smaller particle size, bio-sulfur, etc.

[0010] As a preferred embodiment of the present invention, the elemental sulfur is coated by mixing solid zinc fertilizer with liquid elemental sulfur and stirring the mixture at 130-150° C. for 0.5-1 hour.

[0011] As a preferred embodiment of the present invention, the solid zinc fertilizer is zinc sulfate monohydrate, anhydrous zinc sulfate or zinc oxide.

[0012] More preferably, the solid zinc fertilizer is zinc sulfate monohydrate.

[0013] As a preferred embodiment of the present invention, the particle size of the solid zinc fertilizer is 1 nm to 0.25 mm.

[0014] The present invention also provides zinc-containing diammonium phosphate prepared according to the above method. The zinc-containing diammonium phosphate is composed of elemental sulfur, zinc fertilizer and diammonium phosphate. The elemental sulfur is wrapped around the periphery of the zinc fertilizer to form zinc-sulfur fertilizer particles, and the zinc-sulfur fertilizer particles are filled in the gaps between the diammonium phosphate particles. The added amount of zinc fertilizer accounts for 30% to 100% of the total mass of the elemental sulfur; and the added amount of sulfur-zinc mixed slurry is 1% to 10% based on the total weight of the zinc-containing diammonium phosphate.

[0015] The present invention also provides a fertilizer comprising the zinc-containing diammonium phosphate.

[0016] Compared with existing products and technologies, the present invention has the following advantages:

[0017] 1. The present invention adds zinc fertilizer into a liquid sulfur tank, wraps a layer of elemental sulfur on the outside of the zinc fertilizer, and then directly sprays it into a granulator for granulation through an air compressor pump. Since there is a layer of elemental sulfur between phosphorus and zinc, direct contact and antagonistic reaction between phosphate and zinc ions are avoided, thereby avoiding the degradation of phosphorus and zinc nutrients and maintaining a good proportion of water-soluble zinc content and water-soluble phosphorus content.

[0018] 2. The zinc fertilizer dosage in the present invention is 30-100% of the sulfur dosage. The zinc fertilizer particle size is 1 nm to 0.25 mm, allowing it to be well and evenly coated by the liquid sulfur. The sulfur-containing zinc slurry in the liquid sulfur tank sprayed into the granulator is 1-10% of the total zinc-containing diammonium phosphate. The zinc-containing diammonium phosphate contains 0.5-5% elemental sulfur and 0.1-1.5% zinc, effectively meeting the crop's sulfur and zinc needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The figure is a schematic diagram of the process flow of zinc fertilizer addition according to the present invention.

[0020] Figure 2 This is a schematic structural diagram of the product of the present invention, 1. elemental sulfur; 2. zinc fertilizer; 3. ammonium phosphate.

[0021] Figure 3 This is an X-ray diffraction analysis of the zinc-containing diammonium phosphate sample prepared in Example 1; DAP+ZnSO4+S fusion (Fusion), the zinc-containing diammonium phosphate sample prepared in Example 1; DAP+ZnSO4+S mixture (Mixture), the zinc-containing diammonium phosphate sample prepared by a traditional method, the mixing ratio of zinc fertilizer to diammonium phosphate is the same as in Example 1; (NH4)2HPO4, PDF#97-000-2799 and Zn3(PO4)2PDF#00-030-1490 (RDB) are both standard substances.

[0022] Figure 4 This is an X-ray diffraction analysis of the zinc-containing diammonium phosphate sample prepared in Example 2; DAP+ZnO+S fusion (Fusion), the zinc-containing diammonium phosphate sample prepared in Example 2; DAP+ZnO+S mixture (Mixture), the zinc-containing diammonium phosphate sample prepared by a traditional method, the mixing ratio of zinc fertilizer to diammonium phosphate is the same as in Example 2; (NH4)2HPO4, PDF#97-000-2799 and Zn3(PO4)2PDF#00-030-1490 (RDB) are both standard substances.

[0023] Figures 5 to 9 4. The dry matter weight and nutrient content of Chinese cabbage in Example 4.

[0024] Figures 10-14 5. The dry matter weight and nutrient content of Chinese cabbage in Example 5. DETAILED DESCRIPTION

[0025] The present invention will be further described below with reference to specific examples, but the present invention is not limited to the following examples.

[0026] Diammonium phosphate (DAP) is the primary phosphate fertilizer in my country and the most commonly used by farmers. To supplement zinc nutrition and upgrade traditional phosphate fertilizers, the addition of zinc to DAP has become a common practice within the industry. However, existing addition methods present the following technical issues: zinc fertilizers come into direct contact with phosphate ions in phosphate fertilizers or phosphoric acid, generating poorly (slightly) soluble substances such as zinc phosphate and zinc ammonium phosphate; this also reduces the water-soluble content of phosphorus to a certain extent. Adding chelated zinc can effectively prevent the precipitation reaction of zinc and phosphorus, but the price of chelated zinc fertilizers is much higher than that of ordinary zinc fertilizers. Even a slight increase in the addition amount significantly increases the input costs for fertilizer manufacturers and consumers. Amino acid chelated zinc can also be added to fertilizers, but during the granulation process, especially at the front end of the dryer, the temperatures are high, which can easily lead to amino acid decomposition and carbonization, resulting in a loss of their original properties. Therefore, adding chelated zinc to fertilizers is not the optimal option.

[0027] The invention provides a preparation method of zinc-containing diammonium phosphate, which comprises the following steps: wrapping elemental sulfur on the outer layer of solid zinc fertilizer to obtain sulfur-containing zinc mixed slurry, and then spraying the sulfur-containing zinc mixed slurry onto diammonium phosphate for granulation to obtain zinc-containing diammonium phosphate.

[0028] The present invention adds zinc fertilizer into a liquid sulfur tank, wraps a layer of elemental sulfur on the outside of the zinc fertilizer, and then directly sprays the zinc fertilizer into a granulator for granulation through an air compressor pump. Due to the layer of elemental sulfur between phosphorus and zinc, direct contact and antagonistic reaction between phosphate and zinc ions are avoided, thereby avoiding the degradation of phosphorus and zinc nutrients and maintaining a good proportion of water-soluble zinc content and water-soluble phosphorus content.

[0029] It should be noted that the zinc-containing diammonium phosphate sample prepared by the traditional method described in the examples of the present invention is obtained by directly mixing zinc fertilizer and diammonium phosphate.

[0030] Example 1

[0031] A method for adding zinc fertilizer to diammonium phosphate products, such as Figure 1 As shown, the following steps are included:

[0032] Pass diammonium phosphate (15% N, 42% P2O5) and sulfur through a 60-mesh sieve, and pass zinc sulfate monohydrate (35% Zn) through a 200-mesh sieve for later use. Add an appropriate amount of sulfur into the melting tank to melt the sulfur. The temperature of the melting tank is controlled at 130°C. Add zinc sulfate monohydrate into the liquid sulfur melting tank at a mass ratio of 1:1 with elemental sulfur. After stirring for 30 minutes, a sulfur-containing zinc slurry is formed. The sulfur-containing zinc slurry is directly sprayed onto the diammonium phosphate material in the disc granulator through an air compressor pump for granulation. The amount of sulfur-containing zinc slurry sprayed is 3% of the total material. Particles smaller than 1mm or larger than 4mm are re-crushed and added to the disc granulator for re-granulation. After drying, screening, cooling and packaging, a zinc-containing diammonium phosphate sample is formed. The structural schematic diagram of the zinc-containing diammonium phosphate sample is shown as follows: Figure 2 shown.

[0033] Example 2

[0034] A method for adding zinc fertilizer to diammonium phosphate products, such as Figure 1 As shown, the following steps are included:

[0035] Pass diammonium phosphate (15% N, 42% P2O5), sulfur, and zinc oxide (80% Zn) through a 60-mesh sieve for later use. Add an appropriate amount of sulfur into the melting tank to melt the sulfur. The temperature of the melting tank is controlled at 130°C. Add zinc sulfate monohydrate into the liquid sulfur melting tank at a mass ratio of 1:3 to elemental sulfur. After stirring for 60 minutes, a sulfur-containing zinc slurry is formed. The sulfur-containing zinc slurry is directly sprayed onto the diammonium phosphate material in the disc granulator through an air compressor pump for granulation. The amount of sulfur-containing zinc slurry sprayed is 5% of the total material. Particles smaller than 1mm or larger than 4mm are re-crushed and added to the disc granulator for re-granulation. After drying, screening, cooling and packaging, a zinc-containing diammonium phosphate sample is formed. The structural schematic diagram of the zinc-containing diammonium phosphate sample is shown as follows: Figure 2 shown.

[0036] Example 3

[0037] A method for adding zinc fertilizer to diammonium phosphate products, such as Figure 1 As shown, the following steps are included:

[0038] Pass diammonium phosphate (15% N, 42% P2O5) and sulfur through a 60-mesh sieve, and pass zinc sulfate monohydrate (35% Zn) through a 200-mesh sieve for later use. Add an appropriate amount of sulfur into the melting tank to melt the sulfur. The temperature of the melting tank is controlled at 150°C. Add zinc sulfate monohydrate into the liquid sulfur melting tank at a mass ratio of 1:1 with elemental sulfur. After stirring for 30 minutes, a sulfur-containing zinc slurry is formed. The sulfur-containing zinc slurry is directly sprayed onto the diammonium phosphate material in the disc granulator through an air compressor pump for granulation. The amount of sulfur-containing zinc slurry sprayed is 10% of the total material. Particles smaller than 1mm or larger than 4mm are re-crushed and added to the disc granulator for re-granulation. After drying, screening, cooling and packaging, a zinc-containing diammonium phosphate sample is formed. The structural schematic diagram of the zinc-containing diammonium phosphate sample is shown as follows: Figure 2 shown.

[0039] Example 4

[0040] A method for adding zinc fertilizer to diammonium phosphate products, such as Figure 1 As shown, the following steps are included:

[0041] Pass diammonium phosphate (15% N, 42% P2O5) and sulfur through a 60-mesh sieve, and pass zinc sulfate monohydrate (35% Zn) through a 200-mesh sieve for later use. Add an appropriate amount of sulfur into the melting tank to melt the sulfur. The temperature of the melting tank is controlled at 150°C. Add zinc sulfate monohydrate into the liquid sulfur melting tank at a mass ratio of 1:2 to elemental sulfur. After stirring for 60 minutes, a sulfur-containing zinc slurry is formed. The sulfur-containing zinc slurry is directly sprayed onto the diammonium phosphate material in the disc granulator through an air compressor pump for granulation. The amount of sulfur-containing zinc slurry sprayed is 1% of the total material. Particles smaller than 1mm or larger than 4mm are re-crushed and added to the disc granulator for re-granulation. After drying, screening, cooling and packaging, a zinc-containing diammonium phosphate sample is formed. The structural schematic diagram of the zinc-containing diammonium phosphate sample is shown as follows: Figure 2 shown.

[0042] Since Examples 1 to 4 all prepared zinc-containing diammonium phosphate samples with the expected effects of the present invention, the present invention only uses the zinc-containing diammonium phosphate samples prepared in Examples 1 to 2 as examples to illustrate their properties and effects.

[0043] The samples obtained in Example 1 and Example 2 were subjected to X-ray diffraction analysis to analyze their phase changes. Figure 3 It can be seen that when the diffraction angle (2θ) is between 20-20.7°, 22.72-23.02°, and 28.16-28.72°, the relative diffraction intensity of the molten state is significantly reduced compared with the traditional addition method, indicating that the content of zinc phosphate products in the molten state added fertilizer product prepared by the present invention is reduced. Figure 4 It can be seen that there is no obvious change in the physical phase of the fertilizer product added in the molten state and the conventional mixed state.

[0044] Experimental Example 1

[0045] Fertilizer efficiency test

[0046] The test fertilizer was the fertilizer sample prepared in Example 1 (14.4% N, 42.1% P2O5, 0.90% Zn, 2.70% elemental S). The basic information of the test soil was: pH 8.27, organic matter 1.10%, and total nitrogen content of 690 mg kg -1 , the available potassium is 91.3 mg·kg -1 , the available phosphorus content is 11.6 mg kg -1 , effective sulfur 10.97mg / kg, effective zinc content 1.64mgvkg -1 Test crop: Chinese cabbage. This experiment included two treatments; see Table 1 for details. The mixing ratio of zinc fertilizer to diammonium phosphate in E2 was the same as in Example 1.

[0047] Table 1 Fertilization treatments

[0048] Processing number Processing Name Fertilizer amount (g / pot) Fertilization method Example 1 (E1) <![CDATA[Ammonium dihydrogen phosphate + ZnSO4 (added by melting)]]> 0.88 Apply fertilizer in holes, with a spacing of 4 cm between seeds and fertilizers E2 (prepared by traditional method) <![CDATA[Ammonium dihydrogen phosphate + ZnSO4 (mixed addition)]]> 0.88 Apply fertilizer in holes, with a spacing of 4 cm between seeds and fertilizers

[0049] Each treatment was replicated four times in randomized order, with soil weight per pot weighing 3.5 kg. Ten pakchoy seeds were sown per pot, and one well-grown, evenly growing pakchoy seedling was retained. Watering was done regularly to maintain 75% of field capacity. A fertilizer rate of 0.88 g / pot was applied across all treatments, based on phosphorus as the baseline. Ammonium chloride and potassium chloride were used to supplement nitrogen and potassium.

[0050] Depend on Figures 5 to 9 It can be seen that compared with traditional zinc-containing diammonium phosphate, the dry matter weight, nitrogen content, phosphorus content, sulfur content and zinc content of the aboveground part of Chinese cabbage increased by about 40.00%, 4.23%, 11.02%, 20.00% and 18.37%, respectively.

[0051] Experimental Example 2

[0052] Fertilizer efficiency test

[0053] The test fertilizer was the fertilizer sample prepared in Example 2 (14.6% N, 41.8% P2O5, 0.93% Zn, 2.76% elemental S). The basic information of the test soil was: pH 8.27, organic matter 1.10%, and total nitrogen content of 690 mg / kg. -1 , the available potassium is 91.3 mg·kg -1 , the available phosphorus content is 11.6 mg kg -1 , effective sulfur 10.97mg / kg, effective zinc content 1.64mg·kg -1 Test crop: Chinese cabbage. This experiment included two treatments; see Table 2 for details. The mixing ratio of zinc fertilizer to diammonium phosphate in E4 was the same as in Example 2.

[0054] Table 2 Fertilization treatments

[0055] Processing number Processing Name Fertilizer amount (g / pot) Fertilization method Example 2 (E3) Diammonium phosphate + ZnO (molten addition) 0.87 Apply fertilizer in holes, with a spacing of 4 cm between seeds and fertilizers E4 (prepared by traditional method) Diammonium phosphate + ZnO (mixed addition) 0.87 Apply fertilizer in holes, with a spacing of 4 cm between seeds and fertilizers

[0056] Each treatment was repeated 4 times, randomly arranged, and the soil weight of each pot was 3.5 kg. Ten pakchoy seeds were spread in each pot, and one pakchoy seedling with good growth and uniform growth was retained. Watering was done regularly to maintain 75% of the field water holding capacity. The fertilizer dosage for all treatments was 0.87 g / pot, and the fertilizer dosage was calculated based on phosphorus. The remaining nitrogen and potassium were supplemented with ammonium chloride and potassium chloride. The dry weight and nutrient content of pakchoy are shown in Figure 2. Figures 10-14 shown.

[0057] Compared with the traditional zinc-containing diammonium phosphate addition method, after the zinc-containing diammonium phosphate prepared by the method provided by the present invention is applied, the dry matter weight, nitrogen content, phosphorus content, sulfur content and zinc content of the aboveground part of the second-season Chinese cabbage increase by approximately 30.21%, 12.14%, 9.90%, 20.80% and 18.40%, respectively.

[0058] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for preparing zinc-containing diammonium phosphate, characterized in that: The method comprises wrapping elemental sulfur on the outer layer of solid zinc fertilizer to obtain a sulfur-containing zinc mixed slurry, and then spraying the sulfur-containing zinc mixed slurry onto diammonium phosphate for granulation to obtain zinc-containing diammonium phosphate; the elemental sulfur is wrapped by mixing solid zinc fertilizer with liquid elemental sulfur and stirring at 130-150° C. for 0.5-1 hour; Wherein, the addition amount of the solid zinc fertilizer accounts for 30 to 100% of the total mass of the elemental sulfur; The addition amount of the sulfur-zinc mixed slurry is 1-10% based on the total weight of the zinc-containing diammonium phosphate.

2. The method for preparing zinc-containing diammonium phosphate according to claim 1, wherein The elemental sulfur is sulfur.

3. The method for preparing zinc-containing diammonium phosphate according to claim 1, wherein The solid zinc fertilizer is zinc sulfate monohydrate, anhydrous zinc sulfate or zinc oxide.

4. The method for preparing zinc-containing diammonium phosphate according to claim 3, wherein The solid zinc fertilizer is zinc sulfate monohydrate.

5. The method for preparing zinc-containing diammonium phosphate according to claim 1, wherein The particle size of the solid zinc fertilizer is 1 nm to 0.25 mm.

6. A zinc-containing diammonium phosphate prepared according to the method according to any one of claims 1 to 5, characterized in that: The zinc-containing diammonium phosphate is composed of elemental sulfur, zinc fertilizer and diammonium phosphate. The elemental sulfur is wrapped around the zinc fertilizer to form zinc-sulfur fertilizer particles, and the zinc-sulfur fertilizer particles are filled in the gaps between the diammonium phosphate particles. The added amount of the zinc fertilizer accounts for 30% to 100% of the total mass of the elemental sulfur; and the added amount of the zinc-sulfur fertilizer particles is 1% to 10% based on the total weight of the zinc-containing diammonium phosphate.

7. A fertilizer, characterized in that It comprises the zinc-containing diammonium phosphate according to claim 6.

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