High-strength potassium sulfate type compound fertilizer granules and preparation process thereof

Abstract

The invention provides high-strength potassium sulfate type compound fertilizer granules and a preparation process thereof, and relates to the technical field of compound fertilizers. The high-strength potassium sulfate type compound fertilizer granules are prepared from the following raw materials in parts by weight: 15-20 parts of potassium chloride, 8-10 parts of calcium superphosphate, 20-24 parts of urea, 0.2-0.4 part of copper sulfate, 0.4-0.6 part of sodium carbonate, 0.1-0.2 part of zinc oxide, 0.4-0.6 part of a binder and 0.6-1 part of a fertilizer synergist. The preparation method comprises the following steps: weighing the raw materials as required, uniformly mixing, adding into a granulator, drying at the temperature of 60-80 DEG C, adjusting the moisture content to 3-4%, and granulating to obtain the product. According to the high-strength potassium sulfate type compound fertilizer particles, the strength of the compound fertilizer particles is effectively enhanced, the probability of pulverization and caking is reduced, and the slow-release use effect and economic benefits of the fertilizer are further improved.

Description

Technical Field

[0001] The invention relates to the technical field of compound fertilizers, and in particular to high-strength potassium sulfate type compound fertilizer particles and a preparation process thereof. Background Art

[0002] Potassium sulfate compound fertilizer is an important agricultural fertilizer and is widely used in the production of various crops to meet the crops' demand for potassium and sulfur. However, the traditional production process of potassium sulfate compound fertilizer is insufficient in terms of particle strength, which makes the product prone to powdering and agglomeration during storage and transportation, seriously affecting the use effect and economic benefits of the fertilizer.

[0003] The traditional production process of potassium sulfate compound fertilizer mainly includes the steps of raw material preparation, mixed material preparation, mixed material crushing, granulation, drying, screening and packaging. Among them, the granulation link is the key link that affects the strength of the particles. Traditional granulation methods mostly use steam agglomeration granulation or drum drying technology. Although these technologies can form particles, they have obvious shortcomings in terms of particle strength. The main reason is that sandy materials such as potassium sulfate have low solubility and poor adhesion during granulation, resulting in poor particle compactness and low strength.

[0004] In order to improve the strength of the particles, some domestic manufacturers add anti-powdering agents (adhesives) or adopt high-tower granulation technology during the granulation process. However, these methods either increase the production cost or have high requirements on equipment, making it difficult to promote and apply them on a large scale. In view of the problems of low particle strength, easy pulverization and agglomeration in the prior art, the present invention provides a high-strength potassium sulfate type compound fertilizer particle and a preparation process thereof. Summary of the invention

[0005] The purpose of the present invention is to provide a high-strength potassium sulfate type compound fertilizer granule and a preparation process thereof, which can effectively enhance the strength of the compound fertilizer granule, reduce the probability of pulverization and agglomeration, and further improve the slow-release use effect and economic benefit of the fertilizer.

[0006] On the one hand, the present invention provides a high-strength potassium sulfate type compound fertilizer granule, which is prepared from the following raw materials in parts by weight: 15-20 parts of potassium chloride, 8-10 parts of superphosphate, 20-24 parts of urea, 0.2-0.4 parts of copper sulfate, 0.4-0.6 parts of sodium carbonate, 0.1-0.2 parts of zinc oxide, 0.4-0.6 parts of binder, and 0.6-1 parts of fertilizer synergist.

[0007] Furthermore, the binder comprises a sulfuric acid aqueous solution with a mass concentration of 6-8% and a cyclodextrin-modified carboxymethyl cellulose hydrogel aqueous solution with a mass concentration of 12-14% in a volume ratio of 1:(3-4).

[0008] Furthermore, the preparation method of the cyclodextrin-modified carboxymethyl cellulose hydrogel comprises: adding β-cyclodextrin, carboxymethyl cellulose, 1,4-butanediol diglycidyl ether, and liquid paraffin to a NaOH aqueous solution in sequence under stirring conditions, and stirring the reaction for 20-22 hours; after the reaction is completed, washing the product, and drying the product at 30-40° C. to obtain spherical dry gel particles.

[0009] Furthermore, the concentration of the NaOH aqueous solution is 1-1.2 mol / L; the dosage ratio of the NaOH aqueous solution, β-cyclodextrin, carboxymethyl cellulose, 1,4-butanediol diglycidyl ether, and liquid paraffin is (20-24) mL: (5-5.5) g: (0.8-1) g: (2.6-3) g: (120-140) mL.

[0010] Furthermore, the washing method comprises washing three times with a mixture of deionized water and acetone in a volume ratio of 1:1, and then washing 5-7 times with deionized water.

[0011] Furthermore, the fertilizer synergist is obtained by mixing sepiolite powder and attapulgite powder and then modifying them with a silane coupling agent.

[0012] Furthermore, the preparation method of the fertilizer synergist includes: stirring and dispersing sepiolite powder and attapulgite powder pretreated with a sulfuric acid solution in deionized water to obtain a dispersion A, dispersing a silane coupling agent KH550 in ethanol to obtain a dispersion B, mixing the dispersion A and the dispersion B under reflux stirring at a temperature of 60-70°C for 2-3h; filtering and washing, and drying under vacuum at a temperature of 80-90°C for 12-14h.

[0013] Furthermore, the preparation steps of the pretreated sepiolite powder and attapulgite powder include: grinding and blending the sepiolite powder and attapulgite powder in a weight ratio of (5-6): (1-2), immersing in a sulfuric acid solution with a mass concentration of 10-12%, and stirring for 40-60 minutes at a temperature of 40-50°C; filtering, washing with deionized water to neutrality, drying at a temperature of 55-65°C, and crushing to be able to pass through a 200-mesh sieve to obtain the pretreated sepiolite powder and attapulgite powder.

[0014] Furthermore, the mass ratio of the treated sepiolite powder and attapulgite powder, deionized water, silane coupling agent KH550 and ethanol is (4-6): (60-80): (1-2): (100-120).

[0015] On the other hand, the present invention also provides a preparation process of high-strength potassium sulfate type compound fertilizer particles, the steps comprising: weighing raw materials as required and mixing them evenly, adding them into a granulator, drying them at a temperature of 60-80° C., adjusting the moisture content to 3-4wt%, and granulating them to obtain the particles.

[0016] The beneficial effects of the present invention are:

[0017] In the present invention, potassium chloride, superphosphate and urea are the main nutrients of the compound fertilizer. The appropriate proportion of these raw materials not only ensures the comprehensive nutrition of the fertilizer, but also forms a stable particle structure foundation through chemical reaction and physical mixing. The addition of trace elements such as copper sulfate, sodium carbonate and zinc oxide not only enriches the nutritional composition of the fertilizer, but also promotes the compactness inside the particles through trace chemical reactions and enhances the mechanical strength of the particles.

[0018] The present invention adopts sulfuric acid aqueous solution and cyclodextrin-modified carboxymethyl cellulose hydrogel compound as binding agent, which is the key to enhance particle strength. Wherein the acidic environment of sulfuric acid aqueous solution contributes to the preliminary combination between raw materials, and cyclodextrin-modified carboxymethyl cellulose hydrogel combines β-cyclodextrin, carboxymethyl cellulose and cross-linking agent (such as 1,4-butanediol diglycidyl ether) to form a hydrogel with a three-dimensional network structure. Wherein, carboxymethyl cellulose (CMC) itself has good water solubility and film-forming property, and after being modified by β-cyclodextrin, its molecules can form a more complex three-dimensional network structure, and this structure can maintain certain elasticity and toughness after drying, thereby giving fertilizer particles higher mechanical strength. And cyclodextrin-modified carboxymethyl cellulose hydrogel can penetrate into the micropores of fertilizer particles, and form a close physical and chemical combination with the components inside the particles, and this combination not only enhances the cohesive force inside the particles, but also improves the adhesion of the particle surface and the surrounding environment, and reduces the mutual friction between particles and the pulverization caused by collision. In addition, the water retention and slow release properties of the hydrogel help control the release rate of fertilizer nutrients. When the hydrogel is embedded in the fertilizer particles, it can serve as a storage and release carrier for nutrients, gradually releasing nutrients according to soil moisture and crop needs, thereby improving the utilization rate and slow-release effect of the fertilizer. Therefore, this cyclodextrin-modified carboxymethyl cellulose hydrogel not only enhances the viscosity of the binder and improves the strength of the fertilizer particles, but also improves the slow-release effect of the fertilizer.

[0019] The fertilizer synergist in the present invention is formed by modifying sepiolite powder and attapulgite powder with a silane coupling agent. These natural mineral materials have good adsorption and sustained release properties. After modification, they can be more closely combined with fertilizer particles to form a protective layer to prevent rapid loss of nutrients and help control the release rate of nutrients.

[0020] In addition, sulfuric acid solution pretreatment can remove impurities and pollutants on the surface of sepiolite powder and attapulgite powder, increase their surface activity, and make subsequent silane coupling agent modification easier. At the same time, sulfuric acid treatment also changes the surface charge properties of the mineral powder, further improving its ability to bind nutrients and slow-release effect. During the modification process, the KH550 molecule also combines with the hydroxyl group on the surface of the mineral powder through its reaction end to form an organic-inorganic composite film. This film not only enhances the binding force between the mineral powder and other components in the fertilizer particles, but also improves the density and strength of the entire particle; at the same time, the modification of KH550 also improves the wettability of the mineral powder surface, making it more evenly dispersed in the fertilizer particles, further improving the slow-release effect and stability of the fertilizer. DETAILED DESCRIPTION

[0021] The technical scheme of the present invention is described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention. It should be noted that the raw materials can be obtained commercially.

[0022] Example 1

[0023] This embodiment provides a high-strength potassium sulfate type compound fertilizer granule, which is prepared from the following raw materials in parts by weight: 17 parts of potassium chloride, 9 parts of superphosphate, 22 parts of urea, 0.3 parts of copper sulfate, 0.5 parts of sodium carbonate, 0.15 parts of zinc oxide, 0.5 parts of binder, and 0.8 parts of fertilizer synergist;

[0024] The binder comprises a sulfuric acid aqueous solution with a mass concentration of 7% and a cyclodextrin-modified carboxymethyl cellulose hydrogel aqueous solution with a mass concentration of 13% in a volume ratio of 1:3.5;

[0025] The preparation method of cyclodextrin-modified carboxymethyl cellulose hydrogel comprises: adding β-cyclodextrin, carboxymethyl cellulose, 1,4-butanediol diglycidyl ether and liquid paraffin in sequence to a NaOH aqueous solution with a concentration of 1.1 mol / L under stirring conditions, and stirring for reaction for 21 hours; after the reaction is completed, washing the product with a mixed solution of deionized water and acetone in a volume ratio of 1:1 for 3 times, and then washing it with deionized water for 6 times, and drying the product at 35°C to obtain spherical dry gel particles; the dosage ratio of the NaOH aqueous solution, β-cyclodextrin, carboxymethyl cellulose, 1,4-butanediol diglycidyl ether and liquid paraffin is 22mL:5.25g:0.9g:2.8g:130mL;

[0026] The fertilizer synergist is obtained by mixing sepiolite powder and attapulgite powder and then modifying them with a silane coupling agent. The specific preparation method includes: grinding and blending sepiolite powder and attapulgite powder in a weight ratio of 5.5:1.5, immersing them in a sulfuric acid solution with a mass concentration of 11%, and stirring them at a temperature of 45°C for 50 minutes; filtering and washing them with deionized water to neutrality, drying them at a temperature of 60°C, and crushing them to be able to pass through a 200-mesh sieve to obtain pretreated sepiolite powder and attapulgite powder; The sepiolite powder and attapulgite powder pretreated with sulfuric acid solution are stirred and dispersed in deionized water to obtain dispersion A, and the silane coupling agent KH550 is dispersed in ethanol to obtain dispersion B. The dispersion A and the dispersion B are mixed and refluxed and stirred for 2.5 hours at a temperature of 65°C; filtered and washed, and dried for 13 hours under vacuum at a temperature of 85°C; the mass ratio of the treated sepiolite powder and attapulgite powder, deionized water, silane coupling agent KH550 and ethanol is 5:70:1.5:110;

[0027] The preparation process of the high-strength potassium sulfate type compound fertilizer granules in this embodiment comprises the following steps: weighing raw materials as required and mixing them evenly, adding them into a granulator, drying them at a temperature of 70° C., adjusting the moisture content to 3.5wt%, and granulating them to obtain the granules.

[0028] Example 2

[0029] This embodiment provides a high-strength potassium sulfate type compound fertilizer granules, which are prepared from the following raw materials in parts by weight: 15 parts of potassium chloride, 10 parts of superphosphate, 20 parts of urea, 0.4 parts of copper sulfate, 0.4 parts of sodium carbonate, 0.2 parts of zinc oxide, 0.4 parts of a binder, and 1 part of a fertilizer synergist;

[0030] The binder comprises a sulfuric acid aqueous solution with a mass concentration of 8% and a cyclodextrin-modified carboxymethyl cellulose hydrogel aqueous solution with a mass concentration of 12% in a volume ratio of 1:3;

[0031] The preparation method of cyclodextrin-modified carboxymethyl cellulose hydrogel comprises: adding β-cyclodextrin, carboxymethyl cellulose, 1,4-butanediol diglycidyl ether and liquid paraffin in sequence to a NaOH aqueous solution with a concentration of 1.2 mol / L under stirring conditions, and stirring for reaction for 20 hours; after the reaction is completed, washing the product with a mixed solution of deionized water and acetone in a volume ratio of 1:1 for 3 times, and then washing it with deionized water for 7 times, and drying the product at 30°C to obtain spherical dry gel particles; the amount ratio of the NaOH aqueous solution, β-cyclodextrin, carboxymethyl cellulose, 1,4-butanediol diglycidyl ether and liquid paraffin is 24mL:5g:1g:2.6g:(140mL;

[0032] The fertilizer synergist is obtained by mixing sepiolite powder and attapulgite powder and then modifying them with a silane coupling agent. The specific preparation method includes: grinding and blending sepiolite powder and attapulgite powder in a weight ratio of 5:2, immersing them in a sulfuric acid solution with a mass concentration of 10%, and stirring them at a temperature of 50°C for 40 minutes; filtering and washing them with deionized water to neutrality, drying them at a temperature of 65°C, and crushing them to be able to pass through a 200-mesh sieve to obtain pretreated sepiolite powder and attapulgite powder; The sepiolite powder and attapulgite powder pretreated with sulfuric acid solution are stirred and dispersed in deionized water to obtain dispersion A, and the silane coupling agent KH550 is dispersed in ethanol to obtain dispersion B. The dispersion A and the dispersion B are mixed and refluxed and stirred for 3 hours at a temperature of 60°C; filtered and washed, and dried for 14 hours under vacuum at a temperature of 80°C; the mass ratio of the treated sepiolite powder and attapulgite powder, deionized water, silane coupling agent KH550 and ethanol is 4:80:1:120;

[0033] The preparation process of the high-strength potassium sulfate type compound fertilizer granules in this embodiment comprises the following steps: weighing raw materials as required and mixing them evenly, adding them into a granulator, drying them at a temperature of 60° C., adjusting the moisture content to 4wt%, and granulating them to obtain the granules.

[0034] Example 3

[0035] This embodiment provides a high-strength potassium sulfate type compound fertilizer granules, which are prepared from the following raw materials in parts by weight: 20 parts of potassium chloride, 8 parts of superphosphate, 24 parts of urea, 0.2 parts of copper sulfate, 0.6 parts of sodium carbonate, 0.1 parts of zinc oxide, 0.6 parts of binder, and 0.6 parts of fertilizer synergist;

[0036] The binder comprises a 6% sulfuric acid aqueous solution and a 14% cyclodextrin-modified carboxymethyl cellulose hydrogel aqueous solution in a volume ratio of 1:4;

[0037] The preparation method of cyclodextrin-modified carboxymethyl cellulose hydrogel comprises: adding β-cyclodextrin, carboxymethyl cellulose, 1,4-butanediol diglycidyl ether and liquid paraffin in sequence to a NaOH aqueous solution with a concentration of 1 mol / L under stirring conditions, and stirring for reaction for 22 hours; after the reaction is completed, washing the product with a mixed solution of deionized water and acetone in a volume ratio of 1:1 for 3 times, and then washing it with deionized water for 5 times, and drying the product at 40°C to obtain spherical dry gel particles; the dosage ratio of the NaOH aqueous solution, β-cyclodextrin, carboxymethyl cellulose, 1,4-butanediol diglycidyl ether and liquid paraffin is 20mL:5.5g:0.8g:3g:120mL;

[0038] The fertilizer synergist is obtained by mixing sepiolite powder and attapulgite powder and then modifying them with a silane coupling agent. The specific preparation method includes: grinding and blending sepiolite powder and attapulgite powder in a weight ratio of 6:1, immersing them in a sulfuric acid solution with a mass concentration of 12%, and stirring them at a temperature of 40°C for 60 minutes; filtering and washing them with deionized water to neutrality, drying them at a temperature of 55°C, and crushing them to be able to pass through a 200-mesh sieve to obtain pretreated sepiolite powder and attapulgite powder; The sepiolite powder and attapulgite powder pretreated with sulfuric acid solution are stirred and dispersed in deionized water to obtain dispersion A, and the silane coupling agent KH550 is dispersed in ethanol to obtain dispersion B. The dispersion A and the dispersion B are mixed and refluxed and stirred for 2 hours at a temperature of 70°C; filtered and washed, and dried for 12 hours under vacuum at a temperature of 90°C; the mass ratio of the treated sepiolite powder and attapulgite powder, deionized water, silane coupling agent KH550 and ethanol is 6:60:2:100;

[0039] The preparation process of the high-strength potassium sulfate type compound fertilizer granules in this embodiment comprises the following steps: weighing raw materials as required and mixing them evenly, adding them into a granulator, drying them at a temperature of 80° C., adjusting the moisture content to 3wt%, and granulating them to obtain the granules.

[0040] Example 4

[0041] This embodiment provides a high-strength potassium sulfate type compound fertilizer granule, which is prepared from the following raw materials in parts by weight: 15 parts of potassium chloride, 8 parts of superphosphate, 20 parts of urea, 0.2 parts of copper sulfate, 0.4 parts of sodium carbonate, 0.1 parts of zinc oxide, 0.4 parts of binder, and 0.6 parts of fertilizer synergist;

[0042] The binder comprises a 6% sulfuric acid aqueous solution and a 12% cyclodextrin-modified carboxymethyl cellulose hydrogel aqueous solution in a volume ratio of 1:3;

[0043] The preparation method of cyclodextrin-modified carboxymethyl cellulose hydrogel comprises: adding β-cyclodextrin, carboxymethyl cellulose, 1,4-butanediol diglycidyl ether and liquid paraffin in sequence to a NaOH aqueous solution with a concentration of 1 mol / L under stirring conditions, and stirring for reaction for 20 hours; after the reaction is completed, washing the product with a mixed solution of deionized water and acetone in a volume ratio of 1:1 for 3 times, and then washing it with deionized water for 5 times, and drying the product at 30°C to obtain spherical dry gel particles; the amount ratio of the NaOH aqueous solution, β-cyclodextrin, carboxymethyl cellulose, 1,4-butanediol diglycidyl ether and liquid paraffin is 20mL:5g:0.8g:2.6g:120mL;

[0044] The fertilizer synergist is obtained by mixing sepiolite powder and attapulgite powder and then modifying them with a silane coupling agent. The specific preparation method includes: grinding and blending sepiolite powder and attapulgite powder in a weight ratio of 5:1, immersing them in a sulfuric acid solution with a mass concentration of 10%, and stirring them at a temperature of 40°C for 40 minutes; filtering and washing them with deionized water to neutrality, drying them at a temperature of 55°C, and crushing them to be able to pass through a 200-mesh sieve to obtain pretreated sepiolite powder and attapulgite powder; The sepiolite powder and attapulgite powder pretreated with sulfuric acid solution are stirred and dispersed in deionized water to obtain dispersion A, and the silane coupling agent KH550 is dispersed in ethanol to obtain dispersion B. The dispersion A and the dispersion B are mixed and refluxed and stirred for 2 hours at a temperature of 60°C; filtered and washed, and dried for 12 hours under vacuum and a temperature of 80°C; the mass ratio of the treated sepiolite powder and attapulgite powder, deionized water, silane coupling agent KH550 and ethanol is 4:60:1:100;

[0045] The preparation process of the high-strength potassium sulfate type compound fertilizer granules in this embodiment comprises the following steps: weighing raw materials as required and mixing them evenly, adding them into a granulator, drying them at a temperature of 60° C., adjusting the moisture content to 3wt%, and granulating them to obtain the granules.

[0046] Comparative Example 1

[0047] This comparative example provides a high-strength potassium sulfate type compound fertilizer granules, which are prepared from the following raw materials in parts by weight: 17 parts of potassium chloride, 9 parts of superphosphate, 22 parts of urea, 0.3 parts of copper sulfate, 0.5 parts of sodium carbonate, 0.15 parts of zinc oxide, 0.5 parts of a binder, and 0.8 parts of a fertilizer synergist;

[0048] The binder comprises a 7% sulfuric acid aqueous solution and a 13% carboxymethyl cellulose aqueous solution in a volume ratio of 1:3.5;

[0049] The fertilizer synergist is obtained by mixing sepiolite powder and attapulgite powder and then modifying them with a silane coupling agent. The specific preparation method includes: grinding and blending sepiolite powder and attapulgite powder in a weight ratio of 5.5:1.5, immersing them in a sulfuric acid solution with a mass concentration of 11%, and stirring them at a temperature of 45°C for 50 minutes; filtering and washing them with deionized water to neutrality, drying them at a temperature of 60°C, and crushing them to be able to pass through a 200-mesh sieve to obtain pretreated sepiolite powder and attapulgite powder; The sepiolite powder and attapulgite powder pretreated with sulfuric acid solution are stirred and dispersed in deionized water to obtain dispersion A, and the silane coupling agent KH550 is dispersed in ethanol to obtain dispersion B. The dispersion A and the dispersion B are mixed and refluxed and stirred for 2.5 hours at a temperature of 65°C; filtered and washed, and dried for 13 hours under vacuum at a temperature of 85°C; the mass ratio of the treated sepiolite powder and attapulgite powder, deionized water, silane coupling agent KH550 and ethanol is 5:70:1.5:110;

[0050] The preparation process of the high-strength potassium sulfate type compound fertilizer granules in this comparative example comprises the following steps: weighing raw materials as required and mixing them evenly, adding them into a granulator, drying them at a temperature of 70° C., adjusting the moisture content to 3.5wt%, and granulating them to obtain the granules.

[0051] Comparative Example 2

[0052] This comparative example provides a high-strength potassium sulfate type compound fertilizer granules, which are prepared from the following raw materials in parts by weight: 17 parts of potassium chloride, 9 parts of superphosphate, 22 parts of urea, 0.3 parts of copper sulfate, 0.5 parts of sodium carbonate, 0.15 parts of zinc oxide, 0.5 parts of a binder, and 0.8 parts of a fertilizer synergist;

[0053] Wherein, the binder is a cyclodextrin-modified carboxymethyl cellulose hydrogel aqueous solution with a mass concentration of 13%;

[0054] The preparation method of cyclodextrin-modified carboxymethyl cellulose hydrogel comprises: adding β-cyclodextrin, carboxymethyl cellulose, 1,4-butanediol diglycidyl ether and liquid paraffin in sequence to a NaOH aqueous solution with a concentration of 1.1 mol / L under stirring conditions, and stirring for reaction for 21 hours; after the reaction is completed, washing the product with a mixed solution of deionized water and acetone in a volume ratio of 1:1 for 3 times, and then washing it with deionized water for 6 times, and drying the product at 35°C to obtain spherical dry gel particles; the dosage ratio of the NaOH aqueous solution, β-cyclodextrin, carboxymethyl cellulose, 1,4-butanediol diglycidyl ether and liquid paraffin is 22mL:5.25g:0.9g:2.8g:130mL;

[0055] The fertilizer synergist is obtained by mixing sepiolite powder and attapulgite powder and then modifying them with a silane coupling agent. The specific preparation method includes: grinding and blending sepiolite powder and attapulgite powder in a weight ratio of 5.5:1.5, immersing them in a sulfuric acid solution with a mass concentration of 11%, and stirring them at a temperature of 45°C for 50 minutes; filtering and washing them with deionized water to neutrality, drying them at a temperature of 60°C, and crushing them to be able to pass through a 200-mesh sieve to obtain pretreated sepiolite powder and attapulgite powder; The sepiolite powder and attapulgite powder pretreated with sulfuric acid solution are stirred and dispersed in deionized water to obtain dispersion A, and the silane coupling agent KH550 is dispersed in ethanol to obtain dispersion B. The dispersion A and the dispersion B are mixed and refluxed and stirred for 2.5 hours at a temperature of 65°C; filtered and washed, and dried for 13 hours under vacuum at a temperature of 85°C; the mass ratio of the treated sepiolite powder and attapulgite powder, deionized water, silane coupling agent KH550 and ethanol is 5:70:1.5:110;

[0056] The preparation process of the high-strength potassium sulfate type compound fertilizer granules in this comparative example comprises the following steps: weighing raw materials as required and mixing them evenly, adding them into a granulator, drying them at a temperature of 70° C., adjusting the moisture content to 3.5wt%, and granulating them to obtain the granules.

[0057] Comparative Example 3

[0058] This comparative example provides a high-strength potassium sulfate type compound fertilizer granules, which are prepared from the following raw materials in parts by weight: 17 parts of potassium chloride, 9 parts of superphosphate, 22 parts of urea, 0.3 parts of copper sulfate, 0.5 parts of sodium carbonate, 0.15 parts of zinc oxide, 0.5 parts of a binder, and 0.8 parts of a fertilizer synergist;

[0059] Wherein, the binder is a sulfuric acid aqueous solution with a mass concentration of 7%;

[0060] The fertilizer synergist is obtained by mixing sepiolite powder and attapulgite powder and then modifying them with a silane coupling agent. The specific preparation method includes: grinding and blending sepiolite powder and attapulgite powder in a weight ratio of 5.5:1.5, immersing them in a sulfuric acid solution with a mass concentration of 11%, and stirring them at a temperature of 45°C for 50 minutes; filtering and washing them with deionized water to neutrality, drying them at a temperature of 60°C, and crushing them to be able to pass through a 200-mesh sieve to obtain pretreated sepiolite powder and attapulgite powder; The sepiolite powder and attapulgite powder pretreated with sulfuric acid solution are stirred and dispersed in deionized water to obtain dispersion A, and the silane coupling agent KH550 is dispersed in ethanol to obtain dispersion B. The dispersion A and the dispersion B are mixed and refluxed and stirred for 2.5 hours at a temperature of 65°C; filtered and washed, and dried for 13 hours under vacuum at a temperature of 85°C; the mass ratio of the treated sepiolite powder and attapulgite powder, deionized water, silane coupling agent KH550 and ethanol is 5:70:1.5:110;

[0061] The preparation process of the high-strength potassium sulfate type compound fertilizer granules in this comparative example comprises the following steps: weighing raw materials as required and mixing them evenly, adding them into a granulator, drying them at a temperature of 70° C., adjusting the moisture content to 3.5wt%, and granulating them to obtain the granules.

[0062] Comparative Example 4

[0063] This comparative example provides a high-strength potassium sulfate type compound fertilizer granules, which are prepared from the following raw materials in parts by weight: 17 parts of potassium chloride, 9 parts of superphosphate, 22 parts of urea, 0.3 parts of copper sulfate, 0.5 parts of sodium carbonate, 0.15 parts of zinc oxide, 0.5 parts of a binder, and 0.8 parts of a fertilizer synergist;

[0064] The binder comprises a sulfuric acid aqueous solution with a mass concentration of 7% and a cyclodextrin-modified carboxymethyl cellulose hydrogel aqueous solution with a mass concentration of 13% in a volume ratio of 1:3.5;

[0065] The preparation method of cyclodextrin-modified carboxymethyl cellulose hydrogel comprises: adding β-cyclodextrin, carboxymethyl cellulose, 1,4-butanediol diglycidyl ether and liquid paraffin in sequence to a NaOH aqueous solution with a concentration of 1.1 mol / L under stirring conditions, and stirring for reaction for 21 hours; after the reaction is completed, washing the product with a mixed solution of deionized water and acetone in a volume ratio of 1:1 for 3 times, and then washing it with deionized water for 6 times, and drying the product at 35°C to obtain spherical dry gel particles; the dosage ratio of the NaOH aqueous solution, β-cyclodextrin, carboxymethyl cellulose, 1,4-butanediol diglycidyl ether and liquid paraffin is 22mL:5.25g:0.9g:2.8g:130mL;

[0066] The fertilizer synergist is obtained by mixing sepiolite powder and attapulgite powder and then modifying them with a silane coupling agent. The specific preparation method includes: grinding and blending sepiolite powder and attapulgite powder in a weight ratio of 5.5:1.5, stirring and dispersing them in deionized water to obtain a dispersion A, dispersing the silane coupling agent KH550 in ethanol to obtain a dispersion B, mixing the dispersion A and the dispersion B under reflux stirring at a temperature of 65°C for 2.5 hours; filtering and washing, and drying under vacuum at a temperature of 85°C for 13 hours to obtain the fertilizer synergist; the mass ratio of the treated sepiolite powder and attapulgite powder, deionized water, silane coupling agent KH550 and ethanol is 5:70:1.5:110;

[0067] The preparation process of the high-strength potassium sulfate type compound fertilizer granules in this comparative example comprises the following steps: weighing raw materials as required and mixing them evenly, adding them into a granulator, drying them at a temperature of 70° C., adjusting the moisture content to 3.5wt%, and granulating them to obtain the granules.

[0068] Comparative Example 5

[0069] This comparative example provides a high-strength potassium sulfate type compound fertilizer granules, which are prepared from the following raw materials in parts by weight: 17 parts of potassium chloride, 9 parts of superphosphate, 22 parts of urea, 0.3 parts of copper sulfate, 0.5 parts of sodium carbonate, 0.15 parts of zinc oxide, 0.5 parts of a binder, and 0.8 parts of a fertilizer synergist;

[0070] The binder comprises a sulfuric acid aqueous solution with a mass concentration of 7% and a cyclodextrin-modified carboxymethyl cellulose hydrogel aqueous solution with a mass concentration of 13% in a volume ratio of 1:3.5;

[0071] The preparation method of cyclodextrin-modified carboxymethyl cellulose hydrogel comprises: adding β-cyclodextrin, carboxymethyl cellulose, 1,4-butanediol diglycidyl ether and liquid paraffin in sequence to a NaOH aqueous solution with a concentration of 1.1 mol / L under stirring conditions, and stirring for reaction for 21 hours; after the reaction is completed, washing the product with a mixed solution of deionized water and acetone in a volume ratio of 1:1 for 3 times, and then washing it with deionized water for 6 times, and drying the product at 35°C to obtain spherical dry gel particles; the dosage ratio of the NaOH aqueous solution, β-cyclodextrin, carboxymethyl cellulose, 1,4-butanediol diglycidyl ether and liquid paraffin is 22mL:5.25g:0.9g:2.8g:130mL;

[0072] The fertilizer synergist is obtained by mixing attapulgite powder and modifying it with a silane coupling agent. The specific preparation method includes: grinding and blending the attapulgite powder, immersing it in a sulfuric acid solution with a mass concentration of 11%, and stirring it at a temperature of 45°C for 50 minutes; filtering and washing it with deionized water until it is neutral, drying it at a temperature of 60°C, and crushing it to be able to pass through a 200-mesh sieve to obtain pretreated attapulgite powder; stirring and dispersing the attapulgite powder pretreated with sulfuric acid solution in deionized water to obtain dispersion A, dispersing the silane coupling agent KH550 in ethanol to obtain dispersion B, mixing the dispersion A and the dispersion B at a temperature of 65°C and reflux stirring for 2.5 hours; filtering and washing, and drying it under vacuum at a temperature of 85°C for 13 hours to obtain the obtained product; the mass ratio of the treated attapulgite powder, deionized water, silane coupling agent KH550 and ethanol is 5:70:1.5:110;

[0073] The preparation process of the high-strength potassium sulfate type compound fertilizer granules in this comparative example comprises the following steps: weighing raw materials as required and mixing them evenly, adding them into a granulator, drying them at a temperature of 70° C., adjusting the moisture content to 3.5wt%, and granulating them to obtain the granules.

[0074] Comparative Example 6

[0075] This comparative example provides a high-strength potassium sulfate type compound fertilizer granules, which are prepared from the following raw materials in parts by weight: 17 parts of potassium chloride, 9 parts of superphosphate, 22 parts of urea, 0.3 parts of copper sulfate, 0.5 parts of sodium carbonate, 0.15 parts of zinc oxide, 0.5 parts of a binder, and 0.8 parts of a fertilizer synergist;

[0076] The binder comprises a sulfuric acid aqueous solution with a mass concentration of 7% and a cyclodextrin-modified carboxymethyl cellulose hydrogel aqueous solution with a mass concentration of 13% in a volume ratio of 1:3.5;

[0077] The preparation method of cyclodextrin-modified carboxymethyl cellulose hydrogel comprises: adding β-cyclodextrin, carboxymethyl cellulose, 1,4-butanediol diglycidyl ether and liquid paraffin in sequence to a NaOH aqueous solution with a concentration of 1.1 mol / L under stirring conditions, and stirring for reaction for 21 hours; after the reaction is completed, washing the product with a mixed solution of deionized water and acetone in a volume ratio of 1:1 for 3 times, and then washing it with deionized water for 6 times, and drying the product at 35°C to obtain spherical dry gel particles; the dosage ratio of the NaOH aqueous solution, β-cyclodextrin, carboxymethyl cellulose, 1,4-butanediol diglycidyl ether and liquid paraffin is 22mL:5.25g:0.9g:2.8g:130mL;

[0078] The fertilizer synergist is obtained by mixing sepiolite powder and modifying it with a silane coupling agent. The specific preparation method includes: grinding and blending the sepiolite powder, immersing it in a sulfuric acid solution with a mass concentration of 11%, and stirring it at a temperature of 45°C for 50 minutes; filtering and washing it with deionized water until it is neutral, drying it at a temperature of 60°C, and crushing it to be able to pass through a 200-mesh sieve to obtain pretreated sepiolite powder; stirring and dispersing the sepiolite powder pretreated with the sulfuric acid solution in deionized water to obtain a dispersion A, dispersing the silane coupling agent KH550 in ethanol to obtain a dispersion B, mixing the dispersion A and the dispersion B at a temperature of 65°C and reflux stirring for 2.5 hours; filtering and washing, and drying it under vacuum at a temperature of 85°C for 13 hours to obtain the obtained product; the mass ratio of the treated sepiolite powder, deionized water, silane coupling agent KH550 and ethanol is 5:70:1.5:110;

[0079] The preparation process of the high-strength potassium sulfate type compound fertilizer granules in this comparative example comprises the following steps: weighing raw materials as required and mixing them evenly, adding them into a granulator, drying them at a temperature of 70° C., adjusting the moisture content to 3.5wt%, and granulating them to obtain the granules.

[0080] Test example:

[0081] The particle size of the high-strength potassium sulfate compound fertilizer particles prepared in the above-mentioned Examples 1-4 and Comparative Examples 1-6 is 1-3 mm. The fertilizer particles are subjected to a pressure test using a particle strength tester, and the crushing pressure is recorded. Each group of examples or comparative examples is tested 10 times and the average value is taken;

[0082] The fertilizer application rate is 50 kg / mu. Compared with the conventional fertilizer 15-15-15 NPK, the wheat yield per mu using conventional fertilizer is 530 kg / 667 m 2 , where the yield increase rate refers to the degree of yield increase compared to conventional fertilizers. The above test results are shown in Table 1 below.

[0083] Table 1

[0084] Average strength (N) <![CDATA[Yield per mu (Kg / 667m 2 )]]> Yield increase rate (%) Example 1 53.2 608.4 14.79 Example 2 51.8 604.2 14.00 Example 3 52.3 605.8 14.30 Example 4 51.2 600.1 13.22 Comparative Example 1 45.2 591.2 11.55 Comparative Example 2 40.6 587.2 10.79 Comparative Example 3 36.4 570.8 7.69 Comparative Example 4 47.3 595.6 12.38 Comparative Example 5 43.5 589.8 11.28 Comparative Example 6 42.4 588.4 11.02

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention. Those skilled in the art should understand that the present invention can still be modified or replaced by equivalents. All technical solutions and improvements that do not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A high-strength potassium sulfate compound fertilizer granule, characterized in that: The invention is prepared from the following raw materials in parts by weight: 15-20 parts of potassium chloride, 8-10 parts of superphosphate, 20-24 parts of urea, 0.2-0.4 parts of copper sulfate, 0.4-0.6 parts of sodium carbonate, 0.1-0.2 parts of zinc oxide, 0.4-0.6 parts of binder and 0.6-1 parts of fertilizer synergist.

2. A high-strength potassium sulfate type compound fertilizer granule according to claim 1, characterized in that: The binder comprises a sulfuric acid aqueous solution with a mass concentration of 6-8% and a cyclodextrin-modified carboxymethyl cellulose hydrogel aqueous solution with a mass concentration of 12-14% in a volume ratio of 1:(3-4).

3. A high-strength potassium sulfate type compound fertilizer granule according to claim 1, characterized in that: The preparation method of the cyclodextrin-modified carboxymethyl cellulose hydrogel comprises: adding β-cyclodextrin, carboxymethyl cellulose, 1,4-butanediol diglycidyl ether and liquid paraffin in sequence to a NaOH aqueous solution under stirring conditions, and stirring for reaction for 20-22 hours; after the reaction is completed, washing the product, and drying the product at 30-40° C. to obtain spherical dry gel particles.

4. A high-strength potassium sulfate type compound fertilizer granule according to claim 3, characterized in that: The concentration of the NaOH aqueous solution is 1-1.2 mol / L; the dosage ratio of the NaOH aqueous solution, β-cyclodextrin, carboxymethyl cellulose, 1,4-butanediol diglycidyl ether, and liquid paraffin is (20-24) mL: (5-5.5) g: (0.8-1) g: (2.6-3) g: (120-140) mL.

5. The high-strength potassium sulfate compound fertilizer granules according to claim 3, characterized in that: The washing method comprises washing three times with a mixture of deionized water and acetone in a volume ratio of 1:1, and then washing 5-7 times with deionized water.

6. The high-strength potassium sulfate compound fertilizer granules according to claim 1, characterized in that: The fertilizer synergist is obtained by mixing sepiolite powder and attapulgite powder and modifying them with a silane coupling agent.

7. The high-strength potassium sulfate compound fertilizer granules according to claim 6, characterized in that: The preparation method of the fertilizer synergist comprises: stirring and dispersing sepiolite powder and attapulgite powder pretreated with a sulfuric acid solution in deionized water to obtain a dispersion A, dispersing a silane coupling agent KH550 in ethanol to obtain a dispersion B, mixing the dispersion A and the dispersion B under reflux stirring at a temperature of 60-70° C. for 2-3 hours; filtering and washing, and drying under vacuum at a temperature of 80-90° C. for 12-14 hours to obtain the fertilizer synergist.

8. The high-strength potassium sulfate compound fertilizer granules according to claim 7, characterized in that: The preparation steps of the pretreated sepiolite powder and attapulgite powder include: grinding and blending the sepiolite powder and attapulgite powder in a weight ratio of (5-6):(1-2), immersing in a sulfuric acid solution with a mass concentration of 10-12%, and stirring for 40-60 minutes at a temperature of 40-50°C; filtering, washing with deionized water to neutrality, drying at a temperature of 55-65°C, and crushing to be able to pass through a 200-mesh sieve to obtain the pretreated sepiolite powder and attapulgite powder.

9. The high-strength potassium sulfate compound fertilizer granules according to claim 7, characterized in that: The mass ratio of the treated sepiolite powder and attapulgite powder, deionized water, silane coupling agent KH550 and ethanol is (4-6): (60-80): (1-2): (100-120).

10. A process for preparing high-strength potassium sulfate compound fertilizer particles according to any one of claims 1 to 9, characterized in that the steps include: Weigh the raw materials as required and mix them evenly, add them into a granulator, dry them at a temperature of 60-80° C., adjust the moisture content to 3-4wt%, and granulate them to obtain the product.