Fertilizer granulation auxiliary agent and preparation method and application thereof

Abstract

The invention belongs to the technical field of composite binders, and particularly relates to a fertilizer granulation auxiliary agent and a preparation method and application thereof, and the fertilizer granulation auxiliary agent is prepared from the following raw materials in parts by weight: 2-6 parts of cellulose, 1-2 parts of a gelatin-PAA compound, 1-2 parts of potassium tartrate, 1-2 parts of calcium carbonate, 2 parts of lactose and 6-10 parts of ammonium sulfate. When the granular calcium magnesium phosphate fertilizer is prepared, the cellulose and the gelatin-PAA compound are used as main materials to form a reversible colloid network so as to enhance the cohesion and toughness of particles; meanwhile, a potassium tartrate and calcium carbonate composite pore-forming agent is supplemented to construct a pore structure, so that the dissolvability and compressive strength are improved; lactose promotes the formation of microchannels and improves the disintegration performance of particles; the ammonium sulfate enhances the particle stability and improves the dissolvability through ionic crosslinking. The granular calcium magnesium phosphate fertilizer prepared by the fertilizer granulation aid provided by the invention is high in granulation rate, excellent in mechanical strength, good in dissolution performance and excellent in comprehensive performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of composite binders, and particularly relates to a fertilizer granulation aid and a preparation method and application thereof. BACKGROUND

[0002] Calcium magnesium phosphate fertilizer, as a kind of alkaline phosphate fertilizer, is rich in phosphorus, calcium, magnesium, silicon and other nutrients indispensable for crop growth and development, and can not only effectively supplement soil phosphorus and trace elements, but also adjust the pH value of acidic soil and improve the physical and chemical properties of soil, thus creating an excellent growth environment for crops, and playing a key role in improving crop yield and quality. However, after the traditional calcium magnesium phosphate fertilizer is treated by high-temperature melting, water quenching and crushing processes in the production process, it usually presents a powdery or glassy form, which has many limitations in actual agricultural application.

[0003] From the perspective of fertilization operation, powdery calcium magnesium phosphate fertilizer is prone to produce a large amount of dust during storage, transportation and field spreading, which not only causes waste of fertilizer, but also pollutes the environment and affects the health of the fertilizer applicator. In addition, powdery fertilizer has poor fluidity in mechanized fertilization equipment, making it difficult to achieve precise and quantitative fertilization, and unable to meet the efficient and precise fertilization needs of modern agriculture. However, the granulation of calcium magnesium phosphate fertilizer can effectively solve the above problems, improve the convenience and accuracy of fertilization operation, and significantly improve the application efficiency of fertilizer.

[0004] However, the granulation of calcium magnesium phosphate fertilizer still faces a series of severe challenges. The glassy structure of calcium magnesium phosphate fertilizer makes it lack of internal adhesion, and it is difficult to rely on its own mutual adhesion to form particles, which seriously affects the granulation rate. At the same time, the excessively low particle strength is easily crushed in actual operation process, and cannot adapt to mechanized operation. If the adhesion of the granulation system is enhanced by using a binder, although the granulation rate and particle strength can be improved, the cementation of calcium magnesium phosphate fertilizer rich in silicon, calcium and magnesium elements will occur, affecting the final disintegration of the fertilizer and seriously reducing the nutrient release rate of the granular calcium magnesium phosphate fertilizer product in the soil. Therefore, the development of a binder capable of preparing high-granulation-rate, high-strength and fast-dissolving calcium magnesium phosphate fertilizer has far-reaching practical significance for breaking the current application bottleneck of calcium magnesium phosphate fertilizer, promoting the upgrading and development of the industry, improving the utilization efficiency of agricultural resources and ensuring the sustainable development of agriculture. SUMMARY

[0005] The application provides a fertilizer granulation aid by scientifically selecting the complex ratio of binders, pore-forming agents, dispersing agents and functional enhancers, and combining the synergistic effect of multiple components. When the fertilizer granulation aid is used to prepare calcium magnesium phosphate fertilizer, the granulation rate, mechanical strength and dissolving performance of the calcium magnesium phosphate fertilizer particles are significantly optimized.

[0006] The technical scheme adopted by the application is as follows: The present application provides a fertilizer granulation aid, which is made of the following raw materials by weight: 2-6 parts of cellulose, 1-2 parts of gelatin-PAA compound, 1-2 parts of potassium tartrate, 1-2 parts of calcium carbonate, 2 parts of lactose, 6-10 parts of ammonium sulfate; the cellulose is sodium carboxymethyl cellulose or methyl cellulose; the gelatin-PAA compound is obtained by dissolving gelatin and polyacrylic acid in water and drying.

[0007] Preferably, the fertilizer granulation aid is made of the following raw materials by weight: 4 parts of sodium carboxymethyl cellulose, 1.5 parts of gelatin-PAA compound, 1.5 parts of potassium tartrate, 1.5 parts of calcium carbonate, 2 parts of lactose, and 8 parts of ammonium sulfate.

[0008] The present application provides a preparation method of the fertilizer granulation aid, which comprises the following steps: Respectively weigh the cellulose, gelatin-PAA compound, potassium tartrate, calcium carbonate, lactose, and ammonium sulfate; Mix the cellulose, gelatin-PAA compound, potassium tartrate, calcium carbonate, lactose, and ammonium sulfate after sieving, to obtain the fertilizer granulation aid.

[0009] Preferably, the mesh size of the sieve is 80 mesh.

[0010] The present application provides an application of the fertilizer granulation aid, which is used for preparing granular calcium magnesium phosphate fertilizer.

[0011] The preparation method of the granular calcium magnesium phosphate fertilizer is as follows: Granulation forming: a part of calcium magnesium phosphate fertilizer powder and a part of fertilizer granulation aid are put into a granulation disc to obtain a mixed raw material; water is sprayed to make the mixed raw material form capillary water to promote granulation, and further combine with centrifugal force to form a micro-nucleus; then the remaining calcium magnesium phosphate fertilizer powder and fertilizer granulation aid are added in batches and water is sprayed until there is no dry powder, and the granulation is continued to obtain granules; Sintering and solidification: the granules are dried and cooled to room temperature to obtain the granular calcium magnesium phosphate fertilizer.

[0012] The present application mixes the fertilizer granulation aid and calcium magnesium phosphate fertilizer powder uniformly, and then performs granulation; the cellulose and gelatin-PAA copolymer form a colloidal network to enhance the cohesion and toughness of the calcium magnesium phosphate fertilizer granules to ensure the stability of the granules; the potassium tartrate and calcium carbonate powder react to form multiple-scale pores, and cooperate with lactose to construct water-soluble channels to improve the dispersibility and compressive strength of the calcium magnesium phosphate fertilizer granules; the ammonium sulfate is further strengthened by cross-linking and uniform distribution to further strengthen the granule strength, improve the structure uniformity, and promote nutrient release, so that the granular calcium magnesium phosphate fertilizer with high granulation rate, high granule strength, and high dispersibility is finally prepared.

[0013] Preferably, the ratio of the total weight of the calcium magnesium phosphate fertilizer powder to the total weight of the fertilizer granulation aid is 200:13~24.

[0014] Preferably, the duration of the continuous granulation is 5min.

[0015] Preferably, after the continuous granulation, screening is also required, and the particle size obtained during the screening is 2mm~4.75mm.

[0016] Preferably, the sintering and solidification conditions are 80℃ drying for 3h.

[0017] Compared with the prior art, the beneficial effects of the present application are: The present application provides a kind of fertilizer granulation aid, the fertilizer granulation aid is made of the following weight parts of raw materials: cellulose 2 parts~6 parts, gelatin-PAA complex 1 part~2 parts, potassium tartrate 1 part~2 parts, calcium carbonate 1 part~2 parts, lactose 2 parts, ammonium sulfate 6 parts~10 parts;The cellulose is sodium carboxymethyl cellulose or methyl cellulose;The gelatin-PAA complex is obtained by dissolving gelatin and polyacrylic acid in water, and then drying.Using the fertilizer granulation aid of the present application, a kind of granular calcium magnesium phosphate fertilizer with high granulation rate, excellent mechanical strength, good dispersion performance and excellent comprehensive performance is prepared;Among them, cellulose and gelatin-polyacrylic acid sodium form a reversible colloidal network to enhance the cohesion and toughness of the particles, potassium tartrate and calcium carbonate react to form a porous structure to improve the dispersibility and strength, lactose promotes the formation of microchannels, and ammonium sulfate enhances the stability and improves the dispersibility through ion crosslinking.

[0018] The fertilizer granulation aid of the present application uses cellulose and gelatin-PAA complex as the core binder, and the crosslinking of the two forms a highly stable three-dimensional structure, significantly improving the granulation rate and mechanical strength of the granular calcium magnesium phosphate fertilizer, and ensuring that the particles remain stable during granulation and drying, and are not easy to crack or break.On this basis, other aids play a synergistic role: potassium tartrate and calcium carbonate as a composite pore agent, construct multiple-scale pores by releasing carbon dioxide, significantly increase the specific surface area and accelerate the dispersion of particles;Lactose as a dispersing agent further promotes the formation of internal channels, shortens the particle disintegration time;And ammonium sulfate as a functional enhancer strengthens the particle structure through ion crosslinking, further enhances the mechanical stability. Thus, the various aids act together on the cellulose / gelatin-PAA system, and the forming quality and nutrient release performance of the granular calcium magnesium phosphate fertilizer are comprehensively improved.

[0019] In summary, the lactose, composite pore agent, binder and functional enhancer in the fertilizer granulation aid of the present application work synergistically, complement each other, and maximize the performance improvement of the granular calcium magnesium phosphate fertilizer.

[0020] Compared with the traditional technology, the granular calcium magnesium phosphate fertilizer prepared by using the fertilizer granulation aid disclosed by the application not only reduces the production cost, but also ensures the nutrient content of the granular product. Through the above technical scheme, on the basis of improving the overall performance of the calcium magnesium phosphate fertilizer granules, the production process is also optimized, the market competitiveness of the product is improved, and the application value in the industry is high. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The surface of the granular calcium magnesium phosphate fertilizer prepared by using the fertilizer granulation aid described in Example 2.

[0022] Figure 2 The section of the granular calcium magnesium phosphate fertilizer prepared by using the fertilizer granulation aid described in Example 2. DETAILED DESCRIPTION

[0023] The application will be further described through specific examples below, but the scope of the application is not limited. The details and forms of the technical scheme of the application can be modified or replaced without departing from the spirit and scope of the application, and these modifications or replacements all fall within the protection scope of the application.

[0024] The inventive concept of the application is as follows: The application obtains a fertilizer granulation aid by scientifically selecting the complex ratio of binders, pore-forming agents, dispersing agents and functional enhancers, and combining the synergistic effect of multiple components. After the fertilizer granulation aid is used to prepare calcium magnesium phosphate fertilizer, the granulation rate, mechanical strength and dispersibility of the calcium magnesium phosphate fertilizer granules are significantly optimized.

[0025] The fertilizer granulation aid disclosed by the application selects cellulose and gelatin-sodium polyacrylate copolymer combination as the binder, and enhances the cohesion of the granules in the granulation process by forming a reversible colloidal network. The cellulose forms a strong network structure on the surface of the granules through cross-linking with the gelatin-sodium polyacrylate, ensuring the stability and strength of the granules during the granulation process, and at the same time enhancing the toughness of the granules to avoid breakage of the granules during subsequent drying and transportation.

[0026] Further, the application is assisted by multiple aids to enhance the effect of cellulose and gelatin-PAA complex: potassium tartrate and calcium carbonate as a complex pore-forming agent, forming multiple-scale pores inside the granules through mild acid-base reaction, improving water dispersibility and promoting uniform nutrient release, while enhancing the compressive strength of the granules; lactose powder as a water-soluble dispersing agent, promoting the formation of micro-channels during drying and storage, and improving the disintegration performance of the granules; ammonium sulfate as a functional enhancer, improving the physical strength and structural uniformity of the granules through cross-linking with calcium ions and ammonia ions in the calcium magnesium phosphate fertilizer and other components, and forming micro-dissolution channels to promote rapid nutrient release.

[0027] Through the principles and reactions, the fertilizer granulation aid provided by the application realizes high granulation rate, high granule strength and high solubility of the granular phosphate fertilizer.

[0028] In order to make the skilled in the art better understand the technical solutions of the application can be implemented, the following specific examples of the application is further described. In the description of the application, if not special, the reagents used are commercially available, the methods used are conventional techniques in the art.

[0029] The preparation method of the gelatin-PAA compound is as follows: gelatin and polyacrylic acid are dissolved in water at a mass ratio of 3:7, and then dried to obtain the gelatin-PAA compound. PAA is polyacrylic acid.

[0030] The gelatin and polyacrylic acid are both purchased from Shanghai Aldrin Biochemical Technology Co., Ltd., and the CAS number of polyacrylic acid is 9003-01-4.

[0031] In the following examples, 1 g represents one part by weight.

[0032] Example 1 A preparation method of a fertilizer granulation aid is as follows: 2 g of sodium carboxymethyl cellulose, 1.5 g of gelatin-PAA compound, 1.5 g of potassium tartrate, 1.5 g of calcium carbonate, 2 g of lactose and 8 g of ammonium sulfate are weighed respectively, and then the above raw materials are mixed uniformly after being sieved through an 80-mesh sieve to obtain the fertilizer granulation aid.

[0033] Example 2 A preparation method of a fertilizer granulation aid is as follows: 4 g of sodium carboxymethyl cellulose, 1.5 g of gelatin-PAA compound, 1.5 g of potassium tartrate, 1.5 g of calcium carbonate, 2 g of lactose and 8 g of ammonium sulfate are weighed respectively, and then the above raw materials are mixed uniformly after being sieved through an 80-mesh sieve to obtain the fertilizer granulation aid.

[0034] Example 3 A preparation method of a fertilizer granulation aid is as follows: The fertilizer granulation aid of the present example is to set the mass of sodium carboxymethyl cellulose in Example 2 to 6 g, and the rest of the method is exactly the same as that in Example 2.

[0035] Example 4 A preparation method of a fertilizer granulation aid is as follows: The fertilizer granulation aid of the present example is to set the mass of gelatin-PAA compound in Example 2 to 1 g, and the rest of the method is exactly the same as that in Example 2.

[0036] Example 5 A method for preparing a fertilizer granulation aid is as follows: The fertilizer granulation aid of this example is to set the mass of the gelatin-PAA complex described in Example 2 to 2 g, and the remaining method is exactly the same as Example 2.

[0037] Example 6 A method for preparing a fertilizer granulation aid is as follows: The fertilizer granulation aid of this example is to set the mass of the potassium tartrate described in Example 2 to 1 g, and the mass of the calcium carbonate to 1 g, and the remaining method is exactly the same as Example 2.

[0038] Example 7 A method for preparing a fertilizer granulation aid is as follows: The fertilizer granulation aid of this example is to set the mass of the potassium tartrate described in Example 2 to 2 g, and the mass of the calcium carbonate to 2 g, and the remaining method is exactly the same as Example 2.

[0039] Example 8 A method for preparing a fertilizer granulation aid is as follows: The fertilizer granulation aid of this example is to set the mass of the ammonium sulfate described in Example 2 to 6 g, and the remaining method is exactly the same as Example 2.

[0040] Example 9 A method for preparing a fertilizer granulation aid is as follows: The fertilizer granulation aid of this example is to set the mass of the ammonium sulfate described in Example 2 to 10 g, and the remaining method is exactly the same as Example 2.

[0041] Example 10 A method for preparing a fertilizer granulation aid is as follows: The fertilizer granulation aid of this example is to replace the 4 g of sodium carboxymethyl cellulose described in Example 2 with 4 g of methyl cellulose, and the remaining method is exactly the same as Example 2.

[0042] Comparative Example 1 A method for preparing a fertilizer granulation aid is as follows: The fertilizer granulation aid of this comparative example does not contain sodium carboxymethyl cellulose, and the remaining method is exactly the same as Example 2.

[0043] Comparative Example 2 A method for preparing a fertilizer granulation aid is as follows: The fertilizer granulation aid of this comparative example does not contain a gelatin-PAA complex, and the remaining method is exactly the same as Example 2.

[0044] Comparative Example 3 A method for preparing a fertilizer granulation aid is as follows: The fertilizer granulation aid of the present comparative example does not contain potassium tartrate and calcium carbonate, and the rest of the method is exactly the same as that of Example 2.

[0045] Comparative Example 4 A method for preparing a fertilizer granulation aid is as follows: The fertilizer granulation aid of the present comparative example does not contain lactose, and the rest of the method is exactly the same as that of Example 2.

[0046] Comparative Example 5 A method for preparing a fertilizer granulation aid is as follows: The fertilizer granulation aid of the present comparative example does not contain ammonium sulfate, and the rest of the method is exactly the same as that of Example 2.

[0047] Comparative Example 6 A method for preparing a fertilizer granulation aid is as follows: The fertilizer granulation aid of the present comparative example uses sodium lignosulfonate instead of sodium carboxymethyl cellulose, and the rest of the method is exactly the same as that of Example 2.

[0048] Comparative Example 7 A method for preparing a fertilizer granulation aid is as follows: The fertilizer granulation aid of the present comparative example uses polyvinyl alcohol instead of gelatin-PAA compound, and the rest of the method is exactly the same as that of Example 2.

[0049] Comparative Example 8 A method for preparing a fertilizer granulation aid is as follows: The fertilizer granulation aid of the present comparative example uses sodium tartrate instead of potassium tartrate, and calcium bicarbonate instead of calcium carbonate, and the rest of the method is exactly the same as that of Example 2.

[0050] Comparative Example 9 A method for preparing a fertilizer granulation aid is as follows: The fertilizer granulation aid of the present comparative example uses ammonium chloride instead of ammonium sulfate, and the rest of the method is exactly the same as that of Example 2.

[0051] Example 11 The application of a fertilizer granulation aid is as follows: The fertilizer granulation aids obtained by the preparation methods described in Examples 1-10 and Comparative Examples 1-9 are used to prepare granular calcium-magnesium phosphate fertilizer, respectively. The preparation method of the granular calcium-magnesium phosphate fertilizer is as follows:

[0052] S1, the fertilizer granulation aid is prepared according to the preparation method described in Examples 1-10 and Comparative Examples 1-9.

[0053] S2, granulation molding: a part of calcium magnesium phosphate fertilizer powder is put into a granulation tray, and a part of fertilizer granulation aid is continuously put into the granulation tray to obtain a compound raw material; water is sprayed to make the compound raw material form capillary water to promote granulation, and further form micro-nuclei by centrifugal force; then the remaining calcium magnesium phosphate fertilizer powder and fertilizer granulation aid are added in batches and water is sprayed until there is no dry powder, and the granulation is continuously performed to obtain granules.

[0054] After the calcium magnesium phosphate fertilizer powder is collected after passing through a 80-mesh screen, 200 g is weighed, and half of the calcium magnesium phosphate fertilizer powder is put into a granulation tray, and half of the fertilizer granulation aid is uniformly sprinkled on the calcium magnesium phosphate fertilizer powder, and a brush is used to continuously clean the raw material adhered to the wall of the granulation tray to make it gather together to obtain a compound raw material. Then, a small amount of water is sprayed into the granulation tray in multiple times to make the surface of the compound raw material wet, so as to provide a dissolution and reaction condition for the fertilizer granulation aid. When the calcium magnesium phosphate fertilizer powder adsorbs water under the action of the fertilizer granulation aid and the water content exceeds the maximum molecular combined water content, capillary water is formed. The capillary water can quickly migrate, and the particles around the water droplet are pulled to the center of the water droplet, and the high viscosity provided by the fertilizer granulation aid promotes the granulation process, and further agglomerates to form micro-nuclei under the action of centrifugal force. In this process, the remaining calcium magnesium phosphate fertilizer powder and fertilizer granulation aid are added in batches and water is sprayed into the granulation tray according to the growth of the micro-nuclei to continuously grow the micro-nuclei until there is no dry powder. The granulator is continuously rotated for 5 min to make the micro-nuclei grow to a smooth and round surface, and then the micro-nuclei are screened by using a square hole screen with a size of 2 mm and 4.75 mm.

[0055] S3, sintering and solidification: the granules are dried, and cooled to room temperature to obtain the granular calcium magnesium phosphate fertilizer.

[0056] The granules with a size of 2 mm to 4.75 mm are collected, placed in an oven at 80°C, and dried for 3 h, and then taken out and cooled at room temperature to obtain the granular calcium magnesium phosphate fertilizer.

[0057] Meanwhile, the present application also sets up a blank control for preparing a granular calcium magnesium phosphate fertilizer, and the method is as follows: No fertilizer granulation aid is added, and the rest of the process is consistent with the preparation method of the granular calcium magnesium phosphate fertilizer.

[0058] The performance of the granular calcium magnesium phosphate fertilizer obtained by using different fertilizer granulation aids is evaluated, and the evaluation indexes include granulation rate, granule strength and dispersion rate, and the details are as follows: (1) Granulation rate.

[0059] Calculation formula: .

[0060] In the formula, A : Granulation rate; m 1 : The weight of the granular calcium magnesium phosphate fertilizer, in grams.m 2 Total weight of the fertilizer granulation aid and the calcium magnesium phosphate powder before granulation, in g.

[0061] (2) Granule strength: 30 granular calcium magnesium phosphate fertilizers with uniform size were taken and a KQ-3 granule strength instrument was used for determination.

[0062] (3) Dissolution rate: a certain amount of granular calcium magnesium phosphate fertilizer was taken, and the mass was recorded as m 3 , in g; the sample was soaked in water at room temperature for 10 min, the mass of the sample that did not pass through a 1 mm test sieve was weighed, and the mass was recorded as m 4 , in g; the dissolution rate was recorded as B , and the calculation formula was as follows: .

[0063] The final test results of the granular calcium magnesium phosphate fertilizers prepared by using the fertilizer granulation aids obtained in Examples 1 to 10 and Comparative Examples 1 to 9 are shown in Table 1.

[0064] Table 1: Performance evaluation results of granular calcium magnesium phosphate fertilizers prepared by using different fertilizer granulation aids In Table 1, " / " indicates that there is no such item. It should be noted that since the calcium magnesium phosphate powder cannot be granulated without adding a binder, the product is a fine and fragmented powder, so there is no data for the blank control.

[0065] From Table 1, it can be seen that in Examples 1 to 3, with the increase of the content of sodium carboxymethyl cellulose, the granule strength of the granular calcium magnesium phosphate fertilizer showed a clear increasing trend, the granulation rate first increased and then slightly decreased, and the dissolution rate first increased and then decreased. This is because the sodium carboxymethyl cellulose and the gelatin-PAA complex form a reversible colloidal network, and through cross-linking, a strong network structure is formed on the surface of the granules. The increase of the content of sodium carboxymethyl cellulose and the gelatin-PAA complex can enhance the cohesion of the granular calcium magnesium phosphate fertilizer and the stability of the system, thereby improving the strength; but when excessive, the network structure may be too dense to limit the penetration of water, resulting in a slight decrease in the dissolution rate.

[0066] As can be seen from the comparison of Examples 2, 4 and 5, when the content of the gelatin-PAA complex increased from 1 g to 2 g, the granule strength of the granular calcium magnesium phosphate fertilizer first increased and then decreased, the granulation rate fluctuated slightly, and the dissolution rate was relatively stable. As a synergistic component of cellulose, the gelatin-PAA complex enhances the toughness of the granules through cross-linking with sodium carboxymethyl cellulose, avoiding breakage during drying and transportation; but if excessive, it may disrupt the balance of the colloidal network, resulting in a slight decrease in the granulation rate.

[0067] In Example 2, Example 6 and Example 7, when the content of potassium tartrate and calcium carbonate as composite pore-forming agent increases from 1 g to 2 g, the granulation rate of the granular calcium magnesium phosphate fertilizer first increases and then decreases, the particle strength increases, and the dissolution rate is significantly lower when the content of the pore-forming agent is low. Potassium tartrate and calcium carbonate release carbon dioxide through a mild acid-base reaction, forming multiple-scale pores inside the particles. When the content is low, the low porosity leads to a low dissolution rate. When the content is high, although the porosity increases, the excessive reaction may damage the structural integrity of the particles, leading to a decrease in the granulation rate, while the appropriate porosity can enhance the compressive strength through structural support.

[0068] Example 2, Example 8 and Example 9 show that when the content of functional enhancer-ammonium sulfate increases from 6 g to 10 g, the granulation rate of the granular calcium magnesium phosphate fertilizer first stabilizes and then decreases, the particle strength fluctuates slightly, and the dissolution rate is basically stable. Ammonium sulfate enhances the physical strength by cross-linking calcium ions and ammonia ions with other components, and its high water solubility forms small dissolution channels to improve the dissolution rate. However, when the content is excessive, the high ion concentration may interfere with the cross-linking balance, causing a salting-out effect to damage the binding network, leading to a decrease in the granulation rate.

[0069] Comparing Example 2 with Example 10, replacing sodium carboxymethyl cellulose with methyl cellulose, the granulation rate, particle strength and dissolution rate of the granular calcium magnesium phosphate fertilizer all decrease to some extent, indicating that the colloid network of sodium carboxymethyl cellulose and gelatin-PAA complex has better adaptability and can form a strong and tough structure more efficiently, making it the core choice for fertilizer granulation aids.

[0070] In summary, the granular calcium magnesium phosphate fertilizer prepared in Example 2 using 4 g of sodium carboxymethyl cellulose, 1.5 g of gelatin-PAA complex, 1.5 g of potassium tartrate, 1.5 g of calcium carbonate, 2 g of lactose and 8 g of ammonium sulfate has the highest granulation rate and dissolution rate, and the particle strength is also at a relatively high level. Under this complex ratio, the colloid network is stable, the pore structure is reasonable, and the functional enhancement is moderate, resulting in the best overall effect.

[0071] The blank control does not add fertilizer granulation aids, and the calcium magnesium phosphate fertilizer cannot be granulated, directly proving that the fertilizer granulation aids are necessary for granulation.

[0072] Example 2, Example 8 and Example 9 show that when the content of functional enhancer-ammonium sulfate increases from 6 g to 10 g, the granulation rate of the granular calcium magnesium phosphate fertilizer first stabilizes and then decreases, the particle strength fluctuates slightly, and the dissolution rate is basically stable. Ammonium sulfate enhances the physical strength by cross-linking calcium ions and ammonia ions with other components, and its high water solubility forms small dissolution channels to improve the dissolution rate. However, when the content is excessive, the high ion concentration may interfere with the cross-linking balance, causing a salting-out effect to damage the binding network, leading to a decrease in the granulation rate.

[0073] Example 2, Example 8 and Example 9 show that when the content of functional enhancer-ammonium sulfate increases from 6 g to 10 g, the granulation rate of the granular calcium magnesium phosphate fertilizer first stabilizes and then decreases, the particle strength fluctuates slightly, and the dissolution rate is basically stable. Ammonium sulfate enhances the physical strength by cross-linking calcium ions and ammonia ions with other components, and its high water solubility forms small dissolution channels to improve the dissolution rate. However, when the content is excessive, the high ion concentration may interfere with the cross-linking balance, causing a salting-out effect to damage the binding network, leading to a decrease in the granulation rate.

[0074] Example 2, Example 8 and Example 9 show that when the content of functional enhancer-ammonium sulfate increases from 6 g to 10 g, the granulation rate of the granular calcium magnesium phosphate fertilizer first stabilizes and then decreases, the particle strength fluctuates slightly, and the dissolution rate is basically stable. Ammonium sulfate enhances the physical strength by cross-linking calcium ions and ammonia ions with other components, and its high water solubility forms small dissolution channels to improve the dissolution rate. However, when the content is excessive, the high ion concentration may interfere with the cross-linking balance, causing a salting-out effect to damage the binding network, leading to a decrease in the granulation rate.

[0075] Comparative Example 4 lacks water-soluble dispersion enhancer-lactose, which cannot promote the formation of micro-channels inside the particles, resulting in decreased granulation rate and strength, and impaired dissolution performance.

[0076] Comparative Example 5 does not contain ammonium sulfate, lacking ion cross-linking and dissolution channels, with a dissolution rate of only 30.2%.

[0077] Comparative Example 6 uses sodium lignosulfonate instead of sodium carboxymethyl cellulose, which cannot form a stable colloidal network, resulting in insufficient particle strength and excessively high dissolution rate.

[0078] Comparative Example 7 uses polyvinyl alcohol instead of gelatin-PAA complex, losing the synergistic cross-linking effect with cellulose, and all performance parameters decrease.

[0079] Comparative Example 8 uses sodium tartrate instead of potassium tartrate, and calcium bicarbonate instead of calcium carbonate, resulting in an unreasonable pore structure and a sharp decrease in dissolution rate.

[0080] Comparative Example 9 uses ammonium chloride instead of ammonium sulfate, weakening the ion cross-linking effect and the ability to form dissolution channels, and both the granulation rate and strength decrease.

[0081] The above results further demonstrate that the present application uses cellulose-gelatin-PAA colloidal network as the main material, supplemented by potassium tartrate-calcium carbonate complex pore-forming agent, lactose dispersion agent, and ammonium sulfate functional enhancer, to optimize the performance of calcium-magnesium-phosphorus fertilizer particles through the synergistic effect of multiple components: the colloidal network provides cohesion and toughness; the complex pore-forming agent constructs pores to improve dissolution and compressive strength; lactose promotes the formation of micro-channels to improve disintegration performance; and ammonium sulfate strengthens cross-linking and forms micro-dissolution channels to improve dissolution performance and structural uniformity. Through the synergistic effect of the main material and auxiliary agents, the overall optimization of granulation rate, mechanical strength, and dissolution performance of the particles is achieved.

[0082] To further demonstrate the effectiveness of the present application, SEM characterization analysis was performed on the granular calcium-magnesium-phosphorus fertilizer prepared using the fertilizer granulation aid of Example 2, as shown in Figures 1 and 2. Figure 1 and Figure 2 As can be seen from the figures, the addition of the fertilizer granulation aid of Example 2 makes the surface and cross-section of the granular calcium-magnesium-phosphorus fertilizer more compact, thereby optimizing its physical properties and ultimately improving the particle strength and dissolution rate.

[0083] The technical features of the above-described examples can be combined in any manner. To make the description concise, not all possible combinations of the technical features in the above-described examples are described, but as long as the combinations of the technical features do not contradict each other, they should be considered within the scope of the present disclosure.

[0084] The above embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be noted that for ordinary skilled in the art, without departing from the concept of the present application, several modifications and improvements can be made, which are within the scope of protection of the present application.

Claims

1. A fertilizer granulation aid, characterized in that, The fertilizer granulation aid is made from the following raw materials in parts by weight: The ingredients are: 2-6 parts cellulose, 1-2 parts gelatin-PAA complex, 1-2 parts potassium tartrate, 1-2 parts calcium carbonate, 2 parts lactose, and 6-10 parts ammonium sulfate; wherein the cellulose is sodium carboxymethyl cellulose or methyl cellulose. The gelatin-PAA composite is obtained by dissolving gelatin and polyacrylic acid in water and then drying it.

2. The fertilizer granulation aid as described in claim 1, characterized in that, The fertilizer granulation aid is made from the following raw materials in parts by weight: 4 parts sodium carboxymethyl cellulose, 1.5 parts gelatin-PAA complex, 1.5 parts potassium tartrate, 1.5 parts calcium carbonate, 2 parts lactose, and 8 parts ammonium sulfate.

3. The method for preparing the fertilizer granulation aid as described in claim 1, characterized in that, Includes the following steps: Weigh out cellulose, gelatin-PAA complex, potassium tartrate, calcium carbonate, lactose, and ammonium sulfate separately; The fertilizer granulation aid is obtained by sieving and mixing cellulose, gelatin-PAA complex, potassium tartrate, calcium carbonate, lactose and ammonium sulfate separately.

4. The preparation method according to claim 3, characterized in that, The sieve used for sieving has an 80-mesh aperture.

5. The application of the fertilizer granulation aid as described in claim 1, characterized in that, The fertilizer granulation aid is used to prepare granular calcium magnesium phosphate fertilizer.

6. The application as described in claim 5, characterized in that, The preparation method of the granular calcium magnesium phosphate fertilizer is as follows: Granulation and molding: A portion of calcium magnesium phosphate fertilizer powder is added to the granulation pan, followed by a portion of fertilizer granulation aid to obtain a compound raw material; water is sprayed to form capillary water in the compound raw material to promote granulation, and further combined with centrifugal force to form micro-nuclei; then the remaining calcium magnesium phosphate fertilizer powder and fertilizer granulation aid are added in batches and water is sprayed until there is no dry powder, and granulation is continued to obtain granules. Sintering and solidification: The granules are dried and cooled to room temperature to obtain the granular calcium magnesium phosphate fertilizer.

7. The application as described in claim 6, characterized in that, The ratio of the total weight of the calcium magnesium phosphate fertilizer powder to the total weight of the fertilizer granulation aid is 200:13~24.

8. The application as described in claim 6, characterized in that, The continuous granulation time is 5 minutes.

9. The preparation method according to claim 6, characterized in that, After continuous granulation, sieving is required, and the particle size obtained during sieving is 2mm~4.75mm.

10. The preparation method according to claim 6, characterized in that, The conditions for sintering and solidification are as follows: Dry at 80℃ for 3 hours.

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