High-magnesium medium-trace particle water-soluble fertilizer and preparation method thereof

Abstract

The invention relates to the technical field of water-soluble fertilizers, in particular to a high-magnesium medium-trace particle water-soluble fertilizer and a preparation method thereof. The invention discloses a high-magnesium medium-trace particle water-soluble fertilizer, which is prepared by carrying out spray granulation on granulation slurry in a granulator through a nozzle, the specific gravity of the granulation slurry is greater than or equal to 1.68 g / cm < 3 >, and the mass content of magnesium in the granulation slurry is greater than or equal to 2.0%; in the high-magnesium medium-trace particle water-soluble fertilizer, the mass content of magnesium is greater than or equal to 1.0%. Through the steps of neutralization treatment and filtration impurity removal, free acid and impurities which influence the product quality are effectively removed; by accurately controlling concentration and cooling conditions, the content of free water in the product is reduced, and the physical property of the product is improved; through granulation, the final product has better appearance roundness and stability.

Description

Technical Field

[0001] The invention relates to the technical field of water-soluble fertilizers, in particular to a high-magnesium medium-trace granular water-soluble fertilizer and a preparation method thereof. Background Art

[0002] Granular water-soluble fertilizer is a new category in the water-soluble fertilizer industry. It is a multi-element compound fertilizer that can be completely soluble in water. Calcium nitrate magnesium fertilizer granular water-soluble fertilizer is a type of granular water-soluble fertilizer that can quickly replenish calcium and magnesium elements. Crops can absorb them directly, which can improve the absorption and utilization rate of calcium by crops. It has significant effects on various diseases caused by calcium and magnesium deficiency in crops.

[0003] In granular water-soluble fertilizers, due to the presence of a large number of free water molecules on the surface of a single magnesium nitrate or calcium nitrate crystal (or granule), the product is prone to caking and boarding during packaging and transportation, which is not conducive to long-distance transportation and long-term storage, directly affecting sales and causing inconvenience to farmers in application. In addition, the preparation of existing calcium nitrate and magnesium fertilizers on the market is a simple physical mixture, which leads to frequent instability in content detection.

[0004] At the same time, relevant studies have shown that the efficiency of calcium absorption and utilization by single calcium crops is very low. This is because the absorption of calcium requires the participation of multiple enzymes, and the enzyme cannot be activated and cannot promote the absorption of calcium. However, magnesium can activate the enzyme, so magnesium plays an important role in the absorption of calcium. The existing calcium nitrate magnesium fertilizer adopts simple physical mixing, which leads to the unobvious activation of magnesium on the enzyme. Therefore, if a fertilizer product with no free water on the surface and that can promote enzyme activation can be produced, the absorption of calcium by crops will be greatly improved and convenient for long-distance transportation.

[0005] To this end, the present application provides a high-magnesium trace granular water-soluble fertilizer and a preparation method thereof. Summary of the invention

[0006] The high-magnesium medium-trace granular water-soluble fertilizer and the preparation method thereof described in the present application effectively remove free acids and impurities that affect product quality through neutralization treatment and filtration and impurity removal steps; reduce the free water content in the product and improve the physical properties of the product through precise control of concentration and cooling conditions; and make the final product have better appearance roundness and stability through granulation.

[0007] The technical solution adopted by this application to solve its technical problem is:

[0008] In a first aspect, the present application provides a high-magnesium medium-trace granular water-soluble fertilizer, wherein the high-magnesium medium-trace granular water-soluble fertilizer is obtained by spraying granules in a granulator through a nozzle through a granulating slurry;

[0009] The specific gravity of the granulation slurry is ≥1.68g / cm 3, the mass content of magnesium in the granulation slurry is ≥2.0%;

[0010] The mass content of magnesium in the high-magnesium medium-trace granular water-soluble fertilizer is ≥1.0%.

[0011] In some specific embodiments, in the high-magnesium trace granular water-soluble fertilizer, the sum of the mass content of magnesium and the weight content of calcium is ≥12%.

[0012] In some specific embodiments, the particle strength of the high-magnesium trace granular water-soluble fertilizer is ≥35N.

[0013] In some specific embodiments, a fluidized bed is provided in the granulator, and the temperature of the fluidized return material on the fluidized bed is ≤50°C.

[0014] In some specific embodiments, the nozzle is a two-fluid nozzle, which is used to mix the granulation slurry with compressed air and then spray it out to form fine and uniform droplets.

[0015] In some specific embodiments, the spraying temperature of the nozzle is 90°C-125°C.

[0016] In some specific embodiments, the spraying pressure of the concentrated slurry is controlled at 0.02MPa-0.6MPa, and the pressure of the compressed air is controlled at 0.3MPa-1.0MPa.

[0017] In a second aspect, the present application provides a method for preparing the high-magnesium medium-trace granular water-soluble fertilizer described in the first aspect, comprising the following steps:

[0018] Neutralize the calcium and magnesium solution;

[0019] The neutralized calcium-magnesium solution is filtered and impurities are removed to obtain a calcium-magnesium filtrate;

[0020] The calcium and magnesium filtrates are proportioned to obtain a proportioning liquid;

[0021] The proportioning liquid is concentrated to obtain a granulation slurry;

[0022] The specific gravity of the granulation slurry is ≥1.68g / cm 3 , the mass content of magnesium in the granulation slurry is ≥2.0%;

[0023] The granulation slurry is sprayed and granulated by using a granulator containing a fluidized bed; unqualified particles are removed by screening, and qualified particles are dried to obtain a high-magnesium medium-trace granular water-soluble fertilizer.

[0024] In some specific embodiments, in the screening process, the aperture of the upper sieve is 5 mm, and the aperture of the lower sieve is 1 mm.

[0025] In some specific embodiments, the drying process is carried out at a drying temperature of 30-50°C.

[0026] The beneficial effects of this application are:

[0027] The preparation method described in the present application can be used to process calcium-magnesium leaching solution and calcium nitrate solution in large quantities to obtain high-magnesium medium-trace granular water-soluble fertilizer.

[0028] The high-magnesium medium-trace granular water-soluble fertilizer described in the present application has a magnesium content of 1%-8%, and the granules have a good roundness in appearance, which reduces the content of free water in the product and can meet the requirements of long-distance transportation and storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0030] Figure 1 This is a process flow chart of a high-magnesium trace granular water-soluble fertilizer described in this application.

[0031] Figure 2 This is a schematic diagram of the structure of the water-soluble fertilizer production system described in this application.

[0032] Figure 3 This is a schematic diagram of the structure of the granulation equipment in the water-soluble fertilizer production system described in this application.

[0033] Among them: 1. Proportioning tank; 2. Concentrator; 3. Granulation equipment; 4. Screener; 5. Feeding pump; 301. Granulator; 302. Fluidized bed; 303. Nozzle; 304. Honeycomb plate. DETAILED DESCRIPTION

[0034] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0035] In this application, the term "and / or" describes the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0036] In the present application, "at least one" means one or more, and "plurality" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple, respectively.

[0037] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0038] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0039] The weight of the relevant components mentioned in the embodiment description of the present application can not only refer to the specific content of each component, but also represent the proportional relationship between the weights of the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the embodiment description of the present application, it is within the scope disclosed in the embodiment description of the present application. Specifically, the mass described in the embodiment description of the present application can be a mass unit known in the chemical industry such as μg, mg, g, kg, etc.

[0040] The terms "first" and "second" are used only for descriptive purposes to distinguish objects such as substances from each other, and should not be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. For example, without departing from the scope of the embodiments of the present application, the first XX may also be referred to as the second XX, and similarly, the second XX may also be referred to as the first XX. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0041] Terminology explanation:

[0042] Granulation slurry refers to the liquid material used for spray granulation after a series of treatments (such as neutralization, filtration, proportioning, concentration, etc.). It contains the required nutrients and additives and has a specific specific gravity and magnesium mass content.

[0043] Fluidized Bed: A reactor or processing device in which solid particles are suspended in a gas or liquid fluid. In this state, the solid particles behave like a fluid and can be used for a variety of processes such as heating, cooling, drying or chemical reactions.

[0044] Two-fluid nozzle: A spray device that can spray two different media (usually liquid and gas) at the same time. In this case, the two-fluid nozzle is used to mix the concentrated cooled slurry with compressed air and spray it to form fine and uniform droplets.

[0045] Folding lifting plate: A special shaped plate installed inside the rotating drum. Its function is to continuously lift and throw the material during the material flow process to promote the fusion between new and old particles and ensure that the material is evenly distributed on the fluidized bed.

[0046] Fluidized bed plate: usually refers to a plate-like structure with many small holes, which is used to disperse the airflow so that the gas can be evenly blown into the fluidized bed to maintain a good suspension state of the material.

[0047] The present application provides a high-magnesium medium-trace granular water-soluble fertilizer, which is obtained by spraying granules in a granulator through a nozzle through a granulating slurry;

[0048] The specific gravity of the granulation slurry is ≥1.68g / cm 3 , the mass content of magnesium in the granulation slurry is ≥2.0%;

[0049] The mass content of magnesium in the high-magnesium medium-trace granular water-soluble fertilizer is ≥1.0%.

[0050] In some embodiments, in the high-magnesium trace granular water-soluble fertilizer, the sum of the mass content of magnesium and the weight content of calcium is ≥12%.

[0051] The particle strength of the high-magnesium trace granular water-soluble fertilizer is ≥35N.

[0052] In some embodiments, a fluidized bed is disposed in the granulator, and the temperature of the fluidized return material on the fluidized bed is ≤50°C.

[0053] In some embodiments, the nozzle is a dual-fluid nozzle, which is used to mix the granulation slurry with compressed air and then spray it out to form fine and uniform droplets.

[0054] The spraying temperature of the nozzle is 90°C-125°C, the spraying pressure of the concentrated slurry is controlled at 0.02MPa-0.6MPa, and the pressure of the compressed air is controlled at 0.3MPa-1.0MPa.

[0055] like Figure 1 The preparation method of the above-mentioned high-magnesium trace granular water-soluble fertilizer comprises the following steps:

[0056] Neutralize the calcium and magnesium solution;

[0057] The neutralized calcium-magnesium solution is filtered and impurities are removed to obtain a calcium-magnesium filtrate;

[0058] The calcium and magnesium filtrates are proportioned to obtain a proportioning liquid;

[0059] The proportioning liquid is concentrated to obtain a granulation slurry;

[0060] The specific gravity of the granulation slurry is ≥1.68g / cm 3 , the mass content of magnesium in the granulation slurry is ≥2.0%;

[0061] The granulation slurry is sprayed and granulated by using a granulator containing a fluidized bed; unqualified particles are removed by screening, and qualified particles are dried to obtain a high-magnesium medium-trace granular water-soluble fertilizer.

[0062] Specifically, in the present application, calcium nitrate magnesium liquid (hereinafter referred to as calcium magnesium liquid) which is a by-product of chemical mineral processing is used as a raw material. The pH of the calcium nitrate magnesium liquid is 0-2, which is slightly acidic and needs to be neutralized. In the neutralization section of the calcium magnesium liquid, calcium hydroxide powder or gaseous ammonia is used to neutralize the calcium magnesium liquid, and the pH of the calcium magnesium liquid is neutralized to 6-8. The temperature of the neutralization process is controlled between 60°C and 90°C. If the temperature is low and the reaction is slow (such as 40°C), the calcium hydroxide powder will not react completely, and a coating will easily form, wasting raw materials. If the temperature is high and the reaction is intense (such as 110°C), a large number of bubbles will be generated, and bubbling accidents are prone to occur.

[0063] Since the neutralized calcium-magnesium neutralized solution contains a small amount of acid-insoluble substances and unreacted calcium hydroxide powder, a plate-and-frame filter press is used to perform solid-liquid separation in the filtration process to obtain a clear calcium-magnesium neutralized solution.

[0064] Specifically, the calcium-magnesium neutralization solution is proportioned to obtain a proportioning solution; the proportioning is calculated according to the required magnesium content of the high-magnesium medium-micro granular water-soluble fertilizer. Since the magnesium content in the calcium-magnesium neutralization solution is unstable between 0.5% and 5%, calcium ammonium nitrate needs to be added to reduce the magnesium content or magnesium nitrate needs to be added to increase the magnesium content. The proportioning process needs to control the temperature between 90°C and 110°C. If the temperature is too low, the magnesium nitrate will dissolve slowly, and the low specific gravity of the slurry will affect the subsequent concentration and heating and concentration difficulties. If the temperature is too high, bubbles will be generated, and a tank overflow accident will occur;

[0065] When proportioning, the ratio of calcium-magnesium neutralization solution to calcium ammonia nitrate is calculated by mass, and the control range is 1:0-1:1. The ratio of calcium-magnesium neutralization solution to magnesium nitrate is calculated by mass, and the control range is 1:0-1:0.3.

[0066] Specifically, the proportioning liquid is concentrated to obtain the granulation slurry. The process is as follows: the proportioning liquid is concentrated to reduce the free water content in the slurry. Since the specific gravity (density) of the concentrated slurry needs to change with the magnesium content during the production process, and the specific gravity (density) decreases with the increase of the magnesium content in the slurry, the concentration temperature control range is 148°C-180°C, and the specific gravity (density) control range is 1.68g / cm 3 -1.80g / cm 3 The mass content of magnesium in the pellet slurry is ≥2.0%, and the mass content of magnesium is preferably between 2.0-8.0%.

[0067] Since the cooling, solidification and crystallization time of calcium-magnesium liquid is relatively long, after conventional granulation slurry is sprayed on the return material, it cannot crystallize and solidify in time, resulting in the return material of the granulator being soaked by the slurry and losing fluidity. It is impossible to form a material curtain and accumulate on the fluidized bed and scabbed on the drum wall. In severe cases, the return material will melt and solid particles cannot be formed. Therefore, the granulation slurry needs to be cooled in advance. After cooling, the fluidity of the slurry deteriorates as the magnesium content in the slurry decreases, resulting in the slurry solidifying and clogging the spraying pipe. By controlling the temperature of the granulation slurry between 70℃-125℃, the slurry solidification and clogging of the spraying pipe can be avoided.

[0068] Specifically, a granulator containing a fluidized bed is used to spray granulate the granulation slurry; unqualified particles are removed by screening, and qualified particles are dried to obtain a high-magnesium trace granular water-soluble fertilizer. The process is as follows:

[0069] Granulation process: The granulator adopts a double-fluid nozzle. After the concentrated and cooled slurry enters the nozzle, compressed air is added to increase the pressure of the spray pipe to make the slurry atomization effect better during spraying. The spraying pressure of the concentrated slurry is controlled at 0.02MPa-0.6MPa, and the compressed air pressure is controlled at 0.3MPa-1.0MPa. A fluidized bed is installed inside the granulator. The fluidized bed plane adopts a honeycomb plate. The granulation air is blown out from the honeycomb plate of the fluidized bed. A folding copying plate is installed inside the drum. The copying plate will copy the backflow into the fluidized bed. The granulation air blows the return material to a boiling state and flows down the fluidized bed to form a material curtain. The concentrated and cooled slurry is sprayed on the return material to make it solidify quickly and make the return material grow slowly and increase. It overflows from the granulator and enters the screening process.

[0070] The concentrated and cooled qualified granulation slurry is sent to the granulator through the feeding pump and enters the double-fluid nozzle, and is sprayed on the fluidized return material of the granulator for spray granulation. The granulation uses the device air as the pressurized air. The air main is designed with local and remote pressure gauges and pneumatic control valves. The air is introduced into the nozzle for pressurization through a steel hose. When the spraying pressure is low, the pneumatic valve is opened, and when the pressure is high, the pneumatic control valve is closed, so that the granulation slurry is sprayed evenly in a mist and wrapped on the return material of the granulator. The return material continues to grow to form qualified particles.

[0071] Screening process: The screening process adopts the screening process of calcium nitrate process. After the particles ≥4.75mm are separated, they are crushed by drum crusher and returned to the drum fluidized bed granulator for recycling. The particles ≤1mm are separated and returned to the drum fluidized bed granulator for recycling. The finished particles with a particle size between 1mm-4.75mm enter the cooling process for cooling.

[0072] Cooling process: Since magnesium nitrate, calcium nitrate, ammonium nitrate and other nitrates have very strong water absorption, and high-temperature high-magnesium calcium ammonium nitrate has poor heat dissipation after packaging, it has caused the product to be very easy to harden during storage and transportation after packaging. Therefore, the cooling process uses dehumidified cold air to cool the product and control the packaging temperature between 40℃-50℃ for packaging.

[0073] More specifically, the above-mentioned preparation method is as follows Figure 2 The water-soluble fertilizer production system shown in the figure is produced, and the water-soluble fertilizer production system includes a proportioning tank 1, and the proportioning tank 1 is used to receive the calcium and magnesium solution and adjust it into a proportioning liquid;

[0074] A concentrator 2, wherein the concentrator 2 is connected to the proportioning tank 1;

[0075] A granulation device 3, wherein the concentrator 2 is connected to the granulation device 3;

[0076] A sifter 4 connected to the granulation device 3;

[0077] The granulation equipment 3 includes a granulator 301 , a fluidized bed 302 disposed in the granulator 301 , and a nozzle 303 disposed above the fluidized bed 302 .

[0078] The proportioning tank is used to receive the calcium and magnesium solution and adjust it into a proportioning solution with a specific ratio to ensure that the components are mixed as required;

[0079] The concentrator, connected to the proportioning tank, removes excess water by evaporation and other means, increases the slurry concentration, and controls its specific gravity (density) within an appropriate range;

[0080] Granulation equipment, consisting of a granulator, a built-in fluidized bed and a dual-fluid nozzle, uses compressed air to atomize the slurry and then sprays it on the return material to form particles. At the same time, the fluidized bed provides a good material dispersion environment to ensure uniform growth of particles;

[0081] The screener screens the finished products after granulation, separates qualified large particles, small particles and dust, and returns unqualified materials to the system for reprocessing.

[0082] In one or more embodiments, Figure 3As shown, the nozzle 303 is a dual-fluid nozzle 303, and the nozzle 303 is connected to the feed pump 5, and receives the concentrated and cooled slurry from the concentrator 2 through a pipeline.

[0083] It can be understood that the nozzle is located inside the granulator, connected to the feed pump, receives the concentrated and cooled slurry through the pipeline, and introduces compressed air to spray the concentrated and cooled slurry into mist, which is evenly sprayed and wrapped on the return material.

[0084] It can be understood that a folding plate is provided in the drum of the granulator 301, and the folding plate folds the backflow into the fluidized bed 302. By providing a folding plate in the drum of the granulator, the return material can be continuously scooped up and thrown onto the fluidized bed, ensuring that the material can be evenly distributed in the fluidized bed, thereby improving the granulation efficiency and quality; and the design of the folding plate helps to maintain the good fluidity and dispersibility of the material, so that the sprayed slurry can quickly contact the return material and solidify into particles with regular appearance. When the folding plate rotates with the drum, it will continuously scoop up the material at the bottom and throw it outward. This process not only increases the chance of collision between materials, but also promotes the fusion between new and old particles, and accelerates the growth rate of particles.

[0085] In one or more embodiments, the fluidized bed 302 is connected to the housing of the granulator 301 , and the granulation air is blown out from the honeycomb plate 304 of the fluidized bed 302 .

[0086] Specifically, by blowing granulation air through the honeycomb plate, a stable airflow layer can be formed on the fluidized bed, so that the material is in a suspended state, further enhancing the fluidization effect and facilitating the growth of particles. Compressed air is blown into the fluidized bed through the honeycomb plate to make the material in a boiling state, achieving good dispersion and mixing. In this state, the friction between the materials is reduced, and the fluidity is enhanced, providing an ideal adhesion environment for the sprayed slurry. Since the materials in the fluidized bed are always well dispersed, the risk of local overheating is reduced, which is also conducive to the uniform transfer of heat, improves the cooling efficiency, and ensures the stable formation of particles.

[0087] The high-magnesium medium-trace granular water-soluble fertilizer described in the present application is further illustrated by the following examples and comparative examples.

[0088] Example 1

[0089] The preparation method of high-magnesium medium-trace granular water-soluble fertilizer comprises the following steps:

[0090] Neutralize the calcium and magnesium solution and adjust the pH to 6;

[0091] The neutralized calcium-magnesium solution is filtered to remove impurities, and a plate-and-frame filter press is used to separate solids and liquids to obtain a clear calcium-magnesium neutralized solution;

[0092] The calcium and magnesium neutralization solutions are proportioned to obtain proportioning solutions; the proportioning solutions are concentrated to obtain granulation slurry, and the specific gravity of the granulation slurry is 1.68 g / cm 3 , the mass content of magnesium in the granulation slurry is 2.0%;

[0093] Using a granulator containing a fluidized bed, the granulation slurry is sprayed and granulated;

[0094] The granulator is provided with a dual-fluid nozzle and a fluidized bed, the spraying temperature of the granulation slurry in the dual-fluid nozzle is 90°C, the spraying pressure is controlled at 0.02MPa-0.1MPa, the pressure of the compressed air is controlled at 0.3MPa-0.5MPa, and the temperature of the fluidized return material on the fluidized bed is controlled at 48-50°C to obtain granulated particles; after the granulation is completed, the granulated particles are sieved through an upper sieve and a lower sieve, the aperture of the upper sieve is 5mm, and the aperture of the lower sieve is 2.5mm, unqualified particles are removed by screening, and qualified particles are dried at 30°C to obtain high-magnesium trace granular water-soluble fertilizer.

[0095] Example 2

[0096] The preparation method of high-magnesium medium-trace granular water-soluble fertilizer comprises the following steps:

[0097] Neutralize the calcium and magnesium solution and adjust the pH to 8;

[0098] The neutralized calcium-magnesium solution is filtered to remove impurities, and a plate-and-frame filter press is used to separate solids and liquids to obtain a clear calcium-magnesium neutralized solution;

[0099] The calcium and magnesium neutralization liquid is proportioned to obtain a proportioning liquid; the proportioning liquid is concentrated to obtain a granulation slurry, and the specific gravity of the granulation slurry is 1.80g / cm 3 , the mass content of magnesium in the granulation slurry is 8.0%;

[0100] Using a granulator containing a fluidized bed, the granulation slurry is sprayed and granulated;

[0101] The granulator is provided with a dual-fluid nozzle and a fluidized bed. The spraying temperature of the granulation slurry in the dual-fluid nozzle is 125°C, the spraying pressure is controlled at 0.5-0.6MPa, the pressure of the compressed air is controlled at 0.8-1.0MPa, and the temperature of the fluidized return material on the fluidized bed is 43-45°C to obtain granulated particles. After the granulation is completed, the granulated particles are screened through an upper sieve and a lower sieve, the aperture of the upper sieve is 5mm, and the aperture of the lower sieve is 2.5mm. Unqualified particles are removed by screening, and qualified particles are dried at 50°C to obtain high-magnesium trace granular water-soluble fertilizer.

[0102] Example 3

[0103] The preparation method of high-magnesium medium-trace granular water-soluble fertilizer comprises the following steps:

[0104] Neutralize the calcium and magnesium solution and adjust the pH to 6-8;

[0105] The neutralized calcium-magnesium solution is filtered to remove impurities, and a plate-and-frame filter press is used to separate solids and liquids to obtain a clear calcium-magnesium neutralized solution;

[0106] The calcium and magnesium neutralization liquid is proportioned to obtain a proportioning liquid; the proportioning liquid is concentrated to obtain a granulation slurry, and the specific gravity of the granulation slurry is 1.75g / cm 3 , the mass content of magnesium in the granulation slurry is 5.0%;

[0107] Using a granulator containing a fluidized bed, the granulation slurry is sprayed and granulated;

[0108] The granulator is provided with a dual-fluid nozzle and a fluidized bed. The spraying temperature of the granulation slurry in the dual-fluid nozzle is 110°C, the spraying pressure is 0.4MPa, the pressure of the compressed air is controlled at 0.4MPa, and the temperature of the fluidized return material on the fluidized bed is 45°C to obtain granulated particles. After the granulation is completed, the granulated particles are sieved through an upper sieve and a lower sieve, the aperture of the upper sieve is 5mm, and the aperture of the lower sieve is 2.5mm. Unqualified particles are removed by screening, and qualified particles are dried at 40°C to obtain high-magnesium trace granular water-soluble fertilizer.

[0109] Comparative Example 1

[0110] Preparation method of high-magnesium trace granular water-soluble fertilizer, the specific gravity of granulated slurry is 1.50g / cm 3 , the mass content of magnesium in the granulation slurry is 1.0%; the other conditions are consistent with Example 1.

[0111] Comparative Example 2

[0112] The preparation method of high-magnesium trace granular water-soluble fertilizer, the qualified granules are not dried; the other conditions are the same as those in Example 1.

[0113] Comparative Example 3

[0114] The preparation method of high-magnesium trace granular water-soluble fertilizer is as follows: the spraying temperature of the granulation slurry in the double-fluid nozzle is 80° C., and the other conditions are consistent with those in Example 1.

[0115] Comparative Example 4

[0116] The preparation method of high-magnesium trace granular water-soluble fertilizer is as follows: the temperature of the fluidized return material on the fluidized bed is 65° C., and the other conditions are consistent with those in Example 1.

[0117] Comparative Example 5

[0118] The preparation method of high-magnesium trace granular water-soluble fertilizer is as follows: the spraying pressure is 1 MPa, the pressure of compressed air is 0.1 MPa, and the other conditions are the same as those in Example 1.

[0119] The calcium-magnesium liquids of Examples 1 to 3 and Comparative Examples 1 to 5 are from the same batch of calcium-magnesium liquids, and the mass content of Ca(NO3)2 in the calcium-magnesium liquids is 31.39%, and the mass content of Mg(NO3)2 is 7.88%; the preparation methods of Examples 1 to 3 and Comparative Examples 1 to 5 are carried out in a water-soluble fertilizer production system.

[0120] The high-magnesium medium-trace granular water-soluble fertilizers prepared in Examples 1 to 3 and Comparative Examples 1 to 5 were subjected to the following performance tests, and the relevant results are summarized in Table 1:

[0121] The contents of Ca and Mg were detected by ICP-OES (inductively coupled plasma emission spectrometer); the H2O content was accurately measured by Karl Fischer water determination; the stability was measured by placing the sample at a temperature of 30°C and a humidity of 45% for 20 days to observe whether there was any agglomeration; for particle strength, 100 undamaged particles were selected, and the maximum pressure that each particle could withstand was measured using a particle strength tester, and the average value was taken to obtain the particle strength.

[0122] Table 1

[0123]

[0124]

[0125] From Table 1, we can see that:

[0126] The total mass contents of Ca and Mg in the granular water-soluble fertilizers of Examples 1-3 are 15.33%, 22.02% and 17.78%, respectively, all exceeding the standard of ≥10%, which indicates that the products can provide sufficient calcium and magnesium elements to meet the needs of crops for these two important nutrients.

[0127] The granular water-soluble fertilizers of Examples 1-3 all have low moisture contents (≤1.48%), which meet industry standards; low moisture contents help prevent moisture absorption or agglomeration of the products during storage and transportation, thereby ensuring product stability and ease of use.

[0128] The granular water-soluble fertilizers of Examples 1-3 have high granular strengths, all exceeding 45 N, specifically 48.5 N, 47.9 N, and 48.1 N. This means that the granules have good mechanical strength, are not easily broken, and maintain their intact form during packaging, transportation, and application, reducing the risk of dust pollution.

[0129] After 20 days of storage test, all samples of the granular water-soluble fertilizers of Examples 1-3 showed good stability, that is, "no moisture absorption and no caking". This property is very important for ensuring product quality and extending shelf life, especially in a humid environment.

[0130] In summary, the granular water-soluble fertilizer and preparation method thereof described in the present application, by optimizing the key steps such as neutralization treatment, filtration and impurity removal, proportioning and concentration, effectively removes free acid and impurities that affect product quality, and strictly controls the specific gravity and component ratio of the granulation slurry, ensuring the uniformity and consistency of the final product. By adopting a granulator containing a fluidized bed and a dual-fluid nozzle for spraying granulation, not only the granule appearance roundness is good, but also the compactness of the internal structure of the granule is improved, thereby enhancing the granule strength. At the same time, the good dispersion environment provided by the fluidized bed also helps to form uniform and stable granules.

[0131] The qualified particles after screening are dried at an appropriate temperature (30-50°C), which effectively reduces the free water content in the product and avoids the problem of product agglomeration caused by excessive moisture. In addition, the appropriate drying temperature can also protect the surface of the particles from damage and maintain their physical integrity.

[0132] Therefore, the granular water-soluble fertilizer described in the present application ensures that the ratio of Ca and Mg in the finished product is moderate through the reasonable allocation of calcium and magnesium solution, which not only meets the needs of crops, but also does not affect the absorption and utilization efficiency of other nutrient elements. In particular, the presence of magnesium promotes the activation of enzymes, thereby improving the absorption and utilization rate of calcium by crops.

[0133] In Comparative Example 1, insufficient specific gravity and magnesium content of the granulation slurry resulted in insufficient granule strength and poor stability. The specific analysis is as follows:

[0134] The granular water-soluble fertilizer of Comparative Example 1 has a slightly higher calcium content (17.56%), but a significantly lower magnesium content (0.48%). Since magnesium is essential for promoting enzyme activation, low magnesium content may affect the effect of calcium absorption by crops. The moisture content is higher than that of Example 1 (1.61%), which may cause the product to absorb moisture more easily during storage. The granular strength is lower than 45N because the specific gravity of the granulated slurry is lower (1.50g / cm 3 ), resulting in the internal structure of the particles being not tight enough and easy to break. In terms of stability, it shows moisture absorption and slight agglomeration. This is the result of the combined effect of lower magnesium content and higher moisture content. Low magnesium content reduces the chemical stability of the product, while high moisture content exacerbates the tendency to absorb moisture.

[0135] Comparative Example 2 lacks the necessary drying step, and the moisture content is too high, which seriously affects the physical properties and long-term stability of the product; the specific analysis is as follows:

[0136] The moisture content increased significantly to 5.89%, much higher than 1.42% in Example 1. High moisture content not only affects the physical properties of the product, but also greatly increases the risk of moisture absorption. The particle strength dropped sharply to 30.2N, mainly because the undried particles contain a large amount of free water, which weakens the bonding force between the particles and reduces the mechanical strength. Stability has serious moisture absorption and agglomeration problems, and high moisture content directly leads to this adverse consequence, affecting the long-term stability and ease of use of the product.

[0137] Although the moisture content of Comparative Example 3 is properly controlled, the nozzle temperature is low, which affects the quality of particle formation, making the particle strength and stability slightly inferior to those of Example 1. The specific analysis is as follows:

[0138] The Ca and Mg contents changed slightly, but were generally close to Example 1. This indicates that the lower nozzle temperature has less effect on the ratio of ingredients. The moisture content remained consistent (1.42%), indicating that the change in nozzle temperature did not significantly affect the water evaporation efficiency. The particle strength decreased to 42.8N, mainly because the lower nozzle temperature (80°C) may not be sufficient to fully atomize the granulation slurry, thus affecting the uniformity and compactness of particle formation. The stability showed slight moisture absorption and agglomeration. Although the moisture content was the same, the weakening of the particle strength may make the product more susceptible to external humidity conditions, leading to slight agglomeration.

[0139] In Comparative Example 4, the fluidized return material temperature was too high, resulting in an increase in moisture content and a decrease in particle strength, which affected the stability and mechanical properties of the product. The specific analysis is as follows:

[0140] The Ca and Mg contents increased slightly (Ca from 14.28% to 14.75%, Mg from 1.05% to 1.17%), but these changes did not significantly affect the overall performance. The moisture content increased slightly to 1.57%, which may be due to the high fluidization return temperature, which resulted in some moisture not being completely removed. The granule strength decreased to 44.9N. The high fluidization return temperature may have caused the granule surface to harden prematurely during the granulation process, affecting the compactness of the internal structure and thus reducing the granule strength. Stability showed slight moisture absorption and agglomeration. The higher moisture content and possible structural defects made the product more susceptible to damage during storage, resulting in slight agglomeration.

[0141] In Comparative Example 5, due to the excessively high spraying pressure and the low compressed air pressure, the moisture content increased and the particle strength decreased, which further affected the stability and mechanical properties of the product. The specific analysis is as follows:

[0142] The Ca and Mg contents increased slightly (Ca increased from 14.28% to 15.08%, and Mg increased from 1.05% to 1.24%), but these changes had limited impact on the overall performance. The moisture content increased to 1.67%, which may be due to the combined effect of too high shotcrete pressure and too low compressed air pressure. High shotcrete pressure may lead to poor slurry atomization, while low compressed air pressure cannot provide sufficient dispersion force, which ultimately affects the evaporation efficiency of water. The particle strength dropped to 43.4N. Excessive shotcrete pressure may cause greater impact force during particle formation and destroy the internal structure of the particles. At the same time, insufficient compressed air pressure also affects the uniformity and compactness of the particles. Stability shows slight moisture absorption and agglomeration. The high moisture content and structural defects make the product more susceptible to external humidity, resulting in slight agglomeration.

[0143] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A high-magnesium trace granular water-soluble fertilizer, characterized in that: The high-magnesium medium-trace granular water-soluble fertilizer is obtained by passing granulated slurry through a nozzle and spraying granulation in a granulator; The specific gravity of the granulation slurry is ≥1.68g / cm 3 , the mass content of magnesium in the granulation slurry is ≥2.0%; The mass content of magnesium in the high-magnesium medium-trace granular water-soluble fertilizer is ≥1.0%.

2. The high-magnesium medium-trace granular water-soluble fertilizer according to claim 1, characterized in that: In the high-magnesium medium-trace granular water-soluble fertilizer, the sum of the mass content of magnesium and the weight content of calcium is ≥12%.

3. The high-magnesium medium-trace granular water-soluble fertilizer according to claim 1, characterized in that: The particle strength of the high-magnesium trace granular water-soluble fertilizer is ≥35N.

4. The high-magnesium medium-trace granular water-soluble fertilizer according to claim 1, characterized in that: The granulator is provided with a fluidized bed, and the temperature of the fluidized return material on the fluidized bed is ≤50°C.

5. The high-magnesium medium-trace granular water-soluble fertilizer according to claim 1, characterized in that: The nozzle is a dual-fluid nozzle, which is used to mix the granulation slurry with compressed air and then spray it out to form fine and uniform droplets.

6. The high-magnesium medium-trace granular water-soluble fertilizer according to claim 1, characterized in that: The spraying temperature of the nozzle is 90°C-125°C.

7. The high-magnesium medium-trace granular water-soluble fertilizer according to claim 5, characterized in that: The spraying pressure of the concentrated slurry is controlled at 0.02MPa-0.6MPa, and the pressure of the compressed air is controlled at 0.3MPa-1.0MPa.

8. The method for preparing the high-magnesium medium-trace granular water-soluble fertilizer according to any one of claims 1 to 7, characterized in that: The following steps are involved: Neutralize the calcium and magnesium solution; The neutralized calcium-magnesium solution is filtered and impurities are removed to obtain a calcium-magnesium filtrate; The calcium and magnesium filtrates are proportioned to obtain a proportioning liquid; The proportioning liquid is concentrated to obtain a granulation slurry; The specific gravity of the granulation slurry is ≥1.68g / cm 3 , the mass content of magnesium in the granulation slurry is ≥2.0%; The granulation slurry is sprayed and granulated by using a granulator containing a fluidized bed; unqualified particles are removed by screening, and qualified particles are dried to obtain a high-magnesium medium-trace granular water-soluble fertilizer.

9. The preparation method according to claim 8, characterized in that: In the screening process, the aperture of the upper screen is 5 mm, and the aperture of the lower screen is 1 mm.

10. The preparation method according to claim 8, characterized in that: In the drying process, the drying temperature is controlled at 30-50°C.

Images