Preparation method of stabilized fertilizer and granulation equipment for production

Abstract

The invention discloses a preparation method of a stabilized fertilizer and granulation equipment for production, and relates to the technical field of fertilizer production, and the preparation method comprises the following steps: heating a nitrogen fertilizer in a melting tank to a molten state, and sequentially adding a crushed potash fertilizer, a crushed phosphate fertilizer, a crushed trace element fertilizer and a nitrification inhibitor into the melting tank to obtain a molten mixed fertilizer; feeding the molten-state mixed fertilizer to a high-tower granulation device to obtain an inner core; polylactic acid, acetone, alginate oligosaccharide, glycerin and starch are sequentially sent to a stirring kettle to be stirred and mixed, the mixture is sprayed to the outer wall of the cooled inner core, and an adhesion layer is formed on the outer wall of the inner core after drying; spraying the slurry to the surface of the adhesion layer, and then drying at low temperature to form a dormant bacterium layer on the outer wall of the adhesion layer; and spraying the coating solution to the outer wall of the dormant bacterium layer, and performing low-temperature cooling to obtain an outer coating layer. Therefore, through the combination of the inner core, the adhesion layer, the dormant bacterium layer and the outer coating layer, the fertilizer efficiency release rate is greatly slowed down, so that the fertilizer provided by the scheme can be more lasting and effective.

Description

Technical Field

[0001] The invention relates to the technical field of fertilizer production, and in particular to a preparation method of a stable fertilizer and granulation equipment used for the production. Background Art

[0002] Slow-release fertilizers usually include the following types: First, by adding nitrification inhibitors to the fertilizer, the nitrite bacteria in the soil are inhibited, and the conversion rate of ammonium nitrogen to nitrate nitrogen is slowed down. The second is to use a coating agent to form an outer coating layer on the outer layer of the fertilizer particles. The structural properties of the outer coating layer are different depending on the material used. For example, the outer coating layer is composed of an organic resin with pores on its surface, which makes the nutrients in the fertilizer flow out more slowly and achieve a slow-release function; another example is that the outer coating layer is composed of an airtight inorganic film coating. This setting requires external force to destroy the outer coating layer, and then the nutrients flow out. The third is to coat microbial strains on the surface of the fertilizer and use the microbial strains to slow down the release rate of nutrients.

[0003] However, the above-mentioned methods often have unsatisfactory sustained-release effects when used alone. Summary of the invention

[0004] In view of the above defects, the purpose of the present invention is to provide a method for preparing a stable fertilizer and a granulating device for production, aiming to solve the problem of unsatisfactory slow-release effect of fertilizer in the prior art.

[0005] In order to solve the above technical problems, the technical solution of the present invention is: A method for preparing a stable fertilizer comprises the following steps: Step 1, preparing the kernel; Weighing nitrogen fertilizer, and delivering it to a melting tank through a bucket, heating the nitrogen fertilizer to a molten state in the melting tank, then sequentially adding crushed potassium fertilizer, phosphate fertilizer, trace element fertilizer and nitrification inhibitor to the melting tank, stirring and mixing, and obtaining a molten mixed fertilizer; delivering the molten mixed fertilizer to a high-tower granulation device, and the molten mixed fertilizer enters the high-tower granulation device through a rotating nozzle of the high-tower granulation device to form a droplet-shaped slurry, and the slurry is cooled by an ascending airflow during the descent process, and a core is obtained after solidification; Step 2, spraying the adhesion layer; The polylactic acid, acetone, brown algae oligosaccharide, glycerol and starch are sequentially sent to a stirring kettle for stirring and mixing to obtain an adhesion base liquid, and the adhesion base liquid is sprayed onto the outer wall of the cooled inner core by a fluidized bed spraying method, and an adhesion layer is formed on the outer wall of the inner core after drying; Step three, applying bacteria; The microbial agent, humic acid microspheres, trehalose and deionized water are sequentially sent to a mixing kettle for mixing to obtain a suspended bacterial solution; starch and diatomaceous earth are then added to the suspended bacterial solution to obtain a slurry; the slurry is sprayed onto the surface of the attachment layer, followed by low-temperature drying to form a dormant bacterial layer on the outer wall of the attachment layer; Step 4, coating the coating layer; The lignin, ether, carboxymethyl cellulose, modified starch, cross-linking agent and deionized water are sent to a reactor together for stirring and mixing to obtain a coating solution, which is sprayed onto the outer wall of the dormant bacteria layer, and then cooled at low temperature to obtain an outer coating layer, and then an anti-caking agent is sprayed on the outer wall of the outer coating layer, and the finished fertilizer is obtained after drying.

[0006] Wherein, in step one, the nitrogen fertilizer is urea, the potash fertilizer is potassium sulfate, and the phosphate fertilizer is calcium hydrogen phosphate; by weight, the nitrogen fertilizer is 25-35 parts, the phosphate fertilizer is 20-25 parts, the potash fertilizer is 12-20 parts, the trace elements are 8-15 parts, and the nitrification inhibitor is 5-10 parts.

[0007] Wherein, in step one, the trace element fertilizer is composed of 10-20 parts of zinc chloride, 10-20 parts of magnesium sulfate, 10-20 parts of ferrous sulfate, 10-15 parts of calcium nitrate, 4-5 parts of manganese oxide and 15-20 parts of wood ash, by weight.

[0008] Wherein, in step 1, the nitrification inhibitor is composed of 85-90 parts of DMPP and 10-15 parts of inositol peptide mixed in parts by weight.

[0009] Wherein, by weight, in step 2, polylactic acid is 10-20 parts, acetone is 12-22 parts, brown algae oligosaccharide is 25-35 parts, glycerol is 5-10 parts, and starch is 8-15 parts.

[0010] Wherein, by weight, in step three, the microbial agent is 30-40 parts, the humic acid microspheres are 15-20 parts, the trehalose is 10-15 parts, and the deionized water is 20-25 parts.

[0011] Wherein, in step three, the microbial agent is composed of a mixture of 30-50 parts of filamentous Pleistilium, 10-15 parts of Bacillus subtilis, 5-10 parts of phosphate-solubilizing bacteria and 20-25 parts of nitrogen-fixing bacteria, calculated by weight.

[0012] Wherein, by weight, in step 4, lignin is 20-22 parts, ether is 25-28 parts, carboxymethyl cellulose is 15-20 parts, modified starch is 10-15 parts, cross-linking agent is 5-8 parts, and deionized water is 7-15 parts.

[0013] Among them, in step 4, the cross-linking agent is composed of a mixture of 30-40 parts of sulfur, 20-30 parts of trimethoxysilane and 10-30 parts of aluminum chloride; the anti-caking agent is composed of 20-30 parts of diatomaceous earth, 10-20 parts of sodium aluminosilicate, 10-15 parts of silicon dioxide and 30-35 parts of deionized water.

[0014] A granulation device for stable fertilizer production, comprising a granulation mechanism, a first spraying mechanism, a second spraying mechanism and a third spraying mechanism, wherein a first drying kettle is arranged between the first spraying mechanism and the second spraying mechanism, a second drying kettle is arranged between the second spraying mechanism and the third spraying mechanism, the third spraying mechanism is also connected to the third drying kettle through a pipeline, the first spraying mechanism is connected to a stirring kettle through a pipeline, the second spraying mechanism is connected to a mixing kettle through a pipeline, and the third spraying mechanism is connected to a reaction kettle through a pipeline; the granulation mechanism comprises a granulation chamber and a coating chamber, the coating chamber is located at the bottom of the granulation chamber, and a A particle spray head and a driving motor, wherein the driving motor drives the particle spray head to rotate, one end of the particle spray head is rotatably connected to a feeding pipe, and the end of the feeding pipe away from the particle spray head is connected to a melting tank, an air inlet is arranged on the side wall of the granulation chamber, and the end of the air inlet facing the granulation chamber is covered with a filter screen; a plurality of coating nozzles are installed on the side wall of the coating chamber, the coating nozzles are arranged toward the granulation chamber, a distribution ring tube is arranged on the circumference of the coating chamber, a distribution pipe is arranged between the coating nozzle and the distribution ring tube, a conveying pipe is connected to the side wall of the distribution ring tube, and the end of the conveying pipe away from the distribution ring tube is connected to a stirring kettle.

[0015] After adopting the above technical solution, the beneficial effects of the present invention are: First, the combination of the inner core, the attachment layer, the dormant bacteria layer and the outer coating layer greatly slows down the fertilizer release rate, thereby making the fertilizer provided by the scheme more durable and effective. Second, the granulation chamber and the coating chamber in the granulation equipment realize the dual functions of granulation and spraying, solving the problem of the single function of the existing high-tower granulation device. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The flow chart for the preparation of stable fertilizer; Figure 2 It is the structural diagram of the granulation mechanism; Figure 3 It is a bottom view of the cone platform; Figure 4 is a structural diagram of the first column; Figure 5 It is the structural diagram of the cone platform; Figure 6 is a structural diagram of the second column; Figure 7This is the structural diagram of the feeding auger.

[0017] In the figure: 1-granulation mechanism, 11-granulation chamber, 111-granulation head, 112-driving motor, 113-feeding pipe, 114-air inlet, 115-filter, 116-collecting chamber, 12-coating chamber, 121-coating nozzle, 122-distribution ring pipe, 123-distribution pipe, 124-delivery pipe, 125-distribution filter, 13-first column, 131-conical table, 132-air collecting port, 133-exhaust pipe, 134-recovery mechanism, 135-first adapter, 136-discharging section, 1361-discharging scraper, 1362-fixed frame, 1363-spiral blade, 137-discharging mechanism, 1371-connecting arm, 1372-discharging Material scraper, 1373-spiral fan blade, 1374-air supply hole, 138-second column, 139-connecting section, 140-second adapter, 14-equipment cavity, 141-drive motor, 142-power gear, 143-drive gear, 15-feeding auger, 151-sealing cylinder, 152-power motor, 153-auxiliary table, 154-rotating rod, 155-spiral sheet, 2-first spraying mechanism, 21-first drying kettle, 22-mixing kettle, 3-second spraying mechanism, 31-second drying kettle, 32-reaction kettle, 4-third spraying mechanism, 41-third drying kettle, 42-anti-caking agent storage tank, 5-melting tank, 6-bag dust collector, 7-hot air heater. DETAILED DESCRIPTION

[0018] It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0019] Example: like Figure 1 As shown, a method for preparing a stable fertilizer comprises the following steps: Step 1, preparing the kernel; Weigh the nitrogen fertilizer and deliver it to the melting tank 5 through a bucket lift, heat the nitrogen fertilizer to a molten state in the melting tank 5, then add crushed potassium fertilizer, phosphate fertilizer, trace element fertilizer and nitrification inhibitor to the melting tank 5 in turn, stir and mix, and obtain a molten mixed fertilizer; deliver the molten mixed fertilizer to a high-tower granulation device, the molten mixed fertilizer enters the high-tower granulation device through a rotary nozzle of the high-tower granulation device, and forms a droplet-shaped slurry, which is cooled by the rising airflow during the descent process, and a core is obtained after solidification.

[0020] The kernel in this scheme contains multiple elements. In order to ensure the slow-release effect, a nitrification inhibitor is introduced in the production process. When the kernel releases nutrients, the nitrification inhibitor will be released along with the nutrients, thereby inhibiting the activity of nitrifying bacteria and delaying the conversion of ammonium nitrogen into nitrate nitrogen, thereby slowing down the loss rate of ammonium nitrogen and improving the utilization rate of nitrogen.

[0021] Step 2, spraying the adhesion layer; Polylactic acid, acetone, brown algae oligosaccharide, glycerol and starch are sequentially sent to a stirring kettle for stirring and mixing to obtain an adhesion base liquid, which is then sprayed onto the outer wall of the cooled inner core by a fluidized bed spraying method, and an adhesion layer is formed on the outer wall of the inner core after drying.

[0022] The attachment layer in this scheme has the following functions: Isolate the dormant bacteria layer from the inner core to reduce the probability of direct contact between the two. Due to the enrichment of nutrients in the inner core, if the dormant bacteria are directly attached to the inner core, when the dormant bacteria wake up, the bacteria are easily "burned to death", which causes the bacteria to be unable to work normally. Second, polylactic acid, brown algae oligosaccharides and starch jointly construct a slow-release layer, which further slows down the release rate of nutrients. Third, provide basic nutrients for the dormant bacteria in the dormant bacteria layer to ensure that the bacteria can reproduce rapidly after waking up.

[0023] Step three, applying bacteria; The microbial agent, humic acid microspheres, trehalose and deionized water are sequentially sent to the mixing kettle 22 for mixing to obtain a suspended bacterial liquid; starch and diatomaceous earth are then added to the suspended bacterial liquid to obtain a slurry; the slurry is sprayed onto the surface of the attachment layer, and then dried at low temperature to form a dormant bacterial layer on the outer wall of the attachment layer.

[0024] Step 4, coating the coating layer; The lignin, ether, carboxymethyl cellulose, modified starch, cross-linking agent and deionized water are sent to the reaction kettle 32 for stirring and mixing to obtain a coating solution, which is sprayed onto the outer wall of the dormant bacteria layer, and then cooled at low temperature to obtain an outer coating layer. Subsequently, an anti-caking agent is sprayed on the outer wall of the outer coating layer, and the finished fertilizer is obtained after drying.

[0025] In order to protect the dormant bacteria layer and further slow down the release rate of fertilizer, this scheme introduces an outer coating layer, using lignin, carboxymethyl cellulose and modified starch as the skeleton, and using a cross-linking agent to connect the various materials together.

[0026] In step 1, the nitrogen fertilizer is urea, the potash fertilizer is potassium sulfate, and the phosphate fertilizer is calcium hydrogen phosphate; by weight, the nitrogen fertilizer is 25-35 parts, the phosphate fertilizer is 20-25 parts, the potash fertilizer is 12-20 parts, the trace elements are 8-15 parts, and the nitrification inhibitor is 5-10 parts.

[0027] In terms of weight, in step one, the trace element fertilizer is composed of 10-20 parts of zinc chloride, 10-20 parts of magnesium sulfate, 10-20 parts of ferrous sulfate, 10-15 parts of calcium nitrate, 4-5 parts of manganese oxide and 15-20 parts of wood ash.

[0028] In step 1, the heating temperature of the melting tank 5 is 145-150°C.

[0029] In step 1, the particle size of the inner core is 1.5-3 mm.

[0030] In terms of weight, in step 1, the nitrification inhibitor is composed of 85-90 parts of DMPP and 10-15 parts of inositol peptide.

[0031] Inositol peptides have the following functions: First, it promotes root growth. Inositol peptides can stimulate the growth of capillary roots, form capillary root groups, promote the assimilation of ammonium ions, and enhance the activity of related enzymes and coenzymes, thereby improving the utilization rate of nitrogen fertilizers, increasing the synthesis of amino acids in plants, regulating carbon and nitrogen metabolism, and enhancing plant biomass accumulation.

[0032] The second is to improve the utilization rate of fertilizers. Inositol peptides have strong chelating and adsorption capabilities, which can enrich phosphorus, potassium and trace elements to supply crops, allowing crops to absorb and utilize fertilizers more effectively, reduce the loss of nutrients, and improve fertilizer utilization.

[0033] The third is to improve soil structure. Inositol peptide is rich in water-soluble polymers, which can improve the soil aggregate structure, make the soil loose and porous, and better retain water and fertilizer. At the same time, it provides a good living environment for soil microorganisms and acts as a carrier of fertilizer to transport trace elements to the roots, increasing the vitality of the root system and the nutrients needed for growth.

[0034] The role of DMPP is: DMPP, as a green and environmentally friendly nitrification inhibitor, is highly efficient, non-toxic and cost-effective. It can reduce the pollution of groundwater and atmosphere caused by fertilization and improve the environmental benefits of agricultural production.

[0035] Using the two together can ensure that the nutrients in the kernel can be fully absorbed and utilized by crops.

[0036] In terms of weight, in step 2, the polylactic acid is 10-20 parts, the acetone is 12-22 parts, the brown algae oligosaccharide is 25-35 parts, the glycerol is 5-10 parts, and the starch is 8-15 parts.

[0037] In step 2, the starch is corn starch. Corn starch has a large output and a low price, so the starch in this scheme is preferably corn starch.

[0038] In step 2, the spraying temperature is 50-60° C. and the spraying pressure is 9-12 MPa.

[0039] In terms of weight, in step 3, the microbial agent is 30-40 parts, the humic acid microspheres are 15-20 parts, the trehalose is 10-15 parts, and the deionized water is 20-25 parts. Humic acid microspheres are a type of microsphere material prepared from humic acid and rectorite by a specific process. This type of microsphere has excellent adsorption properties and is widely used in the removal and treatment of heavy metal ions, so it is extremely suitable as an attachment bed for dormant bacteria.

[0040] In terms of weight, in step three, the microbial agent is composed of a mixture of 30-50 parts of filamentous Pristia, 10-15 parts of Bacillus subtilis, 5-10 parts of phosphate-solubilizing bacteria and 20-25 parts of nitrogen-fixing bacteria. Filamentous Pristia does play a significant role in nitrogen conservation and promotion, nitrogen control and nitrogen lock, rooting and efficiency enhancement, and growth and stress resistance. Bacillus subtilis has significant antibacterial activity and stress resistance, which can inhibit the growth of pathogens in the soil and in plants and reduce the occurrence of diseases. Phosphate-solubilizing bacteria provide phosphorus resources around the roots of plants, and can also secrete some special substances to promote the absorption, transformation and utilization of phosphorus by plant roots. The main function of nitrogen-fixing bacteria for crops is to provide nitrogen sources and promote the growth and development of crops.

[0041] By mixing the above-mentioned bacterial species, the dormant bacterial layer can not only slow down the release of nitrogen fertilizer, but also assist crops in absorbing nutrients.

[0042] In step 3, the total amount of bacteria is ≥ 5×10^8 CFU / g.

[0043] In step 3, the spraying temperature is 25-35° C., and the low-temperature drying temperature is 40-45° C. In order to avoid the death of the bacteria due to high temperature, this solution adopts low-temperature spraying to apply the bacteria on the attachment layer.

[0044] In terms of weight, in step 4, lignin is 20-22 parts, ether is 25-28 parts, carboxymethyl cellulose is 15-20 parts, modified starch is 10-15 parts, cross-linking agent is 5-8 parts, and deionized water is 7-15 parts.

[0045] The modified starch is esterified starch obtained by treating corn starch with acetic anhydride, and has certain hydrophobicity.

[0046] In step 4, the crosslinking agent is composed of a mixture of 30-40 parts of sulfur, 20-30 parts of trimethoxysilane and 10-30 parts of aluminum chloride, by weight.

[0047] In step 4, the spraying temperature is 30-40°C and the low temperature cooling temperature is 40-45°C.

[0048] In terms of weight, in step 4, the anti-caking agent is composed of 20-30 parts of diatomaceous earth, 10-20 parts of sodium aluminosilicate, 10-15 parts of silicon dioxide and 30-35 parts of deionized water.

[0049] The existing high tower granulation equipment has a single function. In order to facilitate the fertilizer coating, it is often necessary to feed the fertilizer particles into the fluidized bed spraying equipment.

[0050] To avoid this problem, Figure 1-7 As shown, a granulation equipment for stable fertilizer production includes a granulation mechanism 1, a first spraying mechanism 2, a second spraying mechanism 3 and a third spraying mechanism 4, a first drying kettle 21 is arranged between the first spraying mechanism 2 and the second spraying mechanism 3, a second drying kettle 31 is arranged between the second spraying mechanism 3 and the third spraying mechanism 4, the third spraying mechanism 4 is also connected to a third drying kettle 41 through a pipeline, the first spraying mechanism 2 is connected to a mixing kettle 22 through a pipeline, the second spraying mechanism 3 is connected to a reaction kettle 32 through a pipeline, and the third spraying mechanism 4 is connected to an anti-caking agent storage tank 42 through a pipeline.

[0051] The first spraying mechanism 2 , the second spraying mechanism 3 , and the third spraying mechanism 4 are all equipped with spray heads.

[0052] The granulation mechanism 1 in this scheme is a high-tower granulation equipment, which is connected to a melting tank 5, a first spraying mechanism 2, a bag dust collector 6, and a hot air blower 7 through a pipeline, wherein the melting tank 5 sends the melted and mixed materials to the granulation mechanism 1 for granulation; the manufactured particles are sent to the first spraying mechanism 2 to wait for coating; the bag dust collector 6 is used to filter the air discharged from the granulation mechanism 1.

[0053] The first spray mechanism 2 is also connected to a bag filter 6, the purpose of which is to intercept and recover the attached layer of paint that overflows from the first spray mechanism 2 along with the airflow. The bag filter 6 is also connected to the stirring kettle through a pipeline, the purpose of which is to return the paint to the stirring kettle to avoid waste.

[0054] Similarly, the second spray mechanism 3 and the third spray mechanism 4 are also provided with bag dust collectors 6 to recover and reuse the spilled materials.

[0055] In order to facilitate granulation and coating, the granulation mechanism 1 includes a granulation chamber 11 and a coating chamber 12. The coating chamber 12 is located at the bottom of the granulation chamber 11. A granulation head and a driving motor 112 are arranged at the top of the granulation chamber 11. The driving motor 112 drives the granulation head to rotate. One end of the granulation head is rotatably connected to a feeding pipe 113. The end of the feeding pipe 113 away from the granulation head is connected to a melting tank 5. The molten fertilizer in the melting tank 5 will be squeezed or pumped to the feeding pipe 113, and then reach the granulation head 111 along the feeding pipe 113. An air inlet 114 is arranged on the side wall of the granulation chamber 11, and a filter screen 115 is covered on the end of the air inlet 114 facing the granulation chamber 11. The outer wall of the granulation head 111 is provided with a plurality of meshes. Driven by the driving motor 112, the granulation head 111 rotates rapidly, and the fertilizer in the molten state is sent into the granulation chamber 11 through the mesh. At the same time, the air inlet 114 delivers cooling air to the granulation chamber 11 , and the cooling air and the falling fertilizer move relative to each other. During this process, the molten fertilizer gradually solidifies to form a core, which then falls to the bottom of the granulation chamber 11 for temporary storage.

[0056] The purpose of the filter 115 is to prevent the inner core from entering the air inlet 114 .

[0057] The top of the coating chamber 12 is connected to the bottom of the granulation chamber 11. In order to facilitate the coating chamber 12 to spray the adhesion layer onto the inner core, a plurality of coating nozzles 121 are installed on the side wall of the coating chamber 12. The coating nozzles 121 are arranged toward the granulation chamber 11. A material distribution ring tube 122 is arranged circumferentially of the coating chamber 12. A material distribution pipeline 123 is arranged between the coating nozzles 121 and the material distribution ring tube 122. A conveying pipeline 124 is connected to the side wall of the material distribution ring tube 122. The conveying pipeline 124 is connected to a stirring kettle at one end away from the material distribution ring tube 122. The adhesion coating in the stirring kettle passes through the conveying pipeline 124 and the material distribution ring tube 122 in turn and reaches the coating nozzle 121. Then, it enters the coating chamber 12 in the form of droplets through the coating nozzle 121. At the same time, the inner core descends and collides with the adhesion coating. Since the adhesion coating has adhesion, the adhesion coating will adhere to the outer wall of the inner core and wait for drying and condensation to form an adhesion layer.

[0058] In order to facilitate the extraction of air in the coating chamber 12 and the auxiliary adhesion coating is coated on the outer wall of the inner core, a conical collecting chamber 116 is provided at the bottom of the granulation chamber 11, and the bottom of the collecting chamber 116 is connected to the coating chamber 12. A first column 13 is installed in the coating chamber 12, and the first column 13 is hollow. The length direction of the first column 13 is the same as the length direction of the coating chamber 12. A conical platform 131 is installed on the side wall of the first column 13, and the conical platform 131 is located between the coating nozzle 121 and the collecting chamber 116. The end of the conical platform 131 with a larger bottom area faces the coating nozzle 121. A plurality of air collecting ports 132 are provided at the bottom of the conical platform 131, and the air collecting ports 132 are connected to the first column 13. An exhaust duct 133 is connected to the end of the first column 13 away from the collecting chamber 116, and a recovery mechanism 134 is connected to the end of the exhaust duct 133 away from the first column 13.

[0059] The conical platform 131 has two functions. First, when the kernel in the granulation chamber 11 enters the coating chamber 12, since the end of the conical platform 131 with a smaller bottom area faces the granulation chamber 11, the kernel will be evenly sent to the surroundings by the conical platform 131, which expands the distribution range of the kernel, thereby ensuring that the kernel has sufficient contact area with the attached coating during the falling process. Second, the exhaust duct 133 is connected to the recovery mechanism 134. When the recovery mechanism 134 is working, it will extract the air in the coating chamber 12 through the exhaust duct 133, the first column 13, the conical platform 131, and the air collecting port 132, which will form a negative pressure in the bottom area of ​​the conical platform 131, so the attached material will reach the recovery mechanism 134 along the air collecting port 132, the first column 13, and the exhaust duct 133. In this process, the faster the air flow rate, the greater the resistance encountered by the kernel when it descends, and the slower its descent speed, so that it can fully contact with the attached coating.

[0060] When the kernel falls to the bottom of the coating chamber 12, the vibration will cause part of the adhesion layer to fall off, thereby forming slag. In order to facilitate the recovery of slag, the coating chamber 12 includes an upper cavity and a lower cavity, a sub-filter 125 is arranged between the upper cavity and the lower cavity, the sub-filter 125 is arranged obliquely, a discharge port is arranged at the bottom of the upper cavity, the bottom of the lower cavity is conical, and a feeding auger 15 is installed at the bottom of the lower cavity. The kernel will roll along the sub-filter 125 to the discharge port, and then be sent to the first spraying mechanism 2 through the discharge port. The slag will pass through the sub-filter 125, and then be sent to the external storage tank through the feeding auger 15.

[0061] In order to facilitate material discharge, the sub-filter 125 has an angle α with the horizontal plane, 15°≤α≤30°.

[0062] In order to conveniently control the speed at which the kernel in the granulation chamber 11 enters the coating chamber 12, an equipment chamber 14 is installed at one end of the lower chamber away from the upper chamber, one end of the feeding auger 15 is located in the equipment chamber 14, a driving gear 143 is installed on the side wall of the first column 13, a plurality of driving motors 141 are installed in the equipment chamber 14, and the plurality of driving motors 141 are arranged around the first column 13, a power gear 142 is installed at the power end of the driving motor 141, and the power gear 142 is meshedly connected with the driving gear 143, a first adapter 135 is arranged between the first column 13 and the exhaust duct 133, and the first column 13 and the first adapter 135 are connected to each other. 35 is rotatably connected, the exhaust duct 133 is connected to the side wall of the first adapter 135, the first column 13 is rotatably connected to the sub-filter 125, the top of the first column 13 is connected with a discharge section 136, the discharge section 136 is located in the collecting chamber 116, a fixing frame 1362 is installed on the side wall of the discharge section 136, a discharge scraper 1361 is installed at one end of the fixing frame 1362 away from the discharge section 136, the discharge scraper 1361 is matched with the inner wall of the collecting chamber 116, a plurality of spiral blades 1363 are also arranged on the side wall of the discharge section 136, and the spiral blades 1363 are located between the fixing frame 1362 and the conical platform 131.

[0063] The driving motor 141 drives the power gear 142 to rotate, and the power gear 142 drives the first column 13 to rotate through the driving gear 143. In this process, the first column 13 drives the unloading scraper 1361 and the spiral blade 1363 to rotate. The function of the unloading scraper 1361 is to reduce the probability of the kernel adhering to the inner wall of the collection chamber 116, and the spiral blade 1363 will transport the kernel to the coating chamber 12 during the rotation process.

[0064] In order to facilitate the slag to enter the feeding auger 15, a discharge mechanism 137 is provided in the lower cavity, and the discharge mechanism 137 includes a connecting arm 1371 and a discharge scraper 1372. One end of the connecting arm 1371 is connected to the first column 13, and the other end of the connecting arm 1371 is connected to the discharge scraper 1372. The discharge scraper 1372 is arranged in cooperation with the bottom of the lower cavity. The function of the discharge scraper 1372 is to prevent the slag from adhering to the bottom of the coating chamber 12. Preferably, a plurality of spiral blades 1373 are provided on the side wall of the first column 13, and the plurality of spiral blades 1373 are located between the connecting arm 1371 and the feeding auger 15. The function of the spiral blades 1373 is to promote the slag to enter the feeding auger 15.

[0065] Since the adhesion layer has a certain degree of adhesion, it is necessary to dry the adhesion layer on its surface during the falling process of the kernel to reduce its stickiness. To this end, a second column 138 is installed in the first column 13, a gap is set between the first column 13 and the second column 138, the length direction of the second column 138 is the same as the length direction of the first column 13, and the second column 138 is hollow; the second column 138 is rotatably connected to the second adapter 140 at one end away from the conical platform 131, and an air inlet duct is installed on the side wall of the second adapter 140, and the air inlet duct is connected to the heat generator 7 at one end away from the second adapter 140, the connecting arm 1371 is hollow, and a plurality of air supply holes 1374 are set at one end of the connecting arm 1371 facing the conical platform 131, and the end of the connecting arm 1371 away from the discharge scraper 1372 is connected to the second column 138, and the second column 138 is rotatably connected to the first adapter 135. The hot air generator 7 generates high-speed hot air, and the hot air will reach the air supply hole 1374 along the air inlet duct, the second adapter 140, the second column 138 and the connecting arm 1371, and then be discharged to the coating chamber 12 through the air supply hole 1374. The high-speed hot air will heat the descending kernel and accelerate the drying speed of the attached layer. At the same time, the high-speed hot air will further slow down the descending speed of the kernel, reduce the collision force between the kernel and the sub-filter 125, and thus reduce the generation of slag.

[0066] In order to ensure the stability of the feeding auger 15, the feeding auger 15 includes a sealing cylinder 151, one end of the sealing cylinder 151 is connected to the lower cavity, and the other end of the sealing cylinder 151 is installed with a power motor 152, and an auxiliary platform 153 and a rotating rod 154 are arranged in the sealing cylinder 151, one end of the rotating rod 154 is connected to the power motor 152, and the other end of the rotating rod 154 is connected to the auxiliary platform 153, and a spiral piece 155 is arranged on the side wall of the rotating rod 154, and the auxiliary platform 153 is conical, the first column 13 is rotatably connected to the auxiliary platform 153, and the rotating rod 154 is rotatably connected to the side wall of the auxiliary platform 153.

[0067] Preferably, there is an angle β between the feeding auger 15 and the horizontal plane, 0≤β≤45°.

[0068] In order to facilitate the discharge of hot air in the granulation chamber 11, an air outlet is provided at the top of the granulation chamber 11, and the air outlet pipe is connected to a bag filter 6. After the discharged hot air is filtered by the bag filter 6, the impurities carried by the hot air have been filtered out, but its temperature is relatively high. In order to save energy, we need to reuse the hot air. For this purpose, a pipe is connected between the bag filter 6 and the hot air heater 7. The hot air enters the hot air heater 7 along the pipe, and then is heated by the hot air heater 7 and sent to the coating chamber 12 to dry the adhesion layer on the surface of the inner core.

[0069] Since the second column 138 is nested inside the first column 13 , in order to ensure the stability of both, a plurality of connecting sections 139 are provided between the first column 13 and the second column 138 .

[0070] Embodiment 1: This embodiment adopts the method provided in embodiment 1 to prepare the finished fertilizer, wherein: In terms of weight, in step 1, the nitrogen fertilizer is 25 parts, the phosphorus fertilizer is 20 parts, the potash fertilizer is 12 parts, the trace elements are 8 parts, and the nitrification inhibitor is 5 parts. The trace element fertilizer is composed of 10 parts of zinc chloride, 10 parts of magnesium sulfate, 10 parts of ferrous sulfate, 10 parts of calcium nitrate, 4 parts of manganese oxide and 15 parts of plant ash. The nitrification inhibitor is composed of 85 parts of DMPP and 15 parts of inositol peptide. The heating temperature of the melting tank 5 is 145°C.

[0071] In terms of weight, in step 2, polylactic acid is 10 parts, acetone is 12 parts, brown algae oligosaccharide is 25 parts, glycerol is 5 parts, and starch is 8 parts. The spraying temperature is 50° C. and the spraying pressure is 9 MPa.

[0072] In terms of weight, in step 3, the microbial agent is 30 parts, the humic acid microspheres are 15 parts, the trehalose is 10 parts, and the deionized water is 20 parts. The microbial agent is composed of 30 parts of filamentous Pristia, 10 parts of Bacillus subtilis, 5 parts of phosphate-solubilizing bacteria, and 20 parts of nitrogen-fixing bacteria. The spraying temperature is 25°C, and the low-temperature drying temperature is 40°C.

[0073] In terms of weight, in step 4, lignin is 20 parts, ether is 25 parts, carboxymethyl cellulose is 15 parts, modified starch is 10 parts, cross-linking agent is 5 parts, and deionized water is 7 parts. The cross-linking agent is composed of a mixture of 30 parts of sulfur, 20 parts of trimethoxysilane and 10 parts of aluminum chloride. The spraying temperature is 30°C and the low-temperature cooling temperature is 40°C. The anti-caking agent is composed of 20 parts of diatomaceous earth, 10 parts of sodium aluminosilicate, 10 parts of silicon dioxide and 30 parts of deionized water.

[0074] Embodiment 2: The difference between this embodiment and embodiment 2 is that: In terms of weight, in step 1, the nitrogen fertilizer is 27 parts, the phosphorus fertilizer is 21 parts, the potash fertilizer is 13 parts, the trace elements are 9 parts, and the nitrification inhibitor is 6 parts. The trace element fertilizer is composed of 12 parts of zinc chloride, 12 parts of magnesium sulfate, 12 parts of ferrous sulfate, 11 parts of calcium nitrate, 4.2 parts of manganese oxide and 16 parts of plant ash. The nitrification inhibitor is composed of 87 parts of DMPP and 13 parts of inositol peptide. The heating temperature of the melting tank 5 is 148°C.

[0075] In terms of weight, in step 2, polylactic acid is 12 parts, acetone is 14 parts, brown algae oligosaccharide is 27 parts, glycerol is 6 parts, and starch is 9 parts. The spraying temperature is 52° C. and the spraying pressure is 10 MPa.

[0076] In terms of weight, in step 3, the microbial agent is 32 parts, the humic acid microspheres are 16 parts, the trehalose is 11 parts, and the deionized water is 21 parts. The microbial agent is composed of 32 parts of filamentous Pristia, 11 parts of Bacillus subtilis, 6 parts of phosphate-solubilizing bacteria, and 21 parts of nitrogen-fixing bacteria. The spraying temperature is 26°C, and the low-temperature drying temperature is 42°C.

[0077] In terms of weight, in step 4, lignin is 20.5 parts, ether is 26 parts, carboxymethyl cellulose is 16 parts, modified starch is 11 parts, cross-linking agent is 5.5 parts, and deionized water is 8 parts. The cross-linking agent is composed of 32 parts of sulfur, 22 parts of trimethoxysilane and 12 parts of aluminum chloride. The spraying temperature is 32°C and the low-temperature cooling temperature is 40°C. The anti-caking agent is composed of 22 parts of diatomaceous earth, 12 parts of sodium aluminosilicate, 11 parts of silicon dioxide and 31 parts of deionized water.

[0078] Embodiment 3: The difference between this embodiment and embodiment 2 is that: In terms of weight, in step 1, the nitrogen fertilizer is 30 parts, the phosphorus fertilizer is 23 parts, the potash fertilizer is 15 parts, the trace elements are 10 parts, and the nitrification inhibitor is 8 parts. The trace element fertilizer is composed of 14 parts of zinc chloride, 14 parts of magnesium sulfate, 14 parts of ferrous sulfate, 12 parts of calcium nitrate, 4.5 parts of manganese oxide and 17 parts of plant ash. The nitrification inhibitor is composed of 88 parts of DMPP and 12 parts of inositol peptide. The heating temperature of the melting tank 5 is 150°C.

[0079] In terms of weight, in step 2, polylactic acid is 14 parts, acetone is 16 parts, brown algae oligosaccharide is 30 parts, glycerol is 8 parts, and starch is 11 parts. The spraying temperature is 55° C. and the spraying pressure is 11 MPa.

[0080] In terms of weight, in step 3, the microbial agent is 35 parts, the humic acid microspheres are 18 parts, the trehalose is 12 parts, and the deionized water is 23 parts. The microbial agent is composed of 34 parts of filamentous Pristia, 13 parts of Bacillus subtilis, 7 parts of phosphate-solubilizing bacteria, and 23 parts of nitrogen-fixing bacteria. The spraying temperature is 27°C, and the low-temperature drying temperature is 43°C.

[0081] In terms of weight, in step 4, lignin is 21 parts, ether is 27 parts, carboxymethyl cellulose is 18 parts, modified starch is 12 parts, cross-linking agent is 7 parts, and deionized water is 9 parts. The cross-linking agent is composed of 34 parts of sulfur, 25 parts of trimethoxysilane and 15 parts of aluminum chloride. The spraying temperature is 34°C and the low-temperature cooling temperature is 42°C. The anti-caking agent is composed of 24 parts of diatomaceous earth, 14 parts of sodium aluminosilicate, 12 parts of silicon dioxide and 32 parts of deionized water.

[0082] Embodiment 4: The difference between this embodiment and embodiment 2 is that: In terms of weight, in step 1, the nitrogen fertilizer is 35 parts, the phosphorus fertilizer is 25 parts, the potash fertilizer is 20 parts, the trace elements are 15 parts, and the nitrification inhibitor is 10 parts. The trace element fertilizer is composed of 20 parts of zinc chloride, 20 parts of magnesium sulfate, 20 parts of ferrous sulfate, 15 parts of calcium nitrate, 5 parts of manganese oxide and 20 parts of plant ash. The nitrification inhibitor is composed of 90 parts of DMPP and 10 parts of inositol peptide. The heating temperature of the melting tank 5 is 160°C.

[0083] In terms of weight, in step 2, polylactic acid is 20 parts, acetone is 22 parts, brown algae oligosaccharide is 35 parts, glycerol is 10 parts, and starch is 12 parts. The spraying temperature is 60° C. and the spraying pressure is 12 MPa.

[0084] In terms of weight, in step 3, the microbial agent is 40 parts, the humic acid microspheres are 20 parts, the trehalose is 15 parts, and the deionized water is 25 parts. The microbial agent is composed of 50 parts of filamentous Pristia, 15 parts of Bacillus subtilis, 10 parts of phosphate-solubilizing bacteria, and 25 parts of nitrogen-fixing bacteria. The spraying temperature is 35°C, and the low-temperature drying temperature is 45°C.

[0085] In terms of weight, in step 4, lignin is 22 parts, ether is 28 parts, carboxymethyl cellulose is 20 parts, modified starch is 15 parts, cross-linking agent is 8 parts, and deionized water is 15 parts. The cross-linking agent is composed of a mixture of 40 parts of sulfur, 30 parts of trimethoxysilane and 30 parts of aluminum chloride. The spraying temperature is 40°C and the low-temperature cooling temperature is 45°C. The anti-caking agent is composed of 30 parts of diatomaceous earth, 20 parts of sodium aluminosilicate, 15 parts of silicon dioxide and 35 parts of deionized water.

[0086] Comparative Example 1: In terms of weight, in step 1, the nitrogen fertilizer is 20 parts, the phosphorus fertilizer is 15 parts, the potash fertilizer is 10 parts, the trace elements are 5 parts, and the nitrification inhibitor is 4 parts. The trace element fertilizer is composed of 8 parts of zinc chloride, 8 parts of magnesium sulfate, 8 parts of ferrous sulfate, 8 parts of calcium nitrate, 3 parts of manganese oxide and 12 parts of plant ash. The nitrification inhibitor is composed of 82 parts of DMPP and 8 parts of inositol peptide. The heating temperature of the melting tank 5 is 145°C.

[0087] In terms of weight, in step 2, polylactic acid is 8 parts, acetone is 10 parts, brown algae oligosaccharide is 22 parts, glycerol is 4 parts, and starch is 5 parts. The spraying temperature is 50° C. and the spraying pressure is 9 MPa.

[0088] In terms of weight, in step 3, the microbial agent is 28 parts, the humic acid microspheres are 12 parts, the trehalose is 8 parts, and the deionized water is 18 parts. The microbial agent is composed of 28 parts of filamentous Pristia, 8 parts of Bacillus subtilis, 4 parts of phosphate-solubilizing bacteria, and 18 parts of nitrogen-fixing bacteria. The spraying temperature is 25°C, and the low-temperature drying temperature is 40°C.

[0089] In terms of weight, in step 4, lignin is 18 parts, ether is 22 parts, carboxymethyl cellulose is 12 parts, modified starch is 8 parts, cross-linking agent is 4 parts, and deionized water is 5 parts. The cross-linking agent is composed of 28 parts of sulfur, 17 parts of trimethoxysilane and 8 parts of aluminum chloride. The spraying temperature is 30°C and the low-temperature cooling temperature is 40°C. The anti-caking agent is composed of 18 parts of diatomaceous earth, 8 parts of sodium aluminosilicate, 8 parts of silicon dioxide and 28 parts of deionized water.

[0090] Comparative Example 2: In terms of weight, in step 1, the nitrogen fertilizer is 38 parts, the phosphorus fertilizer is 28 parts, the potash fertilizer is 22 parts, the trace elements are 16 parts, and the nitrification inhibitor is 12 parts. The trace element fertilizer is composed of 22 parts of zinc chloride, 22 parts of magnesium sulfate, 22 parts of ferrous sulfate, 17 parts of calcium nitrate, 6 parts of manganese oxide and 21 parts of plant ash. The nitrification inhibitor is composed of 92 parts of DMPP and 8 parts of inositol peptide. The heating temperature of the melting tank 5 is 145°C.

[0091] In terms of weight, in step 2, polylactic acid is 21 parts, acetone is 23 parts, brown algae oligosaccharide is 36 parts, glycerol is 11 parts, and starch is 16 parts. The spraying temperature is 50° C. and the spraying pressure is 9 MPa.

[0092] In terms of weight, in step 3, the microbial agent is 44 parts, the humic acid microspheres are 121 parts, the trehalose is 16 parts, and the deionized water is 26 parts. The microbial agent is composed of 51 parts of filamentous Pristia, 16 parts of Bacillus subtilis, 11 parts of phosphate-solubilizing bacteria, and 26 parts of nitrogen-fixing bacteria. The spraying temperature is 25°C, and the low-temperature drying temperature is 40°C.

[0093] In terms of weight, in step 4, lignin is 23 parts, ether is 30 parts, carboxymethyl cellulose is 21 parts, modified starch is 16 parts, cross-linking agent is 10 parts, and deionized water is 16 parts. The cross-linking agent is composed of 41 parts of sulfur, 31 parts of trimethoxysilane and 31 parts of aluminum chloride. The spraying temperature is 30°C and the low-temperature cooling temperature is 40°C. The anti-caking agent is composed of 31 parts of diatomaceous earth, 21 parts of sodium aluminosilicate, 16 parts of silicon dioxide and 36 parts of deionized water.

[0094] Comparative Example 3: The difference between this comparative example and Example 2 is that no nitrification inhibitor is added in step 1.

[0095] Comparative Example 4: The difference between this comparative example and Example 2 is that the nitrification inhibitor in step 1 is DMPP.

[0096] Comparative Example 5: The difference between this comparative example and Example 2 is that the nitration inhibitor in step 1 is inositol peptide.

[0097] Comparative Example 6: The difference between this comparative example and Example 2 is that no adhesion layer is provided.

[0098] Comparative Example 7: The difference between this comparative example and Example 2 is that no dormant bacteria layer is provided.

[0099] Comparative Example 8: The difference between this comparative example and Example 2 is that the microbial agent does not contain filamentous Pristia.

[0100] Comparative Example 9: The difference between this comparative example and Example 2 is that no outer coating layer is provided.

[0101] Comparative Example 10: The difference between this embodiment and embodiment 2 is that no anti-caking agent is sprayed.

[0102] The finished fertilizers in Examples 1 to 4 and Comparative Examples 1 to 9 were selected respectively, and the finished fertilizers were placed in the soil of the same environment. The fertilizer release rates (%) thereof are shown in the following table:

[0103] From the comparison between Comparative Example 1 and Example 2, it can be seen that since the dosage of each material in Comparative Example 1 is reduced, the fertilizer release rate of Comparative Example 1 is higher than that of Example 2.

[0104] By comparing Comparative Example 2 with Example 2, it can be seen that although the dosage of each material in Comparative Example 2 is higher than that in Example 2, the fertilizer release rate in Comparative Example 2 is not much different from that in Example 2. Considering the cost issue, the material selection range provided in this solution is optimal.

[0105] It can be seen from the comparison between Comparative Example 3 and Example 2 that in the initial stage, i.e., 1-7 days, due to the multi-layer protection, the fertilizer release rate difference between the two is small. However, in the subsequent 60-240 days, the multi-layer protection gradually fails, so the fertilizer release rate of Comparative Example 3 is greatly improved.

[0106] It can be seen from Comparative Examples 4 and 5 that the combination of DMPP and inositol peptide can effectively inhibit the fertilizer release rate.

[0107] In Comparative Example 6, the fertilizer release rate is greatly improved. It is speculated that this is due to the lack of the attachment layer, which causes the bacteria to directly contact the core, and then the bacteria are "burned to death" due to the high fertilizer concentration during the awakening process, and lose their activity. Therefore, the lack of protection of the attachment layer and the dormant bacteria layer in Comparative Example 6 leads to an excessively high fertilizer release rate. However, due to the limitations of the nitrification inhibitor and the outer coating layer, its release rate can still be limited to a certain extent.

[0108] From the comparison between Comparative Example 7 and Example 2, it can be seen that the fertilizer release rate of Comparative Example 7 and Example 2 is not much different in 1-7 days, but in the subsequent process, the fertilizer release rate of Comparative Example 7 is much higher than that of Example 2. It is speculated that this is because the bacteria in the dormant bacteria layer are not completely awakened in 1-7 days. In the subsequent process, the awakened bacteria have a limiting effect on the fertilizer release rate.

[0109] It can be seen from Comparative Example 8 that the filamentous Pleistia species has a limiting effect on the fertilizer release rate and delays the fertilizer release rate.

[0110] It can be seen from Comparative Example 9 that the fertilizer release rate gradually increases at the beginning, and finally is not much different from Example 2. It is speculated that this is due to the lack of an outer coating layer in the early stage and the incomplete awakening of the dormant bacterial layer. When the dormant bacterial layer awakens and reproduces in large quantities in the later stage, the bacteria limit the release rate of the fertilizer effect.

[0111] Samples of the finished fertilizers in Examples 1 to 4 and Comparative Examples 1 to 10 were taken and respectively put into packaging bags. After assembly, the bags were sealed and placed in a cool place for 45 days. The bags were then opened to check the status. The results are as follows:

[0112] In summary, the advantages of this solution are: first, the fertilizer release rate is greatly slowed down by combining the inner core, the attachment layer, the dormant bacteria layer and the outer coating layer, so that the fertilizer provided by the solution can be more durable and effective. Second, the granulation chamber 11 and the coating chamber 12 in the granulation equipment realize the dual functions of granulation and spraying, solving the problem of the single function of the existing high tower granulation device.

[0113] The present invention is not limited to the above-mentioned specific implementation modes. Various changes made by ordinary technicians in this field based on the above-mentioned concepts without creative work are all within the protection scope of the present invention.

Claims

1. A method for preparing a stable fertilizer, characterized in that: The steps include: Step 1, preparing the kernel; Weighing nitrogen fertilizer and sending the nitrogen fertilizer to a melting tank (5), heating the nitrogen fertilizer to a molten state in the melting tank (5), then sequentially adding crushed potassium fertilizer, phosphorus fertilizer, trace element fertilizer and nitrification inhibitor to the melting tank (5), stirring and mixing, and obtaining a molten mixed fertilizer; The molten mixed fertilizer is sent to the high-tower granulation device. The molten mixed fertilizer enters the high-tower granulation device through the rotating nozzle of the high-tower granulation device to form a droplet-shaped slurry. The slurry is cooled by the rising air flow during the descent process and the core is obtained after solidification. Step 2, spraying the adhesion layer; The polylactic acid, acetone, brown algae oligosaccharide, glycerol and starch are sequentially sent to a stirring kettle for stirring and mixing to obtain an adhesion base liquid, and the adhesion base liquid is sprayed onto the outer wall of the cooled inner core by a fluidized bed spraying method, and an adhesion layer is formed on the outer wall of the inner core after drying; Step three, applying bacteria; The microbial agent, humic acid microspheres, trehalose and deionized water are sequentially sent to a mixing kettle (22) for mixing to obtain a suspended bacterial liquid; starch and diatomaceous earth are then added to the suspended bacterial liquid to obtain a slurry; the slurry is sprayed onto the surface of the attachment layer, followed by low-temperature drying to form a dormant bacterial layer on the outer wall of the attachment layer; Step 4, coating the coating layer; Lignin, ether, carboxymethyl cellulose, modified starch, cross-linking agent and deionized water are sent to a reaction kettle (32) for stirring and mixing to obtain a coating solution, which is sprayed onto the outer wall of the dormant bacteria layer, cooled at low temperature to obtain an outer coating layer, and then an anti-caking agent is sprayed on the outer wall of the outer coating layer, and dried to obtain a finished fertilizer product.

2. The method for preparing the stable fertilizer according to claim 1, characterized in that: In step 1, the nitrogen fertilizer is urea, the potash fertilizer is potassium sulfate, and the phosphate fertilizer is calcium hydrogen phosphate; by weight, the nitrogen fertilizer is 25-35 parts, the phosphate fertilizer is 20-25 parts, the potash fertilizer is 12-20 parts, the trace elements are 8-15 parts, and the nitrification inhibitor is 5-10 parts.

3. The method for preparing the stable fertilizer according to claim 2, characterized in that: In terms of weight, in step one, the trace element fertilizer is composed of 10-20 parts of zinc chloride, 10-20 parts of magnesium sulfate, 10-20 parts of ferrous sulfate, 10-15 parts of calcium nitrate, 4-5 parts of manganese oxide and 15-20 parts of wood ash.

4. The method for preparing the stable fertilizer according to claim 3, characterized in that: In terms of weight, in step 1, the nitrification inhibitor is composed of 85-90 parts of DMPP and 10-15 parts of inositol peptide.

5. The method for preparing the stable fertilizer according to claim 1, characterized in that: In terms of weight, in step 2, the polylactic acid is 10-20 parts, the acetone is 12-22 parts, the brown algae oligosaccharide is 25-35 parts, the glycerol is 5-10 parts, and the starch is 8-15 parts.

6. The method for preparing the stable fertilizer according to claim 1, characterized in that: In terms of weight, in step three, the microbial agent is 30-40 parts, the humic acid microspheres are 15-20 parts, the trehalose is 10-15 parts, and the deionized water is 20-25 parts.

7. The method for preparing the stable fertilizer according to claim 6, characterized in that: In terms of weight, in step 3, the microbial agent is a mixture of 30-50 parts of filamentous Pleistilium, 10-15 parts of Bacillus subtilis, 5-10 parts of phosphate-solubilizing bacteria and 20-25 parts of nitrogen-fixing bacteria.

8. The method for preparing the stable fertilizer according to claim 1, characterized in that: In terms of weight, in step 4, lignin is 20-22 parts, ether is 25-28 parts, carboxymethyl cellulose is 15-20 parts, modified starch is 10-15 parts, cross-linking agent is 5-8 parts, and deionized water is 7-15 parts.

9. The method for preparing the stable fertilizer according to claim 8, characterized in that: In terms of weight, in step 4, the cross-linking agent is composed of a mixture of 30-40 parts of sulfur, 20-30 parts of trimethoxysilane and 10-30 parts of aluminum chloride; the anti-caking agent is composed of 20-30 parts of diatomaceous earth, 10-20 parts of sodium aluminosilicate, 10-15 parts of silicon dioxide and 30-35 parts of deionized water.

10. A granulation device for stable fertilizer production, characterized in that: The invention comprises a granulating mechanism (1), a first spraying mechanism (2), a second spraying mechanism (3) and a third spraying mechanism (4); a first drying kettle (21) is arranged between the first spraying mechanism (2) and the second spraying mechanism (3); a second drying kettle (31) is arranged between the second spraying mechanism (3) and the third spraying mechanism (4); the third spraying mechanism (4) is also connected to a third drying kettle (41) via a pipeline; the first spraying mechanism (2) is connected to a stirring kettle via a pipeline; the second spraying mechanism (3) is connected to a mixing kettle (22) via a pipeline; and the third spraying mechanism (4) is connected to a reaction kettle (32) via a pipeline; the granulating mechanism (1) comprises a granulating chamber (11) and a coating chamber (12); the coating chamber (12) is located at the bottom of the granulating chamber (11); a granulating head and a driving motor (112) are arranged at the top of the granulating chamber (11); the driving motor (112) is connected to the stirring kettle via a pipeline; 12) driving the granulation head to rotate, one end of the granulation head being rotatably connected to a feeding pipe (113), the end of the feeding pipe (113) being away from the granulation head being connected to a melting tank (5), an air inlet (114) being arranged on the side wall of the granulation chamber (11), the end of the air inlet (114) facing the granulation chamber (11) being covered with a filter screen (115); a plurality of coating nozzles (121) being installed on the side wall of the coating chamber (12), the coating nozzles (121) being arranged facing the granulation chamber (11), a material distribution ring tube (122) being arranged in the circumferential direction of the coating chamber (12), a material distribution pipe (123) being arranged between the coating nozzles (121) and the material distribution ring tube (122), a conveying pipe (124) being connected to the side wall of the material distribution ring tube (122), and the end of the conveying pipe (124) being away from the material distribution ring tube (122) being connected to a stirring kettle.

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