Calcium ammonium nitrate particles and granulation method

Abstract

The invention belongs to the technical field of chemical fertilizer production, and discloses calcium ammonium nitrate particles and a granulation method.The method comprises the steps of ingredient concentration, high tower granulation and finished product treatment, specifically, dilute nitric acid reacts with excessive limestone to generate a calcium nitrate solution, the calcium nitrate solution reacts with an ammonia source after being neutralized and filter-pressed, and a dilute calcium ammonium nitrate solution is prepared; the specific gravity and temperature of a specific concentrated solution are set; finished product granulation can be stably and continuously carried out; a unique water-cooling roller cooling process and a process for regulating and controlling the temperature of melt liquid through material returning circulation are adopted. The problems of particle breakage and scabbing caused by traditional cooling are avoided, the obtained particles are high in strength and do not cake or pulverize in a high-temperature and high-humidity environment, the continuous production requirement is met, and the long-standing process and product stability problem in the industry is solved.

Description

Technical Field

[0001] The present invention relates to a calcium ammonium nitrate granule and a granulation method, belonging to the technical field of chemical fertilizer production. Background Art

[0002] At present, the granular calcium ammonium nitrate (5Ca(NO3)2·NH4NO3·10H2O) produced by the "melt method" in high towers in China has lower particle strength compared with the products produced by the drum fluidized bed and fluidized bed spraying granulation methods. It is very easy to cause caking and pulverization of the particles, resulting in extremely unstable granular calcium ammonium nitrate products in high towers, which has become a difficult problem in the industry.

[0003] Under high tower granulation, the particle strength is low. One of the traditional cooling methods is drum air cooling. The drum air cooling contains scraping plates and is very easy to cause particle breakage; the second cooling method is a powder flowing water cooler. This device is a stationary device. Due to the low moisture absorption point of calcium ammonium nitrate, it is very easy to cause scar formation and blockage in the powder flowing water cooler due to the moisture absorption of the particles, resulting in the inability to continue production during the production process.

[0004] 3 At present, the granulation tank of the "melt method" granulation system in high towers in China adjusts the circulating water flow rate to meet the granulation temperature requirements. This method is very easy to cause scar formation on the coil in the mixing tank, resulting in a sharp decline in heat exchange efficiency and making the production process unable to continue. Production has to be carried out intermittently, which has become a difficult problem in the industry.

[0005] In view of the above problems faced in production, there is an urgent need for a method to improve the strength of granular calcium ammonium nitrate produced by high tower granulation and a device for continuous production, so that the granular calcium ammonium nitrate produced by high towers does not cake and meets the requirements of large-scale continuous production. Summary of the Invention

[0006] Aiming at the deficiencies of the above-mentioned prior art, the purpose of the present invention is to provide a granulation method and device for calcium ammonium nitrate granules. According to the implementation scheme of the present invention, the first scheme is provided as follows: A granulation method for calcium ammonium nitrate granules, comprising the following steps: S1. Batching and concentration: React dilute nitric acid with excessive limestone to generate a calcium nitrate solution. After neutralization and pressure filtration, react with an ammonia source and dilute nitric acid in a tubular reactor to generate a dilute calcium ammonium nitrate solution, and then concentrate the dilute calcium ammonium nitrate solution to a concentrated solution with a specific gravity of 1.86 - 1.96 g / cm³ and a temperature of 125°C; S2. High tower granulation: Cool the concentrated solution to 94 - 98°C, granulate it with a differential centrifugal granulator, control the inner rotation frequency at 23 Hz and the outer rotation frequency at 27 Hz, and obtain lower tower particles with a particle size of 1.5 - 3 mm; S3. Finished product treatment: The particles from the lower tower are dried in a fluidized bed and then subjected to primary screening. After screening out the particles outside the particle size threshold of the primary screening, they are cooled by a water-cooled drum and then subjected to secondary screening. The particles within the particle size threshold of the secondary screening are the finished products. The particles screened out by the primary screening and the secondary screening are the returned materials.

[0007] Further, the S1. Batching and concentration step includes: S11. Meter the dilute nitric acid with a concentration of 45%-50% and react it with excessive limestone. S12. Adjust the pH value of the crude calcium nitrate solution generated in the S11 step to 4-6 using lime or lime milk. S13. Remove the insoluble substances from the reactants with the pH reaching the process conditions in the S12 step to obtain a clear solution of calcium nitrate, with the specific gravity controlled at 1.4-1.55 g / cm³. S14. React the clear solution of calcium nitrate obtained in the S13 step with gaseous ammonia or ammonia water and dilute nitric acid to generate a dilute solution of calcium ammonium nitrate with a specific gravity of 1.5-1.6 g / cm³. S15. Concentrate the dilute solution of calcium ammonium nitrate obtained in the S14 step after pressure filtration to obtain a concentrated solution of calcium ammonium nitrate, with the temperature of the concentrated solution controlled at 125°C and the specific gravity at 1.86-1.96 g / cm³.

[0008] Further, in the S2. High tower granulation step includes: S21. Heat exchange and cool the concentrated solution of calcium ammonium nitrate obtained in the S1 step. After heat exchange, the temperature of the concentrated solution of calcium ammonium nitrate is controlled at 105°C. The tube side of the heat exchanger is the concentrated solution of calcium ammonium nitrate, and the shell side is the dilute solution of calcium ammonium nitrate. S22. Transport the temperature of the concentrated solution of calcium ammonium nitrate after heat exchange to the top-level tank in the granulation tower. The dilute solution of calcium ammonium nitrate on the shell side of the heat exchanger returns to the evaporator after heat exchange. Use an automatic regulating valve to control the circulating water volume in the coil of the first-level mixing tank and control the temperature of the first-level mixing tank at 100-105°C to cool the concentrated solution of calcium ammonium nitrate. S23. Mix the molten calcium ammonium nitrate solution cooled in the S22 step with the returned materials by overflow and enter the second-level tank, controlling the temperature of the mixture at 94-98°C.

[0009] Further, in the S2. High tower granulation step also includes: S24. Overflow the mixture obtained in the S23 step into an emulsifier to efficiently break and homogenize the uncompletely melted returned materials, and then enter a differential centrifugal granulator for granulation to obtain the lower tower particles of calcium ammonium nitrate. Granule size control: The proportion of granules between 1.5 - 2 mm is ≥ 70%, the proportion of granules between 2 - 3 mm is ≥ 15%, and the granule strength is 6 - 8 N; The wind speed in the granulation tower is controlled at 0.3 - 2 m / s.

[0010] Further, in S3, the finished product post - treatment step further includes: S31. Dry and cool the surface of the calcium ammonium nitrate lower - tower granules obtained in step S2 through a fluidized bed. The relative humidity of the incoming air is ≤ 20%, the temperature is 25°C. The fluidized - bed air inlet is equipped with a dehumidifying refrigerator and a superheater, which are adjusted according to climatic conditions. The fluidized - bed air outlet is equipped with a water - swirl dust collector. The water for water - swirl makeup comes from the process condensate of the evaporation part, and the concentrated liquid after washing returns to step S15 for concentration.

[0011] Further, in S3, the finished product post - treatment step further includes: S32. Perform primary screening on the granules at the fluidized - bed outlet in step S31. The particle - size threshold range for primary screening is 1.5 mm - 3 mm. The granules exceeding the particle - size threshold range are returned materials, and the returned materials are transported into the secondary tank. The screening equipment preferably uses a swing - type screening machine to reduce granule breakage. S33. Pass the screened granules through a water - cooled drum with a length of 10 - 40 m and a diameter of 1 m - 4 m. The residence time of the granules in the drum is not less than 10 minutes. The inside of the drum has a large - spiral non - scraping plate structure. The water - cooled drum uses desalted water at 20 - 32°C for heat exchange. S34. Further cool the screened granules in step S33 and enter the secondary screening through a bucket elevator. The particle - size threshold range for secondary screening is ≥ 1 mm. The finished products exceeding the particle - size threshold range are returned materials, and the returned materials are transported into the secondary tank. The granules meeting the set particle - size threshold for secondary screening are finished - product granules; S35. Direct the finished - product granules into the packaging silo, and then through packaging and palletizing, prepare spherical calcium ammonium nitrate granules with high strength, no broken grains, not easy to agglomerate, and good flowability.

[0012] Further, in the batching and concentration step, a granule - strength - regulating salt is added, and the addition amount is 0.5% - 3% of the mass of the calcium ammonium nitrate concentrate, forming a double - salt compound with higher granule strength and anti - caking property.

[0013] Further, the granule - strength - regulating salt is one or more of magnesium chloride, magnesium chloride hydrate, calcium chloride, calcium chloride hydrate, or potassium chloride.

[0014] According to the embodiments of the present invention, using the calcium ammonium nitrate granulation method in the first solution provided by the present invention, the second solution is provided as: The calcium ammonium nitrate particles prepared by the calcium ammonium nitrate particle granulation method described above have a particle strength ≥ 35 N and do not cake or powder during production in high-temperature and high-humidity seasons.

[0015] Furthermore, the calcium ammonium nitrate particles contain particle strength regulating salt ions, and the particle strength regulating salt ions are one or more of magnesium ions, potassium ions or calcium ions.

[0016] Compared with the prior art, the beneficial effects of the technical solution provided by this application.

[0017] 1. It provides the best process control parameters for the production of granular calcium ammonium nitrate by the "melt method" in high towers; 2. By adding fillers magnesium chloride, calcium chloride, and potassium chloride at the production batching end, the granular calcium ammonium nitrate produced by the "melt method" in high towers forms a double salt compound with the fillers, stabilizing the crystal system change of calcium ammonium nitrate during storage. Moreover, after adding the fillers, the product strength is significantly improved, the product is not easy to cake and powder, and continuous production can be carried out.

[0018] 3. The recycled material screened from the finished product is used for material recovery and at the same time as a cooling medium to cool the calcium ammonium nitrate concentrate, which can effectively control the cooling effect and does not introduce impurities.

[0019] 4. When the traditional "air-cooled drum" and powder flow do not meet the production requirements, it is a first in the industry to innovatively add a longer water-cooled drum in the finished product cooling treatment part. While reducing the product breakage rate, it increases the residence time of the particles in the water-cooled drum, enabling the particles to complete the product cooling process, the crystal system change process, and the stabilization process of the double salt ionic bond in the water-cooled drum. The packaged product is more stable and does not cake or powder.

[0020] 5. The granulation system cooling system has explored the best energy-saving cooling equipment combination method and index range according to the product characteristics, enabling the smooth implementation of the entire granulation process. The above innovative changes to the traditional cooling and granulation processes are a first in the industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0022] Among them: Figure 1 is the flow chart of the production process in one embodiment; Figure 2Appearance diagram of calcium ammonium nitrate particles just out of the lower tower in an embodiment; Figure 3 Appearance diagram of calcium ammonium nitrate particles during packaging at the outlet of the water-cooled drum in an embodiment. Specific implementation manner

[0023] In order to enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the scope of protection of this application.

[0024] This application has prepared calcium ammonium nitrate particles with high particle strength, and the particle strength ≥ 35 N, and they do not caking or powdering during production in high-temperature and high-humidity seasons.

[0025] The prepared calcium ammonium nitrate particles contain particle strength regulating salt ions, and the particle strength regulating salt ions are one or more of magnesium ions, potassium ions or calcium ions.

[0026] The granulation method of this kind of calcium ammonium nitrate particles with high particle strength is described as follows by way of examples.

[0027] Example 1 S1. Batching and concentration: S11. Dilute nitric acid with a concentration of 45%-50% is metered through a flow meter and enters the acidolysis tower from the bottom to react with the excessive limestone in the acidolysis tower; S12. The crude calcium nitrate solution generated in step S11 overflows from the overflow port of the acidolysis tower into the neutralization tank, and lime or lime milk is used to adjust the pH value to 4-6; S13. The reactants with the pH reaching the process conditions in step S12 are pumped into a filter press to filter out insoluble substances, and a dilute calcium nitrate clear solution is obtained, with the specific gravity controlled at 1.4-1.55 g / cm³; S14. The dilute calcium nitrate solution obtained in step S13, gaseous ammonia or ammonia water, and dilute nitric acid are integrally reacted in a tubular reactor to generate a dilute calcium ammonium nitrate solution with a specific gravity of 1.5-1.6 g / cm³; among them, the calcium nitrate concentration accounts for 72-79%, and the ammonium nitrate accounts for 5-9%.

[0028] S15. The dilute calcium ammonium nitrate solution obtained in step S14 is concentrated through a multi-effect evaporation and concentration system after secondary filtration to obtain a concentrated calcium ammonium nitrate solution, and the temperature of the concentrated solution is controlled at 125 °C; the specific gravity is 1.86-1.96 g / cm³.

[0029] S2. High tower granulation: S21. The calcium ammonium nitrate concentrate obtained in step S1 is transported through a high-lift pump and exchanges heat with a heat exchanger installed on the pump outlet pipeline. After heat exchange, the temperature of the calcium ammonium nitrate concentrate is controlled at 105°C. The tube shell in the heat exchanger contains the calcium ammonium nitrate concentrate, and the shell side contains the dilute calcium ammonium nitrate solution. S22. The calcium ammonium nitrate concentrate after heat exchange is transported into the first-stage tank at the top of the granulation tower. The dilute calcium ammonium nitrate solution on the shell side of the heat exchanger returns to the evaporator after heat exchange. An automatic regulating valve is used to control the circulating water volume in the coil of the first-stage mixing tank, and the temperature of the first-stage mixing tank is controlled at 100 - 105°C to cool the calcium ammonium nitrate concentrate. S23. The cooled molten calcium ammonium nitrate solution in step S22 enters the second-stage tank through overflow and is mixed with the returned material. The temperature of the mixture is controlled at 94 - 98°C. The returned material is screened according to a set threshold range, and the screening particles exceeding the particle size threshold range are used. S24. The mixture obtained in step S23 enters the emulsifier through the overflow of the second-stage tank, where the uncompletely melted returned material is efficiently broken and homogenized, and then enters the differential centrifugal granulator for granulation to obtain the calcium ammonium nitrate particles at the lower tower.

[0030] Granulator parameters: the inner rotation frequency is 23 HZ, the outer rotation frequency is 27 HZ. Granulation particle size control: the proportion of particles between 1.5 - 2 mm is ≥70%, the proportion of particles between 2 - 3 mm is ≥15%, and the particle strength is 6 - 8 N. The wind speed in the granulation tower is controlled at 0.3 - 2 m / s. The height of the granulation tower is selected between 20 m and 120 m according to the product particle size and production capacity, and the tower diameter is selected between 12 m and 24 m according to the production capacity and wind speed.

[0031] It should be noted that 1. When the calcium ammonium nitrate concentrate is cooled to 100 - 105°C, the viscosity of the feed liquid will increase sharply. Controlling the evaporator temperature at about 125°C and setting the heat exchanger on the pump outlet pipeline avoid the problems of reduced evaporation effect caused by high feed liquid viscosity and abnormal pumping of the pump.

[0032] 2. The returned material enters the second-stage tank, and the granulation temperature of the material is adjusted through the mixing of the returned material, avoiding the problem of continuous production interruption caused by the scaling of the heat exchange coil due to the cooling of the second-stage tank by circulating water. It changes the traditional melt granulation process, realizes good process control and cost savings, and has prominent economic benefits.

[0033] 3. Material recycling is carried out, and at the same time, as a cooling medium, it cools the calcium ammonium nitrate concentrate. It can effectively control the cooling effect and does not introduce impurities. Because the low-temperature returned material can be evenly mixed with the calcium ammonium nitrate concentrate according to the proportion and dosage, the cooling is uniform, and the temperature gradient of the calcium ammonium nitrate concentrate will not be caused by the cooling method of the cooling water pipeline.

[0034] S3. Post-treatment of finished products: S31. Lift the calcium ammonium nitrate lower tower particles obtained in step S2 into the fluidized bed through a bucket elevator, and further dry and cool the "moisture" on the surface of the calcium ammonium nitrate lower tower particles through the fluidized bed. The air inlet of the fluidized bed is equipped with a dehumidifying chiller and a superheater. After being treated by the dehumidifier and the superheater, the relative humidity of the incoming air is ≤20%, and the temperature is 25°C. The air outlet of the fluidized bed is equipped with a water cyclone dust collector. The water for the water cyclone makeup comes from the process condensate of the evaporation part, and the concentrated liquid after washing is returned to step S15 for concentration; S32. Perform primary screening on the particles at the outlet of the fluidized bed in step S31. The set particle size threshold range for the primary screening particles is 1.5 mm - 3 mm. The particles exceeding the particle size threshold range are returned materials, and the returned materials are transported into the secondary tank. The screening equipment preferably uses a swing screening machine to reduce particle breakage. S33. Pass the screened particles through a water-cooled drum with a length of 10 - 40 m and a diameter of 1 m - 4 m. The residence time of the particles in the drum is not less than 10 minutes. The inside of the drum has a large spiral structure without a lifter. The water for the water-cooled drum uses desalted water with a temperature of 20 - 32°C for heat exchange; It should be noted that the specific size of the drum can be selected according to the production capacity and residence time.

[0035] S34. Perform secondary screening on the screened particles further cooled in step S33 through a bucket elevator. The set particle size threshold range for the secondary screening particles is ≥1 mm. The finished products exceeding the particle size threshold range are returned materials, and the returned materials are transported into the secondary tank. The particles meeting the set particle size threshold of the secondary screening are finished product particles; S35. Direct the finished product particles into the packaging bin, and then through packaging and palletizing, spherical calcium ammonium nitrate particles with high strength, no broken particles, not easy to agglomerate, and good flowability are prepared.

[0036] The calcium ammonium nitrate particles obtained in this example can maintain non-caking and non-pulverization for the products produced throughout the year in autumn and winter seasons and in the dry northern regions; however, they are prone to slight caking in the high-temperature and high-humidity seasons in summer or when the number of palletized layers exceeds 20 layers.

[0037] The equipment and process used in other examples are the same as those in Example 1, and the differences in specific control parameters are listed in each example.

[0038] Example 2: In step S15, the specific gravity of the calcium ammonium nitrate concentrated solution is ≤1.85 g / cm³, and other process parameters remain unchanged; The product has low strength and is prone to caking and pulverization.

[0039] Example 3: In step S15, the specific gravity of the calcium ammonium nitrate concentrate is > 1.96 g / cm³, and other process parameters remain unchanged; The product has high strength, but the product cakes and pulverizes due to dehydration.

[0040] Example 4: In the dilute calcium ammonium nitrate solution obtained in step S14, magnesium chloride or magnesium chloride hydrate is added, stirred evenly, and then enters the multi-effect concentration evaporation system; the addition amount of magnesium chloride is 0.5 - 3% of the mass concentration of the calcium ammonium nitrate concentrate; In step S15, the calcium ammonium nitrate concentrate added with magnesium chloride or magnesium chloride hydrate has a temperature of 125 °C and a specific gravity of 1.86 - 1.96 g / cm³.

[0041] The product is completely water-soluble and meets the requirements of calcium ammonium nitrate in NY / T 2269-2020 "Calcium Ammonium Nitrate for Agricultural Use and Its Application Regulations".

[0042] The stacking layer number exceeds 20 layers. It does not cake and pulverize during production in high-temperature and high-humidity seasons in summer, has high strength, and can be continuously produced.

[0043] Example 5: In the dilute calcium ammonium nitrate solution obtained in step S14, calcium chloride or calcium chloride hydrate is added, stirred evenly, and then enters the multi-effect concentration evaporation system; the addition amount of calcium chloride is 0.5 - 3% of the mass concentration of the calcium ammonium nitrate concentrate; In step S15, the calcium ammonium nitrate concentrate added with calcium chloride or calcium chloride hydrate has a temperature of 125 °C and a specific gravity of 1.86 - 1.96 g / cm³.

[0044] The product is completely water-soluble and meets the requirements of calcium ammonium nitrate in NY / T 2269-2020 "Calcium Ammonium Nitrate for Agricultural Use and Its Application Regulations".

[0045] The stacking layer number exceeds 20 layers. It does not cake and pulverize during production in high-temperature and high-humidity seasons in summer, has high strength, and can be continuously produced.

[0046] Example 6: In the dilute calcium ammonium nitrate solution obtained in step S14, potassium chloride is added, stirred evenly, and then enters the multi-effect concentration evaporation system; the addition amount of magnesium chloride is 0.5 - 3% of the mass concentration of the calcium ammonium nitrate concentrate; In step S15, the calcium ammonium nitrate concentrate added with potassium chloride has a temperature of 125 °C and a specific gravity of 1.86 - 1.96 g / cm³.

[0047] The product is completely water-soluble and meets the requirements of calcium ammonium nitrate in NY / T 2269-2020 "Calcium Ammonium Nitrate for Agricultural Use and Its Application Regulations".

[0048] The number of stacking layers exceeds 20 layers. During production in high-temperature and high-humidity seasons in summer, it does not caking or powdering, has high strength, and can be continuously produced.

[0049] Examples with other ratios are not listed one by one. In other examples, in the dilute calcium ammonium nitrate solution obtained in step S14, one or more of magnesium chloride or magnesium chloride hydrate, calcium chloride or calcium chloride hydrate, and potassium chloride are added, and the total addition amount is 0.5%-3% of the mass concentration of the calcium ammonium nitrate concentrate; after the addition, the temperature of the calcium ammonium nitrate concentrate is 125°C, and the specific gravity is 1.86-1.96 g / cm³; The finished products obtained in other examples are all completely water-soluble and meet the requirements of the calcium ammonium nitrate for agricultural use and its application regulations (NY / T 2269-2020).

[0050] The number of stacking layers exceeds 20 layers. During production in high-temperature and high-humidity seasons in summer, it does not caking or powdering, has high strength, and can be continuously produced.

[0051] The analysis and detection results of the calcium ammonium nitrate for agricultural use synthesized in Examples 1-6 are as follows: The technical features of the above examples can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above examples are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0052] The above-described examples only represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method for granulating calcium ammonium nitrate particles, characterized in that: The steps include: S1. Ingredient concentration: react dilute nitric acid with excess limestone to generate calcium nitrate solution, which is then reacted with ammonia source and dilute nitric acid to generate dilute calcium ammonium nitrate solution after neutralization and filter pressing, and then the dilute calcium ammonium nitrate solution is reduced to a concentrated solution with a specific gravity of 1.86-1.96g / cm³ and a temperature of 125°C; S2, high tower granulation: the concentrated liquid is cooled to 94-98°C, and granulated by a differential centrifugal granulator, with the internal rotation frequency at 23Hz and the external rotation frequency at 27Hz, to obtain lower tower particles with a particle size of 1.5-3mm; S3, finished product processing: the particles in the lower tower are dried in a fluidized bed and then screened in the first stage. After the particles outside the particle size threshold of the first stage are screened out, they are cooled by a water-cooled drum and screened in the second stage. The particles within the particle size threshold of the second stage are finished products; The particles removed by the primary and secondary screening are returned materials.

2. The method for granulating calcium ammonium nitrate particles according to claim 1, characterized in that: The step of S1, ingredient concentration, comprises: S11, measuring 45%-50% dilute nitric acid and reacting it with excess limestone; S12, adjusting the pH value of the crude calcium nitrate solution generated by the reaction in step S11 to 4-6 using lime or lime milk; S13, removing insoluble matter from the reactants whose pH reaches the process conditions in step S12 to obtain a dilute calcium nitrate clear solution, with a specific gravity controlled at 1.4-1.55 g / cm³; S14, reacting the diluted calcium nitrate solution obtained in step S13 with gaseous ammonia or ammonia water and dilute nitric acid to generate a dilute calcium ammonium nitrate solution with a specific gravity of 1.5-1.6 g / cm³; S15. The dilute calcium ammonium nitrate solution obtained in step S14 is filtered and concentrated to obtain a calcium ammonium nitrate concentrated solution, the temperature of the concentrated solution is controlled to be 125° C. The specific gravity is 1.86-1.96 g / cm³, wherein the concentration of calcium nitrate accounts for 72-79%, and the proportion of ammonium nitrate is between 5-9%.

3. The method for granulating calcium ammonium nitrate particles according to claim 1, characterized in that: In S2, the high tower granulation step includes: S21, cooling the calcium ammonium nitrate concentrate obtained in step S1 by heat exchange, wherein the temperature of the calcium ammonium nitrate concentrate is controlled at 105° C., the shell and tube in the heat exchanger are the calcium ammonium nitrate concentrate, and the shell side is the dilute calcium ammonium nitrate liquid; S22, the concentrated calcium ammonium nitrate liquid after heat exchange is transported to the first tank at the top of the granulation tower, and the shell-side diluted calcium ammonium nitrate liquid enters the evaporator after heat exchange; the circulating water volume in the coil of the first mixing tank is controlled by an automatic regulating valve, and the temperature of the first mixing tank is controlled to 100-105°C to cool the concentrated calcium ammonium nitrate liquid; S23, the calcium ammonium nitrate melt cooled in step S22 is mixed with the return material through overflow and enters the secondary tank, and the temperature of the mixture is controlled at 94-98°C.

4. The method for granulating calcium ammonium nitrate particles according to claim 3, characterized in that: In S2, the high tower granulation step also includes: S24, the mixture obtained in step S23 is overflowed into an emulsifier through a secondary tank to efficiently break up and homogenize the returned material that is not completely melted, and then enters a differential centrifugal granulator for granulation to obtain calcium ammonium nitrate lower tower particles; Granulation particle size control: particles between 1.5-2mm account for ≥70%, particles between 2-3mm account for ≥15%, particle strength is 6-8N; granulation tower wind speed control is 0.3-2m / s.

5. The method for granulating calcium ammonium nitrate particles according to claim 1, characterized in that: In S3, the finished product post-processing step also includes: S31. The calcium ammonium nitrate lower tower particles obtained in step S2 are blown dry and cooled on the surface of the calcium ammonium nitrate lower tower particles through a fluidized bed. The relative humidity of the inlet air is ≤20%, and the temperature is 25°C. The air outlet of the fluidized bed is equipped with a water cyclone dust collector. The water replenishment of the water cyclone comes from the condensate of the evaporation process. The concentrated liquid after washing is returned to step S15 for concentration.

6. The method for granulating calcium ammonium nitrate particles according to claim 1, characterized in that: In S3, the finished product post-processing step also includes: S32, the particles at the outlet of the fluidized bed in step S31 are subjected to primary screening, the primary screening particle size threshold range is 1.5mm-3mm, the particles exceeding the particle size threshold range are returned materials, and the returned materials are transported to the secondary tank. The screening equipment preferably uses a swing screening machine to reduce particle breakage. S33, pass the screened particles through a water-cooled drum with a length of 10-40m and a diameter of 1m-4m, ensuring that the particles stay in the drum for no less than 10 minutes. The drum has a large spiral structure without a lifting plate, and the water in the water-cooled drum uses desalted water at 20-32℃ for heat exchange; S34, the screened particles further cooled in step S33 are sent to the secondary screening through a bucket elevator. The threshold range of the secondary screening particle size is ≥1mm. The finished products exceeding the particle size threshold range are returned materials, which are transported to the secondary tank. The particles that meet the set particle size threshold of the secondary screening particles are finished particles; S35. The finished granules are directly put into the packaging silo, and then packaged and stacked to obtain granular calcium ammonium nitrate with high strength, no broken particles, not easy to agglomerate, spherical shape and good fluidity.

7. The method for granulating calcium ammonium nitrate particles according to any one of claims 1 to 6, characterized in that: In the step of batching and concentration, particle strength adjusting salt is added in an amount of 0.5%-3% of the mass of the calcium ammonium nitrate concentrate to form a complex salt compound with higher particle strength and anti-caking properties.

8. The method for granulating calcium ammonium nitrate particles according to claim 7, characterized in that: The particle strength adjusting salt is one or more of magnesium chloride, magnesium chloride hydrate, calcium chloride, calcium chloride hydrate or potassium chloride.

9. A calcium ammonium nitrate granule prepared by the calcium ammonium nitrate granule granulation method according to any one of claims 1 to 6 and 8, characterized in that: The particle strength is ≥35N, and it will not agglomerate or powderize during production in high temperature and high humidity seasons.

10. The calcium ammonium nitrate granules according to claim 9, characterized in that: The calcium ammonium nitrate particles contain particle strength adjusting salt ions, and the particle strength adjusting salt ions are one or more of magnesium ions, potassium ions or calcium ions.

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