A method for producing spherical calcium ammonium nitrate particles by a prilling tower

Abstract

The present application relates to the technical field of calcium ammonium nitrate, and particularly relates to a method for producing spherical calcium ammonium nitrate particles by high-tower granulation. The present application discloses a method for producing spherical calcium ammonium nitrate particles by high-tower granulation, which comprises the following steps: ingredient mixing, in which calcium ammonium nitrate containing trace amounts of magnesium is delivered into a first mixing tank at the top of a granulation tower, and calcium ammonium nitrate return material is subjected to melt mixing; after the melt mixing is completed, overflow is performed to enter a second mixing tank, and melt mixing is performed again to obtain a melt liquid; granulation and screening, in which the melt liquid is subjected to granulation by overflow into a granulator, and after cooling and screening, calcium ammonium nitrate products are obtained. The method disclosed in the present application adopts a melt method for high-tower melt granulation, and compared with a traditional spray method for granulation, the method has lower energy consumption, very low dust emission, and the calcium ammonium nitrate products have round particles, no irregular particles, and a particle size of 2-4 mm, which meets the requirements of seed and fertilizer intercropping and mechanized large-scale machine sowing.

Description

Technical Field

[0001] This invention relates to the technical field of calcium ammonium nitrate, and in particular to a method for producing spherical calcium ammonium nitrate granules by high-tower granulation. Background Technology

[0002] Currently, the domestic production of granular calcium ammonium nitrate (5Ca(NO3)2·NH4NO3·10H2O) mainly adopts disc, drum fluidized bed, and fluidized bed spraying granulation methods. However, disc and drum fluidized bed granulation methods have relatively high energy consumption and generate a large amount of dust during the granulation process, requiring the configuration of dust recovery devices with even higher energy consumption for treatment. Therefore, the production cost is high, the environmental pressure is great, and the market competitiveness is weak.

[0003] The granules produced by spray granulation have uneven surfaces and irregular shapes, which can easily clog the fertilizer application holes in machine seeders. This makes it impossible to use machine seeders for large-scale continuous fertilizer application and sowing, which does not meet the requirements of promoting simultaneous sowing of seeds and fertilizers and large-scale mechanized planting. It also seriously affects the use of ammonium calcium nitrate fertilizer.

[0004] Therefore, it is necessary to propose a method for producing spherical calcium ammonium nitrate particles by high-tower granulation, so as to produce spherical calcium ammonium nitrate particles with rounded surfaces to meet current market demand. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention provides a method for producing spherical calcium ammonium nitrate granules by high-tower granulation. The method uses a "melt method" high-tower melting granulation, which has lower energy consumption and dust emissions compared to the traditional "spraying method" granulation. Moreover, the calcium ammonium nitrate granules are round and free of irregular particles, with a particle size between 2-4 mm, meeting the requirements for simultaneous sowing of seeds and fertilizers and large-scale mechanized sowing.

[0006] The technical solution adopted by this invention to solve its technical problem is:

[0007] A method for producing spherical calcium ammonium nitrate granules by high-tower granulation includes the following steps:

[0008] S1. Ingredients

[0009] Prepare a mixture of ammonium calcium nitrate containing trace amounts of magnesium;

[0010] Alternatively, prepare a magnesium-free ammonium calcium nitrate mixture;

[0011] S2. Mixing

[0012] The calcium ammonium nitrate mixture containing trace amounts of magnesium is fed into the primary mixing tank at the top of the granulation tower and melt-mixed with the calcium ammonium nitrate return material. After the melt-mixing is completed, it overflows into the secondary mixing tank for further melt-mixing to obtain a molten liquid.

[0013] Alternatively, magnesium-free ammonium calcium nitrate mixture can be transported to the primary mixing tank at the top of the granulation tower for melt mixing with magnesium nitrate or calcium magnesium nitrate; after melt mixing, it can overflow into the secondary mixing tank for melt mixing with the returned ammonium calcium nitrate to obtain molten liquid.

[0014] S3. Granulation and sieving

[0015] The molten liquid overflows into the granulator for granulation. After cooling and sieving, the calcium ammonium nitrate product is obtained.

[0016] Furthermore, the specific gravity of the ammonium calcium nitrate mixture containing trace amounts of magnesium is 1.82-1.83 g / cm³. 3 The mass percentage of elemental magnesium is 0.1-0.5%.

[0017] Furthermore, in step S1, the preparation process of the calcium ammonium nitrate mixture containing trace amounts of magnesium includes: adding a calcium magnesium solution obtained by decompression and filtration using dolomite and nitric acid, or a magnesium nitrate solution obtained by reacting nitric acid and lightly calcined magnesium oxide, to a calcium nitrate solution in proportion; evaporating and concentrating the solution using a triple-effect evaporator to prepare a solution with a magnesium content of 0.1-0.5% and a specific gravity of 1.82-1.83 g / cm³. 3 A mixture of ammonium nitrate and calcium containing trace amounts of magnesium.

[0018] Furthermore, in step S1, the specific gravity of the magnesium-free ammonium calcium nitrate mixture is 1.82-1.83 g / cm³. 3 .

[0019] Furthermore, in step S1, the process of preparing the magnesium-free ammonium calcium nitrate mixture is as follows:

[0020] After limestone and nitric acid react in an acid hydrolysis tank, an acid hydrolysis solution is obtained. The pH of the acid hydrolysis solution is adjusted to 5-6, and then filtered through a filter press to obtain a clear calcium nitrate solution. Ammonium nitrate solution is then added to the clear calcium nitrate solution to obtain a mixed clear solution.

[0021] The mixed clear liquid was concentrated by evaporation using a triple-effect evaporator to prepare a solution with a specific gravity of 1.82-1.83 g / cm³. 3 Magnesium-free ammonium calcium nitrate mixture.

[0022] Furthermore, in step S2, the temperature of the secondary mixing tank is controlled at 90°C.

[0023] Furthermore, in step S2, the calcium magnesium nitrate mixture is conveyed to the first-stage mixing tank at the top of the granulation tower and melt-mixed with magnesium nitrate or calcium magnesium nitrate to obtain a molten mixture with a magnesium weight content of 0.1-0.5%.

[0024] Furthermore, the temperature during evaporation and concentration in the triple-effect evaporator is 120-130℃.

[0025] Furthermore, in step S3, the product temperature in the granulation tower is about 65°C. After being cooled by air in a vibrating fluidized bed, it is then screened by a drum screen to obtain calcium ammonium nitrate product with a particle size of 2-4 mm.

[0026] The beneficial effects of this invention are as follows:

[0027] 1. The method described in this application, by adding magnesium nitrate or finished calcium magnesium nitrate solution to the molten calcium ammonium nitrate solution, or by adding calcium magnesium solution or magnesium nitrate solution to the dilute calcium ammonium nitrate solution, controls the elemental magnesium content in the calcium ammonium nitrate (5Ca(NO3)2·NH4NO3·10H2O) product to between 0.1% and 0.5%. While meeting the national standard for calcium ammonium nitrate NY / T2269-2020 "Calcium Ammonium Nitrate for Agricultural Use", the granulated calcium ammonium nitrate particles are more rounded and stronger, less prone to clumping and pulverization, and suitable for large-scale production.

[0028] 2. The method described in this application adopts the "melt method" high-tower melting granulation method, which has lower energy consumption and very low dust emission compared with the traditional "spraying method" granulation method. Moreover, the ammonium calcium nitrate product has round particles without irregular particles, and the product particle size is between 2-4mm, which meets the requirements of simultaneous sowing of seeds and fertilizers and large-scale mechanized sowing. Attached Figure Description

[0029] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0030] Figure 1 This is a process flow diagram of the method described in this application;

[0031] Figure 2 This is a photograph of the calcium ammonium nitrate product prepared according to Example 1 or Example 2 of this application.

[0032] Figure 3 This is a physical image of the calcium ammonium nitrate product prepared by the spray granulation method of this application (Comparative Example 1);

[0033] Figure 4 This is a photograph of the calcium ammonium nitrate product prepared in Example 3 of this application. Detailed Implementation

[0034] As used herein, “and / or” includes all combinations of any and one or more of the associated listed items. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used herein, the singular forms “a,” “an,” “an,” and “the” are also intended to include the plural forms unless the context clearly indicates otherwise. Further understanding is needed; when used in this specification, “comprising” designates the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or combinations thereof.

[0035] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Further understanding is that terms, such as those defined in common dictionaries, are interpreted in accordance with their meaning in the context of the relevant field and are not idealized or overly formal, unless expressly defined herein.

[0036] The exemplary invention described herein may suitably omit any one or more limiting elements, which are not specifically disclosed herein. Therefore, terms such as “comprising,” “including,” “containing,” etc., should be interpreted broadly and non-limitingly. Furthermore, the terminology used herein is for descriptive purposes without limitation, and it is unintentional to use terms that do not include any equivalent characteristics, but only to describe a portion of their characteristics; however, various modifications are possible within the scope of the invention according to the claims. Therefore, while the invention has been specifically disclosed through preferred embodiments and optional features, variations of the invention embodied by the modifications disclosed herein may be noted by those skilled in the art, and such modifications and variations are considered to be within the scope of the invention.

[0037] All raw materials or reagents used in the embodiments and comparative examples of this invention were purchased from mainstream manufacturers on the market. Those without specified manufacturers or concentrations are all analytical grade raw materials or reagents that are routinely available. There are no particular restrictions as long as they achieve the expected effect. The magnetic stirrers and other instruments and equipment used in this embodiment were all purchased from major manufacturers on the market. There are no particular limitations as long as they achieve the expected effect. Where specific techniques or conditions are not specified in this embodiment, they should be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions.

[0038] To provide spherical calcium ammonium nitrate granules, this application provides a method for producing spherical calcium ammonium nitrate granules by high-tower granulation, comprising the following steps:

[0039] S1. Ingredients

[0040] By adding a calcium magnesium solution (after decompression and filtration using dolomite and nitric acid) or a magnesium nitrate solution (after reaction of nitric acid and lightly calcined magnesium oxide) to a calcium nitrate solution in a specific ratio, and then evaporating and concentrating the solution using a triple-effect evaporator, a solution with a mass ratio of 0.1-0.5% and a specific gravity of 1.82-1.83 g / cm³ is prepared. 3 A mixture of ammonium nitrate and calcium containing trace amounts of magnesium;

[0041] S2. Mixing

[0042] The calcium ammonium nitrate mixture containing trace amounts of magnesium from step S1 is fed to the primary mixing tank at the top of the granulation tower and melted with the calcium ammonium nitrate return material. After melting, it overflows into the secondary mixing tank for further mixing to obtain molten liquid. The final granulation temperature is controlled by controlling the circulating water volume in the coil of the secondary mixing tank.

[0043] Alternatively, magnesium-free calcium ammonium nitrate mixture can be transported to the first-stage mixing tank at the top of the granulation tower, where it can be further mixed and melted with magnesium nitrate hexahydrate, finished calcium magnesium nitrate, and the calcium ammonium nitrate return material from the finished product screening. After overflow, it enters the second-stage mixing tank to obtain molten liquid. The final granulation temperature is controlled by controlling the circulating water volume in the coil of the second-stage mixing tank.

[0044] The process for preparing magnesium-free ammonium calcium nitrate mixture is as follows: limestone and nitric acid are reacted in an acid hydrolysis tank to obtain an acid hydrolysis solution; the pH of the acid hydrolysis solution is adjusted to 5-6, and then filtered through a filter press to obtain a clear calcium nitrate solution; ammonium nitrate solution is then added to the clear calcium nitrate solution to obtain a mixed clear solution; the mixed clear solution is evaporated and concentrated using a triple-effect evaporator to prepare a solution with a specific gravity of 1.82-1.83 g / cm³. 3 Magnesium-free ammonium calcium nitrate mixture.

[0045] S3. Granulation and sieving

[0046] The molten liquid overflows into the granulator for granulation. After cooling and sieving, the calcium ammonium nitrate product is obtained.

[0047] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to embodiments. The content mentioned in the embodiments is not intended to limit the present invention.

[0048] Example 1

[0049] A method for producing spherical calcium ammonium nitrate granules by high-tower granulation includes the following steps:

[0050] After reacting limestone and 45% nitric acid in an acid hydrolysis tank, the pH of the hydrolysis solution is adjusted to between 5 and 6. The solution is then filtered through a filter press to obtain a calcium nitrate solution with a concentration of approximately 45%. Dolomite and nitric acid hydrolysis filtered calcium magnesium solution, or magnesium nitrate solution obtained from the reaction of nitric acid and lightly calcined magnesium oxide, are added to this calcium nitrate solution in a specific ratio. The mixture is then concentrated using a triple-effect evaporator until the final specific gravity of the material is 1.82-1.83 g / cm³. 3 A mixture of ammonium calcium nitrate containing trace amounts of magnesium, with an elemental magnesium content of 0.1-0.5% and a temperature of 120-130℃;

[0051] The calcium ammonium nitrate mixture containing trace amounts of magnesium is then pumped to the primary mixing tank at the top of the granulation tower via a melting pump. It is further mixed and melted with the calcium ammonium nitrate return material from the finished product screening and then overflows into the secondary mixing tank. The circulating water volume in the coil of the secondary mixing tank is controlled by an automatic regulating valve, and the temperature of the secondary mixing tank is finally controlled at 90°C. The water then overflows into the differential granulator for granulation.

[0052] The product temperature at the granulation tower is approximately 65℃. After being cooled by air in a vibrating fluidized bed, the temperature is approximately 45℃. Then, it is screened by a two-stage drum screen to control the particle size. 2 - 4 Between mm in size, the finished product is conveyed by a bucket elevator to a fully automated packaging and palletizing line, resulting in rounded, fully water-soluble ammonium nitrate calcium products that meet the requirements of NY / T2269-2020 "Agricultural Ammonium Calcium Nitrate and Usage Regulations" standard; the product appearance and particle size are as follows... Figure 2 As shown.

[0053] Example 2

[0054] A method for producing spherical calcium ammonium nitrate granules by high-tower granulation includes the following steps:

[0055] After reacting limestone and 45% nitric acid in an acid hydrolysis tank, the pH of the hydrolysate is adjusted to between 5 and 6. The solution is then filtered through a filter press to obtain a calcium nitrate solution with a concentration of approximately 45%. Ammonium nitrate solution is then added to the calcium nitrate solution in a specific ratio, and the mixture is further concentrated using a triple-effect evaporator to a final material specific gravity of 1.82-1.83 g / cm³. 3 Magnesium-free ammonium calcium nitrate mixture at a temperature of 120-130℃.

[0056] Magnesium-free ammonium calcium nitrate mixture is pumped to the primary mixing tank at the top of the granulation tower via a melt pump. In this tank, finished magnesium nitrate hexahydrate or finished calcium magnesium nitrate is added, ultimately controlling the elemental magnesium content in the molten liquid to between 0.1% and 0.5%. This mixture is then further mixed and melted with the returned ammonium calcium nitrate material from the finished product sieve, and overflows into the secondary mixing tank. An automatic regulating valve controls the circulating water volume in the secondary mixing tank coils, ultimately maintaining the temperature of the secondary mixing tank at 90°C. The overflow then enters a differential granulator for granulation.

[0057] The product temperature at the granulation tower is approximately 65℃. After being cooled by air in a vibrating fluidized bed, the temperature is approximately 45℃. Then, it undergoes two-stage drum screening to control the particle size. 2 - 4 The finished product, after passing through a bucket elevator, is sent to a fully automated packaging and palletizing line, resulting in a rounded, fully water-soluble ammonium nitrate calcium product that meets the requirements of NY / T2269-2020 "Agricultural Ammonium Calcium Nitrate and Usage Specifications". The appearance and particle size of the ammonium nitrate calcium product are shown below. Figure 2 As shown.

[0058] Example 3

[0059] A method for producing spherical calcium ammonium nitrate granules by high-tower granulation includes the following steps:

[0060] Magnesium nitrate or calcium magnesium nitrate was not added to the dilute solution or molten calcium ammonium nitrate to adjust the magnesium content. All other operating parameters and procedures were consistent with Example 1. The resulting product particles were not round, had a strength of 20N, and were prone to agglomeration and pulverization. The appearance and particle size of the calcium ammonium nitrate product are shown below. Figure 4 As shown.

[0061] Example 4

[0062] A method for producing spherical calcium ammonium nitrate granules by high-tower granulation includes the following steps:

[0063] The remaining control methods are the same as in Example 2. However, when the granulation temperature is controlled to be greater than 94°C, the granulated calcium ammonium nitrate does not form properly and sticks to the tower severely. When the temperature is controlled to 91-94°C, there are many irregularly shaped particles that are prone to sticking to the tower. The optimal granulation temperature is 90°C.

[0064] Comparative Example 1

[0065] A method for producing spherical calcium ammonium nitrate granules includes the following steps:

[0066] The methods employed are disc granulation, drum fluidized bed granulation, and fluidized bed spray granulation; the remaining steps are consistent with Example 1. The appearance and particle size of the calcium ammonium nitrate product are as follows: Figure 3 As shown.

[0067] The calcium ammonium nitrate products prepared in Examples 1-4 and Comparative Example 1 were tested according to the standard NY / T2269-2020 "Calcium Ammonium Nitrate for Agricultural Use and Usage Procedures". The results are summarized in Table 1 below.

[0068] Table 1

[0069]

[0070]

[0071] The above embodiments are preferred implementations of the present invention. In addition, the present invention can be implemented in other ways. Any obvious substitutions without departing from the concept of the present invention are within the protection scope of the present invention.

Claims

1. A method for producing spherical calcium ammonium nitrate granules by high-tower granulation, characterized in that, Includes the following steps: S1. Ingredients Prepare a mixture of ammonium calcium nitrate containing trace amounts of magnesium; Alternatively, prepare a magnesium-free ammonium calcium nitrate mixture; S2. Mixing The calcium ammonium nitrate mixture containing trace amounts of magnesium is fed into the primary mixing tank at the top of the granulation tower and melt-mixed with the calcium ammonium nitrate return material. After the melt-mixing is completed, it overflows into the secondary mixing tank for further melt-mixing to obtain a molten liquid. Alternatively, magnesium-free ammonium calcium nitrate mixture can be transported to the primary mixing tank at the top of the granulation tower for melt mixing with magnesium nitrate or calcium magnesium nitrate; after melt mixing, it can overflow into the secondary mixing tank for melt mixing with the returned ammonium calcium nitrate to obtain molten liquid. S3. Granulation and sieving The molten liquid overflows into the granulator for granulation, and after cooling and sieving, the calcium ammonium nitrate product is obtained. In step S1, the specific gravity of the calcium ammonium nitrate mixture containing trace amounts of magnesium is 1.82-1.83 g / cm³. 3 The mass percentage of elemental magnesium is 0.1-0.5%; In step S1, the preparation process of the calcium ammonium nitrate mixture containing trace amounts of magnesium includes: adding a calcium magnesium solution obtained by decompression and filtration of dolomite and nitric acid, or a magnesium nitrate solution obtained by reacting nitric acid and lightly calcined magnesium oxide, to a calcium nitrate solution in proportion; evaporating and concentrating the solution using a triple-effect evaporator to prepare a solution with a magnesium content of 0.1-0.5% by mass and a specific gravity of 1.82-1.83 g / cm³. 3 A mixture of ammonium nitrate and calcium containing trace amounts of magnesium; In step S2, the temperature of the secondary mixing tank is controlled at 90°C; In step S3, the product temperature during granulation is approximately 65°C. After being cooled by a vibrating fluidized bed, the product is then screened through a drum screen to obtain calcium ammonium nitrate with a particle size of 2-4 mm.

2. The method according to claim 1, characterized in that, In step S1, the specific gravity of the magnesium-free ammonium calcium nitrate mixture is 1.82-1.83 g / cm³. 3 .

3. The method according to claim 1, characterized in that, In step S1, the process of preparing the magnesium-free ammonium calcium nitrate mixture is as follows: After limestone and nitric acid react in an acid hydrolysis tank, an acid hydrolysis solution is obtained. The pH of the acid hydrolysis solution is adjusted to 5-6, and then filtered through a filter press to obtain a clear calcium nitrate solution. Ammonium nitrate solution is then added to the clear calcium nitrate solution to obtain a mixed clear solution. The mixed clear liquid was concentrated by evaporation using a triple-effect evaporator to prepare a solution with a specific gravity of 1.82-1.83 g / cm³. 3 Magnesium-free ammonium calcium nitrate mixture.

4. The method according to claim 1, characterized in that, In step S2, the calcium magnesium nitrate mixture is conveyed to the first-stage mixing tank at the top of the granulation tower and melt-mixed with magnesium nitrate or calcium magnesium nitrate to obtain a molten mixture with a magnesium weight content of 0.1-0.5%.

5. The method according to claim 1, characterized in that, The temperature during evaporation and concentration in the triple-effect evaporator is 120-130℃.

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