A method for producing amorphous potassium dihydrogen phosphate with adjustable bulk density

Abstract

This invention discloses a method for producing amorphous potassium dihydrogen phosphate with adjustable bulk density, comprising the following steps: S1 Solution adjustment: adding 0.1wt% to 5wt% of carboxylic acid or carboxylate to the potassium dihydrogen phosphate solution, and adjusting the dry matter content of potassium dihydrogen phosphate in the solution to 10wt% to 65wt%; S2 Atomization: atomizing the solution obtained in S1; S3 Drying: hot air drying the atomized solution in S2 to obtain amorphous potassium dihydrogen phosphate. The potassium dihydrogen phosphate prepared by this invention exists in a non-crystalline form, with a specific surface area more than 5 times that of ordinary crystalline potassium dihydrogen phosphate, and a fast dissolution rate. This invention can also adjust the bulk density of amorphous potassium dihydrogen phosphate, solving the problem of potassium dihydrogen phosphate dissolution rate while also improving the marketability of the product.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fertilizer preparation, in particular to a production method of non-crystalline potassium dihydrogen phosphate with adjustable bulk density. BACKGROUND

[0002] Potassium dihydrogen phosphate is a widely used single-element fertilizer in agriculture. Its salt index is much lower than that of potassium sulfate and potassium chloride, and it has little damage to the tender leaves of crops when used for foliar spraying, thus having high safety. It is often used for foliar fertilization of economic crops such as fruit trees and vegetables. In addition, it has a synergistic effect when mixed with some pesticides, and thus is very popular among farmers.

[0003] Most of the commercially available potassium dihydrogen phosphate is crystalline particles or powder. According to relevant data, its solubility in water at 20℃ is 22.6g / 100g water. Because its solubility is small and the specific surface area of the crystal is also small, its dissolution rate in water is very slow. It needs to be stirred for a long time before use to completely dissolve into a uniform solution, which is a great nuisance to users.

[0004] Solubility is a physical property of a substance and cannot be changed by human beings. In order to speed up the dissolution rate of potassium dihydrogen phosphate, the specific surface area of the crystal must be increased. The common method is to grind the potassium dihydrogen phosphate crystal into ultrafine powder of more than 200 mesh to increase its specific surface area. Because the particle size of the target product is very small, the common crushing and screening method cannot meet the requirements. The ultrafine powder of this size can only be obtained through multiple fine grinding and air separation. The mechanical equipment required for this process is expensive, the production efficiency is low, the energy consumption is high, and the cost of the product is much higher than that of the crystal potassium dihydrogen phosphate. The ultrafine powder obtained by mechanical grinding is still a crystal in nature, only the particle size is smaller, and its bulk density is comparable to that of the crystal product (generally greater than 1.0g / cm 3 Therefore, how to prepare a non-crystalline potassium dihydrogen phosphate that has a faster dissolution rate and better marketability is a difficult problem in the current potassium dihydrogen phosphate production industry. SUMMARY

[0005] The present application overcomes the technical problems that most of the commercially available potassium dihydrogen phosphate is crystalline particles or powder, has a small solubility and a slow dissolution rate, and the bulk density of the ultrafine powder of potassium dihydrogen phosphate is difficult to control, resulting in poor marketability of the product, and provides a production method of non-crystalline potassium dihydrogen phosphate with adjustable bulk density.

[0006] To solve the above problems, the present application adopts the following technical scheme:

[0007] A method for producing amorphous potassium dihydrogen phosphate with adjustable bulk density, comprising the following steps:

[0008] S1: adjusting the potassium dihydrogen phosphate solution by adding 0.1wt%-5wt% of carboxylic acid or carboxylic acid salt to the solution and adjusting the dry matter content of potassium dihydrogen phosphate in the solution to 10wt%-65wt%;

[0009] S2: atomizing the solution obtained in S1;

[0010] S3: drying the atomized solution in S2 to obtain amorphous potassium dihydrogen phosphate.

[0011] Further, the carboxylic acid is an organic compound containing a ―COOH group; the carboxylic acid salt is an organic compound containing a ―COO - group.

[0012] Further, the carboxylic acid is preferably one or more of acetic acid, propionic acid, oxalic acid, benzoic acid, citric acid, and lactic acid; the carboxylic acid salt is preferably a salt of one or more of acetic acid, propionic acid, oxalic acid, benzoic acid, citric acid, and lactic acid.

[0013] Further, the atomization is achieved by using one of high-speed centrifugal atomization, high-pressure jet atomization, and high-speed airflow atomization.

[0014] Further, in S2, the diameter of the atomized droplets is 22-112μm. In the present application, the diameter of the atomized droplets is calculated according to the formula d p = 16.56d0 1.52 G L -0.44 σ 0.71 μ L -0.16 (d p , μm, d0, mm, G L , g / s, σ, 10 -5 N / cm, μ L , mPa.s).

[0015] Further, in S3, the inlet air temperature of the hot air drying is 180-400℃, and the outlet air temperature is 100-200℃.

[0016] Another object of the present application is to protect the potassium dihydrogen phosphate produced by the above method for producing amorphous potassium dihydrogen phosphate with adjustable bulk density; the potassium dihydrogen phosphate is amorphous potassium dihydrogen phosphate.

[0017] The bulk density of the potassium dihydrogen phosphate produced by the above method is 0.5-0.9g / cm 3 .

[0018] Compared with the prior art, the present application has the following advantages: the potassium dihydrogen phosphate crystal belongs to the tetragonal system, and the traditional production is mainly through evaporation of water to gradually make the solute reach saturation, at which time a small amount of potassium dihydrogen phosphate crystal nucleus is formed in the solution, and under the action of the crystallization driving force, the crystal grains with complete shape are gradually formed. The mother liquor is separated by centrifugation, and the crystal potassium dihydrogen phosphate product is obtained by air flow drying. The potassium dihydrogen phosphate crystal needs to go through the processes of crystal nucleus formation and crystal growth. In the present application, the over-saturation of the feed liquid is reduced by controlling the dry matter content of potassium dihydrogen phosphate in the feed liquid to inhibit the formation of crystal nucleus, so that the crystal lacks the necessary conditions for generation; in addition, the feed liquid is atomized into fine droplets with a large specific surface area, and since each fine droplet contains only a small amount of potassium dihydrogen phosphate dry matter and water, the water in the droplet is instantly evaporated by hot air flow, and the dry matter becomes amorphous potassium dihydrogen phosphate without sufficient time for growth. On the other hand, a small amount of carboxylic acid or carboxylic acid salt is mixed into the potassium dihydrogen phosphate feed liquid, and at room temperature, the carboxylic acid or carboxylic acid salt uniformly dispersed in the feed liquid can stably exist, and during the high-temperature drying process, the carboxylic acid or carboxylic acid salt is decomposed in situ to generate carbon dioxide, and the carbon dioxide molecules are wrapped in the dried material to form fine cavities, making the material become fluffy and reducing the bulk density of the material, thereby improving the marketability of the product. Therefore, the content of the carboxylic acid or carboxylic acid salt can be adjusted within a certain range, and the bulk density of the amorphous potassium dihydrogen phosphate can be controlled to be 0.5-0.9 g / cm 3 The potassium dihydrogen phosphate prepared by the present application exists in an amorphous state, and the specific surface area is more than 5 times that of ordinary crystalline potassium dihydrogen phosphate (evaluated by dissolution speed), and the dissolution speed is fast; the bulk density of the amorphous potassium dihydrogen phosphate can be adjusted by the present application, which not only solves the problem of dissolution speed of potassium dihydrogen phosphate, but also makes the product have better marketability, and the present application has outstanding technical effects. DETAILED DESCRIPTION

[0019] The present application will be further described below in combination with examples and tests.

[0020] Example 1

[0021] A production method of amorphous potassium dihydrogen phosphate with adjustable bulk density, comprising the following steps:

[0022] S1 feed liquid adjustment: 0.1 wt% of acetic acid is added to the potassium dihydrogen phosphate feed liquid, and the dry matter content of potassium dihydrogen phosphate in the feed liquid is adjusted to 10 wt%;

[0023] S2 atomization: the feed liquid obtained in S1 is atomized into droplets with a diameter of 22 μm by high-speed centrifugal atomization;

[0024] S3 drying: the atomized S2 solution is dried by hot air drying under the conditions of an inlet air temperature of 180℃ and an outlet air temperature of 100℃ to obtain amorphous potassium dihydrogen phosphate.

[0025] Example 2

[0026] A method for producing amorphous potassium dihydrogen phosphate with adjustable bulk density, comprising the following steps:

[0027] S1 solution adjustment: 5wt% of propionic acid is added to the potassium dihydrogen phosphate solution, and the dry matter content of potassium dihydrogen phosphate in the solution is adjusted to 65wt%;

[0028] S2 atomization: the solution obtained in S1 is atomized into mist droplets with a diameter of 112μm by high-pressure jet atomization;

[0029] S3 drying: the atomized S2 solution is dried by hot air drying under the conditions of an inlet air temperature of 400℃ and an outlet air temperature of 200℃ to obtain amorphous potassium dihydrogen phosphate.

[0030] Example 3

[0031] A method for producing amorphous potassium dihydrogen phosphate with adjustable bulk density, comprising the following steps:

[0032] S1 solution adjustment: 3wt% of potassium acetate is added to the potassium dihydrogen phosphate solution, and the dry matter content of potassium dihydrogen phosphate in the solution is adjusted to 30wt%;

[0033] S2 atomization: the solution obtained in S1 is atomized into mist droplets with a diameter of 110μm by high-speed airflow atomization;

[0034] S3 drying: the atomized S2 solution is dried by hot air drying under the conditions of an inlet air temperature of 200℃ and an outlet air temperature of 150℃ to obtain amorphous potassium dihydrogen phosphate.

[0035] Example 4

[0036] A method for producing amorphous potassium dihydrogen phosphate with adjustable bulk density, comprising the following steps:

[0037] S1 solution adjustment: 1wt% of citric acid is added to the potassium dihydrogen phosphate solution, and the dry matter content of potassium dihydrogen phosphate in the solution is adjusted to 45wt%;

[0038] S2 atomization: the solution obtained in S1 is atomized into mist droplets with a diameter of 80μm by high-pressure jet atomization;

[0039] S3 drying: the atomized S2 solution is dried by hot air drying under the conditions of an inlet air temperature of 300℃ and an outlet air temperature of 120℃ to obtain amorphous potassium dihydrogen phosphate.

[0040] Example 5

[0041] A production method of amorphous potassium dihydrogen phosphate with adjustable bulk density, comprising the following steps:

[0042] S1: adjusting the solution: adding 0.5wt% of benzoic acid to the potassium dihydrogen phosphate solution, and adjusting the dry matter content of potassium dihydrogen phosphate in the solution to 20wt%;

[0043] S2: atomization: using high-speed centrifugal atomization to atomize the solution obtained in S1 into mist droplets with a diameter of 30μm;

[0044] S3: drying: drying the solution after S2 atomization under the condition of an inlet air temperature of 220℃ and an outlet air temperature of 180℃ to obtain amorphous potassium dihydrogen phosphate.

[0045] Example 6

[0046] A production method of amorphous potassium dihydrogen phosphate with adjustable bulk density, comprising the following steps:

[0047] S1: adjusting the solution: adding 4wt% of potassium oxalate to the potassium dihydrogen phosphate solution, and adjusting the dry matter content of potassium dihydrogen phosphate in the solution to 25wt%;

[0048] S2: atomization: using high-speed airflow atomization to atomize the solution obtained in S1 into mist droplets with a diameter of 50μm;

[0049] S3: drying: drying the solution after S2 atomization under the condition of an inlet air temperature of 400℃ and an outlet air temperature of 200℃ to obtain amorphous potassium dihydrogen phosphate.

[0050] Example 7

[0051] A production method of amorphous potassium dihydrogen phosphate with adjustable bulk density, comprising the following steps:

[0052] S1: adjusting the solution: adding 0.2wt% of lactic acid to the potassium dihydrogen phosphate solution, and adjusting the dry matter content of potassium dihydrogen phosphate in the solution to 60wt%;

[0053] S2: atomization: using high-speed centrifugal atomization to atomize the solution obtained in S1 into mist droplets with a diameter of 40μm;

[0054] S3: drying: drying the solution after S2 atomization under the condition of an inlet air temperature of 300℃ and an outlet air temperature of 100℃ to obtain amorphous potassium dihydrogen phosphate.

[0055] Control group 1

[0056] The preparation method of potassium dihydrogen phosphate in the control group comprises the following steps:

[0057] S1 solution adjustment: adjust the dry matter content of potassium dihydrogen phosphate to 50wt%, heat to dissolve into a uniform solution;

[0058] S2 cooling crystallization: cool the solution obtained in S1 to room temperature under stirring to obtain a solution containing crystalline potassium dihydrogen phosphate;

[0059] S3 solid-liquid separation: filter the solution containing crystalline potassium dihydrogen phosphate obtained in S2 to separate the mother liquor, and obtain wet potassium dihydrogen phosphate crystals;

[0060] S4 drying: dry the wet potassium dihydrogen phosphate crystals obtained in S3 under the conditions of an inlet air temperature of 180℃ and an outlet air temperature of 100℃ to obtain crystalline potassium dihydrogen phosphate.

[0061] Control group 2:

[0062] A production method of amorphous potassium dihydrogen phosphate, comprising the following steps:

[0063] S1 solution adjustment: adjust the dry matter content of potassium dihydrogen phosphate to 10wt%;

[0064] S2 atomization: atomize the solution obtained in S1 into mist droplets with a diameter of 22μm by high-speed centrifugal atomization;

[0065] S3 drying: dry the solution atomized in S2 under the conditions of an inlet air temperature of 180℃ and an outlet air temperature of 100℃ to obtain amorphous potassium dihydrogen phosphate.

[0066] The indicators of the potassium dihydrogen phosphates obtained in the above examples 1-7 and control groups 1-2 are compared, and the results are shown in Table 1:

[0067] Table 1

[0068]

[0069]

[0070] Note: The content of phosphorus pentoxide and potassium oxide in potassium dihydrogen phosphate is tested according to the standard HG / T 2321-2016, and the result is the average value of multiple parallel tests. The dissolution speed is tested by dissolving 10g of sample in 100g of distilled water under the same temperature, using a magnetic stirrer under the same stirring speed, and the test result is the average value of multiple parallel tests.

[0071] As shown in Table 1, the product forms of Examples 1-7 are all amorphous, and the dissolution rates are all less than 1 min. As compared with Comparative Group 1, it can be seen that the product form of the potassium dihydrogen phosphate produced by the present application is changed, and the dissolution rate is greatly increased. As compared with Comparative Group 2, it can be seen that without adding carboxylic acid or carboxylic acid salt, the bulk density of Comparative Group 2 is greater than that of Examples 1-7, and the dissolution rate is also smaller than that of Examples 1-7, indicating that the carboxylic acid or carboxylic acid salt can adjust the bulk density of the potassium dihydrogen phosphate, and has certain influence on the dissolution rate of the potassium dihydrogen phosphate. By adjusting and controlling the dry matter content of the potassium dihydrogen phosphate in the feed liquid to reduce the supersaturation of the feed liquid, the formation of crystal nucleus can be inhibited, so that the crystal lacks the necessary conditions for generation. In addition, by atomizing the feed liquid into fine droplets with a large specific surface area, the amorphous potassium dihydrogen phosphate can be directly generated after hot gas drying, greatly increasing the dissolution rate of the potassium dihydrogen phosphate. A small amount of carboxylic acid or carboxylic acid salt is mixed into the potassium dihydrogen phosphate feed liquid, and by using the principle that the carboxylic acid or carboxylic acid salt is decomposed into carbon dioxide at high temperature, the material can be made fluffy and the bulk density of the material can be reduced during high-temperature drying, improving the commodity nature of the product. The present application has outstanding technical effects.

[0072] The above description is a detailed description of the preferred embodiments of the present application, but the embodiments are not intended to limit the scope of the patent application of the present application. Any equivalent changes or modifications made under the technical spirit of the present application should be covered by the patent scope of the present application.

Claims

1. A method for producing an amorphous monobasic potassium phosphate having an adjustable bulk density, characterized by: The method comprises the following steps: S1: adjusting the solution, adding 0.1wt%-5wt% carboxylic acid or carboxylic acid salt to the potassium dihydrogen phosphate solution, and adjusting the dry matter content of potassium dihydrogen phosphate in the solution to 10wt%-65wt%; S2: atomizing the solution obtained in S1; S3: drying the atomized solution in S2 to obtain amorphous potassium dihydrogen phosphate.

2. The method for producing amorphous potassium dihydrogen phosphate having an adjustable bulk density according to claim 1, characterized by, The carboxylic acid is an organic compound containing a ―COOH group; the carboxylate is an organic compound containing a ―COO - group.

3. The method for producing an amorphous monobasic potassium phosphate with an adjustable bulk density according to claim 2, characterized by, The carboxylic acid is one or more of acetic acid, propionic acid, oxalic acid, benzoic acid, citric acid, and lactic acid; and the carboxylic acid salt is a salt of one or more of acetic acid, propionic acid, oxalic acid, benzoic acid, citric acid, and lactic acid.

4. The method of producing amorphous monobasic potassium phosphate with adjustable bulk density according to claim 1, characterized in that, The atomization is achieved by one of high-speed centrifugal atomization, high-pressure jet atomization, and high-speed airflow atomization.

5. The method of producing non-crystalline potassium dihydrogen phosphate with adjustable bulk density according to claim 1, characterized in that, In S2, the diameter of the atomized droplets is 22-112μm.

6. The method of producing non-crystalline potassium dihydrogen phosphate with adjustable bulk density according to claim 1, characterized in that, In S3, the inlet air temperature of the hot air drying is 180-400℃, and the outlet air temperature is 100-200℃.

7. Amorphous potassium dihydrogen phosphate prepared by the method of any one of claims 1-6. The amorphous potassium dihydrogen phosphate has a bulk density of 0.3-0.7g / cm3.

8. The potassium dihydrogen phosphate as claimed in claim 7 having a bulk density in the range of 0.5 to 0.9 g / cm 3 .

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