A method for improving the frost resistance of liquid macronutrient water-soluble fertilizers

Abstract

The present invention discloses a method for improving the frost resistance of a liquid macronutrient water-soluble fertilizer. The liquid macronutrient water-soluble fertilizer is a liquid water-soluble fertilizer containing one or two of N and K2O, and P2O5. The method is: adding sodium ions to the liquid macronutrient water-soluble fertilizer and controlling the concentration of sodium ions to be 5-30 g / L, and controlling the proportion of polymeric P2O5 in the total P2O5 in the macronutrient water-soluble fertilizer to be 30-80%. The liquid macronutrient water-soluble fertilizer obtained by the process of the present invention has good frost resistance, and the frost resistance temperature of the fertilizer is between 5°C and -15°C, that is, there is no crystallization even at a low temperature of -15°C, and the effect is remarkable.

Description

Technical Field

[0001] The present invention relates to the technical field of fertilizer preparation, and particularly relates to a method for improving the frost resistance of liquid macronutrient water-soluble fertilizers. Background Art

[0002] With the rise of modern facility agriculture in recent years, the application scale of macronutrient water-soluble fertilizers has been continuously expanding. Macronutrient water-soluble fertilizers are divided into two dosage forms: solid and liquid. Compared with solid macronutrient water-soluble fertilizers, liquid products have the advantages of rich raw material types, simple production process, low production energy consumption, and convenient use.

[0003] According to the latest national agricultural industry standard for macronutrient water-soluble fertilizers, "NY / T 1107-2020 Macronutrient Water-soluble Fertilizers", liquid macronutrient water-soluble fertilizers should contain at least two of N, P2O5, and K2O, and the total nutrient content must be greater than or equal to 400 g / L. When the concentration of macronutrients in the liquid is greater than or equal to 400 g / L, the concentration of solutes in the solution is already close to saturation or has exceeded saturation. Most of the solutes in the liquid are inorganic salts, and their solubility is greatly affected by temperature. Taking potassium dihydrogen phosphate as an example, at 30°C, its solubility is 28 g / 100 g of water, and when the temperature drops to 0°C, its solubility is only 14.8 g / 100 g of water, with a change range of nearly 50%. The solubility difference at different temperatures causes the solutes in liquid macronutrient water-soluble fertilizers to easily crystallize and precipitate at low temperatures. In the light case, it is difficult to pour out from the container, affecting the use. In the severe case, the container will burst, causing irreparable losses. The winter temperature in the northern part of China is below 0°C, while in the southern part, it is mostly above 5°C. Many liquid macronutrient water-soluble fertilizers can only be applied in the south, and their application in the north is severely restricted.

[0004] Frost resistance is for liquid fertilizers. When the temperature drops to a certain value, the solutes in the fertilizer will crystallize and precipitate, affecting the use. Therefore, frost resistance is mainly manifested in that, under the condition of keeping the ratio and pH value of the fertilizer unchanged, the crystallization temperature of the fertilizer is lower. To prevent liquid macronutrient water-soluble fertilizers from crystallizing at low temperatures and improve the frost resistance of liquid fertilizers, it can be achieved by reducing the concentration of solutes. However, products with low concentrations may not meet the requirements of the "NY / T 1107-2020 Macronutrient Water-soluble Fertilizers" standard, and at the same time, the commerciality also deteriorates, which is not an ideal solution. Therefore, it is particularly necessary to seek a method to improve the frost resistance of liquid fertilizers. Summary of the Invention

[0005] The present invention overcomes the technical problems of the prior art that liquid macronutrient water-soluble fertilizers are prone to crystal precipitation and have poor frost resistance under low-temperature conditions, and provides a method for improving the frost resistance of liquid macronutrient water-soluble fertilizers.

[0006] To solve the above problems, the present invention adopts the following technical solutions:

[0007] A method for improving the frost resistance of a liquid macronutrient water-soluble fertilizer, wherein the liquid macronutrient water-soluble fertilizer is a liquid water-soluble fertilizer containing one or both of N and K2O, and P2O5; specifically, the macronutrient water-soluble fertilizer is a water-soluble fertilizer containing N and P2O5, or a water-soluble fertilizer containing P2O5 and K2O, or a water-soluble fertilizer containing N, P2O5 and K2O;

[0008] The method is: adding sodium ions to the macronutrient water-soluble fertilizer and controlling the concentration of sodium ions to be 5 - 30 g / L, and controlling the proportion of polymeric P2O5 in the total P2O5 in the macronutrient water-soluble fertilizer to be 30 - 80%.

[0009] Further, when adding sodium ions, the sodium ions are added in one or more of sodium hydroxide, sodium carbonate or sodium bicarbonate.

[0010] Further, the total P2O5 is a mixture of non-polymeric P2O5 and polymeric P2O5; the polymeric P2O5 is one or a mixture of diphosphate, triphosphate, tetraphosphate, pentaphosphate, hexaphosphate, heptaphosphate and octaphosphate.

[0011] Further, the raw material of N is one or more of urea, ammonium sulfate, ammonium chloride, ammonium nitrate, ammonium bicarbonate, ammonia water and liquid ammonia.

[0012] Further, the raw material of non-polymeric P2O5 is one or more of phosphoric acid, potassium dihydrogen phosphate, potassium hydrogen phosphate, potassium orthophosphate, ammonium dihydrogen phosphate, ammonium hydrogen phosphate, sodium dihydrogen phosphate, sodium hydrogen phosphate and sodium orthophosphate; the raw material of polymeric P2O5 is one or more of polyphosphoric acid, potassium pyrophosphate, potassium tripolyphosphate, potassium tetraphosphate, potassium pentaphosphate, potassium hexaphosphate, potassium heptaphosphate, potassium octaphosphate, ammonium pyrophosphate, ammonium tripolyphosphate, ammonium tetraphosphate, ammonium pentaphosphate, ammonium hexaphosphate, ammonium heptaphosphate and ammonium octaphosphate.

[0013] Further, K2O is derived from one or more of potassium chloride, potassium sulfate, potassium formate, potassium hydroxide, potassium carbonate, potassium bicarbonate, potassium acetate, potassium citrate and potassium nitrate.

[0014] Further, the pH value of the macroelement water-soluble fertilizer is 5 - 8.5 after being diluted according to the mass ratio of fertilizer to water of 1:250. The macroelement water-soluble fertilizer is for crop use, and the more suitable pH for crops is 5 - 8.5. Too high or too low pH has adverse effects on crops. Moreover, when the pH of the macroelement water-soluble fertilizer is less than 5, most of the P2O5 exists in the form of dihydrogen salts, with too small solubility and instability; when it is higher than 8.5, it does not meet the usage requirements.

[0015] Another object of the present invention is also to protect the macroelement water-soluble fertilizer obtained by the method for improving the frost resistance of the above-mentioned liquid macroelement water-soluble fertilizer.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention mainly improves the frost resistance of the product by increasing the solubility of the solute in the liquid macroelement water-soluble fertilizer and reducing the supersaturation of the solute in the product. Specifically, when the pH value of the macroelement water-soluble fertilizer is 5 - 8.5 after being diluted according to the mass ratio of fertilizer to water of 1:250, the phosphorus in the solution exists in the form of a coexistence of monohydrogen phosphate and dihydrogen phosphate. Dihydrogen phosphate combines with potassium ions to form potassium dihydrogen phosphate with small solubility, increasing the supersaturation of the solution and causing crystallization; the charge of monohydrogen phosphate is higher than that of dihydrogen phosphate, and potassium is more likely to lose electrons than sodium. Therefore, potassium monohydrogen phosphate is more stable than sodium monohydrogen phosphate. When sodium ions, potassium ions, dihydrogen phosphate ions, and monohydrogen phosphate ions exist in the mixed solution system, the ions in the solution tend to combine into sodium dihydrogen phosphate and potassium monohydrogen phosphate, and the solution system is the most stable at this time. The solubility of sodium dihydrogen phosphate is nearly 4 times that of potassium dihydrogen phosphate, and the solubility of potassium monohydrogen phosphate is nearly 5 times that of potassium dihydrogen phosphate. Therefore, the present invention can change the composition of phosphates in the product by adding an appropriate amount of sodium ions to the product, reducing the proportion of potassium dihydrogen phosphate and thus reducing the supersaturation of the solution. In addition, replacing non-polymerized P2O5 with polymerized P2O5 in the present invention can also reduce the supersaturation of the solution without changing the phosphorus nutrient content, thereby improving the frost resistance of the product as a whole. The liquid macroelement water-soluble fertilizer obtained by the process of the present invention has good frost resistance, and the frost resistance temperature of the fertilizer is between 5°C and

[0017] -15°C. In fact, for liquid fertilizers, the lower the crystallization temperature, the better. In this way, the applicable area of the fertilizer is wider, and there is no need to worry about crystallization during winter or outdoor storage. However, the lower the crystallization temperature, the more difficult it is to achieve and the greater the cost. Therefore, a suitable crystallization temperature range is the most practical. Generally, the temperature in winter in the south is generally above 5 degrees, while in the north it is lower. But -15°C can already be used for indoor storage in most areas in winter, basically meeting the market requirements. Specific Embodiments

[0018] The present invention will be further described below in conjunction with examples and tests.

[0019] Example 1

[0020] A method for improving the frost resistance of liquid macronutrient water-soluble fertilizers, comprising the following steps:

[0021] By the mass of the materials, take 26.8 parts of phosphoric acid with a concentration of 85%, take 42 parts of polyphosphoric acid with a concentration of 110%, take 67.6 parts of potassium hydroxide with a content of 90%, 3.8 parts of sodium hydroxide, and 33.3 parts of water. Before the reaction, first put water into the reactor, then add all the potassium hydroxide and sodium hydroxide, and then add phosphoric acid and polyphosphoric acid for reaction. After the reaction is completed, supplement the lost water to obtain a macronutrient water-soluble fertilizer product with a ratio of 0-500-510 (N 0 g / L, P2O5 500 g / L, K2O 510 g / L), containing 55% (polymeric P2O5 / total P2O5) polymeric P2O5 and a sodium ion concentration of 21.5 g / L.

[0022] Example 2

[0023] A method for improving the frost resistance of liquid macronutrient water-soluble fertilizers, comprising the following steps:

[0024] By the mass of the materials, take 13 parts of ammonium dihydrogen phosphate, take 20 parts of polyphosphoric acid with a concentration of 116%, 36 parts of polyphosphoric acid with a concentration of 105%, take 10 parts of urea, 44 parts of ammonia water, 1.2 of sodium carbonate, and 16.8 parts of water. Before the reaction, first put water into the reactor, then add all the urea, ammonium dihydrogen phosphate and ammonia water, and then add phosphoric acid, polyphosphoric acid and sodium carbonate for reaction. After the reaction is completed, supplement the lost water to obtain a macronutrient water-soluble fertilizer product with a ratio of 150-520-0 (N 150 g / L, P2O5 520 g / L, K2O 0 g / L), containing 55% (polymeric P2O5 / total P2O5) polymeric P2O5 and a sodium ion concentration of 5 g / L.

[0025] Example 3

[0026] A method for improving the frost resistance of liquid macronutrient water-soluble fertilizers, comprising the following steps:

[0027] By mass of the materials, take 6.7 parts of potassium dihydrogen phosphate, 13.7 parts of potassium tripolyphosphate, 2 parts of potassium hydroxide with a content of 90%, 11 parts of sodium bicarbonate, 32.6 parts of urea, 3 parts of potassium chloride, 23 parts of potassium formate, and 46 parts of water. Before the reaction, first put water into the reactor, then add all of the potassium dihydrogen phosphate, urea, potassium chloride, potassium formate, and sodium bicarbonate, and then add potassium hydroxide and potassium tripolyphosphate for reaction. After the reaction is completed, supplement the lost water to obtain a large-element water-soluble fertilizer product with a ratio of 150 - 100 - 250 (N 150 g / L, P2O5 100 g / L, K2O 250 g / L), containing 65% (polymeric P2O5 / total P2O5) of polymeric P2O5 and a sodium ion concentration of 30 g / L.

[0028] Example 4

[0029] A method for improving the frost resistance of a liquid large-element water-soluble fertilizer, which comprises the following steps:

[0030] By mass of the materials, take 8 parts of potassium dihydrogen phosphate, 3.3 parts of octapolyphosphate potassium, 2.5 parts of potassium hydroxide with a content of 90%, 2.6 parts of sodium hydroxide, 17 parts of urea, 1 part of potassium nitrate, 36 parts of potassium formate, and 62 parts of water. Before the reaction, first put water into the reactor, then add all of the potassium dihydrogen phosphate, urea, potassium nitrate, potassium formate, and sodium hydroxide, and then add potassium hydroxide and octapolyphosphate potassium for reaction. After the reaction is completed, supplement the lost water to obtain a large-element water-soluble fertilizer product with a ratio of 80 - 60 - 260 (N 80 g / L, P2O5 60 g / L, K2O 260 g / L), containing 30% (polymeric P2O5 / total P2O5) of polymeric P2O5 and a sodium ion concentration of 15 g / L.

[0031] Example 5

[0032] A method for improving the frost resistance of a liquid large-element water-soluble fertilizer, which comprises the following steps:

[0033] By mass of the materials, take 3.3 parts of phosphoric acid with a concentration of 85%, 18 parts of polyphosphoric acid with a concentration of 115%, 22.5 parts of potassium hydroxide with a content of 90%, 0.9 part of sodium hydroxide, 37 parts of urea, and 57.3 parts of water. Before the reaction, first put water into the reactor, then add all of the urea, potassium hydroxide, and sodium hydroxide, and then add phosphoric acid and polyphosphoric acid for reaction. After the reaction is completed, supplement the lost water to obtain a large-element water-soluble fertilizer product with a ratio of 170 - 170 - 170 (N 170 g / L, P2O5 170 g / L, K2O 170 g / L), containing 80% (polymeric P2O5 / total P2O5) of polymeric P2O5 and a sodium ion concentration of 5 g / L.

[0034] Control group 1: Without adding sodium hydroxide, use a small amount of potassium hydroxide to replace sodium hydroxide to adjust the pH to the same as that in Example 1, and the other methods are the same as those in Example 1;

[0035] Control group 2: Without adding polyphosphoric acid, use 85% phosphoric acid with the same amount of P2O5 to replace polyphosphoric acid, and the other methods are the same as those in Example 1;

[0036] Control group 3: Without adding sodium hydroxide, use a small amount of potassium hydroxide to replace sodium hydroxide to adjust the pH to the same as that in Example 1; without adding polyphosphoric acid, use 85% phosphoric acid with the same amount of P2O5 to replace polyphosphoric acid, and the other methods are the same as those in Example 1;

[0037] Control group 4: According to the standard "NY / T 1107-2020 Water-soluble fertilizers for major elements", dilute the product of Example 1 according to the mass ratio of fertilizer to water of 1:250, and use polyphosphoric acid to adjust the pH to 4;

[0038] Control group 5: The concentration of sodium ions is 15 g / L, use a small amount of potassium hydroxide to replace the insufficient sodium hydroxide to adjust the pH to the same as that in Example 1, and the other methods are the same as those in Example 1;

[0039] Control group 6: Reduce the polyphosphoric acid to 23 parts, use 85% phosphoric acid with the same amount of P2O5 to replace the reduced polyphosphoric acid, and the other methods are the same as those in Example 1;

[0040] According to the test requirements in the standard "NY / T 1107-2020 Water-soluble fertilizers for major elements", compare the anti-freezing performance, specific gravity and other indexes of the fertilizers obtained in the above Examples 1 to 5 and Control groups 1 to 6. The results are shown in Table 1:

[0041] Table 1

[0042]

[0043]

[0044] As can be seen from Table 1, the liquid macronutrient water-soluble fertilizers prepared in Examples 1 to 5 of the present invention do not crystallize and precipitate at a low temperature of -15°C, indicating that the liquid macronutrient water-soluble fertilizers prepared by the method of the present invention have good frost resistance. In Control Group 1, sodium ions were not added, and the liquid macronutrient water-soluble fertilizer began to crystallize when the temperature was below 0°C, showing poor frost resistance. In Control Group 2, polyphosphoric acid was not added, and the liquid macronutrient water-soluble fertilizer began to crystallize when the temperature was below 5°C, also showing poor frost resistance. In Control Group 3, neither sodium ions nor polyphosphoric acid were added, and the liquid macronutrient water-soluble fertilizer crystallized at 25°C, with extremely poor frost resistance. In Control Group 4, the pH was adjusted to 4 with polyphosphoric acid, and the liquid macronutrient water-soluble fertilizer crystallized at 45°C, indicating that the liquid macronutrient water-soluble fertilizer prepared by adjusting the pH to 4 with polyphosphoric acid has extremely poor stability and frost resistance! In Control Group 5, the concentration of sodium ions was 15 g / L, and a small amount of potassium hydroxide was used to replace the insufficient sodium hydroxide to adjust the pH to the same as that in Example 1. The liquid macronutrient water-soluble fertilizer prepared crystallized at -15°C and did not crystallize at 0°C, indicating that adding a certain amount of sodium ions can improve the frost resistance of the macronutrient water-soluble fertilizer, but the liquid macronutrient water-soluble fertilizer with an appropriate amount of added sodium ions has better frost resistance. In Control Group 5, the polyphosphoric acid was reduced to 230 g, and phosphoric acid with a concentration of 85% equivalent to P2O5 was used to replace polyphosphoric acid to prepare the liquid macronutrient water-soluble fertilizer, which crystallized at 0°C, indicating that the frost resistance also deteriorated after the proportion of polymeric P2O5 in the total P2O5 in the macronutrient water-soluble fertilizer decreased. Through the comparison between Example 1 and Control Groups 1 to 5 above, it can be seen that only when sodium ions are added to the liquid macronutrient water-soluble fertilizer and the concentration of sodium ions is controlled at 5 - 30 g / L, and the proportion of polymeric phosphates in the total phosphorus in the macronutrient water-soluble fertilizer is controlled at 30 - 80%, the frost resistance of the macronutrient water-soluble fertilizer has the best effect, and it can be used without crystallization at 5°C to -15°C, with outstanding technical effects.

[0045] The above description is a detailed description of the preferred feasible embodiments of the present invention, but the embodiments are not intended to limit the scope of the patent application of the present invention. Any equivalent changes or modifications made under the technical spirit disclosed by the present invention shall fall within the scope of the patent covered by the present invention.

Claims

1. A method for improving the frost resistance of liquid macronutrient water-soluble fertilizers, characterized in that: The liquid macronutrient water-soluble fertilizer is a liquid water-soluble fertilizer containing one or both of N and K2O, and P2O5; The method is: adding sodium ions to the liquid macronutrient water-soluble fertilizer and controlling the concentration of sodium ions to be 5-30 g / L, and controlling the proportion of polymeric P2O5 in the total P2O5 in the macronutrient water-soluble fertilizer to be 30-80%.

2. The method for improving the frost resistance of a liquid macronutrient water-soluble fertilizer as claimed in claim 1, wherein When adding sodium ions, the sodium ions are added in one or more of sodium hydroxide, sodium carbonate or sodium bicarbonate.

3. A method for improving the frost resistance of a liquid macronutrient water-soluble fertilizer according to claim 1, characterized in that, The total P2O5 is a mixture of non-polymeric P2O5 and polymeric P2O5; the polymeric P2O5 is one or a mixture of two or more of diphosphate, triphosphate, tetraphosphate, pentaphosphate, hexaphosphate, heptaphosphate and octaphosphate.

4. The method for improving the frost resistance of a liquid macronutrient water-soluble fertilizer as described in claim 1, characterized in that, The raw material of N is one or more of urea, ammonium sulfate, ammonium chloride, ammonium nitrate, ammonium bicarbonate, ammonia water and liquid ammonia.

5. The method for improving the frost resistance of a liquid macronutrient water-soluble fertilizer according to claim 3, characterized in that, The raw material of non-polymeric P2O5 is one or more of phosphoric acid, potassium dihydrogen phosphate, potassium hydrogen phosphate, potassium orthophosphate, ammonium dihydrogen phosphate, ammonium hydrogen phosphate, sodium dihydrogen phosphate, sodium hydrogen phosphate and sodium orthophosphate; the raw material of polymeric P2O5 is one or more of polyphosphoric acid, potassium pyrophosphate, potassium tripolyphosphate, potassium tetraphosphate, potassium pentaphosphate, potassium hexaphosphate, potassium heptaphosphate, potassium octaphosphate, ammonium pyrophosphate, ammonium tripolyphosphate, ammonium tetraphosphate, ammonium pentaphosphate, ammonium hexaphosphate, ammonium heptaphosphate and ammonium octaphosphate.

6. A method for improving the frost resistance of a liquid macronutrient water-soluble fertilizer as described in claim 1, characterized in that, The raw material of K2O is one or more of potassium chloride, potassium sulfate, potassium formate, potassium hydroxide, potassium carbonate, potassium bicarbonate, potassium acetate, potassium citrate and potassium nitrate.

7. A method for improving the frost resistance of a liquid macronutrient water-soluble fertilizer as described in claim 1, characterized in that, The pH value of the macronutrient water-soluble fertilizer after being diluted according to the mass ratio of fertilizer to water of 1:250 is 5-8.

5.

8. A macronutrient water-soluble fertilizer obtained by the method for improving the frost resistance of liquid macronutrient water-soluble fertilizers according to any one of claims 1-7.

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