Low-ammonia volatile nitrogen fertilizer based on calcium and magnesium minerals and preparation process

Abstract

The invention relates to a low-ammonia volatile nitrogen fertilizer based on calcium and magnesium minerals, the nitrogen fertilizer comprises urea and calcium and magnesium minerals, and the urea and the calcium and magnesium minerals in the nitrogen fertilizer are eutectic mixtures. The invention further relates to a preparation process of the low-ammonia volatile nitrogen fertilizer based on the calcium-magnesium mineral substances, which comprises the following steps: S1, introducing urea into a mixing tank, and adding the calcium-magnesium mineral substances in a certain weight ratio into the mixing tank to form a urea-calcium-magnesium mineral substance molten mixture; s2, the urea-calcium magnesium mineral substance molten mixture is introduced into a granulation device, and a urea-calcium magnesium mineral substance eutectic mixture is obtained; and S3, further cooling and granulating to obtain the low-ammonia volatile nitrogen fertilizer based on the calcium and magnesium minerals. By synthesizing the eutectic mixture of urea and calcium-magnesium minerals, the utilization rate of urea nitrogen is increased to a certain extent, and ammonia volatilization is correspondingly reduced.

Description

Technical Field

[0001] The present application relates to the technical field of compound fertilizers, and in particular to a low-ammonia volatile nitrogen fertilizer based on calcium and magnesium minerals and a preparation process thereof. Background Art

[0002] my country is a major agricultural country and a major fertilizer producer and user in the world. However, the nitrogen content of most of my country's cultivated land is less than 0.2%. With the further development of agriculture, the demand for fertilizers is increasing, and it is particularly important to develop fertilizers that are suitable for complex soils. Nitrogen fertilizer is the largest fertilizer variety produced and used in the world; the appropriate amount of nitrogen fertilizer plays an important role in increasing crop yields and improving the quality of agricultural products. Since the 1970s, urea has become the dominant nitrogen fertilizer variety.

[0003] Urea, also known as carbamide, has a chemical formula of CH4N2O or CO(NH2)2. It is an organic compound composed of carbon, nitrogen, oxygen and hydrogen. It is a white crystal. As a neutral fertilizer, urea is suitable for various soils and plants. It is easy to store, easy to use, and has little destructive effect on the soil. It is a chemical nitrogen fertilizer with a large usage and the highest nitrogen content.

[0004] However, urea is highly active and converts quickly in the soil. It can cause gaseous losses through ammonia volatilization or denitrification. After being converted into nitrate nitrogen, it is not easily adsorbed by soil colloids and is easily leached in the soil. The absorption and utilization rate of urea nitrogen by crops is low, and the utilization rate of nitrogen in urea does not exceed 50-60%, which not only causes economic losses but also may seriously pollute the environment. In order to solve this problem, agricultural chemists from all over the world have conducted a lot of research. At present, the main ways to improve the utilization rate of nitrogen in urea are as follows: (1) Coated urea. There are two main types of coating materials used: organic polymers, such as resin polyolefins; and water-insoluble or slightly soluble inorganic materials, such as sulfur; (2) Synthetic urea formaldehyde complexes, that is, urea reacts with formaldehyde, acetaldehyde, isobutyraldehyde, etc. to produce urea formaldehyde complexes with slow release properties, prolong the release time of urea, and improve the utilization rate of urea nitrogen fertilizer; (3) Adding chemical components such as urease inhibitors and nitrification inhibitors during urea production to change the conversion process of urea in the soil and improve the utilization rate of urea nitrogen fertilizer.

[0005] The above method can improve the utilization rate of urea nitrogen to a certain extent and reduce ammonia volatilization accordingly. However, due to technical and economic reasons such as complex process, high production cost and low production capacity, it has not been widely promoted and applied in agricultural production. Summary of the invention

[0006] The present application proposes a low-ammonia volatilizing nitrogen fertilizer based on calcium and magnesium minerals and a preparation process to solve the problems of low nitrogen utilization rate and poor urea stability of existing urea nitrogen fertilizers.

[0007] In order to solve the above technical problems, the present application proposes a low-ammonia volatile nitrogen fertilizer based on calcium-magnesium minerals, wherein the nitrogen fertilizer comprises urea and calcium-magnesium minerals, and the urea and calcium-magnesium minerals in the nitrogen fertilizer are a eutectic mixture.

[0008] Wherein, the weight ratio of the urea to the calcium magnesium mineral is (1-4): (1-4).

[0009] Wherein, the calcium and magnesium minerals are one or more of calcium salts or magnesium salts.

[0010] Wherein, the calcium salt is one or more of calcium nitrate, calcium sulfate, calcium carbonate, and calcium ammonium nitrate; and the magnesium salt is one or more of magnesium sulfate, magnesium nitrate, magnesium carbonate, and magnesium ammonium nitrate.

[0011] Wherein, the calcium and magnesium minerals are one or more of oxides and hydroxides of calcium and magnesium.

[0012] Wherein, the urea and calcium and magnesium minerals in the nitrogen fertilizer are an ionic eutectic mixture.

[0013] In order to solve the above technical problems, the present application proposes a preparation process of a low-ammonia volatile nitrogen fertilizer based on calcium and magnesium minerals, the process comprising:

[0014] S1: passing urea into a mixing tank, and adding a certain weight proportion of calcium and magnesium minerals into the mixing tank to form a urea-calcium and magnesium mineral molten mixture;

[0015] S2: passing the urea-calcium-magnesium mineral molten mixture into a granulation device to obtain a urea-calcium-magnesium mineral eutectic mixture;

[0016] S3: Further cooling and granulation to obtain low ammonia volatile nitrogen fertilizer based on calcium and magnesium minerals.

[0017] Among them, the method for forming a urea-calcium-magnesium mineral molten mixture in step S1 includes: one of dry mixing, slurry mixing, and mechanical reaction mixing. The dry mixing is to dehydrate the calcium-magnesium mineral and then put it into molten urea for dissolution reaction, the slurry mixing is to directly mix the calcium-magnesium mineral with molten urea and then dissolve it, and the mechanical reaction mixing is to directly mix the calcium-magnesium mineral with powdered urea and grind it.

[0018] Wherein, the temperature of mixing urea and calcium and magnesium minerals in step S1 is 133-150°C.

[0019] The granulation method in step S2 is one of high tower granulation, rotary drum fluidized bed granulation, disc granulation and spray granulation, and the granulation temperature is 80-100°C.

[0020] The present application achieves the stability of urea by synthesizing a eutectic mixture of urea and calcium-magnesium minerals based on the interaction between urea and calcium-magnesium minerals, ensures low ammonia volatilization, and reduces volatility. At the same time, it can delay the process of converting ammonium nitrogen into nitrate nitrogen, thereby reducing nitrous oxide emissions and improving nitrogen utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] By reading the detailed description below with reference to the accompanying drawings, the above and other purposes, features and advantages of the exemplary embodiments of the present disclosure will become readily understood. In the accompanying drawings, several embodiments of the present disclosure are shown in an exemplary and non-limiting manner, and the same or corresponding reference numerals represent the same or corresponding parts, wherein:

[0022] Figure 1 It is a diagram of a low-ammonia volatile nitrogen fertilizer product according to an embodiment of the present invention. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present disclosure to clearly and completely describe the technical solutions in the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present disclosure.

[0024] The specific embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.

[0025] The present application proposes a low-ammonia volatile nitrogen fertilizer based on calcium-magnesium minerals, wherein the nitrogen fertilizer comprises urea and calcium-magnesium minerals, and the urea and calcium-magnesium minerals in the nitrogen fertilizer are a eutectic mixture.

[0026] It should be noted that a eutectic is a single-phase crystalline substance with a certain stoichiometric ratio at room temperature formed by two or more different molecules and / or ionic compounds through a specific molecular recognition process under the action of non-covalent bonds, such as hydrogen bonds, van der Waals interactions, halogen bonds, ππ stacking, etc., and there is no proton transfer between the compounds.

[0027] The eutectic mixture provided in the present application contains urea and calcium-magnesium minerals. Based on the interaction between urea and calcium-magnesium minerals, the stability of urea is achieved, low ammonia volatilization is guaranteed, volatility decreases, and the process of ammonium nitrogen conversion into nitrate nitrogen can be delayed, thereby reducing nitrous oxide emissions and improving nitrogen utilization, i.e., low ammonia volatile nitrogen fertilizer based on calcium-magnesium minerals. Urea in the present application, also known as urea and carbonamide, has a chemical formula of CH4N2O or CO(NH2)2, is an organic compound composed of carbon, nitrogen, oxygen, and hydrogen, and is a white crystal. The calcium-magnesium mineral in the present application is a mineral containing calcium and magnesium elements.

[0028] Furthermore, the weight ratio of the urea and the calcium magnesium mineral in the eutectic mixture is (1-4): (1-4), and the weight ratio can be determined according to the actual urea nitrogen fertilizer production process, and the weight ratio can be 1:.1, 2:1, 1:2, etc.

[0029] In the present application, the calcium salt is one or more of calcium nitrate, calcium sulfate, calcium carbonate, and calcium ammonium nitrate, and the magnesium salt is one or more of magnesium sulfate, magnesium nitrate, magnesium carbonate, and magnesium ammonium nitrate. In addition, the calcium and magnesium minerals can also be one or more of oxides and hydroxides of calcium and magnesium, such as calcium oxide, magnesium oxide, calcium hydroxide, magnesium hydroxide, etc.

[0030] In the present application, the urea and calcium and magnesium minerals in the nitrogen fertilizer are an ionic eutectic mixture. That is, the eutectic mixture in the present application is maintained in structure by charge assistance, wherein the charges are calcium and magnesium ions, and the hydrogen bonds are hydrogen bonds between urea molecules.

[0031] The present application also provides a preparation process of a low-ammonia volatile nitrogen fertilizer based on calcium and magnesium minerals, the process comprising:

[0032] S1: passing urea into a mixing tank, and adding a certain weight proportion of calcium and magnesium minerals into the mixing tank to form a urea-calcium and magnesium mineral molten mixture;

[0033] S2: passing the urea-calcium-magnesium mineral molten mixture into a granulation device to obtain a urea-calcium-magnesium mineral eutectic mixture;

[0034] S3: further cooling and granulation to obtain low ammonia volatile nitrogen fertilizer based on calcium and magnesium minerals, such as Figure 1 As shown, Figure 1 This is a diagram of a low-ammonia volatile nitrogen fertilizer product according to an embodiment of the present application.

[0035] It should be noted that the method for forming the urea-calcium-magnesium mineral molten mixture in step S1 includes: dry mixing, slurry mixing, and mechanical reaction mixing.

[0036] Specifically, in dry mixing, the calcium and magnesium minerals must first be dehydrated, and the dehydration treatment is generally carried out by heating and drying. The water adsorbed by the calcium and magnesium minerals is removed through the dehydration treatment to maintain a dry state. The moisture content of the calcium and magnesium minerals is reduced to 0.1% through the dehydration treatment. Then, according to the weight ratio of calcium and magnesium minerals required in the actual production process, the calcium and magnesium minerals are placed in molten urea for dissolution reaction to form a urea-calcium and magnesium mineral molten mixture.

[0037] The slurry method mixing is to directly mix the calcium and magnesium minerals with molten urea and then carry out a dissolution reaction, without pre-treating the calcium and magnesium minerals.

[0038] The mechanical reaction mixing is to directly mix the calcium magnesium mineral with powdered urea and grind it to obtain a reaction principle with a smaller particle size, and ensure that the contact between urea and the calcium magnesium mineral is more sufficient. After they are fully mixed in the solid state, they are heated and dissolved to obtain a urea-calcium magnesium mineral molten mixture.

[0039] In order to ensure that they can be fully mixed and form a molten mixture, and to ensure that they form a eutectic state, it is necessary to control the temperature of forming the urea-calcium-magnesium mineral molten mixture and the temperature of forming the urea-calcium-magnesium mineral eutectic mixture, wherein the temperature of mixing urea and calcium-magnesium mineral in step S1 is 133-150°C, the granulation temperature in step S2 is 80-100°C, and the granulation method is one of high tower granulation, rotary drum fluidized bed granulation, disc granulation, and spray granulation.

[0040] In order to further test the ammonia volatility of low-ammonia volatile nitrogen fertilizers based on calcium and magnesium minerals with different component contents and their effects on crop yield and quality, the present application conducted the following experiments.

[0041] First, the present application prepared low-ammonia volatilization nitrogen fertilizers based on calcium and magnesium minerals with different component contents, and further tested the ammonia volatilization concentration values ​​thereof. The contents of urea and calcium and magnesium minerals in the nitrogen fertilizers are shown in Table 1.

[0042] Table 1: Contents of urea and calcium and magnesium minerals in nitrogen fertilizers of various test examples

[0043]

[0044]

[0045] It should be noted that the CK group is a blank control group, and the UREA group means that all the raw materials in this embodiment are urea. The preparation of nitrogen fertilizers in Test Examples 1-4 is prepared by the preparation process of low-ammonia volatile nitrogen fertilizers based on calcium and magnesium minerals, which will not be repeated here. The calcium and magnesium minerals shown in Test Examples 1-4 are ammonium nitrate salts of calcium ions, i.e., calcium ammonium nitrate, and the calcium and magnesium minerals shown in Test Examples 5-8 are nitrates of magnesium ions, i.e., magnesium nitrate. The content of each component in Table 1 is expressed by weight.

[0046] In this application, the determination of ammonia volatilization adopts the static absorption method, that is, first weigh 250g of the test soil sample and put it into the washing bottle, add 70mL of distilled water, weigh another 250g of the test soil sample and 0.5g of fertilizer and mix them and then put them into the bottle, add 60mL of distilled water, so that the soil water content of the test soil sample reaches 25%, and continuously incubate at room temperature of 25°C. The ammonia volatilization concentration value in the washing bottle was measured by a portable pump suction ammonia detector on the 2nd, 3rd, 4th, 5th, 8th, 9th and 11th days of the test, respectively. The specific test results of each test example are shown in Table 2.

[0047] Table 2: Ammonia volatilization concentration values ​​of various fertilizers under different cultivation days (in ppm)

[0048]

[0049]

[0050] The test results show that the ammonia volatilization concentration of the UREA group is the highest from the second day of cultivation, the ammonia volatilization concentration decreases rapidly from the 3rd to the 5th day, and the ammonia volatilization concentration tends to be stable from the 8th to the 11th day. However, during the entire cultivation process, the ammonia volatilization concentration of the UREA group has always been the highest value among all treatments. In Experimental Example 1, there is an obvious downward trend in the ammonia volatilization value. The ammonia volatilization concentration of Experimental Example 2 is the second highest from the second day of cultivation, but it is about 70% lower than that of the UREA group. The ammonia volatilization concentration value does not change much from the 2nd to the 3rd day, and the ammonia volatilization concentration decreases rapidly from the 4th to the 8th day. The ammonia volatilization concentration is 0 when detected on the 11th day. The ammonia volatilization concentration detected on the second day of cultivation in Experimental Examples 3 and 4 is very low, only 5.62ppm and 3.50ppm respectively. From the 3rd day to the 11th day, the ammonia volatilization concentration detection value is 0ppm, and no ammonia volatilization is detected. The above results show that with the increase of the content of calcium magnesium minerals, namely calcium ammonium nitrate, urea in nitrogen fertilizer is more stable and the ammonia volatilization is also reduced.

[0051] It can be further seen from Test Examples 5-8 that as the content of calcium magnesium mineral, namely magnesium nitrate, increases, urea in the nitrogen fertilizer becomes more stable and the ammonia volatilization amount also decreases.

[0052] In order to further determine the effects of different nitrogen fertilizer components on crop yield and quality, this example uses potted Shanghai Qing for testing. The test seedling medium is mixed evenly. Each pot contains 1.5L of medium. A total of 6 treatment samples are set. Each treatment sample is repeated 3 times, with a total of 18 test samples. The amount of fertilizer for each treatment is shown in Table 3. Other field management is consistent. Fertilization method: evenly spread and then water.

[0053] Table 3: Details of fertilization for experimental treatments

[0054]

[0055]

[0056] Furthermore, the present application analyzes the effects of the treatments in each test example on the products of the bok choy. The specific effects are shown in Table 4.

[0057] Table 4: Effects of treatments in various embodiments on the yield of bok choy

[0058]

[0059] From Table 4 - the effects of the treatments in various embodiments on the yield of Shanghai green, it can be seen that the yield increase rates of Test Examples 3 and Test Examples 7 were higher than that of the CK group, with the yields of Shanghai green increased by 17.19% and 11.52% respectively compared with the CK group. That is, in this test example, the optimal weight ratio of urea and calcium-magnesium minerals is 1:1.5.

[0060] Furthermore, the present application analyzes the effects of the treatments in various embodiments on the quality indicators of Shanghai green, and the specific effects are shown in Table 5.

[0061] Table 5: Effects of treatments in various embodiments on quality indicators of bok choy

[0062]

[0063] From Table 5 - the effects of the treatments in various embodiments on the quality indicators of Shanghai green, it can be seen that among the test examples, the Shanghai green with higher soluble protein content than that of the CK group are Test Example 3 and Test Example 7, which are 15.46% and 13.54% higher in soluble protein content than that of the CK group, respectively.

[0064] The present invention improves the utilization rate of urea nitrogen to a certain extent and reduces ammonia volatilization accordingly by synthesizing a eutectic mixture of urea and calcium-magnesium minerals.

[0065] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0066] Although the preferred embodiments of the present application have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present application.

[0067] Finally, it should be noted that, in this application, relational terms such as first and second, etc., are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or terminal device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or terminal device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or terminal device including the elements.

[0068] Specific examples are used in this application to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core idea of ​​this application. At the same time, for those skilled in the art, according to the idea of ​​this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on this application.

Claims

1. A low-ammonia volatile nitrogen fertilizer based on calcium and magnesium minerals, characterized in that: The nitrogen fertilizer comprises urea and calcium and magnesium minerals, and the urea and calcium and magnesium minerals in the nitrogen fertilizer are a eutectic mixture.

2. The low-ammonia volatile nitrogen fertilizer based on calcium and magnesium minerals according to claim 1, characterized in that: The weight ratio of the urea to the calcium magnesium mineral is (1-4): (1-4).

3. The low-ammonia volatile nitrogen fertilizer based on calcium and magnesium minerals according to claim 1, characterized in that: The calcium and magnesium minerals are one or more of calcium salts or magnesium salts.

4. The low-ammonia volatile nitrogen fertilizer based on calcium and magnesium minerals according to claim 3, characterized in that: The calcium salt is one or more of calcium nitrate, calcium sulfate, calcium carbonate, and calcium ammonium nitrate; the magnesium salt is one or more of magnesium sulfate, magnesium nitrate, magnesium carbonate, and magnesium ammonium nitrate.

5. The low-ammonia volatile nitrogen fertilizer based on calcium and magnesium minerals according to claim 1, characterized in that: The calcium and magnesium minerals are one or more of oxides and hydroxides of calcium and magnesium.

6. The low-ammonia volatile nitrogen fertilizer based on calcium and magnesium minerals according to claim 1, characterized in that: The urea and calcium and magnesium minerals in the nitrogen fertilizer are an ionic eutectic mixture.

7. A preparation process of a low-ammonia volatile nitrogen fertilizer based on calcium and magnesium minerals, the preparation process being used to prepare the low-ammonia volatile nitrogen fertilizer based on calcium and magnesium minerals according to any one of claims 1 to 6, the process comprising: S1: passing urea into a mixing tank, and adding a certain weight proportion of calcium and magnesium minerals into the mixing tank to form a urea-calcium and magnesium mineral molten mixture; S2: passing the urea-calcium-magnesium mineral molten mixture into a granulation device to obtain a urea-calcium-magnesium mineral eutectic mixture; S3: Further cooling and granulation to obtain low ammonia volatile nitrogen fertilizer based on calcium and magnesium minerals.

8. The preparation process of the low-ammonia volatile nitrogen fertilizer based on calcium and magnesium minerals according to claim 7, characterized in that: The method for forming a urea-calcium-magnesium mineral molten mixture in step S1 includes: one of dry mixing, slurry mixing, and mechanical reaction mixing. The dry mixing is to dehydrate the calcium-magnesium mineral and then place it in molten urea for dissolution reaction; the slurry mixing is to directly mix the calcium-magnesium mineral with molten urea and then dissolve it; the mechanical reaction mixing is to directly mix the calcium-magnesium mineral with powdered urea and grind it for reaction.

9. The process for preparing low-ammonia volatile nitrogen fertilizer based on calcium and magnesium minerals according to claim 8, characterized in that: The temperature at which urea and calcium and magnesium minerals are mixed in step S1 is 133-150°C.

10. The preparation process of low-ammonia volatile nitrogen fertilizer based on calcium and magnesium minerals according to claim 7, characterized in that: The granulation method in step S2 is one of high tower granulation, drum fluidized bed granulation, disc granulation and spray granulation, and the granulation temperature is 80-100°C.

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