JPS5935874B2 - Method for producing slow-release granular fertilizer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for coating granular chemical fertilizers, and more specifically, the present invention relates to a method for coating granular chemical fertilizers, and more specifically, coating magnesium ammonium phosphate (M
The purpose of this method is to form a film containing gNH4PO4.H2O as the main component in an ammonia gas atmosphere to slow the release of fertilizer.

Slow-release nitrogen fertilizers have recently attracted attention as part of labor-saving agriculture, and many studies have been reported regarding these fertilizers.

Traditionally, typical nitrogen fertilizers such as ammonium sulfate, urea, ammonium chloride, and ammonium nitrate are all soluble in water, so they often run off before they can be absorbed by plants in the soil, especially in warm climates and areas with high undulations. Under conditions of high soil and rainfall, the loss of nitrogen fertilizer due to rainwater runoff after nitrification is significant, making it impossible to maintain the fertilizer's effectiveness over a long period of time, and therefore it becomes necessary to increase the amount and frequency of topdressing.

Therefore, various methods such as granulation, coating methods, and adding nitrification inhibitors have been proposed in order to eliminate these drawbacks of water-soluble fertilizers and supply fertilizing acids in accordance with the growth of crops.
In particular, a method has been proposed that uses a combination of magnesia ingredients that also include fertilizing ingredients.

For example, ammonium phosphate slurry and magnesium hydroxide powder are added to the granulator together with NPK fertilizer ingredients for granulation, or phosphoric acid and magnesium hydroxide powder are alternately added to the surface of the granulated fertilizer and then the unreacted A method of spraying water to leave the alkaline component of magnesium hydroxide on the particle surface (Japanese Patent Publication No. 17826/1982), or a method of spraying water to leave the alkaline component of magnesium hydroxide on the particle surface, or a method of spraying water containing magnesium oxide or magnesium hydroxide to a granular fertilizer containing a nitrification inhibitor such as dicyandiamide. There is a method of coating the surface with a poorly soluble magnesium acid salt (Japanese Unexamined Patent Publication No. 48-90850).

However, the former method has a problem with processing capacity because it forms a coating of magnesium phosphate by repeating the addition several times, and the latter method has problems in processing capacity because the eluted ammonium salts and phosphates do not flow out onto the coated surface due to diffusion. , reacts with magnesium phosphate on the surface to produce sparingly soluble magnesium ammonium phosphate, so the rate of these reactions in soil is a problem.

As a result of research to solve various problems of these conventional methods, the present inventors found that a method of coating the surface of chemical fertilizer granules while directly producing magnesium ammonium phosphate has an extremely excellent effect. This discovery led to the present invention.

That is, the present invention is a slow-removal method characterized in that the surface of a chemical fertilizer granule is coated with a magnesium phosphate slurry and reacted with ammonia in an ammonification granulator to form a coating of magnesium ammonium phosphate on the surface. This invention relates to a method for producing effective granular fertilizer.

The magnesium phosphate slurry used in Komata is usually P20. It is produced by the reaction of 20 to 45% phosphoric acid with a suitable magnesium compound or magnesium-containing mineral such as magnesium hydroxide, magnesium oxide, serpentine, and peridotite.

The concentration of phosphoric acid used varies depending on the raw material, but if it is too low, it will take time to decompose, and if it is too high, it will become agglomerated and difficult to decompose.

Therefore, a concentration of 20 to 45% is preferred in order to obtain a slurry with adequate fluidity for proper decomposition and coating.

The decomposition temperature is 60-100°C, and the slurry concentration is 30°C.
It is preferable to adjust the solid content to ~60% (solid content).

Note that the coating with the magnesium phosphate slurry may be performed using a magnesium phosphate slurry prepared in a separate step, but it is also possible to carry out the formation reaction of this slurry in the presence of the fertilizer granules and perform the coating at the same time.

The fertilizer granules used in the present invention do not need to be particularly limited in their ingredients (they can be applied to any chemical fertilizer containing water-soluble fertilizer ingredients to impart excellent slow-release properties). can.

Examples of such chemical fertilizers include ammonium sulfate, ammonium urea phosphorus, ammonium chloride, and ammonium phosphorus nitrate complex fertilizers.

The ammonium chloride fertilizer of the present invention will be specifically described below with reference to the accompanying drawings.

Phosphoric acid 2 and magnesium source 3 containing 20-45% P2O undergo a decomposition reaction in a decomposition reaction tank 5.

When using magnesium-containing minerals such as serpentine in this decomposition reaction, they must be crushed to 60 mesh or less.
Preferably, the decomposition is carried out at °C.

The magnesium phosphate slurry thus obtained has a concentration of 30 to 60%, and is 1:0.05 to 1:0.05 to 1:1 of the salted and phosphorous ammonium dry granules prepared in advance in a separate step by a known method.
The surface of the granulated product is coated in the ammonification granulator 6 within a range of 0.5 (weight).

During this time, ammonia 4 is supplied to the ammonia granulator 6 to maintain an ammonia atmosphere with an ammonia concentration of 5 to 20%, and the magnesium phosphate coated on the surface of the granules produces magnesium ammonium phosphate by ammonification. do.

This ammonification is preferably carried out in the presence of 10 to 50% excess ammonia over the amount required to produce magnesium ammonium phosphate.

The obtained granules are dried in the dryer 7 at a temperature of 100 to 12
Dry at 0°C to obtain product 8.

The magnesium compound used in the method of the present invention does not need to be pure, and the amount of magnesium used can be adjusted as appropriate depending on the desired coating or brand.

In addition, nitrogen sources include urea, ammonium sulfate, ammonium nitrate, etc. as well as ammonium chloride, and potassium sources include potassium chloride, potassium sulfate, potassium nitrate, etc. The types and amounts of these fertilizer components are determined according to the desired brand. It can be selected as appropriate, but the phosphoric acid content used to decompose this as a magnesium source, that is, the phosphoric acid content that intervenes from magnesium phosphate, is used in the production of the salted and phosphorous ammonium dry product. It is something to do.

In this way, the present invention divides the phosphoric acid solution into two stages and supplies it, reducing the need for neutralization, mixing, and granulation machines.As it covers conventional surfaces, a uniform and dense coating can be obtained, resulting in higher hardness. There are other effects.

Examples of the present invention will be shown below.

Example 1 1471 kg of P2O5275% phosphoric acid solution and 1827 kg of ammonium chloride were mixed and dissolved at 70°C for 30 minutes, and the mixture was heated and neutralized at 110°C while blowing 0.111 kg of ammonia gas.

1205 kg of potassium chloride and 4.0 kg of reconstituted powder were added to this slurry liquid, and the diameter was 80 CrrL and the depth was 20 CrrL.
Pelletize with a dish-type granulator, and during this time, use a burner from the bottom to
It was heated and kept at ~70°C.

This granulated and dried product (seed rice) was mixed with 1.55 kg of P2O5275% phosphoric acid solution and 0.35 kg of magnesium hydroxide, and reacted at 70°C for 10 minutes to produce MgHPO,
3H20 slurry 1.90kg and ammonia 0.11k
g was added to a drum-type granulator (ammonification granulator) and sprayed to coat the surface of the seed grains with MgNH4PO4.H2O.

Then, this was dried at 110℃ for 2 hours to obtain a particle size of 4T-
3.70 kg of 8 mesh product was obtained.

Product grain composition, hardness and product 12.5gr
The elution rate after immersing the sample in 500 ml of water at 30°C for 24 hours was as follows.

A-N, C-P2O5W-20 C-MgO product grain composition (%) 12.42 16.85
14.45 4.63 Hardness (kg) 1
5.5 Elution rate (NH, -N%) 4'3.5 The elution rate of the uncoated product was 98.5% and the hardness was 8.0 kg.

Example 2 1.55 kg of P2O527, 5% phosphoric acid solution and 0.35 kg of magnesium hydroxide were mixed in the same manner as in Example 1 using 3.00 kg of Shiojiri Rin'an 656 (16-5-16) as seed grains, MgHP produced by reacting at 70°C for 10 minutes
O4.3H20 slurry and ammonia 0, 101<9 were added and sprayed at the same time, and MgNH4PO4.H was added to the surface of the seed grains.
A coating of 2O was produced.

Then, this was dried at 110℃ for 2 hours to obtain a particle size of 4 to 8.
1.62 kg of mesh product was obtained.

The values obtained by analyzing this product in the same manner as in Example 1 are shown below.

A-N C-P2O,, W- to 20 C-MgO
Product grain composition (%) 12.90 13.80
11.6'0 5.30 Hardness (Kg)
140 Elution rate (NH4-N%) 36.3 The elution rate of the uncoated product was 97.8% and the hardness was 6.8 kg.

Example 3 A method similar to Example 2 and the same compounding conditions were used, except that the magnesium source was industrial magnesium oxide (C-Mg0
70%)O, '30ky, and the same treatment was performed below.

A-N C-P2O5W-20 C-MgO product grain composition (%) 12.81 13.72 11
．． 92 5.70 Hardness (kg) 15・
2 Elution rate (NH4-N%) 46.5 Comparative example 1 1.55 kg of P2O527, 5% phosphoric acid solution and 0.35 kg of magnesium hydroxide were added to 3.0 kg of Shiojiri Rin'an 656 (16-5-16) pulverized material. Mix and react at 80-90°C for 15 minutes to obtain a product with a particle size of 4-8 mesh after concentration 1.62
I got kg.

The hardness and nitrogen dissolution rate of this product were measured in the same manner as in Example 1, and the results were as follows.

Hardness (k!9) 12.2 Elution rate (volume) 985 (after 24 hours of NH4-N) Comparative example 2 Shiojiri Rin'an 656 (16-5-16) 3, Okg was used as a seed fertilizer and the diameter was 80 (J, depth) The granules were placed in a 20-tub Rossier granulator and heated with a burner from the bottom to 100°C.

To this, add P2O527.5% phosphoric acid solution and magnesium hydroxide alternately (3 times) separately, totaling 1 phosphoric acid solution addition.
．． 55kg, total addition of magnesium hydroxide 0.35kg
) The surface of the L grains was coated with MgHPO3.3H20.

The granules were then dried at 105°C for 2 hours to obtain a particle size of 4.
~8 mesh products 1. ．． Obtained 55 kg.

The hardness and nitrogen dissolution rate of this product were similarly measured and the results were as follows.

Hardness (kg) 11.8 Elution rate (
卆) 52.0 (NH, -N
24 hours later) Comparative Example 3 P2 on the surface of Shiojiri Rin'an 656 (16-5-16) granules
1.55 kg of O527.5% phosphoric acid solution, 0.35 kg of magnesium hydroxide, and 0.1 kg of ammonia were simultaneously sprayed to form a film of MgNH4PO4.H2O on the seed fertilizer surface.Then, the granules were heated at 105°C. After drying for 2 hours, 1.35 kg of a product with a particle size of 4 to 8 mesh was obtained.

The hardness and nitrogen dissolution rate of this product were similarly measured and the results were as follows.

Comparative Example 4 P2 on the surface of Shiojiri Rin'an 656 (16-5-16) granules
O, 555% phosphoric acid solution 0.7 kg and magnesium oxide 0.24 kg and monoammonium phosphate 0.6
Spray 8 kg onto the surface of the seed fertilizer and add MgNH4PO4.H.
A film of 2O was formed.

The granules were then dried at 105°C for 2 hours to obtain 14.2 kg of a product with a particle size of 4 to 8 mesh.

The hardness and nitrogen elution rate of this product were measured and the results were as follows.

[Brief explanation of drawings]

The accompanying drawing is a flow sheet showing an example of steps for carrying out the method of the present invention.

Claims (1)

[Claims] 1. A slow-release granular fertilizer characterized in that the surface of a chemical fertilizer granule is coated with a magnesium phosphate slurry and reacted with ammonia in an ammonification granulator to form a coating of magnesium ammonium phosphate on the surface. manufacturing method.