JPS594396B2 - Kankouseirinsan Karihiryouno Seizouhouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a slow-release potassium phosphate fertilizer, and more specifically, an improvement in the method for producing a slow-release potassium phosphate fertilizer by calcining raw materials mainly consisting of phosphate rock and potassium compounds. It is related to.

Traditionally, slow-release potassium phosphate fertilizers have been produced by firing the mixture at high temperatures using a mixture of phosphate rock and potassium compounds as raw materials, and methods such as melt firing in an electric furnace or fluidized firing in a fluidized bed are used for firing. However, when using the melt firing method, it is necessary to solidify and pulverize the melt after firing and the operation is complicated, so it is usually preferable to employ the fluidized firing method.

Therefore, in order to sufficiently increase the decomposition rate of the calcined phosphate rock, it is preferable to carry out the firing at a temperature close to the melting point (approximately 1000°C) of the raw material, and usually at a temperature approximately 100°C lower than the melting point, i.e. 900°C. Although it is carried out at a temperature of about .degree. C., there is a problem in that a part of the fired product often fuses, making it impossible to operate stably for a long period of time.

In order to provide a stable production method for slow-release potassium phosphate fertilizer with a high decomposition rate, the present inventors have conducted repeated research on the fluidized firing method for slow-release potassium phosphate fertilizer. If pre-calcination is performed at a specific temperature before firing at a high temperature close to the melting point of the raw material, the melting point of the pre-fired product will be higher than the melting point of the raw material, resulting in less fusion than conventional single-step high-temperature firing. The present invention was achieved based on the knowledge that this is significantly reduced.

The purpose of the present invention is to provide an industrially advantageous manufacturing method for slow-release potassium phosphate fertilizer, and the purpose is to produce a potassium phosphate fertilizer by calcining raw materials mainly consisting of phosphate rock and potassium compounds in a fluidized kiln. 700℃ in manufacturing
Pre-fired at a temperature of above 850℃, then 900℃
This can be easily achieved by carrying out the main firing at a temperature below the melting point of the pre-fired product.

In the detailed description of the present invention, the phosphate rock used in the present invention is not particularly limited and can be used in this type of technology.

For example, Florida phosphate rock, Makatea phosphate rock, Moroccan phosphate rock, etc. are used.

Potassium hydroxides and salts such as caustic potash, potassium sulfate, potassium bisulfate, and potassium chloride are used as potassium compounds, but caustic potash has a particularly high activity during the calcination decomposition of phosphate rock, and it also contains sulfur dioxide during calcination. This is preferable because it does not generate gas, hydrogen sulfide, chlorine gas, etc., and does not cause equipment corrosion or pollution problems.

The blending ratio of these raw materials is CaO: K20: P
205 seven criticisms are 3.3-4.2: 1.2-3.0
: About 1.0 is selected.

In the present invention, by further adding phosphoric acid to the above-mentioned mixture of phosphate rock and potassium compound, calcination becomes easier and a potassium phosphate fertilizer containing highly soluble potassium and phosphoric acid components can be obtained.

In this case, P2O of phosphoric acid relative to P2O5 in phosphate ore
5 is blended in such a manner that the molar ratio of 5 to 5 is about 0.2 or more.

Furthermore, in the present invention, as mentioned above, kaolin group minerals (A1203.2SiO, .2H
When potassium renanit (Ca K P 04 ), the main component of slow-release potassium phosphate fertilizer, is compounded with other acidic substances or ammonium salts by adding silica- and alumina-containing substances such as 20), potassium It is also possible to prevent the disadvantage of components becoming water-soluble.

The silica- and alumina-containing substances may be used alone, but in practice, ores containing silica and alumina at the same time, such as kaolin group minerals (Al□03.
2SiO2・2H20), phyllite ((A1203・4
S t 02・H2O), sillimanite group minerals (A12
It is advantageous to use aluminum silicate-containing substances such as O3.5iO3).

In this case, the blending ratio is 20:5IO2:Al2O3, = 1.0 to 20 of the phosphate rock and potassium compound or the blend of phosphate rock, potassium compound, and phosphoric acid.
: 2.0 to 3.5 : approximately 0.02 to 0.44 is selected.

Furthermore, in the present invention, serpentinite (3Mg0.2Si02), magnesia peridotite (2(Mg, Fe)0.S102) is used as the raw material mainly consisting of phosphate rock and potassium compound.
By adding a magnesium silicic acid-containing substance such as ), the elution rate of the potassium component in the potassium phosphate fertilizer into the soil can be further reduced.

In this case, the blending ratio is generally 0.05 MgO to 1.0 mol of P2O5 in the phosphate rock and potassium compound or the mixture of phosphate rock, potassium compound, and phosphoric acid.
~2.5 moles and a ratio of about 2.6 to 4.3 moles of 5102 is selected.

The blended raw materials mainly consisting of phosphate rock and potassium compounds are crushed, then granulated and dried, and then subjected to firing.

Granulation is carried out using a rotary granulator such as a Rossier granulator or a spray granulator. However, when caustic potash is used as a potassium raw material, an aqueous solution of caustic potash and a raw material mainly composed of phosphate ore are slurried. A method of binding, followed by spray granulation and drying is suitable.

The gist of the present invention is to pre-fire a raw material mainly consisting of granulated and dried phosphate rock and a potassium compound, and then to carry out main firing at a higher temperature than the pre-calcination temperature.

Firing may be performed using multiple firing furnaces, but usually,
The firing furnace is divided into an upper preliminary firing section and a lower main firing section.
The method of continuously transferring the pre-fired granules to the lower main firing section and firing them is advantageous because of its simple operation and good thermal efficiency.

The higher the firing temperature is, the higher the rate of increase in the melting point of the raw materials is preferred for pre-firing, but if it is too high, a part of the raw materials will fuse, so the temperature should be 700°C or higher and 850°C, preferably 750-850°C.
It is carried out up to a temperature of about 50°C.

At a temperature lower than 700°C, the effect of preventing fusion in the furnace by increasing the melting point of the present invention cannot be achieved.

In addition, the melting point of the raw material and the melting point of the pre-fired product are determined by the type of raw material,
Although it cannot be said in part because it varies depending on the properties and blending ratio, for example, if the blending ratio of phosphate rock, caustic potash, serpentine, and clay is 1:0.7:0.3:0.6 (weight ratio) The melting point of the raw material is about 1000°C, and the melting point increases to 1020-1030°C after pre-calcination under the above conditions.

Next, main firing is carried out at a temperature of 900°C or higher and lower than the melting point of the pre-calcined product, but the higher the main firing temperature is, the higher the reaction rate of alkali decomposition of the phosphate rock is, which is preferable, so the main firing temperature should be set to a level that does not cause fusion of the granules. It is better to set the temperature as high as possible.

A firing time of 20 to 30 minutes is usually sufficient.

As detailed above, according to the present invention, by pre-calcining under specific conditions prior to main firing, the problem of clogging of the fluidized kiln due to the fusion of the fired materials, which is a fatal problem when producing potassium phosphate fertilizer, is avoided. However, dogs can decompose phosphate rock efficiently and stably, so they contribute to the production of slow-release potassium phosphate fertilizers.

Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

In addition, the melting point of the granules in Examples and Comparative Examples is that of Granules 2.
0g was placed in a platinum crucible, heated in an electric heater, and the temperature at which melt was observed on the surface of the granules was measured by contacting the granules with a thermocouple thermometer. .

Examples 1 to 3 and Comparative Examples 1 to 4 After pulverizing and mixing phosphate rock, serpentine, and clay, a caustic potassium aqueous solution is added to the slurry, and a spray granulation dryer is used to mix phosphate rock, serpentine, clay, and caustic potassium. The blending ratio of
: 0.3 : 0.6 : 0.7 (weight ratio) and a melting point of 1000° C. was obtained.

Using a fluidized firing furnace divided into upper and lower stages, preliminary firing and subsequent main firing are performed at the temperatures in the upper preliminary firing section and the lower main firing section, respectively, as shown in Table 1 below to apply potassium phosphate fertilizer. Obtained.

Note that the residence time was 30 minutes.

The melting point of the pre-fired product on each side, the presence or absence of fusion of granules in the main firing, and the retention rate of P2O5 in the obtained potassium phosphate fertilizer are shown in Table 1.

From the above table, it can be seen that when the preliminary firing temperature is lower than 700°C, the melting point falls below 100°C, and fusion occurs during the main firing.

Furthermore, when the main firing temperature is low, the P2O5 solubilization rate of the phosphate rock is low, that is, a large amount of insoluble phosphorus remains, which is not preferable.

Claims (1)

[Claims] 1. When producing potassium phosphate fertilizer by firing raw materials mainly consisting of phosphate rock and potassium compounds using a fluidized furnace, pre-calcination is performed at a temperature of 700°C or higher and up to 850°C, and then the pre-calcined product is heated to 900°C or higher. 1. A method for producing a slow-release potassium phosphate fertilizer, which comprises performing main firing at a temperature below the melting point of .