JPS5911555B2 - Production method of soluble potassium magnesium phosphate compound fertilizer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for producing a soluble potassium magnesium phosphate complex fertilizer.

Conventionally, soluble potassium phosphate compound fertilizers include potassium magnesium phosphate, potassium calcium phosphate,
Potassium metaphosphate and the like have been considered, and various methods for producing the same have been proposed.

Among these, as a method for producing the potassium magnesium phosphate compound fertilizer targeted by the present invention, for example,
Japanese Patent Application No. 5186 discloses a method of manufacturing by mixing phosphoric acid and a magnesium-containing substance in a specific ratio and reacting the mixture, and then reacting the obtained reaction product with potassium bicarbonate.

However, in this method, when a substance that also contains calcium, such as dolomite clinker dust, is used as the magnesium-containing substance, large amounts of water-soluble potassium and water-soluble 1'1EIJ acid are present in the resulting composite fertilizer. However, it has the disadvantage of extremely low solubility.

As a result of various searches to find out the reason, the present inventors found that the reason why there is a large amount of water-soluble potassium in the obtained composite fertilizer is due to the combination of calcium and phosphoric acid contained in the magnesium-containing material. The CaHPO obtained in the reaction was heated to 100°C.
I learned that this is because it does not react with potassium bicarbonate at all at the reaction temperature below.

On the other hand, the reason why there is a large amount of water-soluble phosphoric acid in the resulting composite fertilizer is that magnesium and calcium do not easily react with phosphoric acid at reaction temperatures below 100°C, so phosphoric acid is used in excess of the theoretical value. The excess phosphoric acid reacts with potassium bicarbonate to form water-soluble KH2.
I learned that this is because PO4 and 2HPO4 are generated.

Based on this knowledge, the present inventors aimed to establish a method for producing a potassium-magnesium phosphate-based composite fertilizer with a high solubility rate from a substance containing magnesium as well as calcium. I conducted extensive research.

As a result, after mixing the substance containing magnesium and calcium with phosphoric acid and basic potassium salt,
The present invention was completed based on the discovery that a potassium-magnesium phosphate-based composite fertilizer with high resolubility can be produced industrially by firing at 200 to 1400°C.

Substances containing magnesium and calcium used in the present invention include dolomite, dolomite clay linker dust, dolomite calcined product, dolomite-serpentine calcined product, towamite-serpentine calcined linker dust, and magnesium clay. Examples include slaked lime and mixtures thereof, and it is preferable to use slaked lime or a mixture thereof, which has been pulverized into a 100-inch mesh.

Further, the basic potassium salt used in the present invention includes potassium hydroxide, potassium carbonate, potassium bicarbonate, or a mixture thereof, and these substances may be used in the form of either powder or aqueous solution.

In the present invention, first, these substances containing magnesium and calcium and a basic potassium salt are mixed at 10 to 85%
The ratio of wt% phosphoric acid to 20 to (CaO+Mg0):P2O5: is usually 1 to 3:1:0. By mixing the fertilizers at a concentration of 9 to 2, it is possible to arbitrarily produce a soluble potassium-magnesium phosphate-based composite fertilizer containing 40 wt% or more of slow-release potassium based on the total potassium content.

If the firing temperature of these mixtures in the present invention is too low, the magnesium and calcium components will be difficult to react with phosphoric acid, and the CaHPO4 produced by the reaction between the calcium component and phosphoric acid will be difficult to react with the basic potassium salt. Because water-soluble potassium and phosphoric acid components are present in the resulting composite fertilizer, and conversely, even if the temperature is too high, the reaction rate in the baking process remains constant and becomes uneconomical.
It is preferable to perform the firing at 400° C. for 20 to 60 minutes in an electric Matsufuru furnace or rotary kiln.

Next, the reaction mechanism in the firing step of the present invention will be described.

(1) When the molar ratio of (CaO-1-MgO)/P2O5 is 18 to 3 In the present invention, these reactions occur extremely easily during the calcination process, so it is not necessary to use an excessive amount of phosphoric acid. Without,
Also, water-soluble KH2PO, or K 2 HPo 4
Therefore, the solubility of the resulting soluble potassium magnesium phosphate compound fertilizer is extremely high.

Furthermore, when phosphoric acid and basic potassium salt react, water-soluble KH2PO4 or K2HPo4 is produced, so in the conventional method, phosphoric acid and a magnesium-containing substance are first mixed, and then the resulting product is In addition to requiring a two-step mixing operation in which a basic potassium salt is mixed with the fertilizer, a drying process is also required because the resulting composite fertilizer contains water.

In contrast, in the present invention, even if a substance containing magnesium and calcium is mixed with phosphoric acid and a basic potassium salt at the same time, there is no fear that the phosphoric acid and the basic potassium salt will react. Moreover, since the obtained composite fertilizer is sufficiently dry, no drying step is necessary, and the present invention has the advantage that the manufacturing operation is extremely simplified compared to conventional methods.

In addition, in the present invention, when dolomite clinker dust is used as a substance containing magnesium and calcium, dolomite clinker dust is generated at a metal magnesium manufacturing factory and can be a source of pollution, so it must be treated accordingly. In addition to the advantage of being able to make effective use of materials that were previously difficult to use, it also has the advantage that the manufacturing cost of compound fertilizers is extremely low.

In this way, the present invention makes it possible for the first time to produce a potassium-magnesium phosphate-based compound fertilizer with a high solubility rate from a substance containing calcium in addition to magnesium, and its industrial significance is Extremely deep.

Next, examples of the present invention and comparative examples will be given.

The substance containing magnesium and calcium used on each side was the pulverized product of 100 meshes of dolomite clinker dust having the chemical composition shown in Table 1, which was generated at a metal magnesium manufacturing plant.

Example 1 Dolomite clinker dust, 55 wt% phosphoric acid aqueous solution and 48 wt% potassium hydroxide aqueous solution were mixed with (CaO+
The molar ratio of 20 to Mg0)' P2O5 is 1.28:
After mixing to give a ratio of 1.0:1.1, this mixture was fired in an electric Matsufuru furnace at 400° C. for 40 minutes to produce a soluble potassium magnesium phosphate composite fertilizer.

Example 2 An experiment was conducted in the same manner as in Example 1, except that the firing conditions were 1,100° C. for 30 minutes.

Example 3 The mixing ratio of raw materials was (CaO+Mg0): P2O5:
Example 1 except that the molar ratio of 20 to 20 was 2.3:10:12 and the firing temperature was 1,000°C.
An experiment was conducted in the same manner.

Example 4 Dolomite clinker dust, 55 wt% phosphoric acid aqueous solution and 48 wt% potassium hydroxide aqueous solution were mixed into (CaO+
Mg0) diP2o5: K20 molar ratio is 2.0
: 1.0 : 1.3, this mixture was fired in an electric Matsufuru furnace at 800°C for 40 minutes,
A soluble potassium-magnesium phosphate compound was produced.

Example 5 An experiment was conducted in the same manner as in Example 4, except that the firing temperature was 1,200°C.

Comparative Example 1 Dolomite clinker dust and 55 wt % phosphoric acid aqueous solution were mixed so that the (CaO + MgO) :P 205 (7) molar ratio was 2.0: 1.0, and after stirring for several minutes, 48 wt % water was mixed. Potassium oxide aqueous solution 20:P2
They were mixed so that the molar ratio of O3 was 1.3:1.0.

The obtained product was then dried at 100°C to produce a resolubilized potassium magnesium phosphate composite fertilizer.

Example 6 Dolomite clinker dust, a 36.5 wt% phosphoric acid aqueous solution, and potassium carbonate powder with a purity of 99 wt% were mixed into (C
aO+Mg0): P2O,: molar ratio of 20:20:
After mixing at a ratio of 1.0:11, this mixture was
, and 50 minutes in a rotary kiln at 100° C. to produce a soluble potassium magnesium phosphate composite fertilizer.

Comparative Example 2 Dolomite clinker dust and 36.5 wt% phosphoric acid aqueous solution (CaO + MgO): P 205 molar ratio was 2
．． After mixing to give a ratio of 0:1.0 and stirring for several minutes, potassium carbonate powder with a purity of 99 wt% was mixed with 20:P2.
They were mixed so that the molar ratio of O, was 1.1:1.0.

The obtained product was then dried at 100°C to produce a resolubilized potassium magnesium phosphate composite fertilizer.

Examples 7 and 8 The raw materials were mixed at a molar ratio of (CaO+Mg0)2P2O5:20 to 1.9:10:1.6, and the firing temperature was 900°C (Example 7) , 1.3
The experiment was conducted in the same manner as in Example 6, except that 008C (Example 8) was used.

Comparative Example 3 Dolomite clinker dust and 36.5 wt% phosphoric acid aqueous solution were mixed so that the molar ratio of (CaO + Mg0):P2O5 was 1.9:1.0, and potassium carbonate powder with a purity of 99 wt% was mixed. The mixing ratio of
: An experiment was conducted in the same manner as Comparative Example 2 except that the molar ratio of P205 was 1.6:1.0.

Comparative Example 4 An experiment was conducted in the same manner as in Example 1, except that the firing temperature was changed to 160°C.

Next, Table 2 shows the properties of the soluble potassium magnesium phosphate compound fertilizers manufactured by each side.

From the experimental results shown in Table 2, the present invention uses a potassium magnesium phosphate compound fertilizer with a higher solubility than the conventional method.
It was found that the present invention can be produced industrially, and it is recognized that the present invention is an extremely excellent invention.

Claims (1)

[Claims] 1 After mixing a substance containing magnesium and calcium with phosphoric acid and basic potassium salt,
A method for producing a soluble potassium-magnesium phosphate-based composite fertilizer, which comprises firing at a temperature of ~1400°C.