JP3099502B2 - Manufacturing method of calcined phosphate fertilizer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a calcined phosphate fertilizer (hereinafter, calcined phosphorus fertilizer). More specifically, the present invention relates to a method for producing a calcined phosphorus fertilizer using a high siliceous low-grade phosphate ore, which has conventionally had a low utility value.

[0002]

2. Description of the Related Art Conventionally, high siliceous and low-grade phosphate rocks (generally, SiO ₂ content of 10% or more, P ₂ O ₅ content of 30% or less) are mostly used because of their low phosphoric acid content. There was no. However, with concerns about resource depletion,
Motivation to effectively utilize high siliceous low-grade phosphate rock is increasing. According to the conventional technology, when manufacturing a burnt phosphorus fertilizer, expensive sodium carbonate is added as an additive for increasing the dissolution rate of the phosphoric acid component, and further, to a high temperature of about 1300 to 1500 ° C. to promote the reaction. Firing.

[0003]

Generally, since the calcination reaction of apatite Ca ₅ (PO ₄ ) ₃ F and sodium carbonate in a phosphate rock containing silicic acid follows the following formula (a), the preferred amount of sodium carbonate added is as follows: Is theoretically Na ₂ O / P ₂
This is an amount such that O ₅ (molar ratio) becomes 1.33.

[0004]

Embedded image Ca ₅ (PO ₄ ) ₃ F + 2Na ₂ CO ₃ + SiO ₂ → 3NaCaPO ₄ + Ca ₂ SiO ₄ + NaF + 2CO ₂ (a)

However, when producing calcined phosphorus fertilizer from high siliceous low-grade phosphate ore, the following Reference Examples 1 to 10
As shown in the above, when the reaction is carried out at a Na ₂ O / P ₂ O ₅ (molar ratio) around 1.33, which is the theoretical value, the dissolution rate of the obtained calcined phosphorus fertilizer is 40% or less, ₂ O / P ₂ O
_{5 As the} molar ratio increases, the dissolution rate increases and reaches 100% only at around 2.5, which is almost twice the theoretical value. This is because sodium carbonate generally reacts primarily with silica to form vitreous sodium silicate, and then (a) because of the high silica content of high siliceous low grade phosphate rock. ) Formula according to the formula
aPO ₄ ).

In the case of producing lime superphosphate or wet phosphoric acid from high siliceous low-grade phosphate rock in the prior art,
Many difficulties have been pointed out as a large amount of gelled silica is formed. That is, when producing superphosphate, not only the product is highly viscous and difficult to dry, but also the dissolution rate of phosphoric acid is low because unreacted apatite remains,
Moreover, it contains free sulfuric acid. In the case of producing wet phosphoric acid, it is difficult to separate gypsum and the phosphoric acid content is large.

The present inventors have conducted intensive studies to obtain a low-cost, high-performance phosphate fertilizer from high-silicate low-grade phosphate ore as a raw material. It has been found that by adding a sodium compound, a calcium compound and a magnesium compound to a specific molar ratio, a superior calcined phosphorus fertilizer having a lower sintering temperature and a higher quench rate can be obtained. The invention has been reached.

[0008]

That is, the gist of the present invention is as follows.
A sodium compound, a calcium compound and a magnesium compound are added to a high siliceous low-grade phosphate rock by adding P ₂ O ₅ : Na
₂ O: CaO (molar ratio) = 1: 1 to 2: 4 to 6 and Mg
O: (CaO + MgO) (molar ratio) = 0.05-0.3
0 to 1: 1 and sintering.

Hereinafter, the present invention will be described in detail. The high siliceous low-grade phosphorus ore used as a raw material of the present invention is not particularly limited as long as it is a phosphorus ore having a SiO ₂ content of at least 10 wt% and a P ₂ O ₅ content of at most 30 wt%. , P ₂ O ₅ is 20 to 30 wt%, and SiO ₂ is 10 to ₃ wt%.
0 wt%, CaO 30-40 wt%, MgO 0.3
２2 wt%, and Fe ₂ O ₃ , F, A
and those containing l ₂ O _{3 and the} like. Specifically, Patos deminas 55 (from central Brazil), Florida 5
7 (from central Florida) and 60 from Yunnan.

A sodium compound added to the phosphate rock,
Calcium compounds and magnesium compounds are not particularly limited, for example, sodium carbonate, sodium hydroxide such as sodium hydroxide, sodium sulfate, calcium carbonate, calcium hydroxide, calcium sulfate, magnesium hydroxide, magnesium sulfate, etc.
Although carbonates and sulfates are mentioned, sodium carbonate, calcium carbonate, and magnesium hydroxide are preferable from the viewpoint of handleability and cost.

For example, when sodium carbonate is used as the sodium compound,
_It is preferable that ₂ O / P ₂ O ₅ (molar ratio) be an amount of 1 to 2 before and after the theoretical value of 1.33 calculated from the formula (a). The addition amount of the calcium compound is, for example, when sodium carbonate is used as the sodium compound and calcium carbonate is used as the calcium compound, the following reference examples 11 to 2 are used.
As shown in FIG. 1, Na ₂ O / P ₂ O ₅ (molar ratio) was 1.
In 33 CaO / P ₂ O ₅ (molar ratio) in the vicinity of 5 since click溶率is maximum, CaO / P ₂ O ₅ (molar ratio) that is an amount which is a 4 to 6 before and after preferable.

According to the following reaction formula (b), N
It is considered that the formation of a ₂ Ca ₅ (PO ₄ ) ₄ and lenanite (NaCaPO ₄ ) is promoted.

[0013]

## STR2 ## _{Ca 5 (PO 4) 3 F} + XSiO 2 + 2Na 2 CO 3 + 2.5CaCO 3 → 0.5Na 2 Ca 5 (PO 4) 4 + NaCaPO 4 (b) + NaF + NaCa 4 SixO 2 x +4.5 + 4.5CO 2

Therefore, the preferable addition amount of the sodium compound and the calcium compound is P ₂ O ₅ : Na ₂ O: CaO
(Molar ratio) is from 1: 1 to 2: 4 to 6. In the present invention, in order to promote the reaction between apatite and sodium, a magnesium compound is added to remove excess silica in high siliceous low-grade phosphate rock from akermanite (Ca ₂
MgSi ₂ O ₇ ). This reaction is considered to follow the formula (c) or (d) below.

[0015]

Embedded image Ca ₅ (PO ₄ ) ₃ F + XSiO ₂ + 2Na ₂ CO ₃ + (X-2) CaCO ₃ + (X / 2) Mg (OH) ₂ → 3NaCaPO ₄ + NaF (c) + (X / 2) MgSi ₂ O7 + XCO ₂ + (X / 2) H ₂ O

[0016]

Embedded image Ca ₅ (PO ₄ ) ₃ F + XSiO ₂ + 2Na ₂ CO ₃ + (X-2) CaCO ₃ + (X / 2) Mg (OH) ₂ → 0.5 Na ₂ Ca ₅ (PO ₄ ) ₄ + NaCaPO ₄ + NaF (d) + (X / 2−0.25) Ca ₂ MgSi ₂ O ₇ + 0.25Na ₄ MgSi ₂ O ₇ + XCO ₂ + (X / 2) H ₂ O

In this case, P ₂ O ₅ : Na ₂ O: CaO: M
The theoretical value of gO (molar ratio) is 1: 1.33: [(X-2 +
5) /1.5]: [(X / 2) /1.5]. For example, as a high siliceous low-grade phosphate ore, Patos deminus 5
In the case of using 5, since X = 3.75, the above theoretical value is P ₂ O ₅ : Na ₂ O: CaO: MgO (molar ratio) = 1: 1
1.33: 4.5: 1.25. In order to determine a preferable addition amount of the magnesium compound to the calcium compound, P ₂ O ₅ : Na ₂ O: (C
aO + MgO) (molar ratio) is set to 1: 1.33: 5.75, and from the dissolution rate when MgO: (CaO + MgO) (molar ratio) is changed, MgO: (CaO +
MgO) (molar ratio) is 0.05 to 0.30: 1, particularly preferably 0.09 to 0.28: 1.

In the present invention, P ₂ O ₅ , Na ₂ O, C
By setting the molar ratio of aO and MgO as described above,
It is possible to perform calcination of high siliceous low-grade phosphate rock at a lower temperature than before. The preferred firing temperature is 950 to 1250 ° C. from the viewpoint of the dissolution rate of the obtained fired phosphorus fertilizer,
Especially preferably, it is 1000-1150 degreeC. Outside this range, the dissolution rate of the burned phosphorus fertilizer tends to decrease.

The firing time is not particularly limited, but is usually
Sintering for 20 to 40 minutes is sufficient. At each firing temperature
Products were identified by X-ray diffraction at 900 ° C.
Is found to form with the akermanite
At around 1000 ° C, the production of renanite reaches its maximum.
Was. The reaction in this case is generally represented by the above formula (c).
Na around 1050 ° C_TwoCa_Five(PO_Four)_FourProduction
And Lenanite declined slightly. The reaction in this case is roughly
It is shown by the above equation (d). Further, at 1100 ° C or more
Indicates that a part of the fired material is melted and Na_TwoCa_Five(P
O_Four)_Four, Lenanite and Akermanite production reduced
And partly silico carnotite Ca_Five(PO_Four) _TwoSiO_Four
Generated. These are the reaction formulas inferred earlier.
(C) and (d) confirm that they are generally correct.

[0020]

EXAMPLES Specific examples of the present invention will be described below in more detail with reference to Examples and Reference Examples, but the present invention is not limited to the following Examples and Reference Examples.
In the following,% means% by weight. Further, the dissolution rate indicates a value calculated by the following equation.

[0021]

## EQU1 ## Dissolution rate (%) = (2% citric acid-soluble phosphoric acid amount /
Total phosphoric acid amount) x 100

Examples 1-5 High siliceous low-grade phosphate rock from Central Brazil, Patosde Minas 55 (P ₂ O ₅₎
= 25.6%, CaO = 33.7%, MgO = 0.36
%, Al ₂ O ₃ = 2.99%, Fe ₂ O ₃ = 2.10%, F
= 1.77%, SiO ₂ = 27.0%), sodium carbonate was added so that Na ₂ O / P ₂ O ₅ (molar ratio) was 1.33, and simultaneously calcium carbonate and magnesium hydroxide were added. CaO / P ₂ O ₅ (molar ratio) and MgO / P ₂ O
₅ (molar ratio) was added so that each had the value shown in Table 1 below, kneaded by giving a small amount of water, dried at 80 ° C. overnight, and then in an electric furnace at a temperature of 1050 ° C. for 30 minutes. It was calcined and gradually cooled overnight until it reached about 100 ° C. After the obtained fired product was pulverized to 100 mesh or less, the dissolution rate in a 2% citric acid solution was measured.

[0023]

[Table 1]

FIG. 1 shows the dissolution rate of phosphoric acid in the obtained product. As is clear from this, MgO / (CaO + M
As gO) (molar ratio) increased, the dissolution rate of phosphoric acid increased, reaching a maximum at a molar ratio of around 0.22. Example 6-12 in the high siliceous low grade phosphate rock used in Example 1, sodium carbonate, calcium carbonate and magnesium hydroxide _{P 2 O 5: Na 2 O} : CaO: MgO ( molar ratio) is 1:
1.33: 5: 1, and the same treatment as in Example 1 was carried out except that the firing temperature was adjusted as shown below, and the dissolution rate was measured. Table 2 shows the results.

[0025]

[Table 2]

FIG. 2 shows the solubility of the obtained product.
As is clear from this, as the firing temperature increases, the dissolution rate of phosphoric acid increases and reaches a maximum at a firing temperature of around 1050 ° C. Reference Examples 1 to 6 Sodium carbonate was added to the high siliceous low-grade phosphate rock used in Example 1 so that the molar ratio of Na ₂ O / P ₂ O ₅ was as shown in Table 3 below. Calcium carbonate and magnesium hydroxide were not added, and the same treatment as in Example 1 was performed except that the firing temperature was 1300 ° C., and the dissolution rate was measured.
The results are shown in Table-3.

[0027]

[Table 3]

FIG. 3 shows the phosphoric acid dissolution rate of the obtained product.
-●- As is clear from this, Na_TwoO / P_Two
O_Five(Molar ratio) increases, the dissolution rate increases.
The ratio reached a maximum around 2.50. Reference Examples 7 to 10 Phosphorous ore was produced from high siliceous low-grade phosphorus produced in central Florida.
Ore Florida 57 (P _TwoO_Five= 26.3%, CaO = 3
9.9%, MgO = 0.31%, Al_TwoO_Three= 0.26
%, Fe_TwoO_Three= 1.46%, F = 1.54%, SiO_Two
= 24.0%) and the sodium carbonate was changed to Na_TwoO / P_Two
O_Five(Molar ratio) so that the value shown below,
Baking without adding calcium carbonate and magnesium hydroxide
Except that the forming temperature was 1300 ° C., the treatment was the same as in Example 1.
And the dissolution rate was measured. The results are shown in Table-4.

[0029]

[Table 4]

The solubility of phosphoric acid in the obtained product is shown by -− in FIG. As is clear from this, Na ₂ O / P ₂
As the O ₅ (molar ratio) increased, the dissolution rate increased, and reached a maximum near a molar ratio of 2.50. Reference Examples 11 to 16 Sodium carbonate was added to the high siliceous low-grade phosphorus ore used in Example 1 so that the molar ratio of Na ₂ O / P ₂ O ₅ was 1.33, and at the same time, calcium carbonate was added. To CaO / P ₂
O ₅ (molar ratio) was added so as to have the value shown in Table 5 below, and magnesium hydroxide was not added.
Except that the temperature was set to 00 ° C., the same treatment as in Example 1 was performed, and the dissolution rate was measured. The results are shown in Table-5.

[0031]

[Table 5]

The phosphoric acid dissolution rate of the obtained product is shown by-●-in FIG. As is clear from this, CaO / P ₂
As the O ₅ (molar ratio) increased, the dissolution rate increased, and reached a maximum near the molar ratio of 5.0. REFERENCE EXAMPLES 17-21 The phosphate ore was changed to the high siliceous low-grade phosphate ore Florida 57 used in Reference Example 7, and sodium carbonate was changed to Na ₂ O / P ₂ O.
₅ (molar ratio) was added to 1.33, and at the same time, calcium carbonate was added to CaO / P ₂ O ₅ (molar ratio) in the following Table-6.
Was performed in the same manner as in Example 1 except that magnesium hydroxide was not added and the sintering temperature was set to 1300 ° C., and the dissolution rate was measured. Table-Results
6 is shown.

[0033]

[Table 6]

The solubility of phosphoric acid in the obtained product is indicated by-○ in FIG. As is clear from this, CaO / P ₂
As the O ₅ (molar ratio) increased, the dissolution rate increased, and reached a maximum near the molar ratio of 5.0.

[0035]

According to the present invention, a sodium compound, a calcium compound and a magnesium compound are added to a high siliceous low-grade phosphate ore having a low utilization rate as a raw material of a phosphate fertilizer.
By adding at a specific ratio, an excellent calcined phosphorus fertilizer having an extremely high phosphoric acid dissolution rate can be obtained at a calcining temperature lower than before, which is industrially and economically advantageous.

[Brief description of the drawings]

FIG. 1 MgO / (CaO + MgO) during compounding of raw materials
The relationship between (molar ratio) and the solubility of phosphoric acid in the product is shown.

FIG. 2 shows the relationship between the firing temperature and the phosphoric acid dissolution rate of the product.

FIG. 3 shows the relationship between Na ₂ O: P ₂ O ₅ (molar ratio) and the phosphoric acid dissolution rate of the product during the mixing of the raw materials.

FIG. 4 shows the relationship between CaO / P ₂ O ₅ (molar ratio) in the mixing of raw materials and the solubility of phosphoric acid in the product.

Claims (1)

(57) [Claims] 1. A high siliceous low-grade phosphate rock containing a sodium compound, a calcium compound and a magnesium compound in a molar ratio of P ₂ O ₅ : Na ₂ O: CaO = 1: 1 to 1.
2: 4 to 6 and MgO: (CaO + MgO) (molar ratio)
= 0.05 to 0.30: 1, and calcined.