JPS5891021A - Manufacture of wet process phosphoric acid - Google Patents

Abstract

PURPOSE:To prevent the rise of the transition point of gypsum and the formation of fine gypsum particles in the manufacture of wet process phosphoric acid by a dihydrate-hemihydrate method using calcium phosphate as phosphate ore by regulating the ratio of Al/F in the liq. phase of a phosphoric acid slurry. CONSTITUTION:The weight ratio of Al/F in the liq. phase of a phosphoric acid slurry contg. gypsum dihydrate obtd. by decomposing phosphate ore with sulfuric acid in a decomposition vessel is regulated to 0.09-0.16 by adjusting the amount of a used additive contg. Al such as diatomaceous earth (i), using other kind of phosphate ore in combination with said phosphate ore (ii), solidifying and precipitating fluorine as silicofluoride with sodium hydroxide (iii), adding wet process phosphoric acid obtd. in other atage (iv), or applying other method.

Description

[Detailed description of the invention] In manufacturing, phosphate is used as phosphate rock,
And AI in the liquid phase of the phosphoric acid slurry obtained in the decomposition tank
The gist of this is a method for producing wet phosphorus alcohol by adjusting the /F heavy water ratio between 0.09 and 0.016. )
Phosphoric acid slurry containing gypsum dihydrate is obtained by decomposing phosphate rock with sulfuric acid (in this specification, the reactor in which this decomposition is carried out is referred to as [decomposition tank-1]). (2) The above phosphoric acid slurry = (The slurry obtained in this decomposition tank is hereinafter simply referred to as "phosphoric acid slurry-1") is separated into product wet phosphoric acid and trihydrate-containing gypsum. is brought into contact with sulfuric acid or a mixed acid of sulfuric acid and phosphoric acid to transform trihydrate gypsum into hemihydrate gypsum (the reactor that performs this transformation is hereinafter referred to as "modified cypress") (4) ( The slurry obtained in 3) was filtered, and the filtrate obtained in (5) f4) was filtered into (1
This is a method for producing wet phosphoric acid, in which the main process is circulation to a decomposition tank.

Honmen Akiyoshi et al. 1-, Faraboa Mine (South Africa).

Colla ν′. In the course of research on applying the industrial water-cow water method to phosphate ores produced in countries such as the USSR, it was discovered that problems that do not occur with other types of phosphate ores were discovered. ?
．． .

In other words, I) When using phosphorite, when the aluminum content in the phosphoric acid slurry becomes large, (a) the transition point of gypsum in the reforming tank becomes abnormally high, making it necessary to raise the processing temperature of the reforming tank. (2) The crystal growth rate becomes abnormally low and cannot keep up with the transition rate, resulting in fine particles with poor filterability. occurs frequently.

In the production of wet phosphoric acid, diatomists are usually used to remove the negative effects of organic substances and fluorine.

Use silica-containing materials such as bentonite.

These contain 5 to 7 wt% of the outer aluminum of silica and 15 to 20 wt% of the latter, assuming A1+0m, and these add to the aluminum contained in the phosphate rock, and the aluminum content in the phosphate slurry increases. This causes the amount to increase. By the way, when using nodular mormonite such as Florida ore or Moroccan ore or guanoic mormonite such as Nauru ore, the transition point may be too high or the crystallization temperature may be too low due to the high aluminum content in the phosphoric acid slurry. No growth rate problems have arisen.

1) On the other hand, when the aluminum content in the phosphoric acid slurry decreases, the rate of transition from industrial water to semi-water in the reforming tank becomes abnormally high, and this rate overwhelms the crystal growth rate, causing secondary nuclei to form. As a result, fine particles with poor filterability are also generated. Of course, it is theoretically possible to suppress the generation of fine particles by bringing the operating conditions closer to the transition point, but this is industrially difficult because the temperature must be controlled within an extremely narrow range.

In the case of Moroccan ore and Florida ore, the above problems can be avoided simply by adjusting the concentration of sulfuric acid, etc. in the reforming tank, but in the case of phosphate ore, such problems cannot be covered by such methods. It is.

The inventors of the present invention further investigated and found that fluorine also has a large influence on the above problem, and its effect is opposite to that of aluminum.The present invention is based on such findings. It was originally achieved.

That is, the purpose of the present invention is to eliminate the above-mentioned obstacle due to excess or deficiency of aluminum when applying the industrial water-half water method to phosphorite, and this purpose is achieved by the present invention as summarized above. I can do it.

A1/F (wt) ([h1/y of liquid phase of phosphoric acid slurry
The weight ratio 1 is abbreviated as follows. ) and the transition point of gypsum is as follows.From this data, it can be seen that the transition point of Faraborite is more strongly influenced by A1/F (wt-) than other ores. Ru.

1 and 2 respectively show Example 2 (Al/F
(wt) 1.6) and a sketch of hemihydrate gypsum crystals obtained in Comparative Example 1 (wt 1.7). What is the shape of the crystal between 1.6 and 1.7?

You'll see how big they are.

Further, an example of a demo showing the influence of Ax/y (wt) on the trihydric to semihydric transition rate is shown in the table below. However, in order to adjust this *], /y(vt), for example, the following method can be taken.

(c) Adjustment of usability of additives containing aluminum, such as diatomaceous earth and bentonite ■ Combined use of other types of phosphate rock (c) Precipitate NO7 as silicofluoride with sodium hydroxide etc. and release it from the liquid phase. Method of transferring to the same phase C1) Wet phosphoric acid produced by other phosphate rocks or other processes or condensed thereof, 1. <
In carrying out the present invention, the operating conditions of the decomposition tank are such that Al/F (Wt) is (1
The method may be the same as the conventional method using Florida ore, Moroccan ore, etc., except that the above-mentioned (c) to 4 are adjusted so that the value is 0.09 to 0.16. The conditions in the reforming tank are also the same; for example, the appropriate operating temperature to obtain coarse crystals with good filterability varies depending on the type of ore, degree of supersaturation, etc. Basically, the temperature should be 5 to 20°C higher than the transition point.

The present invention will be explained below using specific examples. 7 Examples 1 to 3. Comparative Examples 1 to 2 In the first chamber of a decomposition tank, six chambers with an effective capacity of 11 each equipped with an agitator were connected in series so that the slurry sequentially overflowed, and 600 l/hr of phosphate rock, bentonite or diatomaceous earth, and the following were added. Supplying a portion of the slurry overflowing from the fifth chamber; supplying sulfuric acid with a concentration of 98 wt% and a mixed solution of the slurry furnace liquid overflowing from the reforming tank described below and the cleaning liquid of the rosai to the second chamber; Part of the slurry overflowing from the fifth chamber 20
l! /hr was circulated to the first chamber to equalize the temperature in each chamber. The phosphoric acid slurry overflowing from the sixth chamber was separated into product wet phosphoric acid and wet gypsum using a centrifuge.

Contains water gypsum and once 98 wt% sulfuric acid f effective capacity 31 with stirrer! is supplied to the reforming tank of pto@
The transfer reaction was carried out in a solution containing 2 B Wj% and SOa 8 Wj%. Slurry IJ overflowing from the reforming tank
- filtered through a glass filter and washed with pure water 1
The mixed solution of the obtained filtrate and washing solution was mixed and supplied to the second chamber of the decomposition tank as described above.

The phosphorus magnet, bethonite and diatomaceous earth used and their compositions are as follows.

Phosphate (composition zwt) Faraboiite Moroccanite PtO 39.58 34.14Ca0
53h35 54.32A1*Om
G, 12 0.53Si, O*
1150 2.91F
2.86 4.18 Bentonite Nippon Bentonite Kogyo 3rd layer Aso 5ift: 61.93wt Altos: 2Q
, 64wt Diorite 600 Flin! manufactured by Showa Chemical Industry ■ :89.5wt% AItos: 7.5
Other conditions and results for wt-chi are shown in the table below.

1) A mixture of phosphate rock used in Example 5, 1.7 Araboaite and Moroccanite in a weight ratio of 1:1.

2) In Comparative Example 2, 17k was used.

5) A mixture of the slurry overflowing from the reforming tank and the cleaning solution for the roasted sake.

4) Sketch of the hemihydrate gypsum obtained in Example 2 and Comparative Example 1 are shown in FIG. 1 and FIG. 2, respectively.

[Brief explanation of the drawing]

1 and 2 are sketches of hemihydrate gypsum obtained in Example 2 and Comparative Example 1, respectively. Patent applicant: Toyo Soda Kogyo Co., Ltd. 1

Claims (1)

[Claims] (1) In producing wet phosphoric acid by the industrial water-half water method, apatite is used as the phosphate rock, and the Al/Fl/conversion in the liquid phase of the phosphoric acid slurry obtained in the decomposition tank is A method for producing wet phosphoric acid, characterized by adjusting the phosphoric acid to 009 to 1116,