JPS59116110A - Manufacture of phosphoric acid with high concentration - Google Patents

Abstract

PURPOSE:To enable a hydration reaction using sulfuric acid with low concn. by washing a cake of hemihydrate gypsum to reduce the concn. of phosphoric acid in a hydration system. CONSTITUTION:Crushed phosphate ore and phorphoric acid 2, 3, 4 are charged into a premixer 5, transferred to the 1st and the 2nd decomposition vessels 6, 7, and decomposed with sulfuric acid 8. The resulting phosphoric acid slurry 9 is passed through the 1st filter 10 to take out phosphoric acid 11 as product phosphoric acid 13 through a sealed tank 12. A separated cake 14 of hemihydrate gypsum is fed to the 1st and the 2nd hydration vessels 17, 18, and sulfuric acid 14 and a seed gypsum slurry 16 are also fed to convert the hemihydrate gypsum into gypsum dihydrate. The resulting gypsum slurry 19 is passed through the 2nd filter 20, and the filtrate 21 is poured on the filter 10 through a sealed tank 22 to wash the cake 14. The filtrate after washing is returned to the premixer 5. A gypsum cake 23 separated into the filter 20 is washed with washing water 24 and recovered as by-product gypsum 25.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing highly concentrated phosphoric acid by decomposing phosphate rock with a mixed acid of sulfuric acid and phosphoric acid.

A conventional method for producing high-strength phosphor is shown in FIG. This method converts crushed phosphate rock I into phosphorus Hz,
After mixing in premixer 5 with s#4,
The slurry is placed in first and second decomposition tanks 6 and 7 and decomposed with sulfuric acid 8 to obtain a phosphoric acid slurry 9 consisting of gypsum hemihydrate and phosphoric acid. Next, this phosphoric acid slurry 9 is completely passed through a first filter 10 (a portion is returned to the premixer 5). The phosphorus 11 separated by the first filter IO enters the seal tank I2 and is taken out as product phosphorus W13 (a part is returned to the premixer 5). On the other hand, the gypsum hemihydrate obtained by separation by the first filter 10 Cake 14 was mixed with 915% sulfuric acid slurry 16, etc.
The water enters the hydration tank 17 and the second hydration tank I8 in order. 1st, 2nd
In the hydration tanks 17 and 1B, hemihydrate gypsum is hydrated and transferred to industrial gypsum. Next, the gypsum slurry IJ 79 obtained here
are divided into f by the second filter 20. The obtained juice 21 is
It passes through the seal tank 22 and returns to the premixer 5. In addition, the separated gypsum cake 23 is washed with washing water 24, and the by-product gypsum 2 is washed.
Get 5. The post-washing liquid is returned to the first hydration IJlv via sealed tanks 26,27.

According to this method, after decomposing phosphate rock to obtain a slurry of hemihydrate gypsum and phosphoric acid, it is transferred to hemihydrate gypsum, which is industrial water gypsum.
Since product phosphoric acid and gypsum are obtained, high concentration phosphoric acid and high quality by-product gypsum can be obtained.

However, low concentration waste sulfuric acid (80% H2
80, or less) or when low-grade ore is used as the raw material phosphate rock 1, if the phosphoric acid concentration in the hydrated system is high, the acid concentration (phosphoric acid and sulfuric acid in the first and second hydration tanks 17.1B) (total acid concentration) increases beyond the limit of water utilization reactions. Therefore, there is a problem that the hydration reaction becomes impossible.

The present invention has been made in view of the above circumstances, and its purpose is to reduce the phosphoric acid concentration in the gypsum hemihydrate cake by washing the gypsum hemihydrate cake with a liquid obtained by separating gypsum slurry. , and acid concentration in irrigation systems (phosphoric acid and desulphuric acid)
The object of the present invention is to provide a method for producing high-concentration phosphoric acid that can maintain water availability.

That is, in the present invention, phosphate rock is decomposed with a mixed acid of sulfuric acid and phosphoric acid, and then separated into F4 by a first filter to obtain a phosphoric acid juice liquid and a gypsum hemihydrate cake, and this gypsum hemihydrate cake is stored in a hydration tank together with sulfuric acid and a gypsum seed slurry. In the method for producing high-concentration phosphoric acid, in which the phosphoric acid juice is used as phosphoric acid for decomposing phosphate rock, the phosphoric acid juice is separated by a second filter, and the phosphoric acid juice is used as phosphoric acid for decomposing phosphate rock. The phosphoric acid juice obtained separately was poured into the first filter to wash the gypsum hemihydrate cake, and the total acid S degree of the mixed solution of phosphoric acid and sulfuric acid in the hydration tank containing the gypsum hemihydrate cake was reduced to 19%. The preferred feature is that the number of rice cakes is 28 to 33.

The present invention will be described below with reference to illustrative embodiments. Second
The figure shows a method for producing high concentration phosphoric acid according to the present invention. This method differs from the conventional method shown in FIG.
The juice 21 generated by P separation at 0 is used to pass through the first filter 10.
This is a method for cleaning the upper hemihydrate gypsum cake 14.

That is, crushed phosphate rock 1 is put into a premixer 5 together with phosphoric acid 2,3°4, and then put into first and second decomposition tanks 6, 7 and decomposed with sulfuric acid 8. The obtained phosphoric acid slurry 9 is separated by a first filter 10. The phosphoric acid 11 passes through a sealed tank 12 and is taken out as a product phosphoric acid 13. On the other hand, the hemihydrate stone cake 14 enters the first hydration tank 17 and the second hydration tank 18 together with the sulfur Z5, the stone extraction slurry 16, etc., where the hemihydrate gypsum is transferred to the water gypsum. Then the obtained gypsum slurry I
J 19 is separated by the second filter 20, and the P liquid 2I is passed through the seal tank 22 onto the first filter IO to wash the hemihydrate gypsum cake 14. This washing reduces the amount of phosphoric acid contained in the gypsum hemihydrate cake 14. The juice after washing is returned to the premixer 5.

On the other hand, the gypsum cake 23 separated by the second filter 2o is washed with washing water 24 to obtain a by-product gypsum 25. The washed liquid is returned to the first hydration tank 17 via the sealed tanks 26 and 27.

According to the present invention, however, the gypsum hemihydrate cake 14 is washed to lower the concentration of hydrated phosphoric acid. Therefore, even if low-concentration sulfuric acid is used, the acid concentration can be maintained to enable water utilization reactions. The nickel acid concentration of phosphoric acid and sulfuric acid that can undergo the water utilization reaction here varies depending on the manufacturing conditions such as the phosphate rock used as the raw material and the sulfuric acid concentration, but the acid concentration is 19% or more, preferably 28% to 20%.
The acid concentration is 33%.

EXAMPLE Next, an experimental example showing that the method of the present invention can be operated using low concentration sulfuric acid will be explained.

Using 68% low concentration sulfuric acid, the process was carried out in the manner shown in Figure 2 to obtain product phosphoric acid and by-product gypsum.

The material balance in this case is shown in Table 1.

For comparison, when operating as shown in Figure 1, σ)
The literal balance is also listed in the same table.

Table 1 From Table 1, in the conventional method without cake washing, the acid concentration (Pt 0! . In this example, the upper limit of the acid concentration that allows the hydration reaction is about 33%.

On the other hand, in the present invention, the acid concentration decreased by 30%, and a hydration reaction occurred.

Next, Table 2 shows the results of a conventional operation using high concentration sulfuric acid (80-90%).

Table 2 It can be seen from Table 2 that even with the conventional method, if high concentration sulfuric acid is used, high concentration phosphoric acid of 40 to 42% can be produced at an acid concentration of 28 to 33%, and good gypsum can be obtained.

As described above, according to the present invention, the hemihydrate gypsum cake is washed to lower the hydrated phosphoric acid concentration, so even if low-concentration sulfuric acid is used, high-concentration phosphorus ν and high-quality byproduct gypsum can be obtained. It has a great effect.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a conventional method for producing high-concentration phosphoric acid, and FIG. 2 is an explanatory diagram of 11 methods for producing high-concentration phosphoric acid according to an embodiment of the present invention.

Claims (2)

[Claims] (1) After decomposing phosphate rock with a mixed acid of sulfuric acid and phosphoric acid, it is separated in the first filter to obtain a phosphoric acid solution and a gypsum hemihydrate cake, which are product acids.
A method for producing high-concentration phosphoric acid in which the phosphoric acid solution is placed in a hydration tank together with the ridge slurry for a hydration reaction, and then separated by a second filter to obtain by-product gypsum and phosphoric acid r solution, and this phosphoric acid f solution is used as phosphoric acid for decomposing phosphate rock. In this step, the phosphoric acid P solution obtained by separating the phosphoric acid through the second filter is passed through the first filter to wash the gypsum hemihydrate cake, and the phosphoric acid and #L acid in the hydration tank containing the gypsum hemihydrate cake are A method for producing high threshold phosphoric acid, characterized in that the total acid concentration of the mixed solution is 19% or more. (2) The method for producing high-concentration phosphoric acid according to claim 1, characterized in that the total acid concentration of the mixed solution of phosphoric acid and sulfuric acid in the hydration tank is 28 to 33%.