RU2195439C1 - Method of production of granulated superphosphate - Google Patents

Abstract

FIELD: manufacture of simple granulated superphosphate from apatite as mineral fertilizer. SUBSTANCE: method includes mixing apatite with absorption runoff at simultaneous mechanochemical activation and grinding it to sizes of apatite particles when residue on 0.036-mm sieve ranges from 5 to 35% of total mass of particles; this mixture is subjected to subsequent decomposition at one stage at temperature of 80 to 90 C at introduction of neutralizing additive; chalk is used as such additive which is introduced in pulp in the amount sufficient for reduction of free acid in it by 1.9 to 2 times ; it is introduced into granulation and drying stage or is used for neutralization of ready granules. EFFECT: possibility of producing simple superphosphate from one kind of raw material at high decomposition coefficient. 2 cl, 3 ex

Description

 The invention relates to a method for producing granular simple superphosphate from apatite, widely used as a mineral fertilizer.

 A known method of producing granular simple superphosphate from crushed apatite by the chamber-stream method, including the decomposition of apatite concentrate with sulfuric acid in a continuous superphosphate chamber, where porous superphosphate is formed. The superphosphate cut out of the chamber by a conveyor or directly in flow is fed into a drum granulator, where they neutralize the free acid with chalk, ammonia, phosphum and other neutralizing additives. (Studies on the development of phosphorus fertilizer technology using phosphorite raw materials of various deposits. Review. Inf. NIITEKHIM, M. 1990. Series "Mineral fertilizer industry". P. 57-60).

 The disadvantage of this method is that in the industrial implementation of the method receive a product of unstable quality.

Closest to the described technical essence and the achieved result is another known method for producing granular superphosphate, which involves mixing a portion of apatite with absorption drains to obtain a suspension with T: W = (1.2-1.6), decomposing the resulting mixture with a concentration of sulfuric acid of concentration 75 -98%, taken in an amount of 1.6-2.5 parts by weight for 1 hour. P ₂ O ₅ apatite, at a temperature of 100 ^o C, the supply of pulp containing 11-13% free phosphoric acid (P ₂ O ₅ ) to the second stage of decomposition with the addition of phosphorite to this stage. The resulting pulp with a free acidity of 3-5.5% P ₂ O _{5 is} sent to granulation and drying. The result is a product containing P ₂ O ₅ assy. 19-20%. (RF patent 1465436, class C 05 V 1/02, 1989).

 The disadvantage of this method is the mandatory use of two types of phosphate raw materials (apatite and phosphorite), as well as decomposition in two stages, which greatly complicates the process.

 We set the task to create a method for producing simple granular superphosphate on one type of raw material, while achieving a sufficiently high decomposition coefficient, and to obtain a standard product.

The problem is solved in the proposed method for producing granular simple superphosphate, including mixing apatite with absorption effluent, decomposing the mixture with sulfuric acid, granulating and drying the product. According to the proposed method, apatite concentrate is taken and its mixing with absorption drains is carried out with simultaneous mechanical activation when grinding the concentrate to a particle size at which the residue on a 0.036 mm sieve is 5-25%, and the decomposition of the resulting mixture with sulfuric acid is carried out in one stage at a temperature of 80- 90 ^o With the subsequent introduction of a neutralizing additive. As a neutralizing additive, chalk is taken, which is introduced either into the pulp in the amount necessary to reduce the free acid in it by 1.9-2 times, or to the granulation and drying stage, or the finished granules are neutralized by it.

 The difference between the method is the preliminary mechanochemical activation of apatite concentrate with grinding it to a certain size, as well as the decomposition of raw materials in one stage when using one type of raw material at lower temperatures.

 The invention consists in the following.

For industrial large-tonnage production in the conditions of one enterprise it is much simpler and cheaper to produce simple superphosphate from only one apatite concentrate. However, apatite is, in contrast to phosphorite, monolithic crystals, large particles of which are screened, and their decomposition is difficult. Therefore, in the known method and carry out the decomposition of only part of the feed at a sufficiently high rate of acid in the first stage, and in the second carry out additional decomposition with the addition of another part of the feed in the form of finely dispersed easily decomposable phosphorite. In order for decomposition to go through in one stage of the entire apatite concentrate, it is necessary to activate it with the opening of the surface of the raw grains. Such activation is carried out in an environment of absorption effluents, for example in ball mills. However, this process (activation) must be regulated. It is necessary to obtain apatite concentrate grains of a certain size, which in practice is determined by a sieve residue of 0.036 mm. Such a residue should be 5-25% of the total mass. With a decrease in the residue of less than 5%, energy consumption unnecessarily increases, without giving an improvement at the stage of decomposition of the raw material, and an increase in the residue above 25% leads to the predominance of large crystals in the raw material, and accordingly the effect is not achieved. The temperature range of 80-90 ^o With is necessary and sufficient to achieve the necessary degree of decomposition of raw materials. The resulting pulp contains a sufficiently large amount of free acid, therefore, as one of the options, a neutralizing additive is introduced into it in an amount necessary to reduce the content of free acid in it by 1.9-2 times. It is also possible, depending on the specific technological scheme and equipment, to introduce a neutralizing additive to the granulation and drying stage or to process finished granules with it.

 The method is illustrated by the following examples.

Example 1. 1000 kg of the Khibiny apatite concentrate of the "standard" grade containing 39.2% P ₂ O ₅ , and 1000 kg of absorption effluent are sent to a ball mill, in which the apatite concentrate is activated and ground to size with a sieve residue of 0.036 mm 5%. The resulting pulp is mixed in the reactor with 1167 kg of a solution of sulfuric acid with a concentration of 60% H ₂ SO ₄ in compliance with the ratio of 1.78 wt.h. H ₂ SO ₄ per 1 wt.h. P ₂ About ₅ apatite concentrate. Decomposition is carried out for 1.5 hours at a temperature of 85 ^o C. The resulting pulp with a free acid content of 7.9% is neutralized with chalk in an amount of 100 kg to its content of 3.7% (approximately twice), granulated and dried at a temperature of 115 ^o . When granulating and drying, the content of free acid is reduced to 1.6%. The result is 1800 kg of the finished product (granular simple superphosphate) containing,%: P ₂ O ₅ total. - 21.8; P ₂ About ₅ ass. - 20.0; P ₂ About ₅ water. - 17.0; P ₂ About ₅ freedom - 1.6. The decomposition coefficient is 93%.

Example 2. 1000 kg of Kovdor apatite concentrate containing 37.9% P ₂ O ₅ and 1500 kg of absorption effluent are sent to a ball mill, in which the apatite concentrate is activated and crushed to size with a sieve residue of 0.036 mm 25%. The resulting pulp is mixed in a reactor with 833 kg of a solution of sulfuric acid with a concentration of 84% H ₂ SO ₄ in compliance with a ratio of 1.85 wt. including H ₂ SO ₄ per 1 wt.h. P ₂ About ₅ apatite concentrate. Decomposition is carried out for 1.5 hours at a temperature of 80 ^o C. The pulp containing 6.5% of free acid is fed to BHS (drum granulator-dryer), where 71 kg of chalk is introduced, granulated and dried product at a temperature of 115 ^o C. As a result get 1800 kg of the finished product (granular simple superphosphate), containing,%: P ₂ O ₅ total. - 21.1; P ₂ About ₅ ass. - 19.3; P ₂ About ₅ water. - 16.6; P ₂ About ₅ freedom - 1.3. The decomposition coefficient is 91%.

Example 3. 1000 kg of the Khibiny apatite concentrate of the "super" grade, containing 40.1% P ₂ O ₅ , and 1100 kg of absorption effluent are sent to a ball mill, in which the apatite concentrate is activated and ground to size with a sieve residue of 0.036 mm fifteen%. The resulting pulp is mixed in a reactor with 900 kg of a solution of sulfuric acid with a concentration of 78% H ₂ SO ₄ in compliance with the ratio of 1.75 wt.h. H ₂ SO ₄ per 1 parts by weight P ₂ About ₅ apatite concentrate. Decomposition is carried out for 1.5 hours at a temperature of 90 ^o C. The resulting pulp with a free acid content of 6.8 P ₂ About _{5 is} granulated and dried at a temperature of 115 ^o C. The granules are fed into a drum, which serves 65 kg of chalk. The result is 1810 kg of the finished product (granular simple superphosphate), containing,%: P ₂ O ₅ total. - 22.2; P ₂ About ₅ ass. - 20.7; P ₂ O ₅ water. - 18.4; P ₂ O ₅ - 1.1. The decomposition coefficient is 93%.

 Using the proposed method will allow you to get a simple superphosphate on the flow scheme, the quality of which and technological indicators (decomposition coefficient, expenditure rates) are comparable to the classical chamber method. The flow process is more technological, easily automated. In addition, the method allows the use of one type of phosphate feedstock, which also simplifies the process.

Claims (2)

1. A method of producing granular superphosphate, including mixing apatite with absorption drains, decomposing the mixture with sulfuric acid at elevated temperature, granulating and drying the product, characterized in that the mixing of apatite with absorption drains is carried out with simultaneous mechanochemical activation during grinding to a particle size of apatite, which the residue on a sieve of 0.036 mm is 5-25% of the total mass of particles, the resulting mixture is decomposed in one stage at 80-90 ^o With the introduction of a neutralizing additive.  2. The method according to p. 1, characterized in that chalk is taken as a neutralizing additive, which is added either to the pulp in the amount necessary to reduce the free acid in it by 1.9-2 times, or to the granulation and drying stage, or neutralize the finished granules with it.