RU2271252C1 - Method for production of fine-grained potassium chloride with low content of dust fractions - Google Patents

Abstract

FIELD: potassium chloride production.

SUBSTANCE: claimed method includes crushing, deslurring, sylvinite flotation concentration, and particle size classification of flotation concentrate. To reduce dust fraction quantity in commercial concentrate said fractions are isolated in classification process, aqueous solution thereof is prepared, wherein abovementioned solution has potassium chloride/water mass ratio more than 17 %, and obtained solution is recycled into grinder. Method of present invention makes it possible to reduce dust fraction of size less than 0.1 mum in fine-grained potassium chloride.

EFFECT: improved method for potassium chloride production with low content of dust fractions.

2 cl, 3 ex

Description

The invention relates to a method for producing potassium chloride, including the processes of grinding, desliming, flotation enrichment of sylvinites and classification by size of flotation concentrate.

A known method for producing fine-grained potassium chloride with a low content of dust fractions with a particle size of less than 0.1 mm / 1 /, including the processes of grinding, desliming, flotation enrichment of sylvinites and classification by size of flotation concentrate, as well as the dissolution of part of the fine fraction of flotation concentrate. The resulting salt-unsaturated solution is used in the process for leaching sodium chloride from flotation concentrate.

A disadvantage of the known method is the fact that a solution is used for leaching, in which the mass ratio of potassium chloride to water is not more than 17%. An increase in the concentration of KCl in the leach solution above the specified limit under known conditions existing at sylvinite concentration plants leads to an increase in the fraction of dust fractions in the concentrate.

Closest to the proposed is a method that involves dissolving in hot liquors the finely divided fractions isolated during the classification of the concentrate, and subsequent crystallization in controlled vacuum crystallization plants of coarse crystalline potassium chloride / 2 /. In world practice, there are industries where 10 to 40% of the total volume of potassium chloride concentrate undergoes recrystallization.

The disadvantage of this method is the appearance of significant additional costs for the processing of dust fractions of the concentrate associated with the heating of the solvent liquor and vacuum evaporation during crystallization. These costs most often lead to the economic inexpediency of using this method.

The aim of the invention is to reduce the proportion of dust fractions with a particle size of less than 0.1 mm in fine-grained potassium chloride.

This is achieved by the fact that in the method for producing fine-grained potassium chloride with a low content of dust fractions, including grinding, desliming, flotation enrichment of sylvinites and size classification of flotation concentrate, according to the invention, a highly concentrated potassium chloride is prepared from the fine fraction isolated in the process of concentrate classification an aqueous solution in which the mass ratio of potassium chloride to water exceeds 17%, and the prepared solution is returned to the mill.

The prepared unsaturated solution in which the mass ratio of potassium chloride to water exceeds 17% can be preliminarily used for leaching sodium chloride from the flotation concentrate, while the liquid phase is separated from the concentrate and returned to the mill.

The addition of a solution in which the mass ratio of potassium chloride to water exceeds 17%, in the pulp containing sodium chloride leads at a usual sylvinite concentration plant mother liquor temperature of 20-30 ° C to the natural crystallization of potassium chloride / 3 /. Crystallization occurs due to the better solubility of NaCl with respect to KCl. Potassium chloride crystallization is carried out both on the surface of sylvin grains located in the pulp, and separately in the form of small fractions of potassium chloride.

The formation of fine fractions when a highly concentrated solution of potassium chloride is added to the pulp containing sodium chloride leads to an increase in the mass fraction of fractions with a fineness of less than 0.1 mm in concentrate. Because of this circumstance, in order to solve the problem of concentrate production with a low content of dust fractions, at a sylvinite concentration plant, a highly concentrated solution of potassium chloride is not used in the enrichment process.

When a highly concentrated solution of potassium chloride is returned to the mill, intensive dissolution of salts occurs simultaneously with crystallization. Moreover, as industrial tests have shown, the dissolution of dust fractions in the mill is more intense than their crystallization. As a result, the supply of a solution highly concentrated in potassium chloride to the mill reduces the fraction of dust fractions in the crushed ore and, accordingly, in the flotation concentrate.

To prepare a solution highly concentrated in potassium chloride, industrial water, brine from a sludge storage facility, and effluents from enrichment and drying departments of an enrichment plant can be used as the liquid phase.

The amount of dust fractions of potassium chloride subjected to dissolution is limited by the amount and composition of the liquid phase, which is fed to the dissolution. The supply of a liquid phase in excess of the norms determined by the water balance of the flotation enrichment process will lead to additional losses of the useful component.

The proposed method for producing fine-grained potassium chloride with a low content of dust fractions is illustrated in the following examples.

Example 1

All or part of the flotation concentrate is classified in hydrocyclones before being dehydrated by centrifuges or vacuum filters. Depending on the classification scheme, the yield of the fine product ranges from 10 to 20%, and the mass fraction of dust fractions with a particle size of less than 0.1 mm in the fine classification product is 50-90%. Moreover, the higher the fraction of dust fractions in the fine product of the classification process, the less the yield of this fraction.

Then, the hydrocyclone plums are fed to a flotation machine for thickening. About 80% of potassium chloride is recovered in the foam product, and the mass fraction of solid in the foam product is 25-50%.

The foam product then enters the solvent, into which water is simultaneously supplied at the rate of 10 m ^{3 of} water for every 3 tons of dust fractions of the concentrate entering the solvent. At the outlet of the solvent, a highly concentrated solution is obtained in which the mass fraction of potassium chloride is 19-23%.

Next, the solution enters the flotation machine to clean the amine and insoluble residue. The purified solution is fed directly to the mill together with the chamber product of flotation thickening of the discharge of hydrocyclones.

With the rational conduct of the technological process in accordance with the water balance of the enrichment process of sylvinite, 5-10% of flotation concentrate in the form of dust fractions can be dissolved.

Industrial tests on the supply of a highly concentrated solution of potassium chloride together with the chamber product of flotation thickening of the discharge of hydrocyclones into the mill did not lead to the appearance of an additional amount of dusty fractions of potassium chloride in the crushed product. The particle size distribution of the crushed product when feeding the resulting potassium chloride solution remains almost the same as that which occurs when mother liquor is used as the liquid phase.

Thus, the small product of the classification of the concentrate dissolves and returns to the process, while in the final concentrate after classification, the fraction of dust fractions is reduced by a value reaching 5-10% of the total volume of the concentrate.

Example 2

An unsaturated solution with a mass ratio of potassium chloride to water of about 17% is used to leach sodium chloride from a flotation concentrate. During leaching, the concentration of potassium chloride in the liquid phase increases significantly. After dehydration of the concentrate, the centrates and filtrates are sent to the scheme described in example 1. The resulting solution is partially used for leaching.

The concentration of potassium chloride in the leach solution can be increased, provided that this does not lead to an increase in the fraction of dust fractions in the concentrate.

Industrial tests of the described scheme showed that the use of a leach unsaturated solution in which the mass ratio of potassium chloride to water is about 17% in an amount of 20 m ³ per 100 tons of concentrate leads to an additional reduction in the fraction of dust fractions in the finished product by 2 -3%

Example 3

In the process of drying flotation concentrate in the gas treatment system, 5 to 40% of fine fractions are captured. Partially or completely fine fraction can be subjected to dissolution. The resulting highly concentrated solution with a mass fraction of potassium chloride up to 25% is fed to the mill.

Thus, the implementation of the proposed method at sylvinite processing plants will reduce the mass fraction of dust fractions with a particle size of less than 0.1 mm by 5-10 percent in the finished product. Due to this, you can get the whole volume of the finished product of higher quality, in which the mass fraction of fractions with a particle size of less than 0.1 mm is not more than 5%. Such potassium chloride in the world classification corresponds to the so-called "special standard" and is considered dust-free at 0.1 mm product.

BIBLIOGRAPHY

1. N.N. Teterina, R.Kh. Sabirov, L.Ya. Skvirsky, L.P. Kirichenko. Technology of flotation concentration of potash ores. Perm-Solikamsk-Berezniki, 2002, Section 6.2.

2. S.N. Titkov, A.I. Mamedov, E.I. Soloviev. Enrichment of potash ores. M., Nedra, 1982. Chapter 10.

3. Reference experimental data on the solubility of multicomponent water-salt systems. L., Chemistry, 1973, pp. 236-270.

Claims (2)

1. A method of obtaining fine-grained potassium chloride with a low content of dust fractions, including processes of grinding, desliming, flotation enrichment of sylvinites and classification by size of flotation concentrate, characterized in that a solution in which the mass ratio is prepared from the fine fraction extracted during the classification of the concentrate potassium chloride to water exceeds 17%, and the prepared solution is returned to the mill. 2. The method according to claim 1, characterized in that the prepared unsaturated solution in which the mass ratio of potassium chloride to water exceeds 17% is preliminarily used to leach sodium chloride from the flotation concentrate, and then the liquid phase is separated from the concentrate and returned to the mill.