RU2004495C1 - Method of alumina production - Google Patents

Abstract

Usage: in the production of alumina. Essence: aluminate solution is decomposed, the resulting pulp is filtered to obtain a mother liquor and aluminum hydroxide. The mother liquor is treated with liquid sodium silicate, kept at a temperature of 50-105 ° C; With constant stirring for 2-6 hours, the pulp is filtered to separate the precipitate of sodium hydroaluminosilicate. 1 zp.f.

Description

The invention relates to non-ferrous metallurgy and can be used in the production of alumina from bauxite.

A method is known in which calcined lime is introduced into the mother liquor after decomposition. Calcium oxide from the solution binds alumina into the solid phase to form tricalcium hydroeluminate. In this case, the caustic module of the mother liquor increases from 4.1 to 11.4, which reduces the material flow of the solution, which is then sent to leaching.

The disadvantage of this method is the difficulty in preparing and using high-quality calcined lime, since almost always when calcining lime there is a shortage of CaCO3 that decausticizes the solution, i.e. increases the percentage of carbonic alkali in solution, which requires additional costs for its conclusion from the process.

Closest to the proposed one is a method for producing alumina from bauxite, including decomposition of an aluminate solution, filtering the resulting pulp with the formation of aluminum hydroxide and a mother liquor with a caustic module 3.3-3.5, again sent to bauxite processing.

The disadvantage of this method is the insufficiently deep extraction of aluminum hydroxide from the mother liquor, i.e. insufficiently high caustic modulus of the solution and, as a consequence, large material flows of the solutions.

The aim of the invention is a deeper extraction of alumina hydroxide from the mother liquor and thereby obtain an additional commercial product,

The goal is achieved in that the mother liquor is treated with liquid sodium silicate, kept at a temperature of 50-105 ° C and stirred for 2-6 hours, the pulp is filtered to separate the precipitate of sodium hydroaluminosilicate. Liquid sodium silicate is dosed from a solution of 20-60 g / l SI02.

In the mother liquor after decomposition in the presence of sodium silicate, sodium hydroaluminosilicate (zeolite) is formed - a white crystalline substance, NaaO x AlaOa x USlOz x 4HaO, which is a commercial product used in the chemical industry.

In industrial mother liquors after decomposition, the concentration of A1203 is about 70 g / l, and caustic is 140-150 g / l. caustic module (%) - 3.3-3.5. The stoichiometric mass ratio of A120z and

1.75102 in zeolite is equal, since the molecular weight of both is 102. Therefore, the dosage of ЗУ2 in the mother liquor should not exceed the concentration in

solution, otherwise the latter will be contaminated with silica. In practice, the dosage of SI02 should be less than 70 g / l, since complete binding from the mother liquor is not practical, since

0 degradation of the solution worsens.

Satisfactory depth of desiliconization, i.e. The binding of dosed SI02 to zeolite occurs when SI02 is dosed into a solution of not more than 60-65 g / l.

5 When a zeolite is precipitated from a solution, the caustic modulus of the solution increases because the molecular weight is AI20.3 102 and NaaO 62. In addition, alkali is introduced with dosed sodium silicate. From the technological conveniences of the further use of the mother liquor, it is advisable to increase the caustic modulus of the solution to 5-10, this helps to reduce the material flow in the autoclave leaching department. However, when the caustic modulus of the solution is above 8-10, the W: T ratio of bauxite pulp decreases significantly, which becomes difficult to pump. However, this can be eliminated.

0 by reducing the concentration of the circulating solution or increasing the caustic modulus of not the entire flow of the mother liquor, but only part of it, and in the future mix the high-modulus solution with the usual (o

5 3.5).

At a dosage of 20 g / L SI02 in sodium silicate, a caustic module of up to 4.5 is achieved, at a dosage of 40 g / L Si02 7.5, at a dosage of 60 g / L Si02 about 20. In the first case, to complete the process of zeolite formation at a temperature of 50 ° C is enough for 2 hours, in the second 4 hours, in the third - 6 hours. The technological temperature of the mother liquor after decomposition is about 50 ° C,

5

boiling point of the solution at atmospheric pressure of 105 ° C. The zeolite is filtered out from the pulp formed during crystallization, washed and used as a commercial product. Dosing liquid sodium silicate into the solution provides sodium hydroaluminosilicate that is not contaminated with silica.

Example 1, into the mother liquor after separation of aluminum hydroxide having

5 concentration of 67 g / l, and 3.44. sodium silicate was added at a rate of 20 g / L SI02, incubated for 2 hours at a temperature of 50 ° C with stirring. The result is a solution with a concentration of 52 g / l and rz

4.4. The zeolite formed in the solution is separated from the solution and washed. The yield of zeolite is 60 g / l of solution. The residual content of 5X2 in the solution is 0.8 g / l.

D) Example 2. After separation of aluminum hydroxide having a concentration of 67 g / L, and 3.44, sodium silicate was added to the mother liquor at a rate of 40 g / L SI02, kept for 4 hours at a temperature of 50 ° C with stirring. The result is a solution with a concentration of AlaOz of 34 g / l, about 7 .5. The zeolite formed in the solution is filtered and washed. The residual SI02 content in the solution is 1.3 g / l.

Example 3. Analogously to example 1, aluminum hydroxide is isolated from solution. To the mother liquor having a concentration of A1203 67 g / l, and 3.44, sodium silicate was added at the rate of SI02 65 g / l and incubated for 7 hours at a temperature

50 ° C and stirring. The result is a solution with a concentration of A1203 b g / l, and "30.9. The residual content of 5Syuz in the solution is 4.6 g / l.

Using the method and obtaining higher values of the caustic module of the mother liquor (Ok 5-10) due to the additional release of aluminum hydroxide in the composition of sodium hydroaluminosilicate (zeolite) allows to reduce the material flow of the solution in the autoclave compartment and the heat consumption for leaching by 25-30%. In addition, the resulting sodium hydroaluminosilicate (zeolite) can be used as a commercial product.

(56) Copyright certificate of the USSR No. 275055, cl. C 01 F 7/46, 1970.

Liner A.I. and others. Production of alumina. M .: Metallurgists, 1978, p. 62-63.

Claims (2)

1. METHOD FOR PRODUCING ALUMINUM, including decomposition of an aluminate solution and subsequent filtration of the pulp to obtain a mother liquor and aluminum hydroxide, characterized in that the mother liquor treated with liquid sodium silicate, kept at 50 - 105 ° C and stirring continuously for 2-6 hours, the pulp was filtered to separate the precipitate of sodium hydroaluminosilicate. 2. The method according to claim 1. characterized in that liquid sodium silicate is dosed at a rate of 20-60 g / l.