CN1281503C - Silicon slag treatment method in aluminium oxide production process - Google Patents

Abstract

The present invention relates to a method for treating silicon slag during the process of producing aluminium oxide, which is characterized in that the treating process comprises: after solid-liquid separation, sodium silicon slag slurry is washed and then is mixed with lime milk, alkali is removed at 90 to 100 DEG C, and the reaction is kept for 2 to 4 hours; the surface of dealkalized slag is treated through ball milling, CO2 with the concentration of 8% to 100% is supplied and stirred, and transformation reaction is kept for 2 hours; alkali liquor is added into solution obtained after the solid-liquid separation of slurry after transformation and dealkalized slurry to dissolve aluminium; finally, aluminium dissolved slurry is obtained through solid-liquid separation and is put into a sintering red mud washing system to remove the slag phase. The dealkalizing rate of the method reaches more than 90%, A/S in waste slag is smaller than 0.7, and N/S is smaller than 0.2.

Description

A method for treating silicon slag in alumina production process

technical field

The invention relates to a method for treating silicon slag in the production process of alumina, which relates to the treatment of silicon slag produced in the process of producing alumina by adopting a sintering method, in particular to a method for recovering alumina and sodium oxide from the silicon slag.

Background technique

Most of the bauxite in my country is diaspore type, mainly of medium grade, among which ores with an aluminum-silicon ratio (A/S) of 4 to 8 account for about 80% of the total. The key to the existing alkaline method for producing alumina is the separation of aluminum and silicon. Sodium aluminosilicate hydrate Na ₂ O·Al ₂ O ₃ ·1.7SiO ₂ ·nH ₂ O, namely sodium silicate slag, is the most important reaction product of silicon minerals in alkaline treatment of bauxite. In the amount of sodium silicate slag formed, it also contains a large amount of alkali and alumina. In the process of high-pressure dissolution of medium-grade ore by Bayer method and desiliconization of crude liquid by sintering method, it reaches about 1000kg/t-Al ₂ O ₃ and 200kg/t-Al ₂ O ₃ respectively. At present, the treatment of sodium-silicon slag adopts the sintering method, that is, the red mud of the Bayer method and the silicon slag of the sintering method are sent to and returned to the sintering system for batching and sintering, which makes the alumina production process complicated and the production efficiency reduced.

Since the 1950s, the former Soviet Union, Hungary, and my country have been devoting themselves to the research on the wet-process aluminum-silicon separation technology of sodium-silicon slag, and formed the high-pressure hydrochemical method or Bayer-hydration method to produce alumina. Mainly include: 1) Ponomarev-Saren et al. of the former Soviet Union proposed a high-pressure water chemical method through the study of the equilibrium solid phase of the Na ₂ O-Al ₂ O ₃ -SiO ₂ -CaO-H ₂ O system. The principle is Make silicon generate a slag phase containing no or little aluminum or alkali at a relatively high temperature of 260-350 ° C, such as sodium calcium silicate, hydrated calcium silicate, iron hydrated garnet, etc., while alumina is formed with alumina The sodium form goes into solution. The alkali recovery rate of the method is greater than 80%, and the alumina recovery rate is 40%-70%. However, the alkali concentration of the solution is high, the caustic ratio α _k is as high as 10-30, and it is operated under high temperature and high pressure conditions, which requires strict equipment materials; 2) The hydrothermal method proposed by Czech and Hungarian scholars has an α _k of about 4.0, which is relatively high. The condition of the former is slightly looser, and the alkali in the red mud is mainly recovered, but the recovery rate of alumina is low, and the aluminum-silicon ratio of the treated red mud is still greater than 1, which is economically unreasonable.

Contents of the invention

The purpose of the present invention is to provide a method that can effectively realize the separation of sodium, aluminum and silicon in the sodium-silicon slag and recover the alumina in the sodium-silicon slag, aiming at the above-mentioned shortcomings in the existing silicic acid treatment in the alumina production process. , Sodium oxide silicon slag treatment method.

The purpose of the present invention is achieved through the following technical solutions.

A method for treating silicon slag in the alumina production process, characterized in that the treatment process is:

(1) The sodium-silicon slag slurry after the desiliconization of the sodium aluminate solution is separated from the solid and liquid by the filter and washed, and then the solution is sent to the alumina production process;

(2) Mix the separated sodium-silicon slag with milk of lime according to the molecular ratio CaO/Na ₂ O = 3-4, and stir the reaction under the technological conditions of 90°C-100°C and a liquid-solid ratio of 5-7. ~4 hours dealkalization;

(3) Separating the dealkalization slurry from solid to liquid, passing the dealkalization slag through ball milling for 20-30 minutes, and carrying out surface treatment on the slag, at a liquid-solid ratio of 5-10, at a temperature of 50±10°C, with a concentration of 8% to 100 % CO ₂ stirring for 2 hours transformation reaction;

(4) Add lye to the transformed slurry and dealkalized slurry after solid-liquid separation, so that the caustic concentration reaches 50-100g/L, the liquid-solid ratio is 7-10, and the temperature is 50°C ± 10°C Dissolve the aluminum for 1-2 hours; finally, the solid-liquid separation and the dissolved aluminum slurry are sent to the red mud washing system of the sintering method, and the slag phase is discarded.

The method of the present invention adopts the sodium-silicon slag plus lime milk dealkalization technology at normal temperature and pressure, the dealkalization slag transformation technology and the transformation slag modification technology to treat the sodium-silicon slag, so that the dealkalization rate reaches more than 90%. A/S is less than 0.7, N/S is less than 0.2.

The silicon slag of the sintering method of the present invention recovers the useful components and discards it as waste residue, thereby avoiding the return of a large amount of silicon slag and the internal invalid circulation of ingredients, and has good economical efficiency.

The purpose of filtering and washing the sodium silica slag slurry is to reduce the alumina content of the solution during the treatment of the silica slag. In the process of silicon slag treatment, if there is alumina in the silica slag, when lime is added, the effective calcium oxide in it first reacts with the alumina in the liquid phase and enters the solid phase, resulting in the loss of alumina and reducing the The amount of effective calcium oxide reacted with silicon slag makes the effect of sodium removal worse.

The purpose of the dealkalization slag transformation is to transform the aluminum in the hydrated garnet in the desodiumized slag into aluminum hydroxide and sponsonite which are easily dissolved by alkali, and transform the calcium in the hydrated garnet into hydrated calcium silicate. In order to separate aluminum from silicon and calcium after dissolving aluminum.

The purpose of ball milling in the transformation process is to modify the surface of the dealkalization slag, so as to strengthen the kinetic diffusion process during the transformation process, strengthen the transformation between silicon-containing compounds, and shorten the transformation time of silicon slag.

The purpose of adding alkali in the process of dissolving aluminum is to use alkali to react with amorphous aluminum hydroxide and frasonite at normal temperature and pressure, so that aluminum enters the solution in the form of sodium aluminate, so that the hydrated calcium silicate can be separated to achieve aluminum The purpose of separating from silicon calcium.

Description of drawings

Fig. 1 is a process flow block diagram of the present invention.

Detailed ways

A method for treating silicon slag in the alumina production process. The treatment process is (1) the sodium silicate slag slurry after the desiliconization of the sodium aluminate solution is separated from the solid and liquid by a filter and washed, and then the solution is sent to the alumina production process; (2) ) Mix the separated sodium-silicon slag with milk of lime according to (molecular ratio) CaO/Na ₂ O = 3-4, and stir the reaction at a temperature of 90°C-100°C and a liquid-solid ratio of 5-7 Dealkalization for ~4 hours; (3) Separating the solid and liquid of the dealkalization slurry, and passing the dealkalization slag through ball milling for 20-30 minutes to carry out surface treatment on the slag, at a liquid-solid ratio of 5-10, at a temperature of 50±10°C, use a Concentration 8%～100% CO _Stirring carries out transformation reaction for 2 hours; (4) the slurry after transformation, dealkalization slurry solid-liquid separation solution is added into lye, make caustic alkali concentration reach 50～100g/L, liquid The solid ratio is 7-10, and the aluminum is dissolved at a temperature of 50±10°C for 1-2 hours; finally, the solid-liquid separation and the dissolved aluminum slurry are sent to the red mud washing system of the sintering method, and the slag phase is discarded.

Below by example the method of the present invention is further described as follows.

Example 1

1. Raw materials:

(1) Silicon slag:

Composition of high pressure sodium silicate slag (%) SiO _{2 Fe2O3 _} Al ₂ O ₃ CaO K ₂ O Na ₂ O TiO ₂ 23.74 24.04 13.01 3.52 11.67

(2), Lime: CaO _T 97%, f _CaO 87%

(3), CO2 _{concentration} : 38%

(4), caustic alkali concentration: 50-100g/l

2. Control process technical conditions:

1) Dealkalization: temperature 95°C, CaO/Na ₂ O = 3, liquid-solid ratio 5, reaction time 2h,

2) Transformation: liquid-solid ratio 5, temperature about 50°C, CO ₂ concentration 38%, transformation time about 2 hours; surface treatment time 20 minutes.

3) Dissolving aluminum: the temperature is 50°C, the time is 1 hour, the caustic alkali concentration is 50g/L, and the liquid-solid ratio is 7.

3. Technical and economic indicators;

(1), dealkalization rate 90%

(2), A/S in waste slag is less than 0.7, N/S is less than 0.2

Example 2

1. Raw materials: (1) Silicon slag:

Composition of high pressure sodium silicate slag (%) SiO _{2 Fe2O3 _} Al ₂ O ₃ CaO K ₂ O Na ₂ O TiO ₂ 23.74 24.04 13.01 3.52 11.67

(2), Lime: CaO _T 97%, f _CaO 87%

(3), CO2 _{concentration} : 15%

(4), caustic alkali concentration: 50-100g/l

2. Control process technical conditions:

1) Dealkalization: temperature 95°C, CaO/Na ₂ O = 4, liquid-solid ratio 5, reaction time 2h,

2) Transformation: liquid-solid ratio 5, temperature about 50°C, additive CO ₂ concentration 38%, transformation time 2h; surface treatment time 30 minutes.

3) Dissolving aluminum: the temperature is 50°C, the time is 1 hour, the caustic alkali concentration is 100g/L, and the liquid-solid ratio is 7.

3. Technical and economic indicators;

(1), dealkalization rate 92%

(2), A/S in waste slag is less than 0.65, N/S is less than 0.15

Example 3:

1. Raw materials: (1) Silicon slag:

Composition of high pressure sodium silicate slag (%) SiO _{2 Fe2O3 _} Al ₂ O ₃ CaO K ₂ O Na ₂ O TiO ₂ 23.74 24.04 13.01 3.52 11.67

(2), Lime: CaO _T 97%, f _CaO 87%

(3), CO2 _{concentration} : 8%

(4), caustic alkali concentration: 50-100g/l

2. Control process technical conditions:

1) Dealkalization: temperature 95°C, CaO/Na ₂ O = 4, liquid-solid ratio 5, reaction time 2h,

2) Transformation: liquid-solid ratio 5, temperature 50°C, additive CO ₂ concentration 38%, transformation time 2h; surface treatment time 20 minutes.

3) Dissolving aluminum: the temperature is 50°C, the time is 1 hour, the caustic alkali concentration is 50g/L, and the liquid-solid ratio is 7.

3. Technical and economic indicators;

(1), dealkalization rate 91%

(2) The A/S in the waste residue is less than 0.75, and the N/S is less than 0.17.

Claims (1)

1. A silicon slag processing method in the alumina production process is characterized in that the processing process is: (1) The sodium-silicon slag slurry after the desiliconization of the sodium aluminate solution is separated from the solid and liquid by the filter and washed, and then the solution is sent to the alumina production process; (2) Mix the separated sodium-silicon slag with milk of lime according to the molecular ratio CaO/Na ₂ O = 3-4, and stir the reaction for 2-4 under the process conditions of temperature 90°C-100°C and liquid-solid ratio of 5 hour dealkalization; (3) Separating the solid-liquid of the dealkalization slurry, passing the dealkalization slag through ball milling for 20-30 minutes, and carrying out surface treatment on the slag, at a liquid-solid ratio of 5, at a temperature of 50 ± 10°C, with a concentration of 8% to 100% _CO2 stirring for 2 hours transformation reaction; (4) Add the transformed slurry and dealkalized slurry into the lye solution after solid-liquid separation, so that the caustic concentration reaches 50-100g/L, the liquid-solid ratio is 7, and dissolves aluminum at a temperature of 50±10°C 1-2 hours; finally, the aluminum-dissolved slurry from solid-liquid separation is sent to the red mud washing system of the sintering method, and the slag phase is discarded.