LU507271B1 - PROCESS FOR TREATING HIGHLY CONCENTRATED MOTHER LIQUOR IN ALUMINUM OXIDE PRODUCTION - Google Patents

Abstract

The present invention discloses a process for treating high concentration mother liquor in the production of alumina. The process comprises settling and separating said high concentration mother liquor to obtain concentrated mother liquor and sodium carbonate; sintering aluminum ash with sodium carbonate to obtain clinker, the clinker containing sodium aluminate; slurrying said clinker to obtain a slurry; finely filtering said slurry to obtain a sodium aluminate solution; and treating said sodium aluminate solution with crystal seeds to obtain aluminum hydroxide and seed mother liquor. This process utilizes hazardous aluminum ash waste to treat the high concentrations of Na2CO3 in the high concentration mother liquor produced during the alumina production process, thereby eliminating the sodium carbonate aggravation process while recovering a large amount of sodium carbonate from the Bayer process for producing alumina. In addition, valuable materials are recovered from the aluminum ash and the hazardous aluminum ash is converted into normal waste, which facilitates the handling of toxic and hazardous waste.

Description

Process for the treatment of highly concentrated mother liquor in the LUS07271

alumina production

technical area

This invention relates to the field of chemistry, in particular to a process for treating highly concentrated mother liquor in the production of alumina.

technology in the background

In the process of alumina production according to the Bayer process, the alumina in ore and

CO2 contained in lime reacts with NaOH during the production process, producing Na2CO3.

The gradual enrichment of Na2CO3 reduces the recycling efficiency and increases the

production costs; it also leads to deposits on equipment and in pipes, which affects normal production. Therefore, the Na2CO3 produced in the Bayer process must be

Reaching a certain concentration, the Na2CO3 must be removed to keep it at a low level. Traditional treatment methods involve opening forced evaporators to increase the concentration of the mother liquor, causing Na2CO3 crystals to precipitate. The filtered Na2CO3 crystals and associated liquid react with milk of lime, causing

NaOH is recovered and fed back into the Bayer production system, while the caustic slag is fed directly into the red mud landfill. Traditional

Treatment methods have the following disadvantages: 1. High lime consumption. 2. The addition of

Milk of lime leads to losses of aluminum oxide and increases production costs.

Therefore, there is a need for further research into the treatment of highly concentrated

mother liquor.

Content of the invention

This invention aims to solve at least one of the technical problems of the existing

To this end, it is an object of this invention to propose a process for treating the highly concentrated mother liquor in alumina production, which

Method used to extract sodium carbonate from the highly concentrated mother liquor using

Recovering aluminum ash to generate waste from waste and

to realize resource recycling.

It should be mentioned that this invention is based on the following work of the inventor:

The production of electrolytic aluminum and aluminum processing generates about 1 to 12% aluminum ash. The main components of aluminum ash are about 70% aluminum oxide, about 12% aluminum nitride and about 3% elemental aluminum.

Aluminium ash is a hazardous waste. The sintering of sodium carbonate with

Aluminium ash can convert the aluminium in the ash into sodium aluminate, while the sodium carbonate produced in the Bayer process of alumina production must be removed after reaching a certain concentration. The inventor found that by

Treatment of sodium carbonate in the alumina production process with aluminum ash not only recovers a significant amount of sodium carbonate from the Bayer process, but also recovers valuable substances from the aluminum ash, thereby converting hazardous waste into general waste, which facilitates the treatment of toxic and hazardous

waste easier.

Therefore, according to one aspect of the invention, this invention provides a method for

Treatment of highly concentrated mother liquor in alumina production. According to a

According to an embodiment of the invention, the process comprises: settling and separating highly concentrated mother liquor to obtain a concentrated mother liquor and sodium carbonate; sintering aluminum ash with sodium carbonate to obtain clinker, the clinker containing sodium aluminate.

The clinker is processed into a slurry to obtain a suspension; the

Suspension is subjected to fine filtration to obtain a sodium aluminate solution; the

Sodium aluminate solution is subjected to crystal nucleation to obtain aluminum hydroxide and the highly concentrated mother liquor.

According to an embodiment of the invention for the process for treating the highly concentrated mother liquor in alumina production, the highly concentrated

Mother liquor from the alumina production process using hazardous

Aluminium ash waste is treated, producing large amounts of Na2CO3 without the process of

Sodium carbonate hardening, large quantities of sodium carbonate from the Bayer

Process for aluminum oxide production to recover valuable substances from the

Aluminum ash can be recovered and hazardous aluminum ash waste can be converted into normal waste, which facilitates the treatment of toxic and hazardous waste.

Furthermore, the process for treating the highly concentrated mother liquor in alumina production according to the above-mentioned embodiment of the invention may have additional technical features:

According to an embodiment of the invention, the sintering treatment of the

Aluminium ash and sodium carbonate in a mass ratio of 1: (1-1.2).

According to an embodiment of the invention, the temperature for the

Sintering treatment 700-1600 degrees Celsius.

According to an embodiment of the invention, the temperature for the

Sintering treatment 1100-1200 degrees Celsius.

According to one embodiment of the invention, the time for the sintering treatment is 10-60 minutes.

According to one embodiment of the invention, the sintering treatment is carried out in a

gas flotation furnace, a rotary kiln or an electric furnace.

According to an embodiment of the invention, it further comprises: Before

During slurry treatment, the clinker is ground into fine clinker powder.

According to one embodiment of the invention, the average particle size of the clinker powder is 30-100 µm.

Additional aspects and advantages of the invention will be set forth in part in the description which follows, in part will be obvious from the description which follows, or may be set forth by the

practice of the invention.

Description of the attached drawings

The above and/or additional aspects and advantages of this invention will become clear and understandable from the description of the embodiments in conjunction with the following drawings, in which:

Figure 1 is a flow chart of a process for the treatment of highly concentrated

Mother liquor in alumina production according to an embodiment of the invention;

Figure 2 shows a flow diagram of a process for the treatment of highly concentrated

Mother liquor in alumina production according to an embodiment of the invention/207271.

Detailed description

In the following, embodiments of the invention are described in detail, wherein the

Examples are shown in the drawings in which the same or similar

Reference symbols identical or similar elements or elements with identical or similar

Functions characterize. The embodiments described below with reference to the drawings are exemplary and serve only to explain the invention and must not be understood as a limitation of the invention.

It should be noted that the terms “first”, “second” are used only to

are used for descriptive purposes and should not be understood as an indication of relative importance or as an implicit indication of the number of technical characteristics specified.

Therefore, features referred to as “first”, “second” may explicitly or implicitly include one or more of these features. Furthermore, in the description of these

Invention “several” means, unless otherwise stated, two or more.

According to one aspect of the invention, a process for treating the highly concentrated mother liquor in alumina production is provided.

Referring to Figure 1, the method according to an embodiment of the

Invention:

S100 Sedimentation and Separation

According to one embodiment of the invention, the highly concentrated mother liquor is subjected to sedimentation and separation to obtain concentrated mother liquor and

Sodium carbonate. The highly concentrated mother liquor contains a large amount

Sodium carbonate, which is precipitated by sedimentation, which reduces the reactivity of

Aluminium ash with sodium carbonate crystals increased compared to the concentrated mother liquor. It should be noted that the highly concentrated mother liquor from the Bayer process for

production of aluminum oxide.

S200 sintering treatment

According to an embodiment of the invention, aluminum ash is

Sodium carbonate to obtain clinker containing sodium aluminate. The

The main components of aluminium ash include about 70% aluminium oxide, about 12%

Aluminium nitride and about 3% elemental aluminium. The sintering treatment of

Aluminium ash with sodium carbonate leads to a chemical reaction, the

Reaction equations are as follows:

AIN + 3H20 = AICOH)3 + NH3 ! 2A1 + Na2CO3 + 02 — Na20 * AI203 + CO2

A1203 + Na2CO3 — Na20 * AI203 + CO2!

This will eliminate the use of hazardous waste aluminium ash to react with

Na2CO3 is used, which eliminates the process of hardening the sodium carbonate from the highly concentrated mother liquor and recovers a significant amount of sodium carbonate generated in the Bayer process for producing alumina. In addition, valuable substances are recovered from the aluminum ash and hazardous waste is converted into normal waste, which facilitates the treatment of toxic and hazardous waste / 507271.

According to an embodiment of the invention, the aluminum ash is

Sodium carbonate in a mass ratio of 1: (0.8-1.2). This ensures that the aluminum ash and sodium carbonate react completely, leaving an appropriate

Excess of sodium carbonate guarantees the recovery rate of alumina.

According to an embodiment of the invention, the temperature for the

Sintering treatment at 700-1600 degrees Celsius. Under these temperature conditions, the

Reaction activity of aluminum ash and sodium carbonate is high and the

Reaction rate is fast. According to a preferred embodiment of the invention, the

Temperature for the sintering treatment at 1100-1200 degrees Celsius. This ensures the

Reaction activity of aluminum ash and sodium carbonate significantly increased, the

Reaction time is significantly reduced and the process for treating the highly concentrated

Mother liquor accelerated.

According to an embodiment of the invention, the duration of the sintering treatment can be determined depending on the temperature of the sintering treatment and the amount of sintering reactants.

Typically, the sintering time is 10-60 minutes. For example, for a

Sintering temperature below 800 degrees Celsius for at least 30 minutes so that the

Aluminium oxide reacts completely; at a sintering temperature of about 1100 degrees Celsius, a sintering time of about 20 minutes is sufficient for a complete reaction of the aluminium oxide; and at

For temperatures above 1500 degrees Celsius, a sintering time of about 10 minutes is sufficient.

According to an embodiment of the invention, the device for the

Sintering treatment is not particularly limited, as long as the sintering temperature and time can be achieved to ensure complete reaction. Different devices can be selected according to the production conditions and the properties of the reaction materials.

Some embodiments of the invention may include a gas flotation furnace, a

Use a rotary kiln or an electric furnace for the sintering treatment. In particular, the

Gas flotation furnace has low moisture in the feed material and a short residence time; the

Electric furnace has a high energy consumption and is not suitable for industrial mass production; the rotary kiln places lower demands on the feed material and ensures a safe sintering time.

S300 sludge treatment

According to an embodiment of the invention, the clinker is processed into a slurry to obtain a suspension. The slurry treatment consists in separating the solid

Sodium aluminate in a solution, whereby water can be used directly to dissolve the sodium aluminate. According to some embodiments of the invention, this dilution takes place in a dilution tank, which facilitates the mixing and adjustment of the

sludge relieved.

S400 fine filtration

According to one embodiment of the invention, the slurry is subjected to a fine filtration in order to obtain a sodium aluminate solution. The fine filtration produces}507271

Impurities are removed from the sludge, which reduces the content of impurities in the subsequent

Aluminium hydroxide and the highly concentrated mother liquor are reduced and the quality is improved. 5 S500 Crystal nucleus decomposition

According to one embodiment of the invention, the sodium aluminate solution of a

Crystal nucleus decomposition to obtain aluminium hydroxide and highly concentrated mother liquor. This causes aluminium to precipitate from the sodium aluminate solution in the form of

Aluminum hydroxide, whereby aluminum is separated from the solution and recovered, while the highly concentrated mother liquor can be recycled and used to reduce production costs. According to an embodiment of the invention, the recovery rate of aluminum from aluminum ash reaches over 80%, which not only improves the

Not only does it ensure the harmlessness of aluminium ash, but it also produces high-quality aluminium from

Recovers ash and thus transforms waste into value.

Referring to Figure 2, the method according to an embodiment of the

invention further:

S600 fine grinding

According to an embodiment of the invention, the clinker is

Sludge treatment is finely ground to obtain clinker fine powder. Through fine grinding, solid sodium aluminate is completely dissolved into a solution, which is beneficial for slurry treatment.

According to some embodiments of the invention, the average

Particle size of the clinker fine powder 30-100um. This allows the clinker fine powder to dissolve well and promotes the subsequent slurry treatment. According to a preferred embodiment of the invention, when the average particle size of the clinker fine powder is about 60um, the solubility of sodium aluminate is better and the slurry treatment with this fine powder leads to a better quality of the resulting slurry.

Specific embodiments are given below to explain the invention. It should be noted that these examples are only illustrative and should not be construed as limiting the invention.

It is understood that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. If specific techniques or conditions are not indicated in the examples, they are carried out according to techniques or conditions described in the literature or in accordance with the

product manuals. Reagents or instruments whose manufacturers are not indicated are standard commercial products that can be purchased.

Example 1

Use of the method according to an embodiment of the invention for

Treatment of highly concentrated mother liquor in alumina production, specific

Steps as follows: (1) The highly concentrated mother liquor from the Bayer process for the production of

Alumina is subjected to sedimentation and separation to obtain concentrated

mother liquor and sodium carbonate.

(2) The sodium carbonate is subjected to filter pressing to obtain a filter cake #07271. (3) 50 g of aluminum ash and 53 g of filter cake are sintered at 1150 °C for 30 minutes to obtain clinker. (4) The clinker is dissolved in 200 ml of water to prepare a slurry from which a

(5) After filtration of the sludge, the liquid phase is analyzed, whereby the

Sodium aluminate content is 51.11 g/l, which gives a yield of 71.05% of alumina.

This allows the use of hazardous waste aluminium ash to treat the highly concentrated mother liquor in the production process of alumina, thereby

Process of hardening of sodium carbonate is eliminated. A significant amount of

Sodium carbonate is recovered from the Bayer process and valuable substances from the

Aluminum ash. The recovery rate of aluminum reaches 71.05%, and at the same time, the hazardous waste aluminum ash is converted into normal waste, which

Treatment of toxic and hazardous waste is facilitated.

Example 2

Use of the method according to an embodiment of the invention for

Treatment of highly concentrated mother liquor in alumina production, specific

Steps as follows: (1) The highly concentrated mother liquor from the Bayer process for the production of

Alumina is subjected to sedimentation and separation to obtain concentrated

mother liquor and sodium carbonate. (2) The sodium carbonate is subjected to filter pressing to obtain a filter cake; (3) 50g of aluminum ash and 40g of filter cake are sintered at 1150 ° C for 30 minutes to obtain clinker. (4) The clinker is dissolved in 200 ml of water to prepare a slurry from which a

(5) After filtration of the sludge, the liquid phase is analyzed, whereby the

Sodium aluminate content is 66.21 g/l, which gives a yield of 82.35% of alumina.

This allows the use of hazardous waste aluminium ash to treat the highly concentrated mother liquor in the production process of alumina, thereby

Process of hardening of sodium carbonate is eliminated. A significant amount of

Sodium carbonate is recovered from the Bayer process and valuable substances from the

Aluminum ash. The recovery rate of aluminum reaches 82.35%, and at the same time, the hazardous waste aluminum ash is converted into normal waste, which

Treatment of toxic and hazardous waste is facilitated.

In the description of this document, the referenced term “an embodiment”, “some embodiments”, “example”, “specific example” or “some examples”, etc., means that a specific function, structure, material or feature described with the embodiment or example is included in at least one embodiment or example of the invention. In this document, the exemplary representation of the terms mentioned is not necessarily related to the same embodiment or example.

; In addition, the specific functions, structures, materials odb4507271

Features are suitably combined in one or more embodiments or examples.

Although the embodiments of the invention have been shown and described, a

Those skilled in the art will understand that various changes, modifications, substitutions, and variations can be made without departing from the principles and objectives of the invention as defined by the claims and their equivalents.

Claims (4)

claims LU507271 1. A process for treating highly concentrated mother liquor in alumina production, characterized by: settling and separating said highly concentrated mother liquor to obtain concentrated mother liquor and sodium carbonate; sintering aluminum ash with said sodium carbonate to obtain clinker, the clinker containing sodium aluminate; slurrying said clinker to obtain a slurry; finely filtering said slurry to obtain a sodium aluminate solution; and treating said sodium aluminate solution with crystal seeds to obtain aluminum hydroxide and seed mother liquor, wherein the ratio of aluminum ash to sodium carbonate by weight is 1:(0.8-1.2) for sintering, the sintering temperature is between 1100-1200 degrees Celsius, and the sintering time is 10-60 minutes. 2. Process according to claim 1, characterized in that the sintering is carried out in a gas fluidized bed furnace, rotary kiln or electric furnace. 3. A process according to claim 1, characterized by further including: finely grinding said clinker prior to the slurry treatment to obtain fine clinker powder. 4. Process according to claim 3, characterized in that the average particle size of the fine clinker powder is 30-100 µm.