WO2018233688A1 - Method for preparing aluminum hydroxide by treating medium- and low-grade bauxite by using one-step alkali heat process of andradite - Google Patents

Abstract

Providing a calcium iron garnet one-step alkali thermal treatment method for producing low-grade bauxite to produce aluminum hydroxide, comprising the following steps, S1: crushing fine-grained ore powder of medium-low grade bauxite; S2: ore Powder, sodium ferrite, activated lime and circulating mother liquor are mixed to prepare raw material slurry; S3: raw material slurry is subjected to alkali thermal elution reaction to obtain a dissolution slurry; S4: the dissolved slurry is diluted, and liquid-solid separation is performed to obtain sodium aluminate solution and Dissolving slag; S5: preparing a sodium aluminate solution by reacting a sodium aluminate solution with lime milk; S6: dissolving the tricalcium aluminate slurry for liquid-solid separation; S7: washing the tricalcium aluminate in a sodium carbonate solution The reaction produces calcium carbonate; S8: the calcium carbonate is dissolved out of the slurry for liquid-solid separation to obtain a calcium carbonate solid and a sodium aluminate solution; S9: the sodium aluminate solution is carbonized and liquid-solid separated to obtain a carbon mother liquor and hydrogen. Alumina. This method can greatly increase the dissolution rate of alumina while making the slag almost free of alkali.

Description

Method for producing aluminum hydroxide from medium and low grade bauxite by one-step alkali heat treatment of calcium iron garnet Technical field

The invention belongs to the technical field of aluminum hydroxide production, and particularly relates to a method for producing aluminum hydroxide from low-grade bauxite by a one-step alkali heat treatment of calcium iron garnet.

Background technique

Most of the existing bauxite resources are medium and low grade bauxite, which has the characteristics of high aluminum, high silicon, low aluminum to silicon ratio (A/S), and the general silicon to aluminum ratio (hereinafter referred to as A/S) is 2~. 6. With the reduction of ore grade, the cost of alumina dissolution process in ore is gradually increasing, and Bayer process has the largest increase. According to the basic process and principle of the Bayer process, when the bauxite A/S drops below 5, it will be difficult to use the Bayer process. In view of low-grade bauxite ore, in recent years, the alumina industry has mainly adopted the following methods.

The treatment methods of low-grade bauxite mainly include Bayer method, sintering method and Bayer-sintering method. The enhanced Bayer method is a method based on the Bayer method to adapt to the treatment of low-grade bauxite, mainly including the beneficiation Bayer method and the lime Bayer method. Among them, the beneficiation Bayer method uses the combination of smelting and smelting to treat medium and low grade bauxite. The process is relatively simple, but there are problems such as difficulty in physical beneficiation, large consumption of raw ore, low recovery rate of alumina, and influence of Bayer process by flotation reagents. The ore dressing process produces a large amount of aluminum and silicon tailings that are less than 2, which can not be used, resulting in great waste of resources. The lime Bayer method is based on the Bayer method to increase the alkali consumption by adding excess lime, but the amount of lime added is large. The dissolution rate of alumina is greatly reduced, the red mud discharge is increased, and the red mud sedimentation load is increased. The sintering method mainly includes the soda lime sintering method and the lime sintering method, but the high energy consumption and high production cost are the main shortcomings of the development. The soda lime sintering method belongs to wet compounding and wet sintering. The evaporation of about 40% of the water in the raw slurry of the sintering process greatly increases the total energy consumption, and the stability of 2CaO·SiO _{2 in the} sintered clinker is low. The secondary reaction is serious; the lime sintering method has problems such as high lime ratio, large amount of waste slag, and low leaching rate of clinker alumina. Bayer-sintering combined method includes series method, parallel method and hybrid method, which can deal with medium and low grade bauxite, but it has complicated problems and high energy consumption. It has been basically replaced by Bayer method. Other processes such as acid method and acid-base combination method mainly stay in the laboratory research stage, and there are many problems such as poor quality of alumina products and serious corrosion of equipment.

Throughout the above methods of treating low-grade bauxite, the sintering method and Bayer-sintering method have been basically abandoned due to their energy consumption and cost. The lime Bayer method was developed in response to the problem of alkali consumption in a specific historical period. At present, only the beneficiation Bayer method is applied in the China Aluminum Corporation Zhongzhou Branch. However, after industrial practice in recent years, the problems exposed by the mineral processing Bayer method have seriously hindered the normal operation of the production process and become a bottleneck for its continued promotion and development. Therefore, relying on the unique low-grade diaspore bauxite, it is imperative to develop a new method of efficient and economical treatment.

Summary of the invention

(1) Technical problems to be solved

In order to solve the above problems of the prior art, the object of the present invention is to provide a method for producing low-grade bauxite in the production of aluminum hydroxide by a one-step alkali thermal treatment of calcium iron garnet, and using a one-step alkali heat method to lower the medium and low grade aluminum. The earth ore, sodium ferrite and activated lime are mixed and then dissolved at a high temperature. During the high-temperature dissolution process, aluminum and sodium enter the solution in the form of sodium aluminate, and the silicon remains in the form of calcium iron garnet. The method of the invention can greatly improve the dissolution rate of alumina, and at the same time, the alkali-free in the dissolution slag, the material in the whole process realizes zero discharge.

(2) Technical plan

In order to achieve the above object, the main technical solutions adopted by the present invention include:

A method for producing aluminum hydroxide from medium-low grade bauxite by a one-step alkali heat treatment of calcium iron garnet, comprising the following steps:

S1: crushing and grinding fine ore powder of medium and low grade bauxite;

S2: mixing mineral powder, sodium ferrite, active lime and circulating mother liquor into raw material pulp;

S3: performing alkali thermal elution reaction on the raw material slurry, and obtaining a dissolution slurry after the reaction is completed;

S4: diluting the eluted slurry to obtain a diluent, and performing liquid-solid separation on the diluted solution to obtain a dissolution slag and an eluate, wherein: the eluate is a sodium aluminate solution;

S5: reacting the sodium aluminate solution with lime milk to obtain a tricalcium aluminate dissolution slurry;

S6: dissolving the tricalcium aluminate slurry for liquid-solid separation to obtain a tricalcium aluminate and a polymer ratio sodium aluminate solution;

S7: washing the tricalcium aluminate, and the washed tricalcium aluminate is reacted under the action of a sodium carbonate solution to obtain a calcium carbonate dissolution slurry;

S8: dissolving the calcium carbonate in the slurry for liquid-solid separation to obtain a calcium carbonate precipitate and a sodium aluminate solution;

S9: separating the sodium aluminate solution by carbon and liquid-solid separation to obtain a carbon mother liquor and aluminum hydroxide;

S10: The polymer in the step S6 is prepared as a sodium aluminate solution to prepare a circulating mother liquid used in the step S2.

Preferably, the medium-low grade bauxite has a silicon to aluminum ratio of 2-6.

Preferably, in the raw material slurry composed of bauxite, sodium ferrite or activated lime, the total amount of iron, aluminum, calcium and silicon present in each form is determined by oxide, and the formulation is as follows:

The mass ratio of the total amount of iron oxide to the total amount of alumina is 0.2 to 0.6:1;

The molar ratio of the total amount of calcium oxide to the total amount of iron oxide is from 3 to 6:1.

Preferably, the raw material slurry has a liquid to solid ratio of 2 to 5:1.

Preferably, in the step S10, the polymer is prepared by reacting a caustic alkali concentration with a sodium aluminate solution to obtain a circulating mother liquor, wherein the concentration of the caustic in the circulating mother liquor is 150 to 250 g/L, and the molecular ratio is 5 to 25.

Preferably, the temperature of the dissolution reaction in the step S3 is 150 to 250 ° C, and the reaction time is 0.5 to 2 h.

Preferably, the method further includes:

S11: washing the eluted slag in step S4 and solid-liquid separation to obtain calcium garnet type slag and washing liquid;

S12: The washing liquid is used to dilute the dissolved slurry in step S4.

Preferably, the reaction temperature in the step S5 is 50 to 90 ° C for a period of 1 to 3 hours, and the mass ratio of the active calcium oxide in the lime to the alumina in the sodium aluminate solution is 1.0 to 1.6:1.

Preferably, the method further includes:

S13: calcining the calcium carbonate obtained in the step S8 to obtain lime and carbon dioxide gas, returning the lime to the step S5 to prepare tricalcium aluminate, and the obtained carbon dioxide gas is used for the carbon content of the sodium aluminate solution;

S14: The carbon mother liquid obtained in the step S9 is evaporated and liquid-solid separated to obtain an evaporation mother liquid and sodium carbonate, and the evaporation mother liquid is returned to the step S7, and sodium carbonate is used for preparing sodium ferrite.

(3) Beneficial effects

The beneficial effects of the invention are:

(1) Compared with the conventional Bayer process, the actual dissolution rate of the alumina of the method of the invention is increased by more than 15%, and the dissolution rate of the alumina is greatly improved;

(2) Compared with the conventional Bayer process, the method of the present invention produces a dissolution slag base content of 0.5% or less;

(3) The material in the whole process of the invention realizes zero discharge;

(4) The product aluminum hydroxide can be used as a raw material to prepare other aluminum-containing products, and can also be used as a raw material to prepare metallurgical grade alumina by a simple Bayer process.

DRAWINGS

1 is a process flow diagram of a method for producing aluminum hydroxide in a low-grade bauxite by a one-step alkali thermal treatment of calcium iron garnet according to the present invention.

Detailed ways

The invention is further illustrated below in conjunction with specific embodiments. It is to be understood that the examples are only illustrative of the invention and are not intended to limit the scope of the invention.

In the low-grade bauxite ore in the embodiment of the present invention, the ratio of silicon to aluminum (hereinafter referred to as A/S) is 2-6, and the bauxite contains alumina, wherein bauxite, sodium ferrite, and active lime are composed. In the raw material ore, the mass ratio of the total amount of iron oxide to the total amount of alumina is abbreviated as F/A; the molar ratio of the total amount of calcium oxide to the total amount of iron oxide is abbreviated as C/F; The following is abbreviated as L/S.

Calcium iron garnet one-step alkali heat treatment of low-grade bauxite to produce aluminum hydroxide, which means that the dissolved slag is calcium iron garnet-type red mud, one-step alkali heat method refers to the use of lye (circulating mother liquor) for oxidation The aluminum is subjected to a one-step hydrothermal elution treatment, and the target product produced is aluminum hydroxide.

Example 1

The medium and low grade bauxite used in this embodiment has the main chemical composition (mass percentage, wt%): alumina (Al ₂ O ₃ ) 60.60%, silica (SiO ₂ ) 17.5%, others are impurities, Aluminum to silicon ratio is 3.5;

Sodium ferrite is sintered from iron-containing raw materials and industrial sodium carbonate;

The concentration of caustic in the circulating mother liquor is 200 g / L, the molecular ratio is 25;

F/A = 0.5:1;

C/F = 4.5:1.

A method for producing aluminum hydroxide from a medium-low grade bauxite according to the one-step alkali heat treatment of the calcium iron garnet of the present invention shown in FIG.

S1: crushing and grinding fine ore powder of medium and low grade bauxite;

S2: mixing the mineral powder, sodium ferrite, and active lime, and mixing with the circulating mother liquor according to the ratio of L/S=4:1 to prepare a raw material slurry;

S3: the raw material slurry is subjected to a dissolution reaction in the reaction vessel, the dissolution reaction temperature is 250 ° C, the dissolution reaction time is 2 h, and the dissolution slurry is obtained after the reaction is completed;

After the dissolution reaction treatment in this step, the extraction rate of alumina can reach 83.5%;

S4: diluting the dissolved slurry to obtain a diluent, and performing liquid-solid separation on the diluted solution to obtain a dissolution slag and an eluate, wherein the eluate is a low molecular ratio sodium aluminate solution;

S5: reacting the low molecular weight sodium aluminate obtained in step S4 with lime milk to obtain a tricalcium aluminate dissolution slurry, the reaction temperature is 60 ° C, the time is 1 h, and the lime addition amount is 1.4 times the alumina content;

S6: dissolving the tricalcium aluminate slurry for liquid-solid separation to obtain a tricalcium aluminate and a polymer ratio sodium aluminate solution;

S7: washing the tricalcium aluminate obtained in step S6, and washing the tricalcium aluminate under the action of a sodium carbonate solution to obtain a calcium carbonate dissolution slurry;

S8: dissolving the calcium carbonate in the slurry for liquid-solid separation to obtain a calcium carbonate precipitate and a sodium aluminate solution;

S9: separating the sodium aluminate solution by carbon and liquid-solid separation to obtain a carbon mother liquor and aluminum hydroxide;

S10: evaporating the polymer than the sodium aluminate solution, and then supplementing the caustic to adjust the molecular ratio to prepare the circulating mother liquor used in the step S2;

In this step, the obtained polymer is adjusted than the sodium aluminate solution, so that the adjusted solution can meet the requirements of the circulating mother liquor, and is returned to the step S2 for use in recycling and reusing the material, thereby saving resources and avoiding waste;

S11: washing the eluted slag in step S4 and solid-liquid separation to obtain calcium garnet type slag and washing liquid;

In this step, the low alkali calcium iron garnet type slag is obtained after treatment, so that the silicon and the added iron and calcium remain in the dissolution slag in the form of calcium iron garnet, thereby reducing the alkali content in the dissolution slag;

S12: using the washing liquid for diluting and dissolving the slurry in step S4;

In this step, the generated washing liquid is waste liquid, but the washing liquid is returned to the step S4 for diluting and discharging the pulp, which not only reduces the treatment and discharge of the waste liquid, but also achieves the recycling and reuse of the materials;

S13: calcining the calcium carbonate obtained in step S8 to obtain lime and carbon dioxide gas, digesting the lime into lime milk, returning to step S5 to prepare tricalcium aluminate, and obtaining carbon dioxide gas for sodium carbonate solution carbon;

In this step, the calcium carbonate is calcined and decomposed, and the obtained lime and carbon dioxide are not discharged, but are returned to the whole process for use, so that the whole process is green and clean without pollution;

S14: The carbon mother liquid obtained in the step S9 is evaporated and liquid-solid separated to obtain an evaporation mother liquid and sodium carbonate, and the evaporation mother liquid is returned to the step S7, and the sodium carbonate can be used for synthesizing sodium ferrite.

In this step, the carbon mother liquid is evaporated, and the obtained evaporation mother liquid is returned to the preparation of the tricalcium aluminate, and the sodium carbonate becomes the raw material for the preparation of the sodium ferrite, so that the material is not discharged to the outside, and sufficient is obtained. use.

The obtained aluminum hydroxide is a product.

Example 2

The medium and low grade bauxite used in this embodiment has the main chemical composition (mass percentage, wt%): alumina (Al ₂ O ₃ ) 65.22%, silica (SiO ₂ ) 12.66%, and others are impurities. The ratio of aluminum to silicon is 5.15;

Sodium ferrite is sintered from iron-containing raw materials and industrial sodium carbonate;

The concentration of caustic in the circulating mother liquor is 250 g / L, the molecular ratio is 20;

F/A = 0.6:1;

C/F = 4:1.

A method for producing aluminum hydroxide from a medium-low grade bauxite according to the one-step alkali heat treatment of the calcium iron garnet of the present invention shown in FIG.

S1: crushing and grinding fine ore powder of medium and low grade bauxite;

S2: mixing the mineral powder, sodium ferrite, and active lime, and mixing with the circulating mother liquor according to the ratio of L/S=4:1 to prepare a raw material slurry;

S3: the raw material slurry is subjected to a dissolution reaction in the reaction vessel, the dissolution reaction temperature is 250 ° C, the dissolution reaction time is 2 h, and the dissolution slurry is obtained after the reaction is completed;

After the dissolution reaction treatment in this step, the extraction rate of alumina can reach 83.7%;

S4: diluting the dissolved slurry to obtain a diluent, and performing liquid-solid separation on the diluted solution to obtain a dissolution slag and an eluate, wherein the eluate is a low molecular ratio sodium aluminate solution;

S5: reacting the low molecular weight sodium aluminate obtained in step S4 with lime milk to obtain a tricalcium aluminate dissolution slurry, the reaction temperature is 60 ° C, the time is 1 h, and the lime addition amount is 1.4 times the alumina content;

S6: dissolving the tricalcium aluminate slurry for liquid-solid separation to obtain a tricalcium aluminate and a polymer ratio sodium aluminate solution;

S7: washing the tricalcium aluminate obtained in step S6, and washing the tricalcium aluminate under the action of a sodium carbonate solution to obtain a calcium carbonate dissolution slurry;

S8: dissolving the calcium carbonate in the slurry for liquid-solid separation to obtain a calcium carbonate precipitate and a sodium aluminate solution;

S9: separating the sodium aluminate solution by carbon and liquid-solid separation to obtain a carbon mother liquor and aluminum hydroxide;

S10: evaporating and concentrating the polymer than the sodium aluminate solution, and then supplementing the caustic to adjust the molecular ratio to prepare the circulating mother liquor used in the step S2;

In this step, the obtained polymer is adjusted than the sodium aluminate solution, so that the adjusted solution can meet the requirements of the circulating mother liquor, and is returned to the step S2 for use in recycling and reusing the material, thereby saving resources and avoiding waste;

S11: washing the eluted slag in step S4 and solid-liquid separation to obtain calcium garnet type slag and washing liquid;

In this step, the low alkali calcium iron garnet type slag is obtained after treatment, so that the silicon and the added iron and calcium remain in the dissolution slag in the form of calcium iron garnet, thereby reducing the alkali content in the dissolution slag;

S12: using the washing liquid for diluting and dissolving the slurry in step S4;

In this step, the generated washing liquid is waste liquid, but the washing liquid is returned to the step S4 for diluting and discharging the pulp, which not only reduces the treatment and discharge of the waste liquid, but also achieves the recycling and reuse of the materials;

S13: calcining the calcium carbonate obtained in step S8 to obtain lime and carbon dioxide gas, digesting the lime into lime milk, returning to step S5 to prepare tricalcium aluminate, and obtaining carbon dioxide gas for sodium carbonate solution carbon;

In this step, the calcium carbonate is calcined and analyzed, and the obtained lime and carbon dioxide are not discharged, but are returned to the whole process for use, so that the whole process is green and clean without pollution;

S14, the carbon mother liquid obtained in the step S9 is evaporated and then liquid-solid separated to obtain an evaporation mother liquid and sodium carbonate, and the evaporation mother liquid is returned to the step S7, and sodium carbonate is used for preparing sodium ferrite.

In this step, the carbon mother liquid is evaporated, and the obtained evaporation mother liquid is returned to the preparation of the tricalcium aluminate, and the sodium carbonate becomes the raw material for the preparation of the sodium ferrite, so that the material is not discharged to the outside, and sufficient is obtained. use.

The obtained aluminum hydroxide is a product.

In the method of the invention, the actual dissolution rate of alumina is increased by more than 15% compared with the conventional Bayer process, and the alkali content of the dissolution slag is reduced to 0.5% or less, and the dissolution rate of the alumina is greatly increased, and the elution slag contains almost no alkali. The material has achieved zero emission requirements throughout the process.

It should be noted that: fly ash can also be used for the production of aluminum hydroxide by the method of the invention, and in the furnish, the fly ash can be directly applied without crushing and grinding, so that the process of the invention is shorter, higher efficiency.

Claims (9)

Method for producing aluminum hydroxide from medium-low grade bauxite by one-step alkali heat treatment of calcium iron garnet, characterized in that it comprises the following steps: S1: crushing and grinding fine ore powder of medium and low grade bauxite; S2: mixing mineral powder, sodium ferrite, active lime and circulating mother liquor into raw material pulp; S3: performing alkali thermal elution reaction on the raw material slurry, and obtaining a dissolved pulp after the reaction is completed; S4: diluting the eluted slurry to obtain a diluent, and performing liquid-solid separation on the diluted solution to obtain a dissolution slag and an eluate, wherein the eluate is a sodium aluminate solution; S5: reacting the sodium aluminate solution with lime milk to obtain a tricalcium aluminate dissolution slurry; S6: dissolving the tricalcium aluminate slurry for liquid-solid separation to obtain a tricalcium aluminate and a polymer ratio sodium aluminate solution; S7: washing the tricalcium aluminate, and the washed tricalcium aluminate is reacted under the action of a sodium carbonate solution to obtain a calcium carbonate dissolution slurry; S8: dissolving the calcium carbonate in the slurry for liquid-solid separation to obtain a calcium carbonate precipitate and a sodium aluminate solution; S9: separating the sodium aluminate solution by carbon and liquid-solid separation to obtain a carbon mother liquor and aluminum hydroxide; S10: The polymer in the step S6 is prepared as a sodium aluminate solution to prepare a circulating mother liquid used in the step S2. The method according to claim 1, wherein the medium-low grade bauxite has a silicon to aluminum ratio of 2-6. The method for treating aluminum hydroxide in a medium-low grade bauxite by the one-step alkali thermal treatment of calcium iron garnet according to claim 1, characterized in that: raw material pulp composed of bauxite, sodium ferrite and active lime, each The total amount of iron, aluminum, calcium and silicon in the form is determined by oxide, and the formulation is as follows: The mass ratio of the total amount of iron oxide to the total amount of alumina is 0.2 to 0.6:1; The molar ratio of the total amount of calcium oxide to the total amount of iron oxide is from 3 to 6:1. The method for producing aluminum hydroxide by using a medium-low grade bauxite according to claim 1, wherein the raw material slurry has a liquid-solid ratio of 2 to 5:1. A method for producing aluminum hydroxide from a medium-low grade bauxite by a one-step alkali thermal treatment of calcium iron garnet according to claim 1, wherein the polymer in step S10 is subjected to a caustic concentration modulation than a sodium aluminate solution. After that, a circulating mother liquor is obtained, wherein the concentration of caustic in the circulating mother liquor is 150 to 250 g/L, and the molecular ratio is 5 to 25. The method for producing aluminum hydroxide from a medium-low grade bauxite by the one-step alkali thermal treatment of calcium iron garnet according to claim 1, wherein the temperature of the dissolution reaction in step S3 is 150 to 250 ° C, and the reaction time is 0.5. ~2h. The method for producing aluminum hydroxide from a medium-low grade bauxite by a one-step alkali thermal treatment of calcium iron garnet according to claim 1, wherein the method further comprises: S11: washing the eluted slag in step S4 and solid-liquid separation to obtain calcium garnet type slag and washing liquid; S12: The washing liquid is used to dilute the dissolved slurry in step S4. The method for producing aluminum hydroxide from a medium-low grade bauxite by the one-step alkali thermal treatment of calcium iron garnet according to claim 1, wherein the reaction temperature in the step S5 is 50 to 90 ° C, and the time is 1 to 3 hours. The amount of lime added is 1.0 to 1.8 times the alumina content. The method for producing aluminum hydroxide from a medium-low grade bauxite by a one-step alkali thermal treatment of calcium iron garnet according to claim 1, wherein the method further comprises: S13: calcining the calcium carbonate obtained in step S8 to obtain lime and carbon dioxide gas, digesting the lime into lime milk, returning to step S5 to prepare tricalcium aluminate, and obtaining carbon dioxide gas for sodium carbonate solution carbon; S14, the carbon mother liquid obtained in the step S9 is evaporated and then liquid-solid separated to obtain an evaporation mother liquid and sodium carbonate, and the evaporation mother liquid is returned to the step S7, and sodium carbonate is used for preparing sodium ferrite.

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