WO2018233686A1

WO2018233686A1 - Method for preparing metallurgical-level aluminum oxide by treating medium- and low-grade bauxite by using one-step alkali heat process of andradite

Info

Publication number: WO2018233686A1
Application number: PCT/CN2018/092422
Authority: WO
Inventors: 于海燕; 潘晓林; 吴艳; 毕诗文
Original assignee: 东北大学
Priority date: 2017-06-23
Filing date: 2018-06-22
Publication date: 2018-12-27
Also published as: CN107188209A

Abstract

Provided is a method for preparing metallurgical-level aluminum oxide by treating medium- and low-grade bauxite by using a one-step alkali heat process of andradite. The method comprises the following steps: S1, crushing and finely grinding medium- and low-grade bauxite into mineral powder; S2, mixing the mineral powder, sodium ferrite or calcium ferrite, activated lime and circulating mother liquid to prepare raw-material mineral pulp; S3, allowing the raw-material mineral pulp to have an alkali heat dissolving-out reaction; S4, diluting dissolved-out mineral pulp, and allowing the diluted liquid to experience liquid-solid separation; S5, introducing a carbon dioxide gas into a sodium aluminate solution to carry out carbonation decomposition, so as to obtain crude aluminum hydroxide and carbonation-decomposed mother liquid; and S6, allowing the crude aluminum hydroxide to experience bayer-process treatment, so as to obtain the metallurgical-level aluminum oxide; and S7, causticizing the carbonation-decomposed mother liquid by using lime milk, and carrying out liquid-solid separation to obtain a sodium hydroxide solution, and using the blended sodium hydroxide solution as a circulating mother liquid in step 2. In the method, by adding the lime and the sodium ferrite or the calcium ferrite in a dissolving-out procedure, andradite-type slag instead of conventional dissolved-out slag is generated in the dissolving-out procedure; the dissolving-out rate of the aluminum oxide can be greatly improved; in addition, the metallurgical-level aluminum oxide is prepared; the method has the characteristics of a short procedure and a high efficiency, and the zero release of a material is achieved.

Description

Method for producing metallurgical grade alumina by low-grade bauxite by calcium-iron garnet one-step alkali heat treatment

Technical field

The invention belongs to the technical field of alumina production, and particularly relates to a method for producing metallurgical grade alumina in a medium-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 with high aluminum, high silicon and low aluminum to silicon ratio (A/S). With the reduction of ore grade, the cost of each alumina production process is gradually increasing, and the 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 mineral processing Bayer method is applied in individual enterprises. 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.

Summary of the invention

(1) Technical problems to be solved

In order to solve the above problems of the prior art, an object of the present invention is to provide a method for producing a metallurgical grade alumina in a medium-grade low-grade bauxite by a one-step alkali thermal treatment of calcium iron garnet, and adding sodium ferrite during high-temperature dissolution ( The method of calcium ferrite) and active lime, aluminum enters the solution in the form of sodium aluminate during high temperature dissolution, and the silicon remains in the dissolution slag in the form of calcium iron garnet. The method of the invention can greatly improve the dissolution rate of the metallurgical grade alumina, and at the same time, the dissolution slag contains almost no alkali, and has the characteristics of short process and high efficiency, and the material realizes zero discharge in the whole process.

(2) Technical plan

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

A method for producing metallurgical grade alumina of medium and low grade bauxite by 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 or calcium 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: introducing carbon dioxide gas into the sodium aluminate solution to carry out carbon to obtain crude aluminum hydroxide and carbon mother liquor;

S6: subjecting the crude aluminum hydroxide to a Bayer process to obtain a metallurgical grade alumina;

S7: The carbon mother liquor obtained in step S5 is causticized with calcium oxide to obtain a caustic slurry, and the caustic slurry is subjected to liquid-solid separation to obtain a polymer ratio sodium aluminate solution and calcium carbonate, and the ratio of the polymer is The sodium aluminate solution is prepared as the circulating mother liquor in 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 calcium ferrite, or active lime, the total amount of iron, aluminum, calcium and silicon present in each form is determined by the 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, in step S1, the liquid-solid ratio of the raw material slurry is 2 to 5:1.

Preferably, the concentration of caustic in the circulating mother liquor in step S2 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, in step S5, carbon dioxide gas is introduced into the sodium aluminate obtained after elution and seed crystals are added to carry out carbon fractionation to obtain a slurry of crude aluminum hydroxide, followed by liquid-solid separation to obtain a carbon mother liquor and crude aluminum hydroxide. ,

In step S5, the carbon content temperature is 60 to 90 ° C, the carbon end point is a decomposition rate of 90% or more, and the seed crystal addition coefficient is 0 to 1.0.

Preferably, the method further includes:

Step S8: washing the eluted slag in step S4 and solid-liquid separation to obtain calcium garnet type slag and washing liquid;

Step S9: The washing liquid is used to dilute the dissolved slurry in step S4.

Preferably, the method further comprises the step S10: calcining and decomposing the calcium carbonate obtained in the step S7 to obtain carbon dioxide gas and calcium oxide, and the obtained carbon dioxide gas is used for carbon separation in the step S5, and the obtained calcium oxide is used in the step. Caustic treatment in S7.

Preferably, the sodium ferrite in the step S1 is formed by sintering an iron-containing raw material and an industrial carbon base; the calcium ferrite is obtained by sintering the iron-containing raw material and the lime.

(3) Beneficial effects

The beneficial effects of the invention are:

(1) Compared with the conventional Bayer process, the actual dissolution rate of the metallurgical grade alumina produced by 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, and the slag contains almost no alkali;

(3) The method of the invention has the characteristics of short process and high efficiency, and the material realizes zero discharge in the whole process.

DRAWINGS

1 is a process flow diagram of a method for producing a metallurgical grade alumina 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 in the embodiment of the present invention, the ratio of silicon to aluminum (hereinafter referred to as A/S) is 2-6. In the raw material ore consisting of bauxite, sodium ferrite (or calcium ferrite) and activated lime, the mass ratio of the total amount of iron oxide to the total amount of alumina is abbreviated as F/A; the total amount of calcium oxide The molar ratio of the total amount of iron oxide is abbreviated as C/F. The raw material slurry solid mass ratio is abbreviated as L/S.

Calcium iron garnet one-step alkali heat treatment of medium-low grade bauxite to produce metallurgical grade alumina means that the dissolved slag is calcium iron garnet type slag, and the one-step alkali heat method refers to the oxidation of lye (circulating mother liquor) The aluminum is subjected to a one-step hydrothermal dissolution treatment, and the produced product is metallurgical grade alumina.

Example 1

In this embodiment, a medium-low grade bauxite is used, and the main chemical components (mass percentage, wt%) are: alumina (Al ₂ O ₃ ) 60.60%, silica (SiO ₂ ) 17.5%, others are impurities, and aluminum thereof The silicon ratio is 3.5;

Calcium ferrite is sintered from iron-containing raw materials and lime;

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 metallurgical grade alumina by treating 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. 1 :

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

S2: mixing the mineral powder, calcium 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 alkali thermal elution reaction, 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 of this step, the extraction rate of alumina can reach 83%;

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: sodium aluminate at 80 ° C, seed crystal addition coefficient of 0.8, carbon dioxide and seed crystals for carbon (carbonation decomposition) to a decomposition rate of 95%, to obtain a crude aluminum hydroxide slurry, and Performing liquid-solid separation to obtain a carbon mother liquor and crude aluminum hydroxide;

S6: subjecting the crude aluminum hydroxide obtained in the step S5 to a Bayer process to obtain a metallurgical grade alumina;

S7: The carbon mother liquor obtained in step S5 is causticized with lime milk to obtain a caustic slurry, and the caustic slurry is subjected to liquid-solid separation to obtain a polymer ratio sodium aluminate solution and calcium carbonate. The sodium aluminate solution is prepared as the circulating mother liquor in step S2;

In this step, the carbon mother liquor is treated, and the obtained polymer can be used as a circulating mother liquor to participate in other process processes after adjusting the sodium aluminate solution, so that the process has no efflux and no pollution;

S8: washing the eluted slag in step S4 and solid-liquid separation to obtain calcium garnet type slag and washing liquid;

In this step, the alkali-free 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 slag;

S9: using the washing liquid for diluting the dissolved pulp 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 the dissolved pulp, which not only reduces the treatment and discharge of the waste liquid, but also achieves the effect of recycling, and achieves the recovery of the material. Reuse;

S10: calcining the calcium carbonate obtained in the step S7 at 1000 ° C to obtain carbon dioxide gas and calcium oxide, and the obtained carbon dioxide gas is used for carbon separation in the step S5, and the obtained calcium oxide is used for causticization in the step S7. ;

In this step, the decomposition and reuse of calcium carbonate realizes the recycling of resources, avoids waste of resources, and saves costs.

The resulting metallurgical grade alumina is the product.

Example 2

In this embodiment, a medium-low grade bauxite is used, and the main chemical components (mass percentage, wt%) are: alumina (Al ₂ O ₃ ) 65.22%, silica (SiO ₂ ) 12.66%, others are impurities, and aluminum thereof The silicon ratio is 5.15;

Sodium ferrite is sintered from iron-containing raw materials and industrial carbon base;

The concentration of caustic in the circulating mother liquor was 230 g/L and the molecular ratio was 20.

F/A = 0.6:1;

C/F = 4:1.

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 1 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%;

S5: Under the condition of low molecular ratio sodium aluminate at 80 ° C and a seed crystal addition coefficient of 0.8, carbon dioxide is added to the seed crystal to carry out carbon, and the carbon end point is a decomposition rate of 95% or more. After the carbon is obtained, the crude aluminum hydroxide slurry is subjected to liquid-solid separation to obtain a carbon mother liquor and crude aluminum hydroxide;

S7: The carbon mother liquor obtained in step S5 is causticized with calcium oxide to obtain a caustic slurry, and the caustic slurry is subjected to liquid-solid separation to obtain a polymer ratio sodium aluminate solution and calcium carbonate, and the ratio of the polymer is The sodium aluminate solution is prepared as the circulating mother liquor in step S2;

S9: using the washing liquid for diluting the dissolved pulp in step S4;

The resulting metallurgical grade alumina is the product.

The method of the invention has the characteristics of short process and high efficiency, and the final products of the whole process are metallurgical grade alumina and alkali-free calcium iron garnet type slag, and the rest of the materials are recycled, and the materials in the whole process realize zero discharge. This alkali-free calcium iron garnet type slag has been effectively utilized due to the reduction of alkali content, such as calcium ferrite additive used in steelmaking process, self-stressing, high strength, quick-setting Portland cement and highways, airports. Ideal aggregate for high-strength concrete such as runways, and as a potential raw material for higher value-added products such as glass-ceramics and silicon fertilizers.

Claims

Method for producing metallurgical grade alumina by 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 or calcium 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: introducing carbon dioxide gas into the sodium aluminate solution to carry out carbon, to obtain crude aluminum hydroxide and carbon mother liquor;

S6: subjecting the crude aluminum hydroxide to a Bayer process to obtain a metallurgical grade alumina;

S7: The carbon mother liquor obtained in step S5 is causticized with lime milk to obtain a caustic slurry, and the caustic slurry is subjected to liquid-solid separation to obtain a sodium hydroxide solution and calcium carbonate, and the sodium hydroxide solution is prepared. As the circulating mother liquor in step S2.
The method for producing a metallurgical grade alumina of a medium-low grade bauxite by the one-step alkali thermal treatment of the calcium iron garnet according to claim 1, wherein the medium-low grade bauxite has a silicon to aluminum ratio of 2-6 .
The method for producing a metallurgical grade alumina of a medium-low grade bauxite by a one-step alkali thermal treatment of calcium iron garnet according to claim 1, characterized in that: bauxite, sodium ferrite or calcium ferrite, active lime In the raw material pulp, the total amount of iron, aluminum, calcium and silicon present in each form is determined by the oxide, and the formulation of the ingredients 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 a metallurgical grade alumina of a medium-low grade bauxite by the one-step alkali thermal treatment of calcium iron garnet according to claim 1 or 2, wherein in step S1, the liquid-solid ratio of the raw material slurry is 2 to 5 : 1.
The method for producing metallurgical grade alumina in a medium-low grade bauxite by the one-step alkali thermal treatment of calcium iron garnet according to claim 1, wherein the concentration of caustic in the circulating mother liquor in step S2 is 150-250 g/L The molecular ratio is 5 to 25.
The method for producing a metallurgical grade alumina of a medium-low grade bauxite by the one-step alkali thermal treatment of the calcium iron garnet according to claim 1, wherein the temperature of the dissolution reaction in the step S3 is 150 to 250 ° C, and the reaction time is 0.5 to 2 hours.
The method for producing a metallurgical grade alumina from a medium-low grade bauxite by a one-step alkali thermal treatment of calcium iron garnet according to claim 1, wherein:

In step S5, a carbon dioxide gas is introduced into the low molecular ratio sodium aluminate and a seed crystal is added to carry out carbon, and a crude aluminum hydroxide slurry is obtained, followed by liquid-solid separation to obtain a carbon mother liquor and a crude aluminum hydroxide.

In step S5, the carbon content temperature is 60 to 90 ° C, the carbon end point is a decomposition rate of 90% or more, and the seed crystal addition coefficient is 0 to 1.0.
The method for producing a metallurgical grade alumina of a medium-low grade bauxite by a one-step alkali thermal treatment of the calcium iron garnet according to claim 1, wherein the method further comprises:

Step S8: washing the eluted slag in step S4 and solid-liquid separation to obtain calcium garnet type slag and washing liquid;

Step S9: The washing liquid is used to dilute the dissolved slurry in step S4.
The method for producing a metallurgical grade alumina of a medium-low grade bauxite by the one-step alkali thermal treatment of the calcium iron garnet according to claim 1, wherein the method further comprises the step S10: the calcium carbonate obtained in the step S7 Calcination decomposition is carried out to obtain carbon dioxide gas and calcium oxide, and the obtained carbon dioxide gas is used for carbon separation in step S5, and the obtained calcium oxide is used in the causticized carbon mother liquid in step S7.
The method for producing a metallurgical grade alumina of a medium-low grade bauxite by the one-step alkali thermal treatment of the calcium iron garnet according to claim 1, wherein the sodium ferrite in the step S1 is sintered by the iron-containing raw material and the industrial carbon alkali. Calcium ferrite is a sintered iron-containing material and lime.