CN103614547B - A method for separating iron, aluminum and silicon from diaspore type bauxite - Google Patents

Abstract

The invention discloses a method for separating iron, aluminum and silicon from diasporic bauxite, which comprises the following steps: sequentially carrying out oxidizing roasting and reducing roasting on bauxite; after carrying out water quenching and grinding on the roasted bauxite, dissolving out silicon dioxide with an alkali solution, and carrying out solid-liquid separation to obtain a filter residue and a siliceous alkali solution; and carrying out low intensity magnetic separation on the filter residue to obtain a magnetite concentrate and an alumina concentrate, wherein the alumina concentrate is used for producing alumina by a Bayer process, and the magnetite concentrate is used as an ironmaking raw material. The method implements separation of iron, aluminum and silicon from diasporic bauxite, has the characteristics of simple technical process, low cost, high product quality, high comprehensive utilization ratio of resources, and the like, and provides powerful technical support for sufficient and rational utilization of bauxite resources.

Description

A method for separating iron, aluminum and silicon from diaspore type bauxite

technical field

The invention belongs to the field of mineral processing and relates to a method for separating iron, aluminum and silicon from diaspore type bauxite.

Background technique

Steel and aluminum are the most important material basis for national economic development. With the rapid development of my country's iron and steel industry and alumina industry, the demand for resources has grown rapidly, the contradiction of iron and aluminum ore shortages has become increasingly prominent, and the quantity and quality of domestic high-quality iron ore and bauxite resources have declined sharply. Under the urgent situation that high-quality resources are in short supply, it is urgent to rely on technological progress to fully develop and rationally utilize domestic low-grade complex refractory ore resources to ensure the sustainable and stable development of my country's iron and steel industry and alumina industry.

At present, in China and Southeast Asian countries, there are abundant low-grade high-iron and high-silicon bauxite deposits. In my country, such resources are mainly distributed in Guangxi, Fujian, Hainan, Yunnan, Shanxi and other places. This type of ore has low aluminum grade, high iron and silicon content, and low aluminum-silicon ratio. If this type of ore is directly used in Bayer process production, the actual dissolution rate of alumina will be low, and the output of red mud will be large, which will seriously reduce the economic benefits of alumina production. Due to the difficulty of using high-iron red mud, it is currently impossible to recycle iron in bauxite, resulting in a large waste of iron resources. Therefore, efficiently separate the impurity silicon and iron in bauxite, improve the grade of alumina, increase the ratio of aluminum to silicon, and recycle iron minerals to provide high-quality raw materials for the alumina industry and the iron and steel industry. It is of great practical significance to improve the comprehensive utilization rate of mineral resources in order to meet the pressure of serious shortage of iron ore resources.

There are many studies on bauxite beneficiation at home and abroad, and there are extensive studies on desiliconization and iron removal. In terms of desiliconization of high-silicon bauxite, the main methods are forward flotation, reverse flotation, and chemical methods. The positive flotation method has low cost of chemicals, but the amount of concentrate floated up is large and the dosage of chemicals is high; and the residual amount of chemicals in the concentrate is high, which will have a harmful impact on the subsequent Bayer dissolution process; it is difficult to filter and dehydrate the flotation concentrate, which is not conducive to reducing Energy consumption in the dissolution process of the Bayer method; for bauxite with complex mineral composition and fine particle size, fine grinding is required, and the energy consumption of grinding is high. At the same time, it is easy to cause over-grinding and muddying of aluminosilicate minerals with good grindability , have an adverse effect on the flotation process. The aluminum-silicon ratio of the alumina concentrate obtained by forward flotation can be increased to more than 11, and the recovery rate of Al ₂ O ₃ is 85-90%. Using reverse flotation, because aluminosilicate minerals have low hardness and are easy to grind, while diaspore has high hardness, which is easy to achieve coarse grinding, which is beneficial to reduce grinding energy consumption and concentrate water content; the yield of floating products is small , the dosage of medicament is small; and the concentrate is easy to filter, which will also help reduce the moisture content; less mechanical entrainment will help improve product quality. At present, the aluminum-silicon ratio can be increased to about 9 by using the reverse flotation method, and the recovery rate of Al ₂ O ₃ is about 80%. The heat-activated desilication method is to roast the bauxite at a certain temperature to decompose the aluminosilicate minerals in the ore to form amorphous SiO ₂ , decompose the gibbsite into α-Al ₂ O ₃ , and then utilize The difference in the solubility of amorphous SiO ₂ and α-Al ₂ O ₃ in NaOH solution realizes the separation of aluminum and silicon. Thermal activation desiliconization method, high temperature roasting process, relatively high energy consumption, but this method has high technical indicators, the aluminum-silicon ratio of alumina concentrate can be increased to 11~15, and the recovery rate of Al ₂ O ₃ can reach more than 98% .

Extensive research is being carried out on the separation of aluminum and iron from high-iron bauxite. In recent years, many treatment methods have been proposed, which can be roughly divided into the following 8 categories: mineral processing, magnetization roasting, metallization roasting, reduction sintering, melting smelting, acid and high concentration alkali.

The beneficiation method mainly includes gravity separation, magnetic separation, flotation, electric separation, flocculation and strong magnetic separation-anion reverse flotation and other combined beneficiation processes. For ores with a simple intercalation relationship between iron and aluminum, these methods can achieve the separation of aluminum and iron to a certain extent. However, the iron minerals in general high-iron bauxite have a fine particle size, and the occurrence relationship of aluminum and iron minerals is complex and tightly embedded. Because the geochemical and crystal chemical behaviors of aluminum and iron are similar, isomorphic substitution often occurs. The separation effect of aluminum and iron for such ores is poor.

The acid method is to use the difference in the ability of iron and aluminum to dissolve in acid under different conditions. The iron and aluminum are dissolved in acid respectively, and the obtained iron and aluminum salt solution is concentrated and crystallized, and then thermally decomposed to obtain alumina and iron oxide. The problems and shortcomings of the acid method are: it is difficult to remove iron from the aluminum salt solution; the acid consumption is large, the regeneration process of the acid is complicated, and the recovery and recycling are very difficult, so it is harmful to the environment and the cost is high; the corrosion of the equipment Seriously, expensive acid-resistant equipment is required. These all prevent its application in industrial production.

The magnetization roasting method uses reducing gas or coal as a reducing agent to reduce iron minerals to strong magnetic magnetite, and then separates the magnetite through magnetic separation to obtain iron concentrate and high-grade aluminum concentrate . Alternatively, after magnetization roasting, the Bayer method is used for leaching, and then iron is recovered from the red mud by magnetic separation. For ores with fine particle size embedded in iron minerals, the separation effect of iron by this method is not good, and the recovery rate of iron is low.

The metallization roasting method generally uses coal as a reducing agent to reduce the iron minerals in the ore to a metallic state under solid conditions, and obtain sponge iron through magnetic separation, and the aluminum concentrate is leached by the Bayer method. The problem of using the metallization roasting method is that because the iron mineral particles in the high-iron bauxite are fine, the reduced metal iron grains are difficult to aggregate and grow, so the separation effect of magnetic separation is often poor. Therefore, some researchers mixed sodium salt into high-iron and high-silicon bauxite as an additive to promote the reduction of iron minerals and the growth of iron grains, and carried out metallization reduction roasting, and obtained high-grade sponge iron powder and rich iron powder by magnetic separation. Non-magnetic materials of aluminum; then use sulfuric acid to treat non-magnetic materials, dissolve aluminum and silicon, and use porous adsorbent to absorb silicon in the leaching solution. The adsorbed silicon is used to prepare white carbon black, and the solution after silicon removal is used to prepare aluminum sulfate and other chemical industries. product. This process destroys the ore structure by adding additives, promotes the material migration of iron, and obtains a good iron-aluminum separation effect, and then uses sulfuric acid leaching and activated carbon adsorption to treat aluminum-rich slag to achieve aluminum-silicon separation. The problem becomes a deficiency of the process. In addition, there is a process that promotes the growth of iron grains during the metallization roasting process through high temperature and carburization. This process uses coal as a reducing agent, at a relatively high temperature (1250~1450°C), iron minerals are reduced to granular iron through semi-melting and carburizing, and then sponge iron is obtained through rapid cooling and magnetic separation. and alumina concentrate. However, the energy consumption of this process increases, and the iron grade of the magnetic product is not high.

The reduction sintering method is developed and improved on the basis of the traditional lime soda sintering method in the alumina industry. Soda ash, quicklime and coal powder are added to the high-iron and high-silicon bauxite for reductive sintering; as in the traditional sintering method, aluminum minerals interact with soda ash to form solid sodium aluminate, silicon minerals interact with lime to form calcium silicate, and iron Minerals are reduced to magnetite or metal iron; sintered clinker is leached with sodium carbonate solution, and then magnetic separation is used to recover magnetite or metal iron from red mud slag, or iron and aluminum are separated by magnetic separation, and then The non-magnetic part of sodium aluminate is dissolved to extract alumina and alkali. This method has a large amount of coal blending (10-20% of the furnace charge), high-temperature sintering is difficult, clinker is finely ground by dry method, iron is easily wrapped or mixed with other phases, resulting in the loss of useful components, and the net dissolution rate of alumina is lower than 90%, low iron recovery rate (<80%) and other issues.

The calcium aluminate slag smelting method is to add limestone (or quicklime) and coke to the high-iron bauxite, and sinter or smelt it in a semi-molten or molten state in high-temperature equipment such as a rotary kiln, blast furnace, or electric furnace. Minerals are reduced to metallic iron solid particles or molten iron, and calcium aluminate slag is produced at the same time. The separation of aluminum and iron is realized by separating molten iron from slag iron of calcium aluminate slag, or separating iron particles by magnetic separation. Calcium aluminate slag undergoes self-powdering after slow cooling, and transforms into easily soluble 12CaO·7A1 ₂ O ₃ and CaO·A1 ₂ O ₃ (CA). Finally, calcium aluminate slag is leached with sodium carbonate solution to extract alumina. This method has high smelting temperature, large lime consumption, and large amount of slag; the cooling rate of slag should be controlled below 10°C/min, which takes up a lot of space and poor economic feasibility.

The high-concentration alkali method is to mix bauxite with high-concentration alkali solution or sodium aluminate solution to dissolve aluminum and silicon in the ore as completely as possible, and the leached slag is iron concentrate. Lime is added to the eluate for desiliconization, and silicon slag can be used to prepare zeolite. The high-concentration sodium aluminate solution is divided into two parts, a small part enters the seed crystal decomposition process of alumina production or directly produces sodium aluminate crystals, and most returns to dissolve bauxite. This method realizes efficient separation of iron, aluminum and silicon in the ore, but because most of the sodium aluminate solution returns to the stripping process, the production efficiency is low.

Due to the economic and technical problems of the above aluminum-iron separation processes, such as high energy consumption, long process, serious environmental pollution, or poor technical indicators, none of the processes has been applied to industrial production at present.

To sum up, there have been many studies on the separation of aluminum and iron from high-iron bauxite and desiliconization of high-silicon bauxite, but due to various reasons, there are still no industrial applications. As for bauxite, there is no reasonable process that can economically and effectively realize the separation of aluminum, iron and silicon and the comprehensive recovery of iron and aluminum at the same time.

Contents of the invention

The invention aims to provide a beneficiation method with simple process flow, high production efficiency, low energy consumption and low cost, capable of simultaneously realizing the separation of aluminum, silicon and iron in bauxite and the comprehensive recovery of aluminum concentrate and iron concentrate. The separation effect of iron, aluminum and silicon is good, and all of them are prepared into products; the Al ₂ O ₃ grade of alumina concentrate is high, and the A/S is high, which is a high-quality raw material for the production of alumina by Bayer process; iron concentrate can be used in blast furnace smelting Iron; the recovery rates of iron and aluminum are high, 75% and 85% respectively. Alkaline solution can be recycled and used.

For realizing the above object, technical scheme of the present invention is:

A method for separating iron-aluminum-silicon from diaspore-type bauxite, the method comprising the steps of roasting, alkali leaching to separate silicon and weak magnetic separation to separate iron and aluminum, the roasting method is oxidation roasting followed by reduction roasting , specifically: crush the bauxite to a particle size of less than 15 mm, first oxidize and roast the bauxite in a natural air atmosphere at a temperature of 950 ° C to 1050 ° C for 15 min to 45 min; The roasted ore is obtained by reducing and roasting in the atmosphere for 5 minutes to 12 minutes; the gas composition of the weak reducing atmosphere is CO and CO ₂ , and the volume ratio is CO/(CO+CO ₂ )= 1% to 15%.

Preferably, the particle size of the crushed bauxite is 3 mm to 8 mm; the oxidation roasting temperature is 1000 ° C, and the oxidation roasting time is 25 min to 35 min; the weak reduction roasting temperature is consistent with the oxidation roasting, and the weak reduction atmosphere The gas composition is CO and CO ₂ , the volume ratio is CO/(CO+CO ₂ )=10%~15%, and the reduction roasting time is 5min~10min.

The steps of removing silicon by alkali leaching and separating iron and aluminum by weak magnetic separation are preferably water quenching the roasted ore obtained by roasting, leaching with alkali solution, separating solid and liquid to obtain filter residue and silicon-containing alkali solution, and washing the filter residue with water to remove alkali; The filter residue is subjected to weak magnetic separation to obtain magnetite concentrate and alumina concentrate.

The process parameters of the lye leaching are: the lye is a mixed solution of sodium hydroxide and sodium carbonate, wherein in terms of Na ₂ O _k , the concentration of sodium hydroxide is 100 g/L ~ 150 g/L, and in Na Based on ₂ O _c , the concentration of sodium carbonate is 5 g/L-20 g/L, the leaching temperature is 95°C-105°C, the liquid-solid ratio is 5-12, and the leaching time is 10 min-30 min. Preferred solution:

The process parameters of the weak magnetic separation are preferably as follows: the mass concentration of grinding pulp is 40%~60%, the grinding fineness is -0.074mm, the particle size accounts for 90%~95%, and the magnetic field strength is 1000 Gs~1500 Gs.

The TFe grade of the obtained magnetite concentrate is greater than or equal _to 58%, the recovery rate of Fe is greater than or equal to 75%, the _Al2O3 grade of the alumina concentrate is greater than or equal _to 60%, the A/S is greater than or equal to 8, and the recovery rate of _Al2O3 Greater than or equal to 85%.

It is also preferred to include the step of regenerating the sodium hydroxide solution

Add quicklime to the silicon-containing alkali solution obtained in step 2 according to the calcium-silicon molecular ratio of 0.9~1.1, hydrothermally react at 200~240°C for 4~6h, separate solid and liquid, and the obtained liquid product is sodium hydroxide solution, Return to step 2 to leach new roasted ore, and the solid product is hydrated calcium silicate, which can be used in construction, filling, papermaking and other industries.

The diaspore bauxite is preferably a high-iron and high-silicon diaspore bauxite with a Fe ₂ O ₃ content greater than 15% and a mass ratio of Al ₂ O ₃ to SiO ₂ less than 3.

Principle of the present invention is further explained and illustrated below:

The principle of the present invention is that: the key of the present invention lies in the first step, which is oxidation roasting and then reduction roasting.

When the ore is oxidized and roasted, the aluminosilicate minerals in the bauxite decompose to form amorphous SiO ₂ ; while the gibbsite such as diaspore and gibbsite are dehydrated to form α-Al ₂ O ₃ and γ-Al ₂ O ₃ ; at the same time, various iron minerals (hematite, magnetite and pyrite, etc.) in the ore are dehydrated or oxidized and transformed into hematite. The porosity of the ore after removal of crystallization water increases, and the reducibility of iron minerals can be greatly improved; the hematite obtained from the oxidation and recrystallization of magnetite has good reducibility; this will help the next step of reduction roasting to achieve good results. restoration effect. Oxidation of pyrite can remove harmful impurity sulfur. In addition, the organic matter in the ore is also removed by combustion, which can eliminate its adverse impact on Bayer process production.

During the oxidation roasting process, reasonable control of the roasting temperature and time is required. The selection of roasting temperature and roasting time should follow the following four main principles:

1. Promote the full transformation of silicon in aluminosilicate minerals into amorphous SiO ₂ , so that silicon can be activated to the greatest extent. Amorphous SiO ₂ is very soluble in dilute alkali solution. After the roasting is completed, using the characteristic of amorphous SiO ₂ , dilute alkali solution can be used to dissolve the amorphous SiO ₂ to realize the desiliconization of the ore. The higher the temperature, the faster the decomposition reaction of aluminosilicate minerals; the longer the time, the more fully the decomposition reaction is carried out.

2. To passivate the decomposition products α-Al ₂ O ₃ and γ-Al ₂ O ₃ of aluminum-containing minerals. The calcination temperature and calcination time are different, and the alkali solution dissolution properties of the obtained α-Al ₂ O ₃ and γ-Al ₂ O ₃ are also different. When leaching amorphous SiO ₂ with dilute alkali, Al ₂ O ₃ should also be prevented from dissolving. Therefore, the calcination temperature and calcination time must be well controlled to reduce the solubility of Al ₂ O ₃ in dilute alkali solution as much as possible so that aluminum can be fully passivated.

3. To effectively inhibit the recrystallization of decomposition products (γ-Al ₂ O ₃ and amorphous SiO ₂ ). When the calcination temperature is too high, γ-Al ₂ O ₃ and amorphous SiO ₂ will combine to form mullite, and amorphous SiO ₂ will also transform into cristobalite crystal. The higher the temperature, the faster the reaction rate of compounding and crystallization; the longer the time, the more fully the reaction is carried out. Both cristobalite and mullite are extremely difficult to dissolve in dilute alkali solution. When mullite and cristobalite are formed, silicon will be "passivated", and the desilication effect of alkali leaching will undoubtedly become worse. Therefore, the selection of calcination temperature and time must suppress the combination of γ-Al ₂ O ₃ and amorphous SiO ₂ and the transformation of amorphous SiO ₂ to cristobalite.

4. In the process of oxidation and roasting, it is also necessary to promote the full decomposition and oxidation of iron minerals. Iron minerals are fully decomposed and oxidized, and the better their reducibility is, the more beneficial it is for the subsequent magnetization roasting.

In general, the selection of roasting temperature and roasting time should be based on the main principle of "activating silicon, passivating aluminum, and iron oxide", and should also consider reducing energy consumption as much as possible.

The purpose of reducing and roasting the ore is to reduce the hematite with good reducibility to magnetite, so that it can be separated by magnetic separation. In the reduction roasting process, hematite must be reduced to magnetite, but iron minerals must be prevented from being over-reduced. If the weakly magnetic hematite is not completely reduced to the strong magnetic magnetite, the recovery rate of iron minerals will be low during magnetic separation. Once the iron minerals are over-reduced, non-magnetic fuosite (FeO) will be generated, which will also lead to low iron minerals during magnetic separation. What's more serious is that the presence of fuustenite (FeO) will make amorphous SiO ₂ react rapidly with it, and the desiliconization effect will also deteriorate sharply. Therefore, conditions must be controlled to obtain a suitable reduction degree of iron ore. The theoretical reduction degree of magnetite is 11.11%. During reduction roasting, the degree of reduction (R=(Fe ²⁺ /3TFe)×100%) should be controlled within the range of 10.00%~12.50%, in order to obtain good desiliconization effect and magnetic separation effect. Roasting temperature, calcination time and reducing atmosphere are the most important factors affecting the reduction reaction speed and final reduction degree of iron ore. The higher the temperature, the stronger the reducing atmosphere and the faster the reduction reaction speed; the longer the roasting time, the higher the degree of reduction of iron minerals obtained. Therefore, reasonable control of these three factors is particularly important.

After the roasting is completed, the use of amorphous SiO ₂ is very soluble in dilute alkali solution, while α-Al ₂ O ₃ and γ-Al ₂ O ₃ are passivated, the dissolution rate is extremely low, and iron minerals are insoluble. The alkaline solution leaches the roasted ore and selectively dissolves amorphous SiO ₂ , thereby realizing desiliconization of bauxite. And in this step, aluminum and iron can basically achieve 100% recovery.

After desiliconization, the magnetite is separated by weak magnetic separation to obtain high-quality alumina concentrate and magnetite concentrate, realizing the separation and recovery of iron and aluminum.

After the treatment of this process, the silicon in the bauxite is removed, and the aluminum-silicon ratio is greatly improved; the iron minerals are separated, and the crystal water is removed, so that the aluminum grade of the aluminum concentrate is greatly improved; in addition, the sulfur and organic matter Other impurities are also removed; the main components of the aluminum concentrate are α-Al ₂ O ₃ and γ-Al ₂ O ₃ , both of which have good Bayer dissolution properties. Therefore, the obtained aluminum concentrate is a high-quality raw material for alumina production with high aluminum grade, high aluminum-silicon ratio, low impurity and excellent dissolution performance. The obtained magnetite can be used for sintering and ironmaking, realizes the utilization of iron minerals in bauxite, and improves the comprehensive utilization rate of resources.

In the present invention, by reasonably adjusting temperature, time and atmosphere, the decomposition reaction of aluminum and silicon minerals in bauxite, the sequence of reduction reaction with iron minerals, and the degree of reaction progress are realized, and the aluminosilicate is simultaneously realized in the high-temperature roasting link Decomposition of salt minerals, passivation of aluminum minerals and rapid magnetization of iron minerals, and effectively inhibit the combination and recrystallization of iron, aluminum, and silicon phases, creating favorable conditions for physical and chemical separation, and then through simple Leaching and magnetic separation achieve the separation and recovery of iron, aluminum, and silicon, which solves the problems of high cost, high energy consumption, and low comprehensive utilization of resources in existing separation technologies, and maximizes the comprehensive utilization of bauxite resources use.

Oxidation roasting and reduction roasting are not completely independent two-stage processes. The two stages of roasting process are mutually influencing. Oxidation roasting and reduction roasting both affect the effect of iron selection and desiliconization. Only when the two achieve the best coupling can a good effect of iron selection and desiliconization be obtained. Therefore, the choice of oxidation roasting and reduction roasting temperature needs to take into account both the desiliconization effect and the reduction effect. In order to make the process easy to realize in industry, in this process, the temperature of oxidation roasting and reduction roasting are kept consistent.

Water quenching is a kind of cooling method, and its effect has three points in the present invention. First, rapid cooling to improve production efficiency. Second, the isolation of air can prevent the magnetite from being oxidized due to natural cooling in the air. Third, rapid cooling in water can maintain the activity of amorphous silica, so as not to react with other components when it is slowly cooled in air.

Compared with the prior art, the present invention has the advantages of:

1. By reasonably controlling the sequence and progress of the decomposition reaction of aluminum and silicon minerals and the reduction reaction of iron minerals, the phase transformation of iron and silicon components is simultaneously realized in the roasting process, which provides a good foundation for the subsequent desiliconization and selection. Iron creates favorable mineralogical conditions.

2. Using the "roasting-leaching-magnetic separation" process, the operation is simple, the process is short, the energy consumption is low, the production efficiency is high, and the comprehensive cost is low.

3. The separation effect of iron, aluminum and silicon is good, and all of them are prepared into products; the Al ₂ O ₃ grade of alumina concentrate is high, and the A/S is high, which is a high-quality raw material for the production of alumina by Bayer process; iron concentrate can be used for Blast furnace ironmaking; iron and aluminum recovery rates are high, 75% and 85% respectively. Alkaline solution can be recycled and used.

In summary, the present invention realizes the separation of aluminum, silicon and iron in bauxite, and has the characteristics of simple technological process, low cost, excellent product quality, high recovery rate of iron and aluminum, etc. Provide strong technical support and have broad application prospects.  

Detailed ways

The present invention will be further described in detail below in combination with specific embodiments. The gas composition ratios of the reducing atmosphere described in the examples are volume ratios.

The main chemical components of the diaspore-type bauxite used in the examples of the present invention are shown in Table 1.

Table 1 The main chemical composition of diaspore type bauxite/%

Example 1:

(1) Crush the bauxite to a particle size of 3-8 mm, first carry out oxidation roasting in a natural air atmosphere, the roasting temperature is 1000 °C, and the roasting time is 30 minutes; then, magnetization roasting is carried out in a weak reducing atmosphere, the roasting temperature is 1000 °C ℃, roasting time 10 min, the gas composition of weak reducing atmosphere is CO/(CO+CO ₂ )=10%; the reduction degree of roasted ore is 11.85%.

(2) After the roasted ore is quenched by water, the roasted ore is leached with a mixed alkali solution of sodium carbonate and sodium hydroxide. The leaching temperature is 95°C, the concentration of Na ₂ O _k is 120 g/L, and the concentration of Na ₂ O _c is 10 g/L, the liquid-solid ratio was 7, and the leaching time was 30 min. Under these conditions, the dissolution rate of silicon dioxide was 69%. The content of Al ₂ O ₃ and SiO ₂ in the ore after desiliconization was 5.37%, the A/S ratio is 8.6, and the recovery rate of Al ₂ O ₃ is 96.4%.

(3) Perform weak magnetic separation on the solid product after desiliconization, the magnetic field strength is 1000 Gs, the pulp concentration is 50%, the TFe grade of the obtained magnetite concentrate is 58.77%, the yield rate is 30.85%, and the Fe recovery rate is 76.3% , the Al ₂ O ₃ grade of alumina concentrate is 61.01%, the A/S ratio is 8.7, the TiO ₂ content is 10.10%, and the Al ₂ O ₃ recovery rate is 87.5%.

(4) Add quicklime to the silicon-containing alkali solution obtained by desiliconization at a ratio of calcium-silicon molecular ratio of 1.0, and react at 200°C for 6 hours to obtain a sodium hydroxide solution. Sodium hydroxide can be returned to step (2) for use.

Example 2:

(1) Crush the bauxite to a particle size of 3-8 mm, first carry out oxidation roasting in a natural air atmosphere, the roasting temperature is 1000 °C, and the roasting time is 30 minutes; then, magnetization roasting is carried out in a weak reducing atmosphere, the roasting temperature is 1000 °C ℃, roasting time 10 min, the gas composition of weak reducing atmosphere is CO/(CO+CO ₂ )=5 %; the reduction degree of roasted ore is 11.35%.

(2) After the roasted ore is quenched by water, the roasted ore is leached with a mixed alkali solution of sodium carbonate and sodium hydroxide. The leaching temperature is 95°C, the concentration of Na ₂ O _k is 120 g/L, and the concentration of Na ₂ O _c is 10 g/L, the liquid-solid ratio was 7, and the leaching time was 30 min. Under these conditions, the dissolution rate of silicon dioxide was 72.4%. The content of Al ₂ O ₃ and SiO ₂ in the ore after desilication was 4.74%, the A/S ratio is 9.8, and the recovery rate of Al ₂ O ₃ is 97.6%.

(3) Perform weak magnetic separation on the solid product after desiliconization, the magnetic field strength is 1000 Gs, the pulp concentration is 50%, the TFe grade of the obtained magnetite concentrate is 59.25%, the yield rate is 29.45%, and the Fe recovery rate is 74.3% , the Al ₂ O ₃ grade of alumina concentrate is 61.5%, the A/S ratio is 9.9, the TiO ₂ content is 9.85%, and the Al ₂ O ₃ recovery rate is 91.2%.

(4) Add quicklime to the silicon-containing alkali solution obtained by desiliconization at a ratio of calcium-silicon molecular ratio of 1.0, and react at 200°C for 6 hours to obtain a sodium hydroxide solution. Sodium hydroxide can be returned to step (2) for use.

Example 3:

(1) Crush the bauxite to a particle size of 3-8 mm, first carry out oxidation roasting in a natural air atmosphere, the roasting temperature is 1000 °C, and the roasting time is 30 minutes; then, magnetization roasting is carried out in a weak reducing atmosphere, the roasting temperature is 1000 °C ℃, roasting time 10 min, the gas composition of weak reducing atmosphere is CO/(CO+CO ₂ )=2 %; the reduction degree of roasted ore is 10.43%.

(2) After the roasted ore is quenched by water, the roasted ore is leached with a mixed alkali solution of sodium carbonate and sodium hydroxide. The leaching temperature is 95°C, the concentration of Na ₂ O _k is 120 g/L, and the concentration of Na ₂ O _c is 10 g/L, the liquid-solid ratio was 7, and the leaching time was 30 min. Under these conditions, the dissolution rate of silicon dioxide was 68.26%, and the content of Al ₂ O ₃ and SiO ₂ in the ore after desiliconization was 5.15%, the A/S ratio is 9.12, and the recovery rate of Al ₂ O ₃ is 98.65%.

(3) Perform weak magnetic separation on the solid product after desiliconization, the magnetic field strength is 1000 Gs, the pulp concentration is 50%, the TFe grade of the obtained magnetite concentrate is 59.6%, the yield rate is 28.5%, and the Fe recovery rate is 71.45% , the Al ₂ O ₃ grade of alumina concentrate is 59.8%, the A/S ratio is 8.3, the TiO ₂ content is 9.81%, and the Al ₂ O ₃ recovery rate is 91.00%.

(4) Add quicklime to the silicon-containing alkali solution obtained by desiliconization at a ratio of calcium-silicon molecular ratio of 1.0, and react at 200°C for 6 hours to obtain a sodium hydroxide solution. Sodium hydroxide can be returned to step (2) for use.

Example 4:

(1) Crush the bauxite to a particle size of 3-8 mm. First, oxidize and roast the bauxite in a natural air atmosphere at a roasting temperature of 950°C for a roasting time of 40 minutes; ℃, roasting time 8 min, the gas composition of weak reducing atmosphere is CO/(CO+CO ₂ )=15 %; the reduction degree of roasted ore is 12.32%.

(2) After the roasted ore is quenched by water, the roasted ore is leached with a mixed alkali solution of sodium carbonate and sodium hydroxide. The leaching temperature is 95°C, the concentration of Na ₂ O _k is 120 g/L, and the concentration of Na ₂ O _c is 10 g/L, the _liquid -solid ratio was 7, and the leaching time _was 30 min. Under _these conditions, the dissolution rate of silica was 68.64%. 5.26%, the A/S ratio is 8.8, and the recovery rate of Al ₂ O ₃ is 98.3%.

(3) Perform weak magnetic separation on the solid product after desiliconization, the magnetic field strength is 1000 Gs, the pulp concentration is 50%, the TFe grade of the obtained magnetite concentrate is 58.56%, the yield rate is 30.2%, and the Fe recovery rate is 74.32% , the Al ₂ O ₃ grade of alumina concentrate is 60.23%, the A/S ratio is 8.8, the TiO ₂ content is 9.52%, and the Al ₂ O ₃ recovery rate is 89.3%.

(4) Add quicklime to the silicon-containing alkali solution obtained by desiliconization at a ratio of calcium-silicon molecular ratio of 1.0, and react at 200°C for 6 hours to obtain a sodium hydroxide solution. Sodium hydroxide can be returned to step (2) for use.

Example 5:

(1) Crush the bauxite to a particle size of 3-8 mm, first carry out oxidation roasting in a natural air atmosphere, the roasting temperature is 1050°C, and the roasting time is 20 minutes; then, magnetization roasting is carried out in a weak reducing atmosphere, and the roasting temperature is 1050 °C ℃, roasting time 6 min, the gas composition of weak reducing atmosphere is CO/(CO+CO ₂ )=1 %; the reduction degree of roasted ore is 12.46%.

(2) After the roasted ore is quenched by water, the roasted ore is leached with a mixed alkali solution of sodium carbonate and sodium hydroxide. The leaching temperature is 95°C, the concentration of Na ₂ O _k is 120 g/L, and the concentration of Na ₂ O _c is 10 g/L, the liquid-solid ratio was 7, and the leaching time _was 30 min. Under these conditions, the dissolution rate of silicon _dioxide was _65.12 %. 5.83%, the A/S ratio is 8.0, and the recovery rate of Al ₂ O ₃ is 98.9%.

(3) Perform weak magnetic separation on the solid product after desiliconization, the magnetic field strength is 1000 Gs, the pulp concentration is 50%, the TFe grade of the obtained magnetite concentrate is 57.56%, the yield rate is 29.22%, and the Fe recovery rate is 70.63% , the Al ₂ O ₃ grade of alumina concentrate is 58.8%, the A/S ratio is 8.0, the TiO ₂ content is 10.88%, and the Al ₂ O ₃ recovery rate is 87.36%.

(4) Add quicklime to the silicon-containing alkali solution obtained by desiliconization at a ratio of calcium-silicon molecular ratio of 1.0, and react at 200°C for 6 hours to obtain a sodium hydroxide solution. Sodium hydroxide can be returned to step (2) for use.

Comparative Example 1: (Oxidation roasting-leaching-strong magnetic separation)

(1) Crush the bauxite to a particle size of 3-8 mm, and oxidize and roast it in a natural air atmosphere at a roasting temperature of 1000°C for a roasting time of 30 minutes;

(2) After the roasted ore is quenched by water, the roasted ore is leached with a mixed alkali solution of sodium carbonate and sodium hydroxide. The leaching temperature is 95°C, the concentration of Na ₂ O _k is 120 g/L, and the concentration of Na ₂ O _c is 10 g/L, the liquid-solid ratio was 7, and the leaching time was 30 min. Under these _conditions , the dissolution rate of silicon _dioxide was ₇₃ %. 4.61%, the A/S ratio is 10, and the recovery rate of Al ₂ O ₃ is 97.35%.

(3) Perform strong magnetic separation on the solid product after desiliconization, the magnetic field strength is 9000 Gs, the pulp concentration is 50%, the TFe grade of the obtained magnetite concentrate is 36%, the yield rate is 31%, and the Fe recovery rate is 45% ; The grade of Al ₂ O ₃ of alumina concentrate is 51%, the A/S ratio is 10, and the recovery rate of Al ₂ O ₃ is 75%.

Comparative Example 2: (Oxidation roasting-leaching-strong magnetic separation)

(1) Crush the bauxite to a particle size of 3-8 mm, and oxidize and roast it in a natural air atmosphere at a roasting temperature of 1000°C for a roasting time of 30 minutes;

(2) After the roasted ore is quenched by water, the roasted ore is leached with a mixed alkali solution of sodium carbonate and sodium hydroxide. The leaching temperature is 95°C, the concentration of Na ₂ O _k is 120 g/L, and the concentration of Na ₂ O _c is 10 g/L, the liquid-solid ratio was 7, and the leaching time was 30 min. Under these _conditions , the dissolution rate of silicon _dioxide was ₇₃ %. 4.61%, the A/S ratio is 10, and the recovery rate of Al ₂ O ₃ is 97.35%.

(3) Perform strong magnetic separation on the solid product after desiliconization, the magnetic field strength is 12000 Gs, the pulp concentration is 50%, the TFe grade of the obtained magnetite concentrate is 34%, the yield rate is 44%, and the Fe recovery rate is 60% ; The grade of Al ₂ O ₃ of alumina concentrate is 54%, the A/S ratio is 10, and the recovery rate of Al ₂ O ₃ is 58%.

Comparative Example 3: (reduction roasting-leaching-weak magnetic separation)

(1) Crush the bauxite to a particle size of 3-8 mm, and roast it in a weak reducing atmosphere. The gas composition of the weak reducing atmosphere is CO/(CO+CO ₂ )=1%, the roasting temperature is 1000°C, and the roasting time is 15min, the degree of reduction of iron minerals obtained in the roasted ore is 12.10%;

(2) After the roasted ore is quenched by water, the roasted ore is leached with a mixed alkali solution of sodium carbonate and sodium hydroxide. The leaching temperature is 95°C, the concentration of Na ₂ O _k is 120 g/L, and the concentration of Na ₂ O _c is 10 g/L, the liquid-solid ratio was 7, and the leaching time was 30 min. Under these conditions, the dissolution rate of silica was 54.93%, and the content of Al ₂ O ₃ and SiO ₂ in the ore after desilication was 7.36%, the A/S ratio is 6.56, and the recovery rate of Al ₂ O ₃ is 99.5%.

(3) Perform weak magnetic separation on the solid product after desiliconization, the magnetic field strength is 1000 Gs, the pulp concentration is 50%, the TFe grade of the obtained magnetite concentrate is 45%, the yield rate is 25%, and the Fe recovery rate is 52% ; The grade of Al ₂ O ₃ of alumina concentrate is 53%, the A/S ratio is 6.56, and the recovery rate of Al ₂ O ₃ is 80%.

Comparative Example 4: (reduction roasting-leaching-weak magnetic separation)

(1) Crush the bauxite to a particle size of 3-8 mm, and roast it in a weak reducing atmosphere. The gas composition of the weak reducing atmosphere is CO/(CO+CO ₂ )=1%, the roasting temperature is 1000°C, and the roasting time is 30 min, the reduction degree of iron minerals in the roasted ore was 14.42%;

(2) After the roasted ore is quenched by water, the roasted ore is leached with a mixed alkali solution of sodium carbonate and sodium hydroxide. The leaching temperature is 95°C, the concentration of Na ₂ O _k is 120 g/L, and the concentration of Na ₂ O _c is 10 g/L, the _liquid -solid ratio was 7, and the leaching time _was 30 min. Under _these conditions, the dissolution rate of silica was 56.55%. 8.06%, the A/S ratio is 5.9, and the recovery rate of Al ₂ O ₃ is 98.4%.

(3) Perform weak magnetic separation on the solid product after desiliconization, the magnetic field strength is 1000 Gs, the pulp concentration is 50%, the TFe grade of the obtained magnetite concentrate is 48%, the yield rate is 19%, and the Fe recovery rate is 44% , the Al ₂ O ₃ grade of alumina concentrate is 54%, the A/S ratio is 5.9, and the recovery rate of Al ₂ O ₃ is 84%.

Comparative examples 1-4 illustrate: when the process of "oxidation roasting-leaching-strong magnetic separation" is adopted and the reduction roasting link is omitted, this is equivalent to using the existing technology (patent CN00102465.5) to first desiliconize and then desilicate The final solid product is separated from the hematite by a conventional strong magnetic separation method, which is a physical combination of the prior art. Using this process, a good desiliconization effect can be achieved. However, since hematite is a weak magnetic mineral, it is still difficult to separate it by strong magnetic separation. Therefore, this process can only achieve desiliconization, but cannot separate aluminum and iron. The recovery rate of iron and aluminum is low, and qualified aluminum concentrate and iron concentrate products cannot be obtained.

When the "reduction roasting-leaching-weak magnetic separation" process is adopted and the oxidation roasting link is omitted, in order to decompose the aluminosilicate minerals, the temperature of the reduction roasting is also controlled to be 1000°C. As a result, poor magnetic separation and desiliconization results were obtained. With this process, the reduction reaction of iron minerals and the decomposition reaction of aluminosilicate proceed simultaneously. To fully decompose aluminosilicate minerals, the calcination temperature must be greater than 1000°C, and the calcination time must be at least 15 minutes. However, at a high temperature of 1000 °C, the reduction reaction rate is very fast. Even if the control gas concentration is as low as 1%~2%, and the roasting time is less than or equal to 15 min, over-reduction of iron minerals still occurs. Once the over-reduction of iron minerals occurs, the recovery rate of iron minerals decreases during magnetic separation; the desiliconization effect (dissolution rate of silicon dioxide) also becomes poor due to the rapid formation of fayalite from fuustenite and amorphous SiO ₂ .

Comparative Example 5: (The CO concentration is too high, over-reduction occurs, the desiliconization effect becomes worse, and the magnetic separation also becomes worse)

(1) Crush the bauxite to a particle size of 3-8 mm, first carry out oxidation roasting in a natural air atmosphere, the roasting temperature is 1000 °C, and the roasting time is 30 minutes; then, magnetization roasting is carried out in a weak reducing atmosphere, the roasting temperature is 1000 °C ℃, roasting time 5 min, the gas composition of weak reducing atmosphere is CO/(CO+CO ₂ )=20%; the reduction degree of roasted ore is 14.28%.

(2) After the roasted ore is quenched by water, the roasted ore is leached with a mixed alkali solution of sodium carbonate and sodium hydroxide. The leaching temperature is 95°C, the concentration of Na ₂ O _k is 120 g/L, and the concentration of Na ₂ O _c is 10 g/L, the liquid-solid ratio was 7, and the leaching time was 30 min. Under these conditions, the dissolution rate of silicon dioxide was 56.7%. The content of Al ₂ O ₃ and SiO ₂ in the ore after desilication was 46.66% 7.41%, the A/S ratio is 6.3, and the recovery rate of Al ₂ O ₃ is 99.3%.

(3) Perform weak magnetic separation on the solid product after desiliconization, the magnetic field strength is 1000 Gs, the pulp concentration is 50%, the TFe grade of the obtained magnetite concentrate is 53.36%, the yield rate is 23.4%, and the Fe recovery rate is 52.4% , the Al ₂ O ₃ grade of alumina concentrate is 54.26%, the A/S ratio is 6.3, the TiO ₂ content is 10.21%, and the Al ₂ O ₃ recovery rate is 84.67%.

(4) Add quicklime to the silicon-containing alkali solution obtained by desiliconization at a ratio of calcium-silicon molecular ratio of 1.0, and react at 200°C for 6 hours to obtain a sodium hydroxide solution. Sodium hydroxide can be returned to step (2) for use.

Comparative Example 6: (reduction time is too short, reduction is insufficient, magnetic separation becomes worse, Fe recovery rate is low)

(1) Crush the bauxite to a particle size of 3-8 mm, first carry out oxidation roasting in a natural air atmosphere, the roasting temperature is 1000 °C, and the roasting time is 30 minutes; then, magnetization roasting is carried out in a weak reducing atmosphere, the roasting temperature is 1000 °C ℃, roasting time 3 min, the gas composition of weak reducing atmosphere is CO/(CO+CO ₂ )=10%; the reduction degree of roasted ore is 9.20%.

(2) After the roasted ore is quenched by water, the roasted ore is leached with a mixed alkali solution of sodium carbonate and sodium hydroxide. The leaching temperature is 95°C, the concentration of Na ₂ O _k is 120 g/L, and the concentration of Na ₂ O _c is 10 g/L, the liquid-solid ratio was 7, and the leaching time was 30 min. Under these conditions, the dissolution rate of silicon dioxide was 72.13%. The content of Al ₂ O ₃ and SiO ₂ in the ore after desiliconization was 4.84%, the A/S ratio is 9.49, and the recovery rate of Al ₂ O ₃ is 95.88%.

(3) Perform weak magnetic separation on the solid product after desiliconization, the magnetic field strength is 1000 Gs, the pulp concentration is 50%, the TFe grade of the obtained magnetite concentrate is 55.64%, the yield rate is 25.5%, and the Fe recovery rate is 59.7% , the Al ₂ O ₃ grade of alumina concentrate is 56.87%, the A/S ratio is 9.5, the TiO ₂ content is 10.42%, and the Al ₂ O ₃ recovery rate is 88.78%.

(4) Add quicklime to the silicon-containing alkali solution obtained by desiliconization at a ratio of calcium-silicon molecular ratio of 1.0, and react at 200°C for 6 hours to obtain a sodium hydroxide solution. Sodium hydroxide can be returned to step (2) for use.

Comparative Example 7: (the reduction time is too long, the reduction is excessive, the desiliconization and magnetic separation effects are all deteriorated, the dissolution rate of silicon dioxide is low, and the Fe recovery rate is low)

(1) Crush the bauxite to a particle size of 3-8 mm, first carry out oxidation roasting in a natural air atmosphere, the roasting temperature is 1000 °C, and the roasting time is 30 minutes; then, magnetization roasting is carried out in a weak reducing atmosphere, the roasting temperature is 1000 °C ℃, roasting time 20 min, the gas composition of weak reducing atmosphere is CO/(CO+CO ₂ )=2%; the reduction degree of roasted ore is 13.55%.

(2) After the roasted ore is quenched by water, the roasted ore is leached with a mixed alkali solution of sodium carbonate and sodium hydroxide. The leaching temperature is 95°C, the concentration of Na ₂ O _k is 120 g/L, and the concentration of Na ₂ O _c is 10 g/L, the liquid-solid ratio was 7, and the leaching time was 30 min. Under these conditions, the dissolution rate of silicon dioxide was 58%. The content of Al ₂ O ₃ and SiO ₂ in the ore after desiliconization was 46.51%. 6.46%, the A/S ratio is 7.2, and the recovery rate of Al ₂ O ₃ is 95.7%.

(3) Perform weak magnetic separation on the solid product after desiliconization, the magnetic field strength is 1000 Gs, the pulp concentration is 50%, the TFe grade of the obtained magnetite concentrate is 58%, the yield rate is 24%, and the Fe recovery rate is 55% , the Al ₂ O ₃ grade of alumina concentrate is 54.36%, the A/S ratio is 7.3, the TiO ₂ content is 9.21%, and the Al ₂ O ₃ recovery rate is 86.67%.

(4) Add quicklime to the silicon-containing alkali solution obtained by desiliconization at a ratio of calcium-silicon molecular ratio of 1.0, and react at 200°C for 6 hours to obtain a sodium hydroxide solution. Sodium hydroxide can be returned to step (2) for use.

Comparative examples 5-7 illustrate that in the reduction roasting process, the control of reduction temperature, reduction atmosphere and reduction time is very important. If the weakly magnetic hematite is not completely reduced to the strong magnetic magnetite, the recovery rate of iron minerals will be low during magnetic separation. Once the iron minerals are over-reduced, non-magnetic fuosite (FeO) will be generated, which will also lead to low iron minerals during magnetic separation. What's more serious is that the presence of fuustenite (FeO) will make amorphous SiO ₂ react rapidly with it, and the desiliconization effect will also deteriorate sharply.

Claims (4)

1. a method for separating iron-aluminum-silicon from diaspore type bauxite, the method comprises roasting, alkali leaching separation silicon and weak magnetic separation separation iron-aluminum step, it is characterized in that, the method for described roasting is Oxidation roasting first and then reduction roasting, specifically: crush the bauxite to a particle size of less than 15 mm, first oxidize and roast 15 min to 45 min in a natural air atmosphere at a temperature of 950 ° C ~ 1050 ° C; then, in the same The roasted ore is obtained by reducing and roasting in a weak reducing atmosphere for 5 minutes to 12 minutes at low temperature; the gas composition of the weak reducing atmosphere is CO and CO ₂ , and the volume ratio is CO/(CO+CO ₂ )= 1%~15 %. 2. the method for separating iron-aluminum-silicon from diaspore type bauxite according to claim 1, is characterized in that, described bauxite is crushed to particle size and is 3 mm ~ 8 mm; Oxidation roasting The temperature is 1000℃, and the oxidation roasting time is 25 min ~ 35 min; the temperature of the weak reduction roasting is consistent with the oxidation roasting, the gas composition of the weak reduction atmosphere is CO and CO ₂ , and the volume ratio is CO/(CO+CO ₂ )= 10%~15%, reduction roasting time is 5min~10min. 3. The method for separating iron-aluminum-silicon from diaspore-type bauxite according to claim 1 or 2 is characterized in that, the step of separating silicon by alkali leaching and separating iron-aluminum by weak magnetic separation is to roast the obtained After the roasted ore is quenched with water, it is leached with alkali solution, solid-liquid separation to obtain filter residue and silicon-containing alkali solution, and the filter residue is washed with water to remove alkali; the filter residue is subjected to weak magnetic separation to obtain magnetite concentrate and alumina concentrate. 4. according to the method for separating iron-aluminum-silicon from diaspore type bauxite described in claim 1 or 2, it is characterized in that, in described diaspore type bauxite Fe ₂ O ₃ content is greater than 15%, the mass ratio of Al ₂ O ₃ to SiO ₂ is less than 3.