CN1686812A

CN1686812A - Method for producing alumina

Info

Publication number: CN1686812A
Application number: CN 200510020825
Authority: CN
Inventors: 邓少彬
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-04-29
Filing date: 2005-04-29
Publication date: 2005-10-26
Anticipated expiration: 2025-04-29
Also published as: CN100363262C

Abstract

The present invention relates to a method for producing Al2O3. Said method uses diaspore type ore as raw material, and uses Na2SO4, CaO and C as additive, and adopts the processes of ball-grinding, roasting, hydrolysis, acidizing decomposition, filtering and calcination so as to obtain the invented finished product Y-Al2O3. Besides, said invention also provides the concrete steps of the above-mentioned every process.

Description

Method for producing aluminum oxide

The technical field is as follows:

the present invention relates to a method for producing alumina by using diaspore type ore.

Background art:

the present process for producing alumina from diaspore ore is complex, and under the condition of caustic alkali, the high-temp. (180-240 deg.C) and high-pressure (40 atmospheres) for 60 minutes of autoclaving to convert the aluminum to water-soluble sodium aluminate. Also with Na₂CO₃CaO as additive is roasted at high temp. to generate water-soluble sodium aluminate, which is leached by water or alkali solution, and then Al is added by Bayer process₂O₃Adding CaO as crystal seed to replace aluminum hydroxide, and high temperature calcining to obtain alpha-type aluminum oxide. The method uses NaCO₃The additive has high production cost and causes pollution to the environment. In the first-stage desiliconization process, the impurities are firstly heated to be separated out as precipitates, the precipitates are generated again by pressurization after filtration, and then the sodium aluminate solution is obtained by filtration, so that the production process is complex, the material flow is large, and the cost is high. Adding a large amount of Al in the process of stirring and decomposing refined solution to generate aluminum hydroxide₂O₃Seed crystal has long time, large material flow, low production efficiency and high production cost. The additive cannot be recycled, further increasing the production cost.

The invention comprises the following steps:

the invention aims to provide a method for producing aluminum oxide, which has the advantages of simple production process, easily obtained raw materials and additives, less equipment investment, low production cost, high production efficiency, good product quality and less environmental pollution.

The invention is realized by the following steps:

the method for producing the aluminum oxide comprises the following steps:

(1) using diaspore type ore as raw material and Na₂SO₄CaO and C are used as additive materials,

(2) mixing ore with Na₂SO₄Adding CaO and C into a ball mill together to be ball-milled to 80-120 meshes,

(3) delivering the ball-milled materials into a rotary kiln for roasting at the temperature of 700 ℃ and 1100 ℃, and the time is as follows: 1-2 hours, Na₂SO₄With Al in the ore₂O₃Generation of NaAlO₂，

(4) Putting the roasted material into a high-pressure reaction kettle, adding water, heating and pressurizing simultaneously to fully hydrolyze iron, titanium and dicalcium silicate in the material to separate out as precipitates to obtain a first-stage desiliconization leaching solution,

(5) filtering the leaching solution to obtain sodium aluminate solution and filter residue,

(6) feeding the sodium aluminate solution into a reaction kettle, adding slaked lime milk, heating to combine sodium aluminosilicate in the solution with CaO to generate hydrated garnet precipitate to obtain a second-stage desiliconization solution,

(7) filtering the second-stage desiliconized solution to obtain refined solution,

(8) adding sulfuric acid solution into the refined solution to acidify and decompose the solution to generate aluminum hydroxide precipitate,

(9) filtering the acidified decomposition liquid to obtain aluminum hydroxide precipitate and filtrate,

(10) feeding aluminum hydroxide into a calcining kiln to be heated to generate the diamond, namely Y-Al₂O₃，

(11) Evaporating the filtrate to remove Na₂SO₄More than 75 percent of the additive is recycled as the additive in the step (1).

Process of the invention Na₂SO₄CaO, C are added according to the Al in the diaspore type ore₂O₃、Fe₂O₃、SiO₂、TiO₂The content of (A) is calculated as follows:

Na₂SO₂＝(1.0～1.1)(Al₂O₃+Fe₂O₃)÷43.63％

CaO＝(2.0～2.5)SiO₂

C＝30％×Na₂SO₄。

materials in the step (4): water is 1 to (7 to 9), the temperature is 130 to 200 ℃, the pressure is 0.4 to 1.0Mpa, and the time is 45 to 90 minutes.

The adding amount of the lime milk in the step (6) is calculated according to the following proportion: CaO to Al₂O₃Heating at 100 deg.C for 1 hr at a ratio of 1: 20.

In the step (7), the refined solution is heated and concentrated to make NaAlO₂The content reaches 120 g/L.

H with the weight percentage concentration of 50 percent is added in the step (8)₂SO₄When the pH value of the solution is measured to be 5.5-6.5, stoppingStopping addition of H₂SO₄。

The invention mainly aims at the following specific weight percentages of 45-60% of aluminum oxide, 15-22% of silicon dioxide, 4-20% of ferric oxide, 7.5-8.0% of titanium dioxide and aluminum-silicon ratio: production and extraction technology of diaspore type ore with Al/Si 2.5-5.0%.

The technical characteristics and advantages of the invention are as follows:

changing the original additive Na for production₂CO₃(sodium carbonate) using Na₂SO₄Sodium sulfate as main additive, lime and stone charcoal as reductant in certain amount, alkali ratio of 1.0-1.1 and calcium ratio of 2.0-2.25, and through mixing, roasting in a rotary kiln at 700-1100 deg.c in reducing condition, adding carbon matter in the material, and roasting for 1-2 hr to reach Al as the target component₂O₃With Na as additive₂And O is combined to generate solid sodium aluminate, and the chemical reaction formula is as follows:

in the presence of Na₂SO₄When the compound is used as a main additive, the compound can be well decomposed under a certain temperature condition, namely under the condition that oxidizing atmosphere and reducing atmosphere exist at 840 ℃ simultaneously, and the reaction formula is as follows:

when sulfur trioxide is from Na₂SO₄The compound is separated from the system and combined with impurities and calcium oxide in the material to generate a compound with higher decomposition temperature, and the decomposition temperature is about 1700 ℃ or higher, so that the atmosphere is not polluted. Additive Na in a conventional manner₂CO₃The carbon dioxide gas is easy to decompose, and a large amount of equipment is required for treating pollution and recovering the carbon dioxide gas for carbonation decomposition, so that the labor and the production cost are high. The reaction formula is as follows:

therefore, the pollution source can be effectively controlled from the source, and the production mode does not have fundamental harm conflict with the current national requirements for environmental protection, policy and regulation and the like.

(II) a process for acidifying and decomposing sodium aluminate by adopting sulfuric acid replaces a Bayer process, for example, a seed crystal is added by the Bayer process, the seed crystal is added by 1.0-1.5 times of the aluminum content in the solution (sodium aluminate), and the aluminum in the solution can be completely replaced by stirring for about 72 hours at the temperature of 70-90 ℃, so that the material flow turnover of the alumina is increased, the subsequent calcining operation is correspondingly increased by 1-1.5 times, the quality of the alumina used for the seed crystal is also highly required, the particle size is also strictly required, namely 40-60mu, and the reaction formula is as follows:

taking Bayer process carbonation as an example, a large amount of carbon dioxide gas is used, the carbon dioxide concentration of the gas is controlled to be 23-28%, the temperature is 70-80 ℃, the gas is used for 6 hours, the sodium aluminate solution is decomposed, and sodium carbonate and aluminum hydroxide are generated, and the reaction formula is as follows:

because the carbon dioxide gas decomposed in the roasting process is not enough to completely react the sodium aluminate solution in the solution after being recovered, part of the solution still needs to be separated and stirred and replaced by adding seed crystals, so that the replacement of the aluminum hydroxide can be complete.

The desilication index of the sodium aluminate reaches 1000-1500, namely the content of silicon in the solution is controlled within 0.04-0.1g/L, the dilute sulfuric acid is adopted for heating, stirring, acidifying and decomposing, the time consumption in the process is only 1 hour, meanwhile, sodium sulfate is generated in the solution, the residual liquid can be directly sent for evaporation and recovery without any treatment, and the reaction formula of the acidifying and decomposing is as follows:

because the acidification decomposition is a complete decomposition process, it can not only completely displace the aluminium in the solution, but also its impurities, such as silicon, iron and titanium, etc., can be completely displaced, and because the additive is mainly sodium sulfate in the course of firing, the silicon content in the water-leached solution is higher than that in the traditional NO solution₂CO₃The production mode is reduced by about 76 percent, and sodium silicate is removed through high-pressure reaction and sodium aluminosilicate is removed by adding hydrated lime, so that the silicon content index reaches 1000-1500 and Al thereof reaches 1500₂O₃The silicon content in the solution is 0.04-0.1g/L, even if the solution is completely acidified and decomposed, the silicon content of the product is 0.1 percent and meets the national standard zero-level standard, the iron content is 0.014 percent and meets the national standard special-level standard, and the sodium content is 0.16 percent and meets the national standard special-level standard.

The process flow is simplified, so that the whole production process becomes simple and easy to operate, a seed crystal replacement method and a carbonation decomposition method in the Bayer process are abandoned, the adverse factors such as the process flow, equipment and the like are reduced, and the large logistics turnover amount and the long production period in the production process are reduced, namely, the original production of 1000kg of Al is performed every time₂O₃The period of the method is shortened from 2-3 days to 16 hours, the workload of the calcining process is reduced, the production is increased by 2-3 times, and although the price is not advantageous to the traditional production method, the production yield is increased in a leap way, which is one of the ways of reducing the cost relatively.

The invention not only can widely use the extraction of domestic low-aluminum high-silicon diasporic bauxite, but also can improve the product qualityAdditive Na used₂SO₄The market price is only 450.00 yuan/ton per ton, and the market price of sodium carbonate is 2000.00 yuan/ton per ton, and in the aspect of environmental protection, the problems are fundamentally solved, the investment and the production period of equipment are saved, the production process is simplified, and the operation is easy.

Description of the drawings:

FIG. 1 is a process flow diagram of the present invention.

The specific implementation mode is as follows:

preparation of raw materials

(1) Crushing the ore from large lump ore to about standard ore (5-15mm), sampling, and assaying for Al in the ore₂O₃、Fe₂O₃、SiO₂、TiO₂After the content is calculated, quantitative additives such as: na (Na)₂SO₄、CaO、C

The calculated dosing is as follows:

for example: al (Al)₂O₃56.3% of Fe₂O₃7.28% of SiO₂Is 18.0 percent

Note: na (Na)₂O is in Na₂SO₄The content in the system was 43.63%. When Na is present₂SO₄At 160kg, Na₂The O content was 69.8 kg.

C: is Na₂SO₄30% of the total amount, i.e. Na₂SO₄o 160kg, C48 kg.

(2) Preparing ore:

quantitatively adding Na to the ore₂SO₄CaO and C are fed into a ball mill together for ball milling, the granularity of the mineral powder is required to be more than or equal to 80 percent and more than or equal to 120, namely 0.074mm, and 20 percent and more than or equal to 80 meshes, namely 0.841mm, if the mineral powder is a recovered additive, Na is contained in the solution₂SO₄The amount of the mineral is more than 75 percent, and the mineral are subjected to ball milling in a ball mill, the granularity requirement is the same, and is still 80 percent or more than 120 meshes, and 20 percent or more than 80 meshes.

Secondly, roasting

Ball-milling to required granularity, calcining in rotary kiln at 1000 deg.C at 700-₂SO₄The molecular weight of 142.04 commonly called "Natrii sulfas" and "Natrii sulfas" are white powders, dissolved in water at pH 5.0-11.0), and dissolved at 884 deg.C, and belong to non-decomposable and non-volatile salts, and the pure substance is decomposed at 3177 deg.C under normal pressure to obtain Na₂O and SO₃I.e. per 100kg, Na₂SO₄Containing Na₂O43.63 kg, due to Al₂O₃Is an amphoteric substance, i.e. soluble in acid or alkali, if Na is used alone₂SO₄Even if the temperature is over 1100 ℃, the Al will not be decomposed₂O₃Reaction takes place but on addition of an oxidizing agent, i.e. CaO, Na₂SO₄Decomposition can be carried out, but not completely, and when a reducing agent of carbon is added, Na₂SO₄Can completely decompose Na under reducing atmosphere₂O, and Al₂O₃The target components of the solid sodium aluminate which is soluble in water are generated.

The reaction formula is as follows:

700-1100℃

the sulfur trioxide decomposed by the existence of CaO in the material is combined with CaO to generate CaSO₄Therefore, the air is not polluted, which is the same as the Na used in the traditional production mode₂CO₃And in comparison, the method has the obvious environmental protection advantage that the pollution source is controlled from the source, equipment and manpower for controlling the environment are omitted, and meanwhile, the production cost is reduced.

Thirdly, leaching

Placing the roasted material into a reaction furnace, adding water (the solid-liquid ratio is 1: 4-6), heating and boiling at 100 deg.C for 20min (min) to convert solid sodium aluminate into sodium aluminate of aqueous solution, and making NaFeO be generated in the material₂，CaTiO₂，CaOSiO₂Hydrolysis takes place to form iron hydroxide, titanium dioxide and dicalcium silicate precipitate, and the NaOH separated off is used as NaAlO₂The stabilizer of (2) makes NaAlO in the mother liquor₂The hydrolysis does not occur in advance.

Simultaneously, the roasted material can be put into a high-pressure reaction kettle, water (the solid-liquid ratio is controlled between 1: 7-9) is added to carry out pressure leaching at the temperature of 170 ℃ and the pressure of 0.7mPa, and desilication (namely NaOSiO) is carried out at the same time₂Sodium silicate) for 1 hour, the desilication index of the crude liquid is 400, namely, the silicon content in each 1000ml of the crude liquid is 3-6 g/l, and the aluminum content is 110-120 g/l. Silicon content index thereof

Al / Si = \frac{120}{6} = 30

Per liter after pressure desiliconizationThe amount of silicon of (A) is indicated as

Al / Si = \frac{120}{0.3} = 400

The silicon content of the first section sodium aluminate per liter is 0.3g/L, and the reaction formula is Iron, titanium, dicalcium silicate and the like in the high-pressure leaching can be fully hydrolyzed, and Fe in each liter of solution₂O₃0.013% of Fe₂O₃42.33 percent which is lower than 0.03 percent specified by the national special grade, so the leaching is carried out simultaneously with the sodium silicate removal of the first stage.

Fourthly, filtering

After high-pressure leaching and desiliconization, filtering and separating the residue and the sodium aluminate solution, and conveying the residue to a residue yard for stockpiling.

Five and two-stage desiliconization

Sodium aluminate solution is fed into a reaction kettle, and slaked lime milk of 1000ml 6g CaO/120Al is added₂O₃Boiling at 100 deg.C under normal pressure for 1 hr to allow Na to form₂OAl₂O₃2SiO₂(sodium aluminosilicate) combines with CaO to form a less soluble hydrated garnet, the reaction formula:

the silicon content index after two-stage desiliconization is

Al / Si = \frac{117}{0.1} = 1170

Zero-order or first-order Al meeting national standard for electrolytic aluminum production₂O₃The raw material group, also results in a loss of about 3-6g of alumina per liter.

Sixthly, filtering

The sodium aluminate solution after the calcium aluminosilicate precipitate is filtered again, namely the refined solution, can be used for hydrolyzing Al (OH)₃。

Seventh, acidification and decomposition

Adding 50% H into sodium aluminate solution (refined solution) after first and second stage desiliconization₂SO₄Carrying out acidification decomposition to generate aluminum hydroxide precipitate, wherein the reaction formula is as follows:

the consumption of sulfuric acid was 32.8 kg.

Eighthly, filtering

Filtering the acidified and decomposed aluminum hydroxide precipitate, washing, calcining in calcining kiln at over 950 deg.C, evaporating water from filtrate, and recovering Na₂SO₄Useful target components.

Nine, calcining

Feeding aluminum hydroxide into a calcining kiln, calcining for more than 2 hours at the temperature of 950 ℃ to generate y-Al₂O₃I.e. corundum, which is a raw material for the production of electrolytic aluminum, Al₂O₃The effective extraction rate of (a) was 92.6%.

Ten, evaporation

Evaporating the filtrate to remove water to maximum extent to obtain Na in the solution₂SO₄More than 75% and based on Na₂The loss of O is 5-8 percent, and a certain equivalent of solid Na is added₂SO₄I.e. 12.5 kg.

Claims

1. A method for producing alumina, comprising the steps of:

2. The method of claim 1, wherein Na is₂SO₄CaO, C are added according to the Al in the diaspore type ore₂O₃、Fe₂O₃、SiO₂、TiO₂The content of (A) is calculated as follows:

Na₂SO₂＝(1.0～1.1)(Al₂O₃+Fe₂O₃)÷43.63％

CaO＝(2.0～2.5)SiO₂

C＝30％×Na₂SO₄。

3. the method according to claim 1, wherein in the step (4), the ratio of the material to the water is 1: 7-9, the temperature is 130-200 ℃, the pressure is 0.4-1.0Mpa, and the time is 45-90 minutes.

4. The method according to claim 1, characterized in that the amount of lime milk added in step (6) is calculated according to the following ratio: CaO to Al₂O₃Heating at 100 deg.C for 1 hr at a ratio of 1: 20.

5. The method according to claim 1, wherein in the step (7), the purified solution is concentrated by heating to make NaAlO₂The content reaches 120 g/L.

6. The method of claim 1, wherein 50% by weight H is added in step (8)₂SO₄Stopping adding H when the pH value of the solution is 5.5-6.5₂SO₄。