JPH07166252A - Production of raw material composition for iron making consisting of dissolution residue of bauxite - Google Patents

Abstract

PURPOSE:To produce a compsn. for which iron making raw materials contg. Na2O and Al2O3 at low ratios and contg. Fe2O3 at a high ratio are usable by subjecting the residues after extraction of alumina by treating bauxite by a Bayer process to an acid treatment. CONSTITUTION:The bauxite is treated by an aq. caustic soda soln. and the alumina contained therein is separated and recovered as water-soluble sodium aluminate. Al(OH)3 is added as a precipitation seed to the soln. to precipitate the Al(OH)3 from the aq. sodium aluminate soln. This Al(OH)3 is used as the raw material for the Al2O3. The Al(OH)3 is precipitated from the aq. sodium aluminate soln. and the water-soluble silica is precipitated and separated from the aq. soln. recovered by filtration, thereby yielding the aq. sodium aluminate soln. of high purity. Fe2O3, Al2O3, Na2O, etc., remain in the remaining solid residues after the sepn. of the aq. sodium aluminate soln. and, therefore, a mineral acid is added thereto to elute the Al2O3 as an Al salt and to elute the Na2O as Na2Cl, Na2SO4, etc., by which the ratio of the Fe2O3 in the residues is increased. The raw material for iron making is thus produced by sintering, etc., together with limestone, coke, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a raw material composition for ironmaking comprising a bauxite dissolution residue. More specifically, in a so-called Bayer method of treating alumina with bauxite treated with a sodium-containing solution, it is used as a raw material for iron making or an auxiliary raw material (hereinafter, both may be collectively referred to as raw material for iron making). The present invention relates to a method for producing a bauxite dissolution residue to be obtained.

[0002]

As is well known, in the Bayer method for extracting alumina from bauxite, a large amount of dissolved residue is discharged. In the past, effective utilization methods of this residue have been studied and studied from various viewpoints.

For example, a method of decomposing a dissolution residue to recover a valuable component (Japanese Patent Laid-Open No. 63-261350) or a method of solidifying the dissolution residue and effectively utilizing it as an aggregate for concrete, tiles, road paving agents, etc. JP-A-62-319259), and a method of utilizing a special component in the dissolution residue as a catalyst or a catalyst carrier.

[0004]

However, although various uses are taught in the literature as described above, these dissolution residues are used as road materials and the like for purposes other than landfill today. Only a small amount is used. The reason is that this dissolved residue is in the form of a slurry having a solid content of usually about 300 to 600 g / l, and it is difficult to dehydrate. It is a mixture with various components that conflict with the purpose of use, and the characteristics of any of the components cannot be fully utilized. It contains a large amount of soda and is not suitable as a refractory material or a raw material for ceramics. The particles are very fine and difficult to handle. For example, it is necessary to have a use and technology that can use a large amount of dissolution residue all at once. Therefore, most of them are now used as landfill materials.

Recently, however, the number of coastlines and inland areas that can be landfilled is decreasing, and in addition, the dissolution residue contains a large amount of iron oxide, silicon oxide, etc. From the standpoint of resource conservation, bauxite dissolution residue is effective. There is a need for a more serious solution to use.

On the other hand, Fe ₂ O in the bauxite dissolution residue
_It has long been thought that it could be applied to raw materials for iron making or auxiliary raw materials by focusing on the ₃ content.

As raw materials for iron making, there are a main raw material and an auxiliary raw material (such as a forming agent and a diluent). Iron ores used as main raw materials include magnetite (Fe ₃ O ₄ ) and hematite (α-F
e ₂ O ₃ ) and other iron oxide ores, goethite (α-Fe ₂ O ₃ ·.
H ₂ O), hematite (γ-Fe ₂ O ₃ .H ₂ O), and other iron hydroxide ores, other iron sulfide ores, iron carbonate ores, and iron silicate ores. The iron content of these ores is usually around 70% by weight as Fe of iron oxide ore to F of iron silicate ore.
The value of e varies from about 20% by weight.

Limestone (CaO) and dolomite (CaCO ₃ .Mg) are used as auxiliary materials for iron making (pig making, steel making).
CO ₃ ), light burned dolomite (CaO / MgO), magnesia clinker (MgO), peridotite, serpentine, fluorite (CaF), silica (SiO ₂ ), ferromanganese ore and ilmenite (FeTiO ₃ ), etc. There is, and is used properly for each. (See Iron and Steel Handbook (Maruzen) II, page 55)

In the conventional Bayer method, although not unique depending on the bauxite used and the processing conditions thereof, the composition of the dissolved residue after drying (sometimes referred to as red mud) is 8-12% by weight loss on ignition (LOI), Al ₂ O ₃ 18-25
% By weight, SiO ₂ 15-20% by weight, Fe ₂ O ₃ 30-
40% by weight, Na ₂ O 8-12% by weight, TiO ₂ 2-8
It is about wt% (see Aluminum Industry, Jiro Kitagawa, published by Seibundo Shinkosha, page 76).

However, according to the investigation conducted by the present inventor, when the conventional bauxite dissolution residue is used as a raw material or an auxiliary raw material for iron making, the biggest problem is not the low Fe ₂ O ₃ content but the Na content. ₂ O content and Al ₂ O ₃ content are high. Further, it is preferable that the loss of ignition due to water of crystallization which is still present as a dry body is small. If sodium is present in the raw material for iron making, it vaporizes in the blast furnace and becomes vapor, which has the adverse effect of precipitating and accumulating in the low temperature region of the upper part of the blast furnace and making the refractory brittle, etc. Inhibit. This situation also applies to converters and the like. Therefore, the Na ₂ O content of the ironmaking raw material or the auxiliary raw material is required to be 3% by weight or less, preferably 1% by weight or less.

If the amount of Al ₂ O ₃ present is large, the slag becomes acidic, desulfurization and dephosphorization become difficult, and a large amount of alkaline flux such as quick lime is required, resulting in poor productivity.
In addition, when the amount of Al ₂ O ₃ increases, the reducing and pulverizing property of sinter or pellets increases, causing the strength of lumps to deteriorate, and as a result of hindering the uniform and smooth passage of gas in the blast furnace, the quality and productivity of pig iron are improved. Will be adversely affected.

Al ₂ O ₃ is contained in the iron ore in an amount of 0 to 2% by weight, and 2% by weight is close to the upper limit of the appropriate range of Al ₂ O _{3 in} the slag of the blast furnace. _A lower ₂ O ₃ content is preferred. In general, the Al ₂ O ₃ content of the ironmaking raw material is 10% by weight even when considering the diluted case.
Below, it is required to be preferably 5% by weight or less.

When the amount of ignition loss is large, the amount of ignition loss acts to lower the temperature in the furnace of the sinter or pellet firing equipment, resulting in a significant energy loss. For these reasons, the loss on ignition as an ironmaking raw material or auxiliary raw material is 10
It is required to be less than 8% by weight, preferably less than 8% by weight.

However, as seen in the above "Aluminum Industry", the conventional bauxite dissolution residue is Na ₂ O.
Not only the content but also the Al ₂ O ₃ content and the loss on ignition were not always satisfied, and the application of what was noted for the Fe ₂ O ₃ content in the composition was abandoned.

[0015]

[Means for Solving the Problems] In view of the above problems, the present inventor has conducted diligent studies to obtain a bauxite dissolution residue that can be used as a raw material for ironmaking or an auxiliary raw material, and as a result, The manufacturing method was found and the present invention was completed.

That is, according to the present invention, bauxite and a sodium-containing solution are charged into an extraction apparatus, soluble alumina is extracted from bauxite to obtain a sodium aluminate solution having a high alumina concentration, and then the dissolved residue is removed from the solution. After that, by adding aluminum hydroxide as seeds to the solution to precipitate aluminum hydroxide, in the so-called Bayer method, after extracting the soluble alumina component as much as possible from the bauxite charged in the extraction device, Na ₂ O in the dissolution residue, characterized in that the dissolution residue is separated and removed from the solution, and the separated dissolution residue is treated with an acid.
It is another object of the present invention to provide a method for producing a raw material composition for iron making, which comprises a bauxite dissolution residue having a content of 3% by weight or less and an Al ₂ O ₃ content of 10% by weight or less.

The method of the present invention will be described in more detail below.
In the present invention, bauxai as a raw material composition for iron making
The composition of the dissolution residue (on a dry basis) is Na₂O content
Is 3% by weight or less, Al₂O₃Less than 10% by weight
It Unique due to bauxite raw materials and alumina production equipment
The main other component content is Fe₂O₃content
Is 35% by weight or more, ignition loss is 10% by weight or less, SiO
₂20% by weight or less, TiO₂It is 10% by weight or less,
More preferably Fe₂O₃40% by weight or more, Na₂
O content is less than 1% by weight, Al₂O ₃Content is less than 5% by weight
Lower, ignition loss 8% by weight or less, SiO₂15% by weight or less
Bottom and TiO₂It is 8% by weight or less.

The bauxite dissolution residue having such a composition is obtained as follows. That is, bauxite and a sodium-containing solution are mixed to form a slurry, the slurry is charged into an extraction device, the alumina content is extracted as much as possible, and then, if necessary, the reactive silica eluted in the solution. After precipitation as a desiliconization product by a desiliconization reaction, a dissolution residue (collectively referred to as a dissolution residue when the desiliconization product is included) is separated from the solution from the slurry, and the solution is separated from the solution by a known method. Aluminum hydroxide as the main purpose is added to precipitate aluminum hydroxide. On the other hand, the dissolved residue separated from the slurry is then treated with acid,
Al ₂ O ₃ in the desiliconized product is used as an acidic aluminum solution, and Na ₂ O is neutralized with an acid. As a result, the solid substance has an Al ₂ O ₃ content of 10% by weight or less, preferably 5% by weight.
The Na ₂ O content is 3 wt% or less, preferably 1 or less.
It may be a dissolution residue of not more than wt%.

The bauxite which can be applied in the present invention is generally gibbsite (Al ₂ O ₃ .3H ₂₎ as an alumina component.
O) and / or boehmite (γ-Al ₂ O ₃ · H ₂ O)
Other than this, it also contains die-spores (α-Al ₂ O
₃・ H ₂ O) and kaolinite (Al ₂ O ₃・ 2SiO ₂
・ Clay minerals such as 2H ₂ O) are included.

The conditions for extracting alumina include the extraction temperature,
There are extraction time, alkali concentration, alumina concentration, charged molar ratio, etc., but these factors are affected by bauxite ore. That is, in the monohydrate boehmite type, the Na ₂ O concentration of the extract is about 80 to 200 g / l, the extraction temperature is about 160 to 240 ° C., and in the trihydrate gibbsite type, the Na ₂ O concentration of the extract is Is about 80 to 160 g / l and the extraction temperature is about 110 to 160 ° C. The extraction time is not unique depending on the shape of the reactor used (autoclave or tubular reactor, etc.), Na ₂ O concentration in the extract, extraction temperature, etc., but it is necessary to extract as much alumina as possible in bauxite. Therefore, it is usually about 10 minutes or more in a tubular reactor and 30 minutes to 1 in an autoclave.
Extract for 0 hours. In the present invention, the extraction of the alumina component as much as soluble in bauxite means 96% by weight or more, preferably 98% by weight or more, and more preferably 99% by weight or more of the alumina component contained in bauxite. Means extraction.

One of the objects of the present invention is to reduce the alumina content in the dissolution residue in the effective use of the bauxite dissolution residue as a raw material for iron making. It is to extract the soluble alumina component from the ore as much as possible. Therefore, in the gibbsite-boehmite mixed bauxite containing 5% by weight or more of boehmite, it is necessary to adopt the above-mentioned treatment conditions for bauxite containing mainly boehmite.

From the bauxite, the slurry solution in which the soluble alumina and the soluble silica have been dissolved is retained as it is, or fine particles of the sodalite composition or crushed desiliconized product are added and retained as seeds and extracted into the slurry solution. Precipitate the silica component. In this case, the silica component SiO ₂ reacts with Al ₂ O ₃ and Na ₂ O in the solution and is crystallized as a desiliconization product (sodalite composition).
It is sufficient that the silica removal treatment does not cause the soluble silica in the solution to co-precipitate during the precipitation of aluminum hydroxide, and the conditions are not particularly limited, but usually, the solution temperature is 80 ° C. to 150 ° C. for 30 minutes to
It may be held for about 5 hours.

The slurry solution after the silica removal treatment is then subjected to solid-liquid separation into a dissolution residue and a sodium aluminate solution in the same manner as in the usual Bayer process, and the dissolution residue is washed with water.

Further, in the method of the present invention, a solution obtained by extracting soluble alumina as much as possible from bauxite is
As mentioned above, the silica removal may be carried out in a slurry state with the dissolution residue, but for the purpose of separately collecting the silica removal product,
A method may be adopted in which solid-liquid separation is performed immediately after extraction of soluble alumina, the solution after separation is subjected to a silica removal treatment, and the product removed from the silica is recovered and removed, and then introduced into the aluminum hydroxide precipitation step. In this case, since the desulfurized product is already precipitated and mixed in the solid-liquid separated bauxite dissolution residue during the alumina extraction process, the dissolution residue is introduced into the acid treatment step as in the above method.

In the present invention, the dissolution residue is then treated with acid. The acid treatment has a function of reacting with the desiliconized product and decomposing it, and Al ₂ O ₃ is added to the liquid as an aluminum salt such as aluminum chloride, aluminum sulfate, aluminum nitrate, aluminum phosphate or a basic aluminum salt thereof. Na ₂ O is eluted and neutralized as sodium chloride or sodium sulfate to remove it from the solid residue, and applicable acids include hydrochloric acid, sulfuric acid, nitric acid,
Phosphoric acid etc. can be raised. The treatment conditions with these acids are not unique depending on the type of acid, the concentration of acid, the contact temperature, etc., but in the case of any acid, the temperature is in the range of 0.5 mol / l to 5 mol / l and the temperature is from room temperature to about 80 ° C. It is applied arbitrarily. The acid treatment may be carried out by bringing the acid and the dissolution residue into contact with each other in a container such as a tank with stirring, or by mixing both and passing them through a tubular reactor in a slurry state to bring them into contact with each other.
The contact time is not unique depending on the type of the acid used, the concentration, the temperature, and the shape of the applied reactor, but may be about 5 minutes to about 10 hours. However, in any case, it is preferable to carry out before the silica content eluted from the silica removal product is precipitated as a colloidal substance.

The dissolved residue after the acid treatment is filtered, centrifuged,
After solid-liquid separation and washing with water by a known method such as a filter press, as a raw material composition for iron making, or an acid solution after solid-liquid separation, for example, a solution in the case of hydrochloric acid treatment is silica gel or alumina gel, Can be effectively used separately as a raw material for water glass, PAC, zeolite, etc.

The bauxite dissolution residue separated by the above method has a poor dehydration rate because the dissolution residue is very fine particles, although it depends on the solid-liquid separation method.
~ 800 g / l, usually about 300-600 g / l in the form of a slurry, so it may be dried in the sun or by a rotary kiln or a dryer to a water content required for a raw material composition for iron making. However, sun drying requires a large drying area and transportation cost, and of course, in the case of forced drying with a rotary kiln or a dryer, a large amount of equipment cost and energy are required, which may cause a problem in economic efficiency.

The inventor of the present invention has investigated the use form of the raw material for iron making. When the main raw material and the auxiliary raw material for iron making are used for iron making, various kinds of powdery ores are usually blended and agglomerated, and then, in the furnace. It is known that 1) a sintering method, 2) a pelletizing method, 3) a briquette method, etc. are known as a method of agglomeration.

As for the sintering method, a continuous type Dwightroid type facility suitable for mass production has been developed and has become the mainstream. In the Dwightroid-type sintering equipment for producing sinter, in each raw material tank, iron ore as a main raw material of about -5 mm, various auxiliary raw materials, coke for sintering and water as a binder of about 5 to 5 mm are used. Add 10% by weight into a mill or mixer, mix and granulate, spread the resulting mixture on a pallet through a surge hopper, ignite coke in the mixture while passing through a firing furnace, and self-cake Let it be a sintered body. This sintered body is crushed and sieved, and +5 mm is used as a raw material for the blast furnace.

On the other hand, in the pelletizing method, bentonite for suppressing drop resistance of raw pellets and bursting during drying is mainly added to and mixed with the above-mentioned finely divided iron ore and various ores as auxiliary raw materials, and the binder is added to the raw materials. As a raw material, about 5 to 10% by weight of water is added and granulated by a disk or drum granulator to produce raw pellets.
The raw pellets are fired in a Travelin Great furnace, a Great kiln, a shaft furnace, a rotary kiln, etc., and used as a raw material for a blast furnace.

What should be noted here is that, in both the firing method and the pelletizing method, the powder ore is converted into a lump ore,
The point is that a certain amount of water is added to the mixture, the mixture is molded, and then fired to obtain a lump-shaped raw material for a blast furnace.

Therefore, the present inventor did not dry the bauxite dissolution residue having the composition obtained in the present invention, and added and used the water contained in the bauxite dissolution residue in the steps of the calcination method and the pelletizing method while containing water. Can be used as a substitute for water, i.e., in the case of mixing with other iron-making raw materials and molding and using, the above-mentioned bauxite dissolution residue that is washed and filtered from the buyer process and discharged is previously dried. Found that it can be used without.

In the case of the above-mentioned Dwightroid type sintering machine, an undried bauxite dissolution residue may be used in place of water or the like added as a binder when the raw materials are kneaded in a mill or a mixer. Of course, the components such as iron oxide contained in the bauxite dissolution residue may be converted and used as the raw material composition for steel. Also in the pelletizing method, the undried bauxite dissolution residue may be used as a binder instead of water or the like when kneading the raw materials, as in the case of the Dwightroid type sintering machine. That is, the undried bauxite dissolution residue is mixed with another raw material for iron making and shaped to be applied as a raw material compact for iron making.

In carrying out the present invention, before the step of dissolving (extracting) alumina from bauxite, soluble silica is removed from the bauxite in advance, and the above-described method of the present invention is carried out using the bauxite after the treatment. Of course, it is also possible to do so. In this case, there is no or little elution of soluble silica in the alumina dissolution step,
The silica component eluted in the solution has a merit that the consumed alumina and caustic soda are reduced by forming a silica removal product.

[0035]

EFFECTS OF THE INVENTION According to the present invention described in detail above, the bauxite dissolution residue, which has not been found to be economically useful, can be used as a raw material for iron making, and the desiliconized product is also dissolved in an acid. However, it has the advantage that it can be used as a valuable component by recovering it. In addition, when it is mixed and used at the time of molding of the raw material composition for iron making, it does not require special drying treatment. It can be applied as a raw material, is extremely economical, and its industrial value is enormous.

[0036]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited thereto. The components were analyzed by fluorescent X-ray analysis, and the mineral composition of bauxite was calculated by the composition calculation method. The qualitative analysis of the mineral of the bauxite dissolution residue was identified by X-ray diffraction.

Example 1 180 g of Australian bauxite (gove ore) having the composition shown in Table 1 was heated in an autoclave at 220 ° C.
500 cc of 150 g / l caustic soda solution calculated as Na ₂ O
After 2 hours of treatment to complete the desiliconization reaction in the liquid, solid-liquid separation is performed with a centrifuge to separate the dissolved residue, and after thorough washing, dehydration and drying, analysis of the dissolved residue I went. The results are shown in Table 2. Further, 10 g of the dried product of the dissolution residue was mixed with 500 cc of 1.4 mol / l hydrochloric acid,
Shake on shaker for about 1 hour at room temperature. This was subjected to solid-liquid separation with a centrifuge, thoroughly washed with water, dehydrated and dried, and the residue was analyzed. The results are shown in Table 3.

[0038]

[Table 1]

[0039]

[Table 2]

[0040]

[Table 3]

Comparative Example 1 The same bauxite as that used in Example 1 was used, and the extraction treatment was carried out in the same manner as in Example 1 except that the dissolution (extraction) temperature in the autoclave was 150 ° C. Table 4 shows the analysis results of the dissolved residue after the treatment. In addition, dry body 1 of this dissolution residue
0 g was mixed with 500 cc of 1.4 mol / l hydrochloric acid, and shaken with a shaker for about 1 hour. This was subjected to solid-liquid separation with a centrifuge, thoroughly washed with water, dehydrated and dried, and the residue was analyzed. The results are shown in Table 5.

[0042]

[Table 4]

[0043]

[Table 5]

Example 2 In the same manner as in Example 1 except that Indonesian bauxite (bintan ore) having the composition shown in Table 6 was treated in an autoclave at 150 ° C. for 2 hours with 150 g / l caustic soda solution as Na ₂ O. went. The results are shown in Table 7.
Further, 10 g of the dried product of the dissolution residue was mixed with 500 cc of 1.4 mol / l hydrochloric acid, and shaken with a shaker for about 1 hour. This was subjected to solid-liquid separation with a centrifuge, thoroughly washed with water, dehydrated and dried, and the residue was analyzed. The results are shown in Table 8.

[0045]

[Table 6]

[0046]

[Table 7]

[0047]

[Table 8]

Claims (2)

[Claims] 1. A bauxite and a sodium-containing solution are charged into an extraction apparatus, soluble alumina is extracted from the bauxite to form a sodium aluminate solution having a high alumina concentration, and then the dissolved residue is removed from the solution.
In the so-called Bayer method, in which aluminum hydroxide is precipitated by adding aluminum hydroxide as seeds to the solution, the soluble alumina component is extracted as much as possible from the bauxite charged in the extraction device, and then in the solution. The dissolution residue is separated and removed, and the separated dissolution residue is treated with an acid. The content of Na ₂ O in the dissolution residue is 3% by weight.
Hereinafter, a method for producing a raw material composition for ironmaking comprising a bauxite dissolution residue having an Al ₂ O ₃ content of 10% by weight or less. 2. When separating and removing the dissolution residue from the solution, the soluble alumina component is extracted as much as possible from the bauxite charged in the extraction device, and then the reactive silica eluted in the alkaline solution is removed by a silica removal reaction. The method for producing a raw material composition for iron making comprising a bauxite dissolution residue according to claim 1, wherein the raw material composition is precipitated as a desulfurized product.