DE19833419A1 - Processing crushed aluminum-containing residual material used in the secondary aluminum industry comprises adding a carbon support to the material, mixing and converting to oxide ceramic - Google Patents

Abstract

Processing crushed aluminum-containing residual material comprises adding a carbon support to the residues, mixing to form an intermediate product containing aluminum carbide with the action of heat, and converting the aluminum carbide of the intermediate product in a reaction with water or steam to an oxide ceramic in the from of Al2O3 or Al(OH)3 and methane as gaseous energy carrier.

Description

The invention relates to a method for processing of aluminum-containing residues with a low aluminum content, in which the aluminum-containing residue is crushed. The like aluminum-containing residues, especially with low Aluminum content, fall in large quantities in various Composition especially in the secondary aluminum industry on. It can be with these aluminum-containing residues especially about scabies and scab dust, about salt slag or but also deal with oxide residues. The content of metallic Aluminum in such aluminum-containing residues is in the Usually relatively low, but can also be up to 30% by weight or, especially for dross and dross-like residues up to make up about 80% by weight. The process is aimed at further processing evaluation or recycling of the aluminum.  

A method of the type described at the outset is known. It is about the disposal of oxide residues, the one have a relatively low aluminum content, approximately 5% by weight. These oxide residues from the salt slag processing have so far been used in public landfills brings. In Germany, this is only permitted for a limited time. It is therefore known to crush and remove these oxide residues the production of cement or brick as an additive to recycle the oxide back in this way carried out and to relieve the landfills.

The invention has for its object a method of Provide the type described above, with which it is possible is to process aluminum-containing residues in order to Do not deposit metallic aluminum in the residues must, but to be able to recycle as completely as possible. The relatively high energy content of metallic should also be Aluminum can be used for meaningful recycling.

According to the invention, this is achieved in the process of the type described in the introduction by adding a carbon carrier to the comminuted residue and mixing it with this to form a mixture that consists of the aluminum (Al) in the mixture and the carbon (C) in the carbon carrier under a protective gas atmosphere and under heat an aluminum carbide (Al ₄ C ₃₎ intermediate containing is formed, and in that the aluminum carbide (Al ₄ C ₃₎ of the intermediate product in a reaction with water or steam to a re-usable oxide-ceramic material in the form of aluminum oxide (Al ₂ O ₂₎ or aluminum hydroxide (Al (OH) ₃ ) and methane (CH ₄ ) as a gaseous energy source.

The invention is based on the idea of forming aluminum carbide (Al ₄ C ₃ ) in an intermediate in a first step. For this purpose, a carbon carrier is added to the shredded residue and mixed homogeneously with it, so that a mixture is formed. The aluminum carbide Al ₄ C _{3 is formed} in the intermediate product from the metallic aluminum contained in the mixture and the carbon contained in the carbon carrier under a protective gas atmosphere and under the action of heat. It is understood that the intermediate product also contains other substances. However, the proportion of aluminum carbide in the intermediate product is important for the present process. The implementation is done according to the formula

4 Al + 3 C → Al ₄ C ₃ (1).

The aluminum carbide in the intermediate product is, depending on the active temperature, reacted in a reaction with liquid water or steam to a reusable oxide ceramic material on the one hand and a gaseous energy source in the form of methane on the other hand. This can be done according to the formula

Al ₄ C ₃ + 6 H ₂ O (g) → 2 Al ₂ O ₃ ) ₄ (g) (2)

happen, the aluminum oxide being formed directly. This applies in particular to temperature effects <approx. 400 ° C during the reaction with the water vapor.

On the other hand, it is also possible to form aluminum hydroxide Al (OH) ₃ from the aluminum carbide, this reaction according to the formula

Al ₄ C ₃ + 12 H ₂ O (g) → 4 Al (OH) ₃ + 3 CH ₄ (g) (2 ')

expires. The aluminum hydroxide Al (OH) ₃ can be used either as an end product, for example as a polishing agent, as a filler in the production of plastics or the like. However, it is also possible to use the aluminum hydroxide according to formula 2 'in a further reaction according to formula

2 Al (OH) ₃ ⇒ Al ₂ O ₃ + 3 H ₂ O (g) (3 ')

to be further processed into aluminum oxide as the end product. How with all these possibilities it is evident that it contains aluminum Residual material in a recyclable oxide ceramic material reshaped and thus accessible for meaningful reuse made.

From the stoichiometry of these reactions according to the formulas given above, it can be seen that 1.9 t of aluminum oxide and 622.2 m ^{3 of} methane are obtained from 1 t of aluminum in the aluminum-containing residue with the addition of 0.3 t of carbon and 1 t of water can. Analogously, 2.9 t of aluminum hydroxide and 622.2 m ^{3 of} mathan are obtained from 1 t of aluminum with the addition of 0.3 t of carbon and 2 t of water.

The mixture of the crushed residue and the carbon carrier can be compacted before the conversion to the aluminum carbide (Al ₄ C ₃ ). The compacting can be carried out by pelleting, granulation, briquetting or the like in order to be able to better handle the pieces thus formed during the subsequent process of carbide formation.

If the formation of aluminum carbide (Al ₄ C ₃ ) is carried out under a protective gas atmosphere at temperatures <600 ° C, there are usable reaction speeds on a large industrial scale, although the reaction described generally also takes place at lower temperatures.

From the shredded residue should be added before the Carbon carrier impurities, such as. B. salts if before handle, separated, especially washed out. If the Impurities made of iron can be magnetic Deposition can be used.  

It makes sense to intermediate the product before reacting with water or to crush water vapor, especially to grind it. By this crushing of the intermediate becomes the reaction with favored by water or water vapor.

The aluminum carbide of the intermediate product formed in the first step is processed further to the oxide-ceramic material under the influence of temperature. Depending on the temperature above or below the limit of around 400 ° C, either aluminum oxide or aluminum hydroxide is formed in addition to the methane. The aluminum carbide (Al ₄ C ₃ ) of the intermediate product is exposed to temperature <approx. 400 ° C in the reaction with water vapor to aluminum oxide (AL ₂ O ₃ ) and methane (CH ₄ ). Or it is possible that the aluminum carbide (Al ₄ C ₃ ) of the intermediate product under the influence of temperature (about 400 ° C in the reaction with water or steam to aluminum hydroxide (Al (OH) ₃ ) and methane (CH ₄ ) is implemented.

The recyclable oxide ceramic material can be filmed in terter and / or dried and / or possibly sintered form in the manufacture of a ceramic product. In this way there are various ceramic products producible.

The removal of impurities should be done at a higher temperature temperature, in particular <50 ° C, are carried out. Here too the elevated temperature accelerates the reaction rate speed.

In Fig. 1, the process for processing aluminum-containing residues is shown schematically. According to arrow 2, the aluminum-containing residue 1 passes into a mill 3 , in which it is comminuted. This shredded aluminum-containing residue 1 'is transferred according to arrow 4 into a separating device 5 , which can have a tub provided with an agitator. If in the aluminum-containing residue 1 salts, for. B. AlCl ₃ , NaCl, KCl, CaF ₂ are present, these must first be separated in the separation device. This usually happens through a washing process. The process conditions for the separation or washing are derived from the specific solution behavior of the individual salts in the water. The comminuted aluminum-containing residue 1 'freed from the impurities is then fed to a drying 5 a and reaches together with a carbon carrier 6 according to arrow 7 in a mixing device 8 , which is also seen with an agitator. In the mixing device 8 , a homogeneous mixture is created from the comminuted aluminum-containing residue 1 ′ and the carbon carrier 6 . This mixture is fed to a compacting device 10 according to arrow 9 . The mixture of crushed aluminum-containing residue and carbon carrier leaves the compacting device 10 according to arrow 11 as compacted shaped pieces 12 which are fed to a reactor 14 according to arrow 13 . The reactor 14 is under a protective gas atmosphere, for example argon, and is provided with a heating device 15 , with which temperatures of <600 ° C. can be achieved, but the temperature used can also be above 1000 ° C. Aluminum carbide is formed in an intermediate product 16 . The intermediate product 16 can be supplied to a grinding device 17 who, before it reaches arrow 18 in a boiler 19 , which is also equipped with a heater 20 and also with an agitator 21 . The reaction of the aluminum carbide in the intermediate product 16 with water in the liquid or gaseous phase takes place in the boiler 19 under the influence of temperature. A preferably discontinuous discharge of the oxide ceramic material according to arrow 22 takes place at the bottom of the boiler 19 . The oxide-ceramic material can be filtered with a Filtereinrich device 23 , dried in a dryer 24 and / or sintered in an oven 25 before a ceramic product 26 is made from it. In the boiler 19 , on the other hand, methane is produced as an energy source, which is drawn off in accordance with arrow 27 and fed to a store 28 . An essentially pressure-free gas storage can take place in the store 28 at most at a maximum pressure of 5 mbar. The methane arrives at a consumer 30 from the storage 28 according to arrow 29 .

The method according to the invention is suitable for recycling also those aluminum-containing residues in which aluminum represents only one of the components. It is irrelevant whether the other substances are metallic (e.g. scrap iron or Al alloys) or inorganic (aluminum dross, ceramic, glass, Building materials) are nature.

Below are four individual detailed examples of the Processing of various aluminum-containing residues described:

example 1

A ton of an aluminum-containing residue with 25 wt .-% metallic aluminum is reduced to a grain size (<0.5 mm). Then a quantity of carbon of 83.3 kg in powder form, matched to the aluminum content, is added. The powders are mixed for 2 hours and compacted at 50 MPa into pellets with a diameter of 30 mm. The subsequent pellet firing takes place at a temperature of 1300 ° C in argon with a heating rate of 300 ° C / h and a holding time of 4 hours. After firing, the pellets are again crushed (<100 µm) and mixed in a chemical reactor with 502 kg of water at 70 ° C. The reaction product is 724.7 kg aluminum hydroxide Al (OH) ₃ and 111.8 kg methane (CH ₄ ).

Example 2

A ton of an aluminum-containing residue with 10 wt .-% metallic aluminum is reduced to a grain size (<0.5 mm). Then a quantity of 33.3 kg of carbon in powder form, matched to the aluminum content, is added. Then the powder mixture is mixed for 4 hours and compacted at 50 MPa into pellets with a diameter of 30 mm. The pellets are fired at a temperature of 1500 ° C in argon with a heating rate of 300 ° C / h and a holding time of 3 hours. After firing, the pellets are crushed again (<100 µm) and mixed in a chemical reactor with 200.2 kg of water at 70 ° C. The reaction product is 289 kg of aluminum hydroxide Al (OH) ₃ and 44.6 kg of methane (CH ₄ ). The ceramic powder is converted into an alumina-containing powder in a further sintering process at 1200 ° C., a heating rate of 300 K / h and a holding time of 4 hours. The 289 kg Al (OH) _{3 are converted} into 189 kg Al ₂ O ₃ and 100 kg H ₂ O.

Example 3

A ton of an aluminum-containing residue with 10 wt .-% metallic aluminum is reduced to a grain size (<0.5 mm). Then a quantity of carbon of 33.3 kg in powder form, matched to the aluminum content, is added. The powder mixture is mixed for 2 hours and compacted at 50 MPa into pellets with a diameter of 30 mm. The pellets are fired at a temperature of 1400 ° Cc in argon with a heating rate of 300 ° C / h and a holding time of 3 hours. After firing, the fired pellets are again comminuted (<100 µm) and converted into 188 kg aluminum oxide (Al ₂ O ₃ ) and 44.5 kg methane (CH ₄ ) in a chemical reactor with 100 kg steam at 500 ° C.

Example 4

It becomes a used filter medium from the secondary aluminum Industry freed from aluminum buildup.

100 kg (kg) of a ceramic filter medium containing 5% by weight of aluminum, consisting of aluminum oxide balls with a diameter of 10 mm, is filled into a crucible with 20 kg of powdered carbon. The aluminum oxide balls must be completely surrounded by carbon. The embedded aluminum oxide balls are fired at a temperature of 1500 ° C in argon with a heating rate of 300 ° C / h and a holding time of 2 hours. After the fire, the aluminum oxide balls and the reaction product aluminum carbide are mixed in a chemical reactor with 100 kg of water at 70 ° C. This produces 14.5 kg of aluminum hydroxide Al (OH) ₃ and 2.2 kg of methane (CH ₄ ). The aluminum oxide balls are freed from all aluminum buildup after this process, are dried and can be used again.

Reference list

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Aluminum-containing residue

2nd

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3rd

Mill

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5

Separation device

5

a drying

6

Carbon carrier

7

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Mixing device

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Compacting device

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Fitting

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reactor

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heater

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Intermediate

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Grinding device

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boiler

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heater

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Agitator

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Filter device

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dryer

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oven

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ceramic product

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Methane storage

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consumer

Claims (9)

1. A method for processing aluminum-containing residues with a low aluminum content, in which the aluminum-containing residue is crushed, characterized in that a carbon carrier is added to the crushed residue and mixed with it to form a mixture that from the aluminum (Al) in the mixture and the carbon (C) in the carbon carrier under an inert gas atmosphere and under the action of heat, an intermediate product containing aluminum carbide (Al ₄ C ₂ ) is formed, and that the aluminum carbide (Al ₄ C ₃ ) of the intermediate product in a reaction with water or water vapor to a reusable oxide ceramic material in the form of aluminum oxide (Al ₂ o ₂ ) or aluminum hydroxide (Al (OH) ₃ ) and methane (CH ₄ ) is implemented as a gaseous energy source. 2. The method according to claim 1, characterized in that the mixture of the crushed residue and the carbon carrier is compacted before the reaction to the aluminum carbide (Al ₄ C ₃ ). 3. The method according to claim 1, characterized in that the formation of aluminum carbide (Al ₄ C ₃ ) is carried out under a protective gas atmosphere at temperatures <600 ° C. 4. The method according to claim 1, characterized in that from the shredded residue before adding the carbon carrier impurities such. B. salts, separated, in particular which are washed out. 5. The method according to claim 1, characterized in that the Intermediate before reaction with water or steam crushed, especially ground.   6. The method according to one or more of claims 1 to 5, characterized in that the aluminum carbide (Al ₄ C ₃ ) of the intermediate under the action of temperature <about 400 ° C in the reaction with steam to form aluminum oxide (Al ₂ O ₃ ) and Methane (CH ₄ ) is implemented. 7. The method according to one or more of claims 1 to 5, characterized in that the aluminum carbide (Al ₄ C ₃ ) of the intermediate under the action of temperature <about 400 ° C in the reaction with water or steam to aluminum hydroxide (Al (OH) ₃ ) and methane (CH ₄ ) is implemented. 8. The method according to claim 1, characterized in that the recyclable oxide ceramic material in filtered and / or dried and / or possibly sintered form in the Production of a ceramic product is used. 9. The method according to claim 4, characterized in that the Removal of impurities at elevated temperatures, in particular <50 ° C, is carried out.