JPS6210287B2 - - Google Patents

Description

Claim 1: A method for recovering liquid aluminum from high-temperature slag by compressing the high-temperature slag filled in a mold having a circular cross section, which is disposed between a pressing tool and a table of a unidirectional vertical press, comprising: , the pressing tool is pressed against the top of the slag, and the pressing tool is lowered at the maximum speed until a liquid aluminum flow appears at the bottom of the mold, and then the pressing tool is lowered at a speed that decreases as the liquid aluminum concentration in the slag decreases. A method for recovering liquid aluminum, characterized by lowering a pressing tool.

2. When the liquid aluminum flow appears at the bottom of the mold, the descending speed satisfies the following relational expression: V (mm/min) = Kx (mass of liquid aluminum/mass of slag), and K is 150 to 300. A method according to claim 1, characterized in that:

3 If the height of the slag measured at the periphery of the mold is H and the diameter of the mold is D, then D/H is 0.5 to
The method according to claim 1, characterized in that the mold is filled with slag so that the amount of slag becomes 1.5.

4. A method according to claim 1, characterized in that the periphery of the mold is filled with more slag than the center.

5 The height difference (mm) between the periphery and the center of the mold of the filling slag is 0.5 (D/100) ² to 1.5 (D/100).
100) ² , and D is the diameter (mm) of the mold.

6 Further, after lowering the pressing tool at a slow speed until no liquid aluminum flow appears from the slag, the pressing tool is lifted and the mold filled with compressed slag is raised together with the receiver to press the mold. A method according to claim 1, characterized in that the lower receiver and the slug are removed from the lower part of the mold by being held between the tool and the platform and then lowering the pressing tool.

7. configured to be temporarily placed between the press and the table of the unidirectional press, for recovering liquid aluminum by compressing hot slag and for facilitating extraction of a cake of compressed slag; Apparatus comprising a stand for carrying a cylindrical mold for filling slug with a circular receiver at each end, the upper surface of the stand being provided with an annular groove whose bottom part communicates with the outside, and a downwardly extending groove. A receiver is separable from the base, the diameter of the lower receiver is at least equal to the inner diameter of the groove and in any case less than the outer diameter of the groove, and the continuous upper surface of the lower receiver projects outwardly. A device forming a conical shape, characterized in that between the side wall of the lower receiver and the inner wall of the mold there is a space located in a horizontal plane opposite to the groove and having a constant width.

8. Apparatus according to claim 7, characterized in that the conical shape formed by the upper surface of the lower receiver has an apex half angle of 75 to 85 degrees.

9. Device according to claim 7, characterized in that the width of the space between the side wall of the lower receiver and the inner wall of the mold is between 5 and 20 mm.

10. The apparatus of claim 7, wherein the width of the groove is greater than the space between the side wall of the lower receiver and the inner wall of the mold.

11. The device according to claim 7, characterized in that the bottom of the annular portion is inclined with respect to the horizontal line.

12 The lower surface of the lower receiver is provided with a protrusion perpendicular to the surface, and the protrusion has a cylindrical shape and passes through the void provided in the base. 8. The device of claim 7, characterized in that:

13. The device according to claim 7, wherein the mold is placed on the stand via an engaging portion having a contact surface inclined with respect to the vertical.

14. The device according to claim 7, characterized in that the lower and upper parts of the mold are provided with flanges.

15. Apparatus according to claim 7, characterized in that the low point of the annular groove of the platform opens into an external heated storage tank.

16. Apparatus according to claim 7, characterized in that the outer wall of the mold is provided with a heating device and is thermally insulated.

17. Apparatus according to claim 7, characterized in that the upper receiver is separated from the slug by a thermally insulating layer.

Description The present invention relates to a method and apparatus for recovering liquid aluminum by compressing hot slag. It is noted that the term "aluminum" as used herein also includes all aluminum alloys.

Aluminum production cycles from aluminum ore or recycled waste generally include a metal melting step preceding the casting step. As is known to those skilled in the art, during such melting, a layer of products called "slag" is formed on the surface of the metal in the furnace, and according to analysis results, slag consists of oxides, carbides, nitrides, etc. It has been found to be composed of non-metallic particles containing metal droplets between the particles. For example, if the contents of the furnace are cast as they are, slag will be mixed into the product, which may cause surface or internal defects during subsequent processing such as rolling, and may also cause a loss of product quality. This results in the formation of inclusions within the solid product that cause, at least locally, the appearance of heterogeneous areas.

Naturally, therefore, the slag should be removed from the metal prior to casting, and this is often accomplished by skimming the slag from the hot water using a descaling tool during the descaling operation. however,
Since the metal content of the slag is quite high, amounting to up to 95% of the mass of the slag, removal of the slag results in a significant reduction in the proportion of manufactured metal.

Naturally, those skilled in the art will spare no effort to find a device capable of recovering as much metal as possible contained in the slag. One solution is to treat the slag inside the melting furnace itself with a solvent to coalesce the metal droplets and facilitate the movement of the slag into the hot water. However, in addition to adversely affecting the properties of certain alloys, such solvents also limit the recovery efficiency, so that, regardless of the possibility of treatment in the furnace, the slag must be stored in special equipment after it has been discharged from the furnace. It becomes necessary to treat or reprocess the slag.

It is also known to use mixing devices, in which air is introduced and optionally a solvent is used to stir the slag and oxidize some of the metals contained in the slag. This oxidation reaction generates a large amount of heat, thus keeping the slag at a temperature sufficient for the metal droplets contained in the slag to coalesce, so that the coalesced metal droplets are easily separated from the slag and flow down the tank. do.

Next, the hot slag from which metal droplets have been removed passes through a peening device and is separated according to particle size, so that metals that were not separated during mixing are newly extracted.

A disadvantage of this type of treatment method is that generally more than 10% of the aluminum contained in the slag is lost in order to ensure the oxidation reaction.
In addition, recovery of metal after peening is incomplete;
More than 5% aluminum remains in the discharged slag.

In addition to metal yield issues, this type of processing also suffers from the fact that it emits smoke during the oxidation reaction and is often processed in imperfect sanitary conditions due to the handling of hot slag in the various processing equipment. Furthermore, noise problems and water pollution problems arise due to the discharge of products containing relatively highly soluble solvents that emit harmful ions.

There is therefore a need in the art for methods different from those mentioned above, in particular by avoiding the oxidation step and by rapidly cooling the slag in a rotating cylinder, optionally with a solvent, and by crushing the slag. A method has been devised which consists of a subsequent sieving step to separate out the parts containing more or less aluminum.

However, this requires the installation of very long cylinders to cool the slag, which results in relatively high capital and operating costs, and is nevertheless accompanied by pollution due to smoke generation and significant metal losses. cannot be avoided. Furthermore, fairly large equipment is required to process the large amounts of slag forced out from various furnaces that process alloys of different quality. Therefore, since the composition of the liquid metals extracted is not constant, these metals must be separated and can only be reused under certain conditions.

It is also known to directly subject the hot slag to mechanical treatment, such as centrifugation. However, the disadvantage of slag clogging in the liquid ejector during extraction generally remains in the experimental stage.

Therefore, recognizing that the various methods proposed to date do not completely solve the problems associated with aluminum recovery from slag, the applicant has made efforts to perfect a method that avoids the aforementioned drawbacks. . In other words, the disadvantages are: - Loss of aluminum due to oxidation and limited recovery rate, - Use of expensive and polluting solvents, - Generation of pollution such as smoke and noise, - Mixing of slags of different quality, - Capital investment. and the use of expensive equipment to operate, etc. Applicants have thus turned their attention to a method of compacting slag in a unidirectional vertical press. It has been confirmed that such technology is already in use. For example, in US Pat. No. 2,278,135 a method is known for recovering liquid tin from a slag formed of a solid intermetallic compound of antimony-aluminum in a mold with a diameter of 15 cm. Similarly, German Offenlegungsschrift No. 2312235 describes a method and apparatus for extracting liquid lead by heating small slugs with a diameter of 50 mm and a weight of 500 g to 350° to 550° C.

It has been found that none of the above references makes any mention of any particular use of the press for compacting the slag. Incidentally, the slag in this case is composed of a semi-solid material, the properties of which are quite different from those of most materials commonly subjected to such processing, i.e. powdered materials or other solid materials.

Additionally, the purpose of compaction is to densify and change the shape of the compacted material, in this case to collect and remove microdroplets of liquid dispersed within the slag mass.

On the other hand, the prior art in the above-mentioned document does not take into account any difficulties in applying the method for industrial use. The applicant has confirmed through experiments that difficulties arise when applying a method for compressing 500 g of compressed material in a mold with a diameter of 15 cm to a method for compressing 1 ton of product in a mold of about 1 meter.

In addition, we will discuss a method for processing aluminum slag, which is composed of metal lumps that have a melting point of 660°C and can be melted at approximately 2000°C due to the low thermal conductivity of oxides, and a method for dispersing aluminum slag into slags of different qualities to achieve a melting point of 660°C. is 232℃
There is nothing in common with the method of extracting tin or lead, which has a melting point of 327°C.

The Applicant has therefore identified that in order to recover the liquid aluminum contained in the hot slag on an industrial scale, and preferably to extract a large portion of the metal, it is necessary to improve the compression method.

The method according to the invention includes the step of filling a mold of circular cross-section with a slag, which is positioned between a pressing tool and a table of a unidirectional vertical press, pressing the pressing tool onto the top of the slug and filling the bottom of the mold with a mold. It is characterized in that the pressing tool is lowered at the highest speed until a liquid flow appears, and then at a similar slow speed at which liquid aluminum gradually collects from the slag.

Applicants have thus discovered that it is necessary to operate the presses of the press under special speed conditions to increase the extraction rate of the metal.

The speed conditions are such that the pressing tool is lowered at high speed while the metal is oozing out from the bottom of the slag mass, and then,
When the liquid begins to flow out continuously, the downward movement of the pressing tool is decelerated, and this state continues until the flow ends.

However, the applicant has found that the speed should be varied depending on the composition of the slag or rather on the mass ratio between the liquid contained and the original slag. Thus, the lower the concentration of liquid aluminum in the slag, the lower the downward speed of the pressing tool needs to be.

More specifically, the speed can be expressed by the following relational expression.

Vmm/mn=K×mass of liquid/mass of slag where K is a constant having a value of 150 to 300.

This equation will be easily understood from the fact that the rate of increase in density of the slag mass due to compression effects must not be so fast that collection and flow of liquid droplets cannot be controlled. Therefore, one should try to keep the metal flow constant and only at the end of the compression process the volume of the slag is minimized, ie the maximum pressure is reached. In fact, the velocity is more important than the final pressure reached.

The liquid content of the slag should therefore be taken into account to determine the speed conditions to be applied. In some cases, the speed may be constant, and it is sufficient to separate a standard sample of the slag to be treated to determine it, but it may be variable during the treatment period to account for changes in the liquid concentration of the slag. It is also possible to apply a velocity condition of , in which case the law of change is determined in advance from a standard compression process.

Similarly, the applicant has discovered that the height of the slag charged into the mold is an important factor for increasing the extraction rate. Thus, the height H measured at the periphery of the mold should take into account the diameter D of the mold, and precisely the ratio D/H should be between 0.5 and 1.5.

The applicant has likewise confirmed that the height must not be the same over the entire cross-section of the mold;
The center should be lower than the periphery so that the lower part of the slag mass has a conical concave surface. The conical shape, together with the ratio D/H, is related to the appropriate pressure distribution inside the slag volume, and the height of the slag between the periphery and the center, expressed in mm, Δh is 0.5 (Dmm/100) ²
Must be between 1.5 (Dmm/100) ² .

Note that if the value of D is below 250 mm, Δh can be equal to 0. In other words, there is no benefit in applying such characteristics to experimental types.

The invention also relates to a slag compaction device on an industrial scale.

This device is a special device that is independent of the unidirectional press itself and is temporarily placed between the table of the press and the pressing tool, and is a circular receiver installed at a distance from the inner wall of the mold. a pedestal for carrying a cylindrical mold having a cylindrical mold at each end; the top surface of the pedestal has an annular groove having a bottom communicating with the outside; a lower holder is separable from the pedestal and extends along the inner diameter of the groove; having a diameter at least equal to and in no case less than the outer diameter of the groove, and the continuous upper surface of the lower receiver is conical, and the distance between the wall of the receiver and the inner wall of the mold is of a constant width. , located opposite the groove. Thus, the apparatus according to the invention is a removable mold and table assembly in which the slug in the mold is compressed by the pressing tool as it moves vertically from top to bottom in the direction of the table of the unidirectional press. It can be placed on the table so that it can receive a force. As long as the compressive force is sufficient, various conventional industrial presses can be used by adapting the external shape of the apparatus of the present invention to the dimensions of the press.

The apparatus of the invention thus includes a removable platform made of cast steel whose base rests on the table of the press. A feature of the table is that the upper surface is provided with an annular groove recessed somewhat deeply in the center, and the width of the groove generally exceeds the space from the side wall of the lower receiver to the inner wall of the mold.

The bottom of the groove is inclined with respect to the horizontal and the bottom point communicates with the outside so as to be able to communicate with the top of the storage tank provided with suitable heating devices.

Similarly, in the center of the upper surface of the platform there is provided a cylindrical cavity extending virtually over its entire height to accommodate the protrusion provided on the lower receiver. The disk-shaped receiver is placed horizontally on the stand at a position guided by the protrusion and can be easily separated from the stand. The outer diameter of the receiver is at least equal to the inner diameter of the groove. That is, the outer wall of the receiver may be an extension of the inner wall of the groove, but it may also extend slightly beyond the inner wall so that the wall projects above the groove. However, the diameter must be such that the majority of the groove remains open upwardly.

Similarly, the lower receiver is characterized by having a continuous upper surface. That is, the upper surface is not perforated at all and does not form any outflow orifices. The surface is not flat, projects outward, and preferably has a diameter of 75 to 85
Forms a cone with an apex half angle of degrees.

The device according to the invention further includes a cylinder-type mold made of cast steel, the height and internal diameter of the cylinder being approximately close and the maximum diameter approximately equal to the diameter of the platform.

Each of the lower and upper ends of the cylinder is provided with a collar. The upper collar serves to secure it to the locking device and allows the cylinder to be lifted and placed on a stand. The lower collar constitutes the base of the mold on the table, and the lower part of the lower collar is provided with an engagement part which mates with a corresponding engagement part provided on the upper surface of the table outside the annular groove. Since the contact surfaces of the engaging portions are inclined with respect to the vertical line, there is no need for any reinforcing members between the one member and the other member. Although the contact surfaces are subject to thermal stress, they are nevertheless easily separable.

When the mold is on the table, its inner wall is separated from the wall of the lower receiver by a space of constant width over its entire periphery, which space is located above and in contact with the groove. perpendicular to the The width of the space is 5 to 20 mm, generally less than the width of the groove. The side wall of the mold is coated with at least a material having a temperature above the melting point of aluminum.
That is, a heating device is provided that can maintain the temperature of the mold at 200°C over 860°C.

The side walls of the mold are covered with a thermal insulating material at the surface between the two collars.

Above the mold is placed a steel disc-type upper support, which has a hook on its top surface, is separated from the slug by a heat-insulating layer, and has a very limited play space. can be freely moved inside the mold while holding it.

The operating cycle of the device according to the invention is shown below.
That is, the table/form/storage tank assembly is transported, for example, by a carriage with a fork near the descaling furnace, and then approximately
Slag is filled into a mold held at a temperature of 900℃,
Closed by a thermal insulation layer to completely avoid smoke emission. The assembly is then transported to the table of the press and the upper receiver is lowered into the mold. The presser of the press is then lowered to apply pressure to the slug via the upper receiver such that the height of the slug is gradually reduced to at least one quarter of its initial height. In this state, the liquid aluminum is continuously forced downward and flows out onto the conical surface of the upper supporter, and then flows out from the space provided between the wall of the upper supporter and the inner wall of the mold, forming a downwardly sloping annular shape. They fall into the ditch, exit the platform, and are collected in a storage tank. The width of the space between the mold and the lower receiver is such that the metal can easily flow out of the mold without becoming clogged with slag particles.

Another reason why the method of using compaction to recover aluminum from slag has not been applied industrially is because of the disadvantage of involving cake extraction after compaction. However, the device of the invention does not have the aforementioned drawbacks. In fact, under suitable working conditions, the pressing tool is kept pressed against the cake in order to place the cake and the two supports in place on the platform, i.e. the assembly which can be easily separated from the other parts. Even though it would be sufficient to lift the mold by means of a pulley system attached to the upper collar, in many cases this operation proves impossible. That is, it must be implemented in a different way from the conventional method, but this can be done by making the lower receiver detachable from the base. For this purpose,
After lifting the presser, lift the mold-cake-receiver assembly to release the protrusion on the platform.
The mold is then held in place by a support provided below the upper collar. Subsequently, the pressing tool is lowered to press the upper receiver, and the upper receiver is released from the mold at the same time as the cake and the lower receiver. The cake is thus easily separated from the supports. Such a device has many advantages over those of the prior art.

First, since slag can be collected at the same place where descaling is carried out, there is no need for an intermediate storage location.
Therefore, there is no need to move the slag and it does not become a source of pollution.

Since the slag is processed in relatively small lots from the original slag source, the recovered metal has a known composition and can therefore be reused directly without fractionation. It is.

No loss of aluminum due to oxidation is also recorded, the so-called extraction rate is improved and the total recovery exceeds any other type of equipment. Problems related to solvents are not covered.

Although the apparatus of the present invention uses a press, this does not result in higher capital and operating costs than in the prior art.

The invention will be better understood from the accompanying single drawing in which the claimed device is shown in vertical section. A table 3 having an annular groove 4 is positioned between a press table 1 and a pressing tool 2. This platform comprises a cavity 5 that accommodates a projection 6 of a lower receiver 7 with a conical upper surface. An engaging portion 8 is provided on the platform, and a slug 11 is inserted into the engaging portion via a lower collar 9.
A mold 10 filled with is placed, an insulating layer 12 and an upper support 13 are placed on the slag, and an upper collar 14 is formed on the mold to enable upward movement by a lift device 15. do. Number 16 indicates the space between the lower receiver and the inner wall of the mold.

Examples of the present invention are shown below. i.e. width 130
mm, an annular groove with a depth of 100 to 150 mm and a lower socket with an outer diameter of 1030 mm, an inner diameter of 1050 mm, and a height of 870 mm.
Position the mold heated to 810℃, metal content 50
% slag was filled and placed under the pressing tool of a 600 ton press. The height of the periphery of the slag is 800
mm, the central part reached 710 mm. The average speed of the pressing tool is 75 mm/min, and the initial speed of the cycle is 200 mm/min.
The final speed was varied from 0 to 0 mm/min. As a result, more than 95% of the aluminum contained was recovered.
The final pressure was 8 MPa.

By applying the present invention to the aluminum industry, slag can be processed economically and under desirable sanitary conditions.