JPH0873958A - Treatment of aluminum dross - Google Patents

Abstract

PURPOSE: To enhance the recovery rate of metals and to obtain useful dross having a high metal concn. by compressing the Al dross of a specific thickness housed in a vessel specified in the opening area ratio and form of a bottom plate with the compressing force of a specific range. CONSTITUTION: The Al dross 9 kept at the m.p. of the Al or above is housed into the vessel 1 formed by using a perforated plate 11 having the opening area ratio of >=20%, more preferably >=30% as its bottom plate. The vessel is formed by specifying the ratio of the minor axis and major axis to the side walls passing the centroid of at the cross section of the bottom to 1:1 to 1:2. The vessel is also so formed that the max. housing thickness of the dross 9 attains 0.3 to 0.7 tinges the major axis. The dross 9 is then pressed and compressed by a piston head 41 of a hydraulic pressing cylinder 4 via a pressing plate 8. At this time, the final pressing pressure on the dross 9 is set at 2 to 5MPa.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum dross treatment method, in which metals are recovered from aluminum dross having a melting temperature of aluminum or higher at a high recovery rate, and the metal concentration in the dross after the treatment is increased to increase the dross concentration An object of the present invention is to provide a method for treating aluminum dross that can be advantageously used.

[0002]

2. Description of the Related Art It is inevitable that aluminum dross will be generated during the melting treatment of aluminum or aluminum alloys, and the recovery of metallic aluminum from such aluminum dross has been extensively studied. That is, in order to recover metallic aluminum from such an aluminum dross, a flux is generally added to the dross conventionally stored in a container to heat the aluminum by oxidation to weaken the oxidized film and enhance the fluidity of the molten metallic aluminum, By mechanically stirring such aluminum dross, the oxide film is broken, and the aluminum droplets that have grown by combining the metals are settled at the bottom of the container and separated.

On the other hand, in Japanese Unexamined Patent Publication No. 60-500542 (Japanese Patent Publication No. 62-10287), the pressing tool is pressed to the upper part, and the pressing tool is lowered at the maximum speed until the liquid aluminum flow appears in the lower part of the mold. After that, it is announced that the pressing tool is lowered at a speed which becomes slower as the concentration of liquid aluminum decreases.

On the other hand, JP-A-47-38719 (Japanese Patent Publication No.
(JP-A-37881), there is proposed a synthetic slag adjusting material which is formed in a lump form by using an appropriate binder for the aluminum dross, and in JP-A-51-97524 (Japanese Patent Publication No. 56-30368), this aluminum dross is proposed. With a mixture of lime and lime as the main component and a melting point of 1450-
A synthetic slag adjusting material for steelmaking at 1600 ° C. has been proposed.

Further, JP-A-62-205210 (Japanese Patent Publication No.
-9643), it was announced that a mixture of aluminum dross mixed with iron, steel dust, and the like was charged into a ladle to cause an oxidation reaction, which is disclosed in JP-A-3-12220.
9, JP-A-3-122210 also announced that the refining agent added to the dephosphorization furnace contains aluminum dross together with fluorite.

[0006]

According to the conventional general method for recovering metallic aluminum from aluminum dross as described above, it is impossible to recover 100% of the metal, and the metallic aluminum equivalent to the dross after the treatment is not available. Residue is unavoidable. In addition, since the added flux burns the metal in the aluminum dross to achieve high heat, there is a large metal loss, and there is a risk of explosion due to a rapid oxidation reaction, and further wear and wear of the device due to stirring. There are disadvantages such as being large.

It can be said that the squeezing using pressure according to Japanese Patent Laid-Open No. 60500542 described above eliminates the disadvantages of the conventional general method as described above, but the high temperature aluminum dross is entrained with molten metal aluminum. It consists of fluid such as air and powder such as aluminum oxide and aluminum nitride.When such aluminum dross is filled in a container and a load is applied, an arching phenomenon occurs due to internal friction of coarse dross powder. It will be generated and the transmission of force will be hindered and the discharge of fluid will be insufficient,
The amount of air remaining is still large, and the oxidation of aluminum contained in the dross progresses, resulting in a significant increase in the weight of the dross. It has to be significantly lower. The energy required for squeezing is also large.

The technique of utilizing aluminum dross for the steel refining or slag adjustment according to the above-mentioned JP-A-47-38719 and JP-A-62-205210 is in any case concerned with effective utilization of dross generated during aluminum refining. Although it is clear that this is a technology, the use of such aluminum dross essentially aims to oxidize aluminum to reduce oxygen in the steel and to utilize the heat generated by the oxidation to improve the properties of steel and the like. Therefore, it is important to have a high aluminum metal content in the dross, and the maximum aluminum metal content is 30.
When the dross is as low as about 10%, not only the above-mentioned action is poor, but also the amount of slag generated is increased to make the treatment difficult. Therefore, in the case where the aluminum metal content is low as described above, a special cost is required for the treatment as merely industrial waste, and it is inevitable to dispose of it.

[0009]

Means for Solving the Problems The present invention has been studied to solve the problems of the prior art as described above, and has a form of a container having a bottom plate having a predetermined opening area and a dross accommodation thickness for the container. It is possible to achieve efficient metal recovery and increase the metal concentration in the dross by setting the pressure to a specific range and applying a pressurizing force in the specific range, as described below.

(1) A container having a bottom plate with an opening area ratio of 20% or more and having a ratio of a minor axis to a major axis to a side wall passing through the center of gravity of the bottom cross section of 1: 1 to 1: 2 is the maximum. The dross having a melting temperature of aluminum or higher so as to have a storage thickness of 0.3 to 0.7 times the major axis is stored.
A method for treating aluminum dross, which comprises squeezing the final pressing force against the dross from 2 MPa to 5 MPa.

[0011]

By providing a bottom plate having an opening area ratio of 20% or more, the outflow of metal when pressing the dross can be made relatively easy, the internal frictional resistance is reduced, and the processing is performed with a comparatively light pressure. Excuse me. The upper limit of the opening area ratio is generally 50%, preferably about 45%.

The maximum accommodating thickness is 0.3 to 0.7 times the major axis in the container in which the ratio of the minor axis to the major axis to the side wall passing through the center of gravity of the bottom section is 1: 1 to 1: 2. By accommodating the dross that is above the melting temperature of aluminum as described above, the dross that is relatively thinly accommodated together with the bottom plate having a large opening area as described above under the conditions of relatively low pressure dross wall friction and dross. Metal aluminum in the dross after squeezing by reducing the influence of internal frictional resistance, appropriately discharging molten aluminum and air, reducing the residual air after squeezing, and limiting the oxidation of residual metal aluminum by the air that has entered after squeezing. Prevent the concentration from decreasing. When the dross accommodation thickness is more than 0.7 times the major axis, springback occurs in the dross after compression, and the metal aluminum in the dross is oxidized by the incoming air, and the concentration of metal aluminum in the dross after compression decreases.

By squeezing the final pressing force against the dross stored as described above to 2 MPa to 5 MPa, proper separation of metal components and air is achieved, and aluminum dross, which is advantageous under relatively easy operating conditions, is produced. Perform processing.

The opening area ratio of the bottom plate is 20% or more,
Preferably, it is set to 30% or more to secure a metal recovery rate in the dross of 50% or more, and also to maintain the metal concentration in the dross after pressing at a high level.

When the dross storage thickness is such that the dross thickness after compression is extremely thin, that is, when the dross storage thickness is approximately 300 mm or less regardless of the shape of the container, the metal recovery rate is high, but after the compression. The metallic aluminum in the dross is oxidized and reduced from the bottom opening. That is, there is no lower limit of the storage thickness of the dross only for the purpose of recovering the metal from the dross, but it is preferable not to make the storage thickness extremely thin (200 mm or less) in order to effectively utilize the metal content in the dross. .

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of an apparatus adopted by the present inventors for carrying out the present invention is as shown in FIG. 1, in which a receiving means 2 provided at the bottom of a container 1 has a receiving portion 22 on the circumferential side. Are connected to the bottom of the container 1 by a connecting means 23 so as to be moved.

A perforated plate 11 such as a grating is attached to the bottom surface of the container 1 described above, and the container 1 and the receiver 2 are removed from the receiver 13 at the elevated position of the receiver 13 to remove the aluminum melting furnace. The dross, which is set to the side and is scraped out, is received, is again carried into the machine base, and is subjected to the recovery processing according to the present invention.

A pressing plate 8 is placed on the dross 9 contained in the container 1 and is pressed by the piston head 41 of the pressing cylinder 4 provided on the machine base 10. A pipe 42 from a hydraulic unit is guided to the cylinder 4 to apply pressure.

The cake of dross, which has been compressed and positioned at the bottom of the container 1 in the container 1 as described above, is transferred to a cake receiving pallet and taken out by a cake removing cylinder. Is taken out from the container 1 and taken out on the cake receiving pallet.
The container 1 from which the cake has been removed is transferred to the side of the aluminum melting furnace to receive new aluminum dross.

Some typical examples of the above-mentioned perforated plate 11 are as shown in FIG. 2 and FIG. 3. In FIG. 2, circular through holes 15 are provided to obtain a predetermined opening area ratio. In FIG. 3, the concentric circular through holes 16 are arranged to obtain a predetermined opening area ratio.

However, specifically, the height is 600 mm and the diameter is 600.
mmφ bottom plate replaceable iron cylindrical container with open area ratio of 5%,
The bottom plates with openings of 10%, 20%, 30%, and 40% were installed, and the dross accommodation height was 0.2 to 1.0 times the diameter (major axis). Pressing against aluminum dross 1.5, 2.5,
It was carried out at 3.5 and 4.5 MPa. Separately from this, a rectangular container having a height of 600 mm and a flat surface of 450 mm x 630 mm was also prepared and pressed in the same manner as described above. In those cases, the metal aluminum content in the dross after pressing and the aluminum content The recovery rate and the dross weight gain rate were measured, respectively.

The metal aluminum content of the dross used for the above-mentioned compression treatment was about 80% in all the examples, which was about the same level, and the circular container as described above was used. The summary of the results of each treatment is shown in Table 1 below, the metal recovery rate in Table 1, the metal concentration in the dross after compression in Table 2, and the dross weight increase rate in Table 3 below.

[0023]

[Table 1]

[0024]

[Table 2]

[0025]

[Table 3]

That is, as shown in Table 1, the metal recovery rate increases as the bottom plate opening area ratio increases, and the metal concentration in the dross also changes variously, but generally the bottom plate opening area ratio 20 A tendency that is proportional to the opening area ratio is recognized up to about%, and it can be said that the leveling state is maintained when the opening area ratio is 20% or more. Furthermore, it can be said that the dross weight increase rate (a large value indicates that the aluminum content in the dross is oxidized) is generally reduced by increasing the bottom plate open area ratio.

The dross weight increase rate in Table 3 (a value obtained by dividing the sum of the recovered aluminum weight and the dross weight after squeezing by the dross weight stored), which can be used as an index of the metal oxidation rate, is the stored dross thickness. High in large cases of
Although it is inversely proportional to the opening area ratio, it is substantially the same level at the bottom surface opening area ratio of 20 to 40% as described above, and increases when the dross height exceeds 0.7. The tendency becomes clear. Also, it can be seen that when the pressure is 1.5 Mpa, the aluminum recovery rate is low and not sufficient.

When the dross containing thickness is extremely thin, the aluminum recovery rate is high when the opening area ratio is high, but the concentration of metallic aluminum remaining in the dross after the compression treatment is reduced. This is due to oxidation from the opening. Also in this case, the weight increase rate of the dross was lower than that of the dross stored in a thickness of 400 mm and squeezed, and metal loss occurred due to oxidation of the dross. That is, when only collecting metal from the dross, there is no lower limit to the dross storage thickness, and in order to recycle the dross and avoid metal loss, the dross storage thickness is preferably 0.5 times the container major axis or more. .

As shown in Table 1, the high metal recovery rate obtained by the method of the present invention is effective recovery and utilization of metal from the dross. Also, as shown in Table 2, the dross remaining in the container is A metal concentration as high as 50% or more can be advantageously used for the purpose of heat retention, deoxidation or temperature rise, etc. as a treatment agent in the steel manufacturing process such as iron making, steel making, refining or casting after the treatment. It is clear that the conventional dross having a metal concentration of about 30 to 35% requires a cost for disposal, and is significant in view of the fact that there is no suitable disposal site. Further, as shown in Table 3, the dross weight increase rate is low, and the metal recovery rate is high as shown in Table 1. In any case, effective use of the dross can be obtained, and it is not possible to drastically improve this kind of dross treatment. It's clear.

As a comparative example, in consideration of the size of the dross scraping opening of the furnace, the height is 600 mm and the plane portion is 400 mm × 10.
Prepare a rectangular container of 00 mm (minor diameter: major diameter = 1: 2.5),
Use a bottom plate with an opening area ratio of 40% and set the dross accommodation height to 4
When treated as 00 mm (0.4 times the major axis), the metal recovery rate was 50% or more, and the metal concentration in the dross after pressing was 53%.
% Or more, and a pressing force of 8 Mpa or more was required to achieve a dross weight increase rate of 1.07 or more.

[0031]

According to the present invention as described above, it is necessary to increase the metal recovery rate from the aluminum dross, increase the metal concentration in the dross after the treatment, sufficiently utilize the metal, and make it difficult to dispose of it. There is nothing that requires special additives and equipment,
This is a great effect because the thickness of the dross can be limited in a general squeezing equipment and the compressive force can be controlled to a relatively low level, which can be industrially advantageously processed.

[Brief description of drawings]

FIG. 1 is a front view of an aluminum dross recovery processing apparatus according to the present invention.

FIG. 2 is a plan view showing an example of the perforated plate.

FIG. 3 is a plan view showing another example of the porous plate.

[Explanation of symbols]

 1 container 2 receiving means 4 pressing cylinder 7 guide 8 pressing plate 9 dross 10 machine stand 11 perforated plate 13 receiving stand 15 circular through hole 16 concentric through hole 21 recovered metal 41 pressing cylinder piston head 42 piping

Front Page Continuation (72) Inventor Masatoshi Nanba 3-13-12 Mita, Minato-ku, Tokyo Within Japan Light Metals Co., Ltd. (72) Inventor Kunio Hayashi, 351 Ejiri, Takaoka City, Toyama Prefecture Hokuko Co., Ltd.

Claims (2)

[Claims] 1. A container having a bottom plate having an opening area ratio of 20% or more and having a ratio of a minor axis to a major axis to a side wall passing through a center of gravity of a bottom cross section of 1: 1 to 1: 2 is maximally accommodated. Aluminum which is characterized in that dross having a melting temperature of aluminum higher than the major axis is contained in the dross and the final pressing force against the dross is compressed from 2 MPa to 5 MPa. Dross treatment method. 2. The aluminum dross treatment method according to claim 1, wherein the opening area ratio in the bottom plate is 30% or more.