KR810000588B1 - Method for the production of aluminium-silicon alloys - Google Patents

Abstract

The method of producing an aluminum-silicon type alloy from alumina-silica bearing materials comprises providing the silica and alumina bearing materials in a mixture having a weight ratio of silica to alumina in the range of 0.5 to 1.1. This method further comprises providing a source of carbonaceous material in the mixture and carbothermically reducing it to form the aluminium-silicon alloy.

Description

Manufacturing method of aluminum-silicon alloy

1 is a chart showing the yield of aluminum-silicon alloy product.

The present invention relates to an aluminum-silicon alloy, and more particularly to a method for producing an aluminum-silicon alloy by carbon heat treatment.

Typically, aluminum-silicon alloys are prepared by using alumina obtained from bauxite to produce pure aluminum in an electrolytic cell, followed by addition of relatively pure silicon prepared separately to the resulting aluminum. However, it is usually uneconomical to produce aluminum-silicon alloys in this way.

Because bauxite is not readily available and expensive, considerable research has continued to develop more economical methods for producing aluminum, particularly aluminum silicon alloys, from other sources. Conventionally, aluminum-silicon alloys have been prepared by adding carbon to natural alumina-silica-containing ores and then carbon-thermally reducing the mixture in a furnace. It is known to produce aluminum-silicon alloys in a furnace from alumina-silica ores. However, it is preferred that the ore used contains 5-70% or more of alumina.

Ore with such a high alumina content is limited in its use and therefore the production cost is relatively high. Briquette compositions for producing aluminum-silicon alloys in electric arc furnaces are also known. Briquettes contain a carbonaceous reducing agent, kaolin, alumina and wollastonite. It is known that this briquette composition enhances the sintering of the charges on top by ore heat treatment and prevents the formation of pores and the falling of the charges. However, since alumina must be supplied and reduction is performed in electric arc, it is uneconomical to produce aluminum-silicon alloy.

Compared to the production of aluminum from ores with high alumina content, it is not only very difficult to produce aluminum from carbonaceous heat treatment from alumina-silica-containing ores, such as sandstone, which have a relatively low alumina content, but generally using conventional methods It was proved that the yield was very low. However, ores such as sandstone, for example, are the most abundant source of aluminum, although they have a low alumina content. Therefore, there is a great demand for a method of extracting aluminum from such low grade ores in a very economical way.

The present invention fulfills this desire by providing a very economical method that can be used to produce aluminum from materials with low aluminum content.

According to the present invention, there is provided a method for producing an aluminum-silicon alloy by carbothermally reducing alumina and silica containing materials, which method comprises the steps of: (a) silica and alumina containing materials having a weight ratio of Supplied as a mixture,

(b) adding a source of carbonaceous material for the purpose of reducing the silica of the alumina in the mixture;

(c) carbon-thermally reducing the alumina and silica components in the mixture to produce an aluminum-silicon alloy.

In a preferred embodiment of the present invention the ratio of alumina-silica can be adjusted by the addition of bauxite. In another embodiment, the ratio can be adjusted by removing or adding silica.

In the accompanying drawings, Figure 1 is produced when reducing sandstone (25 weight percent alumina and 55 weight percent silica) and bauxite (50) weight percent alumina 2 weight percent silica together according to the method of the present invention. Is a diagram showing the yield of the aluminum-silicon alloy product.

The aluminum-silicon alloy according to the present invention is supplied from an alumina-silica-containing material such as ore, for example, as a mixture in which the ratio of silica to alumina is 0.5-1.1, and after the carbonaceous material is put into the mixture. This mixture can be prepared by carbothermal reduction to produce an aluminum-silicon alloy. Alumina and silica-containing materials include ores such as sandstone, lower stone, dosonite, bauxite, laterite and shale. Other materials that can be used as alumina sources include ash and coal waste. The main composition of the alumina-silica containing material and other materials used in the present invention is shown in the table below in weight percent.

TABLE 1

Aluminum Raw Material-Chemical Composition Range (wt%)

Substances such as sandstone, lower stone, calcite and dosonite contain significant amounts of CaO, MgO, Na ₂ O and K ₂ O. Plasma rock, which is a mixture of feldspar (CaOAl ₂ O ₃ 2SiO ₂ ) and feldspar (NaAlsi ₃ O ₈ ), is a preferred source of alumina.

In preparing the ore used in the present invention, for example, 14 to -200 (Tyler series) mesh size should be crushed, and preferably -28 to -100 mesh. Prior to controlling the alumina-silica-containing material within the above weight range, it is preferable to purify the material by mechanical separation such as flotation, heavy liquid or magnetic beneficiation. For example, when the ore is sandstone, it is preferable to remove hydrochloric acid purification to remove things such as calcium oxide (CaO) and sodium oxide (NaO). In such treatments, the hydrochloric acid concentration should be 5-20 weight percent and the temperature should be in the range 60-100 ° C. Typical treatment time is usually 1 / 2-3 hours. After such treatment, the ore can be washed with water.

In order to reduce the alumina-silica-containing material by economical carbon heat treatment to produce a high yield aluminum-silicon alloy, the weight ratio of silica-alumina content of the material should be 0.5-1.1, preferably 0.7-1.0, and most preferably 0.9. Suitable. It is preferable that the weight ratio is 0.7-1.1 for several reasons. When the weight ratio is 0.7 or less, there is a tendency to form aluminum carbide which lowers the total yield. Also, at higher ratios, i.e., at higher silica contents, such as in low grade alumina ores, the amount of adjustment to provide the ore within the desired ratio range is greatly reduced. In other words, the higher the ratio of silica to alumina, the more advantageous from an economic point of view. High ratios also provide high yields of the product.

For example, materials with low alumina content, such as sandstone, or materials with low silica content, such as bauxite, can adjust the silica-alumina ratio within the above weight ratio range. Here, a material having a low alumina content means a material having an alumina of 35% by weight or less, and typically has an alumina content of 8-35% by weight. Such low alumina materials usually contain 25-65 weight percent silica. If using a sandstone having a ratio of silica to alumina of about 2.15 as a starting material, the weight ratio can be adjusted within the above range by adding ore having a high alumina content, that is, a low silica content such as bauxite. The bauxite used for this purpose of adjustment should preferably contain at least 35 weight percent alumina. More preferably the bauxite should contain 40-55 weight percent alumina and 0.2-15 weight percent silica. It is also desirable to contain a significant amount of iron oxide in the material or starting material used for this adjustment, such as for example bauxite. Typically iron oxides may be present at 0.5-30 weight percent. The presence of iron oxide is believed to result in the presence of iron in the alloy, thereby lowering the volatility of the alloy during manufacture, resulting in a high yield of product. Purified forms of high alumina materials, such as for example bauxite, may also be used but are much less desirable because of their generally lower yields due to the cost and additional processes involved in purification.

Another method for adjusting the ratio within the stated range includes the removal of silica by physical flotation or leaching. For example, alpha quartz, composed of a high proportion of silica in plagioclase, can be removed to a minimum by treating the ore with hydrofluoric acid. The hydrofluoric acid used to remove the silica should be in the range of 1-10 weight percent. As in the case of hydrochloric acid treatment, the temperature of leaching solution should be in the range of 60-100 ℃ and leaching time should be 1 / 2-3 hours. Sandstone can reduce the weight ratio of silica to alumina to 2.2-1.4 by treating with hydrofluoric acid for leaching at 100 ° C for 1 hour with 10 weight percent HF solution. Thus, the amount of alumina-rich ore required to obtain the desired ratio is greatly reduced. The acid leaching step to remove the silica can be performed in combination with the previous leaching process to remove alkali and alkaline earth metal oxides.

As for shale and fly ash, for example, by leaching with hydrofluoric acid in order to obtain a desired silica-alumina ratio, the content of silica contained therein can be reduced. High ratios greatly reduce the degree of leaching, which is very advantageous for silica leaching.

Another way to provide silica-alumina in the above mentioned weight ratios is to add silica. For example, when bauxite having a silica-alumina weight ratio of 0.02-0.05 is used as the alumina-silica-containing material, a silica source may be added to obtain a desired weight ratio.

These processes for adjusting the silica-alumina weight ratio can be applied in combination. That is, the ore may be partially leached to remove silica, and then bauxite may be added to the partially leached ore to bring it within the desired silica-alumina weight ratio.

In order to reduce, the mixture containing the desired ratio of silica-alumina and the carbonaceous substance should be supplied. This mixture should contain 15-30 weight percent carbonaceous material based on the carbon content of the material, preferably 19-23 weight percent. When using alumina-silica-containing materials such as shale, a certain amount of carbonaceous material may be present in shale, thereby reducing the amount of reducing material to be added. Carbonaceous materials include coke and metallurgical coke is a preferred source because of its high porosity, which favorably proceeds with the reduction reaction.

Preferably, the mixture formed in the form of briquettes can be reduced in a furnace or in an electric furnace and the furnace method is preferred for economic reasons. The mixture should contain 55-90 weight percent carbon for reduction and heating in the furnace. That is, in addition to the carbonaceous material supplied for the reduction, 40-60 weight percent of the carbonaceous material should be supplied in the furnace for heating purposes.

It is preferable to remove volatile hydrocarbons when the alumina-silica-containing material is shale shale. Therefore, it is desirable to remove shale by treating shale prior to adjusting the silica-alumina ratio. Treatments include physical and chemical beneficiation and carbonization to remove volatiles and coke carbonaceous material. Coke present in hot rock reduces the amount of reducing material added as mentioned.

Therefore, the present invention is very advantageous because it can use a low-grade alumina ore to produce aluminum economically, and the present invention is also advantageous to add a material such as elemental silicon or a metal or intermetallic such as iron or an alloy containing such material. It is advantageous because there is no need. In other words, according to the present invention, a high yield of aluminum product can be obtained without charging or supplying the material into the furnace.

The following examples illustrate the invention in more detail.

Example 1

25% alumina, 55% silica containing sandstone, 49.8% alumina, 1.67% silica and 15.8% iron oxide (Fe ₂ O ₃ ) bauxite together were ground to -28 (Tyler series) mesh size and -100 mesh. Mixed with petroleum coke. Sandstone and bauxite were mixed to produce a mixture with silica-alumina ratios as shown in the table below. Each mixture was heated in an electric furnace for 6 hours to a temperature of room temperature-2100 ° C. The amount of aluminum alloy product and the yield obtained from each mixture are shown in the table below.

TABLE 2

Figure 1 shows the yield of the aluminum-silicon alloy products listed in Table 2 for the corresponding mixture of sandstone and bauxite. The yield is based on an aluminum-silicon alloy obtained from alumina and silica present in the mixture charged into the furnace.

From the results of this test it can be seen that the silica-alumina weight ratio in the bauxite or solid rock of the composition must be adjusted to produce the aluminum alloy product. In other words, when the solid sand or bauxite having the above composition was used without adjustment of the silica-alumina ratio, almost no alloy product was produced.

Example 2

In this example, an Al-Si-Fe alloy was manufactured from Chattanooga's shale. 200 g of carbide shale (-28 mesh) containing 66% SiO ₂ , 14% Al ₂ O ₃ , 12% Fe ₂ O _3, and 11% C were mixed with 200 g of bauxite and 87 g of coke. Silica-alumina weight ratio was 0.89. This mixture was heated to about 2100 ° C. as in Example 1 to give 97 g of alloy product, 83% yield.

Example 3

400 g of bauxite (-28 mesh) having the same composition as in Example 1 was mixed with 169 g of silica (-140 mesh) such that the silica-alumina weight ratio was 0.88. 161 g of petroleum coke (-100 mesh) was added. This mixture was heated to 2100 ° C. as in Example 1 to yield 162 g of aluminum alloy product. This is equivalent to 865 yield.

Example 4

165.3 g of bauxite having the same composition as in Example 1 was added to 300 g of non-oxidized (-28 mesh) containing 16.8% alumina and 39.4% by weight silica. To this was added 86.1 g of petroleum coke (-100 mesh). This mixture was heated to about 2100 ° C. as in Example 1. This test yielded 91.5 g of alloy product, 75% yield.

From these examples it can be seen that the aluminum-silicon alloy can be produced from various grades of ore by supplying only silica and alumina in proportions according to the present invention.

Claims (1)

The silica and alumina-containing materials were supplied as a mixture having a weight ratio of silica to alumina in the range of 0.5-1.1, a source of carbonaceous material for reducing alumina and silica was added to the mixture, followed by carbon heat treatment of the alumina and silica components in the mixture. A method of producing an aluminum-silicon alloy by carbon heat treatment reduction of alumina and silica-containing material, characterized in that to produce an aluminum-silicon alloy by reduction.

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