JPS5842148B2 - fused alumina aggregate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to improvements in fused alumina aggregates.

Conventional fused alumina aggregate is made by using Bayer process alumina as a raw material, melting it in an electric furnace, cooling it, solidifying it, and pulverizing it, and is white in color and contains about 0.4% of helium oxide as an impurity.

Mineral composition is mostly corundum and some β-A12
03 is produced, and a trace amount of Na2O remains in a free state.

The disadvantage of fused alumina as an amorphous aggregate is that Na2O is gasified during the melting process and remains in the ingot after solidification, making it porous, thereby reducing particle strength.

Furthermore, due to the presence of free-Na20 and the formation of β-A1203, it can be easily predicted that when used as an amorphous aggregate, these will collect in the matrix and tuxed parts of the refractory material, significantly deteriorating the corrosion resistance.

Therefore, the purpose of the present invention is to obtain a molten alumina aggregate that has lower pores and particle strength than conventional fused alumina aggregates, and has very little Na2O content. It is characterized by containing.

In other words, when Bayer process alumina is melted in an electric furnace, carbon is mixed in and added to it.This increases the C0 partial pressure in the furnace during melting, vaporizes Na2O at a low temperature, and reduces the residual content in the product. Na2O can be extremely reduced.

In addition, by adding carbon, a compound called A1404C fills the pores forming the Mar-IJ tux shape and lowers the porosity.
Additionally, since the boundaries of corundum crystals are filled with peritectics, the strength can be increased.

Furthermore, since carbon is difficult to wet with molten slag and has strong resistance to chemical attack, if an AA-C compound is formed, it can also have properties that are more difficult to wet than conventional molten alumina. .

A certain amount of carbon is required to achieve the effect of reducing Na2O, but on the other hand, adding too much carbon will reduce A1203AA.
As it approaches the eutectic point of 404C, the refractoriness decreases and Al4C3, which easily reacts with water, may be produced, making it unsuitable as a raw material for monolithic refractories.

It has been found that the preferable addition amount is 0.5 to 3.0% in terms of the content in the produced aggregate.

Next, examples of comparative experiments conducted on aggregates having various carbon contents will be shown.

0, 0.5, 2.5. .

*5.0, 10.0, 12.5, ], 5.0
of carbon (99.8% C) was added and mixed in, melted and solidified by arc heat in an electric furnace, and pulverized and sized using a general method to form aggregates of 3 to 5 pieces.

It is preferable that carbon is added and mixed as uniformly as possible with the entire Bayer process alumina raw material.

The chemical composition of this aggregate is shown in Table 1. Table 2 shows the results of measuring the apparent porosity, apparent specific gravity, bulk specific gravity, and particle strength of these aggregates. The hanging specific gravity and bulk specific gravity were measured according to "Single vibration method 2. Measuring method of apparent porosity, apparent specific gravity and bulk specific gravity of magnesian linker".

In addition, single grain crushing strength was used as the particle strength. In this method, the sample is sized to 4,000 to 4,760 microns and made into small samples by the reduction fraction method, and 100 samples are randomly taken from among them, and 2 tons of amsla are collected. was measured and the average value was taken as the particle strength.

Next, FIG. 1 shows the relationship between carbon content and apparent porosity, and FIG. 2 shows the relationship between carbon content and strength.

As is clear from FIGS. 1 and 2, when the carbon content exceeds 0.5 parts by weight, the apparent porosity decreases rapidly, and after that, almost reaches an equilibrium state.

The particle strength also increases rapidly when it exceeds 0.5.

However, as it approaches 3.0, it starts to decline again.

The mineral composition of this aggregate was investigated by X-ray diffraction.

It is shown in Table 3.

As can be seen from the produced minerals, the carbon content is 0 parts by weight.
．． When it is 5 or more, the production of β-A1203 is completely blocked.

Then, A1404 C is generated, which fills the pores, resulting in low porosity and increased particle strength.

However, if excessively added, the proportion of A1404C will increase,
On the contrary, the particle strength also decreases gradually.

As mentioned above, the molten alumina aggregate of this invention is made by adding carbon to Bayer process alumina and melting it, so that it has a mineral composition of β-A1203 and free-N a2.
0 has been removed and a suitable amount of A1404C has been produced, it has characteristics of considerably low porosity and high particle strength, making it ideal as a refractory aggregate.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between carbon content and apparent porosity in the fused alumina aggregate according to the present invention, and FIG. 2 is a diagram showing the relationship between carbon content and particle strength.

Claims (1)

[Claims] 1. In the fused alumina aggregate obtained by melting and solidifying Bayer process alumina and pulverizing and sizing it, the Bayer process alumina raw material is
A fused alumina aggregate characterized in that 0.5 to 3.0 parts by weight of carbon is added and mixed into the Bayer method alumina melt-generated aggregate and melted to produce A1404C as a subcomponent.