Use and function of refractory raw materials

1. Acidic raw material

Mainly siliceous raw materials, such as quartz, tridymite, cristobalite, chalcedony, flint, opal, quartzite, white silica, diatomite, and high-purity magnesia. These siliceous raw materials contain at least more than 90% silicon oxide (SiO2), and the pure raw materials contain more than 99% silicon oxide. Siliceous raw materials are acidic in high temperature chemical dynamics. When metal oxides exist or contact with them, they react chemically and combine to form fusible silicates. Therefore, if a small amount of metal oxide is contained in the siliceous raw material, its heat resistance will be seriously affected.

Use and function of five kinds of natural refractory raw materials

2. Semi-acid raw material (mainly refractory clay)

In the past classification, clay was listed in acidic raw materials, which was not suitable. The acidic basis of refractory raw materials is based on free silica (SiO2), because according to the chemical composition of refractory clay and siliceous raw materials, the free silica in refractory clay is much less than that of siliceous raw materials. Because there is 30%~45% alumina in general refractory clay, and alumina is rarely in free state, it is bound to combine with silica to form kaolinite (Al2O3 · 2SiO2 · 2H2O). Even if there is little excess silica, its effect is very small. Therefore, the acid property of refractory clay is much weaker than that of siliceous raw material. Some people believe that the refractory clay decomposes into free silicic acid and free alumina at high temperature, but it does not remain the same. When it continues to be heated, free silicic acid and free alumina will combine to form Yinglaite (3Al2O3 · 2SiO2). Yinglai stone has good acid resistance to alkaline slag. At the same time, due to the increase of alumina content in refractory clay, its acidic substances gradually become weaker. When the alumina reaches 50%, it will appear alkaline or neutral properties. Especially, the clay brick made under ultra-high pressure has high density, fine compactness, low porosity, and stronger resistance to alkaline slag under high temperature than silica. In terms of its corrosivity, Yinglai stone is also very slow, so we think it is appropriate to list refractory clay as semi-acidic raw material. Refractory clay is a kind of raw material that is Z basic and widely used in refractory industry.

3. Neutral raw materials

Neutral raw materials are mainly chromite, graphite and silicon carbide (manufactured manually), which will not react with acidic or alkaline slag at any temperature. At present, there are two such raw materials in nature, namely chromite and graphite. In addition to natural graphite, there are also artificial graphite. These neutral raw materials have significant resistance to slag. Z is suitable for use as the interlayer of alkaline refractory and acid refractory.

4. Basic refractory raw materials

They are mainly magnesite (magnesite), dolomite, lime, olivine, serpentine, high-alumina raw materials (sometimes neutral). These raw materials have strong resistance to alkaline slag and are mostly used for building alkaline furnaces, but they are particularly easy to react with acid slag to form salts.

5. Special refractory

Mainly zirconia, titanium oxide, beryllium oxide, cerium oxide, thorium oxide, yttrium oxide, etc. These raw materials have different resistance to various kinds of slag. However, due to the limited source of raw materials, they cannot be widely used in the refractory industry, and can only be used in special circumstances. Therefore, they are generally called special refractory raw materials.