Several types of natural refractory mineral raw materials
Last time we mentioned that there are several mineral raw materials that can directly produce refractory materials.
1. Natural refractory stone
2. Natural mineral raw materials: silica, pyrophyllite, olivine, chromite
3. Refractory raw materials: kyanite minerals, zircon, graphite
4. Aluminum bauxite raw material brick
5. Refractory clay, ball clay, bentonite
Today we will talk about natural mineral raw materials in detail.
Natural mineral raw materials are mainly divided into the following types: silica, pyrophyllite, olivine and chromite.
Silica is a general term for vein quartz, quartzite and quartz sandstone. The main chemical component of silica is SiO2, which is the main raw material for siliceous refractories. SiO2 exists in different crystal forms at different temperatures, and is transformed with each other under certain conditions, accompanied by volume changes and stresses. When the silica brick is dry transformed, it will cause large uneven expansion of the brick products, which makes the structure of the product loose and cracked. Therefore, silicon brick ingredients should be added with mineralizers such as iron phosphorus and lime milk. At high temperatures, liquid buffer stress is generated to improve the qualified rate of the product.
The natural massive rock dominated by pyrophyllite is called wax stone, generally containing about 30% Al2O3, SiO2 70%~85%, and about 5% burning reduction and few impurities. During the heating process, the pyrophyllite is dehydrated slowly, the structure is not destroyed after dehydration, the volume is stable, and no calcination is used. The refractory material can be directly produced from raw materials, which can be used for making bricks and as an aggregate and powder of unshaped refractory materials. The dense block wax is sawn into required shapes for use as natural refractory stones.
Anhydrous magnesium silicate rock with olivine as the main mineral is called peridotite. As refractory raw materials, it can be used directly as raw materials without calcination. It can be used for making bricks or aggregates and powders of amorphous refractories. Large pieces of peridotite can also be processed into natural refractory stones and masonry furnaces. It should be noted that as refractory raw materials, the general FeO content cannot exceed 10%.
When the chromite is heated at about 800℃, the thermal expansion is significantly increased, and shrinks sharply again at high temperature about 1500℃. Adding MgO to chromite can eliminate its shrinkage when heated. Chromite requirements for refractory materials: Cr2O3 31%~48%, SiO2 5%~9%. However, due to the toxicity of hexavalent chromium, chromium-containing refractories are limited, affecting their development.
Electrolytic cell construction site of Shaanxi MEIXIN Cooper...Electrolytic cell construction site of Shaanxi Meixin
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