Overview: perlite perlite is a kind of acidic lava erupted by volcano. It is a kind of glassy rock formed by rapid cooling. It is named for its pearl fissure structure. Perlite deposits include perlite, obsidian and turpentine. The difference between the three is that perlite has arc-shaped cracks formed by condensation, which is called perlite structure, with water content of 2 ~ 6%; The turpentine has a unique turpentine luster with a water content of 6 ~ 10%; Obsidian has glassy luster and shell fracture, and its water content is generally less than 2%.
Main industrial indexes of ore deposits
The industrial value of expanded perlite raw materials is mainly determined by their expansion ratio and product bulk density after high temperature roasting.
1. Expansion ratio K0 > 5 ~ 15 times
2. Bulk density ≤ 80kg / m3 ~ 200kg / m3
1. Pure glass, good transparency, light color is high quality.
2. There is no or slight devitrification, and the serious one is inferior.
3. There is no or little crystalline substance, and the one with more is inferior.
4. Chemical composition: SiO2 70% ±， H20 4 ~ 6%, Fe2O3 < 1% is high quality, and > 1% is medium and poor quality.
When acidic lava erupts from the earth's surface, it has a great viscosity due to the sudden cooling of the magma, so that a large amount of water vapor can not escape from the magma and exist in the vitreous. When baking, due to the sudden heating to soften, the combined water in the glass vaporizes to produce a great pressure, and the volume expands rapidly. When the glass is cooled to below the softening temperature, it condenses into a cavity structure and forms porous expanded perlite. Therefore, vitreous is the basic condition of ore expansion, water is the internal cause of ore expansion, and iron is one of the unfavorable factors.
The oxidation and melting temperatures of perlite are as follows: the initial shrinkage temperature is 1025 ℃, the softening temperature is 1175 ℃, the melting temperature is more than 1500 ℃, the softening temperature range is 150 ℃, and the melting temperature range is 325 ℃. The shrinkage temperature of perlite is 120 ℃ lower than that of feldspar, the softening temperature is 75 ℃ lower and the softening range is 95 ℃ wider. Because of these characteristics, perlite can greatly reduce the sintering temperature and improve the sintering quality. Through further study, there is another characteristic of perlite, that is, mullite crystal forms earlier in the ceramic body containing perlite, which is conducive to the sintering process. In this way, the pearlite bearing body not only has the same technological characteristics as the feldspar quartz clay (Kaolin mineral) ternary system body formula, but also can reduce the sintering temperature (from 1280 ℃ to 1180 ℃ - 1160 ℃), and has good thermal stability.
Perlite raw sand can be used as filling material in rubber and plastic products, pigments, paints, inks, synthetic glass, thermal insulation bakelite and some mechanical components and equipment.
Perlite is a new kind of lightweight and multifunctional material after expansion. It has the characteristics of light apparent density, low thermal conductivity, good chemical stability, wide temperature range, small moisture absorption capacity, non-toxic, tasteless, fireproof, sound absorption and so on. It is widely used in a variety of industrial departments.