Vermiculite FOR REFRACTORY APPLICATION
Vermiculite is micaceous mineral, which rapidly exfoliates on heating to produce lightweight aggregate. With these aggregates, we could manufacture various products. To produce lightweight aggregate temperature required is 400 C -1100 C. It depends on quality of raw vermiculite, which exfoliates upto 20 times. Exfoliation takes place at an angle of 900 C to the cleavage plane. Mineral vermiculite is soft, pliable, inelastic, dull in appearance and opaque. It is hydrated magnesium Aluminum silicate. By heating it exfoliates. The colour of raw vermiculite is dark brownish yellow, greenish or almost black. After exfoliation colour changes to lustrous gold or golden brown with a silver tint.
Expanded vermiculite has several advantages. It is lightweight, non-corrosive free flowing non-conductor of electricity, odorless, non – abrasive, acid resistant, chemically inert, reflective, hygroscopic, low thermal conductivity vermin, termite, moth and rodent proof, insoluble in water and inorganic solvents, resistance to heat penetration, high thermal insulation, asbestos free.
It does not crumble with sawing, does not react with gases, have shrinkage, resistance to both hot and cold thermal shocks, economical to many other available insulation bricks and comparable to calcium silicate based products. Its lightweight and its low thermal conductivity on exfoliation make it a very suitable ingredient for refractories.
Application:
It is used as constituent of refractory blocks and firebricks for use in furnace temperature of up to 1300C. It is possible to use vermiculite based refractory blocks as hot face insulation surface in furnace, but it is more common to use them as backup in high temperature applications. Also used as a lightweight ingredient in high temperature and medium strength castables, which are easily castable in awkward positions where it is not possible to use in pre-formed materials, Maximum service temperature 1300 C.