PURPOSE: To cost effectively obtain harmful materials without releasing the same into the atm. by supplying raw materials contg. Si to a melting tank and preheating the materials with a prescribed gas, then heating the same with tank exhaust gases.

CONSTITUTION: The raw materials, such as basalt, are packed in a direction of an arrow 10 into the melting tank from a feeder 26 of the apparatus disposed with a storage vessel 12, a raw material preheater 9, an inflow port 13 for the tank exhaust gases (crude), an outflow port 14 for the purified tank exhaust gases or the like and are preheated, following which the raw materials are introduced into the melting tank in a direction of an arrow 11. On the other hand, powder adsorbents are supplied from a storage silo 27 via a star feeder 28 into the melting tank. Milk of lime and/or milk of lime soda is sprayed from a liquid vessel 29 in a direction of an arrow 21b through a pump 30 and a nozzle 31 and is introduced into a heater 9. This milk is subjected to a purification treatment and is introduced in a direction of an arrow 11 into the melting tank. While the fluorine generated from the melt is separated in a conduit 20, the fluorine is returned again into the melt and asbestos consisting of the mineral wool and more particularly the basal is produced.