Importance

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Abstract

An expanded mineral material suitable for use as a filler, e.g. instead of or in addition to sand or gravel in concrete mixes, is produced by dropping a stream of solid pellets into a rising stream of heated gas contained in a substantially vertical reactor space; the pellets consist essentially of a fusible mineral composition and a latent blowing agent; while falling in counter-current to the gas stream the pellets are heated progressively and expand at least to the point where they are capable to float in the gas stream and are carried in concurrent motion with the gas stream out of the reactor space. This reversal of motion of the expanding particles provides for a substantially self-regulating residence period of the particles in the expansion zone resulting in substantially improved process control and economy.

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First Claim