APPARATUS AND METHOD FOR HEATING AN AGGREGATE MATERIAL

摘要

Relatively coarse aggregate is preheated to a relatively high temperature prior to introduction into a rotary kiln by directing the aggregate downwardly along a predetermined path of travel while maintaining the aggregate in the form of a relatively thin layer and while directing the waste heated gases from the kiln upwardly along a predetermined sinuous path of travel repeatedly passing laterally back and forth through the downwardly moving layer of aggregate from opposite sides thereof to thus provide highly effective contact of the gas with the aggregate, and while supplementally heating the waste heated gases so as to preheat the aggregate to a higher degree. The thin layer of aggregate is guided downwardly through the preheater housing along a passageway formed by a pair of gas permeable retaining walls which extend generally vertically in opposing spaced relation to one another, and which are of a nonlinear zigzag configuration so arranged as to direct the thin layer of aggregate along a sinuous path of travel in the course of its downward movement along the elongate passageway. The supplemental heating means preferably includes a fuel burner located in the lower portion of the preheater housing in the path of the incoming waste heated gases which are received from the kiln for further heating the gases prior to the gases being directed upwardly and into contact with the aggregate.