Pneumatic classifier for refuse material with double vortex airflow

Abstract

An apparatus and operation is disclosed in which light solids material such as shredded paper passes from an upper end of a column and heavier material such as glass and metal particles drop from a lower end of the column. The column includes an air locked feed chute having a downwardly inclined material feeding surface, that opens intermediate the column ends into a stream of air moving upwardly in the column, for admitting mixed light and heavy particles of refuse material to the air stream. A zone of expanded volume is provided at the level where the column and the chute come together and this zone extends upwardly from the material feeding surface and terminates at a level below the upper end of the column where column cross section area is less than beneath the expanded zone. Air drawn upwardly through the column from the lower end and reaching the expanded zone, turns toward the material feeding chute and forms a recirculation zone, herein called a first vortex, within the zone about an axis parallel to and above the intersection of the material feeding surface of the chute with wall structure of the column, before resuming upward flow. A baffle is pivotally journalled in the lower end of the column to pivot about an axis beneath and parallel to the horizontal intersection of the chute with a flat wall structure of the column. The baffle is supported to be pivotable within a range of angularly disposed positions transverse to both a horizontal and a vertical plane through the pivotal axis. Within such range of positions air passing upwardly and over the baffle will be turned to form a second recirculation zone, herein called a second vortex, about and parallel to and beneath the first vortex and pivoting the baffle provides a control of the air flow characteristics created and the separation characteristics of material introduced through the chute.