Air drying apparatus and method

摘要

Apparatus and methods are disclosed for using membranes to reduce the relative humidity of a compressed air stream. Air dryers employing membranes consist of a permeable membrane capable of blocking the passage of nitrogen and oxygen molecules, but allowing water vapor molecules to pass through. A membrane filter may be adapted to receive process flow of contaminated air. A sweep chamber may be positioned adjacent to filtration media to pass a portion of dried air back into contact with a portion of the membrane. A flow metering device may be positioned downstream from the membrane filter to adjust a portion of the air process flow as sweep air. The amount of process flow air diverted as sweep air may be proportional to the pressure and flow of the process flow. In some applications, an optional minimum pressure valve may be employed downstream of the sweep chamber to maintain a minimum threshold pressure of process air flow.