Abstract

A high efficiency system for removing moisture from compressed air and the like as used in pneumatic systems. To effectively achieve dew points of about -100 degrees F., the system utilizes two integrated dryer stages. The first stage causes the incoming air to be cooled to a dew point of about -35 to -40 degrees through the use of a refrigerant flowing in a heat exchanger to remove the heat of the air. Preferably for this cooling there is a precooler in the form of an air-to-air heat exchanger. The refrigerant is derived from a system having a compressor. The second stage of drying is achieved by passing the outlet air from the first stage, after removing moisture droplets and mist via a separator unit, into a heatless bed of desiccant or like material. Preferably, two beds are employed so as to permit one bed to be removing moisture while collected moisture is being removed (purged) from the other bed. This purging is achieved by using a small portion of the product air of the system that is heated by passing this air through a heat exchanger in the refrigerant system so as to use normally waste heat of the heated refrigerant to raise the temperature of the purge gas substantially to more effectively purge the moisture. This substantially reduces the amount of product air that is utilized for the purge; e.g., from about 15% to about 1-3%.