Abstract: A heat of compression gas drying apparatus includes an air inlet fed by a source of compressed moisture laden air, an air outlet and first and second desiccant-containing towers for processing air flowing therethrough. A portion of cooled dried air delivered to the air outlet is selectively diverted to either a pathway having a heater so that heated dried air may be delivered to a tower having its desiccant regenerated, or to a separate pathway so that cooled dried air is delivered to the regenerating tower. In each case, a purge isolation valve is controlled to deliver and hold pressurized dried air in the regenerating tower after which the dried air in the regenerating tower is purged to atmosphere by pulsing an exhaust valve arrangement connected to the regenerating tower.