Adsorption dryers cold 2.5-142 m3 / min, 800-5000 cbm ft / min. HL cold air desiccant dryers use twin adsorption towers with strategically positioned valves to dry the compressed air. Simple cold drying technology directs part of the dried compressed air into a stand-alone tower. The dry air then passes through the dehumidifier and regenerates it. Although the operating costs are higher than heated desiccant dryers, the HL series requires a minimal capital investment.