US Patent 7479176 Sequential adsorption desiccant dryer system

A method and an apparatus for controlling airflow in a desiccant drying system having a plurality of desiccant beds, in which each desiccant bed is located in a chamber, and multi-position valves can be operated to cause the gas to be dried to flow in a serial manner through a plurality of desiccant bed chambers while another desiccant bed is isolated from the gas flow and undergoing regeneration. Once regenerated, the multi-position valves are repositioned to establish a new serial flow gas path in which the freshly regenerated desiccant bed becomes the final bed in the series, and another bed undergoes regeneration.