Adsorptive Type Air Dryers

The adsorptive dryer is made of some type of desiccant, such as silica gel or activated alumina. The desiccant adsorbs and holds water vapor from the air.

The figure provided here illustrates an adsorptive type air dryer.

An adsorption-type dryer consists of two drying towers, each containing an adsorbent. Each tower is also provided with a heating coil. The towers are identical to each other. At any time only one tower is in service (the other is being regenerated.)

Let’s discuss the operation of the unit shown in the figure. The left hand tower is in operation (drying service). Compressed air is routed to it through the point marked “Inlet”. Compressed air flows downward through the desiccant in this tower. The desiccant absorbs the moisture in the air. At the bottom it reverses its path and flows upward to the outlet. The heating coil in this tower is turned off while this tower is in “drying service.”