Heatless Compressed Air Dryer Principles
Posted by IAP on 01/10/2025
From Compressed Air Best Practices
The heatless dryer process was born out of necessity by Dr. Charles W. Skarstrom in 1956 at the Esso refinery in Bayway, New Jersey 1. Dr. Skarstrom, who had worked on the Manhattan Project during World War II, was developing an automatic gas analyzer for his laboratory when the plant’s desiccant air dryer failed. The dryer’s regeneration heater burned out. Acting on the theory of heater-less regeneration, Dr. Skarstrom solicited the assistance of Virgil Mannion and Robert C. Axt, adsorption system engineers, and together they shortened the dryer cycle time sufficiently to conserve the heat of adsorption and continue the drying process without an external heat source. Based on the successful operation, the process was patented 2. Dr. Skarstrom’s laboratory observations are preserved in his patent issued in 1960, and in the 1972 CRC Press publication 3. He discovered that to dry compressed air, the following principles must be applied for the process to continue.
Principle #1: Short cycles and low throughput per cycle are required to conserve the heat of adsorption
Principle #2: Regeneration at low pressure using some of the purified product for countercurrent purge
Principle #3: Actual purge flow rate (acfm) must equal or exceed the throughput flow rate (acfm). The third principle can be restated
in terms of standard cubic feet per minute (scfm):
Purge (scfm) > Feed (scfm) x (Regeneration Pressure, psig + 14.7)/ (Inlet Pressure, psig + 14.7)