PHE- Externally Heated Dryer

A typical external heater dryer includes two towers filled with desiccant, either activated alumina or molecular sieve material. One tower, the initial tower, dries air while the other tower, is regenerated. As the air flows through the initial tower, the desiccant absorbs moisture as the pores of the media have an affinity for moisture and dry air flows out of that tower. When the initial tower is saturated, the towers switch roles
A portion of the dried air, e.g. ~5%, is heated to 350oF/177oC for regeneration and flows through the other tower. The Pioneer design includes monitoring temperature of the air exiting or purged from the regenerating tower. As exit air temperature of in excess of 250oF/121oC signals completion of heating mode and switches the heater off to save energy.


the PIONEER upgraded design includes desiccant cooling with dry air to deliver a lower and more consistent dew point.

Additionally, the design includes monitoring controls to measure the temperature of purge air exiting the regenerating tower. An exit air temperature of in excess of 250oF/121oC signals completion of the heating mode and switches the heater and blower ‘off’ to save energy.

technical title

A typical dryer has an 8 hour cycle time: 4 hours of drying air, 2.5 hours of heating, 1 hour 25 minutes of desiccant cooling and 5 minutes of re-pressurization to line pressure, per tower. The re-pressurization prevents the desiccant from being ‘shocked’ and eroding. After 4 hours, the air flow switches from the left tower to the regenerated right tower