The blower purge is a kind of heat-reactivated type of dryer. The regeneration in this dryer is done by blowing ambient air (atmospheric) by the blower, heating it through a heater for the required temperature and then passing the hot air to regenerate the tower. Cooling is achieved by switching off the heater and directly cooling the bed. This dryer is not suitable in an environment, which is humid and the RH factor of the air is high which creates dew point bump during the starting of the cycle.

The closed system dryer is typically used for achieving lower dew points. In this system, the process gas is not vented to the atmosphere nor is it contaminated with the atmospheric air. In the closed system, the dryer regenerates by re-circulating a certain amount of air through the blower, heater, the tower under regeneration, and the heat exchanger. This system can achieve very low dew points

This type of dryer is used to in power generation plants for the drying of Hydrogen Gas. This dry hydrogen gas is then used for cooling the turbo-generator plant.

The split flow type is a kind of heat-reactivated type of dryer. The regeneration in this dryer is done by splitting the incoming air at 40/60% , the 40% stream is heated to regenerate the bed and cooled to rejoin the 60% steam, the splitting is done by inducing a pressure drop in the process line, heating it through a heater for the required temperature and then passing the hot air to regenerate the tower. Cooling is achieved by switching off the heater and directly cooling the bed in cocurrent direction.

The closed system dryer is typically used for achieving lower dew points. In this system, the process gas is not vented to the atmosphere nor is it contaminated with the atmospheric air. In the closed system, the dryer regenerates by re-circulating a certain amount of air through the , heater, the tower under regeneration, and the heat exchanger. This system can achieve very low dew points.

In this type of dryer, the wet compressed air / gas is made to pass through one of the two towers at a time. The direction of flow of air / gas is controlled with the help of automatically operated valves. As the moisture-laden air passes through the desiccant bed, the desiccant adsorbs the water molecules and dry air comes out from the top. After a particular level of saturation of the desiccant bed, an automatic changeover of the tower takes place. As the second tower comes on the adsorption line, the first tower is simultaneously depressurized. This depressurization is followed by purging the depressurized tower with a small quantity of dry air / gas from the 2nd tower.

As the dry air / gas traverses the adsorbent bed in the counter current direction, it picks up the moisture and reactivates the desiccant bed. This moisture-laden gas is now vented out to the atmosphere through the exhaust valves. To avoid pressure jolts, the reactivated tower is re-pressurized before changeover.

In this type of dryer, works on the principle of refrigeration, the wet compressed air / gas is cooled to abount 3-4 Deg C and the moisture is removed. The system is fully automatic and can give a pressurized dew point of +3-4 Deg C only. The dryers are quite reliable and and are well suited to wide range of application where the dew point requirement is high.