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Sahara Air Products

Blower Purge Air Dryer

Blower Purge Air Dryer

The choice for typical use of drying

large volumes of compressed air

 

 

The Blower Purge air dryer (or BP) is a type of heat-reactivated dryer. They're used when you don't want to lose any compressed air, and are among the most economical dryers to operate.

 

Regeneration is accomplished by blowing ambient air into a heater, heating the air to 375°F, then passing this hot air into the regenerating tower. 

 

The BP operates on an 8 hour time cycle; 4 hours drying, 3 hours heating, and 1 hour cooling. Normally, an electric heater is used; however, if 150 PSIG of waste steam is available, then this is usually more energy efficient and a steam to air heat exchanger may be used to reduced the operating cost of the drying system. When a heat exchanger is selected, it's important to bypass the heater during cooling. Simply shutting off the steam flow results in shortened life of the exchanger.

 

The SAHARA Blower Purge design incorporates a very unique feature to provide constant low dew points. Conventional blower purge designs use the ambient air blower during both heating and cooling. Unfortunately, if the dryer is located in a hot, humid environment, during cooling the moisture present in the ambient air is deposited on the bottom of the desiccant bed. When the dryer shifts towers and that bed is used for drying, the moisture on the bottom of the bed is picked up by the air; thus, there may be a fairly substantial dew point spike at tower shift. To prevent this, Sahara provides a selector switch on the control panel, allowing each user to choose either blower cooling or exhaust cooling. If exhaust cooling is selected then the blower and heater are both turned off after 3 hours of heating. A small (5%) purge of dry air then enters the regenerating tower and cools the desiccant bed. This exhaust cooling has the additional benefit of providing lower dew points than conventional blower cooling.

 

The operating cost of the BP is determined by the blower HP and the heater KW. For more about determining the operating cost of the BP, reference Part 8 of our "Economics of Air Drying" article.

 

Blower Purge air dryers are capable of delivering dew points of -40°F and even as low as -100°F when using exhaust purge cooling.

 

Their rugged construction features rigid copper tubing mounted on vibration isolated supports.

 

They're designed to provide years of trouble-free operation and include many safety features.

 

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