Compressed Air Dryers

Compressed air dryers remove water and other contaminants from compressed air. Apart from the different drying methods other things to be considered while going in for a compressed air dryer include capacity, maximum pressure, minimum output dewpoint, motor power, and operating temperature where:

• Drying capacity is the maximum volume of air through dryer.
• Drying capacity is the maximum volume of air through dryer.
• Drying capacity is the maximum volume of air through dryer.
• Maximum pressure is the maximum rated inlet pressure of dryer
• Dew point is a measure of dryness or the amount of vapor.
• Motor horsepower is a value used to approximate dryer size
• Operating temperature is the full-required range of temperature.

Compressed Air Dryer Technologies
Refrigerant dryers cool the incoming air to a dewpoint of 1-3°C, causing a large portion of the water to condense and be collected by a separator. This involves two heat exchangers

The air-to-air heat exchanger pre-cools the incoming wet air and warms up the dry exhausting air. This reduces the load on air to refrigeration heat exchanger. Exhausting dry air should be close to ambient temperature conditions to prevent water from condensing on the outside of the cool air piping. Refrigerant dryers are generally supplied with a float-type manual drain for the separator

Deliquescent desiccant dryers require a desiccant in the drying process and to carry that they require a shelf inside the air reservoir. The desiccant is a salt that has a stronger affinity for water than the compressed air. This salt dissolves with water and collects at the bottom of the tank to be drained away. The dew points achieved with these systems are approximately 10°C below the temperature of the incoming air and hence should be used with water cooled after-coolers.

Regenerative desiccant dryers use a desiccant such as silica gel to absorb moisture from the air and achieve pressure dew points of 40°C allowing the compressed air to be used in sub-zero conditions without ice blockages. This is often required for sensitive instrumentation. Two dryers are required so that one can be used while the other is being dried. Pre cooling and after cooling is also required for higher efficiency.