Combined compressed air dryers are commonly used to bring the pressure dewpoint well below freezing (commonly -40°F) in order to prevent moisture from precipitating in the compressed air system and production equipment. In most cases, the need is actually seasonal and a refrigerated dryer is perfectly capable of meeting air quality needs for most of the year - and with much lower operating and maintenance costs. It is possible to install separate refrigerated and combined compressed air dryers in series for these applications. Better still are combination or “hybrid” dryer systems that combine dryer technologies into a high performing dryer with even lower operating costs.
These hybrid combined compressed air dryers first incorporate a refrigerated dryer to condense and remove the majority of the water vapor in the compressed air stream. Refrigeration is a very inexpensive method for dehydrating compressed air. Routing compressed air through a refrigeration system prior to treating it with a combined compressed air dryer significantly reduces the cost to produce a -40°F dew point. Refrigeration will typically remove 85% to 88% of the total amount of water vapor. The combined compressed air dryer is then challenged with only the remaining 12% to 15% of the total water removal.
The hybrid arrangement also significantly reduces both operating and maintenance costs compared to any other dryer types equally capable of producing -40°F dew points. The combination system also permits the refrigerated dryer to be operated independently. As the vast majority of compressed air applications simply require the water vapor remaining in the air after treatment to remain in the vapor state, a refrigerated dryer provides adequate drying during warmer months. The desiccant drying is needed only during cooler seasons. Turning off the combined compressed air dryer in warmer months creates significant operating and maintenance cost savings.
This article comes from airbestpractices edit released
