What I need to know.
Regenerative compressed air dryers are specialty dryers used when extremely dry air is needed. When compressed air passes through ares that are below freezing refrigerated dryers are inadequate. This is the common use for regenerative dryers.
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The most commonly used dryers are the refrigerated type that cannot lower the dew point below freezing. Other applications for very dry air are found in chemical use of the air where water vapor is detrimental to a chemical reaction. |
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A regenerative dryers uses the principals of adsorption of water molecules to a desiccant as it passes through the desiccant. The water vapor molecules are attracted to the surface of the desiccant drying the air to a typical -40 Deg F. dew point (dew points to -100 Deg F. can be reached). Since this is a surface active process, the desiccants surface will saturate and need to dried. This is accomplished by using two desiccant beds. One bed provides dry air and another is being regenerated (water being removed).
A portion of the air from the drying tower is diverted and pressure is lowered from plant pressure to near atmospheric pressure. In typical application the pressure dew point of the air at 100 PSIG was -40 Deg F. Now at a much lower pressure, this air is very dry and by allowing it to pass through the regenerating bed it will remove the water accumulated during that beds drying cycle. The dryer alternates between the two tower with one (bed) tower always providing dry air and the other is being regenerated. The most common desiccant is activated aluminum in small bead form.
This provides a very large surface area for drying in a small volume making the equipment compact as possible.
When compared to refrigerated dryers, regenerative dryers are less energy efficient since part of the compressed air is used to regenerate and initial procurement costs are higher. For a typical dryer operating at 100 PSIG with 100 Deg F incoming air being dried will use 15% of the rating of the dryer. Care must be exercised that this 15% flow loss is available in the air compressor(s). The use of external heaters can reduce the regenerating flow and cut this loss. In addition, when flow on the dry varies considerably controls can be optioned that cut the regenerating flow till when it is needed.
Contact Harris Equipment for advise on the proper equipment for your application.
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