Compressed Air Drying Equipment: Lower Costs With the Right Dryer

Why the Regenerative Dryer Might be the Best Option for You

It has been well documented that the presence of water in compressed air systems can have serious ramifications. Consider this: a typical 100 hp compressed air system at common ambient conditions can generate as much as 40 gallons of water in a 24-hour period. As a result, industries lose millions of dollars each year from lost production, increased maintenance costs, and a reduction in quality.  The solution to the problem is to install compressed air drying equipment. While that may seem simple, the key is choosing the appropriate type of drying equipment.

Initially, facility managers need to understand what degree of drying is required. This can be determined by consulting with compressed air system experts and is an important step because drying compressed air beyond the level necessary will result in higher initial and ongoing operational costs.

There are four (4) basic types of compressed air drying equipment available: deliquescent, membrane, refrigerated and regenerative. While there is very limited practical use of the deliquescent and membrane air dryers, both the refrigerated and regenerative air dryers are very common place. While refrigerated air dryers are by far the more frequently applied and well understood method of drying compressed air, this article will focus on the lesser known, yet equally important, regenerative type of compressed air dryer.

Regenerative Air Dryers Many industries including medical, aerospace, food and beverage, and semiconductor, have applications that require very dry compressed air with pressure dew points approaching -40 pdp, even as low as -100 pdp. This is far beyond the range of refrigerated air dryer capabilities and can only be provided by applying some type of regenerative air drying technology.

While there are variations within the family of Regenerative Air Dryers, the five (5) basic regenerative air dryer types based on methods of regeneration include:

  1. Pressure Swing (heatless)
  2. Exhaust Purge (externally/internally heated)
  3. Blower Purge
  4. Vacuum Assist
  5. Heat of Compression

The 5 Basic Types of Regenerative Dryers

1. Pressure Swing (heatless) regenerative air dryers operate without a heat source and achieve low dew points by using dry purge air from the process.

Advantages:

  • Low initial cost
  • Ability to achieve low dew points (-40 pdp or lower)
  • Lower maintenance requirements
  • Simplicity of design

Disadvantages:

  • Consumes process air for regeneration (15%)
  • Higher cost of operation in large sizes
  • Shorter cycle time

2. Exhaust Purge (externally/internally heated) regenerative air dryers utilize both a heat source and dry purge air from the process.

Advantages:

  • Lower cost of operation in large sizes
  • Ability to achieve low dew points (-40 pdp or lower)
  • Longer cycle time

Disadvantages:

  • Moderate initial cost
  • Moderate maintenance costs
  • Consumes process air for regeneration (7% – 8%)
  • Consumes some electrical costs

3. Blower Purge regenerative air dryers utilize a heat source, blower and dry purge air from the process.

Advantages:

  • Lower cost of operation in large sizes
  • Ability to achieve low dew points (-40 pdp or lower)
  • Longer cycle time
  • Consumes a small amount of process air for regeneration (0% – 2% on average)

Disadvantages:

  • Higher initial cost
  • Moderate maintenance costs
  • Possible dew point or temperature spikes at switchover (when process purge air is eliminated)
  • 7% process air purge consumption when regenerating

4. Vacuum Assist regenerative air dryers utilize a heat source and vacuum blower.

Advantages:

  • Lower cost of operation in large sizes
  • Ability to achieve low dew points (-40 pdp or lower)
  • Longer cycle time
  • Eliminates all process air purge use
  • No dew point or temperature spikes at switchover
  • Multiple compressor capability

Disadvantages:

  • Higher initial cost
  • Moderate maintenance costs

5. Heat of Compression regenerative air dryers utilize heat from the air compressor.

Advantages:

  • Lower cost of operation in large sizes
  • Ability to achieve moderate dew points (+10 to -20 pdp)
  • Eliminates all dry purge use
  • No dew point or temperature spikes at switchover

Disadvantages:

  • Higher initial cost
  • Dew points vary with operating conditions
  • Moderate maintenance costs
  • Must be matched to a single compressor
  • Can only be utilized on oil free air compressors

Due to the numerous variations of these types of regenerative air dryers, as well as in their applications, more detailed information may be necessary. For more information and assistance in making the appropriate compressed air drying equipment selection, please contact us at 651.452.8452 or visit www.jhfoster.com.

Ron Nordby Vice President, Sales and Marketing John Henry Foster 651.681.5724 ron.nordby@jhfoster.com

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651-452-8452 | 800-582-5162

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