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Refrigerant vs Desiccant Air Dryers

Why You Need a Dryer on Your Compressor

If you are in the process of purchasing a compressor for your plant, auto body shop, or wood working facility you will want to evaluate the way you remove moisture from your compressed air. Moisture is a natural by product of using an air compressor that when not removed from your compressed air will create a multitude of problems including ruining air tools and causing finish defects in your paint. Two of the most common options to remove moisture from compressed air include a refrigerant dryer or a desiccant dryer. Both units have positives and negatives, the intent of this article is to cover the benefits, drawbacks, and ways each unit works.

How a Refrigerant Dryer Works

Refrigerant dryers cool the air through a series of steps. Air is first brought into the dryer through a heat exchanger which is partially cooled by the refrigerant air in the system. Air then enters the dryer and is further cooled to 38 degrees Fahrenheit by liquid coolant. The air then exits the dryer through another heat exchanger where it leaves through your piped air.

Refrigerant Dryer Pros

  • Affordable  A standard Refrigerant Air Dryer can be sufficient for a large majority of industrial plant applications and if further air purification is needed you can always add an independent desiccant dryer prior to any critical applications (like in a paint booth or prior to a sandblasting application).
  • Effective – A refrigerant dryer will remove most moisture but will not drop the air below the dew point leaving water vapor still present in the compressed air.
  • Not harmed by oil in the air stream – With desiccant dryers you often will need a way to separate oil prior to entering the desiccant dryer so that it doesn’t ruin the equipment
  • Options to reduce operating costs – Cooling air requires a lot of electricity. In fact many people do not realize it but compressed air is often one of the largest expenses in your plant.  Additionally, the refrigerant dryer’s can be a high cost. There are two kinds of air dryers on the market today cycling and non cycling. Cycling dryers will cost more at first but less to run (they adjust there use based on the air being produced by the compressor). Non Cycling dryers cost less to buy but will cost more in running costs as they do not adjust their cooling based on the compressors output.

Refrigerant Dryer Cons

  • Does not adequately remove moisture for most paint applications and related pertinent applications

How a Desiccant Dryer Works

A desiccant dryer uses a media called desiccant to adsorb moisture in the compressed air. The systems used shortly after the compressor include regenerate desiccant dryers or single tower deliquescent dryers. The main difference between these two systems is that one can make use of the desiccant multiple times before replacement while the other will require routine maintenance. Within regenerative dryers their are some that use heat and some that don’t.

Regenerative Desiccant Dryer Pros

  • Able to drop temperature anywhere from -40 to -100 degrees Fahrenheit allowing for removal of almost all vapor.
  • Lower operating cost due to less replacement of desiccant

Regenerative Desiccant Dryer Cons

  • High initial capital expense
  • Must have oil filtered out prior to reaching the regenerative dryer
  • Will have a larger pressure drop

Deliquescent Dryer Type Pros

  • Lower initial cost
  • Requires no electricity
  • No moving parts
  • Can be used in hazardous environments
  • Can be installed outdoors

Deliquescent Dryer Cons

  • Frequent maintenance of media needed
  • Media could travel in your air pipe creating issues
  • Desiccant must be refilled more regularly

Summary

  • If  you do not need air with all vapor removed for all your applications a refigerant dryer can be sufficient with the addition of desiccant dryers in important areas of your shop
  • If you need all of your plants air to be suitable for critical applications you will want to evaluate a desiccant dryer for your compressed air.

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