What is Air Drying, and How Does it Work

Compressed air is an essential component in industrial and petrochemical operations. It powers important machinery and process equipment in their various applications. Clean, dry air is ideal for powering your operations and aids in the prevention of corrosion and control failures. This implies your equipment will last longer and you will save money on maintenance.

Today’s market offers a diverse selection of instrument air dryer kinds. Understanding the various kinds of dryers and their operating principles will allow you to select the best air compressor dryer for your specific application.

What are Air Dryers?

What are Air Dryers?

A compressed air dryer is a device used to remove vapor or wetness from industrial process air (dehumidify). In a typical application, a compressor takes moist air and compresses it, raising the temperature of the air and condenses water vapor out from the unit. There are, however, alternative ways to establish isolation. 

How do Air Dryers Work?

How do Air Dryers Work

Each type of air dryer works by eliminating water vapor out from the air in a different way. The ‘dew point’ of the air after purification is a measure of how dry it is. The lesser the dew point temperature, the less water vapor there is in the air. 

In general, the more water vapor an air drier can eliminate, the more money it will cost to do so. Air dryers are classified into three categories, each with its own set of benefits and limitations, and are utilized in a variety of sectors based on the demand.

Types of Air Dryers

1. Refrigerated Air Dryers

Refrigerated air dryers are a common way to remove water vapors, aerosol, and mist from compressed air systems. They have dew points that are adequate for most uses and are reasonably easy to design, implement, and maintain. A refrigerated air dryer works in the same way as a household refrigerator or air conditioner does. An air-to-air heat exchanger cools the compressed air before it enters the device.

The heated entering air is pre-cooled by the exiting cooled air, which condenses the moist air into liquid water that is discharged from the system. The pre-cooled air is subsequently chilled using a refrigerant in an atmosphere heat exchanger. The moist air condenses into a liquid, which is then drained from the system.

Types of Refrigerated Air Dryers

  • Cycling

A refrigerant is used to cool a liquid or solid mass around the heat exchanger’s air intake in cycling-type dryers. The mass might be glycol or a metal block that helps to cool the compressed air by acting as a heat sink. A thermostat is used to control the temperature by turning off the compressor when there are only partial or no loads, conserving energy.

  • Non-Cycling

The refrigerant flows constantly through the system in a non-cycling air dryer, and there is no periodic shutoff. To complement the volume of compressed air going through the system and maintain a steady temperature range, the refrigerant flow is controlled using a bypass or unloader valve.

2. Regenerated Desiccant Air Dryers

Regenerated Desiccant Air Dryers

This type of air drier comprises two towers, one of which contains a desiccant that eliminates moisture from the compressed air stream, and the other of which regenerates used desiccant once the pressure has decreased to atmospheric levels. 

Adsorbent materials such as molecular sieves are useful in these air dryers as they contain zeolite structures known for effective air drying. In the case that you employ this form of air dryer, we suggest you consult an OEM for 13x Molecular sieves which have the best ROI in the industry.

Types of Regenerated Desiccant Air Dryers

  • Heatless Air Dryers

Desiccant air dryers with no heat employ a desiccant in two towers, one for drying and one for regeneration. Wet compressed air reaches the drying tower, travels over the desiccant, which absorbs the moisture, and then leaves as dry air. The desiccant is recovered in its purest form by the regenerating tower. Internal or external heaters are not required with heatless air dryers.

  • Heated Instrument Air Dryers

The heatless dryer employs a twin-tower system and internal/external heaters to create heat. Humid air travels into the drying tower and is dried by the desiccant, much like in the heatless kind. The desiccant is regenerated by the second tower.

Some of the dry air that exits the tower travels via the heater and desiccant, removing the moisture that has been absorbed. Through a muffler, excess moisture is evacuated from the system.

3. Membrane Air Dryers

Membrane dryers remove moisture from compressed air using semi-permeable membrane fibers. Membrane systems are a low-cost, environmentally friendly alternative to conventional air drier kinds that also save space and require less maintenance.

A membrane air dryer is made up of a bundle of fibers with different porosities that are contained in a hollow cylindrical vessel. A pressure differential within the tube permits water molecules to pass through a porous membrane while dry air travels out the exit, and wet compressed air is delivered via an input. Membrane air dryers’ effectiveness is determined by the membrane’s selectivity, which is determined by the size of pores.

The Bottom Line

The aim of the air drier is to reduce the dew point of compressed air by eliminating moisture. Compressed air may retain humidity, which could also reach the dew point and condense into a hazardous liquid under the appropriate conditions. The preceding post went over some of the fundamentals of air dryers to acquire a better knowledge of the subject.

If you are looking to have your own set-up of compressed air dryers set up for any form of application, chances are you need various industrial equipment such as pipes, valves, etc. We recommend checking out your options for industrial valves and equipment manufacturers for the best deal for your application. Also, remember to get yourself proper personal protective equipment. With that said, all the best with your endeavors!!

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