What Exactly Is a Compressed Air Dryer?
A compressed air dryer is a piece of equipment used to extract water vapor or moisture from industrial process air (dehumidify). In a typical system, a compressor pulls humid air and compresses it, raising the air temperature and condensing water vapor out of the unit.
There are, however, various ways to accomplish isolation. The three primary types of air dryers are refrigerated, desiccant-type, and membrane-type.
Working Principle of a Refrigerated Air Dryer
Refrigerated air dryers are one of the most often utilized kinds in industrial applications due to its simplicity of maintenance and low cost. They are appropriate for air-drying applications that do not have any unique criteria, such as a minimum dew point.
The operating idea of a refrigerated air dryer is to dehumidify air by rapidly chilling it, condensing it, and draining off the moisture. The functioning is similar to that of a home refrigerator or air conditioning system.
Refrigerated air dryers work by dehumidifying the air in the following stages:
- Warm, moist air enters the dryer, where it quickly cools to around 3°C (37.4°F) in a refrigeration unit. Water vapor in the air condenses into pure water at this temperature, which accumulates in a water trap and is supplied into discharge lines. In a condenser, the heated, gaseous refrigerant is cooled and regenerated.
- The chamber’s dry air is reheated to ambient temperature and supplied through an outlet.
Furthermore, there are two types of chilled air dryers: cycling and non-cycling.
- Cycling dryers are devices that operate at 100% duty cycle and can keep the dew point at a consistent temperature.
- Non-cycling dryers operate by shutting down and resuming occasionally to maintain the desired temperature.
Although both variations are helpful in various applications, cycle types tend to increase maintenance expenses.
Working Principle of a Desiccant-Type Air Dryer
A desiccant air dryer system is made up of two towers: one for drying the air and one for replenishing the desiccant. A porous desiccant material in the drying tower blocks water molecules when compressed air from the input passes over it.
The single tower desiccant air dryer is a less frequent type that consists of a single tower carrying a desiccant substance that dries air flowing in from the environment. Single-tower dryers have no mechanical parts and function without the need of power. They are safe to use in corrosive and hazardous situations.
The de-humidification ingredient in these instrument air dryers is a desiccant material, which is a hygroscopic compound with a strong affinity for water. These compressed air dryers have a low dew point, making them appropriate for usage in colder areas and industries that demand extremely dry air.
Desiccant dryer systems are classified into three types: heated, heatless, and heat of compression desiccant air dryers. Let’s take a deeper look at these in the next sections.
Desiccant air dryer that is heated
Heated desiccant air dryers use a heating source within the drying tower to adequately heat the desiccant material to reduce the requirement for purge air. Dew points in heated dryers typically range from -40°C to -73.3 °C (–40 to –100 °F).
Desiccant air dryer with heatless regeneration
Heatless desiccant dryers do not have a heated system in the regeneration tower; instead, “purge air” is used to evacuate moisture from the tower. Dew points in heatless dryers typically range from -40°C to -73.3 °C (–40 to –100 °F).
To maintain a consistent temperature, a heat compression air dryer employs both towers at the same time. This design has reduced running expenses but a less stable dew point.
Working Principle of a Membrane Air Dryer
Membrane dryers collect water vapor from process air using permeable membranes comparable to nitrogen separation membranes or CO2 separation membranes. Because there are no moving parts, these systems are easier to operate, more cost-effective, and require less maintenance. They are appropriate for low-volume air separation.
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