Why is it Important to Dry Compressed Air?
Drying the output air is very important if you want to avoid problems in the compressed air system. Learn more about why drying is needed and how it is done.
Did you know that all atmospheric air contains some amount of water vapor. When air is compressed, the water concentration increases. To avoid future problems in the compressor installation, the compressed air needs to be treated. In this article we are talking about absorption drying and desiccant drying also known as adsorption drying
The general working principle of desiccant air dryers is simple: moist air flows over hygroscopic material (typical materials used are silica gel, molecular sieves, activated alumina) and is thereby dried. The exchange of water vapor from the moist compressed air into the hygroscopic material or "desiccant", causes the desiccant to gradually be saturated with adsorbed water. Therefore, the desiccant needs to be regenerated regularly to regain its drying capacity, and adsorption air dryers are typically built with two drying vessels for that purpose: The first vessel will dry the incoming compressed air while the second one is being regenerated (Similar to the workings of a nitrogen generator). Each vessel ("tower") switches tasks when the other tower is completely regenerated. Typical PDP that can be achieved is -40°C, which makes these dryers suitable for providing very dry air for more critical applications. There are 4 different ways to regenerate the desiccant, and the method used determines the type of adsorption dryer. More energy-efficient types are usually more complex and, consequently, more expensive.
Guaranteed separation and drainage of the condensation water must always be arranged before adsorption drying. If the compressed air has been produced using oil-lubricated compressors, an oil separating filter must also be fitted upstream of the drying equipment. In most cases a particle filter is required after adsorption drying. HOC dryers can only be used with oil-free compressors since they produce heat at sufficiently high temperatures for dryer regeneration A special type of HOC dryer is the rotary drum adsorption dryer. This type of dryer has a rotating drum filled with desiccant of which one sector (a quarter) is regenerated by means of a partial flow of hot compressed air (at 130–200˚C) from the compressor. Regenerated air is subsequently cooled, the condensation is drained and the air is returned via an ejector device into the main compressed air flow. The rest of the drum surface (three-quarters) is used to dry the compressed air coming from the compressor after-cooler. A HOC dryer avoids compressed air loss, and the power requirement is limited to that required for rotating the drum. For example, a dryer with a capacity of 1000 l/s only consumes 120 W of electrical power. In addition, no compressed air is lost and neither oil filters nor particle filters are required.
This e-book on compressed air dryers will tell you all about moisture and the important role of dryers in air treatment.
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Drying the output air is very important if you want to avoid problems in the compressed air system. Learn more about why drying is needed and how it is done.
Choosing the right dryer for a compressed air system is as important as choosing the compressor itself. We will show you what to look out for when buying a dryer.
18 October, 2022
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