Known as ‘adsorption’, taking in water and drying air are the main functions for this particular desiccant. When humidity molecules appear in the air, they can lead to corrosion in machinery as well as ice formations which, as you can imagine, can be dangerous and damaging. Therefore, it is important to remove these molecules so the machinery and equipment can run without disruption.
The process of Activated Alumina is actually simple. Acting like a sponge in water, the moisture within the air will stick to the Alumina as it passes through. They become trapped in the Activated Alumina and the air remains free from moisture. In simple terms, this is like using a sieve in that the water gets left behind and the air continues without the moisture.
Use in Air Drying - At times, it can be easy to tell when the moisture has been removed. Within an area, the pressure dew point will be calculated and areas lower than -40F require a heatless adsorption dryer. This is both cost effective and energy efficient. When in operation, these dryers will use a desiccant such as a Molecular Sieve or Activated Alumina. In fact, these are the two best options currently used in the industry.
Heatless Adsorption Dryer - Holding two adsorption towers of the same size, they will be filled with the chosen desiccant. Although companies will have their favorites, there isn't necessarily a ‘best’ option from Molecular Sieve and Activated Alumina. Since they are both effective, you shouldn't notice much of a difference in the end result.
To start, the compressed air will travel towards the top of the tower and the moisture will be absorbed. Over time, the bed of the desiccant will start to weight down with moisture. As soon as it has reached maximum capacity, the first tower will deactivate and this will need to be removed. After this, dry compressed air will pass from the top in order to purge the desiccant and it will then connect with all the ejected moisture molecules. The second tower will have activated while all this is occurring and will work as normal. Rather than having to shut the whole set up down each time, they can be replaced continuously to keep the dried air in the system.
As the bed of desiccant in tower one regenerates over time, the second will be working away. When there is a constant flow of dry compressed air, this suggests that both towers are working as expected. Ultimately, the adsorption dryers will perform differently depending on their operating pressure, temperature, and even the flow. When the temperature rises somewhat, a difference in production will be seen!