Different 5-ways How Activated Alumina Ball is used for Heatless air Dryer, Heat-Reactivated & HOC Dryer
Activated alumina has the highest water adsorption capacity when compared to its other counterpart. This desiccant is used in numerous applications.
Let’s see below the use of activated alumina balls in three applications namely:
- Heatless air dryers
- Heat-reactivated air dryers
- HOC dryers
Application of activated alumina in heatless air dryers
Heatless air dryers are one of the effective gas or air dryers that work on the principle absorption. A dew point of -40 °C is required for these dryers. Activated alumina balls used in these dryers help in the prevention of channeling of compressed air flow thus keeping the bed velocities at lower levels.
These regenerative heatless air dryers are mostly operated in two separate towered chambers. Both the towers are filled with activated alumina balls for the simultaneous air drying and regeneration process. Now let us understand the operation below:
The inlet air is directed from a pre-filter, wherein the dust particles and other impurities are removed, into an oil removing filter. Once the inlet air is freed from any impurities it is redirected into the first chamber which consists of the air dryer desiccant beads, the activated alumina balls. Thus, the air now travels through the desiccant bed leaving the moisture to be adsorbed by the activation alumina balls. The moisture-free air is then directed for the end-user.
Now the operation of chambers is reversed (by reversing the control valves) and the saturated alumina balls in the first chamber are regenerated while the compressed air dries in the second chamber. Both the process takes place simultaneously. The regeneration of saturated alumina balls is done by purging dry air or gas at atmospheric pressure and temperature in reverse direction.
Application of activated alumina in heat reactivated air dyers
Heat reactivated air dryers use desiccants such as activated alumina balls to generate compressed air and gasses at a very low dew point. When compared to heatless air dryers, the purge loss is less in heat reactivated air dryers and is best suitable for dew points lower than -60 °C to -80°C.
The operation part involves two carbon steel pressure vessels which are packed with the desiccant air dryer beads(activated alumina balls). The inlet air is directed into a pre-filter that removes any dust particles present in the air. This air is then passed into the 1st chamber with activated alumina that adsorbs the moisture content present. This drying process can go up to 4 hours and once the desiccant bed is saturated, the tower beds are reversed. Here, the compressed air drying and regeneration process happens simultaneously. Now the tower with the saturated alumina balls is put to regeneration by purging hot air generated from the electric heaters for 2 hours. By this time the temperature of the alumina balls reaches above 100°C which causes the moisture to leave them thus leading to a complete regeneration process.
Application of activated alumina in HOC dryers
IN HOC (Heat of compression) type air dryers, the compressed air/gas is generated based on the principle of adsorption. Here too, activated alumina is the air dryer desiccant used. Just as the other two air dryers(Heatless and heat-reactivated), the operation of HOC dryers also involves two chambers filled with activated alumina balls. The air drying and regeneration process happens simultaneously in these vessels and are automatically interchanged after every 4 hours. The main advantage of HOC type air dryer is that the operational cost is minimized by eliminating the need for electrical heaters.
The hot air from the compressor is used for the regeneration process of saturated alumina balls. With a minimum temperature of 130°C, this hot air discharged from the compressor is directed to pass through the saturated desiccant, from where it absorbs the moisture content. This air is then cooled and condensed at 40 °C and made to pass through the other drying vessel. The dried air cools the desiccant bed to an optimum temperature. The whole process involves 4 + 4 hours of drying and regeneration process. For being economical, HOC type air dryers are gaining huge popularity.