Can an adsorber be regenerated by means of compressed air? Yes, regeneration using “normal” compressed air is possible.
For this purpose, the loaded adsorber is connected to the usual industrial compressed air and flowed through until the silica gel has changed color back to an orange tone. It should be noted that the loading and regeneration of an adsorber always follows the isotherm of the desiccant. Thus, the adsorber will absorb a lot of water when the air is very humid and release water again when the air is very dry. This effect is used in drying by compressed air. As compressed air is dried to about 7-10% in a compressor, this changes the point on the isotherm of the silica gel.
This new position allows water to be released from the silica gel pores into the dry air. In this way, about 30-35 wt% of
the silica gel is dried. However, it should be noted that regeneration by dry but cold air is not worthwhile in terms of duration and cost. It takes a very long time and the compressed air is thus expensive to regenerate an adsorber.
If sustainability is an important issue, a refillable adsorber should be used. The exchange of the silica gel is by far cheaper.
Figure 1: Isotherms fine-pore silica gel at 20°C, 40°C, 60°, 80°C and 120°C