Reactivation of a silica gel moist air dehumidifier using solar heat

Dry air is used in many manufacturing and chemical industries and plants, and in pneumatic control systems. Silica gel pellets, available in various sizes, are widely used as drying substance as it processes distinct advantages. For reuse in the drying process, it can be quite easily reactivated by heating. In this work a small silica gel drier, fabricated and used earlier by this author, has been used for reactivation. The reactivation process was carried out by passing heated air at about 70°C achieved by a flat-plate solar collector through the moisture-loaded silica gel bed. An analysis of the reactivation process of an adsorbent material has been given, and some useful equations have been included. Experiments were carried out for few days during sunny periods in the IUT campus. Calculated and experimental result are presented in graphical form and compared for different heating period, viz. 30 min, 60 min, 90 min and 120 min. The calculated and experimental results show reasonable agreement with each other. It is also found that higher time of heating results in more drying of the gel at an accelerated rate. Pressure drop through the gel bed has been calculated for a given air flow rate that can be used for selecting the supply air fan. Finally some recommendations for further work have been given.