Heat efficiency of multi-stage zeolite systems for low temperature drying

This work presents the evaluation of multi-stage adsorption dryers with air dehumidification by zeolite and alumina pillared clay. In a multi-stage dryer product is dried in a number of succeeding stages and for each stage the air is dehumidified by the adsorbent. The exhaust air from each stage is reused for product drying in a following stage after passing a bed with adsorbent. The heat efficiency of the drying system is evaluated and compared with a conventional drying system using air dehumidified by condensation. The evaluation concerns the effect of stage number, inlet dryer temperatures 10-50°C and inlet ambient air 10-25°C. Results show that the performance of the multi-stage adsorption dryers increases with the number of stages and a three stage system is economically most promising. For varying ambient air conditions, zeolite as adsorbent is the most favourable.