Magnus Ståhl

Validation of a Mathematical Model by Studying the Effects of Recirculation of Drying Gases

Drying is a costly and energy-consuming process. Consequently, it is of great practical importance to improve its energy efficiency. Our objective, therefore, is to develop and validate a theoretical drying model by studying the recirculation of drying gases. The results show that the amount of recovered energy over the condenser and the dryer efficiency increase with increased recirculation within our test range, implying an energy-efficient operation. The validation shows that the model correlates well with industrial data collected from a full-scale dryer (diameter 3 m, length 9 m, capacity 5 MW) at a Swedish wood fuel pellet plant. Accordingly, it should be possible to use the model industrially to predict capacity changes and recovered energy when changes in drying gas recirculation are made.