Biomass feedstock drying is a key operation for producing durable and storage stable pellets. The operation reduces the average moisture content from about 50 per cent (wet mass basis) to five – seven per cent. The rotary drum dryer is the most common type of dryer used for this task [1, 2]. Depending on the moisture content of the biomass, the operating temperature for such dryers is around 300-600 C . Such a high temperature maximizes the moisture evaporation rate and shortens the residence time of biomass in the drum. The revolving drum tumbles the wet biomass as the drying air passes through the dryer. A series of lifters in the drum pick up the material and drop it through the air stream to maximize heat transfer efficiency. Heavy particles remain in the drum for a longer time while smaller and lighter particles pass through faster.
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