Key Points for the drying process in biomass pellet production from sawdust

Sawdust is the primary raw material for producing biomass pellets. However, its moisture content often fluctuates significantly; attempting to pelletize such material directly frequently leads to issues like loose, structurally weak pellets, low calorific value, and accelerated wear on the pelletizing dies. Drying serves as a critical intermediate stage in biomass pellet production; effectively managing the drying process is essential for ensuring consistent product quality and minimizing production losses.

Raw Material Pre-treatment: Incoming sawdust, wood shavings, and similar materials must first be screened to remove hard impurities—such as stones or metal—that could damage the drying and pelletizing equipment. Clumped or wet material should be broken up beforehand to ensure uniform feeding and prevent uneven drying.

Moisture Content Control: The optimal moisture content for biomass pelletizing is between 12% and 18%. Since raw, wet sawdust often has a moisture content exceeding 40%, it should not be subjected to rapid, high-temperature drying. Such an approach would dry out the outer layer while leaving the interior moist, which can lead to moisture re-absorption (re-dampening) during the cooling phase.

Drying Temperature Management: As a highly flammable biomass material, sawdust requires careful temperature control for safety. The temperature at the feed end should not be too high, as this could cause the sawdust to char or ignite. A rotary dryer is typically used for continuous, low-temperature drying, allowing for stable, controlled hot-air temperatures and reducing the risks of dust-related fires or spontaneous combustion.

Cooling and Buffering: Dried, hot sawdust should not be fed directly into the pelletizer. A cooling and buffer silo is necessary to lower the material's temperature and equilibrate its moisture content, which helps prevent the pellets from cracking due to uneven moisture distribution.

System Integration: A dust collection system should be matched to the production capacity to capture airborne particles generated during drying. Airflow must also be carefully regulated: excessive airflow leads to unnecessary heat loss and higher energy consumption, while insufficient airflow reduces drying efficiency. A stable drying process is the foundation for consistent output and cost reduction in any biomass pellet production line.