In the biomass pellet production chain, the drum dryer is the "key hub" connecting raw material pretreatment and pelletizing. Its core value lies in clearing the "raw material obstacles" for the subsequent pelletizing process by accurately controlling the moisture content, uniformity and physical state of the material - if the material properties do not meet the standards, even if the pelletizer has strong performance, there will be problems such as low molding rate, soaring energy consumption, and increased equipment wear. The optimization function of the drum dryer is essentially to lay the "raw material foundation" for efficient pelletizing through "targeted transformation" of material properties.

1. Precise control of moisture content: the "first threshold" of pelleting

The natural moisture content of biomass materials (such as wood chips, straw, and sawdust) varies greatly (the moisture content of straw is usually 20%-40%, and the moisture content of fresh wood chips can reach more than 50%), and the "golden moisture content range" for pelleting is 12%-15%: if the moisture content is too high, the material is easy to stick to the pelletizer mold, causing blockage (the downtime and cleaning time increases by more than 30%), and the pellets are easy to mold; if the moisture content is too low, the material becomes more brittle and is easy to break during molding (the pellet integrity rate decreases by 20%-30%), and the wear rate of the pelletizer roller increases by 50%.

2. The drum dryer solves this problem through the "hot air circulation + gradient drying" mechanism:

Countercurrent/cocurrent drying design: When the material contacts the hot air in the opposite direction (countercurrent), the high temperature section (80-120℃) quickly evaporates the surface moisture, and the low temperature section (50-70℃) deeply dehydrates to avoid "dry outside and wet inside"; the cocurrent design is suitable for high-fiber materials (such as straw), and the hot air and the material flow synchronously to reduce the uneven drying caused by fiber entanglement.

Intelligent humidity closed-loop control: Equipped with an online moisture content sensor (accuracy ±0.5%) and a variable frequency fan, the hot air temperature (fluctuation range is controlled within ±3℃) and the drum speed (adjustable from 5-15r/min) are adjusted in real time to stabilize the final moisture content of the material at 12%-15%, which is more efficient than traditional drying (moisture content fluctuation ±5%) or oven drying (energy consumption is 30% higher).

Take wood chip pelletizing as an example: when undried wood chips (moisture content 45%) are directly pelletized, the forming rate is only 65%, and the machine needs to be stopped twice per hour to clean the mold; after being processed by a drum dryer (moisture content 13%), the forming rate is increased to 92%, the average daily downtime is shortened from 4 hours to 1 hour, and the energy consumption per ton of pellets is reduced by 18%.