
Why Measure Moisture in Biomass Pellets?
Moisture level in woody material is critial to meet end-product quality and profit goals.
RAW MATERIALS | MEASURED CONSTITUENT | ENVIRONMENTS | PROCESS LOCATIONS | TARGET MOISTURE PERCENTAGE | FINISHED MATERIALS |
Hog Fuel
Micro Chips Sawdust Lumber |
Moisture | High Temperature
Dusty |
Belt Conveyor
Screw Conveyor |
Before dryer: <15%*
After dryer: <8%* |
Wood Pellets
Pellet Fuel |
The moisture level in woody material in pellet production is critial to meet end-product quality and profit goals. Pellets that are too wet can result in incomplete combustion, leading to heating instability. Additionally, stored pellets with a high moisture content can cause microbiological activity, which can lead to sponstaneous combustion in silos. Overdried pellets are also vulnerable because they become fragile, compromising integrity and finished product quality. Unmonitored drying leads to increased energy consumption.
Typical Pellet Production Process
Raw Material Delivery – Large batches of raw materials varying from sawdust, wood chips, hog fuel, micro chips, lumber and trees unsuitable for lumber. This feedstock may be freshly cut, partially dry, or kiln dried. Some manufacturers use sifters or separators to remove non-wood materials such as metal, plastics or rocks.
Chipper – A chipping machine breaks down large non-uniform wood pieces into smaller wood pieces.
Hammermill – Hammermills grind wood pieces into consistent small pieces. These micro chips (3mm) could have wide and inconsistent moisture content ranges.
Dryer – Large high-heat dryer drums, convection ovens, or air blowers dry the sawdust to a consistent moisture level, usually less than 15 percent.
Pellet Mill – The dried sawdust is pressed through heated pellet dies at high pressure. The naturally present lignin, a complex organic polymer, acts as a glue to hold the pellet together.
Cooling – Now hot and soft, pellets must be cooled and dried, usually with blown air. The finished materials moisture content should be no higher than eight percent. Storage or Packaging – Cooled, dry pellets are stored in silos for bulk shipping or bagged for immediate distribution.
*Typical measurements, subject to change per manufacturer’s requirement
SENSORTECH RECOMMENDATIONS
NIR-6000 Industrial-Grade Moisture Analyzer
Location Recommendation:
- After drying process
- Mounted to belt or screw conveyor
Process Control:
The detected moisture value can be transmitted to your PLC, then programmed to adjust the speed of the dryer conveyor.
Benefits:
- Controlled drying process to meet optimal finished pellet quality
- Lowered energy costs
- Reduced waste
- Safer silo storage
- Package weight targets met
- Improved ongoing profit margins
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