PFI Report: Smaller chips, bigger bins mean more pellets
July 25, 2011
By Scott Jamieson
July 25, 2011 - Pellet expert Clyde Stearns extolled the virtues of micro chips and bigger surge capacity as keys to enhanced pellet mill efficiency at the 2011 Pellet Fuels Institute 2011 Annual Conference.
The wood products efficiency veteran from Buhler treated delegates to a shopping list of design and operating tips to get the most production and best quality from their plants. Key factors include the quality and consistency of raw materials, and on that subject Stearns discussed the many benefits of using micro chips to feed your plant. Created either by stationary chippers or the new generation of mobile horizontal grinders, these micro chips combine the consistent size distribution typically seen in pulp chips, with 100% sizing below 3/8 inch.
According to Stearns, benefits include relative ease of adjusting and measuring moisture content (MC), more consistent MC within and between chips, increased grinding capacity, increased drying efficiency, and an overall boost in plant production using the same equipment.
Stearns also discussed the benefits of adding more surge capacity at two key points in the production process: at the bins after the dryer and again between the grinder and the pelletizers. "If you have eight hours surge capacity after the dryer, the moisture content in the chips will completely equalize, which will really enhance the downstream process. That's not practical, but even an hour will make a significant difference." Somewhere between 30 minutes and an hour of storage time after the fine grinders will have a similar effect, he added.
"The result of focusing on raw material – size distribution, variability, moisture – is a more stable operation. Overall, your pelleting process should become routine if you can supply
a more consistent raw material. Often when there is an issue at the
pelletizer, you'll see a lot of people standing around it trying to
solve the problem. They would likely be better off going back to the raw
material and trying to improve that."
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