Agricultural and Forest Waste Feasibility Study

Appendix E: Wood Fuel Pellet Technologies

The process to produce wood fuel pellets involves a raw material of random particle size such a sawdust or other wood waste with a nonuniform water content is carried by a conveyor to a hammermill.  The conveyor separates rocks, metals and other foreign material form the wood

At the hammermill, particle size is adjusted to a uniform maximum dimension, which is approximately 85 percent or less of the minimum thickness of the pellet to be produced.  The product from the hammermill is transported to a rotary drum type dryer where the moisture content of the uniformly dimensioned wood particles are reduced to a range of 16 to 28 percent (dry basis).  

The particles are then moved by conveyor to a pellet machine where the material is fed into a hopper and pressed through a ring-shaped die to the desired shape and diameter for producing compression within the die to cause the temperature of the wood material to reach 325 to 350 degrees F.  Pellet mill load pressures may vary from 8,000 to 40,000 lb/in2 and depend largely on die design.

Examples of pellet products manufactured by the patented processes are listed below along with a brief description of the type and quality of these products.

Woodex

Woodex is refined from almost any organic, fibrous material, including wood waste, bagasse, agricultural waste and peat.  The moisture content of the is product is approximately q0 percent, and has low ash content, no sulfur content, and carbon dioxide emissions equal to the carbon dioxide released into the atmosphere if the raw material were left to naturally decompose.  Natural resins service a as binder for the product which has a bulk density of approximately 35lb/ft and produces about 9,000 BTU per pound of wood pellet fuel.

Lignetics

This product is a densified wood fuel manufactured by a proprietary process from wood waste including sawdust, wood shavings, bark, hog fuel, and trash wood.  A small amount of a polystyrene additive, estimated at approximately 1 percent by volume, is used to facilitate the formation of dust-free pellets, lubricate the dies in the pellet machine, increase the calorific value and accelerate the burning rate.  These pellets produce about 1 percent ash when burned, have moisture content of less than qp percent, and produces 8,500 BTU of energy per pound of wood pellet fuel.

 Roemmc

This product is  fuel pellet, which may be used as a heating fuel for residential and commercial/industrial applications.  The pellets are manufactured from wood, straw, nut hulls, bagasse, corn cobs and peat.  The moisture content of the feed material must not exceed 5 percents.  The average bulk density of the final product is about 40 lb/ft and produces about 8,500 BTU of energy per pound of wood pellet fuel.

Last updated: October 21, 2008