Airflow resistance of chunkwood

Continued interest in biomass for energy, together with efforts to improve the utilization of available biomass, has led to the introduction of a new fuel form called ?chunkwood.? Chunkwood particles are pieces of wood that 1) are much larger than whole-tree chips and require less energy to produce; 2) have a higher bulk density; and 3) can dry faster under certain conditions. The purpose of this study was to define several forms of chunkwood, document their character, and determine their resistance to airflow. These types of data are needed to design or select chunkwood combustion and drying systems or equipment. Three chunkwood forms were studied: whole-tree, delimbed, and reduced chunks. In addition, pulp chips were included for comparison. The test method consisted of measuring the pressure drop that developed across a given quantity of material when subjected to a known airflow rate. A 15-square-foot test chamber was used to subject 2- to 4-foot depths of material to six airflow rates ranging from 50 to 1,000 cubic feet per minute. Delimbed chunks had the least resistance, whole-tree chunks had the highest resistance, and the resistance of the reduced chunks was between the two. All three chunkwood forms exhibited less resistance than chips. Chunks developed from 40 to 77 percent less pressure drop than chips.

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