Processing woody debris biomass for co-milling with pulverized coal
The USDA, Forest Service, Forest Products Lab funds several grants each year for the purpose of studying woody biomass utilization. One selected project proposed removing small diameter stems and unmerchantable woody material from National Forest lands and delivering it to a coal-fired power plant in Alabama for energy conversion. The Alabama Power Company will test the utilization of the woody biomass in one of their energy production facilities to determine the feasibility of this new market. The Talladega National Forest and the Gadsden Steam Plant are serving as the demonstration areas for the project.
One of the first steps in this project was to select in-woods processing equipment. The biomass fuel to be created in this project must meet unique criteria that differentiate fuel chips created for the power plant from those of typical fuel chips. The wood fuel was to be created from whole-tree chips and co-milled with coal. Biomass specifications were primarily limited by size so that the chips would pass through the current fuel handling system in the plant. In addition, the fuel chips must have edges that are fairly clean and sharp to prevent plugging fuel pathways in the plant. One of the initial steps in the project was to examine output from a variety of in-woods processing equipment to determine which could meet the specifications with one-pass processing. After further review, it was determined that a cutting action, as opposed to a shearing action, was needed to meet the raw material handling requirements within the plant. Output from a specially equipped horizontal grinder was the final equipment choice.