Investigation of air control on chunkwood combustor

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Virginia Tech


Many small scale agricultural operations such as greenhouses, peanut drying and tobacco curing, use significant quantities of thermal energy. Direct combustion of biomass is a potential source of heat energy for those agricultural applications to substitute for the electricity or fossil fuels (principally LP gas) currently used. However, small scale combustion equipment often operates with low efficiency and high emissions. A prototype chunkwood combustor was installed and tested. The basis for controlling heat output, was the modulation of air supplied to the primary and secondary combustors. Exhaust gas CO and CO₂ concentrations, combustor efficiency, and useful heat output were measured. The cleanest burn was achieved during a forty minute test, where 50 percent of stoichiometric air was introduced at the primary, and 170 percent at the secondary, for a total of 220 percent stoichiometric. The overall average CO/CO₂ ratio for this test was 0.084, and 0.1 is considered to be an average rating for a combustion in a wood stove. Moreover, the efficiency during this test was 52 percent.