Análise Experimental de uma Fornalha a Lenha de Fluxo Co ...

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ABSTRACT
It has been shown that the grain drying process accounts for most of the energy
expenditure along the post-harvest phase. Most of the Brazilian drying mills use
counter-current flow woodburning furnaces to produce warm air near 100 ºC. On the up
side, wood is a renewable source of energy. On the down side warm air generated in
such furnaces contains high amounts of tar, carbon monoxide, soot and particulate
matter that further compromises the grain quality. It also presents high risks of fire
ignition inside the dryers. Furthermore those furnaces are difficult to control and thus to
deliver the proper air temperature. This work presents an exploratory study of a
concurrent furnace to meet thermal energy needs of dryers while meeting air drying
quality standards. We built a 40kW furnace to investigate the influence of three different
grate sizes, three different wood feeding regimes. We also operated the furnace under
natural and induced draft. That lead to eighteen different experiment set-ups. We
observed carbon monoxide concentration and temperature of the flue gas, and also
operational aspects in each run. Results showed that concurrent wood burning furnaces
can be very successful in providing low levels of carbon monoxide, of tars and of soot as
well. It also showed near constant temperature levels of drying air. Energy wise, the
average performance of the furnace was around 75%.
Key words: clean burning, biomass, pollutants emission.