DRYING OF SOLID-FUEL PARTICLES IN HOT GASES

Drying of solid fuel particles in hot gases (50-200 degrees C) is stud ied both theoretically and experimentally. The measurements are carrie d out by using a thermobalance reactor constructed for drying and pyro lysis studies of particles up to 30 mm by diameter. The model is based on the solution of the conservation equations for mass and energy. Th e drying is considered to consist of three successive periods: a short initial heating period, period of constant rate of drying and period of falling rate of drying. It is assumed that the particle moisture di stribution is uniform during the constant rate of drying. Shrinking co re model is assumed for the falling rate period. Besides fuel particle s, the model is applicable also for other solid particle drying proces ses. Model calculations are compared to measurements for wood chips. T he model can predict the effect of the main parameters reasonably well . These main parameters affecting the drying rate are: particle size, particle shape, initial particle moisture content, gas temperature and gas moisture content, temperature of the reactor walls and slip veloc ity. The irregular shape of practical fuel particles can approximately be simulated as one-dimensional case (plate, cylinder, sphere) by usi ng an equivalent volume to surface area ratio.