Mechanisms of Particle Entrainment and Combustion and How They Affect Emissions from Wood-waste Fired Boilers

An analytical model of a spreader-stoker wood waste fired boiler has been developed for pre­ dicting the size of the largest particle which can be entrained by the upward motion of the furnace gases. This model is based on an entrainment model which equates particle in-situ settling velocity to furnace gas velocity and uses a stirred reactor mod­ el to evaluate furnace conditions. The effects of excess air, furnace size, fuel moisture content, and steam generation rate on furnace temperature and entrained particle size are demonstrated. Calcula­ tion of the burning rate of small wood particles under furnace conditions are presented and it is shown that the larger particles entrained by the gases are not significantly reduced in weight by combustion during their passage upward through the furnace.