Calorific values of the volatile pyrolysis products of wood

Two simple physical and chemical models of a burning wood-waste fuel bed have been developed in order to predict the influence of fuel and operating parameters on particulate emissions from this source. First, a quiescent overfeed fuel bed is considered. Mass and energy balances along with assumptions for off-gas compositions are used to establish the bed off-gas temperature, composition, and bulk flow velocity. These have been used to predict entrainment of fuel particles. Second, the potential for fluidization of the fuel bed under typical operating conditions is considered. A simple comparison of bulk flow velocity with the minimum fluidization velocity for the bed is used as a criterion for fixed bed/fluidized bed operation. The ejected char and ash particles from the fluidized bed are included as part of the entrained particle stream in order to predict particulate emissions with a fluidized fuel bed. These two models are then used to predict the influence of undergrate airflow rate, fuel feed rate, and fuel size distribution on particulate emission from a wood-waste boiler.