Prediction of Conversion of a Packed Bed of Fuel Particles on a Forward Acting Grate by the Discrete Particle Method (DPM)

Abstract

The objective of this contribution is to present a discrete approach that descibes thermal conversion including drying, pyrolysis and combution of wooden fuel partricles on a forward acting grate. Contratry to continuum mechanics approaches for a moving bed, the Discrete Particle Method (DPM) considers a bed to consist of individual fuel particles that may have different sizes, shapes or material properties. For each particle conversion and motion are predicted, so that the entire proces is the sum of all individual particle processes. Conversion is described by one-dimensional and transient differential conservation equations for mass, momentum, species and energy while the Discrete Element Method is employed to predict motion of partilces. The particulate phase is coupled to the gaseous phase in the void space of a moving bed by heat and mass transfer. It is described by well established empirical correlations and defines in conjunction with a CFD-approach temperature, species and velocity distribution for the gas pas phase in the void space.