Simulating municipal solid waste incineration with a DEM/CFD method – Influences of waste properties, grate and furnace design

Abstract

The current work presents an initial approach of using a particle based method (Discrete Element Method, DEM) to simulate municipal solid waste (MSW) incineration on grates. Therefore, an in-house DEM code has been coupled with FLUENT. Models have been formulated for drying, volatile release and char conversion. The volatiles released are converted in the furnace above the waste bed which has been calculated with FLUENT. A comparison of simulations with measurements in an existing MSW incineration plant of CO2, O2, H2O and temperatures above the bed is presented. Agreement is fair considering the measurement uncertainties and the complexity of the process. In a sensitivity study concerning the influence of waste composition (heating value, number of waste fractions), waste particle size distribution and radiative flux onto the waste bed on conversion has been carried out. Finally, the most common grate systems, backward stoking, forward stoking and roller grates have been compared briefly, including different types of furnace geometries above the bed. The results demonstrate that the approach developed gives new insight into the complex interaction of waste movement, waste conversion and gas phase combustion above the bed which can’t be obtained with other approaches, like continuum models for the waste bed.