(93b) Mathematical Modeling of the Mixing of Municipal Solid Waste (MSW) Particles on the Traveling Grate of a Waste-to-Energy (WTE) Combustion Chamber

Nakamura, M. R., Columbia University
Themelis, N. J., Columbia University
Castaldi, M. J., City College of New York

The complex behavior of heterogeneous municipal solid waste (MSW) particles on the traveling grate of a mass-burn waste-to-energy (WTE) combustion chamber affects the steady-state combustion of MSW and often causes an unexpected damage to the walls of a combustion chambers and the traveling grate. In order to understand the parameters that control the combustion processes and designing the grate, we quantified the mixing diffusion coefficient using a stochastic model of MSW particle mixing within a MSW combustion bed. This model was calibrated and validated by means of a full-scale physical model of the Martin reverse acting grate, using tracer particles of sizes ranging from 6 to 22 cm. It was formulated a relationship between the mixing diffusion coefficient and the number of the reciprocating bars in the speed range of 15-90 reciprocations/h of the motion of the reverse acting grate. The ratio of particle diameter to the height of moving bar, d/h, was found to be a major parameter for the mixing diffusion coefficient and the particle residence time at reciprocation speeds exceeding 30 recip./h. Based on these quantitative results and the local MSW particle size distribution, the number of moving bar equipped with the WTE combustion chamber with the grate motion speeds can be designed for optimum operation.