Optimisation study of a large waste-to-energy plant using computational modelling and experimental measurements

In order to maximise the energy recovery efficiency of waste-to-energy plants, it is important to understand the physical processes that are occurring within the furnace. A mathematical model of the furnace section of a large waste-to-energy plant was constructed using FLIC to model combustion of the solid waste particles on the furnace grate and FLUENT to model the gas flow above the burning waste bed. The two models were coupled through their respective boundary conditions. A numerical simulation of the design-case setup of a large waste-to-energy plant was performed, which predicted the presence of a large flow recirculation zone in the radiation shaft. Further numerical simulations were performed using several different configurations of the secondary air jets, which revealed that the large flow recirculation in the radiation shaft could be avoided by changing the distribution of secondary air jets. Experimental measurements of the temperature profile within the burning waste bed of the plant were made using a Ball instrument. The predicted and experimentally measured temperatures within the waste bed compared quite well, but further experimental data is required for validation of the temperature and velocity fields of the gas in the over-bed region.