Study Of Heavy Meatal Vaporization Kinetics During MSW Incineration In Fluidized Bed

Thermal treatment has been considered as a more effective approach to handle growing municipal waste quantities because of the advantages of minimization, sanitation, stabilization, and resource recovery by pyrolysis or incineration. However, almost all of the components of MSW contain some quantity of the heavy metals, which are categorized as toxic at certain concentrations.The objective of this study is to propose a method for determining the kinetics of heavy metal (HM) release from model wastes in fluidized bed. This method is an inverse method which involves only the HM concentration evolution in exhaust gases, and a model developed at the reactor scale. On the one hand, the thermal treatment of metal-spiked model wastes was performed in a lab-scale fluid bed incinerator. A complex matrix, derived from real waste, was spiked with heavy metal and burned in order to simulate the metal release during municipal solid waste incineration. An on-line analysis system was set to the gas outlet of the reactor, it enabled to track the metal vaporization process: the relative HM concentration variation in exhaust gases was measured continuously by ICP-OES. On the other hand, a bubbling bed model was developed, which calculates the HM vaporization rate from its concentration profile in the outlet gas. The direct model of fluidized bed for the reaction system is developed in the paper. The experimental vaporization rate measured with mineral matrices is used as inlet parameter in the direct model, to calculate the concentration of heavy metal in the outlet gas. The sensitivity of parameters k andαis analyzed to the concentration of HM. An inverse model is developed to permit the calculation, for any kind of matrix, of the metal's rate of vaporization from the concentration profile of gas at the outlet. The method is applied to the realistic artificial wastes spiked with heavy metals to predict the rate of vaporization from the measured concentrations of outlet gas.The inverse method consists in identifying the HM vaporization kinetics at the particle level from only the on-line diagnostic results and using the model.