Behavior of hazardous and radioactive metals in a laboratory furnace and a demonstration-scale incinerator

The behaviors of hazardous and radioactive metals in analytical and real combustion conditions were observed to understand their vaporization and to predict their release into the atmosphere at a real incineration plant. In the laboratory furnace experiment, vaporization fluxes were obtained based on the measurement of weight losses with temperatures. Vaporization fluxes were compared to maximum theoretical fluxes obtained from the Herz-Knudsen's kinetic theory of gas. The vaporization coefficient, α, for volatile metal chloride appears to be a characteristic value of the evaporating substance, not varying with increasing temperatures. With some theoretical considerations on interfacial equilibrium, mass transfer coefficient of vaporization, K_G, was determined as a function of absolute temperature. To evaluate the behavior of metals and radionuclides in an incinerator and off-gas treatment system, test burns of simulated waste containing several toxic metals and radioisotopes were performed at the demonstration-scale incineration plant. The previously analyzed characteristics of volatilization of hazardous metals and radioactive nuclides were used to explain their distributions in the demonstration plant. The decontamination factor for low-volatility species was above 10⁵, which was equivalent to the removal efficiency of particulate matter in the plant. The factors for semivolatile components were in the range between 10² and 10⁴, showing the strong dependency on volatility.