Metallic Particle Formation and Growth Dynamics During Incineration

Abstract

A comprehensive model 10 predict the lead aerosol size distribution for typical incinerator operating conditions has been developed. Using the feed rate and incinerator operating conditions, the metal transfer rate to the gas phase is determined using a mass transfer calculation. A detailed, multicomponent aerosol dynamic model is developed accounting for the chemical kinetics and applied to a lead-oxygenchlorine system. Reasonable agreement is obtained between model predictions and experimental data from controlled studies for different aspects of the model. The effect of chlorine on the resulting aerosol size distribution has been determined. The role of the transfer rates of lead to the gas phase on the resulting size distributions have also been determined. Simulations have been performed for typical conditions encountered in a waste incinerator.

Control of Toxic Metal Emissions from Combustors Using Sorbents: A Review

“…First, the properties (such as vapor pressure, surface tension, and density) of the resultant compounds formed are different, and these directly impact the particle-formation characteristics downstream from the combustor. These differences have been illustrated for leadoxygen-chlorine environments by Linak et al 64 and Biswas and co-workers, 35,65 wherein the resultant size distributions of the aerosol formed were very different for lead oxide and lead chloride compounds. Second, the reaction pathways are important for capture and chemical reaction with sorbents.…”

“…The characteristic time for chemical reaction is first estimated for the chlorination and oxidation reactions. Using the reaction-rate constants reported by Lin and Biswas, 35 the reaction rate for formation of lead oxide, R pbO , is estimated to be 3.2 × 10 -3 moles cm -3 s -1 , whereas that of lead chloride, R pbcl2 , is estimated to be 1.12 × 10 -6 moles cm -3 s -1 . Using the initial lead concentration, the characteristic times (calculated using eq 7) for the oxidation reaction and the chlorination reaction are thus 1.45 × 10 -8 s and 4.15 × 10 -5 s, respectively.…”

“…Several studies in the following areas have examined this phenomenon: soils and solid wastes, [36][37][38][39][40] coal, 41,42 mechanistic description of inorganic aerosol formation during suspension heating, 43,44 different waste matrices, 35 and incinerators. 146 Equilibrium calculations provide a quick estimate of the final forms of the metal in the combustor.…”

“…95 Biswas et al 35,65 studied the impact of the chemical kinetics of competing reactions for a lead-oxygen-chlorine system on the resultant aerosol size distribution. Lin and Biswas 35 developed a global, three-reaction mechanism to examine the chemistry in Pb, O, Cl systems. Kinetic data for such reactions is rather limited, and the collision rate theory was used to estimate the reaction rate constants (Table 3).…”

“…The degree of volatilization from the feed matrix and the speciation into different chemical forms (established primarily by radical reactions), which in turn affects the aerosol formation and growth mechanisms, 35 are important steps in the overall process resulting in emissions. Figure 1 illustrates the possible pathways for the metallic species in the gas phase of the combustor.…”