Condensation of lead dichloride fume on silica particles in a hot gas stream

Incinerators are capable of destroying hazardous industrial waste forever in a large volume. However, they can cause air pollution such as heavy metal emissions if the feed stocks contain such metals. Particulates less than one micron in size are difficult to remove with current technologies. These fine hazardous metal emissions limit the application of incineration as a way of waste disposal. Since removal efficiency is a lot higher for larger particles, it is desirable to increase the particle size of the metal fumes generated when feed materials containing heavy metals are incinerated. A process has been developed where selected particles are introduced into a hot gas stream contaminated with metal fumes. It is anticipated that these particles serve as agglomeration agents or condensation sites for the hazardous vapor. Lead dichloride. produced by hydrochloridation of a lead oxide pellet, is chosen as a test model fume; whereas silica particles, generated in situ by the combustion of hexamethyldisiloxane vapor in air, act as the agglomeration or condensation agent. This work studies the effect of silica particles on the size distribution of lead dichloride fumes at temperatures 350, 450, 550 and 650°C. A general increase in the size distribution toward the larger particles has been observed at 350, 450, and 550°C, but not at 650°C. For instance, the peak shifts from 0.02 μm to 0.07 μm at 450°C. In conclusion, this study has identified a possible agglomeration or condensation agent that can result in the shift of the particle size distribution to larger sizes, which in turn may result in higher removal efficiencies in scrubbers such as the venturi types.