Removal of an airborne low volatility metal under fuel-rich and fuel lean conditions through condensation onto soot and/or sorbent particles

The removal by a sorbent of a low volatility heavy metal, barium, from a combustor exhaust stream was investigated experimentally. The barium was introduced into the gas phase through a combustion process simulating incineration of waste materials. Sorbent- and metal-feed-rate, temperature and air intake were varied to study the impact on the gas-to-particle conversion and the metal condensation process. Peak temperature and subsequent temperature drop were found to be the dominant factors affecting the condensation process. Fuel-rich and fuel-lean conditions result in lower peak temperatures and a more rapid temperature drop relative to stoichiometric conditions. Since the metal vapor saturation pressure falls exponentially with temperature a larger condensation rate was observed, as long as nucleation was suppressed. Fuel-rich conditions promote the formation of soot particles. These particles function as sites for subsequent metal-species condensation. Chlorine was injected into the flow, to study the effect on metal vaporization. Chlorine promoted the volatilization of barium and therefore the subsequent condensation capture was made more effective.