Particle emissions from practical combustion systems.

摘要

The health, environmental, and economic effects of particle emissions from stationary combustion systems have been a problem since the start of the industrial revolution and continue to be a concern today. This dissertation presents the results of three studies related to combustion particle formation: rotary kiln incinerator bed temperature, unburned carbon in the fly ash from pulverized coal, and the production of well-characterized surrogate particles for toxicology experiments.; Understanding toxic metal emissions from hazardous waste rotary kiln incinerators requires knowing the temperature of the bed solids. A field investigation showed that the peak bed temperature occurs near the middle of the kiln, not at the end. A modeling study, using an existing computational fluid dynamics-based reacting flow code, showed that the predictions of bed temperature, made using reasonable combinations of operating inputs, overlapped the measurements. Exit gas temperature measurements are not a good predictor of the peak bed temperature due to changes in the gas flow and radiant heat transfer with changes in operating conditions.; Combustion modifications to reduce emissions of nitrogen oxides (NOx) result in increased carbon in the fly ash from pulverized coal. This unburned carbon was shown to be a mixture of ultrafine soot particles and porous particles of unburned char. Techniques were developed to separate the two forms of carbon for quantitative analysis. Under extreme low-NOx combustion conditions, the soot in the furnace exit ash represents 0.2–0.7% of the fuel carbon.; The health effects of fine particles are of increasing concern, but toxicological mechanisms linking specific particle characteristics to observed epidemiological end points remain uncertain. Toxicology studies are facilitated by the use of well-characterized particles from reproducible sources that can be used as surrogates for important classes of ambient particles. Methods were developed to generate size- fractionated particles from coal fly ash and from mineral dusts. These samples have been provided to a collaborating group for studies of the ability of iron to generate reactive oxygen species when cultured human airway epithelial cells are treated with inhalable particles.