Control of toxic metallic emissions formed during the combustion of Ohio coals. Final report, September 1994--March 1996

The objective of this project was to characterize metallic emissions from representative coals and develop strategies for their control. A technique for flue gas desulfurization is the use of calcium based sorbents, and the degree of metals capture of these sorbents under different conditions will be researched. The objective of the first year of the study was to understand the evolution of metallic aerosol size distributions and the capture characteristics of various sorbents. Also, the metallic emissions resulting from the combustion of two seams of Ohio coals were to be characterized. Studies on the evolution of the metallic aerosol size distributions have been completed and the use of silicon and calcium based sorbents for capture of lead species has been examined. Co-injection of metallic compounds along with organometallic silicon indicated a high degree of capture of lead in a certain temperature region. Preliminary results with calcium based sorbents also indicate capture of metallic species. In the second year, the work was extended to examine three different aspects: (1) understanding the mechanisms of capture of metals by vapor phase sorbents; (2) role of chlorine in speciation of metals and its importance in metals capture; and (3) capture of mercury by aerosol transformation. It was established that aerosol formation rates for Hg species is rather slow under typical combustion conditions, and hence would not be an effective way of capture of mercury. However, the use of titania based sorbents have provided exciting results. This is being developed further for effective capture of Hg species in combustion environments. Several theoretical investigations were also carried out to better understand and predict trace metal behavior in combustion environments. Publications and conference presentations resulting from work this year is listed