Mercury is widely used in industry because of its diverse properties, which makes it an important part of industrial processes and an important ingredient in many products. However, concern over health issues has led to a 75% decline in industrial demand for mercury over the past 11 years. The objective of this project was to study the reduction of mercury emission from coal-fired combustors by using HCl provided by high-chlorine coals to help convert elemental mercury to oxidized mercury at relatively low temperatures (500-600 degreesC). By oxidizing elemental mercury inside a fluidized bed combustion (FBC) system, total mercury emissions can be reduced with high efficiency and low cost while maintaining low emissions of other pollutants. The results of the study indicate that using high-chlorine coal in an FBC system converted more than 99% of elemental mercury to an oxidized state, mainly HgCl2. Without secondary air injection and after cooling the flue gas to 400 degreesC by using a convective heat exchange tube bank, the typical concentration of gas-phase mercury in FBC flue gas was 1500-3000 ng/Nm(3) flue gas. Better results were obtained by using high-chlorine coals and a predetermined ratio of secondary air (secondary/primary air ratio > 0.15). Only 0.5% of the total mercury input was emitted from the combustor in the elemental form. When a high-chlorine coal was used, close to 55% of the total mercury input was found in the solid phase (bed and fly ash). Of the mercury found in the solid phase, almost none was found in the bed ash because of its high surrounding temperature (850 degreesC). The gas-phase mercury, which was around 45% of the total mercury input, was determined to be primarily in the oxidized state (40%. of the total mercury input), while only a small portion (4.5% of total mercury input) still existed as elemental mercury in the flue gas even when a high-chlorine (0.42 wt %) coal was burned without the benefit of secondary air injection. Our experimental results indicate that the combustion temperature and secondary/primary air ratio are two major factors that influence mercury emissions in an FBC system when limestone is used as sorbent.