Impact of coal properties on coal combustion by-product quality: examples from a Kentucky power plant

Coal properties impact the quality of coal combustion by-products (CCBs). Tracking impacts can often be difficult, particularly in the eastern United States, because utilities use blended coal feeds to meet their quality specifications. To circumvent this problem, we made arrangements for a single seam/single mine coal to be burned at a 220-MW wall-fired boiler. The feed coal is a medium sulfur, high volatile A bituminous Dean (Fire Clay) seam from Knox County, eastern Kentucky. The coal was mined over a 2-week period in order to supply the utility with sufficient fuel for a 2-day run. The coal was sampled form one location (as a whole channel and benches at the mine), as the shipped coal at the power plant, and as a pulverized coal prior to injection into the boiler. The pulverizer reject, commonly called "pyrites" by utilities, was also sampled. Fly ash was sampled from the economizers, two rows of mechanical hoppers and four rows of electrostatic precipitator (ESP) hoppers. Bottom ash also was sampled. Analyses on the mine and plant samples include, as appropriate, proximate/ultimate/sulfur forms/heating value, major oxides, trace elements, X-ray diffraction, and petrographic composition. The influence of coal properties on fly ash properties in this isolated case will be discussed. While specially arranged bums, such as for this study, are not representative of the reality of coal purchasing and coal combustion in the eastern US, attempts to follow a single coal through the process can be instructive for the purposes of understanding the origin and fate of trace elements in combustion. (C) 2004 Elsevier B.V. All rights reserved.