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

摘要

Coal properties impact the quality of coal combustion by-products. Trackingimpacts can often be difficult, particularly in the eastern United States, because utilitiesuse 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 200 MWboiler.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 two-week periodin order to supply the utility with sufficient fuel for a two-day run. The coal was sampledas a whole channel and benches at the mine, as the shipped coal at the power plant, and asa pulverized coal prior to injection into the boiler. The pulverizer reject, commonlycalled “pyrites” by utilities, was also sampled. Fly ash was sampled from theeconomizers, two rows of mechanical hoppers, and four rows of electrostatic precipitatorhoppers. Bottom ash also was sampled. The plant is not equipped for flue-gasdesulfurization.Analyses on the mine and plant samples include, as appropriate,proximate/ultimate/sulfur forms/heating value, major oxides, trace elements, x-raydiffraction, and petrographic composition. The influence of coal properties on fly ashproperties in this isolated case will be discussed. While specially-arranged burns, such asfor this study, are not representative of the reality of coal purchasing and coal combustionin the eastern US, attempts to follow a single coal through the process can be instructivefor the purposes of understanding the origin and fate of trace elements in combustion.