Seeking to take advantage of the reduced fuel costs and lower emission profile using Powder River Basin (PRB) coal, AEP elected to proceed with fuel blending changes to Tanners Creek Unit 4. The plant currently blends up to 40% PRB with Eastern bituminous coal. The primary goal of the project was to increase the maximum fuel blend percentage of PRB coal to 80% from 40% while reliably maintaining the unit's performance. A secondary objective of the improvement project was to install systems that would allow for the firing of up to 100% PRB. Like most of the plants considering a change to PRB, Tanners Creek Unit 4 was faced with limitations due to the high moisture content, lower heat value, lower ash softening temperature, and high calcium content fly ash of PRB. Also, since PRB is more friable, the plant had significant safety concerns associated with an increased PRB usage. The above issues were present in the existing factors that had limited the PRB blend to 40%. These factors included the coal handling system configuration, a limitation of the coal crusher fineness, inadequate equipment to control boiler slagging and fouling, fly ash handling limitations, and an inability to properly address the hazards of PRB coal. Working closely together, AEP and Sargent & Lundy determined and implemented the changes necessary to reliably burn the 80% blend. The changes included new coal handling equipment, new crushers installed in a new building, additional soot blowers and the addition of water cannons, economizer hoppers and the re-installation of a furnace gas tempering system to the boiler. Changes to address the hazards of PRB included dust control improvements, additional wash down and vacuuming provisions, electrical equipment upgrades and the extension and updating of the fire protection system.
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