The Use of Selective Bunkering to Optimise PRB Utilisation at Nanticoke Generating Station

Many stations are currently blending Powder River Basin (PRB) coals with bituminous coals to various blend ratios. However, this blending is almost always accomplished at the port, coal yard or a dedicated blend facility — i.e. prior to introducing the coal to the unit. As a result, the pulverizers and burners are forced to deal with two (or more) disparate coals, compromising the performance of these systems. Research originating in Europe confirms the negative repercussions of grinding and firing dissimilar blends. This paper will describe the “Selective Bunkering” system in place at Ontario Power Generations Nanticoke GS which involves feeding the pure parent coals to individual mills and conducting blending in the furnace. This innovation has increased the maximum PRB blend ratio from 50% to 70% at full load and also allows for a seamless transition to 100% PRB firing at lower loads. The techniques employed to coordinate and optimize the combustion system will be discussed.