Driven by fuel availability, economics or emission compliance considerations, the amount of PRB coal fired in the U.S. power plants has been increasing considerably over the past decade. However, in most cases, it is a challenge for the power plants to convert to PRB coal if the existing boiler and fuel handling system were originally designed to fire higher quality bituminous coal. Not only will firing PRB coal increase slagging and fouling in the boiler, it will also require an increase in mill system capacity and primary air flow and/or temperature to enable proper drying since PRB coal typically has high moisture content and relatively low HHV. This paper presents an upgrade implemented on the Atrita pulverizer system at James River Power Plant of City Utilities of Springfield to accommodate a desire to fire 100% PRB coal. Discussion will focus on mill system design considerations exclusively for PRB coal application, operational results of the upgraded mill system and the latest mill design improvement for better coal fineness, improved emissions and lower fly ash unburned carbon.
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