Coal is prepared for use by crushing the rough coal to pieces less than 2 inches (5 cm) in size. The coal is then transported from the storage yard to in-plant storage silos by rubberized conveyor belts at rates up to 4,000 short tons per hour.
In plants that burn pulverized coal, silos feed coal pulverizers that take the larger 2-inch pieces, grind them to the consistency of face powder, sort them, and mix them with primary combustion air which transports the coal to the furnace and preheats the coal to drive off excess moisture content. A 500 MWe plant may have six such pulverizers, five of which can supply coal to the furnace at 250 tons per hour under full load.
In plants that do not burn pulverized coal, the larger 2-inch pieces may be directly fed into the silos which then feed the cyclone burners, a specific kind of combustor that can efficiently burn larger pieces of fuel.
In plants that burn pulverized coal, silos feed coal pulverizers that take the larger 2-inch pieces, grind them to the consistency of face powder, sort them, and mix them with primary combustion air which transports the coal to the furnace and preheats the coal to drive off excess moisture content. A 500 MWe plant may have six such pulverizers, five of which can supply coal to the furnace at 250 tons per hour under full load.
In plants that do not burn pulverized coal, the larger 2-inch pieces may be directly fed into the silos which then feed the cyclone burners, a specific kind of combustor that can efficiently burn larger pieces of fuel.
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