market-based advanced coal power systems final report - National ...

Operation Description
Market-Based Advanced Coal Power Systems
For the purposes of this conceptual design, limestone will be delivered to the plant by 25-ton
trucks.
The limestone is unloaded onto a storage pile located above vibrating feeders. The limestone is
fed onto belt conveyors via vibrating feeders and then to a day bin equipped with vent filters. The
day bin supplies a 100 percent capacity size ball mill via a weigh feeder. The wet ball mill accepts
the limestone and grinds the limestone to 90 to 95 percent passing 325 mesh (44 microns). Water
is added at the inlet to the ball mill to create a limestone slurry. The reduced limestone slurry is
then discharged into a mill slurry tank. Mill recycle pumps, two per tank, pump the limestone
water slurry to an assembly of hydroclones and distribution boxes. The slurry is classified into
several streams, based on suspended solids content and size distribution.
The hydroclone underflow is directed back to the mill for further grinding. The hydroclone
overflow is routed to a reagent storage tank. Reagent distribution pumps direct slurry from the
tank to the absorber module.
Technical Requirements and Design Basis
• Limestone usage rate:
– Maximum limestone usage rate = 30,250 lb/h = 15.15 tph plus 10% margin = 16.6 tph
(based on operating at MCR; 155 tph firing rate for design coal and 80% CaCO3 in the
limestone)
– Average limestone usage rate = 25,700 lb/h = 13 tph (based on maximum limestone usage
rate multiplied by 85% capacity factor)
• Limestone delivered to the plant by 25-ton dump trucks
• Total number of trucks per day = 16
• Total unloading time per day = 4 hours
• Total time, interval per truck = 15 minutes/truck
3.1-13 December 1998