OCR Text |
Show Coal Crushing The first step in processing the coal was done at a coal preparation plant where it was washed and crushed to below 5 cm (2 in.) in diameter and shipped to IGT. The coal was then crushed by a hammer mill to minus 3.2 mm (1/8 in.) and was dried during the crushing process. Raw Coal Hopper and Screwfeeder Raw coal, 3.2 mm (1/8 in.) and below, was fed to the fluid energy mill with an inclined screwfeeder attached to a large hopper. The screwfeeder transports the raw coal, 3.2 mm (1/8 in.) and below, from the bottom of the hopper to the fluid energy reduction mill at a rate of 45 to 115 kg/hr (100 to 250 lb/hr) by varying the rotation of the screwfeeder with an adjustable speed gear motor. Figure 6 shows the hopper and screwfeeder installed along with other equipment of the milling system. Air Compressor Compressed air used by the fluid energy mill to grind the coal was supplied by a Worthington Rollair Stationary Air Compressor with a capacity of 13.6 SCM/min at 6.8 atm (480 SCF/min at 100 psig). Fluid Energy Reduction Mill The raw coal, 3.2 mm (1/8 in.) and below, was reduced in size by the fluid energy reduction mill by accelerating the coal particles with pressurized air causing the particles to collide and fracture. The particles collide until their size is reduced in the cyclonic flow (as in a cyclonic separator) to given dimensions. The particles are then entrained by air exiting the mill and are carried to the dust collector. The fluid energy reduction mill used was a Jet-O-Mizer Model 0405-C fabricated by Fluid Energy Processing and Equipment Co. Reverse Pulse Dust Collector The fine-ground coal/low-pressure air mixture (125 mm or 5 in. wc) leaves the fluid energy mill and is tranported to the dust collector for separation. The coal is separated from the air and the air is vented to the atmosphere, and the coal falls to the bin below. 12 |