Ultrasonic Vs Mechanical Comminution of Coal 2: Final Report, July 1, 1984-February 28, 1986

摘要

The USDOE is currently exploring the possibility of using ultrasonic energy to grind coal. The economics of the method appear very favorable; however, little is known about the nature of the ultrasonically produced product. This investigation fills the information gap by characterizing ultrasonically ground coal (using scanning electron microscope/image analysis methodology) and comparing the results with equivalent data derived from conventional grinding equipment. Size, shape, and mineral liberation data were acquired from -140, -200, and -325 mesh Upper Freeport and Illinois No. 6 coal samples ground by ballmill, hammermill, and ultrasonic methods. A comparison of the results shows that the ballmill and the ultrasonic grinders produce similar, narrow size distributions when compared to the hammermill. The shape of the size distribution curves does not vary significantly as a function of size reduction. Statistical analysis of measured and derived shape factors indicates that particulate shape does not vary with grinding method, grind size, or coal type. Visual scanning electron microscope studies confirm this finding. The percentage of mineral matter liberation was found to increase with size reduction; mineral matter liberation percentages are also generally higher for the softer Upper Freeport coal. The percentage of mineral matter freed by ultrasonic grinding is roughly comparable to ballmill and hammermill methods in the -140 and -200 mesh size ranges and is clearly superior in liberating efficiency at the -325 mesh size. Ultrasonic comminution appears to be slightly less efficient than conventional grinders in the area of pyrite liberation. 12 refs., 23 figs. (ERA citation 12:008808)