Ultrasonically enhanced size reduction of coal. Final report, June 1981-December 1982
Ultrasonically enhanced size reduction of coal. Final report, June 1981-December 1982 Increasing needs for pulverized coal necessitate more efficient grinding. Energy inefficiencies, equipment wear and maintenance are significant cost factors, as is the broad size range of resulting particles; in addition to the unnecessary cost of production, too many fines often make difficulties in processing and flowability; for other applications, coarse particles can plug orifices, valves and nozzles. The work reported examined ultrasonic crushing and grinding of coal, focusing on minimal energy consumption during grinding, narrow product size distribution and improved mineral liberation. Energy consumption during ultrasonic grinding was compared with control tests on identical coal samples ground in a laboratory hammermill. The hammermill required 30.4 kWh/ton to grind a 9 mesh by zero Illinois No. 6 sample to 42.4 percent -200 mesh product. Ultrasonic grinding of the same feed coal consumed only 2.4 to 3 kWh/ton to give an 80 percent -200 mesh product. Product size distribution for ultrasonically ground samples was compared to distributions from ballmill and hammermill tests. In all cases, ultrasonic grinding produced a narrower size distribution. Also, increasing ultrasonic energy input did not alter the product size distribution although it increased the grinding rate. Selective grinding was evaluated by carrying out float-sink analyses of ultrasonically ground more »
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