BOND WORK INDEX TEST PROCEDURE FOR DETERMINATION OF THE BOND BALL MILL WORK INDEX The procedure described by Bond (1960) is as follows. The Bond Ball Mill Work Index determination iscarried out in a standard test mill and under standard conditions. The test mill has an internal diameter of 305 mm and is 305 mm long. It has a smooth lining with rounded corners, and no lifters. Theball charge consists of a specified number of balls, weighing approximately 20.1 kg, and ranging in diameter from 15.2 to 44.4 mm (0.6 to 1.75 in.) diameter (43 of 1.75, 67 of 1.17, 10 of 1, 71 of0.75, 94 of 0.61 in.). Mill speed is set at a standard 70 rpm. The circuit being simulated is shown below;
A detailed description of the test procedure follows: 1. 2. 3. The dry feed is crushedto -3360 jam (-6 mesh), using staged crushing. Add the crushed ore, -3.36 mm, to a 1000 mL measuring cylinder to the 700 mL mark, lightly packed and not overly consolidated. Weigh the resulting massof ore, M. The mass M represents the mill charge for each grind. Calculate the Ideal Period Product (IPP) assuming a 250% circulating load (the mass of circulating material is 2.5 times the new feed tothe closed circuit or the screen undersize, at steady state. If the mass of the new feed is 1 and the mass of the circulating load is 2.5 then the mass being ground in the mill is 3.5) IPP = 4. M/3.5Determine the sieve analysis of the feed. Ensure that the test screen size is one of the screens used in the size analysis.
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If the feed sieve analysis showsthat more than 28% is finer than the test screen size, take the number of revolutions for the first period as zero and pass the feed charge directly over the test screen to remove the undersize thenbring the total feed charge mass for the next period up to the desired mass by the addition of a representative amount of new feed. Place the feed charge, Mo, in the mill. Run the mill for N...
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