May 15, 2015 In general, therefore, the required mill power is calculated using the following equation. where n is the number of efficiency factors, EFi, used and fo is the feed rate of new ore to the mill. The power calculated from equation 2 can be looked up in published tables (Rowland and Kjos, 1978) and the correct mill size and type can be selected
For ball mill, Bond (1958) was proposing an empirical formula giving the top size of balls (make-up balls) DM function of the feed size xG (80% passing size - m), the ore true specific gravity sg, the ore Bond Work Index Wi (kWh/st), the fraction of critical speed fc and the inside mill diameter D (m):
Ball Size Distribution In practice, at mill startup, instead of charging a single size of ball, usually a range of ball sizes is initially added.7.6 A ball mill is to produce a grind of 34 micron (Pso) product from a feed size of 200 microns at a rate of 1.5 t/h
Jun 01, 2018 Fig. 5 shows the variation of size class 1 (M1) with the milling time for the two feed size distributions. For this coarser feed the 50 + 20+10 mm ball diameter mix breaks the material at a faster rate compared to the other ball matches. The availability of a ball size for a particular feed size ensures breakage occurs at a faster rate
Ball mills tumble iron or steel balls with the ore. The balls are initially 5–10 cm diameter but gradually wear away as grinding of the ore proceeds. The feed to ball mills (dry basis) is typically 75 vol.-% ore and 25% steel. The ball mill is operated in closed circuit with a particle-size measurement device and size-control cyclones
8.3.2.2 Ball mills. The ball mill is a tumbling mill that uses steel balls as the grinding media. The length of the cylindrical shell is usually 1–1.5 times the shell diameter ( Figure 8.11). The feed can be dry, with less than 3% moisture to minimize ball coating, or slurry containing 20–40% water by weight
Feb 13, 2017 Types of Mill Feed Chute. Scoop Feeders for Ball-Rod Mills are made in various radius sizes. Standard scoops are made of cast iron and for the 3′ size a 13″ or 19″ feeder is supplied, for the 4′ size a 30″ or 36″, for the 5′ a 36″ or 42″, and for the 6′ a 42″ or 48″ feeder
Jul 03, 2017 The procedures in the two tables have one fundamental difference; in table 32 the feed to the rationed ball load was increased on account of the extra efficiency of the rationed sizes, whereas in table 33 the feed was maintained at the same rate but the mill speed was reduced
Bond would say ideal feed is 80% -16mm for a 13 W.I material. If the Material has a higher W.I. there is a Bond formula to calculate the ideal feed size for a normal 1.5 to 1.8 L/D ratio rod mill. Dependent upon the Material and the Process! I seen feed as large as 100mm on soft material
Jun 19, 2015 The ball mill motor power requirement calculated above as 1400 HP is the power that must be applied at the mill drive in order to grind the tonnage of feed from one size distribution. The following shows how the size or select the matching mill required to draw this power is calculated from known tables ‘the old fashion way’
had decreased for the -2 mm +1.4 mm mono-size feed compared to the bigger -4 mm +2.8 mm mono-size feed. This therefore shows that should the material feed size continue to decrease, the smaller balls will perform better than the larger balls during milling, as was mentioned by Katubilwa et al. Effect of ball diameter size on mill power draw
Number, size and mass of each ball size depends on mill load and whether or not the media is being added as the initial charge. For the initial chargin of a mill, Coghill and DeVaney (1937) defined the ball size as a function of the top size of the feed, i.e., d †“V =
Material feed size: ≤ 8 mm Final fineness: ~ 5 m Setting of vibrational frequency: digital, 3 - 30 Hz (180 - 1800 min-1) Planetary Mills 12 . 13 Planetary Ball Mill PM 400 Feed material: soft, hard, brittle, fibrous (dry or wet); Material feed size: 10 mm; Final fineness 1 m;
Jul 26, 2017 Under the right operating conditions, high power rate crushing can bring mill feed size down to near 80% passing 7,000 microns and finer, which can be handled more efficiently by ball mills. Based on average field observations, the crushers can do this for less than half the energy and between one-tenth and one-twentieth of the metal consumed in a rod mill
The feed size to ball mill shall be smaller than 25mm, the output size can be adjusted by revising steel balls ratio. Applied materials: copper, magnetite, molybdenite, zinc ore, iron ore, gold, hematite, fluorspar, lead, zinc, manganese, tungsten, marble, granite, slag, cement, limestone, clinker, coal, etc. Different Types of Ball Mill:
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