The ball mill oversize feed factor (EF 4 BM) is always calculated with the rod mill work index for the optimum feed size and the ball mill work index for EF 4 BM. The model assumes that the calculated value of E ssbm + the specified contingency is greater than the sum of E sag + E peb; otherwise E bm will be negative.
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SAG = SAG mill specific energy from F 80 152 mm to T 80 1.7 mm (kWh/t) R = SAGDesign test mill revolutions (revs) Ms = SAGDesign test mill charge mass (g) K a = Correction factor for feed size K b = Correction factor for pebble crushing T 80 = Mill transfer size, 80% passing (µm) W BM = Ball mill specific energy from T
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size to balance the distribution of power output between primary and secondary grinding, will have been based on mill speed and shell liner/lifter simulations and, particularly, ball charge volume and ball top size, both of which are dependent upon the contingency applied to the transfer size in the SAG circuit product. Iterations of these para ...
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The Ball Charge in SAG and Ball Mills, in other words, the fraction of the mill volume constituted by balls, has a significant impact on the performance of a mill and the greater Grinding circuit. Running at the wrong Ball Charge adversely impacts not only throughput but the consistency of the product particle size (P80) as well.
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With high aspect ratio SAG mills total charge to ball charge ratio should be greater than 2 (up to 2.5) for a coarse mill feed (say F80 > 110 mm). If the mill feed size is fine, say 50 mm or 30 mm, then you are looking at a total charge to ball charge ratio of about 1.5-1.6.
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Material ranging in size from 25mm to ... (19–75 mm) from a SAG mill. At the optimum pebble content of 25% by volume, a 25% saving in steel ball consumption and a 15% saving in energy ...
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SIZE: SAG milling grinding media are available in sizes from 4.0" to 6.5" or ... The theoretical apparent packing density of the balls in a ball charge is 282 lbs/cu-ft or 4,520 kg/m3. Spec Sheet Download ... tension, and optimal head seating are critical components to reduce mill shut down risk. Our product line includes: Oval head liner ...
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Even the SAG ball charge needs to be adjusted based on the size and hardness of ore it's working on. Too many grinding balls can prematurely wear out the grinding balls themselves. Operating a mine mill requires balancing a dynamic set of tradeoffs.
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According to available literature, the operating speeds of AG mills are much higher than conventional tumbling mills and are in the range of 80–85% of the critical speed. SAG mills of comparable size but containing say 10% ball charge (in addition to the rocks), normally, operate between 70 and 75% of the critical speed.
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CHARGE LEVEL. Maintaining an optimum charge in a SAG mill remains one of the fundamentals for efficient mill processing. If the charge level or the ball to charge ratio is incorrect, breaking liners and/or increasing power consumption is inevitable and can only result in degraded mill efficiency.
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The final plan was to increase the ball charge in the SAG and ball mill to 10% v / v and 27% v / v, respectively; set the upper limit of the operating power in the ball mill to 5800 kW; use a TC Series crusher (without a power-/feed rate–controlling device, but with a feed bin) to crush pebbles for recirculation back to the SAG mill feed ...
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optimization of sag mill circuit · optimized the oper ating strategies for the SAG mill circuit at Paracatu op eration in Bra zil. The focus of this project was to reach design t hroughput and final grinding product size, conditions . Mar 21, 2007· The optimal performance of AG/SAG mills is the key to successful plant operation.
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operation of SAG mills. SAG mills are currently the technology of choice in hard rock milling operations for reducing primary-crushed ore to ball mill feed. In recent years, the trend has been towards larger-sized SAG mills with diameters of 10.4 m (34 ft) and above, with the largest being 12.2 m (40 ft) in
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SAG Mill Discharge. Controlling the feed and discharge of a mill is mostly a stabilisation exercise – you need to be able to quickly and accurately control the mill feed rate. If the mill feed setpoint is changed, then the actual feed rate needs to stabilise at the new target in a short period of time. The feed rate setpoint can then be tied ...
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This paper compares the performance of a 25/75 pebble/ball (volume ratio) composite charge to ball-milling, under conditions typical for a ball-mill in SABC circuits, i.e. a large ball top size ...
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APPLICATION ENVIRONMENT For SAG milling applications, the diameter of the balls, mill and throw action of the charge provide for a high impact environment - therefore a balance must be achieved between abrasion resistance and impact resistance in SAG balls to …
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3 SAG mill (8 – 15% ball charge) Variable competency ore 4 High ball charge SAG mill (15 to 25% ball charge) Incompetent ore 5 Low ball charge SAG mill, high mill speed. (4% ball charge, 90% Nc) A cross between AG and SAG for competent, abrasive ores. As typically operated in RSA. 6 SAG mill (configurations 3, and 5 ) with recycle crusher
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The SAG Mill has a "small" circulation load of oversize given be the 3/8″ trommel screen and the 1/2″ x 1 1/4″ discharge grates. The load of 4″ balls in this SAG is "good" but un-measured. SAG Ball consumption is "average" at 400 g/t while Ball Mill grinding media (3″ balls) usage in 550 g/t.
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MINE LINERS Magotteaux. The two main functions of a mill liner consist in protecting the mill shell against wear and in transmitting the energy of the mill motor to the grinding charge to carry out the required size reduction in the most efficient way For a mill liner the design as well as the liner material are to be considered The required movement of the mill charge to carry out effi
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What's the Difference Between SAG Mill and Ball Mill. Nov 26, 2019· The biggest characteristic of the sag mill is that the crushing ratio is large. The particle size of the materials to be ground is 300 ~ 400mm, sometimes even larger, and the minimum particle size of the materials to be discharged can reach 0.1 mm.
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The biggest characteristic of the sag mill is that the crushing ratio is large. The particle size of the materials to be ground is 300 ~ 400mm, sometimes even larger, and the minimum particle size of the materials to be discharged can reach 0.1 mm. The calculation shows that the crushing ratio can reach 3000 ~ 4000, while the ball mill's ...
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The AutoCharge system is primarily suitable for SAG mill balls (100–150 mm). As each ball rolls through the counting chute, an electro-mechanical limit switch is activated, signalling the counter. Each count is added to the last, allowing a continual increasing total count of balls to enter the mill over a set time period.
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and optimal grinding charge trajectory for the SAG, Ball and Rod Mills. • Identified potential benefits could be obtained with an ideal grinding media charge, mill speed as well as optimisation of lifter profile (specialty lifter face 20 angle) which is directly related with mill power draw, internal motion of mill charge,
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mill with a 30 mm graded ball charge and a 30% filling degree. The mill discharge pulp density was increased from 68.8% to 75.9% solids. The data is summarized in Table III. The example in Table III illustrates that the density has a large influence on the grinding efficiency. In this case, the optimum %<75 µis in the region of 73.4% or 1.989 kg/l
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SAG m ills use a ball charge of 8 to 21%. The largest SAG mill is . ... [Show full abstract] of size reduction methods involved in mineral processing using crushing equipments. Crushing is the ...
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5 to 50 TPH SAG Mill. Starting as small as 13 feet (4 m) in diameter on 330 HP and as large as 24′ (14.5 m) in diameter on 3,300 HP, the 911MPE Semi & Fully Autogenous Mills tumble crushed ore without iron or steel grinding media. They are used when the crushed ore pieces are hard enough to perform all the grinding.
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While critical-size could be of any dimension, it is most typically synonymous with pebble-crusher feed, with a size range of 13—75 mm. Critical-sized particles can result from a simple failure of a mill's breakage rates to exceed the breakage rate of incoming particles, and particles generated when breaking larger particles.
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In semi-autogenous grinding (SAG), the grinding mill inventory, (i.e. volume of total charge, volume of ball charge, etc.) is important in determining the optimum operating condition for maximum production (tph), minimum specific energy (kwh/t) or lowest cost ($/t). A two-dimensional graphical method is presented for determining the actual ball charge within …
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"In recent years, the trend to smaller top-size ore feed into SAG mills has been matched by a trend toward smaller but more balls in the SAG mill charge. High ball-to-rock ratios and low overall mill charge levels are now widely used. These practices can result in periodic loss of rock charge and ball-on-liner damage," said Royston.
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Rod mill：The rod mill has the highest efficiency when the feed size is <30mm and the discharge size is about 3mm with uniform particle size and light overcrushing phenomenon. SAG mill: When the weight of the SAG mill is more than 75%, the output is high and the energy consumption is low with a light degree of over-crushing.
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SAG mills mimic the same shortcoming. It follows that in order to obtain the specifi c energy (SE) to achieve a certain transfer size, based on the 80 per cent passing value, an ineffi ciency factor must be applied to the SE of single stage ball mills, rod mills or AG/SAG mills when calculating power according to the Bond Third Theory method.
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mill discharge product size in relation to the lifting effect of the liners. In this specific case, it is obvious that a certain load expansion is needed to allow the coarse particles entering the media charge to be reduced. Therefore, at this stage, a direct measurement of the dynamics in the mill gives very valuable information to the operator.
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As mill feed competency and feed size changes, the optimal volumetric mill filling for maximum feedrate changes. The weight setpoint is adjusted by either an experienced operator or an advanced process control system in response to the feed changes. The SAG mill weight measurement combines mill shell mass, charge mass and liner mass.
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respect with SAG mills being increasingly less sensitive as the ball charge is increased (Morrel S and Valery W, 2001). 2.2. EFFECT OF FEED SIZE DISTRIBUTION ON SAG MILLING The qualitative effect of changes in particle size distributions (PSD) on the SAG mill performance can be addressed by using the grind curves.
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When the feed size of a SAG mill becomes coarser, i.e. α r increases, the energy required to break the ore increases, i.e. φ r and φ f increases (Morrell et al., 1996; Morrell and Valery, 2001 ...
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Before making a change in the SAG mill ball size it is important to test it first in simulation.
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