operating at 90% of its maximum power. The combined power draw of the SAG mill and ball mill was 8658 kW, which caused partial over-grinding. From experience in processing plants outside of China, the power rating of the ball mill should be higher than that of the SAG mill [5]. The pebble crusher had an over-powered configuration.
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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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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 into a SAG mill power optimisation strategy. SAG mill discharge control is quite involved due to few interactive variables, such as mill discharge sump level, classification
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Toor targeted the throughput, energy consumption and product size of the SAG mill, optimized the liner structure, and quantified the benefit of using shorter life liners. The results presented indicated that liners with a reduced mass and shorter life outperform their longer life counter parts in all key production parameters of throughput
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The SGI equation uses a transfer size between a SAG and ball mill; it is proposed that a synthetic transfer size of 2100 µm be used to model single-stage SAG mills. 5.9ˇ √˙˝ ˛ . ˚ 0.96 0.985˜ !"# ˝ $ ˝ √˙˝ %&’() (2) where: SGI is the SAG Grindability Index, minutes, P80 is the SAG hydrocyclone overflow 80% passing size, µm
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The performance of tumbling mills is sensitive to the volumetric mill filling which influences grinding media wear rates, throughput, power draw, and product grind size from the circuit. Each of these performance parameters peaks at different filling values. In order to contin-uously optimize mill operation, it is vital to
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size in the SAG circuit product. Iterations of these para-meters can be performed in some models (e.g., DJB’s “Reduced Recovery” and “Millpower2000”) to determine the desired motor power and drive rating, the maximum design mill speed, and the maximum design ball charge volume (Barratt, 1989). For single pinion and dual pinion drives
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and 2100 µm, respectively. The value T80 is the “synthetic” transfer size between the SAG mill and ball mill – a fines-corrected 80% passing size2 of the SAG mill product (or the combined SAG mill product and crushed pebbles if the circuit is sending crushed pebbles to the ball mill circuit, a.k.a. SABC-B operation). The EF4RM for
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This refers to high-aspect AG/SAG mills. Ball Charge Motion inside a SAG Mill. With a higher density mill charge. SAG mills have a higher installed power density for a given plant footprint relative to AC mills. With the combination of finer grind and a lower installed power density (based on the lower density of the mill charge), a typical AG
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AG/SAG mill feed, trommel screen undersize product (-5.00 +0.00 mm), ball mill discharge and cyclone feed, overflow and underflow have been conducted in order to characterize the particle size distribution in the products and to carry out mass balancing of grinding circuits. Furthermore, an
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Depending on the mill size the SAG mills draws between 2 MW and 17 MW. The product from the SAG mill is further reduced in size using pebble crushers and ball mills. Hence, typical gold or copper ore requires between 2.0 and 7.5 kWh per ton of energy to reduce the particle size.
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The analysis of the influence of ball sizes in SAG grinding hasn''t been developed in detail by considering the effect on process parameters inside the mill, grinding efficiency or internal classification. Historically a conventional grinding reference has been made on the empirical procedure developed by Azzaroni (1980).
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Download scientific diagram | Configuration and performance of the SABC circuit (on the case of maximum theoretical processing capacity) from publication: New developments and optimization of Wu
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This work is aimed at optimizing the SAG mills feed size distribution as this is an important parameter that affects milling performance after ore competency. A lot of operations have recognized the optimization opportunity that can be taken advantage of by manipulating the feed size distribution to improve SAG milling efficiency.
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circuit. The Kinross Paracatu new grinding circ uit consists of one 11.6 x 6.7m (38’ x 22’) SAG mill with. installed po wer of 20MW, followed by two 7.3 x 12.2m (24’ x 40’) ball mills with
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Download scientific diagram | Configuration and performance of the SABC circuit (on the case of maximum theoretical processing capacity) from publication: New developments and optimization of Wu
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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 into a SAG mill power optimisation strategy. SAG mill discharge control is quite involved due to few interactive variables, such as mill discharge sump level, classification
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How to Control a SAG Grinding Mill Circuit circuit and the primary mill must then be run at less than its capacity to keep from overloading the secondary mill. If the critical size is above 13 mm, it will build up in the primary mill circuit filling the primary mill with ore too fine to be effective as grinding media but too coarse to
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SAG MILL BALL MILLS MILL DESIGN DATA. These projects involved SAG mills from 26 to 36 ft in diameter, with installed power in the range 9.7 to 16.8 MW using single, twin pinion, and gearless technology for drives over 16 MW. The ball mills used varied from 13.5 to 25 ft in diameter, with installed power in the range 1.85
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If a SAG mill were to go down 15-20 years ago, there would have been other mills in the comminution circuit that an operation could fall back on. Production would fall, but it wouldn’t cease entirely. Lost production, caused by a SAG mill outage, can add up to as much as €100,000/hour, in some cases
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The modeling and simulation of semiautogenous (SAG) mills have been widely used in the design and optimization of mill performance in terms of its power draw, processing capacity and product size
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The breakage rate function shape of the SAG mill is largely governed by the mill load particle size distribution and mill speed. The feed in the mill contains fractions of ore that serves as the grinding media. Larger ore fractions break the smaller particles but also breakdown themselves and exit the mill as a product.
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The crushed pebbles fall directly onto the SAG mill feed belt and return to the SAG mill. SAG mill product feeds two parallel ball mills of 6.6 m×11.1 m (internal diameter×length), each with a 9.7 MW twin pinion drive. The ball mills are operated at a ball charge volume of 30–32% and 78.5% critical speed.
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(very low recycle loads) the transfer size is a product of the feedra te, the operation o f the AG/SAG mill and it s geomet ry and not the o ther way arou nd. T o borrow an e xpress ion f rom the
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How to Control a SAG Grinding Mill Circuit circuit and the primary mill must then be run at less than its capacity to keep from overloading the secondary mill. If the critical size is above 13 mm, it will build up in the primary mill circuit filling the primary mill with ore too fine to be effective as grinding media but too coarse to
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Further optimization is achieved through the use of a sepol ® separator, which separates the finished product from the ground material. The grits separated out by the separator are fed back into the mill as recirculating material; this prevents overgrinding of the finished product in the ball mill discharge.
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the required SAG comminution of test ore material. Specific energy consumption (SEC) measured in kWh/t is a ratio of the mill drive power to the milling circuit output, without regard to circulating load. At the constant size of the cycle feed and discharge, SEC is a prime characteristic of material grindability in a certain ore pretreatment
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Current operational results show that the SAG mill is operating at 5% ball charge level by volume and is delivering a K80 800 micron product as predicted. Power drawn at the pinion is 448 kW, 13.617 kWh/tonne (SAG mill) and 570 kW, 17.325 kWh/tonne (ball mill) when processing 32.9 mtph, for a total of 30.942 kWh/tonne or 14.6% above the
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AG/SAG mill feed, trommel screen undersize product (-5.00 +0.00 mm), ball mill discharge and cyclone feed, overflow and underflow have been conducted in order to characterize the particle size distribution in the products and to carry out mass balancing of grinding circuits. Furthermore, an
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Figures 8 and 9 on the right show results from a gold plant’s SAG mill achieved with MillStar’s Segregated Ore Feed Controller combined with the Power Optimiser: • The standard deviation of the mill feed control is greatly reduced. • The cyclone feed is more stable, allowing for consistent size separation and feed to downstream processes.
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