5 Low ball charge, high speed SAG mill (4% ball charge, 90% Nc) A cross between AG and SAG for average competency, abrasive ores. Typically operated in RSA on Witwatersrand Gold Ore Driefontein (Underground), Kloof, Jacobina 6 SAG mill with recycle crusher (8 15% ball charge) Competent ores, better suited to coarse grind sizes. High aspect ...
A SAG mill grinds through the impact of rock and grinding media, while an autogenous mill grinds only through the impact of rock. An autogenous mill is more suitable for smaller particle size requirements, while a SAG mill is more suitable for the roughing process and is a relatively mature process. A SAG mill has advantages,
The rotation speed of a mill is an important factor related to its operation and grinding efficiency. Analysis and regulation of the optimal speed under different working conditions can effectively reduce energy loss, improve productivity, and extend the service life of the equipment.
especially in fixed speed mills. Often selected when low steel contamination is required. 2 AG mill + a recycle crusher Competent ore relatively homogenous (the recycle crusher is used to balance the rate of impact breakage within the circuit) 3 SAG mill (8 15% ball charge) Variable competency ore 4 High ball charge SAG mill (15 to 25% ball
Principle of SAG Mill operation SAG mill. SAG is an acronym for semiautogenous grinding. SAG mills are autogenous mills that also use grinding balls like a ball mill. A SAG mill is usually a primary or first stage grinder. SAG mills use a ball charge of 8 to 21%. The largest SAG mill is 42' () in diameter, powered by a 28 MW (38,000 HP ...
A well implemented SAG control philosophy should be able to vary the mill speed, in response to variations in feed characteristics. If the feed ore becomes softer, then the mill control system should respond to reduce the mill speed. You may not need to keep adding grinding media either, if the issue persists too long.
With our SAG mill running at % critical speed (mill RPM), the SER motor speed reference is 850 RPM or 85% of 1000 RPM. We are recovering approximately MW of slip energy; the...
Ball mills and SAG mills, vertica l grinding mills for raw or finishing sec tions all have a constant torq ue speed characteristic, however the starting torques, comminution process and material ...
... This study also showed that the milling power had a linear relationship with the height and distance of the lifters (S/H) and the milling speed. Recently, Jahani Chegeni and Kolahi [23] have...
INTRODUCTION The sequential steps required for the design of any grinding circuit, have changed dramatically in the last seven years. Previously, it was considered necessary to do six foot diameter SAG mill pilot plant tests on representative samples of minus six inch ore (F80), in order to understand design requirements.
Most of these mills are driven by adjustablespeed drive 2000 m (6000 ft) above sea level; synchronous machines, connected to cycloconverters or load 3) lowfrequency output, because large diameter grinding commutated inverters (LCIs) controlling the motor speed and mills must rotate at variable low speeds, in the range from torque [2], [8].
exhibits many of these aspects. Maintaining the SAG mill weight at the optimum value is critical for achieving maximum grind rate efficiency and mill production (Powell,, van der Westhuizen,, Mainza, 2009). However, SAG mill weight is difficult to control as the dynamic response changes as the mill approaches maximum capacity.
The second step to decreasing high wear rates was to reduce the maximum operating speed on the SAG mill from RPM (78% of critical speed) to RPM (75% of critical speed). Justifications were made for the installation of an Omnicone crusher on the SAG pebble oversize material.
Universal mills are classified as high speed rotor pulverizers or disintegrators and produce a finer product compared to coarse crushers or impactors. Selection of the proper crusher, grinding mill or pulverizer is dependent on the material to be processed and the requirements of the end product.
In my experience, SAG Mills are normally variable speed, and Ball Mills are normally fixed speed. There are multiple ways to provide variable speed, the common ones are WRIM+LRS+SER or SCIM+VSD, the top of the range is gearless mill drives.
Nowadays, experimental semiautogenous (SAG) mill and dropweight test are used for evaluation of grinding circuit regarding changes in feed particle size distribution, size of the ball, speed of mill, prediction of energy required, and product size distribution for complete grinding in AG and SAG mills.
According to available literature, the operating speeds of AG mills are much higher than conventional tumbling mills and are in the range of 8085% 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.
at the kiln or mill shell at normal operating speed when the main drive is operating. • Full load running torque required at the kiln or mill shell at inching operating speed. Typically this is set at 120% of main drive operating torque. • The desired output speed at the shell. Usually this is targeted at RPM with a range of +50% / 10%
A Bowler. The report outlines the path Siemens and OK Tedi Mining undertook together from the initial stages of the drive train Audit in 2014 to the subsequent definition of the scope and ...
Single Stage SAG Mill. Using SAG instead of AG increases the capacity as well as application range, but will also increase wear costs and still be dependent on "natural" product size being close to the desired. Common circuit in the US and Canada . Single stage SAG mill circuit [image: (135625)]
the correct power required to grind ore in a SAG mill, by developing ore hardness variability ... mill speed or friction, that causes the cascading ore and steel (in this case 10% steel was used) to hit the shell more than 30o before the ... For the operating load range just beyond the optimum performance conditions, a linear model ...
Modeling SAG Mill Performance. ... To achieve an appropriate range for the variables of interest, throughput should be varied over a relatively wide range. For the high tonnage tests feed rates should be increased to meet or exceed the normally acceptable load on the SAG mill motor, or load in the mill, whichever has been identified as the ...
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 times the shell diameter (Figure ). The feed can be dry, with less than 3% moisture to minimize ball coating, or slurry containing 2040% water by weight.
SAG mill depends on the simulation time (mill actual working time) and the limitation of the rated power. The mill speed, fill level ratio, and steel ball ratio can significantly affect mill operation, and our conclusions can provide a reference for an actual situation. Keywords: SAG mill; DEM; mill power; mill speed; steel ball ratio; fill ...
This index is obtained by a batch grinding test, where two kilograms of ore are ground in a standardised mill setup (10 cm diameter by 30 cm long). The index is obtained by a mathematical ...
Rod mills speed should be limited to a maximum of 70% of critical speed and preferably should be in the 60 to 68 percent critical speed range. Pebble mills are usually run at speeds between 75 and 85 percent of critical speed. Ball Mill Critical Speed . The black dot in the imagery above represents the centre of gravity of the charge.
Singlestage SAG mills can be very beneficial in reducing capital costs for plants with a staged throughput approach, according to FL, which markets the FullerTraylor line of SAG mills that range from 14 to 40feet (ft) in diameter. When future tonnage needs to be increased, the SAG Mill can feed downstream ball mills to boost capacity.
The pump speed is varied to maintain a limited range of levels in the discharge hopper. The mill is controlled to maintain a constant mill weight and circulating load (see control philosophy above). ... Some circuit were initially designed for more abrasive primary ores and required SAG mill comminution testwork. Typically, larger than normal ...
The simulation of the digital model captures an increase in production of % as a function of mineral fragmentation, while there is potential to increase production by decreasing the mill rotational speed, which has a decrease in energy consumption of % for all linear age configurations.
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 mm. The calculation shows that the crushing ratio can reach 3000 ~ 4000, while the ball mill's ...
Mill speed can be adapted to upstream and downstream processes avoids overgrinding, and optimizes load distribution between SAG and ball mill (Mular, Halbe Barratt, 2002). Power consumption is influenced by load respectively torque and mill speed. This means that further energy can be saved if a mill speed below the rate speed is re
Increasing the speed of the mill above the design point of 74% critical speed was also considered but did not result in greater power draw of the mill due to the mill motor design (Dunne et al ...
PDF | On Jan 1, 2011, A. P .P van der Westhuizen and others published Milling curves as a tool for characterising SAG mill performance | Find, read and cite all the research you need on ResearchGate
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