with the combination of finer grind and a lower installed power density based on the lower density of the mill charge , a typical ag mill has a lower throughput, a lower power d, and produces a finer grind. these factors often translate to a higher unit power input kwh/t than an sag circuit milling the same ore.
sustainable optimisation of the bell creek sag mill d. felsher1 involved the installation of a low aspect ratio sag mill to replace the secondary crusher. without operational data on the low aspect mill, combined with a site team that was new to sag milling, there were many challenges in achieving the target throughput from the circuit.
after the mill operator sends the start command, the drive system starts to rump up the speed reference very slowly. it is first fixed in a certain low speed reference. in the rudnik project, the sag mill was turning at0.625 rpm 5% of the rated speed atthis stage, while the torque and mill angle were being monitored.
single stage sag/ag milling design abstract single stage semi-autogenous / autogenous s/ag milling has become a common design for a variety of ore types with the advantages of being comparatively low capital cost and flexible for future expansion. the single stage
mill throughput is a key driver for maintaining profitability at mt keith because of the low head grade 0.5% ni and inherently low nickel recoveries due to the mineralogical makeup of the ore. the nickel west mt keith concentrator nmk has 2 parallel grinding modules consisting of one sag mill and one ball mill per module.
sag milling is followed by a 24 x 39 ft, 13 mw ball mill in closed circuit with a cluster of 26 inch 660 mm cyclones. after classification, the milling product is thickened and pumped as feed to carbon-in-leach tanks.
the one sound operators do not want to hear is the sound of the mills standing still. a gold-processing plant, i visited recently valued their sag mill downtime at us$ 130,000 per hour, so extending the life and availability of mill liners is crucial to them. the reduced damage improves the mills availability and minimises the downtime.
these low throughput rates prompted a study with the aim of identifying a practical solution for throughput predictions. the study identi ed an empirical modelling approach based on actual sag mill throughput rates. the empirical model was then optimised by linear programming to identify the ideal feed blend of unweathered rocks to achieve a maximum sag mill throughput.
single stage crush/single stage sag mills and two stage crush/ball mill circuits are typically selected for low throughput plants <50 t/h where personnel costs are a large component of costs. sab circuits are typically selected for plants of 0.5 to 2 mt/a.
outotec grinding technologies 007 the mill drive train to be brought closer to the mill, which in turn allows for smaller foundations and lower installation costs. mill drives most mills are driven by ring gears, with a 360 fully trunnion supported low aspect sag mill
8-3 centrifugal force outward fc mp and 2 dm 2 8.1 and is the angular velocity, mp is the mass of any particle media or charge in the mill and dm is the diameter of the mill inside the liners. gravitational force fg mpg 8.2 the particle will remain against the wall if these two forces are in balance ie.
production capacity in the sag mill is more often than not the constraining factor for an entire processing plant. improving the throughput of a mill by even a few percentage points can thus have a significant impact on the bottom line.
relation between sag mill solid and product p80 both are dependent on feed size. dependent on volume % solids in sag mill. dependent on ball charge volume. hardness of ore. recirculation load. dependent on p80% size. all other parameters are secondary. in general sag mill solids are kept at 70% by wt. operating grinding circuit is an art.
low sag mill critical speed 7 replies seven trustr mill rpm = lower throughput due to lower circulation rate at critical comminution zone near toe of charge where ore changes direction with maximum ore particle pressure and shear work are exerted. seven trustr mill rpm = lower charge lift shoulder height and therefore lower rock pressure at toe,
sag mill liners breakage 26 replies improve ore throughput >10% , liner shell life increase >20% , reduce kw-hours/ton for the liner life cycle to designate p80 vs. existing system. eliminate liner breakage this survey is at no cost to you.
the data were ranked from low to high throughput rates and the corresponding response from the circuit was evaluated. the sag mill controller precursors were assessed for low and high feed rates. the phu kham sag mill control philosophy was referred to during the pi data evaluation.
in the case of the large sag mill referred to in fig. 1, the mills initial volume is 757m 3 when new liners are installed, with the volume on average increasing to 792 m 3 at the end of shell
sag mill process control 13 replies and 1 comment in both case the most important issue is achieve the nominal power capacity and its use in the comminution processes avoid use in move amount . our strategy is use high ball level until the nominal capacity with low speed max 9,5 rpm , like a ball mill.
the new practice of applying full pre-crushing of sag mill feed to substantially increase throughput is challenged as retrogressive and inefficient at a time the industry desperately needs to