Discrete element method (DEM) modelling has been used to systematically study the effects of changes in mill operating parameters and particle properties on the charge shape and power draw of a 5m ball mill. Specifically, changes in charge fill level, lifter shape (either by design or wear) and lifter pattern are analysed. The effects of changes to the properties of the charge (ball fraction ...
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When the charge volume of cylpebs is between 20% and 35% in the wet ball mill, cylpebs can be replaced by ceramic balls of the same single mass, with the total weight of the ceramic balls being ...
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Steel balls as traditional grinding media are prone to excessive fines generation and high energy consumption. Therefore, in light of this problem, the authors investigated another media—ceramic balls based on the output characteristics of fine particles. This study discusses the effect of ceramic balls on the change of the particle size distribution, zeroorder output characteristics, micro ...
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In SAG milling, wear speeds are dependent on ball size and ball charge volume. The relative performance of high Cr balls to forged steel balls is dependent on the milling environment: a) In high wear rate applications like SAG and primary grinding, the high Cr ball has 0 30% lower wear. b) In low wear rate applications, the high Cr relative ...
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The first one is the Mines Constancia SAG mill of size 36 × ft. The mill is operating at 72% critical speed and 26% mill charge volume. The mill is fitted with trapezoidshaped high and low lifters. The operating power draw was reported to as between and MW.
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End and shell liner design in these mills is much the same as for SAG mills. The effect of liner design on performance is equally as important. For instance, in an iron ore operation using m (21 ft.) mills, mill throughput was increased by 15 percent and power consumption reduced by 13 percent by liner redesign alone.
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the lifters and also reduced the modeled impact of the ball charge on the unprotected liners above the slurry pool. The discovery of excess mill pooling in the SAG mill prompted a review of the "pumping" capacity of the SAG mill. The excess slurry pool inhibited grinding and caused unnecessary power draw
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Effect of Balls Hardness on Rate of Grinding Tests by Coghill and Devaney show that the hardness of the balls has some effect upon the rate of grinding in mill. These results are plotted in Fig. and it is seen that, both for dolomite and chert, there is an increase in the rate of grinding with increasing hardness of ball.
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Low capital investment alternatives such as the optimisation of the SAG mills lifter/liner design, pulp lifters, ball charge level and ball size were studied in the SAG mill circuit as well as an ...
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The effect of shell liner on mill performance has been the subject of various studies (Parks, 1989, ... Another main factor influencing the SAG mill performance is the charge motion inside the mill which has been ..., Mishra,, 1996. Dynamics of ball and rock charge in SAG mills. In: Proceedings Advances in Autogenous and SAG ...
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The ball charge is a function of the bulk fraction of the SAG mill volume (Jb) occupied by balls; the ore retained in the mill is the result of the volumetric filling which depends on the ore size distribution (specially the % +6″ and the % −6″ +1″), on the rotational speed (N/Nc) and on the solid concentration by weight fraction inside ...
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The effect of feed size distribution on SAG mill performance is highly dependent on the grinding circuit flow diagram (whether the SAG mill is in open circuit or i n closed circuit with cyclones as
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Also, an increase in the mill speed may direct the ball charge to the mill shell/liner rather than the rock load and promotes balllinerlifter damage and unnecessary waste of energy (Almond and Valderrama, 2004). Accordingly, this would imply less breakage rate since preferential impact grinding condition would be restricted.
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The same conditions apply in sag mills. However, in this case the required balance between coarse and intermediate size rocks is different to that for ag mills. This is because the steel balls in the sag mill do the duty of the larger rocks. As a result the more balls that are loaded into the sag mill the fewer larger rocks are required.
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Mill grind out In order to measure the ball load in the mill, the feed to the mill was stopped and it was ground out to a ball charge only. As a result of slurry pooling in the mill, the surface of the charge could unfortunately not be inspected, and the % ball level was measured relative to the slurry, 398mm below it.
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The shell liner type, rotation speed, and ball filling percent are the key factors influencing the charge behavior inside the SAG mills, and consequently, their performance.
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PilotScale SAG Mill Facility Will Help to Optimize Charge Motion and Slurry Flow in PlantScale SAG Mills Reducing Energy Consumption The mining industry operates approximately 80 semiautogenous grinding mills (SAG) throughout the United States. Both mine and mill site variables determine SAG mill performance, capacity and grindsize.
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Abstract and Figures. An increase of over 10% in mill throughput was achieved by removing the ball scats from a single stage SAG mill. These scats are non spherical ball fragments resulting from ...
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Cleary et al. (2008) used energy spectra to understand energy utilization in a 36′ SAG mill; a 4 m diameter cement ball mill; a grinding table and an Isamill. Morrison et al. (2009) used such energy spectra to analyse the similarities and differences in performance of tower and ball mills.
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In semiautogenous grinding (SAG), the grinding mill inventory, ( 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 twodimensional graphical method is presented for determining the actual ball charge within the total charge when parameters ...
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The specific rates of breakage of particles in a tumbling ball mill are described by the equation S i = ax α i (Q(z), where Q(z) is the probability function which ranges from 1 to 0 as particle size equation produces a maximum in S, and the particle size of the maximum is related to ball diameter by x m = k 1 d variation of a with ball diameter was found to be of the form ...
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performance (power draw, kWh/t and operating work index) is also presented a product of for each simulation. For Greenfield design of an AG/SAGball mill circuit with JKSimMet, the additional power requirement in the ball mill(s) is determined with the Bond ball mill work index and the phantom cyclone technique. COMMINUTION
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Cleary et al. [5] studied the effect of ball mill rotational rate on charge behavior and mill power, and in 2001, Cleary et al. [6] first applied 3D DEM to calculate the operating power of a SAG mill. The performance of the SAG mill is greatly affected by its structural and operating parameters and the characteristics of the rock material in ...
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of the simulation results, a laboratoryscale SAG mill with dimensions of cm × cm is simulated. The results obtained indicate that the Osborn liner, due to the angularity
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Overcharging results in poor grinding and losses due to abrasion of rods and liners. Undercharging also promotes more abrasion of the rods. The height (or depth) of charge is measured in the same manner as for ball mill. The size of feed particles to a rod mill is coarser than for a ball mill. The usual feed size ranges from 6 to 25 mm.
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SAG mill liner development draws primarily on practical experience from SAG milling operations supported by computerbased modeling of charge motion in SAG mills and on established good design practice. Liner design needs to respond to the process aspects of mill liner action that are critical to good SAG mill performance,, the impact of shell liners on the grinding action and of grates ...
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> Engineering approaches have highlighted mill performance with mill modelling and the use of improved materials > Liner design,with the advent of large diameter SAG mills, the issues of design, selection, monitoring and evaluation of mill performance is critical > Mill trajectory modelling can be used to great effect in improving liner design
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In this research, in order to find a suitable range for the number of lifters in the liner of ball mills, the DEM method is utilized. Initially, a pilotscale ball mill with dimensions of m × ...
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Abstract and Figures. Planetary mills are gaining importance in the area of ultrafine grinding. The charge motion inside the mill is complex and previous works have considered force balance on a ...
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critical to good mill performance. The important process objectives in SAG mill shell lifter design are: • to provide the key between the mill charge and the mill shell for charge motion, • to maximize the rate of delivery of thrown grinding media at the toe of the charge to gain the best milling action, • to avoid liner and ball damage and
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SAG lifter and end cone geometry can change SAG mill performance more than 20%50% depending on P80 transfer size and Axb, some of which is published and some will be published at SAG 2015. SAG mill wear rates and performance changes with wear morphology, grate details, mill speed changes and optimization with speed control Ball feed size SAG ...
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