SAG mill water addition, as characterized by the percent solids content of the mill discharge, exerts a very strong influence on SAG mill performance. Each line of constant volumetric loading is made up of data of similar ore type and SAG ball charge levels. The beneficial effects of increased SAG mill discharge percent solids on SAG mill ...
The critical speed for this mill was 54 revolutions/minute. For most steadystate conditions examined there is no creation of a water pool (which is typical of overflow mills) at the toe of the ball charge. The immediate observation when a slurry is fed into the mill is a very significant reduction in the noise emitted from the mill.
Ball charge (fraction of volumetric loading and ball size) Mill operating conditions including mill speed (for circuits with variablespeed drives), density, and total mill load; The effect of feed hardness is the most significant driver for AG/SAG performance: with variations in ore hardness come variations in circuit throughput. The effect of ...
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.
Publisher Summary. For the vast majority of ounces of gold produced, comminution costs in the form of power, grinding media, and liners represent the single largest cost category of milling. Since, semiautogenous grinding (SAG) ballmill circuits represent the single largest type of gold milling comminution circuits, the chapter focuses on SAG.
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
TABLE 1 Comparison of RoM and SAG mill operating regimes AG/SAG South African RoM Speed, % critical 70 80% 75 90% Charge Filling, % total mill volume 20 30% 35 45% Bali filling, % total mill volume 415% 15 35% Internallength 35m 5 12m Aspect ratio, diameter/length 2 Recycle stream Trommel oversize Cyclone underflow ...
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 ...
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 ...
The role of end liners in dry SAG mills with the objective of obtaining a thorough understanding of the effects of end liners design on the load trajectory and SAG mill performance has been ...
Effects of mill shell liner type on charge shoulder, toe, impact, and head points, also on head height and impact zone length as well as on the creation of cascading, cataracting, and centrifuging ...
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 ...
Based on SAG7 test results, the lack of circulating load in such a scenario showed virtually no effect on the SAG circuit performance. Conversely, the combined effect between excessive impact provided by greater ball charge (12%) and increased mill speed (75%) was deleterious to the mill performance, as shown in the SAG11 test.
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
with sag mills being increasingly less so as the ball charge is increased. ... parameter. This latter effect is illustrated in Figure 3 page I207, which shows two distributions, which have the same F80 but clearly have different distributions. ... Feed Top Size vs. SAG Mill Performance 5000 5500 6000 6500 7000 7500 8000 8500 9000 9500 10000 13 ...
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.
A comparison of SAG and ball mill charge actions is shown below. Figure 1 shows the sliding abrasion action of a ball mill while figure 2 depicts the cascading impact action of a SAG mill. The geometrical differences in the liner system lifters can also be seen.
For SAG feed size is continually monitored using the SPLITTM system for on lower treatment rates, or for slag treatment, one SAG mill and one ball line particle size estimation, and feedback about the variation of the mill could be operated at 400500 tph for ore, while the other SAG mill plant performance with feed size is given to mining ...
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 ...
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 ...
Two new SAG milling models are developed in this work, able to predict power or specific energy consumption, including the usual design variables such as mill size; balls charge level, solids concentration in the SAG mill feed and % of critical speed, but adding a variable that represents the feed size distribution.
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 ratecontrolling device, but with a feed bin) to crush pebbles for recirculation back to the SAG mill feed ...
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