When the mill is rotated without feed or with very fine feed, the rods are in parallel alignment and in contact with one another for their full length. New feed entering at one end of the mill causes the rod charge to spread at that end. This produces a series of wedge shaped slots tapering … Read more
Batch Ball Mill Grinding Capacities and efficiencies in wet and dry ball milling at different speeds and ore charges have been discussed in the foregoing pages. The results are summarized in table 16, which shows that in both capacity and efficiency grinding was at its best with small ore charges and high speed. Likewise, in … Read more
Chert, which is very hard, and dolomite, which is moderately hard, were selected for use in a study of the effect of different speeds and ore charges in batch tests. Mill, ball load, and pulp consistency always were the same. Results for chert are shown in the upper section of table 13, and for dolomite … Read more
When the amount of ore in the mills was the same, no appreciable difference between batch and continuous open-circuit ball-mill grinding was found. This should be so, because the progression in particle size for the duration of a batch run would be expected to be the same as the progression from the feed to the … Read more
We used the original flowsheet for two and a half years and made concentrates containing 16%-18% insol. Then we were asked to reduce the insol content as much as possible without additional capital expenditures in an effort to improve the smelting process. One of the 7 x 10 bail mills had been outfitted with four … Read more
As part of its mission to advance minerals technology, the Federal Bureau of Mines has conducted investigations to determine the feasibility of producing subsieve-size material by an attrition grinding method. The Bureau-patented technique involves the intense agitation of a slurry composed of the material to be ground, a granular grinding medium, and a suspending fluid. … Read more
Accurate modeling of structures by finite elements requires not only that the user estimate the load paths, and areas of stress concentrations or rapid variations, in a structure, but also that he realize the modeling idiosyncracies of each element he is working with. He needs to know limitations in displacement function assumptions, aspect ratios, angles, … Read more
The analysis of particle size distributions has become increasingly important in industrial processes. Particle size is recognized to be fundamental to the control of operations as diverse as grinding, crystallization, emulsification, agglomeration, and more. Particle size determination has traditionally been relegated to the laboratory, and is performed by slow, labor-intensive methods such as sieving, sedimentation … Read more
Shell liners wear very fast in very large diameter autogenous and semi-autogenous mills. In addition to shell liner wear, the ends of the mill are susceptible to very high rates of wear, generally confined to fairly narrow bands. Due to the sheer size of modern mills, extensive downtime is required to replace shell liners or … Read more
The general use of chemical grinding aids involving several different mechanisms for increasing throughput in the wet grinding of ores has been discussed in a number of recent publications. It appears from industrial scale testing that the use of selective dispersants with certain prespecified operating conditions is an approach which can produce two important results: … Read more