Investigation of the particle breakage parameters in locked-cycle ball milling

Acar, Cemil
Size reduction processes, particularly fine grinding systems, in mineral processing and cement production plants constitute a great portion of energy consumption and operating costs. Therefore, the grinding systems should be designed properly and operated under optimum conditions to achieve productive and cost effective operations. The use of simulation based on kinetic mathematical models of grinding has proven useful in this respect. The kinetic models contain two essential parameters, namely, breakage rate and breakage distribution functions, that are to be determined experimentally, and preferably in laboratory, or by back-calculation from the mill product size distribution for a given feed size distribution. Experimental determination of the breakage parameters has been mostly carried out in laboratory batch mills using one-size-fraction material. The breakage rate parameter is obtained from the disappearance rate of this one-size-fraction material, while the breakage distribution parameters are estimated from the short-time grinding of the same material. Such laboratory methods using one-size fraction material, however, are not truly representative of industrial continuous mill operations where the mill contents have a distribution of particle sizes. There is evidence in the literature that the size distribution of the mill contents affects the breakage parameters. This thesis study was undertaken with the main purpose of investigating the effect of the size distribution of the mill hold-up on the brekage parameters of quartz and calcite minerals in lockedcycle dry grinding experiments. The locked-cycle and one-size-fraction experiments were performed in the Bond ball mill instrumented with a torque-measuring device. Different closing screen sizes were used in the locked-cycle work to produce different size distributions of the mill hold-up, and the operating conditions were changed in the one-size-fraction experiments to obtain different power draws. Particle breakage parameters were assessed for these changing conditions. Prior to the experiments related to the main purpose of the study, preliminary experiments were conducted for two reasons: (i) to find the power draw of the Bond mill in relation to the operating conditions with the intention of eliminating the use of costly torque-measuring devices by others; and (ii) to find the most accurate estimation method of breakage distribution functions among the three existing methods, namely, the “zero-order production of fines” method, the BII method, and the G-H method. The G-H method was found to be more appropriate for the current study. The locked-cycle grinding experiments revealed that the breakage rate function of coarse fractions increased with increasing proportion of fines in the mill hold-up. Breakage distribution functions were found to be environment-dependent and non-normalizable by size in one-size-fraction and locked cycle grinding experiments. It was concluded that the cumulative basis breakage rate function could sufficiently represent the breakage characteristics of the two studied materials in a wide range of operating conditions. Therefore, it would be more appropriate to evaluate the breakage characteristics of materials ground in ball mills by linearized form of the size-discretized batch grinding equation using single parameter instead of dealing with two parameters which may not be independent of each other.


Review of Trend Tests for Detection of Wear Out Period for Mining Machineries
Gölbaşı, Onur; Demirel, Nuray (2015-04-17)
Machinery systems are extensively utilized in all mining stages from beginning to end of ore production. They are capital-intensive systems and substantial amount of money is spent annually to keep their functionalities in desired levels. Therefore, implementation of effective maintenance strategy has a vital importance to prevent unexpected breakdowns due to failures and to minimize operational cost. These maintenance strategies can be constituted effectively regarding functional and structural dependencie...
Development of a Dust Violation Control Tool from Plant Data
Erkayaoğlu, Mustafa (null; 2018-11-22)
Mining is an equipment-intensive industry that utilizes machinery both in production and mineral processing. As an essential part of sustainable development, mining is subject to environmental management from many aspects. The decision-making process integrated into all stages of mining has to be based on reliable data. Available technology enables to track and monitor the production stages in mining by using various sensors and systems. Data related to mining and mineral processing activities have differen...
Investigation of Self-Excited Ultrahigh Speed Induction Generators for Distributed Generation Systems
Jardan, Rafael K.; Varga, Zoltan; Nagy, Istvan (2011-09-10)
Application of ultra high speed induction generators (IG) in a system developed for utilization of renewable and waste energies that can be applied in Distributed Generation System is presented. The energy conversion is made by a turbine-generator set. For the electromechanical energy conversion application of special high speed induction generators has been studied and described in the paper. The design and analysis of the system are relied on computer simulation techniques verified by test results.
Effect of soft fine particles on the kinetics and energetics of grinding hard coarse particles
Yılmaz, Selim; Hoşten, Çetin; Department of Mining Engineering (2016)
The main objective of this study is to investigate breakage parameters of a narrow size fraction of coarse particles of a hard mineral when ground in a mixture with fine particles of a soft mineral. For this purpose, quartz and calcite were selected as mixture components varying appreciably in hardness (quartz mohs scale:7 and calcite mohs scale:3) but having quite similar densities. Mixture feeds comprised of -1.18+0.85 mm quartz (hard and coarse) and -106 µm calcite (soft and fine) at various proportions ...
Determination of instantaneous breaking rate by Geological Strength Index, Block Punch Index and power of impact hammer for various rock mass conditions
Aksoy, C. O.; Ozacar, V.; Demirel, Nuray; Ozer, S. C.; Safak, S. (Elsevier BV, 2011-07-01)
In mining and construction industries, selection of appropriate excavation method and equipment significantly affects the project feasibility. In the selection, the most important parameters are the geomechanical properties of the rock mass in the excavation route as extensively reviewed in literature. The most widely used geomechanical parameter is uniaxial compressive strength (UCS). However, UCS laboratory test requires time consuming and expensive sampling and core sample preparation processes, which ca...
Citation Formats
C. Acar, “Investigation of the particle breakage parameters in locked-cycle ball milling,” Ph.D. - Doctoral Program, Middle East Technical University, 2012.