Grinding operation represents an important cost factor in mineral processing plant. At least 50 to 70 of the total energy is consumed in the process of grinding and 97 of energy input for grinding is consumed wastefully, as heat and sound, while a minuscule 1 of the input is consumed in creating new surfaces. The objective of the process, at least in the mineral industry, is to be achieving liberation of the mineral species so that separation of desired mineral could be attained.
The aim of our research work is to make a comparison between grinding of porous and non porous minerals. The selection function and calculated specific surface area are used as measures of grinding operation. The study was conducted on laboratory scale by means of a cylindrical ball mill, with 16 cm inside diameter and 14 cm inside length, which occupied with 50% by steel balls of 19 mm, diameter. The time of grinding was varied from .5 to 5 minutes while the other affecting factors are kept constant.
[...] Inst. Min. Metall. (Sec.C: Mineral Process. Extr. Metall.), Vol No (1966) PP.C37 C56. Cohen, H.E. “Energy usage in mineral processing”, Trans. Inst.Min. Metall. (Sec. Mineral Process. [...]
[...] The work index is the comminution parameter, which expresses the resistance of material to crushing and grinding. Numerically it is the kWh per short ton required to reduce the material from theatrically infinite feed size to 80% passing 100μm . The Bond work index as an indictor of Grindability is not a material constant, but changes with change in the size of the grinding product .This must be taken into consideration when energy consumption is calculated according to the bond formula. [...]
[...] Other physical and mechanical properties of the above mentioned minerals will be identified to help in the interpretation of the results. Grinding performance can be measured with the selection function as well as the produced specific surface area of the comminuted samples. Experimental work Introduction 2.1 -Materials Used: Marble (non-porous) mineral. Quartz (non-porous) mineral. Limestone (porous) mineral - Machines Used: Jaw Crusher shown in fig. Fig. Jaw Crusher Roll Crusher shown in fig. Fig. Roll Crusher Universal Test Machine for Compression Test shown in fig. Fig. Universal Test Machine Set of Screens shown in fig. [...]
[...] It has long been argued and supported by much practical experience, that the optimum speed of rotation is that at which balls riding on top of the highest material in the mill are thrown to land at the toe of the mill where materials accumulate. This optimum speed has been found to be between 50 and 75% of the critical one, which has been defined above. Grinding media. The consumption of balls in the fine grinding of ores is a major item in the costs of milling operation. The power transferred from the linear to the grinding media is dissipated by sliding and collision, causing impact crushing and impact grinding. [...]
[...] Results of table are represented in figures from to While figure represents the selection function of Quartz, figures and represents the selection functions of marble and limestone. The slope of each straight interval of each curve is estimated as its selection function as listed in table (3-11). Table selection function (breakage rate function) of the studied minerals. From table it's clear that limestone is the easiest and fastest grounded mineral due to its porosity and brittleness. These results are in a good agreement with those showed by specific surface area. Fig Selection function of Quartz. Fig Selection function of Marble. Fig Selection function of Limestone. [...]
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