Researches On The New System To Determine The Compression Strength Of Irregular Rock Blocks And Its Application To Grinding

The cost of fragment and milling usually accounts for up to 40% of the total concentrate cost in ore -dressing plants. So the final economical benefits of the plants sensitively depend on whether the ore disintegrating equipment and processing parameters are properly selected, which will inevitably take the important factor into account, the compressive strength of the fragmented object棗the irregular rock materials. So far, the compressive strength used by mineral processing engineers and technicians in their engineering activity generally come from the testing of standard or regular rock specimens of square or circular rock cylinders. The strength value of regular rock specimens is much higher than that of irregular rock, with which the plants are always confronted in their production, because stress concentration occurs easily in the irregular rock blocks under crushing force. As a result, there may be big deviation in the selection of milling equipment and processing parameters. However, the determination of the real value of irregular rock's strength is a notorious aporia because of it's complicated properties. Through his deep study, the author puts forward the conclusion that the irregular rock's strength is 5 times of its tensile strength. By introducing and making use of fractals and chaos theory, the author analyses and reexamines the properties of the rock from the point of the new theory and develops a satisfactory new system to determine the irregular rock's compressive strength. The new system consists: (1 )The accurate formula calculating irregular rock's strength (2)Random processing method of test pattern (3)Setting up of relationship between test times and range reduction of accurate value (4)Orthogonal polynomial regression of irregular rock's strength versus its granularity size As an application in Midi ore-dressing plant, the result derived from the new system shows that the diameter of the mill steel ball should be 100mm instead of 125mm adopted by the plant. The comparative experiment conducted in the plant demppstrates that the new milling system taking steel balls I 00mm in diameter as the biggest ones effects the following achievements: (1 )The unit grain release degrees of titanomagetite, ilmenite and sulphide ores increase 5.59, 4.12 and 6.35 percentage points respectively. (2)Production increases 16.51 tons per miller hour.(3)Concentrate grade increases 0.97 percentage point. Tail1ing grade decreases1 .73 percentage points. Metal recovery increases 2.48 percentape points.(4)Both the consumption of steel ball and that of electricity are cut down to somedegree. Besides, the noise is also reduced a little.All these indicate that the new irregular rock strength determining system hashigh values both in practice and in theory...