Abstract
Abstract This article deals with a study performed at the Experimental Mine of the Research Center of Responsible Mining of the University of Sao Paulo, to examine the correlations between geological environment, blasting parameters and energy consumption in the primary crushing phase. The research is designed to appreciate the relationships between the energy provided for size reduction and the resistances to size reduction. For this purpose, Key Performance Indicators (KPIs) are used to describe the possible improvements on the energy consumption due to crushing. Four blast tests were performed: for each blast, KPIs were recorded regarding the blast design, the particle size distribution, the real power energy consumption at the primary crushing unit and its rate of utilization. The results show that energy consumption at the primary crusher is a sum of two components: energy directly involved in crushing the rock, and additional energy used for winning the inertial resistances of the moving parts of the crusher. We show how explosive energy and delay times influence the production of coarse fragments that jam the crusher, therefore influencing machinery stops and inertia loads related to putting the jaws back into movement.
Highlights
Considering the comminution system as a whole (Da Gama, 1983; Da Gama and Jimeno, 1993; McCarter, 1996; Morrell, 1998; Nielsen, 1998; Bergman, 2005), every size reduction phase contributes to the final result, and this has consequences on the global energy consumption
The two main resistences offered by the jaw demand a higher amount of current to move it: a) mechannical resistance, when bigger blocks enter the crusher and b)Inertial resistance, when the engine is turned on after a stop and must overcome the inertia of the stopped jaw
As for inertial resistance, it frequently happens that big blocks get stuck between the jaws: in this case the crusher must be stopped, and some time will be needed for operators to reduce the block by jackhammer or remove it from the jaws
Summary
Considering the comminution system as a whole (Da Gama, 1983; Da Gama and Jimeno, 1993; McCarter, 1996; Morrell, 1998; Nielsen, 1998; Bergman, 2005), every size reduction phase contributes to the final result, and this has consequences on the global energy consumption. A parallel research conducted at the same site (Seccatore et al, 2015a) showed how the inherent resistance to comminution (Work Index) is reduced when the P.F. is increased. This phenomenon is more evident at finer grinding phases, such as milling, and its measurement was deliberately neglected for primary crushing.
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