A Study On The Breakage Characteristics And Mechanisms Of Porphyry Copper Ores At Diverse Comminution Modes

Investigating the breakage characteristics of ores under the basic breakage modes is of great importance for the development of a general mechanistic model that isolates the effect of comminution equipment factors.It can also provide theoretical support to the industrial optimization of ore comminution circuits.A drop-weight tester and a microcomputer hydraulic servo tester are used to carry out single particle impact tests,single particle compression tests and particle bed tests on porphyry copper ores.The breakage characteristics,energy-breakage model and breakage appearance function of ore particles under the above three basic breakage modes are deeply discussed,as well as the basic processes of particle fracture under the three breakage modes.The effects of applying strain rate and the configuration of particles on the particle strength,progeny distribution characteristics,particle size effect and energy efficiency are investigated.Experiment results show that with the increase of applying strain rate,the percentage of coarse progenies sizing greater than 0.65 normalized decreases and the percentage of fines below 0.2 mm increases.The particle bed breakage results more coarse progeny fragments and fines while less middle-size fragments in comparison with the single particle breakage.It is demonstrated that for single particle breakage the comminution efficiency increases with the decrease of applied strain rate.In addition,single particle compression breakage is more energy efficient than particle bed compression breakage at low stressing intensities,but at high stressing intensities the latter is more efficient.The ore has higher particle strength,more significant particle size effect and lower comminution efficiency when fractured with the breakage mode that applies strain rate.In comparison with particle bed breakage mode,the ore shows higher particle strength when fractured under single particle compression mode.The effect of particle configuration on the intensity of particle size effect is insignificant.Under the single particle breakage mode,the breakage degree achieved is determined by the propagation degree of cracks inside the particles.At high or low strain rate,the sub-processes of single particle breakage are primary fracture caused by main crack propagation,secondary fracture caused by the propagation of minor cracks and the frictions between the fracture surfaces.The initiation and propagation of minor cracks inside the particle is significantly affected by the strain rate,which leads to the variations in the breakage characteristics of ore particles between the tests with different applying strain rates.Under the particle bed breakage mode,the breakage degree achieved is determined by the redaction of porosity.The main reasons causing the variation in particle breakage characteristics between single particle and particle bed breakage modes are the existence of particle rearrangement and porosity reduction in particle bed breakage,and the difference in the degree of particle confinement during the breakage process.Breakage index tF is proposed to characterize the intensity of surface breakage as a supplement to t10.The relationships between t10 and are obtained,and the t10-tn curve is modified with the consideration of t10-tF relationship.The improved t10-tn curve achieves better fitting results with the progenies resulting from particle bed tests.In this thesis,the variations in breakage behaviors of ore particles under single particle impact mode,single particle compression mode and particle bed mode are systematically demonstrated,and the effects of applying strain rate and particle configuration on particle size effect are also revealed,which provides theoretical basis for the improvement of the comminution circuits processing porphyry copper ores.