Study On Discrete Heat Transfer And Thermal Breakage Behaviour Of Charge In Ball Mills

Ball mill is the key milling device,which is wildly used in metallurgy,mineral processing and chemical industry etc.The total amount of material grinded by ball mill is as high as several billion tons per year and its electrical consumption accounts for 2%-5% of the total electricity in our country.The function of the ball mill was to grind and break the ore particles into the required size distribution.However,the effective breakage energy only accounts for 0.5%-1% of the input energy in ball mill that leads to a lower milling efficiency and greater energy consumption.This paper was supported by the National Natural Science Foundation of China,which studied the motion characteristics of grinding media,the discrete heat transfer and the particle thermal-breakage characteristics in ball mill.Understating the energy loss and the particle thermal-breakage characteristics in the milling processes can be helpful to provide the theoretical basis for improving milling efficiency and reducing energy loss.Firstly,based on the kinematics theory of grinding media,the load behavior of the grinding media was studied and which can be provided the theoretical research for the grinding media motion characteristics.Combined with the experiment and the numerical simulation,the variation of the mill parameter such as mill speed,ball filling and lifter angle on the load behavior was analyzed.Besides,this paper constructed a mathematical model that can predict the load behavior of the grinding media.Then,based on the theory of particle breakage,the energy transfer rate of particle breakage was analyzed,the discrete heat transfer model was constructed,and the variation of the heat transfer phenomenon and temperature rise at different milling parameters were studied and analyzed.Finally,based on the nonlinear population balance model,the iron ore breakage experiments were carried out and studied the variation of the breakage rate and the particle size distribution at different feed particle sizes and temperatures.Moreover,this paper analyzed the relationship between charge motion and breakage regime,and compared the thermal-breakage method and general-breakage method.