Theoretical aspects of energy consumption acoustic evaluation at the jet grinding

Abstract

The objective of this work was to develop an acoustic method for evaluating energy consumption during the jet mill operation on the basis of the new generalized physical laws of material dispersion at it destruction. Theoretical explanation is given to the problem of energy consumption diminish in the mode of fine grinding. Dependences between the product dispersion and critical energy density in the course of destruction are described. The acoustic-emissive parameters of dispersion of the samples loaded by compression and results of acoustic estimation of the jet grinding are considered. Interrelation between the gas-jet mill performance and parameters impacting on the energy consumption are analyzed. Grounds are given for using a criterion of extremal control of the working process for maintaining maximal performance. An acoustic size effect of dispersion is formulated by the analogy with dynamic size effect of destruction (DSE). A new approach to evaluation of energy consumed by the jet mill is developed from positions of unity of nature and mechanism of the loaded body destruction with community of manifestation of physical laws of acoustic emission and effects of new surface formation on the destroyed particles. Leading role in the methodology of energy consumption evaluation is given to the coefficient gN (J/imp) of transformation of the consumed energy into acoustic radiation at optimal mode of the mill operations (at maximum performance), which is calculated as a ratio of the reduced work (energy) to the acoustic signal counts in the grinding zone. Current energy consumption ЕDt (J) for period Dt (s) of work is calculated with taking into account coefficient gN (J/imp) and average (for the interval Dt) acoustic activity (imp/s). It is possible to maintain minimum energy consumption at the jet grinding by the snap-acting control of jets loading up to the level of the measured acoustic activity in the grinding zone, at which a “conditionally permanent” value of coefficient gN can be achieved. The results of acoustic evaluation of effective surface energy at optimal grinding mode correspond to the range of estimation gs in the regularity of the DSE destruction. This fact confirms validity of the dispersion theory (including the acoustic size effect) use for evaluating current energy consumption in the course of the jet mill operation.