Using nonlinear ultrasonic measurements to estimate parameters of the sedimentation of slurry solid phase in thickener

Abstract

Purpose. Improvement of the method for estimating sedimentation process parameters of the slurry solid phase particles in thickener on the basis of measurements of the nonlinear characteristics of ultrasonic waves propagating in a controlled medium. Methodology. The following methods were used: analysis of scientific results and practical developments; methods of mathematical statistics for evaluating the results of experiments; methods of analytical synthesis; methods of numerical modeling for the synthesis and analysis of a mathematical model. Findings. It was established that the nonlinearity of the process of propagation of ultrasonic waves in ore slurry, which is determined by the number and size of crushed ore particles in it, can be estimated by determining the amplitudes of several harmonics of the measured acoustic signal. This approach allows maintaining the productivity of the desliming process in accordance with the characteristics of the ore suspension, without allowing the loss of valuable components. Obtaining real-time information about the characteristics of the particle sedimentation process in the ore suspension at the initial stage enables reducing the duration of transitional processes in the control system. Originality. The method for estimating the parameters of the deposition of the solid phase of the pulp in the thickener has been improved, which is based on the fact that the nonlinearity of the process of propagation of a controlled ultrasonic signal in the thickener; this leads to modulation of the generated ultrasonic packet and, consequently, the appearance of higher harmonics. To obtain a more accurate estimate of the nonlinearity of this process, all the values obtained must be normalized to represent only the relative changes in the acoustic nonlinear response. Practical value. A system for automatic control of the thickener operation is proposed, which uses nonlinear ultrasonic measurements to estimate the parameters of the sedimentation of the solid phase of the pulp in the thickener. According to the results of industrial tests of the system of automatic control of the thickener based on ultrasonic control devices, it was established that its use as part of the automated control system for the technological processes of beneficiation of iron ore raw materials at the ore beneficiation factory of the Northern mining works will allow reducing water consumption by 3.5 % and iron-magnetite losses by 0.6–0.7 %.