Design Of Impedance-Based Measurement And Control System For Flotation Tank

In the flotation process of gold mines,the height of slurry level and the thickness of foam layer are important parameters that affect the flotation efficiency and the dosage of mineral processing reagents.Accurate measurement and precise control of these parameters are of great significance.However,existing methods for measuring the liquid level in flotation tanks are affected by the foam layer on top of the slurry and cannot directly obtain accurate measurement results.Furthermore,these methods cannot measure the thickness of the foam layer,which makes it difficult to control the flotation process.As a result,many gold mines still rely on manual visual inspection and control.To address these issues,this thesis proposes an impedance-based measurement and control system for measuring the liquid level and foam layer thickness in flotation tanks.The specific research work is as follows:(1)We designed a comprehensive control scheme for a three-stage continuous flotation tank in a certain gold mine.The measurement and control system mainly consists of four parts,namely,a liquid level height and foam layer thickness measurement device,an intelligent controller,a valve positioner,and pneumatic actuators and valves.The intelligent controller selects the appropriate control strategy based on the deviation between the actual values of the liquid level height and foam layer thickness measured by the measurement device and their set values,and controls the valve positioner to adjust the valve position.The pneumatic actuators are used to adjust the valve opening size to control the flow rate of the inflow and outflow slurry,dosage,and air filling volume,thereby controlling the liquid level height and foam layer thickness.(2)We designed a 32-electrode impedance sensor and an impedance analyzer to measure the liquid level height and foam layer thickness.The 32-electrode sensor was used to measure the complex impedance of the slurry and foam,and the height information was obtained by judging whether each electrode was in the impedance layer or foam layer based on the difference in amplitude and phase,thus achieving direct measurement of the slurry level and foam layer thickness.To address the issue of liquid level fluctuation caused by the agitator stirring in the flotation cell,we designed an anti-interference algorithm to eliminate periodic interference.A flotation cell model was constructed in the laboratory,and the accuracy of the measurement device and the effectiveness of the anti-interference algorithm were verified through experiments.(3)In this study,we optimized the PID control algorithm for the liquid level in the flotation cell and implemented fuzzy control for the foam layer thickness.A mathematical model of the liquid level for a three-stage continuous flotation cell was established.We optimized the tuning method for the PID parameters to reduce overshoot and shorten the adjustment time.We also added feedforward control to compensate for the flow disturbance from the upper stage and enhance the resistance of the latter two flotation cells to interference,thereby shortening the adjustment time.The simulation results using Simulink showed that the control performance significantly improved after optimizing the parameters and adding feedforward control.