| Heavy medium coal preparation is a method of coal preparation with the use of the liquid whose density is between cleaned coal and gangue(or middle coal) as media of coal separation.The method is used for coal preparation in strict accordance with the density of the liquid.Therefore,the density of heavy medium liquid have a decisive influence on the coal separation effect.As the degree of automation of coal preparation plant improves,the control method of heavy medium liquid density has shifted from manual control to automatic control in coal preparation plant,and PID algorithm is widely applied to the heavy medium liquid density control system.As the quality of coal becomes worse day by day, the coal preparation process becomes more complex and the requirements of coal preparation become more stringent,the PID control algorithm can not meet the need of the heavy medium coal preparation properly.Therefore,coal preparation plants need to seek the better control method in line with the current coal preparation process.The magnetic iron powder is widely used in heavy medium coalpreparation as the dense medium.The cost of heavy medium is an important part of the cost of coal washing accounting for about 16% of the direct cost of coal.The medium consumption is a important indicator to evaluate the effect and the cost of production of heavy medium separation. The equipment used for the recovery of magnetic powder is magnetic separator,so the recovery rate of magnetic separator directly affects the medium consumption.Therefore,how to improve the recovery rate of the magnetic separator become the urgent problem for the coal preparation plant.In the light of the problem that the effect of PID algorithm in the heavy medium suspension density control system is not ideal,the dynamic matrix controller based on quadratic programming constrained optimization(QP-DMC)algorithm is adopted to realize the linkage control of heavy medium suspension density and liquid level of qualified medium barrel,which sets the opening degree of clear water valve,flow divider and qualified medium valve as three controlled variables and the heavy medium suspension density and liquid level of qualified medium barrel as two dependent variables.Firstly,the transfer matrix of the heavy medium liquid density control system is derived according to the volume balance and mass balance of medium heavy medium liquid media in the eligibility media bucket;then the ascending curve method is adopted to establish respectively the step response models of the opening degree of clear water valve,flow divider and qualified medium valve to heavy medium suspension density and liquid level of qualified medium barrel,and then the step responsemodel parameters of heavy medium liquid density control system are determined; finally,using the step response models,QP-DMC algorithm is programmed and simulated in MATLAB and contrasting to PID algorithm,QP-DMC algorithm has a better control effect.In the light of the problem that magnetic separator has the low recovery rate,according to the change of the liquid level of dilute medium bucket and the magnetic material content of magnetic separator feed solid,the paper acheves the real-time control for the feed flow and the tailings valve opening of magnetic separator by fuzzy control algorithm.Firstly, an experiment is designed and implemented to explore the effect of the feed flow of magnetic separator,the magnetic material content of magnetic separator feed solid and the tailings valve opening of magnetic separator on the recovery rate of magnetic separator;according to the results of data analysis,fuzzy control rules are established and fuzzy control query tables are obtained;finally, S7-1200 PLC is used as the controller, Kingview 6.55 is used to establish the monitoring interface and VB6.0 is used to realize the programming of the automatic control of the system. |
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