Design And The Development Of Automation System For Heavy Medium Suspension

Dense medium coal separation is based on different densities of coal and gangue, but the density of coal and waste rock are greater than l,that is greater than the density of water, so separation can not be directly in the water.To achieve separation by density, it needs to configure the liquid that density is greater than water, that is dense medium suspension. Dense medium suspension is formed by the solid and liquid with different density, solid particles dispersing in liquid. In dense medium coal separation, dense medium suspension is prepared with magnetite powder, solid and liquid phases include magnetite powder, slurry and water in the actual production. Raw coal is put into the liquid with this density, some with the density less than liquid sink, others float by Archimedes.Fuzzy control is an intelligent control developing by imitation of manual operation of field operators. The object with time-varying of process control, field random noise, inertial lag can not be controlled in accordance with the fixed strategy, so re-examine the characteristics of human control behavior, replace human brain by the fuzzy controller, imitate the operation experience of field operators to achieve control of complex objects.In the automatic control of dense medium separation production process, in order to improve control accuracy, PID control are used in international and domestic at present, using PID controller parameter tuning and line modification, establishing mathematical model of dense medium separation process control system according to the dynamic relationship of the process parameters. Analysis system characteristics, propose to design control system by the use of self-tuning principle, and give the control algorithm. Basically the new HM coal preparation plants achieve the automatic control of dense medium suspension, some of the old plants are also under the transformation of density automatic control, and the control technology uses a mature and reliable PID control algorithm.Density control system consists of two parts, first:when suspension density is higher than the given density, automatic water by controlling the opening size of pipe supply water valve to reduce the density of separation to the set value; Second:when suspension density is lower and slime content is high, need to control the shunt valve action. Specific work process is:when measured density is higher than a given density, drive electric actuators to supply water, gradually reducing the density, this process is to reduce the suspension density. When measured the density is lower than a given density, the electric actuator control the shunt valve to open a large, and return concentrated suspension to the qualified suspension barrel, so that the density gradually increased until the density measurement signal equal to the external given signal, at this point the electric actuators work in a stable position, the process is to improve the suspension density.However, when achieve automatic control to the suspension density, in the automatic diversion, qualified media barrels need to obtain over-dense medium through dilute medium barrel and magnetic separator, and this process takes some time, is a typical large inertia, large time delay process control, overshoot and oscillations are inevitable just using the traditional PID control. At present in coal separation plant, in this part of replenishment is mostly for true automation; in this part of the shunt is still the implementation of the manual control in real time adjustment according to the experience of staff. Manual control alone led to suspension density fluctuations in large, clean coal ash exceeded or the yield decreased the workload driver's big job. To improve the accuracy of coal preparation, this part of the shunt also an urgent need to be automated. If this part is automated, which not only reduce the workload of the driver position, it also will optimize the product structure, improve product quality, increase enterprise efficiency, to high-quality, efficient and clean production.Based on subject object and the actual situation, replenishment is installed on the pipe nearly to inclined lifting wheel separator, it moves quickly and enables to affect the separation density; The diversion device moves away from longer-term, slow and lag process, take a long time to reflect in the separation density changes. So PID involved in controlling replenishment valve, this approach proved to be feasible according to the field experience. The shunt process has large inertia and large delay and parameter uncertain time-varying characteristics, the fuzzy control can be a good solution to this problem. For the above, this issue explores the application of fuzzy control in the dense medium separation process control; establishes a fuzzy control structure with multi-variable input and output. Using PLC as the system fuzzy controller proposes fuzzy control scheme that composite replenishment PID control and shunt fuzzy control of the dense medium suspension density.