Eight, centrifugal concentrator control
According to the nature of ore and slurry, it is reasonable to control the rotating speed of the centrifuge drum and the beneficiation cycle to obtain better beneficiation quality. In the automation design of the concentrator, considering the variability of the ore properties, the PM550 programmable controller (PC) is used as the sequence control device of the centrifuge.
(I) Centrifugal beneficiation and control principle Figure 16 is a schematic diagram of the structure of centrifuge beneficiation. According to different density and particle size, the sedimentation rate of the ore particles in the radial direction is different under the centrifugal force, so that the useful minerals are settled on the centrifuge chamber wall, and the useless minerals are discharged to separate the useful minerals from the useless minerals.
Where r—the size of the ore particle is moving;
D———the diameter of the ore;
Ï s ———mineral density;
Ï———mineral density;
Ω—the angular velocity of the centrifuge drum;
—————The viscosity of the ore flow.
In engineering, the drum angular velocity ω is determined by the speed of the drive motor. Therefore, in the case of a certain nature of the ore flow, the time for the ore to enter the sedimentation zone is
As the slurry flows into the centrifuge, mineral particles deposit on the walls of the centrifuge chamber. If the ore feeding time is too long, the sedimentation layer will be too thick, which will deteriorate the ore dressing quality; if the ore feeding time is too short, the processing volume will be reduced, and the centrifuge efficiency cannot be exerted. Therefore, the centrifuge beneficiation is a process of periodically feeding the mine → breaking the mine → dividing the ore, rushing the mine, and re-feeding the ore. The process time is determined by the nature of the slurry and the drum speed of the centrifuge. [next]
(II) Selection of control devices For a long time, each ore dressing plant has used the photoelectric disc type or time relay method to control the solenoid valves of each process of the centrifuge. When the nature of the ore flow changes frequently, these two methods have large disadvantages. Once the equipment is installed, it is difficult to change the control time; the adaptability and reliability are poor.
Although the performance of the Z80 single-board machine program control device has been improved, the number of intermediate links has increased and the programming is complicated.
The development of PC technology provides a new and effective method for centrifuge control. The PM550 programmable controller is selected here.
(III) Control program preparation In order to balance the power supply to the ore pump, 16 roughing and 8 sweeping centrifuges are divided into 8 groups according to time, and 12 selected poultry machines are divided into 6 groups for control. The sweep control program is shown in Figure 17.
The working cycle of each (group) centrifuge is programmed by ladder diagram. The first roughing centrifuge is taken as an example. The ladder diagram of the program is shown in Figure 18.
In the program design, the solenoid valve malfunction diagnosis link is considered. I.e. each activation of the solenoid iron before the test operation state of the centrifuge, when the centrifuge is running, the solenoid valve is turned on delay; if the centrifuge is stopped, the solenoid valve is de-energized.
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