| De-powder from Coal before the sepeartion is of great significance for raw coalefficiently washing. Especially the improvement of mining mechanization leads to theamount of pulverized coal becoming more and more. The moisture content of the rawcoal is very high. The efficiency of those traditional mechanical griddles becomes low,because the moist coal is easy to jam for the giddles.The emergence of airclassification technology can replace vibrating screen and improve the efficiency ofde-powder from the mosit coal. So the research about air classifier’s automatic controlmust have a positive impact on its industrialization promotion.The core of the system is to control the stability of the required gas flow in the airclassifier, which is to get higher classification efficiency and precision partition size.The primary hardwares have a Shanghai Zhenghang CNS7-200PLC, a SankenSAMCO-VM05frequency converter, a Beijing Gallop LUGB2215vortex flowmeterand a computer. Vortex flowmeter is used to measure the gas flow of the pipe, theresulting current signal is converted into digital signals by the analog input terminal ofthe PLC, and as the parameters of PLC internal PID instruction module. The resultfrom the PID arithmetic is converted into standard voltage signal to change thefrequency of the inverter and to regulate the motor speed of the centrifugal blower.The final goal is to maintain smooth flow in the pipeline of the air classifier. In termsof the software, PLC programming and debugging make use of the Step7-MicroWinSP9and monitoring software is developed by Visual Basic.This article expoundsprogram design thought and realization method of PLC.The control logic of PLC, PIDalgorithm and the realization of human-computer interaction have been studied indetail. We constructed a relatively complete control system of air classifier for themoist coal. The actual test was finished by using the built system, which achievedgood classification effect and reached the desired vision. |
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