With the rapid development of social economy and the improvement of modern science and technology, programmable logic controller (hereinafter referred to as PLC) has been widely used in automatic control of industrial production, especially in the automatic control of coal mine production and transportation, because of its advantages of convenient programming, simple structure and good reliability. This paper mainly analyses the relevant knowledge of the application of programmable controller in coal conveying system, hoping to be helpful to the development of the industry. In recent years, with the development of modern science and technology, the technical level of electric power industry is increasing.
The automatic production control system with computer as the core is becoming more and more perfect. The automatic control program is also widely used in coal conveying, water treatment and ash removal peripheral auxiliary system. It is of great significance to the development of coal conveying system in power plants. The coal conveying system can transmit and statistics real-time data directly and quickly for communication and open standard communication. Through I/O architecture, I/O is set up between I/O and main control module, and corresponding I/O is set between distribution room and each distribution point, so as to reduce interference and cable control, and optimize the system wiring mode. The integrated diagnosis function of the whole system is advanced. It can quickly identify faults such as analog overrun, module misconfiguration and line breakage. In the setting of coal conveying system, its working mode mainly includes in-situ, thermostatic element experiment and centralization. The operation mode can centralize, interlock and unlock in-situ for the start-up of centralized single equipment function. The experimental mode is mainly used for software debugging and hardware wiring inspection. Through the computer, the centralized dispatcher chooses the control mode to switch on-line or centralized control. (1) Before starting the coal conveying system, early warning signals are sent to the field equipment through flute, bell and voice equipment. (2) During the early warning period, if the upper computer of the monitoring system does not receive the on-site prohibition start signal, the equipment is prohibited to start. (3) During start-up, if any equipment fails or sends out a stop start signal, immediately stop the system suspending the start-up process, shut down the coal lock equipment, and delay time. During this time, the equipment after start-up will continue to run, and if the troubleshooting time is short, start-up will continue. Otherwise, start-up equipment will be stopped immediately. Analog signal: collect motor current, power and frequency signals, process parameters, level gauge, level gauge and density gauge, magnetic content meter, pressure transmitter and other sensor signals, collect high-voltage and high-power low-voltage motor bearing temperature signals. For this kind of coal conveying system, the coal conveying system is controlled by the hardware and software equipment of the control room of the electric building of the coal preparation plant. (1) The original hardware configuration: in the central control room set up the corresponding combination of operating desk, industrial control computer, high-definition color display, 24-inch liquid crystal display, A4 laser printer, and UPS power supply control system. (2) The original software configuration. The system integrator provides the corresponding upper computer application, development and operation software, as well as Windows XP system operation and anti-virus software.
PLC control system mainly includes two parts: product warehouse reload point equipment. The terminal of the original PLC module in the power distribution room of the product warehouse is connected, and other equipment is connected to the PLC control system outside the No. 1 reload point. Outside the No. 1 reload point, the PLC control master station in the low-voltage distribution room is equipped with 1756-L61 CPU of a company’s Control-logix series and corresponding modules such as rack, power supply, CPU processor, interface and I/O. According to the characteristics of coal conveying system, the system control mode should be equipped with corresponding remote equation automatic control, interlocking manual control, unlocking manual control and on-site non-interlocking manual control of field equipment. With the help of mouse or keyboard, remote equation sequence automatic control can select the operation of the control system set in advance and the program of each plan to realize the automatic operation of coal conveying equipment. The manual control of remote interlocking and unlocking mainly uses the mouse or keyboard in the main station of PLC operation to operate the symbols of each coal conveying equipment manually. There is no interlocking manual operation on the spot, and the coal conveying equipment is operated on the spot through the local control panel or operation column without using the PLC system. Among these four modes, the first three modes of operation are realized by PLC system, among which remote automatic control is the main one. The operator chooses the corresponding coal conveying path on the monitor to transport coal from the coal hopper to the coal bunker, or chooses a coal hopper and the coal bunker, and has the system internal program to automatically select the best coal conveying route to transport coal from the coal hopper to the coal bunker. In the coal conveying system, the introduction of PLC programmable control system has very important social and economic benefits, which are mainly manifested in several aspects: (1) the reliability of the system is enhanced. The reliability of PLC control system is very high.
Compared with the general control system, the downtime of failure is reduced by 50%. (2) Safety improvement. Influenced by various factors, the traditional control system can not introduce a large number of complex logic relations and interlocking conditions into the process, but after the adoption of PLC technology, it compensates for this disallowment, ensures the safe operation of the process, in order to prevent misoperation and misoperation. (3) The automation of the system has been enhanced.
The control operation of the system is simple, and the functions of automatic monitoring and management are constantly improved. It is necessary to repair and maintain sensor devices in time. In the coal conveying control system, the frequency of sensor failure is relatively high, so it is necessary to carry out regular maintenance and repair. In summary, in coal conveying system of coal mine and power plant in our country, the application time of programmable logic controller is long, and the relatively decentralized equipment can be centralized controlled. The function of automatic control technology and information management of coal conveying system has been improved, the cost of manpower and material resources has been reduced, and the safety of production has been ensured. In recent years, with the development of coal industry and the increasing level of software and hardware of programmable control, as an important control means of coal transportation system, it will be an important trend of future development.