In recent years, with the increasing automation level of coal handling systems, PLC systems have been more widely used in coal handling systems in thermal power plants. PLC can not only complete complex relay logic control, but also intelligent control and analog control, which greatly improves the intelligence and automation of the coal handling system. To this end, the characteristics of the coal handling control system in thermal power plants are introduced first, and then the design of the coal handling system based on PLC is mainly discussed, in order to further improve the working efficiency of the thermal power plant and minimize the damage to the health of the staff.
introduction
With the rapid development of my country's electric power industry, the single unit capacity and production scale of thermal power plants are increasing, the operating parameters are getting higher and higher, and the equipment and systems used are also more complex. As an important part of the power plant, the coal handling system is an important system guarantee to ensure fuel supply. During the whole process from the fuel entering the power plant to the burning in the boiler, the crushing and weighing of the coal are completed in the belt transmission process. It can be said that the working efficiency of the coal conveying system is a key influencing factor in the entire production process of a thermal power plant.
In recent years, PLC technology has been introduced into the coal handling program control system to realize the automatic management of the coal handling system. Compared with the traditional centralized control of strong electricity, the PLC system has many advantages, such as powerful control ability, simple programming, convenient maintenance, online modification and so on. Through the PLC system program control personnel can realize remote control and network control, thus creating conditions for the whole plant to realize computer control and automatic management.
1. Main features of coal transportation control system in thermal power plantsThe main function of the coal conveying system is to complete the coal unloading, coal loading, coal blending, coal storage and other work by controlling the equipment in the relevant coal conveying system. As far as large thermal power plants are concerned, the coal quantity varies greatly within a certain period of time, and therefore, the coal quality varies greatly. In order to meet the relevant requirements of coal blending and rough treatment of coal, the operation mode of the coal conveying system must be flexible and diverse, so as to meet the requirements of stable and full power generation of the unit. There are roughly four main characteristics of coal conveying system in thermal power plant: many equipments, wide system distribution, many system failure points, and harsh operating environment. Among them, the equipment involved are belt conveyors, coal feeders, dumpers, bucket wheel stackers and reclaimers, coal plows, iron removers, dust collectors, coal crushers, roller screens, etc., usually including more than 100 units. The process flow is complicated. The coal handling system equipment is scattered and the operation line is long, and the distribution range is usually within a few kilometers or even farther. Belt deviation, overloading, pulling rope, tearing, over-vibration and over-temperature of coal crusher, coal blocking of coal screener, stuck coal plow, etc. are common system failures. It can be said that the number of system failures is large and the types are complex.
2. Application of PLC in coal conveying system2.1 Software configuration
2.2 Control method
Thermal power plants need to use PLC technology to design the most appropriate control program in combination with their own actual conditions. There are roughly three control modes of the coal conveying control system. These control modes have high and low levels, and they do not have to be used on the upper plane. The three control methods are described in detail below.
(1) Local manual control. This is the most basic control method, which is generally used for the maintenance and adjustment of the equipment of the coal conveying system, or when an emergency occurs, the staff will manually control the control box on the spot.
(2) Remote manual control. This needs to be done on the host computer, including chain manual and unlock manual. Chain manual means that the staff starts the relevant equipment with reference to the direction of the coal flow, or stops the relevant equipment in the direction of the coal flow. This can effectively solve the problem of congestion in the coal transportation process. The essential difference between manual unlocking and manual interlocking is that there is no interlocking relationship between devices, so the staff can stop any device independently. However, this control method requires support without load, and is mostly used for equipment debugging.
(3) Program automatic control. The staff completes the control of the entire system on the host computer, and selects the most reasonable operation path according to the situation of the coal conveying system. The built-in detection system will determine whether the path is optimal. After the above preparations are completed accurately, the staff will issue instructions, and the system will start the relevant equipment one by one according to the instructions. Once an accident occurs in coal handling equipment, the automatic control system will automatically shut down the equipment [5]. If it is necessary to stop all equipment, a staff member is required to complete the emergency shutdown operation.
2.3 Preparation process and coal blending control
The three control methods of the coal conveying system mentioned above have their own advantages and disadvantages, but no matter which control method is used, the control process needs to be compiled. operating instructions. First, do the preparatory work. The staff should be familiar with the logical description of all technological processes in the coal handling system and the interlocking logic description between the systems, and on this basis, make a virtual diagram of the overall logic operation of the coal handling system. Second, consider the characteristics of different process links to select the appropriate chain logic, and analyze the matching intelligent coal blending logic data [6]. Analyze the potential failures in the coal conveying system and design corresponding treatment methods. Third, analyze the relevant electronic equipment according to the logical description formed in the previous two steps, calculate the length and contacts of all coils, and assign the corresponding numbers to the timers. Repeatedly confirm the accuracy of each data area and each register in the PLC system, and design various ladder diagram structures, and finally compile the corresponding program [7].
In terms of coal blending control, coal should be reasonably allocated to each coal bunker according to the actual coal bunker of thermal power plants. Coal blending control is divided into two types: automatic and manual. Automatic coal blending is that the staff enters the corresponding instructions in the upper computer, and the system automatically adds coal into the bunker. The sequence is to blend coal for the coal bunker with low coal level first. When the coal level signals of all coal bunkers are no longer displayed, according to the pre-set bunker bunkering time and coal blending standard, each coal bunker will be cyclically fed with coal. In addition, it is also possible to set the coal bunker in advance to add coal to a certain height and continue to add coal to the next coal bunker [8]. If there is a problem with the coal level over the line during the stoking operation, it should be set to automatically skip the stoking and repaired as soon as possible. Manual coal blending means that the staff uses the keyboard, mouse and other peripherals on the host computer to complete the coal adding operation to the coal-deficient coal bunker. During the whole process, the staff are required to pay attention to the coal consumption of all coal bunkers, avoid too little or too much coal, and add coal in time. Fig. 1 is the design scheme of PLC coal conveying control system.
Epilogue
In short, the coal handling control system with PLC as the main engine is adopted in the thermal power plant, which greatly improves the working efficiency of coal handling control, realizes the automation of coal handling control, effectively ensures the safety of equipment and staff, and prevents the occurrence of safety incidents. . Therefore, it is necessary to strengthen the research on PLC technology, master the application of this technology and related software, and continuously optimize the design of coal transportation control system, so as to promote the improvement of coal transportation efficiency.
Kolon aramid yarn, Kolon Industries Inc,Indoor/Outdoor Optical Cable
Huizhou Fibercan Industrial Co.Ltd , https://www.fibercannetworks.com