Summary of Coal Conveying Program Control System
Most of the fuel used in large thermal power plants in China is coal-fired. Due to the different geographical locations or regions between the coal producing area and the power plant, the coal needs to be transported to the coal yard of the thermal power plant by car, train or ship, and transported to the designated coal bunker or coal barrel through the processes of coal unloading, coal stacking, coal loading and coal blending. The main task of the coal conveying program control system in thermal power plant is to automatically complete coal unloading, coal stacking, coal loading and coal blending, so as to provide coal for the unit (raw coal bunker) on time with good quality and quantity. The entire coal handling control system is a very important support system for thermal power plants, and it is an important condition to ensure the steady development of the unit.

Coal handling program control system structure
The coal handling program control system has the characteristics of many control equipment, complex process flow and scattered equipment. The environmental conditions of the equipment are harsh, such as dust, moisture, vibration, noise, electromagnetic interference and so on. In order to meet the development needs of modern thermal power plants, the coal conveying program control system designed by our company adopts PLC CRT to realize centralized program control of coal conveying system equipment. In order to ensure the supply of raw coal for generator sets on time with good quality and quantity, two sets of controllers are used for redundant control. When problems occur in the system, the standby system will automatically take over the work to ensure the stable supply of raw coal. And industrial television as an auxiliary means of video monitoring of the operating status of field equipment, instead of the traditional on-site inspection, network control can be connected with the power plant management information system to ensure the safe, reliable, efficient and economic production and operation of the coal handling system.

Function of coal conveying program control system
(1) Monitoring function
The operating personnel can monitor the running status of the system through CRT, and the monitoring screen includes:
System Overview
Coal unloading flow chart
Coal Loading Flow Chart
Coal Blending Flow Chart
Equipment Maintenance List
Alarm screen

(2) Control function
This system has three control modes: program control, interlocking manual and unlocking manual.

(3) Coal handling control
The system can automatically perform dynamic process switching under the condition of non-stop coal source according to the on-site coal unloading and coal loading, which reduces the number of start-stop equipment and the time required for start-stop equipment, improves the utilization rate of equipment and saves energy.
The start-stop time of the process is calculated according to the specific parameters of each belt. When the process is started, according to the reverse coal flow direction, the previous level of equipment will be started immediately after one equipment is started and stabilized, which reduces the start-up time of the process, saves the power consumption of the plant, and ensures that there will be no coal stacking, coal blocking, coal leakage, etc. when the equipment is started under heavy load.
When the process stops, according to the direction of coal flow, each equipment will automatically stop immediately when it unloads clean coal.

(4) Coal blending control
Coal blending is optimized according to the signal of high and low coal level in coal bunker. The system has two operation modes: program blending and manual blending:
Program coal blending: after pre-setting, coal blending can automatically control the operation and stop of the blanking truck according to the person's wishes, according to the coal level signal on site and the parking space signal of the blanking truck, as well as the tail warehouse and maintenance truck required on site, and automatically complete the filling and blending of raw coal bunkers according to light, heavy, slow and urgent.
Manual coal blending: the operator will operate the blanking car to run and stop according to the on-site coal position and parking space signals through the upper computer to complete the filling and blending of the raw coal bunker.

(5) Statistical management of coal handling equipment
The system automatically completes the statistics of equipment running time at the same time, and only needs to call up the corresponding report to know the cumulative running time of all equipment, thus drawing the conclusion of good and bad equipment status, and reflecting the equipment utilization rate, which provides a reliable basis for the size repair arrangement of coal handling equipment. Also in the process of coal blending, the metering of the adding amount of each bin is automatically completed, and the statistics of the coal storage amount and adding amount of each class are automatically carried out.

(6) Monitoring signal
The system is equipped with various protection signals such as coal blocking, deviation, skidding, coal level of coal bunker, etc. Once these signals act, they can timely notify the operator of important information such as faulty equipment, fault type, degree, incident time, etc. through sound, alarm window, etc. The upper computer can also memorize the current change of the equipment motor through the graph, so as to analyze, judge and deal with the accident in time.

(7) industrial television monitoring
The monitoring camera can be installed in the key parts of the coal transmission line by industrial TV monitoring, as an auxiliary means to monitor the operation status of the field equipment, instead of the traditional on-site inspection, to ensure the safety of the coal transmission system.

(8) Networking with plant-level MIS