Overview of Coal Conveying Programmable Control System
Most large-scale thermal power plants in China take coal as the main fuel. Due to geographical differences between coal producing areas and power plants, coal is transported to the coal yard by truck, railway or ship, and then delivered to designated coal bunkers or silos through unloading, stacking, conveying and blending processes.
The core task of the coal conveying programmable control system in thermal power plants is to automatically complete coal unloading, stacking, feeding and blending, so as to supply qualified coal to units (raw coal bunkers) on time, in sufficient quantity and with stable quality. As an important auxiliary support system of thermal power units, the coal conveying system is essential to ensure stable and full-load power generation.
Structure of Coal Conveying Programmable Control System
The coal conveying system features a large number of control devices, complex technological processes and widely distributed equipment. The on-site operating environment is harsh with heavy dust, high humidity, mechanical vibration, loud noise and severe electromagnetic interference.
To meet the development demands of modern thermal power plants, our coal conveying control system adopts a PLC + CRT architecture to realize centralized automatic control of all coal conveying equipment. Dual controllers are configured for redundant operation to guarantee continuous coal supply. In case of main system failure, the standby controller will automatically take over to ensure stable and reliable operation.
With industrial television as an auxiliary monitoring measure, real-time video surveillance is realized for key on-site equipment, reducing traditional manual patrol inspection. The system can be networked with the plant-level Management Information System (MIS), ensuring safe, stable, efficient and economical operation of the whole coal conveying system.
Functions of Coal Conveying Programmable Control System
Operators can monitor the overall operating status through CRT display interfaces, including:
- System general layout diagram
- Coal unloading process flow
- Coal feeding process flow
- Coal blending process flow
- Equipment maintenance list
- Alarm display screen
Three operation modes are available: automatic sequence control, interlocked manual control, and unlocked manual control.
The system supports dynamic process switching under continuous coal supply conditions, reducing frequent equipment start-stop and shortening switching time, so as to improve equipment utilization and save energy consumption.
- Process start-up: Equipment starts in the reverse coal flow direction. The next upstream device is started immediately after the previous one runs stably, which shortens startup time, reduces auxiliary power consumption, and effectively prevents coal accumulation, blockage and leakage during heavy-load startup.
- Process shutdown: Equipment stops in the coal flow direction. Each conveyor shuts down automatically after residual coal is completely discharged.
Coal distribution is optimized according to real-time coal level signals of bunkers. Two blending modes are optional:
- Automatic programmed blending: Based on preset parameters, bunker coal level signals, tripper position signals, and settings of maintenance bunkers, the system automatically controls the operation and stop of travelling trippers, and completes intelligent coal feeding in priority order.
- Manual blending: Operators control the tripper via the host computer according to on-site coal level and position information to finish coal feeding manually.
The system automatically records cumulative operating hours of all equipment in real time. Relevant reports can be called to evaluate equipment operating conditions and utilization rate, providing reliable data for overhaul and maintenance planning.
Meanwhile, it automatically calculates the feeding volume of each bunker and completes shift-based statistics of coal storage and feeding quantity.
Multiple protection signals are configured, including coal blockage, belt deviation, belt slipping and bunker coal level monitoring. Once a fault occurs, audible and visual alarms together with popup alarm windows will promptly notify operators of fault location, type, severity and occurrence time.
The host computer records motor current curves for fault analysis, judgment and timely troubleshooting.
Cameras are installed at key positions of the coal conveying line for real-time video monitoring, serving as an effective auxiliary means to replace manual field inspection and enhance system operation safety.
The system supports data interconnection with the plant-level MIS to realize data sharing and integrated management of the whole power plant.
