Currently, the balance of plant of large thermal power plants generally comprise a water system, coal system, and a slag system. Every sub-system is set with a unique monitoring and control point, and every control point is relatively dispersed. The balance of plant of the centralised control room only remotely monitors but does not do any centralised monitoring and controlling. As the inter-industry competition intensifies, the balance of plant system of the power plant also needs to shift from having a single system to having BOP to exercise integrated and centralised control. The monitoring and control of the whole power BOP has to be included in the integrated system, allowing remote monitoring and control, scheduling, and intervention from the centralised control room, and leaving behind an operator station on-site for ad-hoc operations and maintenance, raising efficiency and generating profits. The balance of plant and master control network is integrated further, integrating and releasing many control systems of auxiliary control and master control, creating a future trend of digitising the whole plant and a fully functional operator on duty.
The power plant’s auxiliary water control network provides desalted water for the host machine, and treats condensates to provide industrial coolants for equipment such as air compressors. It is a system that provides water for sub-systems such as coal transporters and ash removers.
The ash network system includes the ash removal system and slag removal system. The ash removal system includes key processes such as ash retrieval, ash transport, and ash storage. The slag removal system involves two major processes which are slag scooping and slag storage.
The ash transport system in the ash network system comprises complicated logic. The ash transport system has three types of control functions, which are automatic, mandatory steps, and monolithic manual. These 3 types of control functions are mutually exclusive, which means that when the system is running on automatic mode, mandatory step control and monolithic manual operations will not be permitted. Other systems include air compressors, fluidised fans, and slag removers, which are linked on a small scale and inter-system control functions.
The control functions include:
Automatic mode of ash transport system
When activating automatic circulation, it is imperative to check the timing where the ash falls in the power plant, and whether the circulation time is set correctly for the whole process. In addition, it is imperative to ensure that automatic activation conditions are in place. If so, the automatic process shall commence when the system receives the automatic activation instruction.
Mandatory step control for ash transportation
It refers to the operator mandatorily placing the power plant in a certain step sequence (generally, only wind blocking step controls are set, but some plants require step controls to be in place for all steps).
Refers to setting the equipment to monolithic manual mode on the interface.
The coal system mainly comprises the coal transportation process and coal blending process. The coal transportation process involves sending the coal from the coal sources (trains, cars, and coal fields) to the coal warehouse via unloading equipment, coal yard stacker equipment, coal feed equipment, belt conveyor equipment, iron removal equipment, bulk remover equipment, and crushing equipment. Coal blending involves using coal plow equipment to allocate the coal on the inter-coal-warehouse conveyer belts to every main coal warehouse. Since the site equipment of the coal transport system is dispersed and the coal transport lines are long, the whole system is generally controlled from a sub-station that manages multiple equipment: A master station is set up at the process control room. A remote control stations is set up in the coal crusher room, transfer station, and between coal warehouses.
The coal transport system can be controlled via 3 modes: Automatic process control, manual interlocking, and manual unlocking. Other than that, there are experimental mode and local control mode.
These are all the modes included: