Overview of Chemical Water Treatment System
In the water steam circulation system of thermal power plants, strict water quality standards are required for working and cooling media. For high pressure boiler feed water, low hardness, extremely low dissolved oxygen, minimal solid content and organic matter content must be guaranteed. Qualified water must be treated by high purity water equipment through sedimentation, filtration, desalination and deaeration. For plants supplied with seawater, additional desalination treatment is required before water enters the circulating system. Water failing to meet feed water standards will endanger the safe and economical operation of power plant equipment.
As an essential auxiliary system, the chemical water treatment workshop of large thermal power plants and heating power plants features large treatment capacity, complex processes and stringent water quality requirements. Its stable operation directly determines the overall safety and reliability of the power plant.
System Composition
Traditional chemical water treatment systems mostly adopt mimic board monitoring with scattered measuring points, decentralized data management, low automation and poor efficiency.
Our chemical water treatment system consists of two upper computers and a redundant PLC system. Through Ethernet, the upper computer system and field monitoring & control units are integrated to realize centralized unified control of the entire water treatment process.
The upper monitoring system adopts Advantech industrial computers to provide powerful remote monitoring and control functions. The PLC control station adopts dual hot standby redundancy and connects field measuring and control points via remote I/O modules. The redundant main controllers realize zero downtime maintenance and minimize manual intervention. High performance industrial Ethernet ensures reliable, safe and stable data communication between upper computers and PLC stations.
Reasonable system design and configuration realize dynamic monitoring and control of the whole process and equipment status, including curve display, historical data storage, authority management, operation logging, alarm prompting and report printing.
The local instrument system includes pressure/temperature transmitters, flowmeters, level gauges, pH meters, acidimeters, alkalinity meters, silicate analyzers, conductivity monitors, pressure and differential pressure switches. It continuously monitors tank liquid level, pipeline pressure, inlet and outlet flow, water temperature and water quality, and provides feedback signals for automatic process regulation.
Field control equipment covers water pumps, fans, pneumatic valves, electric valves and regulating valves. Pumps and fans are driven by motors, while pneumatic valves are controlled by solenoid valves.
System Functions
Upper Computer Functions
Provide multi parameter monitoring screens to display real time and cumulative data of water tank level, pipeline pressure, flow rate, water temperature and water quality indicators.
Record historical data and trigger voice alarms when parameters exceed preset limits; store alarm records for inquiry.
Display equipment operating and fault status; support remote start/stop operation with full operation logging.
Generate audible alarms for equipment faults and record fault time, type and details to facilitate accident analysis.
Support report printing of key parameters, alarms and failure records.
Lower PLC Functions
Collect and process field signals, calculate cumulative flow and equipment running time, and upload data to the upper computer.
Receive control commands from the upper computer, judge interlock and automatic logic, and realize logical control of water pumps, fans and pneumatic valves to complete automatic water treatment procedures.
Overall Control Functions
Multiple operation modes, automatic fault alarming, on site data acquisition, processing and display are fully configured. In the central control room, operators realize centralized monitoring, management and automatic sequence control of the whole process. One to one remote operation of pneumatic valves, electric valves, pumps and fans is available at the operator station.
Local manual control is reserved. Even if the programmable control system fails completely, on site manual operation can still ensure stable qualified water supply for boilers.
Built in PLC programs realize comprehensive alarm and interlock protection. In case of abnormal conditions, the system immediately terminates relevant operations, outputs alarm signals and automatically starts standby equipment.
Rich fault alarms are provided, including valve opening/closing overtime, valve position signal failure, pump/fan start stop overtime, protection trip and power loss alarms. The system can be connected to the plant auxiliary control network through switches to realize remote parameter monitoring and unified management.
