I. INTRODUCTION In recent years, with the rapid development of China's economic construction, many areas in energy supply have experienced a shortage of power resources, so many power plants have been newly constructed or expanded. The original 400MW unit of a group company continued to build #3 and #4 units (2×300MW) to increase its power generation capacity. The original two columns of chemical water treatment systems in the old power plant and the chemical water treatment system of the continued construction project are expanded by a 100 to 140 m3/h chemical desalination system, and the remaining equipment is shared with the existing chemical water treatment system. The original chemical water treatment system uses the traditional analog screen method to monitor, the automation level is not high and the efficiency is very low. After the two units were built, the control system of the original chemical water treatment system was abolished, and the original chemical water treatment system and the expanded chemical water treatment system were collectively controlled using a redundant PLC control system.
Second, chemical water treatment system process 1, chemical water treatment system process The original chemical water treatment system process is: tap water → reservoir → booster pump → activated carbon filter → cation exchanger → remove carbon dioxide → intermediate water tank → middle Water Pump → Anion Exchanger → Mixed Ion Exchanger → Desalting Tank → Desalinated Water Pump. Through the on-site investigation of the existing system's operating conditions and the analysis of the water quality analysis report, the suspended water content in tap water is high, which seriously pollutes the activated carbon and ion exchange resin. Therefore, the extension project added 3 sets of high-efficiency fiber filters for deep filtering of tap water.
Continuing the construction of the chemical water treatment system: tap water → reservoir → booster pump → high-efficiency fiber filter → activated carbon filter → cation exchanger → decarbonizer → intermediate tank → intermediate pump → anion exchanger → mixed ion exchanger → In addition to salt water tank → demineralized water pump.
2. The connection and operation mode of the extension project with the original system The original 120t/h output of the first-stage de-salting + mixed-bed equipment is 2 columns, and the extension project is only to expand the same equipment with an listed force of 120t/h. The demineralized water pump, regenerative water pump, compressed air system, acid-base regeneration system and waste liquid treatment system are shared with the existing system.
The three high-efficiency filters adopt the parallel operation mode, with 2 normal operating conditions and 1 standby. The high-efficiency filter not only pre-treats the tap water required for the renewal project, but also pre-treats the tap water of the original system.
The two activated carbon filters and the first-stage de-salting equipment constitute a series, which adopts the series operation mode, and the normal working conditions are 2 columns and one column is for standby. Each of the 2 activated carbon filters in each series operates when one water quality is good (removal of free residual chlorine), and one set is used as standby; when the quality of influent water deteriorates, two sets are operated simultaneously (removal of organic matter).
The mixed bed is connected in parallel, with 2 normal operating conditions and 1 spare.
Three sets of first desalinization unit and three mixed beds are equipped with switching valves, which are limited by the existing system, only #1 desalination plant and #1 mixed bed and #2 desalination plant and #2 The mixed bed can be run at the same time. The #1 de-salting plant and the #1 mixed bed can be operated simultaneously with the #3 first-stage de-salting plant and the #3 mixed bed. When the unit is started, the above three columns of equipment are put into operation at the same time to meet the maximum amount of recharge water.
Third, the system configuration system consists of two host computer and a redundant PLC system. The upper computer system uses industrial-grade computers to form a powerful monitoring and control system. Intellutiong's FIX7.0 industrial monitoring and control system software is installed on the computer. Through a reasonable system design and system configuration, the entire chemical water treatment process is realized. Dynamic monitoring and control. Through the superior computer system and a powerful industrial control transmission network, the entire production process engineering is managed and controlled automatically.
PLC chooses A5 series PLC controller of the company, and the control system adopts dual-system hot standby redundancy mode to connect the points that need to be monitored and controlled in the field through remote I/O. The remote I/O consists of communication processor and A5 series I. /O module composition. The redundant main control station can guarantee zero maintenance and maintenance of the system and minimize human intervention in the system. A high-performance industrial Ethernet bus transmission network is used between the main control system hot-standby system and the remote I/O control station to achieve reliable, secure, and stable transmission of information.
An industrial Ethernet transmission network is used between the host computer system installation and the PLC control unit. Ethernet is an international standard. Industrial Ethernet has achieved high transmission security and reliability requirements. It has been widely used for program maintenance, transferring plant data to MIS and MES systems, monitoring, connecting human-machine interfaces, and recording events and alarms. Industrial Ethernet with high transfer rate (currently up to 100M), deterministic hub technology, network topology without considering, transmission of multiple physical media (twisted pair, fiber optic, coaxial cable), hub applications regardless of network Expansion and other advantages.
Through the Ethernet network, the upper computer system and the on-site monitoring and control points are integrated into a whole and form a complete system. On such a high-speed transmission network, it is convenient to utilize the unique functions of the PLC system to realize the online remote diagnosis function of the entire control system.
IV. Control Functions All control valves of the water treatment system adopt the local and remote control methods. Even in the case of complete failure of the program control system, manual water production can be achieved through on-site control to ensure the reliable water use of the unit boiler. Three selection switches are used on the control box, namely local open, local close and remote control. When remote control is selected, the control valve is controlled by the operator at the operator station. The operator can perform status monitoring and motion control of the control valve at the operation station, and the control of the control valve can be automatically and manually selected. In the automatic mode, the control valve is controlled by the PLC logic program. In the manual mode, the control valve is directly controlled by the operator on the operation interface.
The commissioning and regeneration of primary desalination equipment is controlled automatically by the PLC, and remote operation can also be performed on the control station's operation station through the keyboard and mouse. When the effluent conductivity of a desalination plant exceeds the specified value or the period of water production reaches a specified value, it is automatically split and alarmed, and then automatically put into the regeneration program. The commissioning and regeneration of the hybrid ion exchanger is controlled automatically by the PLC or remotely via the keyboard and mouse. When the mixed ion exchanger effluent conductivity and silicon dioxide exceed the specified value, or the period of water production reaches the specified value, it will be automatically split and alarmed, and then automatically put into the regeneration program. High-efficiency filters and activated carbon filters are automatically controlled by the PLC, and remote operations can also be performed on the control station's operation station using a keyboard and mouse. When the pressure difference between its inlet and outlet exceeds the specified value, or when the amount of water in the cycle reaches the specified value, it is automatically disaggregated and alarmed, and then it is automatically put into the backwash procedure. The above operations were previously performed by the operator. After performing the new system, the above operations may not require operator intervention.
The water level of the intermediate tank is automatically controlled by the PLC (by adjusting the inlet valve of the positive bed) so that the water level of the intermediate tank is stabilized at the normal position when the primary desalination system is put into operation. The start and stop of the intermediate water pump is interlocked with the middle water level, and the low level start pump and the high level stop pump ensure the safe use of the intermediate pump.
Valve, pump, etc. control status display, automatic/manual/local operation and selection interlock. All flow and pressure of the system can be monitored on the operation interface in real time. The original water flow, the negative bed outlet flow, and the mixed bed outlet flow are cumulatively displayed and historically recorded. The level of demineralization and mixed bed regeneration can be viewed separately.
The system controls the commissioning, stopping and regenerating procedures of each column desalination device, automatic addition of acid and alkali, and automatic/semi-automatic initiation of another column of desalination device procedures. For the sequence control, set necessary step operations, group operations, or individual operations, and perform operations such as skipping, interrupting, or bypassing. System operation and activated carbon cleaning, first stage salt removal and mixed bed regeneration can be automatically completed by the system or operator walk, step manual intervention, display the set time and remaining time of each step on the interface of the operator station, step and step Delay instructions.
V. Concluding remarks After the complete transformation of the company's power plant chemical water treatment system was completed, it was formally put into operation in July 2007. After the transformation, the level of automation was significantly improved, and the water production capacity was increased from the original average of 120m3 per hour to 140-160m3 per hour. Completely guaranteed the water needs of the 6 generator sets. Due to the increase in the level of control, the amount of wastewater generated during the water production process has been significantly reduced, which has played a certain role in environmental protection and energy conservation. The system's high degree of reliability and intuitive and easy operation make the control center duty room from the original 2 people on duty to be on duty for 1 person, which greatly saves manpower cost.
Second, chemical water treatment system process 1, chemical water treatment system process The original chemical water treatment system process is: tap water → reservoir → booster pump → activated carbon filter → cation exchanger → remove carbon dioxide → intermediate water tank → middle Water Pump → Anion Exchanger → Mixed Ion Exchanger → Desalting Tank → Desalinated Water Pump. Through the on-site investigation of the existing system's operating conditions and the analysis of the water quality analysis report, the suspended water content in tap water is high, which seriously pollutes the activated carbon and ion exchange resin. Therefore, the extension project added 3 sets of high-efficiency fiber filters for deep filtering of tap water.
Continuing the construction of the chemical water treatment system: tap water → reservoir → booster pump → high-efficiency fiber filter → activated carbon filter → cation exchanger → decarbonizer → intermediate tank → intermediate pump → anion exchanger → mixed ion exchanger → In addition to salt water tank → demineralized water pump.
2. The connection and operation mode of the extension project with the original system The original 120t/h output of the first-stage de-salting + mixed-bed equipment is 2 columns, and the extension project is only to expand the same equipment with an listed force of 120t/h. The demineralized water pump, regenerative water pump, compressed air system, acid-base regeneration system and waste liquid treatment system are shared with the existing system.
The three high-efficiency filters adopt the parallel operation mode, with 2 normal operating conditions and 1 standby. The high-efficiency filter not only pre-treats the tap water required for the renewal project, but also pre-treats the tap water of the original system.
The two activated carbon filters and the first-stage de-salting equipment constitute a series, which adopts the series operation mode, and the normal working conditions are 2 columns and one column is for standby. Each of the 2 activated carbon filters in each series operates when one water quality is good (removal of free residual chlorine), and one set is used as standby; when the quality of influent water deteriorates, two sets are operated simultaneously (removal of organic matter).
The mixed bed is connected in parallel, with 2 normal operating conditions and 1 spare.
Three sets of first desalinization unit and three mixed beds are equipped with switching valves, which are limited by the existing system, only #1 desalination plant and #1 mixed bed and #2 desalination plant and #2 The mixed bed can be run at the same time. The #1 de-salting plant and the #1 mixed bed can be operated simultaneously with the #3 first-stage de-salting plant and the #3 mixed bed. When the unit is started, the above three columns of equipment are put into operation at the same time to meet the maximum amount of recharge water.
Third, the system configuration system consists of two host computer and a redundant PLC system. The upper computer system uses industrial-grade computers to form a powerful monitoring and control system. Intellutiong's FIX7.0 industrial monitoring and control system software is installed on the computer. Through a reasonable system design and system configuration, the entire chemical water treatment process is realized. Dynamic monitoring and control. Through the superior computer system and a powerful industrial control transmission network, the entire production process engineering is managed and controlled automatically.
PLC chooses A5 series PLC controller of the company, and the control system adopts dual-system hot standby redundancy mode to connect the points that need to be monitored and controlled in the field through remote I/O. The remote I/O consists of communication processor and A5 series I. /O module composition. The redundant main control station can guarantee zero maintenance and maintenance of the system and minimize human intervention in the system. A high-performance industrial Ethernet bus transmission network is used between the main control system hot-standby system and the remote I/O control station to achieve reliable, secure, and stable transmission of information.
An industrial Ethernet transmission network is used between the host computer system installation and the PLC control unit. Ethernet is an international standard. Industrial Ethernet has achieved high transmission security and reliability requirements. It has been widely used for program maintenance, transferring plant data to MIS and MES systems, monitoring, connecting human-machine interfaces, and recording events and alarms. Industrial Ethernet with high transfer rate (currently up to 100M), deterministic hub technology, network topology without considering, transmission of multiple physical media (twisted pair, fiber optic, coaxial cable), hub applications regardless of network Expansion and other advantages.
Through the Ethernet network, the upper computer system and the on-site monitoring and control points are integrated into a whole and form a complete system. On such a high-speed transmission network, it is convenient to utilize the unique functions of the PLC system to realize the online remote diagnosis function of the entire control system.
IV. Control Functions All control valves of the water treatment system adopt the local and remote control methods. Even in the case of complete failure of the program control system, manual water production can be achieved through on-site control to ensure the reliable water use of the unit boiler. Three selection switches are used on the control box, namely local open, local close and remote control. When remote control is selected, the control valve is controlled by the operator at the operator station. The operator can perform status monitoring and motion control of the control valve at the operation station, and the control of the control valve can be automatically and manually selected. In the automatic mode, the control valve is controlled by the PLC logic program. In the manual mode, the control valve is directly controlled by the operator on the operation interface.
The commissioning and regeneration of primary desalination equipment is controlled automatically by the PLC, and remote operation can also be performed on the control station's operation station through the keyboard and mouse. When the effluent conductivity of a desalination plant exceeds the specified value or the period of water production reaches a specified value, it is automatically split and alarmed, and then automatically put into the regeneration program. The commissioning and regeneration of the hybrid ion exchanger is controlled automatically by the PLC or remotely via the keyboard and mouse. When the mixed ion exchanger effluent conductivity and silicon dioxide exceed the specified value, or the period of water production reaches the specified value, it will be automatically split and alarmed, and then automatically put into the regeneration program. High-efficiency filters and activated carbon filters are automatically controlled by the PLC, and remote operations can also be performed on the control station's operation station using a keyboard and mouse. When the pressure difference between its inlet and outlet exceeds the specified value, or when the amount of water in the cycle reaches the specified value, it is automatically disaggregated and alarmed, and then it is automatically put into the backwash procedure. The above operations were previously performed by the operator. After performing the new system, the above operations may not require operator intervention.
The water level of the intermediate tank is automatically controlled by the PLC (by adjusting the inlet valve of the positive bed) so that the water level of the intermediate tank is stabilized at the normal position when the primary desalination system is put into operation. The start and stop of the intermediate water pump is interlocked with the middle water level, and the low level start pump and the high level stop pump ensure the safe use of the intermediate pump.
Valve, pump, etc. control status display, automatic/manual/local operation and selection interlock. All flow and pressure of the system can be monitored on the operation interface in real time. The original water flow, the negative bed outlet flow, and the mixed bed outlet flow are cumulatively displayed and historically recorded. The level of demineralization and mixed bed regeneration can be viewed separately.
The system controls the commissioning, stopping and regenerating procedures of each column desalination device, automatic addition of acid and alkali, and automatic/semi-automatic initiation of another column of desalination device procedures. For the sequence control, set necessary step operations, group operations, or individual operations, and perform operations such as skipping, interrupting, or bypassing. System operation and activated carbon cleaning, first stage salt removal and mixed bed regeneration can be automatically completed by the system or operator walk, step manual intervention, display the set time and remaining time of each step on the interface of the operator station, step and step Delay instructions.
V. Concluding remarks After the complete transformation of the company's power plant chemical water treatment system was completed, it was formally put into operation in July 2007. After the transformation, the level of automation was significantly improved, and the water production capacity was increased from the original average of 120m3 per hour to 140-160m3 per hour. Completely guaranteed the water needs of the 6 generator sets. Due to the increase in the level of control, the amount of wastewater generated during the water production process has been significantly reduced, which has played a certain role in environmental protection and energy conservation. The system's high degree of reliability and intuitive and easy operation make the control center duty room from the original 2 people on duty to be on duty for 1 person, which greatly saves manpower cost.