Solution for the chemical water processing system in the power plant
Operation of the chemical water processingsystem, as an important part of the auxiliary program-controlled system in thepower plant, relates to security and economical efficiency of the whole furnaceand influences safe work and service life of the machine set in the whole powerplant.
Along with continuous renewal and change of treatmenttechnology of chemical water, complexity of automatic control for the system ishigher and higher and its requirements are increasingly stricter; it isrealized based on PLC chemical water treatment automatic control system andcombined with the control system of the bus network on the scene, the functionincludes automatic control, state monitoring, data collection, timely alarm andstatistical printing in process of treating chemical water. The system hastechnical advantages such as reliability, usability and flexibility of PLC,which, compared with routine control schemes, has stronger control function,higher control level and more excellent openness etc.
The control system applies double-machine hotbackup redundancy to connect points which need monitoring and controlling onthe scene via remote I/O. Redundant main control station can ensure that thesystem needs not to be closed down for maintenance, which reduces interferenceto the system to the greatest extent. The upper computer system and the fieldmonitoring can be closely connected with the control point as an integral via Ethernetto form an integral system. Based on such high-speed transport network, you canconveniently use all special functions of PLC system and realize on-line remotediagnosis function of computers in the whole control system.
Systematic functions: the system realizes automaticcontrol, state monitoring, data collection, timely alarm and statisticalprinting to the process of treating chemical water. Sufficient monitoringpictures are designed in the software system according to the technologicalprocess, which can monitor and operate all technological treatment processes. Allmonitoring interfaces can be used to monitor the flow state and operate theflow on the picture; the whole technological process can be reflected on themonitoring picture and the field information can be shown timely on the picturein form of virtual instrument with vivid, dynamic and real-time effect.
Concrete control programs include:
Normal water-making program control
Water level control in the water tank
Control to automatic switchover commissioningof water-making equipment
Cleaning and automatic switchover control to mechanicalfilte
Full-automatic periodic operational control todesalting, backwashing and regenerating
Reproduced program control to the anion bed andthe positive bed
Automatic periodic operational control toregeneration of mixed bed
Control to the souring and alkalizing system
Control to waste acid and waste alkali neutralizationsystem
Control to compressed air system
Other control functions
Commissioning and regeneration of first-classdesalting device is automatically controlled by PLC and can also be remotelyoperated via keyboard and mouse on the operation station in the control room,when its water conductivity exceeds the specified value or the cycle waterproduction reaches the specified value, it steps out and issue alarm spontaneously,then puts into the regeneration program. Commissioning and regeneration ofmixed ion exchange is automatically controlled by PLC or remotely operated viakeyboard and mouse. When its water conductivity and silica exceeds the specifiedvalue or the cycle water production reaches the specified value, it steps outand issue alarm spontaneously, then puts into the regeneration program. High-efficiencyfilter and activated-carbon filter are automatically controlled by PLC and canalso be remotely operated via keyboard and mouse on the operation station inthe control room. When the pressure of the exit and entrance exceeds the specifiedvalue or the cycle water production reaches the specified value, it steps outand issue alarm spontaneously, then puts into the backwashing program. Theabove operations were finished by the operator before, while these in thesystem need no interference of the operator.
The water level in the middle water box isautomatically controlled by PLC (via adjusting the control valve at theentrance of the positive bed) so that it is stable at normal position when thefirst-class desalting system is commissioned. The middle water pump starts andstops and is interlocked with the middle water level, the low liquid levelstarts the pump and the high liquid level stops the pump to ensure safe use ofthe middle water pump.
Automatic/ manual / site operation andselection interlock are shown in the control state of the valve and the pump. Allflows and pressure of the system can be timely monitored on the operationalinterface; the original water flow, the flow at the exit of the anion bed andthe flow at the exit of the mixed bed are shown and integrated with historicalrecord; the first-class desalting production and the mixed-bed regenerationwater production can be looked up respectively.
The system controls commissioning, stoppage, regenerationprogram, automatic program of souring and alkalizing, automatic /half-automatic starting the other desalting device program etc. As for the sequencecontrol, there should be essential substep operation, group operation orindependent operation, and operational functions such as leaping, blocking orby-pass etc. Commissioning of the system, washing of activated carbon, regenerationof the first-class desalting and regeneration of the mixed bed can beautomatically finished by the system or manually interfered by the operatorstep by step; setting time and rest time of all steps and stepping indicationare shown in the interface of the operation station.