main control unit is used C200HE PLC OMRON PLC products for small and medium companies to facilitate the realization of extension of good manufacturing site; it can further enhance the PC s basic functions, reliable and convenient data processing to improve the efficiency of the production site; CX-Programmer is used in the development of OMRON C200H PLC programming software, running on Windows2000 operating system, in all aspects of automation engineering with user-friendly features. It is committed to enrich the production field of information technology to adapt to Windows software; its full range of units, on a wide range of machinery and equipment for optimal control.
1 Introduction Process
this case, the conditions under the original water, boiler water system requirements on the quality of water supply, boiler feed water treatment system process: the original raw water tank ???? ???? ???? original pump heat exchanger ???? ???? Multi Media Filters Activated Carbon Filter ???? reverse osmosis desalination systems devices Pre-intermediate pump ???? ???? ???? intermediate tank mixed bed ion exchange desalting water tank ???? ???? ???? main plant desalination pumps. Another anti-laundering system, including filters, mixed bed ion exchange regeneration system, chemical dosing systems.
of the original water tank for storage of raw water entering the system, its purpose is to adjustSection water flow changes, to prevent fluctuations in the influent to the system running, to ensure the system into the water and water quality stability.
the original water pump system for pretreatment of raw water to provide adequate flow and pressure.
heat exchanger is the role of water maintained at a certain temperature range, in order to facilitate efforts to ensure the stability of reverse osmosis systems.
the role of multi-media filter is to filter the raw water caused by small particles, suspended solids, colloids, organic matter and other impurities, and by dosing after the formation of alum, to ensure its water SDI (pollution index) ????è 4.
the role of activated carbon filter to remove low molecular weight organic matter in water, free chlorine, but also less water, odor, color and odor.
reverse osmosis desalination system using reverse osmosis membrane pre-feature to remove the most soluble salt in water, colloids, organic matter and microorganisms.
the middle of the water tank to withstand reverse osmosis water production side of the low pressure reverse osmosis membrane to prevent back pressure caused by irreversible damage, while the buffer level after the ion exchange system as the valve switches the pressure fluctuations caused by , and through the middle of tank liquid level controlKai reverse osmosis system, stop running.
intermediate role is to pump up water treatment system and water pressure stable.
mixed bed ion exchange effect is to reverse osmosis to remove water retention in the plasma further.
demineralized water tank for water storage capacity of the system, its purpose is to ensure the stability of the boiler water supply.
desalination pump role is to provide a stable pressure boiler system and water.
Figure 1, boiler feed water treatment process
2 control system configuration and description
2.1 overall control requirements and functional
power plant boiler water treatment demand is the automatic control system to automatically control the treatment processSystem and automatic adjustment to make the treated water quality objectives to achieve the required range. Water control room PC in the company issued a directive, it will run during the current time the main working parameters (water quality parameters, flow, level, etc.), operating status and a certain period of time the main process and other information from the field on the curve Water reached the control room PC.
functions are as follows: Control operation: In the water control room equipment can be charged with online real-time control. Display Function: Graphics showing the scene in real time charged with the equipment operating conditions, and the site of state parameters. Data management: changes according to different operating parameters and the importance of speed, the establishment of production history database, storing the raw data produced for the use of statistical analysis. Real-time database and historical data in the database for comparison and analysis, draw some useful empirical parameters, help to optimize control, and some of the parameters and results necessary to show to the real-time images and reports in to. Alarm: When an analog (such as flow, conductivity, water level, etc.) measurements over a given area or volume of a switch (such as motor start and stop, the valve switch) occurs when the deflection can be different depending on the need to issue level of alarm. Another alarm can be diagnosed on the PLC. Print function: can realize a variety of reports and trends in printing and print real-time events and alarms. </ UL>
Figure 2 Boiler Feed Water Treatment Control System Configuration
2.2 PLC Program Structure and Implementation
2.2.1 of the project according to the technical characteristics of PLC programming in the form of the use of subroutine calls, not only program readable, and shorten the PLC scan cycle. With reverse osmosis desalination system control program, for example, reverse osmosis desalination system according to process requirements, including reverse osmosis device control program PC software manual operation valve control (ROSoftoperation), reverse osmosis desalination system standby control (ROStandby), reverse osmosis desalination system operation control (RORunning) and reverse osmosis desalination system, irrigation control (RORinse). The four working condition at the same time is unique, we can be made routine way, process is reverse osmosis (RO) call. Reverse osmosis process (RO) has and alarm procedures (Alarm), the pump control program (PumpControl), analog processing (AD003Setting), address translation process (IOConvert), level interlock program (LevelInterlock) subroutine to be controlled such as the main program (MainProgram) call, this greatly reduces PLC scan time, and control of clear thinking, the program readable. Only in PC operators on the issue simple commands like, soft hand exercise request, the request to run, rinse the request, and control procedures can be requested in accordance with the steps of the process control field devices.
Figure 3 control system part of the human-machine interface
Figure 4 PLC Program Structure diagram