1 Overview
With the development of industry, the improvement of people's material life also produces pollution to our living environment. The environment is the space upon which mankind depends, and it is the treasure house of mankind to obtain the basic living material. Once it is destroyed, being polluted has a direct impact on human life and development. Therefore, the governance of environmental pollution will be an indispensable important task.
2, system composition
In order to ensure the stability and reliability of the system, a two-level control scheme is adopted in the design to monitor the entire sewage treatment system. The upper computer adopts two industrial control computers. The lower computer can select the PAC of the Master Age, and the system composition diagram is as follows:
The host computer provides a human-computer interaction interface, so that the operator can intuitively understand the site's various process parameters and fault alarms through the CRT and analog screen, and issue corresponding control instructions. Mass memory records historical data. The control core adopts PAC, and the programmed PAC can perform real-time monitoring of the system according to internal procedures. The program starts and stops field devices.
Due to the large number of site monitoring points, scattered layouts, and independent process technologies, two PACs were used to monitor the production process to simplify cable laying, reduce system costs, and improve system stability. Among them, 1PAC controls all equipment and sensors for pump stations, grit chambers, oxidation ditch, secondary sedimentation tanks, and return sludge pumping stations. Control all the equipment and sensors of the excess sludge pumping station, mud storage tank, dosing room, and dehydration room from the PAC. No. 1 and No. 2 PAC data are exchanged through TCP/IP to achieve data sharing.
After the operator sends a corresponding control instruction to the PAC through the upper computer, the PAC directly controls the site. Even if the host computer fails (such as crash, power failure, etc.), it will not affect the normal operation of the system. The PAC can process the on-site equipment. At this time, the PAC is equivalent to the advantages of the IPC plus PLC.
3, monitoring and control methods
The entire sewage treatment process can have multiple monitoring points, including level, pH, dissolved oxygen, turbidity, frequency, and pump operating status. Each analog quantity parameter outputs the standard signal of 4~20mA through the corresponding transducer, connects to the AI ​​module of PAC through the shielded cable. The signal is connected from the AO module of the PAC to the corresponding frequency converter via a shielded cable and the valve is opened and closed. The digital input signal is a 24V DC signal and is wired to the PAC's DI module. The digital output control signal is a 24V DC signal that is connected from the DO module of the PAC to the field device via a cable. Each field device principle outputs three status signals on its corresponding local box: fault, run/stop, manual/auto; and a start signal. In order to completely isolate the site from the PAC, auxiliary relays must be added between all digital modules of the PAC and the on-site tank. All output signals (including analog and digital) are controlled by PAC internal programs or host computer instructions.
4, software design
(1) PC software
The upper computer software can adopt the configuration software group as the development platform. The whole system construction has multiple real-time monitoring screens, including the system overview, lifting pump station and sand removing tank, oxidation ditch, secondary sedimentation tank, mud road, and dosing Dehydration room. It indicates the operation status of the equipment through the indicator light. When the motor operation mode is manual, use the mouse to click the lower motor start button on the screen to start the field device remotely. The instantaneous value of the sensor is separately labeled according to the actual installation position in a different distribution process flow chart. The real-time data and historical data are made into sub-screens of the corresponding distribution map, and can be directly clicked into the distribution process flow chart to enter. The entire software interface is arranged in a tree, with easy access and operation. The database is the core of PC monitoring software. Therefore, it must be constructed first according to actual needs, and then the various functional modules should be properly combined. In the actual programming process, when defining variables, the records can be set to not record, data change, and time record. Select corresponding settings according to the actual situation to save storage space. The report is divided into real-time reports and historical reports.
The following figure is the monitoring screen of relevant equipment displayed on the computer by HOMS 5.0
(2), PAC software and display panel
Use Master's PACs for programming. The display panel is directly connected to the PAC host. It also adopts a tree structure design. According to different production process areas, all control equipment is divided into: lifting pump station, sediment removal sand pool, oxidation ditch, secondary sedimentation tank, return sludge pump station. , Surplus sludge pumping station, mud storage tank, dosing room, mud removal equipment. All sensor quantities belong to their respective sub-interfaces.
5, summary
The system implements many functions such as real-time monitoring, fault alarm, storage and query of historical data, display and printing of reports, etc. The user interface operates well and is easy to learn. The system has good versatility, scalability and maintainability. The above design can greatly reduce the labor intensity of workers and improve the management level. The system provides an excellent material reference for the fully automated design of urban sewage treatment.