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SABO DCS Control System with the advanced control technology, perfect functions, open the application software, redundant power supply system, scientific function module, piecewise type isolation technology, exquisite cabinet processing, products and reasonable layout, beautiful integrated wiring, thoughtful field debugging, often by the electric power, metallurgy, petrochemical, building materials, transportation, municipal and other customers of praise. The following is a brief introduction of DCS sewage treatment control system in the north of Jiangsu Province.

1 Background Introduction

With the rapid development of China's economic construction, government on the protection of the environment more attention, built a large number of sewage treatment plant, the new sewage treatment plant according to its own characteristics, the control system performance and price put forward new requirements. a city in Northern Jiangsu sewage treatment plant for treatment of domestic wastewater by cyclic activated sludge system (CASS), daily processing capacity is 3 million tons, the DCS system PLC in the high price for control unit. By using the commercial computer for monitoring station and the whole system in realizing the production automation, reduce the system cost, from 2010 production has been running in good condition.

2 Production Process

Sewage treatment is a continuous process of biochemical reactions, the oxidation ditch process, Ao, SBR and CASS and many different treatment process, the sewage treatment plant in the sewage treatment process for new and improved Cass (cyclic activated sludge system, cyclic activated sludge method) craft, which belongs to an improved type of SBR process, by grille wells, CASS pool, blower room, dosing, storage pond mud, dehydration machine room, contact disinfection pool. The process has the following characteristics:

1) the maximum water decanter can reduce the drainage of water lifting bottom sludge disturbance.

2) strong impact resistance, the removal efficiency of refractory organic matter is high, and has the function of nitrogen and phosphorus removal.

3) short process flow, small floor area, low cost of construction, operation cost.

4) the management is simple, the operation is reliable, the water quality is good, no smell.

5) the sludge production is low, the nature of the sludge is stable, and the sludge is not expanded.

3 Type Selection

1) the control point of the controlled equipment in 800 points, the control process is more complex, but we need the algorithm is not complex, the basic time control and bit based control.

2) the control system should be mature, reliable, easy to debug and maintain.

3) to be considered to have third party products, network communications and the agreement shall be open and standard.

4) measurement equipment and controlled equipment are the traditional equipment, basically no field bus communication capabilities, so the input or output control is based on the traditional I / O.

5) taking into account the economic base of a city in Northern Jiangsu is relatively poor, so as far as possible to meet the requirements of the premise to reduce costs.

After demonstration, the automatic control system of the plant adopts the DCS control system based on PLC. The system can achieve a good balance between the performance and price on the basis of meeting the production requirements.

4 Program Demonstration

Traditional DCS is for instrument of industrial process control system developed, the main function is achieve the continuous physical quantity monitoring and regulating, PLC is developed for the traditional relay control system, the main function is to realize logic control switch quantity. Generally speaking, PLC is a kind of local controller, but with the expansion of the scale of application and the emergence of industrial Ethernet, multiple PLC can be interconnected to form a larger control system. There are several significant changes compared to a single PLC:

1) in the network attached to generic online computer, its role is implementing the configuration of the system, programming and downloading, online monitoring of the controlled process, so that a scene with control layer and the coordinated control layer of the DCS prototype appeared.

2) I / O interface and numerical calculation function is added in the PLC, so that PLC can not only complete the logic control, but also can complete the function of analog quantity monitoring and control and hybrid control.

3) more and more PLC manufacturers to the special network to become a general network, so that the PLC has a variety of conditions and other computer systems and equipment to achieve integration, in order to form a large control system.

The change makes the PLC system have the morphology of DCS, due to the PLC product has entered the market for many years, its I / O interface, programming method, network communication tend to standardization and adapt to the requirements of the open system. At the same time, through expansion to increase the fieldbus communication function, coupled with the PLC in the price advantage, making PLC plays a very important role in the field of distributed control systems, have a considerable competitive advantage in many application fields, so in the end in a city in Northern Jiangsu through the SA Bo electrical based on PLC DCS system demonstration program.

5 Configuration and Composition

1) DCS control system is based on the open network structure of industrial Ethernet, which is composed of three slave stations, PLC0, PLC1, PLC2 station, 1 upper station engineers station and 1 upper station operator station. The topological structure of the graph is shown in figure 1.

2) PLC0 control stations were installed in the central management center of large screen mosaic display simulation, through the Ethernet acquisition signals of the equipment and RS232 communication mode and mosaic screen communications, production of the entire process and the equipment state display.

3) plc1 installed in power transformation and distribution, responsible for controlling the grille wells, sewage lifting pump, grit chamber, CASS pool, No. 1, No. 2 Cass pool, 3 Cass pool, blower room, mud storage tank and flow well flow detection, contact pool disinfection test control, power distribution room of the part of electric parameter monitoring.

4) PLC2 installed in the dosing room, for a full set of dosing equipment control electromagnetic valve, mixer, diaphragm pump, dosing room.

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5) Two central management center of the monitoring computers using OptiPlex DELL series desktop. OptiPlex series desktop orientation on the primary server applications, under the premise of high performance the specially designed wire shielding layer structure and cooling system to ensure the high reliability and stability of system, the monitoring software is based on Microsoft Windows 2000 platform, commercial aircraft to the operating system compatibility than IPC slightly better.

6) the whole control system of the exchange of information and control layer of the two layer, the use of advanced industrial Ethernet, with high speed and reliable characteristics. Industrial Ethernet is a kind of information and control network, which is based on the traditional Ethernet, which is a kind of information and control network, which has the characteristics of reducing the cost of the network.

6 System Function

1) Monitoring software

Monitoring software for the use of kaiwu2000 software, kaiwu2000 Beijing Huafu Huitong developed a common monitoring software, the software of OPC communication support better. OPC (OLE for ProcessContro1) is based on COM (component object mode1) and DCOM (Distributed Component Object mode1) technology of object oriented software protocol, OPC among field devices, automatic control application software and enterprise management application software provides open, interface specification, from different suppliers of software and hardware to provide "plug and play" connection.

Between the system of the monitoring software and DCS hardware communication protocol by OPC, Rockwell rslinx software as OPC sever side and monitoring software as OPC client reads data, by the way communication to avoid the monitoring software of DCS system driver support is not perfect.

2) Control mode

In order to facilitate the operation of debugging and accident emergency handling, system control is divided into three kinds:

a) In situ manual mode. The local control box or MCC button, switch control device;

b) Remote control. Automatic mode of control equipment;

c) By two computers in the central management center in the manual mode. According to the operating conditions, the system automatically completes the start and stop of the equipment. Remote control and local control mode switching is completed by the MCC cabinet or in situ control box; automatic mode and remote control mode switch is completed by the two monitoring computer.

3) Monitoring function

Two computers, respectively, as the operator station and engineer station, set up in the center of the central management center, the whole plant process equipment operating conditions, operating parameters of centralized monitoring, remote control field equipment. Monitor the computer through the integration of 1000M network card and PLC system through the industrial Ethernet data exchange. Main function:

A) Process flow monitoring function. The system can monitor the parameters and equipment status of sewage treatment according to the process requirements, and select the automatic, sequential, timing and other control methods according to the requirements of the process.

B) Alarm and alarm recording function. When the equipment accident, the system will be in the computer, mosaic big screen, local control box on the alarm instructions. At the same time, the computer will record the alarm content, time and confirmation time. A voice alarm is also available on the computer.

C) Interlock protection function of C. When the system detects a local fault, start the corresponding interlock protection program.

D) Parameter setting function. The upper and lower limits, the adjustment parameters, the running time and other parameters of the alarm upper and lower limit, the adjusting parameter and the running time can be carried out on the human machine interface of the central management center of the computer or the field control station.

E) Data record storage function. The system can record and store the important data such as process parameters, working conditions and equipment running time.

F) Operation record function. System automatically save important operation records, such as changes in parameters, operating equipment operator code, time, content, etc..

G) Real time data curve and historical data curve. The important process parameters can be real-time curve display, and record the historical data curve.

H) Multi level password protection function. In the central management center of any one of the monitoring computer can set different operating rights, only the operator of the appropriate operator, in order to access the correct password after the screen.

I) print function. Report printing, curve printing, graphic printing.

7 Engineering Results

This system was implemented in 2009 January, 2010 March transferred to the equipment operation, the DCS system is stable and reliable without damage; the system is put into use, the operating personnel in the central management center will be able to fully understand the operation of the whole factory; DCS system of main equipment and pump water decanter can automatically according to the preset control the parameters of the whole system; only the central management center, the operator will be able to ensure the normal operation of the system, greatly reducing the labor intensity of operator; system operation to solve the sewage treatment plant of low degree of automation, all equipment shall be manually operated, on duty staff labor intensity, easy operation error, the effluent quality is not stable the production process, not the problem of centralized monitoring; the factory as North Jiangsu city model project, the water quality of the city of North Jiangsu Protection has played a positive role, government leaders at all levels repeatedly to the factory to inspect and guide the work, the factory production and technological level gave a good evaluation, and achieved good social and economic benefits.