DCS And ESD System Reconstruction Of 300,000 Tons/year Ethylene Plant Boiler Water Treatment Devices

In chemical manufacturing processes, the preparation of pure water is an indispensable important segment. Water quality in the process of production has played a decisive role. The water treatment unit supplies level I and level II pure water for super-high pressure boiler and ethylene cracking furnace and 1# refining equipment. For the complexity and high risk in polymer's production, it is particularly high quality requirements of the water. Therefore, to design and develop high reliability automatic control system to meet technological requirements will be one of the most important components to ensure pure water production.Based on the DCS and ESD system of 300,000 tons/year ethylene plant boiler water treatment unit of Shanghai petrochemical Co., Ltd., this paper discusses the programmable logic controller (PLC) technology, Profibus-DP communication technology and human-machine interface technology's application in water treatment field. This paper also introduces the process characteristics and control requirements of pure water's preparation, discusses the design of its automatic control system which including the selection of hardware and network configuration and control system configuration, software design, etc.The pure water preparation unit of petrochemical plant includes double efficient floating bed desalting system (level I desalting system), mixed bed desalting refined system (level II desalting system) and regeneration system, etc. Its operation process is very complex, so-many-steps, high reliability requirements. According to the characteristics of the existing pure water preparation devices, our automatic control system selects SIEMENS S7-400 PLC as controller and SIEMENS WinCC V6.0 as PC monitoring software. PLC and WinCC V6.0 communicate through industrial Ethernet. CPU and distributed I / O stations communicate through Profibus-DP. We use the centralized monitoring and control on-site operation. Operators can monitor and control field devices through the PC monitoring pictures.More than 3 years field operation shows our automatic control system can meet the petrochemical plant super-high pressure boiler unit automation control requirements with high reliability and flexible control configuration.