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Based on an annual output of50,000tons seawater desalination plant in shougang jingtang united iron and steel Co. LTD, the paper expounds in detail how to design and develop a control system under simatic s7-400system ring network architecture, which realizes the monitor and control of important manufacturing parameters of whole With thermal vapor compressor for low-temperature multi-effect desalination.To begin with, Introduces the current situation of seawater desalination technology, technology development of seawater desalination is also reviewed. Moreover, sea water intake system, pre processing system, seawater desalination system as well as the main equipment parts, is explained in detail, the control requirements of seawater desalination manufacturing process are advanced.according to above reqirements, the network architecture, hardware and software platform of control system of seawater desalination system are designed.In addition, according to the complex, nonlinear, parameter time-varying and having lag characteristics of temperature control process of seawater desalination plant, the paper applies a method of combined the theory of the fuzzy with PID control, which synthesizes advantages of both PID control system in simple arithmetic, high reliability and low steady error, and fuzzy control system in agility and moronity. So a Fuzzy-PID temperature controller is proposed and the problem of stabilization in temperature control process of seawater desalination plant is resolved.Finally, the whole system including hardware configuration, software function of the control system is accomplished. Since the system has been put into use, the process of production and operation is stable and reliable, that increases production efficiency, reduces operating costs and labour intensity and achieves significant economic and social benefits.
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