Chemical Diagnosis And Auto-control Based On Water Quality Parameters For Thermodynamic Cycle System

Basing on the Water/steam system in thermal system, the significances and excellent prospect of water quality chemical diagnosis research is described according to the features of water/steam quality monitoring as well as the deficiency in fault diagnosis and preventive measures. In this research, the mechanisms and features of faults caused by impurities in Water/steam system is roundly analyzed by using both temperature response of water quality and one real case study. At the mean time a water quality chemical diagnosis expert system and a real-time monitoring software are developed applying with methods of ES (Expert System) and fault diagnosis etc.Six typical working conditions models of boiler water have been chosen to manage the changes in electrical conductivity and pH, which are traced at different temperatures. Following conclusions can be draw by analyzing the experiment results: â‘  Different water sample can lead to great differences in electrical conductivity temperature compensate coefficient, so the temperature compensate coefficient should be chosen according to actual condition. â‘¡ The conductivity temperature responses are coincident with Arrhenius equation. The influences from the temperature to the values of conductivity activation energy (Ea) are slim. Therefore Ea can be acomparison index of thermodynamic parameters for different systems.Taken the air cooled heat exchanger of some company as an example, the corrosion failure of an air-steam heat exchanger was analyzed by means of water quality analysis, temperature response of pH and conductivity as well as SEM, EDS and XRD. The diagnosis concludes that the cooperation of oxygen corrosion and CO₂ corrosion is the primary reason for the failure. The feasibility of using water quality as basic data for fault diagnosis is also validated.In this research, the water/steam fault diagnosis in the company of ES method is discussed. Basing on the results of case study and literatures, some modules of water quality diagnosis expert system, such as such as primarily parameter, form of knowledge and rules of diagnosis, are established;knowledge library, software interface and key rules are developed;function frames of distinguish abnormal real-time data and online diagnosis are constructed. The reasons of fault, influences and corresponding preventive measures have been provided as well.In the end some introductions are given for the developing process of monitoring software, communication between monitoring software and local instruments, communication between monitoring software and diagnosis expert system through DDE(Dynamic Data Exchange) as well as dynamic Web publishing of monitoring interface etc.