Abstract : This paper mainly focuses on the renovation project of the coal slurry water dosing system in four coal preparation plants. It analyzes the operating characteristics of the automatic dosing system for coal slurry water, proposes the necessity of using frequency converters, and discusses the application scope and performance characteristics of ABB frequency converters in the automatic control system for coal slurry water dosing. Keywords : ABB; frequency converter; coal slurry water; automatic dosing [b]1 Overview 1.1 Current Status of Coal Slurry Water Treatment in Four Coal Preparation Plants[/b] The coal slurry water treatment in the four coal preparation plants adopts the method of thickening and classifying coarse coal slurry using hydrocyclones, centrifuging for dewatering and recovery, and thickening fine coal slurry using a thickener, followed by underflow dewatering and recovery using a filter press. During the fine coal slurry thickening process, flocculants are manually added to the feed into the thickener to ensure the thickening effect. However, due to the instability of the quantity and properties of the feed coal slurry and the reliance on experience for manual addition, it is difficult to adapt to actual changes, resulting in the circulating water and underflow thickening of the thickener failing to meet process requirements. 1.2 Characteristics of Coal Slurry Water Treatment Process Adding flocculants to coal slurry water for concentration and sedimentation is one of the effective methods for treating fine coal slurry. However, this is an extremely complex physicochemical process. Many factors affect the sedimentation effect, and there are coupling phenomena between these factors, making the mechanism of action even more complex. The sedimentation process also has nonlinear characteristics; there are obvious nonlinear relationships between the amount of flocculant added and the concentration of circulating water, the underflow concentration of the thickener, and the coal slurry settling velocity. In addition, coal slurry sedimentation is a process with a large time lag, often taking more than ten minutes to complete, and the adjustment of process parameters often lags behind changes in disturbances. These characteristics of the coal slurry sedimentation process bring great difficulties to the establishment of a dynamic model of the sedimentation process and the implementation of model-based control strategies. In view of the above, the four coal preparation plants decided to automate the coal slurry water dosing system. By measuring the feed concentration and flow rate of the thickener and the overflow concentration of the thickener, a frequency converter is used to control the dosing pump motor to add flocculants in a timely and accurate manner to meet the process requirements. 2. Necessity of Applying Frequency Converters (1) Using AC asynchronous motors for frequency conversion speed regulation improves reliability and accuracy, and reduces flocculant consumption. (2) Simplifies the control system, facilitates process control, increases the reliability of the control system, and makes the automatic dosing system maintenance-free. (3) Improves the quality of circulating water and enhances product quality. [b][align=center]For more details, please click: Design of Automatic Flocculant Dosing System and Application of Frequency Converters[/align][/b]