Control System Analysis And Control Of Dissolved Air Flotation In Water Treatment

Flotation is a solid-liquid separation of the water purification technology, widely used at home and abroad. The water treated by flotation method can be achieved lower turbidity and small dosage. It is a green water purification technology. The core part of the flotation process is to control the air content and bubble size. However, for a long time, the technological level of manufacturing tiny air bubbles restrict the application of flotation technology. In this paper, PID control method to realize the control of dissolved air flotation system.This article analyzes the development of domestic and international air flotation technology to the status quo. And then dissolved air flotation system for the process and structure in detail. On this basis, determine the level and pressure of dissolved gas as the core of the control system. Establish a mathematical model of DAF process. Based on controlled conditions, given a set of realistic control scheme. Subsequently, design dissolved air process PID control. Use PID regulator mainly considering that it is the most common industrial process control of the controller, to reduce debugging time and increase efficiency and improve the conditioning effect of regulation is very useful. In the realization of control, selected Rockwell's ControlLogix 1756 Series PAC products, software, part of the core of the controller using the ladder language procedures for the preparation and operation of the screen is given in accordance with operational requirements. Control results by the PID to achieve dissolved gas pressure and liquid level control system can obtain satisfactory results. Finally, the article comprehensive analysis of the PID parameters in the control mechanism, combined with level adjustment process, given the actual PID parameter adjustment process and methods. In optimizing the control parameters, the successful application of dissolved air flotation tank to achieve PID pressure and liquid level control, are ideal control curve. At the same time, combined with the actual operation, summed up the value of flocculation G, return water, dissolved air volume, operating cycle and other parameters, effluent turbidity control in the desired range.At present, the technology has been successfully applied to water daily production work. The treated water meets state standards for existing water treatment industry ("People's Republic of urban construction industry standards" CJ/T206-2005). This research work on the development of Tianjin water has practical value for the flotation tank, provides a generally applicable method on research and use. The results can be applied across the country.