A Two-Phase Computational Fluid Dynamics Model for Ozone Tank Design and Troubleshooting in Water Treatment

Abstract

A computational fluid dynamics (CFD) tool was employed to design and study ozone contactors. The emphasis was to achieve the desired flow distribution. The Eulerian-Eulerian multiphase model was used with the standard k-ε turbulent model. The water surface was slip wall boundary and was specified as a sink to remove ozone bubbles. For a single-column contactor with side entry, the flow pattern was found to be crucially dependent on both the direction and magnitude of the entry velocity from the inlet pipe. It was difficult to achieve uniform gas concentration over the contactor volume. In a multicompartment contactor, the countercurrent flow resulted in a mixed flow condition and the mixing increased with a higher gas rate. For the cocurrent flow, water was accelerated by the gas and the plug flow pattern was achieved. The flow distribution in each compartment can be significantly different even though the overall residence time distribution curves are similar.any different ozone contactor configurations are employed in the water industry (Bellamy, 1995;Langlais et al., 1991). The design aim is to distribute the flow uniformly over the volume of the contactor so that water is in contact with the gas allowing for the mass transfer. The flow in the contactor is governed by both water and gas flow.The inlet distribution of water is employed in many processes in water and wastewater applications. These systems are subject to many design studies and the flow pattern is intuitively understood. Distribution of gas into the tank can be subdivided into two groups: gas into a still water tank and gas into a flow-through system. Distribution of gas through a still tank is employed in, for example, aeration systems and airlift devices. The gas bubbles rise and induce vertical water flow and M

A comparison of the Eulerian and particle tracking approaches for prediction of ozone contactor performance

“…The use of an advanced modelling tool, computational fluid dynamics (CFD), has increasingly been applied for the simulation of various disinfection processes, including chlorination, UV irradiation, and ozonation (Do-Quang et al 1999;Greene 2002;Ta & Hague 2004;Templeton et al 2006;Zhang et al 2008). With a CFD modelling approach, the velocity field, residence time distribution (RTD), and disinfectant profiles can be obtained by numerical solution of the Reynolds-averaged Navier-Stokes and species transport equations (Zhang 2007 CFD modelling has also been employed for directly predicting disinfection treatment efficiency (Do-Quang et al 2002;Greene 2002;Mofidi et al 2004;Ducoste et al 2005).…”