Auto-Aspirated DAF Sparger Study on Flow Hydrodynamics, Bubble Generation and Aeration Efficiency

Dmitry Vladimirovich Gradov,Kari Ullakko,Janne Kauppi,Andrey Saren,Tuomas Koiranen

doi:10.3390/pr8111498

Dmitry Vladimirovich Gradov, Kari Ullakko + Show 3 more

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https://doi.org/10.3390/pr8111498

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Abstract

A novel auto-aspirated sparger is examined experimentally in a closed-loop reactor (CLR) at lab scale using particle image velocimetry, high-speed camera and oxygen mass transfer rate measurements. State-of-the-art 3D printing technology was utilized to develop the sparger design in stainless steel. An insignificant change in the bubble size distribution was observed along the aerated flow, proving the existence of a low coalescence rate in the constraint domain of the CLR pipeline. The studied sparger created macrobubbles evenly dispersed in space. In pure water, the produced bubble size distribution from 190 to 2500 μm is controlled by liquid flow rate. The bubble size dynamics exhibited a power-law function of water flow rate approaching a stable minimum bubble size, which was attributed to the ratio of the fast-growing energy of the bubble surface tension over the kinetic energy of the stream. Potentially, the stream energy can efficiently disperse higher gas flow rates. The oxygen transfer rate was rapid and depended on the water flow rate. The aeration efficiency below 0.4 kW/m3 was superior to the commonly used aerating apparatuses tested at lab scale. The efficient gas dissolution technology has potential in water treatment and carbon capture processes applications.

Highlights

The ongoing sustainable development of the constantly growing worldwide population will not be possible if the existing water treatment issues are not addressed
The stream diameter was assumed to be constant in all the zones
Most of the coalescence was observed in the centre of the stream, and this was attributed to the high turbulence

Summary

Introduction

The ongoing sustainable development of the constantly growing worldwide population will not be possible if the existing water treatment issues are not addressed. Water resources require treatment to remove hazardous pollutants before they can be reused, but technical progress in this regard has been relatively limited. Pulse corona discharge [2], to neutralize the water pollutants of complex organic and inorganic origin, represents an optimal solution. Harmful complex-structure pollutants are converted into prime elements that are non-hazardous. Dissolved air flotation (DAF) processes have been developed over the past few decades and have been found to represent feasible technical solutions for the removal of contaminants from water [3]. DAF processes use solution aeration to remove contaminants such as ions, liquid effluent or solid particles [4,5,6], or fast oxygenation to chemically disintegrate hazardous compounds [3,7]

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