Measuring turbulence in a flotation cell using electrical resistance tomography

Abstract

Measuring turbulence in an industrial flotation environment has long been problematic due to the opaque, aggressive and abrasive three-phase environment in a flotation cell. One of the promising measurement techniques is Electrical Resistance Tomography (ERT). By measuring the conductivity distribution across a measurement area, ERT has been adopted by many researchers to monitor and investigate many processes involving multiphase flows. In the research outlined in this paper, a compact ERT probe was built and then used to measure the conductivity distribution within a 60L flotation cell operated with water and air. Two approaches were then developed to process the ERT data and estimate turbulence related parameters. One is a conductivity variance method and the other is based on the Green-Kubo relations. Both rely and use the fluctuation in the ERT measurement caused by bubbles moving through the measurement area, changing the density of the fluid. Results from both approaches were validated by comparing results produced by the ERT probe in a 60 litre flotation cell operated at different air rates and impeller speeds to that measured using an alternative turbulence measurement device. The second approach is considered superior to the first as the first requires the development of auxiliary information which would not usually be known for a new system.

Mixing of Oil in Water Through Electrical Resistance Tomography and Response Surface Methodology

“…The adjacent strategy is based on applying currents or voltages through a pair of electrodes and obtaining the resultant currents or voltages through all other pairs until all electrode pairs have been employed . This strategy has been widely applied in many studies , . In this strategy, an individual voltage measurement is done through the equation n e ( n e – 3)/2 where n e is the number of electrodes (i.e., 16 in this study) in each plane, providing 104 measurements.…”

A review of turbulence measurement techniques for flotation

“…bubble velocity and size, fluid turbulence, gas holdup, conductivity of the solid, etc.). Meng et al (2015a) have applied ERT for turbulence measurement in a flotation cell. They built an ERT probe that could be inserted into a flotation tank and used for localised turbulence measurement (Fig.…”

“…Though the work of Meng et al (2015a) has proven that ERT can be used for measuring turbulence in a laboratory flotation cell operating with two phases (liquid-gas), it is yet to be tested in more complicated conditions, such as in a three phase turbulent flow. It is also yet to be tested in larger scale flotation cells where there is likely to be larger variations in the bubble size distribution which may adversely affect the ERT data processing algorithm and require correction.…”

Experimental quantification of turbulence and its applications in the study of multiphase flotation pulps

“…Although turbulence plays a key role in wide range of industries, until now it has not been possible to undertake detailed model validation and sufficient study to turbulence due to the lack of proper measurement tools (Meng et al,2014a;Meng, Xie, Runge, et al,2015a), especially for multi-phase flows such as in flotation cells.…”

“…The ERT device used by Meng et al (2015a) has a maximum data frame rate of 1 kHz, meaning that the frequency response is limited to this frame rate. The current derived velocity fluctuation, on the other hand, is just an average value on the measurement plane defined by the electrode array.…”