Electrical resistance tomography coupled with differential pressure measurement to determine phase hold-ups in gas–liquid–solid outer loop bubble column

Radial variation of the gas hold-ups and mean hold-ups are investigated in a 90 mm outer loop bubble column using electrical resistance tomography (ERT) with two axial locations (Plane 1 and Plane 2). In all the experiments, air is used as the gas phase, tap water as liquid phase, and polypropylene particles as solid phase where the superficial gas velocity is varied from 0.02 to 0.25 m/s. The effect of operating conditions, solid concentration on mean hold-ups and radial gas hold-ups distribution is discussed. Gas hold-ups and solid hold-ups results using ERT are in very good agreement with conventional estimation and correlations obtained using pressure transmitter methods. Meanwhile, the results show that the gas hold-ups in the centre region increase constantly with an increase in the superficial gas velocity, namely there is a maximum hold-up at the centre of cross-section. But, solid hold-ups distribution is very homogeneous for high gas velocity. According to the visible image, the gas–liquid flow behaviours are obtained for gas–liquid–solid outer loop bubble column. Furthermore, the results also indicate that ERT is a very powerful tool for diagnosing the ‘inside’ flow behaviour of gas–liquid–solid three phase bubble column.