Gas Holdup in a Shallow Bubble Column Measured by Electrical Capacitance Tomography (ECT)

The influence of orifice gas velocity and orifice diameter on timeaveraged gas holdup distributions were investigated in a 0.14 m inside diameter shallow bubble column using ECT. In all the experiments, deionised water was liquid phase and air was gas phase. The gas hold up profileswere measured at two axial locationsat 4.75 and 17.75 cm above the distributor level. Orifice gas velocity was varied from 4 to 186 m/s. Single nozzle sparger was used as gas distributor. The free area of sparger plates and orifice diameter were varied in the range of 0.14% to 1.31% and 5.3 to 16.0 mm,respectively. It is found that the gas holdup increases with the increase of orifice gas velocity. As the gas velocity increases beyond uN=19 m/s, a change of slope profile marks the regime transition from bubbling regime to jettingregime. Gas holdupincreases with the increase of orifice diameter at the same orifice gas velocity. A higher dominant frequency and a broad band are observed with the increase soforifice diameterInddition,thetransition gas velocity(uN,trans) isobtainedanddecreases with the increase of orifice diameter. Finally, the value of orifice diameter (d0) that distinguished the small and larger orifice is estimated in air-water systems compared with the results of other researchers.