ONLINE GAS AND SOLIDS HOLDUP ESTIMATION IN SOLID-LIQUID-GAS SYSTEMS

A technique for on-line simultaneous estimation of gas and solids holdup (volume fraction), based on a combination of conductivity and pressure difference measurements, is proposed and tested in a laboratory flotation column (10 cm in diameter and 447 cm in height). Fundamental concepts underlying this technique and the effect of relevant parameters are discussed. In the studied range, 3-30 % v/v gas holdup and 2-18 % v/v solids holdup, experimental results showed good agreement between the estimated and actual holdup values (as determined by an isolating technique). The relative accuracy of the solids holdup estimate increased when solids density or solids concentration increased. It was shown that for a given system there is a minimum distance between the pressure sensors to achieve a given relative accuracy of the holdup estimate. Frequent recalibration of pressure transducers was found necessary for accurate phase holdup estimation.