An Electrical Conductivity Method for Axial Gas and Solid Holdup Determination in Three Phase Fluidized Beds

Abstract--- Fluidization is an operation in which solid particles are kept under suspension supported by the upward flow of liquid/gas phase. In classic fluidization the solids density are higher than the liquid, where as in Inverse fluidization the solids density are lower than that of continuous liquid phase. The phase holdup measurements in three phase classic/inverse fluidized beds are very important and difficult to measure. The phase holdups can be estimated with the help of pressure drop data and height of the bed/solids mass balance with an assumption of axial uniform solid holdup. In most of the fluidized bed operations, such as Catalytic fluidized bed and slurry bubble columns the solids holdup varies axially. Such type of systems, holdups estimation is very difficult. The present study is focused on electrical conductivity method to get directly the cross sectional liquid holdup and pressure drop to solve the above problem of axial solid holdup variation and can readily be obtained the cross sectional three phase holdups. The averaged normalized conductance and the liquid holdup are related with liquid conductivity with a power law mode of equation. The dependency of conductivity on liquid also varies with electrode size and non-conducting medium (gas/solid). The experimental results showed that the conductivity method developed in this work was convenient for use and had a good accuracy in a wide range of liquid holdup (0.4 to 1) in the Gas-Liquid–Solid three-phase fluidized bed systems. The effect of temperature on conductivity of liquid phase was also verified and successfully correlated.