A New Graphical Method for Calculation of Mass Transfer Time in a Deep Bubble Bed

Abstract

A new method for graphical determination of mass transfer (saturation) time in a deep bubble bed (BB) was developed. It is based on the spatial distribution of the local liquid-phase concentrations C_L(t) measured by means of an electrical conductivity probe. The raw C_L(t) data were obtained in a 0.289-m-ID bubble column equipped with a perforated plate gas distributor (31 holes × ø2 × 10^–3 m). Three different clear liquid heights (L₀ = 0.56, 1.12 and 1.84 m) were examined. The shallow BB (L₀ = 0.56 m) was aerated at superficial gas velocities u_g = 0.018, 0.031, and 0.038 m·s^–1, respectively. Both medium (L₀ = 1.12 m) and deep (L₀ = 1.84 m) BBs were aerated only at u_g = 0.038 m·s^–1 (churn-turbulent flow regime). It was found that the new graphical method is applicable only for a deep BB (L·D_c^–1 = 7.3). In that particular case, the difference between the experimental mass transfer time and the graphically determined one is reasonable (the maximum relative error is only 6.9%). Therefore, the new graphical method should be adopted for experimental determination of the mass transfer time in a deep BB. The new method is of practical importance because the industrial bubble columns operate with deep BBs.