The Effect of Superficial Gas Velocity and Aerated Liquid Height on the Spatial Distribution of Local Liquid-Phase Axial Dispersion Coefficients in a Bubble Column

JOURNAL OF CHEMICAL ENGINEERING OF JAPAN

Kohei Ogawa¹  Stoyan Nedeltchev¹  Shinichi Ookawara¹ 

[1] Department of Chemical Engineering, Graduate School of Science and Engineering, Tokyo Institute of Technology

关键词: Bubble Column;    Absorption;    Regime Transition;    Axial Dispersion Coefficient;    Spatial Distribution;   

DOI  :  10.1252/jcej.38.1

来源: Maruzen Company Ltd

【 摘 要 】

References(57)Cited-By(1)The spatial liquid-phase concentrations were measured by means of an electrical conductivity probe in a 0.289-m ID bubble column operated at superficial gas velocities (ug) of 0.018, 0.031 and 0.038 m/s, respectively. The column was equipped with a perforated plate gas distributor (0.002 mø × 31 holes). Carbon dioxide was used as a tracer gas, whereas deionized water was used as a liquid phase. The local liquid-phase axial dispersion coefficient EL was derived from the local liquid-phase concentrations by means of the graphical method developed by Khang and Kothari (1980). It was found that the spatial distribution of the local EL coefficients becomes radially non-uniform as a function of ug. At the regime transition velocity (Utrans = 0.031 m/s) between bubbly and transition flow regimes the mean, EL coefficient for the upper zone (UZ) becomes identical to the one for the lower zone (LZ). At both lower and higher ug values EL(UZ) is systematically higher than EL(LZ). The same result also holds if the overall bubble bed (BB) is divided into core and annulus regions. It was proven that, in the bubbly flow regime (ug < Utrans), EL (core region) ≈ EL (annulus region), whereas in the transition flow regime (ug > Utrans), EL (annulus region) > EL (core region). The effect of the aerated liquid height L on the spatial distribution of the local EL coefficients was studied, as well. Three different BBs, viz. L = 0.64 m (shallow BB), 1.28 m (medium BB) and 2.1 m (deep BB) were examined at ug = 0.038 m/s. The spatial distribution of the local EL coefficients was most scattered in the shallow BB (L = 0.64 m). In a medium BB with an aerated liquid height L = 1.28 m the existence of a well-developed helical flow structure was detected.It was shown that the graphically determined mean EL coefficient (for the overall BB) increases as a function of both the superficial gas velocity ug and aerated liquid height L, and a useful empirical correlation was derived. It covers the following range of bed aspect ratios: 2.1 ≤ L/Dc ≤ 7.3.

【 授权许可】

Unknown