(110b) The Impact of Low Dynamic Liquid Levels on the Flow Pattern in Pilot Plant Bubble Column Reactor

Hayder Al-Naseri^€, J. P. Schlegel*, and Muthanna H. Al-Dahhan^{††*♣}

^†Chemical and Biochemical Engineering Department

^*Mining and Nuclear Engineering Department

Missouri University of Science and Technology, Rolla, MO 65409, USA

^♣Cihan University-Erbil, Iraq

^€Chemical Engineering Department, Tikrit University, Tikrit-Iraq

Abstract

Numerous studies on flow pattern were conducted in lab scale bubble columns with high dynamic liquid level (aspect ratio, H/D ≥ 5), while in the industry the typical dimension is H/D ≤ 5. Therefore, the purpose of this work is to study the effect of low aspect ratio (H/D ≤ 5) on the flow regime transitions in an industrial-sized bubble column. The flow regime at three aspect ratios (H/D = 3, 4, and 5) was demarcated experimentally using linear and non-linear methods, which are represented by the drift-flux and Kolmogorov Entropy (KE), respectively. The four-point optical fiber probe technique has been used to quantify the bubble properties at different regimes and to infer the flow pattern. The experiments were conducted in a bubble column of 0.6 m I.D. and 3.89 m height. The superficial gas velocity varied from 0.005 m/s to 0.45 m/s. The results exhibit that the variation in the aspect ratio has a significant impact on the transition velocity to the churn turbulent regime, while the overall gas holdup in the churn turbulent regime increases with the aspect ratio decreasing. Three mean regimes were indicated by the linear method: bubbly, transition, and churn turbulent. Four regimes are demarcated by the nonlinear method: gas maldistribution, bubbly, transition, and churn turbulent. The results for transition velocity show disagreement with data in the literature. While the empirical correlations of Ribeiro [1], and Şal et al. [2], which are validated with experimental results, introduce a good agreement with percentage errors of 8.6-17.3% and 8.26-25.69%, respectively.

Keywords; Bubble column reactors, Flow regime, Fischer-Tropsch (F-T), Bubble Dynamics

[1] C. P. Ribeiro, “On the estimation of the regime transition point in bubble columns,” Chemical Engineering Journal, vol. 140, no. 1–3, pp. 473–482, 2008.

[2] S. Şal, Ömer F. Gül, Mustafa Özdemir, Ö. F. Gül, and M. Özdemir, “The effect of sparger geometry on gas holdup and regime transition points in a bubble column equipped with perforated plate spargers,” Chemical Engineering and Processing: Process Intensification, vol. 70, pp. 259–266, 2013.