Bubble Size Distribution in a Slurry Bubble Column Reactor Operating in the Churn−Turbulent Flow Regime

Significance 

For the proper operation, optimization and modeling of multiphase reactors, adept knowledge of gas bubble sizes and their holdups and various other parameters are an inevitable necessity. In order to investigate the various parameters, intrusive and nonintrusive experimental techniques have been established. Narrowing down to the bubble column reactors and slurry bubble column reactors (SBCRs), the manometric method and the dynamic gas disengagement technique have overtime been used to obtain gas bubble sizes and their holdups. The latter has metamorphosed to the “two-bubble” or “bimodal” class model, which has been widely used to represent the gas bubbles in the convective and dispersive flow schemes within SBCRs. Unfortunately, despite its popularity, the bimodal class model lumps gas bubbles into only two classes, which is a gross oversimplification of the complex hydrodynamics in SBCRs. This causes a misrepresentation of the different gas bubble present in the SBCRs. Therefore, this raises a general concern of the behavior of gas bubbles and their holdups in SBCRs.

Recently, Professor Badie Morsi and Dr. Omar Basha (postdoctoral fellow) from the Department of Chemical and Petroleum Engineering at University of Pittsburgh developed a novel approach that enabled more accurate representation of the different gas bubble classes present in a SBCR operating under high pressures and temperatures. They also focused on developing accurate correlations for predicting the Sauter mean bubble diameter under such conditions. Their work is currently published in the research journal, Industrial & Engineering Chemistry Research.

The research method employed commenced with the utilization of a Gas−Liquid−Solid Systems where a total of 720 dynamic gas disengagement experiments, coupled with the manometric method to measure the overall gas holdup, were conducted in a high-pressure, high-temperature pilot-scale SBCR. Next, the researchers utilized the manometric method to calculate the overall gas holdup in the pilot-scale SBCR for the gases in the corresponding slurry systems. Lastly, they employed the conventional dynamic gas disengagement technique to compute the bubble sizes.

The authors observed that the bubble size distribution obtained using the novel approach followed a log-normal distribution function. They also noted that by correlating the functions of the system’s physical properties and operating conditions, bubble diameters (d32) could be predicted with an absolute average relative error of 11.72%. Moreover, they noted that when the predicted bubble diameter was applied to the values of d32 available in literature, an overall absolute average relative error of 24.27% was obtained.

In summary, Omar Basha-Badie Morsi study presented a novel approach for obtaining the gas bubble size distributions in SBCRs. Generally, they observed that from the correlations undertaken, the new mean and variance correlations coupled with the log-normal distribution function were able to predict the Sauter mean bubble diameters obtained in a pilot scale SBCR. Altogether, for a multiphase system, given the physical properties and operating conditions and the log normal bubble size distributions, the mean, variance, and the Sauter mean bubble diameter can be predicated using the proposed novel correlations with good accuracy.

Reference

Omar M. Basha, Badie I. Morsi. Novel Approach and Correlation for Bubble Size Distribution in a Slurry Bubble Column Reactor Operating in the Churn−Turbulent Flow Regime.. Ind. Eng. Chem. Res. 2018, volume 57, page 5705−5716..

Go To Ind. Eng. Chem. Res. 2018

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