Effects of Sparger and Internals Designs on the Local Hydrodynamics in Slurry Bubble Column Reactors Operating under Typical Fischer-Tropsch Process Conditions - I

Abstract

Our rigorously validated Computational Fluid Dynamics (CFD) model (Basha Omar, M., L. Weng, Z. Men, and I. Morsi Badie. 2016. “CFD Modeling with Experimental Validation of the Internal Hydrodynamics in a Pilot-Scale Slurry Bubble Column Reactor.”International Journal of Chemical Reactor Engineering14(2):599–619), was used to predict the effects of spargers design and internals configuration on the local hydrodynamics and flow structure in a pilot-scale (0.3-m ID) and a large-scale (10-m ID) Slurry Bubble Column Reactors (SBCRs), operating under Fisher-Tropsch (F-T) process conditions. In the pilot-scale SBCR without internals, the 6-arms spider created small/fast liquid recirculations in the vicinity of the sparger and slow/large liquid recirculations at about 1.2 times reactor diameter, whereas, the 3-concentric-rings and perforated plate spargers created slow/large recirculations throughout the reactor. In the pilot-scale SBCR with internals, spargers with downward-pointing orifices created larger Sauter mean bubble diameters (ds), leading to more effective solids suspension when compared with those with upward-pointing orifices. Also, 3-concentric-rings spargers resulted in larger Sauter mean bubble diameter values when compared with those of 6-arms spiders. In the large-scale SBCR provided with a large 3-concentric-rings sparger, the effects of vertical parallel and bundled internals on the local hydrodynamics and flow structures were predicted. Bundled internals led to slower and smaller liquid recirculations, smoother radial gas holdup profiles, larger average gas bubbles size, and smaller local gas holdups, when compared those predicted when using parallel internals.

Novel Approach and Correlation for Bubble Size Distribution in a Slurry Bubble Column Reactor Operating in the Churn–Turbulent Flow Regime

“…The knowledge of gas bubble sizes and their holdups, among other parameters, is required for proper operation, modeling, and optimization of multiphase reactors , as such parameters are needed for solving reactor equations (mass, energy, and momentum balances) whether for numerical modeling or Computational Fluid Dynamics (CFD) simulations. − Intrusive and nonintrusive experimental methods have been developed and employed to investigate such parameters. , In bubble column reactors ,− and slurry bubble column reactors (SBCRs), ,− the manometric method (also known as the hydrostatic-head method) was often used to obtain the overall gas holdup; and the Dynamic Gas Disengagement (DGD) technique, coupled with a correlation relating the bubble rise velocity to the bubble diameter, such as that by Fukuma et al, was employed to calculate the gas bubble sizes as well as their corresponding holdups. This paper is mainly concerned with the behavior of gas bubbles and their holdups in SBCRs.…”