Liquid Dispersion in Large Diameter Bubble Columns, with and without Internals

Abstract

Liquid mixing has been studied in a 1 m diameter bubble column, with and without internals (vertical cooling tubes). The presence of internals significantly affects both large scale recirculation and local dispersion. The most common approach to model liquid mixing is the one‐dimensional axial dispersion model, validated many times in small bubble columns without internals. This paper shows that this model is still appropriate to large columns, but without internals. A two‐dimensional model, taking into account a radially dependent axial velocity profile, and both axial and radial dispersion, is required to account for the internals on liquid mixing.

Modeling and optimization of a large-scale slurry bubble column reactor for producing 10,000bbl/day of Fischer–Tropsch liquid hydrocarbons

“…For perforated plates, the exponent a depends on z, which is expressed as: Table 1 are valid when the volume of internals, commonly used in SBCRs for cooling or heating purposes, is 20% of the reactor volume. This is because several literature findings (Chen et al, 1999;De et al, 1999;Forret et al, 2003;Joseph, 1985;O'Dowd et al, 1987;Saxena et al, 1992;Saxena and Chen, 1994;Shah et al, 1978;Yamashita, 1987) showed limited or no effect of internals on the hydrodynamic and mass transfer parameters as long as their volume fraction remains under 20%. Also, these correlations should be valid for reactor Table 1 Gas holdup, Sauter mean bubble diameter and mass transfer coefficient correlations used in the model Behkish et al, 2006) Total gas holdup (Behkish et al, 2006) e …”

Hydrodynamics in bubble columns with pin-fin tube internals

“…A c c e p t e d M a n u s c r i p t Furthermore, the simulated results were not validated against benchmark experimental data and even showed opposite effects of internals on liquid velocity in comparison with experimental results (Forret et al, 2003b;Zhang et al, 2009). Zhang et al (2011) developed a 1D porous media model to simulate hydrodynamics in bubble column with internals.…”

“…The measured results indicated that internals had little effect on liquid velocity and gas holdup, while the presence of internals significantly decreased the turbulent stresses and eddy diffusivities. Forret et al (2003b) employed a trace technique to investigate liquid dispersion in a 1 m diameter bubble column with 56 tube internals, each 63 mm in diameter and covering 22.2% of total column CSA. They observed that the presence of internals gave rise to decreases of liquid fluctuation velocity and radial dispersion, and an enhancement of large scale liquid circulation, but there were no experimental data presented in the work to reflect the influence of internals on the liquid velocity.…”

Fischer–Tropsch Synthesis in Slurry Bubble Column Reactors: Experimental Investigations and Modeling – A Review

“…The large-scale liquid recirculation increased when internal vertical tubes covered a large cross-sectional area (~22%) [315], while a less covered cross-sectional area (5%) did not affect the liquid recirculation [314]; 10. Forret et al [315] proposed a 2-D model, which seemed to provide good prediction for large BCRs with and without vertical tube internals; and 11. Vertical tubes increased the heat transfer coefficients more than horizontal internals did [332].…”

“…Modeling BCRs with internals was attempted by Forret et al [315], who developed a 2-D model to predict the effect of internals on the liquid mixing by accounting for an axial dispersion coefficient (D ax,2-D ), a radial dispersion coefficient (D rad,2-D ), and a radially dependent axial velocity profile. They reported that the presence of internals decreased the liquid fluctuation velocity and enhanced the large-scale liquid recirculation based on their liquid tracer experiments.…”