Scale-up of Bubble Column Reactors: A Review of Current State-of-the-Art

Abstract

In multiphase flow reaction systems, in general, an extrapolation of small diameter behavior to larger ones is always an important and challenging task. The critical issue in such an extrapolation remains to be mixing and hydrodynamic characteristics. It needs reliable similarity criteria that would result in similar mixing and hydrodynamics and hence transport and performance in two different scales. Numerous experimental and computational studies have been performed to investigate the flow behavior of bubble column reactors for a proper design and scale-up. Experimental techniques vary from simple visual observation to more advanced noninvasive diagnostic techniques. On computational front the progress has been made from simple reactor models to fundamentally based Computational Fluid Dynamics (CFD). Such studies ultimately provide a knowledge that help in understanding the hydrodynamic and mixing characteristics of these reactors and would aid in its scale-up. Based on these studies, various methodologies have been proposed in literature for scale-up and/or to maintain their hydrodynamic and mixing similarity. This article attempts to review the current state of reported dynamic similarity and scale-up methods of bubble column reactors. It mostly covers the methods reported in open literature. The scale-up practices in industry appear to be proprietary for obvious reasons.

Influence of internals on counter-current bubble column hydrodynamics: Holdup, flow regime transition and local flow properties

“…The correct design and operation of these devices rely on the proper prediction of the flow pattern, the flow regime transition, and global and local flow properties (i.e., the holdup, ε G ; the bubble rise velocity, u b ; the local void fraction, ε G,Local ; and the bubble diameter, d b ). The global and local flow properties of the industrial reactors may be extrapolated from the laboratory facilities applying scale-up methods (Shaikh and Al-Dahhan, 2013). Bubble columns are frequently studied without considering internals ("Open Tube", OT, bubble columns), but, in most industrial applications, internal devices are often added to control heat transfer, to foster bubble break-up or to limit liquid phase back mixing (Youssef Ahmed et al, 2013).…”

Compact heat exchange reactor for synthesis of mixed alcohols

“…Heat removal is an important factor to consider when designing a synthesis gas conversion reactor. The commercial reactors for large-scale plants are: multitubular boiling water reactors such as those used by Shell [20] in Bintulu and Pearl GTL, slurry bubble column reactors [21] as used by Sasol, SynFuel China in GTL and CTL plants, and fluidized bed reactors as used by Sasol for high temperature Fischer-Tropsch Synthesis. All these designs are not feasible for small and portable synthesis gas conversion plants.…”

Ebullated bed fluid dynamics relevant to industrial hydroprocessing

“…When reviewing previous bubble column scale-up attempts, Shaikh and Al-Dahhan (2013) noted that no method has yet been able to completely model the local and global behaviour. Nonetheless, the proposed methodologies provide an overview of relevant physical characteristics and general considerations when attempting to achieve dynamic similitude for a gas-liquid-solid fluidized bed.…”

“…Considering the average errors between predictions and experimental results, particularly for the gas holdup, it is difficult to conclude whether the previous correlations would result in suitable local and global fluid dynamic similitude under the high gas holdup conditions of interest. As discussed by Shaikh and Al-Dahhan (2013), scaling approaches for multiphase reactors are currently more of an art than science. It is nonetheless believed that by considering the important geometric and fluid dynamic characteristics of a studied system, in this case the LC-Finer SM , scaling between industrial and laboratory equipment using a dimensionless approach can still provide relevant observations.…”