Mixing performance in continuous oscillatory baffled reactors

Abstract

Areal distribution of mixing intensityIn the current literature, there is limited information on the influence of operating parameters on spatial mixing quality and how a secondary feed should be introduced into continuous oscillatory baffled reac tors (COBR) to achieve good mixing quality. This work explores for the fi rst time the impact of the posi tion of a secondary feed (passive non reactive tracer) on spatial mixing performance in a COBR using transient laminar CFD simulations. Three theoretical feed positions are stuclied covering a range of net flow and oscillatory Reynolds numbers (Re,,.,= 6 27 /Re0 = 24 96), the range being chosen to ensure that the flow field remains two dimensional in ail cases. Macromixing is evaluated by analysing the spa tial uniformity of the tracer with the areal distribution method developed by Alberini et al. (2014a). Introduction of the secondary stream at the reactor wall or upstream of the edge of the first b affle greatly improves mixing quality due to the recirculation edclies, which assist radial mixing. However, introduc tion of the secondary feed at the centreline results in high axial dispersion with limited radial mixing. With an adequate introduction position, mixing quality typically increases with an increment in the velocity ratio. Nevertheless, if the net flow is too low, mixing performance decreases because the sec ondary stream is pushed upstream of the baffles, where it does not benefit from flow recirculation.

Electrochemical oscillatory baffled reactors fabricated with additive manufacturing for efficient continuous-flow oxidations

“…As seen on table 1, an increase in frequency from 1Hz to 5Hz implied an increase of the potential drop for the tested amplitudes (Table 1, entries 1 and 4). The effect of frequency achieved a maximum, evidenced by the lack of significant improvement at 10 Hz (Table 1, entry 7), in line with the behaviour reported for COBRs in the literature [13,26,30]. Regarding the effect of amplitude, at 1Hz, the potential drop…”

Electrochemical Oscillatory Baffled Reactors Fabricated with Additive Manufacturing for Efficient Continuous-Flow Oxidations

“… 12 , 25 This has been explained as once a threshold frequency is trespassed, the effect of the oscillatory flow dominates over the net flow, the continuous reactor operates more likely to a batch reactor, and mixing is hindered. 32 …”

Revisiting the Effect of U-Bends, Flow Parameters, and Feasibility for Scale-Up on Residence Time Distribution Curves for a Continuous Bioprocessing Oscillatory Baffled Flow Reactor

“…This allows higher amplitudes to attain plug flow characteristics while the net flow controls the movement of the tracer. 42 Furthermore, high TiS values are achieved when f is at the lower end of the experimental range corresponding to ψ near 2. The TiS number is maximized around a value of ψ = 2, and hence high x O (8−12 mm) appears to produce higher TiS numbers.…”

“…Therefore, past a velocity ratio of 2.27, the TiS begins to decrease, which coincides with an increase in axial dispersion. 33,42 The fluid kinetics which explains the decrease in TiS, and therefore an increase in axial dispersion relates to both the axial and radial mixing within the reactor. As stated by Smith et al, a minimum axial dispersion is achieved at a certain Re o , where the vortices created by the net flow and fluid oscillation redistribute the tracer in a radial direction only.…”