(495d) Mass Transfer Enhancement as a Function of the Oscillatory Baffled Reactor Design

The oscillatory baffled reactor (OBR) is an intensified design of plug flow reactor (PFR). It is able to achieve a high degree of plug flow at very low flow rate due to the interaction between the oscillatory flow and baffles which improves mixing inside the OBR. It was found that superimposing fluid oscillation in a baffled column enhanced the mass transfer significantly comparing with many devices, for instance, bubble column, internal and external loop column, and stirred tank. This is due to the highly turbulent flow pattern that generated in the OBR as a result of the oscillatory motion which leading to frequent bubble breakage, a subsequent reduction in the Sauter mean diameter, an increase in bubbles retention, when trapped in recirculating vortices, and the gas-liquid contacting area

Recently, oscillatory baffled column (OBC), has used for the same purpose, mass transfer, and presented a significant change in which has been increased up to sixfold comparing with a bubble column. This was due to the combanation effect of baffles and oscillatory motion that increase the radial mixing (diffusion). Also gas-holdup affected by the oscillation frequency and amplitude.

In this study, the volumetric mass transfer coefficient (k_La) in air-water system has been calculated and compared using three designs of OBRs, smooth periodic constrictions (SPC) design, helical baffled design, and single orifice design. This work was conducted over a wide range of oscillation condition and aeration rate, volumetric air flow rate. The SPC presented higher values of k_La than the single orifice baffled reactor and the helical baffled reactor. This indicates that SPC with oscillatory motion provide bigger interfacial contact area between air and water. In addition, the visualisation of bubbles movements inside the three designs of OBR has shown that the bubbles collision and breakage in SPC was more severe. Therefore the bubble size in SPC was smaller than those that achieved in the single orifice OBR then in the helical OBR.