Oscillatory flow reactors (OFRs) for continuous manufacturing and crystallization

In this article we review the concepts and key developments of mixing enhancement through pulsation and oscillation. We focus on more recent research using oscillations in baffled tubes or columns, which generate discrete vortices as distinct from the more random type of flow produced by the well-established pulsed plate and reciprocating plate column devices. The scope of this review ranges from the basic chemical engineering concepts and key findings from recent research projects, including heat/mass transfer and residence time distribution (RTD); to applications and case studies involving specific reactions, e.g. polymerization and process intensification. We hope that this review will enable the reader to identify additional potential and perhaps an unexpectedly wide range of applications for the oscillatory baffled flow technology.

Mixing Through Oscillations and Pulsations—A Guide to Achieving Process Enhancements in the Chemical and Process Industries

Design of a prototype miniature bioreactor for high throughput automated bioprocessing

Oscillatory flow reactors (OFRs) are a novel type of continuous reactor, in which tubes fitted with orifice plate baffles have an oscillatory motion superimposed upon the net flow of the process fluid. The combination of baffles and the oscillatory motion creates a flow pattern conducive to efficient heat and mass transfer while maintaining plug flow. Unlike conventional tubular reactors, where a minimum Reynolds number must be maintained, tube-side mixing is independent of the net flow, allowing long residence times to be achieved in a reactor of greatly reduced length-to-diameter ratio. We have evaluated a pilot-scale OFR as a method for continuous production of sterols in an ester saponification reaction. The OFR achieved the required product specification, in a residence time one-eighth that of a full-scale batch reactor. To better understand the effect of the process variables on the reactor performance, the OFR was modeled using a tanks-in-series residence time distribution, combined with the saponi...

/pdf/operation-and-optimization-of-an-oscillatory-flow-continuous-fhv6eiknc2.pdf

Operation and Optimization of an Oscillatory Flow Continuous Reactor

Oscillatory flow reactors (OFR) have been actively developed over the last fifteen years at a number of UK universities, including the department of Chemical Engineering, University of Cambridge. OFRs exploit the uniform and efficient vortex mixing that can be achieved when an oscillatory fluid motion interacts with orifice plate baffles in a tube. One particularly advantageous application area that has been investigated is for performing ‘long’ (usually over 10 minutes) reactions in configurations which are substantially more compact than batch reactors, and which have substantially smaller length to diameter ratios than conventional tubular reactors. The development of OFRs is at a stage where laboratory and pilot scale feasibility is proven, but where no design methodology exists to implement the OFR on a production scale. In this paper, one such methodology is presented, based on research done over the last four years to develop specific applications for OFRs. The design method is based on a shell-and-tube configuration, whereby a series of standard tube diameters are chosen, and the tube-side steady flow (throughput) and oscillatory mixing conditions are chosen to ensure optimal mixing conditions. The scale-up principle is one of maintaining the same geometric ratios as laboratory scale devices, and ensuring similar values for the oscillatory and net flow Reynolds numbers. Following this protocol should ensure an optimal design, with a near plug flow RTD, efficient heat and mass transfer, effective dispersion (in multi-phase systems) and minimization of power dissipation. Once these criteria have been applied, the reactor is sized on the basis of required residence time, which then fixes the maximum throughput and length for each tube diameter. A choice is then made for the final configuration, based on the throughput requirement, the criteria mentioned above and practical considerations. This method is applied to two industrial case studies, and details are given of feasible designs for full-scale reactors using information from pilot studies already performed.

D.W. Pritchard

Papers

A comparative study of mass transfer in yeast for a batch pulsed baffled bioreactor and a stirred tank fermenter