Oscillatory baffled reactors (OBRs) are a form 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 interaction of the baffles with the oscillatory motion of the fluid generates excellent mixing and enhanced transport rates, whilst maintaining a close approach to plug flow. Unlike conventional tubular reactors, where a minimum Reynolds number must be maintained, the tube-side mixing is independent of any net flow, potentially allowing long residence times to be achieved in a reactor of greatly reduced length-to-diameter ratio. This leads to a niche application in converting long reactions from batch to continuous processing.

An obvious class of long reactions is bioreactions /fermentations. As one major advantage of the OBR is very good uniform mixing, providing a good mass and oxygen transfer, it seems ideal for microbial purposes. The possibility of continuous fermentation is a second advantage as it will minimise the substrate and product inhibition. Lower and more uniform shear rates compared to a stirred tank reactor may be an additional advantage depending on the shear sensitivity of cultures such as mammalian, insect and plant cells, fungi and certain types of algae.

To investigate the possible advantages in this class of reactions, biopolymer, bioethanol and beer production have been investigated at various scales. The design modifications that have been required will be discussed. OBR processing has been shown to result in reduced residence times. Due to its plug flow RTD, the reactor also has the potential to allow various staged additions and parameter profiles along its length.