The importance of baffles in a reactor vessel

A vortex, which forms due to the rotation of an agitator, is detrimental to the mixing in a reactor vessel. If the agitator is a rotating bed reactor, it also disrupts the liquid flow through the RBR. Baffles are features in the reactor vessel that break the circulating flow pattern, preventing vortex formation and improving overall mixing.

baffle (noun): a device to deflect, check, or regulate flow or passage as of a fluid, light, or sound. (Merriam Webster Definition)

The importance of baffles has long been established for stirred tank reactors with agitation by impellers, and baffling is equally important for vessels with an RBR installed. You don't need to take our word for it; customers that have investigated the effect of baffling on their mass-transfer limited reactions have found the same result. The most recent data comes from research at the Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB. They started out with the RBR S3 in a smooth glass vessel. After observing a deep vortex, drawn down into the RBR, and the resulting disappointing performance, one simple flat-blade baffle was installed. The performance for the enzymatic reaction was quantified with and without the flat-blade baffle, and the result is presented in the figure below. As seen from the data, installing one simple baffle resulted in, on average, a doubling of reaction conversion at each time point.

The double-walled glass vessels (V2 and V3) that we at SpinChem offer are custom-made to fit the RBR S2 and S3, respectively. The vessels have structured inner glass walls that serve as 'flower-shaped' baffles, which do not take up the same space as traditional flat-blade baffles. This minimizes the required volume of reaction medium, and maximizes mixing performance.

Some non-baffled vessels perform as if they had flow breakers installed, just through the shape of their vessel walls. For instance, non-round geometries such as rectangular IBC-tanks may provide satisfactory mixing and prevent deep vortex formation. On benchtop scale, the round beaker might be appealing with its simplicity, but a baffled reaction vessel will yield much better performance.

Further reading

• Reactor design supported by computational fluid dynamics (CFD)
• Viscous solutions decolourized using a rotating bed reactor and a stirred tank reactor
• Improving reactions in emulsions using a rotating bed reactor

If you have more questions about this or want to request a quote for a baffled vessel, contact us!