Application 1001 Pattern of rotation

How to find the optimal rotational speed when using a rotating bed reactor

Many heterogeneous processes are limited by mass transfer at typical laboratory or industrial conditions. When using a rotating bed reactor, the mass transfer is most easily controlled using the rotational speed.

Higher speeds yield higher flow rates through the reactor, and increased mass transfer as a consequence. This improves the overall reaction rate and the output of product from the system. However, the rotational speed will also affect other parameters, such as the specification of components and the electricity consumption, which may be important factors on industrial scale.

What rotational speed should I choose?

Finding a rotational speed that eliminates mass transfer problems without wasting energy and complicating scale-up is easily done using a rotating bed reactor on benchtop scale. This application note shows the effect of varying the stirring speed on three applications:

  • Biocatalysis - ammonolysis of dimethyl-3-hydroxy-glutarate by CalB
  • Ion-exchange - Neutralization of a) an acid by Purolite A500P and b) a base by Amberlite IRN99
  • Decolorization - Adsorption of Allura red onto activated carbon

Diagram showing how to find the optimal rotational speed in a biocatalytic application using a rotating bed reactor

Figure showing how to find the optimal RPM when running a biocatalytic reaction with a rotating bed reactor. By varying the RPM you can find the mass transfer limit of the reaction. In this case 400 RPM is enough to maximize mass transfer.

Comparison between anchor stirrer and rotating bed reactor optimal rotational speeds

Difference between anchor stirrer in batch mode and the rotating bed reactor (RBR) where you can see how the benefits of the RBR becomes more prominent above 450 RPM.

Several conclusions can be drawn:

  • Increasing the stirring speed improves the reaction rate for all applications tested.
  • At higher speeds, the external mass transfer limitation was completely eliminated for the biocatalytic application, and further increasing the speed is not necessary.
  • The RBR significantly outperformed the traditional stirred tank reactor under most conditions

Our laboratory range of reaction systems are ideal for reaction screening and process development, before taking the process to full production scale.

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