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How process parameters influence reactor performance

In this article:

  • How stirring speed affects reaction rate and flow through the reactor
  • Why particle size matters for balancing flow rate and surface area
  • Optimizing solid-to-liquid ratio for catalysis vs. adsorption applications
  • Handling high-viscosity liquids with rotating bed reactors
  • Guidelines for linear scale-up from lab to production scale

The SpinChem® rotating bed reactors (RBRs) are engineered to improve heterogeneous reactions by making them faster, simpler to perform and reliably scale up. But getting the most out of your reactor means understanding how parameters like stirring speed, liquid volume, and solid-phase loading will affect performance.

This Insight will help you understand how the reaction rate is influenced by varying a few basic process parameters, whether you are trying to reduce waste or speed the reaction up. By understanding these effects you can save time on experimentation, reduce waste, and get to the results you want more quickly.

Do you want help with predicting your process? Book a meeting with us today!

 

Rotating speed

The easiest parameter to consider is the rotating speed of the RBR. With a higher stirring speed, the flow rate of the reaction medium through the RBR increases. This normally has the effect of increasing the reaction rate too, especially for relatively fast reactions. Try a few different stirring speeds and measure the rate of your process. We are always happy to help you analyze the results!

Choice of solid phase

In heterogeneous applications, the choice of the solid phase has a massive effect on the outcome. This is true whether it’s an adsorbent you select to separate a compound, or a catalyst used to drive a reaction. Generally speaking, larger particles give rise to higher flow rates through the rotating bed reactor. At the same time, adsorbents with a smaller particle size will often offer more surface area per gram of solids. It is therefore worthwhile to try both smaller and larger fractions of the same material to determine the best fit for your application. We can help you in the right direction and recommend compatible materials. Reach out to us for consultation about your process.

Solid-to-liquid ratio

A rotating bed reactor may be filled completely with solids, or only as much as desired. The processing rate of the application (e.g. reaction rate, decolorization rate, etc.) is for many applications linearly correlated to the loading of solids, up to a certain point. For catalytic applications, the cut-off point tends to be around 2-4 % of catalyst per reaction volume. For adsorption processes, loading the system with as much as 20-30% may very well be the best choice. See also:

Viscosity

Experiments have determined that the rotating bed reactor can robustly handle very high viscosities, and with faster reaction rates than comparable stirred tank reactor setups. The flow rate through the reactor can be expected to decrease with increased viscosity, and with it the energy consumption is also decreased. Somewhat counterintuitively, the power required to spin the rotating bed reactor in a viscous oil may actually be much lower than the power required to spin the same reactor at the same speed in water. The reaction rate may however benefit from a reduction in viscosity. It is generally recommended to try a few different reaction temperatures and see if there is a benefit to heating the reaction that justifies the cost.

Scaling it all up

An application performed in a rotating bed reactor can usually be scaled up linearly, by keeping constant the solid phase specifications, ratio of catalyst to reaction volume, reaction temperature and other similar parameters. The stirring speed can usually be turned down as the reaction is scaled up. For many application, keeping the energy input per volume of liquid (W/m3) constant will also preserve the space-time yield to larger scales. You can find some more hints here: Guidelines to Scale-Up with the Rotating Bed Reactor.

SpinChem has lots of experience helping our clients scale their applications up. Reach out to us and let us assist you.

Frequently Asked Questions

How does stirring speed affect my reaction rate?

With a higher stirring speed, the flow rate of the reaction medium through the RBR increases. This normally has the effect of increasing the reaction rate, especially for relatively fast reactions. We recommend trying a few different stirring speeds and measuring the rate of your process to find the optimal setting for your application.

What solid-to-liquid ratio should I use?

The processing rate of your application (reaction rate, decolorization rate, etc.) is for many applications linearly correlated to the loading of solids, up to a certain point. For catalytic applications, the optimal range tends to be around 2-4% of catalyst per reaction volume. For adsorption processes, loading the system with as much as 20-30% may very well be the best choice.

 

Can the rotating bed reactor handle viscous liquids?

Yes. Experiments have determined that the rotating bed reactor can robustly handle very high viscosities, and with faster reaction rates than comparable stirred tank reactor setups. The flow rate through the reactor can be expected to decrease with increased viscosity, and with it the energy consumption is also decreased. Somewhat counterintuitively, the power required to spin the rotating bed reactor in a viscous oil may actually be much lower than the power required to spin the same reactor at the same speed in water.

How do I scale up my process?

An application performed in a rotating bed reactor can usually be scaled up linearly, by keeping constant the solid phase specifications, ratio of catalyst to reaction volume, reaction temperature and other similar parameters. The stirring speed can usually be turned down as the reaction is scaled up. For many applications, keeping the energy input per volume of liquid (W/m3) constant will also preserve the space-time yield to larger scales.

Does particle size of my solid phase matter?

Yes, particle size has a significant effect. Generally speaking, larger particles give rise to higher flow rates through the rotating bed reactor. At the same time, adsorbents with a smaller particle size will often offer more surface area per gram of solids. It is therefore worthwhile to try both smaller and larger fractions of the same material to determine the best fit for your application.