Scale Up

New processes are usually developed at lab-scale in small volumes.  Under these conditions reaction conditions are approximately the same throughout the vessel. 

When processes are scaled up to pilot scale or full production at plant scale, vessel volumes are increased by orders of magnitude and homogenous reaction conditions can no longer be assumed.

This leads to different zones or regions in reaction vessels having different process conditions and can be particularly important in exothermic reactions.  

Process scale up can often then lead to different reaction conditions occurring than in the original process design, which in turn leads to reduced yields or quality issues through side reactions producing by products.

There are a range of scale up rules (such as mixing power per unit volume, matching impeller tip speeds), however these are rules of thumb and do not always hold true, for example with many non-Newtonian fluids.

Developing an understanding of design space and process modelling through CFD or other modelling tools can often help with process scale-up.  However very often such models need validation.

Process scale up is one of the key areas where process tomography can offer significant advantages.  For example the 8-planep2+ can deliver 2,500 measurements at different locations in a vessel several times per second.

This information can be used to:

• validate process conditions

• confirm process models

• visualise a process and determine the extent to which process conditions vary

• identify turbulent and stagnant regions to inform placement of sensors

• determine process end points

Where a process envelope is being developed (such as through QbD or as part of a PAT strategy), process tomography can be an important tool in increasing process understanding.

Key benefits include:

• Dynamically visualise and validate process conditions at different scales

• Confirm process models at different scales

• Identify turbulent / stagnant regions

• Determine process end point by scanning multiple points in process volume

Register to access our case studies and application notes available from the Download section on the right.

Publications:

Mann, R, Wang, M, Forrest, AE, Holden, PJ, Dickin, FJ, Dyakowski, T and Edwards, RB (1999) Gas-Liquid and Miscible Liquid Mixing in a Plant-Scale Vessel Monitored Using Electrical Resistance Tomography, Chem. Eng. Commun., Vol. 175, pp 39-48

Henningsson, M., Regner, M., Ostergren, K., Tragardh, C. and Dejmek, P. (2007) CFD simulation and ERT visualization of the displacement of yoghurt by water on industrial scale, Journal of Food Engineering, Vol.80, No. 1, pp 166-175

Mann, R, Dickin, FJ, Wang, M, Dyakowski, T, Williams, RA, Edwards, RB, Forrest, AE and Holden PJ (1997) Application of Electrical Resistance Tomography to Interrogate Mixing Processes at Plant Scale, Chemical Engineering Science, Vol. 52, No. 13, pp 2087-2097

For more information about this paper, please contact ITS.

In the Press:

•  The Chemical Engineer Feb 2009 - Seeing is believing
• Pharmamanufacturing.com - 2009 - Scaling up and controlling crystallization

Register to access our case studies and application notes available from the Download section on the right.