Thursday, March 4, 2010

Generating QbD insight for filtration and centrifugation

Many chemical engineers and chemists will know that filter cakes are often compressible to a high degree and the consequence is that pushing harder (e.g. via higher filtration pressure or faster centrifuge spin speed) leads to remarkably longer cycle times, rather than shorter.

You can explore these effects for a given slurry/cake using templates available in DynoChem Resources. A sample of results to whet your appetite is shown below. Click on each graph for a closer look.

Filtration of a material with compressibility index=2 shows that above a certain pressure, further increases in filtration pressure are counterproductive.

Centrifugation of the same material shows the same trend: beyond a certain spin speed, higher spin speed is counterproductive. Addition time (or rate) is also a factor and slower addition can in fact limit the extension in cycle time seen at higher spin speed.

The above results can be generated easily using the DynoChem menu in Excel to set up and run scenarios covering the factor ranges of interest. Parameter fitting to lab scale filtration data uses the DynoChem Fitting window to characterize the material.

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