Tag Archives: Sohrab Rohani

Supersaturation Or the Crystal Size Distribution

Supersaturation or the Crystal Size DistributionWhich Measurement Is More Important?

In an ideal world, you may want to directly measure the crystal population within the crystallizer (a critical product quality attribute) and measure the supersaturation which is driving the process (a critical process parameter).  Today’s advanced Process Analytical Technology (PAT) allows you to measure both of these critical parameters in real time. But where should you begin – especially if budget constraints limit you to implementing only one advanced measurement. Continue reading

Crystallization control: measuring supersaturation with ReactIR, or measuring crystal nucleation and growth with FBRM

Crystallization-control-FBRM-EasyMax-crystallizer-METTLER-TOLEDO

Crystallization control

A question was posted regarding crystallization monitoring and control:

“If you had to choose between supersaturation control or FBRM crystal size control on an industrial scale, which would you choose?”

Supersaturation monitoring and control only makes sense if you have a very reliable model of the system (i.e. where you can predict nucleation and growth as a function of supersaturation), stable reactor control, and a precise supersaturation measurement.

In R&D this is certainly achievable, and there are good examples of supersaturation control including this on-demand webinar, by Dr. Mark Barrett, describing calibration-free supersaturation control.

However, in an industrial crystallizer, your supersaturation-based control would likely be based on limiting the level of supersaturation to avoid conditions that would produce high levels of spontaneous or secondary nucleation.

And that’s not really control, just avoidance.

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