[jules]

hi all,

literature usually reports the effect of stirring as positive for crystallisation kinetics

i am thinking of a trial to improve the efficiency of my unit (keeping the cycle time constant), which currently recovers over 70% of the product

i am assuming that today, part of the product does not crystallize because it is not close enough to the cold surface and thus does not cool enough within the cycle time

no propeller is available so i will try to get it stirred by recirculating with a pump.

would any negative effect be expected? in my opinion, worst case would be i stay on same level of efficiency

thanks

[eugenedakin]

Hello jules,

Great question. There are many possibilities for 70% product recovery: 1) the product may be soluble up to 30% in the solvent, 2), the reaction rate may be slow, 3) reaction intermediates or derivative are created with impure feedstocks, 4) loss of intermediate products in gaseous form, etc.. I am sure that you can probably think of more possibilities.

Stirring will increase the reaction rate, and lower the particle size. If the filter that you are using for recovery is too large of a mesh, then you will have a lower recovery.

These are only a few possibilities that I can immediately think of.

Best wishes,

Eugene

[jules]

Thanks Eugene,

will try the stirring with a pump, particle size should be no problem.

Thank you

jules

[discodermolide]

You may get different polymorphs by stirring to hard or cooling to fast etc. Crystallisation is an art not a science

[skbuncks]

Recirculating with a pump may lead to particle attrition and the generation of fines which may blind your filter cloth and/or lead to increased filtration times.

Have you tried optimising the crystallisation in the lab for yield, purity and particle size?
Generation of solubility data via cooling crystallisation and dissolution methods is essential for successful design of crystallisation systems.

skb