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Impellers For Solid-Liquid Mixtures


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#1 A.Kangaris

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Posted 08 September 2020 - 07:25 AM

Hi,

 

Anyone to advise on the type of impeller for a cooling crystallization tank for a pharmaceutical process.

Are baffles a good idea when it comes to cleaning? Is it a common practise?



#2 breizh

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Posted 08 September 2020 - 08:56 PM

Hi ,

I've seen different types of agitators from pitch blades to anchors . One important point is the surface of the equipment(reactor & agitator, baffles) , should be mirror polished to ensure good thermal transfer . Baffles very seldom used.

BTW you don't state anything about the reactor , is it a glass lined or a stainless steel reactor ?

 

Consider the links below to support your work 

 

https://www.dedietri...s-lined-reactor

 

https://www.spxflow.com/lightnin/

 

https://www.postmixing.com/

 

Good luck

 

Breizh 


Edited by breizh, 08 September 2020 - 09:18 PM.


#3 A.Kangaris

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Posted 15 September 2020 - 06:38 AM

Thanks Breizh,

 

I am considering both types of reactors GL and SS. It will more likely be Glass-Lined.



#4 AndyChemEng

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Posted 03 October 2020 - 02:09 PM

Hi Kangaris,

 

We use retreat curve and pitched blades for our crystallation vessels - all GLMS vessels. One recommendation is to invest in a variable speed drive as this provides you with the flexibility in optimising the agitation very easily (no pulleys/gearbox changes). 

This is particularly useful for crystallations as you have to balance mixing (solid suspension / heat transfer) with attrition of solids which could impact your downstream processing (filtration etc).

 

Andrew



#5 A.Kangaris

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Posted 14 October 2020 - 11:17 AM

Hi An

 

Hi Kangaris,

 

We use retreat curve and pitched blades for our crystallation vessels - all GLMS vessels. One recommendation is to invest in a variable speed drive as this provides you with the flexibility in optimising the agitation very easily (no pulleys/gearbox changes). 

This is particularly useful for crystallations as you have to balance mixing (solid suspension / heat transfer) with attrition of solids which could impact your downstream processing (filtration etc).

 

Andrew

That's interesting. When you say attrition, does this mean the particle size of crystals? Does mixing speed affect this?



#6 AndyChemEng

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Posted 11 February 2021 - 03:31 PM

Yes, some crystals are prone to attrition and having the ability to optimise the speed will allow you both to optimise the crystallisation (solid suspension/heat transfer) while also minimise crystal attrition - small bits of crystal breaking off generating fines. These fines can have a significant impact downstream on your filtration system.

Some crystals are more prone to attrition than others.



#7 sts098

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Posted 02 April 2021 - 06:24 PM

ATTRITION

Blade selection, blade speed both have a huge impact on attrition.  Large low speed hydrofoils provide much more pumping and less shear than radial impellers operated at faster speeds 

 

DisperseTech provides information on many of the blade types https://www.disperse...4-mixing-blades

 

It also offers some details on agitation and dispersion operations.  

 

BAFFLES

If viscosity is low and swirl is an issue, offset mounting of your agitator can offer much of the benefits of baffles while avoiding many of the problems.  We avoid baffles in most processes if at all possible.  






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