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Mixing In A Batch Reactor (Homogeneous -Liquid/liquid Reaction)


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#1 SP500

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Posted 12 November 2016 - 01:30 PM

I am designing a batch reactor whereby an aqueous phase reacts with an organic phase.(immiscible)

The aqueous phase has a reactant completely dissolved in it so I am assuming it is 1 phase.

 

I have modelled the kinetics as homogeneous. However, I just read that due to the immiscibility of the liquid phases, mass transfer might control the rate rather than the kinetics, which I thought was only the case in heterogeneous reactions.

 

I want to supply sufficient mixing so to be able to neglect mass transfer and model the reaction in terms of kinetics. How do I know how much mixing is sufficient so to make this assumption?


Edited by SP500, 12 November 2016 - 01:31 PM.


#2 MrShorty

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Posted 14 November 2016 - 01:01 PM

mass transfer might control the rate rather than the kinetics, which I thought was only the case in heterogeneous reactions.
My first thought is, why are we approaching this system as if it is homogeneous, when the problem statement begins describing an immiscible system (which, I thought, was one of the defining traits of a heterogeneous system)?

 

How do I know how much mixing is sufficient so to make this assumption?
I don't know of any shortcuts. I think you need to take what you know about the mass transfer and how mixing will impact the mass transfer rates and compare them to the reaction rates. From that, determine under what, if any, conditions the mass transfer rate is clearly faster than the reaction rates.

#3 Napo

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Posted 14 November 2016 - 02:18 PM   Best Answer

SP500,

 

I attached information about your question from the book "Liquid Mixing and Processing in Stirred Tanks", by F. Holland and F. Chapman, Reinhold, 1966, USA, p.16.

 

Napo.

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