6 replies to this topic

[Marshall Paliga]

Hello fellow professionals,

 

I am having trouble with foam formation during concentration of protein broth by vaccum evaporation. 

 

Currently we're doing pilot scale tests in a mechanically agitated batch evaporator with steam heated jacket. The feed has about 15% (w/w) hydrolyzed protein, some minor components, and water. The goal is to concentrate this broth up to ~50% protein.

 

During the first tests, a considerable amount of foam was formed, being sucked by the vacuum, and flooding the condenser.

 

I am already considering suggesting an anti-foam agent. But the first option would be to use a mechanical device to break the foam.

 

Can someone give me a clue about where to start searching? Do such devices exist?

 

 

Regards,

Marshall

[Pilesar]

I would start with an internet search for terms like "mechanical defoamer' to find relevant literature.

[breizh]

Hi ,

For Defoaming agent , I suggest you to consult Dow , link attached :

https://www.dow.com/...industrial.html

 

This is based on my experience with latex in emulsion . 

 

note : Probably you should be able to reduce the foaming tendency by increasing the cycle time ! This is going to affect the productivity of your unit .

 

what about the technology of your condenser , it could be a direct contact condenser  where water is sprayed over  the gas prior to reach the vacuum system ? 

 

Good luck

Breizh 

Edited by breizh, 11 February 2021 - 07:48 AM.

[Marshall Paliga]

Hi Pilesar,

 

Thank you for the reply.

 

It may not be evident, but I always do my research before opening a topic. I do it in respect of other people's time.

 

I've seem many manufacturers websites, patents and papers (For example: Goldberg and Rubin, 1967, Mechanical foam breaking) 

 

But, as I lack experience in this topic, I am unable to tell the difference between good and bad solutions. Since foaming is a problem that occurs in fractionating columns, I resort to this forum, hoping somebody has faced a similar issue and found a solution.

 

Rectificating my question: Have somebody used mechanical defoamers for a similar application? Is it worth to investigate further, or it is common practice to use chemical anti-foam agents.

 

 

 

Hi Breizh,

 

I'll contact Dow if we go for the anti-foam agent route. 

 

About the cycle time. The system is manually operated, controlling temperature close to boiling point (which increses with time due to concentration). When the liquid starts to boil, foam formation intensifies.

 

I've never used direct contact condensers. At first sight, it seems to me that direct condensers will generate a small product loss (the one entrained in the foam) and wastewater.

 

 

 

Best Regards,
Marshall

 

[latexman]

Back in my phenolic resin days, we called the mechanical device to break the foam a "foam breaker".  It was simply an agitator blade made mainly from 3" or 4" or 6" angle iron.  The top of this foam breaker came at or just below the vessel tangent line, where the top head dish met the straight flange.  It's diameter extended very close to the vessel walls, maybe 1" of clearance.

 

You need some space between the maximum liquid level and the foam breaker.  Say 1-3 feet.  That way the foam breaker is never submerged.  If it gets submerged it can create foam, and that is counter-productive.  1-3 feet will give the foam some time to rise, thin out, and drain down, before the rotating angle iron whacks it and hopefully breaks it up.

 

My numbers are for a "still" with a diameter of 8-12 feet.

Edited by latexman, 11 February 2021 - 02:49 PM.

[Marshall Paliga]

Hi Latexman,

 

Thank you for your input. I'll study this option.

 

Do you recall how many RPM or the blade speed that was used for your foam breaker?

 

I'm thinking about using the same shaft that does the liquid agitation for the foam breaker blade. I've annexed a low quality sketch of what I have in mind.

 

I'll update this topic as we make progress.

 

 

Thank you for all the replies.

 

Best Regads,
Marshall

Attached Files

•  WhatsApp Image 2021-02-12 at 07.54.53.jpeg   55.17KB   0 downloads

Edited by Marshall Paliga, 12 February 2021 - 06:07 AM.

[latexman]

I'm thinking about using the same shaft that does the liquid agitation for the foam breaker blade.

 

That's exactly how we did it.  So, whatever agitator intensity is needed  by the process, RPM, that was the speed the foam breaker turned.