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Author Topic: confused about distillation  (Read 5504 times)

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iScience

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confused about distillation
« on: September 01, 2013, 05:19:29 AM »

when performing a distillation, why does the water inlet always have to go from a lower point to the higher point?
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curiouscat

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Re: confused about distillation
« Reply #1 on: September 01, 2013, 05:23:20 AM »

Huh? That doesn't make much sense.

If you are saying water from feed always ends up in distillate that's wrong.
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Archer

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Re: confused about distillation
« Reply #2 on: September 01, 2013, 05:32:00 AM »

when performing a distillation, why does the water inlet always have to go from a lower point to the higher point?

So that the condenser fills with no air bubbles rather than the water (or any other coolant for that matter) taking the path of least resistance down one side of the condenser.

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curiouscat

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Re: confused about distillation
« Reply #3 on: September 01, 2013, 05:34:25 AM »

when performing a distillation, why does the water inlet always have to go from a lower point to the higher point?

So that the condenser fills with no air bubbles rather than the water (or any other coolant for that matter) taking the path of least resistance down one side of the condenser.

Ah if it's the condenser another reason may be that counter-current cooling is always thermodynamically more efficient at heat transfer than co-current cooling.
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Arkcon

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Re: confused about distillation
« Reply #4 on: September 01, 2013, 06:27:29 AM »

When you actually set one up, you'll see that what Archer: and curiouscat: say is true.  You could also reverse it, to see what doesn't work.
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discodermolide

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Re: confused about distillation
« Reply #5 on: September 01, 2013, 06:48:12 AM »

If you connect the water cooling at the top inlet and have a high BPt. liquid you stand a good chance of cracking the condenser.
So water in at the bottom out at the top.
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JGK

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Re: confused about distillation
« Reply #6 on: September 03, 2013, 11:20:24 AM »

Use one of these Findensers and you avoid the water connection altogether
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Archer

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Re: confused about distillation
« Reply #7 on: September 03, 2013, 06:37:43 PM »

Any idea how much these cost?
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curiouscat

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Re: confused about distillation
« Reply #8 on: September 03, 2013, 07:27:07 PM »

Any idea how much these cost?

And whether they can match water cooled cooling power.
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Archer

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Re: confused about distillation
« Reply #9 on: September 03, 2013, 07:40:21 PM »

The manufacturer boasts "Suitable for most chemical reactions".

This would really suit my set up but I'll bet they are expensive.
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curiouscat

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Re: confused about distillation
« Reply #10 on: September 03, 2013, 07:57:54 PM »

The manufacturer boasts "Suitable for most chemical reactions".

This would really suit my set up but I'll bet they are expensive.

My fear is they don't cool as well as water does.
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magician4

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Re: confused about distillation
« Reply #11 on: September 03, 2013, 08:16:54 PM »

doesn't look like a destillation condenser to me (from the whole setup), but like an reflux condender instead (which would need to perform much less cooling capacity, if the heating source was well regulated)


regards

Ingo
« Last Edit: September 03, 2013, 08:29:44 PM by magician4 »
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Archer

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Re: confused about distillation
« Reply #12 on: September 03, 2013, 08:23:26 PM »

Yes, I can imagine coming in after the weekend to find my precious compound as a black tart and a stirrer bar welded to the bottom of the flask.

I don't think this is designed to be used for distillation.

Personally I have never been responsible for a flood, I use cable ties without fail, but I have seen the devastation that it can cause if the lab is not on the ground floor.

If the airflow around the heat exchanger fails (fume hood stops working) this would be much less efficient and potentially much more of a hazard for escaping, flamable, gas and no extration to remove it.
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“ I love him. He's hops. He's barley. He's protein. He's a meal. ”

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magician4

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Re: confused about distillation
« Reply #13 on: September 03, 2013, 09:06:26 PM »

Quote
If the airflow around the heat exchanger fails (fume hood stops working) this would be much less efficient and potentially much more of a hazard for escaping, flamable, gas and no extration to remove it.
Having worked with aircooling in small to medium sized industrial processes (i.e. up to reactors of 700 L capacity), and hence a bit familiar with the physics involved, too, I'm not as sceptical about reliability here as you are - esp. not if you treated the cooler like any traditional one, i.e. would regulate reflux to only make use of the lower 10-20% of the internal heat exchange surface.

the thing that just stops me from trying for this however is the price : US-$ ~ 350 is quite hefty in my opinion

... and I don't reflux that much anymore these days in my field anyway, so the amortisation calculations given at respective websites don't count for me


anyway, getting one of these from eBay at let's say 20 bucks, I'd give it a try...

regards

Ingo
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