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VM still concept - questions

These usually have the means for returning the spirits to the column and usually allow metering of the take off to help in the reflux.

VM still concept - questions

Postby TheMechwarrior » Tue Oct 19, 2010 5:02 am

First off please tell me if I've posted in the wrong section of the forums!

My original plan of a valved reflux Nixon stone offset head quickly chnaged the moment I found HD and these forums. I've sinced reconfigured from LM to a VM still design.

I'm a little concerned with my layout as I have not seen a VM still in a similar layout before.
Key differences from what I have seen to date:
    2" all the way from the boiler to the condensers (yup, there are two of them!)
    No reduced diameter horizontal offtake for the VM section (left side of my plan)
    No Leibig condensor on the VM side, replaced with a simple double helix coil, same as the other side
    Site glass above the column packing to keep an eye on flooding
    Site glass at the take-off point - I can keep an eye on the level and match manage my offtake via adjustments to the vapour management valve and the condensate outlet

At the site glass and up to the "Y" piece I will have a turbulant ribbon inserted

The "Y" piece will have a temperature probe inserted - I'm concerned that the condensate returning from the reflux side of the still (Right hand side) will interfere with the accuracy of trying to read the vapour temperature - is this a real issue that I need to address?

Column is 1.5m to the site glass and the condeners are 300mm high

Image

I appreciate your time and efforts in providing me with feedback.

Cheers,

Mech.
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Re: VM still concept - questions

Postby Alfred » Tue Oct 19, 2010 5:15 am

Can't comment on the still design, but yes, you did post in the wrong section. Easily fixed, though. No worries.
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Re: VM still concept - questions

Postby myles » Tue Oct 19, 2010 5:54 am

Hello again, see you found you way over here :lol:

If you shift your thermometer port up into the VM side of the branch, then it will be above any returning reflux condensate. You are right to consider it, as drips of condensate on the probe mess up the readings.

If you wish to fit one in the column itself then you need to build a little "roof" over the probe so that it sits in a vapour space. Easy enough to do with a reduced branch T piece.

There is no problem with the coil product condenser, but the orientation might be an issue. It might be better to put it inline with the vapour path, a Graham condenser. As it is at the moment, there is potential for uncondensed vapour to get into your product branch.
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Re: VM still concept - questions

Postby minime » Tue Oct 19, 2010 6:01 am

I'd put the probe on the product branch of the Y. Also the product branch condenser should be under valve not above it IMHO
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Re: VM still concept - questions

Postby TheMechwarrior » Tue Oct 19, 2010 7:10 am

myles wrote:Hello again, see you found you way over here :lol:

Thanks for helping me find this place - it's fan-bloody-tastic!

myles wrote:If you shift your thermometer port up into the VM side of the branch, then it will be above any returning reflux condensate. You are right to consider it, as drips of condensate on the probe mess up the readings.

If you wish to fit one in the column itself then you need to build a little "roof" over the probe so that it sits in a vapour space. Easy enough to do with a reduced branch T piece.


Cheers I've seen a few of your examples and thanks for those -I will go with your first suggestion of relocating the probe up into the product side of the "Y" connection

myles wrote:There is no problem with the coil product condenser, but the orientation might be an issue. It might be better to put it inline with the vapour path, a Graham condenser. As it is at the moment, there is potential for uncondensed vapour to get into your product branch.


If I'm maintaining a liquid level in the site glass at the take off valve will the vapours in the take-off still pose an issue? Additionally any vapours that get to this point will have been exposed to the cooler condensate coming down the 800mm length to the site glass and would surely have become condensed?

Cheers for the feedback guys, looking like this just might work!
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Re: VM still concept - questions

Postby minime » Tue Oct 19, 2010 9:32 am

TheMechwarrior wrote:If I'm maintaining a liquid level in the site glass at the take off valve will the vapours in the take-off still pose an issue? Additionally any vapours that get to this point will have been exposed to the cooler condensate coming down the 800mm length to the site glass and would surely have become condensed?

Actually that's not a good idea. Your valve on the product branch is all you need. Then a condenser to cool the product. What you're doing with the valve and sight glass on the bottom is REALLY going to muddy the water.
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Re: VM still concept - questions

Postby myles » Tue Oct 19, 2010 10:59 am

With this orientation of product condenser you will probably only use part of the coil. Vapour will condense and fall off but it will still be hot. Your valve will be HOT, HOT - as will the T.

If you were to put the vapour into the top of the condenser it would turn to liquid AND THEN GET COOLED MORE as it travels down the length of the coil. And then falls off.

In effect you have put a SECOND vapour splitter into your product line. There will be some product in vapour form heading down to your take off valve, and the only thing cooling this portion will be condensed product. I doubt it will be enough.

Make a temporary mock up and feed in some steam from a kettle or something simmilar, just to see if it wil manage. I suspect the leg down to your take of valve will end up hot too.
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Re: VM still concept - questions

Postby TheMechwarrior » Tue Oct 19, 2010 3:13 pm

Great stuff guys! Thanks.

I'm listening and I've turned the off-take arm around to ensure ALL the vapour passes through the condenser and I've REMOVED the valve and site glass from the off-take arm.
How are we looking now?

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Re: VM still concept - questions

Postby minime » Tue Oct 19, 2010 4:39 pm

TheMechwarrior wrote:Great stuff guys! Thanks.
How are we looking now?


Oughta work like a champ I reckon!
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Re: VM still concept - questions

Postby airhill » Tue Oct 19, 2010 5:53 pm

Actually it looks like a very interesting design :) never seen a Y fitting like that.

Although I wasn't going to do this again (put rough untried still designs on the forum) have a look at Harry's heads bleed LM and think about this.

Small bok plate in the reflux section of the pipe with a bleed or the full works down to the packing.

EDIT


One slight flaw, I'm not sure that that design will auto shutoff as the vapour at split when near the end of run has two upward choices.
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Re: VM still concept - questions

Postby jaerp » Tue Oct 19, 2010 6:00 pm

geez, it looks like you just nabbed all of St. Pat's inventory :D
are the long column sections tri-clampable? if so, where did you get them? the places i've been looking have had hellish prices.
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Re: VM still concept - questions

Postby TheMechwarrior » Tue Oct 19, 2010 6:12 pm

jaerp wrote:geez, it looks like you just nabbed all of St. Pat's inventory :D
are the long column sections tri-clampable? if so, where did you get them? the places i've been looking have had hellish prices.


I get all my stainless from ProChem.
Yes they are all triclamp sealed.

2" Triclamp ferrules are $7.27 each at full trade discount prices. Expect price variations.

You could aslo try Stirlings.

Most of what you see in the pics is not mine, just using these parts to help me mock up a design and then I buy what I need and return the rest.

Cheers,

Mech.
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Re: VM still concept - questions

Postby punkin » Wed Oct 20, 2010 1:09 pm

You need a mechanism in the top (and probably half way down) of your column to center the condensate.
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Re: VM still concept - questions

Postby TheMechwarrior » Wed Oct 20, 2010 4:16 pm

Roger that punkin, myles and a few others have helped me with some centering ring concepts and I'm using a 2" to 1.5" concentric reducer in those 2 locations.

Cheers,
Mech
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Re: VM still concept - questions

Postby NineInchNails » Tue Nov 02, 2010 3:10 pm

You could use a PTFE Orifice Plate and a couple of ferrules. This is the cheapest source I could find: http://www.gvc.net/p/132/ptfe-white-sol ... ice-plates
3” $27.64
2” $16.07

Image

You could cut out any size centering hole you want.
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I thought about doing something similar by making my own Orifice Plate out of copper plate, but I don’t know how well the ferrules would seal without some sort of gasket material. Someone once recommended making Tri Clamp sealing rings using copper wire soldered at the end to make some big copper O-rings then the plate.
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