New VM / CM still

[myles]

Its still in progress but I thought you might like to see the new still. I bought, legaly, a new 30 litre keg that is going to be heated with a 1.5kW hotplate. Tri clamp connection to the column with one of MileHi's adaptor kits. Not cheap with the extra UK tax but well worth it.

2" column with 42" of stainless scrubbers below the VM T section. The T is an equal 1.4" to increase vapour speed and aid in vapour spliting. Above the T it expands back to 2" with another 12" of packing under the reflux condenser. There is a separate 1/2" CM output port which will feed its own liebig.

Reflux condenser will have two coolant flow controls. I is preset so that at low boiler power - say 700w with the VM valve shut it operates at 100% reflux to concentrate the heads. A slight increase in boiler input will bleed the heads off through the CM output port. Then open the second coolant valve to re stabilise the column whilst the boiler increases to VM power level.



There are two centering funnels at 12" and 36". The upper one is just below a thermometer port. The probe is shielded from drips and sits in a void in the packing.









Now that I have seen it in situ, I will be fitting the VM valve after the 2nd thermometer port in the horizontal branch off the T. I ditched the 3rd temp port up near the reflux condenser as being unneccesary. Have not decided about the compression union to join the 2 sections together. I might instead use a slip coupling sealed with distillers tape. That 2" union is much stronger though and the upper section is fairly heavy.

There will be a 12" or so drop in the 1.4" that will reduce in steps before it gets to the product liebig. That will be on its own coolant supply. It should work OK I think.

[kiwistiller]

That is one of the more elegent CM control systems I've seen - setting coolant by opening lines on output and then using PM. Nice.

[myles]

CM is realy good for some things but can be awkward to use for a full run. Needs lots of tweaking. Using it to concentrate the heads before switching to VM mode for the main run seems logical. Use the best bits of both techniques.

Putting the coolant control on the output of the coil has advantages too. The coil is always full at low flow rates, otherwise it tends to auto syphon empty depending on your pluming configuration. Having a preset minimum flow rate makes control easier for stabilisation at the start of the run. With your boiler preset to a known input you know it is in 100% reflux.

It then just takes a tweak of power management to push the heads out of the column. Opening up the second coolant line then kills the column stone dead whilst the power is increased.

When you open up the VM gate the CM port functions as an air vent. If you get any distilate out of it during the run it indicates that something is going wrong - probably too much heat.

[myles]

After thinking about it for a bit I settled on this configuration for the VM output.

VM port, 90 deg bend, thermometer port, stainless valve, double liebig condenser. All mounted in line and just off the horizontal.



The condenser is a 21" 1/2" inside 3/4" liebig, that is in turn mounted inside a 1" inside 1.5" liebig. The outer jacket is a coil instead of a jacket.



I have wound and flushed out the new coil. Just need to connect up the pipework and add the hose connectors.

[myles]

Finaly got round to finishing off the plumbing on the condenser. Just need to add the hose connectors to this condenser and the head. I have another 1/2" inside 3/4" liebig ready as the feints condenser on the CM output that just needs to be connected up.

[loneswinger]

How is this coming along Myles? I want my next build to be some sort of a hybrid like this one. One question: It looks like the upper section is all soldered together. How were you planning to get the packing in and out of it? Or when you just going to leave it empty?

-Loneswinger

[myles]

Been away all week with no computer access. Yes it is all soldered up - but I will be opening it up to make another modification some time soon.

I thought about this for some time. My packing is stainless steel and so far as I am aware it lasts for years, and years, and years. When did ANYONE last change their stainless packing?? It will absolutely get flushed out now and then, but I do not expect to need to change it very often - if ever.

With COPPER packing it is a different issue as that DOES need to be replaced occasionally.

Anyone with experience of the life expectancy of stainless packing please add your views, as it is a good question that has been asked.

[loneswinger]

I had never thought about this before. I always pull my SS packing out after every run and give it a good rinse and soak to get all that nasty tails smell off of it. Yeah, I don't know how long it will last. I would just keep reusing until you notice some changes in the performance (could be years). I can't imagine that it would be a big deal to heat up and separate a solder joint once every year or two to get the packing out. I have done this several times with solder joints and it doesn't take much effort.

-Loneswinger

[myles]

I had never thought about this before. I always pull my SS packing out after every run and give it a good rinse and soak to get all that nasty tails smell off of it. Yeah, I don't know how long it will last. I would just keep reusing until you notice some changes in the performance (could be years). I can't imagine that it would be a big deal to heat up and separate a solder joint once every year or two to get the packing out. I have done this several times with solder joints and it doesn't take much effort.

-Loneswinger

Precisely. Desoldering 2" isn't that big an issue and you will only need to do it once in a blue moon. You don't need to rinse out every run as you always re-equalise your column anyway on each run. When you do that any tails in the packing get flushed back into the boiler anyhow.

It isn't that difficult to back flush your packing in situ if that is what you want to do, or take the column off your boiler and flush it out.

Do you think they bother flushing the packing on a taller column, or washing the plates on a big column? I suspect it is not done often.

[loneswinger]

Do you think they bother flushing the packing on a taller column, or washing the plates on a big column? I suspect it is not done often.

I suspect that you are right. I think I am going to start leaving them in there now. Just never really gave it a thought before.

-Loneswinger

[JethroBodine]

I usually only take mine out to clean when I switch washes, whiskey to rum, rum to vodka, like that. Might not need to, but i just don't want to mix leftovers, especially between rum and whiskey. For neutral, everything, including the boiler, gets a good cleaning.

[loneswinger]

I usually only take mine out to clean when I switch washes, whiskey to rum, rum to vodka, like that. Might not need to, but i just don't want to mix leftovers, especially between rum and whiskey. For neutral, everything, including the boiler, gets a good cleaning.

Yeah that is good advice. I have a dedicated still for neutral and dedicated pot still for everything else. So I don't think I will be cleaning the packing much at all.

-Loneswinger

[myles]

I have decided to add a small modification that has been bouncing about on the forums. Adding in a liquid trap and a bypass so that there is never any liquid inside the vapour splitting chamber. Am thinking of doing it this way.



Almost like putting a single bubble plate above the VM port. A cut down reducing coupler (same as my centering funnels) is the easy way to build the liguid trap.

[JethroBodine]

Looking forward to hearing how this all works out. Please keep us informed

[loneswinger]

Myles,

Will you have about 20 cm of packing above takeoff? The reason I ask was I was looking up the VLE graph of ethanol/ethyl acetate, and it looks like you get about a factor of 2 enrichment of ethyl acetate per theoretical plate high in the column (assuming the ethyl acetate concentrations are low everywhere). So you might get about a factor of 3-4 heads concentration with this design. That should translate to about 3-4 times less heads to run off before the output is clean. So if you normally run off 2 L of heads/run to get to the good stuff, you should only need to run off 500-700 ml.

I bring this up because this still is going to be a little tricky to run. You have to pull heads using the CM function, but make your cut to hearts based on what is coming out the VM output. My prediction is 500-700 ml heads out the CM to get good stuff out the VM. (I am assuming a 40-50 L, 30% still charge)

I guess once you reach equilibrium and started to bleed heads out the CM, you could start a slow ~ 1 drip every few seconds out the VM and just keep tasting it.

Also, once you start collecting output from the VM, you might want to keep a slow bleed from the CM heads trap. This will help ensure that the heads don't start to build again in case there was still some left in the boiler. Also ensures a good reflux temp returning to the top of the column.

Sorry for this message, just getting a little anci for you to finish this build and do a test run.

-Loneswinger

[Manback]

Myles,

Will you have about 20 cm of packing above takeoff? The reason I ask was I was looking up the VLE graph of ethanol/ethyl acetate, and it looks like you get about a factor of 2 enrichment of ethyl acetate per theoretical plate high in the column (assuming the ethyl acetate concentrations are low everywhere). So you might get about a factor of 3-4 heads concentration with this design. That should translate to about 3-4 times less heads to run off before the output is clean. So if you normally run off 2 L of heads/run to get to the good stuff, you should only need to run off 500-700 ml.

I bring this up because this still is going to be a little tricky to run. You have to pull heads using the CM function, but make your cut to hearts based on what is coming out the VM output. My prediction is 500-700 ml heads out the CM to get good stuff out the VM. (I am assuming a 40-50 L, 30% still charge)

500ml from 15lt total alcohol??

3%??

Seems unlikely??

I guess once you reach equilibrium and started to bleed heads out the CM, you could start a slow ~ 1 drip every few seconds out the VM and just keep tasting it.

Also, once you start collecting output from the VM, you might want to keep a slow bleed from the CM heads trap. This will help ensure that the heads don't start to build again in case there was still some left in the boiler. Also ensures a good reflux temp returning to the top of the column.

I thought the point of the bypass was, as much as anything, to avoid oily heads contaminating the VM pathway - wouldn't taking out the VM during heads bleed defeat that point?

And during the run, what comes out the CM is gonna be, in theory, a cross-section of the vapor that goes up past the VM - and therefore the same as the VM output, except maybe some contamination from the condenser etc - how does that benefit? The separation all goes down in the packed column doesn't it?

Sorry to hit you with so many q's, you seem to have some good ideas, just trying to get them straight in my head

[loneswinger]

500ml from 15lt total alcohol??

3%??

Seems unlikely??

Well I was thinking more like 5% of 12 Liters but stil.... Shouldn't seem so unlikely, Riku's designs can get away with ~ 0% heads bleed before taking product, so do large scale rectifying columns.

I thought the point of the bypass was, as much as anything, to avoid oily heads contaminating the VM pathway - wouldn't taking out the VM during heads bleed defeat that point?

And during the run, what comes out the CM is gonna be, in theory, a cross-section of the vapor that goes up past the VM - and therefore the same as the VM output, except maybe some contamination from the condenser etc - how does that benefit? The separation all goes down in the packed column doesn't it?

Sorry to hit you with so many q's, you seem to have some good ideas, just trying to get them straight in my head

Ahhh ok no. You are thinking of Harry's mods, what Myles is building is different. My comments have nothing to do with the liquid by-pass and everything to do there being packing i.e. additional column and separation above the VM takeoff. There WILL be enrichment of heads between the takeoff and the top of the column. The vapor cross section at the takeoff will be heads poor compared to the liquid runoff from the CM at the top of the column. I was trying to estimate that concentration, and hence the heads bleed savings.

Hope that clarifies,

-Loneswinger

[myles]

Folks at the moment there is about 30cm of packing in the CM section of the column above the VM port. I might need to loose a bit of this when I put in the bypass mod. Also my boiler is a small keg, 30 litres, so my charge will only be in the order of 20 to 25 litres at 30%.

Have been thinking that it might be an easier build to do this mod by fitting a smaller T inside a 2" one.



In my case it is a 1.4" inner T, but you could do it with 1". The column extension up the centre is capped off and has holes cut in the side to let the vapour out. Same surface area in the holes as the CSA of the inner T and the VM port for a 50:50 vapour split.

For the liquid by-pass you would only need to drill a single hole in the lower reducer and fit a small liquid trap.
to centre the reflux.

I am intending to run at low boiler power and take the heads off as vapour through the upper CM port. Only when they have been purged will I increase coolant flow and restabilise, after which I shall open the VM valve.

There is no doubt that this is a bit "fiddly" to build, but I used the same technique (T inside T) on my 3 wall liebig and it is both do-able and neat.

[still crazy]

Please please run this puppy
I don't know how you can hold back so long

[myles]

Please please run this puppy
I don't know how you can hold back so long

Am pulling long hours at work, re-moddeling the house and 20 million other tasks. Well it feels like it. Not been in the still room for ages - but I will get to it. I have the bits to build a second identical vapour splitting section, so I can do a direct comparison.

With the bypass mod vs without, just to see how much difference it makes.

[hstuurman]

Please please run this puppy
I don't know how you can hold back so long

Am pulling long hours at work, re-moddeling the house and 20 million other tasks. Well it feels like it. Not been in the still room for ages - but I will get to it. I have the bits to build a second identical vapour splitting section, so I can do a direct comparison.

With the bypass mod vs without, just to see how much difference it makes.

I know this feeling, having a great hobby, a new still, but no time to fire same to me

[loneswinger]

Actually I have given the bypass mod some thought and I really don't think that it will do a damn thing. The reason is that the liquid reflux dripping from the packing above should be in equilibrium with the vapor below. An exception might be if the reflux is overcooling the 'trapped' heads and they find their way in liquid form past the upper packing. If this happens your trap has been breached anyway and those heads will find their way into your product with or without the trap.

So maybe just don't worry about it for now and try running it without the bypass.

-Loneswinger

[myles]

Well folks it is 1 stage closer to being ready. I got both liebigs attached and the controls for the reflux condenser plumbed in. Basically need to find time to connect the coolant hoses and do a leak test and cleaning run.

[vitoboy]

Hey guys...is there a way to recover all the photos from this ol thread?

Cheers

Vito

[Bushman]

I am guessing not! If pictures are posted from outside the forum we have no control if they are taken down.