SD Packed Column VM Build

AceNZ

Here's my first cut at an SD packed column VM build.

The plan for the column is copper foil in the 100mm section below the take-off tee, then a scrubbie to hold things in place, then about 840mm of SPP, and another scrubbie at the lower end. The lower section of the column is insulated.

I'm planning to use a PTFE gasket above the copper, with an opening that has about 20% less area than the pipe. My hope is that it will both introduce a little turbulence into the vapor flow, and also act as a backstop for the copper, so it doesn't slide further up while I'm filling the rest of the column with SPP.

It's a little hard to see in the pic, but the tee on the horizontal section has a cap with a thermowell. It also helps provide some needed distance between the boiler and the product condenser, for space to put a product collection container.

I'm a little concerned that the Big Baby RC / tee setup might not feed reflux back onto the packing in an even way, but I suppose I won't be able to tell until I try it. I placed the valve with the handle pointing up so that the gate is at the bottom, to minimize pooling. Harder to reach that way, though. Probably don't really need the parrot, but had it handy, so why not?

Suggestions for improvements welcome!

TheMechWarrior

Your valve is in the correct orientation. Key is your RC, open to atmosphere at top and capable of knocking down all the power you have available. You have a shell and tube RC, I'd be inclined to loosely pack some scrubber down into the top half. May be completely unnecessary, you run it and test for vapour escaping using a hand-held mirror. Hold it above the RC while in full power reflux mode, if you see condensation you have an issue to deal with.

Smaug

I would definitely install some scrubber material into your RC.

I hope it has enough knock down power to cope with optimal vapor production.

AceNZ

Since most of the SD column builds I've seen are CM, I have a definite sense that many stillers are uncomfortable with the open RC on a VM...

My plan for plumbing the RC and PC is to feed them in parallel, with valves on both to help set their respective flow rates.

I'm planning to not use counter-flow in the RC, to avoid potential issues with trapped air at the top. I'm hoping since it's pretty short, that it won't make much of a difference.

My current pump is pretty tiny (finding any pump at all with dual 1/2-inch male BSP fittings was a huge pain). I've confirmed that it has enough head, so it will be interesting to see how well it does. Fortunately, this time of year city water is relatively cool -- around 17°C.

FloridaCracker

Wow, that is one impressive pile of SPP. So how long of a run do you figure it will take to fill that tub? Might want to start with a smaller collection apparatus :))

grim

@AceNZ said: Since most of the SD column builds I've seen are CM, I have a definite sense that many stillers are uncomfortable with the open RC on a VM...

I think it has more to do with history. Early hobby CM dephlegmators were undersized, weak, and temperature control was miserable. LM provided better reflux control, especially at higher levels of reflux - so they performed better in the real world - the die was cast.

Which was a shame, because the CM approach was simple, elegant, but the heat exchangers were a joke. Go back and look at what people were doing with reflux stills 5 or 10 years ago.

However, today's dephlegmators can easily hit 100% reflux, and with accurate proportional temperature control, today's CM columns are every bit as good as an LM column, especially if they are made with the same parts.

So, today, I'd argue that CM with proportional temperature control beats LM and VM. Not only do you have nearly foolproof repeatability, but you can easily run a column in constant product mode - which is nearly impossible to do with LM or VM (without spending a fortune).

AceNZ

@grim Unfortunately, I don't have access to proportional PID controlled cooling yet (nor have I been able to even source the necessary parts), so it's VM for me for the time being.

I also have a non-SD LM (Boka) + VM column, so I appreciate the utility of LM, too.

grim

With one hand on the needle valve, and one eye on the thermometer, you can be the PID. :))

But yeah, uncomfortable. With a CM - I can determine the potential for vapor release by monitoring the distillate temperature or even the product condenser temperature.

With LM or VM, I don't have those as a proxy.

TheMechWarrior

I'm 100% comfortable running a VM. Just make sure your RC is oversized for the job. I liked double wound helix coils for this reason.

My present old school CM dephleg is undersized for a VM config.

Smaug

My comments are geared more towards the fact that the smaller SD Dephlegmators have a difficult time putting the system into 100% reflux mode when higher volumes of vapor are being produced on a CM config.

My thought process is based on:

More power= more vapor

More vapor=more reflux

More reflux=more purity

And similarly, more vapor= faster collection speeds.

Looking forward to your evaluation.

Kapea

@AceNZ said: Since most of the SD column builds I've seen are CM, I have a definite sense that many stillers are uncomfortable with the open RC on a VM...

Not even a little bit uncomfortable. I run a 2" copper VM column with an 8" long double-wound copper reflux coil in the wide open top. The only things that have ever gotten past that coil are non-condensable gases. I run cooling water to the reflux coil in series with, and downstream from the Liebig product condenser.

Judging from the discoloration (patina, but no green patina) of the copper reflux coil, vapor only makes it < 3" up the coil before being completely condensed.

vooharmy

My 5" reflux condensor seems more than up to the task of 100% reflux. I can see how the regular RC might stuggle though. When work slows down I am building a cm reflux build, which I think will be superior to a VM build if only for the sake of simplicity.

punkin

If you wanted to simplify it and try it in CM mode it's just a matter of removing the valve, capping the tee and moving the RC under the tee.

It will do exactly the same thing as the setup you have now without the worry of vapours escaping. If the RC is not capable of knocking down 100% of the power you turn loose then the still will produce product rather than loose vapours.

AceNZ

@FloridaCracker said: Wow, that is one impressive pile of SPP.

Looks like this column will have about 840mm of SPP, plus a few inches of scrubbies top and bottom, and the copper.

So how long of a run do you figure it will take to fill that tub? Might want to start with a smaller collection apparatus :))

Ah, if only!

I actually do use the tub -- as a re-circulation tank for condenser coolant.

AceNZ

@Smaug said: My comments are geared more towards the fact that the smaller SD Dephlegmators have a difficult time putting the system into 100% reflux mode when higher volumes of vapor are being produced on a CM config.

My estimate is running the column at about 1900W. I'm hopeful that the Big Baby can handle that, but of course I won't know for sure until I try it. I may very well end up needing a somewhat larger pump.

My thought process is based on:

More power= more vapor

Agree.

More vapor=more reflux

Up to a point, provided the RC is large enough.

More reflux=more purity

Up to a point. More reflux can create more turbulence in the zone above the column, actually reducing purity; particularly noticeable with heads and tails.

Maximum heads compression actually requires minimum heat during equalization (at or near 100% reflux).

And similarly, more vapor= faster collection speeds.

Also only up to a point; it ultimately depends on reflux rate. At the extreme, you end up with choking.

TheMechWarrior

You appear to have a 2" column, here's some run data for you on a 2" VM column I put together a couple of years ago when testing a single v twin column VM.

AceNZ

@punkin said: If you wanted to simplify it and try it in CM mode it's just a matter of removing the valve, capping the tee and moving the RC under the tee.

It will do exactly the same thing as the setup you have now without the worry of vapours escaping. If the RC is not capable of knocking down 100% of the power you turn loose then the still will produce product rather than loose vapours.

Sure. Would certainly be an interesting experiment, if nothing else.

My concern about CM is on the control and management side. Without proportional PID controlled cooling, from what I've read, it seems like a constant dance. Without PID, it seems much easier to get consistent product with VM.

AceNZ

@TheMechWarrior said: You appear to have a 2" column, here's some run data for you on a 2" VM column I put together a couple of years ago when testing a single v twin column VM.

Interesting; thanks.

What type of packing?

TheMechWarrior

Stainless pot scrubbers mostly, with 10 x 100% pure copper scrubbers sitting on top of that. I was very happy with it. So much so I was in the process of building a 3" version when I pulled the plug part way and went 6" bubbler for different reasons. I still have the 3" 1500mm column here ready to go should the desire for neutral ever take me again.

Myles

On the VM I have always used the process that was described many years back by snuffy on HD.

Stabilise at low power (about 700 watts) then slightly increase power to remove the heads. Then increase power to your optimum for the column, re stabilise, take off a bit more heads and go into the run.

I used to have both the power controller and the coolant flow pre-set for the low power stabilisation. Optimum power level for me was 80% of the maximum power the column could cope with - I was too nervous to run at higher power levels than that.

Smaug

Yes yes of course "up to a point".

How many times have we fielded questions (here and about) where the end user could not achieve 95% until they were advised to throw a bit more power (up to a point) at the system.

All things in moderation.

Kapea

How did you make the partially filled blue gradient cells in the collection rate column of your tables @TheMechWarrior?

TheMechWarrior

Conditional formatting @Kapea ;)

Kapea

Found it. Data bars and color scales. Cool!

Thanks @TheMechWarrior

AceNZ

@grim said: With one hand on the needle valve, and one eye on the thermometer, you can be the PID. :))

But yeah, uncomfortable. With a CM - I can determine the potential for vapor release by monitoring the distillate temperature or even the product condenser temperature.

With LM or VM, I don't have those as a proxy.

If you were to run CM by hand this way, is there a straightforward process to follow that would allow you to produce repeatable-quality product? Not just azeo, but over a range of %ABV?

Kapea

@grim said: With a CM - I can determine the potential for vapor release by monitoring the distillate temperature or even the product condenser temperature.

With LM or VM, I don't have those as a proxy.

Seriously? Just put thermometers in them.

Of all the stills I run, my VM column is the easiest to operate and gives the most consistant results. I monitor the vapor temps at the base of the column, at the vapor outlet side of the takeoff T, water temp at the PC inlet, PC outlet, RC outlet and the distillate temp at the PC product outlet.

I could throw all but the vapor temp at the takeoff T away and still run the column in my sleep. Once heads are gone the temp at the takeoff T is rock steady through hearts. It only moves up when the tails arrive there. That's when I shut it down.

Kapea

If you want a Swiss Army Knife still, it's going to take a lot of fiddling. You might be better served to have several stills; each one to perform a specific task. A stripper, a bubbler, and an azeotrope column should get you whatever you want.

Myles

The VM is a special case IMO. Once it is set up for neutral it is virtually automatic. If you want it to produce anything else then you need to de-tune it.

I really do think the packed VM is a perfect azeo machine and if you want a different product you should use an alternative design. :D

TheMechWarrior

100% agree with the previous 2 posts. Running a VM for neutral is like driving a top of the line automatic, just sit back and let it do it's thing. Perhaps we make the VM column the secondary column in a multi column rig? For most you are either making brown spirit or neutral.

Kapea

Or a good base spirit for gin.

dad

The top of my 3" and even 4" CCVM is always completely open and never a vapor passes with 5,000watts.

When outside I put a plastic bag over the top as a visual indicator and to keep the wind from whistling through it.