Questions about Mods to VM

kimbodious

gday,

I added a 2" tee with a StillDragon SGK below the 2" tee where I have the takeoff. If it is okay, I'd like to check my plans for the mods with people who have greater experience and knowledge than I have please?

I plan to install the thermometer on the tee with the SGK which will bring it closer to eye level. It was on the tee with the takeoff. This shift to the slightly lower position should not impact on the usefulness of the thermometer, should it?

I plan to have SS potscrubber packing in the tee with the SGK only up as far as the bottom of the horizontal port. This was what I had in the tee with the takeoff when it was on top of the packed column. I plan to remove the SS potscrubber packing from the bottom section of the tee with the takeoff. The distance between the top of the packing and the arm of the takeoff tee will be 8" greater. Will there still be sufficient turbulence in the area of the takeoff for the vapour flow to split effectively?

thanks!

jacksonbrown

@kimbodious said: The distance between the top of the packing and the arm of the takeoff tee will be 8" greater. Will there still be sufficient turbulence in the area of the takeoff for the vapour flow to split effectively?

If I understand you, it doesn't have anything to do with turbulence.
The split is caused by pressure.
Most of the pressure is from the heavy vapour flowing downhill but the vapour velocity plays a small part too.

A picture might give people a better idea of what your intending but if your probe is in fast vapour with zero reflux splashing on it you'll have the most accurate and responsive readings. Stick in a dead leg and the response will be crappy.

kimbodious

cheers jb, I had read that some scrubber just below the takeoff helps break up the laminar flow of the vapour? yes the thermometer would be away from being splashed by reflux but would be in a dead leg if where I thought of putting it in the tee with the SGK

kimbodious

this pic shows where I currently have the thermometer. My plan was to put the thermometer on the same location of a tee (with the SGK) directly below this one.

jacksonbrown

Personally, I'd keep the probe where it is. Its shielded from reflux and in the main vapour stream. Why move it?
Add a sight glass on a tee under it if you want but the inline/tower types wont create a dead leg. (Punkin has 'em too but his site is down for the OS trip)

@kimbodious said: cheers jb, I had read that some scrubber just below the takeoff helps break up the laminar flow of the vapour?

Not sure what is meant there. Most of the time when I hear 'turbulent' over on HD, especially in reference to condensers, it's pretty obvious most people don't understand what turbulent flow actually is.
Stuffed up an undersized liebig it can help with a bit of vapour contact but not really through turbulence.

Kapea

I'm not following your descriptions.

I run an inline VM column made from 2" copper. This I know about my column:

Vapor collapsing in the product condenser creates a vacuum in the takeoff section, drawing vapor in that direction. Once it is drawn into the takeoff path it does not go back out again.

I think your best information is the temperature of the vapor in the takeoff path. That is the actual product. No need to shield from drips in that location either.

Some people put a bit of packing around the reflux condenser to slow the vapor down up there. They are afraid vapor will get past the reflux condenser. My column is open to the atmosphere above the reflux condenser. I have no packing around my reflux condenser. It has way more than enough knockdown power. In seven years of running it, the only thing that has escaped that way is non-condensible gasses that come off at the very beginning of the run. Mostly cabon dioxide that was dissolved in the wash.

If I were going to add a window to my column, I would put it below the reflux condenser, just above the packing so I could see the reflux dripping. I'm not sure of what value a temperature reading at that location would be. But hey I'm an engineer, for me there is no such thing as too much information. You never know what another data point may tell you until you start seeing the data.

jacksonbrown

@Kapea said: Vapor collapsing in the product condenser creates a vacuum in the takeoff section, drawing vapor in that direction. Once it is drawn into the takeoff path it does not go back out again.

There’s another commonly held HD misconception.
We’re not dealing with a closed system.
Both ends of the condenser are open so any ‘vacuum’ created would be drawing in just as much air from the other end.
In reality the both ends opposing each other cancel out any sucking effect do to a vacuum.
There is a slight draw created from the height/length of the take off.
It works exactly the same as a chimney/smoke stack, only upside down.

A window on top of the column can be good if your packing of choice likes to flood.
Below is good to catch foam ups.
If you only run sugar washes and scoria or marbles you probably don’t need anything.

Kapea

Gee. I guess Snuffy and @minime musta been full of shit then. Thank you for clearing that up after all these years

jacksonbrown

You're the engineer.
Makes sense doesn't it?

Kapea

Both ends of the condenser are open so any ‘vacuum’ created would be drawing in just as much air from the other end. In reality the both ends opposing each other cancel out any sucking effect do to a vacuum.

No, that does not make sense. All things being equal at both ends would cause equal suction at both ends. Low pressure caused by collapsing vapor does not just disappear.

However, things are not equal at both ends. There is higher pressure on the column end.

jacksonbrown

So what changes when you turn off the water?
If it were a pot still with a condensate trap on the end you'd have a point but it's a tee with two branches open to atmosphere.
It's never wise to get between men and their belief system but you might want to ponder that one a bit more.

kimbodious

Photo showing from top to bottom, SD Big Baby Condenser, 2" tee for the takeoff (and thermometer) and 2" with the SD SGK.

The yellow 'cap' on the RC is just a temporary cover and is removed when the still is in use.

kimbodious

With this set up the display on the stick thermometer is about 2.7 metres above the floor, it would be easier to see if the thermometer was in the lower position.

Should I continue the packing in the column to the base of the takeoff or is it sufficient to stop the packing at the SG?

I want to use the SG to monitor for flooding.

punkin

Why not just spin the tee you have 180 degrees so the thermo hangs down? You can still read it ipside dowm right?

In the meantime if it was me I'd be looking for a better probe maybe on a long lead for mounting remote. You need .1 degree resolution to run a vm well.

kimbodious

@punkin said: Why not just spin the tee you have 180 degrees so the thermo hangs down? You can still read it ipside dowm right?

Thanks! Ah, so simple, yes that would work. Other thought is to replace stick thermometer with one of the SD electronic ones. That way I can check the temps from central seated distilling position

What about the packing? Where should I take that up to?

punkin

The StillDragon ones are OK and i have used them but spending a little more money on ebay will get you quite a nice unit.

You can kust drill a hole in the tee and wrap some teflon tape round the probe to seal. Get a bluetooth one and you can keep an eye on it from anywhere or get one with a 1m lead and mount it further down the column.

If you want the sg to check for flooding then pack to the bottom of it. Personally i always checked for flooding by listening to the column from the top of the condenser.

Kapea

If you used one of these at the take-off tee you could watch the vapor being pulled into the take-off path.

kimbodious

thanks for your great advice!

kimbodious

Spirit run this week - so slow - achieved azetrope no worries! I learned heaps but still I have questions....?

Firstly, I learned that I can use a much lower flow of cooling water. The tail on the water outlet on the RC is copper so I was able to monitor outflow temps by feeling how warm the copper tail was.

Now I have the sight glass I observed that I can maintain a good few inches of condensate on top of the packing for the vapour to bubble through - it is quite a spectacle! I did not get to the point at any time where product overflowed out the top of the column. So I am running my column in a semi-flooded state even when I had it in full reflux for the hour before taking off foreshots.

My understanding is that with a Boka condensate pools on the slant plate and drawn off via a needle valve?

Then my question is, with my column running in a semi-flooded state, is it a bad thing once I am at the stage of taking off hearts if it is condensate as well as vapour that is being drawn off at the takeoff? All other things were good, temperature was rock steady and product was at or just below azetrope.

Thanks

Myles

It isn't necessarily semi-flooded. OK you have a pool of condensate on top of the packing but that does not mean that the rest of the packing is in a similar condition.

However the other part of the question relates to condensate being blown into the product branch and in general this is not considered to be good. Often folks leave a void between the top of the packing and the VM branch for this reason, or return the condensate to a point a bit lower in the column - possibly an inch or two below the top of the packing via an external path.

dad

My take...

The water temp from the outflow of your Reflux Condenser should be 140-150F.

A pool of reflux on just the top of the packing is bad. Caused by the reflux being too cold (Super Cooled). You want reflux to be warm enough to penetrate down the column not set on top.

Now if the entire column is flooded, top to bottom, it can be acceptable. This is very hard to do with mesh or scrubbies. But just a pool at take off flooded is bad. I see where your upper site glass is. If your seeing a flood that deep, you're probably in good shape.

I also have to ask, is there any chance your Reflux Coil is touching the packing? This would be bad. It would cause the condition you are stating. The tip of your Reflux Condenser must be above the top of the takeoff branch, or it is blocking the take.

Please don't take this as criticism. No wonder you make azeo so easily!

Your takeoff is extremely small. You've reduced the takeoff from 2" to 1" to 1/2" all in the horizontal. The resulting takeoff Minimum Reflux ratio is approx 0.2 to 3.14 or for every ONE ml you takeoff you're dropping approx SIXTEEN in Reflux even when your valve is wide open. This ends in super slow takeoff.

May I ask, what has been your max takeoff rate...I'm guessing less than 300-500ml an hour. A 2" can achieve 1500ml per hour.

To fix this...

You need to keep the 2" take off full 2"es in the horizontal, in the 45-90 deg down tube, and then reduce as little as possible to PC. example...

Your Reflux Condenser is beautiful, but makes you use a valve. Keeping the takeoff as large as the column dia allows you a max 1:1 takeoff to reflux ratio. Get a 2" elbow on the column and as large a valve as you can afford after that.

I don't use valves. I use a movable Reflux Condenser to block or not block the take off.

This was to eliminate the cost of a valve the size of the column. Then I could get the StillDragon 2" Shotgun PC.

But valve less allows the absolute minimum Reflux ration (~1:1) or anything up to 100% reflux. Proven from 2" to 4".

TheMechWarrior

@dad knows, I'm a fan of this simple method.

FullySilenced

My first rig was a sliding condenser based on Manu's drawing... worked a charm...

i still use the same sliding condenser with my bubble caps at times in a 15 degree upturned lyme arm with a drop down take off point.

Why you say... because it just flat works that well

kimbodious

Thanks fellas.

Packing up only as far as bottom of the dead leg on the tee with the SGK. Yes I have a 2" 90 degree elbow and a 2" 45 degree elbow I can put after the takeoff though I thought I had read that I needed to have the gate valve as close to the takeoff as possible?

Yeah I reckon 600ml per hour is as good as I can manage with this set up.

If I back off power to the element I can reduce the flooding and still get product and even in the "flooded" state I can still hear plenty of condensate trickling back in to the boiler.

The copper tail on the output on the RC is warm to touch, I was thinking 45 - 50C or (120 - 130F), next spirit run I can put my needle valve inline and try backing off the coolant flow to the RC some more.

I have a short length of 2" spool I could put in place of the Big Baby RC so a moving CCVM set up is not out of the question but coughing up $$ for a new SD PC will be, likewise for shelling out $$ for a bigger gate valve, I will just have to live with slow spirit runs until I win lotto aye!

Myles

In the ideal world the boiler power will be preset to 80% or thereabouts of the maximum power that the column can handle. By this I mean before it "floods" and you get liquid ethanol fountaining out of your reflux condenser.

You can run cooler for stabilisation and heads removal but during the hearts phase look for an RC coolant output temp of 80C to 85C.

I don't tweak my boiler power at all, it is set (at a point where I feel comfortable) and the product quality is controlled with a valve. IMO the most important dimension is the total cross sectional area of the vapour path in the product condenser. With everything else wide open this is your limiting factor that everything else could be balanced against.

If your Product condenser has a total vapour path area of 1" then you might as well use a 1" output branch because your rig will never max out the capacity of a bigger output.

I run a 3" column with a 1.4" valve, 1.4" vapour splitter and offset RC, and I have never had the valve wide open when taking azeo. Possibly I am not using enough power for the capability of the column, but as it is not my main rig it doesn't matter if it is a bit slow.

kimbodious

If I went to a CCVM as suggested, I was considering what use I would have for the SD Big Baby? Today I thought I'd give it a go as a PC on a pot still stripping run. On my 2" system today I have got the 2200W Keg King element running full on and the Big Baby is knocking down everything I can throw at it! Looks like I have found the PC for my new CCVM still! Any tips where I can get that corrugated SS hose (3/8"?) online in Australia?

jacksonbrown

Nope, but I never had any issues with 1/4" copper and you'll pick that up everywhere.

dad

...........

kimbodious

thanks for the tips, I'll check out local installers of rooftop solar systems!

GD50

Fridgies for 1/4 . Not so common with plumbers as they come to me for a bit when then need it - but we are bush so they cant pop around to the store. I always have plenty of 1/4 scraggies lengths of soft.