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void in column

void in column

Postby kekedog13 » Tue Jun 10, 2014 1:26 pm

When you build a column and make it the recommended height for the diameter, then pack it with the recommended amount of packing there will be a part of the column that has nothing on it. Does this empty section serve a purpose ? Or should you go ahead and pack the whole thing ?
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Re: void in column

Postby Zombie » Tue Jun 10, 2014 1:40 pm

That depends on what you are packing it for.

If it is a reflux still you have to leave a void or empty space directly under the reflux condenser. Generally the equal amount of space to diameter. There should also (ideally) be something to direct this reflux onto the center of the top of the packing so it doesn't simply wick down the column wall.

If the packing is something like copper to remove sulfur compounds (non reflux still) then it is not necessary to leave any space but the copper packing should be removable for cleaning.

There are a few exceptions to these general rules, and it will depend on what type of still you have. Post that up, and perhaps you can get a more precise answer.

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Re: void in column

Postby myles » Tue Jun 10, 2014 1:48 pm

There is another issue. At high vapour speeds you tend to get liquid being blown out of the top of the packing. It is fairly common to leave a void between the top of the packing and the VM or CM take off port, to let gravity do its work.

Also if you are using centering rings, then with some packings you need a small void just below them.
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Re: void in column

Postby kekedog13 » Tue Jun 10, 2014 2:03 pm

This is for a LM/VM TEE Boka. The packing will be copper mesh with Raschig rings on top of that with a centering ring between the two.It will be 36 " from the boiler up to the bottom of the tee.The recommended
amount of packing will only take up about 20 " . I could pack the whole thing I guess.
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Re: void in column

Postby Zombie » Tue Jun 10, 2014 4:47 pm

That is beyond what I know about. Wait for one of the Boka guys to chime in.

What I do know is the rings will not be the most efficient packing for your rig. There is alot of info on packing types, and results from guys that have tried all types. From what I have read the best type are those SSP type. They are small (very expensive) stainless steel wire spirals that have a specific shape/size for each column diameter. The second best is crushed Lava rock (believe it or not).

I never searched here for packing types so give the search feature a try. Also if you search the other forums you don't have to join because Pictures in this case don't matter.

Perhaps Myles will chime back in because he is one of the fellas that really knows this stuff from trial, and error. There are actually lots of guys here that can help so hang tight before you commit to anything.

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Re: void in column

Postby myles » Wed Jun 11, 2014 3:34 am

What is your column dia for 20" of packing?

All these recommendations about packing height are variable dependent on what product you want, and what production speed you want.

If you are going to run slow with a high reflux rate (for absolutely pristine neutral) then you can pack all the way to an inch or so below your VM port. Your vapour speed will be too low to blow much reflux liquid off the top of the packing and into your product branch.

If you are going for a flavoured product at 94%, and want to really push your product output rate to the max potential for your column, then a void between your packing and your product port could be useful.

You can't generalize because you can use the column in such different modes of operation.
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Re: void in column

Postby kekedog13 » Wed Jun 11, 2014 3:07 pm

It's a 2 " column with 36 " from boiler to the take off port. I was planning on about a lb. of copper mesh with a liter of raschig rings on top of that. Above of all is a very robust reflux condenser of flexible stainless steel gas line, 12 inches of coil.The amount of packing was a recommendation from a manufacturer for a rig of their design.
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Re: void in column

Postby myles » Wed Jun 11, 2014 3:55 pm

It will work but there is also a correlation between packed height and product output rate. More packing allows you to run faster, so you have flexibility in design. If you have the height available I would go for more height if run times are an issue for you.

Speed is not everything - it all depends on how you wish the still to run. I am sure it will work just fine.
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Re: void in column

Postby crow » Thu Jun 12, 2014 1:40 pm

I would recommend you toss the rings and just use copper mesh. My 2" is packed to just below the collection point, Dimroth condenser is also packed and it pulls azeo every time.
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Re: void in column

Postby kekedog13 » Thu Jun 12, 2014 2:21 pm

I've already got the rings. That's what they use in the one made by Mile Hi. I've got plenty of the copper mesh too. 36 " is the tallest I can go indoors. Speed is not a real issue but it's nice to get it on and over with so I can do something else with the rest of the day.
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Re: void in column

Postby myles » Thu Jun 12, 2014 5:20 pm

Ok this would be my view (modified if you use an external reflux return line).
Put 1 just below the VM port to increase vapour speed and induce turbulence. Leave an inch or two void and then pack down to the boiler.
Put a ring at the 12" and 24" points measured up from the boiler.
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Re: void in column

Postby kekedog13 » Fri Jun 13, 2014 11:43 am

I'm speaking of the raschig rings.
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Re: void in column

Postby myles » Fri Jun 13, 2014 6:00 pm

Centering rings (or redistributor plates) seem to have a specific use.

They are not needed during the early part of the run. When the reflux is high ABV the surface tension is low, and it wicks into the packing with ease.

Towards the end of the run the ABV is significantly reduced and surface tension becomes a problem. This is why the recommendation is to use the rings in the lower third of the column. If you look at the packed glass column videos, the channeling etc occurs mostly in the lower section of the column.
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Re: void in column

Postby kekedog13 » Sun Sep 07, 2014 7:31 am

Now I have run this several times and am rather disappointed in the out put , proof wise. Using 11 gals of 13 % wash in a 14 gal keg the highest proof is not more than 124 proof . I was really expecting a higher number considering all that went into this rig. 2" copper , 36 " of it packed with 3 tight rolls of copper mesh, topped with a bag of Raschig rings, insulated, a 12" reflux condenser on top with a 1 " vm take off with a 1" ss gate valve.Any ideas why the low proof ?
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Re: void in column

Postby Rockchucker » Sun Sep 07, 2014 7:42 am

How long do you jet it stabilize for? At 36" you should be getting better results. It could be that you have 2 diffent packing materials not allowing for proper equalization. Or it could be your running it too fast, what is your take off rate?
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Re: void in column

Postby kekedog13 » Mon Sep 08, 2014 5:10 am

As I was waiting for it to stabilize alcohol started gushing from the top of the column. So I had to open both valves to relieve it. The temp at and at the VM valve was 178 the top of the kettle was 200 F. I am still learning , there seems to be more info on how to build one of these than on how to run it. I never did measure the take off rate . I was busy just trying to keep it going and adjusting the valve and fire to see if I could increase the % of what was coming out.
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Re: void in column

Postby Stanley » Mon Sep 08, 2014 7:02 am

Kekedog13: I have a 2” LM Boka that is only 27 inches to takeoff. I have packed it with SS scrubbies to just below the takeoff, 1 ½” maybe. I have had the problem with the wash coming out the top of my condenser so I turned the heat down on the boiler. Now I know where to set the temp when I start. I leave it in reflux for at least 30 minutes. You can do it longer if you wish. I then slowly take off the foreshots. I go overboard and take 300ml that’s just me. I then shut the takeoff valve for at least another 15 minutes before I open it up again and collect at a faster rate than the foreshots. As the temp changes in the column and ABV drops I will equalize the column again. I now only do stripping runs then spirit runs. I think this is much faster overall. I collect at 95% ABV or greater. Hope this helps. Stanley :grin:
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Re: void in column

Postby wv_cooker » Wed Sep 10, 2014 7:32 am

kekedog13 wrote:As I was waiting for it to stabilize alcohol started gushing from the top of the column. So I had to open both valves to relieve it. The temp at and at the VM valve was 178 the top of the kettle was 200 F. I am still learning , there seems to be more info on how to build one of these than on how to run it. I never did measure the take off rate . I was busy just trying to keep it going and adjusting the valve and fire to see if I could increase the % of what was coming out.


The first issue of hot vapor coming out the top of the column means you were pushing to much power to the rig for the condenser to handle it. The second issue I see is you shouldn't mix packings, it creates a problem achieving a heat gradient throughout the column for fraction separation. You column can achieve good number if you just pack the 36" with all copper mesh.

You do want the mesh fairly tight but make sure you are still able to blow all the way through the column so that it is not restricted. as for your original question there should be a couple inches for the reflux to return to and allow it to have just a little space so it doesn't fill up and block the column. as for running an lm there is a good read on another forum that does a lot for understanding. here is a link.

http://homedistiller.org/forum/viewtopi ... 63&t=13265

Hope this helps!

edited to say: You don't increase the power to the boiler to up the ABV output if anything you up the reflux ratio and slow the takeoff. your power on an LM should mostly be set and left alone.
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Re: void in column

Postby crow » Mon Nov 10, 2014 3:48 am

kekedog13 wrote:Now I have run this several times and am rather disappointed in the out put , proof wise. Using 11 gals of 13 % wash in a 14 gal keg the highest proof is not more than 124 proof . I was really expecting a higher number considering all that went into this rig. 2" copper , 36 " of it packed with 3 tight rolls of copper mesh, topped with a bag of Raschig rings, insulated, a 12" reflux condenser on top with a 1 " vm take off with a 1" ss gate valve.Any ideas why the low proof ?


yep that's about what I thought would result

crow wrote:would recommend you toss the rings and just use copper mesh. My 2" is packed to just below the collection point, Dimroth condenser is also packed and it pulls azeo every time.
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