How important is column length?

Evan · Post by **Evan** » Wed Feb 09, 2011 9:45 pm

I've been gathering parts here and there for a valved reflux still and I have everything I need. I'm close to putting it all together but I'm a little worried about the column length. I've already had the column welded to my boiler lid, but it's only 2 feet long. Since then I have read that the column length should be 20 to 30 times the column diameter. My column has a 2'' diameter. I've already purchased everything I need to complete the still, so buying another foot or so of 2'' copper pipe and coupling really wouldn't be that big of a deal. Is the additional length worth it? Or should I assemble as is?

Post by **rubber duck** » Wed Feb 09, 2011 10:09 pm

It's really important for making neutral, especially for a beginner. There are some guys that can hit 95% on a 3' packed column but I'm not one of them. Go 4ft and make the column 2 piece that way it will be easier to pack and put centering rings in.

My VM has a 5' packed column.

Evan · Post by **Evan** » Wed Feb 09, 2011 10:38 pm

Thanks for the quick reply RD, will do.

Evan · Post by **Evan** » Thu Feb 10, 2011 9:24 am

When you say my column should be a two piece, do you mean that I should be able to break it down and remove packing/centering rings? Do you have to remove the column packing and centering rings in order to clean them, or can you just occasionally do a vinegar run?

Post by **rubber duck** » Thu Feb 10, 2011 10:17 am

Well you can do a one piece column and that's fine. I guess some guys leave the packing in place and clean it with vinegar, but I don't know how well that works. I like to completely remove my packing for cleaning and on a 5' packed column getting the centering rings and packing out was next to impossible. So I cut my column into 2 pieces, it's also easier to set up and to store. I'm actually thinking of cutting it again to make it easier to handle.

It kinda seems like good clean packing is important for neutral. I guess you could always cut it latter if cleaning becomes a problem.

tafinaf · Post by **tafinaf** » Thu Feb 10, 2011 3:36 pm

Just out of interest, unless it pukes, why do you need to clean the column at all? Isn't steam/hot alcohol vapor the best cleaner anyway? Sorry if that is a silly question...

Related to that, do you clean your spirit containers? I figured that draining and drying them is better than rinsing with tap water as the latter will only introduce minerals.

Post by **rubber duck** » Thu Feb 10, 2011 4:05 pm

Well figure it like this, you know how when you get down into deep tails it has that really nasty taste? Well when you run a packed column that taste from the tails can get caught up in your packing and given enough runs where you go into tails it can effect the taste of your final product.

So sure steam and vinigar will clean an empty still head but it doesn't work so well on a packed column. It's really good to unpack it and clean it by hand every few runs.

It's not a silly question at, it's a very good one.

Post by **Braz** » Thu Feb 10, 2011 5:07 pm

Here's my experience. Not claiming it is right or wrong, just mine. I have about 40" of copper scrubber packed column,with a coupling between the column and the plate/condenser section.

After a run I flush the column/packing with water from a hose and let it run for a few minutes. Then I stick the hose from my shop vac into one end and let it suck air through for an hour or so to dry it out (trying to avoid mold). Every couple of runs I'll slip an end cap on the column and dump quite a bit of baking soda in, fill it water and let is set for a while - then flush and dry. I can't begin to tell you what this does but I do it anyway. I never remove the packing.

One time I got a bitter taste in my neutral and following advice I got here I poured a dilute muriatic acid solution in the column and let it soak for several minutes. Then rinsed and did the baking soda/rinse thing again. That fixed it. I don't know if this acid cleaning is something I need to do every x-number of runs or not. If I get the bitter taste again I'll do it again.

Post by **rubber duck** » Thu Feb 10, 2011 7:43 pm

So there you go, lots of different ways to skin this cat, I like to take mine apart but I'm kinda OCD.

Evan · Post by **Evan** » Sat Feb 12, 2011 3:11 pm

Thanks again RD, ordered another 2 feet of 2'' copper pipe from ebay yesterday. I've done a few searches on the site for centering rings and haven't found a whole lot of info that I can use. Should I just buy a few 2'' reducers and trim them down? I've read that there should be a gap between the centering rings and the packing to prevent flooding. Can the rings just fit snugly, or should they be soldered? How many would you use on a 4 ft column?

Evan

Post by **rubber duck** » Sat Feb 12, 2011 3:22 pm

They don't need to be soldered in. I'm using 2 on 60" of packing one for each section, I think you could go more but I'm not any kind of expert on the subject. I'm using reducers that will slip into the pipe but I think you could build them out of copper flashing.

I don't think your going to find a lot of info on centering rings but using them will increase your run speed, at least that's what I've read. I've always used them so I don't know it to be fact.

Evan · Post by **Evan** » Sat Feb 12, 2011 9:20 pm

I did a google search and found a company that makes 2'' copper discs. Could I drill holes in these discs and stagger them in between rolls of copper mesh in my column instead of using centering rings? The discs are only 2 bucks a pop, which is a lot less than what I would pay for reducers and they would require less work fitting reducers into the column.

Post by **rubber duck** » Sun Feb 13, 2011 6:33 pm

I don't think 2" disks are going to work without a centering rod, without one they will spin around in the tube. you could try to take 3" or 4" disks and make a 2" funnel that will slip in the column, or you can run it as is and add them later when you come across a deal.

Evan · Post by **Evan** » Sun Feb 13, 2011 7:18 pm

Okay that makes sense, I think I can swing that.

Post by **dougyethanol** » Thu Apr 07, 2011 7:18 pm

tafinaf wrote:Just out of interest, unless it pukes, why do you need to clean the column at all? Isn't steam/hot alcohol vapor the best cleaner anyway? Sorry if that is a silly question...

after my run through a clean still, i removed top cap and poured a full kettle of boiling water through it(40mm column x 1 metre).
i have about 800mm of packing in there, once drained/cooled i removed packing and gave it another rinse and collected the water
which revealed alot of oil floaty bits and debris. it appears that the packnig is also acting like a filter as the higher up the column
the cleaner the packing was. i will be cleaning after every run. check out pic of the second rinse water.

: look at the colour. click to enlarge

: look at the debri. click to enlarge

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How important is column length?

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