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Offset head modification

These usually have the means for returning the spirits to the column and usually allow metering of the take off to help in the reflux.

Offset head modification

Postby Mr Clean » Mon Sep 27, 2010 8:02 am

I wanted to pass this along to the group because it really worked out quite good.

I had built an offset head about a year ago and it has worked out quite fine, running it off a 73" long 3" copper packed column, always get 93-94 clean spirits derived from HFCS.

I'm looking at the head and start thinking what if I add a second condenser on the other side of the column head for reflux, so I take off the 2" cap that seals off the other side and add a 3x2 reducer with a 2X1.5 reducer inside to locate the reflux in the center of the column, now I start thinking, I've got the liebig and 2 condensers so water temp will probably go out of sight since I'm running 3/8" plastic tubing for cooling so I ran three individual lines from a manifold to each cooling device and the return lines back into another manifold redirected into my heat exchanger. So everything is ready to go and I've got 4 gallons of leftover strippate from an absinthe run I did a month ago and its 27%.

I hook everything up but use a shorter column, 4.5' 3" packed unit that's part of my 73" column. Fire it up and it comes to boil, immediately, my column temp stabilizes within 3-4 minutes at 77.8 so since this is basically a test anyway, I figure, I'll start to take off.

Starts out at 95% which makes me quite happy after no reflux time, distillate smells fine, tastes good, run for 3 hours or so, temp never changes, stays at 77.8 for the entire time with no adjustments, all product taken off is between 94 and 95+, ended up with 5 quarts, last quart was 92%, temp started to change very slowly but was rock solid during the entire run. Took a little longer than I expected due to a few leaks that need to be repaired during the run causing a shutdown of the system for the repairs. Wound up taking off a little more than 500ml as the temp climbed to 92 so shut it down.

I just wanted to pass this along since I've never really seen anything like this on here, will perhaps do another run this weekend using some strippate I've had for several months sitting on soda and salt, have a few more modification ideas. My only concern now is how to assemble the whole thing with the long column, weight is a consideration.
25g, 4"X60" 10 plate reflux
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Re: Offset head modification

Postby loneswinger » Tue Sep 28, 2010 2:07 pm

I read through this a couple of times and am still not clear on the modification. So you added to the straight section of column a second reflux condenser? So the upgoing vapor is split between the offset head and another path that just returns it as reflux? You are still returning some of the refluxing liquid from the offset head by controlling the liquid you take off right? Which is taller, the condenser in the offset head, or the new condenser that you added? I am just trying to visualize what this looks like.

-Loneswinger
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Re: Offset head modification

Postby Mr Clean » Tue Sep 28, 2010 4:50 pm

loneswinger wrote:I read through this a couple of times and am still not clear on the modification. So you added to the straight section of column a second reflux condenser? So the upgoing vapor is split between the offset head and another path that just returns it as reflux? You are still returning some of the refluxing liquid from the offset head by controlling the liquid you take off right? Which is taller, the condenser in the offset head, or the new condenser that you added? I am just trying to visualize what this looks like.

-Loneswinger



Right on target and the new condenser is a little taller, don't want to disassemble it but do have pictures and will try to figure out how to post them for reference.
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Re: Offset head modification

Postby loneswinger » Tue Sep 28, 2010 5:18 pm

Ok yeah. I really don't know why this improved your purity, or moreover, why you were not getting high purity before. The only reasons I can come up with are that the new column is returning hot reflux, whereas with the old way it was returning cold reflux and some how upsetting equilibrium. The other thing I just thought of was after reading a post earlier today, it sounds like the 1/4" tubing for a liquid reflux return line may not be big enough to cope with the amount of reflux being created. So that liquid reservoir at the bottom of the offset head might have been overflowing with liquid before and not returning the liquid properly to the top of the column.

When you ran it before with both the output line and the return line wide open did anything come out the output? It shouldn't from what I have heard. (I don't run a LM, I run VM, so I am just speaking from what I have read)

Maybe some others here have some ideas but as long as it works right? That is what matters most.

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Re: Offset head modification

Postby Mr Clean » Tue Sep 28, 2010 5:32 pm

loneswinger wrote:Ok yeah. I really don't know why this improved your purity, or moreover, why you were not getting high purity before. The only reasons I can come up with are that the new column is returning hot reflux, whereas with the old way it was returning cold reflux and some how upsetting equilibrium. The other thing I just thought of was after reading a post earlier today, it sounds like the 1/4" tubing for a liquid reflux return line may not be big enough to cope with the amount of reflux being created. So that liquid reservoir at the bottom of the offset head might have been overflowing with liquid before and not returning the liquid properly to the top of the column.

When you ran it before with both the output line and the return line wide open did anything come out the output? It shouldn't from what I have heard. (I don't run a LM, I run VM, so I am just speaking from what I have read)


I think you are right on the money with your comment, I was not able to run it before return line any way but wide open, probably should have went to larger 3/8" or so.

what do you mean about output and return being wide open?
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Re: Offset head modification

Postby loneswinger » Wed Sep 29, 2010 11:33 am

Inside the liquid trap, the output takeoff tube sits at a higher level than the return line tube. This way, even with the output valve open, all of the liquid just goes down the reflux return to the column (when it is wide open too). You then control the output not by the output valve but by restricting the amount of reflux you are allowing to return. This is, from what I have read, the best way to run an LM still. Ask minime about this for a good explanation as to why it should be done this way. Something about a consistent reflux return rate. It also ensures that you are not overfilling the liquid reservoir.

Note: (Your still is a valve away from becoming an oddly design VM)

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Re: Offset head modification

Postby stillton » Wed Sep 29, 2010 1:32 pm

thats sounds like reversed LM (RLM) Loneswinger.
no need for two reflux condensers for that to work
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Re: Offset head modification

Postby loneswinger » Wed Sep 29, 2010 2:04 pm

stillton wrote:thats sounds like reversed LM (RLM) Loneswinger.
no need for two reflux condensers for that to work


Right.

There is really no reason to have two reflux condensers at all, regardless of design. I was just trying to figure out why is wasn't working well before the addition of the second reflux condenser.

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