lm off set head problem

[Grogman]

I have a lm still and cannot seem to get any real amount of relux to occur to raise purity. I use 3000w to heat up and do my run on about 650w. It seems like no matter how much output i return as reflux my head temp stays in the 80 to 81c range. I have a 1/4 double wound spiral condenser i use and water flow through it makes no difference to temps at all. There are two needle valves i use to control take off and reflux. The still head where the valves are connected is always very hot so i think the liquid i send back as reflux is too hot to cause reflux to happen. Is this even possible? I also have the condenser coil mounted thru a 2" cap which goes on top of the column where the condenser goes in to. Should that cap b there at all? My output is slow nomatter how much power i seem to apply. I use copper scrubbers for packing loosely stacked in. Sorry for the long post. All ideas greatly appreciated!

[junkyard dawg]

First, be sure that you have a good wash in there... Are you sure you have alcohol?

Next, when you run, turn off all the reflux and measure how fast the still is producing. You may need to put in more power...

Once you establish that you have a strong flow of distillate, reverse the valves and send all the distillate back into the column. You should see the temp settle in close to 78C. From there you can slowly open the take off valve and begin collecting again. Play around with the valves and power. It takes some getting used to, but its not hard once you get whats going on.

I don't think you need a cap on the condensor. You might need more coolant flow tho...

Do you know what % your wash is?

[Richard7]

I agree with JD. And no cap is required. Mine is wide open, if you look down from the top you can see my coils. One thing I can think of is, with the still off try pouring some water down on top of where your coils are and see if you have good out put through your collection tube. There may be a restriction causing the output to go to your reflux tube.

[Grogman]

My wash was 12% based on potential alcohol on hydrometer readings. There aren't any obstructions in my takeoff tube. It just seems like no matter how much reflux returned to column my head temp won't settle anywhere near 78.1. I tried increasing power and temp goes up but when i decrease power the temp gets very squirrelly..... goes up to about82 and then drops below 70ish. Is the collection cup supposed to be hot? Also is the condenser coil suppose to reach down to the collection cup bottom or not? I'm at a lost right now.

[Grogman]

Would an unsettled wash cause the problem I am experiencing? Thanks for any ideas.

[F6Hawk]

Does cooling water flow rate change during run?
Does cooling water temp (input) change during the run?
What is the temp of your cooling outflow?
Are you using a controller for your element, or does it cycle off/on via a thermostat?
How long do you let it sit at reflux when it gets to 78° (not important what number - what IS important is that it stabilizes, +/- 0.3°

Do you have pics or a description of your still?

[maheel]

post a pic mate that will help us figure it out for you

does the coil pass "through" the area were the vapour comes across the "offset"
if yes the coil may be stopping vapour entering your offset / reflux area and lowering ABV % by stopping reflux happening in the offset area

[wv_cooker]

Several questions - 1. Where is your thermometer placement in your column or head? 2. Is any vapor escaping through your vent in the cap? The needle valves are usually made of Brass and conduct heat very well, yes they get pretty hot. The reason I ask about your thermometer is, if it is placed in such a manner that any liquid hit's it you could be getting a false reading. On my Lm head I don't have a valve on my reflux return, and I have the tube behind a sight glass. when I crack open my take off valve I can watch the reflux and it is always much more than my take off. I here that adjusting the two valves can be a little tricky, you will have too learn how to open the take off valve and reflux valve to work together for the amount of reflux you want. I would crack open my take off valve then adjust my reflux valve until I had the take off rate that I wanted. I hope this helps some and yes the valves and your collection cup can get rather hot. If you are getting product out of your take off or collection tube and no vapor is escaping through the top cap out of your vent, I would lean towards your thermometer being where liquid is hitting it or possibly a bad thermometer. Once your boiler gets to temp the vapor is going to flow up to the condenser. If the condenser has enough knock down power to knock down the vapor without any escaping out of the top, you are going to get product out of your take off. Then it it's a matter of adjusting the valves until you have the reflux rate and take off rate that you want. Below is a link to some good reading on running a LM type still.

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

Hope this helps.

[Grogman]

My coolant flow rate and temp remain pretty constant throughout the run as i am on well water.Yes I am using a scr controller to vary input powr to the boiler. the condenser does enter partially into the vapour path as it exits the offset. I dont get any vapour thru the vent cap at all. my thermometer is in the top of the column as well. I let it sit at full reflux @ 30 -45 mins before starting take off as product but temp still stabilizes in the 80 to 81 area always moving up or down from a few tenths of a degree. never actually fully stabilizes. all my pics are too large to post so will take some more tomorrow and post em then. Thanks again....

[maheel]

thermo might be out
check it in boiling and a ice slurry to see what it reads... i have had them read more than 1deg out (china ones)

stuff a scrubber down your coil as well just in case...

try running at around 2000w and tell us how much output per min you get with the valve wide open

do a water run and tell us what sort of output you can get

something strange going on...

[junkyard dawg]

I'm beginning to suspect the only problem may be in your thermometer.

I would not consider a couple of tenths of a degree variation to mean much... calibrate your thermometer and see what you have.

You also raised this issue as one of increasing purity... What kind of numbers are you getting? Ignoring the temperatures, what % product are you seeing?

[rad14701]

You haven't stated how tall the packed column section is so I'd be looking in that direction first... If the packed section isn't tall enough, or doesn't have the right density of packing, you will have problems attaining and maintaining azeotrope... A 2" column needs ~36", minimum, of structured packing and there should be a small amount of resistance when trying to breathe through the packed section, yet water should run down through it freely at a moderate flow rate... If the packed column isn't adequate you can dick around with the head as much as you want and never improve performance... The packed column is the key to success...

Two things I would suggest... Shoot for 36" - 42" of column filled with structured packing... Perhaps try switching to 100% stainless steel scrubbers because they will have a different density factor within the column than copper which is much finer...

[Grogman]

I think we may have figured this thing out!! My thermometer reads 101.8 deg c for boiling water and I am only about 60 ft above sea level as well I only have about 28 inches of packing in a 52 inch column.... Thought i had more! Plus my wash must have puked into column or something cuz there was some crud around the reflux return line partially blocking it. Gave everything a good scrubbing and will get some more packing to see how it works out then. Thanks guys for the help and your time and thoughts.. wouldnt have figured this out without yas! Not discouraged anymore!

[Prairiepiss]

I use 3000w to heat up and do my run on about 650w.

650w ain't enough to do crap. In a reflux still.