LM / VM Head design questions

[myles]

There is something wrong here. 250 deg F is the boiling point of water in a pressure cooker at 15 PSI above atmospheric pressure. There is NO WAY that your boiler under a reflux column should be getting that hot.

Also I am not sure why you are measuring the vapour temperature inside the reflux condenser. A more logical measurement is that of the water temperature LEAVING the reflux condenser. Ideally your reflux condenser should be removing enough heat to condense the vapour but NOT to cool it any further. That is just a waste of energy. The reflux condensate should be hot when it re-enters the packing, as should be the temperature of the coolant leaving the condenser.

The temperature at which the wash boils in the keg is determined by the composition at that moment in time. Lets say you have it boiling at 192 deg F (arbitrary figure), you then double the power going in by switching on another element. If everything is working correctly YOU WILL NOT increase the temperature at which it boils. The only thing that should happen is that it will boil much more vigorously and release vapour much faster - but at the same temperature as before.

[Ben the Stiller]

Myles/Old Hippie - thanks for the feedback. I admit I'm puzzled. Step 1 will be to check the calibration of the thermometers. I agree that the wash temperature should hold at 192 deg F when it comes to a full boil, based on a 10% alcohol/water mixture. And, in fact, shouldn't I expect the temperature at the top of the column to be the same (192 deg F) until a significant portion of the ethanol is boiled off?

[Old Fart]

Ben, Boiler vapor temperature does indeed stay at 192F throughout most of the run or at least mine does. Creeps up a bit to about 204F as the ethanol is depleated. Taken with a liquid filled Ashcroft thermometerand not mounted under the column. My column temperature is whacked though, I'm getting 166F as it stablizes and a drop to 165-165.5 during collection. Using Mule Kickers PID controller. I guess I need to check calibration as well and to see if I have the right type thermocouple. Came with a J type that is kind of odd. Most common one is K ad will read a little different. It's mounted OUT of the liquid stream. I'd be looking at where yours is mounted and the calibration of it. Hope this helps...


Old Fart

[Ben the Stiller]

Thanks, Old Fart - I have three temperature measuring devices in my still. I have a dial thermometer in the keg, submerged below the wash to measure the temperature of the wash. I have a dial thermometer in the top of reflux column above the (marble) packing, and I have a thermocouple in the vapor leg (if that is what it's called). I have to check the calibration of the one in the keg because it reads unrealistically high, but the one at the top of the column appears to be correct, as it stays right around 192 when the unit is up and running. The thermocouple seems to work well, though it depends on exactly where it is in the vapor leg. If it is too close to the condenser coil it probably gives a bad reading, not representative of the vapor temperature, but closer to the condenser water temperature, so I just use that as a 'relative' measure.

One question I have is this. Does it matter how cool the vapor leg gets? In other words, when the vapor leaves the reflux column it gets condensed and the majority of it is returned to the column and a small amount is taken off as product. I make sure I can't see any vapor coming out of the top of the vapor leg to know that I'm cool enough to condense everything that's coming across. But does it matter if I cool it more than the exact condensing temperature? If the vapor shows up at 192, any drop in temperature (from the condenser) should generate condensate, so I could condense at the lowest cooling flow rate (conserve water) I possibly can. Let's say that's 188 deg. What happens if I run the vapor leg at 180 deg or 175 deg? Seems to me it would still work fine. The only problem is I've cooled the reflux liquid more than it needs to be and it has to get additional heat back in the reflux column. I'm just guessing about that

[Old Fart]

Oh, I forgot to mention that I closly monitor water discharge temperature of both condensers. The 2 dials you see in the picture are for this purpose. My column temperature is taken on the top of the 2" as it reduces to 1". Can't see it in the picture though.
You also need to keep the reflux returning to the column as hot as you can and still maintain a good reflux ratio.

Old Fart

[Old Fart]

Here's where my column temperature is taken.

Old Fart

[Old Fart]

Ben, The arm in question doesn't go into the column, it's soldered on the outside and it's a support for the VM arm as well as a collection point for the hot water from both condensers. There is a similar one on the bottom for the water supply.
Once it's up to temperature and stabilized (takes about 1.5 hrs.) I can run the ethanol off in about 30 minutes at a constant 190+ proof. Having a good reflux the whole time....

Old Fart

[Old Fart]

Here's a better picture

[Ben the Stiller]

thanks - I have to study that some more. How many gallons of wash and how much product do you get? Wow, 30 minutes is really fast, but the good proof says you are doing it right!

[Old Fart]

9 gallons of wash got almost 3 quarts plus heads on the last run. It's my last for a while as I just sold my still. I had a fermenter on Craigs List as I got a better one and a guy came over to buy it today. I asked him what he was fermenting and he said he was thinking about building a still. I took him out to the shed and showed him mine. Next thing I know he's waving $2500 in my face. I didn't really want to but I sold it to him. Gave me another $1000 for my new stainless conical as well. I'm taking the money and going to move with it so I guess I'm not distilling for a while. I still have my original 25 gallon fermenting drum though. Guess I'll put it back on CL.

[Ben the Stiller]

Wow - 3500 will buy you a lot of good store bought hooch. I hope you have an uneventful move. It's the best you can hope for

[Old Fart]

Yeah, I couldn't turn it down. The guy seemed like a yuppie prepper with alot of money. Anyway it came at the right time as things have tightened up at my job business wise and I think lay-off's are in the future. I'm going to build another one day but for now I'll just lurk here from time to time and keep current on things. Maybe a 4" plate column next time. Anyway the ! cleaning run I did taught me a few things about my design so I gained some knowledge and pretty much doubled the money I had invested. Good luck in getting yours right. Just remember to keep the column temperature probe out of the reflux liquid and get it calibrated with some boiling water and another thermometer.....

Old Fart in the wind.

[Ben the Stiller]

O.F. - If you are still checking in, I have a few questions.

First, your 25 gallon fermenting drum. Where do you get such an animal? I'm using a trash can that doesn't seal well. I have never had a problem with air getting in (as far as I know), but my airlock doesn't bubble, so I assume the CO2 is getting out between the can and the lid. I'd like something smaller and with a better seal.

Second, how much heat do you put into your still? I have 3 x 1500 watt submersible heaters in my keg with a 15 gallon wash. I run all three (4500 watts) until it comes up to temp, then I cut back to 2 heaters. I'm curious how much heat you put in. I would guess more if you are getting through the distillation in less than an hour.

I sent a note to the guy I bought the thermometers from telling him I was disappointed with them. He said he'd send me some new ones and he'd check the calibration temp in boiling water. I'm also buying a type J thermocouple for the reflux column.

thanks

BTS

[myles]

BTS I have a load of fermentation drums, all food grade.

160 litre white HDPE tighthead drums that used to contain Coke syrup
200 litre screw top drums that used to contain olives and
slightly smaller screw top drums that used to hold ginger and chillis - about 120 litres

The HPDE drums are fine for fermentation use and should be easy enough to find from recycling places. Look for somewhere that stocks recycled drums for rainwater harvesting.

[Old Fart]

I found a food grade plastic drum with a screw on lid with gasket. Got it on CL from a used barrel place. Not sure what you have available locally. They are hard to find as most are 55 gal but they are out there. FOOD GRADE ONLY!

Second I heated up at 45% power on a 5500W element and then went to 55% power to do the run. Not sure if this was right though, seemed to work OK.

Old Fart

[Ben the Stiller]

Thanks Myles. I checked CL in my area and came up empty. I googled used plastic barrels and found nothing yet in my price range. Some of the barrels weren't bad, but the shipping more than doubled the cost. Guess I'll keep my eyes peeled

BTS