Output volume vs vapour temperature

[scarecrow]

This is my still. Coil reflux condenser, coil product condenser into a shottie into a short liebig. Nothing flash. Liebig has separate reservoir (blue 50 litre tub) and is cold throughout the run. Main cooling goes through shottie into product condenser then out into tank.

Liebig cooling.JPG

I start up at full power (3 ring banjo), throttle back to low power (outside ring only), stabilise 1 hour and take fores at a slow drip and heads at a fast drip. These are done at <78C.

Now my problem (I think). I adjust reflux water to get a faster output of distillate (starts at about 2 LPH and settles down at about 4 LPH). BUT.... the temp wants to run to about 80C. When it gets there, it starts to piss like a mule, sits steady for the most of it and then temp rises very slowly, but can be controlled by my reflux needle valve to within 0.1C.

I just can't seem to keep it at that magical 78.2C. If I do it dribbles like it has prostate problems :laughing-rolling: It seems to find it's own rhythm and then it settles in.
Do I need to keep it this low or can I just let it run as it wants?

I can keep the whole hearts run to 80 - 82C, then it skyrockets as the tails start to kick in. Tails are over in the blink of an eye. :handgestures-thumbupleft:

I also find that it farts and spits till about half way through the run. Everything heats up and it settles down. I've tried packing up the pooper, but it just blows right past. Is this too much heat or not enough cooling? I know it's vapour collapsing, but both shottie and condenser are too hot to touch so something is going on that I don't understand. I thought if I layered the cooling (coil into shottie into liebig) this would stop, but it hasn't. Any ideas?

I see videos of plate stills and wonder what's happening differently to mine. I never see a thermometer after the dephlegmater, always before. Also, a plate still does not have a huge 4" bore. With all the holes and cups it would probably be closer to a 2" pipe. Maybe the plates smooth out the temp stability and surging. Dunno, just brain farting here. Anyway, I just don't want to build a plate still out of principle. :text-offtopic:

Geez, what a rant. :laughing-rolling:

scarecrow

[audistiller]

Quite an operation you got going there Scarecrow, looks a bit like a Bio Fuel setup. :handgestures-thumbupleft:

[R-sole]

That's the trouble with building an experimental design. You don't have the pool of experience to troubleshoot problems. Just something you have to accept at the start of the concept as a risk.

[eminiM]

I just can't seem to keep it at that magical 78.2C. If I do it dribbles like it has prostate problems :laughing-rolling: It seems to find it's own rhythm and then it settles in.

You can't chase temperature. I distill azeotrope at temperatures in the 74C range and it changes by 10ths depending on barometric pressure. Your column is quite short for diameter so I think you'll have trouble staying on target anyway...........

Sounds like you've discovered optimum operating method anyway so relax and enjoy!

[Al Qaemist]

Scarecrow, the way I see it you can choose to do a few things here.

Run as you are - watching the temp between 80-82.
Run it like a pot just monitoring the distillate output rate.
Not sure where the reflux coil in that rig is, but some folks running a CM config monitor the temp of the cooling water coming off the reflux coil - again keeping it within a range.

It sound like you're getting good results, don't hang yourself up chasing a number, find out what works on your rig and build on it. My mid column probe on my VM normally sits about 77.7-77.8 for hearts, but on another thermo its 78, I only use it to indicate change rather than looking for a specific value.


Nice rig by the way.

[scarecrow]

I've done a few more runs trying different heat settings and reflux rates.

Finally managed to get the leibig, shottie and coil working together. I gave the shottie its own flow control and it works well. Product condenser is very low flow and output is very hot. Shottie works best when length of tube is half warm and half too hot to hold. That allows the liebig to be on a slow trickle and product exits at about 24C.

I'm getting too much smearing running it in pot mode. I found 20cm of scrubbies and one ay the bottom of the column gives me the best results.

Maintaining 80-82 is easy, and gives me the greatest hearts yield and then a quick run through the tails and shut down at 96C.

Not sure where the reflux coil in that rig is

Reflux on the left, product on the right.

coil7.jpg

scarecrow