So I’ve caught the extraction bug and am motivated to get these babies optimized before scaling.
I came into this facility already set up, but not running. Over the last few days I’ve at least gotten both 20L online and installed a line of 3x cold traps but am now focused on pulling an optional vacuum.
Solvent: 95% etoh 5% n-heptane
Bulb size: 20L
Bath temp: 46-50°C
Rotation: 87-100 RPM
Vac pumps: 4x - best value 1/2 hp
Condenser coil chiller: set -13°C, cycles at -4°C
Vacuum: between -.09 MPa and -.1 MPa
Math isn’t my strongest skill and although I can google and use the search bar like the responsible human being I try to be, I have been struggling in understanding my gauge and converting MPa (megapascal) to microns so I can follow along with the nomenclature I see being used here.
With that being said, I’ve scrounged the forums and soaked up quite a bit of information.
First thing I’d like to do is upgrade the vac pumps to something more suited to this rig. Thinking of the Welch 2052 2.3 cfm and wondering if this one pump could handle both roto-vapes.
I need to replace all the tubing to heavy wall because they are starting to flatten under the pressure and I’d like to replace the gauges to digital.
If anyone has equipment recommendations or additions to my upgrades i’m all ears!
If it’s running with issues then you can’t optimize it. You’ve exceeded it’s abilities. Optimization is for rotos that can be taken to thier limits and function. This one can’t. It’s very basic in features.
Not to sound stupid but the conversation thing is still getting me. My gauge reads in MPa which is megapascals. I’m using Convert MPa to micron mercury [0 �C] - Conversion of Measurement Units this table here to convert MPa to microns and its comming out at -750061.56130264 when i try to convert -.01 MPa.
30-60 micron seems like an incredibly hard vacuum for a rotovap. Most rotos run on diaphragm pumps which typically don’t go below 15torr (~15000 micron) when connected. Am I wrong?
Yea that’s just low grade pumps, we use vacuubrand. On a vpc or a svc1 we can manage thier low rates all the time. Or use various controllers. There are low vacuum diaphragm pumps and there are medium vacuum diaphragm pumps
Good comment.
EtOh will boil at high vacuum.
No reason to run a rotovap at more than 25" Hg with the water bath at 75 C
You know it is at capacity when all the coils in the condenser are dripping EtOH.
Why pull the vacuum so low that things boil at 30 C when you are going to heat the hell out of the product in the decarb and SPD steps?
20 liter rotovap I see 20-30 liters per hour. (Across)
50 liter rotovap I see about 50 liters per houax and that’s with a 5hp and 12c vario style pump.
I have a new roto I’m releasing that does double what these figures I listed did per size. It’s all about technology and how it’s applied.
Think of your roto-vap as a tug-of-war between the evaporating capabilities in the receiving flask and the condensing capabilities of the condenser.
Ideally your evaporation rate and your condensing rate would be exactly matched to each other. Just like @DaKine said, when your condensing coils are fully saturated and dripping EtOH, that’s an indicator that you’re at your condensing capacity.
Deeper vacuum and higher bath temps will increase your evaporation rate, but if you don’t also increase your condensing ability, you’re just going to lose a bunch of ethanol vapor through your vacuum pump.
@spdking I have seen ethanol spontaneously boil out of winterized crude at very modest vacuum levels when it’s still majority EtOH. After the first little bit boils off and it becomes thicker, then it stops spontaneously boiling.
This…
Boiling point climbs as the solution starts to contain a significant amount of solute.
Higher temperatures or deeper vacuums are required for final solvent stripping but for most of the recovery operation 25 inches Hg will cause boiling at 50 C.
The rate you are boiling up depends an the temperature differential between the outside and inside of the flask because you are heat transfer limited through the glass in a rotovap.
We don’t need a -40 or better chiller for rotos to do real work do we? I got the 20L from mr. atomizer and it sorta works, but then I got a chiller from them that is no where close to the Polyscience one. Can’t we just use something that keeps a better constant temp, but doesn’t have to be so cold?
