[Open Source Design Project] - Falling Film Evaporator



Or maybe a CNC machined distribution plate. The design would be relatively simple, but the manufacturing might be a little expensive.

Definitely not an off the shelf item, and a properly selected spray nozzle is probably an 80% as effective solution at 5% of the cost.


What do you mean by distribution plate? Like a 3-D mesh?
When I say “wetted membrane,” that could be any material in contact with liquid. Not necessarily absorbent (though that would be an option)


I’m thinking like a circular plate milled so as to basically have nozzles on the underside that make the fluid drip into the spaces between the tubes of the exchanger, which should distribute the fluid pretty evenly if you design it right.


Send me a basic hand drawing if you want and I’ll slap together the CAD


That’s exactly what we are doing. Then you flood that top plate so that it evenly disperses out to the gaps on the lower plate


I’m a terrible drafter. Here’s an image showing the basic concept.

I might know someone who is an expert in fluids & nozzles, I’ll ask and see if its possible to get the desired effect with just a single or possibly multiple nozzle set up. I know that generally they don’t have super even spray distribution patterns but I seem to remember finding some precision machined ones do.

I think BZB uses something like 60psi on the input pre-nozzle, which should be sufficient for our purposes.


I doubt these are cheap, but might suit as an off the shelf nozzle option.


Cool. This is very much along the lines of what I considered as a “wetted” membrane. I would think that a single distribution plate works, so long as its flow is reduced enough to achieve even flooding. But a series of plates would definitely work.


Yup, either could be made to work for sure.
I’m personally partial to nozzles because of the possibility of getting some flash evaporation from the pre-warmed input stream being sprayed into the lower pressure/vacuum space of the evaporator, but I suspect that the distribution plate is likely the more consistent and effective design in the long run once it’s dialled in.


A point to note, on my FFE, both the liquid and the vapor exit the primary evaporator from the bottom


Here’s an idea/thought: why doesn’t anyone use plate type HE for falling film designs for our industry? They’re not uncommon in other industries.


Hey Guys I found this thread so compelling I had to sign up for future4200 just to get involved.
Future I have to ask why did you guys go to a deign were the vapour escaped the evaporation chamber at the bottom of the chamber instead of finding a way to let the vapour percolate upward like in a traditional distillation set up ?

PS thanks for all your sharing this is a great open source topic because I’m sure all of you like me feel like were getting our butts handed to us paying 100k plus for just the falling film W/O accessories.


Because then the upward flowing vapor would be interfering with the laminar downward flow of the crude. This way everything is working with gravity and moving towards the vacuum source.

Note, the condenser is setup as a rising film, this is because condensing ethanol falling back down through ethanol vapor is beneficial to overall condensation.


Here’s a nice little handbook on evaporator types. It’s not super comprehensive, but it’s got enough details to get a basic understanding of the various types.

GEA_Evaporation-Technology.pdf (1.0 MB)


Here is a picture of a FFe that I built this year. Havent had enough time to run it but a couple times. But it seems to fdo the job and get about 10 to 15gal/hr recovery. Ive started with a spray nozzle but going to try a sparge arm soon.


Awesome set up! What kind of pumps are you using to drain the condensed ethanol?


looks like a perastaltic pump in the picture.


So this design has the vapor rising out of the evaporator? Looking good!


whats your heat source? How hot are you running at 10-15 gph?


Question: What keeps your feed solution from being sucked right into the condenser (center column)?

Oh, and here ya go, guys. A simple liquid distributor:

I’ll have to do a technical drawing and send it over to a few folks for quotes. Gotta brush up on tolerances/surface finishes as per ASME and I’ll do so. I understand ethanol recovery doesn’t need a pressure vessel by ASME standards, but I would prefer the functionality and build quality of an ASME stamped vessel.

I left out the center hole so that liquid can be filled directly centered using a simple dip-tube. I’m sure you could easily flood the plate with a spray nozzle or a multi-port distribution nozzle above it - but it adds some cost.