I had and idea based on my reading about reflux columns. The purpose of this method is to extract water and methanol out of Biodiesel at the same time thus saving time and a manual step.

The idea would be to heat the Bio up to 185F (using a PID temp controller) and at that temp apply a vacuum. The vapor would then be pulled through the top of the tank through a 90 degree elbow that was then connected to a Tee Fitting filled with marbles. The trunk of the tee would connect the 90 degree elbow off the tank and the branches would face Up-down. The Down side of the Tee would just be pipped into a long piece of additional pipe to collect water and withstand the vacuum. The Up side of the Tee would be attached via hose to the condenser unit and that would then be attached to the Methanol collection vessel and the vessel attached to the vacuum (lets not worry about the vacuum becoming polluted yet.) To improve Methanol purity, an additional length of pipe and marbles could be added between the up portion of the Tee and the vacuum hose.



Currently in my set up there is no reflux column, the vacuum is hooked directly to the top of my processor and even with opening a valve to let air in at the bottom of my tank, I am able to pull a continuous (ok 30 minutes until vacuum pump overheats) vacuum of about -12hg.



Things I know with my current set up:
At 185F is hot enough to pull the water off. I have done this already but was not exactly sure how dry it got my Bio. I will need to do some more calculations next time. I am sure hotter is better and if anybody has some numbers on this, I am open to hearing them.

At 160F, I can get 98% pure methanol.

So here are my questions:

0. Will this idea work at all?
1. How much cooling effect will the marbles have? Like is there any math or table on 1" diam. pipe with 4" of marbles with just air cooling will drop the temp like 5 degree at 185F. (I know this is got to be a complex function, but just some idea would be a great start.)
2. I know I will lose some meth to the water, but I should still get very pure meth out the North Side, right. Also, as a percentage, will I lose a lot of Meth?
3. Assuming I have little water in my WVO to start, how much water is produced in a typical base/base reaction in ml? Otherwords, how much water do I need to 'store' when extracting both the water and meth. I think out of 130 liters (~35 gallons) I get 1 gallon of Meth back from the bio)


Doug

Doug

-you can pull methanol off with a vacum at 145 - 150f. so why not do this recovery in two stages,methanol first, then raise the temp and go after the h2o? seems to me that the marbles will heat up quickly, then what, Tom

You are right. The idea is to save time and then having to go out there and deal with dumping out tanks.

Day1 - Process.
0. Assuming you have dry low titrating Oil.
1. Heat Oil to temp 1-2 hours
2. Process 80% Meth 1 hour
3. Drain 10 minutes
4. Process 20% Meth 1 hour
5. Drain 10 minutes
6. Heat Oil to 185F 1 hour
7. Distill Water and methanol - 4 hours?

Total Time ~ 9 hours

Now that can be done in 1 day.

Wait 60 hours ... well two full days puts you back at night so the next morning is 2.5 days)

Day 4:
8. Drain any remaining glycerin and soap fallout. 10 min
9. Filter Through Wood chips and Thermax (1 pass at 9 gallons/hour is approximately 4 hours for one pass.)


Complete - I think.

Doug

-can you not pull the meth with vacuum after the second base stage,soon as it passes 3/27. The temp would be right for that. pulling meth under vacuum is very quick, as soon as you introduce vacuum to the reactor it really boils. At this point , you will have most of the meth, and it will be of good quality. then continue to raise the temp and pull off the water and residule meth. When I used this method in my old processor, it was done in about 20 min. But that was only 27 ltr. I haven't got that part finished on the new unit yet. Tom

Doug,
Have a look at fabricators reflux condenser. IIRC it consists of a large marble filled reflux column that he has great success with.
Be vary leary of your vacuum pump if its overheating! There will be methanol fumes in it...
Jon

Ok, I have an idea for a test. Perhaps creating water is not even an issue. I will the system as it is now and run a batch and measure for water at the different stages, then post the results.

Thanks
Doug

I have had no issues with water when distilling. I always dewater my oil in processor before I start and I dont add any throughout the process.
After a complete demeth of the glycerol and bio my alcohol tralles always indicates pure methanol. So any water being created in the process is either insignificant or my still is somehow working as a reflux...
Jon

No doubt that you are getting nearly pure methanol out. I am curious how much water is left in the Bio though - created by the processing? (You don't have a Sandy Brae do you?) I am sure it is little, but I think it would be good to know.

Thanks
Doug

My only though is if the methanol also condenses for some reason into the water tank. If its under a vacuum and you have the sections outside of it that start to cool, it may re condense before the condenser. Of course only at the lower temperatures, before everything heats up. Maybe some insulation in parts? Also if you put a valve between the reflux and the water collection, you may be able to get away with a smaller tank and just switch it out occasionally. Put a quick disconnect in there too and you are sure to maintain a vacuum. I think... You could also do the same with the methanol side too, though I'm not entirely sure how you would work a site tube into the system... maybe this would be too complex.

Also, this may be going too far, but we've been using a 3 ft reflux column with metal scrubbies, they have been working pretty well thus far and may prove a cheaper/easier alternative to marbles. We are looking to make the jump to vacuum, looking forward to what you find out!

quote:

Originally posted by Doug Weiner:
(You don't have a Sandy Brae do you?) I am sure it is little, but I think it would be good to know.

Thanks
Doug

No, I wish I did!
I will probably end up making an Imanometer but I don't see any time for that in my near future...
Jon

quote:

Originally posted by KamerosA:
Also, this may be going too far, but we've been using a 3 ft reflux column with metal scrubbies, they have been working pretty well thus far and may prove a cheaper/easier alternative to marbles. We are looking to make the jump to vacuum, looking forward to what you find out!

We got our marbles at the dollar store, IIRC it took less than 3 bags.

quote:

Originally posted by freesoul:
We got our marbles at the dollar store, IIRC it took less than 3 bags.

How do you keep them in? One design I had seen was using either metal screening or a heat tolerant plastic screen.