Hello all!

I am attempting to put together a system which will recover methanol from bio after ion exchange dry washing in a continuous fashion (300mL/min for starters). I have constructed a preliminary design and am tweaking it. I have provided a CRUDE image which should give you an idea of what I am talking about. Please get back to me with any ideas, suggestions or criticisms!



At the moment I am trying to spray pre-heated bio into a heated cylinder coming from the ball valve. As of now I am constricting the ball valve to act like a garden hose, as I have seen in GL's process for enhanced MeOH recovery. This is probably my units downfall though, because it is shooting the bio across the cylinder not giving it enough residence time to evaporate the methanol. I would like to find a spray nozzle that will direct the spray onto the heated walls instead of in a stream. I am going to attempt putting the system under vacuum to direct the MeOH vapors to the condenser.

Questions: What kind of spray nozzles are there that can be applied to this situation?
What temperature/pressure should i shoot for? Was thinking 65oC and vary the vacuum.
Has anyone attempted this??

Thanks!

~Ryan J.

Comercial Flash evaporators are usually a cylinder like your design except mounted vertically, and the feed comes in about 2/3 the way up the side at a tangent so it swirls around the cylinder. They usually flashing of water by heating the incoming flow to above the boiling point of the water and when the pressure drops in the evaporator the steam flashes off to rise out exhaust in the top and the liquids flow out drain in bottom. Using that same design concept you could flash Methanol, but the sizeing of the collector/condenser be the tough part.

Trc

I use a system similar to that for demething in my processor, you are going to want a pipe, or column, on the top of your meoh collection tank stuffed with stainless pot scrubbers for meoh vapor to condense on and drop out into your tank, unless you have very cold water and a very long condenser you will still have some vapor left when it gets to the collection tank.

Thank you for both of you contributions =)

Trc59. Might you have any links to these types of designs?

fabricator, luckily, the only condenser that I had available is 4ft long and my refrigeration unit is high flow so I am pretty sure this will not be a problem. How is the bio allowed to enter your flash vessel? Do you have it under vacuum and at what temperature?

ThnX

~Ryan J.

tokashila

Try this link, has a good drawing of their basic design. flash seperators

Trc

As I went over my process with my adviser, he doesn't think this will work because the FAME outlet is open to the atmosphere, and not to a pressure sealed collection vessel. This will prevent any actual "vacuum" pressures from being developed, and possibly suck FAME up into the condenser. This would also create a methanol/air mixture in the condenser, which sounds dangerous. Does anyone understand this problem (if it is a problem) and what I can look into for fixing it?

Thanks!

~Ryan J.

Just wondering how things were moving along here. But just a quick thought why not just have a collection can and vaccum pump on the FAME side also? I imagine that you would need to have the pressure equalized between the 2 containers.

Hey paulb3,

Thanks for your input and interest.

My group did try to carry out the small scale continuous MeOH recovery, but we did not obtain the desired results. We were able to get the biodiesel and methanol to 70 C with preheating and heating the vessel. The big problem we faced was not being able to put a vacuum on the heating cylinder because the liquid could not escape. One of our other problems was that the 300mL/min flow-rate was not high enough to create any back pressure to be "sprayed" into the vessel, and we feel that it only trickled out into the heated vessel which did not help in making the MeOH vaporize.

I think your idea could work if the MeOH vapors would leave the small cylinder and not also be directed toward the vacuum pressure FAME collection tank. The collection can would have to also be vacuum sealed as well and I don't know if we have the ability to build something like that at the moment.

I think our group is going to stick to evaporating methanol from the vacuum sealed reaction tank, unless work on some new ideas like yours. Thanks!

~Ryan J.

Maybe a long "p" trap like on sinks and plumbing to help reduce the vapors getting sucked into the fame container. I think I read somewhere here also that if your collection container for the MeOH is under vaccum you will most likely need to chill it also to help further condense the vapors.

quote:

Maybe a long "p" trap like on sinks and plumbing to help reduce the vapors getting sucked into the fame container.

But how will you keep the liquid in the P-trap from being sucked out or boiling under the vacuum?

quote:

I think I read somewhere here also that if your collection container for the MeOH is under vaccum you will most likely need to chill it also to help further condense the vapors.

Yes I pack my MeOH vessel with ice and cover with a wool blanket to prevent boiling. Fabricator has a better idea though and thats a large condenser on the output of the collection container.
Jon

Oh I don't really know or profess to be any kind of expert in this just throwing out some ideas.

I would think that if both containers MeOH and FAME had the same pressure that one would not be sucked into the other but in thinking about that then the vapors would not travel the route through the condensor.

So I thought that perhaps a long p trap would work a long "u" perhaps with the spill over going into the FAME container. For the FAME to be sucked out the vaccum would have to pull a long collumn of biodiesel out of the p trap. Like I said just a thought no expertise here :-)

quote:

Oh I don't really know or profess to be any kind of expert in this

Ya me neither
I would postulate though that the pressure would be even across the trap and it would take very little pressure differential to drain it.
Just a thought though.
Jon

You can make this work, but you need at least one additional pump, and probably two. One to pull the de-meth'd FAME out, and one to pump the mix in under pressure.

As TRC mentioned, you probably want to tip it up so it's vertical. And I think you probably want to put something in the vapor path (stainless steel pads? marbles, anything that stops biodiesel and lets the methanol vapors pass.

--- David

Instead of using cold water, I always thought of putting a coil of metal pipe inside a freezer. Just drill a couple holes in the side for the pipe to enter and exit.

You could also use an air conditioner with the AC's evaporator in a container of oil with the MeOH condensor coil.

I looked for a some diagrams for flash evaporator setups and yes what David Miller said seems true you would need to pump the FAME out of the flash evaporator.