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NEW proposed methanol recovery system
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Hi all,

Please take a look at my proposed methanol recovery idea. Make sure to give me some feedback as most users on this site are a lot more experienced than me in this area.

I cannot get the image to fit on the page so check out this link to see full display.

http://i663.photobucket.com/al...anolrecoveryidea.jpg

 
Registered: March 02, 2009Reply With QuoteReport This Post
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I assume there will an outlet on the pressure side of the pump, or a drain port on the storage barrel that you just didn't bother to draw. Gotta get everything back out of there eventually.

On the same note, there will be an intake on the vacuum side of the pump, or something similar on the storage barrel so you can load it initially, too, right?
 
Location: Southern WI, USA | Registered: May 18, 2006Reply With QuoteReport This Post
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Hi Ryan,

Yeh I didn't draw the full integration into the biodiesel process. There will be a fill port on the drum and also a drain valve to pump the BD into storage.
 
Registered: March 02, 2009Reply With QuoteReport This Post
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I know of no liquid trap that will work to keep the methanol out of the vacuum pump and I did some extensive research into such a device. I believe the best option is to put a condenser between the pump and collection vessel or use a liquid ring vacuum pump rated for pumping methanol and place the condenser and collector on the output of the pump at atmospheric pressure. Remember that the collection vessel in your drawing will be under the same amount of vacuum as the flash evaporator so the methanol will be boiling in the collection vessel also...
Why do you want to pump the presumably demethed biodiesel back into the same tank with the methylated biodiesel? It seems counter productive to me, why not just demeth it a batch at a time and forget about the pump?
Jon
 
Location: Wellington County, Ontario Canada | Registered: February 07, 2008Reply With QuoteReport This Post
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Reese123

-you could place a vacuum collection/storage tank in place of the collection device that you have drawn. evacuate this tank to 25hg ,close a tap between the tank and vac pump, then work from the vacuum in that tank that way no methanol ever gets into the vac pump. thats the way it was set up on my old processor, and I never had a problem. Tom


" I don't know what I don't know until I know"
1994 GMC 6.5 Tubo 2005 Dodge ram 3500, 3 VW's 2000, 2002, 2005.
 
Location: Manitoba Canada | Registered: March 24, 2009Reply With QuoteReport This Post
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Biotom I was wondering about that.

So that means once you pull a vacuum you then can valve off the pump and turn it off?

Wasnt sure if you let it run the whole time or as you said, block it off and hten off it.
 
Registered: March 02, 2009Reply With QuoteReport This Post



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quote:
Originally posted by Jon Heron:
I know of no liquid trap that will work to keep the methanol out of the vacuum pump
Jon


Thanks Jon. I saw on fabricators design he had some S.S scrubbers or something he used to try stop liquid getting to pump.

A liquid ring pump that can handle methanol would that be really expensive?

I was wondering about the recirculating pumping. My thought was that I might not be able to get all the methanol off in one pass. To get the methanol in biodiesel from 1% down to say 0.02% would take a fair bit Im guessing. I havent demethed BD before, only glycerine..

I wanted my flash tank to not be very large perhaps 30L max just to save on costs on a pressure rated vessel.
 
Registered: March 02, 2009Reply With QuoteReport This Post
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Reece123

-I pull a vacuum into a 100lb propayne tank then work from that that vacuum, pump is off and yes seperated from the tank by a ball valve. Tom


" I don't know what I don't know until I know"
1994 GMC 6.5 Tubo 2005 Dodge ram 3500, 3 VW's 2000, 2002, 2005.
 
Location: Manitoba Canada | Registered: March 24, 2009Reply With QuoteReport This Post
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Hi Reece123,

There are two reasons why your vac pump might see methanol:-

1. liquid creep - where the liquid pulls itself up the pipe by surface tension (TBH I've no idea if this would be a problem for you). If it is you would combat this phenominon with a liquid capture device like you have shown.

2. Vapour condensation - If you could measure the vacuum around your system, you'd find slightly more vac at the vac pump inlet, and progressively less vac as you went back to your flashing valve. This will mean that unless your methanol is sub cooled (see later), some of it will re-evaporate. As the vac pump blows stuff out its discharge side it must somewhere inside go from vac to pressure, and at higher relative pressure the boiling point of methanol increases.....or to put it another way a bit more methanol vapour will condense inside the pump itself. Be very careful, as this process will have the vapour going through its flamable range, and if that isn't an issue then the methanol could eat through incompatible parts of the pump to find an ignition source.

The condensation process occurs isothermally - at one temperature - giving a liquid at its boiling point. Now if that liquid is subject to a lower pressure, there will be evaporation - which will take some heat from the bulk liquid. In industry we apply sub cooling to prevent this. Subcooling generally requires that you cool the condensed liquid, although I have seen designs using a very cold second condenser positioned on the upleg from the methanol condensate tank.


Hope that helps.

-Paul
 
Location: Leeds | Registered: January 31, 2006Reply With QuoteReport This Post
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quote:
Originally posted by Reece123:
quote:
Originally posted by Jon Heron:
I know of no liquid trap that will work to keep the methanol out of the vacuum pump
Jon


Thanks Jon. I saw on fabricators design he had some S.S scrubbers or something he used to try stop liquid getting to pump.

A liquid ring pump that can handle methanol would that be really expensive?

I was wondering about the recirculating pumping. My thought was that I might not be able to get all the methanol off in one pass. To get the methanol in biodiesel from 1% down to say 0.02% would take a fair bit Im guessing. I havent demethed BD before, only glycerine..

I wanted my flash tank to not be very large perhaps 30L max just to save on costs on a pressure rated vessel.

Yes I believe fabricator has a reflux condenser with pot scrubbers between his pump and vessel.
Liquid ring pumps are very expensive but you do see them used quite often, another option is to use a venturi like GL does on his push/pull...
On my setup (based on the GL push/pull) I use a big rotary vane pump with a small needle valve to atmosphere to regulate the vacuum. I pack the top of my well insulated collection vessel with a bag of ice and wrap the whole thing in an old wool blanket to keep the vessel as cold as possible, I guess this would be considered "sub cooling" along the lines of what Paul is talking about above. As I am circulating and heating the mix up to temp (around 180F) I apply about 5 to 10Hg of vacuum for the hour or so it takes to get up to temp, this supply's a steady flow of methanol into the vessel with NO signs of methanol in the pump or clear vac hose leading to it. Once its up to temp I shut down the mixing pump and valve it off. I then slowly ramp up the vacuum with the needle valve so I don't overwhelm the PD condenser. It usually takes about half an hour to 45m to complete the demething from the point I shut down the heat and mixing pump. I should mention my batch size is 100 litres and its all done in an upside down water heater, they can take the vacuum no problem, I get mine down to 29Hg and it hold fine, even empty...
Then I drain the hot bio into a settling drum and add a bubbler I made thats powered from my large pond aeration compressor and let it bubble all night. This gets out all the methanol every time for me.
This all seems to work excellent on my setup, I get no methanol in the pump unless I ramp up the vacuum to fast.

Here is a pic of my pump (don't mind the mess!) if you look below the gauge you will see the needle valve I use to regulate the vacuum, the silver thing to the right is my collection vessel, a glass wine carboy.

And here is my bubbler.
Jon
 
Location: Wellington County, Ontario Canada | Registered: February 07, 2008Reply With QuoteReport This Post
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On my next setup I will definitely be using a short condenser between the pump and vessel...
Jon
 
Location: Wellington County, Ontario Canada | Registered: February 07, 2008Reply With QuoteReport This Post
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Here's the initial cooling setup. Things have changed considerably since, but this should provide the basic idea. Added a PD before the freezer coil, which now drops directly to the collection tank. Refrigerated cooling coil in the black trashcan is now between the vac pump & tank, along with a coalescing filter to give any escaping methanol the opportunity to condense. Like Jon, needle valve on inlet, need to add one on the outlet. Outlet of vac pump goes back to a quick disconnect to reactor drain hose for oil dewater & final bio bubbling before filtering. 340L batches...
 
Registered: June 03, 2008Reply With QuoteReport This Post



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The pump is going to have issues w/ cavitation while pumping from an evacuated chamber unless you can maintain a sufficient liquid column. Think of two people sucking from separate straws at the dregs of a soda. The pump will be attempting to aerate the bio, assisted by the reduced pressure and liquid breaking surface tension in the vac tank. This will be even more of an issue at the higher vacuum required due to concentration dilution from recirc. Edit: Not to mention you'll need a mag drive pump or similar to prevent mechanical seals from leaking and loading the vac pump even more.

A valve alone won't provide the spray needed to expose optimal surface area for evaporation. You'll need spray nozzles or plates in the vac tank to allow for thin film.

You'll have issues tuning the vacuum & valve for both flow rate and the evaporation rate of the meth unless the bio has the approximately the same amount of residual meth during every batch. Applied heat would have to be tuned as well to meet/surpass the heat of vaporization removed by the vac pump.

Recirc appears to the main source of potential problems. I would rethink this & shoot for single pass demeth at a low flow rate. After getting this sussed out, you can scale the vac side to handle increased flow. Bio is easier to demeth than glyc. Anyway, just my two cents...
 
Registered: June 03, 2008Reply With QuoteReport This Post
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Love it!
Nice use of the old beer fridge jdoughy!
Do you have antifreeze in the freezer portion around the coil?
This year for my condenser water I set up an old apartment size freezer I got for nothing and half filled it with water and glycerin byproduct. I fire up the freezer the night before I am going to start processing and man does it work well, the water/glycerin is still numbing to the hands even after a full push/pull recovery which runs for a few hours...

quote:
Outlet of vac pump goes back to a quick disconnect to reactor drain hose for oil dewater & final bio bubbling before filtering. 340L batches...

Can you elaborate more on this? Are you using the output of the vac to bubble air through the reactor to help dewater you oil?
When I dewater I do much the same as when I demeth; I apply about 10Hg of vac while heating and circulating up to temp (180+F) and then valve off the pump and apply maximum vacuum, from this point it will be done dewatering in less than an hour. My oil is not typically too wet though...
Jon
 
Location: Wellington County, Ontario Canada | Registered: February 07, 2008Reply With QuoteReport This Post
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quote:
Love it! Nice use of the old beer fridge jdoughy!
Do you have antifreeze in the freezer portion around the coil?

Big Grin Thanks! Free & cheap is good, and it does still chill emergency exposure libations, buffer solution, etc. I highly recommend.

The pic is from last year when I was just getting things thrown together. A little antifreeze, mostly water b/c it takes more heat. I've been meaning to look for a chest freezer to handle everything.
quote:
Are you using the output of the vac to bubble air through the reactor to help dewater you oil?

Yeah, I've been getting more particular with dewater & demeth. I've noticed how much longer it takes to keep pulling high vac on 90 gallons of oil. Now I pull to mid 20s, then (while maintaining vacuum) recirculate the air through the reactor using the vac pump. It's too humid here to ensure dry oil pulling in atmospheric. This moves a larger volume through & lets the temp differential do the rest of the work much faster. After the majority of the demeth process is complete, I do the same thing to remove residual then drain the last bit of glyc. It's faster and I no longer bother with the settling tank and bubbling. Run it directly through filtration and it's ready to use. Oh, and I valve off the pump around 10Hg too.
 
Registered: June 03, 2008Reply With QuoteReport This Post
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-jdoughy

-love your set up, How can anyone be that neat! Big Grin Big Grin Tom


" I don't know what I don't know until I know"
1994 GMC 6.5 Tubo 2005 Dodge ram 3500, 3 VW's 2000, 2002, 2005.
 
Location: Manitoba Canada | Registered: March 24, 2009Reply With QuoteReport This Post
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Jdoughy ok I think Im going to start trying to build your system Smile Its very neat.

Also where did you get your red methanol/water storage tank from??

It looks absolutely perfect for the job..

My problem is Im not using a hot water heater, I am using the cone HDPE reaction tank. Therefore I will need a separate tank that can hold a full vacuum.. any ideas?
 
Registered: March 02, 2009Reply With QuoteReport This Post
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quote:
Originally posted by jdoughy:
Recirc appears to the main source of potential problems. I would rethink this & shoot for single pass demeth at a low flow rate. After getting this sussed out, you can scale the vac side to handle increased flow. Bio is easier to demeth than glyc. Anyway, just my two cents...


Good advice. Will just pump at a much lower flow rate and scrap recirc idea.
 
Registered: March 02, 2009Reply With QuoteReport This Post



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tom & reece, thanks for the kind words. never thought anyone would think anything of the ghetto stuff i throw together for personal use.
quote:
I think Im going to start trying to build your system

noooooooo!!!! not that i'm opposed, but that i've been wanting to build a flash evaporator and can't for awhile. so, wanted to live vicariously through someone else's spectacular results. i think fe is a far more elegant solution.

red tank is a 10 gallon fuel tank that was on clearance at northern tool. you can scrounge for these or find'em cheap in all sorts of shapes/sizes.

like others before us, i'm a big fan of decommissioned propane tanks. if you really let your fingers do the walking, you can find steady supplies extremely cheap or free.

super smart guy named tim c cook has this thread on his development of a home brew fe. also, spend some time wading through patents, industry journals & commercial setups.
 
Registered: June 03, 2008Reply With QuoteReport This Post
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my question would be what's the goal?

faster recovery times?
higher purity?
lower energy input to get the methanol out?
a combination of the above?

I see problems with you pump and the vacuum..even a positive displacement pump will not work under high vacuums..

if you have to heat 180F..I start recovering methanol at this temp without a vacuum.


that aside..

there is another way to recovery under a vacuum..but it requires a pump that can handle methanol vapors..take a second and look at a normal fridge..the compressor pressurizes the freon(100-300psi)..to forced through a small opening cools the works..put another way..draw the methanol out under vacuum and pressurize into a storage tank.. pump only see vapor.. the collection tank sees pressure. cool the collection tank below the vapor point and it'll stay liquid..just thinking out loud here..never tried it this way myself.

-dkenny


'84 bluebird school bus, DD8.2L turbo( 4/2011, the bus tranny has died..Frown 8.23.11 bus driven to scrap yard Frown )
2006 Jeep Liberty CRD Smile - the wife's
99 dodge 2500 5.9l 24v..-mine Smile
everything run B100 when its warm enough Smile
 
Location: RTP, North Carolina | Registered: December 15, 2004Reply With QuoteReport This Post
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