Methanol Recovery

[geewizztoo Senior Member Find all posts View Profile Close geewizztoo]

Here's a great website for anyone considering recovering methanol by distillation of the byproduct.

http://www.moonshine-still.com/

There's step by step plans, a bit of theory and instructions how to use a reflux still. If you followed it to the letter you could make a beautiful piece of equipment.

Pot stills are simpler but the purity may not be as high. Anyone like to share their experience?

[geewizztoo Senior Member Find all posts View Profile Close geewizztoo]

Re: Methanol Recovery

No takers so far, maybe I'll get the ball rolling and relay my limited experience.

There are two main types of still, pot and reflux. A pot still is exactly that, a sealed, heated pot with a vent pipe from which the vapours are condensed. A reflux still has a vertical column placed on top to allow some of the higher boiling point (BP) vapours to condense in the column and drain back into the pot. In this way only the lower BP vapours make it to the top and escape through a condenser. Reflux types produce higher purity distillate.

I use the 5% water pre wash method when making biodiesel so my by-product contains a lot of water. So for me the only way to go was build a reflux still. But for homebrewers that don't add water to their reactors, then a pot still may be adequate. I'll post some photos of my crude still made from scrap items later, but for now here's a bit of theory of how reflux stills work.
This has been compiled from two sources so please excuse the mixed units (Celsius and Fahrenheit) and it uses ethanol/water mix as an example (well it was from a moonshine website).

http://www.moonshine-still.com/

http://homedistiller.org/

When you have a mixture of liquids, each with a different boiling point, then the boiling point of the mix will lie somewhere in the middle, and this will depend on the relative concentrations of each liquid. Pure water boils at 100 deg C, and pure methanol boils at 64.7 deg C, but a mixture of water and methanol will boil at some point in between. The major point about distillation is that when a mixture like that boils, then the vapour given off is richer in the most volatile component, and when that vapour condenses then the resulting liquid has a lower boiling point than the mix it came from. By repeating this boiling and recondensation process up a column, using packing to hold the condensed liquid at each stage, you can separate the components more and more.

So if you have a mixture of liquids each with a different boiling point, when you heat the mixture, it will heat up until the new intermediate boiling point is reached. When you first start a distilling run, the packing in the column will be at room temperature, so vapour given off by the boiler condenses on the first cool packing it reaches. In condensing, the vapour gives up a lot of heat, and this warms that packing until the liquid on it boils again. However, this liquid is richer in volatiles than the mix in the boiler, so its boiling point is lower. When it does boil again, from the heat given off by more condensing vapour, what you get is even richer in those most volatile components. This process of boiling and condensing continues up the column and, because the condensed liquid is always getting richer in volatiles, the temperature gradually falls the higher you go. The temperature at any point is governed solely by the boiling point of that particular liquid mix. You'll notice that once boiling, the temperature of the vapour at the top of the column gradually increases, this is because the mixture is being slowly depleted of the most volatile components.
All of these effects are depicted in the graph which shows how the temperature changes over time when an ethanol/water mixture is boiled. Notice that the mixture starts boiling at a temperature of 173° F (the boiling point of ethanol, point C) and rises to 212F (The boiling point of water, point E). Notice also, that once boiling, the temperature rises gradually from point C to E, as the ratio of the mixture varies.
You'll see this kind of temperature behaviour when you distil alcohol. It's best understood by looking at the little inset graph which shows how the concentrations of water and ethanol in the vapours vary during the distillation process. The mixture starts out with about 50% water and 50% ethanol, but the alcohol in the mixture boils at a lower temperature than the water and evaporates more quickly. Consequently, as the boiling continues, the vapour contains less and less alcohol and more and more water. This accounts for the gradual rise in the vapour temperature, because toward the end there is much more water than alcohol and it takes a higher temperature to vaporise the water.
That's the primary reason for the still to have a thermometer mounted at the top of the column. It lets you monitor the vapour temperature as you distil. In turn, this lets you judge the purity of the distillate output without having to measure it with a hydrometer. In a batch distillation, the thermometer becomes a very useful tool to indicate when to begin collecting the distillate, and when to cut it off. This is your first step in optimizing your distillation.

[geewizztoo Senior Member Find all posts View Profile Close geewizztoo]

Re: Methanol Recovery

Here's some photos of my home made reflux still, it's a Heath Robinson contraption made mostly from scrap that I scounged from various places.

The glycerine resevoir is a 25L steel pail with a clamp-on lid that has a rubber seal around the rim. The reflux column is a 1m length of truck exhaust pipe (about 50mm dia) that came with a nice flange. I found it in a skip outside a muffler shop. I couldn't find a straight piece The column is stuffed tightly with fly wire mesh. The metal stuff not plastic. I turned a steel bung to fit in the top of the column and I had to buy a couple of fittings to attach the copper coil and thermocouple.

The condenser is a 3m length of 12mm dia copper pipe coiled inside a plastic bucket. The outlet protrudes through a hole in the bottom of the bucket sealed with a grommet. When it's operating I fill the bucket with water from the garden hose and leave it running. The warm water at the top overflows through the outlet with the green pipe attached. The water gets very warm so forget using ice packs they melt way too fast and you have to change them frequently. You could use bags of ice but the expense defeats the objective.

The heating element is suspended from the lid of the pail. The element is an old electric frypan with the sides cut off. It's hung via a length of threaded rod thru the lid. Both the mount and the wire connection are sealed with copious amounts of silicone.

It takes about 30 mins to heat 20L of by product to the point where distillate starts to drip from the outlet. At this point the temp at the top of the column reads about 69C and steadily rises. I stop collecting when the temp reads 74C. At this point I've collected only about 1.5L from 20L of by-product. The speed of the temp rise concerns me as the boiling point of pure methanol is 65C, I think I'll have to increase the reflux ratio in the column by finding better packing material or introduce a little water cooling to the column (as per the moonshine site). I also need to get my hands on a hydrometer to check the purity.

I built it just to see if I could make one work from the scrap parts I could find and on minmal budget. It cost me about 20 bucks. I'm not convinced it's worth the effort or the electrical energy to recover methanol from such small batches. It would be more efficient to start with warm by-product straight from the reactor. Still, I'll keep experimenting

[hdj80 Senior Member Find all posts View Profile Close hdj80]

Re: Methanol Recovery

I just had a thought...
Why a Reflux Still???
Wouldn't a Pot Still be OK for distilling a Glycerol Methanol mix or are you finding other liquids in the Glycerol that evaporates at 65degrees C.

Explaination::::
I was under the impression that a reflux still is used to get a pure distilation from a liquid mess of alchol and waters. Our by product should only contain Pure Glycerol and Methanol, nothing else to distill.

[Matt Senior Member Find all posts View Profile Close Matt]

Re: Methanol Recovery

Grasshopper, as the temp rises above the boiling pt of the methanol it will start to contain traces of water (read up on glycerine pre wash) by the passage of steam vapours into the condenser.

Matt in Brisvegas with his 24Valve Toyoda (its meant to be tongue in cheek Pete, go back to managing emails and think about it a bit)

[geewizztoo Senior Member Find all posts View Profile Close geewizztoo]

Re: Methanol Recovery

I just had a thought...
Why a Reflux Still???

In my case I'm adding water to the last stages of the reaction, known as the glycerine pre wash. I think I mentioned this in the posts above.
I'm adding 5L of water to every 100L of veg oil, so my 25L of by-product will be roughly 20L glycerine and 5L water.

Yes, I think a pot still would work fine for the standard process (not pre washing). But remember, all oils contain a tiny percentage of water, and water is also produced when the caustic neutralises the FFA in WVO in the reaction. I don't know if these small amounts would affect the purity of methanol recovered from a pot still - probably not. I don't have any experience in this area, maybe others could comment?

[Vernon Smith Junior Member Find all posts View Profile Close Vernon Smith]

Re: Methanol Recovery

Hello all members,
I am involved in the establishment of a bidiesel plant here in the Solomons. Methanol recovery from the glycerine/methoxide residue is an important aspect that is proving a bit difficult. Do any members know of a professional maker of reflux stills preferably with reduced pressure facility. We are looking at batches of about 400 ltrs at a time of residue to distill. This is a bit more than milk churn stills can cope with. Any leads would be most welcome.
Best regards,
Vernon Smith

[hdj80 Senior Member Find all posts View Profile Close hdj80]

Re: Methanol Recovery

Well I gave this a try yesterday and bugger me what a choice thing to do!
I was surprised as to how much copper pipe I'll need in my next condenser which I have 2 thoughts on how I'll do that. One is basically the same idea as yours geewizztoo the other will use a water pump to circulate water along a jacketed condenser. I just depends how I feel on the day.
I only got back around 4 litres of methanol but the condenser was steaming so there was still plenty of potential Methanol that could have been collected. Anyway Prototype 'One' worked surprising well for the little effort in constructing it.
BTW: I thought I'd chuck that other photo in of an up and coming "Master Brewer" at work... I am sooo proud.. and that is my beer on the bar which happens to be the last step in Biodiesel production:

[Tony From West Oz Vice Chairperson of WARFA Find all posts View Profile Close Tony From West Oz]

Re: Methanol Recovery

I just had a thought...
Why a Reflux Still???
Wouldn't a Pot Still be OK for distilling a Glycerol Methanol mix or are you finding other liquids in the Glycerol that evaporates at 65degrees C.

Explaination::::
I was under the impression that a reflux still is used to get a pure distilation from a liquid mess of alchol and waters. Our by product should only contain Pure Glycerol and Methanol, nothing else to distill.

Even if water is present in the evaporator (with the biodiesel byproduct) the methanol will boil off before the water. If distilling ethanol, the water and ethanol form an azeotrope, which prevents the removal of the last 5% of water from the ethanol. A pot still takes at least 3 cycles to achieve 90% ethanol, a reflux still gives 95% in one pass. To dry the remaining water off, you need to use other methods.

Methanol does not suffer from this problem and can be distilled off from water in a pot still.

I would avoid having the evaporator temperature above 90°C, to prevent boiling the water off. By then, the majority of methanol would have been removed anyway.

[tillyfromparadise Senior Member Find all posts View Profile Close tillyfromparadise]

Re: Methanol Recovery

Hello Tony,

In my experience, a pot still does not give a "Clean cut" when methanol and water are both present in the same pot.
I did some tests recovering methanol from glycerine.
When no water was put into the reaction the purity of the methanol output was in the order of 98- 99%.
When Irecovered methanol from glycerine that had undergone the 5% water/glycerine wash, the purity from the first run through the pot was something like 85%.

Tilly

[Vernon Smith Junior Member Find all posts View Profile Close Vernon Smith]

Re: Methanol Recovery

Hi guys,
Since my previous posting I have found a reflux still maker so that's looking good. Hdj80's last posting has me a bit confused. Your photo's look like methanol recovery but I thought you were already distilling the residue. Have you been throwing it away up until yesterday when you gave distillation a try? Sounds expensive if you have. Anyway, I am sure you will get better results than 4 ltrs with an improved still. You certainly need a water jacket around the condenser but not the tower (reflux column) which must be tall enough to cool to atmosphere. 1m high filled with raschig rings would be a good start. Two cooling pipes pass horizontally through the tower, one lower and one near the top. These initiate the reflux process and you control the temperature at the distillate outlet by adjusting the heat going into the distillant.
There are some excellent designs on the moonshine website that geewizztoo posted. Some are works of art but in copper for ethanol distillation so I would caution this material where NaOH is present in the distillant. I am sure s/s would be better.

Anyway, I need a bit of sharp edge help with the residue please. I have conflicting information on what is actually left, especially following geewisstoo's prewash method. I understand you will have a mixture of glycerine, water, methanol and caustic. Quite a lot of water is formed by the transesterification process between the oil and methanol with causic catalyst. Please geewizztoo let me know why you add more water. Oil, caustic and water usually saponify when mixed together making soap. What happens in your process? When you draw off the residue do you get different layers settling out or one homogeneous liquid? Adding water as a prewash would seem undesirable for methanol distillation but I am sure you have sound practical reasons that might not be apparent from my theoretical perspective. Assuming I can recover a worthwhile amount of methanol I then need to look at the remaining glycerine, water, caustic. What do you do with yours? I have an outlet for glycerine but I suspect separating the caustic and water might be difficult. Any ideas would be most welcome.
Regards,
Vernon Smith

[tillyfromparadise Senior Member Find all posts View Profile Close tillyfromparadise]

Re: Methanol Recovery

Hello Vernon,

The main products in the byproduct layer are:
Methanol,
glycerine,
soap,
biodiesel,
water,
NaOH/KOH

There is very little water formed during the transesterfication stage, basically just what is formed when the FFA's are converted to soap.
That is why you will get a high purity output from a pot still, no water in= no water out.

The 5% Water/ Glycerine wash at the end has been found to increase yield by a few % and many people report easier, quicker washing subsiquently.
As an Added bonus the glycerine will often remain liquid over night when NaOH is used.
If you add the 5% water you will need to go to a reflux still when reclaiming methanol.

Tilly

[hdj80 Senior Member Find all posts View Profile Close hdj80]

Re: Methanol Recovery

Here is Prototype II of my still.

[Sheriff Biofuels Forum Newbie Find all posts View Profile Close Sheriff]

Re: Methanol Recovery

I use NaOH and the biproduct is always solid. Should I change to KOH? or am I doing something wrong in processing? or is solid stuff normal? I'd really like to get into methanol recovery.
Sheriff.

[Matt Senior Member Find all posts View Profile Close Matt]

Re: Methanol Recovery

NaOH always results in (well nearly always) solid byproduct. Heat it up a little to say 40 or 50 and see what happensm I cannot predict anything as I have nearly never used NaOH (always KOH).

Use KOH, its better to use, stays liquid, can be had for the same or similar price and its better on the compost heap. Worms/plants won't die either.

Matt