10. Distil Methanol

We now want to extract all the methanol from the biodiesel. This allows us to use methanol which would otherwise be released to environment, and it greatly helps us to clean the biodiesel, because any remaining soap and glycerol in our biodiesel will fall out of solution if there is no methanol present. This phenomenon allows us to clean our biodiesel by using filtration or settling alone, no water is needed.

IMPORTANT: Check that the biodiesel level in your reactor is WELL above the heater element. If it is not, do not under any circumstance proceed, because if your element is exposed in the presence of biodiesel and methanol and air, there is a strong risk of fire or explosion.

If you are happy that your heating element is completely covered, you can proceed to distil.

Check that your distillate collection vessel, byproduct collection vessel and methoxide carboy are all tightly fitted and have no leaks.

Open valves V2 and V6 and V7. Switch on your cooling water feed for the condenser jacket.

Switch on your pump. The flow of biodiesel through the venturi will draw vapour through the condenser, up to the venturi, through V7, where it will be mixed with the biodiesel, be sprayed into the vapour space at the top of your reactor vessel, and will leave thru the top of the reactor tank, freshly laden with methanol fumes, to pass thru the condenser again, on an ever-repeating cycle.

Even at a temperature of only 50C, you will see that you start to collect methanol liquid in your distillate collector.

If all seems to be working well, switch on your heater, and set your thermostat for 90 degrees C. You will soon see that the rate of methanol collection rises steadily, as you approach and reach the boiling point of methanol in your biodiesel.

Your rate of methanol recovery will depend on many factors, mainly heating power and insulation quality of your tank. I use 3kW heating on 80 litres of biodiesel, with a 'Plumber's Delight' condenser 1 metre long. It takes me around 90 minutes to recover around 2 litres of methanol from the 80litres of biodiesel.

Make sure all piping carrying the hot methanol vapours is well insulated, and that the top of the tank is well insulated too. Your cooling water should be as cool as practical, the cooler it is, the faster you will be able to condense the methanol vapour passing thru it.

When you have finished distilling, SWITCH THE HEATER OFF ! Very important. You do NOT want to drain your biodiesel out of the tank with the heater element still on. As the element becomes exposed, it would glow red hot and ignite any fumes in the tank , with possible lethal effect.

Switch off and unplug the heater.

Close valve V7

Turn off the cooling water for the condenser.

A note about thermal insulation

The biggest cause of disappointment in the distillation phase is lack of suitable thermal insulation. If the walls of the tank can cool below 65C, methanol will condense on the inside of the tank and will drip back into the biodiesel. This wastes energy and makes the whole process take much longer. The more insulation you can provide, the faster and more efficient will be your process.

I've highlighted the most important areas for insulation - note that the upper parts of the tank I have shown with thicker insulation - this is the region which will most benefit your distilling stage.




11. Drain and purify the biodiesel

If you are sure that the HEATER IS SWITCHED OFF, you can now pump your biodiesel to an open topped settling tank. Valve V2 should be open, V6 closed, V5 gradually opened to allow the biodiesel to pass to the settling tank.

IMPORTANT! - Do NOT use flexible plastic hose between V5 and the settling tank. Use a fixed metal pipe. This is because the biodiesel is very hot and the hose would soften too much. You would run a serious risk of having hot biodiesel spray onto you.

As the biodiesel cools in the settling tank, soap and any remaining glycerol will drop to the bottom over the next few days.

settling tank

Before your next batch of biodiesel, you can scoop out any settled soap and let it drain in a cloth bag, so that any biodiesel in it returns to the tank. Or you can scoop out the soap after every 2nd, 5th etc batch. It is up to you, depending on the capacity of your settling tank.

You should not completely drain the tank, because the lower layers will always have reasonably high soap content. The upper 50% should be reasonably soap free after several days' settling under gravity alone.

Example of the gravity cleaning process...

Say you have a 200 litre settling tank and you make 100 litre batches (as I do).

After 2 batches your settling tank is full.
After a few days, take off the top 50% and use it.
Then make a new batch and put it on top to fill the settling tank again.
After a few days, take off the top 50% and use it.
Then make a new batch and put it on top to fill the settling tank again.
After a few days, take off the top 50% and use it..... and so on.


However, you don't NEED to wait for it to settle.
You could filter it all clean straight away.
Or you could wash it all straight away - it's up to you.

My preference?

I prefer the 100 litre batch in a 200 litre settling tank, using gravity to separate the soap because it is the easiest method, with least labor, using the least energy, with no risk of emulsions, no wasted water, no filters needed. Win, win, win, win, win!

Every so often, OK, the soap sludge at the bottom of the settling tank needs to be removed, but you don't have to get it all out. You only need to do it every 5th or 10th batch.

If you put this dredged soap into a cloth bag, hanging over the settling tank, any trapped biodiesel will drip though the bag over the next few weeks, leaving a compact slab of soap, which you can use in the workshop. Easy!

Trade Secret - make sure you titrate well and that your oil is bone dry before you process. This will ensure you make very little soap, so the settling is fast, and you need less soap shovelling.

Clear biodiesel purified by gravity alone

And here you see the finished result, crystal clear, with no impurities. I've floated the finished biodiesel on water, given it a good shakeup, and left to settle for a few days. And you can see the result, the water is crystal clear, showing that there was no soap in the biodiesel, and the biodiesel is crystal clear too. Honest, this isn't a trick photograph, and this is typical of the fuel quality you can achieve without any washing at all! All thanks to simple gravity settling!

Here is what the bottom of my settling barrel (45 gallon steel drum) looks like after 2 batches...

Around an inch thick layer of soap gel

The recovered soap makes a good hand cleaner if you've been working on the car. There's a bit too much biodiesel trapped in it for use as a final wash, but to move grease and dirt it is great!

If you want a less greasy soap, put this dredged soap into a cloth bag, hanging over the settling tank. Any trapped biodiesel will drip though the bag over the next few weeks, leaving a compact slab of soap, which you can use in the workshop.

biodiesel hand cleaner

You can easily purge this processor with a small amount of CO2, Nitrogen or other inert gas to run the process in an oxygen-free environment. This keeps oxidation to a minimum, which improves the storage life of your biodiesel. (I am developing an economical inert-blanket system, which uses very little CO2 or Nitrogen - if you're interested in this and want details, let me know and I'll send them to you as soon as I've finished writing up the process).

This greatly reduces the risk of fire or explosion, but you still need to pay close attention to heater and liquid level control.


Extra information...

I am often asked if I have a parts list for this processor. I don't, I'm sorry to say. If you have one, and would like me to publish it here, with credit to you, I'd be pleased to do so.

The reason I don't have a definitive parts list is that this processor can be made in so many different ways, and depending where you are, you will be able to get different components, and may not be able to get others. Some folks want to make big processors, some want to make small ones, some want to use old central heatng tanks, some want to use old oil drums. As a general guide I would suggest you use :-

a. Metal pipework thoughout for all liquid carrying pipes.
b. A pump which can move the whole volume of your tank in 2 minutes or less. (A 120 litre processor should use a pump with at least 60 litres/minute rating)
c. A heater rated at 1kW per 30 litres of oil.
d. A condenser length of 30cm per kW of heating.
e. Full bore ball-valves throughout, preferably rated for gas use, as these will have more resistant seals.
f. A good covering of insulation to minimise heat loss.
g. If you are not electrically experienced or qualified, ask a qualified electrician to do the wiring for you.

There are some examples of parts lists people have published which may help you choose the bits you need.

See here for example.

Examples of other folks' builds of the EcoSystem...



In America and worried you can't get the same parts I used?

This may help you get in touch with others who have built it with American parts ...
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This should help put you in touch with American users of the Plumber's delight ...
--> Click here <--