This is a compact home made biodiesel processor which avoids water-washing and limits methanol release to very small amounts. You can also recover surplus methanol from your biodiesel, which would otherwise be lost in the wash water.
You can de-water your oil in the processor and you can start to recover methanol from as low as 40 degrees C.
Here's a diagram of the system. It includes a simple venturi to recirculate vapour through a condenser. The venturi also sucks methoxide (or water, if you do the 5% prewash) from the methoxide container and mixes it into the oil flow.
Allow a straight horizontal run of around 30cm after the venturi outlet to ensure the venturi will perform properly. This is because the momentum of the out-flowing liquid acts to "pull" on the inlet vapour.
You can mount the methoxide tank higher up, nearer the venturi, if your venturi's performance is marginal. Make sure it is not too high - you don't want to drop the container, spill the methoxide, or hurt your back.
Parts :- You don't need to worry if you can't get exactly the same parts as I've used. The design is quite flexible and there are users all over the world who have successfully adapted the design to suit the parts they could find locally. I've added some links [here] to help put you in touch with other constructors.
My preferred layout ...
Here's another way you can inject methoxide or water - it will be familiar if you've used the appleseed design. Some pumps cavitate and lose suction with this scheme. If in doubt, use the 1st design, with valve V4 going to the venturi inlet.
An alternative way to inject methoxide...
How about a sight tube?
I forgot to draw my sight-tube on the diagrams above.
A sight tube is very handy to show you volume when filling.
It can also show you the pump performance, (when the pump is not performing well, perhaps is it blocked, or is working with thick, cold oil, the level in the sight tube will be higher than normal).
You can use it to see the colour of the tank contents, settling rates etc.
My sight tube has a tap at the bottom so I can isolate it. It is open at the top, going about 20cm above the max liquid level, so is not pressurised and won't overflow.
The same simple PVC tube has lasted me 2 1/2 years of heavy use.
Here's the top end of the sight tube. I've pushed a large funnel in there so I can return any drained-off samples to the tank. If I slightly close valve V2 while the sight tube tap is open, I can empty the sight tube completely.
Notice the max level I fill to, this is including methoxide. The level never quite comes up as high as the venturi.
State diagram for the New Eco-System
This table tells you about the status of each valve, the heater and pump at various stages of the process.
State diagram: Green = open valve, or power applied
Check level before applying heat
Switch to 50C when O/P slows
Titrate oil now. Empty collector. I use NaOH
Allow 20 mins to inject.
Allow 90 mins at 50C
Mix 15 mins
Wait 90 mins
Drain slowly to avoid whirlpool
Ensure heater is OFF first! Caution - Hot! Wear breathing apparatus. Take sample and perform 23/7 test before discharging whole batch.
Description of what's going on in the Process...
1. Oil In
Remove the glycerol collection tank from V3.
Turn on the pump, and open valve V6 only. Shut all other valves.
Your oil storage tank is piped to the 'Oil In' port. It should be above the level of the pump if your pump is not self-priming.
Your oil must be free of large chunks of debris, so your pump doesn't jam. There is no need to filter it (all the fine bits and pieces will end up in your glycerol layer). It must have no visible water in it.
Open valve V1 to load oil into the reactor. Shut valve V1 when the oil level in the reactor reaches 75% of its capacity.
This will leave the correct amount of space for the methoxide which you will add later. Don't under-fill the reactor - too much air space will affect your distillation performance.
2. Heat Oil
Open valves V2 and V6, with the pump running, to recirculate oil around the tank.
Double check that your reactor is filled with the correct amount of oil. (75%)
Switch on the heater now, but ONLY if you are CERTAIN that the reactor is filled to 75% AND that the pump is running.
It is dangerous to add heat if the level is too low, because you may expose the heating element, which would then overheat and ignite the oil in the tank. You could have a tank explosion.
You must run the pump whenever the heater is on, so that there is a steady flow of oil to cool the element.
3. De-water Oil
Dry oil is vital. Wet oil can create a soap-gel in your processor, which can easily block your pipework. Most used oil contains a large amount of water, even though it may look clear, so I recommend you de-water oil every time. This process is unique - you can de-water your oil in the processor, without any smelly, oily steam being given off. Here's how...
Open V2 and V6 and V7
Switch on the pump
Heat the oil to 90C
Circulate cold water thru the condenser
When the oil reaches 90 degrees C, switch everything off and let the oil settle for an hour. It will now be thin because it is hot, so any particles of food will drop quickly to the bottom of the tank. After an hour, carefully open V3 and drain off 5% of the tank volume into a container (leaving the tank 70% full of oil). This drained off oil will contain most of the damp food particles which settled out. You can leave these to settle, then pour the remaining oil back into your WVO tank (not the processor).
Switch on the pump.
The venturi will drag dry air from the bottom of the condenser into the wet oil. As the oil sprays into the processor, it will carry the air with it, which becomes filled with moisture from the oil. The air now escapes out the top of the reactor and down through the condenser, where the water vapour condenses and drips into the distillate tank. The now dried air then goes back up to the venturi to be returned to the wet oil, for the process to repeat until the oil is dry. (You can fill the airspace with CO2 or N2 if you want an inert atmosphere)
You don't need to have a fresh supply of water for the condenser. I use a 45 gallon drum of rainwater, which I pump thru the condenser and back into the drum again, in a closed loop. I use a household heating circulator pump for this. A few litres a minute is enough if your heater is rated at 3kW.
4. Cool the Oil
Maintain circulation of water through the condenser.
By the time the oil has cooled to 50C, it should be dry enough for you to start the reaction...
Take a sample of oil from V3, leave it to cool to around 20C and titrate it, to see how much lye you will need to add to the methanol.
To be safe, unplug your heater completely now, so that there is no way you can accidentally switch it on. Click >here< to see what may happen if you accidentally switch your heater on, while the element is exposed to methanol-laden air.
Close valve V7, and switch off the water pump feeding the cooling water thru your condenser.
Empty the water which collected in the distillate tank. You can put it into the cooling-water reservoir.
Refit the distillate tank.
Fit the glycerol collection tank to V3.
5. Methoxide mixing and injection
Maintain circulation of water through the condenser.
You titrated your dried oil, so can now make up your methoxide.
Calculate how much oil is in your tank. Multiply by 0.22. That is how much methanol you must measure put into the methoxide tank.
If you are using NaOH, you will need 5 grams of NaOH as your base amount, plus titration amount, for every litre of oil. If you are using KOH, the base amount will be 7 grams. Pour the NaOH or KOH into the methanol and agitate until it is all dissolved.
Connect the methoxide tank to V4 and the vent.
Switch on the pump.
Gradually open V4 to allow the suction to draw methoxide out of the carboy.
Aim for a feed rate slow enough so the methoxide is fully dosed into the reactor over a period of around 20 minutes. If you dose too fast, the methoxide may flood into the processor so concentrated, that it just floats on top of the oil. You may also get an unwanted gel forming in the piping or tank, which can cause blockages.
As the tank fills up, the air it displaces (the same volume of air as there was methoxide in the carboy) passes thru the condenser and back into the methoxide carboy. The condenser helps to reduce any outgassing of methanol - don't worry about the drips of methanol which collect in the distillate collection tank. It will be very little, and will not affect your reaction. At least you have saved the methanol, rather than venting it out to the air.
When the dosing is complete, shut off valve V4 and stop the flow of cooling water thru the condenser.
6. The reaction stage
V2 and V6 should be fully open. Check that V4 and V7 are closed, and that the heater is OFF.
Allow the pump to run for around 90 to 120 minutes, which should be long enough for your reaction to reach its peak of conversion from oil to biodiesel. Your temperature should remain at around 50C throughout the reaction, if your insulation on the tank and piping is adequate.
After the reaction period has elapsed, switch off the pump, close V2 and carefully remove the methoxide container - be careful not to spill any methoxide on yourself, wear suitable body protection.
7. The 5% prewash
Fill the methoxide container with water; the amount should be 5% or 1/20th of the amount of oil you dosed the tank with.
Re-connect the container, open valve V2 and switch on the pump. Open V4 fully to allow the pump to draw the water out of the carboy. You can close V2 to allow the pump to draw water fast out of the container, as it is not important for it to be gradually introduced.
When all the water has been pumped out of the container, close V4 and fully open V2. Allow the pump to recirculate the mixture for around 15 minutes to ensure the water has been evenly blended throughout the mixture.
When the 15 minutes have elapsed, switch off the pump and close valve V2. The water will tend to attract soap from the biodiesel, along with glycerol and caustic soda, and together they will drop to the bottom of the tank, where they can then be easily drained off, leaving semi-purified biodiesel behind ...
8. Settle the glycerol
Glycerol and water are both denser than biodiesel so will drop to the bottom of the reaction vessel, carrying with them most of the soap which is formed as a byproduct, and the catalyst. Allow 90 minutes or more for this settling to happen. Be aware that if you leave the processor too long, say more than a few hours, the settled glycerol in the pipework may form a thick gel, especially in cold weather. This can block your pipework and jam the pump.
To prevent this from being a big issue if you need to leave the processor like this for a few hours, you can part-drain the pipework after around 30 minutes. Ensure V2 and V1 are closed, and V6 is open. Open V3 slightly, to drain off the dark glycerol in the pipework. Stop draining when you see the liquid colour turn much lighter, as this will be biodiesel, which you don't want to drain off just yet.
9. Drain the glycerol
Slowly open valve V2. open valve V3 slightly to allow a slow trickle of glycerol to fall into the glycerol collection container. Depending on your oil quality, you can typically expect to collect from 15% to 25% of the volume of the oil you used, as glycerol. You will be able to see when all the glycerol has been drained, because the drained liquid will suddenly become much lighter - biodiesel. Close V3 completely now and wait a couple of minutes. Re-open V3 very slightly and you should be able to drain off a little more glycerol. When no more glycerol flows, close V3.
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.
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.
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.
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.
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...
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.
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.
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.
Examples of other folks' builds of the EcoSystem...
Some other info which may be of interest to you...