A friend of mine makes large batches of biodiesel,1000 litres at a time, and complained to me that it took up to 12 hours of drying to get below 500ppm of water. I showed him a design that I had in mind but had not got around to making since my small system works perfectly well.
He went off and constructed the drier and is very pleased with the result. He can now dry his 1000 litres in a couple of hours.
The drier body is made from a length of 4 inch steel box section about 4 or 5 feet long. The box section must be cut in half along its length and the ridges welded into place before welding the two halves back together. The ridges can be made from half inch square or round rod. A short length of box section is welded on near the bottom to make a duct for the hot air.
The drier should be supported at the angle shown in the picture and washed biodiesel allowed to flow in at the top. The biodiesel cascades slowly down the over the ridges and out the bottom. The hot air provided by a heat gun of the type used for removing paint, exits at the top.
The body of the drier should be insulated to keep the inside nice and hot. A little bit of experimenting with the angle of the body and the flow of fuel will be needed to optimize the drying action.
Skoda Felicia 1.9d estate
Skoda Felicis 1.9d hatchback
both on B100
Alaska burner central heating system on 100% yellow grease.
There is a relationship with drying between the energy you put in the the speed of which the drying takes place.
Running a heat gun for 2 hours would require a lot of energy and magnitudes more than the popular fish tank bubble dryer.
I was thinking the other day about doing a co gen system with one of my small diesels that I have driving a generator. I could add a pump which wouldn't take much to drive for the circulation of the oil and make a HIH type HE for the exhaust and use that to heat the oil .
As the drying is largely influenced by humidity, I was wondering if directing some of the exhaust over the top of the oil would also be beneficial in that it would be drier and speed up the drying process that way.
My engine is air cooled so there is no heat from the coolant but the exhaust should provide KW's of energy and give me plenty of extra energy in the process.
We're able to dry BD to less than 500ppm moisture by bubbling air through the BD while a small blower moves air over the surface of the tank to exhaust the moist air. Overnight is usually adequate.
I agree with DCS that the proposed method uses way too much energy to accomplish a simple task.
From earlier posts imakebiodiesel has made it seems that it is very humid most of the time where he lives so bubbling doesn't work.
I tried a similar thing using house guttering, only I was using the sun/wind to dry it. I gave up because it seemed to rain all the time?
And that's what counts. Glad to hear your design worked out so well.
I probably would have added heat to the bottom and just used a small fan.
Sometimes I wish I lived in your climate,,guys. At present we are having a dry spell and the humidity meter in my workshop has gone down to 65%, it normally hovers around 80%. If you bubble air through washed biodiesel here it gets wetter, not dryer. In order to dry biodiesel we have to heat it to 50degrees C and then pump it through a fountain type nozzle while blowing hot air over it. 2 hours will do my 150litre batch but my friends 1000litres takes 12 hours. In terms of energy use drying is the most expensive part of the process.
The contraflow dryer shown above uses far less energy than our current system. As well as reducing the energy used to dry his fuel by more than half my friend has reduced the time by 9 hours.
In a humid situation an aquarium bubbler does not provide dry air. That's why we use air from a compressor, because it's dry.
Why would the air from a compressor be drier than an air pump? Does your compressor have a condenser or water trap?
In my climatic conditions bubbling air through cold biodiesel doe not work at all but bubbling air through hot biodiesel at 50 degreesC does work but the stones only last a few hours. Up until now the best results were by heating the biodiesel, pumping through a fountain fitting and blowing hot air over the fountain. I think the contra flow drier works better because the air is forced into much closer contact with the biodiesel.
Compressing the air causes the moisture to condense. That's why the air tank has a drain. The compressed air is significantly drier than ambient air. Many compressors also have a cartridge for further drying the air for applications like painting where any moisture in the compressed air would cause problems.
How are you checking the ppm moisture?
Yes I see your point about the compressor versus the air pump, however I dont have a compressor.
I do check the ppm of every batch using the carbide manometer I developed with the help of a lot of people here on this forum.
Typically my biodiesel has 800 to 1000ppm of water after water washing. After two hours of drying it reads 50 to 100 ppm. I always dry my fuel to under 200ppm because biodiesel tends to reabsorb water slowly from the atmosphere.
As I said earlier I have no problem with my setup but my friend who makes large batches finds it too slow. That the reason I developed the contra flow drier shown above.
Yes, I can see how a humid climate like yours would need a more powerful drier. For me to see those high humidities it has to be raining.
I would dried similar to imakebiodiesel but with a AIRSTONE thrown in for luck, however the humidity thing now has me thinking if I'm doing more harm that good .
If the air pump is drawing in moist air from your garage/workshop why not simply move your air pump somewhere dry,for example on top of a central heating boiler/heater/stove or on a window ledge that receives the sun.
In my case my garage is next to my house and with a few metres of tubing and I could have my air pump sitting my kitchen sucking the warm air from inside and pumping it through the biodiesel in my garage or sat above my garage door with receives the sun(it's warm to the touch)and acts like a radiator.
I also use these new airstones which has a high tolerence to biodiesel,I've used the same one now for washing and drying 4 batches
airstone.jpg (18 Kb, 60 downloads)
If you don't have a dehumidifier, then you could try sucking the air through a bed of "Dry-Z-Air", as a means to reduce the relative humidity of the air used to dry the biodiesel. For a long-term solution, I'd recommend a vacuum pump. You don't need a really good one to accelerate drying. If you've got very high humidity, it is likely to take less energy to dry under vacuum than to heat the biodiesel enough to get equally dry.
Several years ago I was impressed by a Swedish biodiesel system that bubbled air into the bottom of the biodiesel tank, and pulled a vacuum from the top of the heated tank. It would work at near 100% RH. It dried the tank-full of washed biodiesel in about an hour!. It used a little diaphragm pump, like a Flo-Jet water pump, to make the vacuum. It didn't need an air pump. The biodiesel was kept warm throughout the process, so there wasn't much additional energy required to keep it warm.
Hi, I know this is a old post but was wandering if anybody had developed a dryer like the one suggested by IMB.
Looks like it could save time, I was thinking of using one prior to processing, would save me at least an hour on my 150 litre batch.
Is the BD preheated prior to entering the dryer?
Uhmm.. I'm not so sure about that.
The act of compressing the air does not cause condensation in itself. In fact, I believe it is just the opposite. The act of compressing the air causes the air to heat up and we all know that warm air holds more moisture than cold air. (which is why the hair dryer works so well)
It is the cooling of the air within the holding tank that causes the water vapor to condense, not the compression.
The cooling can be caused by either ambient thermal loss or by decompression of the tank.
Just thought I'd point that bit out.
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In humid climates, maybe, just loading a propane tank with warm fuel and a vacuum pump for a few hours may be the best course.
In order to dry biodiesel we have to heat it to 50degrees C .
dear Mr. imakebiodiesel I saw your dryer picture, it is grate and I will design it soon. but I would like to ask you tow questions:
first, to what degree c I can heat a sample of biodiesel over a hot plate in a safe manner?
second, what is the chemical titration method for determine water content in the final biodiesel?
The same test methods are used for UVO or biodiesel
To dry either WVO or Bio you need dry air to bring the drying time to a minimum.
This is most easily achieved by placing your air bubbler in a lidded 20L bucket.
There are two simple steps to take, drill dozens of small holes near the bottom of the bucket,
then place a couple of calico bags filled with dried kitty litter into the bucket to half fill it.
Two small holes for the air line and power line need drilling also.
Now you can dry any oil when its pouring rain.
Place a hydro meter on top of the bags to keep a check of the moisture % flowing through the system.
Re dry the bags of litter (or even saw dust) in your oven at low temp,
or take them to bed with you I don't care!
John gerard Hermans