Hi all I have been reading with great interest the discussions on drying biodiesel . My own setup
is a GL design twin 205 litre cone bottomed tanks with clamp on lids fed by a 120l/min Pedrollo pump. It works well but I have a concern with the high 90 deg C temps needed to demeth .Previous to converting the system to a GL design the wash tank / dryer tank used a spray bar and circulation, combined with vigorous bubbling with a compressor.This was effective in drying the fuel in about an hour for 180 litre batches. The downside was high energy consumption and the spray bar was messy, mainly due to the power of the pump.I needed to put in a bypass to regulate the flow to the spray bar to reduce the spatter outside the tank when I read about Imake's turbo dryer.I sense that Imake feels that the mark 2 turbo dryer is his preference to the use of two fans provided everything is well sealed.I have several questions.I note that 12v fans are used. I have two 240 v fans with 20cm diameter blades from a large chest freezer would these be O.K.? I would use one not two.James RL on the Vegetable oil diesel forum advocates using a 60l/min air pump using the bubble and settle method. Would this be too powerful in the turbo dryer. I note that Imake increased the capacity of his air pump to good effect.Thank you all for your input and particularly to Imake who is tireless in his imparting of knowledge. I eagerly await comment.
Hi Jock and welcome.
If the air being used to dry your bio is outside type damp air then the single fan design is definitely the way to go. In the two fan type both the air supply to the bubbler and the headspace fan is predried by the silica gel. If your air is damp the silica gel will be saturated within 30 minutes and become ineffective.
In the single fan type only the air supply to the bubbler is predried and this means that the silica gel lasts for at least 6 hours.
Increasing the capacity of the bubbler will improve the performance up to a point, and I have to admit I dont know what that point is yet. Im using a 400 L/hr pump and it works very well on 300 litre batches. Using a larger pumps exposes more air to the fuel but eventually will run into problems.
A the air will pass through the silica gel too fast and wont dry properly.
B. The increased mass of air will cool the bio too quickly. After predrying, the air is heated by being pumped through the bio. This enhances the ability of the air to absorb moisture.
On the other hand the batch will dry more quickly so this may not matter, I would be more concerned about A than B.
I use a more powerful 240v fan on my larger 300 litre processors because they have a larger headspace. Bear in mind that you will need to enlarge the air supply holes in the lid. The fan should be slightly starved of air but not so much that it will overheat and burn out.
Can you measure your water content? A carbide manometer is a very useful tool when developing an efficient dryer.
Hi Imake Thank you for your reply.A thought I had with regard to the holes in the plywood was to use one or two of those cheap plastic ball valves which one could adjust to suit the wanted flow of air. The one concern I had was to get a complete seal so that all the moisture laden air has to pass through the system.Perhaps use a metal grease pail with the silica tray soldered or brazed in with clamps to hold down the lid.My processor and wash tank have metal lids held in place with a cam lock strap.I have spare lids and the thought was to use one in place of the plywood or chip board. Does one have to have two holes or would one double the size suffice? I am really looking forward to drying this way less mess , less energy cost and lower temperatures. Dewatering and demething at 90 deg C is a concern as used in the GL method. Regards Jock
A metal lid will work fine. 2 holes will work better than one bigger one. Two holes will provide a better cross draft , a single hole may leave dead spots where condensation might form.
The size of the holes is very approximate. Big enough that the fan does not over heat, small enough that the fan is slightly starved of air.
I use 15 litre plastic tubs with snap on lids because they are easy to seal. The silica gel basket is fitted into the lid. Anywhere wires or tubes enter or exit the tub must be sealed well with silicone mastic. the idea is that the pump cannot source air from anywhere else but by drawing it through the gel. The gel basket should be no more than 1" deep.
Its been quite a while since I posted a diagram so her is an up to date one.
Hi Imake Thank you for the diagram . One thing is of concern as the fan motor seems to be in the head space , how do I identify that the fan I'm using is of a type that won't spark and cause an explosion.
You mentioned that you were thinking of using a fan from a fridge unit. I would check it very carefully, in the dark, that it does not have the type of brushed rotor that sparks. For my larger unit I use this fan which works very well.
Hi John,Thank you so much for all your help .I have set up a dryer along the lines of your Mk 2 turbo dryer and I have some questions.
1.Where should the bubbler line be situated in the drum?If right at the bottom will it not stir up
2. I have been using some coarse grained clear crystal cat litter which has a few blue beads in it as I can't get silica gel at the moment. How effective is this likely to be?
3. I intend to use this dryer to dry my WVO before processing and again after to dry the biodiesel. would you recommend this?
$. If I can make this work for me it will be a much safer and effective way of drying my fuel, with great energy saving. Thanks John
Hi John another thought , what is the significance of the strength of the fan in the turbo dryer, what would you consider optimal?
Hi Jock,Happy new year.
You are right, if the bubbler is lying on the bottom of the processor it may stir up any glycerol. Mine is about 6 inches short of the bottom.
I have tested the cat litter versus normal silica gel earlier in this discussion and there is a big difference. You can see the results of the tests here http://biodiesel.infopop.cc/ev...823/m/5697001243/p/9
Drying oil before processing and biodiesel after is no problem.
One of our members Murphy found that some of his commercial clients failed ASTM oxidation tests by doing this but for homebrewers who dont store their biodiesel for long periods its fine.
The power of the fan is not crucial and I would err on the side of too weak rather than too strong.
Hi John, I tried drying a batch of WVO that had a fairly high water content today. Initially I had problems because I had the bubbler too low and it was stirring up glycerol ( I did a glycerol prewash ) then after receiving your message I moved the bubbler to just above the projected glycerol level.After 6 hours I had crystal clear WVO showing no bubbles in a HPT test. I am in the process of calibrating a manometer and will be able to be more precise once this is in action.What is so good about the MK11 dryer is that it uses so little energy and is so effective.I am looking forward to processing the oil tomorrow It looks so good . I will do a two stage no titration. Thanks John you helped me take a big thorn out of my foot. Kind Regards Jock
If you needed to dry your oil after doing a glycerol pre-wash it must have been very wet before.
When you get your manometer set up it will be interesting to do some before and after water tests.
From previous testing I have done, adding 20% glycerol to oil that is @ 2000ppm water will reduce this to <500ppm as long as the oil does not titrate too high.
If there is anyone using this page any more and in the Carlow/Wicklow area that wants an oil supply from 2 chinese takeaways let me know.
One of them gives me 120-150L a month and the other 60-80L a month.
Let me know if you want their details.
I am not making any fuel at the moment and have a few hundred litres there so no room for any more.
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