Hello all.

Built a 55 gallon gravity feed sawdust filtration system. The first 35 gallons that went through the system came out nice and clear and passed 3/27 test.

I have the drum filled about 2/3 full with sawdust. I put in another 25 gallons to filter through during the weekend. The fuel that has been draining out is rather cloudy, almost like an emulsion or under reacted biodiesel. The fuel going into the tank was nice and clear and had methanol removed (as much as possible anyway). The dust used is from a pallet manufacturer and is composed of dried pine, very fine grained. A clean cotton t shirt is used as a strainer in the bottom of the drum to remove any particles.

The fuel coming out had a lot of dropout during the 3/27 test, I have yet to try a shake test. Is there something going on here that I'm not aware of to cause this?

I have never used pine, so I am of little help here.

If you pulled the first 35 gallons off the top of your settling tank, it should have less soap than the BD at the bottom.

Did the BD pass the 3/27 prior to filtering? How long does it take for the BD to filter through the sawdust? Residence time is key in my opinion when it comes to sawdust or wood shavings. I have better success with longer contact time.

A continuous filtration system, where you pump the BD from the bottom of the tank and filter through the wood shavings at the top of the tank will allow any residual methanol to dissipate as it comes in contact with air which will cause more soap to drop out and filter through the sawdust.

Hi Spencenaz, I havent used pine either but I'd bet its resin youre seeing. Even hardwood leeches quite a bit of resin into the biodiesel for the first few gallons in a drum your size. I've mentioned this a few times in posts. If it is resin you'll find taht the water clears to leave a white sticky stuff, which you can spoon out and melt. It burns very well and is soluble in RUG. Thats why I add about 5% RUG to my first batch using new shavings. I should add that softwoods are largely untried.

So,

Should I add 5% by volume RUG to this fuel to remove these contaminants?

You need to first do a shake test to see if your problem is similar to what Jehu mentioned. If it is not soap, spoon it out and see if it will burn with a lighter and then proceed with or without the RUG. I have never used RUG in my diesel. When I get my centrifuge completed, I will probably try a little with some WMO & Biodiesel.

I think I have seen the stuff that Jehu says is resin or sap, but I just keep filtering until it is gone. I run it through my resin tanks a couple of times and a 1 micron filter and it goes away. I bet a fuge would sling it out.

What I'm going to do is just pump that fluid back into the sawdust and filter once more.

quote:

Should I add 5% by volume RUG to this fuel to remove these contaminants?

Wouldn't that just dissolve the contaminant into solution rather than removing it?

Jehu mentioned that he was adding 5% RUG to the batch prior to putting it in the shavings.

quote:

Originally posted by Spencnaz:
Jehu mentioned that he was adding 5% RUG to the batch prior to putting it in the shavings.

No. The RUG is added after it comes thru the shavings. And this is only necessary for the first batch of biodiesel because the resin (or whatever it is) is quickly extracted.

Sending the biodiesel back thru the shavings wont help, the stuff came out of the shavings in the first place, dissolved by the biodiesel. As John Galt says the purpose of the RUG is to keep it dissolved in the biodiesel, as a preventative measure in case it happens to drop out in our car fuel system.

Here is what I found (altho I'm repeating myself as Ive said this a few times already):

1)The biodiesel dissolves resins and what not from the shavings
2)For some reason the presence of water - eg as in a shake-up test - causes it to drop out of the biodiesel, but it doesnt dissolve in the water either
3)This substance burns fiercely and as far as I can tell, completely
4)It dissolves instantly in RUG
5)Therefore the addition of a little RUG to biodiesel containing this extract will - in theory - prevent this substance precipitating in the car fuel system.

Jehu,

Thanks for clarifying.

Hello Specnaz, I haven't been here much over the last month so here is a question. Why are you using Pine instead of a hardwood. With hardwoods I have not experienced this cloudy dropout.

quote:

3)This substance burns fiercely and as far as I can tell, completely

quote:

3)This substance burns fiercely and as far as I can tell, completely

Fuel enhancing additive?

Whats RUG?

quote:

Originally posted by yeyoherrera:
Whats RUG?

Regular unleaded gasoline.
Jon

Hi Spencnaz. I use pine shavings radiata I think, not sawdust. I haven't had any problems so far.

Do you demeth before going thru the sawdust?
You settle and drain the glycerol before?

I was wondering to pass the bio as soon as the process ends thru the sawdust towers, (gravity flow) before settling and draining the glycerol to avoid the long settling time. I know it will clog fast but...
Sawdust is cheap!
After that pass it thru my 2 micron and finally to my purolite towers.
Just wondering.

Thanks. Eduardo
Ps. im using koh