Ok, I step away from these groups for a few months and all my previous understanding might look obsolete. Good work!

I am processing 130 Liters (~34 gallons) of used soybean oil and getting about 27 gallons of demethed bio out of it. It then settles for some time, about two weeks. I currently have a batch made with KOH ready to go but I have second in my processors made with NaOh (man does the glycerin drop out!)

I am also not looking to process fuel every day. After I get 100 gallons ready to go, maybe I will process once every 2 weeks.

Now my plan was to build 2 columns using 4 inch wide PVC drain pipe (black pipe). I am going to make them 48 inches high (because of space I might make them 42" tall). In the first column, I am going to completely fill it with wood chips gathered from a hardwood molding and furniture building shop. Its a mix of hardwood as I get them out of the dumpster so I am not sure what the chips are. In the second column, I was going to place 24 inches of Thermax.

My plan was to put the columns in a series with a setup like this.

Settling Tank with the 2 week settled bio with little to no methanol >>>
Little blue HF pump with a simple flow control found on Graham's website >>>
10 micron screw on filter >>>
Wood chip column >>>
hose to second column >>>
12" of Thermax column >>>
2 micron screw on filter >>>
2nd Tank.


My questions:

1) What flow rate do I need to achieve to make this work? How many pounds is 24 inches x 4 inches of Thermax?
2) Will this set up work?
3) Is it cost effective?
4) I like the idea of this setup as I can turn it on and let it run for hours on end.
2) Am I missing anything here...

Thanks
Doug

Ok did dome math for flow rate and looking for some double checking.

Column:
4 inch diameter
24 inches of thermax

cylinder volume = pi*r^2*h

SO

3.141*(2*2)*24 = 302 cubic inches = 1.3 gallons


Bed volume * 2.5 = optimal flow rate per hour

SO

1.3 * 2.5 = 3.25 gallons per hour



This means it will take approximately 8 hours and 20 minutes hours to clean 27 gallons.


Doug


PS. I think I am going to have to use an air compressor to push the the bio through. Anybody have any idea how air pressure and flow rate relate in this kind of set up?

The air compressor may not be a good idea. You want residence time. BD needs to stay in contact with the resin for a certain amount of time. If you allow your BD to settle for a couple of weeks and then run it through the hardwood shavings, you may not even need the resin.

I don't know what your situation allows, but if you could make a few batches and have an ongoing process, the amount of time filtering the BD could become inconsequential.