For about the last 3 years I have been working on converting my 24 ft propane updraft kiln to fire with WVO, waste vegetable oil aka french fry aka used fryer oil from restaurants. Converting a kiln with no fireboxes is harder than building one from scratch. Although it’s nice that this is a green, renewable fuel my primary motivation has been economic. The oil is free while propane is currently $6.50/gal on Kauai. Propane has been my biggest expense, $300-500/mo. Although there are a few potters on the mainland using oil everybody has a different approach and there is no ‘manual’ for how to build a functional system. Everyone who uses oil is an inventor/tinkerer who is willing to start at the bottom of the learning curve and solve the problems that come up when using oil. I count myself in that group, any normal person would have given up long ago but it seems that every time I give up the universe hands me the next key to the puzzle and I soldier on.
I was originally inspired by Hugh Jenkins, a glass artist from Big Island (Hawaii) who runs his kilns on oil. Based on his ideas, I envisioned and built a hybrid system combining propane and oil. It was a miserable failure. After a year+ of struggle I gave up and went back to propane. A while later I connected with Jon Faulkner (jonfaulknerpottery.com) in the Bahamas who is doing salt firing with oil. He has lots of info on his site about his system and I copied his system and again met with failure though there did seem to be some moments of success. I tested his burner design in my hot front yard in a firebox that I built to see if the two firebox flues would produce the same amount of heat. My burner worked in the yard and I measured the two flues to be very even up to 700 degrees. I then built two fireboxes and burners and tried out my system but my burners wouldn’t light. Despite using a propane torch as a lighter great clouds of disgusting unburnt oil vapor filled my shop, yucchh! Several more failed attempts followed.
My next angel arrived in the form of an Alaskan customer who walked into my shop about this time. He had been a home heater and burner designer and installer in Alaska for 25 years. He talked with me for quite a while and I learned that oil needs to be heated, at a bare minimum, to 80F or it will not burn, even if vaporized. 150F is MUCH better and hotter than that is more better. Many users heat oil to 200-400F before burning. He found videos of burner designs on UTube that led to my current design with a heating coil on the front of the burner.
Mcraine WVO burner 7-30-2012
This burner works and it works great! I use a small amount of propane at first to heat up the coil, then introduce the oil and compressed air. Once the oil ignites (5 minutes) the burner heats up quickly and works very well. NOTE: I DON’T recommend the quick release air connection for propane shown in the picture! It leaks when connecting and disconnecting and I’ve had a couple of fireballs as a result. I’m looking for a better quick connect for the propane.
Oil is hot! WVO has about 140,000 btu’s/gallon vs. 95,000 for propane. This burner can produce up to 400,000 btu’s/ hour! My standard propane pipe burners were 50,000 btu’s. I replaced four propane burners with one of these oil burners. I built fireboxes to distribute the intense heat. My first fireboxes were made from 2300 degree firebrick. I destroyed them in an hour. The bricks melted and broke. My second fireboxes were 26oo degree fiber board. they held up better but still collapsed. My current fireboxes are 2800 degree brick and 3000 degree castable refractory backed by ceramic fiber. These seem to be OK so far after a couple of tests and a full glaze firing to cone 11 (2300F. )
My first successful firing, 7-15-2012, produced some really nice pots. Oil feels like it has a higher vibration than propane. I’ll probably recover my expense and time in a couple of years. Meanwhile, no more propane bills.
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