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cabako

Biodiesel Fired Kiln

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cabako    9

Hi all,

 

I have done some research and found a few write ups and youtube videos of folks firing their kiln with veg oil.  I have an unlimited supply of ASTM quality biodiesel (made from veg oil) at hand and  I'd like to figure out how to build and fire my own kiln with the bio.

 

My goal is to make a small pilot kiln first and then move up to a larger kiln later.  I envision the first small kiln ~ 5-10 cubic ft. to work out of a 5 gallon carboy/jerican of biodiesel.  1 gallon of Biodiesel = ~128,000 BTU.  So my first question is, how do I rough estimate kiln size & cone temp (say cone 10) Vs. BTU required?

 

Second question, how difficult is it to control the temp at such a small kiln size while firing with liquid fuel?

 

I am still working out how to make a air driven venturi style fuel burner, but I assume It would have to be rather small flow rate for 5-10 cu. ft.  Since biodiesel has much lower viscosity than veg oil it would not have to be pre heated in any way. 

 

Anyway just thinking out loud and would love to hear if any input & if members have a liquid oil fired kiln/ burner setup.

 

Thanks,

 

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Foxden    31

I will follow your progress on this as I find it quite interesting. For a number of years I was making my own biodiesel from recycled restaurant oil. At that time I thought about a biodiesel fueled kiln, too. I went so far as to purchase a used Beckett Oil Burner (eBay), used in oil furnaces. I never did hook up the burner to see if it burned the biodiesel as my source for used oil dried up and I quit making the fuel.

 

I think you will find data regarding these burners and the BTU produced. Based on my readings you would need 10-16,000 BTU per cu ft if your kiln is 9inch thick soft brick. Based on output you could calculate the maximum size kiln you could fire with such a burner. It may take more than one burner.

 

Keep us posted.

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I think it is anywhere from 6,000-16,000btu per cubic foot depending on how much insulation you have. Will double check when I get home in my kiln book for the estimated figures.

 

Marcia has posted some burner designs and stuff before but from a quick search I can't find anything.

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cabako    9

FYI All,

 

Here is the video inspiration.  Looks rather simple, but the devil will be the nozzle used, I can't tell what nozzle it is from here.  Ive done some research on "black gold" nozzles, the one in this vid looks almost like a pressure washer nozzle...

 

 

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cabako    9

I'd just like to update this if anyone is interested.  I have acquired some large used kiln brick, a 100 psi air compressor, and a venturi style nozzle and adapter for the burner portion which is: Delavan 17147 adapter (1/8" fuel inlet, 1/4" air inlet) and a DELAVAN 30609-2 (SNA .20) SIPHON NOZZLE. These were purchased off ebay for about $25 each, shipped.  I think this will be the easiest hassle free burner for a small cu ft. kiln.  I'll put the wool around the brick walls, i don't have that much but at least the brick will give it some thermal mass.  I'll post pics when its all setup.

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cabako    9

Alright here is a video link of the first test fire, for those of you following along.  The delavan nozzle system works well...But it needs to be kept as cool as possible obviously and I will have to remove the pipe and build some sort of firebox out of kiln brick.  I will probably also split the air line to inject some air directly behind the nozzle to keep it cool and get a better burn.  It should be possible to control the temp by reducing the regulator pressure, but it will be interesting to see how/if it can achieve a complete firing, and just how easy that temp control will be...

 

Try not to notice the massive amounts of cardboard near the kiln... :rolleyes:

 

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cabako    9

Neil,

I don't have pics of the actual burner, but if you google the two parts : Delavan 17147 and Delavan 30609-2 and you will see images of them.  Just screw the nozzle into the adapter, air goes to the back inlet and fuel to the middle inlet of the adapter body.  The black o-ring could be a definite point of failure if it gets too hot and the nozzle could melt too I guess...It should be designed for high temps...maybe not kiln temps though...I have seen people just crimp down the end of a 1/8" tube or pipe and you will get a good spray, but you still have to make the venturi portion yourself.  

 

A friend has a broken electric kiln shell that I could have, so I think I may get a larger nozzle and put the burner through the bottom peephole.  Should work better than this sad excuse of a kiln...

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triolaz    11

I don't know antthing about this subject but I find it very interesting. I know Sam Clarkson (Santa Cruz, Californina I think) used to fire his kiln with vegetable oil, he may be a valuable resource to you

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cabako    9

Here is a video of 2nd firing, Nozzle can be seen clearly in this one.

 

https://www.youtube.com/watch?v=RkkIJcSrzuE

 

A few observations: the heating seemed to stall around 760-780C.  Typically if heating stopped with my propane burner I would crack the lid slightly and the temp would shoot up again.  That didn't happen in this case, temperature would only decrease.  Even with an extra forced air line at the nozzle/inlet

 

I tried increasing pressure from 5 psi to 10 psi in the hopes of getting more fuel out.  I believe this only increased the air flow.  Larger nozzle size, 0.65 or 1.0 gph may be needed. 

 

The air compressor I am using is very small, cheap and constantly runs.  A larger tank & air production volume is necessary so it won't constantly run & overheat.  This may defeat the point of using this system however.  I will have to calculate the cost of air compressor usage Vs. Electric kiln...

 

Might look into a pre-fab oil burner system...BUT I think at the end of the day the easiest solution is a gravity fed delivery, similar to the 3-tiered veg oil burner system that Sam Clarkson built. (thank you for the reference Triolaz)

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I recommend that you calculate the air requirement for complete combustion of the oil.  From what I have read so far in the thread, I suspect you are using too much air for the amount of oil being burned, and this will be the limiting factor of the kiln max temperature. 
  
Waste vegetable oil carbon, hydrogen, oxygen content should be readily available from an internet search.  If you are using diesel as prototype fuel the necessary composition data is also available from an online search.   Aim to supply a BTU/hr energy rate to the kiln about twice what you would use in an electric kiln and design your burner to handle that amount of oil flow equivalent.  Once you know the oil flow needed, then work on the air supply for atomizing the oil,  and partitioning the primary and secondary air flows. 
  
A well designed setup will include some flow measuring devices for both oil and air.  Otherwise, you are flying blind in the dark with no GPS.
    
Keep going, you are making progress.  The flame looks good,
    
LT

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cabako    9

Ok good point!  From a government website: Biodiesel has an air fuel ratio of 13.8:1  So then 1kg of Soybean C18 based bio needs 13.8kg of air (23% Oxygen wt.) for total combustion.  1 gallon of bio has a density of about 0.880 g/mL which is about 7.34 lbs/gal.  1 gallon of bio contains about 128,000 BTU/Gal. 

 

Lets assume the worst and use HBP's 16,000 BTU/ft^3 number to fire my 3ft^3 thin fiber kiln to cone 10. 16x3 = 48,000 BTUs or 0.375 gal of bio (this seems really low to me...)

 

0.375 x 7.34 = 2.75 lbs or 1.25Kg of bio...

 

1.25 x 13.8 = 17.25Kg of air.  Density of this air coming out hot of air compressor @ 35C = 1.46 Kg/m3 = 25.185 M^3 or 889.4 Cubic Feet needed.

 

Lets say we want to spread the firing out over 8 hrs = 889.4/480 min = 1.85 CFM total required...

 

When sizing the nozzle it is rated in gallons per hour.  In this case I need 0.375/8 = 0.047 Gph. I am at 0.25 Gph @ 5 psi thru nozzle which is using 0.49 CFM.

 

According to this I am over on fuel and low on air. Since this is a fiber kiln it probably requires much much more BTUs...

 

I didn't have my morning coffee today...anyone want to check my math?

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cabako    9

Well the saga continues... I've decided that instead of using a cheap noisy air compressor and burner (the air comp. I think would work properly for this application is $450), a gravity fed drip system of vegetable oil rather than biodiesel is probably the simplest and easiest system.   It seems that many potters have come to this conclusion before me... In this clip the kiln is fired to 1000C using propane, then the propane is turned off and a 2 gallon can of dry, filtered WVO is fed into the kiln via a metal tube and onto a steel plate.  Sorry for the smoke neighbors! Definitely will have to fire this at night.  I think with a small electric fan pointing into the burner port I could achieve cone 10 temps and a cleaner burn.  Please remember this is a TEST kiln :D

 

Takeaways from this attempt was that the oil needs to be introduced at around 1000C rather than 600C i tried previously but the burn rate was not fast enough.  Also more metal pieces in the flow of the oil path will give it greater surface area and chance to burn.  I think un burned oil was dripping down under the fiber and bricks...Will look tomorrow.

 

https://youtu.be/lLIlgGIyPVA

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Marcia Selsor    1,301

Too bad you didn't know Bill Weaver from Western Kentucky University in Bowling Green. His backyard was full of experimental kiln. One thing he did was filter waste oil using Charcoal briquettes in a coffee can along the drip system. Looked like IV unit. I have only fired with diesel oil #2, but I know you need a lot more space in the combustion area for oil than you do for gas. Did you get any clinker build up at high temperatures. That comes from inefficient combustion and can really build up significant mass of rock hard carbon in the combustion chamber. I used a converted household furnace burner with a pump for 100 lb pressure through a nozzle with electrodes for spark ignition. 

There is a whole chapter dedicated to oil in the Studio potter book published in 1978 including one by Dennis Parks, Ann Standard, Paul Soldner and my article. 

Here are a few jpgs.

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cabako    9

Marcia,

Thanks for the feedback & info.  I definitely need a baffle/burner stair system as you have pictured. I am lucky enough to have access to pre filtered and cleaned waste veg oil. It goes through industrial centrifuges to remove particulates and fines and is then vacuum dried.  A forced air burner like you show is probably the best way to go on a larger kiln.  but I would want to use biodiesel and not WVO in a system like that.  I think this model is the cheapest I have found:

http://www.supplyhouse.com/Beckett-B2007-AFG-Flame-Retention-Residential-Oil-Burner?gclid=EAIaIQobChMIgKbWm7Gx1QIVzYuzCh10pAhZEAQYASABEgJuHfD_BwE

 

Nozzle and baffle still need to be sized appropriately of course. 

 

here are pics of the oil inlet & "burner" pieces I have in the kiln.  No clinkers that I can see. But I think some oil did get below the kiln shelf on the left.  Floor will probably need to be replaced. This was a very quick firing just to see how hot I could get.  I think a longer slower firing could build up kilnkers.

post-78762-0-57907400-1501431446_thumb.jpg

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Marcia Selsor    1,301

Sounds great for your source of clean recycled vegetable oil. I got my residential burners at the campus dump for free at Carbondale , Ill. They included a pump, 1 nozzle, pressure gauge, and blower with motor. 

We added 2 more nozzles to control varying BTUs as needed to climb. The nozzles could be used individually tr in combination. We used 0.75, 1.5 and 3.0  gallons per hour. Clinkers come from cold air getting sucked in as secondary air. Also inefficient burning of the oil. You may not run into that with clean vegetable oil. There is very good info in these articles. You could contact Studio potter magazine to see if you can get copies. The alternative fiuels issue was the second issue in 1973 I believe. The book is an Anthology of the first 6 or 7 years. 

 

Marcia

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Mark C.    1,807

A recent article in CM(past year) has a story on one of these burners.

Long time ago folks burned used motor oil-(I had a potter who used this free fuel) now its used vegetable oil-no need to use cleaner biodiesel .

The burner is key for best results.

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cabako    9

Here is a video of 4th test fire trying to reach cone 10.  I started off the kiln to 350C with propane for 1.5 hrs, then switched to biodiesel for about 1.5 hrs until 1000C and then I ran out (only had about a half gallon of bio) and I switched to the waste veg oil.  This video is during the WVO phase.  I had a orton cone 6 and cone 10 placed in hopes to get a test Glaze fire. I tested out recycled filter media which was similar in property to custer feldspar.  I made various test tiles with extra silica, clay, emulsifiers added.  Got some very good consistencies & "glaze" application. 

 

I turned the kiln off shortly after this video as it was too smoky and did not want to draw attention since I am in a residential area.  I realize that this is not a good situation, it looked like Heavy reduction since I am only using a small fan for forced air.  The air and oil is directed to a mass of metal giving surface area to burn.  I waited 30 minutes until full dark to re start start only to find that my oil inlet was plugged with what marcia called "klinkers" this is probably pyrolized oil which was allowed to cool and harden.  I will post a picture of the setup and carbon shortly.

 

https://youtu.be/dyEw098aXzo?t=3s

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cabako    9

Here is a picture of the oil inlets, burner assembly and carbon i punched out of the inlet tube, it was completely solid.  Odd thing is the firing was going fine until I turned the flow off.  In any case, this setup works but needs to be improved, it is a very unstable setup and very dangerous as is. Metal oil lines are required and more oxygen entering the inlet tube would prevent carbon buildup.  Anyway, the glazed pieces are still intact, I may try to re work and refire tonight...maybe...

 

PS I don't know why my pics always turn sideways, apologies...

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Is there a reason the burner is in the kiln?

 

The maths back a little while I think you took a wrong turn. It is 6-16k BTU per hour not total firing. I couldn't follow it that well but it seemed ok until you started dividing by time.

Edited by High Bridge Pottery

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cabako    9

HBP thanks that makes sense now.  Oddly enough its now about a gallon's worth of bio or 128,000 BTU needed for 8 hrs at 16k BTU/hr.  I think I was undersized on the burner nozzle, probably a 1gph nozzle run at lower psi would work.  But I think firing with veg oil is probably the way to go as its ~3x more energy per gal than the biodiesel and little electricity involved.

 

The "burner" doesn't have to be inside I suppose.  It just seemed the logical way to do it with the scrap Iron i could get my hands on.  Eventually I would like to fab up stepped angle iron plates as others have used. Then it just drips in, heats up and vaporizes at the inlet.  

 

I think the next hard part will be getting all the oil oxidized. I'll be away for two weeks and won't be able to fire until mid sept probably.

 

Tyler glad you are enjoying it!  

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