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?My gas kiln is smoking?


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#1 Idahopotter

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Posted 10 December 2012 - 01:21 PM

Ive fired electric for 4 years now. I just got a really old electric kiln for free from the local high school. The kiln is small so I cut only one burner port. I cut out a 7 by 2in chimney. When I began the first test firing it began to smoke within the first 5 min. Not sure why need some advice.
Thanks from Idaho

#2 Mark C.

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Posted 10 December 2012 - 02:25 PM

I'm not sure what you have an electric kiln with a hole cut into it or a converted electric to gas kiln-a better description is needed
I will need more info on what you are doing as far as the kiln?
Are the coils smoking or the ???
Mark
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#3 atanzey

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Posted 10 December 2012 - 02:29 PM

My two-cents worth is 'welcome to gas'. I assume propane? My propane gas kiln coats everything with black soot until it gets up above about 800-1000 degrees (I think, can't remember the exact point), then it starts burning off. Meanwhile, everything in the room gets smoked. A good fan/hood helps, but doesn't eliminate this effect.

Alice

#4 Idahopotter

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Posted 10 December 2012 - 03:08 PM

I'm not sure what you have an electric kiln with a hole cut into it or a converted electric to gas kiln-a better description is needed
I will need more info on what you are doing as far as the kiln?
Are the coils smoking or the ???
Mark


No i have removed the coils from the kiln. It is an electric kiln converted to gas propane. I don't think that this is all that uncommon.

#5 Marcia Selsor

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Posted 10 December 2012 - 03:34 PM

I would say your flame is burning too rich if you are getting that much soot buildup.
Try getting a better mixture with some primary and secondary air and cut back on the gas.

Marcia

#6 Mark C.

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Posted 10 December 2012 - 09:33 PM

I agree that the gas /air mixture is off-as already suggested maybe a different orifice size would cure this?
I fire gas kilns every week with no smoking-me or the kiln do not smoke.

Mark
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#7 Marcia Selsor

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Posted 11 December 2012 - 08:58 AM

Atanzey and Idahopotter,
what types of burners are you both using that you are getting so much soot.?
In Montana when I first started teaching, the kilns had home made burners on natural gas and the start up got soot every where. ..kiln room, classroom, and ceiling of the auditorium. The mechanics room for a 7 story building was attached to the pottery room and sucked the soot into the ventilation system.
Very bad situation. natural gas varies significantly.


Marcia

#8 atanzey

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Posted 11 December 2012 - 09:49 AM

I'm using Ward burners - we upgraded the ones provided by Olympic. I can't GET enough air into them - we've considered adding a blower. (Husband wants to add Oxygen - I'm reluctant.) Small kiln (18"), the two burners are probably 'too much'. But the worst offender in the problem was the really sad pilot that came with the kiln - a long tube with small holes along the length, it produced prodigious amounts of soot. We're in the process of replacing that, but haven't gotten the new pilots completely functional. I've fired once since their installation (the gas/air flow blow out the pilots, and the room smells of gas - can't/won't fire again until we resolve!) There was much less soot this time, but still I can't get enough air to clean up the flame at candle.

Alice

#9 Mark C.

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Posted 11 December 2012 - 12:11 PM

I'm using Ward burners - we upgraded the ones provided by Olympic. I can't GET enough air into them - we've considered adding a blower. (Husband wants to add Oxygen - I'm reluctant.) Small kiln (18"), the two burners are probably 'too much'. But the worst offender in the problem was the really sad pilot that came with the kiln - a long tube with small holes along the length, it produced prodigious amounts of soot. We're in the process of replacing that, but haven't gotten the new pilots completely functional. I've fired once since their installation (the gas/air flow blow out the pilots, and the room smells of gas - can't/won't fire again until we resolve!) There was much less soot this time, but still I can't get enough air to clean up the flame at candle.

Alice


DO NOT ADD OXYGEN

blower is fine once it gets going
Mark Cortright
www.liscomhillpottery.com

#10 atanzey

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Posted 11 December 2012 - 12:50 PM

See! That's MY feeling on the Oxygen.....

My Husband likes living on the edge a little more...

Alice

#11 Mark C.

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Posted 11 December 2012 - 02:16 PM

I have oxygen training from my commercial diving diving experience . I like living on the edge more tha I will say here but you would have more fun throwing old unstable dynamite sticks then blowing yourselves up with oxygen-
Better yet fill the dog house with propane and throw a lit ball into it-If you like this result continue with the explosive gases.

A small variable speed blower on a rheostat will fix your issue safely.
Mark
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#12 Marcia Selsor

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Posted 11 December 2012 - 03:23 PM

Agreed. Oxygen is too dangerous.
Look into an old electrolux vacuum that you can reverse the hose for blowing more air. Or look into a small squirrel cage blower from Grainger's and blow some air with that. Ideally you need to mix the air with the gas inside the burner proper OR around the burner into the secondary air space. Can you turn the pilot off once the burner is lit?

Marcia

#13 atanzey

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Posted 11 December 2012 - 05:58 PM

Marcia - no, the pilots stay on to keep the thermocouple on. I've considered relocating the thermocouple, but if the solution we're working on pans out, all will be well. Then, I can reconsider if we need to add a blower.

Mark - I feel compelled to point out that oxygen is not explosive. It just makes things burn better. Not that I'm leaning that direction, but let's keep the science real.

Alice

#14 Mark C.

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Posted 11 December 2012 - 07:30 PM


Alice,Oxygen is classified as an oxidizer, not as a flammable gas. "O2 appears to be agnitable/explosive at any percentage." It will support oxidation (i.e. burning) but oxygen itself does not burn.


It needs something to mix with say natural gas or propane are you using any of these gases in your kiln????If not then you are ok if so then you have a larger problem.


I own and use a broco underwater torch which only uses oxygen to burn at 10,000 degrees yes 10,000 degrees-it will cut a rock -makes cone 10 look like kid stuff.

You can read about it here
http://www.broco-rankin.com/broco/i_exothermictorchsystems.cfm
I know about oxygen -its not to be taken lightly.
Mark
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#15 Lockley

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Posted 12 December 2012 - 07:48 PM

Homemade conversions are subject to all sorts of problems. The folks at ward burners are very helpful if you ask them. One of the possible causes of your problems may be, strangely. too much resistance from your kiln. Back pressure created by the Kiln contents reduces an atmospheric burners ability to induce air flow into the kiln. The exit of a kiln should be capable exausting at least the volume of the gas and air going in. As a kiln heats atmospheric burners often need their mixtures adjusted to maintain the desired chemistry. A hot kiln creates more back pressure than a cold one.

Lockley


ps. adding oxygen will solve nothing and entail enormous expense. Kiln conversions are created not designed. My experice with the people at Ward's is that they will help you redesign your conversion. they need to know the volume, the inlet sizes, the burners you have , the orifice sizes, and the vent system and its dimensions, as well as the kind of supply system you are using including the specifications of your regulators.






#16 Marcia Selsor

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Posted 12 December 2012 - 08:21 PM

More information also would be your altitude, i.e. ft above sea level, and size of your stack/chimney. You may need more draw as Lockley is suggesting. A taller chimney may be needed.

Marcia

#17 Mark C.

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Posted 12 December 2012 - 09:29 PM

This may be an easy fix -put a light stack on lid to help induce the draft.
This stack would be set on after loading as this is a top loader-it could be just about made from anything light-metal-tin-stainless or whatever.Check out a local scrap metal yard.
You are firing this out side I assume?
Mark
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#18 Marcia Selsor

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Posted 12 December 2012 - 10:09 PM

When you use natural draft burners compared to forced air burners (with blowers) your flame/efficiency of burning/ draft through the kiln is dependent on the draught from the stack/chimney.
. At higher altitudes you need a higher stack. You can test your draught by lighting some newspaper and see how the flame gets drawn into the kiln. Hold it a little to the side of your burner port is in the bottom /floor of your kiln. See if the flame gets drawn into the kiln. Until you see the flame pulled into the kiln, you may have an insufficient ventilation system in your converted kiln. As Mark says, a steel pipe can work. Flue tiles, bricks. But if you are building on top of a soft brick lid, you may have to suspend whatever you use in some other way than setting it on the lid of your electric kiln body.

Marcia




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