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Misusing car parts for cleaner cooking  RSS feed

 
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Location: Wellington, New Zealand
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My riser currently splits into two with the bottom half going into the secondary combustion chamber, and the top half into my blind black oven.

However, until the burn is clean, I am contaminating the black oven .. with of course black soot.

I'm wondering if I can use a diesel truck catalytic converter to make sure all the soot burns before it enters the black oven to make it white!

This one has a diameter of 4", and i've found a wood stove catalytic converter that's a 6" diameter disc alone but it's twice the price.

Maybe it would throttle the gases going into my black oven too much.  I don't know.  Thoughts?
 
pollinator
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Location: Southern Arizona. Zone 8b
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I can't say for sure whether it will work or not, but my understanding is that "catalytic" converters are designed to burn specific substances.
Diesel converters are designed to work with oxygen, carbon monoxide, and unburned hydrocarbons.   I doubt it would work with creosote & soot, etc.  Or it might actually get really hot, possibly to unsafe levels.

Unless you can find an expert you trust, I would error on the side of caution and spend the extra money.
 
Graham Chiu
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Just reading about the ones intended for cars and stoves and they appear to be ceramic honeycomb blocks coated with platinum (or palladium/rhodium).  Cars can also have a three stage converter that includes the catalyst to burn nitrogen products.  The ones designed for diesel engines don't process nitrogen products.

So, unless I'm missing something, it should work .. as long as the ceramic block is not exposed to direct flame which can crack the thing.
 
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I don't know if soot would be volatile enough on its own to burn and break down in a catalytic... Not sure if you wouldn't have to add in some preheated oxygen as well. In car exhaust plenty of oxygens and volatile molecules to use. soot... Simple carbon. All the ceramic cataleptics I've seen in wood stoves use secondary air. Just musings on my part No proof. Similar to charcoal gasification though.
Cheers,  David
 
Graham Chiu
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This article from Mother Earth on a DIY catalytic converter retrofit says that on advice from Corning, and examination of the oxygen levels in the three stoves they tested, that they didn't need secondary air.

Perhaps they filter out soot in diesel engines using a particulate filter so that they don't reach the catalytic converter.
 
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Would a valve blocking the gas entry to the oven work? Sounds less expensive and more reliable to me …
 
Graham Chiu
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A valve would diminish the heat to the stove which might be useful if I want to cut heat when it's too hot. So I've been considering adding such a baffle.

I've found a cheaper converter, 6" diameter and designed for wood stoves. Only USD124 on Amazon.  I think I'll scour the car salvage yards first to see if I can get one cheap enough to see if it actually works. I don't want to crack a new one!
 
Graham Chiu
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Another advantage that these things are supposed to have is increased efficiency. If the smoke hits the cat at the right temperature range it burns so the stove gets hotter than before.
 
pollinator
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Graham Chiu
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No.  I learned that catalytic converters combust things at lower temperatures. But an unwanted side effect is the generation of dioxins and furans etc. because of the temperature range they are used in.
 
gardener
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My take is that the simplest *and* most effective arrangement in the given situation would be to install a damper that closes off circulation to the black oven until full combustion is established (which should only be a few minutes in a well insulated core). Then let the clean hot exhaust flow into the oven.
 
Graham Chiu
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But then you lose all the pre-heating of the oven as you're getting the fire up to steam.
 
Glenn Herbert
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I suppose it depends on your particular timetable... If it usually takes 15 minutes to get the oven up to usable temperature, then 10 minutes lost while the fire is getting established would be relatively a lot. If it takes a half hour to get the oven going and your combustion is strong and clean in 5 minutes, that would be rather negligible.

Rather by definition, it would be the period when the fire is weakest and coolest that it would be dirty and shut off from the oven.
 
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