Sciencemadness Discussion Board

Catalytic burner for wood stove

Twospoons - 11-5-2008 at 14:52

I have a wood fired stove for heating - one of the fancy ones with a glass door, and recirculating air flow designed to improve combustion. I was watching it the other night, and it was clear there were still unburnt gases escaping into the upper chamber and out the flue (as evidenced by creosote and soot buildup in the chimney).
Seems to me what this firebox needs is some sort of catalytic element, placed after the secondary air inlet at the entrance to the upper combustion chamber. That would help to complete combustion and improve the overall heating efficiency.
So what sort of catalyst would be suitable? Does anyone think the catalytic converter from a car would work?

MagicJigPipe - 11-5-2008 at 15:39

So, is this a fireplace you are talking about or one of those metal things that is not in the wall? A catalytic converter will do the same thing it does with car exhaust but it will get dirty VERY FAST. Also, there's so much other crap in wood smoke it really wouldn't be worth it. I suspect you would have to clean it about every other time you have a fire going.

I have a fireplace that is similar to what you describe but it's not a woodburning stove. It seems like it would be incredibly difficult to install a catalytic converter in a fireplace chimney.

leu - 11-5-2008 at 15:45

Catalytic combusters for wood stoves aren't exactly novel:

http://en.wikipedia.org/wiki/Wood-burning_stove

http://www.countryflame.com/main/faq-wood-stoves.html

http://www.env.gov.bc.ca/air/particulates/rwssabi.html

http://www.woodmanspartsplus.com/product.asp?Product_Id=2045...

http://www.dukefire.citymax.com/articles/article/3941815/601...

http://www.chimneysweeponline.com/hocats.htm

http://www.chimneys.com/burning_secrets/chapter_6.html

:P

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7he3ngineer - 11-5-2008 at 16:10

Fail that, introduce a blower and make sure there's more oxygen there and get everything burning more cleanly.

...except then it wouldn't be a heater any more:D

Josh

Twospoons - 11-5-2008 at 16:43

Thanks Leu - your second link led me to http://www.appliedceramics.com/ . Exactly what I had in mind. Looks as though retrofit might be rather difficult, as the catalyst needs to be hot (250C +) before any smoke passes through.

azo - 11-5-2008 at 17:10

I have a combustion heater and it has a ceramic tile placed below the flu so that any parcialy burned timber will burn in a second combustion before going ot the flu but is not that affective when you choke down the air .


I think eveyone thinks that a catylitic converter lowers emissions !! it does by turning C02 into SO2 so it can go up in the air where it condenses with h20 to form sulphuric acid to come down on us when it rains thats clever aint it.
And it does not stop the formation of oxides of nitrogen WHICH IS MORE DANGEROUS.


azo

stygian - 11-5-2008 at 18:33

I do believe that the common practice is to occasionally clean the chimney with either a magnesium flare-type device thrown into the fire, or a handful of salt thrown into a roaring fire.

[Edited on by stygian]

12AX7 - 11-5-2008 at 19:14

Sheesh, build a better stove...

I hate fires that burn bad... every fall-winter-spring our neighbors often burn a half-assed fire in their fireplace that makes the whole block smell like a steakhouse (which though delicious, makes me shudder to think what their flue looks like inside). If they even just knew how to stoke a fire, there would be hardly any of that.

I've tossed wood into my furnace before, started the blower and within five minutes of adding the wood (to an already hot bed of coals), the whole thing is back up to blistering yellow-white heat. A steel rod held in the flue starts throwing sparks (near 1500C). The exhaust has no smell whatsoever, only the sensation of warm, humid, stuffy air, being almost all CO2 and H2O after all. I don't recall any NOx. That's one hell (literally) of a fire, and quite clean burning too. Melts aluminum and bronze nicely!

Tim

Twospoons - 11-5-2008 at 19:41

Mmm, well a fan-forced furnace in the living room might be a bit much. I fire I've got is very good ($3000 good!) - brick lined cast iron, pre-heat on the primary air, separate secondary air to complete burning. Manufacturer claims it can achieve 1000C in the firebox - which I'd believe, as the ash after a couple of good burns is sintered into a hard lump.
I just can't help looking for that little bit of extra performance :D

MagicJigPipe - 11-5-2008 at 20:48

I don't understand why efficiency is such a concern with burning wood. It's cheap, plentiful and if you have a decent fireplace (adjustable air intake/flu) you can keep a fire going all night with no problems.

For some reason I was just never concerned with efficiency. Perhaps I should be?

However, if I'm going for maximum efficiency I'll just turn on the heater (natural gas). I mean, if I was really concerned with pollution. Somehow I doubt it's a really big deal seeing as though forest fires burning millions of tons of organic matter are a natural part of the ecosystem. And we prevent a lot of them... Only you can prevent forest fires! (Smokey the Bear reference).

12AX7 - 11-5-2008 at 20:52

Quote:
Originally posted by Twospoons
Mmm, well a fan-forced furnace in the living room might be a bit much. I fire I've got is very good ($3000 good!) - brick lined cast iron, pre-heat on the primary air, separate secondary air to complete burning. Manufacturer claims it can achieve 1000C in the firebox - which I'd believe, as the ash after a couple of good burns is sintered into a hard lump.


Sounds pretty good then.

Don't worry about carbon, it's carbon neutral! ...Right? I mean, logs grow on trees, don't they? :P

Tim

7he3ngineer - 11-5-2008 at 21:17

Quote:

Don't worry about carbon, it's carbon neutral! ...Right? I mean, logs grow on trees, don't they?

...yes, but you can argue that with lower efficiency, more trees are burnt over time, resulting in less trees to absorb CO2 and provide nice, clean O2:P

Wait, this is a chemistry forum... destructively distil your wood, collect some goodies like pyroligneous acid (never buy methanol again;)), and be left with some nice, clean burning charcoal:D

Josh

Twospoons - 11-5-2008 at 21:46

All I want is as much warmth as possible from my pile of wood - its all got to be cut, split and carried by me, so better efficiency means less work for moi. Also less time wasted feeding in more logs or cleaning chimneys. I'm not worried about carbon - as 12AX7 said, its basically carbon neutral.

MagicJigPipe - 11-5-2008 at 21:52

Yes, but wood for burning usually isn't cut specifically for that purpose (I'm pretty sure). It's usally just scrap or trees that were going to be cut down anyway so I think the less trees thing doesn't really matter. Besides, if the wood is from a "tree farm" (not likely, I mean, why burn wood that could be used to build things?) then new trees are planted in their place.

The only thing I don't like about cutting down trees (when they are replaced) is that pine trees are usually the replacement. Hardwoods are so much prettier and it sucks to see them replaced with the all to common pine tree.

I know you weren't completely serious but methanol is so cheap that getting it from wood would be a waste of money and energy (for the home chemist). You need heat to perform the distillation (more than you would get from the charcoal) so it would be a negative effect. Even if you used wood to distill the wood it would still be difficult to keep the cost under $2 a gallon unless you have a lot of land, use hand saws and are a good lumberjack (imagine the work)!

Not to mention the subsequent fractionation!

[Edited on 5-11-2008 by MagicJigPipe]

7he3ngineer - 12-5-2008 at 00:55

Quote:

Mmm, well a fan-forced furnace in the living room might be a bit much


My (no longer) neighbour started building an indoor forge in his lounge room (in the fireplace) at one point... never finished it... could never work out why:P
Quote:
Originally posted by MagicJigPipe
I know you weren't completely serious but methanol is so cheap that getting it from wood would be a waste of money and energy (for the home chemist). You need heat to perform the distillation (more than you would get from the charcoal) so it would be a negative effect. Even if you used wood to distill the wood it would still be difficult to keep the cost under $2 a gallon unless you have a lot of land, use hand saws and are a good lumberjack (imagine the work)!

Not to mention the subsequent fractionation!


You're telling me you have never even thought about distilling wood, just for funsies? No? Maybe its just me:)

Actually, making charcoal isn't that much work. Its made all the time by forgers/casters/enthusiastic bbqers (although there's nothing high-tec there... its just cooking wood essentially). I think Tim had something on his site about making it somewhere actually. I used to do it every so often (but havn't since moving to a duplex:()... never collected any vapours though... plan to some day. Collecting methanol wouldn't be that bad (industry did it for years), although expecting to be able to collect any acetone or acetic acid seems to me to be nothing other then delerious.

Sorry Twospoons, won't trash your thread any more;)

Josh

Pulverulescent - 12-5-2008 at 03:52

Quote:
Originally posted by Twospoons
Does anyone think the catalytic converter from a car would work?


'Verrry doubtful, since the catalyst elements are within the porous ceramic formers.

I've noticed H2S in auto emissions, so that's a reduction.

'Not too sure what 3-way-cat means, but NOX and SO2 are reduced (presumably?) and CO oxidised.

I have an open living room coal fire; it's very inefficient and the flue requires cleaning every 4 months.

'Leads the neighbours to say, That bollocks is on the roof. . .again!

If you're feeelthy reeech you could put in a platinum mesh---that should work!

Just kidding!

Or, you could get tiny amounts of catalyst wire from disused catalytic cigarette-lighters.

You'd need a lot of them, of course!

Oh, and when I had even less sense than I do, now, I thought I could destructively distill coal to get benzene.

'Go figure!

P

Vogelzang - 12-5-2008 at 14:38

Read these articles.

http://www.backwoodshome.com/articles/frandsen36.html

http://www.backwoodshome.com/articles2/lee90.html

http://www.backwoodshome.com/articles2/lee108.html

http://www.backwoodshome.com/articles2/earl83.html