Catalytic

[larsmith]

I'm suspicious that having a quarter inch steel pipe for a heat riser is similar ( or the same ? ) as having a steel-plate catalytic converter design in a more traditional steel-plate wood stove.

I'm wondering if anyone has considered or tested ( or knows of anyone having done either ) any form of catalytic converter in a rocket heater ( other than having the steel heat riser ) ?

I'm suspicious that any means of incuding steel, stainless or otherwise, in the heat riser portion of the rocket ... or even in the burn tunnel ... to act as a catalytic converter has the potential of improving the speed @ which the heater comes up to temp and burns more efficiently.

I'm even considering using some form of wire mesh ... anything that can get nasty hot & retain it's shape and not burn up. using metals which aren't strong enough to stand up to the heat & which would have to be periodically replaced. Since my rocket heater design includes access to the base of the heat riser, I could periodically ( frequently ) replace the "catalytic converter".

I'm also considering how big a converter will need to be for max efficiency &/or how far up the heat riser the catalytic converter would need to be placed.

Comments ? Observations ?

[canyon]

I am not sure about this but my understanding of a catalytic converter for a wood burning device is that it is a piece of highly conductive material (usually platinum?) that takes some of the heat from primary combustion and gives it to the gasses that pass over it further down the line so as to encourage a secondary combustion of the gasses. The design of the rocket heat riser with insulation encourages this inherently. I think adding anything to this might slow things down and actually work against clean burning. But if you try it please share your results as I am only talking hypothetically , not from experience. Stainless steel is not very conductive so I doubt it would make a good catalyst.

[Donkey]

Hmm..
Catalytic converters are typically installed to repair a less than ideal situation. Air tight stoves, for instance, where it's a feature to provide an inefficient combustion environment.

It's my opinion that in the case of rocket stoves, catalytic converters are completely unnecessary.
The heat riser should already be showing sustained heats of over 1100 deg. F.. You've already got conditions for complete burn of all the fuels, why add a bit that does nothing of value and will need periodic replacement?

It matters little what the riser is made of, as long as it allows for the temps necessary. I like the steel 'cause it gets hot fast (as long as it's well insulated). My stove here at home is cast, store-bought refractory. It allows PLENTY of heat, PLENTY fast!

My opinion?? Keep it simple.

[larsmith]

I was sensing a "prevailing wind" that the "right" way to do a rocket was with a 1/4" steel insulate heat riser.

My current materials on hand are abundant fire brick ( enough to easily build two rockets but no steel for a riser.

I was considering putting some steel rods or steel plate(s) of some sort just out of reach of the flame in my all-brick rocket to see if it would help the lower portion of the heat riser to come up to high temp reach most efficient burning of gasses earlier ( noticeably earlier ? ) than just a fire-brick heat riser would on its own.

I've been thinking of making the base of the heat riser "a bit" larger than necessary for the ~7" system I'm building ( plan to build ), to accomodate a piece or two of steel, perhaps a 6" length of 6" pipe, with holes drilled all thru its sides, thru which gasses can flow and hopefully see additional combustion of gasses there.

An interesting feature of catalytic converters I've seen is that there's abundant "passage ways" thru which the gasses can pass ... small openings so that the gasses will flow past multiple "walls" of very hot surface.

I'm hoping to find a way to increase the # of HOT surfaces with which the gasses come in contact, as they make their way out of the heat riser.

I've even started designing a "slim" rocket ... with a feed box that's made up of 2 parallel slender channels, 2.5 by 8" inches a piece, running the full length of the burn tube to the base of the heat riser.

From there, I'm considering having the heat riser be 2.5" deep by approx 18" wide, on the theory that the more of the hot gasses which brush again the firebrick, the faster that we'll see heat transferred into the brick.

So ... back to the idea of catalytic converter, on the theory that the more heatable surface the hot gasses can touch, the more quickly the heat will be removed from the gasses and into the brick where it can then do some good.

I've considered using some form of "mesh" or chain-link material ... anything that'll get hot and cause other gasses to be burned more hot & efficiently than fire brick alone.

[chronictom]

Maybe I'm mis-understanding what you mean by catalitic converter, but on car exhausts, they use platinum, palladium, rhodium, or other materials which cause a reaction that allows unburnt emissions to burn.

If that is right, then it would makes sense that on a normal stove that doesn't get up to top temperatures would benefit by one, but with a rocket stove, the whole point is to get the temp hot enough to burn them without any additives...

reading up on them did make me wonder if maybe all you would need for your purposes would be the catalyst support. From wiki;

"The core, or substrate. In modern catalytic converters, this is most often a ceramic honeycomb, however stainless steel foil honeycombs are also used. The purpose of the core is to "support the catalyst" and therefore it is often called a "catalyst support". The ceramic substrate was invented by Rodney Bagley, Irwin Lachman and Ronald Lewis at Corning Glass for which they were inducted into the National Inventors Hall of Fame in 2002."

That honeycomb ceramic substrate could do what you wanted without the involvement of metals...

[larsmith]

To a degree, my question harbors evidence of a degree of (hopefully explainable) ignorance on my part ... and that is regarding the proper definition of "Catalytic Converter" ... and I've since learned that perhaps I shouldn't have used that term, since it does indeed generally mean a platinum coated ceramic honeycomb structure ( etc ).

Having confessed my ignorance, let me see if I can recover a little face by stating that what I want is to be to add something in the heat riser which, when it in turn gets hot, will result in more efficient burning of the exhaust gasses.

As mentioned above, I'm presently seeking to go "all firebrick" for all of my Rocket, including the heat riser. Since there is a segment of the rocket heater world who are strong proponents of a steel riser because that results in faster high temps achieved in the heat riser, I'm hoping to be able to achieve high temperatures in my firebrick heat riser by introducing some shape / size of steel across / around which all gasses must pass. I'm hoping that passing by a very hot piece ( or pieces ) of steel will result in a more efficient burn.

What I've wrongfully done is to use the term "catalytic converter" to describe that "something" which I'm considering adding to my design. My apologies for the confusion created by my mis-use of the term.

[chronictom]

okay, well names aside... I still think the ceramic part of them, the honeycomb structure would do it. I have this old electric heater that has a ceramic core with heating coils wrapped around it, when left on too long, that ceramic core literally glows almost (but not quite) white. That was what I was thinking of when I said it may work. Once it heats up, any air (or gasses) going by it would contact an extreme amount of very hot surface material...

lol, of course, I really have no clue what one of them look like from a car system, but I'll know in a day or two, I called a buddy who has a scrapyard and he is going to rip one apart for me and send some pics of the interior.

[canyon]

Larsmith,
While steel is convenient and easy to use and has the round advantage, don't discount your firebrick. If you don't have or can't locate steel don't worry about it. Firebrick can still work fine. Once up to temp, it might be at least as good as steel. And, it probably won't take all that much extra to get up to temp. As recommended prior, keep it simple. You don't need a catalyst or whatever you want to call it and in fact I think it might create problems not to mention all of the design,construction, and maintenance issues.

[larsmith]

The feedback's been both informative and encouraging thus far. Plz keep it up !

I especially appreciated chronic's comment re: a converter from a car ... it kinda sparked a tho't ... I've a friend who's all about cars and I'm betting that from him I could get different ones from him as well. I've no idea if they'd be useful / helpful but it would be an interesting learning experience none-the-less.

Canyon, TY for your comments as well. I've been around the block enough times to know that if yer going to "do it", it's best to do it right & thus do it once & not to have to keep re-doing it. I'm wanting to put this rocket together to benefit the family and protect our pocket book this (cold) winter. I can't afford mistakes. You've helped me with my confidence to proceed with plans. Again, thanks.

[Donkey]

Oh, yeah... The all fire brick rocket stove as shown in the book is not a broken system. It works just fine, gets hot enough, fast enough and does the job admirably!

Really, all the extras can be fun to play with and all..
Keep it simple is the BEST ADVISE I can provide. Try to avoid the urge to fix an unbroken system till later..

Really, "doing it right" is about sealing it all up well, insulating the bejeepers out of the heat riser and burn tunnel, making SURE there are no constrictions anywhere and placing the chimney in a good place with a primer box conveniently located.
You have more than enough bricks, rejoice!