[Cob] wood stove

[Shannon C. Dealy]

On Wed, 25 Aug 2004, Joseph R Dupont wrote:

> What about catalytic convereters in stoves..
> Do they help?

Catalytic converters are not particularly helpful for bench stoves (which
have no need of them), they were introduced by the wood stove industry in
order to clean up exhaust gases and meet new polution regulations without
having to redesign their stoves, unfortunately, over the long haul they do
not actually serve this purpose, they just allow the stoves to be sold
under current pollution regulations.  Catalytic converters are:

   1 - Expensive

   2 - Have a short life, can be as little as a few years with heavy use
       (also depends on the fuel you are using).  After they fail, the
       stove is just as polluting as any stove sold 30 years ago unless
       the catalytic converter is replaced, which given the price, most
       people are unlikely to do.

   3 - Will not get you any cleaner exhaust than a properly designed and
       built rocket bench stove will without the use of a catalytic
       converter.

> I've heard that charcole burned in an upper chamber does the same thing.
[snip]

I hadn't heard of this, however, doing so (if I understand you
correctly) has it's own problems:

   1 - You are wasting heat/fuel, since if you burn it in an "upper"
       chamber, the heat from the charcoal is just going right out the
       exhaust.

   2 - If you are using it to clean up combustion just before the exhaust
       gases leave the building, then all the piping preceeding it (if you
       were to use the earlier idea of running it through a bench before
       venting) is likely to have serious creosote build up problems.

The rocket bench stoves work well because they split the design of the
stove into two independent stages, each designed to do it's job as
efficiently as possible, first, a very fast, high temperature combustion
process, followed by an exhaust system whose only job is to extract the
heat from the gases given off by the combustion system.  Because the
combustion process is so efficient, there are no unburned residues left to
condense in the exhaust system (which is what causes creosote build up).


Shannon C. Dealy      |               DeaTech Research Inc.
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