[Stoves] Stoves and chimneys

[Philip Lloyd]

Otto Formo said "Fuel efficiency and clean burning, are more or less linked
together." 

Yes indeed! It helps to realize that smoke is fuel in its own right.  For
some fuels, the smoke has a higher heat energy content (MJ/kg) than the fuel
itself, which means that if you have an inefficient stove that produces
smoke, the fuel left behind once the smoke has been driven off actually has
less energy than the fuel you started with.

Start clean and then add a chimney. If you can get quite a clean burn with a
natural draft, then adding a chimney should improve the burn further because
of the added draft. Only then will your chimney remain clean for years.

Many cheap chimneys are thin galvanized metal.  Starting and stopping the
fire causes some condensation, and residual NOx and SOx then give rise to
rapid corrosion. So the best chimneys are brick or clay, with relatively
thick metal a good alternative. And yes, even biomass can give SOx.

Always check the possible size of chimneys in the field.  I once tested a
fuel in a lab stove that had a 3m chimney, and it worked really well.  The
same fuel in the same stove in the field was a total failure because the
maximum chimney was about 1.5m. 

The first cancer directly linked to human activities was a scrotal cancer in
Victorian chimney sweeps, who had to climb up the huge chimneys with brooms
to keep them clean. If the soot was allowed to build up, it could eventually
catch alight and burn the house down. 

Prof Philip Lloyd
Energy Institute
Cape Peninsula University of Technology
PO Box 652, Cape Town 8000
Tel:021 460 4216
Fax:021 460 3828
Cell: 083 441 5247


 

-----Original Message-----
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Sent: 09 February 2012 03:07
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Subject: Stoves Digest, Vol 18, Issue 10

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Today's Topics:

   1. Re: Grates and chimneys (Otto Formo)
   2. Re: Grates and chimneys (Xavier Brandao)
   3. Re: Grates and chimneys (Fireside Hearth)


----------------------------------------------------------------------

Message: 1
Date: Wed, 8 Feb 2012 19:06:52 +0100 (MET)
From: Otto Formo <formo-o at online.no>
To: "Paul S. Anderson" <psanders at ilstu.edu>,	Discussion of biomass
	cooking stoves <stoves at lists.bioenergylists.org>, 	Otto Formo
	<formo-o at online.no>
Cc: stoves at lists.bioenergylists.org
Subject: Re: [Stoves] Grates and chimneys
Message-ID:
	<22416121.7323.1328724412919.JavaMail.adm-moff at moffice10.nsc.no>
Content-Type: text/plain; charset="iso-8859-1"

Dear all,
Yes, nobody should clog their chimneys.
On the other hand, nobody should belive that stoves with chimneys are clean
burning, any how.
A chimney will "only" make sure that we will have no more indoor polution,
while outdoor polution in larger cities are a huge problem, related to
insufficient combustion. 

According to Paal, top lit fireplaces ,will have a very positive effect on
outdoor polution too.

Fuel efficiency and clean burning, are more or less linked together. If you
aim for a "very" clean burning stove, you will most likely have a fuel
efficient stove, as well.
On the other hand, you have no "guarantee", that a fuel efficient stove are
"very" clean burning.

Focusing on the new ISO standard Workshop for Clean burning and Efficient
Cookstoves in Holland at the end of this month, we should stress on the
clean burn in stoves and not so much at efficiency.
CO and PM are the most important issues, when it comes to indoor polution.

Otto
Still a TLUD ND gasifier fan.......without a fan.....