[Stoves] Reducing smoke with steam

[IPC]

Dear Peter

Thanks for your input.  I think the only point where I would slightly
disagree is where you say "The chemical reaction only converts combustible
gases into other combustible gases."  

What happens is that the steam reacts with combustible particulates
("smoke").  Being particulates, they do not burn rapidly even in the
presence of oxygen.  So the chemical reaction converts combustible
particulates into combustible gases. The gases can burn rapidly once there
is enough oxygen. The net effect is to prevent smoke forming - which is most
desirable!  

If you let the particulates reach the edge of a diffusion flame, they make
smoke - which you can easily see if you hold a cold plate at an angle above
a candle.  The flame, being chilled by the plate, lays down a nice layer of
soot.  You can do the same with every flame of the diffusion type. Most
solid fuels have diffusion flames, because you can't premix the fuel with
air (unless you atomize it in the first place).

Hope that clarifies things.

(Dr)Philip Lloyd
Energy Research Centre
University of Cape Town
Private Bag Rondebosch 7701
South Africa
Tel +27 (0)21 650 3896
Fax +27 (0)21 650 2830
 

-----Original Message-----
From: stoves-bounces at listserv.repp.org
[mailto:stoves-bounces at listserv.repp.org] On Behalf Of Peter Verhaart
Sent: 02 January 2008 01:27
To: Discussion of biomass cooking stoves
Subject: Re: [Stoves] Reducing smoke with steam

First of all a happy New Year to all readers.
Even if a chemical reaction takes place, it does not supply oxygen where it
is needed. The chemical reaction only converts combustible gases into other
combustible gases. The oxygen has to diffuse into the flame to burn it,
enabled by the increased area of the interface.

Cheers,

Peter Verhaart