[Stoves] Re Alexis Belonio article

[Crispin Pemberton-Pigott]

Dear Alexio

Your interesting article also provokes a couple of questions from me, so if 
Ron Larson's are not already overwhelming you, could you say a little about 
the flame?

>From the article http://www.bioenergylists.org/en/beloniosupermar07
"As the steam passes through the burner, hydrogen gas is released and is 
ignited inside the burner. "

What is the hydrogen gas released from?  The water?

While I understand the idea principle, I have not actually seen something 
explaining how the water breaks down in a flame into hydrogen and oxygen and 
then recombines either immediately or at a different place in the fire.  I 
agree the flame has an unusual colour, but can you tell me anything about 
the idea that the injection of steam into what appears to be an ordinary 
flame causes the H2O to break down and reform?

It would be helpful if someone could tell us all what the spectrum of the 
flame indicates about what is happening inside it.  Why is it pink?  Is that 
the colour of superheated steam? It is the colour of a blue flame that has 
been cooled by water vapour?

I am asking these questions because it seems to me that there are two 
possiblities about the role of steam in the flame: providing hydrogen, which 
seems unlikely, or reacting (as H2O) with other things.  Water is a pretty 
reactive molecule and when it is really hot perhaps it is catalysing 
reactions that usually take place but in an alternative way.  Or it is 
burning PICs' that usually escape, or ....??

If the H2O is disintegrating and reforming, absorbing then yielding 15.7 
kJ/gm and giving no net benefit in terms of heat, what is the point?  If the 
overall effect is to shorten the flame length, for whatever reason then 
perhaps it is worth adding the complexity of the steam tank.

It seems to me that if the H2O were to 'break down' because of being heated 
it would immediately (instantaneously) reform because it is far above its 
ignition temperature.  What mechanism could separate H2 and O and keep them 
apart at a high temperature?

"The most important points are that the minimum ignition energy of hydrogen 
is extremely low, its flammability limits are much wider, its flame 
temperature is somewhat higher, and its reference laminar flame speed is far 
greater in comparison to the respective properties for gaseous 
hydrocarbons."
    from 
http://www.princeton.edu/~combust/h2_safety/Dryer_et_al_CST_179_2007.pdf p.4

If that actually happened, the heat produced would be such as to break it 
apart again, reigniting it and re-breaking it.

If the overall gas velocity is increased by the expanding steam and the heat 
is not recovered by the pot, then there is a distinct disadvantage. 
Increasing the volume of the gases without increasing the heat content makes 
heat recover more difficult.

If the steam is actually there to drive the air flow, replacing the fan, 
(which is absent, as Ron notes) then OK, but I have lingering doubts that 
the steam is really fuelling a 'hydrogen fire' as water doesn't burn.

Finally, has someone tested the emissions of the flame with and without the 
steam, remembering to provide the same amount of 'driven air' so that the 
effect of the presence or absence of water/steam can be seen?

Many thanks
Crispin