[Stoves] venturi system -ratios of air and gas?

Julien Winter winter.julien at gmail.com
Sat Jan 9 06:05:45 CST 2016


Hi folks;

I believe that thorough mixing of secondary air with somewhat (don't know
how much yet) more than the stoichiochmetric requirement for oxygen is
important for clean-burning wood gas in natural draft burners.  This is
because the wood gas is very complex containing fast-reacting H2, CO, CH4
and slower reacting tars.  If oxygen is sufficient, then the fast gases,
slow gases, suspended droplets and particles, and secondary products like
soot, will oxidize in close proximity.  If oxyen is limited, then fast
gases will react, and we loose heat from the site of reaction; heat that
would have provide activation energy, and accelerated the reaction rates of
the slower species.

Conservng the heat is important for people who design gas burners that add
air in stages.  It is also why I am cautious about adding secondary air
through the side-walls of ND-TLUD reactors.  If this isn't done carefully,
we end up with unburnt wood gas and products of incomplete combustion that
we can't ignite because the reactants are too cold and too dilute.

For a TLUD, the stoichiometric requirement for secondary air will depend
inversely on the rate of primary air, where the combustion begins.  I
recall that Mukunda lab in India reported that the ratio of secondary to
primary air changed from 6:1 to 3:1 as the rate of forced draft
gasification of pellets increased.

Cheers,
Julien


-- 
Julien Winter
Cobourg, ON, CANADA
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.bioenergylists.org/pipermail/stoves_lists.bioenergylists.org/attachments/20160109/98d4079a/attachment.html>


More information about the Stoves mailing list