[Gasification] the most important thing (quite possibly) > i've learned to date

Ken Boak ken.boak at gmail.com
Tue Oct 19 01:54:58 CDT 2010


I'd also like to start a discussion about direct contact of the wood chips
with the exhaust gas.  A pre-processing reactor that cooks the chips a
little batch at a time then dumps them into the main gasifier reactor, via
auger feed. As you say a "just in time" pipeline flow of pre-cooked, pre-
heated reactants.  Water can be added if necessary as steam.

Clearly the wood will become torrified, and the exhaust gas stream will
drive off and purge the wood fuel of moisture and volatiles, whilst raising
the temperature of the fuel considerably.  There will also be an increase in
fuel energy density.

If diesel exhaust was used (I'm thinking of a dual fuel Lister being started
up on diesel to raise process heat and provide mechanical and electrical
power for starting up gasifier), this will contain between 8% and 17% unused
oxygen, and around 80% nitrogen.  Would the O2 be of sufficient quantity to
cause partial oxidation of the fuel and possibly more heat?

If the exhaust is from a woodgas engine - it will again be around 80%
nitrogen, plus CO2 and CO.   If this relatively inert hot gas is used to
purge the woodfuel of all moisture and volatiles - is the resultant off-gas
ever going to have sufficient combustible constituents that it could be
ignited in any sort of air fed burner - or is the nitrogen loading just too

Thoughts appreciated,


On 19 October 2010 02:13, andy schofield <scothebuilder at hotmail.com> wrote:

> Jim,
>    Pushing calories around in the DTU graphic model, I find moving heat
> into the fuel is indeed the best use, for loose BTUs.
>  In practice, heat transfer into wood is not easy because of limited
> conduction and radiation, and zero convection in a mound of fuel.
>  The GEK method is like stir-frying vegetables in a wok; forcing
> convection. As each particle, contacts the walls of the pyrocoil; they cook.
> Someday I want to attempt direct contact of the wood with engine exhaust
> gas, after solving a certain sealing problem.
> A "just in time" inventory of heated wood; roasted to perfection.
> It is a shovel ready project.
> Looking forward to your findings.
> Andy
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