[Stoves] pre-mix of wood-smoke with air? and how?

[Paul S. Anderson]

Dear Martin,

As far as I remember, this has not been discussed specifically.

However, I believe the simple answer is to not pre-mix.

By pre-mixing, I am assuming that there is some additional time and space
allowed for the pre-mixing in the interval between the creation of the
wood-smoke (wood-gas or pyro-gas) and the final combustion.

In the TLUD gasifiers, we generally want the final combustion to be quite soon
after the creation of the gases because:

1.  Delays cause some loss of heat, while our objective is to get as much heat
as possible to the final target-of-appliation.  Unless the entering air for
pre-mixing is as hot or hotter than the pyro-gas, it will cause undesirable
cooling.

2.  Loss of heat will result is some condensation of volatiles, meaning 
deposits
that could accumulate and clog, and also less matter reaching the area of
combustion (therefore less final heat).

The only exception that I know of is the successful work of Alexis Belonio who
can move at least several meters the gases made from TLUD gasification of rice
husk to the final burner.  I am quite sure that in that case he does not have
any pre-mixing of air with the combustible gases.

I believe that the people working on pyro-gas (wood-smoke, wood-gas, rice-gas,
agri-gas, etc) are focused on getting good mixing of the gas with the air
precisely at the area of the final combustion.

[On the other hand, if you are referring to "producer gas" from gasifiers, AND
if that gas does not have tars, there could be more options to pre-mix.]

In summary, in my opinion, gases that contain condensible volatiles should not
be pre-mixed with air.

Paul

-- 
Paul S. Anderson, Ph.D., Geography professor - Emeritus
Telephone:  USA-309-452-7072 (residence and office)
Internet site:  www.ilstu.edu/~psanders
For my gasifier stoves info, go to:
http://bioenergylists.org/contributors#Paul_Anderson


Quoting "Boll, Martin Dr." <boll.bn at t-online.de>:

> Dear Stovers-woodgas-burners.
>
>
>
> Is it desirable to pre-mix wood-smoke with air, as it is made in normal
> (e.g. butane-) gas-burners?
>
> -What ratio of air to smoke?
>
> - What is the desirable temperature of the mix, in order to get in a second
> step simply ignited, but not self-ignited before reaching the burner?
>
> - Is it at all desirable, because possible condensation of smoke could
> diminish the nozzles-diameter by time? Is this condensation possibly only a
> question of temperature?
>
> What other arguments/ideas about that theme do you have?
>
>
>
> -If you would know, this was already discussed, I would be pleased to get a
> hint for re-reading about that in the archives.
>
>
>
> Thanks
>
>
>
> Martin
>
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