[Gasification] First flames

[doug.williams]

 Hello Douglas D, and Colleagues.

You report your experience:

>I am very glad to inform that the small pioneer class gasifier
>Works wonderfully.

It is very pleasing to me that you have followed the instructions, and not 
tried to re-invent the design.

>The first tests have been made with charcoal, very irregular in size and
>shape. The gas flow is constant and just stops after a couple of hours when
>the air injection nozzles go uncovered.

You should stop the gasifier before the fuel drops to the level of the 
nozzles, as it can cause the oxidation temperatures to move closer to the 
throat tube, possibly burning the metal.

>What is really amazing is the turn down ratio; we can go from 4" W.C down 
>to
>less than 1/2" and it still works nicely.

You should be able to increase the pressure to more than 4" W.G. but the 
fuel will consume faster, so you must check the fuel consumption, closely 
against time.

>After testing with charcoal we tried wood pellets 1/4" diam. & 1" in 
>length,
>that was a big change.

The temptation to use fuel other than specified ( big wood chips, small 
blocks), straight away begins to create problems. Wood pellets DO NOT WORK 
IN A GASIFIER WITH A SEALED FUEL HOPPER.  The steam atmosphere causes the 
pellet to expand and fall apart. This then closes the interstitial spaces of 
the packed char bed, and eventually opens channels through the reduction 
zone. Grate agitation only creates disturbance in the char bed, and this 
results in a wide fluctuation of the gas quality.

>Smoke can be seen in the center of the flame for a
>very long time, until the whole system is really hot, and the flame colors
>are always reddish.

The smoke is probably CO2, and or, tar vapours. The red colour is most 
likely carbon dust , ot tar, because you do not have a cleaning system.

> The other problem with pellets is that they tend to
>block the system and gas flow is very irregular. I suppose that can be
>solved with some vibration on the grate.

Grate agitation should be available to assist at specific times during 
operation, but not for the purpose of keeping the gasifier going. In my 
experience, wood gasifiers should not need agitation if using the correct 
fuel, except on the odd occasion, just to clear an unusual pressure drop.

>The only thing we haven't worked out is how to stop the damn thing, a 
>couple
>of times we've had some nice explosions. (We've stopped to check before
>running out of fuel to see how it looked inside)
>Pleas advice on the safer way to stop for checking.

The reason you get a back-fire into the gasifier when you stop the fan, and 
open the filler lid, is that the hopper smoke coming out the lid, create a 
suction on the gas outlet pipe. Air is drawn back into the chamber under the 
grate, and that can go poof!  Then again, if you are dropping the fuel level 
to the nozzles, then air can flow through the nozzles into the gas smoke 
over the fire, and poof, again. Try closing the air inlet manifold first to 
see if it becomes more stable to refuel. If it still goes poof, then make a 
plug to shut off the gas flare pipe.

Please remember that with a very basic gasifier, there are things to 
consider in the way you operate the system for these first trials. It should 
also be pointed out, that if you hurt yourself, or any body watching, it 
will create a false impression of what to expect from a gasifier, so do not 
invite crowds of people to come and see your creation until you have learnt 
to operate it safely.

>Any questions I'll be very glad to answer, after receiving so much help how
>could I refuse.( remember I'm just a apprentice,  I can tell you how I
>copied it, but how it works,  only Mr. Williams and god know )

I have not had the pleasure of meeting this other gasifier authority, but no 
doubt the time will come (:-)

Hope this helps.
Doug Williams,
Fluidyne Gasification.