Updraft and Stratified Downdraft Gasifier Tests

Updraft and Stratified Downdraft Gasifier Tests
Brennan Henderson, Canada, January 2, 2007

Select image to enlarge.
These first three photos are of the gasifier operating in bottom-lit updraft mode. It should be called the gas-o-tar 5000. There was a lot of tar with a very luminous flare. In one updraft mode gasifier test, 33 lbs of fir pellets (3.5% m.c. w.b.) were consumed in 31 minutes, while supplying 18 scfm of gasification air. I can only feed the gasifier in batches right now. I built the gasifier with 12" 150psi 12 bolt flanges at each end so that I can have the option to run with compressed air in the future.

These five photos are of the gasifier running in stratified downdraft mode. There was no tar or condensate dripping out of the bottom of the flare as in the updraft mode and the intensity of the flare was very reactive to any changes in supplied air flow. The first time I tried the gasifier in downdraft mode there was some channeling with the pellets and the air almost reached the grate on one side only. The stainless steel sleeve of the gasifier warped and the 1/4" thick wall of the outer pipe started to glow cherry red. The second time I tested it, I kept shaking and tapping the gasifier (I have no grate shaker or agitator yet) and this seemed to help. Early in the run the flare was fairly luminous and I was supplying 18 scfm of air with excursions to 10 and 32 scfm. There was a lot of glowing particulates and sparks in the flare. (I don't have a cyclone yet) Near the end of the test the flare became very blue, almost white. I don't have any firm wood consumption for these tests because I had to stop partway through the first run and added more wood later. I also don't have a riser sleeve for the cyclonic combustor yet, but it seemed to work alright without it for now, after holding the tiger torch in the combustor for 30 seconds or so, the flare would keep itself lit.


Grate mechanism

What type of grate agitation mechanism was adopted in down draft gasifier?
toolman911965 replied on December 10, 2009 - 3:30pm Permalink

Do you have a diagram of how your system is set up. I am building one from an old water heater tank for the outside with an insert which will be heavier to serve as the wood chamber. Your system looks pretty effective and I am trying to build an outdoor boiler system. you can email me at with any information. Thank You very much for any assistance you may offer.

Brennan Henderson replied on December 13, 2009 - 9:52am Permalink
Agitator and diagram

In regards to the grate agitator... The project has been put on hold and no agitator has been added. If anyone has any questions about the gasifier please email me at cirruspower at gmail.com


Practical Application: