Re: can't get my gas to light!

["Graeme Williams" <graeme@powerlink.co.nz>]

Hi Joel

Your persistance deserves an answer and it should be relatively simple to
prove to yourself the cause of your erratic gas ignition.

By your using a pipe air supply with injector air holes into the fine fuel,
oxidation (or combustion to be correct), consumes the fuel in a tracking
pathway of least resistance to the top of the fuel bed.  This channelling
first produces a thick rich pyrolysis gas, then deteriorates into CO2 and
acrid smoke as the channel opens up losing contact between the gas and fuel.

This can be duplicated so it can be seen to by sticking piped air into a
similar size fuel pile out in the open.  You are experiencing the same
problem as larger early model fluidised bed gasifiers.  In your current
situation, the only suggestion I can make to keep the gas coming, is to
ensure  you have  at least 15 inches of fuel over gently inlet air, and add
a vibration to literally fluidise the bed preventing the channelling.  You
will only get dirty gas but it will burn.  Cooling the gas will result in
sticky tar filling pipes, so use it hot.

Regards
Doug Williams
Fluidyne Gasification.
http://members.nbci.com/whitools/

> Date: Thu, 15 Feb 2001 22:46:36 -0900
> To: <gasification@crest.org>
> From: "Joel Florian" <joflo@yifan.net>
> Subject: can't get my gas to light!
> Message-ID: <009601c097ec$9a133540$139570d1@bennmeh>
>
> Dear gasifiers,
>
> So far my sawdust gasifier science fair project has been a failure.  I can
> make smoke varying from wispy whitish to thick black (stinky)  I've tried
> adding secondary air in different ways.  The smoke will ignite for an
> instant and then the flame disappears.  Sometimes I even get an explosive
> flame -- but I want a nice clean torch or cooking flame. I suppose I could
> post a picture or two of my apparatus on the web if that would help you
> diagnose my problem.  I notice that most pictures I see of gasifiers have
> insulation wrapped around parts of it.  Is that to keep the temperature
high
> in the secondary combustion zone?  Does the gas need to be hot to
> ignite?Alex English mentioned flame speed vs gas speed.  I've tried
> different diameters of combustion chambers, nozzles, varying the air flow,
> etc but either I haven't gotten the right combination of air and gas or
I'm
> missing something important.  I know most of you have jobs solving the
> world's problems, but you would make one little girl's day if you could
help
> us get her demo working.
>
> Thanks,
> Joel Florian
>