[Stoves] Gas analysis. was Re: More on flaming pyrolysis

[Bruno M.]

At 20:34 3/06/2007, Frank wrote:

> > >    Tom Reed wished for a gas 
> analyzer.  Maybe 8-10 years ago I reported on this
> > >list (I think) on tests I had made with some borrowed (from the University
> > >of Denver) expensive hydrocarbon gas monitoring apparatus.  The (well
> > >described by others) 1) very low carbon dioxide, 2) lots of CO and 3) zero
> > >oxygen above the pyrolysis front (but still in the charcoal and below the
> > >secondary air port) were easy to see.
>
>I am wondering how hydrogen is measured? I noticed the GC-TCD  only goes down
>to about 4% (on a good day) and wonder if that is low enough for our purposes?
>And are there other ways more in the 'wet chemistry' style that can be used?
>For example water coming from the stack collected in moisture traps and
>subtracted from the fuel moisture?
>
>And does anyone know what column type and temperature setting are best for
>this purpose? I can find out but thought if someone is using one their
>experience would be helpful. I have available an old HP-GC I might be able to
>set up for testing purposes. Its been about 30 years since the last time I
>packed columns and used one -and things have changed.
>
>Thanks
>Frank
>www.compostlab.com              www.greenrooflab.com
>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Hi Frank,

I'm no stoves specialist,
besides being a mastercomposter in my spare time, I do quality control
in different labs at a big Chem company for a living.
So i use GC's alot, and I believe next numbers could be useful to you:

For analyses in the ppm range there are other 
methods, this will do for 0.1% to 100% v/v range.
A standard FID detector can't do it, and standard 
H2 gas as a carrier is also useless.

For detection of  H2, O2, N2 and CO, CH4 use external standards ( mixture?),
argon as carrier gas, 2 detectors in series, 
first a thermal conductivity detector (TCD) at 170°C
for the H2, O2, N2 detection; then lead the gas 
stream trough a Methanizer ( at 370°C)
and then in to a FID ( at 250°C)  to detect the 
CO and CH4 ( the methanizer converts CO to CH4 ).

You need the methanizer and the second detector only if you need CH4 and CO
to measure in smaller concentrations like < 1000 ppm.

Packed column, ss 1/8" 2à3 meter, filled with molecular sieve 5Å, 80 mesh

Samples could be carried from the stoves setup to 
the GC by means of steel or glass cylinders,
rubber bladders, or nowadays in mylar foil bags.

Sample holders must have some pressure, if to low,
blow in some Argon, or heat them in a hot air oven at 60°C.
inject 1 or 2 ml of the gas sample , starting 
temp  60°C than up to 150°C if you can program 
this, and after a couple of minutes again up to 290 °C.
After analysis you can turn off the TCD, but you 
may like to keep the oven very hot for a few hours if
there were higher boiling components in your sample.
Mind you that CO2 is not measured here but can 
stick on your column, also to be removed by prolonged heating.

This is not a specific stoves GC analysis but maybe useful.

;-)
Grts
Bruno M.
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