[Gasification] Two Tars and Two Stoves

[Greg and April]

In response, to " TWO KINDS OF TAR ", I am left with the feeling, that we 
only have two choices, and neither one is suitable for use as a vehicle 
fuel.

OTOH, I am also left wondering about any tar produced in the region between 
500* - 700* C.

Is anything produced, and is it useful ( particularly as a vehicle fuel )?


Greg H.


----- Original Message ----- 
From: "Thomas Reed" <tombreed at comcast.net>
To: "Discussion of biomass cooking stoves" <stoves at listserv.repp.org>; "
Subject: [Gasification] Two Tars and Two Stoves


>
> TWO KINDS OF "TAR":
> In examining mass spectra of "tars" produced in various gasifiers and
> pyrolysers I noticed that there were two vastly different classes:
> Those produce below 500C; and those produced above 700C.
>
> Pyrolysis of biomass and coal at temperatures below ~500 C produces
> compounds clearly related to the polymers that make up biomass
> (Cellulose, hemicellulose and lignin) or coal (the aromatics and
> aliphatics left from decaying lignin 500 M years ago in the great coal
> swamps). Once upon a time "coal oil", made by low temperature pyrolysis
> of coal, was an accepted substitute for kerosene.  However the low
> temperature pyrolysis of biomass produces hundreds of compounds, only a
> few of which (methanol, acetic acid, acetone...) had a practical use.
>
> Gasification and pyrolysis above 700 C on the other hand produces the
> same same slate of phenols and aromatics, whether starting from biomass,
> coal or gas in ethylene crackers, composed of benzene, naphthalene,
> anthracene etc. (chicken-wire compounds) and phenols.  These compounds
> all have a high temperature stability not possessed by the oxygenates,
> which crack to CO and H1 above ~500 C, reducing the volatile level by a
> facto of 10 - 100.