[Gasification] Gasification Air/Fuel Ratio

[Ken Boak]

Greg, Brennan and List,

If gasifiers can be considered as thermally driven matter transformers,
especially when you detatch the oxidisation zone and supply heat from
another source, would it be correct to assume that gas could be generated
solely by passing hot nitrogen through the fuel,  assuming that the nitrogen
was hot enough?  Whilst the drying and torrefaction of woody biomass will
occur a temperatures below  300 C,  some of the tar reduction and thermal
cracking processes require higher temperatures.

However, in order to reach the high temperatures needed within the reduction
zone  - say 1000 C, it is much easier to achieve these temperatures by the
sacrificial combustion of a layer of the biomass in an atmosphere that
contains some oxygen.

Is oxygen liberated from the fuel in sufficient quantities to supply the
combustion zone, or will oxygen always have to be supplied from atmospheric
air?


regards,


Ken

----- Original Message ----- 
From: "Greg Manning" <a31ford at inetlink.ca>
To: "A Gasification" <gasification at listserv.repp.org>; "Brennan R Henderson"
<climbers at telus.net>
Sent: Wednesday, November 15, 2006 3:54 AM
Subject: Re: [Gasification] Gasification Air/Fuel Ratio


>
> Greetings Brennan and list members.
>
> Brennan, some light on interpretation, page 24 I do not know the tables,
but
> the pages in the PDF document are in volume as a ratio. if it was mass,
the
> amount of air consumed would be astronomical.
>
> Any gasifier (up/down or fluid) has a very small output, compared to the
> same physical size equipment dealing only in combustion.
>
> Gasifiers are NOT combustors, rather, they are thermally driven matter
> reformers. One can substitute an external source of heat, in lue of the
> small portion of combustion within a gasifier, and run the gasifier in
this
> mode, however, the amount of external heat needed to produce the reaction,
> out weighs the result.
>
> Air is needed for partial combustion, leaving a pipeable gas that can be
> used "un-coupled" (loose coupled) from the gasifier (referring to close
> coupled dual combustors, vs. gasifiers). after the initial combustion for
> the required heat to drive the reaction, air is NOT required (or wanted)
at
> later stages of gasification (thermally driven chemical reduction).
>
> Do NOT compare combustor levels of air needed, to gasifiers, this will
> confuse even me.......(not that I know much, in the first place).
>
> Your best answers would be to ask Mr. Tom Reed, as I believe they are his
> articles in the first place.
>
> Greg Manning,
> Brandon, Manitoba, Canada
>