Re: GAS-L: maximum pressure

["Hauserman" <hauserman@corpcomm.net>]

Dear Bram, et al. -

    Re. Maximum pressure for biomass gasification:  There are no
"fundamental" barriers to gasifying biomass at 50 bar, or any other
pressure.  In fact, it's been done, quite a few times - under rather
expensive R&D projects. Certainly there are possible chemical advantages.
And high pressures would permit much smaller reactor volumes for the same
production rates, which would contribute to reduced capital costs.  However,
this appears to be rather decisively off-set by a whole array of practical
mechanical and economic constraints.  The etermal problem of  feeding light
fluffy, bridging, non-free-flowing stuff thru lock hoppers into a gas-tight
vessel becomes far more formidable as pressure increases. The same goes for
ash removal. Then, although the reaction vessels, gas conditioning steps and
piping may be a lot smaller, they are also  a lot more costly, per capacity.
Though gases take up less space at high pressures, solids (feed and ash) do
not. So these components are just as big but must be designed for higher
pressures. Estimating these higher costs is even prohibitive, since few or
none of these components are standard equipment, and will generally have to
be designed/specified from scratch for any conceivable project. (I know  a
few of you out there have done good work in this area: Tom Miles?  Michael
Antal? Can you add anything more positive to this?)  My own hands-on in
pressurized gasification  has only been with more-or-less-free-flowing
coal, which is enough of a PinA to handle at high pressures, even 10 bar,
and appears to be  potentially economic - if at all - only on huge scales.
So -- until atmospheric biomass gasification becomes generally accepted
commercially, probably in some future generation, I would not recommend
worrying about pressurized processes --  appealing tho they may be to
design.  But on the other hand -- Yeah, we need a backlog of good ideas
whose times haven't come.

              Bill Hauserman


----- Original Message -----
From: Drift, A. van der <vanderdrift@ecn.nl>
To: <gasification@crest.org>
Sent: Monday, January 28, 2002 2:05 AM
Subject: GAS-L: maximum pressure


> Dear members,
>
> Can anyone give me arguments why biomass gasification is or is not
possible
> at 50 bar? I know that the composition changes, tar concentration
increases
> and the inert gas consumption is high, but are there any fundamental
> barriers?
>
> Greetings,
>
> Bram van der Drift
> ECN Biomass
> POBox 1
> NL  1755 ZG Petten, the Netherlands
> tel: (31) 224-564515
> fax: (31) 224-568487
> Email: vanderdrift@ecn.nl
>
>
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