[Gasification] CO2 recycling

[Daniel Chisholm]

On Mon, 2007-15-10 at 19:41 -0400, gfwhell at aol.com wrote:
>  Dan,
> ?Lets visualize we have an enclosed retort containing biomass. it is
> heated by the exhaust of a fully loaded IC engine and is glowing a
> dull red.

OK.  So if the exhaust temp is 600C, the pyrolysis gas coming out will
be a bit less than that.

I think that you ought to be able to succeed in driving off the majority
of the volatiles in the biomass in this way (i.e. you'll get about 75%
of your biomass coming out as pyrolysis gas, and you'll be leaving
behind about 25% char)

> The pyrolization products from this retort are piped to a Faraday cage
> and added to a stream of hot CO2

How hot is the CO2, how much is there, and if it is hotter than ~600C
(engine exhaust temp), how is it heated beyond 600C?

>  together with super heated steam.

OK.  Same questions as with the CO2...

> A plasma is created as these gases mix within this plasma, they?
> disassociate and recombine.

OK.  To raise the temperature of this ~600C gas to 6000C takes a *lot*
of energy (see my previous email to Ken Boak for my guesstimate).

> What do we have?
> A clean combustable gas suitable for running an IC Engine. Did I
> mention nitrogen?

I agree, what you describe could produce a good nitrogen-free medium-BTU
engine grade gas, on par or even better than oxygen-blown syngas.

My point is that as near as I can guesstimate, for each BTU of this
good-quality gas that you produce, you will consume several BTUs of
electrical energy in raising the 600C or 1200C products up to a 6000C
plasma.  In order to be promising (i.e. to turn an energy profit) a
process should be using less than 0.1BTU of electricity for each BTU
worth of syngas that it produces.


For specialized high-value uses (e.g. making rocket fuel, incinerating
medical or municipal waste, etc), there's nothing economically wrong
with a process running at an electrical energy deficit.

But for primary fuel production, or processing, or upgrading, you must
absolutely be turning a "profit" (I put "profit" in quotes to mean that
the energy, economics, environmental etc. tradeoffs have been weighted
appropriately).


-- 
- Daniel
Fredericton, NB  Canada