[Gasification] CO2 Recycling

[Daniel Chisholm]

On Wed, 2007-17-10 at 08:39 +0200, Zietsman, Rex wrote:
> Dan, Ken, Gf and List,
> 
> Somewhere along the line, I think there is a misconception. The way I
> understand plasmas is that in the direct line/area/volume of the plasma,
> the temperature reaches 6000C and more. Now, that does not mean that all
> of the gas has to be heated to that temperature, it is necessary only to
> get some of the gas up to that that temperature so that after
> recombining, the cracking reactions will take place. 

Hi Rex, thanks!  Perhaps I have misunderstood things after all - your
description (heating only a small fraction of the flow to a plasma
state, then allowing this to mix with the majority of the flow) makes
much more sense, both for waste incineration purposes as well as for
producer gas detarring.  My understanding of "heat the whole stream to a
plasma" was a continued stumbling block to me accepting the viability of
the process.

> Also, if I recall correctly, ionization of droplets ala mist
> precipitators causes the droplets to absorb electrical charge sufficient

What a cute idea!

> for them to deviate in a downstream magnetic field. If the initial
> ionization energy is stepped up, sufficient energy could be absorbed by
> the tar droplets (I am assuming preferentially to the gas) for them to
> heat up beyond the cracking temperature. This will break them down. 

OK, so what you are describing is (from a black-box, stand-back
perspective) electrically superheating the gas stream for the purpose of
thermal tar destruction, and at the same time also perhaps charging
remaining particles of tar or dust for electrostatic or magnetic
separation.

I would think that for engine-grade gas it would make sense to provide
most of the process heat from waste heat recovery plus partial
oxidation, at which point little or no electrical superheating would be
needed.

I don't understand the cost effectiveness of pursuing low-N2 higher-BTU
gas for engine use....?  Perhaps if the gas was wanted as a chemical
feedstock, it might make sense to go to the effort of mostly eliminating
the N2, and substantially decreasing the CO2, that this sort of process
could deliver.  But for straight engine use, I am not seeing why this is
needed...?


> Am I missing something here?

(No, I don't think _you're_ the one who was missing anything!!! ;-)


-- 
- Daniel
Fredericton, NB  Canada