[Gasification] Charcoal Gasifier No 2.

[Thomas Reed]

Dear All:

If the world put a proper evaluation on carbon dioxide sequestration and 
non-CO2 enhancing fuels, charcoal gasifiers would be economically 
attractive -PROVIDED you used the byproduct gases also for green heat/power.

TOM REED       BEF

Daniel Chisholm wrote:
> On Tue, 2007-24-07 at 21:43 +1200, doug.williams wrote:
>   
>> ...charcoal gasifiers ...
>>     
>
> Thanks Doug for starting discussion on charcoal gasifiers.
>
> I have a question for you and the list, and perhaps a suggestion to make
> too.  (I've had a number of ideas that I've been meaning to throw out to
> the list for comments and suggestions, and you've just forced my hand on
> one of them.  A good thing too, or I might never haven gotten a around
> to it!)
>
> The question: are charcoal gasifiers largely free of tar production
> problems?  (I suspect that the answer is "yes", but I want to make sure
> I'm not missing something...)
>
> If so, then here is my suggestion: for engine grade gas applications,
> shouldn't we consider using charcoal as the fuel source?  I.e. instead
> of solving the tar problem directly, take the easy way out and and solve
> it by avoiding it?
>
> Basically what I am suggesting is that for biomass-fuelled engines we
> adopt the model successfully used for petroleum-fuelled engines, i.e.
> you process your raw feedstock (crude oil, biomass) at a few large
> central facilities (refineries, charcoal plants), producing a
> high-quality dense convenient and easy to transport fuel (gasoline,
> processed charcoal), that can be effectively used on a small scale
> end-user engine.
>
> Gasoline and charcoal have several advantages over their raw precursors:
>
> - storage and handling (gasoline is easy to pump; charcoal can be
> processed into a variety of consistent handle-able forms, e.g. dust,
> pellets, briquettes)
>
> - volumetric energy density (both charcoal and gasoline are on the order
> of 1kg per litre
>
> - mass energy density (charcoal is ~14KBTU/lb, gasoline ~18KBTU/lb; both
> are much higher than bone-dry raw biomass at ~9KBTU/lb)
>
> - efficient and clean burning.  Burning crude oil or raw biomass cleanly
> and completely is difficult on a small scale (i.e. anything smaller than
> a chemical plant).  Burning gasoline or charcoal cleanly completely and
> effectively is challenging enough, but it is a much more achievable
> engineering problem.
>
> - pollutant precursors can be removed at the refining stage (e.g. remove
> most of the sulfur and ash from crude oil; remove the tar-forming
> volatiles from biomass)
>
>
> I will suggest that an effective way to manufacture charcoal dust would
> be at a handful of relatively large central plants that have a use for
> the high quality heat that is available from the volatiles during the
> charcoal production process - e.g. steam plants for heating, or power
> plants, or sawmill or pulp mill steam plants.  Consider wood waste and
> hog fuel for now, because they are some of the kindest biomass fuels
> (low ash, sulfur, etc).  It is quite straightforward for a large simple
> furnace to burn the volatiles away, and capture the char.  In fact, it
> can be a bit of a challenge to retain and fully consume the fixed
> carbon.  Might as well turn this into a virtue - consume the volatiles
> to produce heat, and capture the char for use as a higher value fuel
> outside of the thermal plant.
>
> I think it is appropriate to consider paying a higher amount per MMBTU
> for a processed charcoal fuel for engine use, since this permits a
> simpler design of an engine gas gasifier.  Gasifying (to engine grade)
> an engineered fuel feed is challenging enough; designing an all-in-one
> chemical processing plant (which is what a raw biomass--> engine gas
> plant it) is perhaps not the best choice to make.  A simpler gasifier
> design ought to mean reduced capital and maintenance cost, and smaller
> size and weight.  Like many other tradeoffs, this could well be worth
> making, even if it means paying (say) $5/MMBTU for a processed charcoal
> fuel that is derived from a fuel feed stock costing only $3/MMBTU.
>
>
>
>
>
>   

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