[Gasification] a proposed mobile gasifer concept

[Daniel Chisholm]

On Mon, 2007-19-11 at 16:16 -0600, Bob Stuart wrote:
> It sounds fine to me.  Maybe the occasional flares can be a point of  
> celebration, like loud pipes.

You are _such_ a redneck!  Now I am really miffed - why didn't _I_ think
of that???!? ;-)

> If the charcoal preparation becomes a wasteful process, I'd try for a  
> system that would automatically feed wood chips.  The fuel spec would  
> be fairly tight for average dryness (blending permitted) and maximum  
> size, but fairly easy to meet with a chipper, seasoning shed, and an  
> experienced operator.

I don't think it is reasonable to expect the user to be involved in any
fuel processing at all (OK of course for experimenters).  We don't
home-refine crude oil.  We (putting on our users hat) shouldn't have to
home-prep our solid fuel.  Fuels processing (liquid or solid) is almost
certainly more efficiently done on a larger scale.

And there's no need for charcoal prep to be wasteful at all.  If you
have a use for the volatiles, they are not wasted.  If you burn the
"easy" 75% volatiles part of hog fuel ($3/MMBTU), and put it to good use
(e.g. steam generation at a district heating plant), you are not wasting
any of the volatiles, you are using them to replace heavy fuel oil
($9/MMBTU), or light fuel oil ($17/MMBTU) or natural gas ($10/MMBTU).
You're already saving money during your char-production phase.

The remaining char is much more difficult to burn fully.  But if you
have a market for the char you don't have to - so you can save money by
not needing to design your boiler for high char burnout.  Just burn off
the volatiles, capture the char, grind it (quite a low energy operation
compared to grinding wood), package and then sell it.

> It seems to me that when we think about liquid or gaseous fuels, we  
> assume a refined product.  It is probably time to think of standards  
> for refined solid fuel of several grades, and plants dedicated to  
> producing them.  Wood pellets are a start, and widely available.   
> Would they work on a mobile gasifier?

The biggest problem with wood pellets is that they are so desirable,
that their price is so high as to be nearly uncompetitive.  Where I live
(a forestry province!) wood pellets sell for $225-$250 per tonne, which
$12-$13/MMbtu.  This is not a whole lot cheaper than fuel oil(!!).

I think it is fair to contemplate designing systems that use
well-spec'd, "refined" solid fuels, be they biomass or char.  I don't
complain about the fact that my gasoline powered car is unable to burn
vegetable oil, waste lube oil, furnace oil or wood.  Or that my propane
grill doesn't burn butane, natural gas, naptha or gasoline.  Likewise, a
char-dust gasifier can only be reasonably expected to burn the spec'd
fuel.  There is no need for small gasifiers to be fuel-flexible - they
can in fact be extremely picky, and their designs made practical as a
result.


-- 
- Daniel
Fredericton, NB  Canada