[Stoves] Aside on coconut husk - in TLUDs

[Paul S. Anderson]

Quoting AJH <list at sylva.icuklive.co.uk>:

> On Wed, 11 Apr 2007 19:51:51 -0500, Paul S. Anderson wrote:
>
>> If the dry coconut husks yield a smokey traditional fire, that is of little
>> consequence for the TLUD gasifier usage of husks.  TLUDs as gasifiers are
>> constructed to produce smoke and then SEPARATELY burn the smoke.  More smoke
>> yields more flame.
>
> [Andrew wrote:]  If this is a difficult fuel then there must be 
> reasons it doesn't
> readily burn the smoke in a [traditional] secondary flame, have you 
> any especial
> reason to think the TLUD secondary combustion is better than any other
secondary combustion chambers?  One of the things about TLUD is that it
> provides a hot, high calorific value offgas with minimal dilution by
> N2 or CO2. Now if, for any reason, this *dry* husk material needs a
> much higher primary air then a consequence of this will be the cv of
> the offgas will be lower but maybe hotter, Low cv burners need a lot
> more mixing and recycling of heat.

The key to the success of the smoke burning by the TLUDs with any fuel
(including the difficult ones like coconut husks) is in exactly what you wrote
above (but as a question):  "...the TLUD secondary combustion is better than
any other secondary combustion chambers"

Furthermore, it is not EXACTLY the specific chamber, but it is because ONLY
gases are present in the secondary combustion chamber of a true 
gasifier. There is no solid raw fuel there to get into the way of good 
mixing of the
secondary air with whatever combustible gases are present.  We can make better
and better chambers to improve the mixing and insulation (prevent heat loss in
the TLUD structure), but the underlying fact remains:

Of any and all of the existing designs for COMBUSTION in cookstoves 
using solid
biomass fuels, ONLY the gasifiers allow for the combustion of the 
created gases
totally separate from where the combustible gases are created.  Every 
other type
of stove (even the quasi-gasifiers or semi-gasifiers) have a 
significant amount
of secondary combustion down in the area where the raw fuel is located. 
Period.  Full-stop.  Absolutely true.  It is in the definition that I 
use of
what is a true gasifier.

Therefore, yes, coconut husks can be consumed with minimal emissions in true
gasifiers.  We will need to refine the actual physical pieces of the stove to
get the very best combustion that is possible.  But I have already done a very
successful burn of coconut husks in Mozambique about 3 or 4 years ago in a
large TLUD made there.  It was a prototype and had some awkward operational
issues that need to be addressed and can certainly be solved, but the
combustion was classic TLUD performance with no observable smoke at the start,
during, and end of the full batch cycle.

Yes, I have at least one photo that I will look for and make available.

Why did I stop that project?
1.  That trip to Mozambique was at an end.
2.  Coconuts are truly "tropical".  For example, in Florida the palms produce
coconuts only in the southern third of that state, and not much coconut
production even there.  So I have only small samples of husks in my fuels
collection in Illinois.
3.  Close to zero funding except from my own pension and savings, and 
there are
many other aspects of gasifiers and fuels to which I must give my 
attention and
resources.

Thankfully, there is now one serious effort underway about using coconut husks
and shells and fronds in TLUD gasifiers for cookstoves.  Results will be
reported when success (or failure) can be documented and replicated with
confidence (maybe in 2 months, maybe sooner).

Meanwhile, if you live in far southern Florida or have relatives/friends there
who are willing to collect a significant amount of dry coconuts and ship them
to me at no cost to me, I would love to have them here in Illinois.  (  227
South Orr Drive, Normal, IL 61761  )

Paul



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