[Gasification] Sodium in fuels (coconut husks)

[Paul S. Anderson]

Doug,

WOW!!!  Your knowledge AGAIN is so evident and appreciated.  I am sending this
reply (including your comments) to the Stoves ListServ where there are several
(even many) who will appreciate your inputs.  (including Alexis Belonio,
Michael Trevor, Walter Bradley at Baylor Univ, myself, and others who have
coconuts-as-fuel interests.)

I am quite happy with your suggestion that the coconut husks might best be
limited to updraft gasifiers and for thermal uses only.  Now all we need to do
is to tweak the TLUDs and other updraft units to make useful devices.

Thanks again,

Paul
-- 
Paul S. Anderson, Ph.D., Geography professor - Emeritus
Telephone:  USA-309-452-7072 (residence and office)
Internet site:  www.ilstu.edu/~psanders
For my gasifier stoves info, go to:
http://bioenergylists.org/contributors#Paul_Anderson


Quoting "doug.williams" <Doug.Williams at orcon.net.nz>:

>
> Hi Paul,
>
> You ask:
>> What is it about sodium that makes biomass difficult to burn or gasify?
>
> Where sodium is present in biomass, it combines with potassium usually to
> form a eutectic flux, that assists ash fusion, and clinker formation.
>
>> What biomass has high sodium and should be avoided?  Specifically, does
>> coconut
>> husk (coir) have high sodium?
>
> The worst case fuel I have encountered was coppice willow, which has a lot
> of tip wood and leaves, and I advise to avoid trying to gasify the fines
> from these types of stick fuel crops. We found that you could drop the fines
> out of the throw from the harvester, by adjusting the distance to the
> collection trailer.
>
> Coconut  is not a problem in this regard, but does have a high siliceous
> ash content, which can cause problems if allowed to stay in the packed char
> bed. You should also know that husks from coconut have a very large air to
> surface ratio, and difficult to create a high temperature oxidation zone.
> The shell however, is a better fuel, but you still need to tune the gasifier
> for these fuels. When we tested coconut shell and husk, the best result was
> to smash up the shell into about 20mm bits with husk attached. It's not my
> favourite fuel!
>
>> Is there a way to gasify high sodium fuels, such as by reaching a
>> sufficiently
>> high temperature?
>
> If you had only these fuels to work with, possibly the best way is a low
> temperature pyrolysis gas application for process heat, or you could go
> updraft, but still only for heat generation.  High temperature would not get
> you into a tar free gas making system.
>
>> The late, great Gus Johanssen of South Africa told me once of husk
>> drying sheds
>> at some project on islands in the Indian Ocean, and implied that the
>> husks were
>> quite acceptable as fuels in his downdraft gasifiers.
>
> This would have been in the Seychelles back in the 1980's, and they were
> gasifying the husk and shell together. I'm sure I have a report from that
> time, but it was at a time when tar was plaguing all who tried to make gas.
> If I get a chance, I will dig it out some info for posting tomorrow.
> Hope this helps,
> Doug Williams,
> Fluidyne.
>
>
>
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