I guess I'm sorry I opened my big mouth. When dealing with Plastics - i should
have been more specific. the most prevelent plastic in my own household/shop
waste stream (Plastic being used in a commonly understood term and not the
technical State-of-being sense) would be HDPE (2) which is near paraffin in
nature (wax like) it's binding qualities with rough sawdust make it such that
very little is used as a percent by weight or volume and it's use prescribed
only for ( Dried-semi dried) wood where natural Lignins are insufficient to
bind into pellets (about the size of a AAA battery cut in half), The HDPE is
shredded fine and mixed before extrusion and the heat from extrusion is what
binds the whole (Usually no additional heating of the compacting chamber is
needed). (this is a very similar albeit not heated process used to create
"Plastic Wood" Deckboards and Plastic/Wood Mouldings - however much less
plastic is needed to simply bind it for non
structural purposes).
Using dried wood saw dust -I may well have gotten differing results then might
be found with wood at a higher moisture content
Since I've not gotten to Gasifying for engine (syngas) uses yet - I only know
that forced air induction into the stove/boiler chamber gives me a very clean
(no visible smoke) burn and ash fines show no characteristics of plastic
residue and the fuel shows very little disintegration (dust) in augering. (
the pelletizing was done on a 2 week test with a borrowed 10kw "oil extruder"
and no unusually wear was noted, first batch was done with heat, then heat
decreased in subsequent batches till no heat was used).
I leave the suitability for gasification to you experts (i'm usually just a
lurker/dreaming if electircal power from my waste). syngas stove
modifications may well be needed
Regards
Paul
________________________________
From: doug.williams <[email protected]>
To: [email protected]
Sent: Friday, July 19, 2013 10:12 PM
Subject: [Gasification] Plastic bonded wood fuel (was oil from plastic)
Hi Peter and Gasification
Colleagues,
This discussion revolving around waste
plastic disposal hopefully for better use than Landfill, is a carrot yet to be
bitten by those who have yet to get it's bitter taste of experience. I do refer
of course to gasification of plastics mixed with chips or other forms of
biomass, and not refinable oils as Indian researchers are demonstrating. This
is
a technology already well developed and producing commercial product in the USA
and probably other countries in the pursuit of reducing plastic
pollution.
Peter offers some interesting suggestions
on what may be possible if conventional gasification in all the ways we use it
could be utilized to render know toxic combustibles in to harmless usable
gas.
>We have successfully gasified Gycerin waste
from a biodiesel plant added to wood chip without any measured toxic emissions,
indeed it produced a higher calorific >value gas compared to straight wood
chip as it displaced the need for some of the normal air as an oxygen source
(thereby reducing dilution with the normal nitrogen >fraction as well as
releasing more H2 from the added gycerin itself) so would not anticipate any
issues with it as a binder in pellets where they were used in this way (at
>least through our system). We will have the opportunity to test this at
least in the form of briquettes after August. The combustion engineers present
for the earlier test >were all a bit red faced at the time as I recall since
they were predicting all sorts of dire things.
It is not unnatural for anyone involved with combustion to only see
problems with what they see as burning toxic material, and who isn't a bit red
faces in all honesty when you are shown to be wrong? But when we start to think
as gasifier promoters/developers/builders, that all we have to do is use
plastics etc, as a binder for other problematical biomess (not a spelling
mistake), our fantastic garden shed understanding of tradition gasification
technology is going to provide a few bitter pills for those paying for it to be
proven.
>We are going through an EPA process at the moment to have our system
"exempted" from the need for pollution permits, starting with clean wood waste
as the >benchmark but will be adding things like plastics and glycerin (along
with much more problematic organics) in due course.
This is good news, and should be a doddle for any gasification
process that creates a tar free gas using wood. My understanding of EPA
regulations however in a general sense, is that smaller gasifiers are already
exempt, but in saying that, if you are in the bigger operating size, I
doubt very much if a blanket permit would be issued. In fact with Australia
having both Federal and State Governments offering only cosmetic
support for renewable technologies, you might reconsider how your $$$ are
going to vanish faster than the time it takes to get such a permit
passed.
>The real barrier to overcome is the insistence by
the ignorant or mischievous in the environmental movement that gasification and
combustion are interchangeable >terms with similar problems. The result from
a practical point of view is the cost of the stringent emission tests required
is in the order of $25,000 per material being >included where no dioxins are
anticipated and only one targeted analysis for this is included (amongst the 20
general sample tests required) to confirm, up to $150,000 >should they
believe dioxins might be possible and this has to be repeated with all 20
samples.
That we may have a better understanding of what and why we can do
things deemed impossible by others has always been a challenge, but it is also
the reason why testing is important to those who are also trying to prove you
are correct in presenting your technologies capability. Testing is not to prove
you wrong just because it's gasification, but one might wonder if we
keep being hoisted on our own petard, if the fault must be other
than bureaucratic.
>What is amazing to us is our
perpetual researcher "competitors" in this space in Australia generally have
access to significant public grants, yet can't give a lab >certified gas
analysis from their systems only a "predicted" value based on a literature
review, mostly of course citing references where the same thing was
done...
Been there, done that, but the bottom line is that they are
not our competitors for clients with $$$, only for the funding that is
presented as research grants. Don't expect handouts from any source, and find
the right client/s to work with to obtain your testing requirements, which
returns me back to plastics and wood chip.
In the first instance, there are quite a few companies already
exploring their commercial options with plastic bonded mixes, both round puck
sizes, and extruded log style briquettes. They are being promoted by their
"developers" as boiler fuel, perfect fuel for gasifiers and all the other
potential heating applications one might think of, but in offering this license
for their fuel processing technology, it does not come with the equipment to
convert this fuel with all the certification the market place demands.
Briquettes and pucks need larger spaces relevant to their size
to get them into a gasifier, where the heat can melt their plastic
bonding at fairly low temperature. Plastic will flow and separate from the
biomass rather than form a carbonizing bond. The change to smaller particle
size and interstitial spaces then can cause plugging followed by
channeling through the bed. How these plastic flows
develop depends on the plastic mixtures, and it is possible for harder plastics
to become encased in a char insulation allowing them to drop right down into
the bed channeling, allowing release their toxic chemical mix, without
disassociation into the exiting gas stream.
Incoming fuel can just fall apart and then bridge on the
agglomerated fuel stuck to the walls, so the ability to maintain a packed char
bed without toxic emissions would be tough for any operator to guarantee. When
you add to this the large amounts of metal foils not separated of the waste
plastics, their presence and agglomeration will block grates and restrict
moving
components.
I hope the two photos attached will give you some idea of what
might be encountered if considering trials of these fuels. One shows the
incoming fuel just melting then solidifying into a bridge, and the other of a
carbonized briquette with raw plastic still encased.
Hope this may be of interest.
Doug Williams,
Fluidyne.
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