[Gasification] Plastic bonded wood fuel (was oil from plastic)

Sat Jul 20 07:30:44 CDT 2013

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 <Doug.Williams at orcon.net.nz>
To: gasification at bioenergylists.org 
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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