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

doug.williams Doug.Williams at orcon.net.nz
Fri Jul 19 22:12:27 CDT 2013


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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