[Gasification] Making char vs producer gas

[Peter Davies]

Hi Doug,

Thanks, yes we do have it sorted out and during our development years 
playing with early packed beds have experienced most of the things you 
observed.  I recall an awful lot of bed profiling work looking at 
particle distribution at different time and output changes to see what 
was going on. However our mature system is not low temperature and no we 
do not get torrefied chip out but rather a very high fixed carbon 
charcoal (>85%) with little if any remaining volatiles. Tested gas 
outputs show  up to 55% combustible gas high H2, slightly lower but 
roughly equivalent CO and less than 1% total CH4 and higher molecules. 
Nowadays the systems are normally started on the char bed from the 
previous run and  on larger models if this is within twelve hours of 
shutdown then engine grade gas is achieved within 2 minutes without need 
for external re-ignition of the hearth. We have proven the design 
parameters from 20kg/hr models through to 500kg/hr so far.

RE: Sydney; Yes the supplier was from Vermont. Our understanding is that 
what was installed has never run on site and is being removed. We were 
asked to come and "fix" it but we declined as we have already lost IP to 
the people involved in the past and had no desire to be further 
compromised, quite apart from the false assumption that our own systems 
were sufficiently similar that we could just "tweak It". They lurk on 
this list so given the saga is far from over and investigation 
continuing it would be unwise to say anything further other than for 
those contemplating a purchase please do your due diligence! And if 
anyone claims to be the "originator' of our tech you can safely assume 
they are lying.



On 3/14/2014 5:58 PM, Doug wrote:
> Hi Peter and Colleagues,
>
> As it happens, my work this last few months has been pretty involved around these packed beds and charcoal, so naturally I am focus on how these differing systems work.
>
> On Fri, 14 Mar 2014 09:48:15 +1100
> Peter Davies<idgasifier at gmail.com>  wrote:
>
>> Thanks Doug, given the level of prior art reinventing the wheel is an
>> occupational hazard. Yes we have observed what you describe, the point
>> of differentiation though is where we were starting on straight (dry)
>> wood chips each run rather than charcoal from the previous run.
> The key thing about all these systems is what your main need is from the process. If you were planning on running an engine, then no way do you start-up on raw fuel, as it will contaminate your gas cleaning system with tar. Process heat and charcoal however is different, unless you have a blown system.
>
>   >It became clear that substantial improvements in gas calorific value and
>> useful volume were possible that we seemed to be missing out on.
> Naturally raw fuel will always create high calorific gas, due to the pyrolysis gases tar chemistry, and no oxidizing charcoal to create the necessary exothermic heat, so you end up with a low temperature bed, higher carbon content to the char, and a rich gas to burn in a furnace.
>
>   It was
>> study of this that led to the refinements in design we now enjoy the
>> benefits of.
> As it may be of interest to others that, when you mix the phenomena of low temperature packed beds with charcoal extraction, the raw chip is only torrified, charred on the outside, raw on the inside. The low temperatures are around say, <900C without free oxygen and a reducing atmosphere, enough to char and make crude gas, as the hydrocarbon content is still locked inside. As the chip drops, the 900C gas flow sets the conditions that fix the hydrocarbons, hence the better char. If you want to improve the gas quality, because it will be low in H2 but have CO,CH4,C2H5/6 from being low temperature distillation gases released from the surface charring, you need a deeper bed to increase the contact time, BUUUT, if you do this, you begin to initiate CO reversion into soot and CO2 while the bed is above 500C Then if your char extraction rate is not quite right, you can also get H2 reversion and are back to mediocre gas.
>
> Peter has obviously sorted this out, but more than a few are chasing shadows for the wrong reason. I heard a whisper that there is a failed gasifier project in Sydney Australia, supplied from a USA manufacturer. Can anyone of our Forum members offer more comment about this project?
>
> Doug Williams,
> Fluidyne.
>
>
-- 
Peter Davies
Director
ID Gasifiers Pty Ltd
Delegate River, Victoria
Australia
Ph: 0402 845 295