[Gasification] Making char vs producer gas

Wed Mar 12 17:20:52 CDT 2014

David,

Most of the temperature studies have been done on pyrolysis chars rather
than gasifier chars. Gasifier char have been insufficiently characterized
for use as biochar. People tend to regard them as "high temperature chars"
and discount them compare with pyrolysis chars. In fact the gasifier chars
perform very well and probably account for the bulk of the biochar
production and use today.   

Gasifiers generate high temperatures - 800C-1200C - in the oxidation and
reduction zones but we have had discussions here about whether the char
actually sees the 800C or something more like 500C. When it comes to burning
out volatiles time is also important. Most gasifier chars that I have seen
have low volatile content and probably low labile carbon which would not
suggest breakdown different that chars of similar quality. 

It would be useful to survey commercial chars from a variety of processes.
Studies in 2008 favored high temperature gasifier chars compared with
pyrolysis chars for metal adsorption. In general I would say that or data
and knowledge of gasifier chars is incomplete. From a practical standpoint
they seem to be improving soil fertility and capturing metals. 

Tom 

-----Original Message-----
From: Gasification [mailto:gasification-bounces at lists.bioenergylists.org] On
Behalf Of David Coote
Sent: Wednesday, March 12, 2014 2:45 PM
To: gasification at lists.bioenergylists.org
Subject: Re: [Gasification] Making char vs producer gas

Thanks Tom. Much appreciated.

The other issue is the nature of the char produced. I attended a workshop on
small-scale biochar manufacturing last year. According to some of the
presentations at this workshop, a number of char manufacturing system and
operational parameters affect various material characteristics of the char
which in turn affect the utility of the char as a soil conditioner. The char
will still function as a carbon sequestration mechanism although the rate of
breakdown in the soil may also be affected by the nature of the char. As
temperature profiles during the char making process were emphasised as one
driver of char quality, again I wonder how this would affect producer gas
quality

Bye for now

David

>
>
> ------------------------------
>
> Message: 3
> Date: Tue, 11 Mar 2014 14:52:25 -0700
> From: "Tom Miles"<tmiles at trmiles.com>
> To: "'Discussion of biomass pyrolysis and gasification'"
> 	<gasification at lists.bioenergylists.org>
> Subject: Re: [Gasification] Making char vs producer gas 
> Message-ID:<006b01cf3d74$3107f720$9317e560$@trmiles.com>
> Content-Type: text/plain;	charset="us-ascii"
>
> David,
>
> Phoenix Energy in California is generating power and making biochar in 
> two installations in California at 500 kWe and 1 MWe with Ankur 
> Scientific downdraft gasifiers.  I don't know if the Ankur gasifiers 
> meet Harrie's criteria. In the Phoenix case making biochar has not 
> impacted the cost of gas cleaning. With the large number of Ankur and 
> Ankur look alikes in use around the world it is likely that char from 
> these gasifiers is increasingly being used as biochar.
> http://www.phoenixenergy.net/
> You can find presentations by Greg Stangl of Phoenix at the US Biochar 
> Initiative 2013 Symposium session on CHP and Biochar 
> http://scholarworks.umass.edu/biochar/2013/Scale/4/ You will also find 
> presentations Olivier Lepez of Biogreen Energy and Lenny Roberts who 
> seeks to install a Biogen DR gasifier and make char.
>
> The Biogreen Energy pyrolyzer was demonstrated at USBI Biochar 2010 in 
> Ames, Iowa. A unit will be installed in Utah. There are currently 
> about 5 in operation in France and Asia.
> http://www.biogreen-energy.com/
> http://www.youtube.com/watch?v=OPzcAmNZQ3g
>
> Updraft gasifiers would be suitable to making char by removing the 
> char faster than you are consuming it. In that case there is no gas 
> cleaning because updrafts are normally used for generating heat rather 
> than power. An example of updraft pyrolysis generating heat and power 
> is the Black Carbon, where Thomas Harttung uses a Stirling engine for
generating power.
> http://www.blackcarbon.dk/Contact.aspx  Other systems use ORC, like 
> the Green Machine by  Electratherm (http://electratherm.com/products/ 
> ) for the power generation. The gas is not engine quality gas. Char 
> from many commercial updraft gasifiers is already being used and sold 
> commercially as biochar.
>
> Tom
>
> -----Original Message-----
> From: Gasification 
> [mailto:gasification-bounces at lists.bioenergylists.org] On Behalf Of 
> David Coote
> Sent: Tuesday, March 11, 2014 2:04 PM
> To: gasification at lists.bioenergylists.org
> Subject: [Gasification] Making char vs producer gas
>
> I'm curious about the effects of trying to achieve the multiple 
> objectives of char production and producer gas. One combustion 
> engineer I've spoken to who has done a lot of work in gasification 
> stated that from his perspective char was a sign of an inefficient 
> gasification process. If the inefficiency is just a reduced yield of 
> producer gas then this might be OK for a particular application. But 
> if the inefficiency results in a gas that needs more filtering/volume this
may adversely affect the economics.
>
> I haven't found any mixed char and producer gas systems in operation 
> that meet Knoef's commercial criteria which makes me wonder if 
> detuning the gasification in favour of char does affect the quality of the
gas.
>
> Is anyone aware of mixed char and producer gas systems in operation 
> that meet Knoef's criteria? Perhaps a good paper that summarises the 
> producer gas characteristics over a range of char manufacturing
percentage?
>
> Thanks
>
> David
>
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