[Gasification] Making char vs producer gas

[Tom Miles]

Peter,

No harm done with this question. In most gasifiers it is a trade-off between
char yield and gas quantity and quality. Normally the higher the gas quality
the lower the char yield. Compare a typical downdraft gasifier making engine
quality gas at less than 5% char, more typically about 2%, to a downdraft
making 25% or more char and a tarry gas. The engine quality gas needs
cooling and dry filtering with a final polishing step for light oils if
necessary. The tarry gas needs scrubbing with liquid and filtering before
use in an engine. There are costs associated with handling the black soup
from a scrubber that are not incurred with dry cleaning. If you have aunique
design that makes a high quality gaas an dproduces variable quantiites of
char then the choice is which carbon is has the higher net value, so it is a
cost/revenue decision rather than just a cost issue. 

Tom       

-----Original Message-----
From: Gasification [mailto:gasification-bounces at lists.bioenergylists.org] On
Behalf Of Peter Davies
Sent: Tuesday, March 11, 2014 3:31 PM
To: gasification at lists.bioenergylists.org
Subject: Re: [Gasification] Making char vs producer gas

David, on a number of occasions you have been personally invited to view our
systems here in Australia, including public demonstrations. When you finally
do I hope you will stop putting out statements like this below. 
One of the biggest barriers to commercialisation we have found is the
seemingly willful ignorance of consultants and engineers with vested
interest in the field who point to statements like this to justify their
positions.

As Tom Reed will also tell you gas quality can increase with deliberate
co-production of char and in our own case is a system design choice that is
adjustable depending on project needs. It can in no way be descibed as
"De-tuning" the gasifier, it is rather "Optimising for co-products". 
Planned char outputs can have a number of uses including as a processed
fuel, so are not efficiency losses in such a system.

Kind regards,
Peter


On 3/12/2014 8:03 AM, David Coote wrote:
> 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.

--
Peter Davies
Director
ID Gasifiers Pty Ltd
Delegate River, Victoria
Australia
Ph: 0402 845 295


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