Dear Rex
In principle, the way to increase the Hydrogen content of "Wood Gas" is to
add external heat to the gasifier inputs, and to reduce the "input heat
loads".
Actions that accomplish these goals would be :
1: Dry the wood.
2: Preheat the wood.
3: Preheat the air.
4: Add superheated steam to the air
Best wishes,
Kevin
----- Original Message -----
From: "Rex Zietsman" <[email protected]>
To: <[email protected]>
Sent: Friday, December 20, 2013 3:32 AM
Subject: Re: [Gasification] raising H2 concentration in
downdraftgasification
Hi All,
The deafening silence on this post is quite interesting. At the very least
I
would have thought that someone would have suggested adding steam to the
reduction zone. What about a charcoal gasifier with steam addition?
Any comments on a 1.6MW/2MW thermal gasifier?
Kind regards
Rex
-----Original Message-----
From: Rex Zietsman [mailto:[email protected]]
Sent: 16 December 2013 09:57 AM
Subject: raising H2 concentration in downdraft gasification
Hi All,
We are looking at a system that will hydrotreat bio oils from pyrolysis,
catalytic cracking and vegetable oil. For this we need in the region of
30kg
hydrogen/ton oil. At small scale ie 1 ton oil/hour, this works out at, you
guessed it, 30kg of hydrogen/hour. As this is a small amount in the
overall
scheme of things, we are looking at gasifying wood chips and to recover
the
hydrogen using pressure swing absorption. What I would like to know is
whether we can increase the H2 concentration in syngas by tweaking the
gasifier. Clearly we can look at the water gas shift reaction but, as the
syngas has to be cooled, washed, pressurised and reheated, it is quite an
additional investment for the scale we are looking at. If we could simply
up
the H2 content, we would go straight from washing to PSA. Residual gas
would
be piped to a diesel generator where CO and the like will be combusted
prior
to exhaust to atmosphere.
For easy mental arithmetic, let us assume a 33% H2 concentration in dry
syngas. 30kg/hour of H2 is 15kmol/hour or 15/0.33 = 45kmol/hour of syngas.
A
kmol of gas has a volume of 22.4 Nm3. So, to get 30kg/hour requires 22.4 x
45 = 1000 Nm3 syngas/hour (mental arithmetic here, go with the flow).
Assuming an 80% PSA recovery this means that we need 1250Nm3/hour of
syngas.
Not a bad sized downdraft gasifier! Assuming 6MJ/Nm3, this is around a 2MW
thermal unit. If we can get the H2 concentration up to say 40%, then the
syngas requirement would be 37.5kmol/hour or 37.5/45 x 1250 = roughly 80%
of
1250 or roughly 1000 Nm3 syngas/hour. This reduces the size of gasifier to
1.6MW thermal and more sensible in size.
---
This email is free from viruses and malware because avast! Antivirus
protection is active.
http://www.avast.com
_______________________________________________
Gasification mailing list
to Send a Message to the list, use the email address
[email protected]
to UNSUBSCRIBE or Change your List Settings use the web page
http://lists.bioenergylists.org/mailman/listinfo/gasification_lists.bioenergylists.org
for more Gasifiers, News and Information see our web site:
http://gasifiers.bioenergylists.org/
_______________________________________________
Gasification mailing list
to Send a Message to the list, use the email address
[email protected]
to UNSUBSCRIBE or Change your List Settings use the web page
http://lists.bioenergylists.org/mailman/listinfo/gasification_lists.bioenergylists.org
for more Gasifiers, News and Information see our web site:
http://gasifiers.bioenergylists.org/
