[Gasification] Low and high temp gasifiers

[Big Daddy]

It has more to do with complete oxidation/reduction, and in my opinion,
surface area of the feedstock. 

You'll find that at 1,200 C+, CO2 is almost non-existent, because of its
near-complete conversion to CO. That means ~10% of the typical CO2 (a
non-combustible dilution) is no longer in the entrained gas flow.
Additionally, if you spray H2O in the form of steam into the reaction zone,
you'll "crack" that steam at high temps, which also has the added
side-effect of lowering nitrogen levels in the gas flow -- also a
non-combustible.

Charcoal gasification is best for this "cracking" effect, as pure carbon
burns hotter with few impurities, and more consistency. There are, however,
less BTU's (energy) in pyrolyzed biomass, than in typical dried biomass.

There is no free lunch for high-temperature gasification. It all depends on
which aspect of the "holistic lifecycle" is most important. 

Troy

-----Original Message-----
From: Gasification [mailto:gasification-bounces at lists.bioenergylists.org] On
Behalf Of Gao Pronove
Sent: Sunday, September 14, 2014 7:27 PM
To: gasification at lists.bioenergylists.org
Subject: [Gasification] Low and high temp gasifiers

There seems to be a split between low temp gasifiers (700 C and below) and
high temp (1,000 C and above). The high temp group claims to have cleaner
gas because they "burn" off most of the hydro carbons while the low temp
leave a lot of tar in the gas. Is this the common view?

Thanks
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