[Gasification] Coke and Char

doug.williams Doug.Williams at orcon.net.nz
Mon Dec 26 01:45:06 CST 2011

Hi again KT,

This must prove very difficult to understand:

In the Chinese language, the name of coke and char is the same, called "Jiao Tan".

This proves that there is important information lost in translation to many researchers.

In a recent paper, 

Hosokai, S., K., Norinaga, T. Kimura, M. Nakano, C.-Z. Li, and J. Hayashi, "Reforming of Volatiles from the Biomass Pyrolysis over Charcoal in a Sequence  of Coke Deposition and Steam Gasification of Coke," Energy Fuels, 25, 5387-5393 (2011), 

I haven't read this paper.

the authors said "tar compounds are converted to coke in the micropores of the char" (see p. 5390). It is really confused for me.

To me, the term coke as applied to pyrolysis gas from biomass, refers to the tars that cook and dry out in the absence of oxygen. The moisture has gone leaving only the carbons which are porous. We see it in gasifiers in packed carbon beds that are not moving, or areas that allow leakage of the pyrolysis gases to by-pass the oxidation zones.

As the paper refers to steam gasification, one might expect to see coke form in the microspores of the char, as there is a lot of carbon molecules swapping places, and this endothermic reaction probably helps to "freeze" the coke in the char, instead of converting it to gas. Having said that, there are many possible explanations, and it would be necessary to see exactly how these tests were done.

Happy New Year

Yes, a New Year is waiting for us, and our World is an unhappy place for many. Celebrate as you can, and hope our differences draw us together, rather than push us apart.

Doug Williams.

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