[Gasification] Coke and Char

ktwu at itri.org.tw ktwu at itri.org.tw
Sun Dec 25 23:43:20 CST 2011

Dear Doug

Thanks for the valuable information.

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

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),

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

Happy New Year

from Taiwan

寄件者: gasification-bounces at lists.bioenergylists.org [gasification-bounces at lists.bioenergylists.org] 代表 doug.williams [Doug.Williams at orcon.net.nz]
寄件日期: 2011年12月26日 上午 02:49
收件者: Discussion of biomass pyrolysis and gasification
主旨: Re: [Gasification] Coke and Char

Hi KT,

You ask some interesting questions:

> What is difference between coke and char?

I believe the problem of identification caused by the English language. Coke is made in a retort from coal, and char is made in a retort from biomass.

 Coke from coal and char from biomass?

Others will give you a more academic answer.

And what's about soot?

I have only worked with soot made in high temperature gasification systems 12-1500>C, and these were studied in 1978 here in New Zealand by Dr J. Cousins. I wrote about these soot in 2008 for our Fluidyne Archive  www.fluidynenz.250x.com<http://www.fluidynenz.250x.com>  Scroll down the file list and you will find it 14 from the top.

> According to Franklin's research in 1950s, she mentioned that while the cokes could be graphitized by heat treatments above about 2200 deg-C, the chars could not be transformed into crystalline graphite, even at 3000 deg-C.

If I offer a comment it will be conjecture, because the current work being done on our soot and chars is new research, and not published at this time. Having said that, it was these comments that opened up the research, so may offer you a clue to follow your interest.

The soot of interest to me are those that form from volatiles in the unstable chemistry of the sealed retort, which then pass down through the upper boundary reduction zone,
then the high temperature oxidation, before passing through the reduction at 12-1500C. These are probably those seen in Dr Cousins photos. The remaining char has none of these original volatile carbons present, so no amount of heating will create a crystalline graphite.

Others can provide a qualified answer about coke from coal.

I have a couple of photos that I used  for the presentation of the "Enigma of Gasification" at the Workshop following the IEA Gasification Task Force Meeting in Christchurch in April 2011, that show one of these soot  (C57 O ) for the first time. I will try to get these up on the  Fluidyne Archive as soon as possible, and advise accordingly

Hope this may help.

Doug Williams,
Fluidyne Gasification.

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