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  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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