QUO VADIS

1. ? QUO VADIS Combustion Working Group

2. During the last 6 years, the Combustion Working Group has continued, under the co-convenorship of Ed Lester and myself, with the work initiated in 1986 (we apologize for not being able to arrange a Round Robin Exercise for this year). Both classic and modern approaches were tried. Some of them worked, others did not: • The 1997 exercise explored the possibility of a very simplified scheme, where only three types of char MATERIAL were considered: Thick walled, thin walled and unfused. The results were very poor • The optical texture (iso/aniso) was superimposed to that scheme in the 1998 exercise. Slightly improved results, but still unacceptable • Two exercises were carried out in 1999, both making use of a more complex classification scheme where the morphology of the whole PARTICLE was taken into account (seven classes): one of the exercises was a conventional point counting analysis on a char block, which yielded quite satisfactory results, given the increased complexity of the system • The other was an exercise of char classification based on 140 microscopy images stored in a CD and sent to participants • CD exercises were also carried out in the years 2000 (190 images) and 2001 (170 images). And this is what came out of it... See results See results See results See results

3. Vol. % THIN 100.0 THICK UNFUSED 80.0 60.0 40.0 20.0 0.0 1 2 3 4 5 6 7 8 9 10 11 12 Participant THIN WALLED: 0.0 - 64.0 % THICK WALLED: 19.8 - 92.4 % UNFUSED: 3.0 - 17.4 % Definitely not too good results

4. Freq. % 100 Participant Freq. % 80 40 60 30 40 20 20 10 0 20 30 10 Vol. % Unfused 0 50 30 10 Vol. % THIN WALLED: 7.1 - 48.0 % THICK WALLED: 41.2 – 78.9 % UNFUSED: 10.0 – 28.0 % Better, better... ANISOTROPIC CHAR: 36.2 –81.6% WE EVEN GOT MODAL VALUES !!! Freq. % Participant 50 40 30 Vol. % 20 10 0 80 40 60 Vol. % Thin Vol. % Thick Freq. % 40 35 30 25 Participant 20 15 10 5 0 40 60 80 Vol. % Aniso

5. Much better! Most results lie in the band of statistical uncertainty of the point-counting analysis.

6. The idea was to benefit from the expertise acquired in previous exercises. A total of 500 images were distributed in the three CD exercises. About a half of these were recognized as belonging to a given char type by the majority of participants. Those images were compiled in a CD atlas of char morphologies. Image analysis was carried out on these images in order to accurately measure the morphological parameters relevant to the classification scheme, namely Porosity Wall Breadth distribution Radial Mass distribution and The CD atlas is available on request to the Editor. At present, I´m sure that no less than half a dozen copies have been sold, and this is the modest contribution of the Combustion Working Group to the wealth and glory of the ICCP Next, please

7. Area in red Area in red+grey POROSITY= (=69%) HOW DO WE MEASURE POROSITY? “FILL” COMMAND

8. HOW DO WE MEASURE WALL THICKNESSES? DISTANCE MAP MASKED COPY The length distribution of wall thicknesses is given by the Grey Level histogram of this image SKELETONIZE

9. Area in inner core Total area RMD= HOW DO WE MEASURE “CENOSPHERICITY”? Distance map Fill Thresholding Masked copy

10. One thing to be remarked is that the CD approach proved to be much more attractive than the conventional Round Robin exercises on char blocks. In fact, after the report of the first CD exercise, a lot of new members were recruited ... Participants 8 new participants

11. although these at least managed to maintain (or slightly improve) their standards of excellence. 2001 (Veterans) ...but this didn´t help much. Please notice how every year we got lower percentages of images with a given rate of agreement. It seems that the CD atlas did not prove to be of great help as a learning tool for new members of the WG, nor it did as a feedback for the veterans Percentage of agreement Percentage of images

12. So, we´re not learning much: a) Because we only come to an agreement in the most obvious structures, and dubious cases are never included in the atlas b) Because we simply don´t have a look at the atlas

13. 14 25 M.DENSE CENO´s NETWORK mixed dense 12 mixed porous 20 Inertoid 10 Cenospheres 15 INERTOID 8 Network Particles Particles M.POROUS 6 10 4 5 2 0 0 10 40 60 Porosity (%) Radial Mass Distribution (%) THICK THIN 30 THICK The image analysis data suggest precisely the opposite: many of the structures agreed fall well beyond the theoretical limits imposed to each char type THIN 25 20 15 10 5 0 50 m Length percentage < 3 m

14. I would personally adhere to that possibility...

15. This was a summary of the activities carried out since 1997. So, the WG is now...fifteen!!! years old. I think it is about time to decide what do we want to do with it...in the next fifteen. May I give my humble opinion about what the next step could be? Please, do No, not really

16. Anyone there? Yes? In that case, let me tell you what I wittnessed in last six years in&out the Working Group: 1.- Outside, in the real world, the number of published papers in the last ten years where char petrography data were reported was hardly a dozen. In the late 80´s there was a clear interest in char petrography and a need of a standardized analytical technique for char analysis. Both vanished. Even if we manage to develop now an applicable classification system, we won´t probably revitalize the subject. 2.- Indoors: I boast that I belong to one of the most active WG´s of the ICCP. We are quite a lot of participants, and everyone made generous and continuing contributions to the WG. And this is so despite the fact that most participants, novice or veterans, only run a char analysis once a year: the Round Robin Exercise. 3.- So, we only do char petrography very seldom. And we´re developing a char classification system for the others...but the others have gone. Next, please

17. 4.- The Inertinite in Combustion WG was closed a couple of years ago, and it was closed for good. An atlas is being developed, based on the work done by participants, which will be a compilation of the pyrolysis behaviour of the different inertinites and at different ranks...and that´s it. There was an objective and it was fulfilled. We are more or less in the same situation. The atlas only needs some rearrangements in order to make it less tedious to navigate. But it´s good stuff, and contains all the expertise acquired by the WG. We can make it bigger, but we cannot make it much better. I sincerely think that this route should be closed. 5.- There is room for a decent paper about the current classification system and how the manual results compare with the image analysis data (er...unfortunately, they don´t match too nicely) Next, please

18. 6.- We should concentrate on real problems regarding coal combustion (of course from the point of view of char petrography). Very little is known about the combustion behaviour of coal blends, and we have ample expertise in a most powerful tool for the study of such systems (tell them, Angeles). We can trace back the origin of an unburnt coal particle in a complex flyash, at that´s MAGIC (and I don´t mean critical, just amazing) to people working in a power plant. I bet we would get an excellent agreement in the analysis of a coal blend flyash, not the percentage of ceno´s or nets but the percentages of char coming from sub-bituminous, anthracite and two or three sub-groups in the bituminous range. I would like to encourage you to try that. 7.- If you want to continue with the improvement of the Char Classification Scheme, my advice is to concentrate the efforts. If we change the scheme every couple of years, we´ll never get to a robust system (the 1997-1998 system was not a bad one, but we abandoned it when it was starting to work). The working group needs a leader, not merely a convenor. Next, please

19. And this is my modest view of the Combustion WG. I beg your pardon if you disliked any of my opinions. But please remember that they are just that: opinions. I still wish to be an active member of the WG, under the convenorship of Ed Lester and/or whoever else, but at this stage I don´t feel enough enthusiastic to continue as a convenor. I wish to thank you very much for the confidence you deposited in me for the commitment, and also for your attention to this presentation (with my apologies for not being able to attend the meeting and give it myself). I look forward to seeing you all in Utrecht All the best, Diego Last advice: If you didn´t like the speech, then just...KILL THE MESSENGER