1. Examination of reactivity for metallurgical coke using micro-CT analysis
David Jenkins, Merrick Mahoney, Alex Deev, Jason Donnelly, Rowan Davidson, Sherry Mayo, Richard Sakurovs
CSIRO Australia
NIER, University of Newcastle, Australia

2. Talk outline Background on coke Project objectives
Reaction and imaging
Results and conclusions
Acknowledgements

3. What is coke? made from crushed (metallurgical/coking) coal
coal heated in absence of air
undergoes transformation:
coal -> plastic phase -> coke
particles soften
gas evolves, bubbles form, grow and coalesce
re-solidifies to form a strong, hard substance
used for reduction of iron ore in an ironmaking blast furnace
part of the integrated steelmaking process

4. source: World Steel Association (worldsteel.org)
(2016)

5. Source: Resources and Energy Quarterly, June 2017 (www. industry. gov
Source: Resources and Energy Quarterly, June 2017 (

6. Our approach – building understanding through examination of fundamental processes
How does a packed bed of coal transform to a solidified porous composite to form the final coke?
blends of coal from different sources
Coal chemistry and structure  plastic layer behaviour
Formation of structures – plastic layer behaviour
Weak / strong structures incl. reactivity

7. Objectives
Develop a detailed understanding of the effect of coke reaction with carbon dioxide upon the microstructure of coke.
Focus on (industry standard) test for reactivity.
Examine the selective degradation/reaction of the coke components.
Link the change in coke microstructure due to reaction with change in coke strength through:
finite element modelling,
pore structure analysis and
measurement of strength.

8. Coke microstructure | David Jenkins
samples
coke samples:
5 different cokes
CSR lumps
6 samples from each coke
react 3 samples at 1100oC
react 3 samples at 900oC
Coke microstructure | David Jenkins

9. 1100oC
30 mins
reaction time
CSIRO Labs
Clayton
CO2
4 laps

10. stressing of samples
CSIRO Labs
Clayton
5th lap

11. 3D image acquisition high resolution 3D microstructure imaging:
Imaging and Medical Beamline
Australian Synchrotron
3D CT scan of coke CSR lumps
~9mm voxel size
~15 mins/scan
~10Gb image per sample
>150 images

12. coke reaction component
carried out by CSIRO Mineral Resources, Clayton lab
testing/ validation phase before main experiment
2 furnaces
1100oC
900oC
CO2 flowrate 3.5 l/min
protocol:
20 mins cool zone
30 mins reaction zone
10 mins cool zone
remove

13. Coal/coke properties

14. C187 particle 1 @ 1100oC 26. 4% mass loss (c. f
C187 particle 1100oC 26.4% mass loss (c.f. CRI of 22 in standard test)
(1) registered the image of the unreacted particle with the image of the particle after 30, 60, 90, 120 minutes of reaction
(2) then subtracted reacted particle image from the original

15. unreacted particle

16. reacted mins
difference 0 -> 30

17. reacted mins
difference 0 -> 60

18. reacted mins
difference 0 -> 90

19. reacted mins
difference 0 -> 120

21. C188 particle 1 @ 1100oC 45. 5% mass loss (c. f
C188 particle 1100oC 45.5% mass loss (c.f. CRI of 41 in standard test)
(1) registered the image of the unreacted particle with the image of the particle after 30, 60, 90, 120 minutes of reaction
(2) then subtracted reacted particle image from the original

22. unreacted particle

23. reacted mins
difference 0 -> 30

24. reacted mins
difference 0 -> 60

25. reacted mins
difference 0 -> 90

26. reacted mins
difference 0 -> 120

28. Why the difference? Porosity? Seems to be the case that
lumps with higher porosity have flat reaction profiles
lumps with lower porosity have steep reaction profiles
Indication that gas transport through pores is limiting factor

29. Overall porosity change

30. Why the difference? Porosity? limitation due to resolution of image
Seems to be the case that
lumps with higher porosity have flat reaction profiles
lumps with lower porosity have steep reaction profiles
Indication that gas transport through pores is limiting factor
limitation due to resolution of image
smallest pores ~10-20mm across
some porosity “missed”
Limited study – only 5 cokes

31. 3D stress analysis Solve elasticity problem for loaded particle
Effectively “squeezing” particle
3D microstructure used as input
Very large computation
Calculate distribution of von Mises stress
Compare high stress in outer shell (~2mm) with core of particle

34. What causes difference in inert reactivity?
Mineral content?
Inert pore structure?
2017 ACARP proposal:
“Imaging gas penetration inside coals and cokes at nanoscale and determining its influence on coke reactivity”
Sherry Mayo (CSIRO) & Merrick Mahoney (NIER)

35. Discussion
high resolution micro-CT imaging of progressively reacted coke
shows
selective reactivity of IMDC and RMDC
different reaction behaviour for different inerts
shows transport (pore diffusion limited) control of reaction important
indications that pore diffusion limited by “micro” and “macro” pores
indication of higher stress in outer shell due to transport limited reaction
Next step to image gas penetration into inerts

36. Acknowledgements Funding from ACARP
Coal/coke from various coal companies
Merit-based access to IMBL/Australian Synchrotron
Peter Tyson, CSIRO – high performance computing support
Hannah Lomas & Gareth Penny (Newcastle), Karryn Warren & Lukas Koval (CSIRO) – sample preparation and imaging