ACARP Project Number: C18043
Published: April
16
Philip Bennett, William Cash
Extended Abstract
To better understand how coal transforms into
coke requires the ability to relate the main microstructural and
microtextural features of the coke to properties of the coal. This
project aims to identify the influence of these features on coke
quality.
There are two parts to this project:
- Optical
imaging to determine the fused and unfused components of the coke
structure. Subsequent analysis of the unfused component for shape,
size and porous feature and the fused component for pore
structure;
- SEM
based mineral analysis techniques to identify changes due to
mineral phases would also lead to better understanding of the major
mineral related factors influencing coke degradation after reaction
with CO2.
Optical Imaging of Coke to Examine Coke
Strength
In this extension the image analysis techniques
developed in ACARP Project C18043 (Bennett, et al., 2012) were to
be further developed to allow the determination of the size of the
unfused material. As discussed in this report this approach was not
taken and manual identification of the unfused components was
carried out to ensure similar unfused structures were identified as
Kubota et al. (2008). The criteria used in the identification of an
unfused region was that it was a region that was mostly
inert-derived maceral component (IDMC) and had the same structure
within that region. A wide range of parameters were determine from
the identified unfused regions and remaining fused structure which
were related to coke strength, in particular coke drum
indices.
MLA Characterisation of Minerals
In order to better understand the effect of
mineral matter on coke reactivity, Mineral Liberation Analysis
(MLA) was used to categorise the minerals on the surface of a
prepared coke core. This core was then put through a reactivity rig
before having the surface of the core imaged again using an optical
microscope to observe the topology of the surface.
Recommendations
Imaging of coke to determine structural features
is not a cost effective tool for the evaluation of coke and thus
determining the value of the feed coking coal. The investment in
this project by both ACARP and ALS Coal will only be realised if
the coke structural features identified in this project can be
linked to properties of coal. While it has been demonstrated that
the fused and unfused parts of the coke structure are related to
Vitrinite and Inertinite, it is the size of the Inertite (> 95%
Inertinite) or Inertinite Dominant grains that is of most
importance to the Australian coking coal industry. ACARP Project
C24058 will examine how this may be done using CGA developed by
CSIRO.
The image analysis techniques used to determine
the strength of structures are continually evolving, mostly in the
areas of metal foams, biological cell structure and bone structure.
To assist further understanding of coke structure ALS Coal will
make available all images and software to researchers in the field
of coke structure.
The use of MLA and optical imaging of coal
assist in clarify the role the minerals are playing. The combined
understanding of the coke structure and association of minerals
with the different regions within that structure will allow
producers to be better understand what maybe influencing the coke
quality produced from their coals.
