the effect of binder pitch quinoline insolubles content - Coke Oven ...

BINDER PITCH QI CONTENT – ALUMINIUM ANODE
450 – 600
600 - 900
900 - 1200
132
Coking – Formation and growth
of mesophase leading to the
transition from a plastic to a
solid binder matrix. The binder
coke forms “bridges” between
the filler particles. Release of the
major amount of non-coking
volatiles.
Post coking – Release of heavy
cracked volatiles, methane, and
hydrogen. Annealing of tensions
in the coked structure
Crystalline re-orientation and
growth of the binder carbon and
possibly the lowest calcined
filler coke.
The formation and growth of mesophase in the binder pitch has a
strong influence on anode properties [2]. If mesophase can grow and
coalesce unhindered, the resulting binder coke will be well ordered
with an anisotropic “flow” optical texture when examined under a
microscope using cross-polarised light. Anisotropic binder cokes
tend to reduce the electrical resistivity and reactivity of the anode;
however the anode strength can also be reduced due to cleavage
between the layers in the structure [2]. Disruption of mesophase
development results in a more disordered or isotropic coke structure
that imparts greater strength to the anode. The influence of normal
QI on this carbonization process, and hence anode properties,
has been studied extensively. A feature of these studies, however is
wide disagreement on what the effect is of varying amounts of
normal QI on binder pitch performance.
A review of the literature shows that the following have been
attributed to the presence of normal QI in pitch:
Wetting of the filler particles: There is disagreement as to whether
normal QI improves the coating of petroleum coke particles by pitch
[3,4], makes it worse [5,6] or has no influence [7].