The coke yield and by product yield from any cokemaking process is a function primarily of the
coals from which they are produced and the carbonising conditions. The figure below shows that
about 64% of the as received coal is used in the blast furnace (BF).
As shown by this figure below there are two factors that influence the yield of blast furnace (BF)
coke:
- Yield of dry wharf coke, this depends mostly on the volatile matter of the feed coal and can
be estimated from -
- Yield of lumped BF - After the wharf coke is stabilised (usually by dropping from a fixed
height) it is sized to remove the coke breeze. The coke breeze is used mainly as a fuel in the
sinter plant. The yield of lumped BF coke after sizing is dependent on the fission formation
during the coking process and coke morphology .
Low rank, high volatile coking coals yield predominately a very porous highly reactive isotropic
carbon with only a small proportion of fine textured anisotropic domains. Thus, the proportion of
edge carbon remains high and hence the reactivity is also high. The situation improves gradually
as the rank increases and in blends with prime coking coal, the hydrogen donor capacity is high
enough to effect some improvement in coke texture relative to that expected from some lower rank
components in a blend if there were no fluid phase interactions. There are no significant
interactions between higher rank, low volatile, coals with prime coking coals in a blend with respect
to texture development. The former contribute to wall thickness and strength, as well as the coke
yield and can also decrease the pore size if the volatile yield is greater than about 12% and the
there is some fluidity.
