There has been a gradual increase in the volume of internationally traded
thermal and coking coal, with emphasis on blending of coals rather than single
coal usage. New Zealand can take advantage of this situation, especially with
its low ash and sulphur content coals. However, there is a need to clarify the
thermal and coking behaviour of these coals as they relate to other market
players, to benefit both the consumer and supplier.
The high volatile matter contents of New Zealand coking coals are due to
their high vitrinite content, which causes them to demonstrate stronger coking
properties over a wider rank range than Gondwana coals. These same high
vitrinite levels appear to correspond with lower initial softening temperatures
than for Gondwana coals of similar rank. Preliminary results using
thermogravimetric analysis also suggest that New Zealand high volatile
bituminous coals can be used to substitute for higher rank Gondwana coals in
combustion processes.