The development of the modern injection lances has greatly improved the combustion of coal within the tuyere and raceway.  For coals with a volatile matter greater than 10% there is only small differences between the combustibility of coals and it is likely that these difference can accommodated by adjustment of BF operating conditions.   The impact of unburnt char on BF permeability is not that significant compared to the impact of coke fines and changes to slag viscosity around the raceway. 

The full understanding of the all the physical and chemical mechanisms that influence the devolatilisation, fragmentation and char burnout under the intense conditions within the tuyere and raceway is not yet known.