Abstract The association of mineral matter with organic matter is extremely important for coal utilization process such as pf coal combustion. With the development of advanced analytical instruments such as QEMSCAN, it is now possible to measure directly the mineral matter–organic matter association on a particle-by-particle basis. The mineral matter and mineral–organic associations of a suite of fourteen CCSD coal bank coals (as pf) have been determined by QEMSCAN. An interface program was developed to make QEMSCAN data compatible with the CCSEM-based ash formation model developed previously in CCSD. Size and chemistry of flyash was predicted by a partial coalescence sub-model for included mineral grains, and a fragmentation sub-model for excluded mineral grains, respectively. The size and chemistry of predicted flyash was estimated on a particle-by-particle basis, and was used to rank the ash effect on heat transfer reduction for all the CCSD coals using the CCSEM-based model, in which coal property, furnace geometry and operational conditions have been taken into account. Other applications and further developments of the technique are also outlined.