Predicting the slagging potential of co-fired coal with sewage sludge and wood biomass

► A numerical coal slagging index has been modified to predict co-firing. ► The modified slagging index (MSI) has been tested on coal with 20% biomass. ► MSI predictions are consistent with experimental data on co-firing. ► K, Ti and Fe play a major role in predicting the overall ash slagging behaviour.