Wall-slagging is a serious problem faced by many furnace operators. It reduces heat-transfer to furnace walls, and consequently furnace efficiency. At Callide B power station in Queensland, Australia, the problem was exacerbated by high-iron coals, which tend to form slag easily, and it drove a combined experimental and computational study into the causes of slag build-up. Using details of the flow pattern leading to slag formation obtained from numerical modelling, operators proposed a range of possible modifications. One proposal was to reduce near-wall temperatures by introducing an air-curtain along one of the affected walls; the air-curtain modification could be evaluated by means of a computer model to predict the effect on near-wall gas temperatures and particle-wall impacts. This modification, having shown initial promise, was subsequently implemented and a series of measurements were taken of gas temperature and velocity. Comparison of these measurements with model predictions helped to explain the air-curtain＇s effect on slag formation, and it also aided model validation.