HEAT-TRANSFER FROM A MOLTEN PHASE TO AN IMMERSED COAL PARTICLE DURINGDEVOLATILIZATION

In seuerul developmental and commercial processes, coal purticles come into direct contuct with a high-temperature molten phase. These proce sses include molten carbonate coal gasification and bath smelting for the production of iron. Recently, real-time X-ray fluoroscopic images have been published that show volatile matter evolving rapidly from co al particles immersed in molten phases, displacing the surrounding mel t andproducing a periodic cycle offormation, rise, and detachment of g as cavities. Thepresent work makes use of these obseruations to develo p a model of heat transferfrom the melt to particles undergoing gas ev olution. The model is developed for the general case and applied to pr edict melt-particle heat transfer coefficients under conditions releua nt to bath smelting processes. The model shows that the presence of th e gas film can actually increase the overall heat transfer rate under certain conditions.