The use of permeable refractory linings for enhancement of the thermal performance of a high-temperature furnace

A mathematical model is developed to simulate the replacement of part of the conventional refractory lining in a continuously-operated gas-fired furnace by a permeable ceramic section. This involved a sub-model of the flow and heat transfer through the porous section of the lining linked together with another sub-model of heat transfer in the furnace chamber. The overall model was applied to predict the thermal performance of the furnace when heating steel billets to a nominal discharge temperature of 1250 degrees C. The effects of varying the emissivity, size, orientation and location of the permeable section were studied and, in addition, simulations were undertaken for a range of furnace thermal inputs and billet throughputs. The model predicts that the rate of radiative heat transfer to the steel billets can be substantially increased with consequent improvements in both furnace throughput and efficiency. Therefore, it appears that installing permeable sections in a conventional refractory lining may provide significantly improved furnace performance.