Requisites of refractory material or essential requirements of good refractory:
a. It should be able to withstand high temperature. The appropriate refractory is chosen to withstand chemical attack of slag, fuel ashes, and the reaction products at different temperature in the furnace.
b. It should be chemically inert to slag, fuel ashes, other reactant and product in the furnace.
c. It should be able to withstand abrading action of furnace change and presence of load.
d. The structure of the refractory should not change at operating temperature. Such changes would result in cracking, splitting, pitting and flaking of the furnace.
e. It should be able to withstand sudden change of temperature. Generally it happens during the introductions of cold charge or sudden rush of cold air in empty furnace.
f. It should be impervious to materials present in the furnace.