Refractory Technology
Hot face insulating linings of high purity alumina fused mullite are used, where

Very high temperatures are involved
Highly reducing conditions are involved
All of these
Presence of iron or silica is harmful

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Refractory Technology
Thermal conductivity of refractory bricks

Is independent of its porosity and is maximum for insulating bricks
Increases with the amount of air entrapped in pores
Decreases with decreases in porosity
Increases with decrease in porosity

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