5. The following data refers to wall of an industrial furnace: Temperature of gases in the furnace = 1700C Temperature of air outside the furnace = 35C Combined convective and radiative heat transfer coefficient of the furnace gases = $50 W/mK. Heat transfer coefficient of surrounding air = 10 W/m.K. The inner wall of the furnace is made of refractory bricks [k=0.28 (1+0.000833T) W/m.C], 250 mm thick and it is followed by diatomaceous brick layer. [k=0.113 (1+0.000206T) W/m.C]. Calculate the thickness of diatomaceous brick layer, so the heat loss to surrounding air should not exceed 900 W/m. Research and give examples of industrial furnaces used in metal industries and their impact to the society and how to mitigate it.