Refractory Technology

71. High alumina refractories are used in the

1. Dome of blast furnace stoves
2. Electric arc furnace roof
3. Glass melting furnaces
4. All (A), (B) and (C)

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72. High alumina refractory compared to fireclay bricks have

1. Less load bearing capacity
2. Less resistance to slag attack
3. Low refractoriness
4. High resistance to thermal shock and creep

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73. High density refractory bricks have lower

1. Spalling resistance
2. Thermal conductivity
3. Fusion point
4. Slag penetration resistance

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74. High porosity refractory bricks have

1. Poor resistance to the penetration of molten slag, metal & flue gases
2. Poor heat conductivity & low strength
3. Better thermal spalling resistance
4. All (A), (B) and (C)

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75. High refractoriness of refractory bricks means, that it has a

1. High spalling resistance
2. Low spalling resistance
3. High resistance to fusion
4. Low porosity

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76. High thermal conductivity of a refractory material is not important, when it is to be used in the

1. Coke oven regenerators
2. Muffle furnace
3. Blast furnace
4. Recuperators

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77. Highest melting (m.p = 3070°C) oxide refractory is

1. Alumina
2. Thoria
3. Zirconia
4. Magnesia

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78. Hollow refractory bricks are made by

1. Slip casting
2. Hand moulding
3. pressing/machine moulding
4. Extrusion

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79. Hot blast main (carrying air at 1000°C) in blast furnace are lined with _________ bricks.

1. Silica
2. Fireclay
3. Magnesite
4. Zirconia

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80. Hot face insulating linings of high purity alumina fused mullite are used, where

1. Very high temperatures are involved
2. Highly reducing conditions are involved
3. Presence of iron or silica is harmful
4. All (A), (B) and (C)

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