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.Management Sciences
Category: Refractory Technology
Carbon refractories_____________________?
A. Do not burn/oxidise, when exposed to air on heating
B. Are not attacked by slags, as they are not wetted by melts
C. Do not resist temperature fluctuations
D. Have extremely low thermal & electrical conductivities
Which is the stable form of silica upto 1470°C ?
A. Quartz
B. Cristobalite
C. Tridymite
D. None of these
Chrome magnesite bricks are_________________?
A. Acidic in nature
B. Neutral in nature
C. Having higher RUL than silica bricks
D. Made by mixing 30% Chromite and 70% Periclase
Graphite or carbon refractories______________________?
A. Exhibit wetting characteristics
B. Should be used in neutral or reducing atmosphere
C. Exhibit high shrinkage on thermal treatment
D. Are not resistant to corrosion by slag
Refractoriness under load (RUL) is the most important property for the refractory bricks_________________?
A. At the hearth bottom of the furnace on which stock is placed
B. Used for furnace insulation
C. Used in the roof of the furnace
D. None of these
Bauxite calcining rotary kilns are lined with ________________ bricks?
A. Fireclay
B. Carbon
C. 85% alumina
D. Corundum
In chemical process equipments, the conical bottom heads used, usually has an apex angle of____________________?
A. 20°
B. 40°
C. 60°
D. 80°
Silica refractories are not used in _________________?
A. Coke oven walls
B. Beehive coke ovens
C. Dome and upper portion of B.F. stoves
D. Open hearth furnace roof
With increase in the density of silica refractories, its_______________?
A. Resistance to slag attack increases
B. Spalling resistance reduces
C. Both A. and B.
D. Neither A. nor B.
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