Refractory Technology MCQs

Chemical Engineering Objective Questions

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8. Carborundum used for making crucibles for melting non-ferrous metals is chemically

A. Silicon carbide

B. Silicon nitride

C. Crystalline magnesia

D. Zirconium sulphate

9. Thermal conductivity of refractory bricks

A. Increases with decrease in porosity

B. Decreases with decreases in porosity

C. Is independent of its porosity and is maximum for insulating bricks

D. Increases with the amount of air entrapped in pores

10. 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

11. Fireclay refractories

A. Are not resistant to the action of basic slags

B. Combine with salts (e.g. chlorides sulphates etc.) & bases (e.g. lime, magnesia etc.) forming fusible aluminates silicates etc

C. Shrink during firing

D. All of the above

12. Zirconia refractory

A. Does not react with basic slags

B. Is produced from baddeleyite

C. Can not be used as an insulator

D. Has poor electrical conductivity at high temperature

13. Because of its very high refractoriness of the order of __________ °C, silicon carbide refractories are used in zinc smelting furnace, muffle furnace and for supporting the wares in tunnel kilns.

14. Pyrometric cone equivalent (PCE) value (Segar cone) of 'superduty refractories' is more than 33 which corresponds to a temperature of __________ °C.

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