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  • Question
  • Natural silica


  • Options
  • A. mainly contains quartz.
  • B. is not stable at high temperature.
  • C. transforms to other allotropic forms i.e tridymite and cristoballite involving very high volume changes.
  • D. all (a), (b) and (c).

  • Correct Answer
  • all (a), (b) and (c). 


  • Refractory Technology problems


    Search Results


    • 1. The highest melting pure oxide (m.p. > 3000°C)is

    • Options
    • A. thoria
    • B. alumina
    • C. beryllia
    • D. zirconia
    • Discuss
    • 2. __________ is not a single oxiderefractory.

    • Options
    • A. Zirconia
    • B. Silicon carbide
    • C. Magnesia
    • D. None of these
    • Discuss
    • 3. Fusion temperature of pure silica (SiO2) is __________ °C.

    • Options
    • A. 1350
    • B. 1715
    • C. 2570
    • D. 2800
    • Discuss
    • 4. Fireclay bricks is not used for lining the

    • Options
    • A. cupola.
    • B. gas producer.
    • C. bottom of hot metal mixer.
    • D. roof of open hearth furnace.
    • Discuss
    • 5. With increase in the density of silica refractories, its

    • Options
    • A. resistance to slag attack increases.
    • B. spalling resistance reduces.
    • C. both (a) and (b).
    • D. neither (a) nor (b).
    • Discuss
    • 6. Bottom of basic open hearth furnace are constructed of

    • Options
    • A. dead burnt magnesite ramming mass.
    • B. porous fireclay bricks.
    • C. semi-silica bricks.
    • D. silicon carbide bricks.
    • Discuss
    • 7. Refractories used in/for __________ should have low thermal conductivity.

    • Options
    • A. coke ovens
    • B. insulation
    • C. regenerators
    • D. muffle furnaces
    • Discuss
    • 8. Magnesite refractories are generally not used in the

    • Options
    • A. electric furnace walls.
    • B. steel melting furnace.
    • C. open hearth furnace.
    • D. burning zone of cement kilns.
    • Discuss
    • 9. Carborundum used for making crucibles for melting non-ferrous metals is chemically

    • Options
    • A. silicon carbide
    • B. silicon nitride
    • C. crystalline magnesia
    • D. zirconium sulphate
    • Discuss
    • 10. Refractories subjected to alternate cycles of heating & cooling are liable to loose their resistance to

    • Options
    • A. thermal spalling
    • B. slag attack
    • C. fusion under load
    • D. CO attack
    • Discuss


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