Chemical Engineering MCQs

Page No. 257

Thoria is an expensive refractory material and is radioactive in nature. Thorium oxide is used in the manufacture of______________?


aSegar cones

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bMuffles for muffle furnaces

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cInsulating bricks

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dCrucibles used for melting of high purity metals

✓



Cold crushing strength of ordinary fireclay brick is about 950 kg/cm2. On exposure to a temperature of about 1500°C, its crushing strength may come down to as low as ______________ kg/cm2?


a450

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b250

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c150

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d65

✓


View Answer 65

Walls, roofs & combustion chambers of annealing furnaces are made of ______________ bricks?


aHigh duty fireclay

✓


bSilica

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cMullite

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dCarborundum

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View Answer High duty fireclay

With increasing alumina content, the fusion point of high alumina refractories__________________?


aIncreases

✓


bDecreases

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cRemain constant

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dMay increase or decrease; depends on its alumina content

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View Answer Increases

Vacuum steel degassing units are lined with__________________?


aSilica bricks

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bLow duty firebricks

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cHigh alumina bricks

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dGraphite blocks

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View Answer High alumina bricks

Chromite refractories are_____________________?


aAcidic refractory

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bNeutral refractory

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cBasic refractory

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dFired at a temperature of 600°C only

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View Answer Neutral refractory

Thoria__________________?


aHas high fusion temperature (> 3000°C) but poor resistance to thermal shock

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bHas high resistance to basic slags

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cWhich is expensive & radioactive, is used in crucibles for melting high purity metals

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dAll A., B. and C.

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View Answer All A., B. and C.

Cold crushing strength of a refractory does not depend upon its ____________________?


aShape

✓


bComposition

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cFiring temperature

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dTexture

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View Answer Shape

Which is the stable form of silica between 1470°C and the melting point 1713°C ?


aCristobalite

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bTridymite

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cQuartz

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dNone of these

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View Answer Cristobalite

Maximum safe working temperature for fireclay bricks is about __________ °C?


a1150

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b1300

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c1300

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d1550

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View Answer 1550

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