Question is ⇒ Refractories used in/for __________ should have low thermal conductivity., Options are ⇒ (A) coke ovens, (B) insulation, (C) regenerators, (D) muffle furnaces, (E) , Leave your comments or Download question paper.

Question is ⇒ Refractories used in/for __________ should have low thermal conductivity., Options are ⇒ (A) coke ovens, (B) insulation, (C) regenerators, (D) muffle furnaces, (E) , Leave your comments or Download question paper. Previous question Next question


Q1.	Refractories used in/for __________ should have low thermal conductivity.
A.	coke ovens [Wrong Answer]
B.	insulation [Correct Answer]
C.	regenerators [Wrong Answer]
D.	muffle furnaces [Wrong Answer]
View Answer 1 -1 Explanation:- Answer : B Discuss it below : !! OOPS Login [Click here] is required to post your answer/result Help other students, write article, leave your comments

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⇒ __________ of carbon blocks in the hearth of blast furnace helps in avoiding skull formation, when it becomes cold.
High thermal conductivity
Low porosity
Non-wetting characteristics
High density

⇒ Chromite refractories are
acidic refractory.
neutral refractory.
basic refractory.
fired at a temperature of 600°C only.

⇒ Dolomite bricks have good resistance to attack by
molten steel
iron oxide
lime slag
none of these

⇒ Which is the most stable crystalline form of silica at room temperature ?
Quartz
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None of these

⇒ 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 .
450
250
150
65

⇒ Cermets are combination of ceramic and metallic materials due to which they have high strength & resistance to high temperature. Cermets are used in the
hearth of the blast furnace.
nuclear reactors, missiles & space crafts.
insulation of high temperature furnaces.
roof of electric furnaces.

⇒ Crushing strength of a refractory
increases with rise in service temperature.
decreases with rise in service temperature.
is unaffected with change in service temperature.
decreases with increase in porosity.

⇒ Dry mix hydraulic compositions of refractory aggregates with suitable bonding materials are called refractory
mortars
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10
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⇒ An indication of degree of firing in silica brick is its
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fusion point
RUL
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⇒ Thermal spalling mainly occurs during __________ of furnaces.
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⇒ Refractories subjected to alternate cycles of heating & cooling are liable to loose their resistance to
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⇒ Permeability of bricks is a measure of the
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rate at which a fluid will pass through the pores.
expansion during heating.

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⇒ Mullite is chemically represented by
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⇒ Rotary kilns meant for calcination of limestone are lined with chrome magnesite in __________ zone.
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⇒ 10 to 30% magnesite is added to chromite to produce chrome-magnesite refractories. Magnesite addition is mainly done to improve the __________ of chromite.
spalling resistance
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⇒ Rate of slag attack on refractories increases with rise in temperature due to the
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increased thermal conductivity of brick.
oxidising condition in the furnace.
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⇒ Refractoriness/fusion points of 'superduty' refractories is __________ °C.
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1630-1670
> 1730
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⇒ Tar dolomite bricks are used in the
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basic open hearth furnace
electric furnaces
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⇒ Faster rate of drying of moulded refractories results in high __________ of refractories.
green strength
voids
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finer grog size.
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coke oven regenerator.
burning zone of limestone rotary kilns.

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permanent linear change
resistance to CO attack
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45
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80
95

⇒ Silliminite (Al₂O₃.SiO₂) refractory, which is a neutral refractory, is not used in
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glass melting furnace
crucibles
gas retorts