chemical engineering refractory technology Mcqs
151. Chemically, mullite refractories is____________________?
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A. ZrSO4

B. Al2O3

C. ThO2

D. 3Al2O3.2SiO2
152. Insulating refractories should have_______________?
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A. High porosity

B. Low thermal conductivity

C. Both A. and B.

D. Neither A. not B.

153. Use of higher percentage of lime for bonding silica bricks, reduces their__________________?
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A. Strength

B. Abrasion resistance

C. Both A. & B.

D. Neither A. nor B.

154. Si percentage in silica refractories used in the walls of coke oven is about______________________?
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A. 95

B. 45

C. 80

D. 60

155. Porosity is induced in insulating refractories by adding________________?
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A. Ammonium chloride/sulphate

B. Powdered naphthalene

C. Calcium phosphate

D. All A., B. and C.
156. Which of the following is not an acidic refractory?
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A. Magnesia bricks

B. Silica bricks

C. Fireclay bricks

D. Bauxite bricks

157. Rotary kilns meant for calcination of limestone are lined with chrome magnesite in ______________ zone?
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A. Burning

B. All the above

C. Cooling

D. Preheating

158. Rate of slag attack on refractories increases with rise in temperature due to the___________________?
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A. Decreased viscosity of slag

B. Oxidising condition in the furnace

C. Increased thermal conductivity of brick

D. None of these

159. Silicon carbide refractories are used in the _____________?
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A. All A., B. and C.

B. Ceramic recuperators

C. Muffle furnace

D. Zinc smelting furnace

160. Grog__________________?
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A. Contains both alumina and silica

B. Is crushed firebrick

C. Is a non-plastic material

D. All A., B. and C.
161. Basic bricks are not made of ___________________?
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A. Forsterite

B. Fireclay

C. Chromite

D. Magnesite

162. Resistance to slag attack of a refractory _____________________?
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A. Decreases, if defective joints & cracks exist in the refractory

B. Decreases at higher temperature

C. All A., B. and C.

D. Depends on the nature of slag & refractory

163. Cold crushing strength of refractories depends upon its_________________?
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A. Texture

B. Composition

C. Firing temperature

D. All A., B. and C.
164. Most Cermets, which normally have high thermal conductivity and high thermal shock resistance, comprises of ceramic & metallic components of ______________ percent respectively?
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A. 80 and 20

B. 50 and 50

C. 60 and 40

D. 20 and 80

165. Mixing of ground refractory material and water is done in a ______________ mill?
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A. Pug

B. Ball

C. Tube

D. Rod

166. Magnesite refractories are used for the construction of those furnaces, which are________________?
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A. Not required to resist the corrosive action of basic slag

B. Not subjected to fluctuation in temperature

C. Used for raising & maintaining high temperature

D. Both B. and C.
167. ____________ of carbon blocks in the hearth of blast furnace helps in avoiding skull formation, when it becomes cold?
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A. High density

B. Non-wetting characteristics

C. Low porosity

D. High thermal conductivity

168. Natural silica___________________?
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A. Transforms to other allotropic forms i.e. Tridymite and Cristobalite involving very high

B. ume changes

C. All A., B. and C.

D. Mainly contains quartz

E. Is not stable at high temperature

169. Spalling resistance of a refractory cannot be increased by ____________________?
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A. Increasing its porosity

B. Decreasing its thermal co-efficient of expansion

C. Using a coarser grog during its manufacture

D. Making it denser
170. Maximum apparent porosity of magnesite bricks is about _____________ percent?
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A. 8

B. 24

C. 58

D. 44

171. Which one expands on heating ?
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A. Silica bricks

B. Fireclay bricks

C. Both A. & B.

D. Neither A. nor B.

172. Which is not an alumino-silicate refractory ?
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A. Mullite bricks

B. Fireclay bricks

C. High alumina bricks

D. Tar dolomite bricks
173. Maximum shrinkage in volume occurring during burning/firing of dried refractories may be as high as ______________ percent?
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A. 10

B. 15

C. 20

D. 30
174. Fireclay bricks are never used in the______________?
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A. Coke oven walls

B. Beehive oven

C. Lead blast furnace

D. Zinc roaster

175. Lower part of hot metal mixer are lined with _____________ bricks?
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A. Superduty fireclay

B. Silica

C. High alumina

D. Carborundum
176. In panel test for spalling resistance, the average face temperature of panel assembly is maintained at ______________ C for 24 hours?
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A. 2000

B. 700

C. 1600

D. 1000

177. Pick out the wrong statement ?
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A. For reducing spalling tendency, the refractory should be well fired and its porosity should be

B. Refractories used in muffle furnace should have low thermal conductivity

C. e

D. Refractoriness under load (RUL) of a refractory is always less than its refractoriness

E. The electrical resistivity of refractories drops rapidly with rise in temperature

178. Highest melting (m.p = 3070C) oxide refractory is__________________?
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A. Zirconia

B. Magnesia

C. Thoria

D. Alumina

179. Thermal conductivity of refractory bricks_________________?
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A. Is independent of its porosity and is maximum for insulating bricks

B. Decreases with decreases in porosity

C. Increases with the amount of air entrapped in pores

D. Increases with decrease in porosity
180. Refractory bricks with lower permeability is produced by using __________________?
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A. Finer grog size

B. Higher moulding pressure

C. Higher firing temperature

D. All A., B. and C.
181. Pick out the wrong statement ?
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A. A ceramic material which becomes fluid upon heating and can be moulded in liquid/viscous

B. Ceramic materials are brittle in nature

C. Non-oxide ceramic materials generally act as a semi-conductor

D. te is termed s glass

E. Ceramic materials do not undergo vitrification on heating
182. Fusion point of a basic refractory material is__________________?
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A. Increased by the addition of acid oxides

B. Always less than 1000C

C. Not affected by the addition of acid oxides

D. Reduced by the addition of acid oxides
183. Refractory bricks having lower porosity have_________________________?
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A. High insulating properties

B. Greater strength

C. Low thermal conductivity

D. Low heat capacity

184. Pick out the wrong statement?
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A. Silica occurs in nature in all cellular, amorphous or crystalline form

B. Sand & coke is the main raw material for the manufacture of silicon carbide

C. Carbon refractories cannot be used in the furnaces operating under reducing conditions

D. Mullite can be obtained by the heating of alusite, kyanite or sillimanite

185. Pure bauxite is the best raw material for the manufacture of high alumina refractories, in which maximum alumina content can be as high as _____________ percent?
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A. 55

B. 80

C. 90

D. 70

186. Hot blast main (carrying air at 1000C) in blast furnace are lined with ______________ bricks?
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A. Fireclay

B. Magnesite

C. Silica

D. Zirconia

187. Permeability of bricks is a measure of the_________________?
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A. Rate at which a fluid will pass through the pores

B. Melting point

C. Expansion during heating

D. Refractoriness

188. Pick out the wrong statement ?
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A. Graphite and metals are the good electrical conductor among the refractories and others are all

B. naces</strong>

C. Electrical conductivity of refractory is not important, when these are to be used in electrical

D. ductivity

E. Refractories used for lining electrical furnaces should ordinarily have very low electrical

F. Electrical conductivity of porous refractory material is low

189. High alumina refractory compared to fireclay bricks have____________________?
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A. High resistance to thermal shock and creep

B. Low refractoriness

C. Less load bearing capacity

D. Less resistance to slag attack

190. Addition of zircon to silica refractory brick improves its_____________________?
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A. Crushing strength

B. Resistance to slag attack

C. Both A. and B.

D. Neither A. nor B.

191. Which of the following is not a high alumina refractory material ?
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A. Sillimanite

B. Periclase

C. Kyanite

D. Diaspore

192. Fireclay bricks is not used for lining the__________________?
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A. Cupola

B. Roof of open hearth furnace

C. Bottom of hot metal mixer

D. Gas producer

193. Pick out the wrong statement?
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A. Main constituents of clay are alumina and silica

B. Fluxing material like lime is added in clay to reduce the vitrification temperature

C. Vitrification of fireclay material is done to increase its porosity

D. uces its shrinkage on burning

E. Addition of sand in ceramic materials makes it non-plastic, increases its fusion point and

194. Bottom of basic open hearth furnace are constructed of__________________?
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A. Silicon carbide bricks

B. Porous fireclay bricks

C. Semi-silica bricks

D. Dead burnt magnesite ramming mass
195. Fireclay bricks are not used in the_____________________?
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A. Blast furnace

B. Cupola

C. Wall of coke oven

D. Hot blast stove

196. The maximum linear expansion of silica bricks during firing is about ______________ percent?
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A. 0.5

B. 2

C. 1

D. 3.5
197. Which is not a natural insulating material ?
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A. Vermiculite

B. Asbestos

C. Diatomaceous earth/kieselgur

D. None of these
198. ______________ bricks should not be used in oxidising atmosphere?
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A. Silica

B. Fireclay

C. Tar dolomite

D. Carbon
199. Carborundum used for making crucibles for melting non-ferrous metals is chemically________________?
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A. Silicon carbide

B. Zirconium sulphate

C. Silicon nitride

D. Crystalline magnesia

200. Ceramic recuperators used for waste heat recovery from high temperature flue gas going out of the furnace is made of________________?
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A. Corundum

B. Siliceous fireclay

C. Fireclay

D. Silicon carbide