chemical engineering mechanical operations Mcqs
101. Moore filter is a ______________ filter ?
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A. Leaf

B. Rotary

C. Sand

D. Press

102. Highly viscous liquids & pastes are agitated by________________?
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A. Multiple blade paddles

B. Turbine agitators

C. None of these

D. Propellers

103. In a ball mill, the volume occupied by the balls (when the mill is stopped) is about _______________ percent of the volume of the mill?
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A. 70

B. 50

C. 85

D. 35

104. Energy requirement (per unit mass of material crushed/ground) is highest for__________________?
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A. Jaw crusher

B. Ball mill

C. Fluid energy mill

D. Rod mill

105. The specific cake resistance for compressible sludges is a function of the pressure drop__________________?
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A. Overall

B. None of these

C. Over cake

D. Over medium

106. Size measurement of ultrafine particles can be best expressed in terms of___________________?
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A. Centimetre

B. Micron

C. Screen size

D. Surface area per unit mass
107. Filtration operation carried out by continuous increase of the inlet pressure of slurry, is called the _____________ filtration?
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A. Constant pressure

B. Varying pressure

C. Constant rate

D. Varying rate

108. Theoretical capacity of crushing rolls in tons/hr is given by (where, V = peripheral velocity, m/sec. W = width of rolls, m Dr = distance between rolls ? = density of material to be crushed, kg/m3 here, V =?ND where, N = speed of the rolls in rotation per second (rps) D = diameter of rolls, m) ?
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A. 3.6 W.Dr.?

B. 3.6 V.W.Dr.?

C. 3.6 V.W. ?

D. 3.6 V.W.Dr/?

109. Agglomeration of individual particles into clusters (flocs) is called flocculation. To prevent flocculation, the most commonly used dispersing agents are________________?
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A. Sulphates

B. Bi-carbonates

C. Carbonates

D. Silicates & phosphates
110. Half the angle of nip, (?), for a roll crusher is given by (where, dr, dp and df are diameters of crushing rolls, feed particles and rolls gap respectively) ?
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A. cos ? = (dr + dp)/(dr + df)

B. cos ? = (dr + df)/(dr + dp)

C. sin ? = (dr + dp)/(dr + df)

D. tan ? = (dr + dp)/(dr + df)

111. _______________ mill is normally used for grinding of talc?
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A. Ring-roll

B. Tube

C. Pebble

D. Compartment

112. Reciprocal of sphericity is termed as the________________?
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A. Surface area per unit mass

B. Sauter diameter

C. Shape factor

D. Specific surface ratio

113. Gravity settling process is not involved in the working of a________________?
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A. Classifier

B. Dorr-thickener

C. Hydrocyclone

D. Sedimentation tank

114. Filtration of water in a paper mill is done by a/an _______________ filter?
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A. Vacuum leaf

B. Sparkler

C. Open sand

D. Plate and frame

115. During filtration operation, the filtrate encounters the resistance of the ___________________?
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A. Cake

B. Filter medium

C. Channel carrying the slurry to the upstream side of the cake and filtrate away from the filter

D. All A., B. and C.

E. ium

116. Which of the following terminology is not used for size reduction of materials to fine sizes or powders ?
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A. Compression

B. Comminution

C. Pulverisation

D. Dispersion

117. Capacity (in tons/hr) of jaw/gyratory crusher is equal to (where, L = length of the receiving opening, cm S = greater width of the discharge opening, cm) ?
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A. L.S

B. 0.087 L.S

C. L.S/0.087

D. 0.01 L.S

118. A _______________ employs a set of screen across a flow channel for the separation of dirt/rust from a flowing liquid stream?
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A. Strainer

B. Thickener

C. Clarifier

D. Classifier

119. A screen is said to be blinded, when the___________________?
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A. Over-sizes are present in undersize fraction

B. Screen is plugged with solid particles

C. Under-sizes are retained in oversize fraction

D. Screen capacity is abruptly increased

120. As per Taggarts formula, the capacity (kg/hr) of Jaw & Gyratory crushers (for gapes of 10 to 60 cms) is equal to (where, L = Length of feed opening, cms S = Maximum width of discharge opening, cms) ?
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A. ?(LS)

B. 250 LS

C. LS

D. 93 LS
121. Which of the following is not used as a filter medium in case of corrosive liquids?
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A. Metal cloth of monel or stainless steel

B. Glass cloth

C. Cotton fabric

D. Nylon

122. Cumulative analysis for determining surface is more precise than differential analysis, because of the_______________?
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A. Fact that screening is more effective

B. Assumption that all particles in a single fraction are equal in size, is not needed

C. Assumption that all particles in a single fraction are equal in size

D. None of these

123. The crushed material received for separation is called feed or_________________?
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A. Heading

B. Tailing

C. Concentrate

D. Middling

124. Grinding characteristic of a material is given by its___________________?
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A. HGI

B. Angle of repose

C. Shatter index

D. Abrasion index

125. Separation of particles of various sizes, shapes and densities by allowing them to settle in a fluid is called__________________?
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A. Clarification

B. Thickening

C. Froth floatation

D. Classification
126. In case of a ball mill ?
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A. None of these

B. Coarse feed requires a larger ball

C. Operating speed should be more than the critical speed

D. Fine feed requires a larger ball

127. If radius of a batch basket centrifuge is halved & the r.p.m. is doubled, then the_________________?
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A. Linear speed of the basket is doubled

B. Linear speed of the basket is halved

C. Capacity of centrifuge is increased

D. Centrifugal force is doubled
128. Which of the following achieves the least reduction ratio for a given feed size ?
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A. Gyratory crusher

B. Jaw crusher

C. Cone crusher

D. Roll crusher
129. Rittingers number designates the new surface created per unit mechanical energy absorbed by the material being crushed. Larger value of Rittingers number of a material indicates its________________?
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A. High power consumption in grinding

B. Easier grindability

C. None of these

D. Poor grindability

130. A suspension of glass beads in ethylene glycol has a hindered settling velocity of 1.7 mm/s, while the terminal settling velocity of a single glass bead in ethylene glycol is 17 mm/s. If the Richardson-Zaki hindered settling index is 4.5, the volume fraction of solids in the suspension is_____________?
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A. 0.1

B. None of these

C. 0.4

D. 0.6
131. Paddle agitator_________________?
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A. None of these

B. Produces axial flow

C. Moves at very high speed

D. Is suitable for mixing low viscosity liquids
132. In classification, particles are said to be equal settling, if they have the same terminal velocities in the_______________?
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A. Different fluids

B. Same fluid

C. Same field of force

D. Both B. and C.
133. In a grinding operation, the limiting particle size is the size of the _______________ particle in the sample?
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A. Smallest

B. Either A. or B.

C. Largest

D. Neither A. nor B.
134. Activators are those chemicals which help buoying up one mineral in preference to the other in the froth floatation process. Which of the following is an activator ?
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A. Cresylic acid

B. Calcium carbonate

C. Copper sulphate

D. Sodium carbonate

135. The most suitable equipment for the transportation of 200 mesh size particles is a _______________?
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A. Screw conveyor

B. Bucket elevator

C. Pneumatic conveyor

D. Belt conveyor

136. Removal of activated carbon from glycerine is done by _________________?
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A. Rotary vacuum filter

B. Batch basket centrifuge

C. None of these

D. Plate and frame filter
137. Pine oil used in froth floatation technique acts as a/an_____________________?
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A. Modifier

B. Frother

C. Collector

D. Activator

138. _______________ is defined as the geometric mean of the relative rejections and the relative recoveries of two minerals?
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A. Selectivity index

B. Separation efficiency

C. Concentration ratio

D. None of these

139. ______________ are used for the separation of coarse particles from a slurry of fine particles?
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A. Classifiers

B. Decanters

C. Hydrocyclones

D. Thickeners

140. Sphericity for a non-spherical particle is given by (where, V and S are volume and surface area respectively of one particle. and, D = equivalent diameter of particle)?
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A. V/D.S

B. 6.V/D.S

C. V/6D.S

D. D.S/V

141. To remove dirt from the flowing fluid, we use a ____________________?
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A. Coagulant

B. Strains

C. Clarifier

D. Gravity settler

142. Mixing mechanism employed in a pan mixer is by ________________?
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A. Kneading

B. None of these

C. Dispersion

D. Mulling
143. There is practically no alternative/competitor to _________________ in the beneficiation treatment of sulphide ores?
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A. Jigging

B. Froth floatation

C. Tabling

D. Classification

144. As particle size is reduced__________________?
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A. Screening becomes progressively more difficult

B. Capacity and effectiveness of the screen is increased

C. Screening becomes progressively easier

D. None of these

145. Capacity of flight conveyor in tons/hr is given by (where, W & D = width and depth of flight respectively in metre V = speed of the conveyor, metre/second ? = bulk density of material, kg/m3) ?
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A. 3.6 W.V.?

B. 3.6 W.D.V

C. 3.6 D.V.?

D. 3.6 W.D.V.?
146. Which of the following equations is Rittingers crushing law? (Where P = power required by the machine, m = feed rate, k = a constant, D? sa & D? sb = volume surface mean diameter of feed & product respectively) ?
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A. P/m = K/ ?Dp

B. None of these

C. P/m = K . (1/ D? sb 1/D? sa)

D. P/m = K . ln D? sa/D? sb

147. In constant pressure filtration ?
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A. Rate of filtration decreases with time

B. Rate of filtration is constant

C. Resistance decreases with time

D. Rate of filtration increases with time

148. The optimum moisture content in solids to be crushed/ground ranges from _______________ percent?
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A. 8 to 10

B. 15 to 20

C. 3 to 4

D. 10 to 15

149. Which of the following is not a wet classifier ?
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A. Sharpies super-centrifuge

B. None of these

C. Dorr Oliver rake classifier

D. Hydrocyclones

150. The specific surface of spherical particles is given by (where D and ? are diameter and density of particle) ?
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A. 12/D.?

B. 6/D.?

C. 4/D.?

D. 2/D.?