chemical engineering mechanical operations Mcqs
201. Run of mine (ROM) coal is crushed by a _________________________ for use in domestic ovens?
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A. Hammer crusher

B. Jaw crusher

C. Ball mill

D. Tube mill

202. Apron conveyors are used for ___________________ ?
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A. Heavy loads & short runs

B. Heavy loads & long runs

C. None of these

D. Small loads & long runs

203. Separation of solid suspended in liquid into a supernatant clear liquid and a denser slurry employs a process termed as the___________________?
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A. Flocculation

B. Sedimentation

C. Coagulation

D. Clarification

204. Bond crushing law_________________?
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A. States that the work required to form particle of any size from very large feed is proportional

B. Calls for relatively less energy for the smaller product particles, than does the Rittinger law

C. Is less realistic in estimating the power requirements of commercial crushers

D. the square root of the volume to surface ratio of the product

E. States that the work required for the crushing is proportional to the new surface created

205. A tube mill as compared to a ball mill__________________?
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A. Gives finer size reduction but consumes more power

B. All A., B. and C.

C. Has larger length/diameter ratio (>2 as compared to 1 for ball mill)

D. Employs smaller balls

206. Ultracentrifuges running at speeds upto 100000 rpm is normally used for the_____________________?
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A. Concentration of rubber latex

B. Dewaxing of lubricating oil

C. Separation of cream from milk

D. Separation of isotopes based on their density or molecular weights difference
207. The main size reduction operation in ultrafine grinders is_____________?
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A. Cutting

B. Compression

C. Attrition

D. Impact

208. Rittinger number which designates the new surface produced per unit of mechanical energy absorbed by the material being crushed, depends on the ______________________?
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A. All A., B. and C.

B. Elastic constant of the material

C. State or manner of application of the crushing force

D. Ultimate strength of the material

209. Which of the following relationships between co-efficient of friction (?) between rock & roll and a (half of the angle of nip) of the particle to be crushed is correct ?
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A. ? > tan 2?

B. ? ? tan ?

C. ? ? tan ?

D. ? > tan ?

210. Ball mills and tube mills with flint or porcelain balls are used for size reduction of_______________?
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A. Limestone

B. Rubber

C. Asbestos

D. Non-metallic ores
211. Which of the following conveyors cannot be recommended for transportation of abrasive materials ?
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A. Flight conveyor

B. Belt conveyor

C. Chain conveyor

D. Apron conveyor

212. In case of grinding in a ball mill__________________?
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A. Its capacity decreases with increasing fineness of the products

B. All A., B. and C

C. Wet grinding achieves a finer product size than dry grinding

D. Grinding cost and power requirement increases with increasing fineness of the products

213. In washing type plate and frame filter press, the ratio of washing rate to the final filtrate rate is__________________?
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A. 2-Jan

B. 4

C. 1

D. 1/4
214. To get ultrafine particles, the equipment used is a _________________?
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A. Hammer crusher

B. Fluid energy mill

C. Ball mill

D. Rod mill

215. The opening of a 200 mesh screen (Taylor series) is__________________?
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A. 0.0074 cm

B. 74 milli-microns

C. 0.0047 cm

D. 0.0074 mm

216. The sphericity of a solid particle of cubical shape is ___________________?
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A. ?

B. (?/6)1/2

C. ?/3

D. (?/6)1/3
217. Size reduction of _____________ is accomplished in steam heated rollers and roll crushers?
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A. Resins

B. Hard rubber

C. Waxes

D. Gums

218. A fluid energy mill is used for_________________?
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A. Grinding

B. Crushing

C. Cutting

D. Ultra grinding
219. Separation of isotopes is generally done using a/an _______________ centrifuge?
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A. Ultra

B. Disk-bowl

C. Both A. & B.

D. Neither A. nor B.

220. In screen analysis, the notation +5 mm/-10 mm means particles passing through ____________________?
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A. 10 mm screen and retained on 5 mm screen

B. 5 mm screen and retained on 10 mm screen

C. Both 5 mm and 10 mm screens

D. Neither 5 mm nor 10 mm screen

221. Which of the following can be most effectively used for clarification of lube oil and printing ink ?
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A. Sparkler filter

B. Pre-coat filter

C. Disc-bowl centrifuge

D. Sharpies super-centrifuge
222. Pulverised coal passing through 200 mesh screen has a diameter of 0.074 mm (74 micron). The same passing through 50 mesh screen will have a dia of ____________ mm?
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A. 0.014

B. 0.30

C. 50

D. 0.007

223. The important dimensional group involved in the power requirement calculation in mixing operation is the _____________ number?
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A. Reynolds

B. Froude

C. Both A. & B.

D. Neither A. nor B.

224. Which of the following gives the work required for size reduction of coal to -200 mesh in a ball mill most accurately?
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A. None of these

B. Rittingers law

C. Kicks law

D. Bonds law

225. The ratio of the area of openings in one screen (Taylor series) to that of the openings in the next smaller screen is_________________?
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A. ?2

B. 1.5

C. None of these

D. 1

226. Vacuum filter is most suitable for the_______________?
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A. Liquids of very high viscosity

B. Liquids having high vapour pressure

C. None of these

D. Removal of fines from liquid

227. Wet grinding in a revolving mill ______________ as compared to dry grinding ?
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A. Gives less wear on chamber walls

B. Increases capacity

C. Requires more energy

D. Complicates handling of the product

228. Sizing of very fine particles of the order of 5 to 10 microns is done by elutriation, which is a _____________ operation?
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A. Sedimentation

B. Clarification

C. Classification

D. Flocculation

229. Chance process is used for the________________?
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A. Concentration of pyrites

B. Concentration of iron ore

C. Water treatment

D. Cleaning of coal
230. Range of compressibility co-efficient of the commercial compressible cake obtained in filtration operation is_____________________?
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A. 0.2 to 0.4

B. 0.01 to 0.1

C. 0.1 to 0.3

D. 0.2 to 0.8
231. Separation of a suspension or slurry into a supernatant clear liquid (free from particles) and a thick sludge containing a high concentration of solid is called__________________?
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A. Sedimentation

B. Classification

C. Clarification

D. Decantation

232. _______________ is a cohesive solid ?
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A. Wheat

B. Sand

C. Wet clay

D. None of these

233. Which of the following is not an industrial screening equipment ?
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A. Vibrating screen

B. Grizzly

C. Sharpies centrifuge

D. Trommel

234. For Indian standard (IS) screens, the mesh number is equal to its aperture size expressed to the nearest deca-micron (0.01 mm). Aperture width of IS screen of mesh number 50 will be approximately _____________ microns?
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A. 500

B. 5

C. 50

D. 5000

235. Feed size of ? 25 cms can be accepted by _______________________?
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A. Fluid energy mill

B. Ball mill

C. Rod mill

D. Jaw crusher
236. In a size reduction crushing operation, feed size is 100 to 300 mm. while the product size is 10 to 50 mm. This is a case of the _____________ crushing?
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A. Ultrafine

B. Primary

C. Fine

D. Secondary
237. For sizing of fine materials, the most suitable equipment is a____________________?
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A. Grizzly

B. Trommel

C. Shaking screen

D. Vibrating screen
238. increasing the capacity of a screen _______________ the screen effectiveness?
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A. Increases

B. Decreases

C. Does not effect

D. None of these

239. The sphericity of a cylinder of 1 mm diameter and length 3 mm is_________________?
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A. 0.78

B. 0.6

C. 0.5

D. 0.9
240. A fluid energy mill is used for __________________?
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A. Grinding

B. Cutting

C. Ultra-grinding

D. Crushing

241. Which of the following is the hardest material ?
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A. Gypsum

B. Corundum

C. Calcite

D. Quartz

242. Where the density difference of the two liquid phase to be separated is very small (as in milk cream separator), the most suitable separator is a____________________?
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A. Batch basket centrifuge

B. Sharpies super-centrifuge

C. Sparkler filter

D. Disc bowl centrifuge
243. Use of grinding aids is done in _______________ grinding?
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A. Wet

B. Intermediate

C. Ultrafine

D. Dry
244. _____________ mills are termed as impactors?
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A. Hammer

B. Cage

C. None of these

D. Rolling-compression

245. During agitation of liquids, power consumption during laminar flow is not proportional to the ________________?
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A. Cube of impeller diameters

B. Square of rotational speed

C. Density of the liquid

D. Viscosity of the liquid

246. For a non-spherical particle, the sphericity__________________?
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A. Is defined as the ratio of surface area of a sphere having the same volume as the particle to the

B. ume of the particle

C. ual surface area of the particle</strong>

D. Has the dimension of length

E. Is the ratio of volume of a sphere having the same surface area as the particle to the actual

F. Is always less than 1

247. Which of the following parts of a jaw crusher is subjected to maximum wear and tear during its operation ?
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A. Crush shaft

B. Jaw plates

C. Toggles

D. Check plates

248. The controlling resistance in a rotary drum vacuum filter is the ________________ resistance?
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A. None of these

B. Piping

C. Filter medium

D. Cake
249. About 2-3 hp, power per gallon of a thin liquid provides vigorous agitation in an agitator. Power number in agitation is given by __________________?
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A. P. gc/n3. D2. ?

B. P. gc. ?/?2

C. P. gc/n2. D2. ?

D. n3. D3. ?/P. gc

250. Solid particles of different densities are separated by _____________________?
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A. Sorting classifier

B. Filters

C. Cyclones

D. Thickness