chemical engineering Mcqs
2451. 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. Classification

B. Clarification

C. Sedimentation

D. Decantation

2452. General mechanism of size reduction in intermediate and fine grinder is by __________________?
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A. Compression and tearing

B. Compression

C. Impact and attrition

D. Cutting action

2453. Reciprocating screens are normally inclined at an angle of 5 with the horizontal and employ gyratory motion at feed end & reciprocating motion at the discharge end. They are not suitable for the screening of the ___________________?
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A. Powdered food & granular materials

B. Heavy tonnages of rocks or gravel

C. Dry chemicals

D. Light metal powder down upto 4 mesh size

2454. The unit of filter medium resistance is________________?
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A. cm/gm-1

B. cm-1

C. gm-1

D. gm/cm-1

2455. For achieving rapid drying rate in a spray dryer, the diameter of the particles in the feed should be in the range of _______________ microns (1 mm = 1000 microns)?
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A. 5-Jan

B. 200-300

C. > 500

D. 10-60
2456. Which of the following is the most suitable filter for separation of abrasive solids suspended in a corrosive liquid ?
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A. Sand bed filter

B. Plate and frame filter press

C. Vacuum filter

D. Batch basket centrifuge

2457. Weight of 1 m3 of humid air as compared to 1 m3 of dry air, under the same conditions, is_________________?
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A. Unpredictable

B. Same

C. More

D. Less
2458. Wet grinding in a revolving mill ______________ as compared to dry grinding ?
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A. Complicates handling of the product

B. Gives less wear on chamber walls

C. Increases capacity

D. Requires more energy

2459. The drying time between fixed moisture contents within the constant rate period is proportional to (assuming that drying occurs from all surfaces of the solid) (where, T = thickness of the solid) ?
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A. T3

B. ?T

C. T

D. T1.5

2460. Particle size range in which dust catcher (gravity settling chamber) works most effectively and efficiently is ______________ microns?
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A. 10 to 25

B. < 5

C. < 74

D. > 1000

2461. The specific cake resistance for incompressible sludges is (where ?P = pressure drop over cake)__________________?
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A. ? 1/ ?P

B. ? ??P

C. Independent of ?P

D. ? ?P

2462. Washability curve based on float and sink test enables an assessment to be made of the possibility of cleaning a coal fraction based on the____________________?
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A. Volatile matter content

B. Differential wettability

C. Density separation

D. Size

2463. Which of the following clay mixing devices is vacuum operated for deairation of clay ?
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A. Banbury mixer

B. Muller-mixer

C. Pug mill

D. None of these

2464. If a1 and a2 are the relative volatilities when the pressure in the distillation column is 1 and 2 atm respectively. Pick out the correct statement ?
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A. a1 = 0.5 a2

B. a1 = a2

C. a1 = 2a2

D. None of these
2465. Soft & non-abrasive materials can be made into fines by________________________?
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A. Compression

B. None of these

C. Attrition

D. Cutting

2466. In case of a hammer crusher, the final product size depends on the____________________?
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A. Feed rate

B. All A., B. and C.

C. Clearance between hammer & grinding plates

D. Rotor speed

2467. Sphericity of pulverised coal is__________________?
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A. 1

B. ?

C. < 1

D. > 1

2468. Which of the following is a fine crusher ?
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A. Toothed roll crusher

B. Blake jaw crusher

C. Gyratory crusher

D. Dodge jaw crusher

2469. Use of grinding aids is done in _______________ grinding?
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A. Intermediate

B. Dry

C. Wet

D. Ultrafine

2470. Size reduction of asbestos and mica is done by____________________?
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A. Hammer mills

B. Rod mills

C. Gyratory crushers

D. Crushing rolls

2471. Cumulative analysis for determining surface is more precise than differential analysis, because of the_______________?
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A. Assumption that all particles in a single fraction are equal in size, is not needed

B. None of these

C. Fact that screening is more effective

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

2472. The energy consumed by a ball mill depends on__________________?
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A. Its speed

B. Its ball load

C. All A., B. and C.

D. The density of the material being ground

2473. Which of the following is not a wet classifier ?
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A. Hydrocyclones

B. Dorr Oliver rake classifier

C. Sharpies super-centrifuge

D. None of these
2474. Raw materials are charged in the iron blast furnace using____________________?
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A. Bucket elevator

B. Screw conveyor

C. None of these

D. Skip hoist
2475. Ion exchange process is similar to___________________?
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A. Extraction

B. Adsorption

C. Absorption

D. Leaching

2476. General crushing equation is given by d(P/m) = -K (dD? S/D? n S). Bonds crushing law is obtained by solving this equation for n = _____________ and feed of infinite size?
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A. 2

B. 2.5

C. 1.5

D. 1

2477. During agitation of liquids, power consumption during laminar flow is not proportional to the ________________?
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A. Density of the liquid

B. Viscosity of the liquid

C. Square of rotational speed

D. Cube of impeller diameters

2478. For a sphere falling in the constant drag co-efficient regime, its terminal velocity depends on its diameter D. as_________________?
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A. d

B. 1/d

C. d2

D. ?d

2479. The process by which fine solids is removed from liquids is termed as _____________________?
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A. Classification

B. Flocculation

C. Sedimentation

D. Decantation

2480. Corresponding to Prandtl number in heat transfer, the dimensionless group in mass transfer is the _______________ number?
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A. Sherwood

B. Schmidt

C. Peclet

D. Stanton

2481. Which of the following grinding mills has the horizontally arranged rods as the grinding elements thereby delivering more uniform granular products with minimum fines ?
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A. Tube mill

B. Pebble mill

C. Rod mill

D. Compartment mill

2482. In saturated gas, the__________________?
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A. Vapour is in equilibrium with the liquid at the gas temperature

B. Vapour is in equilibrium with the liquid at the room temperature

C. None of these

D. Partial pressure of vapour equals the vapour pressure of the liquid at room temperature

2483. Gravity stamp mill is meant for the ___________________ crushing?
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A. Intermediate

B. Ultrafine

C. Primary

D. Fine
2484. Feed size of ? 25 cms can be accepted by _______________________?
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A. Fluid energy mill

B. Rod mill

C. Ball mill

D. Jaw crusher
2485. A screen is said to be blinded, when the___________________?
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A. Under-sizes are retained in oversize fraction

B. Screen capacity is abruptly increased

C. Screen is plugged with solid particles

D. Over-sizes are present in undersize fraction

2486. During filtration operation, the filtrate encounters the resistance of the ___________________?
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A. All A., B. and C.

B. Cake

C. ium

D. Filter medium

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

2487. Maximum size reduction in a fluid energy mill is achieved by___________________?
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A. Interparticle attrition

B. Impact

C. Cutting

D. Compression

2488. Which of the following is not used as filter aid ?
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A. Asbestos

B. Rice husk

C. Purified wood cellulose

D. Diatomaceous earth

2489. Height of liquid in agitation tank is normally maintained equal to the tank diameter. However, if the tank is too tall and a large liquid hold up is desired, then two or more impellers mounted on the same shaft may be used. The clearance between the tank bottom and the bottom most impeller should be about (where, D = impeller diameter) ?
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A. D

B. 0.5 D

C. 1.5 D

D. 2 D

2490. Leaching of sugar from sugar beets is done by___________________?
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A. Hexane

B. Lime water

C. Dilute H2SO4

D. Hot water
2491. A fluid energy mill is used for_________________?
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A. Crushing

B. Cutting

C. Ultra grinding

D. Grinding

2492. Percentage of drum submerged in the slurry in case of rotary drum filter is ________________?
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A. 85

B. 3

C. 30

D. 25

2493. The minimum number of theoretical plates is required for achieving a given separation in distillation column with_________________?
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A. No reflux

B. Minimum reflux ratio

C. Zero reflux ratio

D. Total reflux
2494. Which of the following is a vacuum filter ?
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A. Batch basket centrifuge

B. Tank filter (Nutsche filter)

C. Rotary disc filter

D. Filter press

2495. 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

2496. During agitation of liquids, the_________________?
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A. Froude number is independent for the curves between power number and Reynolds number in

B. fled system

C. All A., B. and C.

D. Power number becomes independent of impellers Reynolds number at high Reynolds number,

E. er number

F. Froude number is used to account for the effect of surface (e.g., the centre vortex) on the

2497. At low Reynolds number, the power (P) required for agitating a fluid in a stirred tank becomes independent of inertial forces. In this limit, indicate which of the following relations is satisfied: Po = ?/?N3 D5: Power number Re = ? N D2/?: Reynolds number N is the impeller rotational speed, and D is the impeller diameter ?
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A. Po ? Re0.5

B. Po ? Re1.0

C. Po ? Re0.0

D. Po ? Re-1.0

2498. Crushing of mineral particles is accomplished in a cage mill, when one or more alloy steel bars are revolved in opposite directions. It is a type of ______________ mill?
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A. Roll

B. Vibratory

C. Impact

D. None of these

2499. Energy consumption in a crusher decreases with increase in the________________________?
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A. Size of feed (at constant reduction ratio)

B. Size of the product (at constant feed size)

C. All A., B. & C.

D. Capacity of the crushing machine

2500. Which of the following terminology is not used for size reduction of materials to fine sizes or powders ?
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A. Pulverisation

B. Comminution

C. Compression

D. Dispersion