All Free Chemical Engineering MCQs with Answers

• A. Roll-crusher
• B. Ball mill
• C. Squirrel-cage disintegrator
• D. Tube mill

Explanation: A squirrel-cage disintegrator is effective for fibrous materials because its rotating impact elements tear and disintegrate the fibres.

• A. Energy (kWh/ton of feed) needed to crush small feed to such a size that 80% of the product
• B. the product passes through a 100 micron screen
• C. Energy needed to crush one tonne of feed to 200 microns
• D. Gross energy (kWh/ton of feed) needed to reduce very large feed to such a size that 80% of
• E. passes a 200 mesh screen
• F. Energy needed to crush one ton of feed to 100 microns

Explanation: Bond's work index is the gross energy in kWh per tonne required to reduce a very large feed until 80% of the product passes a…

• A. Elasticity
• B. Size
• C. Toughness
• D. Hardness

Explanation: Grindability is an intrinsic response of a material and is related to properties such as hardness, toughness, and elasticity.

• A. Sizing
• B. Clarification
• C. Sorting
• D. Dispersion

Explanation: Sorting separates solid particles according to a property such as density, whereas sizing separates them according to particle size.

• A. Hammer crusher
• B. Gyratory crusher
• C. Roll crusher
• D. Ball mill

Explanation: A ball mill provides repeated impact and attrition, making it suitable for pulverising coal to a fine size such as 200 mesh.

• A. Dry powders
• B. Lumpy solids and low viscosity liquids
• C. High viscosity liquids
• D. Thick pastes

Explanation: Ribbon blenders are designed mainly for mixing dry powders and other free-flowing solids using helical ribbons.

• A. Ratio of discharge opening to feed opening
• B. Ratio of feed opening to discharge opening
• C. Determining factor for minimum dia of the feed and the product
• D. None of these

Explanation: The reduction ratio compares the characteristic feed size with the product or discharge size, so it is represented here by the feed…

• A. Compartment mill
• B. Pebble mill
• C. Cage mill
• D. Rod mill

Explanation: Compartment, pebble, and rod mills are tumbling mills in which the grinding charge revolves with the shell.

• A. (S/V)p
• B. (S/V)f
• C. (S/V)2p
• D. √(S/V)p

Explanation: Bond's law makes work proportional to the difference in the reciprocals of the square roots of feed and product sizes.

• A. Electromagnets
• B. Either A., B. or C.
• C. Unbalanced flywheels
• D. Cams or eccentric shafts

Explanation: Vibratory motion in screens may be produced mechanically by cams or eccentric shafts, dynamically by unbalanced flywheels, or electrically…

• A. m/ρ . Vp
• B. m . ρ/Vp
• C. m . Vp/ρ
• D. Vp/m . ρ

Explanation: The mass of one particle is ρVp, so the number of particles is total mass divided by this particle mass: m/(ρVp).

• A. Slow compression
• B. Impact
• C. Cutting action
• D. Attrition

Explanation: Ultrafine grinding requires very small size reduction and is chiefly achieved by attrition, where particles rub against one another or the…

• A. Volume-surface
• B. Arithmetic
• C. Mass
• D. Geometric

Explanation: The Sauter mean diameter is defined by equal volume-to-surface-area behavior, so it is also called the volume-surface mean diameter.

• A. Employ a steel shell having L/D ratio of 1.5 to 3.0
• B. All A , B & C
• C. Employ steel rods of 2-12 cms diameter extending over full length of the mill
• D. Is useful for handling sticky materials

Explanation: Rod mills commonly have an L/D ratio of about 1.5 to 3, use long steel rods roughly 2 to 12 cm in diameter, and can handle somewhat sticky…

• A. 5 to 10
• B. 0.1 to 2
• C. 20 to 25
• D. 50 to 70

Explanation: Only a small fraction of the energy supplied to a crusher creates new surface; most is lost through friction, deformation, noise, and…

• A. None of these
• B. No
• C. Only two
• D. Horizontal

Explanation: Horizontal baffles or lifter projections are fitted inside ball mills to lift and cascade the balls instead of allowing them to slide…

• A. Coagulant
• B. Vacuum filter
• C. Centrifugal filter
• D. Pressure filter

Explanation: When only a small amount of extremely fine solid is dispersed in a liquid, a coagulant is added to aggregate the particles into larger…

• A. Crushing takes place by impact breaking
• B. All A., B. and C.
• C. Reduction ratio can be varied by adjusting the distance from cage to hammers
• D. Maximum acceptable feed size is 30 cms

Explanation: A hammer crusher breaks particles primarily by impact. Its feed limit and reduction ratio are controlled by the crusher design, including…

• A. Decreasing size of product at constant size of feed
• B. Decreasing machine capacity
• C. Increasing size of feed at constant reduction ratio
• D. None of these

Explanation: At a fixed reduction ratio, increasing the feed size produces less new surface area per unit mass, so the specific energy requirement…

• A. Abrasive
• B. Non-sticky
• C. Coarse
• D. Large quantity of very fine

Explanation: Wet sieving is preferred when the feed contains a large amount of very fine material, because liquid prevents fine particles from blinding…