All Free Chemical Engineering MCQs with Answers
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6,983 questions · page 228 of 350
4541. Which of the following size reduction equipments employs mainly attrition for ultrafine grinding ?
- A. Jet mills
- B. Fluid energy mill
- C. All A., B. and C.
- D. Micronizer
Explanation: Jet mills, fluid-energy mills and micronizers are essentially related types of equipment for ultrafine grinding.
Correct answer: All A., B. and C.- A. Blending miscible liquids
- B. Continuous mixing
- C. Bath mixing
- D. Non-flowing powder and thin pastes
Explanation: Ribbon blenders are horizontal mixers designed mainly for dry, non-flowing powders and can also handle thin pastes.
Correct answer: Non-flowing powder and thin pastes- A. Nc = (1/4π). √(g/R1 - R2)
- B. Nc = (1/2π). √(g/R1 - R2)
- C. Nc = (1/π). √(g/R1 - R2)
- D. Nc = (1/2π). √(R1 - R2/g)
Explanation: At critical speed, a ball just remains in contact with the mill wall at the top, giving Nc = (1/2π)√[g/(R1 − R2)].
Correct answer: Nc = (1/2π). √(g/R1 - R2)4544. The optimum moisture content in solids to be crushed/ground ranges from _______________ percent?
- A. 8 to 10
- B. 3 to 4
- C. 10 to 15
- D. 15 to 20
Explanation: A small moisture content, usually about 3 to 4 percent, can improve crushing and grinding by reducing dust and helping control particle…
Correct answer: 3 to 4- A. Batch basket centrifuge
- B. Sharpies super-centrifuge
- C. Disc bowl centrifuge
- D. Sparkler filter
Explanation: A disc-bowl centrifuge is especially suitable for liquid-liquid separation when the phases have only a small density difference, as in…
Correct answer: Disc bowl centrifuge- A. 3
- B. 30
- C. 85
- D. 25
Explanation: In a rotary drum vacuum filter, approximately 30 percent of the drum surface is normally submerged in the slurry.
Correct answer: 30- A. Secondary
- B. Primary
- C. Fine
- D. Ultrafine
Explanation: Primary crushing handles the large run-of-mine feed, while secondary crushing reduces the material further to roughly the 10 to 50 mm…
Correct answer: Secondary- A. Canvas fabric
- B. Diatomaceous earth
- C. Calcined lime
- D. None of these
Explanation: Diatomaceous earth forms a porous, permeable cake that retains fine particles while allowing liquid to pass, making it a common filter…
Correct answer: Diatomaceous earth- A. Runs at very slow speed (2 rpm)
- B. Is used for mixing high viscosity pastes
- C. Produces mainly axial flow
- D. All A., B. and C.
Explanation: A propeller agitator is a high-speed impeller that produces predominantly axial flow.
Correct answer: Produces mainly axial flow- A. Thickener
- B. Classifier
- C. Clarifier
- D. Strainer
Explanation: A strainer uses a screen or mesh across a flowing stream to catch coarse solids such as dirt, rust, and debris.
Correct answer: Strainer- A. < 10
- B. > 10
- C. > 100
- D. < 100
Explanation: For stirred tanks, the laminar agitation regime is conventionally taken as Reynolds number below about 10.
Correct answer: < 10- A. √μ
- B. 1/√μ
- C. 1/μ
- D. 1/μ2
Explanation: With filter-medium resistance negligible compared with cake resistance, the filtration rate varies inversely with the square root of…
Correct answer: 1/√μ- A. Kremser
- B. Hagen-Poiseuille's
- C. Fanning's
- D. Kozeny-Carman
Explanation: Flow through a porous filter cake is described using the Kozeny-Carman relationship, which relates resistance to cake porosity, particle…
Correct answer: Kozeny-Carman- A. Rice husk
- B. Diatomaceous earth
- C. Purified wood cellulose
- D. Asbestos
Explanation: Common filter aids include diatomaceous earth, asbestos, and purified cellulose because they form a permeable porous cake.
Correct answer: Rice husk- A. Is lower than
- B. Is greater than
- C. Is same as
- D. Cannot be predicted as data are insufficient
Explanation: An irrigated packed bed has liquid holdup and additional interaction between the gas and liquid phases, increasing resistance to gas flow.
Correct answer: Is greater than- A. μ
- B. √μ
- C. 1/μ
- D. μ2
Explanation: Poiseuille's law gives capillary flow proportional to the pressure gradient and inversely proportional to viscosity, with permeability…
Correct answer: 1/μ- A. Classification
- B. Leaching
- C. Clarification
- D. Sedimentation
Explanation: A Dorr thickener is a continuous settling tank in which suspended solids settle under gravity and are withdrawn as a concentrated…
Correct answer: Sedimentation- A. More
- B. Less
- C. Equal
- D. Either A. or B.; depends on the packing height
Explanation: For the same separation duty, a plate tower normally causes a greater pressure drop because gas must pass through liquid on every tray.
Correct answer: More- A. Decreases
- B. Remains unchanged
- C. Increases
- D. Decreases exponentially
Explanation: A higher liquid rate increases liquid holdup and wetted packing surface, adding resistance to gas flow through the bed.
Correct answer: Increases- A. 23
- B. 23/2
- C. 25/2
- D. 21/3
Explanation: For a centrifugal pump, head varies as speed squared and power varies as speed cubed.
Correct answer: 23/2