Particle Size Reduction and Classification - Fluid Mechanics and Mechanical Operations - Chemical Engineering Previous Year Questions

1

2007 · Chemical Engineering · Fluid Mechanics and Mechanical Operations · Particle Size Reduction and Classification

Chemical Engineering (CH) 2007

In Tyler series, the ratio of the aperture size of a screen to that of the next smaller screen is

A

\(1/\sqrt{2}\)

B

\(\sqrt{2}\)

C

1.5

D

2

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2

2007 · Chemical Engineering · Fluid Mechanics and Mechanical Operations · Particle Size Reduction and Classification

Chemical Engineering (CH) 2007

Size reduction of coarse hard solids using a crusher is accomplished by

A

attrition

B

compression

C

cutting

D

impact

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3

2008 · Chemical Engineering · Fluid Mechanics and Mechanical Operations · Particle Size Reduction and Classification

Chemical Engineering (CH) 2008

Q.14 The power required for size reduction in crushing is

A

proportional to \(\frac{1}{\text{Surface energy of the material}} \)

B

proportional to \(\sqrt{\frac{1}{\text{Surface energy of the material}}} \)

C

proportional to Surface energy of the material

D

independent of the Surface energy of the material

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4

2010 · Chemical Engineering · Fluid Mechanics and Mechanical Operations · Particle Size Reduction and Classification

Chemical Engineering (CH) 2010

The critical speed (revolutions per unit time) of a ball mill of radius R, which uses balls of radius r, is

A

\(\frac{1}{2\pi} \sqrt{\frac{g}{R+r}} \)

B

\(\frac{1}{2\pi} \sqrt{\frac{g}{R}} \)

C

\(\frac{1}{2\pi} \sqrt{\frac{g}{r}} \)

D

\(\frac{1}{2\pi} \sqrt{\frac{g}{R-r}} \)

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5

2013 · Chemical Engineering · Fluid Mechanics and Mechanical Operations · Particle Size Reduction and Classification

Chemical Engineering (CH) 2013

In the Tyler standard screen scale series, when the mesh number increases from 3 mesh to 10 mesh, then

A

the clear opening decreases

B

the clear opening increases

C

the clear opening is unchanged

D

the wire diameter increases

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6

2013 · Chemical Engineering · Fluid Mechanics and Mechanical Operations · Particle Size Reduction and Classification

Chemical Engineering (CH) 2013

100 ton/h of a rock feed, of which 80% passed through a mesh size of 2.54 mm, were reduced in size such that 80% of the crushed product passed through a mesh size of 1.27 mm. The power consumption was 100 kW. If 100 ton/h of the same material is similarly crushed from a mesh size of 5.08 mm to a mesh size of 2.54 mm, the power consumption (in kW, to the nearest integer) using Bond's law, is ______

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7

2014 · Chemical Engineering · Fluid Mechanics and Mechanical Operations · Particle Size Reduction and Classification

Chemical Engineering (CH) 2014

In order to produce fine solid particles between 5 and 10 \(\mu m\), the appropriate size reducing equipment is

A

fluid energy mill

B

hammer mill

C

jaw crusher

D

smooth roll crusher

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8

2017 · Chemical Engineering · Fluid Mechanics and Mechanical Operations · Particle Size Reduction and Classification

Chemical Engineering (CH) 2017

Which of the following is the correct sequence of equipment for size reduction of solids?

A

Fluid energy mill → Jaw crusher → Hammer mill

B

Hammer mill → Jaw crusher → Fluid energy mill

C

Fluid energy mill → Hammer mill → Jaw crusher

D

Jaw crusher → Hammer mill → Fluid energy mill

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9

2017 · Chemical Engineering · Fluid Mechanics and Mechanical Operations · Particle Size Reduction and Classification

Chemical Engineering (CH) 2017

Size analysis was carried out on a sample of gravel. The data for mass fraction (\( x_i \)) and average particle diameter (\( D_{pi} \)) of the fraction is given in the table below:

\( x_i \)	\( D_{pi} \) (mm)
0.2	5
0.4	10
0.4	20

The mass mean diameter of the sample, to the nearest integer, is ______ mm.

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10

2018 · Chemical Engineering · Fluid Mechanics and Mechanical Operations · Particle Size Reduction and Classification

Chemical Engineering (CH) 2018

Critical speed of a ball mill depends on

A

the radius of the mill (shell) and the radius of the particles

B

the radius of the mill (shell) and the density of the particles

C

the radius of the balls and the radius of the particles

D

the radius of the balls and the radius of the mill (shell)

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11

2018 · Chemical Engineering · Fluid Mechanics and Mechanical Operations · Particle Size Reduction and Classification

Chemical Engineering (CH) 2018

Match the equipment in Column A with the corresponding process in Column B

A

P-I, Q-IV, R-II, S-III

B

P-III, Q-IV, R-II, S-I

C

P-IV, Q-I, R-II, S-III

D

P-IV, Q-III, R-I, S-II

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12

2019 · Chemical Engineering · Fluid Mechanics and Mechanical Operations · Particle Size Reduction and Classification

Chemical Engineering (CH) 2019

Consider a cylinder (diameter \( D \) and length \( D \)), a sphere (diameter \( D \)) and a cube (side length \( D \)). Which of the following statements concerning the sphericity (\( \Phi \)) of the above objects is true:

A

\(\Phi_{sphere} > \Phi_{cylinder} > \Phi_{cube} \)

B

\(\Phi_{sphere} = \Phi_{cylinder} = \Phi_{cube} \)

C

\(\Phi_{sphere} < \Phi_{cylinder} < \Phi_{cube} \)

D

\(\Phi_{cylinder} > \Phi_{sphere} = \Phi_{cube} \)

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13

2025 · Chemical Engineering · Fluid Mechanics and Mechanical Operations · Particle Size Reduction and Classification

Chemical Engineering (CH) 2025

A catalyst particle is modeled as a symmetrical double cone solid as shown in the figure. For each conical sub-part, the radius of the base is \( r \) and the height is \( h \). The sphericity of the particle is given by

A

\(\frac{2 \left( \frac{r^2 h}{2} \right)^{1/3}}{r \sqrt{r^2 + h^2}} \)

B

\(\frac{\left( \frac{r^2 h}{2} \right)^{1/3}}{r \sqrt{r^2 + h^2}} \)

C

\(\frac{2 \left( \frac{r^2 h}{2} \right)^{2/3}}{r \sqrt{r^2 + h^2}} \)

D

\(\frac{\left( \frac{r^2 h}{2} \right)^{2/3}}{r \sqrt{r^2 + h^2}} \)

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14

2026 · Chemical Engineering · Fluid Mechanics and Mechanical Operations · Particle Size Reduction and Classification

Chemical Engineering (CH) 2026

Which one of the following is NOT a type of chain conveyor?

A

apron conveyor

B

bucket conveyor

C

scraper conveyor

D

screw conveyor

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15

2026 · Chemical Engineering · Fluid Mechanics and Mechanical Operations · Particle Size Reduction and Classification

Chemical Engineering (CH) 2026

The gross energy requirement, to reduce a very large feed of coal to such a size that 80% of the product passes through a 100 μm screen, is 13 kWh per ton of feed. In a process, 250 tons \( h^{-1} \) of coal is crushed. The range of feed sizes is such that 80% of the feed passes through an opening of 100 mm. The product size range is to be such that 80% of the product passes through an opening of 25 mm. According to the Bond’s law, which one of the following is the power consumption (in kW)?

A

12.8

B

25.7

C

51.4

D

102.7

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