## Solid Fluid Mechanical Operations - Dec 2015

### Chemical Engineering (Semester 4)

TOTAL MARKS: 80

TOTAL TIME: 3 HOURS
(1) Question 1 is compulsory.

(2) Attempt any **three** from the remaining questions.

(3) Assume data if required.

(4) Figures to the right indicate full marks.
**1(a)** Explain in brief different particle size measurement techniques.(4 marks)
**1(b)** Write applications of fluidization(4 marks)
**1(c)** Write short note on Ribben Blender.(4 marks)
**1(d)** Write short note on Elutriation.(4 marks)
**1(e)** What is minimum fluidization velocity.(4 marks)
**2(a)** If crushing rolls, 1 m in diameter, are set so that the crushing surfaces are 12.5 mm apart and the angle of nip is 31°, what is the maximum size of particle which should be fed to the rolls?

If the actual capacity of the machine is 12% of the theoretical, calculate the throughput in Kg/sec when running at 2.0 Hz if the working face of the roll is 0.4m long and the bulk density of the feed is 2500 kg/m^{3}.(10 marks)
**2(b)** Discuss conditions for Fluidization in details.(10 marks)
**3(a)** A slurry containing 5 kg of water/kg of solid is to be thickened to a sludge containing 1.5 kg of water/kg of solids in a continuous operation. A labroatory test five different concentrations of slurry yielded the following results:

Conc. (Kg water/kg of solid) 5.0 4.2 3.7 3.1 2.5

Rate of Sedimentation, (mm/sec) 0.20 0.12 0.094 0.070 0.052

Calculate the minimum area of the thickener to effect the separation of 1.33 kg/s of solids.(10 marks)
**3(b)** Discuss constant pressure filtration and constant rate filtration.(10 marks)
**4(a)** Derive the expression to estimate the size of smallest particle that can be separated in Cyclone separator.(10 marks)
**4(b)** Write construction, operation of continuous vacuum filtration unit and Derive the mathematical expression.(10 marks)
**5(a)** Discuss Blake Jaw Crusher in detail.(10 marks)
**5(b)** A sample of pyrite was screened. The screen analysis is given below.

Mesh | 8/10 | 10/14 | 14/20 | 20/28 | 28/35 | 38/48 | 48/65 |

Mass fraction retained | 0 | 21.2 | 19.6 | 17.4 | 14 | 15.8 | 12 |

Aperture, mm | 1.651 | 1.168 | 0.833 | 0.589 | 0.417 | 0.295 | 0.208 |

(i) Calculate the mean surface diameter. Specific Gravity of pyrite is 5.0

(ii) Find specific surface.(10 marks)

**6(a)**Write short note on :

(i) Bag Filter

(ii) Belt conveyor(10 marks)

**6(b)**A bed of ion-exchange beads 2.4 m deep is to be backwashed with water to remove dirt

The particles have a density of 1.24 g/cm

^{3}and an average size of 1.1 mm. What is the minimum fluidization velocity using water at 20°C, and what velocity is required to expand the bed by 25 percent? The beads are assumed to be spherical (Φ

_{s}= 1).

Given: ∈

_{M}= 0.40; m=3.9(10 marks)