Subject Code: 2170501
GUJARAT TECHNOLOGICAL UNIVERSITY
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BE - SEMESTER-VII (NEW) EXAMINATION — WINTER 2017Subject Name: Chemical Reaction Engineering - II
Time: 10:30 AM TO 01:00 PM
Instructions:
- Attempt all questions.
- Make suitable assumptions wherever necessary.
- Figures to the right indicate full marks.
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Q.1 (a) Define the factors required to formulate contacting patterns. [03]
(b) Prove that degree of segregation does not have any effect on the conversion for first order reaction in CSTR. [04]
(c) The tabulated data represent a continuous response to pulse input into a closed vessel which is to be used as chemical reaction. Calculate the mean residence time of fluid in the vessel and tabulate and construct E curve. Determine the fraction of material leaving the vessel that has spent between 10 and 15 min in the vessel. [07]
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t, min | 0 | 5 | 10 | 15 | 20 | 25 | 30 | 35
Cpulse, gm/l | 0 | 3 | 5 | 5 | 4 | 2 | 1 | 0
Q.2 (a) Discuss the factors to consider in selecting contactors for fluid- fluid reactions. [03]
(b) Explain the enhancement factor and Hatta modulus. [04]
(c) Discuss with diagrams various contacting patterns for two phase system. [07]
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OR
Q.2 (a) Describe all eight cases for mass transfer and reaction for fluid-fluid reactions with neat sketch [07]
Q.3 (a) Give some industrial examples of fluid particle reactions. [03]
(b) Describe Progressive Conversion Model (PCM) with appropriate diagram. [04]
(c) Derive the expression for fractional conversion for the reaction between solid and fluid when particles of solid are changing in size and Diffusion through Gas film controls. [07]
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OR
Q.3 (a) Discuss the limitation of Shrinking Core Model. [03]
(b) Discuss the effects of temperature, time and particle size on determination of rate controlling step for fluid particle reactions. [04]
(c) Spherical particles of Znic blends of size R=1 mm are roasted in an 8% oxygen stream at 900°C and 1 atm. The stoichiometry of the reaction is
2ZnS +3O2 = 2ZnO + 2SO2
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Assuming that reaction proceeds by the shrinking core model calculate the time needed for complete conversion of a particle and the relative resistance of ash layer diffusion during this operation. Film resistance can safely be neglected as long as a growing ash layer is present. [07]Data:
Density of solid ?B=4.13 gm/cm3
Reaction rate constant k” =2 cm/sec
For gases in the ZnO layer D= 0.08 cm2/sec
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Q.4 (a) Explain catalyst promoters. Catalyst inhibitors, Catalyst poisons, molecular sieves. [03]
(b) Discuss various industrial catalytic reactors. [07]
OR
Q.4 (a) Discuss classification of catalyst. [03]
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(b) Write short notes on Tank in series model for the non Ideal Reactor. [04](c) Give merits and Demerits of fixed bed and fluidized bed reactor. [07]
Q.5 (a) Determine the amount of catalyst needed in a packed bed reactor with a very large recycle rate for 35% conversion of A to R for a feed rate of 2000 mol/hr of pure A at 3.2 atm and 117°C.
The reaction at given temperature is A?4R. Assume mixed flow reaction. [03]
(b) Discuss in detail deviations from ideal flow pattern with examples. [04]
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(c) Explain various experimental methods for finding reaction rates [07]OR
Q.5 (a) Explain difference between activity and selectivity of catalyst. [03]
(b) Explain the mechanism of solid catalysed reactions. [04]
(c) Discuss heat effects during solid catalysed reactions. [07]
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Date: 02/11/2017
Total Marks: 70
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