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Q18

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type=MCQ · page=7–8 · marks=2 · content_conf=0.7999999999999999 · math_conf=0.79

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file: GATE CH 2020 (with Solutions).pdf

pages: 7–8

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In a laboratory experiment, a unit pulse input of tracer is given to an ideal plug flow reactor operating at steady state with a recycle ration, R = 1. The exit age distribution E (t ), of the tracer at the outlet of the reactor is measured. The first four pulses observed at t₁ , t ₂,t₃, and t₄ are shown below.

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R = 1t_1t_2t_3t_4

Time, s In addition, use the following data and assumptions • R is defined as ratio of the volume of fluid returned to the entrance of the reactor to the volume leaving the system • No reaction occurs in the reactor • Ignore any dead volume in the recycle loop If the space time of the plug flow reactor is τ seconds, which one of the following is correct?

Options

A.
$t_1 = /tau{},t₂=2\tau{},t₃=3\tau{},t₄=4\tau{}$
B.
$t_1 = /tau{},/2 t₂=\tau{},t₃=3\tau{},/2 t₄=2\tau{}$
C.
$t_1 = /tau{},/3 t₂=2\tau{},/3 t₃=\tau{},t₄=4\tau{}/3$
D.
$t_1 = /tau{},/2 t₂=\tau{},/4 t₃=\tau{},/8 t₄=\tau{}/16$

Answer

Solution

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So, here in case of PFR with recycle stream,

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Third pulse will leave at,

t_3 = /tau{}_p'+/tau{}_p'+/tau{}_p = /frac{3}{2/tau{}_p}t_4 = t_3+/frac{/tau{}_p}{2} = 2/tau{}_p

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Source PDF: GATE CH 2020 (with Solutions).pdf

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