Chemical Reaction Engineering Quiz on “Applications of Design Equations for Continuous – Flow Reactors”.
1. Find the volume of reactor needed for 70% conversion of A to product. Aqueous feed of A and B (200lit/min, 20mmolA/lit, 50mmolB/lit) is fed to MFR. Reaction kinetics is as follows
A+B → P
-rA = 200CACB mol/lit-min
a) 12.5
b) 3.6
c) 6.4
d) 1.5
Answer: c
Clarification:
CA0*XA = CB0*XB
XB = (frac{20*0.7}{50}) = 0.28
(frac{τ}{CA0} = frac{XA}{-rA})
τ = (frac{0.7*20*10^{-3}}{200*10^{-6}[20(1-0.7)*50(1-0.28)])}) = 0.032 = (frac{V}{v0} )
V = 0.032*200 = 6.4 lit.
2. An existing MFR is to be replaced by the one 4 times larger than it. Find the new conversion if a homogeneous liquid phase reaction with reaction kinetics as follows.
A → R
-rA = kCA2 with 30% conversion.
a) 0.67
b) 0.45
c) 0.53
d) 0.92
Answer: c
Clarification:
(frac{τ}{CA0} = frac{XA}{-rA} )
(frac{V}{CA0 V0} = frac{0.3}{k[ CA0(1-0.3)]^2} )
(frac{V}{CA0 V0}) = kτCA0 = 0.6122
When replaced by new reactor
(frac{4τ}{CA0} = frac{XA}{-rA} )
(frac{4Vk}{CA0 V0} = frac{XA}{(1-XA)^2} )
XA = 0.53.
3. Replace the existing MFR with a PFR and calculate the new conversion if a homogeneous liquid phase reaction with reaction kinetics as follows.
A → R
-rA = kCA2 with 30% conversion
a) 0.65
b) 0.43
c) 0.38
d) 0.92
Answer: c
Clarification:
(frac{τ}{CA0} = frac{XA}{-rA} )
(frac{V}{CA0 V0} = frac{0.3}{k[ CA0(1-0.3)]^2} )
(frac{Vk}{CA0 V0} ) = kτCA0 = 0.6122
When replaced with a new PFR
(frac{τ}{CA0} = int_0^{XA} frac{dXA}{-rA} )
For 2nd order on Integration we get,
kτCA0 = (frac{XA}{1-XA}) = 0.6122
XA = 0.38.
4. Find the conversion of a 25 litre PFR if a gaseous feed of pure A (2 mol/lit, 150 mol/min)
Is decomposed, kinetics are as follows.
A → 2.5R
-rA = (15min-1) CA
a) 0.89
b) 0.92
c) 0.45
d) 0.68