北京化工大学-2004年化学反应工程期末考试参考答案(英文)

2004年化学反应工程期末考试参考答案
A.Choose one of the four answers (5 points for each one, 25 points in
total)
θ
( C ) mean residence time ?1
>
reactor, the final concentration of A is 0.01 mol/l. If the initial concentration C A0 is 1 mol/l, it takes 283[sec]. If the initial concentration C A0 is 5 mol/l, it takes 285[sec]. How long we need if the initial is 5 mol/l
B. A liquid-phase reaction A+B→products is conducted in an isothermal
batch reactor. The reaction is first order with respect to each reactant,
第 1 页
第 2 页
with k A =0.025 Lmol -1s -1, C A0=0.5molL -1, and C B0=1.0molL -1. Determine the time required for 75% conversion of A.
(20 points) ()
()[]sec 3.73025.05.01
12025.05.0125
.05.0125.05.000===⎪⎪⎭⎫ ⎝⎛+-=+--==-=-⎰
⎰t t dC C C t
C C dC C C C C C kC dt
dCA
C kC r Solution
A A A
A A A
A A
B B B A B A A
C. For a mixed flow reactor of volume 6m 3 operating with a steady-state (liquid) feed rate of 0.4m 3 min -1, what fraction of the exit stream (i) is of age less than 10 min? (ii) has been in the tank longer than 30 min?
(20 points) []()()()135.011-1 sec 30n longer tha 487
.0 sec 10 than lass 215
30667.015
10
sec 154
.06
20
2667
.000
10
212
1
=-=-======
==
==
⎰⎰⎰
⎰⎰-----θθθθθθθ
θθθθθθ
θθθ
θ
θd e d e F d e d e F d e F t Solution
D. A reaction A →R is to take place on a porous catalyst pellet (dp=6 mm, De=10-6m 3/m.cat.s ). How much is the rate slowed by pore diffusional resistance if the concentration of reactant bathing the particle is 100 mol/m 3 and the diffusion-free kinetics are given by
()⎪⎪⎭
⎫ ⎝
⎛
'''+=⎥⎦
⎤
⎢⎣⎡='''--De
C k n L M s cat m m ol C r n A
T A
A
21 modulus t hiele T he .1.01
32
第 3 页
(20 points) ()()236.087.33187.33187.313131187.310
2100
1.03001
.0001.03
6
=⎪⎪
⎭⎫ ⎝⎛⨯-⨯=⎪⎪⎭⎫ ⎝
⎛-=
=⨯⨯⨯===
-th M M th M M R
L Solution
T T T
T η
Choose one of the following two problems to solve as you like, don ’t choose both.
E. To deduce the residence time distribution for a mixed flow reactor. (15 points) ()()()()θ
θθ
θθθθθθτ
--==
=-=⎪⎪⎭
⎫ ⎝
⎛
-
-====-=
==-+=e d dF E F e C C
C C C t C
C dC d dt
dt
dC
V C C v dt dC V vC vC Solution R
R 11ln 00
,00
0000
F. The reaction
()210002
1k k C C S
R A S R k k ≠==−→−−→−
takes place in a mixed flow reactor. Determine the optimal space time and the maximal concentration of main product R.
(15 points)
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()()()()
()()()()()()()2
211202
12
221212110211
0211A0R
21001A0A 11
1111111011C C R For 11C C A For ⎪⎪⎭
⎫
⎝⎛⎪⎪⎭⎫ ⎝⎛+==
+++++-++==++=
+-+=-+=+=
k k C C k k k k k k k k k C k k k C d dC k k k V
C k C k vC vC V r vC vC k Solution
A RMAX mopt m m m m m A m m A m R
m m m R A R R R R R m
τττττττττττττ。