Corresponding Solutions for Chemical Reaction Engineering
CHAPTER 1 OVERVIEW OF CHEMICAL REACTION ENGINEERING .................................................. 1 CHAPTER 2 KINETICS OF HOMOGENEOUS REACTIONS ...................................................................... 3 CHAPTER 3 INTERPRETATION OF BATCH REACTOR DATA ................................................................ 7 CHAPTER 4 INTRODUCTION TO REACTOR DESIGN ............................................................................ 19 CHAPTER 5 IDEAL REACTOR FOR A SINGLE REACTOR ..................................................................... 22 CHAPTER 6 DESIGN FOR SINGLE REACTIONS ...................................................................................... 26 CHAPTER 10 CHOOSING THE RIGHT KIND OF REACTOR .................................................................. 32 CHAPTER 11 BASICS OF NON-IDEAL FLOW ............................................................................................ 34 CHAPTER 18 SOLID CATALYZED REACTIONS........................................................................................ 43
Chapter 1 Overview of Chemical Reaction Engineering
1.1 Municipal waste water treatment plant. Consider a municipal water treatment plant for a small community (Fig.P1.1). Waste water, 32000 m3/day, flows through the treatment plant with a mean residence time of 8 hr, air is bubbled through the tanks, and microbes in the tank attack and break down the organic material
icrobes???? (organic waste) +O2 ?mCO2 + H2O
A typical entering feed has a BOD (biological oxygen demand) of 200 mg O2/liter, while the effluent has a megligible BOD. Find the rate of reaction, or decrease in BOD in the treatment tanks.
Waste water
32,000 m3/day
Waste water Treatment plant Clean water 32,000 m3/day
200 mg O2 needed/liter
Mean residence time t =8 hr Figure P1.1
Zero O2 needed
Solution:
?rA??dNAVdt1m3mg1g1000L32g?32000?(?day)?(200?0)/313dayL1000mgmmol ??1m31day32000?day3day3?18.75mol/(m3?day)?2.17?10?4mol/(m3?s)
1.2 Coal burning electrical power station. Large central power stations (about 1000 MW electrical) using fluiding bed combustors may be built some day (see Fig.P1.2). These giants would be fed 240 tons of coal/hr (90% C, 10%H2), 50% of which would burn within the battery of primary fluidized beds, the other 50% elsewhere in the system. One suggested design would use a battery of 10 fluidized beds, each 20 m long, 4 m wide, and containing solids to a depth of 1 m. Find the rate of reaction within the beds, based on the oxygen used.
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Solution:
V?(20?4?1)?10?800m3
?Nc?t??240?103coalhr?0.5?0.9kgckgckgcoal??108?103hr??9000molc/(bed?hr)rO2??rc??1?NcV?t??1?90003800?1?11.25kmolO2/(m?hr)
dO2dt?9000?1?120004?12000mol/(bed?hr) ?r?1dO2?1.5?104mol/(bed?hr)O2?4.17mol/(m3Vdt800?s)
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Chapter 2 Kinetics of Homogeneous Reactions
2.1 A reaction has the stoichiometric equation A + B =2R . What is the order of reaction? Solution: Because we don’t know whether it is an elementary reaction or not, we can’t tell the index of the reaction.
2.2 Given the reaction 2NO2 + 1/2 O2 = N2O5 , what is the relation between the rates of
formation and disappearance of the three reaction components? Solution: ?rNO2??4rO2?2rN2O5
2.3 A reaction with stoichiometric equation 0.5 A + B = R +0.5 S has the following rate
expression
-rA = 2 C0.5 ACB
What is the rate expression for this reaction if the stoichiometric equation is written as
A + 2B = 2R + S
Solution: No change. The stoichiometric equation can’t effect the rate equation, so it doesn’t change.
2.4 For the enzyme-substrate reaction of Example 2, the rate of disappearance of substrate is
given by
-rA =
1760[A][E0] , mol/m3·s
6?CA What are the units of the two constants? Solution: [?rA]?mol[k][A][E0] ?3m?s[6]?[CA]?[6]?[CA]?mol/m3
molmol/m31 [k]?3??m?s(mol/m3)(mol/m3)s
rate expression
-rA = k1[A][B]
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2.5 For the complex reaction with stoichiometry A + 3B → 2R + S and with second-order
are the reaction rates related as follows: rA= rB= rR? If the rates are not so related, then how are they related? Please account for the sings , + or - .
11Solution: ?rA??rB?rR
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2.6 A certain reaction has a rate given by
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-rA = 0.005 C2 min A , mol/cm·
If the concentration is to be expressed in mol/liter and time in hours, what would be
the value and units of the rate constant? Solution:
'(?rA)?'??rA?molmol?(?rA)?3 L?hrcm?minL?hrmol22?3(?rA)?104?6?rA?6?104?0.005CA?300CA molcm?minmolmol?(CA)?3Lcm
Lmol'?CA??3?CA?103CAmolcm'(CA)?'2'2'?(?rA)?300CA?300?(10?3CA)?3?10?4CA
2?k'?3?10?4
2.7 For a gas reaction at 400 K the rate is reported as -
dpA = 3.66 p2 A, atm/hr dt (a) What are the units of the rate constant?
(b) What is the value of the rate constant for this reaction if the rate equation is
expressed as
-rA = - Solution:
(a) The unit of the rate constant is [1/atm?hr] (b) ?rA??1dNA
Vdt1dNAVdt3
= k C2 s A , mol/m·
Because it’s a gas reaction occuring at the fined terperatuse, so V=constant, and T=constant, so the equation can be reduced to
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