PTT 248 REACTOR ENGINEERING CHAPTER 2 CONVERSION REACTOR

Reactors in Series The exit stream of one reactor is fed to the next

CSTR in Series Reactor 1: Mole Balance: In – Out + Generation = 0

CSTR in Series Reactor 2: Mole Balance: (1) In – Out + Generation =

CSTR in Series (1) FA 1 = FA 0 – FA 0 X 1

CSTR in Series EXAMPLE 3 X [FA 0/-r. A](m 3) 0. 0 0. 89

EXAMPLE 3 X [FA 0/-r. A](m 3) 0. 0 0. 89 0. 1 1.

EXAMPLE 3 CSTR in Series Levenspiel Plot of CSTR in series 9. 00 8.

PFR in Series V 1 V 2 The overall conversion of two PFRs in

PFR in Series EXAMPLE 4 X [FA 0/-r. A](m 3) 0. 0 0. 89

X [FA 0/-r. A](m 3) 0. 0 0. 89 0. 1 1. 08 0.

COMBINATION OF CSTR & PFR FA 0/-r. A V 1, CSTR X 1 V

Space Time Space time/Mean residence time/Holding time : Time necessary to process one reactor

Space Velocity, SV Space velocity can be defined as: 2 types of SV that

Summary Conversion: Batch reactor: Design equation: Batch: Flow Reactors CSTR: PFR: PBR: Reactor in

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PTT 248 REACTOR ENGINEERING CHAPTER 2 CONVERSION & REACTOR SIZING (PART 3) 1

Reactors in Series The exit stream of one reactor is fed to the next one 2

CSTR in Series Reactor 1: Mole Balance: In – Out + Generation = 0 FA 0 – FA 1 + r. A 1 V 1 = 0 [1] The molar flow rate of A at point 1: FA 1 = FA 0 – FA 0 X 1 (1) (2) [2] Combining [1] & [2]: 3

CSTR in Series Reactor 2: Mole Balance: (1) In – Out + Generation = 0 FA 1 – FA 2 + r. A 2 V 2 = 0 [3] (2) The molar flow rate of A at point 2: FA 2 = FA 0 – FA 0 X 2 [4] Expressed in eq [2] & [4] [5] 4

CSTR in Series (1) FA 1 = FA 0 – FA 0 X 1 [2] FA 2 = FA 0 – FA 0 X 2 [4] [5] (2) X 2=0. 8 Substituting [2] &[4] into [5]; 5

CSTR in Series EXAMPLE 3 X [FA 0/-r. A](m 3) 0. 0 0. 89 0. 1 1. 08 0. 2 1. 33 0. 4 2. 05 0. 6 3. 54 0. 7 5. 06 0. 8 8. 0 For the two CSTRs in series, 40% conversion is achieved in the first reactor. What is the volume of each of the two reactors necessary to achieve 80% overall conversion of entering species? 6

EXAMPLE 3 X [FA 0/-r. A](m 3) 0. 0 0. 89 0. 1 1. 08 0. 2 1. 33 0. 4 2. 05 0. 6 3. 54 0. 7 5. 06 0. 8 8. 0 For reactor 1, X = 0. 4 For reactor 2, X = 0. 8 7

EXAMPLE 3 CSTR in Series Levenspiel Plot of CSTR in series 9. 00 8. 00 FA 0/-r. A (m 3) 7. 00 6. 00 5. 00 4. 00 3. 00 2. 00 V 2 V 1 1. 00 0 0. 1 0. 2 0. 3 0. 4 0. 5 Conversion X 0. 6 0. 7 0. 8 0. 9 8

PFR in Series V 1 V 2 The overall conversion of two PFRs in series is the same as ONE PFR with the same total volume. FA 0/-r. A (m 3) 9. 00 8. 00 7. 00 6. 00 5. 00 4. 00 3. 00 2. 00 1. 00 0. 00 V 1, PFR 0 0. 2 0. 4 V 2, PFR 0. 6 Conversion X 0. 8 1 9

PFR in Series EXAMPLE 4 X [FA 0/-r. A](m 3) 0. 0 0. 89 0. 1 1. 08 0. 2 1. 33 0. 4 2. 05 0. 6 3. 54 0. 7 5. 06 0. 8 8. 0 Calculate the reactor volume V 1 and V 2 for the plug-flow sequence shown below when the intermediate conversion is 40% & the final conversion is 80%. 10

X [FA 0/-r. A](m 3) 0. 0 0. 89 0. 1 1. 08 0. 2 1. 33 0. 4 2. 05 0. 6 3. 54 0. 7 5. 06 0. 8 8. 0 Using Simpsons One-Third Rule; For reactor 1, ∆X=0. 2, X 0 = 0, X 1 = 0. 2, X 2 = 0. 4 11

X [FA 0/-r. A](m 3) 0. 0 0. 89 0. 1 1. 08 0. 2 1. 33 0. 4 2. 05 0. 6 3. 54 0. 7 5. 06 0. 8 8. 0 For reactor 2, ∆X=0. 2, X 0 = 0. 4, X 1 = 0. 6, X 2 = 0. 8 Total volume; 12

COMBINATION OF CSTR & PFR FA 0/-r. A V 1, CSTR X 1 V 3, CSTR V 2, PFR X 2 X 3 X 13

Space Time Space time/Mean residence time/Holding time : Time necessary to process one reactor volume of fluid based on entrance conditions time taken for a fluid to either completely enter or completely exit the reactor Eg: If V=0. 2 m 3, v 0= 0. 01 m 3/s, what is τ? Answer: τ = 20 s 14

Space Velocity, SV Space velocity can be defined as: 2 types of SV that is commonly used in industry: Liquid-hourly space velocity (LHSV) –measures liquid volumetric rate at 60°F or 75°F Gas-hourly space velocity (GHSV)-measures gas volumetric at standard temperature & pressure (STP) 15

Summary Conversion: Batch reactor: Design equation: Batch: Flow Reactors CSTR: PFR: PBR: Reactor in series: Conversion: CSTR in series: PFR in series: 16