PTT 248 REACTOR ENGINEERING CHAPTER 2 CONVERSION REACTOR
- Slides: 18
PTT 248 REACTOR ENGINEERING CHAPTER 2 CONVERSION & REACTOR SIZING (PART 2) 1
Reactor Sizing: CSTR & PFR With a given –r. A as a function of conversion, X, we can size any type of reactor. HOW? ? ? Construct Levenspiel Plot FA 0/-r. A vs. X Volume of the reactors can be represented as the shaded areas in the Levelspiel Plots: 2
Reactor Sizing Consider a first order reaction; A plot of 1/-r. A vs. X can be constructed; 3
Reactor Sizing 1/-r. A (m 3. s/mol) Conversion X 4
Reactor Sizing: Sizing A CSTR EXAMPLE 1 5
EXAMPLE 1 Calculate the volume to achieve 80% conversion in a CSTR. Given, species A enters the reactor at a molar flow rate of 0. 4 mol/s. SOLUTION: 1. Find – 1/r. A at X=0. 8 2. Calculate V. 6
Sizing A CSTR EXAMPLE 1 X r. A FA 0/r. A Levelspiel Plot: 0 0. 45 0. 89 0. 1 0. 37 1. 08 0. 2 0. 3 1. 33 0. 4 0. 195 2. 05 0. 6 0. 113 3. 54 0. 7 0. 079 5. 06 0. 8 0. 05 8. 00 FA 0/-r. A (m 3) Conversion X 7
Reactor Sizing: Sizing A PFR Volume of a PFR can be calculated using integration formulas: Trapezoidal Rule (2 -point) Simpson’s One-Third Rule (3 -point) Simpson’s Three-Eighths Rule (4 -point) Five-Point Quadrature Formula 8
Reactor Sizing: Sizing A PFR Trapezoidal Rule (2 -point): Simpson’s One-Third Rule (3 -point): 9
Reactor Sizing: Sizing A PFR Simpson’s Three-Eighths Rule (4 -point): Five-Point Quadrature Formula: 10
Sizing A PFR EXAMPLE 2 Calculate the volume to achieve 80% conversion in a PFR. Given, species A enters the reactor at a molar flow rate of 0. 4 mol/s. 11
Reactor Sizing: Sizing A PFR Recall the design equation of PFR: For X=0. 8, 12
Sizing A PFR EXAMPLE 2 X r. A FA 0/r. A Levelspiel Plot: 0 0. 45 0. 89 0. 1 0. 37 1. 08 0. 2 0. 3 1. 33 0. 4 0. 195 2. 05 0. 6 0. 113 3. 54 0. 7 0. 079 5. 06 0. 8 0. 05 8. 00 9. 00 8. 00 7. 00 6. 00 5. 00 FA 0/-r. A (m 3) 4. 00 3. 00 2. 00 1. 00 0 0. 2 0. 4 Conversion X 0. 6 0. 8 1 13
Sizing A PFR Recall 5 -Point Quadrature Rule: Find h (∆X): 14
Sizing A PFR EXAMPLE 2 X r. A FA 0/r. A Levelspiel Plot: 0 0. 45 0. 89 0. 1 0. 37 1. 08 0. 2 0. 3 1. 33 0. 4 0. 195 2. 05 0. 6 0. 113 3. 54 0. 7 0. 079 5. 06 0. 8 0. 05 8. 00 9. 00 8. 00 7. 00 6. 00 5. 00 FA 0/-r. A (m 3) 4. 00 3. 00 2. 00 1. 00 0 0. 2 0. 4 Conversion X 0. 6 0. 8 1 15
Sizing A PFR Find V: Substituting the numerical values: --> PFR with volume of 2. 165 m 3 is required to reach 80% conversion 16
Comparing Volume of CSTR &PFR 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 Difference btwn CSTR & PFR volumes=4. 235 m 3 0. 2 0. 4 0. 6 Conversion X 0. 8 1 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 FA 0/-r. A (m 3) 0 9. 00 8. 00 7. 00 6. 00 5. 00 4. 00 3. 00 2. 00 1. 00 0 0. 2 0. 4 0. 6 0. 8 1 Conversion X 0 0. 2 0. 4 0. 6 Conversion X 0. 8 1 17
Comparing Volume of CSTR &PFR 8. 00 6. 00 FA 0/-r. A (m 3) 10. 00 6. 00 4. 00 2. 00 0 0. 2 0. 4 0. 6 0. 8 Conversion X 1 0. 00 0 0. 2 0. 4 0. 6 0. 8 1 Conversion X VCSTR > VPFR for the same conversion & rxn condition. WHY? ? ? 18
