1. Isothermal Reactor Design
Chapter 4
Isothermal Reactor Design

2. Overview
Chapter 1 and 2 focus on mole balances on reactors to predict the volume
Chapter 3 focuses on reactions
Cahpter 4 combine previous chapters to obtain optimum reactor design

3. Design Algorithm Mole balance (reactor type)
Reaction rate law (reaction type, orders)
Stoichiometry (reaction coefficients)
Combine steps 1, 2 and 3
Evaluate (integrate) either
Analytically Graphically
Numerically Polymath

5. Liquid Phase Batch For the irrev, 2nd order reaction Mole balance step
Rate law step
Stoichiometry step
Combine step
Evaluate step

6. 4.3 CSTR For 1st order and irrev reaction Mole balance step
Rate law step
Stoichiometry step
Combine step
Evaluate step
Damkohler number Da
Da gives the degree of conversion in flow reactor

7. 4.3.2 CSTRs in Series
For equal size CSTRs τ1=τ2=τ operate at the same T k1=k2=k and constant ν0
For n equal size CSTRs τ1=τ2=…=τn=τ operate at the same T k1=k2=…=kn=k

8. 4.3.3 CSTRs in Parallel
For identical individual reactor volume, Vi, conversion, Xi, and reaction rate -rAi
The conversion by each reactor is the same as if the total feed is charged to one large reactor of volume V

9. 4.3.4 2nd order reaction in a CSTR
For 2nd order, liquid phase reaction in a CSTR

10. 4.4 Tubular Reactors Consider 2nd order reaction in PFR
For liquid phase
For constant T and P gas phase

11. Three reaction types A→nB
n<1, ε<0 (δ<0) → ν↓, the molecules will spend longer time and ↑X than if v=v0
n>1, ε>0 (δ>0) ν ↑, the molecules will spend less time and ↓ X than if v=v0
n=1, ε=0 (δ=0) v=v0

12. 4.5 Pressure Drop in Reactors
For liquid phase reactions the pressure drop can be ignored because the effect of pressure on the concs is small.
For gas phase reactions the conc. of the reacting species is directly proportional to the total pressure
Accounting for the pressure drop is a key factor in the proper reactor operation

13. 4.5.1 Pressure drop and the rate law
To account for pressure drop differential form design equation must be used
For gas phase 2nd order reaction in PBR

14. 4.5.2 Flow through a packed beds
If y is defined as y=P/P0
For a gas phase reactions in PBR of catalyst particles
α is the bed characteristics

15. 4.5.4 Analytical solution
For 2nd order isothermal reaction with ε=0 in PBR

16. Integrating with X=0 @ W=0 and
Solving for X and W gives