1. Reaction Kinetics and Reactors Review
Greg Jarnutowski, Oliver Meade,
Ben Brock, Kyle Patrick, James Stephen

2. Overview Reaction Kinetics Batch Reactors
Continuous Stirred Tank Reactors
Plug Flow Reactors
Transient Processes

3. Main Kinetics Takeaways
Kinetics, Reaction Rate, and Conversion
Kinetics is important
Profitability
Safety
Rate = Change in Molarity/sec
r=k*Reactant1A*Reactant2B
k=Rate constant
Raghavan CHBE 440 Lecture 1

4. Zero, First, and Greater than First Order Rxns
Rate
[M]/s
Time

5. Batch Reactor Kinetics
Design Equations:
Assumptions for a Batch Reactor:
Closed System
Uniform Mixing
Constant Volume
Constant Pressure
➜Constant Volume
➜Variable Volume
Where C is concentration, N is moles, V is volume, v is stoichiometric coefficient, and r is rate
A batch reactor is a reactor that allows the reaction to take place with adding or removing anything throughout the reaction.
The design equations are on the left of the slide, where C is concentration, N is moles, V is volume, v is stoichiometric coefficient, and r is rate.
For the design equations, the following assumptions are made.
The system is closed, this is because nothing is entering or leaving the reactor during the process.
The system is assumed to be well-mixed to ensure the rate is constant throughout the reactor because it is dependent on concentration.
The reactor also has constant volume and pressure.
The reactor temperature is easily controlled with a heating and cooling jacket, which is important for processes that have very exothermic reactions.

6. Batch Reactors in Industry
Usage in Industry:
•Pharmaceutical Production
•Fermentation
•Smaller Scale Production
High conversion per unit volume
Batch reactors are used in industry for a few applications.
Batch reactors are used for pharmaceuticals because of the precise temperature control.
They are also used in fermentation, like for making beer.
The batch reactor is used for smaller scale production because the reaction takes longer to reach the desired conversion.
The reactors allow for a high conversion per unit volume because the time in the reactor can be as high as desired.
For large scale production, the batch reactor is less effective because of how long the process takes.

7. Continuous Stirred Tank Reactor Kinetics
Design Equation:
Assumptions in the CSTR Design Equation:
•Steady state (no accumulation)
•Well mixed with same concentration throughout
Key Facts:
•Concentration and rate of reaction is constant throughout a CSTR
•CSTRs typically achieve a lower conversion than PFRs for the same reactor volume
•Many CSTRs in series will behave similar to a single PFR with the same total volume
Image source: wikipedia.com

8. The main advantage of CSTRs over PFRs is better temperature control
Energy Balance:
Heat removed by cooling jacket
Heat removed by flow
Heat generated or removed by reaction
CSTR is a well-mixed reactor so the temperature is constant throughout
•Constant heating/cooling rate over whole reactor
•PFRs require different heating rates down the length of reactor
PFRs require different heating rates down the length of reactor
Image source:

9. Plug Flow Reactor Kinetics
Design Equation:
Assumptions in the PFR Design Equation:
Plug FLow
No Axial Mixing, Uniform concentration at a given Z
Steady State
CA is dependent on position in reactor.
Key Facts:
•Concentration and rate of reaction varies along the length of the reactor
•Single pass conversion depends on reactor length

10. Plug Flow Reactors in Industry
Pros:
Large Processing Volume
Low Maintenance Costs
Creative Spacing Options
More Effective Conversion/Volume
Cons:
More Difficult to Control Temperature
Plug Flow not valid assumption, may get lower yields than expected

11. Transient Processes
Processes often not at steady state (most of the time)
Nonzero accumulation term
Transient CSTR:

12. Transient CSTR ODE Solution: Time to reach steady state (99%)
tss is k dependent: small for a large k,
large for a small k

13. Semibatch Reactor Cross between a CSTR and a batch reactor
Useful for maximizing selectivity, controlling exothermic temperature release
Mass balance:

14. Questions?

15. Bibliography
Batch Reactors, umich.edu/~elements/asyLearn/bits/batch/index.htm.
(Dr. Raghavan Slides)
“Plug Flow Reactors.” Visual Encyclopedia of Chemical Engineering, encyclopedia.che.engin.umich.edu/Pages/Reactors/PFR/PFR.html.(PFR Image #1)
library.automationdirect.com/wp-content/uploads/2015/07/Portable-Water-Treatment-Platform-3.jpg.(PFR Image #2)
Woodard, Barney, et al. Fermentation Science and Biopharmaceutical Production. Vol. 2, Vandalay Publishing, 2017.