1. ChemCad Tutorial: Reactors
CHBE 464
Team # 11
Pooneh Azadikhah
Levy Minchala
Theo Nimpson
Linka Touch
Date: Feb 3, 2017

2. Get Started Select components Adjust unit Select your unit operations
4 Types of Reactors:
Stoichiometric
Equilibrium
Gibb
Kinetic

3. Water-Gas Shift Reaction
Used to improve H2 production in steam reforming of methane
Most Important reaction used in the Fischer-Tropsch Process to balance H2/CO ratio
Water-Gas Shift reaction: CO + H2O → CO2 + H2

4. Conditions
Conditions chosen are similar to those used during steam reforming process:
Temperature °C
Pressure - 1 atm
Pressure drop – atm
H2O = 30 kmol/hr CO = 10 kmol/hr

5. Stoichiometric Reactor
Need to specify stoichiometry of reaction, key component, and fraction conversion in order to have ChemCad calculate product compositions and heat duty

6. Stoichiometric Reactor
Assume adiabatic for simplicity
Reaction:
CO + H2O → CO2 + H2

7. Stoichiometric Reactor
Pros:
Simplest reactor model
Mostly use for a preliminary model
Initial calculation/observation
Cons:
Use only for a single reaction
Normally would change to other reactor for accuracy

8. Equilibrium Reactor Pros: Cons: Simple reactor model and easy to use
Used to perform multiple reactions
Cons:
Normally would change to other reactor for accuracy

9. Equilibrium Reactor
Make sure to enter the number of reactions occurring and the pressure drop
Choose the expected phase conditions of the reaction

10. Equilibrium Reactor
The General equilibrium reactor model used for most reactions
There are two exceptions:
Water-Gas shift reactions
CO + H2O → CO2 + H2
Methanation reactions
CO + 3H2 → CH4 + H2O
Each exception has a unique model

11. Choose the appropriate thermal mode
Specify the calculation mode to set...
the reactions as dependent (Series) or independent (Parallel) of each other
the temperature range
Or total extent of reaction

12. Choose the appropriate thermal mode
Specify the calculation mode to set...
the reactions as dependent (Series) or independent (Parallel) of each other
the temperature range
Or total extent of reaction

13. General model
Shift model
Methanation model

14. Specify one of the following
Choose a reference compound for the reaction
Specify the phase of the reaction
Include all compounds involved in the reaction
Include stoichiometric coefficient for each compound

15. Gibbs Reactor
Calculates product rates, compositions, and thermal conditions by minimizing Gibbs free energy
Pros
Cons
Easy - Minimum input is identity of feed. No reaction stoichiometry required
No time dependency - Can only determine hypothetical equilibrium mixture

16. Can select Vapor/Mixed or Liquid Streams
Specify optional air/fuel streams here.
Lambda factor is air/fuel ratio on molar basis. Inputting value here adjusts air stream to meet fuel stream at the specified ratio
Calculated Heat of Reaction appears here
Select calculation based on ideal solution or activity factors
Defaults are 10, 1E-5
If selecting adiabatic or heat duty mode, the calculated outlet T will appear here
If no pressure specified, default is the feed pressure
Default Pressure drop is 0. Approach DT is the delta T value used in calculations
For adiabatic, sets allowable T range for calculation. If minimum Gibbs energy occurs outside this range, the min or max value is used instead

17. Solids and Inerts Tabs

18. Gibbs Reactor
Second Window - Only requires input if using user-created components

19. After running the reactor

20. Kinetic Reactor Several reaction can be used, about 300
By knowing the conversion, the size of the reactor can be calculated and vice versa
Reaction can be in liquid and vapor phase or mix phase
First few steps are like the other types of reactors, like choosing the components and changing the units to SI units and also feed stream properties

21. Kinetic Reactor Specify conversion 0.633 Calculate the size
Kinetic reactor modes:
Adiabatic
Isothermal
Specified heat duty
Specified temperature profile
Specified utility condition

22. Kinetic Reactor We need to specify Frequency factor Activation energy
Stoichiometric coefficient
Run

23. Conclusion Each type of ChemCad reactor has different role
Stoichiometric, Equilibrium, Gibbs, and Kinetic
Stoichiometric Reactor for when you want quick results for a simple reaction
Equilibrium Reactors for when you want quick results for multiple reactions
Gibbs Reactors for when you want to know the equilibrium mixture
Kinetics Reactor for CSTR and PFR reactions
Each reactor has its pros and cons
It is up to the engineer to choose the correct one for his/her design