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

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

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

Conditions Conditions chosen are similar to those used during steam reforming process: Temperature - 1000 °C Pressure - 1 atm Pressure drop – 0.001 atm H2O = 30 kmol/hr CO = 10 kmol/hr

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

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

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

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

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

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

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

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

General model Shift model Methanation model

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

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

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

Solids and Inerts Tabs

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

After running the reactor

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

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

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

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