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CHEE 321: Chemical Reaction Engineering Module 6: Non-Isothermal Reactors (Chapter 8, Fogler). Topics to be covered in this Module. Module 6a (Sections 8.2, 8.3, 8.4, 8.6.1 – Fogler, 4 th Edition) Develop Energy Balance equations for flow reactors.
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CHEE 321: Chemical Reaction EngineeringModule 6: Non-Isothermal Reactors (Chapter 8, Fogler)
Topics to be covered in this Module Module 6a (Sections 8.2, 8.3, 8.4, 8.6.1 – Fogler, 4th Edition) • Develop Energy Balance equations for flow reactors. • Enthalpy, Heat Capacity, and Heat of Reaction and relationship between them • Heat transfer rates for CSTR and PFR/PBR • Algorithms for Non-isothermal CSTR and PFR Module 6b (Sections 8.5) • Equilibrium Conversion (Reversible Reactions) in Reactors • Conversion attainable during adiabatic operation of endothermic and exothermic reactors • Increasing Conversion by inter-stage cooling and heating
Chemical Equilibrium and Equilibrium Constant The equilibrium constant (K) is a function of temperature only and related to Gibbs free energy change for the reaction by the following relationship The gibbs free energy change for a reaction can be calculated from gibbs free energy of formation data and knowledge of stoichiometry Consider, the Reaction: The Gibbs free energy change for the reaction can be written as
Exothermic Exothermic Kp Xe Endothermic Endothermic T T Temperature Dependence of Equilibrium Constant Van’t Hoff Relationship for Kp and T (Appendix C of Fogler)
Reaction: Equilibrium X T Adiabatic Operation & Equilibrium Conversion For a reactor operating adiabatically, the maximum conversion that may be achieved is the equilibrium conversion. How can we calculate this ? Step-1: Calculate Xe as a function of T
Equilibrium EB The above equation is obtained by substituting Q =0 and Ws=0 in the general EB equation below X T Adiabatic Operation & Equilibrium Conversion • Step-2: Calculate XEB as a function of Temperature from Steady State Energy Balance Equation
Equilibrium Xe X EB Adiabatic Temperature T T01 T02 Exothermic Reaction: A Closer Look at Adiabatic Conversion Increasing the inlet temperature results in shifting of the EB equation to the RIGHT
Exothermic Reactions: Achieving Higher Conversion by Inter-stage Cooling
Endothermic Reaction: A Closer Look at Adiabatic Conversion Equilibrium Increasing the inlet temperature results in shifting of the EB equation to the RIGHT Xe X EB T T01 T02 Adiabatic Temperature
Xe X3 X X2 X1 T Endothermic Reactions: Achieving Higher Conversion by Inter-stage Heating