Ch E 441: Chemical Kinetics and Reaction Engineering  Mole Balances in Reacting Systems  Reactor Design Equations

Ch E 441: Chemical Kinetics and Reaction Engineering Mole Balances in Reacting Systems Reactor Design Equations PowerPoint PPT Presentation


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Learning Objectives. Describe photos of real reactors. Define the rate of chemical reaction. Apply a general mole balance to a batch reactor, a continuous stirred tank reactor (CSTR), a plug flow reactor (PFR), and a packed bed reactor (PBR). . Chemical Identity. A chemical species has reacted w

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Ch E 441: Chemical Kinetics and Reaction Engineering Mole Balances in Reacting Systems Reactor Design Equations

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1. Ch E 441: Chemical Kinetics and Reaction Engineering Mole Balances in Reacting Systems & Reactor Design Equations David A. Rockstraw, Ph.D., P.E. New Mexico State University Chemical Engineering

2. Learning Objectives Describe photos of real reactors. Define the rate of chemical reaction. Apply a general mole balance to a batch reactor, a continuous stirred tank reactor (CSTR), a plug flow reactor (PFR), and a packed bed reactor (PBR).

3. Chemical Identity A chemical species has reacted when it has lost its chemical identity. The identity of a chemical species is determined by the kind, number, and configuration of that species' atoms. Three ways a chemical species can lose its chemical identity: decomposition combination isomerization

4. Reaction Rate The reaction rate is the rate at which a species looses its chemical identity per unit volume. The rate of a reaction can be expressed as the rate of disappearance of a reactant or as the rate of appearance of a product. Consider species A: rA = rate of formation of A per unit vol -rA = rate of a disappearance of A per unit vol For a catalytic reaction, -rA' is the rate of disappearance of species A on a per mass of catalyst basis. NOTE: dCA/dt is not the rate of reaction

5. Reaction Rate Consider in general terms, species j… The rate, rj is the rate of formation of species j per unit volume a function of concentration, temperature, pressure, and the type of catalyst (if any) independent of the type of reaction system (batch, plug flow, etc.) an algebraic equation, not a differential equation

6. General Mole Balance Equation

7. General Mole Balance Equation If rj varies with position in the system,

8. General Mole Balance Equation

9. GMBE Applied to Batch Reactors For a batch reactor (no flows): GMBE reduces to:

10. GMBE Applied to Batch Reactors Assuming perfect mixing:

11. GMBE Applied to Batch Reactors For the simple reaction A ? products: In a constant volume reactor,

12. GMBE Applied to Batch Reactors For the simple reaction A ? products: In a constant pressure reactor,

13. GMBE Applied to Flow Reactors Continuous Stirred-Tank Reactor (CSTR):

14. GMBE Applied to Flow Reactors Continuous Stirred-Tank Reactor (CSTR):

15. GMBE Applied to Flow Reactors Tubular (Plug Flow) Reactor (PFR):

16. GMBE Applied to Flow Reactors Tubular (Plug Flow) Reactor (PFR):

17. GMBE Applied to Flow Reactors Tubular (Plug Flow) Reactor (PFR):

18. GMBE Applied to Flow Reactors Tubular (Plug Flow) Reactor (PFR):

19. GMBE Applied to Packed Bed Reactors PBR used for fluid/solid catalytic reaction:

20. GMBE Applied to Packed Bed Reactors PBR used for fluid/solid catalytic reaction:

21. GMBE Applied to Packed Bed Reactors PBR used for fluid/solid catalytic reaction:

22. Design Equation Summary

23. Next Session Define conversion and space time. Write the mole balances in terms of conversion for a batch reactor, CSTR, PFR, and PBR. Size reactors either alone or in series once given the molar flow rate of A, and the rate of reaction, -rA, as a function of conversion, X.

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