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Adiabatic Operation

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Adiabatic Operation

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  1. Lecture18 Thursday 3/13/08Solution to Tuesdays In-class Problem .User Friendly Energy Balance DerivationsAdiabatic (Tuesday’s lecture) .Heat Exchange Constant Ta .Heat Exchange Variable Ta Co-current .Heat Exchange Variable Ta Counter Current

  2. Adiabatic Operation Elementary liquid phase reaction carried out in a CSTR The feed consists of both inerts I and Species A with the ratio of inerts to the species A being 2 to 1. (a) Assuming the reaction is irreversible, A  B, (KC = 0) what reactor volume is necessary to achieve 80% conversion? (b) If the exiting temperature to the reactor is 360K, what is the corresponding reactor volume? (c) Make a Levenspiel Plot and then determine the PFR reactor volume for 60% conversion and 95% conversion. Compare with the CSTR volumes at these conversions (d) Now assume the reaction is reversible, make a plot of the equilibrium conversion as a function of temperature between 290K and 400K.

  3. CSTR Adiabatic Mole Balance Rate Law Stoichiometry

  4. Energy Balance – Adiabatic, DCP = 0

  5. Irreversible for Parts (a) through (c) (a) Given X = 0.8, find T and V

  6. (b)

  7. (c)  Levenspiel Plot

  8. CSTR     X = 0.6     T = 360 CSTR     X = 0.95     T = 395

  9. PFR     X = 0.6 PFR     X = 0.95

  10. Summary

  11. (d) At Equilibrium

  12. (e) Te = 358 Xe = 0.59

  13. User Friendly Equations Relate T and X or Fi

  14. User Friendly Equations Relate T and X or Fi

  15. Heat Exchange Elementary liquid phase reaction carried out in a PFR The feed consists of both inerts I and Species A with the ratio of inerts to the species A being 2 to 1.

  16. Mole Balance (1) Rate Law (2) (3) (4) Stoichiometry (5) (6) Parameters (7) – (15)

  17. Energy Balance Adiabatic and (16A) Additional Parameters (17A)&(17B) Heat Exchange (16B)

  18. A. Constant Ta (17B) Ta = 300K Additional Parameters (18B – (20B): B. Variable Ta Co-Current (17C) C. Variable Ta Counter Current (18C) Guess Ta at V = 0 to match Ta = Tao at exit, i.e., V = Vf

  19. More heat effects mc HC Ta Ta T Fi Fi T FA, Fi V V+ΔV V V+ΔV In - Out + Heat Added = 0

  20. Heat generated Heat removed

  21. Example: Constant Ta Find conversion, Xeq and T as a function of reactor volume Xeq X T rate X V V V • Mole balance • Rates • Stoich • Heat effects Parameters

  22. Example: Variable Ta CoCurrent Coolant balance: In - Out + Heat Added = 0 All equations can be used from before except Ta parameter, use differential Ta instead, adding mC and CPC Example: Variable Ta Counter - Current In - Out + Heat Added = 0 All equations can be used from before except dTa/dV which must be changed to a negative to arrive at the correct integration we must guess the Ta value at V=0, integrate and see if Ta0 matches; if not, reguess the value for Ta at V=0

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