Chemical Reaction Engineering

Transcription

1 Lectue hemical Reaction Engineeing (RE) is the field that studies the ates and mechanisms of chemical eactions and the design of the eactos in which they take place.

2 Web Lectue lass Lectue 8-husday Multiple Reactions with Heat Effects

3 Multiple Reactions with Heat Effects PR/PBR: SR: U d dv Ua a ij H Rxij m m j n i j H 0 a 0 j Pi i Pj 0 q i ij Rxij 3 hese equations ae coupled with the mole balances and ate law equations.

4 Multiple Reactions with Heat Effects Multiple Reactions Make sue it is in espect to ; Subscipts must agee d dv g i Pi g ij H Rxij H Rx H Rx 4

5 Multiple Reactions with Heat Effects Multiple Reactions ) Mole Balances: evey species (no convesion!) ) Rate Laws: elative ates net ates 3) Stoichiomety: 0 y 0 5 dy dw y 0 0

6 Multiple Reactions with Heat Effects Multiple Reactions 4) Heat Effects: d dv g g g heat poduced heat emoved ij i Pi H Ua( - Rxij a ) (must have matching i, j) 6

7 Multiple Reactions with Heat Effects 4) Heat Effects: d dv g d a dv i Ua g P i H i R Ua m i Pcool Pi a a P H B R PB P D PD 7 5) Paametes E, E, 0, Ua,...etc

8 8 Multiple Reactions with Heat Effects 4) Heat Effects: d dv H H g Rx RxB to get g B e.g., - Use elative i Pi kj H 8kJ Rx ates in tems () B of of 3 /( mole 3 /( mole of k H RxB eaction the 3 of eacted B eacted ate B - - B law that D then in in B eaction ) eaction ) is given fo eaction 3,

9 he complex gas phase eactions () B k B H RxB 5,000 cal mol B () D k H Rx 0,000 cal mol take place in a 0 dm 3 PR with a heat exchange. Plot the tempeatue, concentations, mola flow ates down the length of the eacto fo the following opeations. E.g., Note any maximums o minimums on you plot along with how they change fo the diffeent types of opeations. (a) diabatic opeation (b) Heat exchange with constant a (c) o cuent heat exchange (d) ounte cuent heat exchange (e) o pats (c) and (d), plot and g down the length of the eacto. What do you obseve? dditional Infomation P 0 cal mol K PB 0 cal mol K P 30 cal mol K PD 0 cal mol K k 40 dm 3 mol s K at 300K and E 8,000 cal mol k dm 3 mol s K at 300K and E,000 cal mol 0 0. mol dm 3, Pool cal g K, Ý m ool 0g s 9 Ua 80 cal dm 3 s K, ao 35K, 0 300K 0 5 mol s, B0 0 mol s, 0 0, D0 0

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14 Multiple Reactions with Heat Effects Multiple Reactions d dv 4) Heat Effects: H d dv g g ij i Pi H Rij Rx g Ua i a Pi (must have matching i, heat poduced heat emoved j) 4

15 Multiple Reactions with Heat Effects in a PR and SR Examples: () B k B and H R 0,000cal mol 5 () 3 D k 3 and H R 0,000cal mol

16 Example : Liquid Phase SR ( ) B k B NOE: he specific eaction ate k is defined with espect to species. ( ) 3 D k 3 NOE: he specific eaction ate k is defined with espect to species. 6

17 Example : Liquid Phase SR he complex liquid phase eactions take place in a,500 dm 3 SR. he feed is equal mola in and B with 0 =00 mol/min, the volumetic flow ate is 00 dm 3 /min and the eation volume is 50 dm 3. ind the concentations of, B, and D existing in the eacto along with the existing selectivity. Plot, B,, D and S /D as a function of V 7

18 8 Example : Liquid Phase SR Solution Liquid Phase SR ) Mole Balances: () () (3) (4) ) Net Rates: (5) f V f B 0 B 0 0 B B V f 0 V f D 0 D D V

19 9 Example : Liquid Phase SR 3) Stoichiomety: (6) (7) (8) (9) (0) B B D D 4) Paametes: () () dm k k min 3 dm mol min 3 4 dm mol min

20 Example B: Liquid Phase PR akes place in a PR. he feed is equal mola in and B and 0 =00 mol/min and the volumetic flow ate is 00 dm 3 /min. he eaction volume is 50 dm 3 and the ate constants ae: k 0dm 3 mol min k 5dm 3 mol 4 min Rate laws ae the same as Example. Plot, B,, D and S /D as a function of V. 0

21 Example B: Liquid Phase PR ) Mole Balances:

22 Example B: Liquid Phase PR ) Net Rates: (5) (6) (7) B B (8) ) Rate Laws: (9) (0) D D k B k 3

23 Example B: Liquid Phase PR ) Relative Rates: B () B () Reaction Reaction 3 (3) (4) 3 D 3 D 3

24 6 3 / 5 3 / exp 7 6 exp 5 3 D B D D B B B B R E k k k R E k k k 4 Example B: Liquid Phase PR ) Rate Laws:

25 Example B: Liquid Phase PR 3) Stoichiomety: 0 y 0 B 0 7 y 8 B 0 0 y 0 D 0 9 y 0 D 0 B D dy dv y 0 0 5

26 Multiple Reactions with Heat Effects 6 4) Heat Effects: d dv d dv g a g i Pi Ua m Ua P i Pcool a 3 6 H R H R 4 a 5 7 P Paametes: E, E, 0,... B PB P D PD

27 Selectivity If one wee to wite S /D = / D in the Polymath pogam, Polymath would not execute because at V=0, =0 esulting in an undefined volume (infinity) at V=0. o get aound this poblem we stat the calculation 0-4 dm 3 fom the eacto entance whee D will not be zeo and use the following I statement. (5) S D if V 0.00 then D else 0 7

28 8 Selectivity 3) Stoichiomety: (6) (7) (8) (9) (0) B B Paametes: () () D D dm k k min 3 dm mol min 3 4 dm mol min

29 End of Web Lectue lass Lectue 8 9