Lecture 22

1. Lecture 22 Chemical Reaction Engineering (CRE) is the field that studies the rates and mechanisms of chemical reactions and the design of the reactors in which they take place.

2. Today’slecture • Blowout Velocity • CSTR Explosion • Batch Reactor Explosion

3. Last Lecture CSTRs with Heat Effects

4. Energy balance for CSTRs

5. Energy balance for CSTRs

6. Steady State Energy Balance for CSTRs At Steady State

7. Energy balance for CSTRs Solving for X Solving for T

8. Energy balance for CSTRs Increasing T0 R(T) Variation of heat removal line with inlettemperature. T

9. Energy balance for CSTRs κ=∞ R(T) κ=0 T0 Increase κ Ta T Variation of heat removal line with κ (κ=UA/CP0FA0)

10. 1) Mole Balance: 2) Rate Law:

11. 3) Stoichiometry: 4) Combine:

13. Variation of heat generation curve with space-time.

14. Finding Multiple Steady States with T0 varied

15. Finding Multiple Steady States with T0 varied

16. Temperature ignition-extinction curve

17. Heat Effects Isothermal Design Stoichiometry Rate Laws Mole Balance

18. Isothermal Design Heat Effects Rate Laws Stoichiometry Mole Balance

19. Example B: LiquidPhase CSTR Same reactions, rate laws, and rate constants as example A NOTE: The specificreaction rate k1A is defined with respect to species A. NOTE: The specificreaction rate k2C is defined with respect to species C.

20. Example B: LiquidPhase CSTR The complexliquidphasereactionstakeplace in a 2,500 dm3 CSTR. The feed is equal molar in A and B with FA0=200 mol/min, the volumetric flow rate is 100 dm3/min and the reationvolume is 50 dm3. Find the concentrations of A, B, C and D existing in the reactoralong with the existingselectivity. Plot FA, FB, FC, FD and SC/D as a function of V

21. Example B: LiquidPhase CSTR Solution Liquid CSTR MoleBalances: (1) (2) Net Rates: (3) (5) (4)

22. Selectivity Ifonewere to write SC/D=FC/FD in the Polymath program, Polymathwould not executebecause at V=0, FC=0 resulting in an undefinedvolume (infinity) at V=0. To get around this problem we start the calculation 10-4 dm3 from the reactorentrancewhere FDwill not be zero and use the following IF statement. (15)

23. Selectivity Stoichiometry: (16) (17) (18) Parameters: (19) (20) (21) (22)

27. Example 1: Safety in Chemical Reactors

28. Example 1: Safety in Chemical Reactors FA0 FI0 A

29. Example 1: Safety in Chemical Reactors If the flow rate shut off, the temperature will rise (possibly to point of explosion!)

30. Rearranging: Additional information (approximate but close to the real case):

31. Complete conversion FA = 0 • Batch Reactors with Heat Effects • Single Reactions • Multiple Reactions • Risk Rupture

32. Complete conversion FA = 0 • Batch Reactors with Heat Effects • Single Reactions • Multiple Reactions • Risk Rupture

33. Keeping MBAs Away From Chemical Reactors • The process worked for 19 years before they showed up! • Why did they come? • What did they want?

38. NO2 NO2 Cl NH2 + 2NH3 + NH4Cl ONCB + Ammonia Nitroanaline + Ammonium Chloride Nitroaniline Synthesis Reaction

39. NH3 in H2O ONCB Autoclave 175 oC ~550 psi NH3 Separation Filter Press O-Nitroaniline Product Stream “fast” Orange Nitroaniline Synthesis Process To Crystallizing Tanks

40. Old 3 kmol ONCB 43 kmol Ammonia 100 kmol Water V = 3.25 m3 Nitroaniline Synthesis Reactor

41. NO2 NO2 Cl NH2 + 2NH3 + NH4Cl ONCB + Ammonia Nitroanaline + Ammonium Chloride Nitroaniline Synthesis Reaction Batch Reactor, 24 hour reaction time Management said:TRIPLE PRODUCTION

42. New 9 kmol ONCB 33 kmol Ammonia 100 kmol Water V = 5 m3 MBA Style Nitroaniline Synthesis Reactor

43. Monsanto Accident

46. 400 Temperature oC Cooling Restored Isothermal Operation 200 175 9:55 t = 0 10:40 10:50 midnight 12:18 Temperature-time trajectory fuse

47. Temperature-time trajectory

48. End of Lecture 22