Problems Flash, HX, Pump, Valve, Compressor, Reactors & Distillation Basics

1. ProblemsFlash, HX, Pump, Valve, Compressor, Reactors & Distillation Basics 조 정 호 Ph.D. 1st Day (Afternoon) Monday, July 24, 2000

2. Ex-1 : Flash Calculation • Calculate the bubble point pressure at 45oC and dew point temperature at 1.5 bar of the following hydrocarbon stream. • Use SRK for your simulation. • Regard C6+ as NC6(1), NC7(2) and NC8(3) and compare the results. When finished, save in backup format (Run-ID.BKP) Filename: EX-1A.BKP EX-1B.BKP EX-1C.BKP

3. Step 1 : general process information (Setup Specifications)

4. Step 1 : general process information (Setup Specifications) continued

5. Step 2 : chemical species (Component Specifications Selection form)

6. Step 3 : physical property (Property Specifications Global Form)

7. Step 4 : stream variables (Stream Specifications form)

8. Step 5 : equipment parameters (Block [Flash2] Specifications Form)

9. Step 5 : equipment parameters (Block [Flash2] Specifications Form)

10. Examine result : Aspen Plus Output

11. Examine result : Aspen Plus Output

12. Results Summary for Ex-1 • Characterization of C6 plus heavier cut is very important in the calculation of dew point temperature. • EX-1A.BKP, EX-1B.BKP, EX-1C.BKP

13. Dew & Bubble Point Calculation • Bubble Point is the very state at which vaporization is about to occur. Bubble P Calculation at a given T Bubble T Calculation at a given P • Dew Point is the very state at which condensation is about to occur. Dew P Calculation at a given T Dew T Calculation at a given P

14. Txy Plot & BUBT, DEWT Calculation • Plot the Txy Plot at a constant pressure (1.013 bar). • Use 1) Ideal, 2) Wilson, 3) RK-Soave for your simulation. • Calculate the Bubble Point Temperature at 1.013 bar. • Calculate the Dew Point Temperature at 1.013 bar. When finished, save in backup format (Run-ID.BKP) Filename: Ideal-P.BKP Wilson-P.BKP SRK-P.BKP

18. Ex-2 : Bubble Pressure Failure • Calculate the bubble pressure at 85oC of the following stream. • Did you get a converged solution? If not, can you explain the reason? (Bubble-F.BKP)

20. Differences between “Gas” & “Vapor” • For Gas : T > Tc • For Vapor : T < Tc • T : System temperature, Tc : Critical temperature • In this example, Mixture pseudo-critical temperature is –27.6oC, so, this system is at supercritical state. • We usually say “methane gas” but not “methane vapor”. • We usually say “water vapor” but not “water gas”.

21. Ex-3 : Hydrocarbon Distillation • Feed composition : 600 Kmole/hr (C3) / 400 Kmole/hr (IC4) • Refrigerant : c/w (Reflux drum temperature = 45oC) • Condenser type : Bubble condenser • C3 yield at overhead product (97% recovery for feed) • IC4 yield at bottom product (96% recovery for feed) • Operating pressure of the condenser (EX-3A.BKP) • Minimum number of trays for separation (EX-3B.BKP) • Optimum reflux ratio(EX-3C.BKP) • Rigorous Simulation using RadFrac (EX-3D.BKP) • Use 1) PR, 2) RK-Soave for your simulation. • Condenser pressure drop = 0.3 bar • Column pressure drop = 0.5 bar

22. Bubble Condenser 45oC • C3 Recovery = 97% • IC4 Recovery = 96% Process Flowsheet for Depropanizer Modeling

23. Determination of Condenser Pressure • Overhead component flowrate : 600 x 0.97 = 582 Kgmole of C3 + 400 x 0.04 = 16 Kgmole of IC4 • Bottom component flowrate : 600 – 582 = 18 Kgmole of C3 + 400 - 16 = 384 Kgmole of IC4 Determine the bubble pressure of the above composition at 45oC.

31. BVLE at 15.39 bar (column top pressure)

32. 계단작도법에 의한 최소이론단수 (12.5)

33. DSTWU modeling

34. DSTWU modeling

35. DSTWU modeling

36. DSTWU modeling

37. DSTWU modeling

38. DSTWU modeling Results

39. DSTWU modeling Results

40. DSTWU modeling Case Study • Minimum Reflux Ratio = 1.67 • Minimum Number of Stages = 11.3

41. Reflux Ratio vs. # of Stages & Utility Consumptions 17 5.7 3.1

42. Shortcut Modeling Results using DSTWU • File Name = EX-3B.BKP • Optimum Reflux Ratio = 3.1 • Optimum Number of Stages = 17 • Feed Tray Location = 8 • Bubble Condenser Temperature = 45 oC • Overhead Condenser Heat Duty = 7.88 MM Kcal/Hr • Bottom Reboiler Heat Duty = 9.06 MM Kcal/Hr • C3 Recovery at Overhead Product = 97 % • NC4 Recovery at Bottom Product = 96 %

43. Shortcut Modeling using DISTIL • File Name = EX-3C.BKP • Modeling using ‘DISTIL’ is an intermediate step between • DSTWU and RadFrac • DSTWU : • - Nmin, Rmin, • - Ratio, R/Rmin • - Ropt, Nopt, FTRAYopt • DISTIL tells us a preliminary modeling results such as • condenser, reboiler heat duties, condenser temperature & • material balances prior to performing rigorous modeling.

44. DISTIL

45. Comparison between ‘DSTWU’ and ‘DISTIL’

46. RadFrac (General Setup)

47. RadFrac (Component Specification)

48. RadFrac (Physical Property Specification)

49. RadFrac (Stream Specification)

50. RadFrac (Block Specification)