ENTHALPY-BASED DISTILLATION MODELING

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PONCHON-SAVARIT ANALYSIS. ENTHALPY CONCENTRATION EQUILIBRIUM DIAGRAM POINTS REPRESENT CONCENTRATION, x OR y, AND ENTHALPY, Hy OR hx.ANALYSIS INCLUDES CHANGES IN V/L AS A FUNCTION OF ?Hvap.. ENTHALPY EQUILIBRIUM DIAGRAM. http://www.hyper-tvt.ethz.ch/images/enthalpy.jpg. FORM OF SIMULATION DIAGRAM. ENTHALPY CONCENTRATION COORDINATE SYSTEM.

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ENTHALPY-BASED DISTILLATION MODELING

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1. ENTHALPY-BASED DISTILLATION MODELING PONCHON-SAVARITT ANALYSIS

2. PONCHON-SAVARIT ANALYSIS ENTHALPY CONCENTRATION EQUILIBRIUM DIAGRAM POINTS REPRESENT CONCENTRATION, x OR y, AND ENTHALPY, Hy OR hx. ANALYSIS INCLUDES CHANGES IN V/L AS A FUNCTION OF ?Hvap.

3. ENTHALPY EQUILIBRIUM DIAGRAM

4. FORM OF SIMULATION DIAGRAM

5. ENTHALPY CONCENTRATION COORDINATE SYSTEM

6. ENTHALPY CONCENTRATION RECTIFICATION SECTION

7. ENTHALPY CONCENTRATION STRIPPING SECTION

8. OPTIONS DATA FOR MIXTURE VALUES NOT READILY AVAILABLE CAN ASSUME IDEAL MIXTURES AND USE PURE COMPONENT DATA AT TERMINAL POINTS - THEN CONNECT WITH STRAIGHT LINE. EQULIBRIUM TIE LINES, LINK EQUILIBRIUM LIQUID & VAPOR CONCENTRATIONS ON EACH ENTHALPY LINE. SHOWN AS DASHED LINES FIG 11.6-1

9. SIMPLIFIED P-S DIAGRAM

10. ENTHALPY BALANCES OVERALL CONDENSER

11. CONSTRUCTION FOR GRAPHICAL MODEL ENTHALPY RIGOROUS EQUATION OR DATA SIMPLIFIED VERSION EQUILIBRIUM DATA FROM VLE DATA

12. EQUILIBRIUM DATA TRANSFER

13. REBOILER HEAT BALANCE REBOILER OVERALL

14. LOCATION OF FEED LINE BASED ON FEED CONC. & ENTHALPY - RELATIVE TO q VALUES ON McCABE-THEILE SAT'D LIQ., q = 1, ON SAT'D LIQ. ENTHALPY LINE SAT'D VAPOR, q = 0, SAT'D VAP. ENTHALPY LINE PARTIAL SAT'D VAPOR, 0 < q < 1, BETWEEN SAT'D ENTHALPY LINES WITH CONCENTRATION IN EACH PHASE BASED ON EQUILIBRIUM TIE LINES. SUPERCOOLED LIQ, q > 1, BELOW SAT'D LIQ. ENTHALPY LINE AT xF. SUPERHEATED VAP., q < 1, ABOVE SAT'D VAP. ENTHALPY LINE AT xF

15. COMPLETION OF DIAGRAM FEED POINT, POINTS H’D AND H’B LIE ON A COMMON LINE TO CLOSE THE ENTHALPY BALANCE PRODUCT ENTHALPIES LOCATION OF H'D IS BASED ON REFLUX RATIO: LOCATION OF H’B IS BASED ON BOILUP RATIO

16. LIMITING CASES TOTAL REFLUX CONSTRUCTION HAS STEPS THAT ASSUME H’D IS LOCATED AT 8 SO VERTICAL OPERATING LINES START AT ONE PRODUCT AND GO TO THE OTHER RED LINES FOLLOW EQUILIBRIUM VALUES

17. LIMITING CASES INFINITE STAGES - RdMIN, LINE THROUGH FEED POINT FOLLOWS EQULIBRIUM LINE INTERSECTS WITH H’DMIN AT VERTICAL EXTENSION THROUGH PRODUCT CONCENTRATION

18. ACTUAL NUMBER OF STAGES RdDZN > RdMIN SO H’D > H’Dmin CONSTRUCTION PASSES THROUGH H’D AND H’B STAGES ARE CALCULATED ABOVE & BELOW FEED

19. COMPARISON WITH M-T P-S ANALYSIS CAN BE TRANSFERRED TO M-C OPERATING LINE IS ADJUSTED TO ALLOW FOR CHANGES IN ?Hvap RESULTING NUMBER OF STAGES CAN DIFFER FROM STRAIGHT OPERATING LINE CALCULATIONS SEE FIGURE 11.6-3 FOR EXAMPLE M-T EQUILIBRIUM LINES ARE VERTICAL LINES AND POINTS ARE INTERCHANGED BETWEEN THE TWO METHODS.

20. ACTUAL STAGE COUNT FACTORS INTERSECTIONS OF OPERATING LINE WITH ENTHALPY LINES REPRESENT ACTUAL STAGE CONCENTRATIONS EQUILIBRIUM CONCENTRATIONS ON EACH STAGE ARE REPRESENTED BY EQUILIBRIUM TIE LINES MURPHREE EFFICIENCY STAGE TO STAGE CONSTRUCTION IS ADJUSTED SO THE ACTUAL CONCENTRATION CHANGE IS A FRACTION OF THE IDEAL

21. ADDITIONAL DESIGN FACTORS FEED LOCATION IDEAL LOCATION IS ON A TRAY WHERE: TRAY CONCENTRATION = FEED CONCENTRATON FEED TEMP = SATURATION TEMP DEVIATIONS FROM THIS EQUALITY RESULTS IN SOME LOSS IN EFFICIENCY IT IS MINOR IS INEVITABLE

22. TRAY DESIGN COMPONENTS TRAYS DOWNCOMERS SUPPORTS TYPES - USED FOR GAS LIQUID CONTACTING CAP VALVES SIEVES

23. TRAY HYDRODYNAMICS PRESSURE DROPS (ENERGY LOSSES)AFFECT EQUILIBRIUM AND SYSTEM ENERGY DEMANDS LIQUID ?P COMPENSATED BY GRAVITY FRICTION LOSSES THROUGH DOWNCOMER UNDER DOWNCOMER OVER DOWNCOMER INERTIAL LOSS - CHANGE IN FLOW DIRECTION ON TRAY CONTRACTION/EXPANSION LOSSES DUE TO CHANGE IN FLOW CROSS-SECTION AREA EDDY LOSSES AT WALLS AT CAPS OR VALVES

24. TRAY HYDRODYNAMICS VAPOR ?P IS ALL THAT IS NORMALLY CONSIDERED: hLIQUID HEAD BASED ON LIQUID LEVEL ON TRAY RELATED TO RESIDENCE TIME OF THE BUBBLE IN THE LIQUID BASED ON WEIR HEIGHT LEVEL PLUS HEIGHT OF LIQUID FLOW OVER WEIR

25. CORRELATION EQUATIONS FLOW OVER A WEIR (FRANCIS EQN.) ORIFICE DROP SIEVE TRAYS

26. CORRELATION EQUATIONS BUBBLE CAPS ARE OF THE FORM VALVE TRAYS HAVE SIMILAR FORMS SEE PERRY’S Pp. 14-11 THROUGH 14-38 FOR TRAYS AND 14-38 – THROUGH 14-58 FOR PACKING

27. LIQUID-IN-VAPOR ENTRAINMENT CONTROLLED THROUGH DESIGN OF: TRAY SPACING VAPOR VELOCITY LIQUID HEIGHT VAPOR DENSITY LIQUID SURFACE TENSION HOLE DIAMETER VAPOR-IN-LIQUID ENTRAINMENT (FOAMING) CAN RESULT IN VAPOR BEING CARRIED DOWN THE THE LOWER TRAYS OR LIQUID AS BUBBLES BEING CARRIED TO THE TRAY ABOVE

28. TRAY EFFICIENCY CONTROLLING VARIABLES: PATH LENGTH BACKMIXING BUBBLE FORMATION MECHANISM AND PHASE CONTACT ORIFICE SIZE FREE AREA FOR BUBBLING RELATIVE VAPOR/LIQUID RATES

29. CORRELATIONS OF EMPIRICAL DATA USE PECLET NUMBER AIChE STANDARD METHOD (1958) FOR BUBBLE CAPS GENERAL DIMENSIONLESS FORM USES AS POSSIBLE VARIABLES: VAPOR & LIQUID DENSITY, VISCOSITY AND DIFFUSIVITY LIQUID SURFACE TENSION GENERAL FORM ˜ + 12% ACCURACY

30. SUMMARY OF COLUMN DESIGN COLUMN OPERATING PRESSURE AND TEMPERATURE REFLUX RATIO NUMBER OF TRAYS FEED AND DRAW-OFF LOCATIONS COLUMN DIAMETER TRAY SPACING TRAY TYPE AND ARRANGEMENT ACTIVE AREA DOWNCOMER TYPE, AREA & CLEARANCE MATERIALS OF CONSTRUCTION

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