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PETE 310

PETE 310. Lectures # 6 & # 7 Phase Behavior – Pure Substances (Lecture # 5) Two Component Mixtures Three & Multicomponent Mixtures. Learning Objectives. After completing this chapter you will be able to:

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PETE 310

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  1. PETE 310 Lectures # 6 & # 7 Phase Behavior – Pure Substances (Lecture # 5) Two Component Mixtures Three & Multicomponent Mixtures

  2. Learning Objectives After completing this chapter you will be able to: • Understand pure component phase behavior as a function of pressure, temperature, and molecular size. • Understand the behavior of binary and multicomponent mixtures • Behavior understood through proper interpretation of phase diagrams

  3. Phase Diagrams • Types of phase diagrams for a single component (pure substance) • (PT) • (PV) or (Pr) • (TV) or (Tr)

  4. Fusion Curve Critical 2 phases Point P c Solid Liquid (1 phase) (1 phase) Pressure Vapor Pressure Curve (2 phases) Vapor (1 phase) Triple Point (3 phases) Sublimation Curve (2 phases) T Temperature c Phase Diagrams Single Component Phase Diagram

  5. Critical Point r P l c Pressure Liquid r v Vapor T c Temperature Phase Diagrams Vapor Pressure Curve

  6. Hydrocarbon Families Physical Properties One point in the Vapor Pressure Curve

  7. T ) psia CP Tc Pressure ( 2-phase V V L v Specific Volume (ft3 / lbm) Pressure vs Specific Volume Pure Substance

  8. Pure Component Properties • Tabulated critical properties (McCain)

  9. d P v Lv = T D V dT Heat Effects Accompanying Phase Changes of Pure Substances Clapeyron equation Btu/lb-mol With DV = VMg-VMl

  10. d P v Lv V dT Lv d P v P v dT 2 R T Heat Effects Accompanying Phase Changes of Pure Substances = T D Approximate relation (Clausius - Clapeyron Equation) =

  11. Example of Heat Effects Accompanying Phase Changes • Steam flooding Problem: Calculate how many BTU/day (just from the latent heat of steam) are provided to a reservoir by injecting 6000 bbl/day of steam at 80% quality and at a T=462 oF

  12. COX - Vapor Pressure Charts(normal paraffins) Log scale heavier Pressure Temperature Non-linear scale

  13. 1 2 3 4 5 gas gas b V V V = V t1 t2 V t3 t4 t5 V liquid liquid liquid liquid liquid Hg Hg Hg Hg Hg >> P P > P P = P P = P P =P P 1 s 2 s 3 s 4 s 5 s Determination of Fluid Properties Ps =saturation pressure Temperature of Test Constant

  14. Vapor Pressure Determination T2 Pressure P S T1 V L Volume

  15. Binary Mixtures • Relationships to analyze: P, T, molar or specific volume or (molar or mass density) - as for a pure component – + • COMPOSITION – Molar Composition

  16. Hydrocarbon Composition • The hydrocarbon composition may be expressed on a weight basis or on a molar basis (most common) • Recall

  17. Hydrocarbon Composition • By convention liquid compositions (mole fractions) are indicated with an x and gas compositions with a y.

  18. Our Systems of Concern Gas system open Oil system

  19. yi(T1,P2) P1 > P2 zi(T1,P1) T1,P2 xi(T1,P2) A separator

  20. Mathematical Relationships with In general

  21. Key Concepts • Fraction of vapor (fv) • Mole fractions in vapor (or gas) phase  yi • Mole fractions in liquid (or oil) phase  xi • Overall mole fractions (zi)  combining gas & liquid

  22. Phase Diagrams for Binary Mixtures • Types of phase diagrams for a two- component mixture • Most common • (PT) zi at a fixed composition • (Pzi) T at a fixed T • (Tzi) Pat a fixed P • (PV) zi or (Pr) zi

  23. Zi = fixed CB CP Liquid CT Bubble Curve Pressure 2 Phases Gas Dew Curve Temperature Pressure vsTemperature Diagram (PT)zi

  24. CP1 Ta Liquid P1v P1v Bubble Curve Pressure 2-phases CP2 Dew Curve P2v Vapor P2v 1 Ta 0 Temperature x1, y1 Pressure Composition Diagrams - Binary Systems

  25. Temperature vs. Composition Diagrams – Binary Systems Pa T2s CP1 Dew Curve Pressure 2-phases CP2 Pa Bubble Curve T1s T2s Temperature 1 T1s x1, y1 0

  26. A z = fix ed 1 T = T CP a B M P B C Pressure P D y 1 T 0 x z 1 a 1 1 Temperature Gas-Liquid Relations z1=overall mole fraction of [1], y1=vapor mole fraction of [1], x1=liquid mole fraction of [1]

  27. Supercritical Conditions Binary Mixture

  28. Quantitative Phase Equilibrium Exercise

  29. Quantitative Phase Equilibrium Exercise

  30. Ternary Diagrams: Review

  31. C1 C1 C1 Gas Gas Gas 2-phase 2-phase Liquid Liquid nC5 C3 nC5 C3 nC5 C3 p=500 psia p=14.7 psia p=380 psia C1 C1 C1 Gas Gas 2-phase 2-phase Liquid Liquid Liquid nC5 C3 nC5 nC5 p=2000 psia p=2350 psia p=1500 psia Ternary Diagrams: Review Pressure Effect C3 C3

  32. Ternary Diagrams: Review Dilution Lines

  33. Ternary Diagrams: Review Quantitative Representation of Phase Equilibria - Tie (or equilibrium) lines • Tie lines join equilibrium conditions of the gas and liquid at a given pressure and temperature. • Dew point curve gives the gas composition. • Bubble point curve gives the liquid composition.

  34. Ternary Diagrams: Review Quantitative Representation of Phase Equilibria - Tie (or equilibrium) lines • All mixtures whose overall composition (zi) is along a tie line have the SAME equilibrium gas (yi) and liquid composition (xi), but the relative amounts on a molar basis of gas and liquid (fv and fl) change linearly (0 – vapor at B.P., 1 – liquid at B.P.).

  35. Illustration of Phase Envelope and Tie Lines

  36. Uses of Ternary Diagrams Representation of Multi-Component Phase Behavior with a Pseudoternary Diagram • Ternary diagrams may approximate phase behavior of multi-component mixtures by grouping them into 3 pseudocomponents • heavy (C7+) • intermediate (C2-C6) • light (C1, CO2 , N2- C1, CO2-C2, ...)

  37. Uses of Ternary Diagrams Miscible Recovery Processes Solvent2 Solvent1 oil

  38. Exercise Find overall composition of mixture made with 100 moles oil "O" + 10 moles of mixture "A". __________________________ ________________________ _______________________ _____________________ ___________________ _________________

  39. T=180F P=200 psia T=180F P=14.7 psia T=180F P=600 psia Pressure Effect Pressure Effect Pressure Effect Pressure Effect T=180F P=400 psia C1-C3-C10 O O O O Practice Ternary Diagrams Pressure Effect

  40. Pressure Effect Pressure Effect T=180F P=4000 psia T=180F P=1000 psia T=180F P=2000 psia T=180F P=3000 psia T=180F P=1500 psia O O O O O Practice Ternary Diagrams Pressure Effect

  41. Temperature Effect Temperature Effect Temperature Effect Temperature Effect T=100F P=2000 psia T=200F P=2000 psia T=150F P=2000 psia T=300F P=2000 psia O O O O Practice Ternary Diagrams Temperature Effect

  42. Temperature Effect Temperature Effect Temperature Effect T=400F P=2000 psia T=450F P=2000 psia T=350F P=2000 psia O O O Practice Ternary Diagrams Temperature Effect

  43. 1-Phase 1-Phase CP Bubble-Curve 60% 0% Reservoir Pressure 20% 2-Phase Dew-Curve Reservoir Temperature Pressure-Temperature Diagram for Multicomponent Systems

  44. t t 1 Production Production t 2 2 Gas Gas Pressure Injection Injection t t 3 3 Temperature Changes During Production and Injection

  45. Homework • See Syllabus please

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