PETE 310

1
PETE 310

• Lectures 6 7
• Phase Behavior Pure Substances (Lecture 5)
• Two Component Mixtures
• Three Multicomponent Mixtures

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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

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Phase Diagrams

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

4
Phase Diagrams

• Single Component Phase Diagram

5
Phase Diagrams
Vapor Pressure Curve
6
Hydrocarbon Families Physical Properties
One point in the Vapor Pressure Curve
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Pressure vs Specific Volume Pure Substance
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Pure Component Properties

• Tabulated critical properties (McCain)

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Heat Effects Accompanying Phase Changes of Pure
Substances 
Clapeyron equation
Btu/lb-mol
With
DV VMg-VMl
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Heat Effects Accompanying Phase Changes of Pure
Substances 


T
D
Approximate relation (Clausius - Clapeyron
Equation)


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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 T462 oF

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

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Determination of Fluid Properties

• Ps saturation pressure

Temperature of Test Constant
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Vapor Pressure Determination
T2
Pressure
P
S
T1
V
L
Volume

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Binary Mixtures

• Relationships to analyze P, T, molar or specific
  volume or (molar or mass density) - as for a
  pure component
• COMPOSITION Molar Composition

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Hydrocarbon Composition

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

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Hydrocarbon Composition

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

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Our Systems of Concern
Gas system
open
Oil system
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A separator
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Mathematical Relationships

• with
• In general

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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

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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) P at a fixed P
• (PV) zi or (Pr) zi

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Pressure vsTemperature Diagram (PT)zi
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Pressure Composition Diagrams - Binary Systems

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

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Gas-Liquid Relations
z1overall mole fraction of 1, y1vapor mole
fraction of 1, x1liquid mole fraction of 1
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Supercritical Conditions Binary Mixture
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Quantitative Phase Equilibrium Exercise
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Quantitative Phase Equilibrium Exercise
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Ternary Diagrams Review
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Ternary Diagrams Review

• Pressure Effect

C3
C3
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Ternary Diagrams Review

• Dilution Lines

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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.

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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.).

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Illustration of Phase Envelope and Tie Lines
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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, ...)

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Uses of Ternary Diagrams

• Miscible Recovery Processes

Solvent2
Solvent1
oil
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Exercise

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

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Practice Ternary Diagrams

• Pressure Effect

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Practice Ternary Diagrams

• Pressure Effect

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Practice Ternary Diagrams

• Temperature Effect

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Practice Ternary Diagrams

• Temperature Effect

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Pressure-Temperature Diagram for Multicomponent
Systems
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Changes During Production and Injection
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Homework

• See Syllabus please