Introduction to Mass Transfer Operations

Introduction to Mass Transfer Operations

• Mass transfer involves the movement of a component from a high-concentration region to a lower-concentration region in a mixture.
• This process occurs in gases (vapors) and liquids.
• Mass transfer can be driven by molecular diffusion or eddy diffusion (in turbulent fluids).

Contents

• Definition of Mass Transfer: The movement of a component in a mixture from a high-concentration area to a lower-concentration area.

• Examples of Mass Transfer:

  • Transfer of nitrogen (N₂) and oxygen (O₂) between compartments in a tank.
  • Water vapor from liquid water into the air.
  • Carbon dioxide (CO₂) from dry ice into the air.
  • Sugar from solid coffee granules into a liquid.
  • Iron from iron into carbon

• Mass Transfer Operations: Processes utilizing mass transfer for practical applications.

• Basic Concepts:

  • Concentrations: Methods of expressing the amount of a substance in a mixture.
    • Molar Concentration (Ci): Moles of a component (i) per unit volume of the mixture. (Ci = ni/V)
    • Mass Concentration (Pi): Mass of a component (i) per unit volume of the mixture. (Pi = mi/V)
    • Mole Fraction (xi): Ratio of the molar concentration of a component (i) to the total molar concentration of all components in a mixture. (xi = Ci / C)
    • Mass Fraction (Wi): Ratio of the mass concentration of a component(i) to the total mass concentration of all components in a mixture. (Wi = Pi / ρ)

Introduction

• Fundamental transfer processes: Momentum transfer (AP), Heat transfer (AT), Mass transfer (AC)

Definition of Mass Transfer (Detailed)

• Mass transfer happens when one component in a mixture moves from a region of high concentration to one of low concentration.
• It occurs in gases (vapors) and liquids.
• The driving force is the difference in concentration.

Examples of Mass Transfer (Further examples)

• Illustrate various ways mass transfer occurs in different states of matter (e.g., liquid to gas, solid to gas, solid to solid transitions).
• This can involve substances in different phases (solid, liquid, gas).

Mass Transfer Operations (Process-focused insight)

• Focus on how mass transfer is used in separation processes.
• Examples of how separation processes use mass transfer concepts

Separation Processes

• Separation: Separating desired components from a mixture
• Methods:
  • Separation of phases (e.g., liquid and gas by flash drums)
  • Transferring components from one stream to another. (e.g., separating components A and B by absorption)

Classification of Separation Processes

• Different methods for separating mixtures to achieve desired purity, using methods that leverage the unique properties and characteristics of the components to be separated;
  • Evaporation
  • Drying
  • Distillation
  • Absorption
  • Membrane separation
  • liquid-liquid extraction

Examples of Separation Processes (specific types)

• Use diagrams and descriptions to visually illustrate and explain various separation processes.
• Separating distinct phases (e.g., liquids, gases)
• Transferring specific components from one mixture to another.

Separation Processes (detailed types)

• Adsorption
• Ion exchange
• Liquid-solid leaching
• Crystallization
• Mechanical/physical separation (e.g., filtration, centrifugation)

Concentrations (Mathematical details)

• Mass concentration: Total mass concentration within a mixture equals overall density
• ρ = Σ Pi, where n is the number of different species.

Molar Concentration (Further details)

• Total molar concentration, C = Σ Ci, where n is the number of different species.

Relation Between Partial Pressure and Concentration (Mathematical link)

• Molar concentration of species i in an ideal gas mixture (Ci) using the Ideal Gas Law: Ci = Pi / RT. (where Pi is the partial pressure of species i, R is the ideal gas constant, and T is the temperature.)
• Total concentration (C) in a gaseous mixture, C = Σ Pi/ RT

Mole Fraction and Mass Fraction (Formulas and definitions)

• Mole fraction (xi) or (Yi) = molar concentration of component i / total molar concentration.
• Mass Fraction (Wi) = mass concentration of component i / total mass concentration.