Stagewise Intro Lecture 1

download Stagewise Intro Lecture 1

of 23

Transcript of Stagewise Intro Lecture 1

  • 7/30/2019 Stagewise Intro Lecture 1

    1/23

    5/11/2013

    Equilibrium SeparationOperations

    Lecture 1: IntroductionReading Assignment:

    1. Foust, 1980 pp. 1-27

    2. Geankoplis pp 653-6603. Geankoplis pp.696-705

    SHORT QUIZ (30 min) 7/17/2007

  • 7/30/2019 Stagewise Intro Lecture 1

    2/23

    5/11/2013

    Separations

    Crucial in Chemical Engineering

    Most equipment - purifying products

    Chemical Plants

    50 - 90 % capital investment

  • 7/30/2019 Stagewise Intro Lecture 1

    3/23

    5/11/2013

    Common Separation Methods

    Distillation

    flash

    continuous column

    batch

    Absorption/Stripping

    Extraction

  • 7/30/2019 Stagewise Intro Lecture 1

    4/23

    5/11/2013

    Similarities of These Methods

    Two phases contacted

    Designed and analyzed as equilibrium stageprocesses

  • 7/30/2019 Stagewise Intro Lecture 1

    5/23

    5/11/2013

    Distillation

    Separation depends on distribution of

    components between gas and liquid phase

    All components distribute at equilibrium

  • 7/30/2019 Stagewise Intro Lecture 1

    6/23

    5/11/2013

    Distillation

    Gas phase - application of heat

    Liquid phase - removal of heat

  • 7/30/2019 Stagewise Intro Lecture 1

    7/23

    5/11/2013

    Absorption/Stripping

    Gas mixture contacted with liquid

    Absorption - dissolving components of gasinto liquid

    Stripping - mass transfer goes from liquid togas

  • 7/30/2019 Stagewise Intro Lecture 1

    8/23

    5/11/2013

    Liquid Extraction

    Liquid solution contacted with another

    insoluble liquid.

    Constituents distribute differently between the

    2 liquid phases

  • 7/30/2019 Stagewise Intro Lecture 1

    9/23

    5/11/2013

    Key terms for understanding

    equilibrium staged processes

  • 7/30/2019 Stagewise Intro Lecture 1

    10/23

    5/11/2013

    Unit operation

    Basic design principles for a given separation

    method are always the same

    Specific design depends on chemicals being

    separated

  • 7/30/2019 Stagewise Intro Lecture 1

    11/23

    5/11/2013

    Stage

    Device or combination of a device

    2 insoluble phases are brought into intimatecontact

    mass transfer occurs between the phases tending

    to bring them to equilibrium

    phases are mechanically separated

  • 7/30/2019 Stagewise Intro Lecture 1

    12/23

    5/11/2013

    Tray tower

    Vertical assembly of trays on which vapor

    and liquid are contacted

    Liquid flows down tower due to gravity

    Vapor flows upward as a result of a slightpressure drop from tray to tray

  • 7/30/2019 Stagewise Intro Lecture 1

    13/23

    5/11/2013

    Equilibrium stage

    Equilibrium, ideal, or theoretical stage

    Contacting device - a vessel - 2 or more phases incontact sufficiently to achieve equilibrium

    Streams leaving a stage are in equilibrium

    Building block of multistage processes

  • 7/30/2019 Stagewise Intro Lecture 1

    14/23

    5/11/2013

    Stage Efficiency

    Fractional approach to equilibrium

    Equilibrium stages coupled with stageefficiency -actual stages

  • 7/30/2019 Stagewise Intro Lecture 1

    15/23

    5/11/2013

    Cascade

    A group of stages interconnected

    Purpose - to increase the extent of masstransfer over and above that which is

    possible with a single stage.

  • 7/30/2019 Stagewise Intro Lecture 1

    16/23

    5/11/2013

    3 Principles:Distribution of substances between 2

    insoluble phases

    Fixed temperature and pressure, there

    exists a set of equilibrium relationships

    No net diffusion of the components

    between phases in equilibrium.

  • 7/30/2019 Stagewise Intro Lecture 1

    17/23

    5/11/2013

    3 Principles:Distribution of substances between 2

    insoluble phases

    If the system is not in equilibrium, diffusion of

    the components between the phases will

    occur so as to bring the system to a condition

    of equilibrium.

  • 7/30/2019 Stagewise Intro Lecture 1

    18/23

  • 7/30/2019 Stagewise Intro Lecture 1

    19/23

    5/11/2013

    Not at equilibrium

    Liquid and vapor can be:

    at different pressure

    at different temperature

    present in different mole fractions

  • 7/30/2019 Stagewise Intro Lecture 1

    20/23

    5/11/2013

    At equilibrium

    Temperature ceases to change

    Pressure ceases to change

    Fractions of the 2 phases cease to change

  • 7/30/2019 Stagewise Intro Lecture 1

    21/23

    5/11/2013

    Thermal Equilibrium

    Heat transfer stops

    Tliquid = Tvapor

  • 7/30/2019 Stagewise Intro Lecture 1

    22/23

    5/11/2013

    Mechanical Equilibrium

    Forces between vapor and liquid balance

    Staged separation processes:

    Pliquid = Pvapor

  • 7/30/2019 Stagewise Intro Lecture 1

    23/23

    5/11/2013

    Phase Equilibrium Rate at which each species is

    vaporizing is just equal to the rate at

    which it is condensing

    No change in composition (mole fraction).

    Compositions of liquid and vapor are not

    equal.(chemical potential i)liquid = (chemical potential i)vapor