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    CHAPTER 1

    Mohd Asmadi Bin Mohammed Yussuf

    Faculty of Chemical Engineering

    Universiti Teknologi Malaysia, 81310 UTM

    Johor, Johor Bahru, Malaysia

    Chemical Reaction Engineeri ng Group, Universiti Teknologi Malaysia

    Introduction to Chemical

    Engineering Thermodynamics

    N02 2-6, 11.00 1.00P.M Feb 10, 2013 (Mon)

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    Week Topic Topic Outcomes

    1 Introduction to Chemical

    Engineering Thermodynamics

    Overview of thermodynamic

    application in chemical

    industry

    Application of thermodynamic

    properties and equations inchemical process

    It is expected that students are

    able to:

    Describe the importance of

    chemical engineering

    thermodynamics in chemical

    engineering profession.

    Apply the thermodynamicsproperties in the chemical process

    simulators.

    Chemical Reaction Engineeri ng Group, Universiti Teknologi Malaysia

    Topic Outcomes

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    Chemical Reaction Engineeri ng Group, Universiti Teknologi Malaysia

    Scope of Lecture

    Overview of thermodynamic appl icat ion

    in chem ical indus try

    Appl icat ion of thermodynam ic propert ies

    and equat ions in chem ical process

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    Thermodynamic Applications

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    Definition

    The study of the effects of work, heat and energy on thesystem).

    Only concerned with large scale observations.

    Ref: NASA . Available from: http://www.grc.nasa.gov/WWW/k-12/airplane/thermo.html. (Accessed 8 Feb, 2013).

    0thLaw:

    Thermodynamic

    equilibrium, temperature

    1st Law:

    Work, heat, energy

    2ndLaw:

    Entropy

    3rdLaw:

    As the T of a substance

    approaches absolute zero

    itsentropy approaches zero

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    Applications of Thermodynamics

    Types of process applications of thermodynamics, namely:

    Ref: Edmister W C (1945) Applications of Thermodynamics to the Process Industries. Journal of Chemical Education. pp13 - 19

    Combustion

    Heat balances

    Power

    Phase equilibrium

    Chemical reaction equilibrium

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    Chemical Engineer & Thermodynamics

    Why is thermodynamics useful to chemical engineers?

    Heat transfer

    Mass transfer

    Separation process

    Chemical reactions

    Ref: Girard-Lauriault P-L . Chemical Engineering Thermodynamics

    CHEE220. (Accessed 8 Feb, 2013); Selis . KMU 220 -

    Chemical Engineering Thermodynamics (Accessed 8 Feb, 2013)

    Calculation of heat and work requirements for physical and

    chemical processes.

    Transfer of chemical

    species between phases

    Determination of

    equilibrium conditions

    Physical processes

    (e.g. distillation)

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    Chem. Engineer & Thermo. (Cont.)

    Thermodynamics permits

    to determine how far

    processes will proceed.

    Chemical kinetics

    helps evaluate how

    fast.

    The 2 concepts are at the base of many of the

    considerations of Chemical Engineers.

    Ref: Girard-Lauriault P-L . Chemical Engineering Thermodynamics

    CHEE220. (Accessed 8 Feb, 2013); Selis . KMU 220 -

    Chemical Engineering Thermodynamics (Accessed 8 Feb, 2013)

    Deals with driving force

    Does not deal with RATEs of

    physical or chemical phenomena.

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    Examples

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    Manufacture of Ethylene Glycol

    Desired reactionH2C CH2 1/2O2

    CatalystH2C CH2

    O

    +

    H = 24.7 kcal/gmole

    Need to be heated to 250 C before enter the reactor

    To design the preheater

    MUST KNOW HOW MUCH HEAT IS TRANSFERRED

    CATALYTIC OXIDATION REACTIONMost effective when carried out at T 250 C

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    T

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    Undesired Reaction

    H2C CH2 3O2+ 2CO2 + 2H2O

    H = 320 kcal/gmole

    Combustion reaction

    Tend to raise the temperature

    Heat is removed from reactor

    T does not rise much above 250 C

    To design the reactor

    REQUIRES KNOWLEDGE OF THE RATE OF HEAT TRANSFER

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    Hydrolysis Reaction

    H2C CH2

    O + H2O HOCH2CH2OH

    Recovered by distillation,vaporization & condensation

    Heat evolved because of

    Phase change

    Dissolution process

    Hydration reaction between the

    dissolved ethylene oxide and H2O

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    CSTRs with Heat Exchanger

    Ref: Fogler H S (1999). Chapter 8: Elements of Chemical Reaction Engineering, 3rd Ed. Prentice Hall. Pp 426 477; CSTR:

    Continuous stirred-tank reactor.

    Continuous-flowreactors

    outoutinin EFEFWQdt

    Ed

    0HFHFWQ i

    n

    1i

    ii0

    n

    1i

    i0s

    At steady state,

    CSTR with heat exchange

    n

    1i

    i0piiRpR

    o

    RX

    A0

    a T-TCTTC)( THXF

    TTUA ~

    RPRRX

    i0pii

    A0

    a

    EBTTC)( TH

    TTCF

    TTUA

    X

    ~

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    Determination of X & T

    5. Energy Balance (Calculate XEB)

    6. Calculate XMB

    Elementary irreversible liquid phase reaction A B

    Non-adiabatic

    RX

    0PAA0aEB

    H

    )T( TC) /FTUA( TX

    ~

    A0

    A0

    0MB F

    VC

    V

    ;.k1

    .k

    X

    E/RTAek

    7. Plot X vs. T

    X

    T

    XEB

    XMB

    Ref: Fogler H S (1999). Chapter 8: Elements of Chemical Reaction Engineering, 3rdEd. Prentice Hall. Pp 426 477; X: Conversion,

    T: Temperature; EB: Energy balance; MB: Mole balance.

    Algorithm

    1. Design equation

    2. Rate law

    3. Stoichiometry

    4. Combining

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    Properties & Equations

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    Thermodynamic Properties

    The thermodynamic properties required for the manyfluids handled in the process industries include:

    Densities

    Vapor pressures

    Critical state

    Fugacities

    Entropies

    Enthalpies

    Free energies

    Some of these propertiesexperimentally determined Others are computedfrom basicexperimental data

    thermodynamicequations.

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    Some Basic Relations in Thermodynamics

    First law:

    Second law:

    Phase equilibrium relations:

    Chemical reaction equilibrium:

    genEflowEWQEt

    genSflowST

    QSt

    iii fff

    GRTlnK

    iv

    0

    i

    i

    f

    f

    K

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    Dimensions & Units

    Dimension SI Unit English Unit

    Time second, s

    Distance meter, m

    foot, ft

    (1 ft = 0.3048 m)

    (1 m = 3.28084 ft)

    Mass kilogram, kg

    pound mass, Ibm

    (1 Ibm= 0.4536 kg)

    (1 kg = 2.2046 Ibm

    Temperature Kelvin, k Rankine, R

    T(R) = 1.8T(K)

    Amount of substance gram mole, g molepound mole, Ib mol

    (1 Ib mol = 453.59 g mol)

    Note: Appendix A : Table A.1, Conversion factors

    f f S

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    Prefixes for SI Units

    Multiple Prefix Symbol Multiple Prefix Symbol

    1015 femto f 102 hecto h

    1012 pico p 102 kilo k

    109 nano n 106 mega M

    106 micro 109 giga G

    103

    milli m 1012

    tera T

    102 centi c 1015 peta P

    Note: Appendix A : Table A.1, Conversion factors

    M f A & Si

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    Measures of Amount & Size

    3 basic measures

    Mass, m(kg)

    Number f moles, n(mol)

    Total volume, Vt(m3)v

    4 derivatives Specific volume,

    Molar volume,

    Specific density,

    Molar density,

    /kgmm

    VV 3

    t

    /molmn

    VV 3

    t

    3t

    kg/mV

    1

    V

    m

    3t

    mol/m

    V

    1

    V

    n

    F (N t 2 d L )

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    Force(Newton 2ndLaw)

    SI units:

    English units:

    maF

    mag1Fc

    Force(N = kg ms-2), defined as that force

    which accelerates 1 kg mass 1.0 ms

    -2

    Mass(kg)

    Acceleration(ms-2), 1 ms-2= 3.20808 (ft)(s)-2

    The acceleration of gravity a = g = 9.81ms-2

    Force (Ibf), 1 Ibf represents the force that

    accelerates 1 Ibm at a = 32.1740 (ft)(s-2)

    Mass(Ibm)

    Acceleration(ft)(s)-232.1740 (Ibm)(ft)(Ibf)-1(s)-2

    T t

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    Temperature

    Temperature scale

    The Celsius Scale : 0C & 100C correspond to the ice point (freezing

    point) & the steam point (boiling point) of pure water

    at standard atmospheric pressure.

    The Fahrenheit scale : T (F) = 1.8T (C) + 32 or T (C) = [T (F)32]5/9

    The Kelvin scale

    (absolute T)

    : T (K) = T (C) + 273.15

    The Rankine scale : T (R) = 1.8 T (K)

    T (R) = T (F) + 459.67

    R l ti hi A T S l

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    Relationship Among T Scales

    Celsius FahrenheitKelvin RankineSteam point

    Ice point

    Absolute zero

    P

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    Pressure

    Defined as the normal force exerted by a fluid on a

    surface per unit area of the surface.

    SI units : N/m2= Pascal (Pa)

    English units : (lbf)/(in)2= pound force per square inch (psi).

    1 psi = 6894.8 Pa

    1 atm = 101325 Pa

    1 atm = 14.7 psi

    M t M th d

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    Measurement MethodDead-Weight Gauge Manometer

    To pressuresource

    h

    Weight

    PanPiston

    Cylinder

    Oil

    To pressure

    source

    A

    mg

    A

    FP

    gh

    A

    gAh

    A

    mg

    A

    FP

    m-the mass of the piston, pan and weights;

    g- the local acceleration of gravity;

    A- the cross-sectional area of the piston.

    h- the relative height of the fluid;

    - the fluid density;

    g- the local acceleration of gravity.

    P (C t )

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    Pressure (Cont.)

    Gauge Pressure vs. Absolute Pressure

    Different SI units for Pressure

    Readings from most pressure gauges and the manometers correspondto gauge pressures which are the difference between the pressure of

    interest and the pressure of the surrounding atmosphere.

    P (absolute) = P (gauge) + P (barometric)

    1 kPa = 103Pa

    1 MPa = 106Pa

    1 torr = 1 mm Hg = 133.32 Pa

    1 atm = 101325 Pa

    = 101.325 kPa = 0.101325 MPa

    = 760 mm Hg = 760 torr

    = 14.7 psi

    1 bar = 105Pa = 0.986923 atm

    W k

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    Work

    Push-Pull Work

    dlFdW

    SI units : Joule (J), 1 J = 1 N m = 1 Pa. m3

    English units : (Ibf)(ft), 1 (Ibf)(ft) = (4.4482 N)(0.3048) =1.3558 J

    2

    1

    l

    lFdlW

    Work done by the force Fover the distance of (l2l1)

    Sign of the work:

    +ve when the displacement d l is in the same direction as the

    applied force.

    -ve when they are in opposite directions.

    W k (C t )

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    Work (Cont.)

    PV Work

    tt

    pdVA

    VdPAdlFdW

    2

    1

    V

    V

    tPdVW

    Sign of the work:

    +ve for compression

    -ve for expansion.

    C l l ti f PV W k

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    Calculation of PV Work

    Graphical method

    2

    1

    V

    V

    tPdVWRelationshipbetweenP and V

    AreaW

    E

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    Energy

    Energy is something that a body can store, and

    which it can receive or give away as workor heat.

    Thus, energy, workand heatare closely related.

    Work and heat are energy in transit, and are

    never regarded as residing in a body.

    Energy, work and heat have the same units:

    Joule (SI)or lb ft (English)

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    P t ti l E (E )

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    Potential Energy (EP)

    Consider a body of mass m, acted upon by a force F =

    mg, is raised from position z = z1to z = z2.

    The total work done by theF is

    p

    z

    z

    z

    z

    E

    mgzmgzmgzdlmgFdlW

    12

    2

    1

    2

    1

    SI system : EPmgz Units of Joule or N.m or kgm2s-2English system : Epmgz/gc Units of (Ibf)(ft),

    where gc= 32.1740 (Ibm)(ft)(Ibf)-1(s)-2

    Energ Conser ation

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    Energy ConservationConsider a body of mass m, falls freely from position z

    = z1to z = z2, where the body gains in velocity u1u2.

    2121

    2

    1

    2

    2

    22

    mgzmgzzzmgFlWmumu

    EK

    In this process, the body gains in kinetic energy is

    the work done by the force of gravity, i.e.,

    While in this process, the change in the bodys

    potential energy is EP= (mgz) = (mgz2mgz1)

    Thus, EK+ E

    P= (mgz

    1mg

    2) + (mgz

    2mgz

    1)

    Therefore, for purely mechanical processes without

    friction, the energy conserves, i.e.,

    0 KK EE 22

    2

    1

    2

    1

    22mgz

    mumgz

    muor

    Heat

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    HeatHeat (Q) always transfers from a high temp. body to a lower temp. one.

    The rate of heat transfer ( ) is proportional to the temp. difference T

    Like work, heat exists only as energy in transitfrom one body to another

    or between a system and its surroundings.

    When energy in the form of heat is added to a system, this part of

    energy is stored NOT as heat, but as kinetic and potential energy of

    atoms/molecules in the system.

    Q

    Units of heat

    SI system : Joule (J)Calorie (Cal), 1 Cal = 4.184 J

    British system : (Ibf)(ft), 1 (Ibf)(ft) = 1.3558 J

    British thermal Unit (Btu), 1 (Btu) = 1055.04 J