KKA 3306 PROCESS AND PLANT DESIGN Lecture 6 - PowerPoint PPT Presentation

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KKA 3306 PROCESS AND PLANT DESIGN Lecture 6

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KKA 3306 PROCESS AND PLANT DESIGN Lecture 6 – PowerPoint PPT presentation

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Title: KKA 3306 PROCESS AND PLANT DESIGN Lecture 6


1
KKA 3306 - PROCESS AND PLANT DESIGN Lecture 6
By Robiah yunus Faculty of engineering Universiti
putra malaysia Serdang,43400 selangor.
2
MASS AND ENERGY BALANCES
  • Introduction
  • Mass and energy balances are simple, fast and
    useful methods for evaluating the selected
    flowsheet
  • consider only systematic and simplified methods
  • detailed and time consuming
  • precedes plant equipment sizing and costing

3
MASS AND ENERGY BALANCES
  • Introduction
  • Typical flowsheet will have large set of
    equations non-linear and linear equations
    describing
  • connectivity of units via process streams
  • specific equation for units I.e. internal mass
    and energy balances and equilibrium relationships
  • physical property relationships I.e.H, Keq,, m,
    etc

4
MASS AND ENERGY BALANCES
  • Introduction
  • The equations are solved either by sequential
    modular or equation oriented approaches
  • sequential modular
  • equations for each unit written so that one
    calculates output stream values of a unit, given
    its input values and unit parameter values
  • Use guess values for recycle s and iterate on
    these guesses

5
MASS AND ENERGY BALANCES
  • Introduction
  • Equation oriented
  • all equations are written in general form and
    stored as equation sets
  • equations are solved simultaneously for unknown
    variables
  • solution procedure is to solve a sparse matrix
    containing many thousand equations

6
MASS AND ENERGY BALANCES
  • Introduction
  • Preliminary Design
  • use approximations to solve non-linear equations
  • ideal solutions/relations
  • streams as saturated vapor or liquid only
  • represent the flowsheet as linear system of
    equations
  • Simulation strategies for more rigorous models
    will be covered later.

7
MASS AND ENERGY BALANCES
  • Developing Unit Models for Linear Mass Balances
  • Given P,T of feed and output streams, develop
    linear equations for each unit based on this
    steps
  • Fix T and Ps of all process streams
  • approximate split fraction of outputs in relation
    to inputs of each unit
  • combine linear equations and solve the overall
    mass balance
  • Recalculate T and P based on equilibrium
    relationships
  • If there is large difference, recalculate, if not
    proceeds with energy balance.

8
MASS AND ENERGY BALANCES
  • Flash Calculations
  • most important and fundamental in flow sheeting
    calculations
  • building blocks for deriving linear models in
    equilibrium staged calculations i.e.
    distillation, absorption, etc.

Typical Specifications 1. T P - Isothermal 2.
P Q 3. T V/F (or yi or di) 4. P V/F
(or yi or di) 5. V/F (or yi or si) Q
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