공장설계 (chemical plant design)

Process Simulator CHEMICAL PROCESS DESIGN

© Myung-June Park Chemical Engineering

공장설계 (Chemical Plant Design)

LECTURE 3: SIMULATION TO ASSIST

IN PROCESS CREATION

Myung-June Park

Department of Chemical Engineering

Ajou University

http://www.ajou.ac.kr/



On completing this part of the course, you should:

Understand the role of process simulators in process creation

Be able to create a simulation flowsheet, involving the selection

of models for the process units and the sequence in which

process units associated with recycle loops are solved to obtain

converged material and energy balances

Learn the step-by-step procedures for using ASPEN PLUS and

HYSYS.Plant (CD-ROM)

Objectives




• (Chap 4) Process creation

– The generation of process flowsheets

• (This chapter) Process analysis

– To find the solution of the material and energy balances coupled with phase equilibria and the equations of transport and chemical kinetics

– Utilization of process simulators to simulate potential processes in the steady state

– Determination of unknown T, P, component and total flow rates

– To locate malfunctions, and to predict the performance of processes

– Mathematical model: Relationship between process variables and operation variables

– ASPEN PLUS, HYSYS.Plant (UniSim), CHEMCAD, PRO/II for st. st.

– BATCH PLUS, SUPER PRO DESIGNER for batch processes

– Procedures (module or blocks)-based approach

Introduction




• Collection of icons to represent process units and arcs to represent the flow of materials

Process Flowsheets

[Source] Figure 5.1; Seider et al., Product and Process Design Principles, 3rd Ed.

Figure




• Collection of simulation units to represent computer programs (subroutines or models) and arcs to represent the flow of information

Simulation Flowsheets


Figure




Simulation Flowsheets

Model name = block = subroutine

cf. Table 5.1 List of subroutines for each process simulator


Figure




• Degree of Freedom

– ND = NVariables – NEquations

– Examples 5.1 & 5.2

• Bidirectional Information Flow

• Control Blocks (Adjust in HYSYS)

• Define Fluid Package

– Property Package

• Set Up the Simulation

– User Interface

– Stream

– Units

– Unit Catalog (Flash): How to apply the theory of phase equilibrium

– Do It Yourself

Getting Started in HYSYS




• Most distributions of chemicals involve recycle streams

• For the simple distribution

– Direct calculation of the flow rates of the species in the recycle stream. (cf. VCM in Chap 4)

• Recycle stream is a complex function of operating conditions

– When the reaction involves a reversible reaction

– Purge streams exist

• Requirement of information recycle loops

– Tear one stream

– Recycle convergence units (compare & re-guess)

Recycle

guessed calculated

For the convergence subroutines • Successive substitution (direct iteration) • Wegstein method • Others


Figure




• Successive substitution

– xnew = f(xold)

• Wegstein’s method

– Extrapolation of xnew and f(xold)

Convergence

( 1) ( ) ( )

( ) ( 1)

( ) ( 1)

1 ( )

( ) ( )where ,

1

k k k

k k

k k

x qx q f x

s f x f xq s

s x x

convergence

divergence Slope of the extrapolated line




Iteration

• Newton-Raphson method

– Approximation for Jacobian

– Required number = n+1

• Secant method

• Successive method

• Wegstein’s method

( )

( 1) ( ) 1 ( ) ( )

( ) ( ) ( )

( )

where

column, rowk

k k k k

k k k

k i

j x

x x J x y x

y x f x x

yJ x i j

x

, 1, ,p

i i i

j j

y y yi j n

x x

( ) ( 1)( 1) ( ) ( )

( ) ( 1)

k kk k k

k k

x xx x f x

f x f x

( )kJ x I

( ) ( ) ( )1k k kJ x A x diag s x

No interaction!!!




Two Recycles

[Source] Figure 5.12a; Seider et al., Product and Process Design Principles, 3rd Ed.

Figure




• Option 1

Two Recycles

[Source] Figure 5.12b; Seider et al., Product and Process Design Principles, 3rd Ed.

Figure




• Option 2

Two Recycles

[Source] Figure 5.12c; Seider et al., Product and Process Design Principles, 3rd Ed.

Figure




• Option 3

Two Recycles

Inner loop

Outer loop

When the units outside C1 require extensive computations

[Source] Figure 5.12d; Seider et al., Product and Process Design Principles, 3rd Ed.

Figure




Three Recycles

[Source] Figure 5.13a; Seider et al., Product and Process Design Principles, 3rd Ed.

Figure




• Option 1

Three Recycles

CONV2 F G CONV1 D A B C (RETURN CONV1) E (RETURN CONV2) [Source] Figure 5.13b; Seider et al., Product and Process Design Principles, 3rd Ed.

Figure




• Option 2

Three Recycles

CONV3 F G D A B C E (RETURN CONV3) [Source] Figure 5.13c; Seider et al., Product and Process Design Principles, 3rd Ed.

Figure




• Example for HYSYS (UniSim) – Ex 5.1a,b

– CD: Getting Started in HYSYS Convergence

– CD: HYSYS Separation Flash

– CD: HYSYS Pumps, Compressors, & Expanders Pumps

Flash with Recycle Problem


Figure


공장설계 (chemical plant design)

Documents