Distillation columns: Introduction to chemical process simulators - coco - dwsim - aspen - hysys -...

INTRODUCTION TO CHEMICAL PROCESS SIMULATORS

A. Carrero, N. Quirante, J. Javaloyes

October 2016

DWSIM Chemical Process Simulator

A. Carrero , N. Quirante & J. Javaloyes

Introduction to Chemical Process Simulators

2

Contents

Monday, October 3rd 2016

Introduction to Sequential – Modular Steady State ProcessSimulators

Get used to working with DWSIM and COCO

Monday, October 10th 2016

Simulation of Chemical Reactors


Simulation of Distillation Columns


Case studies



3


Feed

Distillate

Bottoms

Condenser

Reboiler

Rectifying section

Stripping section

Equilibrium Stage

Conventional Distillation Column

Feed

Distillate

Bottoms



4

Simulation of Distillation ColumnsjV

,i j

V

j

j

y

H

T

,

j

i j

F

j

F

j

F

z

H

T

, 1

1

1

i j

V

j

j

y

H

T

,i j

L

j

j

x

H

T

, 1

1

1

i j

L

j

j

x

H

T

1jV jL

1jL

jU

if from stage

if to stage

jQ

jW

FeedHeat Transfer

Liquid

Side Stream

Vapor

Side Stream

Stage j



5

Simulation of Distillation ColumnsjV

,i j

V

j

j

y

H

T

,

j

i j

F

j

F

j

F

z

H

T

, 1

1

1

i j

V

j

j

y

H

T

,i j

L

j

j

x

H

T

, 1

1

1

i j

L

j

j

x

H

T

1jV jL

1jL

jU

if from stage

if to stage

jQ

jW

FeedHeat Transfer

Liquid

Side Stream

Vapor

Side Stream

Stage j

, ,

, ,

, ,

, , ,

, ,

L V

i j i j

L

i j j j i j

V

i j j j i j

f f

f f T P x i C j NS

f f T P y

1 , 1 1 , 1 , ,

, 0 ,

j i j j i j j i j j j i j

j j i j

L x V y F z L U x

V W y i C j NS

, ,

1 1

1, 0C C

i j i j

i i

y x j NS

1 1 1 1

,

,

0

, ,

, ,

L V F L

j j j j j j j j j

V

j j j j

L

j j j i j

V

j j j i j

L H V H F H L U H

V W H Q j NS

H f T P x

H f T P y

Material Balance

Vapor-Liquid Equilibrium Relation

Summation Equations

Energy BalanceMESH Equations



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MESH Equations fully describe the behavior of a distillation column.

External to de column: these equations define the overall column totalmaterial balances, energy balances and product composition

Internal to de column: they describe equilibrium conditions, internalcomponent, total material and energy balances in each tray.

Bubble-point methods (BP)

Sum-rate methods (SR)

2N Newton methods

Nonlinear and Nonconvex algebraic system of equations

Simultaneous correction methods (SC)

Inside-out methods (IO)

Rigorous Computational Methods



7

Main Steps for the Simulation of a Conventional Distillation Column

# 1. Component Selection

# 2. Fluid package Selection

# 3. Flash Algorithm Selection

# 4. Add Distillation Column Object

# 5. Set Column Properties Condenser & Reboiler Pressure Condenser type Condenser & Reboiler Specifications

# 6. Set Number of Stages

# 7. Set Column Pressure Profile

# 8. Edit Column Connections

# 9. Solving Method Selection

# 10. Run Model




8

Example

Molar Flow 200 kmol/hPressure 1.1 barVapor fraction 0

Molar CompositionxBz = 0.35xT = 0.29xM-xy = 0.12xO-xy = 0.12xP-xy = 0.12

99% recovery of Bz98% purity of Bz




9

Column Diameter Estimation

V LLV

L V

MLF

V M

0.22

2

exp 2.979 0.717ln 0.0865 ln20

0.997ln 0.07973ln ln

0.256 ln

T LV LV

T LV T

T

K F F

H F H

H

L VT F T

V

v f K

4 Vcolumn

A V S T

M VD

f f v

FLV Liquid-Vapor flow parameter

L, V Liquid/Vapor molar flowrate [kmol s-1]

ML,MV Liquid/Vapor molar mass [kg kmol-1]

L, V Liquid/Vapor density [kg m-3]

KT Parameter for terminal velocity [m s-1]

Surface tension [dyne cm-1]

HT Tray spacing [m] (0,25 – 0,6 m)

vT Vapor flooding velocity [m s-1]

fF Foaming factor

Low/ Moderate foaming ~ [0,9 - 0,85 ]

fA Net area factor (~0,9)

fS Flooding velocity safety factor (~0,8)

[R. Smith. Chemical Process Design and Integration][H. Kister. Distillation Design]

Distillation columns: Introduction to chemical process simulators - coco - dwsim - aspen - hysys -...

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