SELECTING THERMODYNAMIC PROPERTY METHODS

flinkexistenceMechanics

Oct 27, 2013 (4 years and 12 days ago)

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SELECTING THERMODYNAMIC
PROPERTY METHODS


A

key

requirement

of

process

design

is

the

need

to

accurately

reproduce

the

various

physical

properties

that

describes

chemical

species
.


The

property

packages

available

in

HYSYS

allow

you

to

predict

properties

of

mixtures

ranging

from

well

defined

light

hydrocarbon

systems

to

complex

oil

mixtures

and

highly

non
-
ideal

(
non
-
electrolyte)

chemical

systems
.

PHYSICAL PROPERTIES

The physical properties required for modeling and simulation
often includes,


Molecular reaction and kinetic data.


Thermodynamic properties


Transport properties

MOLECULAR REACTION & KINETIC DATA

In this case Critical properties are,


Rate equation


Activation energies


Reaction mechanism

THERMODYNAMIC PROPERTIES



Enthalpy


Entropy


Fugacity coefficient


Gibbs free energy

TRANSPORT PROPERTIES



Diffusion coefficient


Thermal conductivities


Viscosities


HYSYS

provides

enhanced

equations

of

state

(
PR

and

PRSV)

for

rigorous

treatment

of

hydrocarbon

systems
;

semi

empirical

and

vapour

pressure

models

for

the

heavier

hydrocarbon

systems
;

steam

correlations

for

accurate

steam

property

predictions
;

and

activity

coefficient

models

for

chemical

systems
.

All

of

these

equations

have

their

own

inherent

limitations
.

So

HYSYS

includes

following

methods

for

the

estimation

of

Physical

properties,


Equations

of

state


Activity

models


Chao
-
Seader

based

empirical

methods


Vapour

pressure

models

an


Miscellaneous

methods
.


EQUATIONS OF STATES


The

table

lists

some

typical

systems

and

recommended

correlations
.

PENG
-
ROBINSON EOS


For

oil,

gas

and

petrochemical

applications,

the

Peng
-
Robinson

EOS

(
PR
)

is

generally

the

recommended

property

package
.


It

rigorously

solves

any

single,

two
-
phase

or

three
-
phase

system

with

a

high

degree

of

efficiency

and

reliability,

and

is

applicable

over

a

wide

range

of

conditions
,

as

shown

in

the

following

table
.


the

Peng
-
Robinson

equation

of

state

supports

the

widest

range

of

operating

conditions

and

the

greatest

variety

of

systems
.

The

Peng
-
Robinson

and

Soave
-
Redlich
-
Kwong

equations

of

state

(EOS)

generate

all

required

equilibrium

and

thermodynamic

properties

directly
.

PR AND SRK


The

PR

equation

of

state

applies

a

functionality

to

some

specific

component
-
component

interaction

parameters
.

Key

components

receiving

special

treatment

include

He,

H
2
,

N
2
,

CO
2
,

H
2
S,

H
2
O,

CH
3
OH


The

PR

or

SRK

EOS

should

not

be

used

for

non

ideal

chemicals

such

as

alcohols
,

acids

or

other

components
.

They

are

more

accurately

handled

by

the

Activity

Models

(highly

non

ideal)

or

the

PRSV

EOS

(moderately

non
-
ideal)
.

LEE KESLER PLÖCKER EQUATION


The

Lee

Kesler

Plöcker

equation

is

an

accurate

general

method

for

non

polar

substances

and

mixtures
.

ACTIVITY MODELS

ACTIVITY MODELS

Although

equation

of

state

models

have

proven

to

be

very

reliable

in

predicting

properties

of

most

hydrocarbon

based

fluids

over

a

large

range

of

operating

conditions,

their

application

has

been

limited

to

primarily

non
-
polar

or

slightly

polar

components
.

Polar

or

non
-
ideal

chemical

systems

have

traditionally

been

handled

using

dual

model

approaches
.

EXTENDED AND GENERAL NRTL

With

a

wide

boiling

point

range

between

components
.

where

you

require

simultaneous

solution

of

VLE

and

LLE,

and

there

exists

a

wide

boiling

point

range

or

concentration

range

between

components
.

CHAO

SEADER

MODELS

VAPOUR PRESSURE MODELS

MISCELLANEOUS MODELS

VAPOUR PRESSURE MODEL


The

Vapour

Pressure

options

include

the

Modified

Antoine,

BraunK
10
,

and

EssoK

packages

MISCELLANEOUS
-

SPECIAL

APPLICATION METHODS


Amines Property Package

STEAM PACKAGE

HYSYS

includes

two

steam

packages
:



ASME

Steam



NBS

Steam

Both

of

these

property

packages

are

restricted

to

a

single

component,

namely

H
2
O
.


ASME

Steam

accesses

the

ASME

1967

steam

tables
.

The

limitations

of

this

steam

package

are

the

same

as

those

of

the

original

ASME

steam

tables
,

i
.
e
.
,

pressures

less

than

15000

psia

and

temperatures

greater

than

32
°
F

(
0
°
C)

and

less

than

1500
°
F
.


Selecting

NBS_Steam

utilizes

the

NBS

1984

Steam

Tables,

which

reportedly

has

better

calculations

near

the

Critical

Point
.

ASSIGNMENT

PUMP


Pumps

are

used

to

move

liquids
.

The

pump

increases

the

pressure

of

the

liquid
.

Water

120

C

and

3

bar

is

fed

into

a

pump

that

has

only

10
%

efficiency
.

The

flow

rate

of

the

water

is

100

kgmole
/h

and

its

outlet

pressure

from

the

pump

is

84

bar
.

Using

Peng
-
Robinson

equation

of

state

as

a

fluid

package,

determine

the

outlet

temperature

of

the

water
.


RESULTS


This

example

shows

that

pumping

liquid

can

increase

their

temperature
.

In

this

case,

the

pump

was

only

10
%

efficient

and

it

caused

18
°
C

in

the

temperature

of

the

water
.

The

less

efficient

a

pump

is,

the

greater

the

increase

in

the

temperature

of

the

fluid

being

pumped
.

This

arises

because

in

a

low

efficient

pump,

more

energy

is

needed

to

pump

the

liquid

to

get

the

same

outlet

pressure

of

a

more

efficient

pump
.

So

the

extra

energy

gets

transferred

to

the

fluid
.


COMPRESSOR



Compressors

are

used

to

move

gases
.

The

compressor

increases

the

pressure

of

the

gases
.

A

mixture

of

natural

gas

(C
1
,

C
2
,

C
3
,

i
-
C
4
,

n
-
C
4
,

i
-
C
5
,

n
-
C
5
,

n
-
C
6
,

C
7

)

at

100

C

and

1

bar

is

fed

into

a

compressor

that

has

only

30
%

efficiency
.

The

flow

rate

of

the

natural

gas

is

100

kgmole
/h

and

its

outlet

pressure

from

the

compressor

is

5

bar
.

Using

Peng
-
Robinson

equation

of

state

as

a

fluid

package,

determine

the

outlet

temperature

of

the

natural

gas
.


If

the

outlet

temperature

is

400

C
,

what

is

the

efficiency

of

the

compressor?