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Practical guide to process modeling

choose your Thermodynamic model!

What do you mean by data?

What is a property?

What is a parameter?

What is a thermodynamic model?

Definitions to know

INNOVATION

COST OPTIMIZATION

SAFETY

Why should I choose the right thermodynamic model?

Which model?

Which data ?

Individual examples of use

2° step: Fluid type

1° step: Process type

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Just a few questions to define your perfect model!

Energy system

Flow Assurance

Reaction

Separation

1- Which process?

Liquid-liquid decantation

Flash drum

LIQUID-SOLID

LIQUID-LIQUID

LIQUID-VAPOR

Supercritical extraction

Stripping

Distillation

Solvent absorption

Crystallization

Liquid-liquid extraction

Select the type of separation process

Extractive Distillation

Severe specifications

Close boiling

Select the type of distillation process?

Inifinite dilution activity coefficient (or Henry constants) of impurities in the main component in the distillate

A severe specification consists in not exceeding very low concentration of some impurities in the distillate

Key data to collect for model parameterization / validation:

part 2

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Severe Specifications

Close boiling pure compounds vapour pressures

Key data to collect for model parameterization / validation:

Compounds with close boiling point are expected to form an azeotropic mixture

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Azeotrope data (temperature, pressure, composition) Only azeotropes in the cut point region are of interest!

Close boiling

Key data to collect for model parameterization / validation:

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Distribution coefficients (Ki) of key compounds in the solvent

Extractive distillation

Azeotrope data for close boiling components

Key data to collect for model parameterization / validation:

part 2

part 2

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Distribution coefficients (Ki) of key compounds

Flash drum

Solubility (mole fraction) of the solutes in the liquid solvent

Low and high solubilities of the solutes:

Low solubility of the solutes:

Key data to collect for model parameterization / validation:

part 2

part 2

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TRY AGAIN

Henry constant of solutes in the liquid solvent

Solvent absorption

Distribution coefficients (Ki) of key compounds in the solvent

Key data to collect for model parameterization / validation:

part 2

part 2

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TRY AGAIN

Supercritical extration

Henry constant of the stripping gas in the solvent

Distribution coefficients (Ki) of key compounds in the solvent

Key data to collect for model parameterization / validation:

part 2

part 2

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TRY AGAIN

Stripping

Inifinite dilution activity coefficient of low-concenration components

Liquid-liquid equilibrium data (tie-lines)

Low and high solubilities of the solutes:

Low solubility of the solutes:

Key data to collect for model parameterization / validation:

part 2

part 2

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Liquid-liquid decantation

(often, ternary data between solute + solvent 1 + co-solvent)

Inifinite dilution activity coefficient of solutes in the solvent / co-solvent

If low solubility of the solutes:

Partitioning coefficients of the key components to be extracted

Key data to collect for model parameterization / validation:

part 2

part 2

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Liquid-liquid extraction

Key data to collect for model parameterization / validation:

part 2

part 2

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TRY AGAIN

Pure component : melting temperature and melting enthalpy Mixtures : Solid + Fluid equilibrium data Beware to eutectic points !

Crystallization

Wagner, N., & Pross, A. (2011). The nature of stability in replicating systems. Entropy, 13(2), 518–527. https://doi.org/10.3390/e13020518

Kinetic control

Thermodynamic control

Specify the type of reactor modelling

Multiphase systems

No thermodynamic issues

Single phase systems

Key data to collect for model parameterization / validation:

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Solubilities of reactants and products in the reacting phase must be known. Focus on the rate limiting species.

Kinetic control

Solubilities of reactants and products in the reacting phase must be known.

Multiphase systems:

Enthalpies of the reaction(s)

Equilibrium constant of the reaction(s)

All systems:

Key data to collect for model parameterization / validation:

part 2

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Thermodynamic control

Two phase flow

Liquid flow

Gas flow

In which phase is the fluid flow?

Vapor appearance

Solid appearance

Which is the most likely risk of appearance?

Focus on data involving the lighest component of the mixture

Key data to collect for model parameterization / validation:

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Bubble temperature (or pressure) of the liquid mixture

Liquid flow Vapor appearance risk

SCALES

ASPHALTENES

WAXES

HYDRATES

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Which kind of solid is expected to form ?

Liquid flow Solid appearance risk

Hydrate appearance temperature (or pressure) with or without hydrate inhibitor

Key data to collect for model parameterization / validation:

part 2

part 2

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Hydrate

Wax amount formed at a given temperature and pressure

Wax appearance temperature (WAT)

Key data to collect for model parameterization / validation:

part 2

part 2

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Wax

Fraction of asphaltene precipitated

Onset pressures: upper (UOP) and/or lower (LOP)

Key data to collect for model parameterization / validation:

part 2

part 2

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Asphaltene

Equilibrium constants of the salt formation reactions

Brine analysis

Key data to collect for model parameterization / validation:

part 2

part 2

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TRY AGAIN

Scales

Liquid appearance

Solid appearance

Which is the most likely risk of appearance?

Focus on data involving the heaviest component of the mixture

Key data to collect for model parameterization / validation:

part 2

part 2

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TRY AGAIN

Dew temperature (or pressure) of the vapor mixture

Gas flow Liquid appearance risk

HYDRATES

Which kind of solid is expected to form ?

DEPOSITION

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Gas flow Solid appearance risk

Look also the specific properties for the liquid flow and vapor flow !

Key data to collect for model parameterization / validation:

Distribution coefficients (Ki) of key compounds

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Two phase flow

Phase enthalpy

Phase density

Look also the specific risks for the liquid flow and vapor flow !

Compressor, pump, heat exchangers,...

Key data to collect for model parameterization / validation:

part 2

part 2

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TRY AGAIN

Energy system

MIXTURE

PURE COMPONENT

Select the type of fluid to model

2- Model Selection

Vapor - High pressure ( > 10 bara)

Vapor - Low pressure ( < 10 bara)

Liquid (or unknown)

What is the state of the pure component fluid ?

Pure component

IDEAL GAS

Finally! Here are the models proposed for your process.

No!

Yes!

Do I need only properties of the saturated liquid ?

Pure component Liquid state

Specific correlations for pure liquid saturated properties

Finally! Here are the models proposed for your process.

No! (or I don't know!)

Yes!

Is there a specific equation of state for your component ?

Pure component

Specific Equation of State

Finally! Here are the models proposed for your process.

Select the property type to analyze

Phase property

Phase equilibrium property

Mixture with H2 (large quantity)

Mixture of non polar compounds

Mixture with polar compounds

Which type of mixture ?

Other molecules

Hydrocarbons < C16

H2

Which other components ?

Cubic EOS (PR, SRK)with T-dependent kij

GRAYSON - STREED

Finally! Here are the models proposed for your process.

Cubic EOS (PR, SRK)with T-dependent kij

Finally! Here are the models proposed for your process.

No

Yes!

Close boiling point process ?

Reminder of data needs

Cubic EOS (PR, SRK)- Beware to alpha function ! - Adjust kij !

Finally! Here are the models proposed for your process.

Almost there...

Yes, it is available

No, I have no data

Do you have key experimental data for your process?

Cubic EOS (PR, SRK)- Adjust kij !

Finally! Here are the models proposed for your process.

PPR78

Consider this!

Finally! Here are the models proposed for your process.

No! (or I don't know)

Yes!

Large size asymetry ?

Low pressure P < 10 bara

High pressure P > 10 bara

What is the operating pressure?

Almost there...

Yes, it is available

No, I have no data

Do you have key experimental data for your process?

Equations of state

Activity coefficient models

SAFT

UNIQUAC

Finally! Here are the models proposed for your process.

FLORY

Consider this!

GC-SAFT

UNIFAC

Equations of state

Activity coefficient models

Finally! Here are the models proposed for your process.

Almost there...

Yes, it is available

No, I have no data

Do you have key experimental data for your process?

Equations of state

SAFT

Finally! Here are the models proposed for your process.

Consider this!

GC-SAFT

Equations of state

Finally! Here are the models proposed for your process.

No!

Just in case...

Yes!

Does your process contain electrolyte species?

Almost there...

Yes, it is available

No, I have no data

Do you have key experimental data for your process?

Consider this!

LIFAC

Activity coefficient model

Finally! Here are the models proposed for your process.

LIQUAC(pure and mixed solvents)

Ion-dependant

Global salinity

Pitzer(water)

Soreide & Whitson

e-PC-SAFT

e-CPA

e-NRTL(pure and mixed solvents)

Equations of state (low and high pressure)

Activity coefficient models (low pressure)

Finally! Here are the models proposed for your process.

T > min(Tc,i)

OR

P > 10 bara

T < min(Tc,i)

AND

P < 10 bara

About operating pressure and temperature

Almost there...

Yes, it is available

No, I have no data

Do you have key experimental data for your process?

Consider this!

UNIFAC

Activity coefficient models

Finally! Here are the models proposed for your process.

Activity coefficient models

NRTL

UNIQUAC

Finally! Here are the models proposed for your process.

Almost there...

Yes, it is available

No, I have no data

Do you have key experimental data for your process?

No!

Yes! (or I don't know!)

Does your process contain Hydrogen-bonded molecules ?

Equations of state

PPR78

Consider this!

Finally! Here are the models proposed for your process.

Consider this!

GC-SAFT

PSRK

Equations of state

Finally! Here are the models proposed for your process.

Cubic EOS + asymetric kij mixing rules(ex: SRK -Twu)

CPA

SAFT

Cubic EOS + GE mixing rules(ex: PRH, SRK-MHV2)

Equations of state

Finally! Here are the models proposed for your process.

Polar interactions

Non polar interactions

What is the type of interaction in the system ?

LEE-KESLER

Finally! Here are the models proposed for your process.

Almost there...

Yes, it is available

No, I have no data

Do you have key experimental data for your process?

SAFT

Finally! Here are the models proposed for your process.

Consider this!

GC-SAFT

VTPR

Equations of state

Finally! Here are the models proposed for your process.

CO2 capture unit

Ethanol to Ethylene Dehydration Unit

3- Process examples

Ethane / Ethylene Splitter

Dryer

Water washing

Compressor

Flash drum

Reactor

Which model?

Ethanol to Ethylene Dehydration unit

Enthalpies of reaction to determine outlet temperature

Equilibrium constant to determine extend of reaction

Key data to collect for model parameterization / validation:

Ethanol to Ethylene Dehydration unit

Reactor

Monophasic adiabatic reactor, thermodynamic control (main reaction)

To separate water from the ethylene-rich vapour phase

Distribution coefficients (Ki) : water, ethylene, non-converted ethanol, ethane, diethylether, acétaldehyde

Flash drum

Key data to collect for model parameterization / validation:

Ethanol to Ethylene Dehydration unit

Phase enthalpy

Phase density

Compressor

Key data to collect for model parameterization / validation:

Ethanol to Ethylene Dehydration unit

Water washing

Solubilities (mole fraction) of the soluble solutes (ethanol, acetaldehyde) in liquid water

Henry constant of light solutes (ethylene, ethane, ether) in liquid water

Key data to collect for model parameterization / validation:

Ethanol to Ethylene Dehydration unit

To correctly size the dryer, the data needed are: Hydrate appearance temperature as a function of water content

Cool down a wet gas pressurized gas Risk of hydrate formation!

Dryer and cooler

Key data to collect for model parameterization / validation:

Ethanol to Ethylene Dehydration unit

Azeotrope data (Possibly)

Pure compounds vapour pressures

Close boiling distillation

Ethane - Ethylene splitter

Key data to collect for model parameterization / validation:

Ethanol to Ethylene Dehydration unit

Data available

No electrolytes

No large size asymetry

Mixture with polar compounds

Phase equilibrium property

Model Selection

Ethanol to Ethylene Dehydration unit

Cubic EOS + asymetric kij mixing rules(ex: SRK -Twu)

T > min(Tc,i)

OR

P > 10 bara

Cubic EOS + GE mixing rules(ex: PRH, SRK-MHV2)

Heat exchangers

Reactive Stripper

Reactive Absorber

Which model?

CO2 Capture process

Reactive stripper

Henry constant of light solutes (CO2, H2S, COS, ...) in liquid amine solvent

* Gas absorption/desorption * Chemical reactions under thermodynamic control

Reactive absorber

Enthalpies of reaction to determine duties

Equilibrium constants to determine extend of reactions

Key data to collect for model parameterization / validation:

CO2 Capture process

Phase enthalpy

Phase density

Key data to collect for model parameterization / validation:

CO2 Capture process

Activity coefficient models (low pressure) with mixed solvent (aqueous amine)

Data available

with electrolytes

No large size asymetry

Mixture with polar compounds

Phase equilibrium property

Model Selection

LIQUAC

CO2 Capture process

e-NRTL

EXEMPLES

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