2014 software global client conferenceiom.invensys.com/en/softwaregcc14presentations/technical...

2014 Software Global Client Conference

Simulation

Thermodynamics:

Best Practices

Part II: Assuring the optimal

Thermodynamic Methods for

your simulation

John R. Cunningham

NA Technical Support

Oct. 2, 2014

Orlando Florida


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Overview What are the steps prior to a project start, necessary to assure that you

are using the optimal property packages and thermodynamic methods for

your simulation and design.

Part I

●Which physical properties will impact thermo method selection

●Adding new components

●When property estimates are appropriate

Part II

●How composition plays an important part in method selection

●How characterization and cut selection can impact design

●When measured data may be absolutely necessary.


Parts of a simulation

● Individual Component Properties (Part I)

From Library, Characterization, Estimates

●Combined Stream Properties

Thermodynamic Methods

●Combined Stream Behavior

Thermodynamic Methods

●Unit Operation Algorithm


From Fundamentals to Properties

●We have seen that reliable pure component properties can be obtained

from the simulators libraries, most of the data in PRO/II component

libraries originate from either DIPPR or PPDS/NEL in the UK

●Many non-library component properties can be estimated via group

contribution methods available in PRO/II or TDM

●There is often a need to verify pure component values


Important Questions

We have pure component properties, what more do we need?

Mixture Properties!

What are the mixture components, what is the amount of each?

Where are the process conditions located with respect to the

phase envelope?


From Fundamentals to Properties

●An unambiguous definition of a thermodynamic state may be given by:

• Temperature

• Pressure

• Composition

• Physical State (ideal gas, vapor, liquid, solid)

●Method selection decisions can be made on the basis of the above

based on both the properties available and those required.


Mixtures with limited numbers of components



0

10

20

30

40

50

60

70

80

90

100

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Tem

pera

ture

, C

Composition, Mole Fraction PROPANE, (P = 0.50000 MPa)

T-X-Y Plot for PROPANE and PENTANE


Lets talk about composition

●Next Question:

●What is the key composition range?

●Most cases it’s the majority components that impact the calculation

●On occasion it can be an impurity that matters


● Next Questions:

● Is the mixture ideal or non-ideal, What type and to what degree is the

extent of this non-ideality

● How do we think about non-ideality?

● Raoult’s Law:

● Activity coefficient:




● When non-ideality is due to attraction or repulsion between

molecules we call it enthalpic (or residual) effects. Attraction

results in positive deviations from ideality while repulsion

tends to result in negative deviations

● If the non-ideality is due to molecular size it is know as

entropic (or combinatorial) effects

●


Finally different Methods may be good for

different phases/properties


Considerations in the Critical Region: Simulation Considerations


Other considerations in the Critical Region:

Property Considerations

●Heat capacity example, Cp going to infinity


Considerations in the Critical Region: Complex Phase Boundaries

● Phase boundary for water/ethyl benzene: representative of 20 or so more

complex phase boundary systems


Considerations in the Critical Region:

Thermodynamic Model Considerations ●Liquid Activity models (or Gamma Phi approach) uses pure component

vapor pressures to calculate phase equilibria

●Vapor Pressure is undefined above the critical point

●Henrys Law is used

●Replaced by:

K

y

x

Pv

RTP P

Pi

i

i

i

l

i

sat

i

sat i

l

i

sat

i

v

exp

Ky

x

H

Pi

i

i

i mix

,


The upcoming method Selection tree is from:

”SELECT THERMODYNAMIC MODELS FOR PROCESS SIMULATION”: A

practical Guide using a Three Steps Methodology,” Jean-Charles de Hemptinne,

Jean-Marie Ledanois, Pascal Mougin, Alain Barreau, Edition Technip, Paris 2012.

● http://books.ifpenergiesnouvelles.fr/ebooks/thermodynamics/table_of_contents.html

http://books.ifpenergiesnouvelles.fr/ebooks/thermodynamics/table_of_contents.html

http://books.ifpenergiesnouvelles.fr/ebooks/thermodynamics/table_of_contents.html


We have Modified the decision tree below to be more SimSci centric


Working through the HC Portion of the Tree

● Pretty Easy

● The Yes side of only HC?

● i.e. H2/nC20 or Methane/Tetralin

●Our First Solution: I like CEOS

where fitted alphas and Kijs are

available

●The No side of only HC;

●Yes for azeotropy?

●Next solution: Fitted CEOS or

PPR78 (French Version of PR with

generated [filled] Kijs)



● No for azeotropy?

● Yes for close to critical?

●Next solution: Fitted CEOS or PPR78

● No for close to critical?

● No for P>0.1 MPa (1 atm.)

●Next solution: CEOS or PPR78

● Yes for P>0.1 MPa ● Yes for pseudo?

●BK10; No, CEOS w/fitted alphas


Working through the non-HC Portion of the Tree

● Pretty Easy again

● Yes for size asymmetry?

● Yes or No for P>1 MPa

●Both answers essentially lead to

Polymer thermo solutions

● No for size asymmetry?

● No for Water + HC?



● No for water + HC?

●I would like this better as water + organics

●Low pressure use an activity coefficient

approach, high pressures an advanced CE0S

●Parameters are Absolutely Necessary!



●Yes for water + HC?

●I would like this better as water + organics

● No for electrolytes?

●Advanced CEOS

● Yes for electrolytes?

●Electrolyte Methods in PRO/II are OLI’s

Pitzer based method and the e-UNIQUAC

MSE which is available for additional fee


Are the Thermo Method and Physical Properties the

only fluid characteristics that can impact answer?

●Yes for defined components (library or user added)

●No, for Assays and petroleum components

● Characterization can impact both Assay and Petro Components

● The number of Cutpoints will impact the separation of Assay streams

●Upon convergence rerun while increasing the number of cuts till product

stream rates stabilize


Table 1: Stripped product stream rates for different cutpoint sets

Stream Default cutpoint set “Small_cuts” cutpoint set

Kero Steam

Naphtha

Kerosene

Diesel

Gas Oil (AGO)

Resid

2443 kg/hr

167 m3/hr

105 m3/hr

84.9 m3/hr

126 m3/hr

312 m3/hr

5359 lb/hr

1050 bbl/hr

661 bbl/hr

534 bbl/hr

795 bbl/hr

1962 bbl/hr

880.8 kg/hr

167.3 m3/hr

106.0 m3/hr

86.19 m3/hr

136.3 m3/hr

299.5 m3/hr

1971 lb/hr

1052 bbl/hr

669.5 bbl/hr

539.5 bbl/hr

858.5 bbl/hr

1882 bbl/hr

Are your answers really correct?

• Not in this case! Default cutpoint set is not adequate

• Always check your answers


Important Background Information

●Know what methods are available and what data are present in the

property databanks

●Keep in mind what the intended usage for each method is and when

you’re “stretching” those limits

●Help is available:

● On line documentation:

●Reference Manual, Volume 1

●Keyword input manual; Component and Thermodynamics volumes

●Pay the price! Know what information is available.

● You can call the NA hotline number at any time, you will get an experienced

engineer


Important Background - Tools ●Available in PRO/II’s GUI (Provision)

● BVLE

●Viewing binary Phase Behavior

● HCURVE

●Tracking Pure and mixture properties

● PHASE

●Important for light ends processing and production

● Regression via TDM or PRO/II

●Developing correlation Coefficients

● Component Properties


Important Background - Tools ●TDM

● Database Manipulation

●Creation of library files

●Loading the various pure component and mixture databases

● Property Regression

●Converting data into correlated forms for databank storage for use

in simulation

● VLE Regression

●Available in TDM 3.0; PRO/II 8.1 (better reliability 3.3 and 8.3) and

later

● Data generated can be permanently stored in user libraries


Additional Background - Tools

●Keyword files

● UPSTREAM UNIT

●Matching data for production streams

● OPTIMIZERS and CONTROLLERS and Calculator

●Can be used as mathematical solvers

● Output file

●Interaction Reprint


Kij Input reprint, Important!

Default after 8.3!


Related Support, Services, Training

> (800) 746-7241

> [email protected]

> C:/Program Files (x86)/SIMSCI/PROII93/

Manual/

Support

Training

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> http://software.invensys.com/products/simsci/webinar-series/

> [email protected]

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mic-simulation-and-operator-training-simulator-

services/

> [email protected]

Services

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