Properties of pure fluids and mixtures,
multiphase equilibria, process simulation
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Excel / Matlab application example : vapor-liquid-liquid phase envelope
Prode Properties can calculate many different types of phase equilibria, since the first editions in 1995 Prode Properties can include methods to generate:
- vapor-liquid phase envelope / phase diagram.
- vapor-liquid-liquid phase envelope / phase diagram.
- vapor-liquid-solid phase envelope / phase diagram.
Prode Properties allows to show / edit / print the diagrams directly in Excel, Matlab or any compatible application including custom software.
First step: define the stream (components, compositions etc.)
Properties includes a Stream editor which permits to access all informations (as compositions, operating conditions, models, options) for all streams which you need to define, to access the Stream editor from Excel Properties menu select Edit Properties
The Stream editor includes several pages, from the first page you can select a stream (Properties can store all the streams required to define a medium size plant) solve a series of flash operations and see the resulting compositions in the different phases, in this page select the stream you wish to define, for example the first.
In the second page you can define a new composition or modify an existing composition, in this example we define C1 0.7 CO2 0.15 H2S 0.15 as molar fractions
In the third page you can define the package (thermodynamic models and related options) , here we define API Soave Redlick Kwong.
The fourth page provides access to BIP (Binary Interaction Parameters) for the different models, you can enter specific values or click on "Load BIPs" button to get the predefined BIPs from databank.
Finally we must save the new data, in the first page click on "Save" button, note that you can redefine the name of the stream as you wish (editing the cell near the button "Save"), you can define / modify many streams following the procedure described.
Once defined the stream you may wish to define the units which we wish to utilize in our problem, in stream editor go then to the "Units" dialog
here you can select the units which you need for a specific problem, in this example for the pressure (first row) select Bar.a , notice that unit for temperature is K (but you can set the units which you prefer) then click on Ok button to accept new values and leave the Properties editor.
Now you are ready to use Properties for calculating all the properties which you need, however there is still a last thing to do if you do not wish to lose all data when leaving a Excel page, precisely to save data to a file, to save data to a file from Excel Properties menu select "Save a Archive"
then select the file "def.ppp" if you wish that Properties utilizes this data as default (this is the normal , recommended option), differently set a different name (you can for example define different names for different projects) but you will need to load that specific Archive before to make calc's for that project and since Excel reloads Properties with any new page this may result tedious...
Properties saves on the file also the units of measurement so you can define different streams and different units in different projects.
Now you can calculate all the properties which you need with the units which you prefer for all the streams defined in that project.
Second step: generate a vapor-liquid-liquid phase envelope in Excel.
For generating the phase envelope we’ll use a predefined Excel page distributed with Prode Properties, from Excel menu File->open , in Excel folder (Prode Properties installation) select the file phasenv.xls
This page contains a little VBA code to tranfer the calculated equilibrium values (for the different vapor-liquid, liquid-liquid-vapor, vapor-liquid-liquid lines) from Prode Properties to Excel, if required you can easily modify the code for printing a series of lines with specified liquid or vapor fraction. To print a phase envelope you must define the stream (we select the first stream, which we defined with composition C1 0.7 CO2 0.15 H2S 0.15 , SRK as model and multiphase vapor+liquid option, the multiphase option instructs the procedure to generate a vapor-liquid-liquid phase envelope) we specify 0.3 value for liquid fraction, finally click on the button "calculate phase diagram".
Properties does all the work and the calculated equilibrium points including critical points, cricondentherm and cricondenbar are printed in Excel page for your analysis.
The phase envelope for this mixture shows a three phase area (notice the second line near the liquid-liquid-vapor bubble line and the third liquid-vapor-liquid line
The calculated values for Critical Points, CricondenBar and CricondenTherm are available in Excel.
Note that Prode Properties calculates the TRUE critical points (not the estimated values), Prode Properties includes a proprietary procedure based on Gibbs minimization method.
the procedure allows to specify any value (from 0 -dew line- to 1 -bubble line-) for phase fractions, herebelow the example of a line with 0.05 liquid fraction.
The Vapor-Liquid-Liquid phase envelope constitutes the ideal tool to investigate the phase equilibria for mixtures of hydrocarbons + water
The example shows the phase envelope for a 12 components (hydrocarbons + water) mixture, notice the large three phase area where liquid water is present.
Note that even simple compositions can show a complex behaviour, herebelow is the example of the mixture with composition Methane 0.9 H2S 0.1 model API Soave Redlick Kwong.
The bubble line is a three phase (liquid-liquid-vapor) line, a vapor-liquid line connects the end of the liquid-liquid-vapor line with critical point, the dew line doesn't stop at critical point but continues, the blue line shows a liquid fraction of 0.05
The Newton solver included in the base version of Prode Properties is reasonably fast (different versions based on simplified models are available on request), for a ten components natural gas mixture it calculates a vapor-liquid-liquid phase envelope (with TRUE values for critical points) in about 5 seconds.
Note that Prode Properties includes methods for calculating critical points, CricondenBar and CricondenTherm in Excel cells, see the paragraph "Methods for thermodynamic calc’s" in operating manual for the details.
- methods StrPc() and StrTc() returns the critical pressure (or temperature) of the nth (from 1 to 5) critical point found.
- methods StrCBp() and StrCBt() returns the pressure (or temperature) of the CricondenBar (the equilibrium point with maximum pressure).
- methods StrCTp() and StrCTt() returns the pressure (or temperature) of the CricondenTherm (the equilibrium point with maximum temperature).
To get the value of critical pressure enter the macro =StrPc(1,1) where (1,1) refers to the stream 1 and first critical point detected, we enter this macro in B1, in B2 we enter the macro =StrTc(1,1) to calculate the critical temperature in the same way, in cells B3 and B4 we enter the macros = StrCBp(1) for CricodenBar pressure and = StrCTt(1) for CricodenTherm temperature.
Print a phase envelope in Matlab.
For calculating and printing the phase envelope we’ll use a predefined script distributed with Prode Properties, in Matlab command line type
where (1) is the number of stream.
Prode Properties will calculate the phase envelope and print the result on Matlab, if you wish to obtain additional properties as cricondentherm, cricondenbar or critical points just enter the name of Properties method in Matlab, for example
will return the true critical pressure of stream 1.
Herebelow a short list of the properties available, read the operating manual for additional information.
- Phase fraction (vapor, liquid, solid)
- (True) critical point pressure of mixtures
- (True) critical point temperature of mixtures
- Cricondentherm temperature of mixtures
- Cricondentherm pressure of mixtures
- CricondenBar temperature of mixtures
- CricondenBar pressure of mixtures
- Cloud point temperature of mixtures
- Cloud point pressure of mixtures
- Enthalpy of gas / vapor phase
- Enthalpy of liquid phase
- Enthalpy of solid phase
- Entropy of gas / vapor phase
- Entropy of liquid phase
- Entropy of solid phase
- Density of gas / vapor phase
- Density of liquid phase
- Density of solid phase
- Isobaric specific heat (Cp) of gas / vapor phase
- Isobaric specific heat (Cp) of liquid phase
- Isochoric specific heat (Cv) of gas / vapor phase
- Isochoric specific heat (Cv) of liquid phase
- Gas heating value
- Gas Wobbe index
- Gas Specific gravity
- Joule Thomson coefficients of gas / vapor phase
- Joule Thomson coefficients of liquid phase
- Isothermal compressibility of gas / vapor phase
- Isothermal compressibility of liquid phase
- Volumetric expansivity of gas / vapor phase
- Volumetric expansivity of liquid phase
- Speed of sound in gas / vapor phase
- Speed of sound in liquid phase
- Speed of sound in gas+liquid (mixed) phase
- Viscosity of gas / vapor phase
- Viscosity of liquid phase
- Thermal conductivity of gas / vapor phase
- Thermal conductivity of liquid phase
- liquid Surface tension
Technical features overview (Windows version)
- Entirely written in C++, Microsoft MFC provides Microsoft Windows functionalities.
- Up to 100 different streams with up to 50 components per stream (user can redefine)
- Several compilations of chemical data and BIPs are available, the user can add new components and BIPs
- Proprietary compilation with data on more than 1500 chemicals and 25000 BIPs
- flexible database format (support for up to 30 different correlations) works with all majour standards including DIPPR.
- Comprehensive set of thermodynamic models, base version includes
- Soave-Redlich-Kwong (standard and extended version with parameters calculated for best fitting of vapor pressure, density and enthalpy)
- Peng-Robinson (standard and extended version with parameters calculated for best fitting of vapor pressure, density and enthalpy)
- Benedict Webb Rubin (Starling) BWRS
- Steam Tables IAPWS 95
- ISO 18453 (GERG 2004)
- ISO 20765 (AGA model)
- Lee-Kesler (Plocker) LKP
- Cubic Plus Association (SRK and PR variants)
- Hydrates (Cubic Plus Association, Van Der Waals-Platteeuw)
- additional models as Pitzer, NRTL for electrolyte solutions, PC SAFT (with association contribute), GERG (2008) etc. available in extended versions.
- van der Waals and complex mixing rules (Huron Vidal, Wong Sandler etc.)
- Base and Extended (to fit experimental data) EOS parameters.
- Selectable units of measurement
- Procedure for solving single phase, two phase, multiphase fluid flow
- Procedure for solving staged columns
- Rigorous solution of distillation columns, fractionations, absorbers, strippers...
- Procedure for calculating temperature / pressure formation of gas hydrates
- hydrate phase equilibria based on Cubic Plus Association and Van Der Waals-Platteeuw models
- Procedure for solving polytropic compression with phase equilibria
- Huntington method for gas phase
- Proprietary method for solving a polytropic process with phase equilibria
- Procedure for solving isentropic nozzle (safety, relief valve with single and two phase flow)
- HEM, Homogeneous Equilibrium
- HNE-DS, Homogeneous Non-equilibrium
- NHNE, Non-homogeneous Non-equilibrium
- Procedure for simulating fluid flow in piping (pipelines) with heat transfer
- Beggs and Brill and proprietary methods for single phase and multiphase fluid flow with heat transfer
- Procedure to generate / edit / print a phase envelope / phase diagram
- vapor-liquid phase envelope / phase diagram
- vapor-liquid-liquid phase envelope / phase diagram
- vapor-liquid-solid phase envelope / phase diagram
- Procedure for fitting BIP to measured VLE / LLE / SLE data points (data regression)
- Procedure for fitting BIP to VLE values calculated with UNIFAC
- Functions for simulating operating blocks (mixer, gas separator, liquid separator) **
- Functions for accessing component data in database (the user can define mixing rules)
- gas / vapor-liquid-solid fugacity plus derivatives vs. temperature pressure composition
- gas / vapor-liquid-solid enthalpy plus derivatives vs. temperature pressure composition
- gas / vapor-liquid-solid entropy plus derivatives vs. temperature pressure composition
- gas / vapor-liquid-solid molar volume plus derivatives vs. temperature pressure composition
- Flash at Bubble and Dew point specifications and P (or T)
- Flash at given temperature (T) and pressure (P) multiphase vapor-liquid-solid, isothermal flash
- Flash at given phase fraction and P (or T), solves up to 5 different points
- Flash at given enthalpy (H) and P multiphase vapor-liquid-solid, includes adiabatic flash
- Flash at given enthalpy (H) and T multiphase vapor-liquid-solid, includes adiabatic flash
- Flash at given entropy (S) and P multiphase vapor-liquid-solid, includes isentropic flash
- Flash at given entropy (S) and T multiphase vapor-liquid-solid, includes isentropic flash
- Flash at given volume (V) and P multiphase vapor-liquid-solid, includes isochoric flash
- Flash at given volume (V) and T multiphase vapor-liquid-solid, includes isochoric flash
- Rigorous (True) critical point plus Cricondentherm and Cricondenbar
- Complete set of properties for different states
- gas / vapor-liquid-solid density
- gas / vapor-liquid Isobaric specific heat (Cp) and Isochoric specific heat (Cv) plus cp/cv
- Gas heating value
- Gas Wobbe index
- Gas Specific gravity
- gas / vapor-liquid Joule Thomson coefficients
- gas / vapor-liquid Isothermal compressibility
- gas / vapor-liquid Volumetric expansivity
- gas / vapor-liquid Speed of sound
- gas / vapor-liquid Viscosity
- gas / vapor-liquid-solid Thermal conductivity
- gas / vapor compressibility factor
- liquid Surface tension
- Fluid properties in Excel, Matlab and other Windows and UNIX (**) applications
- Thermodynamics, physical, thermophysical properties
- Phase envelope for hydrocarbons, natural gas mixtures
- Process simulation
- Heat / Material Balance
- Process Control
- Process Optimization
- Equipment's Design
- Instrument's Design
- Realtime applications
- petroleum, refining, natural gas, hydrocarbon, chemical, petrochemical, pharmaceutical, air conditioning, energy, mechanical industry
Perspective users are invited to contact Prode for discussing the applications of Prode Properties