Sour Water¶

DWSIM Plus

Available with a DWSIM Plus (Patreon) subscription.

Sour water package (Edwards, Maurer, Newman and Prausnitz) for water with dissolved H2S, NH3, CO2 and HCN, with the ionic speciation and the pH built into the K-values.

DWSIM.Extensions.PropertyPackages.Electrolytes.PropertyPackages.SourWaterPropertyPackage
Assembly DWSIM.Extensions.PropertyPackages.Electrolytes.dll · Object ← PropertyPackage ← ActivityCoefficientPropertyPackage ← SourWaterPropertyPackage
Name in the flowsheet Sour Water · FluentAPI PropertyPackages.Plus.SourWater

Scope¶

The package describes refinery and gas-plant sour water: water with dissolved hydrogen sulfide, ammonia, carbon dioxide and hydrogen cyanide, as fed to sour water strippers and found in overhead condensates and wash waters. The four solutes are molecular compounds of the flowsheet; the ions they form in the liquid (HS^-, S^2-, NH₄⁺, HCO₃^-, CO₃^2-, CN^-, H⁺, OH^-) are not compounds: the speciation is computed inside the K-values, and the flash conserves the moles of each compound. The ammonia that binds H₂S as NH₄⁺HS^- lowers the volatility of both, which is what the example shows.

The model follows Edwards, Maurer, Newman and Prausnitz (1978). Only the molecular form of each solute is volatile, p_i = H_i(T) c_i γ_i, with ln γ_i = β_i I (β = -0.324 for H₂S, -0.190 for NH₃, -0.292 for CO₂, -0.160 for HCN, kg/mol). The molecular fraction of each solute comes from its dissociation constants at the solution pH, and the pH from the charge balance of all the ions. The equilibrium constants at 25 °C (K_a1 and K_a2 of H₂S, K_b of NH₃, K_a1 and K_a2 of CO₂, K_a of HCN and K_w) are carried to temperature by van't Hoff, and the Henry constants by H(T) = H₂₅ exp[-C(1/T - 1/298.15)]. Water follows its vapor pressure; other compounds (hydrocarbons, nitrogen) take their vapor pressure or Henry constant.

Stream properties. The liquid pH and ionic strength are those of the speciation. The liquid viscosity and thermal conductivity take the Jones-Dole and Riedel ion corrections, with the ion concentrations of the speciation. Enthalpies are referred to the liquid at 298.15 K: the liquid is the integral of its heat capacity, the vapor the heat of vaporization at 298.15 K plus the ideal-gas heat capacity integral, so the vapor heat capacity stays the ideal-gas value at every temperature. Heats of solution and reaction of the solutes are not included.

Limitations¶

The model finds the compounds by name: Water, Hydrogen sulfide, Ammonia, Carbon dioxide and Hydrogen cyanide. Any subset of them, in any order and with other compounds, is accepted.
Concentrations are taken as c = 55.5 x_i/x_w mol/L (dilute solution).
The vapor is ideal unless VaporPhaseFugacityCalculationMode is set to Peng-Robinson.
For strong electrolytes (NaCl, caustic) in the water use Electrolyte NRTL or Extended UNIQUAC.

Example¶

This code runs on every build of this site, and the output below is what it printed.

Python

fs = (Flowsheet.Create("SourWaterExample")
      .WithCompounds("Water", "Hydrogen sulfide", "Ammonia", "Carbon dioxide", "Hydrogen cyanide")
      .WithPropertyPackage(PropertyPackages.Plus.SourWater))

kg_water = 1.0 / 0.018015          # mol of water in 1 kg
# Stripper feed: 0.6 mol/kg NH3 (1.0 wt%) and 0.45 mol/kg H2S (1.5 wt%), at 40 C and 10 bar
feed = (fs.AddMaterialStream("Sour water").At(Q.Celsius(40.0), Q.Bar(10.0))
        .SetCompoundMolarFlow("Water", kg_water)
        .SetCompoundMolarFlow("Ammonia", 0.6)
        .SetCompoundMolarFlow("Hydrogen sulfide", 0.45))
# The same H2S without ammonia
h2s = (fs.AddMaterialStream("H2S water").At(Q.Celsius(40.0), Q.Bar(10.0))
       .SetCompoundMolarFlow("Water", kg_water)
       .SetCompoundMolarFlow("Hydrogen sulfide", 0.45))

fs.Solve()

def partial_pressure(stream, name):
    # equilibrium partial pressure over the liquid: x * phi * P
    liq = stream.Object.Phases[3]
    c = liq.Compounds[name]
    return c.MoleFraction * c.FugacityCoeff * stream.Object.Phases[0].Properties.pressure / 1000.0

liq = feed.Object.Phases[3]
print(f"Vapor fraction                = {feed.Object.Phases[2].Properties.molarfraction or 0.0:.3f}")
print(f"pH                            = {liq.Properties.pH:.2f}")
print(f"H2S partial pressure          = {partial_pressure(feed, 'Hydrogen sulfide'):.1f} kPa")
print(f"NH3 partial pressure          = {partial_pressure(feed, 'Ammonia'):.2f} kPa")
print(f"Without NH3: H2S partial pressure = {partial_pressure(h2s, 'Hydrogen sulfide'):.0f} kPa, "
      f"pH {h2s.Object.Phases[3].Properties.pH:.2f}")

Output

Vapor fraction                = 0.000
pH                            = 8.38
H2S partial pressure          = 14.3 kPa
NH3 partial pressure          = 0.51 kPa
Without NH3: H2S partial pressure = 638 kPa, pH 3.58

DWSIM 10.2.11.0, generated 2026-10-08.

Property methods¶

How the package calculates each property, as it reports it in PropertyMethodsInfo (the property package editor shows the same list).

Property	Method
Vapor fugacity	Ideal / Peng-Robinson EOS
Liquid fugacity	Edwards Activity Coefficient + Henry's Law / Vapor Pressure
Vapor enthalpy, entropy, Cp/Cv	Vaporization Enthalpy at 298.15 K + Ideal Gas Cp (liquid at 298.15 K as the reference)
Liquid enthalpy, entropy, Cp/Cv	Liquid Cp integral from 298.15 K (liquid at 298.15 K as the reference)
Vapor density	Ideal Gas / Peng-Robinson EOS
Liquid density	Experimental Data / Rackett
Vapor viscosity	Experimental / Lucas / Jossi-Stiel-Thodos
Liquid viscosity	Experimental / Letsou-Stiel
Vapor thermal conductivity	Experimental / Ely-Hanley
Liquid thermal conductivity	Experimental / Latini
Surface tension	Experimental / Brock-Bird
Solid density	Experimental Data / User-Defined
Solid enthalpy, entropy, Cp/Cv	Experimental Solid Cp / From Liquid Phase Enthalpy + Enthalpy of Fusion

Default flash algorithm: Nested_Loops_VLE.

Configuration saved with the flowsheet¶

The package writes its settings to the simulation file (SaveData) and reads them back on load (LoadData). The elements below are the ones this package adds to those of every property package, as written for the example.

This package adds no elements of its own.

Settings common to every property package, as saved for the example

Element	Value
`Type`	88 characters
`ComponentName`	`Sour Water`
`ComponentDescription`	`Sour Water model`
`Tag`	`Sour Water`
`UseHenryConstants`	`true`
`AutoEstimateMissingNRTLUNIQUACParameters`	`true`
`UseImmiscibleListForLiquid2InitialEstimates`	`true`
`SingleCompoundCheckThreshold`	`0.99999`
`OverrideKvalFugCoeff`	`false`
`OverrideEnthalpyCalculation`	`false`
`OverrideEntropyCalculation`	`false`
`LiquidDensityCalculationMode_Subcritical`	`Rackett_and_ExpData`
`LiquidDensityCalculationMode_Supercritical`	`Rackett_and_ExpData`
`LiquidDensity_CorrectExpDataForPressure`	`true`
`LiquidDensity_UsePenelouxVolumeTranslation`	`true`
`LiquidViscosityCalculationMode_Subcritical`	`ExpData`
`LiquidViscosityCalculationMode_Supercritical`	`Letsou_Stiel`
`LiquidViscosity_CorrectExpDataForPressure`	`true`
`LiquidViscosity_MixingRule`	`MoleAverage`
`VaporPhaseFugacityCalculationMode`	`Ideal`
`SolidPhaseFugacityCalculationMethod`	`FromLiquidFugacity`
`SolidPhaseFugacity_UseIdealLiquidPhaseFugacity`	`false`
`SolidPhaseEnthalpy_UsesCp`	`false`
`EnthalpyEntropyCpCvCalculationMode`	`ExpData`
`LiquidEnthalpyEntropyCpCvCalculationMode_EOS`	`EOS`
`LiquidFugacity_UsePoyntingCorrectionFactor`	`true`
`ActivityCoefficientModels_IgnoreMissingInteractionParameters`	`false`
`IgnoreVaporFractionLimit`	`false`
`IgnoreSalinityLimit`	`false`
`CalculateAdditionalMaterialStreamProperties`	`true`
`FlashCalculationApproach`	`NestedLoops`
`DisplayMissingCompoundPropertiesWarning`	`false`
`ForcedSolids`	`[]`
`PropertyOverrides`	`{}`
`FlashSettings`	36 `Setting` entries

Learn more¶

User guide
Used with

API members¶

Public members declared by this class. Inherited members are documented on the base classes.

Constructors¶

SourWaterPropertyPackage()

C#VB.NET

public SourWaterPropertyPackage()

Public Sub New()

SourWaterPropertyPackage(bool)

Parameter	Type	Description
`comode`	`Boolean`

C#VB.NET

public SourWaterPropertyPackage(bool comode)

Public Sub New(comode As Boolean)

Properties¶

FlashBase: Returns the FlashAlgorithm object instance for this property package.

Returns the FlashAlgorithm object instance for this property package.

C#VB.NET

public override FlashAlgorithm FlashBase { get; }

Public Overrides ReadOnly Property FlashBase As FlashAlgorithm

ImplementsAnalyticalDerivatives: Advertises analytical derivatives (activating the NestedLoops PV/TV flash branch and the column-solver analytical...

Advertises analytical derivatives (activating the NestedLoops PV/TV flash branch and the column-solver analytical Jacobian) only for models with a closed-form GAMMA_DERIVS, and only when the runtime kill-switch is not set.

C#VB.NET

public override bool ImplementsAnalyticalDerivatives { get; }

Public Overrides ReadOnly Property ImplementsAnalyticalDerivatives As Boolean

ShouldUseKvalueMethod3

C#VB.NET

public override bool ShouldUseKvalueMethod3 { get; }

Public Overrides ReadOnly Property ShouldUseKvalueMethod3 As Boolean

Methods¶

CheckMissingInteractionParameters(double[])

Parameter	Type	Description
`Vx`	`Double[]`

C#VB.NET

public override bool CheckMissingInteractionParameters(double[] Vx)

Public Overrides Function CheckMissingInteractionParameters(Vx As Double()) As Boolean

Clone()

C#VB.NET

public override PropertyPackage Clone()

Public Overrides Function Clone() As PropertyPackage

DW_CalcdKdComposition(double[], double[], double, double, State, string): Composition (mole-number) derivative of the equilibrium K-values, d(K_i)/dn_j, with respect to the mole numbers of...

Composition (mole-number) derivative of the equilibrium K-values, d(K_i)/dn_j, with respect to the mole numbers of the phase indicated by withRespectTo (State.Liquid perturbs Vx, State.Vapor perturbs Vy), on a total-moles = 1 basis. Returns an (nc x nc) matrix. Base implementation is a finite difference; EOS/activity packages override it using the analytical d(ln phi)/dn (or d(ln gamma)/dx) building blocks.

Parameter	Type	Description
`Vx`	`Double[]`
`Vy`	`Double[]`
`T`	`Double`
`P`	`Double`
`withRespectTo`	`State`
`type`	`String`

C#VB.NET

public override double[,] DW_CalcdKdComposition(double[] Vx, double[] Vy, double T, double P, State withRespectTo, string type = "LV")

Public Overrides Function DW_CalcdKdComposition(Vx As Double(), Vy As Double(), T As Double, P As Double, withRespectTo As State, type As String = "LV") As Double(,)

DW_CalcdKdT(double[], double[], double, double, string): Analytical temperature derivative of the K-values for the activity-model packages, assembled from the liquid/vapour...

Analytical temperature derivative of the K-values for the activity-model packages, assembled from the liquid/vapour d(ln phi)/dT above: dK_i/dT = K_i * (d ln phi_i^L/dT - d ln phi_i^V/dT). This is what the analytical branch of the NestedLoops PV/TV flashes consumes. Falls back to finite differences for non-standard (non-"LV") requests or near-critical mixtures.

Parameter	Type	Description
`Vx`	`Double[]`
`Vy`	`Double[]`
`T`	`Double`
`P`	`Double`
`type`	`String`

C#VB.NET

public override double[] DW_CalcdKdT(double[] Vx, double[] Vy, double T, double P, string type = "LV")

Public Overrides Function DW_CalcdKdT(Vx As Double(), Vy As Double(), T As Double, P As Double, type As String = "LV") As Double()

DW_CalcEnthalpy(Array, double, double, State): Calculates the enthalpy of a mixture.

Calculates the enthalpy of a mixture.

Parameter	Type	Description
`Vx`	`Array`	Vector of doubles containing the molar composition of the mixture.
`T`	`Double`	Temperature (K)
`P`	`Double`	Pressure (Pa)
`st`	`State`	State enum indicating the state of the mixture (liquid or vapor).

C#VB.NET

public override double DW_CalcEnthalpy(Array Vx, double T, double P, State st)

Public Overrides Function DW_CalcEnthalpy(Vx As Array, T As Double, P As Double, st As State) As Double

DW_CalcEntropy(Array, double, double, State): Calculates the entropy of a mixture.

Calculates the entropy of a mixture.

Parameter	Type	Description
`Vx`	`Array`	Vector of doubles containing the molar composition of the mixture.
`T`	`Double`	Temperature (K)
`P`	`Double`	Pressure (Pa)
`st`	`State`	State enum indicating the state of the mixture (liquid or vapor).

C#VB.NET

public override double DW_CalcEntropy(Array Vx, double T, double P, State st)

Public Overrides Function DW_CalcEntropy(Vx As Array, T As Double, P As Double, st As State) As Double

DW_CalcFugCoeff(Array, double, double, State): Calculates fugacity coefficients for the specified composition at the specified conditions.

Calculates fugacity coefficients for the specified composition at the specified conditions.

Parameter	Type	Description
`Vx`	`Array`	Vector of doubles containing the molar composition of the mixture.
`T`	`Double`	Temperature in K
`P`	`Double`	Pressure in Pa
`st`	`State`	Mixture state (Liquid or Vapor)

C#VB.NET

public override double[] DW_CalcFugCoeff(Array Vx, double T, double P, State st)

Public Overrides Function DW_CalcFugCoeff(Vx As Array, T As Double, P As Double, st As State) As Double()

DW_CalcKvalue3(double[], double[], double, double): Calculates K-values using the Edwards sour water model for H2S, CO2, NH3, and HCN.

Calculates K-values using the Edwards sour water model for H2S, CO2, NH3, and HCN. For other compounds, falls back to standard fugacity coefficient K-values.

Parameter	Type	Description
`Vnx`	`Double[]`	Molar flows of the liquid phase
`Vny`	`Double[]`	Molar flows of the vapor phase
`T`	`Double`	Temperature in K
`P`	`Double`	Pressure in Pa

C#VB.NET

public override double[] DW_CalcKvalue3(double[] Vnx, double[] Vny, double T, double P)

Public Overrides Function DW_CalcKvalue3(Vnx As Double(), Vny As Double(), T As Double, P As Double) As Double()

DW_CalcPhaseProps(Phase)

Parameter	Type	Description
`Phase`	`Phase`

C#VB.NET

public override void DW_CalcPhaseProps(Phase Phase)

Public Overrides Sub DW_CalcPhaseProps(Phase As Phase)

GetArguments()

C#VB.NET

public override object GetArguments()

Public Overrides Function GetArguments() As Object

LoadData(List<XElement>): Loads the saved package data.

Loads the saved package data. The liquid density default is the compounds' experimental liquid density data (water within 0.1 % of IAPWS-95 from 0 to 100 C), where COSTALD put water at 1007 kg/m3 at 25 C. A file that does not record a liquid density mode keeps COSTALD, the mode it was solved with.

Parameter	Type	Description
`data`	`List<XElement>`

C#VB.NET

public override bool LoadData(List<XElement> data)

Public Overrides Function LoadData(data As List(Of XElement)) As Boolean

ReturnInstance(string)

Parameter	Type	Description
`typename`	`String`

C#VB.NET

public override object ReturnInstance(string typename)

Public Overrides Function ReturnInstance(typename As String) As Object

RunPostMaterialStreamSetRoutine()

C#VB.NET

public override void RunPostMaterialStreamSetRoutine()

Public Overrides Sub RunPostMaterialStreamSetRoutine()

SaveData()

C#VB.NET

public override List<XElement> SaveData()

Public Overrides Function SaveData() As List(Of XElement)