Sprungmarken

Servicenavigation

Hauptnavigation

Sie sind hier:

Hauptinhalt

Examples

Examples for phase equilibria from the PC-SAFT equation of state

The Perturbed-Chain SAFT equation of state is very successful in describing phase equilibria of components of all molecular sizes and their mixtures. In the following pages, PC-SAFT shall be compared to experimental phase equilibria data. The abilities of PC-SAFT theory for prediction, correlation and extrapolation will be demonstrated.

Since the original SAFT model is one of the most successful and widely applied equations of state, we do compare the PC-SAFT theory to the original SAFT model.

The PC-SAFT theory was designed for molecules of all sizes. Phase diagrams will be presented for high volatile components (gases), solvents and polymer systems:

  • pure components
  • vapor liquid equilibria in hydrocarbon systems
  • vapor liquid equilibria in CO2 sytems
  • modeling of associating compounds (self- and cross-associating systems)
  • alkane-ethylene systems
  • polyethylene systems



Pure components

Pure components of all molecular weights are generally very well described with the Perturbed-Chain SAFT  model. Here are a few examples.

image15

Comparison between Perturbed-Chain SAFT and the original SAFT model. Experimental data from Vargaftik, 1975 and VDI-Wärmeatlas, 1998.

Heat vaporization of n-decane

image13

Heat of vaporization of n-decane. Comparison of Perturbed-Chain SAFT and the original SAFT model. Experimental data from Vargaftik, 1975 and VDI-Wärmeatlas, 1998.

Heat capacities of the saturated coexisting phases

image14

Heat capacities of saturated liquid and vapor phases of n-decane. Comparison of Perturbed-Chain SAFT and the original SAFT model. Experimental data from VDI-Wärmeatlas, 1998.


Vapor - liquid equilibria in hydrocarbon systems

image18

Prediction of the high-pressure phase behavior of methane – butane at T=21.1°C

image19

Prediction of the high-pressure phase behavior of ethane – decane at T=171 °C and 238 °C.


Vapor - liquid equilibria in the cyclohexane - CO2 system

image20

Comparison of the Perturbed-Chain SAFT and the original SAFT model. Experimental data from Krichevskiri, 1960; Nagarajan et al., 1987; Kritschewskij and Sorina, 1960

deca-co2

Comparison of the Perturbed-Chain SAFT and the original SAFT model.


Modeling of associating compounds (self- and cross associating systems)

The association expression of Chapman [1] is included for associating components. The two additional pure component parameter are identified from vapor pressures and coexisting densities of the pure components.

The cross-association parameters are obtained from mixing rules (of Berthelot-Lorenz type). Only one binary interaction parameter kij is used to correct the dispersion energy.

[1]  W.G. Chapman, G. Jackson, K.E. Gubbins, Mol. Phys. 65 (1988) 1057.

Methanol-cyclohexane at P=1.013 bar

image27

Calculation of VLE and LLE region with one konstant binary paramter kij.

H2O - methanol at P=1.013 bar

image29

image28

Water - methanol as an example for a cross associating systems.

One binary kij-parameter is used to correct the dispersive interactions.

H2O - ethanol at P=1.013 bar

image31

image30

Water - ethanol as an another example for a cross associating systems.

One binary kij-parameter is used to correct the dispersive interactions.


Phase equilibria in alkane - ethylene systems

image21

Comparison of the Perturbed-Chain SAFT and the original SAFT model. Experimental data from de Loos et al., 1986.


Phase equilibria in polyethylene - systems

image22

P-w diagram for a polydisperse polyethylene – ethylene system (Mn=43 kg/mol; Mw=118 kg/mol; Mz=231 kg/mol). Comparison of the Perturbed-Chain SAFT and the original SAFT model. Experimental data from de Loos et al., 1983. (The polymer polydispersity is accounted for in the calculations).

image23

P-T diagram for a polydisperse polyethylene – ethylene system (Mn=43 kg/mol; Mw=118 kg/mol; Mz=231 kg/mol). Comparison of the Perturbed-Chain SAFT and the original SAFT model. Experimental data from de Loos et al., 1983. (The polymer polydispersity is accounted for in the calculations).

image24

P-w diagram for a polydisperse polyethylene – pentane system (Mn=20 kg/mol; Mw=131 kg/mol). Comparison of the Perturbed-Chain SAFT and the original SAFT model. Experimental data from Kiran et al., 1994. (The polymer polydispersity is accounted for in the calculations).

image25

Solubility of CO2 in polyethylene at 90 bar. Comparison of the Perturbed-Chain SAFT and the original SAFT model. Experimental data from Liu and Prausnitz et al., 1976.

image26

Vapor-liquid equilibria of polyethylene – toluene at 120°C in a P-w-diagram. Comparison of the Perturbed-Chain SAFT and the original SAFT model. Experimental data from Wohlfarth, 1993.



Nebeninhalt

Kontakt

Foto von Prof. Dr. Gabriele Sadowski

Prof. Dr. Gabriele Sadowski

Adresse:

TU Dortmund
Fakultät Bio- und Chemieingenieurwesen
Emil-Figge-Str. 70
44227 Dortmund

Raum G2-519a