Aspen Physical Property System - Physical Property Models

ai
bi
kij
50 2 Thermodynamic Property Models
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=
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The model has option codes which can be used to customize the model, by
selecting a different alpha function and other model options. See Peng-
Robinson Alpha Functions for a description of the alpha functions. See Option
Codes for Equation of State Models (under ESPRSTD) for a list of the option
codes.
For best results, the binary parameter kij must be determined from regression
of phase equilibrium data such as VLE data. The Aspen Physical Property
System also has built-in kij for a large number of component pairs in the EOS-
LIT databank. These parameters are used automatically with the PENG-ROB
property method. Values in the databank can be different than those used
with other models such as Soave-Redlich-Kwong or Redlich-Kwong-Soave,
and this can produce different results.
Parameter
Name/Element
Symbol Default MDS Lower
Limit
Upper
Limit
Units
TCPRS T ci TC x 5.0 2000.0 TEMPERATURE
PCPRS p ci PC x 10 5
OMGPRS � i
PRKBV/1 k ij (1)
PRKBV/2 k ij (2)
PRKBV/3 k ij (3)
10 8
OMEGA x -0.5 2.0 —
0 x - - -
PRESSURE
0 x - - TEMPERATURE
0 x - - TEMPERATURE
PRKBV/4 T lower 0 x - - TEMPERATURE
PRKBV/5 T upper 1000 x - - TEMPERATURE
References
D.-Y. Peng and D. B. Robinson, "A New Two-Constant Equation-of-state," Ind.
Eng. Chem. Fundam., Vol. 15, (1976), pp. 59–64.
Peng-Robinson-MHV2
This model uses the Peng-Robinson equation-of-state for pure compounds.
The mixing rules are the predictive MHV2 rules. Several alpha functions can
be used in the Peng-Robinson-MHV2 equation-of-state model for a more
accurate description of the pure component behavior. The pure component
behavior and parameter requirements are described in Standard Peng-
Robinson, or in Peng-Robinson Alpha Functions.
The MHV2 mixing rules are an example of modified Huron-Vidal mixing rules.
A brief introduction is provided in Huron-Vidal Mixing Rules. For more details,
see MHV2 Mixing Rules.