Aspen Physical Property System - Physical Property Models

A databank called PC-SAFT contains both unary and binary PC-SAFT
parameters available from literature; it must be used with the PC-SAFT
property method. The unary parameters available for segments are stored in
the SEGMENT databank. If unary parameters are not available for a species
(solvent or segment) in a calculation, the user can perform an Aspen Plus
Data Regression Run (DRS) to obtain unary parameters. For non-polymer
components (mainly solvents), the unary parameters are usually obtained by
fitting experimental vapor pressure and liquid molar volume data. To obtain
unary parameters for a segment, experimental data on liquid density of the
homopolymer that is built by the segment should be regressed. Once the
unary parameters are available for a segment, the ideal-gas heat capacity
parameter CPIG may be regressed for the same segment using experimental
liquid heat capacity data for the same homopolymer. In addition to unary
parameters, the binary parameter PCSKIJ for each solvent-solvent pair, or
each solvent-segment pair, or each segment-segment pair, can be regressed
using vapor-liquid equilibrium (VLE) data in the form of TPXY data in Aspen
Plus.
Note: In Data Regression Run, a homopolymer must be defined as an
OLIGOMER type, and the number of the segment that builds the oligomer
must be specified.
Peng-Robinson
The Peng-Robinson equation-of-state is the basis for the PENG-ROB and PR-
BM property methods. The model has been implemented with choices of
different alpha functions (see Peng-Robinson Alpha Functions) and has been
extended to include advanced asymmetric mixing rules.
Note: You can choose any of the available alpha functions, but you cannot
define multiple property methods based on this model using different alpha
functions within the same run.
By default, the PENG-ROB property method uses the literature version of the
alpha function and mixing rules. The PR-BM property method uses the
Boston-Mathias alpha function and standard mixing rules. These default
property methods are recommended for hydrocarbon processing applications
such as gas processing, refinery, and petrochemical processes. Their results
are comparable to those of the property methods that use the standard
Redlich-Kwong-Soave equation-of-state.
When advanced alpha function and asymmetric mixing rules are used with
appropriately obtained parameters, the Peng-Robinson model can be used to
accurately model polar, non-ideal chemical systems. Similar capability is also
available for the Soave-Redlich-Kwong model.
The equation for the Peng-Robinson model is:
Where:
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