|
发表于 2009-11-16 09:42:43
显示全部楼层
* Product Upgrades for v8.3.1 (patch 1) *
*******************************************
1. RATEFRAC now supports electrolyte thermodynamics for equilibrium and non
equilibrium systems. To use RATEFRAC with electrolytes, v7.0 OLI chemistry
models must be used. RATEFRAC/Electrolytes support both the OLI aqueous
model and also the newer MSE model. Within PRO/II, supplied models created
in OLI v7.0 end with the characters 70. Built in model SW0170 is created
using OLI v7.0 and SW0166 is created using OLI v6.6. Only models created
in 7.0 can be used in RATEFRAC. Users creating their own models should
use Chem Wizard 2 or Chem Wizard 3 to create compatible v7.0 models.
The OLI aqueous model requires that the water mole fraction be greater than
0.6 on every stage or packed column segment. The newer MSE model
allows the water mole fraction to vary from 0 to 1. However, OLI is still
regressing data for the newer MSE model, and some components are not yet
available. In particular, amines are not yet available using the MSE model.
Note that RATEFRAC supports both equilibrium and non-equilibrium stages.
Therefore RATEFRAC provides an alternative algorithm to Eldist for solving
electrolytic distillation models.
RATEFRAC/Electrolytes for non equilibrium systems requires transport
properties. At the current time, OLI provides rigorous liquid viscosity
for electrolyte systems, but not surface tension or liquid thermal
conductivity. OLI does provide diffusion coefficients for electrolyte
systems.
RATEFRAC/Electrolytes does not support solid precipitates forming within
the column. Chemistry models including solids may be used, but the solid
reactions and components will be ignored by RATEFRAC.
Following are the rules for transport property usage within PRO/II:
a) Diffusion Coefficients
The OLI supplied diffusion coefficients are always used. No other option
is available.
b) Liquid Viscosity
By default, the OLI viscosity is used. Alternatively, the user can
select a PRO/II method such as library. In this case, the apparent mole
fractions will be used with the apparent mole fractions to calculate the
viscosity. Note that the OLI method takes into account the true species
composition (ions and neutral aqueous species) and is the preferred
method.
c) Vapor Viscosity
By default, water properties are used for the vapor viscosity. The user
can select a PRO/II method. However, OLI adds additional components to
the model beyond what the user specifies in the OLI Chemistry Wizard,
and these additional components also require viscosity correlations.
d) Surface Tension
Currently OLI does not provide a rigorous surface tension method for
electrolyte systems. OLI estimates availability the end of first
quarter 2010. Currently, RATEFRAC will use water properties for
surface tension. The user can also supply the surface tension via
library correlations based on apparent compositions. Surface tension
can also be supplied on a tray by tray basis for the tower being
simulated.
e) Liquid Thermal Conductivity
Same rules as surface tension.
f) Vapor Thermal Conductivity
Same rules as vapor viscosity
2. OLI's Chemistry Wizard version 3.0 is included in the PRO/II 8.3.1
release. This Chemistry Wizard allows users to generate custom
electrolyte models with three new types of components: Assay, Pseudo and
Inert Solids. By default the Assay and Pseudo components invoke the
"Second Liquid" phase calculations. This option works well for modeling
desalters with flash drums, but for column modeling we suggest turning
off the "Second Liquid" phase calculations.
The Assay curve input requires a minimum of 5 percent / boiling point
temperature data pairs that must be in ascending temperature order. The
Assay curve calculations generate a list of assay cut components named by
boiling point temperature and a component with the assay name. The
component with the assay name can be given a flow rate using the
normal PRO/II Stream Data Entry Window and the OLI calculation engine
will distribute that flow rate over the list of assay cuts.
The Inert Solids are in the Chemistry Wizard "Available Components" Data
Entry Window. The four new components are "Ash", "Carbon", "Coal" and
"Coke". OLI provides default density and heat capacity for these
components and allows user overrides. |
|