Specifying Material Streams

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

In the previous section you specified the stream
conditions in the Workbook property view. Next you
will input the composition information in the Stream
property view.
The PFD becomes visible and displays a light blue
arrow on it, labeled Feed 1. That arrow is the stream
Feed 1 that you just created.
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In addition to the method you just learned, there are several
alternative ways to define streams.

Access the Object Palette by pressing F4. Then Click the
Material Stream icon on the Object Palette, then click on the
Add Object icon.

Press F11.

From the Flowsheet menu, select Add Stream.
Each of the above three methods creates a new stream and access
the property view of the new stream.
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
Click on the Composition page. By default, the
components are listed by Mole Fractions.

When you have entered the fraction of each component
the total at the bottom of the property view will equal
1.0000.
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
The compositions currently appear in
Mass Fraction. To change this, click the
Basis
button,
then
select
the
appropriate radio button in the
Composition Basis group of the
property view that appears.
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
The properties of Feed 1 appear below. The
values you specified are blue and the
calculated
values
are
black.
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
The ideal gas equation of state ,which relates the pressure, temperature, and
specific volume, is a familiar equation:

The term p is the absolute pressure , V is the volume, n is the number of
moles ,R is the gas constant , and T is the absolute temperature. This
equation is quite adequate when the pressure is low (such as one
atmosphere).However, many chemical processes take place at very high
pressure. Under these condition ,the ideal gas equation of state may not be
valid representation of reality.
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
Other equations of states have been developed to address chemical
processes at high pressure. The first generalization of the ideal gas law was
the van der Waals equation of state:

This extension is just a first step, however, because it will not be a good
approximation at extremely high pressure. The Redlich-Kwong equation of
state is a modification of Vander Waal s equation of state, and then was
modified further by Soave-Redlich-Kwong (SRK) equation of state. Which
is a common one in process simulators. Another variation of RedlichKwong equation of state is Peng-Robinson (PR)equation of state .
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
For oil, gas and petrochemical applications, the Peng
Robinson Equation of State is generally the
recommended property package. Hyprotech’s
enhancements to this equation of state enable it to be
accurate for a variety of systems over a wide range of
conditions. It rigorously solves most single phase,
two phase and three-phase systems with a high
degree of efficiency and reliability. All equation of
state methods and their specific applications are
described below:
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
Although Equation of State models have proven to be
very reliable in predicting the properties of most
hydrocarbon based fluids over a wide range of
operating conditions, their application has been limited
to primarily non-polar or slightly polar components.
Highly non-ideal systems are best modelled using
Activity Models. The following Activity Model
Property Packages are available:
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
The Chao Seader and Grayson Streed methods are
older, semi empirical methods. The Grayson Streed
correlation is an extension of the Chao Seader method
with special emphasis on hydrogen. Only the
equilibrium data produced by these correlations is used
by HYSYS. The Lee-Kesler method is used for liquid
and vapour enthalpies and entropies.
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
Vapour Pressure K-value models may be used for ideal
mixtures at low pressures. Ideal mixtures include
hydrocarbon systems and mixtures such as ketones and
alcohols, where the liquid phase behaviour is
approximately ideal. The models may also be used as
first approximations for non-ideal systems:
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
The Miscellaneous group contains Property Packages that are
unique and do not fit into the groups previously mentioned.
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