selecting chemical property method.pptx

7/28/2019 Selecting Chemical Property method.pptx

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SELECTING THERMODYNAMICPROPERTY METHODS


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A key requirement of process design is the need

to accurately reproduce the various physicalproperties that describes chemical species.

The property packages available in HYSYS allow

you to predict properties of mixtures ranging from

well defined light hydrocarbon systems tocomplex oil mixtures and highly non-ideal (non-

electrolyte) chemical systems.


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PHYSICAL PROPERTIES

The physical properties required for modeling and

simulation often includes,

Molecular reaction and kinetic data.

Thermodynamic properties

Transport properties


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MOLECULAR REACTION & KINETIC DATA

In this case Critical properties are,

Rate equation

Activation energies

Reaction mechanism


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THERMODYNAMIC PROPERTIES

Enthalpy

Entropy

Fugacity coefficient

Gibbs free energy


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TRANSPORT PROPERTIES

Diffusion coefficient

Thermal conductivities

Viscosities


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HYSYS provides enhanced equations of state(PR and PRSV) for rigorous treatment ofhydrocarbon systems; semi empirical andvapour pressure models for the heavier

hydrocarbon systems; steam correlations foraccurate steam property predictions; and activity

coefficient models for chemical systems. All of

these equations have their own inherent

limitations.


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So HYSYS includes following methods for theestimation of Physical properties,

Equations of state

Activity models Chao-Seader based empirical methods

Vapour pressure models an

Miscellaneous methods.


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EQUATIONS OF STATES


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The table lists some

typical systems and

recommendedcorrelations.


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PENG-ROBINSON EOS

For oil, gas and petrochemical applications, the

Peng-Robinson EOS (PR) is generally therecommended property package.


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It rigorously solves any single, two-phase or three-

phase system with a high degree of efficiency and

reliability, and is applicable over a wide range of

conditions, as shown in the following table.


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the Peng-Robinson equation of state supports thewidest range of operating conditions and the

greatest variety of systems. The Peng-Robinson

and Soave-Redlich-Kwong equations of state

(EOS) generate all required equilibrium andthermodynamic properties directly.


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PR AND SRK The PR equation of state applies a

functionality to some specific component-component interaction parameters. Key

components receiving special treatment include

He, H2, N2, CO2, H2S, H2O, CH3OH


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The PR or SRK EOS should not be used for nonideal chemicals such as alcohols, acids or other

components. They are more accurately handled

by the Activity Models (highly non ideal) or the

PRSV EOS (moderately non-ideal).


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LEE KESLER PLCKER EQUATION

The Lee Kesler Plcker equation is an accurate

general method for non polar substances and

mixtures.


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ACTIVITY MODELS


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ACTIVITY MODELSAlthough equation of state models have proven to

be very reliable in predicting properties of most

hydrocarbon based fluids over a large range of

operating conditions, their application has been

limited to primarily non-polar or slightly polarcomponents. Polar or non-ideal chemical systems

have traditionally been handled using dual model

approaches.


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EXTENDED AND GENERAL NRTL

With a wide boiling point range betweencomponents. where you require simultaneoussolution of VLE and LLE, and there exists awide boiling point range or concentration range

between components.


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CHAO SEADER MODELS


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VAPOUR PRESSURE MODELS


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MISCELLANEOUS MODELS


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VAPOUR PRESSURE MODEL

The Vapour Pressure options include the ModifiedAntoine, BraunK10, and EssoK packages


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MISCELLANEOUS - SPECIALAPPLICATION METHODS

Amines Property Package


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STEAM PACKAGEHYSYS includes two steam packages:

ASME Steam

NBS Steam

Both of these property packages are restricted to asingle component, namely H2O.


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ASME Steam accesses the ASME 1967 steamtables. The limitations of this steam packageare the same as those of the original ASME

steam tables, i.e., pressures less than 15000 psia

and temperatures greater than 32F (0C) andless than 1500F.

Selecting NBS_Steam utilizes the NBS 1984Steam Tables, which reportedly has bettercalculations near the Critical Point.


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ASSIGNMENT


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PUMP Pumps are used to move liquids. The pump

increases the pressure of the liquid. Water

120 C and 3 bar is fed into a pump that has only

10% efficiency. The flow rate of the water is 100

kgmole/h and its outlet pressure from the pump is84 bar. Using Peng-Robinson equation of state

as a fluid package, determine the outlet

temperature of the water.


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RESULTS This example shows that pumping liquid can

increase their temperature. In this case, the

pump was only 10% efficient and it caused 18C

in the temperature of the water. The less efficient

a pump is, the greater the increase in thetemperature of the fluid being pumped. This

arises because in a low efficient pump, more

energy is needed to pump the liquid to get the

same outlet pressure of a more efficient pump. Sothe extra energy gets transferred to the fluid.


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COMPRESSOR

Compressors are used to move gases. Thecompressor increases the pressure of the gases.A mixture of natural gas (C1, C2, C3, i-C4, n-C4,i-C5, n-C5, n-C6, C7 ) at 100 C and 1 bar is fed

into a compressor that has only 30% efficiency.The flow rate of the natural gas is 100 kgmole/hand its outlet pressure from the compressor is 5bar. Using Peng-Robinson equation of state as afluid package, determine the outlet temperature of

the natural gas. If the outlet temperature is 400C, what is the

efficiency of the compressor?

selecting chemical property method.pptx

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