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SELECTING THERMODYNAMIC PROPERTY METHODS. A key requirement of process design is the need to accurately reproduce the various physical properties that describes chemical species.

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## SELECTING THERMODYNAMIC PROPERTY METHODS

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**A key requirement of process design is the need to**accurately reproduce the various physical properties that describes chemical species. • The property packages available in HYSYS allow you to predict properties of mixtures ranging from well defined light hydrocarbon systems to complex oil mixtures and highly non-ideal (non-electrolyte) chemical systems.**PHYSICAL PROPERTIES**The physical properties required for modeling and simulation often includes, • Molecular reaction and kinetic data. • Thermodynamic properties • Transport properties**MOLECULAR REACTION & KINETIC DATA**In this case Critical properties are, • Rate equation • Activation energies • Reaction mechanism**THERMODYNAMIC PROPERTIES**• Enthalpy • Entropy • Fugacity coefficient • Gibbs free energy**TRANSPORT PROPERTIES**• Diffusion coefficient • Thermal conductivities • Viscosities**HYSYS provides enhanced equations of state (PR and PRSV) for**rigorous treatment of hydrocarbon systems; semi empirical and vapour pressure models for the heavier hydrocarbon systems; steam correlations for accurate steam property predictions; and activity coefficient models for chemical systems. All of these equations have their own inherent limitations.**So HYSYS includes following methods for the estimation of**Physical properties, • Equations of state • Activity models • Chao-Seader based empirical methods • Vapour pressure models an • Miscellaneous methods.**The table lists some typical systems and recommended**correlations.**PENG-ROBINSON EOS**• For oil, gas and petrochemical applications, the Peng-Robinson EOS (PR) is generally the recommended property package.**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.**the Peng-Robinson equation of state supports the widest**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 and thermodynamic properties directly.**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**The PR or SRK EOS should not be used for non ideal 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).**LEE KESLER PLÖCKER EQUATION**• The Lee KeslerPlöcker equation is an accurate general method for non polar substances and mixtures.**ACTIVITY MODELS**Although 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 polar components. Polar or non-ideal chemical systems have traditionally been handled using dual model approaches.**EXTENDED AND GENERAL NRTL**With a wide boiling point range between components.where you require simultaneous solution of VLE and LLE, and there exists a wide boiling point range or concentration range between components.**VAPOUR PRESSURE MODEL**• The Vapour Pressure options include the Modified Antoine, BraunK10, and EssoK packages**MISCELLANEOUS - SPECIALAPPLICATION METHODS**• Amines Property Package**STEAM PACKAGE**HYSYS includes two steam packages: • ASME Steam • NBS Steam Both of these property packages are restricted to a single component, namely H2O.**ASME Steam accesses the ASME 1967 steam tables. The**limitations of this steam package are the same as those of the original ASME steam tables, i.e., pressures less than 15000 psia and temperatures greater than 32°F (0°C) and less than 1500°F. • Selecting NBS_Steam utilizes the NBS 1984 Steam Tables, which reportedly has better calculations near the Critical Point.**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 is 84 bar. Using Peng-Robinson equation of state as a fluid package, determine the outlet temperature of the water.**RESULTS**• This example shows that pumping liquid can increase their temperature. In this case, the pump was only 10% efficient and it caused 18°C in the temperature of the water. The less efficient a pump is, the greater the increase in the temperature 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. So the extra energy gets transferred to the fluid.**COMPRESSOR**• Compressors are used to move gases. The compressor 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/h and its outlet pressure from the compressor is 5 bar. Using Peng-Robinson equation of state as a fluid package, determine the outlet temperature of the natural gas. • If the outlet temperature is 400⁰C, what is the efficiency of the compressor?

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