Comparison of pure component thermodynamic properties from CHEMCAD with direct calculation using the Peng-Robinson equation of state

doi:10.1016/j.cdc.2020.100571

Chemical Data Collections

Volume 30, December 2020, 100571

https://doi.org/10.1016/j.cdc.2020.100571 Get rights and content

Highlights

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A systematic analysis of thermodynamic properties calculated using the CHEMCAD process simulator was undertaken to assess the accuracy of the results.
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The results were very good with a few small yet significant discrepancies for the molecules nitric oxide, dinitrogen tetroxide, nitrogen dioxide, and sulfur dioxide.

Abstract

Accurate calculations of properties such as enthalpy, entropy, and fugacity are crucial for chemical process design. These properties are calculated from equations of state in commonly used process design software such as CHEMCAD[1], and software-based calculations of properties have been routine for decades. Correct application of chemical thermodynamics by the user is a requirement for successful process simulations. Users should be able to easily reproduce the calculations to verify choices made during the development of a simulation. In a previous study [4], we reproduced the compressibility factors, enthalpy, entropy, and fugacity coefficients from CHEMCAD using the Lee-Kesler method. In this paper, we extend our study to include the Peng-Robinson equation of state [5]. We compare the thermodynamic properties of 48 molecules at two different states. Our results show good consistency for most of these molecules, with percent errors generally less than 1%. The property changes for the difference between the two states show deviations for hydrogen, nitric oxide, and water. For absolute (stream) enthalpies, we observe deviations for air, hydrogen sulfide, nitrogen, oxygen, and water. For absolute (stream) entropies, we observe deviations for hydrogen, hydrogen chloride, nitric oxide, and water.

Graphical abstract

Section snippets

Specifications Table

Subject area

Chemical Engineering

Compounds

Methane, ethane, propane, n-butane, isobutane, n-pentane, n-hexane, n-heptane, n-octane, ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, acetaldehyde, acetylene, benzene, 1,3-butadiene, cyclohexane, ethanol, ethylbenzene, ethylene oxide, formaldehyde, methanol, styrene, toluene, air, ammonia, bromine, carbon monoxide, carbon dioxide, carbon disulfide, chlorine, hydrogen, hydrogen sulfide, hydrogen chloride, hydrogen cyanide,

Rationale

Chemical process simulators such as CHEMCAD [1] are very important design tools. Simulators access property databases such as DIPPr [2] or DDB [3] to calculate thermophysical properties at design conditions. The results of these calculations are then used for equipment and process design. Inappropriate models or inaccurate calculations of properties can lead to incorrect designs. On the other hand, creative application of thermodynamic models in the simulator can lead to the development of

Procedure

Our general approach was similar to that published earlier [4]. We first calculated the aforementioned properties at two defined states and then calculated the changes in properties between the two states. In this study, we used the Peng-Robinson equation and associated thermodynamic relations [5], [6], [7]. State 1 in our study is defined in terms of reduced temperature and pressure as $T_{r_{1}} = 0.90$ and $P_{r_{1}} = 0.10,$ and state 2 is defined as $T_{r_{2}} = 2.2$ and $P_{r_{2}} = 0.8,$ where $T_{r} = T / T_{c}$ and $P_{r} = P / P_{c}$ . We selected

Data, value and validation

Results are shown in Tables 1 through 6. The results in the tables include a comparison of our calculations with the results obtained from CHEMCAD. Table 1, Table 2, Table 3, Table 4 are comparisons of absolute enthalpies, absolute entropies, fugacity coefficients, and compressibility factors, respectively. Table 5 is a comparison of the change in enthalpy and entropy from State 1 to State 2. All comparisons are at State 1 and State 2, where State 1 is at a reduced temperature and reduced

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

References (10)

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Chemical data collections
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(1976)

There are more references available in the full text version of this article.

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We do not see any significant difference in precision between states 1 and 2 when the average modified percentage error is used as a metric. Previously, we reported that the average error in state 2 was significantly greater than for state 1 with the Peng–Robinson calculations [5] and attributed this to the possible accumulation of error in the numerical integrals. That does not appear to be the case when the percentage error is corrected.
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Data ArticleComparison of pure component thermodynamic properties from CHEMCAD with direct calculation using the Peng-Robinson equation of state

Highlights

Abstract

Graphical abstract

Section snippets

Specifications Table

Rationale

Procedure

Data, value and validation

Declaration of Competing Interest

Chem. Data Collect.

A new two-constant equation of state

Ind. Eng. Chem. Fundam.

Data Article
Comparison of pure component thermodynamic properties from CHEMCAD with direct calculation using the Peng-Robinson equation of state