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Since Peng and Robinson proposed their cubic equation of state (cubic EoS) in 1976, several attempts were made to improve its performance and to extend its application to an increasing number of substances. Many authors have focused in vapor pressure calculation, which in great part signifies the proposal of a new alpha function for the attractive term. In this work, 20 alpha function models were compared in vapor pressure estimation for 56 compounds with the Peng−Robinson EoS. The values calculated with the EoS were compared with values obtained from the DIPPR database. The parameters are presented as an useful data bank for future applications. With these results, it was possible to show which model had the best performance for each class of compounds, which is important information for the development of new alpha function models. The alpha functions of Androulakis et al., Schwartzentruber et al., and Almeida−Aznar−Telles obtained the best results among all the models evaluated.

Cryogenic air separation is a well-established technology. However, due to its associated energy intensity and hazardousness, new studies are always emerging on this topic. Nevertheless, economic feasibility studies of cryogenic separation plants are still scarce. Studies of this type are essential because installing an air separation unit can also be considered at the design stage of other common industrial projects, such as oxidation/ combustion processes and ammonia production. This study aims to elucidate the technical and economic aspects of a real-size air separation unit and analyze the feasibility of incorporating some alternatives recently proposed in the literature, such as multistage compression with and without an organic Rankine cycle for energy saving, integrated argon column, energy recovery systems in turbines, and a PSA unit for CO 2 removal, and in the implementation of a new plant. For this, we performed a rigorous simulation and a robust economic evaluation. Thus, it was possible to identify the main bottlenecks of the process, which may become the subject for future work. As a result, the relevance of the compression (34−36%) and refrigeration (54−55%) stages in the capital cost and the importance of conscious electricity (29−32% of the production costs) and maintenance spending for the process' economic viability were shown. Flowsheets and economic analysis are presented in detail so that they could be used as a base case for future developments in this field.

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