Capabilities and Limitations of Predictive Engineering Theories for Multicomponent Adsorption

Multicomponent adsorption of gas mixtures on diverse solid surfaces is important in many applications. However, there are still many questions on the practical applicability of the available theories, especially for polar systems. In this work, we consider three well-known theories suitable for the prediction of multicomponent adsorption with parameters obtained solely from correlating single gas/solid data. We have tested them over an extensive database with emphasis on polar systems (both gases and solids). The three theories are the multicomponent Langmuir, the ideal adsorbed solution theory (IAST), and the multicomponent potential adsorption theory (MPTA). We have not attempted to improve/modify the methods in any way but have used them in their original form, as the purpose of our work is to illustrate the capabilities and inherent limitations of the models for predicting multicomponent adsorption. We have ensured that the description of single gas/solid systems is as accurate as possible, but besides this, the calculations for multicomponent systems are straight predictions. The work revealed on one side that all three theories yield for some systems similar predictions, with IAST and MPTA performing overall better than the multicomponent Langmuir. On the other hand, it is also shown that all the three theories, despite the good results in some cases, have serious limitations particularly for water and to some extent also for certain polar solids. Both strengths and weaknesses of the three models are discussed

An Eclectic Methodology for Assessment of the Regional Economic Effects of the Femern Belt Link Between Scandinavia and Germany

JENSEN-BUTLER C. and MADSEN B. (1999) An eclectic methodology for assessment of the regional economic effects of the Femern belt link between Scandinavia and Germany, Reg. Studies 33 , 751‐768. The paper describes a theoretically eclectic methodology developed for assessment of the regional economic effects of the proposed fixed link between Denmark and Germany, across the Femern Belt. The methodology is compared with alternative modelling frameworks. Estimates of the regional economic effects of this fixed link are presented, including evaluation of the synergy effects of this link seen in relation to two other fixed links in the Western Baltic. The short and medium term regional economic effects of this infrastructure investment appear to be limited and perhaps greater in regions somewhat more distant from the link. JENSEN-BUTLER C. et MADSEN B. (1999) Une méthodologie éclectique pour évaluer les retombées économiques régionales du Chenal de Femern qui va relier la Scandinavie et l'Allemagne, Reg. Studies 33 , 751-768. Cet article présente une méthodologie théoriquement éclectique qui a été développée afin de permettre une évaluation des retombées économiques régionales de la liaison fixe qui va relier le Danemark et l'Allemagne à travers le Chenal de Femern. La méthodologie se voit comparer à d'autres structures de modélisation. On présente des estimations des retombées économiques régionales de cette liaison fixe, y compris une évaluation de la synergie de cette liaison par rapport à deux autres liaisons fixes situées dans la Baltique occidentale. Il semble que les retombées économiques régionales à moyen terme de cet investissement sont limitées et sont d'autant plus importantes que les régions sont plus éloignées de la liaison. JENSEN-BUTLER C. und MADSEN B. (1999) Eine eklektische Methodik zur Einschätzung regionalwirtschaftlicher Auswirkungen der Fehmarn Beltverbindung zwischen Skandinavien und Deutschland, Reg. Studies 33 , 751‐768. Dieser Aufsatz beschreibt eine theoretisch eklektische Methodik, die zur Einschätzung der regionalwirtschaftlichen Auswirkungen der geplanten festen Verbindung zwischen Dänemark und Deutschland über den Fehmarn Belt entwickelt worden ist. Die Methodik wird mit alternativen Rahmenmodellen verglichen. Es werden Schätzungen der regionalwirtschaftlichen Auswirkungen dieser festen Verbindung vorgelegt, einschließlich der Bewertung synergetischer Wirkungen dieser Verbindung in bezug auf zwei andere feste Verbindungen in der westlichen Ostsee. Die mittelfristigen regionalwirtschaftlichen Auswirkungen dieser infrastrukturellen Investierung scheinen begrenzt zu sein, jedoch möglicherweise größer in Gebieten, die weiter von der Verbindung entfernt liegen.Transport Infrastructure, Regional Economic Effects, Synergy Effects, Evaluation Models,

Uncertainty analysis of the CPA and a quadrupolar CPA equation of state – With emphasis on CO2

The parameters of thermodynamic models, such as the cubic plus association (CPA) equation of state, are subject to uncertainties due to measurement errors in the experimental data that the models are correlated to. More importantly as the number of adjustable parameters increase, the parameter estimation problem becomes more complicated due to parameter identifiability issues. In this work the uncertainties in the pure compound parameters of CO2 are investigated using several different CPA approaches, including a new quadrupolar CPA. The uncertainties are estimated using both least squares estimation and the bootstrap method for parameter estimation. The uncertainties in the parameters estimated from the bootstrap method are propagated to physical property and vapor liquid equilibrium predictions using Monte Carlo simulations. The results indicate that both the pure compound parameter uncertainty and the propagated uncertainty are negligible for the modeling approaches which employ three adjustable parameters. For modeling approaches with more than three adjustable parameters, however, there may be significant uncertainties in the pure compound parameters, as well as a high degree of correlation between the adjustable parameters. This results in significant propagated errors for certain output properties. To reduce the uncertainty in the adjustable model parameters the heat of vaporization was included as additional correlation data. This resulted in parameter distributions which followed a normal distribution more closely, however, the correlation between the adjustable parameters remained high. Overall the results indicate, that it is important to report parameter uncertainties together with their correlation matrix when a model is developed, so that better informed decisions can be made, for instance about which model extension, or association scheme should be employed