<i>110th Anniversary</i>: Column Efficiency: From Conception, through Complexity, to Simplicity

Taylor, Ross; Duss, Markus

doi:10.1021/acs.iecr.9b02378

Cited by 6 publications

(4 citation statements)

References 73 publications

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“…21 Another method involves measuring R total by changing the balance gas from N 2 to He and separating the components based on the sensitivity ratio of the gas species to molecular diffusion, which was reported by Nonoyama et al 22 In this study, we adopted the latter method. Using the Fuller−Schettler−Giddings equation, 23 the binary gas phase diffusivity of oxygen (for N 2 , He, and H 2 O) was calculated, and the diffusivity in the mixed balance gas, D Od 2 : Nd 2 _Hd 2 O and D Od 2 : He_Hd 2 O , was determined. By comparing two diffusivity values, the sensitivity ratio was obtained, yielding results of 2.92 at 80 °C, 3.15 at 65 °C, and 3.29 at 50 °C under 30% RH.…”

Section: Preparation Of Ionomer Solutionmentioning

confidence: 99%

Effects of Humidity and Produced Water on Specific Adsorption of High Oxygen Permeability Ionomers Composed Entirely of Cyclic Monomers on Cathode Performance for Polymer Electrolyte Fuel Cells

Hirai,

Hommura,

Watakabe

et al. 2024

ACS Appl. Energy Mater.

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To enhance polymer electrolyte fuel cell (PEFC) performance, it is necessary to improve cathode ionomer performance, with attention to the development of high oxygen permeability ionomers (HOPIs) to mitigate the oxygen reduction reaction rate-limiting process of oxygen transport. We developed a new synthetic route for a cyclic monomer with a fluorosulfonyl group and synthesized a novel ionomer composed entirely of cyclic monomers. Preliminary investigations showed that it exhibited the expected HOPI performance while maintaining basic electrolyte performance. Cell evaluation of the MEA with the HOPI as a cathode ionomer confirmed improvements, especially under low humidity and high current density conditions. Overvoltage component analysis verified activation overvoltage lowering due to improved catalytic activity and concentration overvoltage decrease due to improved oxygen permeability. This was attributed to the ability of HOPI to avoid specific adsorption, to improve oxygen solubility, to improve oxygen transport due to increased ionomer permeability, and to improve Knudsen diffusion due to pore volume preservation in the catalyst layer. Careful humidity dependence examinations revealed a characteristic step in the Tafel plot under low humidity conditions, which was sensitive to ionomer differences. While the step occurrence mechanism remains debatable, we hypothesize that the step reflects the specific adsorption of the ionomer on Pt. Specific adsorption is not a static phenomenon but rather a dynamic one, which can vary according to the amount of water present near the catalyst surface. The difference in current density around the step could reflect the loss of Pt active surface area due to specific adsorption, enabling quantitative analysis of ionomer-induced performance degradation in MEAs. Cell evaluations combined with a high-performance membrane showed that an MEA using the HOPI as the cathode ionomer exhibited improved performance and high robustness versus humidity variations.

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Section: Preparation Of Ionomer Solutionmentioning

confidence: 99%

Effects of Humidity and Produced Water on Specific Adsorption of High Oxygen Permeability Ionomers Composed Entirely of Cyclic Monomers on Cathode Performance for Polymer Electrolyte Fuel Cells

Hirai,

Hommura,

Watakabe

et al. 2024

ACS Appl. Energy Mater.

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“…The equilibrium stage concept remains a cornerstone of separation science. 1 The McCabe−Thiele graphical method for determining the number of equilibrium stages needed to perform a binary separation, outlined in 1925, endures as an important teaching tool in undergraduate chemical engineering programs. 2 Real trays, however, do not often behave as ideal stages.…”

Section: ■ Introductionmentioning

confidence: 99%

Reconsidering the Reliability of Chemical Process Simulators I: Implementation of the Murphree and Vaporization Efficiencies

Braswell,

Hanley,

Ragsdale

2024

Ind. Eng. Chem. Res.

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Most chemical process simulators in widespread use today allow users to apply some type of efficiency correction to individual equilibrium stages or to equilibrium stage sections in order to align the stage or section separation performance more closely to actual tray performance in the field. Some simulators even allow for the use of component efficiencies on individual stages or in stage sections. It is our contention, however, that two of the more commonly available efficiency models, the vaporization efficiency and Murphree vapor phase efficiency, have generally been implemented incorrectly. The three major conceptual inconsistencies are (1) the assumption that the liquid and vapor exit a stage at the same temperature even in the presence of stage or component efficiencies, (2) specification of all “C” component efficiencies when only “C-1” are independent, and (3) in the case of the vaporization efficiency, the assumption that there can be equal component efficiencies for all components. All three assumptions can lead to impossible column composition and temperature profiles, coupled with violations of some of the most fundamental thermodynamic principles. To correct these mathematical and thermodynamic issues, we suggest: (1) the liquid and vapor streams exiting a stage always be treated as bubble point liquids and dew point vapors, (2) specification of only “C-1” component efficiencies, and, perhaps most importantly, (3) an improved understanding of solution thermodynamics on the part of programmers and a reevaluation of the quality assurance function at organizations producing chemical process simulation software.

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“…Tray Efficiency. Among the existing definitions of tray efficiency, the one proposed by Murphree 30 is the most preferred in common use, 31 and thus, it has been applied in this work. The Murphree tray efficiency represents the extent of separation achieved on a real cross-flow tray with respect to an ideal stage.…”

Section: Introductionmentioning

confidence: 99%

Direct Tray and Point Efficiency Measurements Including Weeping Effects through a Convenient Add-On for Air–Water Simulators

Marchini

Vishwakarma

Schubert

et al. 2021

Ind. Eng. Chem. Res.

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A direct approach for determining the tray and point efficiencies of an industrial-scale distillation tray is proposed. The stripping of isobutyl acetate from an aqueous solution with air was used, which is a manageable and nonhazardous method applicable for performance tests in large hydraulic column mockups. This work represents the first application of this system in the case of tray columns exemplified for a sieve tray. A column of 800 mm internal diameter was used for conducting the stripping experiments. The distribution of isobutyl acetate in the liquid phase on the tray was obtained via liquid sampling at several deck positions and UVspectroscopy analysis. A definition for the liquid-side tray efficiency in weeping conditions is proposed together with an experimental approach for determining tray and point efficiencies in such conditions. The derived efficiency data show good agreement with the model predictions and correlations.

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110th Anniversary: Column Efficiency: From Conception, through Complexity, to Simplicity

Abstract: One of the most enduring concepts in chemical engineering is that of the efficiency of column operations such as distillation, absorption, and stripping. The concept was first articulated by W. K. Lewis in a paper published in the

Cited by 6 publications

References 73 publications

Effects of Humidity and Produced Water on Specific Adsorption of High Oxygen Permeability Ionomers Composed Entirely of Cyclic Monomers on Cathode Performance for Polymer Electrolyte Fuel Cells

Effects of Humidity and Produced Water on Specific Adsorption of High Oxygen Permeability Ionomers Composed Entirely of Cyclic Monomers on Cathode Performance for Polymer Electrolyte Fuel Cells

Reconsidering the Reliability of Chemical Process Simulators I: Implementation of the Murphree and Vaporization Efficiencies

Direct Tray and Point Efficiency Measurements Including Weeping Effects through a Convenient Add-On for Air–Water Simulators

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