Low-Energy Separations for the Process Industry

Humphrey, J. L.; Fair, James R.

doi:10.1080/01496398308056126

Cited by 11 publications

(15 citation statements)

References 4 publications

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“…The main disadvantage of kinetic adsorbents is that, when kinetics is slow, only a small amount of the total equilibrium capacity of the column is used. 5 Although the separation can be well-performed by kinetic adsorbents, large units should be built and unit productivity values are much lower than what they should be based on equilibrium capacities.…”

Section: Layered Vacuum Pressure-swing Adsorptionmentioning

confidence: 99%

Layered Vacuum Pressure-Swing Adsorption for Biogas Upgrading

Grande

Rodrigues

2007

Ind. Eng. Chem. Res.

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Biogas is an important source of renewable raw methane that can be upgraded and applied as fuel for vehicles. One of the economic limitations of the upgrading relies in the bulk separation of CO 2 . In a previous communication (Grande, C. A.; Rodrigues, A. E. Ind. Eng. Chem. Res. 2006, 46, 4595), we have compared the performance of equilibrium-and kinetic-based adsorbents for application in vacuum pressure-swing adsorption (VPSA) processes for biogas upgrading. The main disadvantage of using carbon molecular sieves (CMSs) is that less than 40% of the total capacity to remove CO 2 is employed to satisfy purity requirements of methane product (>98%) with direct impact in process productivity. In this work, we report a new adsorbent layering strategy to improve the total productivity of CO 2 removal, resulting in a kinetic VPSA process with size reductions up to 60%.

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Section: Layered Vacuum Pressure-swing Adsorptionmentioning

confidence: 99%

Layered Vacuum Pressure-Swing Adsorption for Biogas Upgrading

Grande

Rodrigues

2007

Ind. Eng. Chem. Res.

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“…At the same time π bonds between alkenes and transition-metal ions are weak enough to be broken during simple engineering operations such as raising the temperature or decreasing the pressure in the system. 18 Several materials preparation variables including the synthesis route and the method of metal addition were shown to affect selective adsorption of alkenes. 2,9,12,13 The external form and size of the adsorbent preparations is another factor to be taken into consideration in the process design.…”

Section: Introductionmentioning

confidence: 99%

Copper- and Silver-Containing Monolithic Silica-Supported Preparations for Selective Propene−Propane Adsorption from the Gas Phase

et al. 2005

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Cylindrically shaped macroscopic-in-size bodies of aluminum-doped silica possessing uniformly sized mesopores have been used as supports for copper- and silver-based formulations in the selective adsorption of propene against propane in the gas phase. The metal addition was achieved using AgNO3 or Cu(NO3)2 in aqueous solution by either postsynthesis incipient wetness impregnation or direct incorporation in the synthesis stage, the overall metal content in samples being 2, 5, 10, and 20 wt %. The effect of metal addition on the degree of Al insertion into the silica matrix was evaluated by 27Al magic-angle spinning NMR. The nature of surface metal species was studied by X-ray photoelectron spectroscopy and temperature-programmed reduction by H2. Individual adsorption of propene and propane was measured at room temperature, and the selectivity coefficient was calculated as a function of the pressure and molar fraction of propene in the binary gas mixture. Within the series of Cu-derivatized adsorbents, the equilibrium selectivity is a complex function of the nature, amount, and dispersion degree of the copper species available on the surface. Contrary to expectations, both Cu(I) and Cu(II) states may give good propene−propane selectivity performance. For Ag-containing adsorbents the selectivity is mainly related to the nature and distribution of the silver species exposed on the surface, showing little dependence upon the overall Ag(I) content. The shaped sample functionalized with only 5 wt % of silver in the synthesis stage (Ag5SiAl20) appears to be the best monolithic adsorbent since it combines good selectivity performance (selectivity ratio of 37) and high specific surface area (ca. 900 m2 g-1). Compared to fine-particle porous materials previously reported in the literature, the monolithic adsorbent form is more useful for industrial uses.

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“…Distillation is the most widely used industrial separation method; however, the large amounts of heat needed to create a second phase for vapor−liquid contact make this unit operation very energy-intensive. Distillation operations are responsible for as much as 30% of the total energy use in the industry 1 and for 90−95% of separation energy. 2 In order to develop more energy-efficient distillation processes, we need an accurate model that can be solved reliably under all process conditions encountered during column design and flowsheet optimization.…”

Section: ■ Introductionmentioning

confidence: 99%

Multiple Steady States and Nonsmooth Bifurcations in Dry and Vaporless Distillation Columns

Cavalcanti

Barton

2020

Ind. Eng. Chem. Res.

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Many process systems, such as distillation columns and other equipment with phase change, exhibit multiple modes of physical behavior that can be described by non-differentiable (i.e., nonsmooth) models. In this paper, we introduce a nonsmooth model for steady-state multistage distillation that can describe columns with dry and/or vaporless stages reliably. The model consists of a system of nonsmooth MESH and specification equations, without inequality or complementarity constraints, that can be directly solved with the semismooth Newton method using automatically computed generalized derivatives. With a modified version of pseudo-arclength continuation, we have been able to observe several novel types of bifurcations in dry and/or vaporless distillation columns. Many of the bifurcations exhibit degenerate behavior with an infinite number of steady states for certain critical input specifications, and occur in general multistage distillation systems regardless of the mixture components or thermodynamic models chosen. We present case studies drawn from the literature and analyze the occurrence and behavior of the bifurcations with respect to several types of column configurations, involving ideal stages, stage efficiencies, pressure gradients, tray heat transfer, multiple feeds, and side products. The associated bifurcation curves are inherently nonsmooth and can be described mathematically by the concept of piecewise-smooth manifolds introduced in this paper.

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Low-Energy Separations for the Process Industry

Cited by 11 publications

References 4 publications

Layered Vacuum Pressure-Swing Adsorption for Biogas Upgrading

Layered Vacuum Pressure-Swing Adsorption for Biogas Upgrading

Copper- and Silver-Containing Monolithic Silica-Supported Preparations for Selective Propene−Propane Adsorption from the Gas Phase

Multiple Steady States and Nonsmooth Bifurcations in Dry and Vaporless Distillation Columns

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