A comparison of mathematical model formulations for organic vapor transport in porous media

Fen, Chiu‐Shia; Abriola, Linda M.

doi:10.1016/j.advwatres.2004.07.006

Cited by 35 publications

(36 citation statements)

References 36 publications

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“…Results obtained using the DGM (7) (Figure 4b) are slightly different than those obtained using the equimolar Stefan-Maxwell equations ( (11) and (12)) because the DGM includes a nonequimolar flux component as well as Knudsen diffusion. A more detailed comparison between the two formulations is beyond the scope of this paper; the reader is referred to other works [Massmann and Farrier, 1992;Sleep, 1998;Fen and Abriola, 2004]. It can be observed that the oxidation of methane leads to a decrease in pressure gradient in the reaction zone, which in turn results in a decrease in the advective velocity ( Figure 5a).…”

Section: à13mentioning

confidence: 99%

“…The results obtained with the DGM presented by Fen and Abriola [2004] (hereinafter referred to as FA) for the transport of N 2 and CH 4 in a 1-D horizontal domain under three different sets of conditions are compared to results obtained using the present DGM formulation (equation (7)). Simulation parameters are presented in Table 1.…”

Section: Nonreactive Binary Transport In the Molecular And Transitionmentioning

confidence: 99%

“…] being the free phase binary diffusion coefficient between gas species i and j, and t g the gas tortuosity coefficient (see equations (A6) [Thorstenson and Pollock, 1989;Massmann and Farrier, 1992;Sleep, 1998;Fen and Abriola, 2004]:…”

Section: Molins and Mayer: Reactive Gas And Solute Transportmentioning

confidence: 99%

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Coupling between geochemical reactions and multicomponent gas and solute transport in unsaturated media: A reactive transport modeling study

Molins

Mayer

2007

Water Resources Research

107

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[1] The two-way coupling that exists between biogeochemical reactions and vadose zone transport processes, in particular gas phase transport, determines the composition of soil gas. To explore these feedback processes quantitatively, multicomponent gas diffusion and advection are implemented into an existing reactive transport model that includes a full suite of geochemical reactions. Multicomponent gas diffusion is described on the basis of the dusty gas model, which accounts for all relevant gas diffusion mechanisms. The simulation of gas attenuation in partially saturated landfill soil covers, methane production, and oxidation in aquifers contaminated by organic compounds (e.g., an oil spill site) and pyrite oxidation in mine tailings demonstrate that both diffusive and advective gas transport can be affected by geochemical reactions. Methane oxidation in landfill covers reduces the existing upward pressure gradient, thereby decreasing the contribution of advective methane emissions to the atmosphere and enhancing the net flux of atmospheric oxygen into the soil column. At an oil spill site, methane oxidation causes a reversal in the direction of gas advection, which results in advective transport toward the zone of oxidation both from the ground surface and the deeper zone of methane production. Both diffusion and advection contribute to supply atmospheric oxygen into the subsurface, and methane emissions to the atmosphere are averted. During pyrite oxidation in mine tailings, pressure reduction in the reaction zone drives advective gas flow into the sediment column, enhancing the oxidation process. In carbonate-rich mine tailings, calcite dissolution releases carbon dioxide, which partly offsets the pressure reduction caused by O 2 consumption.Citation: Molins, S., and K. U. Mayer (2007), Coupling between geochemical reactions and multicomponent gas and solute transport in unsaturated media: A reactive transport modeling study, Water Resour. Res., 43, W05435,

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Section: à13mentioning

confidence: 99%

Section: Nonreactive Binary Transport In the Molecular And Transitionmentioning

confidence: 99%

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Coupling between geochemical reactions and multicomponent gas and solute transport in unsaturated media: A reactive transport modeling study

Molins

Mayer

2007

Water Resources Research

107

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“…The purpose of this study was to determine not only the dispersivities, but also the tortuosities from both the column experiments and the DG model simulations. Although Costanza-Robinson and Brusseau (2002) determined tortuosities using the Penman-Millington Quirk model (Moldrup et al, 1997), and Fen and Abriola (2004) determined tortuosities with the DG model for a binary gas system, tortuosities for multi-component gas systems have not yet been obtained directly from column experiments.…”

Section: Introductionmentioning

confidence: 99%

Investigation for Necessity of Dispersivity and Tortuosity in the Dusty Gas Model for a Binary Gas System in Soil

Hibi

Fujinawa

Nishizaki

et al. 2010

Soils and Foundations

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DiŠusion, dispersion, and advection are important processes in multi-gas systems in soils. To date, both Fick's model and the Dusty Gas (DG) model have been used to model the movement of gases in these systems. Dispersion is included in the dispersion-advection equation with Fick's Model for the movement of gases in gas-phase of soil, yet the movement of gases in multi-component gas-soil systems is considered to be expressed more accurately by the DG model than by Fick's model. However to date, no study has investigated the necessity of considering dispersion in the Dusty Gas (DG) model. We carried out column experiments for nitrogen-methane, nitrogen-carbon dioxide, and carbon dioxide-methane binary gas systems in sandy soil, and also did simulations on the same systems using both Fick's model and the DG model. A comparison of the results of the column experiments with our simulations conˆrmed that there was no need to consider the dispersion in the advection-diŠusion equations with the DG model when the velocity of gas was 0.05-0.4 cm/s in Toyoura sand. Furthermore, our experiments and simulations with the DG model showed that, rather than dispersion, tortuosity should be taken into account in application of the DG model to the above condition.

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“…For example, Jaynes and Rogowski [12], Amali et al [2] and Webb and Pruess [29] mentioned a Fickian expression is valid only for a binary gas diffusion system with a trace gas and for a ternary gas diffusion system with a stagnant gas. Fen and Abriola [9] used the DGM equations to obtain the component diffusive flux in a Fickian form for a two-component gas transport system with gas components of equal molecular masses under isothermal and isobaric conditions. A correction factor, called the obstruction factor, is defined in the DGM, to account for the obstruction of soil particles to molecular diffusion.…”

Section: Introductionmentioning

confidence: 99%

Effective gas-phase diffusion coefficient in soils

Fen¹

2006

WIT Transactions on Ecology and the Environment, 94

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Determination of the effective gas-phase diffusion coefficient is important to quantify gas diffusion for a number of environmental pollution problems involving migration and release of hazardous gases or organic vapors in soils. Conventionally, the only considered transport mechanism for this coefficient is molecular diffusion. This study additionally considers the effects of Knudsen diffusion and nonequimolar flux on this coefficient and proposes a relationship of this coefficient with both molecular and Knudsen diffusion coefficients, ratio of molar masses and composition of component gases for gas diffusion in soils. Through investigating calculation results of this relationship for hypothetical diffusion systems having different soil permeabilities and diffusing gases at a range of water saturation levels, it is found that the Knudsen and nonequimolar effects can only be substantial for systems with dry soil permeabilities less than 10 -13 m 2 at any saturation. The Knudsen effect on this relationship is further demonstrated through comparing results obtained from this relationship to the measured effective diffusion coefficients for 72 soil cores, which all have high silt and clay contents, given in the literature.

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A comparison of mathematical model formulations for organic vapor transport in porous media

Cited by 35 publications

References 36 publications

Coupling between geochemical reactions and multicomponent gas and solute transport in unsaturated media: A reactive transport modeling study

Coupling between geochemical reactions and multicomponent gas and solute transport in unsaturated media: A reactive transport modeling study

Investigation for Necessity of Dispersivity and Tortuosity in the Dusty Gas Model for a Binary Gas System in Soil

Effective gas-phase diffusion coefficient in soils

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