A Physically Based Model of Dissolution of Nonaqueous Phase Liquids in the Saturated Zone |
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Authors: | Zhou Dengen Dillard Leslie A Blunt Martin J |
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Institution: | (1) Department of Petroleum Engineering, Stanford University, Stanford, CA, 94305-2220, U.S.A;(2) Department of Geological and Environmental Sciences, Stanford University, Stanford, CA, 94305-2115, U.S.A |
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Abstract: | The design of remediation strategies for nonaqueous phase liquid (NAPL) contaminants involves predicting the rate of NAPL dissolution. A physically based model of an idealized pore geometry was developed to predict nonaqueous phase liquid dissolution rate coefficients. A bundle of parallel pores in series model is used to represent NAPL dissolution as a function of three processes: pore diffusion, corner diffusion, and mixing and multiple contact. The dissolution rate coefficient is expressed in terms of the modified Sherwood number (Sh ) and is a function of Peclet (Pe) number. The model captures the complex behavior of Sh versus Pe data for both water-wet (Powers, 1992) and NAPL-wet (Parker et al., 1991) media. For water-wet media, the observed behavior can be broken down into four distinct regions. Each region represents a different physical process controlling NAPL dissolution: the low-Pe region is controlled by pore diffusion; the low- to moderate-Pe region is a transition zone; the moderate-Pe region is controlled by mixing and multiple contact; and the high-Pe region is controlled by corner diffusion. For the high-Pe conditions typical of most column experiments, the model involves only one fitting parameter. For NAPL-wet media, NAPL dissolution is governed exclusively by corner diffusion, and the model again involves only one fitting parameter. |
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Keywords: | corner diffusion pore diffusion mixing and multiple contact bundle of parallel pores in series blob ganglia dissolution rate coefficient dissolution NAPL |
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