TY - JOUR
T1 - Effect of water content on transient nonequilibrium NAPL - Gas mass transfer during soil vapor extraction
AU - Yoon, Hongkyu
AU - Kim, Joong Hoon
AU - Liljestrand, Howard M.
AU - Khim, Jeehyeong
N1 - Copyright:
Copyright 2008 Elsevier B.V., All rights reserved.
PY - 2002
Y1 - 2002
N2 - The effect of water content on the volatilization of nonaqueous phase liquid (NAPL) in unsaturated soils was characterized by one-dimensional venting experiments conducted to evaluate the lumped mass transfer coefficient. An empirical correlation based upon the modified Sherwood number, Peclet number, and normalized mean grain size was used to estimate initial lumped mass transfer coefficients over a range of water content. The effects of water content on the soil vapor extraction SVE process have been investigated through experimentation and mathematical modeling. The experimental results indicated that a rate-limited NAPL-gas mass transfer occurred in water-wet soils. A severe mass transfer limitation was observed at 61.0% water saturation where the normalized effluent gas concentrations fell below 1.0 almost immediately, declined exponentially from the initiation of venting, and showed long tailing. This result was attributed to the reduction of interfacial area between the NAPL and mobile gas phases due to the increased water content. A transient mathematical model describing the change of the lumped mass transfer coefficient was used. Simulations showed that the nonequilibrium mass transfer process could be characterized by the exponent β, a parameter which described the reduction of the specific area available for NAPL volatilization. The nonequilibrium mass transfer limitations were controlled by the soil mean grain size and pore gas velocity, were well described by β values below 1.0 at low water saturation, and were well predicted with β values greater than 1.0 at high water saturation.
AB - The effect of water content on the volatilization of nonaqueous phase liquid (NAPL) in unsaturated soils was characterized by one-dimensional venting experiments conducted to evaluate the lumped mass transfer coefficient. An empirical correlation based upon the modified Sherwood number, Peclet number, and normalized mean grain size was used to estimate initial lumped mass transfer coefficients over a range of water content. The effects of water content on the soil vapor extraction SVE process have been investigated through experimentation and mathematical modeling. The experimental results indicated that a rate-limited NAPL-gas mass transfer occurred in water-wet soils. A severe mass transfer limitation was observed at 61.0% water saturation where the normalized effluent gas concentrations fell below 1.0 almost immediately, declined exponentially from the initiation of venting, and showed long tailing. This result was attributed to the reduction of interfacial area between the NAPL and mobile gas phases due to the increased water content. A transient mathematical model describing the change of the lumped mass transfer coefficient was used. Simulations showed that the nonequilibrium mass transfer process could be characterized by the exponent β, a parameter which described the reduction of the specific area available for NAPL volatilization. The nonequilibrium mass transfer limitations were controlled by the soil mean grain size and pore gas velocity, were well described by β values below 1.0 at low water saturation, and were well predicted with β values greater than 1.0 at high water saturation.
KW - Mass transfer
KW - Nonaqueous phase liquid (NAPL)
KW - Soil vapor extraction
KW - Volatilization
KW - Water saturation
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U2 - 10.1016/S0169-7722(01)00164-4
DO - 10.1016/S0169-7722(01)00164-4
M3 - Article
C2 - 11848263
AN - SCOPUS:0036137444
VL - 54
SP - 1
EP - 18
JO - Journal of Contaminant Hydrology
JF - Journal of Contaminant Hydrology
SN - 0169-7722
IS - 1-2
ER -