Characterization of the evaporation rates of complex hydrocarbon mixtures under environmental conditions

Authors

  • S. R. Goodwin,

    1. Department of Chemical Engineering and Applied Chemistry and Institute for Environmental Studies, University of Toronto, Toronto, Ontario, M5S 1A4
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  • D. Mackay,

    Corresponding author
    1. Department of Chemical Engineering and Applied Chemistry and Institute for Environmental Studies, University of Toronto, Toronto, Ontario, M5S 1A4
    • Department of Chemical Engineering and Applied Chemistry and Institute for Environmental Studies, University of Toronto, Toronto, Ontario, M5S 1A4
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  • W. Y. Shiu

    1. Department of Chemical Engineering and Applied Chemistry and Institute for Environmental Studies, University of Toronto, Toronto, Ontario, M5S 1A4
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Abstract

The characterization of the evaporation rate of complex hydrocarbon mixtures, such as commercial oil fractions, under environmental conditions is discussed. It is shown that the relevant thermodynamic quantity is the total volume of vapour (per unit of initial oil mass) removed under isothermal differential distillation conditions (V m3/kg) as a function of the mass fraction of the oil remaining (F). Plots of F versus V for various isothermal conditions can be used to estimate evaporation rates since it is shown that V is equivalent to the group KsAsτs/Ms where Ks is the evaporation mass transfer coefficient (m/s), As is the spill area (m2), τs is the evaporation time (s) and Ms is the spill mass (kg). The basis of a methodology for estimating environmental evaporation rates is thus outlined. Methods of obtaining V versus F data are discussed, with calibrated wind tunnel evaporations being preferred. The estimation of evaporation rates under spreading and non-isothermal conditions and the analogous dissolution process are discussed briefly.

Abstract

On discute la caractérisation du taux d'évaporation de mélanges complexes d'hydrocarbures (tels que les fractions d'huiles commerciales) dans les conditions ambiantes. On démontre que la quantité thermodynamique pertinente est le volume total de vapeur (par unité de masse initiate d'huile) enlevé dans les conditions isothermiques de la distillation différentielle (V m3/kg.) en fonction de la fraction de masse de l'huile restante (F). Ont peut employer des représentations graphiques de F, en fonction de V pour diverses conditions isothermiques, pour évaluer les taux d'évaporation, vu qu'on constate que V équivaut au groupe KsAs/Ms, où Ks est le coefficient de transfert de masse par évaporation (m/s), As est la surface de la mare (m2), τs est le temps d'évaporation (s) et M2 est la masse de la mare (k.g.). On expose ainsi la base d'une méthodologie pour évaluer les taux d'évaporation ambiante. On discute les méthodes pour obtenir des données en tunnel aérodynamique. On discute brièvement l'évaluation des taux d'évaporation dans des conditions non isothermiques et impliquant l'expansion de l'huile.

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