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Interfacial contamination of batches of refined petroleum products transported through multiproduct pipelines is a long standing problem in the petroleum industry. Determination of the extent of mixing depends on various factors including fluid properties, operating conditions and flow regimes. The convective-diffusion model along with a fictional parameter, known as the axial dispersion coefficient introduced by Sir G. I. Taylor, is the commonly employed methodology to evaluate longitudinal mixing. However, the model was formulated with a uniform turbulent or laminar flow across the entire flow field. It is argued that the assumption of a uniform flow regime leads to inaccuracies in predicting the extent of contamination at the interface. This study incorporates both the turbulent and the viscous effects in predicting the interfacial contamination volume. Taylor’s analysis of dispersion coefficients has been reviewed, and an improved model combining the weighted effects of the viscous boundary layer contributions and the turbulent core contributions to axial dispersion is proposed. The proposed model provides a possible explanation for the underlying physics of interfacial contamination in flow through straight pipes without pipe fittings and other devices. A comparison of the model predictions with literature data demonstrates the importance of considering both turbulent and viscous effects to achieve better overall prediction accuracy.

Low temperature ash (LTA) samples prepared from nine US coals were characterized by X-ray diffraction. X-ray fluorescence, and surface area analyses. The results showed that illite, kaolinite, quartz and pyrite are major components in LTAs and that SFe ratios of some LTAs decreased significantly after H2 treatment implying the occurrence of a partial reduction of pyrite during this treatment. Surface areas of LTAs increased drastically on H2 treatment but decreased after exposure to sulphur and nitrogen compounds in activity testing. Correlations for the surface areas of LTAs before and after H2 treatment were found in terms of clay content and element concentrations.

Precipitation chemistry from different regions of the Continental United States is characterized in terms of a graph of annual mean μ (+) vs μ(−), where μ (+) = Ca2+ +Mg+2 + NH+4 + K+ and Na+,and σ (−) = SO2−4 + NO −3 + Cl−; concentrations are given in μeq. l−1. Sites receiving acid precipitation (pH 4.5) tend to cluster near a line of slope one. Four regions. North Central (Minnesota, Wisconsin), Midwest (Illinois, Ohio), East Central (North Carolina, Virginia), and North East (Pennsylvania, New York, Vermont, New Hampshire, Maine) are presented as areas in terms of minimum and maximum μ (+) and μ (−) values. Seasonal variations of μ (+) and σ (−) tend to occur along lines of constant slope within these regions. The results from the last decade have been compared with the few measurements from the 1950s. Although one possible interpretation from this comparison is that σ(−) has increased in one or more of the regions considered, this view is tempered by the inherent difficulty in comparing single sites with regions.