Dispersion Arrhenius Coefficients

Table 4-82 Arrhenius coefficients and conversion in the DSC pyrolysis in 1 bar argon. Dispersion medium from blown bitumens...

There is no statistical difference in the Arrhenius coefficients between the bitumen and the dispersion medium, nor between the petroleum resins and the asphaltenes. The statisti-... 

Differences in the Arrhenius coefficients for the three components of the coUoid system (the dispersion medium, petroleum resins, and asphaltenes) do exist, but prove to be smaller than was at first assumed. 

Even the corresponding peak temperatures of the blown bitumens show very small variances in the tests in 10 bar methane and also permit the calculation of statistical means. The resulting coefficients of variation are 3.0 % maximum. This is also true for the colloid components, except for the dispersion medium of the two bitumens 85/40 (sample III) and 85/25 (sample IV). Here again a weight loss caused by distillation even occurs under pressure with the consequence of low values for the activation energy and frequency factor. Only the data of the other three samples was included in the statistics. The average values of the Arrhenius coefficients calculated in this manner and the means of the conversion aie shown in Table 4-93. 

Comparison of the means shows that there is a significant difference in the Arrhenius coefficients for distillation and blown bitumens and their colloid components. The conversions only differ for the dispersion medium whereas the bitumens, the petroleum resins, and the asphaltenes do not differ in the conversions, either in 1 bar argon or in 10 bar methane. 

Table 4-104 Arrhenius coefficients of the oxidation of dispersion medium in 7 bar air. 

The blown bitumens do not exhibit peaks in the evaporation range when the system pressure is inereased to 10 bar, except for the dispersion medium of the bitumens 85/40 and 85/25, which demonstrate only an evaporation loss. The Arrhenius coefficients of the blown bitumen showed greater differences than those of the distillation bitumens. In the plot of half life time, versus the inverse Kelvin temperature, the distillation bitumens and their colloid components follow almost parallel lines, whereas the graphs for the blown bitumens and their colloid components diverge. The plot of versus 1 000/T shows the residence time required to achieve a conversion of fifty percent, at a preset reaction temperature, or which temperature is required to achieve a preset conversion at a preset residence time. This information is valuable in thermal processing, for example in selection of the crack severity of the visbreaking process. 

The behavior described above is exemplified in figure 10.11, where Arrhenius plots of solid/liquid conventional partition coefficients for transition elements reveal more or less linear trends, with some dispersion of points ascribable to compositional effects. 

The viscosity of fully gelatinized starch suspensions generally decreases with increase in temperature. This rheological response of heated starch dispersions has been shown to follow an Arrhenius dependency of the consistency coefficient on temperature as shown in Equation 4.49. 

C cell number density, number of cells/m c specific heat of medium, J/kg K collector diameter, m dp particle diameter, m rfj pipe diameter, m D axial dispersion coefficient, m /s Dsr diffusivity due to the Brownian motion, m /s Erf activation energy for thermal cell destruction in Arrhenius equation, J/kmol... 

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