Bitumen Kinetics

Catalytic Air-Blowing Process for Bitumen-Kinetic Aspects... 

Numerous kinetic mechanisms have been proposed for oil shale pyrolysis reactions (11—14). It has been generally accepted that the kinetics of the oil shale pyrolysis could be represented by a simple first-order reaction (kerogen — bitumen — oil), or... 

MODELING OF BITUMEN OXIDATION AND CRACKING KINETICS USING DATA FROM ALBERTA OIL SANDS... 

In the laboratory of Professor R.G. Moore at the University of Calgary, kinetic data were obtained using bitumen samples of the North Bodo and Athabasca oil sands of northern Alberta. Low temperature oxidation data were taken at 50, 75, 100, 125 and 150"C whereas the high temperature thermal cracking data at 360, 397 and 420"C. 

Hanson, K. and N. Kalogerakis, "Kinetic Reaction Models for Low Temperature Oxidation and High Temperature Cracking of Athabasca and North Bodo Oil Sands Bitumen", NSERC Report, University of Calgary, AB, Canada, 1984. 

Kinetics and Energetics of Oxidation of Bitumen in Relation to In Situ Combustion Processes... 

Using a "home made" aneroid calorimeter, we have measured rates of production of heat and thence rates of oxidation of Athabasca bitumen under nearly isothermal conditions in the temperature range 155-320°C. Results of these kinetic measurements, supported by chemical analyses, mass balances, and fuel-energy relationships, indicate that there are two principal classes of oxidation reactions in the specified temperature region. At temperatures much lc er than 285°C, the principal reactions of oxygen with Athabasca bitumen lead to deposition of "fuel" or coke. At temperatures much higher than 285°C, the principal oxidation reactions lead to formation of carbon oxides and water. We have fitted an overall mathematical model (related to the factorial design of the experiments) to the kinetic results, and have also developed a "two reaction chemical model". 

Subsequent measurements in which water vapor has been introduced along with oxygen have led to modified kinetics and also a modified chemical model for wet oxidation of Athabasca bitumen. 

The focus of our investigations of the kinetics of oxidation of Athabasca bitumen has been on the use of an aneroid calorimeter ( 1 ) for measuring rates of heat production under nearly isothermal (AT < 1.2°C in each experiment) conditions. Initial attention was given to just two of the variables that affect the kinetics of oxidation (i) temperature and (ii) pressure of oxygen. 

Table I. Values of Kinetic Parameters for Low Temperature Oxidation of Athabasca Bitumen...

Removal of the carbonate minerals by HC1 treatment, Sample C, resulted in a significant increase of 8.6 wt% in the net pyrolysis yield. The carbonate DTG maximum near 730°C is noticeably absent from the Sample C DTG curve, Figure 4. The postulated explanation of the increased yield of the bitumen-, carbonate-free shale is a combination of several factors. It appears that the carbonate minerals, thermochemically and/or kinetically, act to hamper the pyrolysis yield or possibly modify the mechanistic reaction pathway so as to yield a higher percentage of residual carbon. The observed increase in the pyrolysis yield is not due to the release of bitumen trapped by the carbonate minerals because such bitumens were removed by Soxhlet extraction prior to the TG analysis. 

In the present study this model has been successfully uses to quantitatively assess the oxidation rate of bitumen as a function of operating conditions, catalyst and feed stock characteristics. Kinetic parameters of the model used to describe the process are presented... 

In order to determine an< kc individually, the kinetically determined values for the sum (k + kc) must be used in consort with the expression for the coke yield 0.8 f2 kc/(k2+kc). The calculated values of the ratio kc/(k2+kc) together with the kinetically obtained values of (k2 + kc) are given in the Appendix. The resulting k2 and kc values show some interesting characteristics k2 is independent of particle size whereas kc is proportional to particle size. Both have the same temperature dependence because the coke yield is constant with temperature. The temperature dependence and the particle size dependence of kc are shown explicitly in Table III. kc is seen to dominate over k2 even for the 0.4 mm particles. For the 3 mm particles, k2 is insignificant in relation to kc implying complete coking of the bitumen. 

Modeling of Bitumen Oxidation and Cracking Kinetics Using Data from Alberta Oil Sands... 

Tannenbaum E., Starinsky A. and Aizenshtat Z. (1987) Light oils transformation to heavy oils and asphalts. In Exploration for Heavy Crude Oils and Natural Bitumen. Studies in Geology (ed. R. F. Meyer), pp. 221-231. American Association of Petroleum Geologists Series 25, American Association of Petroleum Geologists, Tulsa. Williamson M. A. and Rimstidt J. D. (1990) Thermodynamic and kinetic controls on e aqueous oxidation of sulfide minerals. In Goldschmidt International Conference for Advancement of Geochemistry, pp. 91-103. 

Solid particles were observed at or near the oil-water interface on several occasions in toluene-diluted bitumen films. The particles were easily pushed away from the film into the meniscus region when the films were first formed and never appeared in the film itself. For the solids fraction to play a role in emulsion stability, we thus expect that the fine clay particles probably build up in the Plateau borders around water droplets and clog the drainage routes through the emulsion, contributing to its additional, kinetic stability. Therefore, it may be expected that the fine solids may have a contribution to the overall W/0 emulsion stability, but this is not the leading factor. 

Emulsions formed in crude oil and bitumen during extraction operations are usually water-in-oil (W/O) macroemulsions (>0.1 to 100 om in diameter). Macroemulsions are kinetically stable, unlike microe-mulsions, which are thermodynamically stable. In conventional oil recovery (high-energy process), the crude is often in contact with formation water or injection water, as in secondary recovery. In tertiary or enhanced oil recovery, surfactants are used purposely in water floods to make microemulsions for enhancing the flowability of the crude. Crude-oil macroemulsions are produced when two immiscible liquid phases such as oil and water are mixed via the input of mechanical or thermal energy into the processes. Conventional crudes held under high pressures and temperatures amidst... 

KA Ferwom. Thermodynamic and Kinetic Modelling of Asphaltene Precipitation from Heavy Oils and Bitumens. PhD thesis. University of Calgary, Alberta, 1995. 

If bitumens are regared as model substances for heavy residues, then their Arrhenius coefficients can serve as the basis for the calculation of the kinetics of pyrolysis reactions in thermal conversion processes (thermal cracking, visbreaking, hydrotreating etc.). Integration of the peak areas gives a value for the energy required for pyrolysis reactions. 

The onset temperature, and the temperature and kinetic data of the first oxidation peak maximum are the criteria which define the practical behavior of bitumens in its applications. Calculation of the reaction rate constants and of the half-life time using the Arrhenius coefficients gives values, which may be reproduced by other methods, although the oxidation does not obey the first order reaction law. The plot of the log versus the inverse Kelvin temperature (1 000/T) is shown in Fig. 4-78. Corresponding graphs for the other peaks show the increase in the half-life times. However, they are only of theoretical interest and do not have any relevance to practical behavior in production and manufacturing. Fig. 4-78 and Table 4-102 show that oxidation commences at temperatures... 

Knowledge of the kinetics of the oxidation reaction permits extrapolation of the resulting half life time to lower temperatures, producing information about the oxidation stability at manufacturing temperatures and the application of the bitumens. This only gives a rough estimate of the behavior on the actual road surface, since there are additional... 

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