Bitumen Athabasca

Bitumen. There are wide variations both in the bitumen saturation of tar sand (0—18 wt % bitumen), even within a particular deposit, and the viscosity. Of particular note is the variation of density of Athabasca bitumen with temperature, and the maximum density difference between bitumen and water (70—80°C (160—175°F)) hence the choice of the operating temperature of the hot-water bitumen-extraction process. 

Recovering the bitumen is not easy, and the deposits are either strip-mined if they are near the surface, or recovered in situ if they are in deeper beds. The bitumen could be extracted by using hot water and steam and adding some alkali to disperse it. The produced bitumen is a very thick material having a density of approximately 1.05 g/cm. It is then subjected to a cracking process to produce distillate fuels and coke. The distillates are hydrotreated to saturate olefinic components. Table 1-8 is a typical analysis of Athabasca bitumen. ... 

Isaacs and Smolek [211 observed that low tensions obtained for an Athabasca bitumen/brine-suIfonate surfactant system were likely associated with the formation of a surfactant-rich film lying between the oil and water, which can be hindered by an increase in temperature. Babu et al. [221 obtained little effect of temperature on interfacial tensions however, values of about 0.02 mN/m were obtained for a light crude (39°API), and were about an order of magnitude lower than those observed for a heavy crude (14°API) with the same aqueous surfactant formulations. For pure hydrocarbon phases and ambient conditions, it is well established that the interfacial tension behavior is dependent on the oleic phase [15.231 In general, interfacial tension values of crude oiI-containing systems are considerably higher than the equivalent values observed with pure hydrocarbons. 

This type of difficulty associated with measurements using chemical ly iI I-defined substrates was also observed during sessile drop measurements carried out on Athabasca bitumen in D20 T311. Values in the range of 15-20 mN/m were obtained for measurements with several drops of bitumen, while interfacial tensions for other pure aqueous and oleic systems were accurate to 0.5 mN/m. 

Effect of NaCI Concentration. The presence of surfactant in brine can have a dramatic effect on crude oil-aqueous surfactant tensions even at elevated temperatures r5,211. Figure 5 shows that the effect of sodium chloride concentration on Athabasca bitumen-D20 interfacial tensions measured at constant surfactant... 

Figure 5 Effect of NaCI concentration on the Athabasca bitumen/DJ) interfacial tension for Enordet C18 18, Sun Tech IV and TRS 10-80. Closed triangle represents the data measured for Enordet C16 18 at concentrations up to 160 g/L NaCI.

Table III Interfacial tension data for the Athabasca bitumen/D20 and Enordet C1618 (2 g/L) system as a function of NaCI concentration and temperature...

Figure 7 Variation of interfacial tension between Athabasca bitumen and D20 containing Sun Tech IV (2 g/L) as a function of pH and temperature at constant ionic strength of 10 M. The dashed line represents data from reference T211 at 50 C in the absence of added surfactant or brine.

Temperature Oxidation of Athabasca Bitumen". J. Canad. Petroleum Technol., (May-June 1987), P 24-32. 

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. 

Preliminary studies into a third variable, the partial pressure of water vapor in the system, are discussed in Part 3 of the Results and Calculations section. Each calorimetric sample ( 1 g, 13.47 mass % bitumen) came from a large sample of "reconstructed" oil sand consisting of Athabasca bitumen loaded onto a chemically inert solid support material (60/80 mesh acid washed Chromosorb W) of well-defined particle size. 

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

Table VI. Residual Coke and Conversion of Available Carbon During Wet Oxidation of Athabasca Bitumen at 225°C a ...

Carbazole is a non-basic nitrogen compound, whose removal via hydrotreating is limited by its low reactivity. The removal of nitrogen by hydrotreatment involves a number of steps that take place on the catalyst surface. The weak interaction of neutral nitrogen compounds with catalysts precludes carbazole and its derivatives from being denitro-genated and makes them the most recalcitrant components in HDN of gas oils [308], In fact, it has been found that the nitrogen content of hydrotreated gas oil from Athabasca bitumen was composed primarily of alkyl carbazoles [309],... 

Jokuty, P., and Gray, M. R., Resistant Nitrogen Compounds in Hydrotreated Gas Oil From Athabasca, bitumen,. Energy Fuels, 1991. 5 pp. 791-795. 

Macdonald, D.D., Greidanus, J.W., Hyne, J.B., Hydrothermal (Water) Reactions of Athabasca Bitumen Organosulphur Model Compounds and Asphaltene , The Oil Sands of Canada-Venezuela 1977, CIM Special Volume 17. 

Recently, studies have been made to determine the properties of Utah bitumens (I, 2). Others (3-9) have studied the properties of Athabasca bitumens. The analyses of the bitumens have generally included physical properties, elemental analyses, distillation, and infrared... 

The elemental analysis of oil sand bitumen (extra heavy oil) has also been widely reported (Speight, 1990), but the data suffer from the disadvantage that identification of the source is too general (i.e., Athabasca bitumen which covers several deposits) and is often not site specific. In addition, the analysis is quoted for separated bitumen, which may have been obtained by any one of several procedures and may therefore not be representative of the total bitumen on the sand. However, recent efforts have focused on a program to produce sound, reproducible data from samples for which the origin is carefully identified (Wallace et al., 1988). It is to be hoped that this program continues as it will provide a valuable database for tar sand and bitumen characterization. 

Figure 2-11 Variation of specific gravity (density) of Athabasca bitumen and water with temperature.

Source Arabian hvy vacuum resid Athabasca bitumen... 

Currently, delayed coking and fluid coking are the processes of choice for conversion of Athabasca bitumen to liquid products. Both processes are termed the primary conversion processes for the tar sand plants in Ft. McMurray, Canada. The unstable liquid product streams are hydrotreated before recombining to the synthetic crude oil. 

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