Bitumen density

Hot-Water Process. The hot-water process is the only successflil commercial process to be appHed to bitumen recovery from mined tar sands in North America as of 1997 (2). The process utilizes linear and nonlinear variations of bitumen density and water density, respectively, with temperature so that the bitumen that is heavier than water at room temperature becomes lighter than water at 80°C. Surface-active materials in tar sand also contribute to the process (2). The essentials of the hot-water process involve conditioning, separation, and scavenging (Fig. 9). 

The froth contains typically about 60% bitumen, 30% water, and 10% solids. To remove solids and water, the froth is diluted with a diluent, in both existing operations this is locally produced naphtha. Bitumen density is about the same as that of water. Addition of a light solvent lowers the density of the oil phase and, at die same time, lowers its viscosity, making water and solids separation possible. In the froth-treatment operation, scroll and disk centrifuges as well as incline plate settlers (IPSs) are used for cleaning the froth diluted with naphtha. The product, which usually contains less than 2% water and less flian 0.4% fine solids, is then fed to upgrading. Here, in die first operation, the diluent is recovered and recycled to froth treatment. 

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. 

An attempt has been made to develop the hot-water process for the Utah sands (Fig. 10) (20). With od-wet Utah sands, this process differs significantly from that used for the water-wet Canadian sands, necessitating disengagement by hot-water digestion in a high shear force field under appropriate conditions of pulp density and alkalinity. The dispersed bitumen droplets can also be recovered by aeration and froth flotation (21). 

The maximum protected length 2 L is given in Fig. 10-1 and the required protection current in Fig. 10-2. For pipelines with carefully mill-applied PE and excellent field-applied coating of the girth weld area, the protection current densities lie between 1 and 3 jJ.A m With carefully buried pipelines with bitumen (or coal tar) coating, the protection current densities lie between 10 and 30 jUA mr. ... 

Based on past experience, it has been found that the protection current density for buried storage tanks coated with bitumen is over 100 /xA m. With coatings in very good condition, it can amount to a few tens of jiA but for coatings in a very poor state, it can rise to a level of mA The protection current demand can... 

Covering the foundations of the tank with bitumen or a mixture of bitumen, sand and gravel ( oiled-sand ) reduces the protection current requirement considerably. Figure 12-8 shows the protection current requirement of the base of some flat-bottomed tanks. The protection current densities of tank bases 1,3 and 4 lie between 0.5 and 2 mA m. The protection current density of tank No. 2 is very much greater. 

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. ... 

Residual products (No. 6 fuel oil, bunker C oil) these products have little (usually, no) ability to evaporate. When spilled, persistent surface and intertidal area contamination is likely with long-term contamination of the sediment. The products are very viscous to semisolid and often become less viscous when warmed. They weather (oxidize) slowly and may form tar balls that can sink in waterways (depending on product density and water density). They are highly adhesive to soil. Heavy oil, a viscous petroleum, and bitumen from tar sand deposits also come into this category of contaminant. 

The first three methods involve water as the separating medium. These are based on the well known observation that the bulk of the sand, on the order of 99%, is not in direct contact with the bitumen but is "protected by an envelope of water. On adding further water, the sand is "liberated into the bulk water phase, and the bitumen, which was previously interspersed among the grains of sand, retracts into discrete flecks. These flecks are usually small, and having approximately the same density as water, remain dispersed in the water as an oil-in-water emulsion. 

The third approach is to add an organic solvent to decrease the density of the bitumen and thus allow a gravity separation from water and sand. In one case a centrifuge is used to enhance the rate of separation. 

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

Example. In the primary flotation vessel of an oil sands processing plant, two different process conditions yield the following data for the flotation of bitumen mean bitumen droplet diameter, 0.26 mm, mean droplet density,... 

Slurry condition 1 density, 1.33 g/cm3 viscosity, 89 mPa- s Slurry condition 2 density, 1.20 g/cm3 viscosity, 3.2 mPa - s From the slurry introduction point, bitumen droplets must rise a distance of 0.80 m within the mean vessel residence time of 45 min in order to reach the froth layer and be recovered. What kind of oil recovery efficiencies would be predicted for each case ... 

Example. Bitumen is recovered in the form of a froth when a separation-flotation process is applied to surface mined oil sand. Once de aerated, this bituminous froth is a W/O emulsion from which the water must be removed prior to upgrading and refining. At process temperature (80 °C) the emulsion viscosity is similar to that of the bitumen, but the density, due to entrained solids, is higher. Taking t) = 500 mPa-s and f> = 1.04 g/mL, the rate of creaming of 20 pm diameter water droplets under gravitational force will be very slow ... 

For emulsions, the interfacial tension is usually of most interest. Here, the du Noiiy ring, Wilhelmy plate, drop volume, pendant, or sessile drop methods are the most commonly used. The spinning drop or captive drop techniques are applicable to the very low interfacial tensions encountered in the enhanced oil recovery and microemulsion fields. The maximum droplet pressure technique can be used when there is little or no density contrast between the phases, such as in bitumen-water systems at elevated temperature. 

Tar sands are small particles of sandstone surrounded by an organic material called bitumen. The bitumen is a highly viscous hydrocarbon that clings tenaciously to the sandstone thus, it is easy to think of the mixture as a solid form of petroleum. Yet, it is a mixture of high-density liquid on a supporting solid. 

LITHANTHRAX, PIT COAL, STONE COAL — A species of Gagates, and nothing but Bitumen indurated and excocted by heat under the surface of the earth. There are two species of this Coal, one of which is light and of little density, while the other is heavy. It is said that the former will sometimes float upon the surface of water, and it is referred to by Theophrastus as an earthy or stony pit coal. The second species was known to the Greeks, but it is not mentioned by Pliny, and was in all probability unknown to him. It seems to have been described by Theophrastus as a sort of Bituminous Stone, and has therefore an affinity with the fissile slate, which has also a bituminous nature. 

Energy. Thermal. The addition of heat promotes the treatment process. First, it reduces the viscosity of the oil. This effect is especially instrumental in the handling and treatment of heavy crude oils or bitumen emulsions. Second, it weakens or ruptures the film between the oil and water droplets by expanding the water present. Last, heat increases the difference in densities of the fluids and thereby tends to reduce the settling time. 

CANMET has a pilot-scaled emulsion-treatment plant (Figure B.l) available to industry for pilot-scaled investigation of heavy-oil-bitumen separation from oil-field-produced waters. This facility is designed to process emulsions at a throughput between 130 L/h (20 barrels per day) and 460 L/h (70 barrels per day) for raw bitumen-oil of API gravity between 8 and 15 (i.e., density between 1014 and 966 kg/m, respectively). 

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