Bituminous froth

Retorting of the total oil sand to produce cracked products was tested extensively, and other than the high heat loss to the sand, it appeared to be a very workable scheme. A combination scheme involving hot water washing to produce a wet bituminous froth followed by fluid coking of this froth was the basic operation recommended in the Blair report in 1950 (4). 

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 ... 

Example. Consider the observed properties of bituminous froth produced in the oil sands hot water flotation process. When fresh, the froth is very viscous when stagnant (hard to pump) but becomes less viscous (twice as easy to pump) when it is flowing. As it is handled, or stored, the entrained air is released and it becomes less viscous (eventually six times as easy to pump). 

Foams and emulsions may also be encountered simultaneously [114]. Figure 1.5 shows an example of an aqueous foam with oil droplets residing in its Plateau borders (see Section 5.6.7). In addition to containing gas, an aqueous phase, and an oleic phase, foams can also contain dispersed solid particles. Oil-assisted flotation of mineral particles provides one example (Chapter 10). Oil-sand flotation of bitumen provides another (Chapter 11). In the case of oil-sands flotation, an emulsion of oil dispersed in water is created and then further separated by a flotation process, the products of which are bituminous froths that may be either air (and water) dispersed in oil (from primary flotation) or air (and oil) dispersed in water (from secondary flotation). In either case, the froths must be broken and de-aerated before the bitumen can be upgraded to synthetic crude oil. (See Section 11.3.2). 

Shaw, R.C. Czarnecki, J. Schramm, L.L. Axelson, D. Bituminous Froths in the Hot-Water Flotation Process in Foams Fundamentals and Applications in the Petroleum Industry, Schramm, L.L., Ed., American Chemical Society Washington, 1994 pp. 423-459. 

Emulsions may contain not just oil and water, but also solid particles and even gas. In the large mining and processing operations applied to Canadian oil sands, bitumen is separated from the sand matrix in large tumblers as an emulsion of oil dispersed in water, and then further separated from the tumbler slurry by a flotation process. The product of the flotation process is bituminous froth, an emulsion that may be either water (and air) dispersed in the oil (primary flotation) or the reverse, oil (and air) dispersed in water (secondary flotation). In either case, the emulsions must be broken and the water removed before the bitumen can be upgraded to synthetic crude oil, but the presence of solid particles and film-forming components from the bitumen can make this removal step very difficult. 

The problem of deaerated bituminous froth produced from the hot-water flotation of bitumen from oil sands can serve as an illustration. This... 

A special kind of nonaqueous foam known as bituminous froth is produced during the application of the hot-water flotation process to Athabasca oil sands, a large-scale commercial application of mined oil sands technology. These froths are multiphase, composed of oil, water gas, and solids, and form an interesting kind of petroleum industry foam. This chapter presents a review of the occurrence, nature, properties, and treatment of bituminous froths. 

Of the Canadian deposits, the largest, Athabasca, is at least 4 times the size of the largest conventional oil field, Ghawar, in Saudi Arabia (5). Of the Athabasca s estimated 600 billion barrels of bitumen, about 60 billion barrels could be recovered by surface mining of the oil sand followed by beneficiation to separate the oil. Currently two commercial plants are producing synthetic crude oil from the Athabasca deposit. In these operations, the oil sands are first mined, and the bitumen is extracted by a hot-water flotation process, which produces a bituminous froth. After breaking the froth, the separated bitumen is subsequently upgraded by refineiy-type processes to produce synthetic crude oil. In order to understand the nature of the froths produced, the nature of oil-sand structure will be reviewed first, and then the flotation process from which froths are produced will be examined. 

Froth A type of foam in which solid particles are also dispersed in the liquid (in addition to the gas bubbles) the solid particles may be the stabilizing agent. The term froth is sometimes used to refer simply to a concentrated foam, which is not preferred usage. Example Bituminous froth is a nonaqueous (oleic) foam that also contains water and solids (See also Chapter 11). 

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