TOSCO II process

History

TOSCO II process is a refinement of the Swedish Aspeco process. |archive-url=https://web.archive.org/web/20110414112241/http://www.time.com/time/magazine/article/0,9171,824979,00.html |url-status=dead |archive-date=April 14, 2011 The Tosco Corporation purchased its patent rights in 1952. In 1956, the Denver Research Institute performed research and development of this technology, including testing of a 24-ton-per-day pilot plant, which operated until 1966. Later the technology development was continued under Tosco's own directions. In 1964, Tosco, Standard Oil of Ohio, and Cleveland Cliffs Iron Company formed Colony Development, a joint venture company to develop the Colony Shale Oil Project and to commercialize the TOSCO II technology. The project was ended in April 1972. | author-link = Office of Technology Assessment

Technology

The TOSCO II process is classified as a hot recycled solids technology. After entering into retort, oil shale is mixed with hot ceramic balls with temperatures of 1200-1600 °F. This increases the oil-shale temperature to 900-1100 °F, in which pyrolysis occurs. In the pyrolysis process, kerogen decomposes to oil-shale gas and oil vapors, while the remainder of the oil shale forms spent shale. Vapors are transferred to a condensor (fractionator) for separation into various fractions. At the kiln passage, the spent shale and the ceramic balls are separated in a perforated rotating separation drum (trommel). The crushed spent shale falls through holes in the trommel, while ceramic balls are transferred to the ball heater. Combustible shale gas is burned in the ball heater to reheat the ceramic balls.

The overall thermal efficiency of the TOSCO II process is low because the energy of the spent shale is not recovered, and much of the produced shale gas is consumed by the process itself. The efficiency could be increased by burning char (carbonaceous residue in the spent shale) instead of shale gas as a fuel of the ball heater. The process's other disadvantages are mechanical complexity and large number of moving parts. Also, the lifetime of the ceramic balls is limited. Disposal of spent shale includes environmental problems because it is very finely crushed and contains carbon residue.

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