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OCR for page 183
F
Retorting Technologies for Oil Shale
HOT GAS RETORTING PROCESSES
In the Paraho internal combustion retort a moving bed of shale travels
downward and is heated by hot gas flowing upward through it. The hot gas
is provided by combustion of hydrocarbon gas and char within the retort.
Oil produced from the pyrolysis process is carried out of the retort by the
gas stream in the form of vapor and oil mist (liquid). Paraho demonstrated
this process at a scale of about 300 tons/day.
In the Union B and Petrosix retorts the hot gas is provided by heating the
hydrocarbon gases produced by pyrolysis in an external heater. The hot gas
flows countercurrent to the shale particles. In the Union B process the
shale is pumped upward and the gas flows downward; in the Petrosix proc-
ess the shale moves downward and the gas flows upward. Fuel from an
external source is normally supplied to operate the heater. Petrosix has
been operating in Brazil more or less continuously since 1972 at 2200 tons/
day (800 bbl/day) in a retort 18 ft in diameter and is constructing a 7800-
ton/day (3300-bbl/day) retort with a diameter of 36 ft. Union has con-
structed a plant to produce 10,000 bbl/day. Construction was finished in
1983, and oil shipments began in 1986. Work continues in an effort to
increase the achieved capacity of 7000 bbl/day to design capacity.
In a modified in-situ process a fixed bed retort is constructed under-
ground by some combination of mining and blasting. Downward-flowing
gas is heated by burning the char in the retort. Occidental Petroleum and
the U.S. Department of Energy have been the most active in developing this
process, demonstrating its feasibility at Logan Wash in the early 1980s.
Occidental Petroleum is proposing to demonstrate its process on its Colo-
rado tract, C-b, where commercial-sized mine shafts have been constructed.
183
OCR for page 184
184
APPENDIX F
Rio Blanco (Gulf and Amoco) developed variations of the process in the
early 1980s. Geokinetics was also active then in developing a horizontal
insitu process, which avoided mining by using near-surface blasting.
HOT SOLID RETORTING PROCESSES
In the Tosco II process hot ceramic balls are mixed with smaller shale
particles in a rotating drum. After the shale is pyrolyzed, the balls are
separated and reheated in a ball heater using gas as fuel. The retorted shale
is discarded. Tosco operated this process on a scale of 1000 bbl/day in the
late 1970s and early 1980s.
In the Lurgi process hot burned shale is rapidly mixed with raw shale in
a screw mixer and then held in a surge bin for a few minutes to complete
pyrolysis. After pyrolysis the shale is fed to a lift pipe (dilute fluid bed),
where it is burned as it is pneumatically lifted in a stream of air. The hot
burned shale exiting from the lift pipe provides a continuous source of hot
solid. Rio Blanco (Gulf and Amoco) operated a 1- to 5-tons/day pilot until
1984.
In the Chevron process raw shale and hot burned shale are mixed in a
staged fluidized bed and held there until pyrolysis is complete. A lift pipe
is used to burn the retorted shale and provide hot solid, as in the Lurgi
process. Chevron constructed and briefly operated a 350-tons/day pilot
plant until 1984.
In the Lawrence Liverm ore National Laboratory (LLNL), hot solids proc-
ess mixing of recycled hot shale with raw shale occurs in a few tens of
seconds in a fluidized bed. Pyrolysis is completed in a few minutes as the
hot shale particles flow through a bin. The char is burned to produce hot
solid in a cascading burner. Solid particles cascade down through a series
of rods that slow their fall and provide sufficient residence time for com-
bustion. Oxygen is provided by air flowing across the tumbling solid par-
ticles. The LLNL has operated a laboratory-scale retort at 1 ton/day, which
is currently being enlarged to 4 tons/day.
Representative terms from entire chapter:
hot solid
