Page 139 - Synthetic Fuels Handbook

FUELS FROM TAR SAND BITUMEN 125

A partial coking or thermal deasphalting process provides a minimal upgrading of
bitumen. In partial coking, the hot water process froth is distilled at atmospheric pres-
sure and minerals and water are removed. A dehydrated mineral-free bitumen product
is obtained that contains most of the asphaltenes and coke precursors. The process has
been carried out in batch equipment in laboratory tests over periods ranging from
30 minutes to 4 hours. Thermal cracking begins as the liquid temperature passes 340°C
(644°F). The distillation is continued into the range 370 to 450°C (698–842°F). With
slow heating [10°C (50°F) temperature rise per hour] the coke production rate is approx-
imately 1 percent weight of feed per hour. As the coke forms about the entrained mineral
particles, 1 to 4 percent weight of coke up to 50 percent v/v of the feed is recovered as
distillate. After this treatment the residue may be filtered to yield an essentially ash-free
production suitable for applications such as metallurgic coke or production of bitumi-
nous paints, for which the original mineral content would have disqualified it.
In the flexicoking process, a gasifier vessel is added to the system in order to
gasify excess coke with a gas-air mixture to a low heating-value gas that can be
desulfurized and used as a plant fuel. The Eureka process is a variant of delayed
coking and uses steam stripping to enhance yield and produce a heavy pitch rather
than coke byproduct.

4.6.4 Hydrogen Production
Current synthetic crude oil production operations meet the hydrogen requirements using
steam-methane reforming with natural gas used for both feedstock and fuel. However, the
increasing price of natural gas is increasing production costs and partial oxidation (gas-
ification) of a bitumen stream or coal could well be the mode of hydrogen generation for
future projects.

4.7 SYNTHETIC CRUDE OIL

Synthetic crude oil is not a naturally occurring material and is currently produced by
upgrading tar sand bitumen. Synthetic crude usually requires further refining to produce
gasoline and other types of petroleum products. Another product dilbit (bitumen diluted
with condensate or with naphtha) has also found a market.
Synthetic crude oil is a blend of naphtha, distillate, and gas oil range materials, with no
residuum [1050°F+ (565°C+) material]. Canadian synthetic crude oil first became available
in 1967 when Suncor (then Great Canadian Oil Sands) started to market a blend produced
by hydrotreating the naphtha, distillate, and gas oil generated in a delayed coking unit. The
light, sweet synthetic crude marketed by Suncor today is called Suncor Oil Sands Blend A
(OSA). Syncrude Canada Ltd. started production in 1978, marketing a fully-hydrotreated
blend utilizing fluidized-bed coking technology as the primary upgrading step. This prod-
uct is referred to as Syncrude sweet blend (SSB).
Suncor is planning to build a third bitumen upgrader for its oil sands operations and
plans to construct new sulfur recovery plant in support of its existing upgrader capacity.
The eventual aim is to raise the production capacity of Suncor’s oil sands processing
to more than 500,000 bbl/day over the next 5 to 7 years. The new plant, which would
be built about half a kilometer from the existing upgrader site, would include cokers,
hydrotreaters, and a 50-km bitumen pipeline to connect the upgrader with Suncor’s
mining operations.