THE FUTURE
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properties of shale oil vary as a function of the production (retorting) process. Fine mineral matter carried over from the retorting
process and the high viscosity and instability of shale oil produced
by present retorting processes have necessitated upgrading of the
shale oil before transport to a refinery.
Upgrading, or partial refining, to improve the properties of a crude
shale oil may be carried out using different options. Hydrotreating
is the option of choice to produce a stable product that is comparable to benchmark crude oils (Chapter 4). In terms of refining and
catalyst activity, the nitrogen content of shale oil is a disadvantage.
If not removed, the arsenic and iron in shale oil would poison and
foul the supported catalysts used in hydrotreating.
Blending shale oil products with corresponding crude oil products,
using shale oil fractions obtained from a very mildly hydrogen
treated shale oil, yields kerosene and diesel fuel of satisfactory properties. Hydroprocessing shale oil products, either alone or in a blend
with the corresponding crude oil fractions, is therefore necessary.
The severity of the hydroprocessing has to be adjusted according to
the particular properties of the feed and the required level of the stability of the product.
The fundamental problem with all oil shale technologies is the
need to provide large amounts of heat energy to decompose the
kerogen to liquid and gas products. More than one ton of shale
must be heated to temperatures in the range 850° and 1000°F (425
to 525°C) for each barrel of oil generated, and the heat supplied
must be of relatively high quality to reach retorting temperature.
Once the reaction is complete, recovering sensible heat from the hot
rock is very desirable for optimum process economics. This leads to
three areas where new technology could improve the economics of
oil recovery:
1. Recovering heat from the spent shale.
2. Disposal of spent shale, especially if the shale is discharged at temperatures where the char can catch fire
in the air.
3. Concurrent generation of large volumes of carbon
dioxide.
The heat recovery from hot solids is generally not efficient, unless
it is in the area of fluidized bed technology. However, to apply fluidized bed technology to oil shale would require grinding the shale
257
properties of shale oil vary as a function of the production (retorting) process. Fine mineral matter carried over from the retorting
process and the high viscosity and instability of shale oil produced
by present retorting processes have necessitated upgrading of the
shale oil before transport to a refinery.
Upgrading, or partial refining, to improve the properties of a crude
shale oil may be carried out using different options. Hydrotreating
is the option of choice to produce a stable product that is comparable to benchmark crude oils (Chapter 4). In terms of refining and
catalyst activity, the nitrogen content of shale oil is a disadvantage.
If not removed, the arsenic and iron in shale oil would poison and
foul the supported catalysts used in hydrotreating.
Blending shale oil products with corresponding crude oil products,
using shale oil fractions obtained from a very mildly hydrogen
treated shale oil, yields kerosene and diesel fuel of satisfactory properties. Hydroprocessing shale oil products, either alone or in a blend
with the corresponding crude oil fractions, is therefore necessary.
The severity of the hydroprocessing has to be adjusted according to
the particular properties of the feed and the required level of the stability of the product.
The fundamental problem with all oil shale technologies is the
need to provide large amounts of heat energy to decompose the
kerogen to liquid and gas products. More than one ton of shale
must be heated to temperatures in the range 850° and 1000°F (425
to 525°C) for each barrel of oil generated, and the heat supplied
must be of relatively high quality to reach retorting temperature.
Once the reaction is complete, recovering sensible heat from the hot
rock is very desirable for optimum process economics. This leads to
three areas where new technology could improve the economics of
oil recovery:
1. Recovering heat from the spent shale.
2. Disposal of spent shale, especially if the shale is discharged at temperatures where the char can catch fire
in the air.
3. Concurrent generation of large volumes of carbon
dioxide.
The heat recovery from hot solids is generally not efficient, unless
it is in the area of fluidized bed technology. However, to apply fluidized bed technology to oil shale would require grinding the shale