Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates generally to the recovery of hydro-
carbons from sources not commercially exploited at present, and more parti-
cularly to a novel apparatus and method for recovering hydrocarbons such as
gasoline, diesel fuel, fuel oil, and lubricants from oil shale and tar sand.
Oil shale is broadly defined as a fine-grained, compact sedimentary
rock, generally laminated and containing an organic, high-molecular-weight
mineraloid called kerogen. The organic matter of oil shales is presently in
amounts ranging from a trace to 40% by weight. The analysis of oil shale
from Colorado shows that it contains as much as 10.6% oil, 0.7% water, 2.1%
gas, and 86.6% spent shale.
Where the deposits of oil shale are close to the surface, modern
surface mining techniques can be used. These in~lude stripping the overbur-
den with drag line or bucket-wheel excavators, and drilling and shooting the
exposed oil shale to loosen it so that it can be loaded by large shovels
either into trucks or onto conveyor belts for transportation to the retorting
plant.
Where the deposits are hundreds of feet underground, the material
can be mined in the same manner as mineral ores or coal with the sinking of
shafts and the construction of laterals.
The present invention avoids the ~iw~ disadvantages of the prior
art and provides the me~hod of recovering hydrocarbons from oil shale or
tar sand which includes the steps of: moving a fluidized mass of oil shale
or tar sand through a pipe maintained at a temperature of about 1100F. for
a time sufficient to vaporize hydrocarbons in said oil shale or tar sand;
and withdrawing the vaporized hydrocarbons from said pipe adjacent the out-
let end thereof.
According to one aspect I have discovered that fuel oil and fuel
gas can be -o~tained from oil shale or tar sand by adding to chunks of such
substances an amount of diesel fuel oil sufficient to form a slurry or to
fluidize the mass for movement through a pipe which is embedded in a molten
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salt bath maintained at a temperature of about 1100F., and witW rawing vo-
latilized hydrocarbons from adjacent the end of the pipe and recovering the
sameJ whereby the solid material which exits from the end of the pipe con-
sists essentially of spent shale or sand.
An embodiment of the invention is illustrated in the drawing which
is a schematic elevational view, in the nature of a flow diagram, illustrat-
ing apparatus for practicing the teachings of the present invention.
In the drawing a mixer 10 for fluidizing the oil shale or tar
sand, includes a vessel 12 having an inlet 14 at the upper end thereof, two
rows of counter-rotating mixing paddles 16 driven by an electric motor 18,
and a screw conveyor 20, at the bottom of the vessel, driven by a second
electric motor 22.
Positioned above the inlet 14 are an endless conveyor 24 for carry-
ing chunks or discrete pieces 26 of oil shale or tar sand, usually about 4
inches to 6 inches in diameter, to the inlet of the vessel, and a pipe 28
for admitting a liquid hydrocarbon such as diesel fuel oil into the vessel
to be intermixed with the solids.
Because the oil shale is relatively hard and rigidJ the diesel fuel
oil functions as a "carrier" to assist in the movement of the material through
the pipes in the retorts. HoweverJ as to the tar sandJ I have discovered
that the use of a sufficient amount of diesel fuel oil to saturate the tar
sand will cause the chunks of sand to disintegrateJ and the rate of disinte-
gration can be greatly increased by the further addition of from about 6%
to 1O%J by volume, of a chlorinated aromatic solvent such as ethylene dichlo-
ride.
As will be discussed more fully hereinafter, both the diesel fuel
oil and the solvent are recovered during the extraction process, and can be
reused.
An outlet pipe 30 extends from the vessel 12 and connects with a
steel pipe 31 which extends through a first enclosed retort 32 which has an
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exhaust vent 34 at the top thereof. The retort contains a salt bath 36
which will be described more fully hereinafter, and which is preferably heated
by means of a gas burner 38, said salt bath being in heat-exchange relationship
-. with the pipe 31. The temperature of the molten salt bath in the first retort
is about 625 F.
Interconnecting the pipe 31 with a second retort 40 is a connecting
conduit 42 to which is connected~a vacuum pump 44 for removing volatilized
hydrocarbons which have been driven out of the oil shale or tar sand by the
heat in the first retort.
As with the first retort, the second retort 40 contains an exhaust
vent 46, a salt bath 48, and is also preferably heated with a gas burner 50.
The temperature of the salt bath in the second retort is maintained at about
1100 F.
Extending through the second retort in heat-exchange relationship
with the salt bath is a steel pipe 52 which connects with a second conduit
54 which also contains a vacuum pump 56 for withdrawing the remainder of the
volatilized hydrocarbons from the shale or sand. The screw conveyor 20 ex-
tends through the pipes and conduits 30, 31, 42, 52 and 54, whereby the solids
58, which aresspent shale or sand, exit from the conduit 54 onto a conveyor
60 for transmission to a disposal area.
Although two retorts and two vacuum pumps are shown, it is to be
understood that additional retorts and vacuum pumps can be used, as where it
is desirable to withdraw the vaporized hydrocarbons at moTe frequent tempera-
ture intervals . . . much in the same manner as with a conventional "cracking"
tower. Also, inasmuch as one of the products obtained from the oil shale or
tar sand is fuel gas, such gas can be used in the burners 3~ and 50 once the
system has been brought up to operating range.
Returning to a consideration of the salt bath, I have discovered
that salts of the type which are used for the tempering and heat treating of
cutting tools, are ideally suited for a molten salt bath for heating the
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fluidized oil shale or tar sand as it passes through the pipes within the
retorts. Such a salt bath is relatively stable and clean, with very little
losses which are exhausted through the vents 34 and 46. For the method des-
cribed herein, the preferred salt is one which has a melting point of about
600F. and a working range between 625F. and 1100F. In general, these
salts are nitrate andlor nitrate mixtures.
A salt which I have successfully used is Tempering-Salt No. 460,
obtained from Payne Chemical Corporation, Pasadena, California, which salt
has a melting point of 430F., and a working range between 460F. and 1100F.
This salt has a weight of 100 pounds per cubic foot at 1000F., and an ap-
proximate analysis as follows:
Sulphates None
Nitrites None
Nitrates 64.7%
Carbonates None
Chlorides .13%
Alkaline earth oxides None
Silica None
Fluorides None
Moisture .18%
~ater Insoluable None
pH of 1% Solution 6.9%
Clear liquid 445 F.
Melting Point 430 F.
Another acceptable salt is Payne Chemical Corp. Tempering No. 3-11
which melts at 285F. and has a working range of 300F. to 1100F.
As illustrated in the drawing, the chunks 26 of oil shale or tar
sand, usually about 4 inches to 6 inches in diameter, are carried by the
conveyor 24 into the inlet 14 of the vessel 12. At the same time, diesel
fuel oil enters the inlet 14 through the pipe 28. As previously described,
when tar sand is being processed, it is advantageous to use a chlorinated
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aromatic solvent such as ethylene dichloride with the diesel oil, to increase
the rate of disintegration of the lumps of tar sand.
The screw conveyor 20 at the bottom of the vessel 12, moves the
fluidized mass of oil shale or tar sand through the pipe 31 which is embedded
in the molten salt bath 36 maintained at a temperature of about 625F. This
temperature causes the volatilization of some hydrocarbons contained in the
oil shale or tar sand, which hydrocarbons are drawn off through the vacuum
pump 44. The oil shale or tar sand then continues to be moved through the
pipe 52 in the second retort 40, where the molten salt bath is maintained at
a temperature of about 1100F. Here again, additional hydrocarbons are vo-
latilized and are removed by means of the vacuum pump 56. I have discovered
that by using two or more such retorts with a maximum temperature of 1100F.,
substantially all of the hydrocarbons are vaporized from both the oil shale
or tar sand and the fluidizing liquid such as diesel fuel oil, such that the
only remaining solid material 58 is clean ash or sand. If desired, addition-
al retorts and vacuum pumps can be used, with the retorts operating at in-
termediate temperatures, whereby the hydrocarbons can be removed at different
stages, much in the same manner as with a "cracking" tower.
Thus, it is apparent that there has been provided a novel apparatus
and method for the efficient recovery of hydrocarbons from oil shale and tar
sand without polluting the atmosphere, and which fulfills all of the objects
and advantages sought therefor.
