Note: Descriptions are shown in the official language in which they were submitted.
CA 02449464 2003-11-14
PROCESS AND APPARATUS FOR GENERATING
HYDROGEN FROM OIL SHALE
BACKGROUND OF THE fNVENTION
The Field of the Invention.
The present invention relates generally to hydrogen production, and
more particularly, but not necessarily entirely, to a process and apparatus
for
producing hydrogen from oil shale.
Descr~tion of Related Art.
The concept of releasing oil from oil shale is well known. "Oil shale" is
a naturally occurring sedimentary rock, typically a black or dark brown shale
or silt-stone, that is rich in petroleum hydrocarbons, and other materials
generally associated with the definition of the broad term "petroleum,"
"kerogen" or "bitumen," from which shale oil can be obtained. The shale oil is
produced from the petroleum hydrocarbons, and released from the shale,
through pyrolysis, which refers to the subjection of the oil shale to very
high
temperatures. The petroleum hydrocarbons are released initially in gaseous
form. After being cooled they are bituminous-like in form, as they will not
flow
unless heated to about 400 degrees or more.
Producing commercial quantities of oil from oil shale remains cost
prohibitive. The world continues to procure fuel oil by pumping crude oil from
natural reserves, and refining the crude. Rapid increases in the price of
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crude oil, and the continued depletion of our natural oil reserves, may change
that.
Large quantities of oil shale reside throughout the world. In the United
States, substantial oil shale deposits are found in Colorado, Utah, Wyoming
and Texas. The usual process of releasing oil from the oil shale, though it
has been cost prohibitive from a commercial standpoint, comprises mining
the shale, crushing it, and conducting pyrolysis by subjecting the crushed
shale to heat at temperatures of 1000 degrees F - 1400 degrees F. The
pyrolysis phase is conducted in the farm of "destructive distillation," a
process
by which organic substances such as oil shale, wood or coal are
decomposed by heat in the absence of air and distilled to produce useful
products, in this case, oils. Other products such as coke, charcoal and gases
are also the result of destructive distillation.
The liberation of oil from the oil shale by destructive distillation causes
considerable coking of the oil shale residue, leaving behind a "retorted oil
shale." The term "coking" refers to the production of coke; which is the solid
residue of impure carbon obtained from carbonaceous materials such as oil
shale, bituminous coal and the like, after removal of volatile material by
destructive distillation.
The phrase "retorted oil shale," as used herein, is a form of cake, and
refers to oil shale that has been subjected to destructive distillation to
liberate
the petroleum hydrocarbons, or oils, leaving an inorganic residue containing
carbon. Therefore, the phrases "retorted oil shale," "carbon residue," and
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"carbon containing material," as used herein, are related in meaning, and as
used herein, are interchangeable.
The phrase "spent oil shale," as used herein, refers to oil shale from
which petroleum hydrocarbons and carbon have been removed.
The term "fluid," as used herein, shall refer broadly to both liquids and
gases.
Attempts have been made in the prior art to improve upon the process
of liberating oil from oil shale. Many such attempts are described in the
following U:S. patents, which are incorporated herein by reference: 4,028,222
(granted June 7, 1977 to Prull); 3,503,868 (granted March 31, 1970 to
Shields); 4,548,702 (granted October 22, 1985 to York et al.); 4,536,278
(granted August 20, 1985 to Tatterson et al.); 4,505,809 (granted March 19,
1985 to Brunner et al.); 4,304,656 (granted December 8, 1981 to Lee);
3,652,447 (granted March 28, 1972 to Yant); 3,941,423 (granted March 2,
1976 to Garte); and 4,357,231 (granted November 2, 1982 to Estes et al.).
It is noteworthy that none of the prior art known to applicant provides
an apparatus or method that optimizes the use of heat, and the reactants in
the combustion cycle, in a more efficient manner. There is a long felt need
for a destructive distillation process applicable to oil shale that is capable
of
{i) employing a recurring combustion/reaction cycle for a longer period of
time
by minimizing the presence of nonessential gases, (ii) recovering unused
heat instead of permitting the heat to escape into atmosphere, and (iii)
reusing and regenerating some of the reactants in the process.
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Moreover, there is an increasing need for hydrogen for various uses
such as in fuel cells. Fuel cells are electrochemical cells in which the
energy
of a reaction between a fuel, such as hydrogen, and an oxidant, such as
oxygen, is converted directly and continuously into electrical energy. When
hydrogen and oxygen react in a fuel cell, water is produced rather than the
various pollutants that are generated in combustion of hydrocarbons.
Accordingly, fuel cells are increasingly being used for power generation in
both stationary and transportation applications to take advantage of the
environmental benefits of fuel cells. It would therefore be an advancement in
the prior art to provide a process for extracting hydrogen from oil shale.
The prior art is thus characterized by several disadvantages, or long-
felt needs, that are addressed by the present invention. The present
invention minimizes, and in some aspects eliminates, the above-mentioned
failures, and other problems, by utilizing the methods and structural features
described herein.
BRIEF DESCRIPTION OF THE DRAWINGS
The features and advantages of the invention will become apparent
from a consideration of the subsequent detailed description presented in
connection with the accompanying drawings in ~nrhich:
FIG. 1 is a schematic view of an apparatus for extracting oil from oil
shale, made in accordance with the principles of the present invention;
FIG. 2 is a schematic view of an apparatus for producing hydrogen;
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FIG. 3 is a schematic view of an alternative apparatus for producing
hydrogen.
DETAILED DESCRIPTION OF THE INVENTION
For the purposes of promoting an understanding of the principles in
accordance with the invention, reference will now be made to the
embodiments illustrated in the drawings and specific language will be used to
describe the same. It will nevertheless be understood that no limitation of
the
scope of the invention is thereby intended. Any alterations and further
modifications of the inventive features illustrated herein, and any additional
applications of the principles of the invention as illustrated herein, which
would normally occur to one skilled in the relevant art and having possession
of this disclosure, are to be considered within the scope of the invention
claimed.
Applicant has discovered that oil can be produced from oil shale more
efficiently by using a relatively sealed combustion and reaction process,
recovering and reusing heat, and by regenerating most, if not all, of the
reactants in the combustion process. Furthermore, useable carbon monoxide
can be produced or regenerated effectively, for use as a utility gas.
Referring now to F1G. 1, there is shown a schematic view of an
apparatus for reducing oil shale into useable oil, carbon monoxide, calcites,
and limes, the apparatus being designated generally at 10. The operation of
the apparatus 10 will first be described briefly in terms of its key, basic
features, after which mare detail pertaining to those features will be
provided.
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The apparatus 10 includes a combustion chamber 12, which may also
be referred to herein as a "combustian and regeneration chamber 12." The
combustion chamber 12 is preferably a rotary kiln, such as a rotating
pyrolysis drum retort, but may alternatively comprise any suitable retort such
as a static mixer retort, a gravity flow retort, a fluid bed retort, a screw
conveyor retort, or some other type of retort useable in accordance with the
principles of the invention. The combustion chamber 12 preferably includes a
combustion zone 14, a gas generation zone 16, and a destructive distillation
zone 18.
A crushed shale source 20 preferably comprises a hopper 20a and an
auger conveyor 20b, for transporting crushed oil shale from the hopper 20a
into the destructive distillation zone 18 of the combustion chamber 12.
A movement path 22 is disposed in communication with the
combustion chamber 12. The path 22 is preferably a pipe or some suitable
conduit capable of transporting fluids. The movement path 22 preferably
extends from the combustion chamber 12 to a particle separator 24, then to a
blower 26, then to a heat exchanger 28, at which point the path 22 preferably
separates into a heavy oil path 22a, which preferably extends from the heat
exchanger 28 back to the combustion and regeneration chamber 12, and a
cooled effluent gas path 22b, which preferably extends from the heat
exchanger 28 to a fractional separator 40. The fractional separator 40 is
preferably a fractional distillation tower. A light gas path 22c preferably
extends from the fractional distillation tower 40 to a gas storage tank 60 and
to the heat exchanger 28, by operation of a control valve 62 as shown. The
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light gas path 22c is preferably routed through the heat exchanger 28 then
preferably back into the combustian zone 14 of the combustion chamber 12.
Discharge lines 68 and 70 extend from the combustion chamber 12.
In operation, relatively pure oxygen (02), and carbon monoxide (CO),
are transported into the combustion zone 14 of the combustion chamber 12
by supply lines 64 and 66, respectively, and the flow of said gases is
controlled by valves 64a and 66a, respectively. The relatively pure oxygen
and the carbon monoxide are combusted in the combustion zone 14 to form
carbon dioxide (C02), and the combustion is preferably controlled to produce
heat having a temperature of at least 1200 degrees F (Fahrenheit). At the
same time, crushed oil shale is transported into fihe destructive distillation
zone 18 of the combustion chamber 12.
The combustion so described, along with the supply of crushed oil
shale into the destructive distillation zone 18, causes simultaneous reactions
within the combustion chamber 12 as part of a recurring combustionlreaction
cycle, in which the heat of the combustion breaks down the crushed oil shale
to release the petroleum hydrocarbons contained in the shale, leaving
retorted oil shale containing carbon residue which is exposed to the carbon
dioxide to react and regenerate a carbon monoxide product, leaving spent oil
shale, preferably to be discharged as a calcite (CaC03) or as a calcium oxide
lime (Ca0) (depending upon the temperatures present in the chamber 12,
and in particular in the destructive distillation zone 18) from discharge
lines
68 and 70 extending from the combustion chamber 12. The heat of the
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combustion releases other volatile gases from the crushed oil shale, along
with the petroleum hydrocarbons.
The released petroleum hydrocarbons, other volatile gases, and the
carbon monoxide product, are transported from the combustion chamber 12
along the movement path 22 through the particle separator 24, which
removes particulates from the gaseous stream. When the petroleum
hydrocarbons and the carbon monoxide product reach the heat exchanger
28, the heat exchanger withdraws heat from them and transfers that heat to
re-routed carbon monoxide product and other light gases travelling along
light gas path 22c as shown.
In the heat exchanger 28, a "higher temperature" cooling is made, or a
"partial cooling," by removing some, but not all, of the heat from the
released
petroleum hydrocarbons, carbon monoxide by-product, and other volatile
gases. It is preferable to transport only the lighter gases to the fractional
distillation tower 40, and since the heaviest gases condense first at higher
temperatures than the condensation point of the lighter gases, the heat
exchanger 28 and associated controls are adapted to remove enough heat
from the gases to cause the heavier gases to condense yet still maintain the
lighter gases in gaseous form. As illustrated schematically in FIG. 1, the
lighter gases and carbon monoxide being re-routed slang light gas path 22c
operate to absorb heat from the hot gases flowing along movement path 22.
There is accordingly a limit to how much heat can be transferred, and if it is
desired to remove more heat from the hot gases flowing along movement
path 22 that the lighter gases from along light gas path 22c are capable of
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removing, a coolant may be required, such as water or any suitable cooling
compound, in order to remove more of the heat. It is also to be understood
that a user of the apparatus 10 may choose to cool the gases sufficiently to
cause not only the heavier gases to condense, but also some of the lighter
hydrocarbons as well, and pass them back to the combustion chamber 12 in
condensed form along the heavy oil path 22a to break them down further
through heat-cracking (defined below).
The heaviest gases condense into a heavy oil that is transported from
the heat exchanger 28 along the heavy oil path 22a back into the combustion
chamber, preferably at or near the combustion zone 14, in order to reheat
and "crack" the heavy oil as the term "crack" is understood in the field to
refer
to the breaking down of heavy oil into carbons and lighter hydrocarbons. The
lighter hydrocarbons produced by "cracking" the heavy oil may be produced
in gaseous or liquid form, depending on the circumstances. The lighter
petroleum hydrocarbons, along with the regenerated carbon monoxide by-
product, are passed from the heat exchanger 28 along the cooled effluent
gas path 22b, still in gaseous form, to the fractional separator 40 to undergo
"lower temperature cooling" than is accomplished in the heat exchanger 28.
The light petroleum hydrocarbons are thereby cooled and processed into
useable oils as petroleum products, by any suitable manner known to those
skilled in the art of oil processing by a fractional distillation tower.
Accordingly, in the fractional distillation tower 40, cooled effluent gas
transported to the tower 40 along the path 22b, is cooled even more in the
tower 40, and separated into fractions of light hydrocarbon gases (along with
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the regenerated carbon monoxide by-product), light shale oil, and middle
shale oil, the oils being separable in a range of several different densities.
The fractions of light and middle shale oils are discharged from the tower 40
through lines 42, 44, 46, 48, 50, 52, 54, 56, and 58, in accordance with their
decreasing densities, respectively. Accordingly, the heavier shale oils are
generally discharged from the lower lines 42, 44, 46, 48 and 50, for example,
and the lighter shale oils are generally discharged from the higher lines 52,
54, 56 and 58. The fractions of Light hydrocarbon gases, and the carbon
monoxide by-product, are discharged into light gas path 22c, which
preferably extends from the tower 40 to a gas storage tank 60 and to the heat
exchanger 28, by operation of a control valve 62 as shown. The light
hydrocarbon gases and the carbon monoxide by-product may be transported
from the storage tank 60, or directly from the fight gas path 22c, as a
utility
gas for other commercial purposes in other industries.
The exposure of retorted oil shale to heated carbon dioxide in the
combustion chamber 12 operates to utilize the retorted oil shale as a carbon
source for regenerating carbon monoxide as described above. However,
although oil shale is the preferred material for use in the inventive
processes
described herein, the phrase "carbon source" as used herein shall refer
broadly to any carbon containing material capable of reacting with carbon
dioxide to produce carbon monoxide. Some examples of a carbon source
include oil shale, retorted oil shale, tar sand, retorted tar sand; coal,
lignite,
municipal waste, forest underbrush and the like.
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Those having ordinary skill in the art will recognize that other carbon
containing materials could also operate as a "carbon source" under the above
definition, Therefore, the phrase "carbon source" as used herein is limited
only by functionality, and is in reference to any carbon containing material
that can react with carbon dioxide to form carbon monoxide, including the
specific examples fisted above and any others not listed but that are capable
of functioning in the manner described.
The cycle of simultaneous combustion and reaction occurring in the
different zones 14, 16 and 18 in the combustion chamber 12 as described
above, can be represented stoichiometrically as follows:
(1 ) (oxidation) 2C0 + 02 ----> 2C02 +-135,200 calories per unit of
~2
(2) (reduction) 2C02 + 2C ---> 4C0 -81,600 calories per unit of
original OZ from reaction (1 ).
Total heatlenergy produced: +53,600 calories per unit of
original 02 from reaction (1 ).
It is seen from the above that reaction (1 ) is exothermic, while reaction
(2) is endothermic. Reaction (2) assumes that there is a sufficient amount of
carbon (C) to react with all of the carbon dioxide (C02) produced in reaction
(1 ), in which case it is noted that the amount of the carbon monoxide by-
product of reaction (2) would be twice the amount of carbon monoxide
supplied originally as part of reaction (1 ) above. Of course, if a lesser
amount of carbon (C) is supplied to the combustion chamber 12, then the
proportions represented above would be different.
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The total energy exhausted by the two-step combustion reaction cycla
above amounts to +53,600 calories per unit of oxygen (Oz), which is the result
of the +135,200 calories per unit of oxygen (OZ) produce from the exothermic
reaction (1 ) above, reduced by the -81,600 calories per unit of OZ that is
absorbed by the endothermic reaction (2).
The prior art combustion methods used in the destructive distillation of
oil shale have utilized the combustion of carbon (C) and oxygen (02) in the
ambient air. Carbon that is combusted with ambient air combusts at a much
lower temperature than the combustion of carbon monoxide (CO) with
relatively pure oxygen (02) as utilized in accordance with the principles of
the
present invention. The prior art combustion reaction is illustrated as
follows:
C + 02 (from ambient air) -----> COZ -94,400 calories per unit 02 in
air
It will be appreciated, by those having ordinary skill in the art; that the
+135,200 calories per unit of oxygen (OZ) produced by burning carbon
monoxide is a much higher heat of combustion than the +94,400 calories per
unit of oxygen (OZ) (from ambient air) produced by the prior art combustion
reaction above. Applicant prefers to utilize the excess heat by absorbing it
directly into the endothermic follow-up reaction (2) above by heating the oil
shale to regenerate carbon monoxide (CO) and caicining the calcite in the
retorted oil shale residing in the destructive distillation zone 18, without
using
a heat-transferring medium and the related heat-loss inefficiencies thereof,
to
regenerate the carbon monoxide (CO) product. Accordingly, the "hot carbon
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dioxide" (C02) produced by reaction (1 ) above is a necessary part of one
aspect of the invention.
Applicant discovered the benefit of combusting carbon monoxide (CO)
with pure oxygen because that reaction combusts at a higher temperature
than carbon (C) combusts with ambient air or which oxygen in an excessive
carbonous environment, and combustion of carbon monoxide with pure
oxygen thus liberates more heat per unit of oxygen (02) consumed than does
carbon (C), and because the carbon dioxide (C02) by-product can be used to
regenerate carbon monoxide (CO) while consuming the carbon residue
normally remaining as retorted oil shale. The purpose of this approach is to
recover the heat of combustion as well as to produce carbon monoxide. The
process is efficient and excess heat is put to good use by the follow-up
reaction (2) above. The prior art processes are disadvantageous because
they operate the combustion phase at some location remote from the heat
chamber in which the oil shale is transported, the heat of combustion being
transmitted to the oii shale by a heat transferring medium through a conduit,
which is less efficient and causes heat to be lost.
Further, it will be appreciated that it is in accordance with the
principles of the present invention to utilize the apparatus 10 (or portians
equivalent to it) to produce carbon monoxide regardless of whether useable
oil is also produced. For example, carbon monoxide may be produced,
without producing oil, by supplying coal and an alternative source of carbon
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dioxide' into the combustion chamber. For example, by using dolomite
(CaMg(C03)2) as the alternative source of carbon monoxide, when subjected
to the high temperatures in the combustion chamber 12 the dolomite would
release carbon dioxide, and that carbon dioxide would react with carbon
contained by the coal, as would the carbon dioxide produced by the
combustion of carbon monoxide and oxygen, to~ produce carbon monoxide.
The alternative source of carbon dioxide would be used as an energy-
balancing imperative (just as the calcite in the oil shale is used), in that
some
of the heat energy produced by the combustion would be absorbed by the
dolomite by heating the dolomite to release the carbon dioxide and causing
that carbon dioxide product to react with the carbon contained in the coal.
It is thus within the scope of the present invention to regenerate
carbon monoxide in any suitable manner desired. For example, a method of
generating carbon monoxide in accordance with the principles of the present
invention, in a most basic form, could involve the following part:
(a) reacting a hot carbon dioxide with a carbon source to thereby
produce carbon monoxide.
A method of regenerating carbon monoxide in accordance with the
principles of the present invention could involve the following parts:
(a) combusting axygen and a first source of carbon monoxide to
thereby form a hot carbon dioxide by-product; and
Any suitable alternative source of carbon dioxide may be utilized, such as by
directly supplying relatively pure carbon dioxide, or by utilizing carbon
dioxide
that is released in a chemical reaction as is knovvn in conjunction with
dolomite (CaMg(C03)2).
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(b) conveying the hot carbon dioxide by-product into contact with a
carbon source within a reaction chamber, wherein said hot carbon dioxide
reacts with said carbon source to regenerate a carbon monoxide by-product.
The method above may be further augmented with the following part:
(c) transporting the carbon monoxide to a storage tank or to a work site
for use in a process at said work site.
The method above may be still further augmented, wherein part (b)
further comprises producing a carbon monoxide by-product that is
approximately twice the volume of carbon monoxide utilized in the
combusting of carbon monoxide from said first source of carbon monoxide in
part {a).
The method above may be still further augmented, wherein part (a}
further comprises combusting relatively pure oxygen and a first source of
carbon monoxide to thereby form the hot carbon dioxide by-product.
The method above may be additionally augmented, wherein the
carbon source of part (b} comprises coal.
It is to be understood that the phrase "conveying the hat carbon
dioxide by-product into contact with a carbon source within a reaction
chamber," in part (b) of the method above, could be accomplished by the
apparatus 10, or any suitable modification thereof. For example, the
combustion of carbon monoxide and relatively pure oxygen could be
accomplished at some location separate and remote from the chamber 12,
and the hot carbon dioxide by-product thereafter conveyed into the chamber
12, making it essentially a reaction chamber and not a combustion chamber.
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As noted herein previously, the combustion (reaction (1 ) above) is
preferably controlled to produce heat having a temperature of at Least 1200
degrees F (Fahrenheit). It will be appreciated that the actual temperature of
the combustion, and of the carbon dioxide (C02) by-product, can be
controlled despite the heat energy being produced by the combustion, simply
by controlling the amount of carbon monoxide (CO) supplied for the
combustion step (1 ), because combustion requires oxygen (OZ) and the
amount of carbon monoxide that can be burned i'n a reaction with oxygen is
thus limited by the amount of oxygen present.
Accordingly, if more carbon monoxide is supplied to the combustion
chamber 12 than can react with the amount of the oxygen that is supplied,
part of the carbon monoxide will remain unreacted and will therefore not burn.
Therefore, if a sufficiently larger amount of carbon monoxide is supplied, it
will remain at its lower, unreacted temperature to thereby "dilute" the
temperature of the heat of the combustion. Accordingly, the overall
temperature inside the reaction chamber 12, at the combustion zone 14 and
elsewhere, can be reduced by increasing the amount or rate of carbon
monoxide being supplied, and vice versa.
More specifically, one aspect of the invention is to reduce the
temperature of the combustion zone 14 by increasing the carbon monoxide
supply rate relative to the oxygen supply rate, or alternatively by decreasing
the oxygen supply rate. Another aspect of the invention is to increase the
temperature of the combustion zone 14 by reducing the carbon monoxide
supply rate relative to the oxygen supply rate, or by increasing the oxygen
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supply rate. Accordingly, users have the option to increase or decrease the
temperature, and total heat usage, of the apparatus 10, in these manners.
It was mentioned above that spent oil shale is preferably discharged
from the combustion chamber 12 as a calcite (CaC03) or as a calcium oxide
lime (Ca0) from discharge lines 68 and 70 extending from the combustion
chamber 12, depending upon the temperatures present in the chamber 12,
and in particular in the destructive distillation zone 18. More specifically,
it is
noted that calcites can be produced as part of the combustion step, if the
temperature within the combustion chamber is maintained low enough. It is
presently understood by applicant that exposing oil shale to a high-
temperature heat that is less than 1648 degrees F, at standard atmospheric
pressure, will reduce the oil shale to a calcite. A further aspect of the
invention, in accordance with applicant's present understanding, is that the
oil
shale will be transformed to a caicium'oxide time product if the temperature
maintained in the destructive distillation zone 18 is greater than 1648
degrees F, at standard atmospheric pressure. Controlling the temperatures
present within the combustion chamber 12, therefore, is an important aspect
of the present invention in choosing whether to transform the spent oil shale
into a calcite or a calcium oxide lime. The calcite or the calcium oxide lime
can be put to many constructive, industrial uses, such as in producing
cement.
In accordance with the features and combinations described above, a
preferred method of extracting oil from oil shale includes the following
parts:
(a) producing combustion within a combustion chamber;
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(b) transporting oil shale into the combustion chamber; and
(c) heating the oil shale by exposing it directly to the heat from the
products of the combustion, without aid of an intervening heat-transferring
medium, to thereby heat the oil shale to a temperature sufficient to release
oil
therefrom.
The phrase "without aid of an intervening heat-transferring medium"
shall refer broadly to the concept of exposing the oil shale to the heat
produced by the combustion of oxygen and carbon monoxide and to hot
carbon dioxide which is the product of that combustion, without an intervening
element operating to (i) withdraw heat from the combusting gases and (ii)
either dispense the heat to the oil shale or transport heated gases from a
combustion chamber to a retort chamber. It is to be understood that although
the gases produced by the combustion phase of the present invention serve
to transport heat within the chamber 12, said gases would not constitute an
"intervening heat-transferring medium" relative to the combustion or the oil
shale, as that phrase is intended, because those gases are either part of the
combustion itself or are a product of the combustion.
An example of an "intervening heat-transferring medium" would include
the use of a solid heat-carrying material, such as spent oil shale, spent
dried
sludge, clay pellets, or metal pellets, which are heated and then moved into
contact with oil shale (preferably by conveying the heat-carrying material
through a heat carrier line at high temperatures and discharged from the line
into the chamber containing the oil shale). Another example would be a heat
carrier line itself, separate from the retort chamber, for conveying a heat
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carrier (whether the heat carrier is a solid or a gas) from a combustion
chamber to a separate retort chamber, in which a primary purpose of the hne
is simply to transport the heat carrier for communication with the oil shale.
The use of an intervening heat-transferring medium is described, for
example, in U.S. Patent No. 4,670,104 (granted June 2, 1987 to Taylor),
which is incorporated herein by reference.
Referring now to FIG. 2, there is shown a schematic view of an
apparatus, designated generally at 110; for producing hydrogen. It will be
appreciated that the depiction in FIG. 2 is schematic in nature, and is
therefore not intended to depict the apparatus 110 in detail. As previously
discussed, the present embodiments of the invention illustrated herein are
merely exemplary of the possible embodiments of the invention, including
that illustrated in FIG. 2. It will be appreciated that the hydrogen producing
apparatus 110 may be used in combination with the oil shale reduction
apparatus 10, as excess carbon monoxide produced from the oil shale
reduction apparatus 10 may be used with the hydrogen producing apparatus
110. The carbon monoxide may be diverted from valve 62 of the oil shale
reduction apparatus 10 for use with the hydrogen producing apparatus 110.
It will also be understood that the hydrogen producing apparatus 110 may be
used without any connection to the oil shale reduction apparatus 10.
The hydrogen producing apparatus 110 may include a hydrogen
producing combustion chamber 112, also sometimes referred to herein as a
reaction chamber. The chamber 112 may be formed in a similar manner as
the combustion chamber 12 discussed above. For example the chamber 112
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may include a rotary kiln, such as a rotating pyrolysis drum retort, a static
mixer retort, a gravity flow retort, a fluid bed retort, a screw conveyor
retort, or
some other type of retort useable in accordance with the pririciples of the
invention. The chamber 112 may include a first zone 114, a second zone
116, and a third zone 118.
Reactions and phenomena occurring in the different zones 114, 116
and 118 in the chamber 112, and in other portions of the hydrogen producing
apparatus 110 can be represented stoichiometrically as follows:
(1a) 200 + Oz ----> 2002 +135,200 calorieslmole;
(1b) COZ + C ----> 200 -40,800 calorieslmole;
(2a) 2H2 + 02 ----> 2H20 +115,600 calorieslmole;
(2b) H20 + C ----> HZ + CO -31,400 calorieslmole;
(3) CnH~2n+2~ ----> C~ + H~2~+2~ - approximately 5,000 calories per n, where n
is an integer;
(4) C~H~Zn+Za (solid) + Heat ----> vapor C~H~Zn+a>;
(5) OZ at ambient temperature ----> 02 superheated;
(6) H20 ----> superheated H20;
(7) CO + HZO + catalyst ----> COZ + H2.
The general location where each of the above reactions takes place is
indicated by the corresponding reaction numbers in FIG. 2. It will be
understood that the heat of reaction values indicated above are approximate
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values for illustrative purposes only, and that other heat of reaction values
may occur within the scope of the present invention.
The apparatus 110 may also include an input hopper 120, for loading
an input, such as oil shale, into the chamber 112 near the third zone 118.
The oil shale may be crushed, for example, into particles ranging from 0 to 25
millimeters, and carried to the chamber 112 using sealed conveyance means
121.
The chamber 112 may be operated by placing input such as oil shale
in the input hopper 120. The oil shale may enter the third zone 118 of the
chamber 112 where the temperature may range from a low of between
approximately 300-400 degrees F up to approximately 800 degrees F. The
oil shale may then travel through the chamber 112 from the third zone 118 to
the second zone 116 to the first zone 114. The temperatures in the second
zone 116 may range from approximately 800 degrees F adjacent to the third
zone 118 up to approximately 1100 degrees F adjacent to the first zone 114.
The first zone 114 may have temperatures ranging from between
approximately 1100 degrees F near the second zone 116 to approximately
1800 degrees F at the end of the first zone 114 opposite the second zone
116. It will be appreciated that other temperatures may be used in the
chamber 112 within the scope of the present invention.
Carbon monoxide may be introduced into the first zone 114 of the
chamber 112 through a carbon monoxide line 122. As discussed above, the
carbon monoxide may be supplied from the valve 62 of the shale reduction
apparatus 10, or from any other source within the scope of the present
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invention. The oil shale in the chamber 112 may be heated from the
combustion of carbon monoxide along with minimal amounts of hydrogen and
with oxygen which originates in the first zone 114 of the chamber 112. The
heat that is derived from reactions 1 a and 2a may be conveyed from the first
zone 114 to the third zone 118 by means of gases that may be generated
through a series of reactions that occur in the first zone 114 and the second
zone 116. The hydrocarbons in the shale may be heated by the sensible
heat in these gases, which flows countercurrent to the shale, transferring
sufficient heat to vaporize the hydrocarbons completely before the shale
passes downward to the first zone 114. This is characterize by reaction 4.
These vapors may be drawn off from the upper end of the third zone 118
through a first gas re-circulation line 140. Also, spent heat conveying gases,
mainly hydrogen and carbon monoxide, may be directed through the first gas
re-circulation line 140 by means of a first blower 142. The gases may be
transferred to the lower end of the second zone 116 through the first gas re-
circulation line 140. As the gases and hydrocarbon vapor discharge from the
first gas re-circulation line 140 and enter the second zone 116 they may be
meet with a blast of super hot gases from the first zone 114. These gases
may heat the hydrocarbon vapor above a temperature for which it may be
decomposed into free hydrogen and carbon. This reaction, R3, may absorb
about 5,000 caIICH2 and similarly about 5,000 calories for each segment of
the chain of the molecular structure, in compounds of the methane series of
hydrocarbons. The carbon may precipitate forming a coke coating on the
shale as it tumbles along the chamber 112. The hydrogen may be re-
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circulated with the carbon monoxide through the third zone 118, conveying
more sensible heat to vaporize the hydrocarbons. A portion of the hydrogen
may also be withdrawn through ports in the shell of the chamber 112 into an
effluent gas output line or path 148. These gases may be at an appropriate
temperature to be further processed down stream. This process is described
in greater detail below.
The shale may be allowed to tumble downward in the chamber 112
into the first zone 114. Here the carbonized shale may be buffeted by the
gases from reactions 1 a and 2a from the combustion of the gases
recirculating through a second gas re-circulation line 144. The second gas
re-circulation line 144 may be used to direct gas., including carbon monoxide,
from the junction between the first zone 114 and the second zone 116 to the
opposite end of the first zone 114. A second blower 146 may be positioned
on the second gas re-circulation line 144 to force the flow of gas in the
desired direction.
Super heated oxygen may be injected into the first zone 114 from an
oxygen pre-heater 128. The flow of oxygen may be controlled by an oxygen
valve 132. The oxygen may ascend upward through hot descending spent
shale in the oxygen pre-heater 128. Reactions 1 a and 2a may occur in the
first zone 114, producing much thermal energy, carbon dioxide and super
heated steam. These hot gases may impinge on the coke or carbonized
shale resulting in reactions 1 b and 2b, to take place producing carbon
monoxide and hydrogen and consuming the carbureted material along with
absorbing considerable quantities of thermal energy. A portion of these
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gases may be re-circulated through the second gas re-circulation line 144 by
means of the second blower 146. The combustion of theses gases with
oxygen may furnish all the thermal energy for the reactions, both chemical
and physical, that take place in the chamber 112. The summation of the
energy released from reaction 1 a and 1 b may be approximately 53,600
callmole of oxygen consumed. This may be far excessive for the thermal
requirements of the process. To compensate for this excessive energy and
to convert the excessive thermal energy to a useful chemical energy and
moderate the climate in first zone 114, a flow of steam may be introduced into
a steam pre-heater 128x. The steam may also be super heated by hot spent
shale which may be ejected from the first zone 114 through the oxygen pre-
heater 128, and on into the steam pre-heater 128a. The steam may be
derived from a boiler 154. The boiler 154 may include a series of tubes for
receiving water. As the hot effluent from the chamber 112 is passed through
the boiler 154, the heat from the effluent may be absorbed by the water in the
tubes. Accordingly, the temperature of the effluent may be reduced and
steam may be generated.
Steam generated from the boiler 154 may be circulated for use in the
chamber 112 through steam path 156, 156a, 15E3b. It will also be understood
that steam may likewise be diverted from the boiler 154 for some other use.
The steam may be conveyed through steam path 156, 156a and injected into
the first zone 114 through steam path 156b. It will be appreciated that the
flow of steam may be controlled by steam control valves, such as a first
steam control valve 134, a second steam control valve 135, a third steam
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control valve 136, a fourth steam control valve 137, and a fifth steam control
valve 138. Moreover, it will be appreciated that various different
configurations and quantities of valves may be used to control the flow of
gasses within the scope of the present invention.
The steam may react with the coke generating more hydrogen and
carbon monoxide and absorbing heat, characterized by reaction 2b. Thus by
controlling the flow of the oxygen and steam, such as through the oxygen
valve 132 and the second steam control valve 135, the thermal climate and
rate of the process can be controlled. The spent shale may be rejected from
the steam pre-heater 128a through a waste port 130 after heating the
moderating gas. The coke may pass through the waste port 130 for use as a
product or waste. The coke material passing through the waste port 130 may
include residue from the oil shale such as calcium carbonates.
It may be desirable to synchronized the rate of feed of the oil shale
into the chamber 112 with the flow of the oxygen, steam and carbon dioxide
such that the coke which is coating the shale is consumed only slightly before
it is discharged into the oxygen pre-heater 128. By accomplishing this the
spent shale can be insulated from the buffeting heat. Also, the shale may be
prevented from being calcined, robbing energy from the process and
producing carbon dioxide from an unwanted source. In the event the coke
coating the shale is not completely consumed before the shale is discharged
into the oxygen pre-heater 128, the oxygen reacts with the coke in the oxygen
pre-heater 128 producing an extremely high temperature. To compensate for
this, steam may be injected into the oxygen pre-heater 128 through the first
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steam control valve 134 and conduit 139, to moderate the temperature in the
oxygen pre-heater 128 until the coke is consumed.
It may be desirable to have the temperature of the hydrogen and
carbon monoxide discharged from second zone 116 into the gas output. line
148 ranging at around 500 degrees C, or between approximately 900
degrees and 950 degrees F for example. These gases may be conveyed to a
particle separator 150 en route to a catalytic converter 152 through the gas
output line 148a by means of catalytic converter blower 153. The particle
separator 150 may include any variety of devices configured for removing
particulates from a gaseous stream. The catalytic converter 152 may be a
chamber for reactions that may contain a metal catalyst into which the
effluent gasses from the chamber 112 may be passed so that hydrogen and
carbon dioxide may be produced. The metal catalyst may be disposed on
surfaces within the catalytic converter 152 so as to contact the effluent
gasses. Various different metals may be used as the catalyst. For example,
ferric oxide (Fe203) or chromic oxide (Cr203) may be used as well as any
other substance known in the art of catalytic converters. Examples of the
reactions occurring in the catalytic converter 152 include the following= if
desired, possible, or feasible:
3H20 + 2Fe ----> Fe203 + 3H2;
Fe203 + 3C0 ----> 2Fe + 3C02.
The catalytic converter 152 can be used to carry oxygen from the steam to
the carbon monoxide to produce a hydrogen and carbon dioxide effluent.
The hydrogen and carbon dioxide effluent of the catalytic converter 152 may
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be carried through effluent path 148b to be cooled by passing through the
boiler 154.
The hydrogen and carbon monoxide discharged from the second zone
116 may percolate up through multiple beds of ;elected metal oxides and
catalysts, along with steam. This steam may be generated in the boiler 154.
The steam may flow directly to the catalytic converter 152 through the steam
path 156 and the fourth steam control valve 137 as saturated steam or the
steam may flow into the steam pre-heater 128a, being super heated by the
hot spent shale. The steam may then be discharged through the steam line
124 and the fifth steam control valve 138 into them gas output line 148 along
with the carbon monoxide and hydrogen before i't is conveyed through
particle separator 150 en route to the catalytic convert 152. It wilt be
understood that the steam entering the catalytic converter 152 may be super-
heated to a temperature of approximately 500 degrees C, either through a
super-heater included as part of the boiler 154, or other super heating device
or method known in the art.
The catalyst in the catalytic converter 152: may progressively remove
oxygen from the steam transferring it to the carbon monoxide and producing
carbon dioxide and hydrogen characterized by reaction 7. This process is
slightly to moderately exothermic. The summation of the thermal energy of
the gases leaving the catalytic converter 152 being somewhat greater than
the gases entering it, these gases may beat a thermal state such that their
sensible heat can generate a significant quantity of steam in the boiler 154.
This steam may be utilized as previously described. The hydrogen, carbon
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dioxide and steam may be conveyed through thf: gas output line 148c to a
cooler 158. Cooler 158 may include any variety of cooling devices known in
the art such as cooling towers in which water is circulated to absorb heat and
lower the temperature of the effluent gasses through evaporation. In one
embodiment, water may be supplied to the cooler 158 from a cooling pond
160. A pump 162 may be used to circulate the water from the cooling pond
160 to the cooler 158. Accordingly, the water vapor, hydrogen and carbon
dioxide from the effluent of the boiler 154 may be cooled. Most of the water
vapor may be condensed in the cooler 158.
The remaining hydrogen and carbon dioxide from the cooler 158 may
be conveyed to a scrubber 166 through gas output line 148d by means of a
high pressure blower 164. The scrubber 166 may be configured in any
manner known in the art. For example, the scrubber 166 may include an
enclosure for receiving a solution configured to absorb the carbon dioxide.
The solution for absorbing carbon dioxide may be sodium carbonate
(Na2C03) in water for example. However, it will be appreciated that any
carbon dioxide absorbing material known to those skilled in the art of
scrubbers may be used, such as sodium hydroxide (NaOH) or calcium oxide
(Ca0), for example.
The scrubber 166 may be pressurized by the gases from the blower
164. The middle portion of the scrubber 166 may be filled with strong and
chemically inert nodules of a moderate and uniform size such that they will
allow the gases and the liquid to counter flow passed one another. A torrent
of a solution of water and sodium carbonate may be pumped up through a
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scrubber re-circulation line 168 by means of a pressure pump 170. The
solution may enter the scrubber 166 flooding the top of the nodules and
cascading downward through the nodules as the gases percolate up through
this mass of nodules. This action may create a condition wherein the carbon
dioxide goes into solution and is swept downward to a reservoir 169 as solute
in the soluble water. l'-his pressurized solution of water may now be laden
with carbon dioxide. As the solution continually cascades downward, the
carbon dioxide being fairly soluble and hydrogen being only very slightly
soluble, the carbon dioxide may be leached frorr~ the gas solution leaving the
gas that bubbles to the surface, or top of the scrubber 166, being fairly pure
hydrogen gas. The reservoir 169 of water may be retained by a water level
control valve 172 which may prevent the gases from exhausting through an
intake 173. As the water level rises the control valve 172 may release the
flow of water in accordance to the water level in the reservoir 169. The water
may flow through a water line 175 to a holding tank 178 where it may be
depressurized and the carbon dioxide may rise out of the solution. The
carbon dioxide may be removed through a carbon dioxide outlet 176 for
disposal or use.
The hydrogen, after being cleansed in thE: scrubber 166, may be
discharged through a scrubber outlet 174, and pressure relief valve 180 en
route to a pressure vessel 184 by means of a compressor 182. The
hydrogen can now be distributed through hydrogen outlet 176a and valve
186.
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In as much as a phase in period may be required for a transition from
the widespread use of petroleum to a widespread use of hydrogen fuel, the
present invention provides an optional feature that may accommodate this
need. A portion of the hydrocarbon vapors in the first gas re-circulation line
140 may be diverted through optional diversion means 141. The vapors may
be then processed to the desired products and the unusable hydrocarbons
and carbon monoxide may be returned back to the hydrogen generating
apparatus 110 through gas return means 143 to be used in generating
hydrogen. For example, the gas in the first gas re-circulation line 140 may
include vaporized hydrocarbons which rnay be diverted through the optional
diversion means 141 for use outside the hydrogen generating apparatus 110
if so desired. The gasses diverted through the optional diversion means 141
may include hydrocarbons, carbon monoxide and hydrogen. These gasses
may be used to produce oil products. Light hydrocarbons, carbon monoxide
and hydrogen remaining after the oil products have been produced rnay be
directed back into the re-circulation line 140 through gas return means 143.
Referring now to FIG. 3, there is shown a schematic view of a further
embodiment of the apparatus, designated generally at 210, for producing
hydrogen. As previously discussed; the present embodiments of the
invention illustrated herein are merely exemplary of the possible
embodiments of the invention, including that illu:>trated in FIG. 3.
It will be appreciated that the embodiment: of the invention illustrated in
FIG. 3 contains many of the same structures represented in FIG. 2 and only
the new or different structures will be explained t.o most succinctly explain
the
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additional advantages which come with the embodiments of the invention
illustrated in FIG. 3.
Reactions and phenomena occurring in the different zones 114, 116
and 118 in the chamber 112, and in other portions of the hydrogen producing
apparatus 210 can be represented stoichiometrically as follows:
(R1 a) 2C0 + OZ -----> 2C02 +135,200 calories/imole;
(R1 b) COZ + C ----> 2C0 -40,800 calorieslmole;
{R2a) 2H2 + OZ ----> 2H20 +115,660 calorieslmole;
(R2b) H20 + C ----> HZ + CO -31,400 calories/mole;
(R3) C~H~2~+Z~ ----> C~ + H~2~+2~ - approximately 5,000 calories per n, where
n is
an integer;
(R4) CnH~2n+2~ (solid) + Heat ----> vapor C~H(Zn+z>;
(R5) 02 at ambient temperature ----> OZ superheated;
(R6) H20 + C02 ----> superheated H20 + CO2;
(R7) Fe304 + 4H2 ----> 3Fe + 4H20;
(R8) Fe304 + 4C0 ----> 3Fe + 4C02;
(R9) 3Fe + 4H20 ----> Fe304 + 4H2.
The general location where each of the above reactions takes place is
indicated by the corresponding reaction numbers in FIG. 3. As indicated
above, it will be understood that the heat of reaction values presented are
approximate values for illustrative purposes only, and that other heat of
reaction values may occur within the scope of the present invention.
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Operation of the chamber 112 for the embodiment depicted in FIG. 3 may be
similar to that described above for FIG. 2.
The hydrogen and carbon monoxide discharged from the chamber 112
into the gas output line 148 may be conveyed to the particle separator 150 in
route to an inverted conical collector 212 of a ferrous deoxidizes 226,
through
conduit 214 and a blower 216. The hydrogen and carbon monoxide may then
percolate up in the ferrous deoxidizes 226 through multiple fluidized beds of
magnetite which progressively move downward. The hydrogen and carbon
monoxide remove the oxygen from the magnetite reducing the Fe304 to Fe.
The hydrogen and carbon monoxide may be oxidized to H20 and COZ
characterized by reactions R7 and R8: Portions of these gasses rnay be
discharged through conduit 218 through blower 219 into the steam pre-heater
128a. The remaining gas may be discharged through conduit 221. This hot
gas along with the heat combined from the hot gases conducted through
conduits 220 and 222 may furnish the heat necessary to generate steam in a
heat extracting apparatus 224. It will be appreciated that the heat extracting
apparatus 224 may be comprised of any variety of heat exchanger or cooling
device known in the art for extracting heat, and ~>ossibly generating steam.
The steam may be injected back into ferrous deoxidizes 226. This steam may
react with metallic iron in a metallic iron chamber 228 generating hydragen
and magnetite characterized by reaction R9. The iron may serve as a vehicle
to carry oxygen from the Hz0 in the metallic iron chamber 228 to the carbon
monoxide and hydrogen. This process may generate a near pure hydrogen
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and magnetite in the metallic iron chamber 228, and carbon dioxide, steam
and metallic iron in the ferrous deoxidizer chamber 230.
The metallic iron may be collected in inverted conical collector 212
then ejected through gas locks 232 into a conduit 234. The metallic iron may
be conveyed through conduit 234 up into a separator 236 by means of a hot
gas conveyor 250. The hot gas conveyor 250 may include a combustion
chamber eguipped with an air supply controlled by an air supply control valve
252. Also, a gas supply may be provided to the hot gas conveyor 250
through a gas conduit 254 and a gas control valve 256. An exhaust conduit
258 may be used to eject hot gasses from the hot gas conveyor 250 into the
conduit 234 propelling the metallic iron up into the separator 236. After the
hot gasses pass through the separator 236, the gas may continue through
conduit 220 to the heat extracting apparatus 22~I. It will be understood,
however, that other conveyance means known in the art may be used within
the scope of the present invention to transport the metallic iron to the
separator 236.
The metallic iron may be composed of small particles of two to three
millimeters and smaller. These particles may descend into distribution tubes
238. When the tubes 238 are filled with the varying sizes of particles, it
makes a near gas tight seal between separator 236 and the metallic iron
chamber 228. These particles descend downward from fluidized bed to bed
as the steam percolates up through the particles, thereby completing a
continuous cycle.
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The gases ejected from the chamber 112 may be 500 degrees C or
above and the summation of reactions R7 and R8 may be slightly exothermic.
Reaction R9 may be somewhat more exothermic:. The volumes of the gases
entering the ferrous deaxidizer 226, also referred to as a hydrogen generator,
may be equal to the volume exiting it. The thermal energy exiting the
hydrogen generator 226 may exceed the requirement to generate steam for
the hydrogen generator' 226. After heat is extracted from these gases, the
waste may be disposed and the hydrogen may be cooled in cooler 242,
compressed using a compressor 244, and stored in a storage tank 246 for
distribution.
It will be understood that other materials besides iron may be used to
carry oxygen from the H20 in the hydrogen generator 226 within the scope of
the present invention.
Those having ordinary skill in the relevant art will appreciate the
advantages provide by the features of the present invention. For example, it
is a feature of the present invention to provide a process and apparatus for
producing hydrogen from oil shale that is simple in design and operation. It
is
an additional feature of the present invention to provide a process and
apparatus for producing hydrogen from oil shale that is efficient in use of
heat
and fuel. It is a further feature of the present invention to provide a
process
and apparatus for extracting oil from oil shale that is simple in design and
operation. It is another feature of the present invention, in accordance with
one aspect thereof, to provide such an apparatus that can produce an excess
of carbon monoxide for use as a commercial fuel in other industries. It is an
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additional feature of the present invention, in accordance with one aspect
thereof, to provide such an apparatus that minimizes the presence of gases
that are nonessential to the extraction of oil from oil shale. It is a further
feature of the present invention, in accordance with one aspect thereof, to
provide such an apparatus that is capable of recovering unused heat
produced in a combustion phase of the oil extraction process. It is an
additional feature of the invention, in accordance with one aspect thereof, to
provide such an apparatus in which a reactant in the process is regenerated
and is reusable in the process.
It is to be understood that the above-described arrangements are only
illustrative of the application of the principles of 'the present invention.
Numerous modifications and alternative arrangements may be devised by
those skilled in the art without departing from the spirit and scope of the
present invention and the appended claims are intended to cover such
modifications and arrangements. Thus, while the present invention has been
shown in the drawings and fully described above with particularity and detail
in connection with what is presently deemed to be the most practical and
preferred embodiments) of the invention, it will be apparent to those of
ordinary skill in the art that numerous modifications, including, but not
limited
to, variations in size, materials, shape, form, function and manner of
operation, assembly and use may be made without departing from the
principles and concepts set forth herein.
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