Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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23327-114
The present invention relates to a method of recovering oil
and gas from oil sand, oil chalk and/or oil shale by pyrolysis in a fluidized
bed heated indirectly to from 400 to 1000C.
Amounts of oil bonded in oil sand and oil shale are known to be
comparable to those present in the known places of mineral oil occurrences
(Taylor, R.B.; Chemical Engineering, September 7, 1981, page 63). So, oils
contained solely in the Canadian oil sands or the Alberta region covering
about 48.000 km2 amount to more than 124 billion tons (Stausz, O.P. Lown,
E.M.; Oil Sand a. Oil Shale Chemistry, Verlag Chemie, Weinheim-New York 1978).
The oil shale reserves in the world containing an oil proportion of more than
10 per cent are even estimated to comprise 2,550 billion tons oE bonded oil.
Oil sand and oil shale occurrences are distributed all over the
world. The main occurrences are situated in the United States of America,
Canada, Brazil, Australia, hlorocco, Jordan, USSR, and China. There are some
smaller occurrences in the Federal Republic of Germany.
The exploitation of oil shale for the recovery of paraffins is
older than the exploitation of mineral oil. However, in spite of the enormous
reserves, no utilization worth mentioning has taken place to date. Altogether,
only a few million tons of oil per annum are recovered from oil sand and oil
shale according to the methods of recovery known to date (Grant, K.; Chemical
Engineering, April 5, 1982, page 20E-20H). This is attributed to the fact that
the economical and ecologically tolerable utilization of oil sand and oil shale
poses considerably greater problems than the recovery of mineral oil. I~ith the
methods known to date these problems consist, in the separation of the oil from
the sand or shale with oil contents of only 7 to 15 per cent and, furthermore,
in the high proportions of 8 to 25 per cent of asphalts, as well as in a
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sulphur content of from 3 to 7 per cent.
It is known that according to the method of the Syncrude L-td.,
as used in Alberta, Canada, oil may be recovered using superheated water vapour
or hot water (Rammler, R.W.; Oil Shale Processing Technology, East Brunswick,
New Jersey 1982, page 83). In this process, a residue will occur comprising
the sand, largely freed of ~he oil but also still containing an oil/water
sludge, which may result in too great an impairment of the environments. The
thus recovered oil sand extract is not directly suited for use ~ithout any
further after-treatment because it has too high a viscosity, too higll a pro-
portion of asphalts, and too lligh a sulphur content. Therefore, the extract
must be split into utilizable products in series-arranged hydro cracking plants.
Through this manner of processing, on the one hand, oil is lost and, on the
other hand, the remainders of oil together with the simultaneously used large
amounts of extraction water give rise to waste disposal problems. These dis-
advantages have already led to closure of some of these plants.
It is furthermore known that oil shale is at the present time
being utilized in sonne smaller plants such as the Lurgi-Ruhrgas process, the
Kiviter process, the Tosco II process, and the Paraho process, as well as some
other similar processes ~Allred V.D.; Oil Shale Processing Technology, The
Center for Professional Advancement, East Brunswick, New Jersey 1982).
It is in addition known that in these processes use is made of
circulating fluidizecl beds. Witll the Lurgi-Ruhrgas process, burnt hot sand
which is circulated at temperatures of 630C serves to pyrolyze the oil shale.
The pyrolysis takes place in a mixer with one part of oil shale being mixed
Witll 4 to 8 parts o:E sand. Thus, considerable amounts of hot sand must be
transported. The same is equally applicable to processes in which burnt solid
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pyrolysis residues are circulated as heat carriers (United States patent letters
4,199,432, Tamm et al and 4,293,401, Sieg et al). ~ith the carrier process the
oil shale is pyrolized by hot gas. The hot gas is produced in a retort by
partial oxidation and introduction of vapour ~just as in United States patent
3,491,016). A portion o the oil is burnt in this manner.
In contrast to the above, the Tosco II process makes use of
ceramic balls for the transfer of heat to the oil shale, the ceramic balls being
moved in a rotary tube furnace. The ceramic balls are screened from the
residue after pyrolysis and re-heated in a separate process step. The Paraho
reactor consists of a vertically arranged, brick-lined shaft. The energy neces-
sary for de-oiling is covered by additional supply of air and thus partial
oxidation. Thereby, however, also the pyrolysis oils that have been ormed
are partially oxidized.
For the supply of the necessary splitting energy, the known pro-
cesses either use mechanically moved devices, circulating amounts of sand, or
partial oxidation. But since the proportion of oil in the materials is at only
10 to 15 per cent, considerable masses must be moved in the mechanical pro-
cesses. The partial oxidation, in particular, results in a drastic deteriora-
tion of the oil qualities. Those processes working-with vapour, on the other
hand, leave a residue which is hardly ecologically tolerable.
Through work performed at the University of Hamburg it became
known that fluidi~ed beds which are indirectly heated by jet type heating tubes
are suited to pyrolyze plastic wastes and old tires into aromatic carbon com-
pounds~ e.g. reusable carbon black and gases rich in heating energy (German
patent 26 58 371).
It is, therefore, the object of the invention to overcome the dis-
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advantages of the prior art and provide a process renderlng
possible the deoiling of oil sandr oil shale or oil chalk to form
petrochemicals having properties superior to those provided by the
prior art, with a far reaching desulphurization taking place
during pyrolysis. It is a further object to produce a clean
residue which may unobjectionably be disposed of.
These objects are accomplished according to the inven-
tion using a process of the type indicated at the beginnin~, which
is characterized in that the heating of the pyrolysis fluidized
bed takes place indirectly through the use of heating tubes.
The present invention therefore provides a method of
recovering oil and gas from oil sand, oil shale and/or oil chalk
by pyrolysis in a fluidized bed heated indlrectly to a temperature
of from 400 to 1000C, wherein either the fluidized bed is heated
by preheated pyrolysis gas freed of oil which is combusted ln
heating tubes, or the fluidized bed is heated by heating tubes
containing waste gas as the heat carrier, and wherein the heat
carrier waste gas is heated in a second fluidized bed in which the
pyrolysis residue is burnt.
It is possible, according to the process of the
invention, to pyrolyze oil sand, oil shale or oil chalk in
indirectly heated fluidized beds without the known disadvantages
of the prior art, with the pyrolysis oils formed exhibiting
particularly superior properties, and with the pyrolysis residue
being adapted to be converted into a clean sand or shale capable
of being disposed of in a series-connected heat exchanger using
air under generation of energy.
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Using this process, the following advantages are
obtained over the prior art:
(a) No mechanically moving parts are present in the hot
zone;
(b) There is no need for any large amounts of sand or
shale to be circulated;
(c) There is no partial oxidation of the starting
material or products taking place in the fluidized bed reactor,
owing to the preclusion of air;
(d) Aromatic compounds are predominantly ~ormed as the
oils, which may be directly further processed without any after-
treatment in hydrogenating or cracking plants;
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~ e) The resulting residues are solid, clean substances which
are ecologically tolerable.
It is surprising that the fluidized bed does not become sticky
even when the fine grained oil sand or ground oil shale is introduced and the
layer is fluidized Wit}l the pyrolysis gas freed of the liquid products. This
is all the more amazing since, in case of sewage sludge combustion, for example,
which also moves a high proportion of inorganic solids, caking phenomena always
occur in fluidized bed furnaces, although here the caked materials is partially
burnt by partial oxidation.
With the process according to the invention such caking is pre-
vented, as evidenced by examinations of individual sand grains or shale part-
icles graphitizing in the reducing atmosphere and not sticking to one another.
Moreover, on the other hand, due to the lubricating effect of the graphite,
there is no erosion in the fluidized bed reactor.
The invention will be explained in further detail with the aid
of the attached drawing which schematically shows, by way of example, a plant
suitable for practising the invention. With the process according to the
invention, as will be seen in the drawing, the oil sand, oil shale and/or the
oil chalk is preferably introduced into the fluidized bed in a heat exchanger
where it is indirectly heated by jet type heating tubes to 400 to 1000C ~pre-
ferably to 500 to 750C) through locks, screws or pneumatically.
Through an overflow pipe, or some other discharging device per-
forming a metering action, just as much pyrolysis residue is dispensed per unit
of time from the fluidized bed reactor as is formed through pyrolysis of the
introduced oil sand, oil shale or oil chalk.
Surprisingly, the hot pyrolysis residue as withdrawn is self-burning
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upon supply of air in the heat exchanger 1 and covers the greatest proportion
of the energy required for the pyrolysis in the fluidized bed reactor. Advan-
tageously, the heat exchanger 1 is designed to provide a fluidized bed. Ilow-
ever, rotary pipes or other solid heat exchangers may also be used for this
purpose.
The pyrolysis gases leaving the fluidized bed reactor are largely
freed of entrained solids particles in a separator such as a cyclone, for
example, and then are decomposed according to ~he prior art in quenching coolers
~ld washers into oil .md gas which constitute valuable petrochemicals. Such a
cyclone is shown labelled "Cyclone 1" in the drawing.
The burnt off pyrolysis sand and the used fluidized bed material
leave the heat exchanger through an overflow pipe, thereby dispensing further
heat in heat exchanger 2 to the required combustion air or, because exchange-
able, to the pyrolysis gas ~hich has been freed of oils. T'ne residue is free
of oil and carbon black remainders, and may, without any hesitation, be disposed
of or used for other purposes.
The heating of the fluidized bed in the pyrolysis furnace is per-
formed by reheating waste gases via heat exchanger pipes in the heat exchanger 1
and by passing them into pipes through the pyrolysis reactor. For initially
heating the pyrolysis reactor, and for generating additional energy, jet type
heating pipes may additionally be incorporated which are fired with the pyro-
lysis gas as the latter is produced.
In a third heat excllallger, labelled 3 in the drawing, the gases
required for fluidization are preheated using the waste gases. It is possible
~o incorporate further heat exchangers to improve the energy balance.
Through tlle arrangement according to -the invention of the pyrolysis
fluidized bed, ancl the heat exchanger 1, etc., an optimal energy yield may be
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obtained, thereby minimizing the solids flow through absence of circulation
of the pyrolysis residue.
It is surprising that over 90% of the pyrolysis oils are convert-
ed into aromatic compounds in spite of the great proportion of solids in the
starting material. In this connection, attention is drawn to Table 1 below.
PyRoLy SIS
In the p~roly~is of oil sand, oil shale or oil chalk according to
the process of the invention, more than 75 per cent of the bonded oil is
converted into utilizable products. Again, attention is drawn to Table 1.
It is also surprising that, in spite of the great proportion of
solids in the starting material and the predominantly paraffinic structure of
the bonded oil, and in contrast to the known processes, the pyrolysis oil formed
is more than 90 per cent converted into aromatic compounds ~see Table 2 below).
Particularly high is the proportion of benzene and toluene. Fortunately, it is
these BTX aromatic compounds that are the most sought after petrochemicals for
fuels and for the chemical industry.
Moreover, the gas produced according to the process of the inven-
tion exhibits some surprising properties (See Table 3 below). It contains high
proportions (up to 22 weight per cent) of ethylene, and with more than 30.000
kJ/m , has so high a heating value that it may be compared to natural gas.
With regard to the high quality of the pyrolysis products formed,
the process according to the invention will be seen to be superior to all the
known processes discussed above.
The advantages of the process according to the invention are fur-
ther enhanced by the fact that sulphur, WhiC}l occurs in all types of oil sands
and oil shales, is transformed into inorganic salts by reactions with basic
materials in the fluidized bed. Frequently these basic substances are already
contained in a sufficient amount in the starting material. This is particular-
ly true in the cases of oil chalks. In the absence of basic substances, the
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starting material may have chalk or dolomite added thereto in the required
amounts. The pyrolysis products are then almost free of hydrogen sulphide.
Because of the high quality pyrolysis products it may also be
reasonable to utiliæe, in the practising of the method of the invention,
concentrates of oil sand or oil shale which have been produced according to
known processes.
TABLE 1
Products, in weight per cent, from the pyrolysis of oil sand and oi.l shale
performed, according to the invention, at 740& .
Starting Material Oil Sand Oil Shale
Oil Content Weight-O 13.5 15.0
Amount Employed ~kg) 380 3.5
Gas 5.3 10.5
Oil, thereof 5.2 6.9
Benzene fraction 0.8 1.1
Toluene fraction 2.6 3.2
Tar 1.8 2.6
Water 0.6 14.7
Residue ~Sand, Carbon Black) 88.9 67.5
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TAB~E 2
Composition of the liquid products from the pyrolysis of oil sand perormed,
according to the invention, at 740 C.
Benzene and Tar
Weight-% Toluene Fraction
Cyclopentadiene 1.8
Benzene 35.5 1.3
Toluene 20.7 0.2
~thylbenzene/~ylene 6.9 0.1
Styrene 4.5 0.1
Indene 3.6 0.5
Naphthalene 4.3 2.i
Methylnaphthalene 3.1 5.4
Diphenyl 0.1 1.5
Fluorene 3 3
Anthracene/Phenantrene - 3.2
Other aromatic compounds 19.5 82.3
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TABLE 3
Composition of the gases from the pyrolysis of oil sand and oil shale
performed, according to the invention, at 740C.
Starting Material Oil Sand Oil Shale
Plant Technical Plant Laboratory Plant
Weight-% Vol-% Weight-% Vol-%
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Hydrogen 2.2 19.6 2.0 20.5
Methane 47.3 52.4 28.3 36.4
Ethane 12.1 7.2 7.4 5.1
10Ethylene 22.1 14.1 14.5 10.6
Propene 5.3 2.3 4.1 2.0
Butadiene 0.8 `0.3 1.1 0.4
Benzene 1.3 0.3 3.0 0.8
Toluene 0,4 0.1 0.1 0.02
Carbon dioxide 1.2 0.5 16.9 7.9
Carbon monoxide 1.3 0.8 21.6 15.9
Hydrogen sulphide 2.9 1.5 0.02 0.01
Other gases 3.1 0.9 0.98 0.37
Density at 20 C ~kg/m3) 0.742 0.856
20Heating value 37500 30500
., , ~
