Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to hydrocracking and, more
particularly, to the simultaneous hydrocracking of coal and
a heavy hydrocarbon oil, such as bitumen from tar sands.
Hydrocracking processes for the conversion of heavy
hydrocarbon oils to light and intermediate naphthas of good
quality for reforming feed stock, fuel oil and gas oil are
well known. These heavy hydrocarbon oils can be such materials
as petroleum crude oil, atmospheric tar bottoms products,
vacuum tar bottoms products, heavy cycle oils, shale oils,
coal derived fluids, crude oil residuum, topped crude oils
and the heavy bituminous oils extracted from tar sands. Of
particular interest are the oils extracted from tar sands
which contain wide boiling range materials from naphtha
through kerosene, gas oil, pitch, etc., and which contain
a large portion, usually more than 50 weight percent of mat-
erial boiling above 524C., equivalent atmospheric boiling
point.
The heavy hydrocarbon oils of the above type
tend to contain nitrogenous and sulphurous compounds in
quite large concentrations. In addition, such heavy
hydrocarbon fractions frequently contain excessive quantities
of organo-metallic contaminants which tend to be extremely
detrimental to various catalytic processes that may
subsequently be carried out, such as hydrofining. Of the
metallic contaminants, those containing nickel and vanadium
are most common, although other metals are often present.
These metallic contaminants, as well as others,arP usually
present within the bituminous material as organo-metallic
compounds of relatively high molecular weight. A considerable
quantity of the organometallic complexes are linked ~-ith
asphaltenic material and contains sulphur. Of course, in
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catalytic hydrocrackiny procedures, the presence of large
quantities of asphaltenic material and organic-metallic
compounds interferes considerably with the activity of the
catalyst with respect to the destructive removal of nitro-
genous, sulphurous and oxygenated compounds. A typical
Athabasca bitumen may contain 53.76wt. % material boiling
above 524C., 4.74-wt. ~ sulphur, 0.59 wt. % nitrogen, 162
ppm vanadium and 72 ppm nickel.
As the reserves of conventional crude oils decline,
these heavy oils must be upgraded to meet the demands. In
this upgrading, the heavier material is converted to lighter
fractions and most of the sulfur, nitrogen and metals must
be removed. This is usually done by a coking process such as
delayed or fluidized coking or by a hydrogen addition process
such as thermal or catalytic hydrocracking. The distillate
yield from the coking process is about 70 weight percent and
this process also yields about 23 wt. % coke as by-product
which cannot be used as fuel because of low hydrogen:carbon
ratio, and high mineral and sulfur content. Depending on
operating conditions, hydrogenation processes can give a
distillate yield of over 87 wt. %.
It has been shown in Ternan et al Canadian patent
application serial number 269,020 filed December 31, 1976 and
Ranganathan et al., Canadian patent application serial number
289,320, filed October 24, lg77 that the addition of coal or
coal-based ca-talyst results in a reduction of coke deposition
during hydrocracking and a generally improved operation. The
coal additive acts as a l'getterll for coke deposits and prevents
accumulation of coke. It is also possible -that coal mineral
matter acts as a coke-preventing catalyst. In these previous
procedures the hydrogenation of the coal represented only a
secondary consideration.
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In the hydrocracking of coal, the hydrogen:coal
process involves slurrying coal with a coal-derived oil
and subsequent reaction with hydrogen at high temperatures
and pressures in the presence of Co-Mo/alumina catalyst.
Other processes for converting coal such as SRC (solvent
refined coal), EDS (Exxon donor solvent) and Synthoil pro-
cesses also recycle distillate fractions derived from coal
as solvents. These processes are described, for instance,
by Richardson, F.W. "Oil From Coal", Noyes Data Corporation,
Parkridge, New Jersey, 1975, 386 pp.
Not only the bitumen, but also the coal contains
heavy asphaltenes and mineral matter which rapidly poison
the catalyst. This results in excessive catalyst usage and
high operating costs. For both bitumen and coal upgrading
processes, the fixed bed catalytic processes are not economical
because of bed plugging resulting in costly shut-downs. An
ebullated bed of catalyst is more suitable for hydrocracking
bitumen or coal. Both the hydrogen:coal and the hydrogen:
oil processes use this mode of operation. In the ebullated
bed, the upward passage of liquid and gaseous materials main-
tains the catalyst in a fluidized state. Catalyst can be
added and withdrawn continuously so that a constant activity
can be maintained. However, the hydrogen:coal or hydrogen:
oil process uses an expensive Co-Mo/alumina catalyst which
deactivates rapidly at high conversions, resulting in excessive
operating costs.
As has been shown in the above patent applications,
the operating costs can be reduced by using cheap throw-away
type catalysts and, for instance, serial number 289,320 des-
cribes the use of iron-coal catalyst which enables operation
at lower pressures and at higher conversions. The use of
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coal and Co, Mo and Al on coal catalysts are described in
serial number 269,020.
It is the object of the present invention to take
advantage of the solvent and hydrogen donor action of a bitu-
men feed stock as well as the catalytic action of coal
mineral ma-tter so as to provide a novel hydrocracking process
showing improved economics.
SUMMARY OF THE INVENTION
.. . ......
In accordance with the present invention, there is
described a process for hydrocracking a heavy hydrocarbon
oil, a substantial portion of which boils above 524C., which
comprises:
a) passing a slurry of said heavy hydrocarbon oil
and from about 2 - 50 wt. ~ coal in the presence of 50~-50,000
s.c.f. of hydrogen per barrel of said hydrocarbon oil through
a confined hydrocracking zone, said hydrocracking zone being
maintained at a temperature between about 400 and 500C.,
: a pressure of at least 200 psig. and a space velocity between
about 0.5 and 4 volume of hydrocarbon oil per hour per volume
of hydrocracking zone capacity,
b) removing from said hydrocracking zone a mixed
effluent containing a gaseous phase comprising hydrogen and
vaporous hydrocarbons and a liquid phase comprising heavy
hydrocarbons, and
c) separating said effluent into a gaseous stream
containing hydrogen and vaporous hydrocarbons and a liquid
stream containing heavy hydrocarbons.
This process provides a simultaneous hydrocracking
of the heavy oil and coal, with the heavy oil acting as a
good solvent vehicle and the coal acting as a catalyst,
preventing coke formation reactions.
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~ 7hile the process of this invention is particularly
well suited for the treatment of bitumen, it is also very
well suited for the treatment of topped bitumen or pitch.
It can be operated at quite moderate pressures, e.g. in the
range of 200 to 3,500 psig, without coke formation in the
hydrocracking zone.
The hydrocracking process of this inv~ntion can be
carried out in a variety of known reactors with either up
or down flow. Thus, the hydrocracking reactor zone can be
an empty tubular reactor, an ebullated bed reactor or a
fluidized bed reactor. The empty tubular reactor has been
found to be particularly convenient with the effluent from
the top being separated in a hot separator and the gaseous
stream from the hot separator being fed to a low temperature-
high pressure separator where it is separated into a gaseous
stream containing hydrogen and lesser amounts of gaseous
hydrocarbons and a liquid product stream containing light
oil products. It is also possible to have the reactors in
stages where the first reactor is an empty tubular reactor
and the second reactor contains an ebullated bed of catalyst
extrudates.
Any type of coal, such as lignite, sub-bituminous,
bituminous, etc., can be used as the coal portion of the charge
slurry. The coal can be used as is without any additive or
it may be coated with up to about 10 wt.~ of metal salts
such as iron, cobalt, molybdenum, zinc, tin, tungsten,
nickel or other catalytically active salts. The use of
the catalytic materials improve the conversion of coal and
bituman as well as the operability of the process, but the
metal loading must depend on the cost of materials, tolerable
ash content and optimum catalyst activity.
The catalyst can be coated on the coal by spraying
the aqueous solution of the metal salt on the coal particles.
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The coal is then dried to reduce the moisture content before
blending with the feed stock.
The coal particles used should be quite small, ~.g.
less than 60 mesh (Canadian Standard Seive) and it is parti-
cularly preferred to use a material which will pass through
a 100 mesh sieve. The coal should be mixed with the bitumen
in such a manner as to avoid formation of lumps and, if
desired, additional homogeneous or heterogeneous catalysts
may be mixed with the coal-bitumen slurry.
The simultaneous hydrogenation process produces
pitch which contains asphaltenes, ash and residues from both
bitumen and coal. Depending on the type of coal used, and
the feed stock, the pitch properties vary. For example,
low sulfur sub-bituminous coals obtained from Western Canada
produce a low-sulfur pitch. This reduces the cost of s-tack
gas cleanup, while increasing the ash content of the pitch.
The presence of the large amounts of coal in the
slurry, as stated above, suppresses coke formation during
hydrocracking. The result is that the simultaneous coal-
bitumen hydrocracking can be performed at quite low pressures.Nevertheless, in certain situations it is desirable to
operate at higher pressures so as to maximize liquid yields
as well as product quality.
According to a preferred embodiment, the bitumen
and coal are mixed in a feed tank and pumped with hydrogen
through a vertical empty tube reactor. The liquid-gas mix-
ture from the top of the hydrocracking zone is separated in
a hot separator maintained at a temperature in the range of
about 200 - 470~C. and at the pressure of the hydrocracking
zone. The heavy hydrocarbon product from the hot separator
can be partially recycled to the hydrocracking zone or sent
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to secondary treatment.
The gaseous stream from the ho-t separator contain-
ing a mixture of hydrocarbon gases and hydrogen is further
cooled and separated in a low temperature-high pressure
separator. By using this type of separator, the outlet
gaseous stream obtained contains mostly hydrogen with some
impurities such as hydrogen sulfide and light hydrocarbon
gases. This gaseous stream is passed through a scrubber and
the scrubbed hydrogen is recycled as part of the hydrogen
feed to the hydrocracking process. The recycled hydrogen
gas purity is maintained by adjusting scrubbing conditions
and by adding make-up hydrogen.
The liquid stream from the low temperature- high
pressure separator represents the light hydrocarbon product
of the present process and can be sent for secondary treat-
ment.
Some of the coal may be carried over with the heavy
oil product from the hot separator and found in the 524C.+
pitch fraction. This coal can conveniently be burned or
gasified with the pitch.
For a better understanding of the invention, ref-
erence is made to the accompanying drawing which illustrates
diagrammatically a preferred embodiment of the present
invention.
Heavy hydrocarbon oil feed and coal are mixed
together in a feed tank 10 to form a slurry. This slurry
is pumped via feed pump 11 through inlet line 12 into the
bottom of an empty tower 13. Recycled hydrogen and make up
hydrogen from line 30 is simultaneously fed into the tower
13 throuyh line 12. A gas-liquid mixture is wi-thdrawn from the
top of the -tower through line 14 and introduced into a hot
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separator 15. In the hot separator the effluent from tower
13 is separated into a gaseous stream 18 and a liyuid stream
16. The liquid stream 16 is in the form of heavy oil which
is collected at 17.
The gaseous stream from hot separator 15 is
carried by way of line 18 into a high pressure-low temp-
erature separator l9. Within -this separator the product is
separated into a gaseous stream rich in hydrogen which is
drawn off through line 22 and an oil product which is
drawn off through line 20 and collected at 21.
The hydrogen rich stream 2Z is passed through
a packed scrubbing tower 23 where it is scrubbed by means
of a scrubbing liquid 24 which is cycled through the tower
by means of pump 25 and recycle loop 26. The scrubbed
hydrogen rich stream emerges from the scrubber via line 27
and is combined with fresh make up hydrogen added through
line 28 and recycled through recycle gas pump 29 and line 30 ~ack
to tower 13.
Certain preferred embodiments of this invention
will now be further illustrated by the following non-
limitative examples.
Example 1.
A sub-bituminous coal was obtained from the '~hite
Wood coal mine and this coal had the following properties:
Calorific Value*, kJ/kg25900
Carbon*, wt. % 67.1
Hydrogen*, wt. % 4.0
Sulphur*, wt. % 0.2
Nitrogen*, wt. % 0.9
Ash*, wt. % 9 5
Oxygen, wt. % ~by difference) 18.3
Moisture (as received), wt.% 9.6
Pentane Insolubles, wt. % 94.8
Toluene Insolub]es, wt. % 91.6
* Properties of coal on dry basis.
The above coal was crushed and screened to provide a
60 mesh material.
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The bitumen used was an Athabasca bitumen having
the following properties: ,
Specific Gravity, 15/15C. 1.013
Sulphur, wt.% 4.74
Nitrogen, wt. % 0.59
Ash , wt. % 0.59
Viscosity at 99C., cst 213
Conradson Carbon Residue, wt.% 14.9
Pentane insolubles, wt. ~ 16.8
Benzene insolubles, wt.~ 0.52
Nickel, ppm (wt) 72
Vanadium, ppm (wt.) 162
Pitch content, wt. %53.76
Sulphur in 524C.- dist., wt.% 2.96
Sulphur in 524C+ pitch, wt.% 6.18
A blended slurry of the bitumen and 10% by weight
of the coal was prepared and this slurry was used as the
feedstock to a hydrocrackiny pilot plant. The pilot plant
used the reaction sequence shown in the attached drawing
and was operated under the following reaction conditions:
Reaction pressure, psig. 2000
Reactor temperature, C. 460
Feed rate, g/h 9000
Gas rate, scf/h 197.0
Hydrogen, concentration, vol.% 85.0
Hot separator temperature, C. 370
- 20 The results obtained ~rom this run were as follows:
Pitch* (524C.~) conversion, wt.% 74.85
Sulphur conversion, wt. % 45.3
Hydrogen consumed, scf/bbl 786
Product volume yield, vol. %97.6
Product weight yield, wt. % 90.9
Product gravity, 15/15C. 0.943
Sulphur in 524C.- distillate, wt.% 2.33
Pitch in product, wt. % 16.16
Ash in product pitch, wt. % 11.0
Sulphur in pitch, wt. % 3.43
* Includes coal-based on pitch determination on feed, in-
cluding coal; and product, including coal.
Example 2
The above hydrocracking procedure was repe~ted under
identical conditions, but without the addition o~ any coal
to the bitumen charge stock. The results obtained were as
follows:
Pitch (524C+ conv.), wt. % 76.1
Sulphur conversion, wt. % 45.4
Hydrogen consumed, scf/bbl 847
Product gravity, 15/15C. 0.928
Sulphur in 524C- dist., wt. % 2.54
Sulphur in pitch, wt. % 5.12
From the above examples it will be seen that the
pitch conversion in the presence of coal compared very
favorably to conversion in the procedure without coal.
The degree of sulphur removal was also similar. The major
difference was the sulphur content of the pitch.
Based on material balance of sulphur and pentane
insolubles, it has been found that close to 50% of the coal
has been converted to either liquid or gaseous products.
Based on the carbon content of the coal as received (60.7
Wt. %), conversion to liquids is about 82~ of possible
carbon conversion and based on the estimate that only
50% of the coal added remained in the product pitch, the
conversion of the bitumen-pitch fractlon is in the order of
82%. This indicates that the presence of coal significantly
enhances liquid yield, resulting in a more efficient process,
together with the added advantage of providing a pitch of
decreased sulphur content. The conversion of coal and
liquid product qualities can be varied with the catalytically
active metal salts or type of coal used.
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