Note: Descriptions are shown in the official language in which they were submitted.
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T 5711
PROC~SS FOR TH~ UPGRADING OF ~I~AVY HYDROCARBON OILS
The present invention relates to a process for the upgrading
of heavy hydrocarbon oils as well as to hydrocarbon oils thus
upgraded.
Heavy hydrocarbon oils and in particular residues obtained
therefrom need further treatment in order to render them suitable
for use in further processing into valuable products. Basically,
the refiner has the choice between carbon removal and hydrogen
addition for upgrading heavy material having an unfavourable
hydrogen/carbon (H/C) ratio.
Coking is a well-known, relatively inexpensive, process but it
suffers inherently from low liquid yield due to coke formation.
Alternatively, hydrogen addition routes offer much better liquid
yields but need more complex equipment and are therefore more
capital intensive.
Since heavy hydrocarbons generally contain rather large
amounts of metal contaminants it is often necessary to subject them
to a hydrodemetallization treatment which in essence is a catalytic
treatment wherein the metals are substantially removed. The catalysts
normally applied are also active, to some extent, as hydroconversion
catalysts. The hydrodemetallization process which requires periodical
catalyst replacement is typically suited for partial conversion of
heavy material which necessitates the presence of further equipment,
in particular a catalytic cracker, to obtain a bottomless synthetic
crude.
It would thus be useful to be able to increase the total
conversion level of the material subjected to catalytic hydro-
demetallization, in particular to such an extent that treatment in
catalytic cracker would no longer be required.
It is known from Japanese unexamined published patent applica-
tion 60170695 to subject heavy hydrocarbon oils to a hydrogenation
treatment carried out in two zones using a hydrogen donor obtained
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by hydrogenation of aromatic compounds in the first (thermal) zone
and gaseous hydrogen and a solid catalyst in the second zone to
effect catalytic hydrogenation. The use of hydrogen donor materials
which have to be rehydrogenated after use is well known in the art
as exemp]ified by IJ.S. patent specifications 2,953,513 and 4,294,686.
It is a severe disadvantage of such processes, however, that
either an extraneous donor material (which should also be easily
rehydrogenatable) has to be introduced into the process such as
rather low boiling naphthenic compounds which are converted into
aromatic compounds during the non-catalytic thermal hydrogenation
and subsequently rehydrogenated and recycled, or that additional
internal or external hydrogenation facilities and catalysts are
required to provide the required hydrogen transfer material.
It has now been found that part of the product obtained after
a hydrodemetallization treatment can be used advantageously to
support the non-catalytic thermal hydrogenation of heavy hydrocarbon
oils. It appears that high conversion levels can be achieved which
may be attributed to the favourable H/C ratio of part of the
atmospheric distillate obtained after hydrodemetallization.
The present invention thus relates to a process for upgrading
heavy hydrocarbon oils involving a non-catalytic thermal
hydrogenation zone and a hydrodemetallization zone wherein at least
part of the hydrodemetallized product is subjected to atmospheric
distillation and wherein at least part of an atmospheric distillate
obtained is recycled to the non-catalytic thermal hydrogenation
zone.
It has also been found that the process according to the
present invention is preferably carried out in a hydrogen-rich
environment. The presence of a hydrogen-rich environment has the
additional advantage that a significant reduction in operation
pressure in the non-catalytic thermal treatment can be realized.
The hydrogen-rich environment to be maintained in the non-catalytic
thermal treatment can be obtained - in addition to the contribution
from the recycled atmospheric distillate obtained after the hydro-
demetallization step - by introducing hydrogen into the vessel in
which the non-catalytic thermal hydrogenation is or will be carried
out and/or by introducing one or more fresh or recycled streams
comprising a favourable H/C molar ratio, for instance a hydrogen-
transfer medium which is capable of releasing the required amount
of hydrogen during the non-catalytic thermal treatment. It is
preferred to carry out the non-catalytic thermal treatment in the
presence of a hydrogen-rich environment containing the recycled
atmospheric distillate described hereinbefore and molecular hydrogen.
If desired streams originating from the process and having a
favourable H/C ratio may also contribute to the hydrogen-rich
environment, for instance hydrogen-donor materials as known from
the state of the art.
The process according to the present invention will now be
illustrated by means of the following Figures (I-V) wherein similar
numbers have similar meanings in each of the Figures.
In Figure I the upgrading of a residual fraction is described
by subjecting it to a non-catalytic thermal hydrogenation in a
hydrogen-rich environment, subjecting the product obtained to a
hydrodemetallization treatment, and subjecting the product obtained
to an atmospheric distillation and recycling at least part of an
atmospheric distillate to the non-catalytic thermal hydrogenation
zone;
In Figure II a process is described as depicted in Figure I,
but wherein an atmospheric residue is used as starting material
which is sub;ected to a vacuum distillation and wherein the vacuum
distillate together with non-recycled product(s) of the atmospheric
distillation unit to which the hydrodemetallization effluent has
been subjected forms a reconstituted crude;
In Figure III a process is described as depicted in Figure II,
but wherein the product obtained in the non-catalytic thermal
hydrogenation is subjected to an atmospheric distillation prior to
the hydrodemetallization treatment and wherein the atmospheric
distiIlate thus obtained forms part of the reconstituted crude;
In Figure IV a process is described as depicted in Figure III,
but wherein part of thc atmospheric distillate obtained in the
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distillation of the product obtained in the non-catalytic thermal
hydrogenation is subjected to a (catalytic) hydrogenation treatment
and wherein the product of said hydrogenation treatment is at least
partly recycled to the non-catalytic thermal hydrogenation zone,
the part not being recycled forming part of the reconstituted
crude; and
In Figure V a process is described as depicted in Figure III
or Figure IV, but wherein the hydrocarbon oil to be treated is
firstly subjected to atmospheric distillation and wherein the
atmospheric residue obtained after distillation of the product of
the non-catalytic thermal hydrogenation is subjected to vacuum
distillation prior to the hydrodemetallization treatment.
In the process as described in Figure I a starting material 1
which may be an atmospheric distillate, a vacuum distillate or a
residual material is introduced into a non-catalytic thermal
hydrogenation vessel 10 which is operated at a pressure in the
range of from 45 to 90 bar and at a temperature in the range from
380 to 430 C.
The product obtained in the non-catalytic thermal hydrogenation
is transported via line 3 to the hydrodemetallization vessel 20 to
which fresh or make up hydrogen is introduced via line 4. Suitable
hydrodemetallization catalysts comprise Group V, Group VI and/or
Group VIII metals or metal compounds on a carrier. Preference is
given to the use of one or more of nickel and cobalt as Group VIII
metal (compounds), vanadium as Group V metal (compound) and one or
more of molybdenum and tungsten as Group VI metal (compounds).
Suitable carriers comprise silica, alumina and silica-alumina. The
metals having hydrogenating activity are normally used in amounts
between 0.1 and 30% by weight. The hydrodemetallization treatment
is normally carried out at a temperature in the range of from 370
to 450 C, a hydrogen partial pressure of between 50 and 250 bar
and at a space velocity between 0.05 and 10 kg/l.h. Hydrodemetal-
lized product is obtained via line 5 and subjected to an
atmospheric distillation in unit 30 with a view to obtain apart
from a small gas make (line 6) at least two atmospheric
distillates, one of which is at least partly recycled via line 7 to
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the feed to be subjected to the non-catalytic thermal hydrogenation
in vessel 10 via line 1. The other fraction 8 serves, optionally
with the remainder of the first distillate 7 as the product of the
process according to the present invention. Preferably a fraction
boiling between 150 and 370 C, in particular between 200 and
370 ~C is used as recycle stream 7 since it has a H/C ratio which
can be used advantageously in the non-catalytic thermal hydrogenation.
The amount of material to be recycled depends to some extent on the
severity applied in the non-catalytic hydrogenation. In general at
least 35 %v of the 150 to 370 C distillate will be recycled,
preferably between 40 and 60 %v. Part or all of the atmospheric
residue (line 9) can be combined with the product stream 8 via
line 11 to form part of the reconstituted crude. If desired, part
or all of the atmospheric residue may be discarded via line 9.
The hydrogen-rich environment preferred to be maintained in
the process according to the present invention is provided for by
line 2 which represents the introduction of hydrogen and/or a
hydrogen-transfer medium containing component to vessel 10. The
hydrogen supplied to the vessel may be fresh or recycled hydrogen
which need not to be of 100% purity. Streams containing a substantial
amount of hydrogen (e.g. at least 70 %v) can be suitably applied.
The hydrogen-transfer medium to be introduced as such or in
combination with hydrogen can be any of a number of well-known
hydrogen-transfer media, either generated on purpose or readily
available to the refiner. If desired, the hydrogen-transfer media
may be mixed with the feedstock and/or the recycled atmospheric
distillate prior to introduction into the non-catalytic thermal
hydrogenation zone.
In the process as depicted in Figure II an atmospheric residue 12
is used as the starting material. It is firstly subjected to a
vacuum distillation in unit 40 from which a vacuum distillate is
obtained which is transported via line 13 to contribute to the
reconstituted crude. The vacuum residue obtained is fed through
line 1 to the non-catalytic thermal hydrogenation vessel 10. The
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reconstituted crude obtained when using this embodiment of the
process according to the present invention comprises at least the
vacuum distillate 13 and at least one distillate obtained after the
hydrodemetallization treatment~ via line 8, and optionally part of
a further atmospheric distillate via line 7 and an atmospheric
residue via line 11.
The process as depicted in Figure III is closely related to
the process depicted in Figure II with the difference that a
further atmospheric distillation unit 50 is present between the
non-catalytic thermal hydrogenation zone 10 and the hydrodemetall-
ization zone 20 which allows the production of a further atmospheric
distillate 15 which suitably via line 13, but separate if desired,
contributes to the reconstituted crude.
In the process depicted in Figure IV a further embodiment is
incorporated which can be used suitably in addition to the various
processes described thusfar. Not only is the atmospheric distillation
unit 50 used to produce the atmospheric distillate 15 and the
atmospheric residue 3 to be hydrodemetallized, but it also serves
to produce a further distillate fraction 16 which is led to a
hydrogenation unit 60. The hydrogenation unit is suitably operated
at a temperature between 300 and 370 C and at a hydrogen pressure
betweer. 30 and 90 bar to increase the amount of transferable
hydrogen in the distillate fraction 17 which is at least in part
recycled to the non-catalytic thermal hydrogenation vessel 10,
preferably via line 1. If desired, part of the product of the
hydrogenation treatment may be collected via line 18 to form part
of the reconstituted crude. The hydrogen required in unit 60 can be
introduced either by units supplying lines 2 or 4 or can be
introduced separately (not shown).
In the process depicted in Figure V a further embodiment is
incorporated wherein a crude material is introduced via line 12
into atmospheric distillation unit 70 which allows production of an
atmospheric distillate which can be used as such, as part of the
reconstituted crude or can be used (as depicted in Figure V) as
part of the feed to be subjected to non-catalytic thermal
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hydrogenation via line 22. Use is made in particular of this
fraction as co-feed for the non-catalytic thermal hydrogenation
step because o its favourable H/C ratio. A further feature of the
process depicted in Figure V resides in the presence of a vacuum
distillation unit ôO to obtain a further (vacuum) distillate
fraction 24 from the atmospheric residue 23. The vacuum residue 3
is subjected to hydrodemetallization in unit 20. It is, of course,
also possible to carry out the embodiment depicted in Figure V
without the hydrogenation stage in vessel 60.
It will be clear that the preferred embodiment of the process
according to the present invention resides in the use of molecular
hydrogen together with at least part of a fraction of the distillate
obtained after hydrodemetallization as the hydrogen-rich environment.
By also making use of the atmospheric distillate via line Z2 which
has not been subjected to any hydrotreatment but which has an
intrinsically high H/C ratio, and optionally a re-hydrogenated
distillate via line 17 a large variety of hydrotreatment conditions
can be provided for in the non-catalytic thermal treatment
stage 10. This also allows a high degree of flexibility in
determining the composition of the final product as well as the
preferred boiling point range and amount of atmospheric distillate
ex hydrodemetallization to be recycled.
Example
Based on Figure V as described hereinabove 100 pbw of Peace
River bitumen can be upgraded by subjecting it to atmospheric
distillation yielding 2 pbw of 200 C material to be collected as
reconstituted crude, 19 pbw of 200-370 C material to be used in
the non-catalytic thermal hydrogenation and 79 pbw of atmospheric
residue. This atmospheric residue is then subjected to vacuum
distillation to yield 24 pbw of vacuum distillate to be collected
as part of reconstituted crude and 55 pbw of vacuum residue to be
processed in the non-catalytic thermal hydrogenation unit. The feed
to this unit amounts to 116 pbw containing also 15 pbw recycled
vacuum residue obtained after the hydrodemetallization treatment,
7 pbw of a 200-370 C atmospheric distillate obtained after
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hydrodemetallization and 20 pbw atmospheric distillate obtained as
discussed hereinafter. The non-catalytic thermal hydrogenation is
carried out at a temperature of 420 C and a pressure of 60 bar.
Thc effluent from the non-catalytic thermal hydrogenation
treatment is subjected to distillation yielding 4 pbw of gaseous
products, 14 pbw of 200 C materia1, 52 pbw of 200-370 C of which
20 pbw is recycled to the non-catalytic thermal hydrogenation zone
and 32 pbw is collected to form part of reconstituted crude, 12 pbw
of 370-520 C material also forming part of reconstituted crude and
34 pbw of residue which is subjected to hydrodemetallization.
The hydrodemetallization is carried out at 405 C and an
operating pressure of 150 bar using a commercially available Ni/Mo
on alumina catalyst. The effluent from the hydrodemetallization
treatment is then subjected to distillation to yield 2 pbw of
gaseous products, 2 pbw of 200 C material contributing to recon-
stituted crude, 7 pbw of 200-370 C which is recycled to the
non-catalytic thermal hydrogenation unit to serve as the atmospheric
distillate ex hydrodemetallization, 8 pbw of 370-520 ~C material
also forming part of reconstituted crude and 15 pbw of residue
which is recycled to the non-catalytic thermal hydrogenation unit.
If desired, the vacuum distillates obtained prior to and after
the non-catalytic thermal hydrogenation can be subjected, either
together or separate to a hydrogenation treatment using standard
hydrogenation catalysts to increase the quality of the reconstituted
crude. A similar treatment can be carried out on the atmospheric
distillates boiling predominantly in the naphtha mode obtained
prior to and/or after the non-catalytic thermal hydrogenation.
