U.S. patent application number 10/450127 was filed with the patent office on 2004-03-25 for method for hydrotreatment of a heavy hydrocarbon fraction with switchable reactors and reactors capable of being shorted out.
Invention is credited to Kressmann, Stephane, Tromeur, Pascal.
Application Number | 20040055934 10/450127 |
Document ID | / |
Family ID | 8848233 |
Filed Date | 2004-03-25 |
United States Patent
Application |
20040055934 |
Kind Code |
A1 |
Tromeur, Pascal ; et
al. |
March 25, 2004 |
Method for hydrotreatment of a heavy hydrocarbon fraction with
switchable reactors and reactors capable of being shorted out
Abstract
The invention consists in a process for hydrotreating a heavy
hydrocarbon fraction in a first hydrodemetallisation section, then
in a second hydrodesulphurisation section into which the effluent
from the first section is passed. The hydrodemetallisation section
is preceded by at least one guard zone. Said hydrotreatment process
comprises the following steps: a) a step in which the guard zone is
used; b) a step during which the guard zone is short-circuited and
the catalyst it contains is regenerated and/or replaced; c) a step
during which the guard zone in which the catalyst has been
regenerated and/or replaced is reconnected; d) a step in which at
least one of the reactors from the hydrodemetallisation section
and/or the hydrodesulphurisation section can be short-circuited and
the catalyst it contains regenerated and/or replaced.
Inventors: |
Tromeur, Pascal; (Sevres,
FR) ; Kressmann, Stephane; (Serezin Du Rhone,
FR) |
Correspondence
Address: |
Millen White Zelano & Branigan
Arlington Courthouse Plaza 1
Suite 1400
2200 Clarendon Blvd
Arlington
VA
22201
US
|
Family ID: |
8848233 |
Appl. No.: |
10/450127 |
Filed: |
October 14, 2003 |
PCT Filed: |
December 11, 2000 |
PCT NO: |
PCT/FR00/03472 |
Current U.S.
Class: |
208/210 ;
208/211; 208/213; 208/253 |
Current CPC
Class: |
C10G 2300/205 20130101;
C10G 2300/1074 20130101; C10G 2300/206 20130101; C10G 2300/44
20130101; C10G 2300/107 20130101; C10G 2300/202 20130101; C10G
2300/4081 20130101; C10G 2300/301 20130101; C10G 65/04 20130101;
C10G 2300/1059 20130101 |
Class at
Publication: |
208/210 ;
208/211; 208/213; 208/253 |
International
Class: |
C10G 025/00; C10G
045/00; C10G 045/04; C10G 045/60; C10G 029/04 |
Claims
1. A process for hydrotreating, in at least two sections, a heavy
hydrocarbon fraction containing sulphur-containing and metallic
impurities, in which, in a first hydrodemetallisation section, the
hydrocarbon feed and hydrogen are passed over a
hydrodemetallisation catalyst under hydrodemetallisation
conditions, then the effluent from the first stage is passed over a
hydrodesulphurisation catalyst in a subsequent second section under
hydrodesulphurisation conditions, and in which the
hydrodemetallisation section comprises one or more
hydrodemetallisation zones preceded by at least two
hydrodemetallisation guard zones disposed in series for use in
cycles consisting of successive repetitions of steps b) and c)
defined below, the hydrodemetallisation and/or
hydrodesulphurisation sections being composed of one or more
reactors which can be short-circuited separately or otherwise
following step d) defined below, said hydrotreatment process
comprising: a) a step in which the guard zones are used all
together for a period at most equal to the deactivation time and/or
clogging time of one thereof; b) a step during which the
deactivated and/or clogged guard zone is short-circuited and the
catalyst it contains is regenerated and/or replaced by fresh-or
regenerated catalyst; c) a step during which the guard zones are
used all together, the guard zone in which the catalyst has been
regenerated and/or replaced during the preceding step being
reconnected and said step being carried out for a period at most
equal to the deactivation and/or clogging time of one of the guard
zones; d) a step in which at least one of the reactors from the
hydrodemetallisation section and/or the hydrodesulphurisation
section can be short-circuited during a cycle when the catalyst is
deactivated and/or clogged for regeneration and/or replacement by
fresh or regenerated catalyst.
2. A process for hydrotreating, in at least two sections, a heavy
hydrocarbon fraction containing sulphur-containing and metallic
impurities, in which, in a first hydrodemetallisation section, the
hydrocarbon feed and hydrogen are passed over a
hydrodemetallisation catalyst under hydrodemetallisation
conditions, then the effluent from the first stage is passed over a
hydrodesulphurisation catalyst in a subsequent second section under
hydrodesulphurisation conditions, and in which the
hydrodemetallisation section comprises one or more
hydrodemetallisation zones preceded by at least one guard zone, the
hydrodemetallisation and/or hydrodesulphurisation sections being
composed of one or more reactors which can be short-circuited
separately or otherwise following step d) defined below, said
hydrotreatment process comprising: a) a step in which the guard
zone is used for a period at most equal to the deactivation time
and/or clogging time of said zone; b) a step during which the
deactivated and/or clogged guard zone is short-circuited and the
catalyst it contains is regenerated and/or replaced by fresh or
regenerated catalyst; c) a step during which the guard zone in
which the catalyst has been regenerated and/or replaced during the
preceding step is reconnected, said step being carried out for a
period at most equal to the deactivation and/or clogging time of
one of the guard zones; d) a step in which at least one of the
reactors from the hydrodemetallisation section and/or the
hydrodesulphurisation section can be short-circuited during a cycle
when the catalyst is deactivated and/or clogged for regeneration
and/or replacement by fresh or regenerated catalyst.
3. A process for hydrotreating, in at least two sections, a heavy
hydrocarbon fraction containing sulphur-containing and metallic
impurities in which, in a first hydrodemetallisation section, the
hydrocarbon feed and hydrogen are passed over a
hydrodemetallisation catalyst under hydrodemetallisation
conditions, then the effluent from the first stage is passed over a
hydrodesulphurisation catalyst in a subsequent second section under
hydrodesulphurisation conditions, and in which the
hydrodemetallisation section comprises one or more
hydrodemetallisation zones preceded by at least two
hydrodemetallisation guard zones comprising one or more reactors,
preferably fixed or ebullated bed reactors, disposed in series for
use in cycles consisting of successive repetitions of steps b) and
c) defined below, the hydrodemetallisation and/or
hydrodesulphurisation sections being composed of one or more
reactors which can be short-circuited separately or otherwise
following step d) defined below, said hydrotreatment process
comprising: a) a step in which the guard zones are all used
together for a period at most equal to the deactivation and/or
clogging time of the guard zone the most upstream with respect to
the overall direction of circulation of the treated feed; b) a step
during which the feed penetrates directly into the guard zone
located immediately after that which was the most upstream during
the preceding step and during which the guard zone which was the
most upstream during the preceding step is short-circuited and the
catalyst which it contains is regenerated and/or replaced by fresh
catalyst; and c) a step during which the guard zones are used all
together, the guard zone in which the catalyst has been regenerated
and/or replaced during step b) being reconnected so as to be
downstream of the set of guard zones and said step being continued
for a period at most equal to the deactivation and/or clogging time
of the guard zone which during this step is the most upstream with
respect to the overall direction of circulation of the treated
feed; d) a step in which at least one of the reactors from the
hydrodemetallisation section and/or hydrodesulphurisation section
can be short-circuited during the cycle when the catalyst is
deactivated and/or clogged to be regenerated and/or replaced by
fresh or regenerated catalyst.
4. A process according to any one of claims 1 to 3, in which a
quantity of middle distillate representing 0.5% to 80% by weight
with respect to the weight of hydrocarbon feed is introduced into
the inlet to the first operating guard zone.
5. A process according to claim 4, in which the atmospheric
distillate introduced with the hydrocarbon feed is a straight run
gas oil.
6. A process according to any one of claims 1 to 5, in which the
product from the hydrodesulphurisation step is sent to an
atmospheric distillation zone from which an atmospheric distillate
is recovered at least a portion of which is recycled to the inlet
to the first functioning guard zone, and an atmospheric residue is
also recovered.
7. A process according to claim 6, in which at least a portion of a
gas oil fraction from the atmospheric distillation step following
the hydrodesulphurisation step is recycled to the inlet to the
first functioning guard zone.
8. A process according to claim 5 or claim 7, in which the recycled
gas oil fraction is a cut with an initial boiling point of about
140.degree. C. and an end point of about 400.degree. C.
9. A process according to any one of claims 4 to 8, in which the
quantity of atmospheric distillate and/or gas oil introduced to the
inlet to the first functioning guard zone at the same time as the
feed represents about 1% to 50% by weight with respect to the
feed.
10. A process according to claim 6 or claim 7, in which at least a
portion of the atmospheric residue from the atmospheric
distillation zone is sent to a vacuum distillation zone from which
a vacuum distillate is recovered, at least a portion of which is
recycled to the inlet to the first functioning guard zone, and a
vacuum residue is also recovered.
11. A process according to claim 10, in which at least a portion of
the atmospheric residue and/or vacuum distillate is sent to a
catalytic cracking unit from which an LCO fraction and an HCO
fraction are recovered, and at least a portion of one or the other
or a mixture of the two fractions is sent to the inlet to the first
functioning guard zone.
12. A process according to any one of claims 1 to 3, in which
during step c), the guard zones are used all together, the guard
zone in which the catalyst has been regenerated during step b)
being reconnected such that the connection is identical to that it
had before it was short-circuited during step b).
13. A process according to any one of claims 1 to 12, in which a
conditioning section is associated with the guard zone or zones,
which zone enables short-circuiting or permutation during operation
of said guard zone or zones, without the unit ceasing operation,
said section being regulated so as to condition the catalyst
contained in the guard zone which is not functioning, at a pressure
in the range 1 MPa to 5 MPa.
14. A process according to any one of claims 1 to 13, in which, in
order to treat a feed constituted by a heavy oil or a heavy oil
fraction containing asphaltenes, the feed is initially subjected to
hydrovisbreaking conditions, mixed with hydrogen, before sending
the feed to the guard zone or zones.
15. A process according to any one of claims 7, 10 or 11, in which
the atmospheric residue undergoes deasphalting using a solvent or a
solvent mixture and at least a portion of the deasphalted product
is recycled to the inlet to the first functioning guard zone.
16. A process according to claim 10 or claim 11, in which the
vacuum residue undergoes deasphalting using a solvent or solvent
mixture and at least a portion of the deasphalted product is
recycled to the inlet to the first functioning guard zone.
17. A process according to any one of claims 1 to 16, in which all
of the reactors are fixed bed reactors.
18. A process according to any one of claims 1 to 17, in which at
least one of the guard zone and/or hydrodemetallisation section
and/or hydrodesulphurisation section reactors is an ebullated bed
reactor.
19. A process according to claim 18, in which all of the reactors
for the guard zones are fixed bed reactors, and all of the reactors
in the hydrodesulphurisation zone are ebullated bed reactors.
20. A process according to claim 18 or claim 19, in which all of
the reactors in the guard zones are fixed bed reactors, and all the
reactors in the hydrodemetallisation zone are ebullated bed
reactors.
Description
[0001] The present invention relates to refining and converting
heavy hydrocarbon fractions containing, inter alia,
sulphur-containing and metallic impurities, such as atmospheric
residues, vacuum residues, deasphalted oils, pitches, asphalts
mixed with an aromatic distillate, coal hydrogenates, heavy oils of
any origin and in particular those from bituminous schists or
sands. In particular, it relates to treating liquid feeds. The
scope of the invention also encompasses asphaltenes also being
contained in the liquid feed.
[0002] Feeds which can be treated in accordance with the invention
normally comprise at least 0.5 ppm by weight of metals (nickel
and/or vanadium) and at least 0.5% by weight of sulphur.
[0003] The aim of catalytic hydrotreatment of such feeds is both to
refine, i.e., to substantially reduce their metal, sulphur and
other impurity contents while increasing the hydrogen-to-carbon
ratio (H/C) while transforming them to a greater or lesser extent
to lighter cuts, the different effluents obtained possibly serving
as bases for the production of high quality fuel, gas oil and
gasoline, or feeds for other units such as residue cracking or
cracking vacuum distillates.
[0004] The problem with catalytic hydrotreatment of such feeds
originates from the fact that such impurities gradually deposit
themselves on the catalyst in the form of metals and coke, and tend
to rapidly deactivate and clog the catalytic system, which
necessitates a stoppage to replace it.
[0005] Processes for hydrotreating that type of feed must therefore
be designed to allow as long as possible a cycle of operation
without stopping the unit, the aim being to attain a minimum one
year cycle of operation.
[0006] A variety of treatments for this type of feed exist. Such
treatments have until now been carried out:
[0007] either in processes using fixed catalyst beds (for example
the HYVAHL-F process from the Institut Francais du Ptrole);
[0008] or in processes comprising at least one reactor enabling the
catalyst to be replaced quasi-continuously (for example the
HYVAHL-M moving bed process from the Institut Francais du
Ptrole).
[0009] The process of the present invention is an improvement over
prior art processes, in particular fixed or ebullated bed
processes. In such processes, the feed circulates through a
plurality of reactors, preferably fixed or ebullated bed reactors,
disposed in series, the first reactor or reactors being used to
carry out hydrodemetallisation (HDM) of the feed in particular and
part of the hydrodesulphurisation, the final reactor or reactors
being used to carry out deep refining of the feed, and in
particular hydrodesulphurisation (HDS step). The effluents are
withdrawn from the last HDS reactor.
[0010] In such processes, specific catalysts adapted to each step
are usually used, under average operating conditions of about 5 MPa
to about 25 MPa, preferably about 10 MPa to about 20 MPa, and a
temperature of about 370.degree. C. to 420.degree. C.
[0011] For the HDM step, the ideal catalyst must be suitable for
treating feeds which are rich in asphaltenes, while having a high
demetallisation capacity associated with a high metal retention
capacity and a high resistance to coking. The Applicant has
developed such a catalyst on a particular macroporous support (the
"sea urchin" structure) which endows it with precisely the desired
qualities for this step (European patents EP-B-0 113 297 and EP-B-0
113 284):
[0012] a degree of demetallisation of at least 10% to 90% in the
HDM step;
[0013] a metal retention capacity of more than 10% with respect to
the weight of new catalyst, which results in longer cycles of
operation;
[0014] high resistance to coking even at temperatures of more than
390.degree. C. which contributes to extending the cycle period
which is often limited by increasing the pressure drop and the
activity loss due to coke production, and which means that the
majority of the thermal conversion can be carried out in this
step.
[0015] For the HDS step, the ideal catalyst must have a high
hydrogenating power so as to carry out deep refining of the
products: desulphurisation, continuation of demetallisation,
reducing the Conradson carbon and possibly the amount of
asphaltenes. The Applicant has developed such a catalyst (EP-B-0
113 297 and EP-B-0 113 284) which is particularly suitable for
treating that type of feed.
[0016] The disadvantage of that type of high hydrogenating capacity
catalyst is that it rapidly deactivates in the presence of metals
or coke. For this reason, combining a suitable HDM catalyst, which
can function at a relatively high temperature to carry out most of
the conversion and demetallisation, with a suitable HDS catalyst,
which can be operated at a relatively low temperatures as it is
protected from metals and other impurities by the HDM catalyst
which encourages deep hydrogenation and limits coking, then in the
end overall refining performances are obtained which are higher
than those obtained with a single catalytic system or with those
obtained with a similar HDM/HDS arrangement using an increasing
temperature profile which leads to rapid coking of the HDS
catalyst.
[0017] The importance of fixed bed processes is that high refining
performances are obtained because of the high catalytic efficacy of
fixed beds. In contrast, above a certain quantity of metals in the
feed (for example 50 to 150 ppm), even though better catalytic
systems are used, the performances and especially the operating
period for such processes becomes insufficient: the reactors (in
particular the first HDM reactor) rapidly become charged with
metals and thus deactivate; to compensate for that deactivation,
the temperatures are increased, which encourages coke formation and
increases pressure drops; further, it is known that the first
catalytic bed is susceptible to becoming clogged quite rapidly
because of the asphaltenes and sediments contained in the feed or
as a result of operating problems.
[0018] The result is that the unit has to be stopped a minimum of
every 2 to 6 months to replace the first deactivated or clogged
catalytic beds, that operation possibly lasting up to three weeks
and further reducing the service factor of the unit.
[0019] The importance of ebullated bed processes is that the
conversion performance is high due to the possibility of working at
high temperatures. The Applicant has developed a process that is
eminently suitable for treating conventional and heavy feeds
(Canadian patent CA-2 171 894, French patent application
FR-98/00530).
[0020] Although the best catalytic systems are used, the operation
time can be reduced during problems in operations and/or during use
not suited to the feed. The unit is thus stopped depending on how
much coke is present in the reactor. We have attempted to solve
these problems of operation and use of the catalyst.
[0021] We have also sought to overcome the disadvantages of fixed
bed arrangements in different manners.
[0022] Thus, one or more moving bed reactors have been proposed,
installed at the head of the HDM step (United States patents U.S.
Pat. No. 3,910,834 or British patent GB-B-2 124 252). Such moving
beds can operate in co-current mode (the HYCON process from SHELL,
for example) or in counter-current mode (the Applicant's HYVAHL-M
process, for example). This protects the reactors, for example
fixed bed reactors by carrying out part of the demetallisation and
filtering the particles contained in the feed which could lead to
clogging. Further, quasi-continuous replacement of the catalyst in
that or those moving bed reactors avoids the need to stop the unit
every 3 to 6 months.
[0023] The disadvantage of such moving bed techniques is that
overall, their performances and efficiency are rather inferior to
those for fixed beds of the same size, that they cause attrition of
the circulating catalyst which can lead to obstruction of the fixed
beds located downstream, and which above all, under the operating
conditions used, the risks of coking and thus the formation of
agglomerates of catalyst are far from negligible with such heavy
feeds, in particular in the event of problems. These agglomerates
can prevent the catalyst from circulating either in the reactor or
in the used catalyst withdrawal lines, and finally cause stoppage
of the unit to clean the reactor and the withdrawal lines.
[0024] In order to retain excellent performance while maintaining
an acceptable service factor, the addition of a guard reactor,
preferably a fixed bed reactor (space velocity HSV=2 to 4) in front
of the HDM reactors has been considered (U.S. Pat. No. 4,118,310
and U.S. Pat. No. 3,968,026). Usually, this guard reactor can be
short-circuited by using an isolation valve in particular. Thus the
principal reactors are temporarily protected against clogging. When
the guard reactor is clogged it is short-circuited, but then the
following principal reactor can become clogged in its turn and lead
to stoppage of the unit. Further, the small size of the guard
reactor does not ensure a high degree of demetallisation of the
feed and thus is a poor protector of the principal HDM reactors
against the deposition of metals in the case of metal-rich feeds
(more than 100 ppm, for example). Thus those reactors undergo
accelerated deactivation leading to too frequent stoppages of the
unit and thus to service factors which are still insufficient.
[0025] FR-B1-2 681 871 describes a system that combines good fixed
bed performance with a high service factor for the treatment of
feeds with a high metal content (1 to 1500 ppm but usually 100 to
1000 and preferably 150 to 350 ppm) which consists in a
hydrotreatment process carried out in at least two steps to
hydrotreat a heavy hydrocarbon fraction containing
sulphur-containing impurities and metallic impurities in which in a
first section, hydrodemetallisation, the hydrocarbon feed and
hydrogen are passed over a hydrodemetallisation catalyst under
hydrodemetallisation conditions then in a subsequent second step,
the effluent from the first section is passed over a
hydrodesulphurisation catalyst under hydrodesulphurisation
conditions. In this process, the hydrodemetallisation section
comprises one or more hydrodemetallisation zones, preferably with
fixed beds, preceded by at least two hydrodemetallisation guard
zones, also preferably with fixed beds, disposed in series for
cyclic use consisting of successive repetition of steps b) and c)
defined below:
[0026] a) a step in which the guard zones are used together for a
period at most equal to the deactivation time and/or clogging time
for one thereof;
[0027] b) a step during which the deactivated and/or clogged guard
zone is short-circuited and the catalyst it contains is regenerated
and/or replaced by fresh catalyst; and
[0028] c) a step during which the guard zones are all used
together, the guard zone where the catalyst has been regenerated
during the preceding step being reconnected and said step being
carried out for a period at most equal to the deactivation and/or
clogging time for one of the guard zones.
[0029] This process produces a cycle period which is in general at
least 11 months for the principal HDM and HDS reactors with high
performances for refining and conversion while retaining the
stability of the products. The overall desulphurisation is of the
order of 90% and the overall demetallisation is of the order of
95%.
[0030] The disadvantage of this technology is the difficulty of
obtaining overall desulphurisation performances of more than about
90% and/or overall demetallisation performances of more than about
95%, and the difficulty of obtaining cycle times of more than 11
months independent of performance levels. It has surprisingly been
discovered that short-circuiting one or more reactors of the
hydrodemetallisation and/or hydrodesulphurisation section can
maintain the catalytic activity for each of the steps and/or
improve the cycle time.
[0031] The present invention concerns the possibility of
short-circuiting one or more reactors when the catalyst is
deactivated and/or clogged by sediments or coke to be regenerated
and/or replaced by fresh or regenerated catalyst. This invention
concerns both reactors from the hydrodemetallisation section and
reactors from the hydrodesulphurisation section.
[0032] It follows that the reactors from the hydrodemetallisation
section and/or hydrodesulphurisation section are, for example,
short-circuited every 6 months to replace the deactivated or
clogged catalytic beds; this operation improves the service factor
of the unit.
[0033] The invention consists in a process for hydrotreating a
heavy hydrocarbon fraction in a first hydrodemetallisation section,
then in a second hydrodesulphurisation section into which the
effluent from the first section is passed. The hydrodemetallisation
section is preceded by at least one guard zone. Said hydrotreatment
process comprises the following steps:
[0034] a) a step in which the guard zone is used;
[0035] b) a step during which the guard zone is short-circuited and
the catalyst it contains is regenerated and/or replaced;
[0036] c) a step during which the guard zone in which the catalyst
has been regenerated and/or replaced is reconnected;
[0037] d) a step in which at least one of the reactors from the
hydrodemetallisation section and/or the hydrodesulphurisation
section can be short-circuited and the catalyst it contains
regenerated and/or replaced.
[0038] A route for improving fixed bed performance, summarised
below, has also been described by the Applicant in FR-A-2 784 687.
That concept can also be applied to the present invention.
[0039] However, there is some difficulty associated with the high
viscosity of the feed and the total liquid effluent which causes
high pressure drops in the reactor and difficulties in the
operation of the recycling compressor, often resulting in a rather
low hydrogen pressure which does not encourage either good
hydrodemetallisation or good hydrodesulphurisation. Further, it has
been shown that the gas oil fraction obtained normally cannot
directly be used as its sulphur content is higher than current
specifications allow.
[0040] It is desirable and possible to improve the performance of a
process such as that described by the Applicant in French patents
FR-B1-2 681 871 and FR-A-2 784 687. In particular, the process of
the present invention can very substantially reduce the viscosity
of the liquid effluents, resulting in a substantial reduction in
the pressure drops in the reactors, better operation of the
recycling compressor and the production of a higher hydrogen
pressure. This results in higher overall desulphurisation and a gas
oil fraction with a much lower sulphur content, satisfying the
current specifications and which can be directly used in the gas
oil pool of the refinery. Further, in the process of the present
invention, the preheat furnaces function better because of better
heat transfer and thus the skin temperature of these furnaces is
lower which helps to increase the service life of the furnaces and
thus contributes to reducing the operating costs of the unit.
[0041] The process of the invention, which combines high
performances of the reactors, preferably fixed bed reactors or
ebullated bed reactors, with a high service factor for treating
feeds with high metal contents (1 to 1500 ppm, but usually 100 to
1000 and preferably 150 to 350 ppm) can be defined in one of its
variations as a process for hydrotreating, in at least two
sections, a heavy hydrocarbon fraction containing
sulphur-containing and metallic impurities in which, in a first,
hydrodemetallisation, section, the hydrocarbon feed and hydrogen
are passed over a hydrodemetallisation catalyst under
hydrodemetallisation conditions, then the effluent from the first
section is passed over a hydrodesulphurisation catalyst in a
subsequent second section under hydrodesulphurisation conditions,
and in which the hydrodemetallisation section comprises one or more
hydrodemetallisation zones, preferably fixed bed or ebullated bed
zones, preceded by at least one or possibly two
hydrodemetallisation guard zones, also preferably fixed bed or
ebullated bed zones, disposed in series for use in a cycle
consisting of successive repetitions of steps b) and c) defined
below, the hydrodemetallisation and/or hydrodesulphurisation
sections being composed of one or more reactors, preferably fixed
bed or ebullated bed reactors, which can be short-circuited
separately or otherwise following step d) defined below. When two
guard zones are used, the process of the invention is a
hydrotreatment process comprising:
[0042] a) a step in which the guard zones are used all together for
a period at most equal to the deactivation time and/or clogging
time of one thereof;
[0043] b) a step during which the deactivated and/or clogged guard
zone is short-circuited and the catalyst it contains is regenerated
and/or replaced by fresh or regenerated catalyst;
[0044] c) a step during which the guard zones are used all
together, the guard zone in which the catalyst has been regenerated
and/or replaced during the preceding step being reconnected and
said step being carried out for a period at most equal to the
deactivation and/or clogging time of one of the guard zones;
[0045] d) a step in which at least one of the reactors from the
hydrodemetallisation section and/or the hydrodesulphurisation
section can be short-circuited during a cycle when the catalyst is
deactivated and/or clogged for regeneration and/or replacement by
fresh or regenerated catalyst.
[0046] A further variation of the process of the invention consists
in a process for hydrotreating, in at least two sections, a heavy
hydrocarbon fraction containing sulphur-containing and metallic
impurities, in which in a first hydrodemetallisation, section, the
hydrocarbon feed and hydrogen are passed over a
hydrodemetallisation catalyst under hydrodemetallisation
conditions, then the effluent from the first step is passed over a
hydrodesulphurisation catalyst in a subsequent second section under
hydrodesulphurisation conditions, and in which the
hydrodemetallisation section comprises one or more
hydrodemetallisation zones preceded by at least one
hydrodemetallisation guard zone, the hydrodemetallisation and/or
hydrodesulphurisation sections being composed of one or more
reactors which can be short-circuited separately or otherwise
following step d) defined below, said hydrotreatment process
comprising:
[0047] a) a step in which the guard zone is used for a period at
most equal to the deactivation time and/or clogging time of said
zone;
[0048] b) a step during which the deactivated and/or clogged guard
zone is short-circuited and the catalyst it contains is regenerated
and/or replaced by fresh or regenerated catalyst;
[0049] c) a step during which the guard zone in which the catalyst
has been regenerated and/or replaced during the preceding step is
reconnected, said step being carried out for a period at most equal
to the deactivation and/or clogging time of one of the guard
zones;
[0050] d) a step in which at least one of the reactors from the
hydrodemetallisation section and/or the hydrodesulphurisation
section can be short-circuited during a cycle when the catalyst is
deactivated and/or clogged for regeneration and/or replacement by
fresh or regenerated catalyst.
[0051] In a variation of the process of the invention, the feed for
said process is a heavy hydrocarbon fraction containing
sulphur-containing and metallic impurities, in general at least 0.5
ppm by weight of metals, for example a fraction obtained by vacuum
distillation, termed a vacuum distillate (VD).
[0052] Preferably, in the process of the invention, a quantity of
middle distillate generally representing about 0.5% to about 80% by
weight with respect to the weight of hydrocarbon feed is introduced
into the first functioning guard zone.
[0053] More preferably, the quantity of middle distillate
introduced represents about 1% to about 50%, by weight, highly
preferably about 5% to about 25% by weight with respect to the
weight of hydrocarbon feed.
[0054] In a particular implementation, the atmospheric distillate
which is introduced with the hydrocarbon feed is a straight run gas
oil.
[0055] In a further implementation, the product from the
hydrodesulphurisation step is sent to an atmospheric distillation
zone from which an atmospheric distillate is recovered at least a
portion of which is recycled to the inlet to the first functioning
guard zone, and an atmospheric residue is recovered.
[0056] In a particular variation, at least a portion of a gas oil
fraction from the atmospheric distillation is recycled. In this
case, the gas oil cut which is recycled is usually a cut with an
initial boiling point of about 140.degree. C. and with an end point
of about 400.degree. C. Usually this cut is a 150-370.degree. C.
cut, or a 170-350.degree. C. cut.
[0057] In a further possible variation of the process of the
invention, a gas oil from a unit functioning using the HYVAHL
process can be recycled, or a light gas oil from a catalytic
cracking unit, usually known as an LCO (light cycle oil) with an
initial boiling point generally in the range about 140.degree. C.
to about 220.degree. C. and an end point generally in the range
about 340.degree. C. to about 400.degree. C. It is also possible to
recycle a fraction of heavy gas oil from catalytic cracking,
usually termed an HCO (high cycle oil) with an initial boiling
point in the range about 340.degree. C. to about 380.degree. C. and
with a final boiling point generally in the range about 350.degree.
C. to about 550.degree. C.
[0058] The quantity of atmospheric distillate and/or gas oil which
is recycled represents about 1% to 50%, preferably 5% to 25%, more
preferably about 10% to 20% by weight, with respect to the
feed.
[0059] In a further variation, at least a portion of the
atmospheric residue from the atmospheric distillation zone is sent
to a vacuum distillation zone from which a vacuum distillate is
recovered at least a portion of which is recycled to the inlet to
the first functioning guard zone, and a vacuum residue is also
recovered which can be sent to the refinery fuel pool.
[0060] In a further variation, at least a portion of the
atmospheric residue and/or vacuum distillate is sent to a catalytic
cracking unit, preferably a fluidised bed catalytic cracking unit,
for example a unit such as that using the R2R process developed by
the Applicant. From this catalytic cracking unit, an LCO fraction
and an HCO fraction in particular are recovered at least part of
either one or the other, or a mixture of the two, can be added to
the fresh feed which is sent to the hydrotreatment process of the
present invention. Usually, a gas oil fraction, a gasoline fraction
and a gaseous fraction are also recovered. At least a portion of
this gas oil fraction can optionally be recycled to the inlet to
the first functioning guard zone.
[0061] The catalytic cracking step can be carried out in a
conventional manner known to skilled persons under suitable residue
cracking conditions to produce hydrocarbon-containing products with
a lower molecular weight. Descriptions of the operation and
catalysts which can be used in fluidised bed cracking can be found,
for example, in U.S. Pat. No. 4,695,370, EP-B-0 184 517, U.S. Pat.
No. 4,959,334, EP-B-0 323 297, U.S. Pat. No. 4,965,232, U.S. Pat.
No. 5,120,691, U.S. Pat. No. 5,344,544, U.S. Pat. No. 5,449,496,
EP-A-0 485 259, U.S. Pat. No. 5,286,690, U.S. Pat. No. 5,324,696
and EP-A-0 699 224 the descriptions of which are hereby
incorporated into the present description by dint of their
mention.
[0062] The fluidised bed catalytic cracking reactor can function in
upflow or downflow mode. While this is not a preferred embodiment
of the invention, it is also possible to carry out catalytic
cracking in a moving bed reactor. Particularly preferred catalytic
cracking catalysts are those which contain at least one zeolite
usually mixed with an appropriate matrix such as alumina, silica or
silica-alumina.
[0063] The process of the invention includes a particular variation
in which during step c) the guard zones are used all together, the
guard zone where the catalyst has been regenerated during step b)
being reconnected such that its connection is identical to that
which it had before it was short-circuited during step b).
[0064] The process of the invention comprises a further variation,
which constitutes a preferred implementation of the present
invention, comprising the following steps:
[0065] a) a step in which the guard zones are all used together for
a period at most equal to the deactivation and/or clogging time of
the guard zone the most upstream with respect to the overall
direction of circulation of the treated feed;
[0066] b) a step during which the feed penetrates directly into the
guard zone located immediately after that which was the most
upstream during the preceding step and during which the guard zone
which was the most upstream during the preceding step is
short-circuited and the catalyst which it contains is regenerated
and/or replaced by fresh or regenerated catalyst; and
[0067] c) a step during which the guard zones are used all
together, the guard zone in which the catalyst has been regenerated
and/or replaced during the preceding step being reconnected so as
to be downstream of the set of guard zones and said step being
continued for a period at most equal to the deactivation and/or
clogging time of the guard zone which during this step is the most
upstream with respect to the overall direction of circulation of
the treated feed;
[0068] d) a step in which at least one of the reactors from the
hydrodemetallisation section and/or hydrodesulphurisation section
can be short-circuited during the cycle when the catalyst is
deactivated and/or clogged to be regenerated and/or replaced by
fresh or regenerated catalyst.
[0069] In the preferred implementation of the process, the guard
zone which is the most upstream in the overall direction of
circulation of the feed gradually becomes charged with metals,
coke, sediments and a variety of other impurities and is
disconnected when desired but usually when the catalyst it contains
is practically saturated with metals and various impurities.
[0070] In a preferred implementation, a particular conditioning
section is used which permits permutation of these guard zones
during operation, i.e., without stopping the unit's operation:
firstly, a system which operates under moderate pressure (1 to 5
MPa but preferably 1.5 to 2.5 MPa) carries out the following
operations on the disconnected guard reactor: washing, stripping,
cooling, before discharging the used catalyst; then heating and
sulphurisation after charging with fresh catalyst; then a further
pressurisation/depressurisation and tap/valve system using
appropriate technology effectively interchanges these guard zones
without stopping the unit, i.e., without affecting the service
factor, since all of the washing, stripping, discharging of used
catalyst, recharging of fresh catalyst, heating and sulphurisation
operations are carried out on the disconnected reactor or guard
zone.
[0071] The reactors of the hydrotreatment unit usually function
with the following hourly space velocities (HSV):
1 HSV (h.sup.-1) HSV (h.sup.-1) Broad range Preferred range Total
HDM step: (including 0.2-4.0 0.3-0.4 guard reactors) Total HDS
step: 0.2-4.0 0.25-0.4 Overall (HDM + HDS): 0.10-2.0 0.12-0.30
[0072] The preferred mode consists of operating the guard reactors
or zones in service at an overall HSV of about 0.1 to 4.0 h.sup.-1,
usually about 0.2 to 1.0 h.sup.-1, which differs from other
processes using smaller guard reactors, in particular as described
in U.S. Pat. No. 3,968,026 where smaller guard reactors are used.
The value of the HSV of each functioning guard reactor is
preferably about 0.5 to 8 h.sup.-1 and usually about 1 to 2
h.sup.-1. The overall HSV of the guard reactors and that of each
reactor is selected so as to carry out maximum hydrodemetallisation
(HDM) while controlling the reaction temperature (limiting the
exothermicity).
[0073] In an advantageous implementation, the unit comprises a
conditioning section, not shown in the Figures, provided with
circulation means, heating means, cooling means and suitable
separation means functioning independently of the reaction section,
whereby with the aid of lines and valves, the operations of
preparing fresh or regenerated catalyst contained in the guard
reactor and for the short-circuited reactor just before being
connected, with the unit in operation, can be carried out, namely:
pre-heating the guard reactor during permutation or
short-circuiting, sulphurising the catalyst it contains, and
bringing it to the required pressure and temperature conditions.
When the permutation or short-circuiting operation of this guard
reactor has been carried out using a set of suitable valves, this
same section can also carry out the operations of conditioning the
used catalyst contained in the guard reactor just after
disconnection of the reaction section, namely: washing and
stripping the used catalyst under the required conditions, then
cooling before proceeding to the operations of discharging this
used catalyst then replacing it with fresh or regenerated
catalyst.
[0074] Preferably again, these catalysts are those described in the
Applicant's patents EP-B-0 098 764 and the French patent filed with
national registration number 97/07149. They contain a support and
0.1% to 30% by weight, expressed as the metal oxides, of at least
one metal or compound of a metal of at least one of groups V, VI
and VHI of the periodic table and in the form of a plurality of
juxtaposed agglomerates each formed from a plurality of acicular
platelets, the platelets of each agglomerate generally being
radially orientated with respect to each other and with respect to
the centre of the agglomerate.
[0075] More particularly, the present patent application concerns
the treatment of heavy petroleum or petroleum fractions, with the
aim of converting them into lighter fractions, that are easier to
transport or treat using the usual refining processes. Oils from
coal hydrogenation can also be treated. In this case, it is
preferable to use ebullated bed reactors.
[0076] More particularly, the invention solves the problem of
transforming a non transportable viscous heavy oil, which is rich
in metals and sulphur, and contains more than 50% of constituents
with a normal boiling point of more than 520.degree. C. to a stable
hydrocarbon-containing product which can easily be transported, and
having a reduced metals and asphaltenes content and a reduced
content, for example less than 20% by weight, of constituents with
a normal boiling point of more than 520.degree. C.
[0077] In a particular implementation, before sending the feed to
the guard reactors, it is first mixed with hydrogen and subjected
to hydrovisbreaking conditions.
[0078] In a further implementation, the atmospheric residue or
vacuum residue can undergo deasphalting using a solvent, for
example a hydrocarbon-containing solvent or a solvent mixture. The
most frequently used hydrocarbon-containing solvent is a
paraffinic, olefinic or alicyclic hydrocarbon (or hydrocarbon
mixture) containing 3 to 7 carbon atoms. This treatment is
generally carried out under conditions that can produce a
deasphalted product containing less than 0.05% by weight of
asphaltenes precipitated by heptane in accordance with the AFNOR NF
T 60115 standard. This deasphalting can be carried out using the
procedure described in the Applicant's patent U.S. Pat. No.
4,715,946. The solvent/feed volume ratio will usually be about 3:1
to about 4:1 and the elementary physico-chemical operations which
are comprised in the overall deasphalting operation
(mixing-precipitation, decanting the asphaltene phase,
washing-precipitation of the asphaltene phase) will usually be
carried out separately. The deasphalted product is then normally at
least partially recycled to the inlet to the first functioning
guard zone.
[0079] Normally the solvent for washing the asphaltene phase is the
same as that used for precipitation.
[0080] The mixture between the feed to be deasphalted and
deasphalting solvent is usually carried out upstream of the
exchanger which adjusts the temperature of the mixture to a value
required to carry out proper precipitation and good
decantation.
[0081] The feed-solvent mixture preferably passes into the tubes of
the exchanger and not on the shell side.
[0082] The residence time of the feed-solvent mixture in the
mixture precipitation zone is generally about 5 seconds (s) to
about 5 minutes (min), preferably about 20 s to about 2 min.
[0083] The residence time for the mixture in the decanting zone is
normally about 4 min to about 20 min.
[0084] The residence time for the mixture in the washing zone
generally remains between about 4 min and about 20 min.
[0085] The rate of rise of the mixtures both in the decanting zone
and in the washing zone are usually less than about 1 centimetre
per second (cm/s), preferably less than about 0.5 cm/s.
[0086] The temperature applied in the washing zone is usually less
than that applied in the decanting zone. The temperature difference
between these two zones will normally be about 5.degree. C. to
about 50.degree. C.
[0087] The mixture from the washing zone will usually be recycled
in the decanter and advantageously upstream of the exchanger
located at the inlet to the decanting zone.
[0088] The solvent/asphaltene ratio recommended in the washing zone
is about 0.5:1 to about 8:1 and preferably about 1:1 to about
5:1.
[0089] Deasphalting can comprise two stages, each stage including
the three elementary phases of precipitation, decanting and
washing. In this precise case, the temperature recommended in each
phase of the first stage is preferably on average less than about
10.degree. C. to about 40.degree. C. at the temperature of each
phase corresponding to the second stage.
[0090] The solvents which are used can also be C1 to C6 alcohols or
phenols or glycol type solvents. However, paraffinic and/or
olefinic solvents containing 3 to 6 carbon atoms are highly
advantageously used.
[0091] In summary, in one variation, the process of the invention
consists in a process for hydrotreating, in at least two sections,
a heavy hydrocarbon fraction containing sulphur-containing and
metallic impurities, in which in a first, hydrodemetallisation,
section, the hydrocarbon feed and hydrogen are passed over a
hydrodemetallisation catalyst under hydrodemetallisation
conditions, then the effluent from the first stage is passed over a
hydrodesulphurisation catalyst in a subsequent second section under
hydrodesulphurisation conditions, and in which the
hydrodemetallisation section comprises one or more
hydrodemetallisation zones preceded by at least two
hydrodemetallisation guard zones disposed in series for use in a
cycle consisting of successive repetitions of steps b) and c)
defined below, the hydrodemetallisation and/or
hydrodesulphurisation sections being composed of one or more
reactors which can be short-circuited separately or otherwise
following step d) defined below, said hydrotreatment process
comprising:
[0092] a) a step in which the guard zones are used all together for
a period at most equal to the deactivation time and/or clogging
time of one thereof;
[0093] b) a step during which the deactivated and/or clogged guard
zone is short-circuited and the catalyst it contains is regenerated
and/or replaced by fresh or regenerated catalyst;
[0094] c) a step during which the guard zones are used all
together, the guard zone in which the catalyst has been regenerated
and/or replaced during the preceding step being reconnected and
said step being carried out for a period at most equal to the
deactivation and/or clogging time of one of the guard zones;
[0095] d) a step in which at least one of the reactors from the
hydrodemetallisation section and/or the hydrodesulphurisation
section can be short-circuited during a cycle when the catalyst is
deactivated and/or clogged for regeneration and/or replacement by
fresh or regenerated catalyst.
[0096] In a further variation, the process of the invention
consists in a process for hydrotreating, in at least two sections,
a heavy hydrocarbon fraction containing sulphur-containing and
metallic impurities, in which in a first, hydrodemetallisation,
section, the hydrocarbon feed and hydrogen are passed over a
hydrodemetallisation catalyst under hydrodemetallisation
conditions, then the effluent from the first stage is passed over a
hydrodesulphurisation catalyst in a subsequent second section under
hydrodesulphurisation conditions, and in which the
hydrodemetallisation section comprises one or more
hydrodemetallisation zones preceded by at least one
hydrodemetallisation guard zone, the hydrodemetallisation and/or
hydrodesulphurisation sections being composed of one or more
reactors which can be short-circuited separately or otherwise
following step d) defined below, said hydrotreatment process
comprising:
[0097] a) a step in which the guard zone is used for a period at
most-equal to the deactivation time and/or clogging time of said
zone;
[0098] b) a step during which the deactivated and/or clogged guard
zone is short-circuited and the catalyst it contains is regenerated
and/or replaced by fresh or regenerated catalyst;
[0099] c) a step during which the guard zone in which the catalyst
has been regenerated and/or replaced during the preceding step is
reconnected, said step being carried out for a period at most equal
to the deactivation and/or clogging time of one of the guard
zones;
[0100] d) a step in which at least one of the reactors from the
hydrodemetallisation section and/or the hydrodesulphurisation
section can be short-circuited during a cycle when the catalyst is
deactivated and/or clogged for regeneration and/or replacement by
fresh or regenerated catalyst.
[0101] In a further variation, the process of the invention
consists in a process for hydrotreating, in at least two sections,
a heavy hydrocarbon fraction containing sulphur-containing and
metallic impurities, in which in a first, hydrodemetallisation,
section, the hydrocarbon feed and hydrogen are passed over a
hydrodemetallisation catalyst under hydrodemetallisation
conditions, then the effluent from the first section is passed over
a hydrodesulphurisation catalyst in a subsequent second section
under hydrodesulphurisation conditions, and in which the
hydrodemetallisation section comprises one or more
hydrodemetallisation zones preceded by at least two
hydrodemetallisation guard zones comprising one or more reactors,
preferably fixed bed or ebullated bed zones, disposed in series for
use in a cycle consisting of successive repetitions of steps b) and
c) defined below, the hydrodemetallisation and/or
hydrodesulphurisation sections being composed of one or more
reactors which can be short-circuited separately or otherwise
following step d) defined below, said hydrotreatment process
comprising:
[0102] a) a step in which the guard zones are all used together for
a period at most equal to the deactivation and/or clogging time of
the guard zone the most upstream with respect to the overall
direction of circulation of the treated feed;
[0103] b) a step during which the feed penetrates directly into the
guard zone located immediately after that which was the most
upstream during the preceding step and during which the guard zone
which was the most upstream during the preceding step is
short-circuited and the catalyst which it contains is regenerated
and/or replaced by fresh catalyst; and
[0104] c) a step during which the guard zones are used all
together, the guard zone in which the catalyst has been regenerated
and/or replaced during step b) being reconnected so as to be
downstream of the set of guard zones and said step being continued
for a period at most equal to the deactivation and/or clogging time
of the guard zone which during this step is the most upstream with
respect to the overall direction of circulation of the treated
feed;
[0105] d) a step in which at least one of the reactors from the
hydrodemetallisation section and/or hydrodesulphurisation section
can be short-circuited during the cycle when the catalyst is
deactivated and/or clogged to be regenerated and/or replaced by
fresh or regenerated catalyst.
[0106] Preferably, in the process of the invention, a quantity of
middle distillate generally representing 0.5% to 80% by weight with
respect to the weight of hydrocarbon feed is introduced into the
inlet to the first functioning guard zone. More preferably, the
atmospheric distillate introduced with the hydrocarbon feed is a
straight run gas oil.
[0107] In the process of the invention, the product from the
hydrodesulphurisation step is preferably sent to an atmospheric
distillation zone from which an atmospheric distillate is recovered
at least a portion or which is preferably recycled to the inlet to
the first functioning guard zone, and an atmospheric residue is
also recovered. More preferably, at least a portion of a gas oil
fraction from the atmospheric distillation step following:the
hydrodesulphurisation step is recycled to the inlet to the first
functioning guard zone.
[0108] In a preferred variation of the process of the invention,
the recycled gas oil fraction is a cut with an-initial boiling
point of about 140.degree. C. and an end point of about 400.degree.
C.
[0109] In these preferred variations, the quantity of atmospheric
distillate and/or gas oil introduced to the inlet to the first
functioning guard zone at the same time as the feed preferably
represents about 1% to 50% by weight with respect to the feed.
[0110] It is also possible to send at least a portion of the
atmospheric residue from the atmospheric distillation zone to a
vacuum distillation zone from which a vacuum distillate is
recovered, at least a portion of which is recycled to the inlet to
the first functioning guard zone, and a vacuum residue is also
recovered. In this case, in a preferred variation, at least a
portion of the atmospheric residue and/or vacuum distillate is sent
to a catalytic cracking unit from which an LCO fraction and an HCO
fraction are recovered, and at least a portion of one or the other
or a mixture of the two fractions is sent to the inlet to the first
functioning guard zone.
[0111] In a preferred mode of the process of the invention, during
step c), the guard zones are used all together, the guard zone in
which the catalyst has been regenerated during step b) being
reconnected such that the connection is identical to that it had
before it was short-circuited during step b).
[0112] In a further preferred mode of the process of the invention,
a conditioning section is associated with the guard zone or zones,
which section enables short-circuiting or permutation of said guard
zone or zones during operation, without the unit ceasing operation,
said section being regulated so as to condition the catalyst
contained in the guard zone which is not functioning, at a pressure
in the range 1 MPa to 5 MPa.
[0113] In a preferred mode of the process of the invention, in
order to treat a feed constituted by a heavy oil or a heavy oil
fraction containing asphaltenes, the feed is initially subjected to
hydrovisbreaking conditions, mixed with hydrogen, before sending
the feed to the guard zone or zones.
[0114] In a preferred mode of the process of the invention, the
atmospheric residue obtained from the optional atmospheric
distillation step undergoes deasphalting using a solvent or a
solvent mixture and at least a portion of the deasphalted product
is recycled to the inlet to the first functioning guard zone.
[0115] In a preferred mode of the process of the invention, the
vacuum residue obtained from the optional vacuum distillation step
undergoes deasphalting using a solvent or solvent mixture and at
least a portion of the deasphalted product is recycled to the inlet
to the first functioning guard zone.
[0116] In a further preferred variation of the process of the
invention, all of the reactors are fixed bed reactors. In a further
preferred variation, at least one of the guard reactors and/or
hydrodemetallisation sections and/or hydrodesulphurisation sections
is an ebullated bed reactor. In a further preferred variation, the
reactors for the guard zones are fixed bed reactors, and all of the
reactors in the hydrodesulphurisation zone are ebullated bed
reactors.
[0117] In a yet still further preferred variation, all of the
reactors in the guard zone are fixed bed reactors, and all the
reactors in the hydrodemetallisation zone are ebullated bed
reactors, and optionally and highly preferably, all of the
hydrodesulphurisation zone reactors are also ebullated bed
reactors. It is also possible to operate the process of the
invention with only ebullated bed reactors in the guard zones and
in the hydrodemetallisation and hydrodesulphurisation sections.
[0118] FIG. 1 briefly illustrates the invention.
[0119] The feed arrives in guard zones 1A and 1B via line 1 and
leaves these zones via line 13, line 23 and/or line 24. The feed
leaving the guard zone or zones arrives via line 13 in the HDM
section which is shown here by a reaction section 2 constituted by
one or more reactor(s), each reactor being provided with its own
short-circuit. The effluent from section 2 is withdrawn via line 14
then sent to a hydrodesulphurisation section 3 which can comprise
one or more reactors that may be in series, and my optionally be
provided with their own short-circuit. The effluent from section 3
is withdrawn via line 15.
[0120] In the illustration of FIG. 1, a middle distillate is
introduced via line 55 and is mixed with the hydrocarbon feed in
line 1.
[0121] In the case shown in FIG. 1, the guard zone comprises 2
reactors; in its preferred implementation, the process will
comprise a series of cycles each comprising four successive
periods:
[0122] a first period during which the feed successively traverses
zone 1A then zone 1B and in which the gas oil fraction from
atmospheric distillation which is recycled is introduced with the
feed into zone 1A; during the first period [step a) of the
process], the feed is introduced via line 1 and line 21 comprising
a valve 31 open towards the guard reactor 1A. During this period,
valves 32, 33 and 35 are closed. The effluent from zone 1A is sent
via a line 23, line 26, comprising an open valve 34 and line 22 to
guard reactor 1B. The effluent from zone 1B is sent via line 24,
comprising an open valve 36, and line 13, which comprises an open
valve 37, to HDM section 2.
[0123] a second period during which the feed traverses only zone 1B
and in which the gas oil fraction from atmospheric distillation
which is recycled is introduced with the feed into zone 1B. During
the second period [step b) of the process], valves 31, 33, 34 and
35 are closed and the feed is introduced via line 1 and line 22,
comprising an open valve 32, into zone 1B. During this period the
effluent from zone 1B is sent via line 24 comprising an open valve
36 and line 13, which comprises an open valve 37 to HDM section
2;
[0124] a third period during which the feed successively traverses
zone 1B then zone 1A and in which the gas oil fraction from
atmospheric distillation which is recycled is introduced into zone
1B with the feed. During the third period [step c) of the process],
valves 31, 34 and 36 are closed and valves 32, 33 and 35 are open.
The feed is introduced via line 1 and line 22 into zone 1B. The
effluent from zone 1B is sent via line 24, line 27 and line 21 to
guard reactor 1A. The effluent from zone 1A is sent via line 23 and
line 13, which comprises an open valve 37, to HDM section 2;
[0125] a fourth period during which the feed only traverses guard
zone 1A and in which the gas oil fraction from atmospheric
distillation which is recycled is introduced into zone 1A with the
feed.
[0126] The number of cycles carried out for the guard reactors is a
function of the duration of the operating cycle of the whole unit
and the average frequency of permutation of zones 1A and 1B. During
the fourth period, valves 32, 33, 34 and 36 are closed and valves
31 and 35 are open. The feed is introduced into zone 1A via line 1
and line 21. During this period, the effluent from zone 1A is sent
to HDM section 2 via line 23 and line 13 which comprises an open
valve 37.
[0127] In the case shown in FIG. 1, hydrodemetallisation (HDM)
section 2 can comprise one or more reactors. Each or a plurality of
these reactors can be temporarily isolated for periodic renewal of
the catalyst(s) [step d) of the process]. In its preferred
implementation, the process comprises a series of cycles each
comprising three successive periods:
[0128] a first period during which the feed successively traverses
guard zones 1A, 1B and HDM section 2, then finally HDS section 3.
During this period, the gas oil fraction from atmospheric
distillation which is recycled is introduced into guard zone 1A
with the feed. During this period, valves 32, 33, 35, 38 and 41 are
closed. The feed is introduced into zone 1A via line 1 and line 21.
The effluent from zone 1A is sent to guard zone 1B via a line 23,
line 26, comprising an open valve 34 and line 22. The effluent from
zone 1B is sent to HDM section 2 via line 24, comprising an open
valve 36, and line 13, which comprises an open valve 37. The
effluent from section 2 is sent to HDS section 3 via line 14 which
comprises two open valves 42 and 39. The effluent from section 3 is
then sent to a fractionation unit (not shown) via line 15 which
comprises an open valve 40.
[0129] a second period during which the feed successively traverses
guard zones 1A and 1B, then HDS section 3. During this period, the
gas oil fraction from atmospheric distillation which is recycled is
introduced into zone 1B with the feed. During this operation,
valves 32, 33, 35, 37, 41 and 42 are closed. The feed is introduced
into zone 1A via line 1 and line 21. The effluent from zone 1A is
sent to guard zone 1B via line 23, line 26 which comprises an open
valve 34, and line 22. The effluent from zone 1B is sent to HDS
section 3 via line 24, which comprises an open valve 36, and line
25 which comprises two open valves 38 and 39. The effluent from
section 3 is then sent to fractionation unit (not shown), via line
15, which comprises an open valve 40. During this period, the HDM
catalyst is renewed, then said catalyst is conditioned using the
method described in this invention. This conditioning is
particularly necessary if the catalyst is in the oxide form;
[0130] a third period during which the feed successively traverses
guard zones 1A and 1B, and HDM section 2, then HDS section 3.
During this period, the gas oil fraction from the atmospheric
distillation step which is recycled is introduced with the feed
into guard zone 1B. This situation is identical to the first period
and allows the reactor containing the fresh catalyst to be replaced
in an identical position, in the fluid circuit, compared with that
described in the first period.
[0131] In the case represented in FIG. 1, hydrodesulphurisation
section 3 can comprise one or more reactors; each or a plurality of
these reactors can be temporarily isolated to renew the catalyst
periodically [step d) of the process]. In its preferred
implementation, the process comprises a series of cycles each
comprising three successive periods:
[0132] a first period during which the feed successively traverses
guard zones 1A, 1B and HDM section 2, then HDS section 3. During
this period, the gas oil fraction from atmospheric distillation
which is recycled is introduced with the feed into guard zone 1A.
During this period, valves 32, 33, 35, 38 and 41 are closed. The
feed is introduced into guard zone 1A via line 1 and line 21. The
effluent from guard zone 1A is sent to guard zone 1B via line 23,
line 26, comprising an open valve 34 and line 22. The effluent from
guard zone 1B is sent to HDM section 2 via line 24, comprising an
open valve 36, and line 13, which comprises an open valve 37. The
effluent from section 2 is sent to section 3 via line 14 which
comprises two open valves 42 and 39. The effluent from section 3 is
then sent to a fractionation unit (not shown) via line 15 which
comprises an open valve 40.
[0133] a second period during which the feed successively traverses
guard zones 1A and 1B, then HDM section 2. During this period, the
gas oil fraction from atmospheric distillation which is recycled is
introduced with the feed into zone 1B. During this operation,
valves 32, 33, 35, 38, 39 and 40 are closed. The feed is introduced
into zone 1A via line 1 and line 21. The effluent from zone 1A is
sent to zone 1B via line 23, line 26 which comprises an open valve
34, and line 22. The effluent from zone 1B is sent to HDM section 2
via line 24, which comprises an open valve 36, and line 13 which
comprises an open valve 37. The effluent from section 2 is then
sent to fractionation unit (not shown), via line 14, which
comprises an open valve 42, and line 16, which comprises an open
valve 41. During this period, the catalyst or catalysts from
section 3 are renewed, then said catalyst or catalysts are
conditioned using the method described in this invention. This
conditioning is particularly necessary when the catalyst is in the
oxide form;
[0134] a third period during which the feed successively traverses
guard zones 1A and 1B, and HDM section 2, then HDS section 3.
During this period, the gas oil fraction from the atmospheric
distillation step which is recycled is introduced into zone 1B with
the feed. This situation is identical to that described in period 1
and allows the reactor containing the fresh catalyst(s) to be
replaced in the same position, in the fluid circuit, as that
described in the first period.
* * * * *