U.S. patent application number 13/978546 was filed with the patent office on 2014-01-02 for method for hydrotreating heavy hydrocarbon feedstocks using permutable reactors, including at least one step of short-circuiting a catalyst bed.
This patent application is currently assigned to IFP Energies nouvelles. The applicant listed for this patent is Frederic Bazer-Bachi, Christophe Boyer, Isabelle Guibard, Nicolas Marchal, Cecile Plain. Invention is credited to Frederic Bazer-Bachi, Christophe Boyer, Isabelle Guibard, Nicolas Marchal, Cecile Plain.
Application Number | 20140001089 13/978546 |
Document ID | / |
Family ID | 44340259 |
Filed Date | 2014-01-02 |
United States Patent
Application |
20140001089 |
Kind Code |
A1 |
Bazer-Bachi; Frederic ; et
al. |
January 2, 2014 |
METHOD FOR HYDROTREATING HEAVY HYDROCARBON FEEDSTOCKS USING
PERMUTABLE REACTORS, INCLUDING AT LEAST ONE STEP OF
SHORT-CIRCUITING A CATALYST BED
Abstract
Process for hydrotreating a heavy hydrocarbon fraction using a
system of switchable fixed bed guard zones each containing at least
two catalyst beds and in which whenever the catalyst bed that is
brought initially into contact with the feed is deactivated and/or
clogged during the steps in which the feed passes successively
through all the guard zones, the point of introduction of the feed
is shifted downstream. The present invention also relates to an
installation for implementing this process.
Inventors: |
Bazer-Bachi; Frederic;
(Irigny, FR) ; Boyer; Christophe; (Charly, FR)
; Guibard; Isabelle; (St Symphorien D'Ozon, FR) ;
Marchal; Nicolas; (Le Chesnay, FR) ; Plain;
Cecile; (Saint Germain En Laye, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Bazer-Bachi; Frederic
Boyer; Christophe
Guibard; Isabelle
Marchal; Nicolas
Plain; Cecile |
Irigny
Charly
St Symphorien D'Ozon
Le Chesnay
Saint Germain En Laye |
|
FR
FR
FR
FR
FR |
|
|
Assignee: |
IFP Energies nouvelles
Rueil-Malmaison Cedex
FR
|
Family ID: |
44340259 |
Appl. No.: |
13/978546 |
Filed: |
December 20, 2011 |
PCT Filed: |
December 20, 2011 |
PCT NO: |
PCT/FR2011/000668 |
371 Date: |
September 12, 2013 |
Current U.S.
Class: |
208/57 ; 208/108;
208/134; 208/143; 208/213; 208/251H; 208/254H; 208/264; 208/309;
208/59; 208/60; 208/64; 208/86; 208/89; 208/97; 422/187;
422/630 |
Current CPC
Class: |
C10G 2300/202 20130101;
C10G 2300/205 20130101; C10G 2300/206 20130101; C10G 2300/208
20130101; C10G 65/04 20130101 |
Class at
Publication: |
208/57 ; 208/143;
208/213; 208/254.H; 208/251.H; 208/264; 208/134; 208/108; 208/309;
208/59; 208/60; 208/64; 208/86; 208/89; 208/97; 422/630;
422/187 |
International
Class: |
C10G 65/04 20060101
C10G065/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 10, 2011 |
FR |
11/00074 |
Claims
1. Process for hydrotreating a heavy hydrocarbon fraction
containing asphaltenes, sediments, sulphur-containing,
nitrogen-containing and metallic impurities, in which the feed of
hydrocarbons and hydrogen is passed, under conditions of
hydrotreating, over a hydrotreating catalyst, in at least two fixed
bed hydrotreating guard zones each containing at least two catalyst
beds, the guard zones being arranged in series to be used
cyclically, consisting of successive repetition of steps b), c) and
c') defined below: a step a) during which the feed passes through
all the catalyst beds of the guard zones for a period at most equal
to the deactivation time and/or clogging time of a guard zone, a
step a') during which the feed is introduced, by-passing the
deactivated and/or clogged catalyst bed, onto the next catalyst bed
not yet deactivated and/or clogged of the same guard zone for a
period at most equal to the deactivation time and/or clogging time
of a guard zone, step a') being repeated until the feed is
introduced onto the last catalyst bed not yet deactivated and/or
clogged of the same guard zone for a period at most equal to the
deactivation time and/or clogging time, a step b) during which the
deactivated and/or clogged guard zone is by-passed and the catalyst
that it contains is regenerated and/or replaced with fresh catalyst
and during which the other guard zone(s) are used, a step c) during
which the feed passes through all the catalyst beds of the guard
zones, the guard zone of which the catalyst was regenerated during
the preceding step being reconnected so as to be downstream of all
the other guard zones and said step being continued for a period at
most equal to the deactivation time and/or clogging time of a guard
zone, a step c') during which the feed is introduced onto the next
catalyst bed not yet deactivated and/or clogged of the same guard
zone for a period at most equal to the deactivation time and/or
clogging time of a guard zone, step c') being repeated until the
feed is introduced onto the last catalyst bed not yet deactivated
and/or clogged of the same guard zone for a period at most equal to
the deactivation time and/or clogging time of a guard zone.
2. Process according to claim 1 in which each guard zone has n
beds, each bed i having a volume V.sub.i, the total catalyst volume
of the guard zone V.sub.tot being the sum of the volumes V.sub.i of
the n beds; each volume V.sub.i of a bed i included in the n-1
first beds of the guard zone has a volume V.sub.i defined between
5% of the total volume V.sub.tot and the percentage resulting from
the total volume V.sub.tot divided by the number of beds n; and in
which for two consecutive beds i and i+1, the volume of the first
bed V.sub.i is less than or equal to the volume of the next bed
V.sub.i+1, except for the last two consecutive beds V.sub.n-1 and
V.sub.n where the volume of the penultimate bed V.sub.n-1 is
strictly less than the volume of the last bed V.sub.n.
3. Process according to claim 1 in which during steps a') and c')
the maximum volume of the by-passed catalyst bed(s) in a guard zone
is defined as less than the volume given by the formula ((n-1)
V.sub.tot)/n, n being the total number of catalyst beds, V.sub.tot
being the total catalyst volume of the guard zone which is defined
by the sum of the volumes of the n catalyst beds of the guard
zone.
4. Process according to claim 1 in which the degree of
hydrotreating is maintained by a temperature increase.
5. Process according to claim 1 in which, at the entrance of each
guard zone, the feed passes through a filtering distributor plate
composed of a single stage or of two successive stages, said plate
is situated upstream of the catalyst beds.
6. Process according to claim 1 in which the feed passes through a
filtering distributor plate upstream of each catalyst bed of a
guard zone.
7. Process according to claim 1, characterized in that it precedes
a fixed bed or ebullating bed hydrotreating process.
8. Installation for implementing the process according to claim 1
comprising at least two fixed bed reactors (R1a, R1b) arranged in
series and each containing at least two catalyst beds (A1, A2; B1,
B2), the first bed of each reactor having at least one inlet pipe
for a gas and an inlet pipe for a hydrocarbon feed (21, 22), said
feed inlet pipes each containing a valve (V1, V3) and being
connected by a common pipe (3), each reactor having at least one
outlet pipe (23, 24) each containing a valve (V5, V6) for removal
of the effluent, the outlet pipe of each reactor (23, 24) being
connected by an additional pipe (26, 27) having a valve (V2, V4) to
the feed inlet pipe (22, 21) of the reactor downstream,
characterized in that the installation further comprises, for each
reactor, a feed inlet pipe for each catalyst bed (31, 32), said
pipes each having a valve (V1', V3') and being connected to said
inlet pipe for the hydrocarbon feed of the first bed (21, 22), each
valve of the installation being able to be opened or closed
separately.
9. Installation according to claim 8, characterized in that it
comprises a filtering distributor plate composed of a single stage
or of two successive stages at the entrance of each reactor, said
plate is situated upstream of the catalyst beds.
10. Installation according to claim 8, characterized in that it
comprises a filtering distributor plate composed of a single stage
or of two successive stages upstream of each catalyst bed.
Description
[0001] The present invention relates to a process for hydrotreating
a heavy hydrocarbon fraction using a system of switchable fixed bed
guard zones each containing at least two catalyst beds and in which
whenever the catalyst bed that is brought initially into contact
with the feed is deactivated and/or clogged during the steps in
which the feed passes successively through all the guard zones, the
point of introduction of the feed is shifted downstream. The
present invention also relates to an installation for implementing
this process.
[0002] Hydrotreating of hydrocarbon feeds is becoming increasingly
important in refining practice with the increasing need to reduce
the quantity of sulphur in petroleum cuts and to convert heavy
fractions to lighter fractions, which can be upgraded as fuels
and/or chemical products. It is in fact necessary, in view of the
standard specifications imposed by each country for commercial
fuels, for imported crudes, which have higher and higher contents
of heavy fractions, of heteroatoms and of metals, and lower and
lower hydrogen contents, to be upgraded as far as possible.
[0003] Catalytic hydrotreating makes it possible, by bringing a
hydrocarbon feed into contact with a catalyst in the presence of
hydrogen, to reduce its content of asphaltenes, metals, sulphur and
other impurities considerably, while improving the ratio of
hydrogen to carbon (H/C) and while transforming it more or less
partially into lighter cuts. Thus, hydrotreating (HDT) in
particular means reactions of hydrodesulphurization (HDS) by which
are meant the reactions for removing sulphur from the feed with
production of H.sub.2S, reactions of hydrodenitrogenation (HDN) by
which are meant the reactions for removing nitrogen from the feed
with production of NH.sub.3, and reactions of hydrodemetallization
by which are meant the reactions for removing metals from the feed
by precipitation, but also hydrogenation, hydrodeoxygenation,
hydrodearomatization, hydroisomerization, hydrodealkylation and
hydro-deasphalting.
[0004] There are two types of hydrotreating process for treating
heavy feeds such as atmospheric residues (AR) or vacuum residues
(VR): fixed bed processes and ebullating bed processes. Zong et al.
(Recent Patents on Chemical Engineering, 2009, 2, 22-36) summarize
the various processes known in the treatment of heavy petroleum
feeds.
[0005] The technology of the fixed bed processes has found the
widest industrial application owing to its technical maturity,
lower cost and stable and reliable performance. In these processes,
the feed circulates through several fixed bed reactors arranged in
series, the first reactor(s) being used in particular for
performing hydrodemetallization of the feed (so-called HDM step) as
well as a proportion of hydrodesulphurization, the last reactor(s)
being used for performing deep refining of the feed (hydrotreating
step, HDT), and in particular hydrodesulphurization (so-called HDS
step). The effluents are withdrawn from the last HDT reactor.
[0006] The fixed bed processes lead to high performance in refining
(production of 370.degree. C..sup.+ cuts with less than 0.5 wt. %
of sulphur and containing less than 20 ppm of metals) from feed
containing up to 5 wt. % of sulphur and up to 300 ppm of metals, in
particular nickel and vanadium). The various effluents thus
obtained can serve as a basis for the production of heavy fuel oils
of good quality, of gas oil and gasoline, or feeds for other units
such as catalytic cracking.
[0007] Beyond this content of metals, it is known that the first
catalyst beds can quickly be deactivated because of the
considerable deposit of metals that is produced. To compensate for
this deactivation, the temperature of the reactor is then
increased. However, this increase in temperature promotes the
deposition of coke, accelerating the processes of intragranular
clogging (plugging of the catalyst pores) and extragranular
clogging (plugging of the catalyst bed). Beyond these contents of
metals in the feed, ebullating bed processes are thus generally
preferred. In fact, one problem posed by fixed bed catalytic
hydrotreating of these feeds arises because during the
hydrotreating reactions of petroleum fractions containing
organometallic complexes, most of these complexes are destroyed in
the presence of hydrogen, hydrogen sulphide, and a hydrotreating
catalyst. The metal constituent of these complexes then
precipitates in the form of a solid sulphide, which will adhere to
the catalyst. This is particularly so with complexes of vanadium,
nickel, iron, sodium, titanium, silicon and copper, which are
naturally present in crude oils at a varying level depending on the
origin of the petroleum, and which, during the operations of
distillation, tend to become concentrated in high boiling point
fractions and in particular in residues. In addition to these
impurities, coke is also deposited, and together they then tend to
deactivate and clog the catalytic system very quickly. These
phenomena lead to stoppage of the hydrotreating units for replacing
the solids and to an overconsumption of catalyst, which a person
skilled in the art wishes to minimize.
[0008] Another problem posed by fixed bed catalytic hydrotreating
of these feeds is clogging. It is known that catalyst beds, in
particular the upper portions of catalyst beds, and more
particularly the upper portions of the first catalyst bed in
contact with the feed, are likely to clog quite quickly because of
the asphaltenes and sediments contained in the feed, which is
manifested firstly by an increase in head loss and sooner or later
requires a stoppage of the unit for replacing the catalyst.
[0009] Therefore it becomes necessary to stop the unit in order to
replace the first catalyst beds, which are deactivated and/or
clogged. The hydrotreating processes for feeds of this type must
therefore be designed so as to permit an operating cycle that is as
long as possible without stopping the unit.
STATE OF THE ART
[0010] There have been attempts to resolve these drawbacks of the
fixed bed arrangements in various ways, in particular by using
guard beds installed upstream of the main reactors. The main task
of the guard beds is to protect the catalysts of the main HDM and
HDT reactors downstream, by performing a proportion of the
demetallization and by filtering the particles contained in the
feed that can lead to clogging. The guard beds are generally
integrated in the HDM section in a process for hydrotreating heavy
feeds generally including a first HDM section and then a second HDT
section. Although the guard beds are generally used for performing
a first hydrodemetallization and a filtration, other hydrotreating
reactions (HDS, HDN, etc.) will inevitably take place in these
reactors owing to the presence of hydrogen and a catalyst.
[0011] Thus, installation of one or more moving-bed reactors at the
head of the HDM step has been considered (U.S. Pat. No. 3,910,834
or GB2124252). The operation of these moving beds can be co-current
(SHELL's HYCON process for example) or counter-current (OCR process
of Chevron Lummus Global and the applicant's HYVAHL-M.TM. process
for example).
[0012] Adding a fixed bed guard reactor in front of the HDM
reactors has also been considered (U.S. Pat. No. 4,118,310 and U.S.
Pat. No. 3,968,026). Most often this guard reactor can be by-passed
in particular by using an isolating valve. This provides temporary
protection of the main reactors against clogging.
[0013] Moreover, a system has also been described, in particular by
the applicant (FR2681871 and U.S. Pat. No. 5,417,846), for
combining the high performance of the fixed bed with a high
operating factor for treating feeds with high contents of metals,
which consists of a hydrotreating process in at least two steps for
a heavy hydrocarbon fraction containing asphaltenes,
sulphur-containing impurities and metallic impurities, in which,
during the first so-called HDM step, the feed of hydrocarbons and
hydrogen is passed, under conditions of HDM, over an HDM catalyst,
then, during the next, second step, the effluent from the first
step is passed, under conditions of HDT, over an HDT catalyst. The
HDM step comprises one or more fixed bed HDM zones preceded by at
least two guard HDM zones, also called "switchable reactors", also
of fixed bed design, arranged in series to be used cyclically
consisting of successive repetition of steps b) and c) defined
below:
a) a step in which the guard zones are all used together for a
period at most equal to the deactivation time and/or clogging time
of one of them, b) a step during which the deactivated and/or
clogged guard zone is by-passed and the catalyst that it contains
is regenerated and/or replaced with fresh catalyst and during which
the other guard zone(s) are used, c) a step during which the guard
zones are all used together, the guard zone of which the catalyst
was regenerated during the preceding step being reconnected and
said step being continued for a period at most equal to the
deactivation time and/or clogging time of one of the guard
zones.
[0014] This process, known by the name HYVAHL-F.TM., can provide an
overall desulphurization greater than 90% and an overall
demetallization of the order of 95%. The use of switchable reactors
permits continuous cyclic operation.
[0015] It has now been discovered, surprisingly, that it is
possible to increase the time of use of the switchable reactors
before replacement of the catalyst contained in a switchable
reactor becomes necessary. The present invention thus improves the
performance of switchable reactors as described by the applicant in
patent FR2681871 by integrating into this process at least two
catalyst beds in each switchable reactor and by integrating into
certain steps of the process at least one step of by-passing
deactivated and/or clogged catalyst beds, also called a by-pass
step.
[0016] In the catalyst beds, clogging occurs a priori in the upper
portions of the catalyst beds, and in particular in the upper
portions of the first catalyst bed brought into contact with the
feed in the direction of flow. The same applies to deactivation of
the catalyst (deposition of metals). According to the invention,
whenever a catalyst bed is deactivated and/or clogged, this
catalyst bed is by-passed and the point of introduction of the feed
is shifted relative to this bed downstream onto the next catalyst
bed, not yet deactivated and/or clogged, of the same switchable
reactor. Thus, by successive by-pass steps of the most clogged
and/or deactivated portion(s) of the reactor, the volume of each
switchable reactor is fully utilized until it is exhausted (i.e.
until its last catalyst bed is also deactivated and/or clogged),
while maintaining the cyclic operation of the switchable reactors.
Thus, the bed(s) downstream of the deactivated and/or clogged
bed(s) of the same reactor are used for a longer time. This has the
effect of increasing the duration of each step of the cycle of the
switchable reactors during which the feed passes successively
through all the reactors, which provides a longer operating cycle
of the switchable reactors.
[0017] This lengthening of the cycle leads to an increase in the
operating factor of the unit as well as a saving of time, a
reduction of operating costs and a reduction of the consumption of
fresh catalyst. The aim of the present application is thus to
increase the cycle time of the switchable reactors.
DETAILED DESCRIPTION
[0018] The present invention provides an improvement of the
hydrotreating process carried out using guard zones (switchable
reactors) as described in patent FR2681871. The operation of the
guard zones according to FR2681871 is described in FIG. 1,
comprising two guard zones (or switchable reactors) R1a and R1b.
This hydrotreating process comprises a series of cycles each
comprising four successive steps: [0019] a first step (called "step
a" hereinafter) during which the feed passes successively through
reactor R1a, then reactor R1b, [0020] a second step (called "step
b" hereinafter) during which the feed only passes through reactor
R1b, reactor R1a being by-passed for catalyst regeneration and/or
replacement, [0021] a third step (called "step c" hereinafter)
during which the feed passes successively through reactor R1b, then
reactor R1a, [0022] a fourth step (called "step d" hereinafter)
during which the feed only passes through reactor R1a, reactor R1b
being by-passed for catalyst regeneration and/or replacement.
[0023] During step a) of the process, the feed is introduced via
line 3 and line 21, having an open valve V1, into line 21' and the
guard reactor R1a containing a fixed catalyst bed A. During this
period, valves V3, V4 and V5 are closed. The effluent from reactor
R1a is sent via pipe 23, pipe 26, having an open valve V2, and pipe
22' into the guard reactor R1b containing a fixed catalyst bed B.
The effluent from reactor R1b is sent via pipes 24 and 24', having
an open valve V6, and pipe 13 to the main hydrotreating section
14.
[0024] During step b) of the process, valves V1, V2, V4 and V5 are
closed and the feed is introduced via line 3 and line 22, having an
open valve V3, into line 22' and reactor R1b. During this period
the effluent from reactor R1b is sent via pipes 24 and 24', having
an open valve V6, and pipe 13 to the main hydrotreating section
14.
[0025] During step c), valves V1, V2 and V6 are closed and valves
V3, V4 and V5 are open. The feed is introduced via line 3 and lines
22 and 22' into reactor R1b. The effluent from reactor R1b is sent
via pipe 24, pipe 27, having an open valve V4, and pipe 21' to the
guard reactor R1a. The effluent from reactor R1a is sent via pipes
23 and 23', having an open valve V5, and pipe 13 to the main
hydrotreating section 14.
[0026] During step d), valves V2, V3, V4 and V6 are closed and
valves V1 and V5 are open. The feed is introduced via line 3 and
lines 21 and 21' into reactor R1a. During this period the effluent
from reactor R1a is sent via pipes 23 and 23', having an open valve
V5, and pipe 13 to the main hydrotreating section 14.
[0027] The cycle then begins again. The operations on the valves of
the unit enabling the functioning of the switchable reactors
according to FR2681871 are presented in Table 1.
TABLE-US-00001 TABLE 1 Operations on the valves around the
switchable reactors according to FR2681871 (without external
by-pass) Step in Cycle Intervention V1 V2 V3 V4 V5 V6 a R1A + R1B
-- O* O C** C C O b R1B R1A C C O C C O c R1B + R1A -- C C O O O C
d R1A R1B O C C C O C a R1A + R1B -- O O C C C O *O = open, **C =
closed
[0028] According to the present invention, additional by-pass steps
of deactivated and/or clogged catalyst beds (steps a' and c') in
the steps of the cycle during which the feed passes successively
through the two reactors (steps a) and c)), are added to the
process steps as described above.
[0029] More particularly, the present invention relates to a
process for hydrotreating a heavy hydrocarbon fraction containing
asphaltenes, sediments, sulphur-containing, nitrogen-containing and
metallic impurities, in which the feed of hydrocarbons and hydrogen
is passed, under conditions of hydrotreating, over a hydrotreating
catalyst, in at least two fixed bed hydrotreating guard zones each
containing at least two catalyst beds, the guard zones being
arranged in series to be used cyclically, consisting of successive
repetition of steps b), c) and c') defined below: [0030] a step a)
during which the feed passes through all the catalyst beds of the
guard zones for a period at most equal to the deactivation time
and/or clogging time of a guard zone, [0031] a step a') during
which the feed is introduced, by-passing the deactivated and/or
clogged catalyst bed, onto the next catalyst bed not yet
deactivated and/or clogged of the same guard zone for a period at
most equal to the deactivation time and/or clogging time of a guard
zone, step a') being repeated until the feed is introduced onto the
last catalyst bed not yet deactivated and/or clogged of the same
guard zone for a period at most equal to the deactivation time
and/or clogging time of a guard zone, [0032] a step b) during which
the deactivated and/or clogged guard zone is by-passed and the
catalyst that it contains is regenerated and/or replaced with fresh
catalyst and during which the other guard zone(s) are used, [0033]
a step c) during which the feed passes through all the catalyst
beds of the guard zones, the guard zone of which the catalyst was
regenerated during the preceding step being reconnected so as to be
downstream of all the other guard zones and said step being
continued for a period at most equal to the deactivation time
and/or clogging time of a guard zone, [0034] a step c') during
which the feed is introduced onto the next catalyst bed not yet
deactivated and/or clogged of the same guard zone for a period at
most equal to the deactivation time and/or clogging time of a guard
zone, step c') being repeated until the feed is introduced onto the
last catalyst bed not yet deactivated and/or clogged of the same
guard zone for a period at most equal to the deactivation time
and/or clogging time of a guard zone, [0035] a step d) during which
the deactivated and/or clogged guard zone is by-passed and the
catalyst that it contains is regenerated and/or replaced with fresh
catalyst and during which the other guard zone(s) are used.
[0036] The guard zones, in particular the first guard zone brought
into contact with the feed, gradually become laden with metals,
coke, sediments and various other impurities. When the catalyst or
catalysts that they contain is/are practically saturated with
metals and various impurities, the zones must be disconnected for
carrying out replacement and/or regeneration of the catalyst(s).
Preferably, the catalysts are replaced. This moment is called the
deactivation time and/or clogging time. Although the deactivation
time and/or clogging time varies in relation to the feed, the
operating conditions and the catalyst(s) used, it is generally
manifested by a drop in catalyst performance (an increase in the
concentration of metals and/or other impurities in the effluent),
an increase in the temperature required for maintaining constant
hydrotreating or, in the specific case of clogging, by a
significant increase in head loss. The head loss .DELTA.p,
expressing a degree of clogging, is measured continuously
throughout the cycle on each of the zones and can be defined by an
increase in pressure resulting from partially blocked passage of
the flow through the zone. The temperature is also measured
continuously throughout the cycle on each of the two zones. In
order to define a deactivation time and/or clogging time, a person
skilled in the art first defines a maximum tolerable value of the
head loss .DELTA.p and/or of the temperature as a function of the
feed to be treated, the operating conditions and catalysts
selected, and starting from which it is necessary to proceed to
by-passing of a catalyst bed or to disconnection of the guard zone.
The deactivation time and/or clogging time is thus defined as the
time when the limit value of head loss and/or of temperature is
reached. As a general rule the limit value of head loss and/or of
temperature is confirmed during initial commissioning of the
reactors. In the case of a process for hydrotreating heavy
fractions, the limit value of head loss is generally between 0.3
and 1 MPa (3 and 10 bar), preferably between 0.5 and 0.8 MPa (5 and
8 bar). The limit value of temperature is generally between
400.degree. C. and 430.degree. C., the temperature corresponding,
here and hereinafter, to the average measured temperature of the
catalyst bed. Another limit value for the temperatures, indicating
that deactivation is reached (lower level of exothermic reactions),
is that the temperature difference (.DELTA.T) on a catalyst bed
becomes less than 5.degree. C., regardless of the average
temperature value.
[0037] FIG. 2 shows the hydrotreating process according to the
present invention using a system of two switchable reactors each
containing two catalyst beds and in which the catalyst beds can be
by-passed. In the case shown in FIG. 2 the process comprises a
series of cycles each having six successive steps, steps a), b), c)
and d) being identical to the process described in FR2681871:
[0038] a step a) during which the feed passes successively through
all the catalyst beds of reactor R1a, then all the catalyst beds of
reactor R1b, [0039] a step a') (by-pass step) during which the feed
by-passes the deactivated and/or clogged catalyst bed A1 of the
first reactor R1a and is introduced into the next catalyst bed A2
downstream, then passes through all the catalyst beds of reactor
R1b, [0040] a step b), after deactivation and/or clogging of bed
A2, during which the feed passes through all the catalyst beds of
reactor R1b only, reactor R1a being by-passed for catalyst
regeneration and/or replacement, [0041] a step c) during which the
feed passes successively through all the catalyst beds of reactor
R1b, then all the catalyst beds of reactor R1a, [0042] a step c')
(by-pass step) during which the feed by-passes the deactivated
and/or clogged catalyst bed B1 of reactor R1b and is introduced
into the next catalyst bed B2 downstream, then passes through all
the catalyst beds of reactor R1a, [0043] a step d), after
deactivation and/or clogging of bed B2, during which the feed
passes through all the catalyst beds of reactor R1a only, reactor
R1b being by-passed for catalyst regeneration and/or
replacement.
[0044] Thus, at step a) the feed is introduced via line 3 and lines
21 and 21', having an open valve V1, into the guard reactor R1a and
passes through the fixed beds A1 and A2. During this period, valves
V1', V3, V3', V4 and V5 are closed. The effluent from reactor R1a
is sent via pipe 23, pipe 26, having an open valve V2, and pipe 22'
to the guard reactor R1b and passes through the catalyst beds B1
and B2. The effluent is removed from reactor R1b via pipes 24 and
24', having an open valve V6, and pipe 13.
[0045] Gradually, the catalyst beds, and in particular the first
catalyst bed, on being brought into contact with the feed (A1 of
reactor R1a), will become clogged and/or deactivated. The moment
when it is considered that the first catalyst bed brought into
contact with the feed is deactivated and/or clogged is measured
from the head loss .DELTA.p and/or temperature of a guard zone. A
maximum tolerable value for the head loss and/or temperature from
which it is necessary either to by-pass the deactivated and/or
clogged catalyst bed, or to proceed with replacement of the
catalyst in the reactor, is defined beforehand. Each time that this
limit value is reached, the catalyst bed that is clogged and/or
deactivated is by-passed by introducing the feed by a by-pass
device outside the reactor onto the next catalyst bed not yet
deactivated and/or clogged downstream of said reactor.
[0046] Thus, according to FIG. 2, once the maximum value of head
loss and/or of temperature is reached, valve V1 is closed and the
feed is introduced via line 31, having an open valve V1', onto the
next catalyst bed A2 in reactor R1a (step a'). The deactivated
and/or clogged catalyst bed A1 is therefore by-passed. Catalyst bed
A2 is much less clogged and/or deactivated than the first bed A1,
permitting a considerable increase in the length of the first
period, by using the lower bed A2 for a longer time.
[0047] Gradually, this next catalyst bed A2 is also clogged and/or
deactivated. When the maximum value of head loss and/or of
temperature is reached, step b) is then carried out, during which
the feed passes through all the catalyst beds of reactor R1b only,
reactor R1a being by-passed for catalyst regeneration and/or
replacement. Thus, during step b), valves V1, V1', V2, V3', V4 and
V5 are closed and the feed is introduced via line 3 and lines 22
and 22', having an open valve V3, into reactor R1b. During this
period the effluent from reactor R1b is removed via pipes 24 and
24', having an open valve V6, and via pipe 13.
[0048] After reconnection of reactor R1a, of which the catalyst was
regenerated or replaced downstream of reactor R1b, step c) of the
process is then carried out, during which the feed passes
successively through reactor R1b, then reactor R1a. Thus, during
step c), valves V1, V1', V2, V3' and V6 are closed and valves V3,
V4 and V5 are open. The feed is introduced via line 1 and lines 22
and 22' into reactor R1b. The effluent from reactor R1b is sent via
pipe 24, pipe 27, having an open valve V4, and pipe 21' to the
guard reactor R1a. The effluent from reactor R1a is removed via
pipes 23 and 23', having open valve V5, and via pipe 13.
[0049] Gradually, the catalyst beds, and in particular the first
bed B1 of reactor R1b, will become clogged and/or deactivated.
Then, just as in step a'), by-passing of the deactivated and/or
clogged catalyst bed B1, called step c'), is carried out. Thus,
according to FIG. 2, once the maximum value of head loss and/or of
temperature is reached, valve V3 is closed and the feed is
introduced into the reactor via line 32, having an open valve V3',
onto the next bed B2 in reactor R1b. The deactivated and/or clogged
catalyst bed B1 is therefore by-passed. The catalyst bed B2 is much
less clogged and/or deactivated than the first catalyst bed B1,
permitting a considerable increase in the length of the third
period, by using the lower bed B2 for a longer time.
[0050] Gradually, this next catalyst bed B2 is also clogged and/or
deactivated. When the maximum value of head loss and/or of
temperature is reached, step d) is then carried out, during which
the feed passes through all the catalyst beds of reactor R1a only,
reactor R1b being by-passed for catalyst regeneration and/or
replacement. During this step valves V1', V2, V3, V3', V4 and V6
are closed and valves V1 and V5 are open. The feed is introduced
via line 3 and lines 21 and 21' into reactor R1a. During this
period the effluent from reactor R1a is removed via pipes 23 and
23', having open valve V5, and via pipe 13.
[0051] After catalyst regeneration and/or replacement in reactor
R1b, this reactor is reconnected downstream of reactor R1a and the
cycle begins again.
[0052] The operations on the valves of the unit permitting
functioning of the two switchable reactors having two catalyst beds
that can be by-passed according to the present invention are
presented in Table 2.
TABLE-US-00002 TABLE 2 Operations on the valves for the system of
switchable reactors with external by-pass (according to the
invention) Step in Cycle Intervention V1 V1' V2 V3 V3' V4 V5 V6 a
R1A + R1B -- O* C** O C C C C O a' R1A + R1B -- C O O C C C C O b
R1B R1A C C C O C C C O c R1B + R1A -- C C C O C O O C c' R1B + R1A
-- C C C C O O O C d R1A R1B O C C C C C O C a R1A + R1B -- O C O C
C C C O *O = open, **C = closed
[0053] The system of switchable reactors with external by-pass can
be extended to reactors having more than two catalyst beds, for
example 3, 4 or 5 catalyst beds. In this case, the external by-pass
feeds, by additional lines and valves, respectively, the next
catalyst bed downstream of the deactivated and/or clogged catalyst
bed once the maximum value of head loss and/or of temperature is
reached. Thus, step a') or c') as defined above is repeated. This
by-passing of catalyst beds can continue until the last catalyst
bed of the reactor in the direction of flow is deactivated and/or
clogged. It is then necessary to replace the catalyst contained in
the reactor. FIG. 3 shows the hydrotreating process according to
the present invention using a system of two switchable reactors
each containing three catalyst beds A1, A2, A3 and B1, B2 and B3
respectively. In FIG. 3, steps a), a'), b), c) c') and d) (and
reference symbols) are identical to FIG. 2, except that steps a')
and c') are repeated. This repetition only will be described for
this figure.
[0054] Thus, during step a'), once catalyst bed A1, and then
catalyst bed A2 are deactivated and/or clogged, valve V1' is closed
and the feed is introduced via line 33, having an open valve V1'',
onto the next catalyst bed A3 in reactor R1a. When this third bed
A3 is also clogged and/or deactivated, step b)
(replacement/regeneration of reactor R1a) is then carried out.
Similarly, during step c'), once catalyst bed B1, and then catalyst
bed B2 are deactivated and/or clogged, valve V3' is closed and the
feed is introduced via line 34, having an open valve V3'', onto the
next catalyst bed B3 in reactor R1b. When this third bed B3 is also
clogged and/or deactivated, step d) (replacement/regeneration of
reactor R1b) is then carried out.
[0055] In a preferred embodiment, the catalyst beds contained in a
guard zone can be of different or identical volumes but with the
condition that the volume of the last bed is greater than each
volume of the other beds. Preferably, the catalyst beds in one and
the same guard zone have volumes that increase in the direction of
flow. In fact, since clogging and/or deactivation occurs mainly on
the first catalyst bed, it is advantageous to minimize the volume
of this first bed.
[0056] The volume of each bed can be defined as follows:
[0057] Each guard zone has n beds, each bed i having a volume
V.sub.i, the total catalyst volume of the reactor V.sub.tot being
the sum of the volumes V.sub.i of the n beds:
Vtot=V.sub.1+ . . . V.sub.i+V.sub.i+1 . . . +V.sub.n-1+V.sub.n
[0058] Each volume V.sub.i of a bed i included in the n-1 first
beds of the guard zone is defined between 5% of the total volume
V.sub.tot and the percentage resulting from the total volume
V.sub.tot divided by the number of beds n:
5% Vtot.gtoreq.Vi.gtoreq.(Vtot/n)
[0059] For two consecutive beds i and i+1, the volume of the first
bed V.sub.i is less than or equal to the volume of the next bed
V.sub.i+1, except for the last two consecutive beds V.sub.n-1 and
where the volume of the penultimate bed V.sub.n-1 is strictly less
than the volume of the last bed V.sub.n.
[0060] In the case of two catalyst beds in a guard zone, the volume
V1 of the first bed is thus between 5 and 49%, the volume of the
second bed is between 51 and 95%.
[0061] In the case of three catalyst beds in a guard zone, the
volume V1 of the first bed is thus between 5 and 33%, the volume V2
of the second bed is between 5 and 33% and the volume V3 of the
third bed is between 34 and 90%.
[0062] The maximum volume of the by-passed catalyst bed(s) in a
guard zone during steps a') and c'), also called "by-passable
fraction", is the sum of the volumes V.sub.1+ . . .
V.sub.i+V.sub.i+1 . . . +V.sub.n-1 of the n-1 beds (or the total
volume minus the volume of the last bed n). This maximum volume of
the by-passed catalyst bed(s) is defined as being less than the
percentage expressed by the formula ((n-1) V.sub.tot)/n, n being
the bed number in a guard zone, V.sub.tot being the total catalyst
volume of the guard zone.
[0063] Starting from a certain value of by-passed fraction,
generally greater than or equal to ((n-1) V.sub.tot)/n, the
quantity of fouling material and metals accumulated in the last bed
of the first reactor and that accumulated in the second reactor
become very similar. Thus, a head loss and/or temperature increase
may be observed, reaching the maximum value in the two reactors
almost at the same time, and can lead to continuous malfunction of
the reactors. It is thus important to have a minimum volume that
cannot be by-passed in the first reactor to protect the second
reactor and have time to regenerate the first reactor before there
is an increase in head loss and/or temperature in the second
reactor. In order to maximize the duration of a step during which
the feed passes successively through all the reactors, it is
therefore beneficial to by-pass a substantial quantity of the
reactor, but without exceeding a limit value.
[0064] In a preferred embodiment, a catalyst conditioning section
is used, allowing these guard zones to be switched while in
operation, i.e. without stopping the operation of the unit: first,
a system that operates at moderate pressure (from 10 to 50 bar, but
preferably from 15 to 25 bar) allows the following operations to be
performed on the disconnected guard reactor: washing, stripping,
cooling, before discharging the used catalyst; then heating and
sulphurization after loading the fresh catalyst; then another
system for pressurization/depressurization, with gate valves of
appropriate design, permits efficient switching of these guard
zones without stopping the unit, i.e. without affecting its
operating factor, since all the operations of washing, stripping,
discharge of the used catalyst, loading of the fresh catalyst,
heating, and sulphurization are carried out on the disconnected
reactor or guard zone. Alternatively, a pre-activity catalyst can
be used in the conditioning section so as to simplify the procedure
for switching while in operation.
[0065] Each guard zone contains at least two catalyst beds (for
example 2, 3, 4, or 5 catalyst beds). Each catalyst bed contains at
least one catalyst layer containing one or more catalysts,
optionally supplemented with at least one inert layer. The
catalysts used in the catalyst bed(s) may be identical or
different.
[0066] The hydrotreating process using switchable reactors with
external by-pass can thus greatly increase the duration of a cycle.
During the by-pass steps the feed has a shorter residence time in
the switchable reactors because of the by-pass. In order to
maintain a constant degree of hydrotreating at the outlet of the
last reactor, the temperature in the guard zones is thus gradually
increased. The latter is also increased overall during the cycle to
counteract the catalyst deactivation. However, this temperature
increase promotes the deposition of coke, accelerating the
processes of clogging. Thus, to limit an excessive temperature
rise, the by-passed fraction must be all the more restricted. The
reactor fraction that is by-passed is thus based on optimization
between the gain in cycle time and limited temperature rise.
[0067] According to a preferred variant, at the entrance of each
guard zone the feed passes through a filtering distributor plate
composed of a single stage or of two successive stages, said plate
is situated upstream of the catalyst beds, preferably upstream of
each catalyst bed. This filtering distributor plate, described in
patent US2009177023, makes it possible to trap the clogging
particles contained in the feed by means of a special distributor
plate comprising a filtering medium. Thus, the filtering plate
makes it possible to increase the gain of cycle time in the
hydrotreating process using switchable guard zones. This filtering
plate simultaneously provides distribution of the gas phase
(hydrogen and the gaseous portion of the feed) and the liquid phase
(the liquid portion of the feed) feeding the reactor while
providing a filtration function with respect to the impurities
contained in the feed. Moreover, the filtering plate ensures a more
uniform distribution of the mixture over the whole surface of the
catalyst bed and limits the problems of poor distribution during
the phase of clogging of the plate itself.
[0068] More precisely, the filtering plate is a device for
filtration and distribution, said device comprising a plate
situated upstream of the catalyst bed, said plate consisting of a
base that is approximately horizontal and integral with the walls
of the reactor and to which approximately vertical chimneys are
fixed, open at the top for admission of the gas, and at the bottom
for removing the gas-liquid mixture intended to feed the catalyst
bed situated downstream, said chimneys being pierced over a certain
fraction of their height by a continuous lateral slit or by lateral
orifices for admission of liquid, said plate supporting a filtering
bed surrounding the chimneys, and said filtering bed consisting of
at least one layer of particles of size less than or equal to the
size of the particles of the catalyst bed. The filtering bed
consists of particles that are generally inert but can also
comprise at least one layer of catalyst identical to or belonging
to the same family as the catalyst of the catalyst bed. This
last-mentioned variant makes it possible to reduce the volume of
catalyst beds in the reactor.
[0069] The filtering distributor plate can also comprise two stages
and be composed of two successive plates: the first plate
supporting a guard bed composed of internal particles and of at
least one layer of catalyst identical to or belonging to the same
family as the catalyst of the catalyst bed. This plate is described
in patent US2009177023. The bed is arranged on a grating, the
liquid phase flows through the guard bed and the gas through the
chimneys passing through the guard bed and the first plate. At the
end of clogging the liquid and the gas flow simultaneously through
the chimneys while allowing the second plate to continue to provide
its distribution function. The second plate provides the function
of distribution of the gas and liquid: it can be composed of
chimneys with lateral perforations for passage of the liquid or be
composed of bubble-caps or vapour-lift.
[0070] According to another variant, the hydrotreating process
according to the present invention can comprise more than two
switchable reactors (for example 3, 4 or 5) functioning according
to the same principle of switching and by-pass, each switchable
reactor having at least two catalyst beds.
[0071] FIG. 4 shows the case of three guard zones each having two
catalyst beds. The process will comprise, in its preferred
embodiment, a series of cycles each having nine successive steps:
[0072] a step a) during which the feed passes successively through
all the catalyst beds of reactor R1a, then all the catalyst beds of
reactor R1b and finally all the catalyst beds of reactor R1c,
[0073] a step a') (by-pass step) during which the feed by-passes
the deactivated and/or clogged catalyst bed A1 of the first reactor
R1a and is introduced into the next catalyst bed A2 downstream of
reactor R1a, then passes through all the catalyst beds of reactor
R1b and finally all the catalyst beds of reactor R1c, [0074] a step
b) during which the feed passes through all the catalyst beds of
reactor R1b, then all the catalyst beds of reactor R1c, reactor R1a
being by-passed for catalyst regeneration and/or replacement,
[0075] a step c) during which the feed passes successively through
all the catalyst beds of reactor R1b then all the catalyst beds of
reactor R1c and finally all the catalyst beds of reactor R1a,
[0076] a step c') (by-pass step) during which the feed by-passes
the deactivated and/or clogged catalyst bed B1 of the second
reactor R1b and is introduced into the next catalyst bed B2
downstream of reactor R1b, then passes through all the catalyst
beds of reactor R1c, and finally all the catalyst beds of reactor
R1a, [0077] a step d) during which the feed passes through all the
catalyst beds of reactor R1c, then all the catalyst beds of reactor
R1a, reactor R1b being by-passed for catalyst regeneration and/or
replacement, [0078] a step e) during which the feed passes
successively through all the catalyst beds of reactor R1c then all
the catalyst beds of reactor R1a and finally all the catalyst beds
of reactor R1b, [0079] a step e') (by-pass step) during which the
feed by-passes the deactivated and/or clogged catalyst bed C1 of
third reactor R1c and is introduced into the next catalyst bed C2
downstream of reactor R1c, then passes through all the catalyst
beds of reactor R1a, and finally all the catalyst beds of reactor
R1b, [0080] a step f) during which the feed passes through all the
catalyst beds of reactor R1a, then all the catalyst beds of reactor
R1b, reactor R1c being by-passed for catalyst regeneration and/or
replacement.
[0081] In the case shown schematically in FIG. 4 the process
functions in an equivalent manner to that described in connection
with FIG. 2 (the reference symbols for the lines have been omitted
for reasons of legibility).
[0082] During step a), valves V1, V2, V7 and V8 are open and valves
V1', V3, V3', V5, V6, V9, V10 and V10' are closed.
[0083] During step a'), valves V1', V2, V7, V8 are open and valves
V1, V3, V3', V5, V6, V9, V10 and V10' are closed.
[0084] During step b), valves V3, V7 and V8 are open and valves V1,
V1', V2, V3', V5, V6, V9, V10 and V10' are closed.
[0085] During step c), valves V3, V7, V9 and V5 are open and valves
V1, V1', V2, V3', V6, V8, V10 and V10' are closed.
[0086] During step c'), valves V3', V7, V9 and V5 are open and
valves V1, V1', V2, V3, V6, V8, V10 and V10' are closed.
[0087] During step d), valves V10, V9 and V5 are open and valves
V1, V1', V2, V3, V3', V6, V7, V8 and V10' are closed.
[0088] During step e), valves V10, V9, V2 and V6 are open and
valves V1, V1', V3, V3', V5, V7, V8 and V10' are closed.
[0089] During step e'), valves V10', V9, V2 and V6 are open and
valves V1, V1', V3, V3', V5, V7, V8 and V10 are closed.
[0090] During step f), valves V1, V2 and V6 are open and valves
V1', V3, V3', V5, V7, V8, V9, V10 and V10' are closed.
[0091] The different variants of the process described above for a
system of two switchable reactors having two catalyst beds also
apply to a system having more than two switchable reactors. These
different variants are in particular: the conditioning system, the
possibility of having more than two catalyst beds per reactor, the
possibility of having beds with different volumes as defined above,
the volume of the by-passed catalyst bed(s) in one guard zone being
less than ((n-1)Vtot)/n, maintaining the degree of hydrotreating by
raising the temperature, integration of a filtering plate at the
entrance of each reactor upstream of the first catalyst bed,
preferably upstream of each catalyst bed.
[0092] The process according to the invention can advantageously be
carried out at a temperature between 320.degree. C. and 430.degree.
C., preferably 350.degree. C. to 410.degree. C., at a hydrogen
partial pressure advantageously between 3 MPa and 30 MPa,
preferably between 10 and 20 MPa, at a space velocity (HSV)
advantageously between 0.05 and 5 volumes of feed per volume of
catalyst and per hour, and with a ratio of hydrogen gas to liquid
hydrocarbon feed advantageously between 200 and 5000 normal cubic
metres per cubic metre, preferably 500 to 1500 normal cubic metres
per cubic metre. The value of HSV of each switchable reactor in
operation is preferably from about 0.5 to 4 h.sup.-1 and most often
from about 1 to 2 h.sup.-1. The overall value of HSV of the
switchable reactors and that of each reactor is selected so as to
achieve maximum HDM while controlling the reaction temperature
(limiting the exothermic effect).
[0093] The hydrotreating catalysts used are preferably known
catalysts and are generally granular catalysts comprising, on a
support, at least one metal or metal compound having a
hydro-dehydrogenating function. These catalysts are advantageously
catalysts comprising at least one group VIII metal, generally
selected from the group comprising nickel and/or cobalt, and/or at
least one group VIB metal, preferably molybdenum and/or tungsten.
The support used is generally selected from the group comprising
alumina, silica, silica-aluminas, magnesia, clays and mixtures of
at least two of these minerals.
[0094] Prior to injection of the feed, the catalysts used in the
process according to the present invention are preferably subjected
to a sulphurization treatment for transforming, at least partly,
the metallic species to sulphide before they are brought into
contact with the feed to be treated. This treatment of activation
by sulphurization is well known to a person skilled in the art and
can be carried out by any method already described in the
literature, either in situ, i.e. in the reactor, or ex situ.
[0095] The feeds treated in the process according to the invention
are advantageously selected from atmospheric residues, vacuum
residues from direct distillation, crude oils, topped crude oils,
deasphalted oils, residues from conversion processes such as for
example those originating from coking, from fixed-bed,
ebullating-bed, or moving-bed hydroconversion, heavy oils of any
origin and in particular those obtained from oil sands or oil
shale, used alone or mixed. These feeds can advantageously be used
as they are or diluted with a hydrocarbon fraction or a mixture of
hydrocarbon fractions that can be selected from the products
obtained from a fluid catalytic cracking (FCC) process, a light cut
of oil (Light Cycle Oil, LCO), a heavy cut of oil (Heavy Cycle Oil,
HCO), a decanted oil (DO), a residue from FCC, or that can be
obtained from distillation, the gas oil fractions, in particular
those obtained by vacuum distillation (Vacuum Gas Oil, VGO). The
heavy feeds can also advantageously comprise cuts obtained from the
coal liquefaction process, aromatic extracts, or any other
hydrocarbon cuts or also non-petroleum feeds such as gaseous and/or
liquid derivatives (containing little if any solids) from thermal
conversion (with or without catalyst and with or without hydrogen)
of coal, biomass or industrial waste, such as for example recycled
polymers.
[0096] Said heavy feeds generally have more than 1 wt. % of
molecules having a boiling point above 500.degree. C., a content of
metals Ni+V above 1 ppm by weight, preferably above 20 ppm by
weight, a content of asphaltenes, precipitated in heptane, above
0.05 wt. %, preferably, above 1 wt. %.
[0097] The hydrotreating process according to the invention makes
it possible to effect 50% or more of HDM of the feed at the outlet
of the switchable reactors (and more precisely from 50 to 95% of
HDM) owing to the HSV selected and the efficiency of the HDM
catalyst.
[0098] The hydrotreating process according to the invention using
the system of switchable guard zones including at least one by-pass
step advantageously precedes a fixed bed or ebullating bed process
for hydrotreating heavy hydrocarbon feeds.
[0099] Preferably, it precedes the applicant's Hyvahl-F.TM. process
comprising at least one hydrodemetallization step and at least one
hydrodesulphurization step. The process according to the invention
is preferably integrated upstream of the HDM section, the
switchable reactors being used as guard beds. In the case shown in
FIG. 1, the feed 1 enters the switchable guard reactor(s) via pipe
1 and leaves said reactor(s) via pipe 13. The feed leaving the
guard reactor(s) enters, via pipe 13, the hydrotreating section 14
and more precisely the HDM section 15 comprising one or more
reactors. The effluent from the HDM section 15 is withdrawn via
pipe 16, and then sent to the HDT section 17 comprising one or more
reactors. The final effluent is withdrawn via pipe 18.
[0100] The present invention also relates to an installation (FIG.
2) for implementing the process according to the invention
comprising at least two fixed bed reactors (R1a, R1b) arranged in
series and each containing at least two catalyst beds (A1,A2;
B1,B2), the first bed of each reactor having at least one inlet
pipe for a gas (not shown) and an inlet pipe for a hydrocarbon feed
(21, 22), said inlet pipes for the feed each containing a valve
(V1, V3) and being connected by a common pipe (3), each reactor
having at least one outlet pipe (23, 24) each containing a valve
(V5, V6) for removal of the effluent, the outlet pipe of each
reactor (23, 24) being connected by an additional pipe (26, 27)
having a valve (V2, V4) to the inlet pipe (22, 21) of the feed of
the reactor downstream, characterized in that the installation
further comprises, for each reactor, a feed inlet pipe for each
catalyst bed (31, 32), said pipes each having a valve (V1', V3')
and being connected to said inlet pipe for the hydrocarbon feed of
the first bed (21, 22), and each valve of the installation being
able to be opened or closed separately.
[0101] According to a preferred variant, the installation comprises
a filtering distributor plate composed of a single stage or of two
successive stages at the entrance of each reactor, situated
upstream of the catalyst beds, preferably upstream of each catalyst
bed.
Example 1
Not According to the Invention
[0102] The feed consists of a mixture (70/30 wt. %) of atmospheric
residue (AR) of Middle East origin (Arabian Medium) and of a vacuum
residue (VR) of Middle East origin (Arabian Light). This mixture is
characterized by a high viscosity (0.91 cP) at ambient temperature,
a density of 994 kg/m.sup.3, high contents of Conradson carbon (14
wt. %) and asphaltenes (6 wt. %) and a high level of nickel (22 ppm
by weight), vanadium (99 ppm by weight) and sulphur (4.3 wt.
%).
[0103] The hydrotreating process is carried out according to the
process described in FR2681871 and comprises the use of two
switchable reactors. The two reactors are loaded with a
CoMoNi/alumina hydrodemetallization catalyst. A cycle is defined as
integrating the steps from a) to d). The deactivation time and/or
clogging time is reached when the head loss reaches 0.7 MPa (7 bar)
and/or the average temperature of a bed reaches 405.degree. C.
and/or when the temperature difference on a catalyst bed becomes
less than 5.degree. C.
[0104] The process is carried out at a pressure of 19 MPa, a
temperature at reactor inlet at the start of the cycle of
360.degree. C. and at the end of the cycle of 400.degree. C., and
an HSV=2h.sup.-1 per reactor, allowing a degree of demetallization
close to 60% to be maintained.
[0105] Table 3 and FIG. 5 show the operating time (in days) for the
process according to FR 2681871 (without by-pass). Thus, according
to FIG. 5, the curve of reactor R1a according to the state of the
art (base case R1a) shows, at the start of the cycle, an increase
of head loss in the first reactor R1a up to its maximum tolerable
value (.DELTA.p=0.7 MPa or 7 bar), after which catalyst replacement
is required. In the case of the state of the art (FR268187), the
operating time of reactor R1a is therefore 210 days. At the time of
replacement of the catalyst of reactor R1a, the head loss in
reactor R1b reached about 3 bar. During the next phase in which the
feed passes through reactor R1b and then reactor R1a containing
fresh catalyst, the head loss of reactor R1b increases up to the
maximum tolerable value, which is reached after 320 days of
operation. A second cycle can be envisaged on these switchable
reactors, replacing the catalyst of reactor R1b.
[0106] The deactivation time and/or clogging time (or the operating
time) of the first zone is therefore 210 days. Overall, a cycle
time of 320 days for the first cycle and of 627 days for two cycles
is observed.
Example 2
According to the Invention
[0107] The hydrotreating process is repeated with the same feed and
under the same operating conditions and with the same catalyst
according to example 1, except that the process comprises the use
of two switchable reactors, each reactor containing two catalyst
beds, the first catalyst bed representing a volume of 20%, and the
second representing a volume of 80% (by-pass of 20%), and the
process according to the invention is carried out. A cycle is
defined as integrating the steps from a) to d). The deactivation
time and/or clogging time is reached when the head loss reaches 0.7
MPa (7 bar) and/or the average temperature of a bed reaches
405.degree. C. and/or when the temperature difference on a catalyst
bed becomes less than 5.degree. C. The degree of HDM is maintained
at 60%.
[0108] Table 3 and FIG. 5 show the gain in operating time (in days)
for the process according to the invention with a by-passed
fraction of 20% in each reactor.
TABLE-US-00003 TABLE 3 Gain in operating time (days) without
external by-pass (according to FR2681871) and with a by-pass of 20%
in each reactor. Base (by-pass 0%) (not By-Pass 20% according to
the (according to the Case invention) invention) Duration R1-A
Cycle 1 210 d 252 d Duration R1-B Cycle 1 320 d 380 d Total gain
End 1 cycle -- 60 d Duration R1-A Cycle 2 487 d 577 d Duration R1-B
Cycle 2 627 d 741 d Total gain End 2 cycles -- 114 d
[0109] It can therefore be seen that the hydrotreating process
integrating a by-passed fraction of 20% makes it possible to
increase the duration of a first cycle by 60 days (i.e. by 18.75%)
and by 114 days for two cycles (i.e. by 18.2%) while maintaining a
degree of HDM of 75%, equivalent to the degree of HDM according to
the process without external by-pass.
[0110] FIG. 5 shows the variation of head loss during the time
measured in reactors R1a and R1b without external by-pass
(according to FR2681871, curves for the Base Cases R1a and R1b) and
in reactors R1a and R1b with an external by-pass of 20% (according
to the invention, curves PRS ByP R1a and R1b).
[0111] Thus, according to FIG. 5, the curve of reactor R1a (curve
PRS ByP R1a) shows, at the start of the cycle, an increase of head
loss in the first reactor R1a up to its maximum tolerable value
(.DELTA.p=0.07 MPa or 7 bar). When this value is reached, the first
bed is by-passed and the feed is introduced onto the second bed A2
of reactor R1a. The head loss in the reactor then drops suddenly
(hook in curve PRS ByP R1a), without returning to the initial head
loss, to gradually increase again up to the point where the next
(second) bed is clogged and the limit value of the head loss is
reached again. The gain in time obtained at the end of step a') is
then .DELTA.t.sub.C1-R1a (32 days). The head loss of reactor R1a
then drops abruptly because the system passes to step b), during
which the catalyst of reactor R1a is replaced. The feed then only
passes through reactor R1b, and then R1b and R1a after
replacement.
[0112] Curve R1b (curve PRS ByP R1b) shows the head loss of the
second reactor R1b as a function of time. The same phenomenon of
gain of time by external by-pass is observed at the end of step
c'): .DELTA.t.sub.C2-R1b (60 days).
[0113] FIG. 2 also shows a second cycle of switchable reactors. The
gain of time after 2 successive cycles is then .DELTA.t.sub.C2-R1b
(114 days). It can be seen that the more cycles there are, the
larger the gain of time.
* * * * *