U.S. patent application number 11/096372 was filed with the patent office on 2005-12-15 for method for revamping fixed-bed catalytic reformers.
Invention is credited to Fiutowska, Bozena M., Fojtasek, Brian D., Goldstein, Stuart S., Graziani, Kenneth R., Iaccino, Larry L., Marshall, Greg A., Melli, Tomas R., Thurtell, John H., Viets, John W..
Application Number | 20050274648 11/096372 |
Document ID | / |
Family ID | 34966305 |
Filed Date | 2005-12-15 |
United States Patent
Application |
20050274648 |
Kind Code |
A1 |
Goldstein, Stuart S. ; et
al. |
December 15, 2005 |
Method for revamping fixed-bed catalytic reformers
Abstract
A fixed-bed catalytic reformer unit is converted to moving bed
reactor/cyclic regenerator operation by re-using the fixed bed
reactors of the original unit as regenerator vessels operated in
cyclic regeneration mode in a new catalyst regeneration section. A
flow connection, suitably a liftpipe, is provided to convey spent
catalyst from the spent catalyst outlet of a new moving bed reactor
section to the converted regenerator section, together with a flow
connection for regenerated catalyst from the regenerator section to
the regenerated catalyst inlet of the new moving bed reactor
section. A flow control distributor directs spent catalyst
sequentially to each of the regenerator vessels to carry out the
regeneration with regeneration gas. Each regenerator vessel is
cycled through a fill, regeneration, discharge sequence to maintain
a continuous flow of catalyst to and from the reactor section.
Inventors: |
Goldstein, Stuart S.;
(Fairfax, VA) ; Viets, John W.; (Fairfax, VA)
; Fiutowska, Bozena M.; (Toronto, CA) ; Fojtasek,
Brian D.; (Manassas, VA) ; Thurtell, John H.;
(Houston, TX) ; Marshall, Greg A.; (Kingwood,
TX) ; Melli, Tomas R.; (Haymarket, VA) ;
Iaccino, Larry L.; (Seabrook, TX) ; Graziani, Kenneth
R.; (Fairfax, VA) |
Correspondence
Address: |
EXXONMOBIL RESEARCH AND ENGINEERING COMPANY
P.O. BOX 900
1545 ROUTE 22 EAST
ANNANDALE
NJ
08801-0900
US
|
Family ID: |
34966305 |
Appl. No.: |
11/096372 |
Filed: |
April 1, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60564133 |
Apr 21, 2004 |
|
|
|
Current U.S.
Class: |
208/134 |
Current CPC
Class: |
C10G 59/02 20130101;
B01J 8/12 20130101; C10G 49/002 20130101; C10G 35/12 20130101 |
Class at
Publication: |
208/134 |
International
Class: |
C10G 035/04 |
Claims
What is claimed is:
1. A method for the conversion of a fixed bed catalytic reformer
unit having at least one fixed-bed catalytic reforming reactor to
moving bed reactor/cyclic regenerator operation, the method
comprising: providing a moving bed, continuous reforming reactor
section for carrying out catalytic reforming reactions on a
reformer feed; converting at least one fixed bed reforming reactor
of the fixed-bed catalytic reformer unit to a catalyst regenerator
vessel in a catalyst regeneration section; providing a flow
connection for spent catalyst from a spent catalyst outlet of the
moving bed reactor section to the catalyst regenerator vessel and
providing a flow connection for regenerated catalyst from a
regenerated catalyst outlet of the catalyst regenerator vessel to a
regenerated catalyst inlet of the moving bed reactor section.
2. A method according to claim 1 in which the fixed-bed catalytic
reformer unit has a plurality of fixed-bed catalytic reforming
reactors which are converted to a plurality of cyclic operation
catalyst regenerator vessels.
3. A method according to claim 2 which includes providing (i) a
flow connection for spent catalyst from the spent catalyst outlet
of the moving bed reactor section to one of the catalyst
regenerator vessels and (ii) a flow connection for regenerated
catalyst from the regenerated catalyst outlet of one of the
catalyst regenerator vessels to the regenerated catalyst inlet of
the moving bed reactor.
4. A method according to claim 3 in which the flow connection for
the spent catalyst from the spent catalyst outlet of the moving bed
reactor section is connected at the end remote from the reactor
section to a spent catalyst flow distributor for selectively
directing spent catalyst to one of the plurality of catalyst
regenerator vessels.
5. A method according to claim 3 in which the flow connection for
the regenerated catalyst from the catalyst regenerator vessel is
connected at the end remote from the catalyst regenerator vessel to
a regenerated catalyst collector for directing regenerated catalyst
to the catalyst inlet of the moving bed reactor section.
6. A method according to claim 4 in which each regeneration vessel
has an inlet and an outlet for reforming catalyst regeneration
gas.
7. A method according to claim 1 in which the moving bed,
continuous reforming reactor section comprises a plurality of
reforming reactors in a vertically stacked configuration and the
catalyst regeneration section comprises a plurality of catalyst
regeneration vessels converted from the fixed bed reactors of the
fixed bed reforming unit.
8. A method according to claim 7 in which the spent catalyst outlet
of the moving bed reactor section is connected for spent catalyst
flow to a spent catalyst lift engager which has a spent catalyst
outlet connected for spent catalyst flow to a liftpipe to convey
spent catalyst to a spent catalyst flow distributor for directing
spent catalyst to one of the plurality of catalyst regenerator
vessels.
9. A method according to claim 8 in which each of the plurality of
catalyst regenerator vessels is connected for regenerated catalyst
flow to a regenerated catalyst lift engager which has an outlet for
regenerated catalyst flow to a liftpipe to convey regenerated
catalyst to the catalyst inlet of the moving bed reactor
section.
10. A method according to claim 9 which includes means for
selectively directing regenerated catalyst flow from each of the
plurality of catalyst regenerator vessels in sequence to the
regenerated catalyst lift engager.
11. A method for the conversion of a fixed-bed catalytic reformer
unit having a plurality of fixed bed catalytic reforming reactors
to moving bed reactor/cyclic regenerator operation and for the
operation of the converted unit, the method comprising: providing a
fixed bed catalytic reforming unit having a plurality of fixed bed
reforming reactors in which catalytic reforming reactions on a
reformer feed are carried out, providing a moving bed, continuous
reforming reactor section for carrying out catalytic reforming
reactions on a reformer feed; converting a plurality of the fixed
bed reforming reactors of the fixed-bed catalytic reformer unit to
catalyst regenerator vessels in a catalyst regeneration section
which is connected for spent and regenerated catalyst flow between
the moving bed reactor section and the catalyst regeneration
section; providing a flow connection for spent catalyst from a
spent catalyst outlet of the moving bed reforming reactor section
to each catalyst regenerator vessel and providing a flow connection
for regenerated catalyst from a regenerated catalyst outlet of each
catalyst regenerator vessel to the regenerated catalyst inlet of
the moving bed reactor section, providing a flow controller for
selectively directing reforming catalyst regeneration gas to each
catalyst regeneration vessel reforming a reformer feed in the
moving bed rector section, removing spent reforming catalyst from
the spent catalyst outlet of the moving bed reactor section,
passing the spent reforming catalyst removed from the catalyst
outlet of the moving bed reactor section to a catalyst regeneration
vessel in the catalyst regeneration section regenerating the spent
reforming catalyst in the catalyst regeneration vessel by directing
reforming catalyst regeneration gas through the catalyst in the
regeneration vessel, withdrawing regenerated reforming catalyst
from the regeneration vessel when regeneration is complete, and
returning the regenerated reforming catalyst to the catalyst inlet
of the reforming reactor section.
12. A method according to claim 11 in which the fixed-bed catalytic
reformer unit includes a plurality of fixed bed reforming reactors
each of which is converted to a catalyst regenerator vessel in the
catalyst regeneration section, each catalyst regeneration vessel
having (i) a spent catalyst inlet connectable for spent catalyst
flow to the spent catalyst outlet of the moving bed reactor section
and (ii) a regenerated catalyst outlet connectable for regenerated
catalyst flow to the catalyst inlet of the moving bed reactor
section.
13. A method according to claim 12 in which the inlets of the
catalyst regenerator vessels are each sequentially connected for
spent catalyst flow between the spent catalyst outlet of the moving
bed reactor section and the spent catalyst inlet of the regenerator
vessel to admit spent catalyst to the regenerator vessel in
sequence for regeneration.
14. A method according to claim 13 in which each catalyst
regenerator vessel sequentially; first, receives spent catalyst
from the spent catalyst outlet of the moving bed reactor section;
second, receives reforming catalyst regeneration gas to regenerate
the spent reforming catalyst in the regeneration vessel; third,
discharges regenerated catalyst for return to the catalyst inlet of
the moving bed reactor section.
15. A method according to claim 14 in which each of the catalyst
regenerator vessels is sequentially connected for regenerated
catalyst discharge to a regenerated catalyst lift engager which has
an outlet for regenerated catalyst flow to a liftpipe to convey
regenerated catalyst to the catalyst inlet of the reactor
section.
16. A method according to claim 15 which includes means for
selectively discharging regenerated catalyst flow from each of the
plurality of catalyst regenerator vessels in sequence to the
regenerated catalyst lift engager.
17. A method according to claim 13 in which the spent catalyst
outlet of the reactor section is connected for spent catalyst flow
to a spent catalyst lift engager which has a spent catalyst outlet
connected for spent catalyst flow to a liftpipe to convey spent
catalyst to a spent catalyst flow distributor for directing spent
catalyst sequentially to each of the catalyst regenerator
vessels.
18. A method according to claim 11 in which the fixed bed catalytic
reforming unit is a cyclic reforming unit including a regeneration
circuit which is incorporated into the converted unit to direct
catalyst regeneration gas through the catalyst in the regeneration
vessel during the regeneration step.
19. A method according to claim 18 in which the catalyst
regeneration gas directed through the catalyst includes a sequence
of purge gas, oxidative gas to remove coke from the catalyst and
halogen-containing gas for catalyst rejuvenation.
20. A method according to claim 13 in which the moving bed,
continuous reforming reactor section comprises a plurality of
reforming reactors in a vertically stacked configuration and the
catalyst regeneration section comprises a plurality of catalyst
regeneration vessels converted from the fixed bed reactors of the
fixed bed reforming unit.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application relates to a method of converting or
revamping fixed bed catalyic reformers to moving bed reactor
operation and, as such, is related to US 2004/0129605 A1, published
Jul. 8, 2004, which described a different conversion scheme.
[0002] This application claims the benefit of U.S. Ser. No.
60/564,133 filed Apr. 21, 2004.
FIELD OF THE INVENTION
[0003] The invention relates generally to catalytic reformers. More
particularly, the invention relates to an improved method for
converting or revamping high pressure, fixed-bed catalytic
reformers to catalytic reformers with continuous, moving-bed
reactors.
BACKGROUND OF THE INVENTION
[0004] Catalytic reforming is an established petroleum refinery
process. It is used for improving the octane quality of hydrocarbon
feeds. Generally, reforming refers to the total effect of molecular
changes on a hydrocarbon feed, produced by a number of reactions.
Typical reforming reactions include dehydrogenation of
cyclohexanes, dehydroisomerization of alkylcyclopentanes,
dehydrocyclization of paraffins and olefins, isomerization of
substituted aromatics, and hydrocracking of paraffins. Typical
reforming catalysts are multifunctional catalysts having a
hydrogenation-dehydrogenation component dispersed on a porous,
inorganic oxide support. The support may typically also contain an
acid functionality needed to mediate the reforming reactions.
[0005] Reforming reactions are both endothermic and exothermic.
Endothermic reactions are typically predominant in the early stages
of reforming while exothermic reactions predominate in the later
reaction stages although the process as a whole is markedly
endothermic. A reforming unit typically comprises a plurality of
serially connected reactors with furnaces for supplying additional
heat to the reaction stream as it passes from one reactor to the
next in order to compensate for the heat taken up in the overall
endothermic character of the process. Conventionally, reforming
processes have been operated as semi-regenerative or cyclic
processes using fixed bed reactors or continuous processes such as
UOP CCR Platforming.TM. (Continuous Catalytic Regeneration
Platforming.TM.) using moving bed reactors.
[0006] Proposals have been made for combining fixed and moving bed
reactors with the regeneration mode appropriate to the reactor
types used in the hybrid configuration, so that the fixed bed
reactors have retained the fixed bed type regeneration, usually
semiregenerative, and the moving bed reactors in the unit have
retained the dedicated moving bed regenerator. Units of this hybrid
type are disclosed, for example, in U.S. Pat. No. 5,190,638; U.S.
Pat. No. 5,190,639; U.S. Pat. No. 5,196,110; U.S. Pat. No.
5,211,838; U.S. Pat. No. 5,221,463; U.S. Pat. No. 5,354,451; U.S.
Pat. No. 5,368,720 and U.S. Pat. No. 5,417,843. The unit described
in U.S. Pat. No. 5,417,843 uses two trains of fixed bed reactors
with each train having a final moving bed reactor at the end and
the moving bed reactors sharing a moving bed regenerator. The unit
shown in U.S. Pat. No. 5,190,639 uses two trains of fixed bed units
feeding into a shared moving bed reactor with its own dedicated,
fully integrated regenerator. Similar hybrid reforming units using
combinations of fixed bed and moving bed reactors are described in
NPRA Paper No. AM-96-50 "IFP Solutions for Revamping Catalytic
Reforming Units" (1996 NPRA Annual Meeting, 17-19 Mar. 1996). U.S.
Pat. No. 4,498,973 describes a moving bed reforming unit in which
two moving bed reactor stacks share a common regenerator. UOP has
recently announced its CycleX.TM. Process for increased hydrogen
production from a fixed bed reforming unit by the addition of a
circulating catalyst reactor as the final reactor in the reactor
sequence. This reactor is provided with its own heater and
regenerator as an expansion of existing assets rather than as a
substitution of them: NPRA Paper AM-03-93.
[0007] In semiregenerative reforming, the entire reforming process
unit is operated by gradually and progressively increasing the
temperature to compensate for deactivation of the catalyst caused
by coke deposition, until finally the entire unit is shut-down for
regeneration and reactivation of the catalyst which is carried out
with the catalyst remaining in the reactor cases. In cyclic
reforming, the reactors are individually isolated by various piping
arrangements. The catalyst is regenerated and then reactivated
while the other reactors of the series remain on line. A "swing
reactor" temporarily replaces the reactor which is removed from the
series for regeneration and reactivation of the catalyst, which is
then put back in the series. In continuous reforming, the reactors
are moving-bed reactors with continuous or intermittent addition
and withdrawal of catalyst through which the catalyst moves
progressively before it is passed to a regeneration zone for
regeneration and rejuvenation before being returned once again to
the reactor. In the regenerator, at least a portion of the
deposited coke is burned off and the regenerated catalyst is
recycled to the reactor to continue the cycle. Commercial
continuous reforming units may have the reactors arranged in a
side-by-side or in a stacked configuration. Because the continuous
mode of operation with its frequent regeneration can tolerate a
higher degree of coke lay-down on the catalyst, it is possible to
operate continuous units at lower pressures than those normally
used with semi-regenerative and cyclic units in which it is
important or at least desirable to extend catalyst life between
successive regenerations.
[0008] Environmental concerns have driven the removal of lead from
the gasoline pool and the introduction of premium grade, higher
octane, lead-free gasoline in Europe and the United States. In
response, petroleum refmers have changed the manner in which
refinery units are run to meet the concomitant demand for higher
octane, lead-free gasoline. Catalytic reforming units produce a
major portion of the refinery gasoline pool and for this reason,
improved reforming methods and units are needed for producing
lead-free fuel products with adequate octane ratings. Reforming can
also be an attractive source of hydrogen in the refinery,
especially when the sulfur level of fuels must be reduced to meet
government regulations.
[0009] Semiregenerative reforming units may be converted to
continuous moving-bed units to take advantage of the improved yield
of higher octane reformate and hydrogen associated with continuous
operation but the conversions which have so far been considered are
essentially entire unit replacements which require replacement of
all existing vessels and most of the ancillary equipment as well as
installation of an integrated catalyst regenerator which is one of
the most costly items in the conversion. The cost of the
regenerator can be as much as about 80 percent of the total cost
required for the conversion, making this option less attractive
when the original fixed bed units are still capable of service.
[0010] US 2004/0129605 A1 describes an economically attractive
method for converting fixed bed catalytic reforming units to
continuous reactor operation while reducing the costs associated
with continuous regeneration. In this conversion scheme, a
fixed-bed catalytic reformer with at least one fixed-bed is
converted semiregenerative to a moving-bed catalytic reformer
reactor which allows continuous or intermittent addition of fresh
or regenerated catalyst through suitable feed facilities to its
catalyst inlet. Provision is made for continuous or intermittent
removal of spent catalyst from the catalyst outlet of the reactor
by way of spent catalyst recovery facilities for collecting the
spent catalyst, storing it temporarily, and transferring it to a
catalyst regeneration facility. The moving-bed reactor, the
catalyst feeding facilities and the catalyst recovery facilities
are operatively connected between themselves and to the existing
facilities (piping, ancillary equipment) of the fixed-bed unit that
do not require replacement.
SUMMARY OF THE INVENTION
[0011] The present invention relates to a scheme for converting
fixed-bed, catalytic reformer units to units with moving bed
reactors. It differs from the scheme described in US 2004/0129605
A1 in that it makes use of existing reactor vessels; in the present
case, these vessels are placed into new service, this time for
catalyst regeneration. Because this conversion scheme requires only
new reactors, it avoids the major expense connected with the
provision of a moving bed regenerator and so presents an
economically favorable case for conversion to moving bed reactor
operation. The costs of conversion associated with the present
conversion technique will be significantly less than conversions in
which both the reactors and the regenerators are converted to
moving bed operation because the present conversion technique makes
use of existing facilities in addition to making new use of the
reactor vessels while, at the same time, not requiring dedicated
onsite continuous catalyst regeneration facilities. One advantage
of the present conversion scheme is that the full advantages of
moving bed reactor operation are secured with the reactors operated
at the lower pressures characteristic of continuous operation so as
to improve reformate quality and yield.
[0012] According to the present invention, a fixed-bed catalytic
reformer unit is converted to moving bed reactor/cyclic regenerator
operation by re-using the fixed bed reactors of the original unit
as regenerator vessels operated in cyclic regeneration mode in a
converted regeneration section. A flow connection, suitably a
liftpipe, is provided to convey spent catalyst from the spent
catalyst outlet of a new moving bed reactor section to the
converted regenerator section, together with a flow connection for
regenerated catalyst from the regenerator section to the catalyst
inlet of the new moving bed reactor section. A flow control
distributor directs spent catalyst sequentially to each of the
regenerator vessels to carry out the regeneration with regeneration
gas. Each regenerator vessel is cycled through a fill,
regeneration, discharge sequence to maintain a continuous flow of
catalyst to and from the reactor section.
[0013] In the present conversion technique and its allied
operational mode, a fixed bed reformer unit with a plurality of
reactor vessels is converted to a continuous reformer unit with a
moving bed reactor section and a multi-vessel catalyst regeneration
section operating in cyclic fashion, using the former reactor
vessels for regeneration. The former reactor vessels are re-used
for regeneration in the new, cyclical operation, typically on a
three-vessel fill/regenerate/discharge cycle, in which one vessel
receives spent catalyst, while another is in the regeneration cycle
and another is discharging regenerated catalyst for recycle to the
reactor stack. This conversion scheme is particularly well adapted
to the conversion of cyclic reforming units where the regeneration
circuit (compressor, furnace, chemical injection facilities,
valving, piping and manifolding) can be used with advantage for the
purposes of cyclic regeneration in the converted unit. The
conversion scheme may, however, be also applied to existing
semi-regenerative units although here with the marginal economic
disadvantage of having to provide a new regeneration circuit.
THE DRAWING
[0014] FIG. 1 shows a continuous moving-bed reforming process built
from an existing cyclic reformer unit.
DETAILED DESCRIPTION
[0015] The present invention provides a substantially lower cost
option for refiners to make significant improvements to the
performance and service factor of existing fixed-bed reformer
units. Non-continuous (or fixed-bed) catalytic reformers which can
be subjected to the present conversion scheme could be
semi-regenerative catalytic reformers or swing-reactor (also
referred to as cyclic regeneration) reformers or hybrid systems
(with both fixed and moving bed sections), all of which are
known.
[0016] The present conversion scheme is best adapted to the
conversion of cyclic reformer units because the required catalyst
regeneration equipment will already be in place and can be applied
directly to the new service: the compressors, furnace, chemical
injection facilities as well as piping, valving and manifolding can
be used without substantial modification to the mode of cyclic
regeneration used in the converted unit. Cyclic, fixed-bed
reformers have been well-known. In units of this type, a plurality
of reactors are used, typically from three to five, with one
reactor being the so-called "swing" reactor. The actual reforming
is carried out in the remaining reactors according to the normal
reforming reactor sequence while the catalyst in the "swing"
reactor is being regenerated by the flow of regeneration gas
through the catalyst. In the normal operation sequence, the reactor
with the catalyst which has aged the most, is withdrawn from the
reforming sequence (taken "off-oil"): after the oil feed is cut
off, the catalyst in the vessel is subjected to regeneration
sequence typically with a purge of residual hydrocarbons (nitrogen
purge), oxidative regeneration to burn off the accumulated coke on
the catalyst, halogenative rejuvenation (usually a chlorination
treatment), followed by a purge of oxides and residual occluded
gases and a final hydrogen reduction, after which the reactor is
returned on line by bringing it "on-oil" again while another vessel
is taken off-oil for regeneration. Normally, the swing time has
been about three to five days. For convenience, the term
"regeneration gas" is used here to comprehend the various gases
used in the regeneration sequence referred to above, including the
heated purge gas (usually nitrogen), oxidative gas for coke
burn-off, halogenation gas for rejuvenation, purge gas, hydrogen
for reduction and, if required by the catalyst chemistry, the
pre-sulfiding gas treatment.
[0017] It is not essential, however, that the fixed bed unit being
subjected to conversion should be a cyclic unit; conversion of
semi-regenerative units is feasible since these units will also
provide multiple reactor vessels as assets for conversion to cyclic
regeneration use. This type of conversion, however, will be
accompanied by the necessity to provide additional ancillary
equipment for the regeneration circuit including compressors,
furnace, piping, valving and manifolding. Semi-regenerative units
typically contain one or more fixed-bed reactors operating in
series with inter-bed heaters to maintain operating severity as the
catalyst deactivates by increasing the reaction temperature and to
maintain the desired temperature profile across the unit as the
ratio of endothermic to exothermic reactions increases in
successive reactors. Eventually, a semi-regenerative unit is shut
down for catalyst regeneration and reactivation in its original
mode of operation. After conversion according to the present
scheme, however, the reactor vessels are used as
cyclically-operated regenerator vessels for a continuous, moving
bed reactor stack.
[0018] The fixed-bed reformer unit is converted to a moving-bed
reformer reactor that allows continuous addition of freshly
regenerated catalyst to an inlet of the reactor and continuous
removal of spent catalyst from an outlet of the reactor. Although
the regeneration is carried out in a cyclical operation with the
spent catalyst passing successively between the new moving bed
reactor section the former reactor vessels (now functioning as
regenerator vessels), the provision of suitable spent and
regenerated catalyst receivers (along with an adequate catalyst
inventory) will allow for continuous catalyst flow to the reactor
section.
[0019] The conversion of a fixed bed (semi-regenerative or cyclic)
reformer unit to operation with moving-bed reactors comprehends the
replacement of the fixed bed reactors by a moving bed reactor
section. Normally, since moving bed operation provides optimal
reforming performance, all the former fixed-bed reactors will be
replaced by the moving bed reactor section but, if for some reason,
it is desired to have a hybrid type unit with a fixed/moving bed
configuration, some of the fixed bed reactors may be retained in
the hybrid service. The reactor section will have, as is
conventional, a number of moving bed reactors connected in sequence
for reformer feed flow and for catalyst flow from one reactor to
the next. The moving bed reactors may be disposed in a side-by-side
or stacked arrangement, depending on site requirements although the
stacked configuration provides for ready catalyst transfer between
successive reactors by gravitational flow. The conversion does
require addition of catalyst transfer facilities between the new
moving bed reactor(s) and the converted, fixed bed vessels now used
in the cyclic regeneration sequence but much ancillary equipment of
the fixed bed unit can be retained and put to new use, especially,
as noted above, the piping associated with cyclic units. Feed (oil)
arrangements will need to be modified as required to suit the
layout of the converted unit and its operational requirements.
[0020] As mentioned above, a former cyclic reforming unit has the
necessary catalyst regeneration circuit ready for use in the new
application. Since the equipment in this circuit is adapted to
regenerating the catalyst in place in the reactor vessels, with the
appropriate sequence of regeneration gas, this same equipment can
be directly applied to the cyclic regeneration mode which is used
in the converted unit. If, however, a former semi-regenerative
reformer is converted to the new mode of operation, a catalyst
regeneration circuit with its associated compressors, furnace,
chemical injection facilities as well as valving, piping and
manifolding will need to be supplied and connected appropriately to
the former reactor vessels. The general form of this equipment as
well as its service requirements and manner of use will follow
those of conventional cyclic units and, being well known, will not
be described in detail here.
[0021] FIG. 1, given for example only, shows a continuous catalytic
moving-bed reforming process unit which has been converted from a
former cyclic reformer. The converted unit is composed of a moving
bed reactor section 10 which is integrated with a regeneration
section 11 with three regeneration vessels, 12, 13, 14 which are
the former reactors of a cyclic reformer; the former reactors and
regeneration system are enclosed by dashed line 15. The figure
concerns itself only with the catalyst handling circuit, omitting
details of the hydrocarbon feed and recovery equipment as well as
furnaces and other ancillary items which are conventional for the
reactor stack.
[0022] In operation, the reactor section is operated in the
conventional way for a stacked reactor configuration with
hydrocarbon feed being introduced into the reactor at the top of
the stack and effluent removed from the last reactor at the bottom
of the stack. Catalyst moves down through the reactors of the stack
progressively from bed to bed, entering the catalyst inlet 10A at
the top of the stack and leaving at the spent catalyst outlet 10B
at the bottom of the last reactor in the stack (here, the fourth
reactor). The spent catalyst passes down from the catalyst outlet
through a spent catalyst removal line 20, lock valves 21 to
catalyst lift pot or lift entrainer 23 in which the spent catalyst
is entrained by lift gas which elevates the catalyst up liftpipe
24. The lift gas, supplied through conduit 25 under the control of
differential pressure/flow controller 27, is suitably booster gas,
that is, gas from the compressor of the recycle gas circuit,
comprising mainly hydrogen with minor quantities of hydrocarbons,
which is heated to approximately 350.degree. C. (about 700.degree.
F.) in effluent heat exchanger 28.
[0023] After being conveyed upwards in liftpipe 24, the spent
catalyst passes into disengager 30 and then into surge
vessel/elutriator 31 in which the lift gas is separated and fines
removed. The fines are recovered in the fmes recovery section with
filters 32A and 32B and fines collector 33; gas passes out to the
gas circuit through line 34.
[0024] From the surge vessel/elutriator 31, the spent catalyst
passes through lock 35 to flow control hopper/distributor 36. Flow
control hopper/distributor 36 enables catalyst to be distributed to
each of regenerator vessels 12, 13 or 14. The catalyst passes from
flow control hopper/distributor in lines 37, 38, 39, through locks
40A, 40B, 40C and double block and bleed valves 41A, 41B, 41C, to
regenerator vessels 12, 13 and 14. Block gas supply to the double
and bleed valves is provided in conventional manner as shown with
gas supplies, suitably of refinery fuel gas through lines 42A, 42B,
42C. Similar locks 43A, 43B, 43C and double block and bleed valves
44A, 44B, 44C, are provided at the catalyst outlets of vessels 12,
13 and 14. Block gas supply to the double and bleed valves on the
outlets is provided in conventional manner as shown with gas
supplies, suitably of refinery fuel gas through lines 45A, 45B,
45C. Make up catalyst can be admitted when required through valve
71 from catalyst drum 70.
[0025] Regenerator vessels 12, 13, 14 are the previously used axial
reactors which were made redundant when they were replaced by the
moving bed continuous reactors. Typically, at any point in time,
one of the three regeneration vessels is in the "Spent Catalyst
Fill" mode, one is in the "Regeneration" mode, and the remaining
one is in the "Regenerated Catalyst Discharge" mode. The double
block and bleed motor operated valves on the regenerator flow allow
the reactors to be isolated from regeneration gas flow when they
are in the "Spent Catalyst Fill" mode or the "Regenerated Catalyst
Discharge" mode.
[0026] "Spent Catalyst Fill" Mode
[0027] When a regeneration vessel is filling it is isolated from
regeneration gas flow by double block and bleed valve arrangements
41A, 41B, 41C at the inlets and 44A, 44B, 44C at the outlets of the
vessels. Catalyst is flowing from the flow control
hopper/distributor 36 into the selected regenerator vessel through
the spent catalyst fill line that protrudes through the
regeneration flow inlet spool piece 12A, 13A, 14A of the selected
vessel. The regenerated catalyst emptying line that protrudes
through each regeneration flow outlet spool piece 12B, 13B, 14B is
closed.
[0028] "Regeneration" Mode
[0029] During catalyst regeneration in one of the three
regeneration vessels, the appropriate spent catalyst filling line
37, 38, 39 and the corresponding regenerated catalyst emptying line
is closed. Regeneration gas flows into the regenerator vessel
through the respective regeneration gas inlet spool piece 12A, 13A,
14A, and out of the vessel through the regeneration gas outlet
spool piece 12B, 13B, 14B as indicated by gas flow arrows (not
numbered). Regeneration off-gases are sent to the scrubber in the
conventional way. The catalyst lines are isolated from the
regeneration gas with the double block and bleed valve arrangements
41A, 41B, 41C, 44A, 44B, 44C on the inlet and outlet sides
respectively. The regeneration circuit that was used in the cyclic
unit before the conversion provides the facilities required for
compression, furnace, heat exchange, and regeneration gas and
chemical injection during the regeneration. These facilities will
be flexible enough to meet the regeneration procedure requirements
for known reforming catalysts. The regeneration sequence with its
purge, coke burn-off, halogenation, purge, reduction and, if
desired, pre-sulfiding, can be carried out according to
conventional practice as dictated by operational requirements and
catalyst chemistry in a manner comparable to that used in
conventional cyclic units.
[0030] "Regenerated Catalyst Discharge" Mode
[0031] When a regenerator vessel is being emptied, it is isolated
from regeneration gas flow by double block and bleed valve
arrangements at the vapor inlet and outlet of the reactor. Catalyst
is discharged from the regenerator vessel through the appropriate
regenerated catalyst discharge line 50, 51, 52 that protrudes
through the vapor outlet spool piece 12B, 13B, 14B of the
respective vessel and passes into a lift entrainer 60 beneath the
regenerator vessel group. Recycle gas supplied through line 61
under control of differential pressure/flow controller 62 is used
to entrain the regenerated catalyst in lift entrainer 60 and
elevate it through liftpipe 63 up to the catalyst disengaging
vessel 64 located above the reduction zone 10B at the top of moving
bed reactor 10. The spent catalyst filling line that protrudes
through the regeneration flow inlet spool piece 12A, 13A, 14A,
respectively, is closed.
[0032] Cycle Control
[0033] The regeneration cycle operation is under the control of a
sequential cycle controller (not shown) and associated control
equipment, all of which is of conventional type. The controller
acts to maintain the flow of spent catalyst from the flow control
hopper/distributor to the selected regeneration vessel which is in
the "Spent Catalyst Filling" mode while, at the same time
regulating the valving to the other vessels to put the regenerator
vessel in the "Regeneration" mode into the regeneration cycle and
the third vessel into the "Regenerated Catalyst Emptying" mode.
This involves actuation of the catalyst flow valves and the gas
flow valves and blocks to obtain the required actions, all of which
can be carried out by conventional controllers, control circuits,
actuators and related equipment. The regeneration cycle for the
catalyst will be determined by catalyst and operational
requirements and may be under the control of the main cycle
controller or a regeneration sub-controller operating under the
overall control of the main controller. The regeneration cycle
controller of either type will need mainly to control the flow of
regeneration gas to the vessel which is in the "Regeneration" mode.
Typically, this will include a regeneration gas sequence comprising
a hydrocarbon purge (hot nitrogen), coke burn (hot
oxygen-containing gas), oxy-chlorination, oxides purge (hot
nitrogen), and reduction (hydrogen). The reduction step may,
however, be carried out at the inlet of the reactor section, for
example, above the first reactor in a stacked configuration and, if
so provided, may be omitted from the sequence carried out in the
regeneration section. Other variations in the sequence will be
dictated by catalyst requirements and can be accommodated by
conventional modifications to the cycle control and appropriate
provision in the regeneration system.
[0034] Unit Layout
[0035] Because this is essentially a conversion or revamp scheme,
the final unit layout will normally be determined to a large degree
by specific site requirements. So, the configuration and location
of the reactor section may well be constrained by the site as well
as the relative location of the regeneration section; normally,
cost considerations will preclude relocation of the old fixed bed
reactors to a new location, especially if the old unit were a
cyclic unit with the associated piping in the regeneration circuit.
This will often require appropriate siting of the new moving bed
reactor section. With a stacked reactor configuration, the
side-by-side configuration typical of old cyclic and
semi-regenerative units will require the use of lift systems for
the spent and regenerated catalyst flows, as described above but
this is by no means inherent in the character of the conversion; if
alternative arrangements are more suitable, resort may be made to
them as necessary or convenient.
[0036] Reforming Catalyst
[0037] Any typical reforming catalyst suitable for moving bed
operation may be used, consistent with the equipment limitations
and feed and operational requirements. Suitable catalysts include
those comprising one or more Group VIII noble metals on a
refractory support. The catalyst will contain a
hydrogenation-dehydrogenation function (hydrogen transfer) and an
acid function. Examples include catalysts comprising platinum, tin,
rhenium, iridium, tin or combinations of these metals. A preferred
support includes substantially spherical alumina support particles.
A preferred catalyst comprises platinum, platinum and tin, or
platinum and rhenium on substantially spherical alumina support
particles. Spherical particles are preferred for movement through
the moving bed reactors and other equipment with minimal
attrition.
[0038] Reforming Catalyst Regeneration
[0039] A typical regeneration procedure includes a hydrocarbon
purge, coke burn, halogenqtion (usually oxy-chlorination), oxides
purge, and reduction procedure. However, depending on the type of
catalyst it may also include presulfiding as part of the
regeneration procedure. The oxy-chlorination procedure may vary
significantly. At a minimum it may include the addition of a
chloride containing agent such as Cl.sub.2,HCl, or a pumpable
organic chloride after the coke burn to replace the chloride lost
during the coke burn. However, it may also include a continuous
addition of a chloride agent during the coke burn. It may also
include over-chlorination after the coke burn followed by a
chloride equilibration step after the platinum metal has been
thoroughly redispersed. The actual regeneration procedure might
include any combination of these chlorination techniques.
* * * * *