U.S. patent application number 12/746249 was filed with the patent office on 2010-10-07 for reactor and process for endothermic gas phase reactions on a solid catalyst.
This patent application is currently assigned to IFP. Invention is credited to Gilles Ferschneider, Beatrice Fischer.
Application Number | 20100252482 12/746249 |
Document ID | / |
Family ID | 39587935 |
Filed Date | 2010-10-07 |
United States Patent
Application |
20100252482 |
Kind Code |
A1 |
Ferschneider; Gilles ; et
al. |
October 7, 2010 |
REACTOR AND PROCESS FOR ENDOTHERMIC GAS PHASE REACTIONS ON A SOLID
CATALYST
Abstract
The invention concerns a reactor for catalytic reforming or for
hydrocarbon dehydrogenation, having a cylindrical shape along a
vertical axis, an upper head and a lower bottom comprising at least
two annular zones centred on the vertical axis, said two annular
zones being a zone termed a catalytic zone and a zone termed the
exchange zone. Vertical hermetic panels divide the reactor into
sectors, said sectors each comprising at least one exchange section
and at least one catalytic section, the ensemble of said exchange
sections forming the exchange zone and the ensemble of said
catalytic sections forming the catalytic zone. The invention also
concerns the process employing the reactor of the invention.
Inventors: |
Ferschneider; Gilles;
(Chaponnay, FR) ; Fischer; Beatrice; (Lyon,
FR) |
Correspondence
Address: |
MILLEN, WHITE, ZELANO & BRANIGAN, P.C.
2200 CLARENDON BLVD., SUITE 1400
ARLINGTON
VA
22201
US
|
Assignee: |
IFP
Rueil-Malmaison Cedex
FR
|
Family ID: |
39587935 |
Appl. No.: |
12/746249 |
Filed: |
December 1, 2008 |
PCT Filed: |
December 1, 2008 |
PCT NO: |
PCT/FR08/01675 |
371 Date: |
June 4, 2010 |
Current U.S.
Class: |
208/49 ; 196/46;
208/108 |
Current CPC
Class: |
B01J 2219/00006
20130101; B01J 2208/00884 20130101; C01B 2203/066 20130101; B01J
2208/00707 20130101; B01J 2208/00761 20130101; C01B 2203/0811
20130101; B01J 2219/2462 20130101; C01B 2203/063 20130101; B01J
2219/185 20130101; B01J 19/249 20130101; B01J 2208/00212 20130101;
B01J 2208/022 20130101; B01J 2219/1943 20130101; B01J 2219/2481
20130101; B01J 2219/2455 20130101; C01B 3/384 20130101; C10G 35/04
20130101; B01J 2208/00752 20130101; B01J 2208/00504 20130101; B01J
2219/2458 20130101; B01J 8/12 20130101; B01J 2208/00814 20130101;
B01J 2208/00194 20130101; B01J 8/0438 20130101; C01B 2203/148
20130101 |
Class at
Publication: |
208/49 ; 208/108;
196/46 |
International
Class: |
C10G 47/24 20060101
C10G047/24; C10G 65/02 20060101 C10G065/02 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 6, 2007 |
FR |
0708560 |
Claims
1. A reactor for carrying out an endothermic gas phase reaction,
having a cylindrical shape along a vertical axis and comprising: at
least two annular zones, centred on the vertical axis: a catalytic
zone and an exchange zone; vertical hermetic panels (65) located
along the radii of the cylindrical reactor which divide the reactor
into sectors, said sectors each comprising at least one exchange
section (61) and at least one catalytic section (62), an ensemble
of said exchange sections forming the exchange zone (204) and an
ensemble of said catalytic sections forming the catalytic zone
(202).
2. A reactor according to claim 1, in which the catalytic zone then
the exchange zone are in succession from the edge towards the
centre of the reactor.
3. A reactor according to claim 1, wherein in which at least four
annular zones centred on the vertical axis are in succession from
the edge towards the centre of the reactor, namely a first zone
(201) termed the supply zone, a second zone (202) termed the
catalytic zone, a third zone (203) termed the collection zone and a
fourth zone (204) termed the exchange zone.
4. A reactor according to claim 1, wherein the vertical hermetic
panels (65) are fixed along a central cylindrical zone (205), said
sectors each comprising an exchange section (61), a catalytic
section (62), a supply section (161) and a collection section
(162), an ensemble of said exchange sections forming the exchange
zone (204), an ensemble of said catalytic sections forming the
catalytic zone (202), an ensemble of said supply sections forming
the supply zone (201) and an ensemble of said collection sectors
forming the collection zone (203).
5. A reactor according to claim 1, comprising at least one pipe
(163) per sector passing through the upper head of the reactor to
supply the catalytic sections with catalyst and at least one pipe
(263) per sector passing through the lower bottom of the reactor to
evacuate catalyst from the catalytic sections.
6. A reactor according to claim 1, comprising an upper head and a
lower bottom and: a supply conduit (17) passing through the upper
head of the reactor for supplying a sector, denoted the first
sector, with reaction mixture; an evacuation conduit (18) passing
through the upper head of the reactor for evacuating the reaction
mixture from the last sector of the reactor; a conduit (67)
connecting the collection zone of the last sector to the evacuation
conduit (18) in order to evacuate the reaction mixture.
7. A reactor according to claim 6, comprising: an inlet conduit (6)
passing through the lower bottom of the reactor and connected to
conduits (70) leading to tubular chambers (71), said tubular
chambers distributing combustion gas by means of tubular plates
(69) via the bottom of the reactor and into each exchange section;
tubular chambers (72) for collecting combustion gas from the top of
each exchange section, and conduits (73) provided with expansion
bellows (74) for evacuating the combustion gas towards an outlet
conduit (7) passing through the upper head of the reactor.
8. A reactor according to claim 1, in which each catalytic section
comprises two concentric metal screens.
9. A reactor according to claim 1, in which each exchange section
comprises tubular exchangers.
10. A reactor according to claim 1, in which each exchange section
is constituted by plate exchangers.
11. A reactor according to claim 1, comprising a plurality of
exchange sections having identical surface areas.
12. A reactor according to claim 1, comprising a plurality of
exchanges wherein surface area of each exchanger increases from the
first to the last exchange section.
13. A reactor according to claim 1, having a plurality of catalytic
sections having the same dimensions.
14. A reactor according to one claim 1, in which the dimensions of
the catalytic sections increase from the first to the last
catalytic section.
15. A reactor according to claim 4, comprising a conduit (64)
connecting the collection section of each sector, with the
exception of the last sector, to the exchange section of the next
sector.
16. A reactor according to claim 1, said vertical hermetic panels
(65) dividing the reactor into 3, 4, 6 or 8 sectors.
17. A process comprising providing a reactor according to claim 1
and carrying out a catalytic reforming reaction or a hydrocarbon
dehydrogenation reaction in said reactor.
18. A process for carrying out a catalytic reforming or hydrocarbon
dehydrogenation reaction in a reactor according to claim 15, in
which the reaction mixture enters the reactor via the conduit (17)
then moves from top to bottom in the first exchange section (61),
passes under the first catalytic section (62) between catalyst down
pipes (263), then passes radially through a first catalytic section
(62), passing from the supply zone (201) to the collection zone
(203) of the reactor, passes to the exchange section of a second
sector via the conduit (64) then moves in succession and in
alternating manner in the next exchange sections and the next
catalytic sections.
19. A process according to claim 18, in which the catalyst moves
from top to bottom at the same rate in all of the catalytic
sections.
20. A process according to claim 18, in which the catalyst moves
from top to bottom at a rate which increases from the first to the
last catalytic section.
21. A process according to claim 17, wherein pressurized combustion
gas heats the reaction mixture by indirect heat exchange.
22. A process according to claim 21, further comprising a process
for producing the combustion gas supplying the reactor (60) via the
conduit (6) includes heating air at atmospheric pressure moving via
a line (1) to an air compressor (2) then via a line (3) towards a
combustion chamber (4) in which burning of a fuel gas moving via a
line (5) can heat the combustion gas to a temperature in the range
600.degree. C. to 800.degree. C.
23. A process according to claim 21, further comprising a process
for producing the combustion gas supplying the reactor (60) via the
conduit (6) including heating air at atmospheric pressure moving
via a line (1) towards an air compressor (2) then via a line (3)
towards a combustion chamber (4) in which burning of a fuel gas
moving via a line (5) can heat the combustion air which then passes
via an expansion turbine (12) which is on the same shaft as the air
compressor and which provides the power necessary for compression,
the combustion gas leaving the expansion turbine (12) being at a
pressure in the range 0.2 to 0.45 MPa, and at a temperature in the
range 600.degree. C. to 800.degree. C.
24. A process according to claim 23, in which the combustion gas
leaving the reactor via the conduit (7) is re-heated in a
combustion chamber (8) before being sent to a turbo-expander (10)
to produce electricity.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a reactor and a process employing
said reactor for endothermic gas phase reactions over a solid
catalyst. Said reactor is particularly suitable for catalytic
reforming and for hydrocarbon dehydrogenation reactions.
[0002] The present invention relates to a reactor which can recover
heat from pressurized combustion gas and use it for reactions.
[0003] The process uses a combustion gas under pressure to heat the
reactor by indirect heat exchange inside the reactor.
PRIOR ART
[0004] Heavy gasoline cuts (80-180.degree. C.) principally
comprising C.sub.6 to C.sub.10 hydrocarbons deriving from the
initial distillation of oil is normally processed to bring their
octane number to a high value for use in an automotive vehicle
engine.
[0005] The catalytic reforming process can carry out that
operation. That process consists of passing the gasoline cut, in
the presence of hydrogen, over a catalyst including precious metals
at a high temperature (close to 500.degree. C.). The catalytic
reforming reactions principally consist of dehydrogenating
naphthenes and paraffins present in the feed to transform them into
aromatics which have a high octane number and to isomerize the
remaining paraffins to additionally increase the octane number of
the gasoline. A first unwanted reaction is cracking, which produces
light hydrocarbons such as methane, ethane, propane and butane and
which reduces the yield of the operation. A second unwanted
reaction is coking of the catalyst, which reduces the activity of
the catalyst and necessitates its periodic regeneration by burning
the coke to re-establish its activity. Cracking is greater with
increased pressure. Thus, the yields are better at low pressure.
However, coking is higher with a lower partial pressure of
hydrogen.
[0006] Old units operated at high pressure (approximately 15 to 30
bars), with a high hydrogen recycle ratio, giving mediocre yields,
and could operate for approximately 11 months before the catalyst
had to be regenerated.
[0007] Continuous catalyst regeneration units can regenerate all of
a catalyst in a few days, to allow low pressure operation
(approximately 3 to 5 bars), and thus increase the yields. The
catalyst moves continuously in the reactors, which are thus radial
in type, and is sent to a regeneration section in order to be
regenerated before being returned to the first reactor.
Dehydrogenation reactions are highly endothermic and the reactions
stop when the temperature is too low. Current processes generally
comprise three or four reactors and as many furnaces in series.
Each furnace is followed by a reactor. Because of the high
temperatures, the furnace yields are low and it is normal to
produce steam to improve the overall yield of the furnace. It is
also normal to use that steam to actuate a turbine which drives the
recycle compressor and the hydrogen exportation compressor.
Recently, it has become more usual to use a variable speed electric
motor for the compressors and less steam is used in modern
refineries which for economic reasons tend to prefer using
electricity. For that reason, the use of large size furnaces which
generate steam with the associated operation and maintenance
problems is now considered to be a drawback of the process.
[0008] Other hydrocarbon dehydrogenation processes such as long
chain paraffin dehydrogenation use a process which is identical to
catalytic reforming and suffer from the same problems.
BRIEF DESCRIPTION OF THE INVENTION
[0009] The invention concerns a reactor for catalytic reforming or
for hydrocarbon dehydrogenation, having a cylindrical shape along a
vertical axis, an upper head and a lower bottom, comprising at
least two annular zones centred on the vertical axis, said two
annular zones being a zone termed a catalytic zone and a zone
termed the exchange zone. Vertical hermetic panels divide the
reactor into sectors, said sectors each comprising at least one
exchange section and at least one catalytic section, the ensemble
of said exchange sections forming the exchange zone and the
ensemble of said catalytic sections forming the catalytic zone.
[0010] The invention also concerns the process using the reactor of
the invention.
[0011] In order to heat the reactor, preferably a reforming
reactor, the present invention generally employs pressurized
combustion gases which means that electricity can be produced for
the catalytic reforming unit, and possibly for other units. A
single reactor is generally used, with special internal means which
mean that the sections for heating by exchange with the combustion
gas can be alternated with the adiabatic catalytic sections, with
the catalyst being able to move in the reactor under gravity. The
overall footprint of the unit, the amount of equipment and the cost
of the reaction section are thus reduced.
[0012] If the reactor dimensions are too large, then in the case of
very large capacities, several reactors of this type may be
present, preferably in parallel.
[0013] Each reactor is then generally supplied by a dedicated air
compressor and a dedicated burner.
DETAILED DESCRIPTION OF THE INVENTION
[0014] Throughout the text, 1 bar is equivalent to 0.1 MPa.
[0015] The invention concerns a reactor for carrying out an
endothermic gas phase reaction in the gas phase, having a
cylindrical shape along a vertical axis and comprising: [0016] at
least two annular zones centred on the vertical axis: a catalytic
zone and an exchange zone; [0017] vertical hermietic panels 65
located along the radii of the cylindrical reactor which divide the
reactor into sectors, said sectors each comprising at least one
exchange section 61 and at least one catalytic section 62, the
ensemble of said exchange sections forming the exchange zone 204
and the ensemble of said catalytic sections forming the catalytic
zone 202.
[0018] In the context of the invention, the first sector is defined
as the sector in which the reactor is supplied with reaction
mixture. The other sectors are termed the second sector, third
sector up to the last sector, following the order in which the
reaction mixture moves in the reactor. As an example, in the case
of 4 sectors, the first sector is that to which the reaction
mixture is supplied to the reactor. The reaction mixture then moves
in succession in said first sector then in the second sector, then
in the third sector then in the last sector before being evacuated
from the reactor.
[0019] In a preferred implementation, the catalytic zone and the
exchange zone are in succession from the edge towards the centre of
the reactor.
[0020] In a preferred implementation, at least four annular zones
centred on the vertical axis are in succession from the edge
towards the centre of the reactor, namely a first zone 201 termed
the supply zone, a second zone 202 termed the catalytic zone, a
third zone 203 termed the collection zone and a fourth zone 204
termed the exchange zone. In this variation, the vertical hermetic
panels 65 dividing the reactor into sectors are fixed along a
central cylindrical zone 205. In general, the sectors each comprise
an exchange section 61, a catalytic section 62, a supply section
161 and a collection section 162, the ensemble of said exchange
sections forming the exchange zone 204, the ensemble of said
catalytic sections forming the catalytic zone 202, the ensemble of
said supply sections forming the supply zone 201 and the ensemble
of said collection sectors forming the collection zone 203, In
general, the reactor comprises an upper head and a lower
bottom.
[0021] At least one pipe 163 per section generally passes through
the upper head of the reactor to supply the catalytic sections with
catalyst and at least one pipe 263 per section passes through the
lower bottom of the reactor to evacuate catalyst from the catalytic
sections. In general, a supply conduit 17 passing through the upper
head of the reactor can supply a sector, denoted the first sector,
with reaction mixture, an evacuation conduit 18 passing through the
upper head of the reactor can evacuate reaction mixture from the
last sector of the reactor. A conduit 67 which connects the
collection zone of the last sector to the conduit 18 in order to
evacuate the reaction mixture is generally present. In this same
variation, an inlet conduit 6 passing through the lower bottom of
the reactor is connected to conduits 70 leading to tubular chambers
71. Said tubular chambers distribute combustion gas by means of
tubular plates 69 via the bottom of the reactor into each exchange
section. Tubular chambers 72 can collect combustion gas from the
top of each exchange section, then conduits 73 provided with
expansion bellows 74 can evacuate the combustion gas towards the
outlet conduit 7 which passes through the upper head of the
reactor.
[0022] Each exchange section is generally constituted by tubular
exchangers or plate exchangers. Each exchange section has either an
identical surface area, or the exchange surface area increases from
the first to the last exchange section.
[0023] Each catalytic section is generally formed by two concentric
metal screens, preferably of the "Johnson screen" type. All of the
catalytic sections generally have the same dimensions or the
dimensions of the catalytic sections increase from the first to the
last sector.
[0024] The vertical hermetic panels 65 generally divide the reactor
into 3, 4, 6 or 8 sectors, preferably into 4 or 6 sectors.
[0025] In a highly preferred embodiment, a conduit (64) connects
the collection section of each sector, with the exception of the
last sector, to the exchange section of the following sector.
[0026] The invention also concerns the process for carrying out a
catalytic reforming reaction or hydrocarbon dehydrogenation
reaction in a reactor in accordance with the invention.
[0027] The invention also concerns a process for carrying out an
endothermic gas phase catalytic reforming or hydrocarbon
dehydrogenation reaction over a solid catalyst in a reactor in
accordance with the highly preferred embodiment of the invention,
in which the reaction mixture enters the reactor via the conduit 17
then moves from top to bottom in the first exchange section 61.
Said reaction mixture then passes under the first catalytic section
62 between the catalyst down pipes 263, then passes radially
through the first catalytic section 62, passing from the supply
zone 201 to the collection zone 203 of the reactor, passes to the
exchange section of the second sector via the conduit 64. Finally,
the reaction mixture moves in succession and in alternating manner
in the next exchange sections and the next catalytic sections.
[0028] The catalyst generally moves from top to bottom at the same
speed in all the catalytic sections. The catalyst can move from top
to bottom at a speed which increases from the first to the last
catalytic section.
[0029] The invention also concerns the process in which the
pressurized combustion gas heats the reaction mixture by indirect
heat exchange.
[0030] In a first variation of combustion gas production, the
combustion gas supplying the reactor 60 via the conduit 6 derives
from heating air at atmospheric pressure moving via line 1 to an
air compressor 2 then via the line 3 towards a combustion chamber 4
in which burning a fuel gas moving via 5 can heat the combustion
gas to a temperature in the range 600.degree. C. to 800.degree. C.,
preferably in the range 650.degree. C. to 750.degree. C.
[0031] In a second variation of combustion gas production, the
combustion gas supplying the reactor 60 via the conduit 6 derives
from heating air at atmospheric pressure moving via the line 1
towards an air compressor 2 then via the line 3 towards a
combustion chamber 4 in which burning of a fuel gas moving via the
line 5 can heat the combustion air which then passes via an
expansion turbine 12 which is on the same shaft as the air
compressor and which provides the power necessary for compression;
the combustion gas leaving the expansion turbine 12 is at a
pressure in the range 0.2 to 0.45 MPa, and at a temperature in the
range 600.degree. C. to 800.degree. C., and preferably in the range
650.degree. C. to 750.degree. C.
[0032] In each of the two combustion gas production variations, the
combustion gas leaving the reactor via the conduit 7 can be
reheated in a combustion chamber 8 before being sent to a
turbo-expander 10 to produce electricity.
DESCRIPTION OF FIGURES
[0033] FIG. 1 describes one of the ways of providing heat to the
reactor. Atmospheric air is supplied via a line 1 to an air
compressor 2. The air is compressed to a pressure close to 4 bars
absolute (0.4 MPa) and is then sent via a line 3 to a combustion
chamber 4. A fuel gas is supplied via a line 5 for burning in the
combustion chamber 4. The depleted air which has been heated by
combustion at a temperature of close to 700.degree. C. is sent via
a line 6 to the reactor 60.
[0034] The reaction mixture enters via a line 17 and leaves via a
line 18. The combustion gas cools by exchange with the reaction
mixture which is undergoing an endothermic catalytic reforming
reaction.
[0035] At the reactor outlet, the cooled gas is sent via a line 7
to a second combustion chamber 8 where it is reheated by combustion
of fuel gas supplied via a line 9. At the outlet from the
combustion chamber, the hot gas is sent at a temperature close to
750.degree. C. to a turbo-expander 10 which drives an alternator 11
to produce electricity.
[0036] FIG. 2 describes an alternative manner of supplying heat to
the reactor 60. Atmospheric air is supplied via line 1 to air
compressor 2. Air compressed to a pressure of close to 20 bars is
then sent via line 3 to combustion chamber 4. A fuel gas is
supplied via line 5 for burning in the combustion chamber 4. The
depleted air which has been heated by combustion to a temperature
of close to 1300.degree. C. is sent to a turbo-expander 12 which
drives the air compressor 2. The gas at the turbine outlet is at
about 3 bars and at a temperature of close to 700.degree. C. It is
sent via line 6 to reactor 60.
[0037] The reaction mixture enters via a line 17 and leaves via a
line 18. The combustion gas cools by exchange with the reaction
mixture which is undergoing an endothermic catalytic reforming
reaction.
[0038] At the reactor outlet, the cooled gas is sent via line 7 to
a second combustion chamber 8 where it is reheated by combustion of
fuel gas supplied via line 9. At the outlet from the combustion
chamber, the hot gas is sent at a temperature of close to
750.degree. C. to a turbo-expander 10 which drives an alternator 11
to produce electricity.
[0039] FIG. 3 describes a variation of FIG. 1 in which heat is
recovered from hot gases moving via a line 40 at the outlet from
the turbine 10. The exchanger 41 can recover heat either: [0040] by
producing steam which may be used in the refinery or to produce
electricity; [0041] or by heating a heat transfer fluid (hot oil)
which may, for example, be used to reboil the columns of the
process.
[0042] The effluent gasoline from the exchanger 41 moves via a line
42.
[0043] Clearly, this variation is also possible in the same manner
in the case of FIG. 2 (not shown).
[0044] FIG. 4 shows the reaction section of a catalytic reforming
section in accordance with the invention.
[0045] The combustion gas enters the reactor 60 via line 6 and
leaves via line 7.
[0046] The feed arrives at a feed pump 15 via a line 14. The feed
is sent from the pump outlet via a line 16 to the heat exchanger 19
which is preferably of the Packinox type.
[0047] The recycle gas which moves via a line 26 is also sent to
said exchanger 19 for mixing with the feed moving via the line 16
in the exchanger and heated to a temperature close to 440.degree.
C. by exchange with the reaction mixture leaving the reactor 60 via
line 18. At the outlet from the heat exchanger 19, the reaction
mixture is sent to the reactor 60 via line 17. The reaction mixture
leaving the reactor via line 18 is at about 490.degree. C. and is
sent to the top of the heat exchanger 19 where it is cooled to
about 100.degree. C. At the outlet from the heat exchanger 19, the
effluent is sent via the line 20 to a heat exchanger 21, where it
is cooled by heat exchange with air or cooling water. At the outlet
from the exchanger 21, the cooled and partially condensed effluent
is sent via a line 22 to a separator tank 23. The liquid from the
tank is withdrawn via a line 28 to a stabilization section. Part of
the gas phase from the separator tank 24, principally constituted
by hydrogen, is used to constitute a gas recycle, compressed by
compressor 25 then moving via line 26, the remainder being sent to
a purification section via a line 27.
[0048] FIGS. 5, 6, 7 and 8 show different sections of a preferred
version of the reactor.
[0049] FIG. 5 diagrammatically shows the reactor 60 in cross
sectional side view.
[0050] Four annular zones centred about the vertical axis are in
succession from the edge towards the centre of the reactor, namely
a first zone (visible in FIG. 6, reference numeral 201) termed the
supply zone, a second zone (visible in FIG. 6 as reference numeral
202) termed the catalytic zone, a third zone (visible in FIG. 6 as
reference numeral 203) termed the collection zone and a fourth zone
(visible in FIG. 6 as reference numeral 204) termed the exchange
zone.
[0051] Vertical hermetic panels (visible in FIG. 6 as reference
numeral 65) are fixed on the cylindrical central zone (visible in
FIG. 6 as reference numeral 205) and divide the reactor into
sectors.
[0052] Each sector comprises an exchange section 61 and a catalytic
section 62. The ensemble of the exchange sections forms the
exchange zone 204 and the ensemble of the catalytic sections forms
the catalytic zone 202. Each sector comprises a supply section 161
and a collection section 162. The ensemble of supply sections forms
the supply zone 201 and the ensemble of collection sections forms
the collection zone 203.
[0053] The combustion gas moves from bottom to top in the reactor.
Combustion gas is supplied via the bottom of the reactor via the
inlet conduit 6 then is distributed into each exchange section via
conduits 70 then via tubular chambers 71 before being distributed
via tubular plates 69 into tubes 99. At the outlet from the tubes,
the combustion gas is collected from the top of the reactor in
tubular chambers 72 then sent via conduits 73 provided with
expansion bellows 74 to the outlet conduit 7.
[0054] The reaction mixture passes through all the sectors in
succession. The reaction mixture enters via the conduit 17 and at
the collection section of the last sector, it is collected via the
conduit (visible in FIG. 6 as reference numeral 67) then leaves the
reactor via the conduit 18.
[0055] The movement of the reaction mixture, comprising hydrogen
and hydrocarbons, is represented by the arrows.
[0056] The pressure at the reactor inlet is approximately 4 bars.
The reaction mixture enters the exchange zone of the first sector
via the inlet 66 (see arrow 101). In this first sector, the
reaction mixture heats up while dropping (arrow 102) as a counter
current to the combustion gas and leaves the first exchange section
via the outlet 75. The gas passes below the catalytic section 62
(arrow 103) between the catalyst down pipes 263, rises along the
shell and passes through the catalytic section 62 (arrows 104). The
reaction mixture reacts and cools very rapidly on the catalyst as
the naphthenes present in the feed react very rapidly and in a
highly endothermic manner.
[0057] The temperature is generally less than 400.degree. C. at the
outlet from the first catalyst section. The reaction mixture is
then evacuated from the first section at the top of the reactor and
sent to the second section via a conduit (visible in FIG. 6,
numeral 64). The reaction mixture is heated up again in the
exchange section of the second sector then cooled, reacting in the
catalytic section of the second sector.
[0058] As the reactions progress, fewer and fewer naphthenes
remain, the paraffins are slower to react and exothermic cracking
partially compensates for the endothermic nature of the other
reactions. The outlet and thus inlet temperature profile of the
reaction mixture in the successive sectors is thus ascending, which
is considered to be favourable to yields.
[0059] At the outlet from the last sector, the reaction mixture is
collected by the conduit (visible in FIG. 6, reference numeral 67)
then sent to the outlet conduit 18.
[0060] FIG. 6 shows the reactor viewed from the top and in
section.
[0061] Four annular zones centred on the vertical axis are in
succession from the edge to the centre of the reactor: the supply
zone 201, the catalytic zone 202, the collection zone 203 and the
exchange zone 204.
[0062] Vertical hermetic panels 65 are fixed on the central
cylindrical zone 205 and divide the reactor into 8 sectors.
[0063] The conduits 64 allow passage from one sector to another.
The reaction mixture enters the first exchange section via the
inlet 66. At the outlet from the last sector, the reaction mixture
is collected via the conduit 67.
[0064] FIG. 7 represents a sector viewed from the centre of the
reactor, with the two connected exchange sections 61 in the
foreground, the tubular plate 69 and the catalytic section 62 in
the background, with the catalyst down pipes 163 and 263 and the
closing plates 68. FIG. 8 shows the same sector viewed from the
shell, with the exchange section 61 in the background, the
catalytic section 62 in the foreground, the exchange section outlet
75, the passage 64 from one sector to another and a closing plate
68.
EXAMPLE
[0065] The configuration of the reactor shown in FIGS. 5 to 8 was
employed in this example.
[0066] Consider a catalytic reforming unit processing 60 tonnes per
hour of feed with 35 tonnes of catalyst.
[0067] The feed was a 90-170.degree. C. cut with a paraffins
content of 60% by volume, a naphthenes content of 25% by volume and
an aromatics content of 15% by volume.
[0068] The pure hydrogen/feed molar ratio was 2.5.
[0069] The target octane number was 102.
[0070] The whole catalyst was regenerated continuously in 2.5
days.
[0071] To provide the heat for the reaction, approximately 75.24
million kJ/h (18 million kcal/h), 330 tonnes of air was compressed
to 4 bars absolute. The centrifugal air compressor had a polytropic
efficiency of 80% and consumed 16.7 MW. The temperature at the
compressor outlet was 192.degree. C. In the first combustion
chamber, 4160 kg/h of natural gas at 15.degree. C. was burned with
a lower calorific power of 46439.8 kJ/kg (11110 kcal/kg). The
temperature at the combustion chamber outlet was 700.degree. C. The
combustion gas arrived via the conduit 6 at approximately
700.degree. C.
[0072] The inlet and catalytic reforming side outlet temperatures
in the various sectors were as follows:
REACTION MIXTURE
[0073] The reaction mixture arrived at the reactor at 450.degree.
C. from the Packinox feed-effluent exchanger. It was heated up by
exchange with the hot fumes from the first sector and arrived in
the catalyst of the first sector at 486.degree. C. and was then
sent to the second sector where it was heated up before being
supplied to the second sector. There were 8 sectors in this
example: [0074] Catalytic section 1: entered catalyst at
486.degree. C., exited at 396.degree. C.; [0075] Catalytic section
2: entered catalyst at 441.degree. C., exited at 419.degree. C.;
[0076] Catalytic section 3: entered at 460.degree. C., exited at
437.degree. C.; [0077] Catalytic section 4: entered at 475.degree.
C., exited at 451.degree. C.; [0078] Catalytic section 5: entered
at 487.degree. C., exited at 463.degree. C.; [0079] Catalytic
section 6: entered at 497.degree. C., exited at 475.degree. C.
[0080] Catalytic section 7: entered at 507.degree. C., exited at
487.degree. C.; [0081] Catalytic section 8: entered at 517.degree.
C., exited at 501.degree. C. (at 4.8 bars absolute).
COMBUSTION GAS
[0081] [0082] 1.sup.st exchange section: entered at 700.degree. C.,
exited at 471.degree. C.; [0083] 2.sup.nd exchange section: entered
at 700.degree. C., exited at 422.degree. C.; [0084] 3.sup.rd
exchange section: entered at 700.degree. C., exited at 442.degree.
C.; [0085] 4.sup.th exchange section: entered at 700.degree. C.,
exited at 460.degree. C.; [0086] 5.sup.th exchange section: entered
at 700.degree. C., exited at 472.degree. C. [0087] 6.sup.th
exchange section: entered at 700.degree. C., exited at 483.degree.
C.; [0088] 7.sup.th exchange section: entered at 700.degree. C.,
exited at 494.degree. C.; [0089] 8.sup.th exchange section: entered
at 700.degree. C., exited at 505.degree. C.
[0090] The combustion gas left the reactor at 469.degree. C. after
having given up 88.198 million KJ/h (21.1 MM Kcal/h) to the
reaction mixture.
[0091] The effluent combustion gas was sent to a second combustion
chamber where 2560 kg/h of fuel gas was burned in order to reach
760.degree. C. at a pressure of 3.4 bars absolute at the inlet to
an expansion turbine. This turbine had a polytropic efficiency of
85% and provided approximately 26 MW of electrical power which
could drive the air compressor and supply sufficient electricity
for the catalytic reforming and pre-treatment units.
[0092] At the turbine outlet, the gaseous effluent was at a
temperature of 526.degree. C. which meant that either more
electricity could be produced by generating steam, or a heat
transfer fluid could be re-heated, which could reboil the columns
of the process (the stripping column for pre-treatment and
stabilization of reforming).
[0093] In this example, 48.07 million kJ/h (11.5 MM kcal/h) was
available between 526.degree. C. and 400.degree. C., which was more
than sufficient for the two columns.
[0094] An exchange surface of approximately 4000 m.sup.2 was
necessary, i.e. 8 times 500 m.sup.2. This corresponded to 8 times
350 tubes 30 mm in diameter and 15 m long.
[0095] The example is given for tubular exchangers to simplify the
calculations, but the scope of the invention also encompasses using
other types of exchanger, for example Packinox type welded plate
exchangers, which could result in a much more compact
configuration.
[0096] The tubes were installed in a triangular pattern with a
pitch P=38 mm. At this pitch, a cross section of 0.00125 m.sup.2
(0.866.times.P.sup.2 ) was required to house one tube, and thus
approximately 3.5 m.sup.2 to house the 2800 tubes.
[0097] By leaving an access 0.8 m in diameter at the centre and
increasing the surface area by 15% to take the sectioning into
account, then a surface area of 0.5+3.5.times.1.15 =4.5 m.sup.2 was
required for the whole exchange zone, i.e. a diameter of 2.4
in.
[0098] The catalyst was installed in an annular zone with an
internal diameter of 3.2 m and over a height of close to 14 m.
There were 35 tonnes of catalyst, i.e. about 50 m.sup.3, and thus
3.6 m.sup.2 of catalytic zone (50/14). The external diameter of the
annular catalytic zone was thus 3.85 m.
[0099] Thus, each sector comprised, starting from the outer shell:
[0100] an empty section (approximately 60 cm); [0101] a section
filled with catalyst between two Johnson screens or the equivalent
thereof (approximately 65 cm); [0102] a free section (approximately
40 cm); [0103] an exchange section (approximately 80 cm) filled
with vertical tubes 30 mm in diameter; [0104] a central free
section (radius approximately 40 cm).
[0105] In order to install the exchange tubes and the catalyst as
explained above, then, a shell 5.7 m in internal diameter and
approximately 16.5 m high was required.
[0106] The amount of coke produced was very small in the first
sector and increased from sector to sector, being highest in the
last sector (8% of coke if the catalyst moved in that sector for
2.5 days). One solution is to circulate the catalyst at the same
rate throughout, to mix the catalyst at the reactor outlet in order
to send it to the regenerator and to regenerate it as a mixture,
the mean coke content then being only approximately 4%, thus
allowing safe regeneration.
[0107] However, this means that the catalyst in the first sectors
is regenerated before it is necessary, so it is clearly preferable
to make the dimensions of the catalyst downflow devices such that
the catalyst from the first sectors drops more slowly and the
catalyst from the last sectors drops more quickly.
* * * * *