U.S. patent application number 10/308772 was filed with the patent office on 2003-07-10 for slurry phase apparatus.
This patent application is currently assigned to SASOL Technology (Proprietary) Limited. Invention is credited to Steynberg, Andre Peter.
Application Number | 20030129110 10/308772 |
Document ID | / |
Family ID | 25589396 |
Filed Date | 2003-07-10 |
United States Patent
Application |
20030129110 |
Kind Code |
A1 |
Steynberg, Andre Peter |
July 10, 2003 |
Slurry phase apparatus
Abstract
Slurry phase apparatus is provided which includes a slurry
vessel for holding a slurry comprising a liquid and solid particles
and gas distribution means for injecting a gas into the slurry. The
gas distribution means includes a sparger device which includes an
apertured sparger portion inside the slurry vessel, an inlet
portion leading into the slurry vessel and an outlet portion
leading from the slurry vessel. The gas distribution means also
includes closure means, external of the slurry vessel, and being
operable to allow or deny flow from the sparger portion out through
the outlet portion of the sparger device. The invention extends to
a method of introducing or reintroducing a gas into a slurry
vessel.
Inventors: |
Steynberg, Andre Peter;
(Gauteng Province, ZA) |
Correspondence
Address: |
MARSHALL, GERSTEIN & BORUN
6300 SEARS TOWER
233 SOUTH WACKER
CHICAGO
IL
60606-6357
US
|
Assignee: |
SASOL Technology (Proprietary)
Limited
|
Family ID: |
25589396 |
Appl. No.: |
10/308772 |
Filed: |
December 3, 2002 |
Current U.S.
Class: |
422/245.1 |
Current CPC
Class: |
B01J 8/1827 20130101;
B01J 2208/00132 20130101; B01J 8/22 20130101; B01J 2219/00245
20130101; C10G 1/02 20130101; B01J 8/44 20130101; B01J 8/226
20130101; B01J 2208/00884 20130101; C07C 29/152 20130101; C10G
2/342 20130101; B01J 8/1818 20130101; C07C 29/152 20130101; C07C
31/04 20130101; B01J 2208/00141 20130101; B01J 2208/00362 20130101;
B01J 2219/00006 20130101; B01J 2219/00268 20130101; B01J 2219/00247
20130101; B01J 4/002 20130101; B01J 8/006 20130101; C10G 31/06
20130101; B01J 19/26 20130101; B01J 2219/00252 20130101 |
Class at
Publication: |
422/245.1 |
International
Class: |
B01D 009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 4, 2001 |
ZA |
2001/9976 |
Claims
1. Slurry phase apparatus which includes a slurry vessel for
holding a slurry comprising a liquid and solid particles and gas
distribution means for injecting a gas into the slurry, the gas
distribution means including: a sparger device comprising an
apertured sparger portion inside the slurry vessel, an inlet
portion leading into the slurry vessel and an outlet portion
leading from the slurry vessel; and closure means, external of the
slurry vessel, operable to allow or deny flow from the sparger
portion out through the outlet portion of the sparger device.
2. Slurry phase apparatus as claimed in claim 1, wherein the inlet
portion of the sparger device enters the slurry vessel at an
elevation which is the same as, or above, the elevation at which
the sparger portion is located inside the slurry vessel.
3. Slurry phase apparatus as claimed in claim 2, wherein the inlet
portion of the sparger device includes a flow leg inside the slurry
vessel, the flow leg being substantially vertically orientated.
4. Slurry phase apparatus as claimed in claim 1, wherein the outlet
portion of the sparger device leads from the slurry vessel at an
elevation which is the same as, or lower than, the elevation at
which the sparger portion is located inside the slurry vessel.
5. Slurry phase apparatus as claimed in claim 1, wherein the gas
distribution means includes a collection vessel into which the
outlet portion of the sparger device leads.
6. Slurry phase apparatus as claimed in claim 5, wherein the gas
distribution means includes a return line leading from the
collection vessel into the slurry vessel.
7. Slurry phase apparatus as claimed in claim 1, wherein the gas
distribution means includes a purge fluid line leading into the
sparger device for purging the sparger device.
8. Slurry phase apparatus as claimed in claim 1, which includes: an
apertured support for supporting settled solid particles, the
apertured support being located inside the slurry vessel below the
sparger portion of the sparger device; and a fluid inlet for
introducing a fluid into the slurry vessel below the apertured
support.
9. Slurry phase apparatus comprising: a slurry vessel for holding a
slurry comprising a liquid and solid particles gas distribution
means comprising a sparger device, a portion of which extends into
the slurry vessel for injecting a gas into the slurry; an apertured
support below the portion of the sparger device inside the slurry
vessel for supporting settled solid particles; and a fluid inlet
for introducing a fluid into the slurry vessel below the apertured
support.
10. Slurry phase apparatus as claimed in claim 9, wherein the
apertures of the apertured support are small enough to prevent at
least 90% by mass of the solid particles in the slurry from passing
therethrough.
11. Slurry phase apparatus as claimed in claim 9, wherein the
apertured support includes a plurality of parallel spaced rows or
strips of wedge wire which between them define the apertures.
12. Slurry phase apparatus as claimed in claim 9, which includes a
quench fluid sparger and cooling medium conduits inside the slurry
vessel, the quench fluid sparger being located above the portion of
the sparger device inside the slurry vessel, but below the cooling
medium conduits.
13. A method of quenching a slurry in a slurry vessel of slurry
phase apparatus which comprises gas distribution means arranged to
inject a gas into the slurry at a predetermined level, and an
apertured solid particles support below the level at which the gas
distribution means is disposed to inject the gas, the method
including introducing a quenching fluid into the slurry vessel
below the apertured support and passing the quenching fluid into
the slurry through the apertures of the apertured support.
14. A method as claimed in claim 13, wherein the method of claim 13
comprises a step in a process selected from the group consisting of
coal liquification, methanol synthesis, higher alcohol synthesis, a
hydrogenation process, and hydrocarbon synthesis from carbon
monoxide and hydrogen.
15. A method as claimed in claim 13, wherein the quenching fluid is
a liquid at a temperature which is lower than the temperature of
the slurry in the slurry vessel, and wherein the slurry vessel
holds a slurry in which an exothermic reaction takes place.
16. A method as claimed in claim 13, including the step of
introducing a quench fluid into the slurry vessel at a level above
the predetermined level at which gas is injected into the
slurry.
17. A method as claimed in claim 16, wherein the quench fluid is a
liquid at a temperature which is lower than the temperature of the
slurry in the slurry vessel, and wherein the quench liquid is
introduced through a liquid sparger.
18. A method of introducing or reintroducing a gas into a slurry
vessel of slurry phase apparatus as claimed in claim 1, the method
comprising: operating the closure means to allow flow through the
outlet portion of the sparger device; flushing the sparger device
through the outlet portion to remove settled material which may be
present in the sparger device; operating the closure means to deny
flow through the outlet portion of the sparger device; and
introducing or reintroducing the gas into the slurry vessel through
the sparger device.
19. A method as claimed in claim 18, wherein the slurry phase
apparatus includes an apertured support for supporting settled
solid particles, the apertured support being located inside the
slurry vessel below the sparger portion of the sparger device; and
a fluid inlet for introducing a fluid into the slurry vessel below
the apertured support, the method including passing a fluid upwards
through the apertured support to assist with suspension of
particulate solids which have settled onto the apertured
support.
20. A method as claimed in claim 18, including the step of flushing
any settled material from the sparger device into a collection
vessel, and further including the step of returning material
flushed into the collection vessel to the slurry vessel.
21. A method as claimed in claim 19, including flushing any settled
material from the sparger device into a collection vessel, and
further including the step of returning material flushed into the
collection vessel to the slurry vessel.
Description
[0001] THIS INVENTION relates to slurry phase apparatus.
[0002] There are many applications in the chemical process industry
in which a gas is injected into a slurry which comprises particular
solids suspended in a liquid. Typically, a gas distributor is used
to inject gas into the slurry. A commonly used gas distributor
comprises an apertured sparger pipe or device for uniformly
distributing the gas into the slurry.
[0003] Problems associated with the use of a sparger device such as
a sparger pipe include plugging of the apertures or gas injectors
of the sparger pipe, backflow of slurry into and through the
sparger pipe in the event of an interruption in the flow of gas and
settling of the particular solids in stagnant zones. A
characteristic of many slurries is that once the particular solids,
e.g. catalysts, have settled out of the liquid phase it is
difficult to resuspend the solids in the liquid phase. In many
slurry phase reaction applications, settled solid catalysts will
also be problematic due to resulting poor heat transfer causing hot
and cold temperature spots inside the slurry that may be dangerous
or detrimental to the reaction or reactions taking place or to the
particular solid catalysts employed.
[0004] It is an object of the present invention to provide slurry
phase or suspension apparatus which at least alleviates the
abovementioned problems associated with the use of a sparger
device, particularly when an interruption of the gas flow to the
sparger device is experienced. It is also an object of the present
invention to provide improved methods of quenching a slurry and of
dealing with the results of slurry backflow into a sparger
device.
[0005] According to one aspect of the invention, there is provided
slurry phase apparatus which includes a slurry vessel for holding a
slurry comprising a liquid and solid particles and gas distribution
means for injecting a gas into the slurry, the gas distribution
means including
[0006] a sparger device which includes an apertured sparger portion
inside the slurry vessel, an inlet portion leading into the slurry
vessel and an outlet portion leading from the slurry vessel;
and
[0007] closure means, external of the slurry vessel, operable to
allow or deny flow from the sparger portion out through the outlet
portion of the sparger device.
[0008] The inlet portion of the sparger device may enter the slurry
vessel at an elevation which is the same as, or above, the
elevation at which the sparger portion is located inside the slurry
vessel. Preferably, the inlet portion includes a flow leg inside
the slurry vessel, the flow leg being substantially vertically
orientated.
[0009] The outlet portion of the sparger device may lead from the
slurry vessel at an elevation which is the same as, or lower than,
the elevation at which the sparger portion is located inside the
slurry vessel.
[0010] The gas distribution means may include a collection vessel
into which the outlet portion of the sparger device leads.
Typically, the closure means includes at least one valve which is
typically located between the slurry vessel and the collection
vessel. However, it is to be appreciated that the closure means,
when in the form of a valve or valves, may be located in a line or
lines leading into and/or out of the collection vessel, thereby
also allowing opening or closing of the outlet portion of the
sparger pipe as desired, through the collection vessel.
[0011] The gas distribution means may include a return line leading
from the collection vessel into the slurry vessel. Typically, a
valve will be located in the return line between the collection
vessel and the slurry vessel.
[0012] The gas distribution means may include a line or lines which
can be used to pressurise or depressurise the collection
vessel.
[0013] The sparger device is thus typically characterised by the
vertical down orientation of a length or leg of the inlet portion
inside the slurry vessel, the absence of a valve inside the slurry
vessel in the inlet portion, a continuous flow path without dead
spaces through the sparger portion, and the outlet portion which
extends through a wall of the slurry vessel into the collection
vessel, with a normally closed valve in the outlet portion of the
sparger device between the slurry vessel and the collection
vessel.
[0014] The sparger portion of the sparger device may include a
plurality of gas injectors, which may be of any known design
suitable for injecting a gas into a slurry comprising particulate
solids suspended in a liquid. If desired, the gas injectors may
each include a conduit through which the gas passes after exiting
through the aperture or orifice in the sparger portion and prior to
entering the slurry. In this way the gas velocity as the gas exits
the gas injector is advantageously decreased, to inhibit solids
attrition.
[0015] It will be appreciated that the sparger device may have more
than one inlet portion and/or more than one outlet portion. It will
also be appreciated that the apparatus of the invention may include
more than one sparger device, in which case the sparger portions of
the sparger devices should preferably be in more or less the same
horizontal plane.
[0016] In one embodiment of the invention, the sparger portion of
the sparger device is in the form of a pipe arranged in a spiral in
a horizontal plane. However, it is to be appreciated that other
geometries may be used for the sparger portion or sparger
portions.
[0017] The gas distribution means may include a purge fluid line
leading into the sparger device for purging the sparger device.
Typically, the purge fluid line leads into the inlet portion of the
sparger device.
[0018] The apparatus may include
[0019] an apertured support for supporting settled solid particles,
the apertured support being located inside the slurry vessel below
the sparger portion of the sparger device; and
[0020] a fluid inlet for introducing a fluid into the slurry vessel
below the apertured support.
[0021] Typically, the apertures of the apertured support are small
enough in use to prevent at least 90% by mass, preferably at least
96% by mass, e.g. about 98% by mass of the solid particles in the
slurry from passing therethrough.
[0022] In use, a fluid, typically a liquid, may be-fed by means of
the fluid inlet into the slurry vessel below the apertured support,
and passed upwardly through the apertures, to assist with
particulate solids suspension, particularly when gas flow through
the sparger device is first introduced or reintroduced following
interruption of gas flow, and/or as a quench fluid.
[0023] Preferably, at least some of the orifices or apertures of
the sparger portion, or at least some of the gas injectors, when
present, are orientated towards the apertured support, in use to
ensure that the slurry is sufficiently agitated to avoid the
settling of solids onto the apertured support below the sparger
portion. Preferably, each gas injector, when present, and each
aperture or orifice in the sparger portion is free draining.
[0024] The apertured support may include a plurality of parallel
spaced rows or strips of wedge wire which between them define the
apertures. The wedge wire strips may be supported on a plurality of
spaced bonding strips.
[0025] The slurry phase apparatus may include a quench fluid
sparger, in addition to the apertured support and fluid inlet, and
may also include cooling medium conduits. The quench fluid sparger
may be located above the portion of the sparger device which is
located inside the slurry vessel. Typically, when cooling medium
conduits, such as boiler circulation water conduits, are present,
the quench fluid sparger is located below the cooling medium
conduits. Although the quench fluid sparger may be a gas sparger,
it will typically be a liquid sparger for sparging a quench liquid
into the slurry.
[0026] According to another aspect of the invention, there is
provided slurry phase apparatus which includes
[0027] a slurry vessel for holding a slurry comprising a liquid and
solid particles;
[0028] gas distribution means which includes a sparger device, a
portion of which extends into the slurry vessel for injecting a gas
into the slurry;
[0029] an apertured support below the portion of the sparger device
inside the slurry vessel for supporting settled solid particles;
and
[0030] a fluid inlet for introducing a fluid into the slurry vessel
below the apertured support.
[0031] The gas distribution means and the apertured support may be
as hereinbefore described.
[0032] The invention extends to the use of slurry phase apparatus
as hereinbefore described in a process in which a gas is injected
into a slurry which includes particulate solids suspended in a
liquid.
[0033] The process may be selected from the group consisting of
coal liquefaction, methanol synthesis, higher alcohol synthesis,
hydrogenation processes, and hydrocarbon synthesis from carbon
monoxide and hydrogen. In one particular embodiment of the
invention, the process is a Fischer-Tropsch process for hydrocarbon
synthesis from carbon monoxide and hydrogen.
[0034] According to a further aspect of the invention, there is
provided a method of quenching a slurry in a slurry vessel of
slurry phase apparatus which comprises gas distribution means
arranged to inject a gas into the slurry at a predetermined level,
and an apertured solid particles support below the level at which
the gas distribution means is arranged to inject the gas, the
method including introducing a quenching fluid into the slurry
vessel below the apertured support and passing the quenching fluid
into the slurry through the apertures of the apertured support.
[0035] Typically, the quenching fluid is a liquid at a temperature
which is lower than the temperature of the, slurry in the slurry
vessel, and the slurry vessel is typically being used for holding a
slurry in which an exothermic reaction takes place.
[0036] According to yet another aspect of the invention, there is
provided a method of introducing or reintroducing a gas into a
slurry vessel of slurry phase apparatus as hereinbefore described,
the method including operating the closure means to allow flow
through the outlet portion of the sparger device;
[0037] flushing the sparger device out through the outlet portion
to remove settled material which may be present in the sparger
device;
[0038] operating the closure means to deny flow through the outlet
portion of the sparger device; and
[0039] introducing or reintroducing the gas into the slurry vessel
through the sparger device.
[0040] The method may include flushing any settled material from
the sparger device into the collection vessel.
[0041] Flushing the settled material from the sparger device may
include purging the sparger device with a purging fluid, which may
be a liquid, a liquid followed by a gas, or a gas only.
[0042] The method may include passing a fluid upwards through the
apertured support to assist with suspension of particulate solids
which have settled onto the apertured support. Typically, the fluid
is a liquid.
[0043] The method may include returning material flushed into the
collection vessel to the slurry vessel, e.g. by pressurising the
collection vessel.
[0044] The invention will now be described, by way of example, with
reference to the accompanying diagrammatic drawings.
[0045] In the drawings,
[0046] FIG. 1 shows a simplified flow diagram of slurry phase
apparatus in accordance with one embodiment of the invention;
[0047] FIG. 2 shows a schematic top plan view of one embodiment of
gas distribution means, which includes a sparger pipe, which
extends through a slurry vessel of the apparatus of FIG. 1;
[0048] FIG. 3 shows a schematic top plan view of two sparger pipes
extending through a slurry vessel in accordance with another
embodiment of the gas distribution means;
[0049] FIG. 4 shows a schematic top plan view of an apertured
support located inside the slurry vessel of the apparatus of FIG.
1; and
[0050] FIG. 5 shows an enlarged vertical section taken at V-V
through the apertured support of FIG. 4.
[0051] Referring to FIG. 1 of the drawings, reference numeral 10
generally indicates slurry phase or suspension apparatus in
accordance with the invention. The apparatus 10 includes an upright
cylindrical Fischer-Tropsch synthesis slurry phase reactor vessel
12 and gas distribution means generally indicated by reference
numeral 14.
[0052] The vessel 12 provides a slurry bed zone normally containing
a slurry bed 16 of catalyst particles suspended in liquid product
and through which gas is passing, as described in more detail
hereunder. The slurry bed 16 has an upper surface 18, and an
expanded height of the slurry bed 16 while gas passes through it is
typically between 10 metres and 40 metres, depending on the length
of the vessel 12.
[0053] The gas distribution means 14 comprises a sparger pipe 20.
The sparger pipe 20 has an inlet portion 22, a horizontal apertured
sparger portion 24 and an outlet portion 26. The inlet portion 22
extends through the cylindrical wall of the reactor vessel 12 to
the centre of the reactor vessel 12, whereafter it turns vertically
downwardly to provide a leg 28 which is substantially vertically
orientated.
[0054] As is clearly shown in FIG. 2 of the drawings, the apertured
sparger portion 24 is arranged in a spiral. As shown in FIG. 1 of
the drawings, the spiral is located in a horizontal plane inside
the reactor vessel 12. The inlet portion 22 of the sparger pipe 20
thus enters the reactor vessel 12 at an elevation which is above
the elevation at which the sparger portion 24 is located inside the
reactor vessel 12. The vertical distance between the elevation at
which the inlet portion 22 enters the reactor vessel 12 and the
elevation at which the spiral coil of the sparger portion 24 is
located, may be any desired and practical distance.
[0055] The gas distribution means 14 further includes a collection
vessel 30 into which the outlet portion 26 of the sparger pipe 20
runs. The collection vessel 30 is at more or less the same
elevation as the sparger portion 24, so that the outlet portion 26
of the sparger pipe 20 leads from the reactor vessel 12 at an
elevation which is the same as the elevation at which the sparger
portion 24 is located, and which remains at this elevation until
the outlet portion 26 opens out into the collection vessel 30.
Between the vertical leg 28 of the inlet portion 22, and the
collection vessel 30, there is thus a continuous flow path without
any dead spaces. A normally closed valve 32 is located in the
outlet portion 26 of the sparger pipe 20, between the reactor
vessel 12 and the collection vessel 30.
[0056] A line 34, which can be used to pressurise the collection
vessel 30, is isolated from the collection vessel 30 by means of a
normally closed valve 36. A vent line 38 is isolated from the
collection vessel 30 by means of a normally closed valve 40. A
return line 42 leads from the collection vessel 30 back to the
reactor vessel 12 and enters the reactor vessel 12 at an elevation
which is above the sparger portion 24. A normally closed valve 44
is located in the return line 42 between the collection vessel 30
and the reactor vessel 12.
[0057] A synthesis gas flow line or conduit 46 is connected to the
inlet portion 22 of the sparger pipe 20 via a shut-off valve 48. A
purge fluid line 50 joins the inlet portion 22 of the sparger pipe
20 between the shut-off valve 48 and the reactor vessel 12. A
normally closed valve 52 is located in the purge fluid line 50.
[0058] A gas withdrawal flow line or conduit 54 leads from a gas
outlet (not shown) provided at the top of the reactor vessel 12. A
quench liquid line 56 enters the reactor vessel 12 at the bottom of
the reactor vessel 12, below the sparger portion 24. The quench
liquid line 56 is provided with a normally closed valve 58.
[0059] An apertured support 60 for supporting settled solid
catalyst particles, is located inside the reactor vessel 12 below
the sparger portion 24 of the sparger pipe 20. The apertured
support 60 comprises a plurality of parallel spaced rows or strips
of wedge wire 62 as shown in FIGS. 4 and 5 of the drawings. The
rows of wedge wire 62 are supported on a plurality of parallel
spaced bonding strips 64, only some of which are shown in FIG. 4 of
the drawings. Apertures 65 are thus defined between the wedge wire
rows or strips 62 through which liquid may pass in an upward
direction. However, the apertures are sized such that their maximum
dimensions are smaller than the minimum dimensions of the solid
catalyst particles in the slurry bed 16.
[0060] The apparatus 10 may also include a plurality of filter
elements 66, only one of which is shown in FIG. 1 of the drawings.
The filter elements 66 are connected to a liquid product withdrawal
line 68 through which liquid product can be withdrawn. The filter
elements 66 are typically configured and operated as disclosed in
WO 00/45948, the specification of which is incorporated herein by
reference. However, it is to be appreciated that any suitable
solids separation arrangement for separating catalyst particles
from the liquid product may be used and this arrangement may be
located either inside or outside the vessel 12.
[0061] Cooling pipes, generally indicated by reference numeral 70
are provided for removing heat from the slurry bed 16 in use.
Furthermore, although not shown in FIG. 1 of the drawings, the
reactor vessel 12 will typically include downcomers, as also
disclosed in WO 00/45948.
[0062] In use, synthesis gas, comprising mainly carbon monoxide and
hydrogen, enters the sparger pipe 20 from the synthesis gas flow
line 46 and is injected into the slurry bed 16 through the
apertures or orifices of the sparger portion 24, in order to
maintain the slurry bed 16 in the reactor vessel 12. Typically, the
apertures or orifices of the sparger portion 24 are located in the
bottom of the sparger portion 24, so that the sparger portion 24 is
self-draining and so that gas is injected downwardly towards the
apertured support 60. This assists in agitating the slurry above
the apertured support 60 to a sufficient extent to inhibit the
settling of solid catalyst particles onto the apertured support
during normal operation of the apparatus 10. If desired, any
suitable kind of gas injector can be used in conjunction with the
apertures or orifices in the sparger pipe, to reduce the gas
velocity before the gas enters the slurry bed 16, thereby to
inhibit solids attrition. However,, it is to be appreciated that it
is an advantage of the apparatus 10, as illustrated, that gas
injectors with barriers or valve arrangements are not required.
[0063] The slurry bed 16 comprises the catalyst particles suspended
in liquid product, i.e. liquid wax produced in the reactor vessel
12 on the action of the gaseous reactants. The catalyst particles
are maintained in suspended state in the slurry bed 16 by means of
the turbulence created therein by the gas passing upwardly
therethrough.
[0064] The reactor vessel 12 is typically maintained at an
operating pressure of between about 10 bar and about 40 bar, more
typically between about 20 bar and about 30 bar, and at an
operating temperature of between 180.degree. C. and 280.degree. C.,
typically about 220.degree. C. to 260.degree. C. The operating
pressure and the operating temperature selected may depend on the
nature and spread of gaseous and liquid product required and the
type of catalyst used. Naturally, the reactor vessel 12 is provided
with suitable temperature control means, such as the cooling pipes
70 for controlling the reaction temperatures, as well as suitable
pressure control means such as one or more pressure control valves
(not shown).
[0065] In the reactor vessel 12, as the synthesis gas passes
through the slurry bed 16, the carbon monoxide and hydrogen react
to form a range of products in accordance with known
Fischer-Tropsch reactions. Some of these products are in gaseous
form at the operating conditions of the vessel 12 and are
withdrawn, together with unreacted synthesis gas, along the flow
line 54. Some of the products produced, such as the wax already
mentioned, are in liquid form at the operating conditions of the
reactor vessel 12, and act as the suspension medium for the
catalyst particles. As liquid product is formed, the level 18 of
the slurry bed 16 naturally rises, and the liquid product is thus
withdrawn, by means of the filter elements 66 and the liquid
product withdrawal line 68 to maintain the slurry bed level.
[0066] When gas flow through the sparger pipe 20 is interrupted for
any reason, the slurry bed 16 slumps and a number of potentially
problematic events occur.
[0067] The catalyst particles settle on the apertured support 60
and once settled, it may be very difficult to resuspend the settled
particles in the liquid phase. The settled solid catalyst will
continue to catalyse reactions at the bottom of the reactor vessel
12 but, as slurry circulation into upper regions of the reactor
vessel 12, where heat removal by means of the cooling pipes 70 is
done, no longer takes place, high temperatures which may damage the
solid catalyst are experienced at the bottom of the reactor vessel
12 when the synthesis gas flow is interrupted. This unwanted effect
is enhanced by the fact that no cooling occurs as the result of
colder synthesis gas entering the reactor vessel 12. Lastly,
problems may be encountered due to the backflow of slurry into and
through the sparger pipe 20 in the event of an interruption of the
synthesis gas flow. Some of these problems only manifest upon the
reintroduction of the synthesis gas flow to the sparger pipe 20,
such as plugging of the apertures or orifices of the sparger
portion 24 from the upstream side thereof upon reintroduction of
the synthesis gas flow.
[0068] The present invention provides a simple and effective
solution to the abovementioned problems, avoiding the need for any
moving parts, such as barrier or valve type arrangements for gas
injectors. The apparatus 10 of the invention also does not require
the use of a valve in the inlet to the sparger pipe 20 inside the
reactor vessel 12 to prevent the backflow of slurry into the
sparger pipe 20 in the event that the synthesis gas flow is
interrupted.
[0069] In the event of slurry backflow into the sparger portion 24
as a result of an interruption in the synthesis gas flow, the
slurry can be cleared easily from the sparger pipe 20 prior to
re-establishing normal operating conditions, i.e. prior to
reestablishing synthesis gas flow. The slurry is removed from the
sparger pipe 20 by establishing a lower pressure in the collection
vessel 30, e.g. by opening the valve 40 so that the collection
vessel 30 loses pressure to atmosphere, typically through a flare.
Thereafter, the valve 32 between the collection vessel 30 and the
sparger portion 24 is opened to flush slurry and any settled solids
from the sparger pipe 20 into the collection vessel 30. As a result
of the design of the inlet portion 22 of the sparger pipe 20, and
in particular the presence of the vertical leg 28, there may be
sufficient liquid inside the sparger pipe 20 to flush the settled
solids into the collection vessel 30. However, if required, a purge
fluid, typically a liquid or a liquid followed by a gas, but in
some cases a gas only, is introduced through the purge fluid line
50, with the shut-off valve 48 being closed. The purge fluid is
then used to assist with the sweep of the settled solids from the
sparger pipe 20 into the collection vessel 30. Naturally, the
pressure inside the sparger pipe 20 must be kept higher than the
pressure inside the reactor vessel 12 during the flushing
operation, to prevent further ingress of slurry into the sparger
pipe 20. As a result, some of the liquid and solids may flow out of
the sparger pipe 20 via the apertures or orifices, and the gas
injectors, if present, into the slurry bed 16.
[0070] In order to take care of the problems of settled solids on
the apertured support 60, and high temperatures in the bottom
region of the reactor vessel 12 when the synthesis gas flow to the
sparger pipe 20 is interrupted, a quench liquid is passed through
the quench liquid line 56 into the reactor vessel 12, below the
apertured support 60, after the valve 58 has been opened. The
quench liquid may be liquid product at a temperature lower than the
temperature of the slurry bed 16. Liquid is passed through the
apertures 65 in the apertured support 60 in an upward direction to
quench reactions taking place in the bottom region of the reactor
vessel 12 catalysed by the settled solid catalyst. As will be
appreciated, this liquid flow can also advantageously be used to
assist with the suspension or resuspension of catalyst particles
when the synthesis gas flow is first introduced or is reintroduced
into the reactor vessel 12 through the sparger pipe 20. It will
also be appreciated that the line 56 and the apertured support 60
can be used intermittently during normal operation of the apparatus
10, to resuspend catalyst particles settling into stagnant zones on
the apertured support 60.
[0071] Although not shown in the drawings, the apparatus 10
includes a further, quench liquid sparger above the sparger portion
24 but below the cooling pipes 70. Thus, when synthesis gas flow
through the sparger pipe 20 is interrupted, the quench liquid is
also fed into the slurry bed 16 by means of the quench liquid
sparger, advantageously assisting in preventing temperatures inside
the slurry bed 16, below the cooling pipes 70, from becoming too
high. Simultaneously, recycle gas may be fed into the sparger pipe
20 in an attempt to keep the sparger pipe 20 open.
[0072] Referring to FIG. 3 of the drawings, gas distribution means
comprising two sparger pipes 20.1 and 20.2 is shown. The sparger
pipes 20.1 and 20.2 thus each has an inlet portion, a horizontal
apertured sparger portion and an outlet portion. As with the
sparger pipe 20, the sparger pipes 20.1 and 20.2 each has a
vertical leg (not shown in FIG. 3) typically forming part of the
inlet portion, with the inlet portion extending through the
cylindrical wall of the reactor vessel 12 at an elevation which is
above the elevation of the sparger portions inside the reactor
vessel 12.
[0073] As illustrated in FIG. 3 of the drawings, instead of using a
single sparger pipe 20, two or more sparger pipes, such as the
sparger pipes 20.1 and 20.2, can be used to maintain the slurry bed
16 in the reactor vessel 12. As will be appreciated, each sparger
pipe 20.1 and 20.2 may be connected to its own collection vessel
and purge line, or, instead, a common collection vessel and a
common purge line may be used.
* * * * *