Note: Descriptions are shown in the official language in which they were submitted.
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EBULLATED BED REACTOR HAVING TOP-MOUNTED RECYCLE PUMP
BACKGROUND OF INVENTION
Field of Inventlon
This invention pertains to an improved process and
apparatus for chemically reacting liquids or slurries of
liquids and solids with gasiform materials by the ebullated
bed process. It is particularly directed to such process
utilizing a liquid recycle pump mounted in the upper portion
of the ebullated bed reactor.
Description of Prior Art
The ebullated bed reaction process generally comprises
passing concurrently flowing streams of liquids or slurries
of liquids and solids and gasiform materials upwardly through
a generally cylindrical vessel which contains a mass of
particulate contact material. The contact particles are
placed in random motion in the liquid medium, and said par-
ticles have a gross volume dispersed through the liquid
medium greater than the volume of the particle mass when
stationary. This technology has found commercial application
in th~ upgrading of heavy liquid hydrocarbons and for
converting coal to synthetic oils.
The ebullated bed reaction process is generally described
in U.S. Patent Re. ~5,770 to Johanson, with particular
reference to oil and coal conversion. A mixture of
hydrocarbon liquid and hydrogen is passed upwardly through a
bed of catalyst particles at a rate such that the particles
are placed into random motion as the liquid and gas are
passed upwardly through the bed, and the catalyst bed motion
is controlled by a recycled liquid flow such that the
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majority of the catalyst particles do not rise above an upper
level in the reactor. The liquid, which is being
hydrogenated along with the vapors present in the reaction,
pass through that upper level of catalyst particles and are
removed from the upper portion of the reactor.
In the normal operation of such a system, substantial
amounts of hydrogen gas and light hydrocarbon vapors rise
through the reaction zone into the liquid-gas separation
section, from which some liquid is recycled to the bottom of
the reactor and the remainder provides a liquid effluent
stream. The gases and vapors are separated from the liquid,
and a liquid portion is recycled to the bottom of the reactor
through a pump which is controlled so as to maintain the desired
expansion and random motion of catalyst particles at a
relatively constant and stable level. Any gases or vapors
present in the recycled liquid materially decrease the capa-
city and efficiency of the recycle pump as well as alters the
desired flow patterns, and thus decrease the stability of the
ebullated bed. Also, the recycle of reactor liquid through
the bed must be reliably maintained to prevent any slumping
of the bed,which can cause uneven temperature distribution ~ ooking
which present severe problems in reebullating the bed.
Typically, reactors employed in catalytic hydrogenation
processes using ebullated beds of catalyst particles are
provided with a vertical conduit for recycling clean liquid
from the upper level above the ebullated catalyst bed to the
su~tion of a recycle pump used for recirculating the liquid
upwardly through the catalytic reaction zone. Such recycling
of liquid from the upper portion of the reactor serves to
ebullate the catalys~ bed, provide good liquid-gas contacting
therein and maintain substantially uniform temperature
throughout the reactor.
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One prior art reactor having gas-liquid separation and
reactor liquid recycle is shown in U.S. Patent 3,124,518 to
Gu~ et al, which discloses a li~d d ~ cGmer cond~t fitt~
with a large entrance cone. This cone permits the upward
velocity of the liquid to slow relative to the gas, so that
gas which is entrained in the liquid can separate and rise to
the liquid-gas interface above the cone, prior to recycling
the liquid through the downcomer. conduit and the bed.
Another reactor liquid recycle configuration is disclosed in
U.S. Patent 3,227,528 to Jaeger, which shows a downcomer
conduit leading to a pump at its lower end for recycle of
reactor liquid. Although such use of a pump mounted at the
lower end of a downcomer conduit for recycle of reactor
liquid has usually been satisfactory, problems can arise
during any reactor operational upsets in which the catalyst
bed may be expanded excessively and a quantity of catalyst
undesirably carried over into the recycle pump suction and
cause erosion damage to the pump. Following any such
operational upset periods, it is usually necessary ~o shut
down the process and remove the lower recycle pump for
cleaning or repair, thus requiring considerable plant outage
time.
There has thus been a need in the operation of ebullated-
bed reactors not only for improved reliability in the recycle
of reactor liquid for bed ebullation, but also for an
improved means for removing any catalyst from the downcomer
conduit and lower pump suction region without undesirable
removal and possible disassembly of the pump, so that the
reliability and efficiency of the entire hydrogenation
reaction process c~uld be significantly improved. To meet
this need, this invention discloses an ebullated bed reactor
having a recycle pump assembly advantageously mounted in the
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upper portion of the reactor for recirculating the reactor
liquid upwardly through the catalyst bed to expand and
ebullate the bed.
SUMMARY OF INVENTIO~
The present invention provides a continuous reaction
process for treating viscous liquids, wherein the feedstock
liquid or liquid-solids slurry is contacted with a reaction
gas at elevated temperature and pressure conditions in a
reaction zone containing an ebullated 'bed of contact
particles. The liquid or liquid-solids slurry is introduced
into a lower portion of the reaction zone with gas at an
upward flow rate sufficient to produce random motion of the
contact particles and expand the bed in the reaction zone.
The ebullated bed of contact particles is maintained in ran-
dom motion in the reaction zone as described in U.S. Patent
Re. 25,770, and the bed has volumetric expansion of between
about 10-200~ greater than when in a settled condition.
Treated liquid and gas pass upwardly from the reaction zone
without substantial contact particle entrainment into an
adjacent phase separation zone, so as to accomplish substan-
tial disengagement of the gas from the liquid. A major por-
tion of the treated vapor-reduced liquid is collected and
recycled from the phase separation zone downwardly through a
conduit means having an enlarged upper portion and a recycle
pump impeller advantageously located in the conduit upper
end. The remai~ing portion of the treated liqu,id and gas
mixture from the phase separation is withdrawn from above the
phase separation zone.
More specifically. the feedstock and gas are introduced
into the lower end of the reaction zone, which contains an
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ebullated bed of particulate contact solids or preferably a
catalyst material, and rises uniformly through the reaction zone
to the phase separation zone, which contains a phase separation-
collection device. This device provides for effective separatlon
of the gas portion from the rising liquid-gas mixture, so that a
substantially vapor-free liquid is collected and returned through
the downcomer conduit to at least one recycle pump having its
impeller located in the conduit upper end below the phase
separation-collection device. The pump provides for
recirculation of reactor liquid through the reaction zone to
maintain the desired uniform ebullated bed expansion therein.
Accordingly, it is an object of this invention to provide an
ebullated bed reaction process wherein the reliability and
efficiency of the process, such as for the catalytic
hydrogenation of hydrocarbon feedstocks, employing an ebullated
catalyst bed reaction is significantly increased.
It is another object of this invention to provide an upper
recycle or ebullating pump assembly, which can be used alone or
in combination with a lower recycle pump for reliably
recirculating the reaction liquid upwardly through an ebullated
catalyst bed.
The present invention, in one aspect, resides in a reactor
assembly for treating liquid and gas feedstreams, comprising:
(a) a generally vertical pressurizable vessel having upper and
lower heads; (b) means for introducing liquid and gasiform feed
materials into the lower portion of the vessel below a flow
distribution means; (c) a phase separation-collection device
located in the upper portion of said vessel for separating the
upflowing reacted fluid into liquid and gas portions; (d) a
generally vertical downcomer liquid conduit disposed within the
vessel, said conduit having its upper end in fluid communication
with the phase separation-collection device, and having its lower
end in fluid communication with the lower portion of the vessel;
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(e) a pump assembly supported from the reactor upper head and
having its impeller located in the upper end of said conduit for
recirculation of reactor liquid through the reactor, said
impeller being supported by an adjacent bearing attached to a
conical-shaped pressurizable housing structure adapted for
providing a clear compatible fluid into the housing structure to
prevent undesired entry of a reactor liquid therein; and (f)
means for withdrawing a product stream from the upper portion of
the reactor above the phase separation-collection device.
The present invention further provides a reactor assembly
for treating liquid and gas feedstreams, comprising: (a) a
generally vertical pressurizable vessel having upper and lower
heads; (b) means for introducing liquid and gasiform feed
materials into the lower portion of the vessel below a flow
distribution means; (c) a phase separation-collection device
located in the upper portion of said vessel for separating the
upflowing reacted fluid into liquid and gas portions; (d) a
generally vertical conduit disposed within the vessel, said
conduit having its upper end in fluid communication with the
phase separation-collection device and having its lower end in
fluid communication with the lower portion of the vessel; (e) a
liguid recycle pump assembly supported from the reactor upper
head, said pump assembly having an elongated drive ~shaft and
having its impeller located in the upper end of said conduit for
recirculation of reactor liquid through the reactor, said pump
impeller having a bearing located adjacent the impeller and
attached to a conical-shaped pressurizable housing adapted for
providing a clean compatible fluid within the houslng to exclude
reactor liquid from the bearing, said pump assembly having at
least one anti-vortex vane ~cated upstream of said pump
impeller; (f) a secon~ recycle pump provided in series flow
relationship with the upper pump assembly for recycle of reactor
liquid; and (g) means for withdrawing a product stream from the
upper portion of the reactor above the phase separation-
collection device.
5(a)
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In another aspect, the present invention resides in a
removable pump assembly for mounting in a reactor, comprlsing:
(a~ a drive motor attached to a mounting flange; (b) an elongated
conical-shaped support structure attached to the flange, and
containing a bearing means at the structure outer end; (c) a
drive shaft extending from the motor through the bearing means;
(d) an impeller mounted on the outer end of said drive shaft; and
(e) multiple radial vanes extending from the outer surface of
said conical-shaped support structure adjacent the bearing.
The reactor upper recycle pump assembly has an impeller
located within the upper portion of the recycle liquid
conduit and below but near the separation-collection device,
and the pump assembly is removably mounted from the reactor
upper head. The pump impeller or rotor has an adjacent
bearing and seal, which are sealed against any entry of
slurry liquid particles by a small flow of a suitable clean
fluid compatible with the reactor liquid, such as hydrogen
gas or oil, flowing outwardly through the bearing and seal. The
5(b)
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pump preferably utilizes a bearing located above or inboard
from the Lmpeller, which bearing is continuously lubricated
and purged using a d ean compatible fluid. Sufficient
hydrogen gas pressure is usually maintained in the housing
w~ich contains the bearing assembly to depress the reactor
liquid level therein and prevent such liquid containing fine
solid particles from contacting the bearing or ~eal
surfaces. Also, to help prevent gas or vapor becoming unde-
~irably entrained in the pump suction liquid, due to vortex
flow, multiple flow straightening or anti-vortex vanes are
preferably provided just upstream of the pump impeller.
If desired for improved reliability, the recirculation
of reac~or liquid through the reaction zone can be assisted
by a second recycle pump located at the lower end of the
liquid downcomer conduit and in series flow relationship
with the upper recycle pump. Alternatively, such recir-
culation of reactor liquid upwardly through the ebullated
bed can be assisted by a second recycle pump located exter-
nal to the reactor.
Important advantages for using a top-mounted recycle or
ebullating pump in an ebullated-bed reactor are that the
pump can be removed conveniently without draining all the
reactor liquid. The upper pump can also be operated in
reversed flow direction for use in unplugging the reactor.
Furthermore, the upper pump can be either used alone as the
primary recycle pump, or it can be advantageously operated
in series flow relation with a second buttom mounted recycle
p~mp .
Although this process and apparatus are suitable for
treating and reacting any fluent feedstock with a reactive
gas in an ebullated bed of contact par~icles or catalyst
at elevated temperature and pressure condi ions, the
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feedstock is preferably a fluent hydrocarbon from the group
consisting of petroleum crude oil~ residuum~shale oil, tar
sands bitumen~coal and lignite7and the gas is hydrogen.
DESCRIPTION OF THE DRAWINGS
Figure 1 i5 a sectional view of an ebullated bed cata-
lytic reactor showing upper and lower recycle pumps for use
within the reactor.
Figure 2 is a sectional view of a portion of the upper
recycle pump~ showing the impeller and associated inboard
bearing mounted within the reactor liquid downcomer conduit.
Figure 3 is a sectional view of an alternative arrange-
ment for the reactor with upper and lower recycle pumps, the
upper pump havins an outboard-type bearing mounted within the
reactor liquid downcomer conduit.
Figure 4 is a sectional view of a portion of the upper
recycle pump showing the impeller and associated outboard
bearing configuration and anti-vortex vanes.
DETAILED DESC~IPTION OF INVENTION
While this invention is applicable to any process for
chemically reacting liquid and gasiform materials in the
presence of a mass of solid contact particles, the invention
will be described with particular reference to the liquefac-
tlon of coal, as generally disclosed in U.S. Patent3,607,719, Johnson et al, issued September 21, 1971.
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In general, the reactor vessel is divided into two zones,
a lower reaction zone and an upper phase separation zone.
The feed liquid and gas are introduced into the lower end of
the reaction zone, which contains a bed of particulate solids
or preferably a catalyst material, and rise uniformly through
the reaction æone, thereby expanding the catalyst bed.
Liquid and gas pass upwardly to the phase separation zone
which contains a phase separation-collection device 9 which
provides effective separation of the gaseous and vapor
portion of the rising liquid-gas mixture. A substantially
vapor-free liquid portion is collected and returned through a
downcomer conduit to at least an upper recycle pump for
recirculating the liquid upwardly through the ebullated bed
reaction zone to maintain the desired ebullated bed expansion
therein. The separation-collection device has an enlarged
upper portion, which is usually conical or frusto-conical in
shape, and is connected at its lower end to a liquid
downcomer conduit containing the impeller of the recycle pump
located in the upper portion of the reactor.
The invention is further described by reference to Figure
1 showing reactor vessel 10, w~ch is preferably cYl~rical in
shape and oriented in a vertical position. Although this
Figure 1 drawing is schematic, it will be understood that the
reactor 10 is constructed in such manner that it is suitable
for reacting liquids, liquid-solid slurries, solids and gases
at elevated temperatures and pressures, and in a preferred
embodiment is suitable for treating hydrocarbon liquids and
coal-oil slusries with hydrogen at high temperatures and
pressures, such as 500-1500F and 1000-5000 psi. The reactor
10 is provided with inlet conduit 12 for feeding a heavy oil,
or a mixture of oil with s~all particles of coal, and a
hydrogen-containing gas. Outlet conduits are provided in the
A
.
upper portion of reactor 10, condult 14 being arranged to
withdraw combined vapor and liquid, and conduit 16 to
withdraw mainly liquid product if desired. The reactor may
also contain means for introducing and withdrawing catalyst
particles, which are shown schematically as inlet connection
15 and outlet connection 17.
A feedstock, such as heavy oil or oil slurried with coal
particlesl is introduced through conduit 11, while hydrogen-
contain.ing gas is introduced through conduit 13, and i5 com-
bined with the feedstock and fed into the bottom of reactor
10 through conduit 12. The incoming fluid passes through
grid 18 containing suitable fluid distribution means, such as
bubble caps 19, but it is understood that any suitable device
known in the art which serves to uniformly distribute the
fluid from conduit 12 over the entire cross-sectional area of
reactor 10 may be utilized.
The mixture of liquid and gas flows upwardly through the
catalyst bed 22, and the catalyst particles are thereby pro-
vided with a random ebullated movement by the combined flows
of gas, feed liquid, and recycled liquid flow being provided
by recycle pump 20 having impeller 21 located in the upper
end of downcomer conduit 24. The liquid flow delivered by
this recycle pump impelIer or rotor 21 is sufficient to cause
the mass of catalyst particles in bed 22 to expand by at
least 10~ and usually by 20-200% over their settled height,
due to gas and liquid upward flow, as generally shown by
direction arrow 22a through bed 22, at a steady ra-te.
Because of the upwardly directed fluid flows provided by the
recycle pump and the downward forces provided by gravity, the
catalyst bed particles will reach an upper level of movement
or ebullation while the lighter liquid and gas will continue
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to move upward beyond that level.- The upper level of
catalyst or catalyst interface is generally shown at 23, and
the reaction zone extends from grid tray 18 to level 23.
Ca~alyst particles in bed 22 move in random motion and are
generally uniformly distributed through the entire reaction
zone in reactor 10, while substantially no catalyst particles
rise above catalyst interface 23.
The volume above the catalyst interface 23 contains
liquid and entrained gas or vapor up to the liquid-gas
interface shown as level 25. The upper portion of the reac-
tor is the phase-separation zone in which the liquid and qas
are separated in a separation-collection device 28 to collect
and recycle through downcomer 24 a liquid having only minor
gas and vapor content. Outlet conduit 14 terminates in the
vapor space and is usually used to withdraw a combined vapor
and liquid effluent stream. However if desired, a
substanti~lly liquid stream may be withdrawn separately from
gas and vapor through outlet 16.
me upper portion of d ~ ~ er cond~t 24 is enl ~ ~ at 28 ~
is preferably an inverted frusto-conical shape and may
contain vertical conduits incorporated therein for additional
fluid flow. Annular space 26, between the interior wall of
reactor 10 and phase separator-collection device 28, permits
upward fluid flow therethrough. Gas-entrained fluid moves
generally upwardly through the phase separation-collection
device, wherein the liquid portion reverses direction and
flows downwardly to and through downcomer 24 to the inlet of
recycle pump 2Q, and thereby i5 recycléd through the lower
portion of reactor 10. Conduit 24 is preferably centrally
located within reactor 10. Gases and vapors which are
separated from the liquid rise to the liquid-gas interface 25
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and are collected in the upper portion of reactor 10 and
removed through outlet conduit 14. The ga~es and vapors
removed at this point are further processed u~ing
conventional means to recover as much hydrogen as po9sible
for recycle into the gas feed inlet 13. The liquid portion
is further processed to remove particulate solids, if
necessary, and to fractionate it into desire~ product
streams.
Figure 2 shows a preferred arrangement ~or the upper
recycle p ~ assembly 20 in w~ch the pump is suppo~ed f ~ the
rea~or u~r ~ by bolted flange 31 (~'ig. 1). qhe p ~ shaft 3~ ~
shaft bearing 33 are located above the pump impeller 21,
i~e., inboard between the pump impeller 21 and the drive
m~tor 34 (Fig. 2). me ~ing is supported by housing s ~ cture 36,
which is made conical shaped so as to provide increased
rigidity to the rotating parts and is attached to motor
flange 34a. The pump assembly 20 is made removable through
upper flanged opening at 31. A clean compatible fluid such
as hydrogen gas is provided to space 37 at a pressure
slightly above the reactor pressure for pressuring and
sealing the bearing 33 to prevent the undesired entry of any
slurry liquid. Lubricating oil is provided to bearing 33
usually through tubing 39 supportably attached to housing
structure 36, or can be supplied through a central longitu-
dinal passageway 32a in shaft 3~. Impeller 21 should be
located below the lower end conical portion of phase separa-
tor 28, by a distance at least equal.to 0.5 the diameter of
conduit 24, and preferably by 0.6-6 times that diameter. If
desired, pump rotor 21 and motor 34 can be made reversible in
operation if needed for removing any material such as
unreacted coal solids and catalyst in conduit 24 causing flow
restrictions.
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To substantially prevent vapor from the phase
separation-collection device 28 being entrained into the
suction of pump 20, at least one and preferably 2-8 sta-
tionary vanes 38 are provided upstream but near impeller 21.
The vanes are generally radially disposed and are con-
veniently attached to the pump support structure 36, and
serve as flow straightening or anti-vortex vanes, which
substantially prevent vapor from space 25a being carried
into the pump inlet by swirling or vortex flow of the
liquid. The outer ends of vanes 38 should have a diameter
at least equal to ~ t of p ~ impeller 21, but ~ller than
the inner diameter of conduit 24. If desired, additional
radially-oriented vanes can advantageously be rigidly
attached to the inner surface of the phase separator cone at
its lower end, and arranged so as to permit the upward
removal of pump assembly 20.
A seoond recycle pump ass ~ ly 50 having ~ eller 51, dri-
ven by moto~ 52, can be preferably provided in reactor 10
at the lower end of liquid conduit 24, as shown in Figure 1.
This pump is preferably operated in series flow arrangement
with upper pump assembly 20 to provide for increased
reliability for the continuous recycle of reac~or liquid to
ebullated catalyst bed 22. Alternatively, a lower recycle
pump assembly 55 can be located external to the reactor
vessel lO,with a conduit extension. 54 leading to the pump
suction and conduit 56 leading from the pump discharge to
the space below flow distributor grid 18, as shown in Figure
3.
Figure 4 ~hows a cross-sectional view of an alternative
configuration for upper recycle pump assembly 40, whlch is
supported from flange 31 and has its impeller located within
liquid downcomer conduit 24. The pump impeller or rotor 41
is driven by a suitable motor 44 through elongated tubular
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shaft 42. An outboard bearing 43 is provided for pump
impeller 41 and is supported from downcomer conduit 24 by a
radial structure 46 which has a close-fitting central non-
n~atable ~de b~hing 47. Lubricant oil is p~ided to
bearing 43 through tubing 49 ~ttached to support tube 60>in
combination with longitudinal passageway 49Rin the lower end
of shaft 42. Also, to prevent the reactor liquid containing
fine particulate solids from entering the outboard bearing
43, the space 43a above the bearing i9 pressurized to
slightly above reactor pressure wit~ a clean fluid which is
compatible with the reactor liquid~such as hydrogen or oil.
Thus, a small outward flow of such clean fluid is provided
through sha~t seal 45. If desired, the pump rotor 41 and
motor 44 can be made reversible in operation.
To reduce swirling of liquid and to substantially prevent
vapor from the vapor space 25a being entrained in the suction
of pump 40,multiple radially-oriented anti-vortex vanes 58
are provided attached to a support tube 60, which can be made
cylindrical but is preferably tapered outwardly for improved
risidity. Vanes 58 and tube 60 are attached to motor flange
44a and are removable to permit the upward removal of pump
impeller 41 from reactor 10 when necessary. Also, to further
reduce liquid swirling in the pump suction, multiple
radially-oriented anti-vortex vanes 62 can be additionally
provided attached to the inner surface of the phase
separation-collection device 28, preferably to its lower
inclined surface portion. The inner ends of such vanes 62
form a diameter D, which is made slightly larger than the
diameter of pump impeller 41 so as to permit removal of the
pump assembly upwardly from the reactor.
Although the invention has been described with reference
to certain preferred embodiments, it will be understood that
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modifications and variations in the configurations described
can be made within the spirit and scope of the invention,
which is defined by the following claims.
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