Note: Descriptions are shown in the official language in which they were submitted.
DOWNW~RDLY-DIRECTED FLUID FLOW DISTRIBUTION SYSTEM FOR
EBULLATED BED REACTOR
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BACKGROUND OF INVENTION
This invention pertains to a fluid flow
distributor device and system for intxoducing feed and
recycle fluid streams uniformly into a plenum and an
ebullated catalyst bed of a reactor. It pertains
particularly to such a flow distribution system for
- handling petroleum and coal-oil slurry and gas streams in
which the flow is initially directed downwardly for
substantially uniform mixing and flow distribution into an
ebullated catalyst bed.
Experience in operating pilot plant and commercial
reactors used in H-Oil~ and H-Coal M processes has shown
that improper design of the inlet flow distribution in the
reactor plenum can cause operational difficulties, such as
~ coke formation in the plenum, flow maldistribution in the
; ~ catalyst bed, localized catalyst bed slumping, and
formation of coke in the bed. These problems have reduced
catalyst utilization, and resulted in frequent reactor
shutdowns and shortened periods of operation.
The prior art has apparently not provided an
adequate solution to this flow distribution problem in
fluidized bed catalytic reactors. For example, U.S. Patent
25 No. 3,197,288 to Johanson shows a catalytic reactor
configuration using simple conduits for introducing the
inlet feed and recycle liquid into the reactor plenum
chamber, and U.S. Patent 3,202,603 to Keith et al, shows
use of dual spargers in the lower end of a reactor. Also,
30 U.S. Patent 3,540,995 to Woik et al generally discloses
operation of a coal hydrogenation process using an
ebullated catalyst bed reactor in which feed and recycle
; liquid streams are introduced into the reac~or lower end
plenum below a flow distribution grid means. ~owever~
introducing such gas and liquid streams into a reactor
plenum at hi~h velocity requires more specific arrangements
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for the streams to achieve adequate mixing and uniform
flow distribution. For this reason, improved designs of
flow distribu~or devices to provide desirably uniform flow
patterns in the reactor plenum have now been developed.
SUMMARY OF INVENTION
The present invention provides a fluid flow
distributor device and flow distribution system for
feeding hydrocarbon liquid or slurry and a gas uniformly
into a plenum chamber and upwardly into an ebullated
catalyst bed of a reactor. The invention comprises a
flow distributor device for providing uniform flow
distribution of a gas/liquid mixture into an ebullated bed
of a reactor, the flow distributor device being located
in a plenum of the reactor, said plenum being formed by a
distribution grid and the lower end and lower walls of the
reactor below the grid, the flow distributor device compris-
ing a conduit extending into said plenum from outside the
reactor with the conduit inner end being directed
downwardly in the plenum and a baffled nozzle positioned at
the inner end of the conduit within the plenum and downward-
ly directed toward the lower walls of the reactor for
recycling a hydrocarbon fluid at least partially derived
from a reaction within the ebullated bed, said baffled
nozzle having at least two substantially parallel baffles
spaced apart from each other and rigidly attached to the
inner end of said conduit, the innermost or downstream
baffle consisting of a solid plate, and at least one other
upstream baffle having a central opening and located
upstream of the solid plate downstream baffle, whereby said
baffled nozzle mixes a gas and a liquid material fed
through said conduit downwardly into said plenum and is
arranged in combination with said distribution cJrid to
effect a substantially uniform mixing and flow distribution
of the gas/liquid mixture upwardly into said ebullated bed
of the xeactor.
The invention also comprises a fluid flow
distribution system for providing a uniform flow
distribution of a fluid material into an ebullated
catalyst bed of a reactor, the distribution system
comprising a plenum provided in the lower part of the
reactor and formed by the lower end and side walls and
also by a distribution grid located below the ebullated
bed in the reactor; a conduit extending into the plenum
for carrying a flowable fluid material initially
downwardly into the plenum; and a flow distributor device
located in the lower end of the plenum and associated in
flow relationship with the conduit, whereby the
distributor device mixes a gas and a liquid material fed
through said conduit downwardly into said plenum and is so
arranged in combination with the distribution grid as to
effect a substantially uniform mixing and flow
lS distribution of the gas/liquid mixture upwardly into the
ebullated bed of the reactor.
In another embodiment of the invention, the flow
distribution system comprises a plenum provided in the lower
part of the reactor and formed by the reactor lower end and
side walls and also by a distribution grid located below
the ebullated bed in the reactor; a conduit extending into
said plenum for carrying a flowable fluid material
initally downwardly into the plenum; and comprises a conical-
shaped f 1QW deflector device located in the lower end of the
plenum, said deflector having its base rigidly attached to
the plenum lower end and having its apex oriented toward the
inner end of the conduit, the centerline of the conical-
shaped deflector being substantially aligned with the
centerline of the inner end of the conduit, whereby said
conical deflector mixes a gas and a liquid material fed
through said conduit into said plenum and is arranged in
combination with the distribution grid to effect a
substantially uniform mixing and flow distribution of the
gas~liquid mixture uniformly upwardly into said ebullated
bed of the reactor.
This invention is particularly useful for
handling hydrocarbon eedstreams such as petroleum and coal
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slurries for uniform distribution together with hydrogen
gas into an ebullated catalyst bed reactor, partlcularly
when the superficial velocity in the feed conduit exceeds
about 8 ft./sec. Accordingly, the texm gas/liquid mixture
is understood to include also a gas/liquid slurry mixture
containing fine particulate solids.
BRIEE' DESCRIPTION OF DRAWINGS
FIG. 1 is a vertical cross-sectional view of the
lower portion of an ebullated bed reactor utilizing the
invention and including a plenum and flow distributor device.
FIG. 2 is a vertical cross-sectional detail vie~7
of a baffled nozæle flow distributor device used in the
invention.
FIG. 3 shows a vertical cross-sectional view of an
alternative embodiment of the invention in which feed and
recycle streams are introduced into the plenum through
separate flow devices.
FIG. 4 shows another embodiment of the invention
similar to FIG. 3 but utilizing a centrally located conical
shaped deflector device.
DESCRIPTION OF INVENTION
In the present invention, the fluid feed stream
such as a mixture of coal-derived liquid slurry and
hydrogen at 650-950F temperature and 500-3000 psig pressure
25 conditions is passed through a conduit and a distributor
device such as a disc-donut type baffled nozzle into a
plenum located at the lower end of a reactor~ The inner
end of the conduit is downwardly-directed and the plenum
distributor device is positioned at the inner end of the
conduit within the plenum and is also downwardly directed
toward the lower wall of the reactor. The distributor
device usually contains a series of substantially parallel
spaced apart baffle plates located at an angle of 45-90
to the centerline of conduit inner end, which device
provides lateral or radially outward flow deflection
within the plen~m. The inlet flow distributor device for
the reactor plenum of gas-liquid-solids fluidized bed
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reactors provides a fouling-free distributor device for
dispersion of the kinetic energy in the flowing fluids fed
into the plenum chamber~ The distributor device prevents
"jetting" of the recycle liquid and gas stream in the
plenum, and disperses the liquid flow uniformly in the
plenum.
Depending on the reactor operating conditions and
the space available in the plenum, the flow distributor
device can have various configurations. The liquid flow
distributor device can consist of at least two preferably
circular baffle plates located at the outlet of the
recycle liquid conduit. For a central vertical baffled
nozzle location within the plenum, these baffle plates are
usually e~ually spaced from each other. The distributor
device bottom plate is solid, and deflects the inlet flow
laterally to prevent direct impingement of liquid on the
bottom of the plenum. The other baffle or dispersion plates
in the device have central openings sized to intercept and
deflect portions of the liquid flow laterally or radially
outwardly into the plenum. The flow paths of these lateral
streams are directed to sweep the plenum bottom to
eliminate stagnation æones and provide good mixing of
gas/liquid (or gas/liquid slurry) and substantially uniform
flow distribution upwardly through openings in the flow
distribution grid into the ebullated bed.
The percent o~ total material flowing radially
outwardly from the spac~ between each baffle plate can be
varied by selecting the dimensions of the distributor
device, but usually a greater percentage of the flow is
emitted from the lowest space~ In a typical deflector
device design, about 40-45% of the inlet liquid flow is
deflected by the first plate, 25-35% i5 deflected by the
middle plate, and the remaining flow is deflected radially
outwardly by the bottom innermost plate. For a nozzle
configuration entering the plenum from one ~ide and not
located on the pl~num cen~-erline, the baf~le plates are
oriented a~ an angle varying from about 0 ~o about 10
s~
with the adj~cent baffle to provide a uniform disper~ion of
the gas/liquid flow within the plenum.
For small diameter reactors having inside
diameters less than about 5 feet, it is usually more
convenient to mix the feed liquid and gas streams with the
reactor recycle liquid external to the reactor prior to
uniformly distributing the combined mixture in the reactor
plenum, utilizing the distributor device of FIG. 1 as
described below. For reactors having diameters larger than
about 6 ft., it is usually desirable to introduce the feed
liquid and gas mixture into the reactor plenum through
separate distributor devices. For example, a circular
perforated sparger ring is usually located in the plenum
upper portion and can be used to distribute the gas-liquid
feed mixture uniformly across the reactor plenum. Uniform
flow of small bubbles and liquid feed is produced by
providing a pressure drop across the sparger and directing
the mixed gas-liquid streams from the sparger downwardly
to substantially dissipate the stream kinetic energy in the
liquid. This kinetic energy is utilized to increase the
intensity of liquid backmixing in the plenum. Pressure
drops across the sparger ring openings usually range from
1-15 psi for typical heavy petroleum crude upgrading and
coal liquefaction processes.
In an alternative embodiment of the invention,
the flow distributor device consists of a conduit and a
conical-shaped deflector having its base rigidly attached to
the plenum lower wall and having its apex oriented toward
and substantially aligned with the centerline of the inner
3Q end of the conduit.
This lnlet flow distributor device is used
upstream and in combination with the reactor flow
distribution grid to provide an improved flow distribution
system for an ebullated bed catalyst reactor. The pres~ure
drop across the baffled nozzle distribu~or device at rated
flow is usually 5-25% of the total pressure drop across
bo~h the distributor device and the distribution grid.
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Al-though the distributi.on grid can consist of a perfordted
plate, it preferably contains multiple vertical tubes each
provided with a cap over the tube upper end. This
distribution system provides improved gas-liquid
contacting and gas mixing in the reactor plen~, eliminates
undesired direct impingement of the fluid streams on the
distribution grid, and minimizes coke formation in the
plenum and in the catalyst bed support above the grirl.
The invention will be further described with
reference to FIG. 1, which shows an inlet conduit 10 inserted
into a plenum chamber 12 of reactor 14. The conduit has a
baffled nozzle or disc donut type flow distributor device
16 oriented generally downwardly in the plenum for feeding
a liquid and gas mixture into the plenum, then passing the
mixtu.re uniformly upwardly through openings 19 in flow
distribution grid 18 into ebullated catalyst bed 20.
Reactor liquid is withdrawn from above the catalyst bed
downward through central conduit 24 to a recycle pump (not
shown3, from which the liquid is recycled together with
fresh liquid and gas feed through inlet conduit 10 to flow
distributor 16. The plenum 12 preferably has a height
equal to S-10 times the inner diameter conduit 10, and
distribution grid 18 preferably has a diameter equal to
4-12 times the inner diameter of conduit 10
As shown in greater detail in FI~ 2, flow
distributor device 16 comprises at least one annular-
shaped plate 30 having central opening 31 located upstream
of bottom circular solid plate 32, and all retained
toget~er by three circumferentially equally-spaced
structural rods 33, which are preferably located at the
baffle plate outer edges. Usually an additional annular-
shaped plate 34, having progressively smallex central opening
35, can be located intermediate plates 30 and 32 to provide
a preferred baffled nozzle confi~uration for further radial
distribution of the flow from conduit 10. The greater
percentage of flow should preferably be emitted from the
lowest or downstream space, because of the greater
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distance of fluid travel in plenum 12 before reaching dis-
tribution qrid 18. For a flow distributor device 16 having
three pla-tes, the plate dimensions are preferably selected
such that about 40-45 volume percent of the fluid flow is
deflected radially outwardly by bottom solid or downstream
baffle 32, about 25-35 volume percent is deflected
outwardly by the second or intermediate baffle 34, and the
remaining flow radially deflected by top or upstream baffle
plate 30. If desired, at least one 10w straightening vane
36 can be centrally oriented longitudinally inside conduit
10, so that the flow pattern reaching the distributor
device 16 is substantially unidirectional. Such flow
straightening vane is particularly useful when the angle of
deflection for the flowing fluid in conduit 10 exceed about
30.
FIG. 3 shows an alternative configuration of the
fluid flow distribution system of this invention, wherein
the flow distributor device 16 is centrally located on the
longitudinal center line of the plenum and downwardly
oriented in the bottom part of plenum chamber 12 below
distribution grid 18, and is located above the bottom of the
reactor plenum by a distance equal to 1.0-2.0 times the
inside diameter of the inlet conduit. The flow distribution
grid 18 preierably contains multiple vertical tubes 26
having an inner diameter of 0.75-1.5 inches and which extend
below the grid ~y a distance equal to 4 10 times tne tube
inner diameter. Tubes 26 extend above the grid by a
distance equal to about 1.5-4 times the tube inner
diameter. ~bove the upper end of each tube 26, a
cylindrical-shaped cap 28 is provided, which is spaced away
from the tube and is rigidly supported from the tube by
suitable structural m~mbers ~not shown). Cap 28 is
oriented 50 as to prevent en~ry of ca~alyst solid particles
22 from the ebullated bed into tubes 26 whenever there is no
upward fluid 10w through the tube, such as may occur during
operationai upsets or occurs at process shutdowll.
A circular annular-shaped sparger ring 40 havinq
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uniformly spaced openings ~1 on its lower side is provided
above flow distributor device 16 to uniformly distribute
gas and liquid flow in the upper portion 12a of the plenum
chamber. The sparger ring 40 encircles downcomer conduit
24 and is particularly useful for large diameter reactors,
such as exceeding about 8 feet inside diameter. Multiple
spaced openings 41 in the sparger ring 40 are sized to
provide a uniform pressure drop and are located to direct
the flow downwardly so as to substantially dissipate its
kinetic energy and increase the back-mixing action of gas
and liquid in the plenum 12.
In another embodiment of the invention as shown
by FIG. 4, the flow distributor device consists of a conduit
and a conical-shaped deflector 46 which is centrally-
located within the bottom portion of the plenum 12, and hasits base rigidly attached to the plenum bottom wall 49. The
apex 48 of the deflector 46 is centrally aligned with downwardly
oriented end 11 of inlet conduit 10, so that the flow from
conduit 10 is deflected substantially uniformly radially
outwardly against the lower walls 49 of th~ plenum 12. The
conical surface of deflector 46 can be made straight, or
curved outwardly at the lower end to facilitate a gradual
outward deflection of the flow of the gas/liquid mixture in
the plenum. Thus, flow deflector device 46 operates
similarly as for distribu~or device 16, whereby the total flow
passes radially outwardly and against the walls of the
plenum. Circular sparger 40 is provided in plenum chamber
12 centrally located above flow distribution device 46,
simmlarly as for the FIG. 3 configuration. The conduit 10
contains at least one flow straightening vane.
The effectiveness of using the inlet flow
distributor device configuration is illustrated by ~he
following examples, which should not be regarded as
limiting the scope of the invention.
EXAMPLES
In a coal hydrogenation plant using the "~-Coal"~
Process for coal liquefaction and having an ebullated bed
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catalyst reactor with 5 ft. inside diameter, (200 tons/day
Catlettsburg "H~Coal"TM Pilot Plant Reactor), the feed coal
slurry and gas is mixed with the recycle ebullation liquid
flow external to the reactor. The total combined stream is
then distributed through a side-entering downwardly directed
baffled nozzle equipped with three inclined baffle plates,
as generally described in the F`IG. 1 embodiment of this
invention. Following installation of the flow distributor
nozzle in the plenum, coking in the reactor ebullated
catalyst bed due to flow maldistribution therein is
substantially eliminated.
In a commercial "H-Coal" (18,000 tons/day)
Plant reactor design having an 11 ft. inside diameter, the
inlet flow distribution system in the plenum contains a
side-entering downwardly directed baffled nozzle e~uipped
with three inclined baffle plates for dispersion of the
recycle liquid slurry flow and a circular sparger ring
located above the nozzle for distributing the feed liquid
slurry and gas. In a commercial H-Oil~ ~35,000 bbl/day~
Plant reactor design, having 10 ft~ inside diameter, the
inlet flow distribution system in the reactor plenum
consists of a centrally located vertically oriented
baffled nozzle equipped with three horizontal plates for
dispersion of ~he recycle ebullating liquid flow, and a
sparger ring located above ~he nozzle for uniform flow
distribution of the feedstream liquid and gas.
Althouyh this invention has been described
broadly and in terms of various specific embodiments, it
will be understood that modification~ and variations can be
made and some elements used without o~hers all within the
spirit and ~cope of the invention, which is defined b~ the
following claims,
