Fluid flow distribution system for fluidized bed reactor

An improved flow distribution system for a catalytic reactor plenum chamber for a gas-liquid-solids ebullated bed reactor incudes a baffled nozzle device containing at least two baffle plates usually oriented substantially normal to the nozzle inlet flow direction for providing good mixing and uniform flow distribution of gas-liquid materials in the lower portion of the plenum, used in combination with distribution grid to effect a substantially uniform flow distribution of the gas/liquid mixture upwardly into the ebullated catalyst bed. A sparger can be provided in the plenum above the baffled flow distributor device for feeding additional gas-liquid mixture into the reactor. The flow distribution system provides a substantially uniform flow distribution of the gas-liquid mixture into the ebullated bed and thereby provides fouling-free operation of the reactor.

BACKGROUND OF THE INVENTION 
This invention pertains to a fluid flow distributor device and system for 
introducing 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 for providing substantially uniform flow distribution upwardly 
into an ebullated catalyst bed in a reactor. 
Experience in operating pilot plant and commercial ebullated bed catalytic 
reactors used in H-Oil.RTM. and H-Coal.TM. 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 normal 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. Pat. 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. Pat. No. 
3,202,603 to Keith, et al, shows use of dual spargers in the lower end of 
a reactor. Also, U.S. Pat. No. 3,540,995 to Wolk, et al generally 
discloses operation of a coal hydrogeneration process using an ebullated 
catalyst bed reactor in which feed and recycle liquid streams are 
introduced into the reactor lower end plenum below a flow distribution 
grid means. However, introducing such gas and liquid streams into a 
reactor plenum at high velocity requires more specific arrangements for 
the streams to achieve adequate mixing and uniform flow distribution. For 
this reason, improved designs of flow distributor devices to provide 
desirably uniform flow patterns in the reactor plenum and upwardly through 
the distribution grid means into the catalyst bed have now been developed. 
SUMMARY OF THE INVENTION 
The present invention provides a fluid flow distributor device and flow 
distribution system for feeding hydrocarbon liquids or slurries and a gas 
uniformly into the plenum chamber and ebullated catalyst bed of a reactor. 
The invention comprises a flow distributor device for providing flow 
distribtuion of a liquid/gas mixture into an ebullated bed 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 comprises 
a baffled nozzle positioned at the inner end of a conduit entering the 
plenum for recycling a hydrocarbon fluid at least partially derived from a 
reaction within the ebullated bed, said baffled nozzle being directed 
upwardly and having at least two baffles spaced apart from each other and 
rigidly attached to the inner end of said conduit, the innermost baffle 
consisting of a solid plate, and at least one other baffle having a 
central opening and located upstream of the solid plate baffle, whereby 
said baffled nozzle mixes a gas and a liquid material fed through said 
conduit into said plenum, and is arranged in combination with said 
distribution grid to effect a substantially uniform flow distribution of 
the gas/liquid mixture upwardly into the ebullated bed. 
This invention also comprises a flow distribution system for providing a 
uniform flow distribution of a fluid material into an ebullated bed of a 
reactor, said distribution system comprising a plenum provided in the 
lower part of the reactor and formed by the reactor lower end and side 
walls and by a distribution grid located below the ebullated bed in the 
reactor, a conduit extending into said plenum for carrying a flowable 
fluid material into the plenum; and a baffled nozzle rigidly attached to 
the inner end of said conduit, said baffled nozzle being directed upwardly 
and having at least two baffles spaced apart from each other, the 
innermost baffle consisting of a solid plate, and at least one other 
baffle having a central opening and located upstream of the solid plate 
baffle, whereby said baffled nozzle mixes a gas and a liquid material fed 
through said conduit into said plenum and is arranged in combination with 
said distribution grid to effect a substantially uniform flow distribution 
of the gas/liquid mixture into said ebullated bed. 
This invention is particularly useful and advantegeous for handling 
hydrocarbon feedstreams such as petroleum and coal slurries for uniform 
distribution together with hydrogen gas into an ebullated catalyst bed 
reactor. Accordingly, the term gas/liquid mixture is understood to include 
also gas/liquid slurry mixture containing fine particulate solids.

DESCRIPTION OF INVENTION 
In the present invention, the fluid stream such as a mixture of 
coal-derived liquid slurry and hydrogen is passed through a conduit and a 
disc-donut type baffled nozzle distributor device into a plenum located at 
the lower end of a reactor. The distributor device usually contains a 
series of substantially parallel spaced-apart baffle plates located at an 
angle of 45.degree.-90.degree. to the centerline of the conduit inner end, 
which device provides lateral or radially outward flow deflection within 
the plenum. Also, the central axis of the baffled nozzle distributor 
device is located at an angle of 0.degree.-60.degree. with the centerline 
of the plenum and reactor vessel. The baffled inlet flow distributor 
device for the reactor plenum of gas-liquid-solids fluidized bed reactors 
provides a fouling-free distributor device for dispersion of the kinetic 
energy of 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 
entering the plenum. For a central vertical nozzle location within the 
plenum, these baffle plates are usually equally spaced from each other. 
The distributor device innermost or top plate is solid, and deflects the 
inlet flow laterally to prevent direct inpingement of liquid on the lower 
surface of the grid plate. 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 zones and provide good mixing of gas/liquid (or 
gas/liquid slurry) and substantially uniform flow upwardly through 
openings in the flow distribution grid into the ebullated catalyst bed. 
The percent of total material flowing radially outwardly from the space 
between adjacent baffle plates can be varied by selecting the dimensions 
of the distributor device, but usually a greater percentage of the total 
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 or 
upstream plate, 25-35% is deflected by the middle plate, and the remaining 
flow is deflected radially outwardly by the top or innermost plate. For a 
nozzle configuration entering the plenum from one side, the baffle plates 
are usually oriented at an angle varying from about 0.degree. to about 
10.degree. with the adjacent baffle plate to provide a uniform dispersion 
of the recycle 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 separae 
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 downcomer conduit for 
the reactor recycle liquid can pass through the center of the baffled 
distributor device, which preferably consists of three baffle plates. The 
recycled reactor liquid enters the reactor plenum through an annular area 
between the liquid downcomer conduit and the inlet nozzle. The central 
openings of the first and middle baffle plates are sized to disperse the 
liquid flow laterally and uniformly radially outward across the reactor 
plenum, and to sweep the plenum bottom to eliminate any stagnant zones. 
The top solid baffle plate prevents direct impingement of liquid on the 
bottom side of the distribution grid. 
This inlet flow baffled nozzle distributor device is used upstream and in 
combination with the reactor distribution grid to provide an improved flow 
distribution system for an ebullated catalyst bed reactor. The pressure 
drop across the baffled nozzle distributor device at rated flow is usually 
about 5-25% of the total pressure drop across both the distributor device 
and the distribution grid. Although the distribution grid can consist of a 
perforated plate, it preferably contains multiple 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 plenum, eliminates 
undesired direct impingement of the fluid streams on the distribution 
grid, and minimizes coke formation in the plenum and in the catalyst bed. 
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, 
which may be lined with refractory insulation 15. The conduit has a 
baffled nozzle or disc-donut flow distributor device 16 oriented generally 
upwardly therein for feeding a liquid and gas mixture into the plenum, 
then 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 
shown) from which the liquid is recycled together with fresh liquid and 
gas feed through inlet pipe 10 to flow distributor 16. The plenum 12 
preferably has a height equal to 5-10 times the inner diameter of conduit 
10, and distribution grid 18 preferably has a diameter equal to 4-12 times 
the inner diameter of conduit 10. The flow distributor device 16 
perferable extends into the plenum 12 so as to be spaced below the flow 
distribution grid plate 18 by a distance equal to about 2.5-9 times the 
inner diameter of the inlet conduit 10. 
As shown in greater detail in FIG. 2, the flow distributor device 16 
comprises at least one annular-shaped plate 30 having central opening 31 
located upstream of circular solid plate 32, and all retained together by 
three circumferentially equally-spaced structural rods 33, which are 
preferably located at the baffle plate outer edges. Usually, one 
additional annular-shaped plate 34, having progressively smaller central 
opening 35 is located intermediate plates 30 and 32 to provide a preferred 
distributor device configuration for further radial distribution of the 
flow from conduit 10. Thus as shown in FIG. 2, the solid baffle 32 is 
designated the downstream or innermost baffle, annular-shape plate 30 is 
designated the upstream baffle, and annular-shaped plate 34 is designated 
the intermediate baffle. The central opening 31 of upstream baffle 30 has 
a diameter of 0.6-0.75 times the inner diameter of conduit 10, and the 
central opening 35 of intermediate baffle 34 has a diameter of 0.3-0.5 
times the inner diameter of conduit 10. The three baffle plates, i.e., 
upstream baffle 30, downstream solid baffle 32, and intermediate baffle 
34, are spaced apart from each other by distance equal to 0.3-0.5 times 
the inner diameter of conduit 10. The greater percentage of flow should 
preferably be emitted from the lowest space, because of its greater 
distance for fluid travel in plenum 12 before reaching distribution grid 
18. For a preferred flow distributor device having three plates, the plate 
dimensions are preferably selected such that about 40-45 volume percent of 
the fluid flow is deflected radially outwardly by the first or upstream 
baffle 30, about 25-35 volume percent is deflected outwardly by the second 
or intermediate baffle 34, and the remaining flow radially deflected by 
solid top or downstream plate 32. 
The three spaced-apart baffle plates are located at an angle of 
45.degree.-90.degree. with the centerline of the inner end of the conduit 
10. Also the baffled nozzle axis is located at an angle .alpha. of 
0.degree.-60.degree. with the centerline of the plenum 12 and the reactor 
14. Furthermore, if desired, each baffle plate can be oriented at an angle 
of 0.degree.-10.degree. with the adjacent baffle plate to provide a 
uniform dispersion of the gas/liquid mixture within the plenum 12. 
FIG. 3 shows an alternative configuration of the fluid flow distribution 
system of this invention, wherein the flow distributor device 16 is 
centrally located in the bottom of plenum chamber 12 below distribution 
grid 18, and extends above the bottom of the plenum by a distance equal to 
1.0-2.5 times the inside diameter of the inlet conduit. The flow 
distribution grid 18 preferably contains multiple vertical tubes 26 having 
inner diameter of 0.75-1.5 inches and which tubes each extend below the 
grid by a distance equal to 4-10 times the tube inner diameter. Tubes 26 
extend above the grid by a distance equal to about 1.5-24 times the tube 
inner diameter. Above 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 members (not shown). Cap 28 
is oriented so as to prevent entry of catalyst solid particles 22 from the 
ebullated bed 20 into tubes 26 whenever there is no upward fluid flow 
through the tube, such as may occur during operational upsets or occurs at 
process shutdown. A circular sparger ring 40 having uniformly spaced 
openings 41 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 40 encircles downcomer conduit 24, and is 
particularly useful for large diameter reactors, such as exceeding about 8 
feet inside diameter. The openings 41 are each sized to provide a uniform 
pressure drop and are located to direct to 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, downcomer 
conduit 44 passes through the center of baffled flow distributor device 
46. The distributor device consists of three annular-shaped plates 
supported from conduit 44 and to which upward fluid flow is provided by 
annular conduit 45. Upper solid plate 47 is rigidly attached as by welding 
to conduit 44 and located substantially perpendicular to conduit 44. 
Intermediate plate 48 is attached to plate 47 by three equally-spaced rods 
53 and has an annular opening 49. Lower plate 50 has annular opening 51 
somewhat larger than the opening 49 in intermediate plate 48. Thus, flow 
distributor device 46 operates similarly as for distributor device 16, 
whereby a portion of the total upward fluid flow passes radially outwardly 
through the spaces between the adjacent plates. Circular sparger 60 having 
a plurality of uniformaly spaced openings on its lower side is also 
provided in plenum chamber 12 and is centrally located above flow 
distribution device 46, similarly as in sparger 40 for the FIG. 3 
configuration. 
The effectiveness of using the inlet flow distributor device and system 
configuration is illustrated by the following examples, which should not 
be regarded as limiting the scope of the invention. 
EXAMPLES 
In a coal hydrogenation plant using the H-Coal.TM. Process for coal 
liquefaction and having an ebullated bed catalyst reactor with 5 ft. 
inside diameter, (200 tons/day H-Coal Pilot Plant Reactor), the feed coal 
slurry and hydrogen gas was mixed with the recycle ebullation liquid flow 
external to the reactor. The total combined stream was then distributed 
through a side-entering nozzle equipped with three inclined baffle plates, 
as described for the FIG. 1 embodiment of this invention. Following 
installation of the distributor nozzle in the reactor plenum, coking in 
the reactor ebullated catalyst bed due to flow maldistribution therein was 
substantially eliminated. 
In a commercial H-Coal (18,000 tons/day) Plant reactor design, having 11 ft 
inside diameter, the plenum contains a side-entering nozzle equipped with 
three inclined baffle plates for dispersion of the recycle liquid slurry 
flow and a circular sparger ring for distributing the feed liquid slurry 
and gas. In a commercial H-Oil.RTM. (35,000 bbl/day) Plant reactor design 
having 10 ft. inside diameter, the inlet flow distribution system in the 
reactor plenum consists of a vertical nozzle equipped with three 
horizontal plates for dispersion of the recycle ebullating liquid flow and 
a sparger ring for distribution of the feedstream liquid and gas. 
Although this invention has been described broadly and in terms of various 
specific embodiments, it will be understood that modifications and 
variations can be made and some elements used without others all within 
the spirit and scope of the invention, which is defined by the following 
claims.