|Publication number||US3592613 A|
|Publication date||Jul 13, 1971|
|Filing date||Dec 30, 1968|
|Priority date||Dec 30, 1968|
|Publication number||US 3592613 A, US 3592613A, US-A-3592613, US3592613 A, US3592613A|
|Inventors||David M Boyd|
|Original Assignee||Universal Oil Prod Co|
|Export Citation||BiBTeX, EndNote, RefMan|
|Referenced by (11), Classifications (24)|
|External Links: USPTO, USPTO Assignment, Espacenet|
July 13, 1971 D M BOYD 3,592,613
APPARATUS FOR F'LUI'D DISTRIBUTION IN A I FLUID-SOLIDS CONTACTING CHAMBER Filed Dec. 50, 1968 4 Sheets-Sheet 1 FIG. NCAA A INVENTOR: DAVID M. BOYD ATTORNEYS July 13, 1971 BOYD 3,592,613
APPARATUS FOR FLUID DISTRIBUTION IN A FLUID-SOLIDS CONTACTING CHAMBER Filed Dec. 30, 1968 4 Sheets-Sheet :7
INVENTOR: DAVID M. aovo BY: Zuzan 1L.
/ ATTORNEYS July 13, 1971 D. M. BOYD APPARATUS FOR FLUID DISTRIBUTION IN A FLUID-SOLIDS CONTACTING CHAMBER 4 Sheets-Sheet 3 Filed Dec. 30, 1968 FIGS FIG.7
INVENTOR 1 BOYD DAVID M.
ATTORNEYS y 13, 1971 D. M. BOYD 3,592,613
APPARATUS FOR FLUID DISTRIBUTION IN A FLUIDSOLID$ CONTACTING CHAMBER Filed Dec. 30, 1968 4 Sheets-Sheet A.
o co m m E O n 5 E T? i. j s3 0 f 52 i o 2 3 u o .E O 1;; E O o 3 LL O (\I 5 m in o o I l l I l l l l O o o o O Q o o o O 00 N (0 LO Q m 0 u l p H Pm n INVENTOR DAVID M. BOYD y A/ z; ZZW Q ATTORNEYS FIG.9
United States Patent US. Cl. 23-288 7 Claims ABSTRACT OF THE DISCLOSURE A fluid distributing means for use in fluid-solids contact chambers containing a plurality of fixed beds of particulated contact solids. The means comprises a plurality of fluid downcomers which encompass openings in an imperforate deck plate and rise a finite distance above the plate. The downcomers are perforated to provide greater open area for fluid flow with respect to increasing distance from the face of the plate. A preferred embodiment is a deck containing downcomer means comprising screen means having screen openings of increasing dimension with respect to increasing distance from the deck plate. A further preferred embodiment is a deck containing downcomer means comprising tubular screen means formed by the helical winding of a continuous rod member around a plurality of spaced longitudinal bar members to produce a continuous helical slot opening of continuously increasing slot width.
BACKGROUND OF THE INVENTION The present invention relates to a method and apparatus for contacting two fluids in a fluid-solids contacting zone such as an adsorption zone or a reaction Zone. More particularly, the invention is directed to the contacting of two fluids comprising a liquid phase and a vapor phase in a fluid-solids contacting zone, and to means and methods for effecting improved heat exchange between the vapor and liquid phases in the contacting vessel. More specifically, the invention relates to a new and improved method and apparatus for uniformly distributing mixed phases of vapor and liquid to a granular or particulated solids contacting zone, as in an absorption tower or in a catalytic reactor such as a hydrogenation, hydrotreating, hydrocracking, or a hydrodealkylation reactor.
Among the most important of the various commercial processes are those involving the physical or chemical treatment of hydrocarbons and other organic materials with bodies of granular or particulated solid contact materials. Many of these processes involve the contacting of two fluids with the contacting material, and often the two fluids will comprise a liquid phase and a gas or vapor phase. It has been the experience in the art that the introduction of such mixtures of liquid and vapor into a bed of particulated contact solids in a uniformly distributed manner is difiicult to achieve.
Typical of the art wherein uniform distribution of liquid and gas phases is necessary but infrequently achieved, is that of catalytic hydrocarbon processing such as the catalytic hydrocracking of various hydrocarbon oils. It is Well known that the feed to such a reaction zone comprises liquid hydrocarbon, vaporized hydrocarbon, and a hydrogen-rich gas, and that this feed is introduced into the reaction zone at an elevated temperature. It is further known that the reactions which are encountered in this catalytic environment are exothermic, and that the temperature of the vapor phase and of the liquid hydrocarbon phase is increased due to the exothermic heat of reaction. In order to avoid excessive temperature within the catalyst bed it is, therefore, typical to arrange the catalyst in a plurality of separate fixed beds so that diluent or quench vapors may be distributed between the beds during the reaction. The cool quench vapors, normally comprising hydrogen-rich gas, reduce the temperature of the eflluent from the bed above and before the liquid-vapor mixture of hydrocarbon and hydrogen is fed into the bed of catalyst below.
It is typical in the art to support each individual bed of catalyst upon a perforated support plate. It is also typical in the art to introduce the quench hydrogen between the fixed beds of catalyst by means of a perforated pipe grid or other means which is positioned throughout the cross-section of the reactor vessel at the quench point. The eflluent from the catalyst bed above thus rains down from the perforated support plate throughout the crosssectional area of the reactor, while the quench hydrogen is distributed by the perforated grid throughout the cross-sectional area of the reactor.
This prior art type of fluid distributing apparatus, comprising a perforated catalyst support plate and a hydrogen quench grid distributor, is utilized with the intent of achieving a complete distribution of liqud and gas phases as uniformly as possible throughout the cross-sectional area of the reactor vessel and of the catalyst bed below. It is also the purpose of this typical fluid distributing apparatus to provide an intimate contact between hot effluent from the bed above and cool quench in order to achieve a uniform temperature of the constituents that pass into the bed below.
However, this typical prior art design has proven to be relatively ineffective in accomplishing these objectives. The problem is complicated by the fact that it is normal to add a relatively small amount of cool quench hydrogen to a large quantity of hot etfluent hydrocarbon and hydrogen which is leaving the bed above at an elevated temperature. The problem is additionally complicated by the fact that the amount of cold quench material is relatively small in relation to the large cross-sectional area which must be covered in order to maintain a proper uniform distribution of liquid and vapor to the bed of catalyst below.
The problem is further complicated by the fact that there is a mixed-phase condition within the reactor itself. There is evidence that the heavier viscous liquids tend to channel down the side of the reactor whereas the less viscous liquids tend to channel in the central region of the catalyst bed with the vaporized hydrocarbon and hydrogen. The result is that the temperature encountered within the catalyst bed will be quite uneven and localized undesirable hot spots are often found in each bed. It is well known by those skilled in the art that the existence of such hot spots within the catalyst beds leads to indiscriminate or non-selective hydrocracking of the hydrocarbon constituents, which is an undesirable result.
Since the more viscous liquid tends to rain down through the support plate near the walls of the reactor, these viscous materials Will also continue to channel along the walls in the beds below. This results in an ineffective quench between the beds, and the resulting continuation of liquid channelling produces further danger of localized hot spots in the lower catalyst beds.
SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to provide an improved apparatus for contacting two fluids in a fluid-solids contacting zone such as an adsorption zone or a reaction zone. It is another object of this invention to provide an improved apparatus for contacting and distributing mixed phases of vapor and liquid in fluidsolids contacting zones. It is a further object of this invention to provide a fluid distribution means whereby a greatly improved mixture of vapor and liquid phases occurs at their point of introduction into a bed of particulated contact solids. It is a still further object to provide a means of improved heat exchange between a liquid phase and a vapor phase of fluid passing to a fluid-solids contacting zone where the vapor and liquid are at different temperatures so that the resulting fluid mixture enters a subsequent contacting zone at a substantially uniform temperature.
These and other objectives, and the advantages of the present invention will become more readily apparent as the invention is more clearly set forth hereinafter.
In the present invention, the objectives are achieved by the use of a novel catalyst support and eflluent redistribution apparatus wherein there is incorporated a novel downcomer means which provides for the retention of a liquid inventory upon the distributing deck in order to provide a degree of mixing of the fluids thereon.
Broadly speaking, the catlayst support and fluid redistribution apparatus of the present invention comprises a substantially imperforate support plate which is provided with a plurality of fluid openings spaced over the face of the plate. Associated with each fluid opening there is a downcomer conduit means of novel construction which directs the efliuent fluids from the bed of particulated solids above to the bed of particulated solids below. Under each fluid opening there is provided a means for injecting quench hydrogen into the fluid stream which is discharged from each fluid opening.
In the present invention the downcomer means which is associated with each fluid opening within the face of the distributing deck comprises a perforated longitudinal conduit having perforations which provide for a greater open area with respect to the increasing distance from the face of the plate. That is to say, the perforation in the downcomer conduit will provide a smaller open area unit of height at the bottom of the downcomer conduit than will the perforations per unit height at the top of the conduit, with a gradual increase in the total area of perforation per unit of height progressing from the bottom to the top of the conduit.
In contrast to the prior art perforated catalyst support and fluid distribution apparatus which discharges the eifluent fluids in a rain of liquid to the bed below, the imperforated support plate of the present fluid distributing deck provides that efliuent liquids which channel down from the bed above will be retained for a time on the deck. Thus, the heavier viscous liquids will be given ample opportunity to remix with the lighter less viscous liquids on the distributing deck. As the level of liquid retained upon the deck increases, the mixed liquids flow through the downcomer perforations and down the downcomer with the vaporized hydrocarbon and hydrogen of the gaseous phase. Since the open area of the downcomer increases with liquid height, any increase in fluid throughput through the fluid-solids contacting chamber will be automatically compensated for, since as the liquid level rises on the distributor deck there is a greater open area of perforations in the downcomer available with increasing downcomer height which thus provides for an increased throughput of the liquid phase. Similarly, if the rate of throughput through the liquid-solids contacting chamber is decreased, a reservoir of liquid will still be maintained on the distributing deck, although at a lower liquid height, since the open area of the perforations decreases with decreasing height of the downcomer.
Since the effluent from the particulated bed above no longer rains through the entire cross-sectional area of the fluid-solids contacting chamber in the prior art manner, it is no longer necessary to provide that the quench hydrogen be discharged throughout the cross-sectional area of the chamber when utiliizng the fluid distributing deck of the present invention. Therefore, the hydrogen quench grid may be provided with discharge openings for the quench hydrogen which are located directly below each of the fluid openings of the distributor deck from which 4 the hot effluent is discharged from the bed above. Thus, there is provided improved opportunity for hot effluent and cold quench hydrogen to be more effectively intermixed before passing into the bed of particulated solids below.
Broadly speaking, therefore, the present invention may be characterized as a fluid distributing means which comprises in combination, a substantially imperforate plate containing a plurality of fluid openings spaced over the facial area of the plate; and a fluid conduit means encompassing and extending from each of the openings to a finite distance from the plate, and comprising a perforated longitudinal section having perforations providing greater open area with respect to increasing distance from the plate.
Additionally, the present invention may be characterized as a fluid-solids contacting chamber containing a plurality of fixed beds of particulated solids which comprises: a vertically elongated confined chamber having at least one upper fluid port and one lower fluid port to provide for a generally downward flow of fluid therethrough; a plurality of spaced horizontally positioned substantially imperforate support plate members holding and retaining particulated contact solids in a plurality of separate superimposed packed beds, and containing a plurality of fluid openings spaced over the horizontal area of each support plate member; a fluid downcomer means encompassing and extending above each of the fluid openings to a finite distance above the plate, and comprising a perforated longitudinal conduit having perforations providing greater open area with respect to increasing distance from the plate.
The present invention may be further characterized as the fluid-solids contacting chamber set forth in the paragraph immediately above wherein there is provided a fluid inlet means directly below each of the fluid openings.
These and other embodiments of the present invention may now be more clearly understood by referring to the accompanying figures.
DESCRIPTION OF THE FIGURES FIG. 1 is a partially cut-away elevational view indicating a typical hydrocracking reactor vessel wherein the inventive fluid distributing means is employed.
FIG. 2 indicates a partially cut-away elevational view of a downcomer means which comprises a tubular screen section which is formed by the helical winding and attachment of a continuous rod member around a plurality of spaced longitudinal bar members in a manner sufficient to provide a continuous helical slot opening of continuously increasing slot width.
FIG. 3 is a sectional plan view indicating the manner of construction of the downcomer means of FIG. 2 taken on the line 33 of FIG. 2.
FIGS. 4A through 4C indicate partial sectional views of the continuous rod members and longitudinal members of the downcomer means of FIGS. 2 and 3, showing various cross-sectional configurations for the rod members.
FIGS. 5 and 6 are partially cut-away elevational views of the downcomer conduit of the inventive fluid distributing deck wherein woven screen means are employed in order to obtain the desired perforations with increasing screen opening.
FIGS. 7 and 8 show a downcomer conduit means employing a solid conduit containing perforations of increasing dimension.
FIG. 9 comprises a graph which illustrates the effectiveness of fluid flow through the downcomer means of the inventive fluid distributing deck.
Referring now to FIG. 1, there is shown in partially cut-away elevation, a typical hydrocracking reactor ves sel containing four catalyst beds, and comprising a vertically elongated shell 1 containing an upper fluid port 2 for the introduction of feed material and a lower fluid port 3 for the discharge of reactor effluent. In addition,
there is provided a fluid port 4 below each of the first three catalyst beds A, B, and C, whereby quench hydrogen may be introduced into the hot effluent passing into beds B, C, and D from the catalyst bed above.
Each catalyst bed contains particulated or granulated hydrocracking catalyst material 5 which may be present in pilled, spherical, or extruded form. Each bed of catalyst is sup-ported upon an inert support material 6 which typically comprises ceramic balls, Raschig Rings, Berl Saddles, or any other inert support material which is well known to those skilled in the art. The top of each catalyst bed contains a layer 7 of the same support material. As is well known to those skilled in the art, this top layer of material provides a method of enhancing distribution of fluid into the bed of catalyst particles 5 below, while simultaneously weighing down the bed of catalyst particles so that it may not be dislodged by any fluctuations or sudden surges of pressure.
Each catalyst bed comprising catalyst particles 5, inert support layer 6, and inert support layer 7 is held and retained upon the inventive fluid distributing deck which comprises a substantially imperforate support plate 8 containing a plurality of fluid openings 9. Encompassing each fluid opening 9 and rising a finite distance above the upper face of support plate 8 there is provided a downcomer conduit 10 which is capped by an imperforate plate or other means 11. The downcomer conduit 10 is provided with perforations or other ingress openings which are sufiicient to allow the flow of fluid therethrough while retaining the particulated solids of the catalyst bed supported above.
Between each catalyst bed there is a void space 12 which is confined between the support plate 8 of the inventive distributing apparatus and the layer of inert support material 7 of the bed below. Into this open space there projects a hydrogen quench means 13. Typically, hydrogen quench means 13 will comprise a pipe grid or other conduit means having perforations 14 located directly below each fluid opening 9 in order to provide for a direct and intimate contact between the hot effluent mixture of liquid and vapor and the relatively cool quench hydrogen gas.
By providing the imperforate suppport plate 8 in combination with the perforated downcomers 10, the inventive fluid distributing deck provides assurance that liquid channelling down from the catalyst bed above will be retained on the deck in a liquid reservoir with a sufficient retention time to allow mixing of heavier viscous liquids, which normally channel along the walls of chamber 1, with the lighter relatively non-viscous liquids which tend to channel throughout the central regions of the catalyst bed. As the liquids collect upon the distributor deck 8 they achieve an equilibrium liquid level due to pressure drop through the openings of perforate downcomer 10. The liquid will flow through the lower perforations of the downcomer due to liquid head while the vaporized hydrocarbon and reactant hydrogen of the gaseous-vapor phase will pass through the perforations in downcomer 10 which are above the liquid level.
As the eflluent mixture of liquid and vapor passes through fluid opening 9, it meets the cold quench hydrogen which is discharged from perforations 14 in quench grid 13 directly below fluid opening 9. Thus, there is provided a means for direct contact of hot effluent and cold quench so that the resulting mixture will pass into the catalyst bed below at a substantially cooler and uniform temperature and in a substantially uniform mixture of heavy hydrocarbon liquids, light hydrocarbon liquids, vaporized hydrocarbon, and hydrogen gas. This relatively uniform mixture thus is discharged substantially uniformly into the cross-sectional area of the catalyst bed below.
As noted in the summary of the invention as disclosed hereinabove, downcomer 10 comprises a perforated or slotted longitudinal conduit having perforations or slots providing greater open area with respect to increasing dis tance from the imperforate support plate 8. Thus, as the charge rate to the catalytic reactor 1 is reduced, the liquid level retained upon imperforate support plate 8 will tend to fall. However, as the level falls the area of the perforations which are available for liquid flow decreases, thereby providing that a reservoir of liquid will always be retained upon support plate 8 so that the liquids which channel down from the catalyst bed above are afforded sufficient time for mixing before they pass into the catalyst bed below. Similarly, if the charge rate of materials to the reactor vessel of FIG. 1 is increased, the liquid reservoir retained upon imperforate support plate 8 will rise to a greater depth. As the liquid level rises, however, the open area provided by the perforations in the downcomers 10 increases therethough as the liquid level seeks a higher height.
FIG. 2 illustrates a particularly preferred perforated downcomer for use in the inventive fluid distributing deck. The downcomer means illustrated in FIG. 2 comprises a tubular screen means which is formed by the helical winding and attachment of a continuous rod member around a plurality of spaced longitudinal bar members in a manner suflicient to provide a continuous helical slot opening of continuously increased slot width. For screens of this general type, reference may be made to U.S. Pats. Nos. 2,046,456; 2,046,457; 2,046,458; and 3,101,526. As will also be noted in connection with the foregoing patents, a preferable form of screen makes use of triangular or wedge shaped rod members in the helical winding step so that self-cleaning types of cylindrical screens will be formed. This self-cleaning characteristic will be more fully discussed hereinafter.
Referring now to FIG. 2, there is shown in partially cut-away elevation, the imperforate support plate 8 of the inventive distributing deck and a typical fluid opening 9. The tubular screen means which constitutes the downcomer 10 of FIG. 1 is covered by an imperforate plate 11. The tubular screen means is formed by the continuous helical winding of the continuous rod member 22 around the plurality of spaced longitudinal bar members 21, which are spaced in a circular tubular configuration in this embodiment. The helical winding of rod member 22 produces a continuous slot 23 between adjacent coils of the helically wound rod member 22. As the continuous rod member 22 is helically wound around the longitudinal bar members, it is continually attached or fused thereto, preferably by electrical resistance so as to provide spot welding of the touching rod member 22 to the longitudinal bar members 21. The result is a structurally strong tied together cylindrical form screen section containing fluid openings 24 which are formed by the sectioning of the helical slot opening 23 by the longitudinal bar members 21.
FIG. 3 is a sectional plan view of the tubular screen means of FIG. 2 which is taken along line 33 in FIG. 2. FIG. 3 shows the imperforate support plate 8 and the fluid opening 9. There is also shown the longitudinal bar members 21 spaced in a circular configuration with continuous rod member 22 helically wound around and attached thereto. While the spacing of the longitudinal bar members 21 is preferably in a circular configuration, the tubular screen may also be formed by winding the con tinuous rod member and attaching it to bar members spaced in an elliptical or oval configuration.
Again, referring to FIG. 2, a close inspection thereof clearly indicates that the slot opening 23 is very narrow adjacent to imperforate support plate 8. However, the slot opening 23 increases with increasing height of the tubular screen means. This is accomplished by winding the continuous rod member 22 around the longitudinal bar members 21 in a continuous helix which has an increasingly wider spread between adjacent turns of the rod member. In this manner, there is provided a continuous helical slot opening 23 of continuously increasing slot width. The net result is that the fluid openings 24 which are confined between continuous rod member 22 and longitudinal 7 bar members 21 provide a greater open area for fluid flow with respect to increasing distance from the face of imperforate support plate 8.
Thus, those skilled in the art will readily ascertain that as the liquid level builds upon the fluid distributing deck 8 of the present invention, the fluid openings 24 which are exposed to liquid and available for fluid flow therethrough, provide an increasing open area for fluid flow as the height of liquid on imperforate support plate 8 increases. Thus, if the throughput in the reactor of FIG. 1 is increased, the liquid level will rise higher and be exposed to greater sized fluid openings 24 at the higher liquid level. Thus the increased flow rate is easily handled through the downcomers 10 without a large increase in pressure drop through the reactor vessel. As the throughput to the reactor of FIG. 1 is decreased, the liquid level falls and is exposed to fluid opening 24 of lesser area thus, providing that some liquid will always be retained in a liquid reservoir on imperforate support plate 8.
Referring now to FIGS. 4A through 4C, there is shown partial sectional views through the continuous rod member 22 showing various cross-sections of the rod member. Thus, in FIG. 4A, there is shown longitudinal bar member 21 and continuous rod member 22 having a circular crosssectional area. It will be noted that the cross-section of the slot has a converging configuration in the direction of fluid flow so that the slot becomes narrower at the diameters of adjacent turns or helical coils of rod member 22. Thus, any particulated solid such as catalyst fines may become lodged in slot 23 and blind a portion of the tubular screen downcomer.
It is, therefore, a preferred embodiment that the continuous rod member 22 have a triangular or wedge shaped cross-section as shown in FIGS. 4B and 4C. By having the wider portion of the wedge shaped cross-section of rod member 22 along the outside surface of the screen, the slot opening 23 is thereby provided with an increasing sized fluid passageway for flow of fluid, and once any entrained particulated matter such as catalyst fines passes into the the slot opening 23 it can more readily pass outward toward the inside of the screen. It will be seen in FIG. 4B and in FIG. 40 that the slot opening 23 also results in a triangular or wedge shaped cross-section for this fluid passageway, with the widest portion of the wedge shaped slot opening toward the inside surface of the screen. Thus, by employing the triangular or wedge shaped cross-sectional configuration for the rod member 22, the tubular screen of FIG. 2 is a self-cleaning type screen since retention of solids and blinding of the screen is mini mized.
FIG. 4B specifically illustrates the cross-sectional area of rod member 22 having a solid trapezoidal shape. FIG. 40 illustrates a channel type cross-section wherein the open end of the channel is narrower than the flange end of the channel, thereby providing the desired wedged shape. This channel-type of continuous rod member is more particularly discussed and illustrated in US. Pat. 3,101,526 previously cited.
FIGS. 5 and 6 disclose partially cut-away elevational views of the present invention wherein the downcomer means of the inventive distributor deck comprises a woven screen type of wall construction. FIG. 5 illustrates a woven screen wherein the mesh of the screen is tightest at the bottom of the downcomer and the mesh of the screen is wider with increasing height of the downcomer. FIG. 6 illustrates the downcomer wherein there is provided a series of screen sections of various sized mesh.
Referring now to FIG. 5 there is shown the imperforate support plate 8 of the distributor deck and a fluid opening 9. Encompassing fluid opening 9 and rising to a finite height above, there is a downcomer comprising a woven screen 25. The top of the downcomer conduit is capped with an imperforate plate 11. As may be seen in FIG. 5, the wire mesh of the woven screen has 8 a tighter weave at the bottom of the downcomer and an increasing looseness of the weave with increasing distance from the imperforate support plate 8. Thus, the woven screen 25 provides a greater open area to fluid flow with increasing downcomer height since the screen openings have increased dimensions with respect to increasing distance from support plate 8.
Referring now to FIG. 6, there is again shown imperforate support plate 8 encompassing a fluid opening 9. Rising a finite distance above fluid opening 9 and encompassing the opening is a downcomer conduit comprising a number of screen sections. Each section has a different size mesh of woven screen. For purposes of illustration, there is shown a first section of narrowest screen opening 26, a second section of a larger screen opening 27, a third section of further increased screen opening 28, a fourth section of still further increased screen opening 29, and a fifth section of Widest screen opening 30. The five screen sections are held together by any suitable means of fastening such as flange type stiffener rings 31 to which the woven screens may be suitably attached as by welding. The top of the downcomer comprising the five screen sections is capped by an imperforate plate 11. While the downcomer of FIG. 6 has been shown with the flange type stiffener rings, those skilled in the art will perceive that the sections of increasing wire mesh screen could be supported on longitudinal bar members such as members 21 illustrated in FIG. 2, and that the individual screen sections could be welded thereto and to one another without the use of stiffener rings 31.
Referring now to FIGS. 7 and 8, there is shown in elevation a still further embodiment of the present invention wherein the fluid distributing deck is provided with a downcomer means comprising a conduit device containing perforations.
In FIG. 7, there is shown imperforate support plate 8 and a fluid opening 9. Encompassing fluid opening 9 and rising a finite distance above plate 8 is a tubular conduit such as a pipe of cylindrical shape or a tubular device having a non-circular cross-section. This downcomer conduit means 33 is perforated with holes 34 of varying diameters. Thus, the holes nearest support plate 8 are smallest in diameter and the holes increase in diameter as the distance from plate 8 increases. The downcomer conduit 33 is capped with the imperforate plate 11 as in the previous embodiment.
FIG. 8 illustrates a device similar to FIG. 7 comprising imperforate support plate 8, fluid opening 9, conduit means 33, and the cap, imperforate plate 11. However, the downcomer shown in FIG. 8 contains perforations wherein the holes are all of the same diameter. However, as the distance from imperforate support plate 8 increases, the number of holes increases thereby providing a greater open area for fluid flow with respect to increasing distance from the plate.
FIG. 9 illustrates test results which show the effectiveness of the inventive fluid distributing deck for retaining an inventory of liquid at varying flow rates.
Tests were run utilizing four downcomers which were fabricated by winding a continuous rod member over longitudinal bar members to produce a screen of the type shown in FIG. 2. The continuous rod member had a wedge shaped cross-sectional area as illustrated in FIG. 48 with the wide part of the wedge on the outer screen surface having a width of of an inch. All four screens were two inches in outside diameter and provided a downcomer height of eight inches. However, the first three screens had constant helical slot widths of 0.003 inch, 0.010 inch, and 0.030 inch. The fourth screen had a continuously expanding helical slot width of the type which has been disclosed with particularity in reference to FIG. 2. This fourth screen had a slot opening of 0.003 inch at the bottom of the tubular screen downcomer and the continuously expanding helical slot opening had a width of 0.030 inch at the top of the tubular screen down comer.
Capacity tests for the four downcomers were individually made using water in ambient air and the results are shown in FIG. 9 wherein there is plotted height of liquid versus rate of flow. While the tests were not in an environment of hydrocarbon and hydrogen gas at elevated temperature and pressure, the results are qualitatively indicative of the effectiveness of operation of the inventive distributing deck in any environment.
Referring now to FIG. 9, it is seen that inches of liquid head is plotted against gallons per minute (g.p.m.) of liquid flow. Note that at the low flow rates, the downcomers having 0.003 inch and 0.010 inch slot openings retain a high liquid level on the deck. Thus, in operation in a hydrocracking reactor of the type shown in FIG. 1 liquids channelling down from the catalyst beds above would have a relatively high residence time and would be afforded ample opportunity to intermix before passing down into the catalyst bed below via the downcomer. However, it will be seen that for these small slot openings, the total throughput for these downcomer screens is limited. Thus, at the total emersion of the downcomer at eight inches of liquid head the slotted screen having the 0.003 inch helical slot can only pass about 25 g.p.m. while the downcomer having the 0.010 inch helical slot can only pass about 40 g.p.m. It will be seen that the downcomer having the helical slot of 0.030 inch can readily pass a high rate of liquid flow. However, at a low flow rate, the downcomer will only retain a small liquid head on the fluid distributing deck, thus providing a low residence time and minimizing etfective mixing of fluids which may channel down from the catalyst bed above. The advantage of the 0.030 inch slot opening downcomer is that it aflords high liquid throughput without covering the total downcomer height with liquid, so that it still contains slot openings above the liquid level for the passage of vapor flow.
It is thus seen that the fourth downcomer having the continuously expanding helical slot opening combines the advantages and eliminates the disadvantages of the first three downcomer devices tested. By referring to FIG. 9, it will be seen that at low flow rates the downcomer with the expanding slot opening is capable of retaining a high liquid level on the distributing deck, thus affording a high residence time and ample opportunity for mixing of the liquids which channel down from the catalyst bed above. As the throughput increases, however, since the helical slot is expanding in a continuous manner to expose a greater fluid opening through the tubular screen downcomer, the rate of flow through the downcomer increases greatly while the liquid level is increased only moderately. Thus, the downcomer with the continuously expanding helical slot opening is capable of passing a high rate of liquid flow while still retaining a sufficient amount of screen opening exposed to the vapor phase for vapor flow therethrough.
PREFERRED EMBODIMENTS From the foregoing description, it may now be summarized that a preferred embodiment of the present invention may be characterized as a fluid distributing means which comprises in combination, a substantially imperforate plate containing a plurality of fluid openings spaced over the facial area of the plate; and a fluid downcomer means encompassing and extending above each of the openings to a finite distance above the plate, and comprising a perforated longitudinal section containing screen means having screen openings of increasing dimension with respect to increasing distance from the plate.
From the foregoing description, it will also be readily apparent that a particularly preferred embodiment of this invention comprises the fluid distributing means wherein the downcomer comprises a tubular screen means which is formed by the helical winding and attachment of a continuous rod member around a plurality of spaced longitudinal bar members in a manner sufficient to provide a continuous helical slot opening of continuously increasing slot width.
Furthermore, from the disclosure hereinabove, it will be readily apparent that the particularly preferred embodiment of the present invention comprises application of the inventive apparatus within a fluid-solids contacting chamber comprising a catalytic reaction zone for the processing of hydrocarbon constituents in the presence of hydrogen. Additionally, as noted hereinabove, specific application of the present invention is in hydrogenation, hydrotreating, hydrocracking, and hydrodealkylation reaction zones wherein hydrogen stream is utilized for the thermal quench of reactant hydrocarbon between catalyst beds. In such applications, the inventive fluid distributing means will comprise, in combination, fluid inlet means didirectly below each fluid opening in the face of the imperforate plate.
Those skilled in the art will perceive that the design of the distributor deck and of those elements comprising the deck will vary with any specific application wherein it is used.
For example, the height of each downcomer conduit will be preferaby four or more inches, and typically will be from eight to twelve inches. The diameter of the fluid opening 9 and associated downcomer 10 will be selected so as to minimize the pressure drop of fluids passing through the opening, Typically, the fluid opening and associated downcomer will have diameters in the range of from one to eight inches, although a range of two to four inches is preferred. The screen openings or other perforations in the perforated downcomer means will vary in number and increase in size in a manner sufiicient to minimize the pressure drop of the fluids flowing therethrough while retaining a liquid level on plate 8 which is sufiicient for liquid mixing, and also allowing vapor to pass through the openings or perforations in the downcomer which are above the liquid level.
Additionally, the number of fluid openings 9 and associated downcomers 10 on the face of the deck may vary from one to one hundred or more, depending upon pressure drop considerations. The number will, of course, depend upon the total throughput of fluids which must be passed through the distributing deck and the diameter of the chamber containing the deck. The number must also be selected so that the eflluent passing through the deck is uniformly distributed to the bed of solids located below.
It will be apparent to those skilled in the art that the spacing of the fluid openings 9 and associated downcomers 10 over the facial area of imperforate support plate 8 will vary with the specific application and with the number of fluid openings incorporated in the inventive fluid distribution deck. Thus, in a very small fluid-solids contacting chamber wherein only a single downcomer is necessary, the fluid opening will be positioned in the center of the circular plate. Where four openings are required, they will typically be spaced equidistant away from the center on radii at from each other in order to fully distribute the fluid passing therethrough in a substantially uniform manner over the circular cross-section of the particulated solids bed below. Where seven openings are required, they may be positioned with one opening in the center of the circular support plate, and the other six openings spaced away equidistant from the center on radii at 60 from each other. Where a great many fluid openings are required in a large chamber, for example ten or more, the fluid openings may be spaced over the face of the imperforate support plate in concentric circles, in a square pitch distribution, in a triangular pitch distribution, or in any other pattern sufficient to provide a substantially uniform distribution of fluid over the cross-section of the bed below.
Among the many factors which must be considered in sizing the elements of the inventive apparatus are the flow rates of liquid and vapor phases and the flowing density of each phase. Additionally, the molecular weight of the flowing fluids must be considered as well as the temperature and pressure of the environment wherein the inventive fluid distributing means is utilized.
The manner of operation of the inventive fluid distributing apparatus and its design are readily ascertainable to those skilled in the art from the teachings that have been presented hereinabove, and the advantages to be accrued from the inventive device are equally apparent.
While the embodiments disclosed hereinabove have been directed to the catalytic reaction of hydrocarbons in a hydrogen atmosphere, the invention is not so limited. Those skilled in the art will perceive that the method of redistributing the fluids in a fluid-solids contacting zone and the apparatus therefor have equal application in any fluid-solids contacting zone such as in adsorption zones, Additionally, the apparatus is not limited to the support of fixed beds of particulated contact solids, but it can also find application as the feed distribution apparatus at the top of the first bed contained within the contacting chamber.
The method of fluid redistribution and the apparatus also are not limited to the specific fluids discussed hereinabove. Thus, the inventive fluid distribution apparatus will function with equal effectiveness in holding an interfacial level between two liquid phases in a liquid-liquid contacting system such as in an extractioin zone. Thus, if downcomer 10 were oriented to rise to a height above support plate 8 as shown in the figures and discusssed hereinabove, the height of heavy liquid phase accumulated below a light liquid phase upon plate 8 would be effected by liquid flow rates in the manner which has been described hereinabove in relation to the accumulation of hydrocarbon liquid below a hydrogen-rich vapor phase. If the apparatus were inverted, however, so that downcomer 10 extended to a distance below support plate 8, then the increasing screen openings of increasing dimension with respect to increasing distance from the plate, would function to adjust the height of light liquid phase confined below plate 8 and above the heavy liquid phase by functioning as an upcomer for the light liquid phase. The utility and method of operation for the inventive apparatus in a liquid-liquid environment are readily ascertainable to those skilled in the art.
Additionally, the imperforate means 11 which caps downcomer 10 in the embodiments shown in the figures could be a perforate means, provided that the perforations are sufficient to retain the particulated solids of the bed above. Also the perforations disclosed in FIGS. 7 and 8 need not be circular holes as shown, but any type of slot or oblong perforation may be employed within the scope of the present invention. It must further be pointed out that the downcomers have been disclosed as being cylindrical, but that the downcomers may have any cross-sectional configuration. These and other modifications of the inventive apparatus will be readily ascertainable to those skilled in the art without detracting from the scope of the present invention.
The invention claimed:
1. A fluid distributing means which comprises in combination: a substantially imperforate plate containing a plurality of fluid openings spaced over the area of said plate, a fluid conduit means encompassing and extending from each of said openings to a finite distance from the face of said plate, said conduit means comprising a tubular screen means which is formed by the helical winding and attachment of a continuous rod member 12 around a plurality of spaced longitudinal bar members in a manner suflicient to provide a continuous helical slot opening of continuously increasing slot width with respect to increasing distance from said plate.
2. The fluid distributing means of claim 1 wherein said continuous rod member is of wedge shaped cross-section with the wider portion thereof along the outer screen surface resulting in a helical slot opening having a wedge shaped cross-section with the wider portion thereof along the inner screen surface.
3. The fluid distributing means of claim 2 wherein said continuous rod member has a channel shaped crosssection.
4. A fluid-solids contacting chamber containing a plurality of fixed beds of particulated solids which comprises in combination:
(a) a vertically elongated confined chamber having at least one upper fluid port and one lower fluid port to provide for a generally downward flow of fluid therethrough;
(b) a plurality of spaced, horizontally positioned, substantially imperforate support plate members containing a plurality of fluid openings spaced over the horizontal area of each support plate member, said plate members holding and retaining particulated contact solids in a plurality of separate superimposed packed beds;
(c) a fluid downcomer means encompassing and extending above each of said openings to a finite distance above said plate, each said downcomer means comprising a tubular screen means which is formed by the helical winding and attachment of a continuous rod member around a plurality of spaced longitudinal bar members in a manner sufficient to provide a continuous helical slot opening of continuously increasing slot width with respect to increasing distance from said plate.
5. The chamber of claim 4 wherein fluid inlet means are located directly below each of said fluid openings.
6. The chamber of claim 4 wherein said continuous rod member is of wedge shaped cross-section with the wider portion thereof along the outer screen surface resulting in a helical slot opening having a wedge shaped cross-section with the wider portion thereof along the inner screen surface.
7. The chamber of claim 6 wherein said continuous rod member has a channel shaped cross-section.
References Cited UNITED STATES PATENTS 2,006,986 7/1935 De Florez 261-114 2,072,382 3/1937 Robinson 261-97UX 2,607,662 8/1952 Huff 23284X 2,632,638 3/1953 Turner 261-114 2,729,548 1/1956 Forkel 23-284 2,863,931 12/1958 Summers 23288X 2,871,003 1/1959 Galbreath 261-114 2,981,677 4/1961 Bowles 208-146 3,235,344 2/1966 Dreyer et al 23288X 3,378,349 4/1968 Shirk 23-288 3,509,043 4/1970 McMaster et al. 23288X 3,524,731 8/1970 Effron et al. 23-288 MORRIS O. WOLK, Primary Examiner o B. S. RICHMAN, Assistant Examiner U.S. Cl. X.R.
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|U.S. Classification||422/605, 208/146, 261/97, 208/108, 261/DIG.720, 261/114.1, 422/607, 422/638, 422/647|
|International Classification||C10G47/00, B01J8/04, B01J8/02, C10G49/00|
|Cooperative Classification||B01J8/0278, Y10S261/72, C10G47/00, B01J8/0492, B01J8/0453, C10G49/002|
|European Classification||B01J8/04D2D, C10G47/00, C10G49/00B, B01J8/02F, B01J8/04F|