CA1101195A - Moving bed radial flow solids-fluid contacting apparatus - Google Patents
Moving bed radial flow solids-fluid contacting apparatusInfo
- Publication number
- CA1101195A CA1101195A CA307,313A CA307313A CA1101195A CA 1101195 A CA1101195 A CA 1101195A CA 307313 A CA307313 A CA 307313A CA 1101195 A CA1101195 A CA 1101195A
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- Canada
- Prior art keywords
- particle
- screen
- volume
- scoop
- catalyst
- Prior art date
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Abstract
* * ABSTRACT * *
An improved radial flow moving bed reactor, or other type of fluid-solid contacting vessel, in which stagnant catalyst volumes are reduced. The improvement results from the placement of a plurality of catalyst collection scoops which are attached to and extend above catalyst withdrawal conduits.
An improved radial flow moving bed reactor, or other type of fluid-solid contacting vessel, in which stagnant catalyst volumes are reduced. The improvement results from the placement of a plurality of catalyst collection scoops which are attached to and extend above catalyst withdrawal conduits.
Description
MOVING BED RADIAL FLOW SOLIDS~
FL~ID CONTACTING APPARATUS
* * SPECIFICATION * *
Radial flow fluid-solids contacting apparatus may be used in a wide variety of ~ndustrial processes. Examples are the radlal flow reactors used in a variety of hydrocarbon con-version processes~ These processes include the isomerization of normal paraffins, the dehydrogenation of normal paraffins ' and the reforming of naphtha boiling range petroleum fractions.
~j In a radial flow reactor the various reactants flow along ra-¦ dials extending from the major central axis of the reactor to j its periphery. The subject apparatus is directed to those reactors in which the reactant flow is inward. That is, the reactants flow inward from the annular reactant distribution volume to a cylindrical reactant collection volume. This central reactant collection volume is enclosed by the inner ~¦ catalyst retention screen, which is commonly referred to as the centerpipe of the reactor. Radial flow may also be used .
in other contacting apparatus such as adsorbent chambers and treaters. As a corollary to its use as a moving bed reactor the subject apparatus may be used as a moving bed regenerator for the decarboniæation, reduction or halogenation of used `~ 20 catalyst or adsorbents.
:~
The term "moving bed" as it is used herein is intended to refer to a particulate-containing system in which the particles rest upon one another in a dense bed and the inventory of the bed-is grad-:~
., ~.~
, 1, -2- ~
.
- . - - - ~ . .
.liU~19~
ually replaced -through the removal of used particles at the bottom and t~e addition of fresh or regenerated particles at the top. The subject invention is therefore not directed to ebullated or fluidized bed contacting apparatus. The apparatus may be used with either vapor or liquid phase fluids.
It is believed that heretofore the particles have been withdrawn from annular beds through a number of centrally located openings at the bottom of the vessel. Centrally located is used in this context to indicate the particle ox catalyst withdrawal conduits are located approximately midway between the two particle retention screens or within the middle 50% of the distance between the screens. The outlet conduit was often covered by a cap or inverted cone such as shown in United States Patents 3,706,536; 3,785,963 and 3,854,887. The reason for utilizing these caps and the central placement of the withdrawal conduits was to promote a uniform withdrawal of particles from all parts of the bed. That is, it was hoped this prior art structure would effect with withdrawal of the particles adjacent both screens at equal rates.
Experience has indicated that these prior art systems do not achieve uniform catalyst withdrawal. Rather, they may leave a sizable amount of catalyst or particles in place within the apparatus. This stagnant material eventually becomes ineffective in its specific function and exerts a detrimental influence on the performance of the equipment. More specifical-ly, it has been discovered that stagnant particle areas may occur in the lower portion of the vessel adjacent to the inner retention screen, especially at higher vapor or liquid velocities i .
through the particle bed. Undoubtedly, this is caused at least in part by the inward vapor flow.
A second undesirable effect which has been observed using the prior art particle withdrawal systems is the accumu-lation of particle fines caused by the normal movement-induced attrition of the particulate material in the zone of stagnant particles. These fines are moved toward the stagnant zone by the inward vapor flow ~ut are not removed as would occur if this stagnant zone did not exist. Eventually this seals a number of small vapor passageways and causes a higher pressure drop across the bottom of the particle bed than at the top.
This in turn distorts the desired equal flow rate through all parts of the annular particle bed. In a reactor this results in the actual space velocity being higher at the top of the reactor than at the bottom.
It is an objective of this invention to provide a moving bed radial flow solids-fluid contact apparatus. It is a further objective to provide a moving bed radial flow ¦ reactor having a minimum of stagnant catalyst and which lessens the accumulation of stagnant catalyst against the surface of the centerpipe during inward vapor flow.
In a broad ernbodirnent the invention provides a radial flow moving bed contact apparatus which comprises:
(a) a vertically oriented vessel having an internal volume located within a cylindrical side wall having an inner surface, the outer vessel being divided into upper and lower sections;
(b) a first vertically oriènted particle retaining ,~
` - 4 -.. .
,, , - : , ' .
11C~119S
screen located within the outer vessel a distance radially inward from the inner surface of the outer vessel and defin-ing a fluid distri~ution volume between the first particle retaining screen and the outer vessel;
(c) a second vertically oriented particle retaining screen located within the first particle retaining screen a distance radially inward from the first particle retaining screen and defining an annular particle retention volume having an upper and a lower end and located between the first and the second particle retaininy screens and also defining a cylin-drical fluid collection volume located within the second particle retaining screen;
(d) a plurality of particle inlet conduits located in the upper section of the outer vessel and communicating with the upper end of the annular particle retention volume;
(e) a fluid inlet means communicating with the fluid distribution volume;
(f) a fluid outlet means communicating with the cylindrical fluid collection volume; and, (g) a particle withdrawal means located between the first and the second particle retention screens at the lower end of the annular particle retention volume, the particle withdrawal means comprising:
(i) a plurality of tubular particle withdrawal conduits distributed in a circular pattern encircling the second particle retent.ion screen, each particle ¦ ~ withdrawal conduit having an unsealed upper end which - communicates with the annular particle retention volume;
and, ..
J
(ii) a plurality of particle collection scoops, each scoop having an open upper first end which faces the second particle retention screen and a lower second end which is attached to the upper end of a particle withdrawal conduit, ~ith one particle collection scoop being positioned over each of the particle withdrawal conduits, and with each particle collection scoop having a greater cross~
sectional area at the upper first end than at the lower second end and reposing at an angle of from about 5-60 above horizontal.
In the drawings, Figure 1 shows a moving bed radial flow reactor while Figures 2 to S, inclusive, illustrate - different views of a catalyst collection scoop used for withdrawing used catalyst from the reactor.
Referring to Figure 1, there is shown a moving bed radial flow reactor formed in part by the outer vessel 1 and which conforms to a preferred embodiment of the invention.
This vessel is a vertically oriented cylinder enclosed by upper end section 36 and lower end section or cap 37. A
first or outer catalyst retention screen 2 is also cylin-drical in shape, as is the inne~ or sec~nd cata~yst ~ete~tio~ sc~e~ 3, ~Dth ~ thes~ ~cIeens are c~n~ ic about the central vertical axis of the reactor. The outer surface of the ~irst screen and the cylindrical inner surface of the outer vessel define an annular fluid or reactant distribution volume 38, into which the reactants flow from inlet conduit 6. An annular shaped bed of catalyst 4 is retained ~etween the two screens. This catalyst bed is intermittently replenished with fresh catalyst which falls through catalyst inlet conduits 5 and 5'. For simplicity only two catalyst inlet conduits are shown; normally at least about eight are used. The top of the porous portion of each screen is preferably .: ' ' ' . ' llC~l~9S
below the upper inner surface of the vessel, and the top of the catalyst bed is sealed off by an imperforate disk-shaped plate 10.
The reactants pass inward through the catalyst bed and enter the cylindrical fluid or reactant collection volume. The reactants and reaction products are then removed from the reactor through the reactant outlet conduit 7. The top of the reactant collection volume is sealed with a circular cover plate 9. The used catalyst is withdrawn from the reactor through a plurality of catalyst collec~ion scoops represented by scoops 8 and 8'. Each scoop has an open upper end which faces the inner catalyst retention screen. The catalyst enters through this upper end and is therefore withdrawn in an annular pattern much closer to the inner screen than the outer screen. Each scoop has a lower end connected to a catalyst withdrawal conduit such as 39 and 39'. These conduits encircle the inner screen and pass through the lower end section 37. The catalyst collection scoops and the upper portion of the catalyst withdrawal conduits are filled with catalyst during operation of the reactor. This description of the preferred applica-~ion of the invention is not intended to limit the apparatus to use as a reactor.
In FIGURE 2, a slde view of a catalyst collection scoop 13 is shown in greater detail. The lower end of the scoop is attached to a catalyst withdrawal conduit 12. This vertical conduit extends through the horizontal outer wall 11 of the reactor to a series of valves or a catalyst collection hopper as the case may be. Alternatively, the ; 30 conduit may directly feed catalyst to another reactor in a "stacked" reactor ~,, ' design. The scoop is positioned such that opening 41 at the upper end of the scoop faces the inner catalyst retention screen 4~ and is adjacent this screen. The opening theref~re Eaces radially inward. The outer catalyst retention screen 14 is closer to the lower end of the scoop. For simplicity, only a few of the large number of perforations in the screen are illustrated. As shown, the scoop is preferably formed by parallel, planar upper and lower imperforate panels. These panels have an angle "a" above horizontal as measured from the lower end of the scoop. The sides of the scoop are enclosed by opposing planar side walls.
In FIGURE ', the view seen when looking downward at a catalyst collection scoop 13 is presented. This scoop is similar to that shown in FIGURE 2. The lower end of the scoop covers the open upper end of the catalyst withdrawal conduit 12. The upper panel of the scoop has an upper edge 17 which is spaced further from the inner catalyst retention screen than the upper edge 18 of the lower panel. The triangular shaped panels result in the scoop having a larger cross-sectional area at its upper end than at its lower end.
FIGURE 4 illustrates the preferred arcuate shape of the panel edges forming the upper end of a catalyst collection scoop 19. Again, the lower end of the scoop is positioned to direct catalyst into the withdrawal conduit 20. The upper edges of the panels are once again horizontally staggered to collect cataIyst, with upper edge 21 being positioned further from the inner catalyst retention screen 35 than the lower panel edge 23. In the preferred embodiment the upper edge of the ,, - ~
l9S
upper p~nel 22 and of the lower panel are arcuate and have a radius o~ curvature which is correlated to that of the inner screen such thaL the distance measured radially between the inner screen and either edge is uniform at all points along each edge as shown. This view also shows the use of a scalloped outer catalyst screen 44 adjacent the cylindrical outer wall 43 of the reactor.
In FIGURE 5 the view seen looking toward the upper open end of a catalyst collection scoop 13 is presented. This scoop is similar to those shown in FIGURES 2 and 3 rather than the arcuate edged SCOGp, ~f FIGURE 4. The lowex end of the scoop is attached to a catalyst withdrawal conduit 12. The edge 17 of the upper panel is connected to the edge 18 of the l~wer panel by opposing, vertical, imperforate side walls 27 and 27'.
The open upper end of the SGOOp iS therefore circumscribed by elements 17, 18, 27 and 27'.
The particulate matter used in the apparatus is pre-ferably a hydrocarbon conversion catalyst, but it may be an adsorbent including activated carbon, a zeolite or an alumina as may be used to treat gas streams for the removal of water, sulfur compounds or halogen-containing chemicals. The particulate material may also be a solid acceptor used for the removal of sulfur oxides from a flue gas stream as disclosed in United States Patents 3,776,854 and 3,832,445. Preferablyl the par-ticulate matter is spherical and has a diameter within the range - of 0.15 to 1.25 cm. ~he words "catalyst" and "particle" are used interchangeably in many instances herein when referring ~o -~ various elements of-the apparatus. ^The use of either word is llU~l~S
not intended to limit the ~pplication or function of these elements in a manner which unduly limits the invention. Catalyst used in the apparatus will preferably comprise an inorganic oxide support, such as alumina or silica, with a catalytically effective amount of a metal or metal oxide. The metal may be one or more chosen from the following group: nickel, cohalt, iron, platinum, tin, palladium, manganese or magnesium.
The outer vessel is preferably made of a suitable metal such as carbon or stainless steel, but may be formed from other materials including fi~er reinforcel plastics if the conditions of temperature, pressure, etc., allow their use.
The two particle or catalyst retention screens are pre-ferably fabricated using wedge-shape wire having a cross-section which decreases in the direction that is away from the particle side of the screen. This results in a self cleaning surface such that as any particles, or pieces thereof, pass through the openings between the screens they may fall free of the screen on the other side. Preferably, the wedge-shaped wires are aligned vertically to minimize catalyst attrition as the , catalyst moves downward against the screen. The outer particle ¦ retention screen may be either cylindrical to provide an annular fluid distribution volume or it may be a scalloped screen as shown in FIGURE 4.
¦ 25 The contact apparatus will be provided with a plurality of particle inlet -conduits which pass through the upper section of the~outer vessel and communicate with the top of the annular j particle retention volume. About 6-10 inlet conduits are :,. :: . ' . . .
S
normally adequate to give proper distribution of the particu-late material. The `retention screens preferably have an imper-forate section at the top to provide a seal which prevents any portion of the fluid stream from passing over the particle bed through possible void spaces. The screens may be capped as shown in FIGURE 1 or they ma~ be extended upward to the inner surface of the vessel. The inlet conduits will normally be connected to a valve for controlling the rate of particle ad-dition or directly to a hopper vessel used to distribute the particles Alternatively the inlet conduits may be connected to the outlet conduits of vessels (reactors) located a~ove as in a stacked design.
In a preferred embodiment the appara~us comprises a -plurality of particle collection scoops which are arranged around the bottom of the centerpipe in a circular pattern, such that the tips of adjacent scoops come together or in close proxi-mity (within 15 cm) of each other to form an annular catalyst collection area which is uniformly disposed about the center-pipe. The width of this zone, which is the same as the distance between the centerpipe and the upper edge of the respective scoop preferably should be less than 30 centimeters. Preferably the distance for the upper edge is less than 10 centimeters and is less than 5 centimeters for the lower edge when arcuate scoops are used. An average distance is specified since the Z5 straight ed~e scoops, such as shown in FIGURE 3, will result in a varyiny distance. Preferably, the uppèr and lower edge of the scoop panels are arcuate and conform to the curvature of thc centerpipe to present a uniform distance between the s~oop , il~ll9S
and the centerpipe. Other edge shapes not shown may also be employed if desired.
The individual scoops are hollowform. That is, they are not solid but have a void interior space which conforms to their outer shape. Preferably, the upper and lower panels and side walls which enclose the scoops are imperforate. These elements of the scoops may be relatively porous, however, as to provide for drainage or vapor circulation. ~his may be desired in some cases to prevent coking or the entrapment of liquids in the particle withdrawal conduits. The cross-sectional area of the interior o~ each scoop is larger at the upper end which face~
the centerpipe than at the lower end which is attached to the particle withdrawal outlet. The scoops are in this regard funnel-li~e particle collectors. To aid in the collection of the particles the lower edge of the scoop ~the upper horizontal edge of the lower panel) is located closer to the centerpipe than the upper edge as illustrated in FIGURES 2 and 3.
The particle collection scoops, or catalyst collection scoops if the apparatus is used as a reactor, are inclined at an angle of from about 5-60 above horizontal. This is measured as the angle"a" of FIGURE 2. A preferred range for this angle is from 15-45, with 30 being particularly preferred.
It is preferred that the upper and lower panels of the scoop are parallel and therefore have the same angle. This is not a necessity and the scoops may taper vertically also. The scoops - may be surr~unded by the same particulate material which is moved through the apparatus, or inert spacers such as ceramic - ~ spheres may be placed in the bottom of the vessel. Several t , 11C~1195 suppor~s may be placed around and under the scoops to pre- .
vent their movemen-t and distortion during the operation of the apparatus.
.
'.' ' , ' " . ' ', - ' - ~ ~ ~ '
FL~ID CONTACTING APPARATUS
* * SPECIFICATION * *
Radial flow fluid-solids contacting apparatus may be used in a wide variety of ~ndustrial processes. Examples are the radlal flow reactors used in a variety of hydrocarbon con-version processes~ These processes include the isomerization of normal paraffins, the dehydrogenation of normal paraffins ' and the reforming of naphtha boiling range petroleum fractions.
~j In a radial flow reactor the various reactants flow along ra-¦ dials extending from the major central axis of the reactor to j its periphery. The subject apparatus is directed to those reactors in which the reactant flow is inward. That is, the reactants flow inward from the annular reactant distribution volume to a cylindrical reactant collection volume. This central reactant collection volume is enclosed by the inner ~¦ catalyst retention screen, which is commonly referred to as the centerpipe of the reactor. Radial flow may also be used .
in other contacting apparatus such as adsorbent chambers and treaters. As a corollary to its use as a moving bed reactor the subject apparatus may be used as a moving bed regenerator for the decarboniæation, reduction or halogenation of used `~ 20 catalyst or adsorbents.
:~
The term "moving bed" as it is used herein is intended to refer to a particulate-containing system in which the particles rest upon one another in a dense bed and the inventory of the bed-is grad-:~
., ~.~
, 1, -2- ~
.
- . - - - ~ . .
.liU~19~
ually replaced -through the removal of used particles at the bottom and t~e addition of fresh or regenerated particles at the top. The subject invention is therefore not directed to ebullated or fluidized bed contacting apparatus. The apparatus may be used with either vapor or liquid phase fluids.
It is believed that heretofore the particles have been withdrawn from annular beds through a number of centrally located openings at the bottom of the vessel. Centrally located is used in this context to indicate the particle ox catalyst withdrawal conduits are located approximately midway between the two particle retention screens or within the middle 50% of the distance between the screens. The outlet conduit was often covered by a cap or inverted cone such as shown in United States Patents 3,706,536; 3,785,963 and 3,854,887. The reason for utilizing these caps and the central placement of the withdrawal conduits was to promote a uniform withdrawal of particles from all parts of the bed. That is, it was hoped this prior art structure would effect with withdrawal of the particles adjacent both screens at equal rates.
Experience has indicated that these prior art systems do not achieve uniform catalyst withdrawal. Rather, they may leave a sizable amount of catalyst or particles in place within the apparatus. This stagnant material eventually becomes ineffective in its specific function and exerts a detrimental influence on the performance of the equipment. More specifical-ly, it has been discovered that stagnant particle areas may occur in the lower portion of the vessel adjacent to the inner retention screen, especially at higher vapor or liquid velocities i .
through the particle bed. Undoubtedly, this is caused at least in part by the inward vapor flow.
A second undesirable effect which has been observed using the prior art particle withdrawal systems is the accumu-lation of particle fines caused by the normal movement-induced attrition of the particulate material in the zone of stagnant particles. These fines are moved toward the stagnant zone by the inward vapor flow ~ut are not removed as would occur if this stagnant zone did not exist. Eventually this seals a number of small vapor passageways and causes a higher pressure drop across the bottom of the particle bed than at the top.
This in turn distorts the desired equal flow rate through all parts of the annular particle bed. In a reactor this results in the actual space velocity being higher at the top of the reactor than at the bottom.
It is an objective of this invention to provide a moving bed radial flow solids-fluid contact apparatus. It is a further objective to provide a moving bed radial flow ¦ reactor having a minimum of stagnant catalyst and which lessens the accumulation of stagnant catalyst against the surface of the centerpipe during inward vapor flow.
In a broad ernbodirnent the invention provides a radial flow moving bed contact apparatus which comprises:
(a) a vertically oriented vessel having an internal volume located within a cylindrical side wall having an inner surface, the outer vessel being divided into upper and lower sections;
(b) a first vertically oriènted particle retaining ,~
` - 4 -.. .
,, , - : , ' .
11C~119S
screen located within the outer vessel a distance radially inward from the inner surface of the outer vessel and defin-ing a fluid distri~ution volume between the first particle retaining screen and the outer vessel;
(c) a second vertically oriented particle retaining screen located within the first particle retaining screen a distance radially inward from the first particle retaining screen and defining an annular particle retention volume having an upper and a lower end and located between the first and the second particle retaininy screens and also defining a cylin-drical fluid collection volume located within the second particle retaining screen;
(d) a plurality of particle inlet conduits located in the upper section of the outer vessel and communicating with the upper end of the annular particle retention volume;
(e) a fluid inlet means communicating with the fluid distribution volume;
(f) a fluid outlet means communicating with the cylindrical fluid collection volume; and, (g) a particle withdrawal means located between the first and the second particle retention screens at the lower end of the annular particle retention volume, the particle withdrawal means comprising:
(i) a plurality of tubular particle withdrawal conduits distributed in a circular pattern encircling the second particle retent.ion screen, each particle ¦ ~ withdrawal conduit having an unsealed upper end which - communicates with the annular particle retention volume;
and, ..
J
(ii) a plurality of particle collection scoops, each scoop having an open upper first end which faces the second particle retention screen and a lower second end which is attached to the upper end of a particle withdrawal conduit, ~ith one particle collection scoop being positioned over each of the particle withdrawal conduits, and with each particle collection scoop having a greater cross~
sectional area at the upper first end than at the lower second end and reposing at an angle of from about 5-60 above horizontal.
In the drawings, Figure 1 shows a moving bed radial flow reactor while Figures 2 to S, inclusive, illustrate - different views of a catalyst collection scoop used for withdrawing used catalyst from the reactor.
Referring to Figure 1, there is shown a moving bed radial flow reactor formed in part by the outer vessel 1 and which conforms to a preferred embodiment of the invention.
This vessel is a vertically oriented cylinder enclosed by upper end section 36 and lower end section or cap 37. A
first or outer catalyst retention screen 2 is also cylin-drical in shape, as is the inne~ or sec~nd cata~yst ~ete~tio~ sc~e~ 3, ~Dth ~ thes~ ~cIeens are c~n~ ic about the central vertical axis of the reactor. The outer surface of the ~irst screen and the cylindrical inner surface of the outer vessel define an annular fluid or reactant distribution volume 38, into which the reactants flow from inlet conduit 6. An annular shaped bed of catalyst 4 is retained ~etween the two screens. This catalyst bed is intermittently replenished with fresh catalyst which falls through catalyst inlet conduits 5 and 5'. For simplicity only two catalyst inlet conduits are shown; normally at least about eight are used. The top of the porous portion of each screen is preferably .: ' ' ' . ' llC~l~9S
below the upper inner surface of the vessel, and the top of the catalyst bed is sealed off by an imperforate disk-shaped plate 10.
The reactants pass inward through the catalyst bed and enter the cylindrical fluid or reactant collection volume. The reactants and reaction products are then removed from the reactor through the reactant outlet conduit 7. The top of the reactant collection volume is sealed with a circular cover plate 9. The used catalyst is withdrawn from the reactor through a plurality of catalyst collec~ion scoops represented by scoops 8 and 8'. Each scoop has an open upper end which faces the inner catalyst retention screen. The catalyst enters through this upper end and is therefore withdrawn in an annular pattern much closer to the inner screen than the outer screen. Each scoop has a lower end connected to a catalyst withdrawal conduit such as 39 and 39'. These conduits encircle the inner screen and pass through the lower end section 37. The catalyst collection scoops and the upper portion of the catalyst withdrawal conduits are filled with catalyst during operation of the reactor. This description of the preferred applica-~ion of the invention is not intended to limit the apparatus to use as a reactor.
In FIGURE 2, a slde view of a catalyst collection scoop 13 is shown in greater detail. The lower end of the scoop is attached to a catalyst withdrawal conduit 12. This vertical conduit extends through the horizontal outer wall 11 of the reactor to a series of valves or a catalyst collection hopper as the case may be. Alternatively, the ; 30 conduit may directly feed catalyst to another reactor in a "stacked" reactor ~,, ' design. The scoop is positioned such that opening 41 at the upper end of the scoop faces the inner catalyst retention screen 4~ and is adjacent this screen. The opening theref~re Eaces radially inward. The outer catalyst retention screen 14 is closer to the lower end of the scoop. For simplicity, only a few of the large number of perforations in the screen are illustrated. As shown, the scoop is preferably formed by parallel, planar upper and lower imperforate panels. These panels have an angle "a" above horizontal as measured from the lower end of the scoop. The sides of the scoop are enclosed by opposing planar side walls.
In FIGURE ', the view seen when looking downward at a catalyst collection scoop 13 is presented. This scoop is similar to that shown in FIGURE 2. The lower end of the scoop covers the open upper end of the catalyst withdrawal conduit 12. The upper panel of the scoop has an upper edge 17 which is spaced further from the inner catalyst retention screen than the upper edge 18 of the lower panel. The triangular shaped panels result in the scoop having a larger cross-sectional area at its upper end than at its lower end.
FIGURE 4 illustrates the preferred arcuate shape of the panel edges forming the upper end of a catalyst collection scoop 19. Again, the lower end of the scoop is positioned to direct catalyst into the withdrawal conduit 20. The upper edges of the panels are once again horizontally staggered to collect cataIyst, with upper edge 21 being positioned further from the inner catalyst retention screen 35 than the lower panel edge 23. In the preferred embodiment the upper edge of the ,, - ~
l9S
upper p~nel 22 and of the lower panel are arcuate and have a radius o~ curvature which is correlated to that of the inner screen such thaL the distance measured radially between the inner screen and either edge is uniform at all points along each edge as shown. This view also shows the use of a scalloped outer catalyst screen 44 adjacent the cylindrical outer wall 43 of the reactor.
In FIGURE 5 the view seen looking toward the upper open end of a catalyst collection scoop 13 is presented. This scoop is similar to those shown in FIGURES 2 and 3 rather than the arcuate edged SCOGp, ~f FIGURE 4. The lowex end of the scoop is attached to a catalyst withdrawal conduit 12. The edge 17 of the upper panel is connected to the edge 18 of the l~wer panel by opposing, vertical, imperforate side walls 27 and 27'.
The open upper end of the SGOOp iS therefore circumscribed by elements 17, 18, 27 and 27'.
The particulate matter used in the apparatus is pre-ferably a hydrocarbon conversion catalyst, but it may be an adsorbent including activated carbon, a zeolite or an alumina as may be used to treat gas streams for the removal of water, sulfur compounds or halogen-containing chemicals. The particulate material may also be a solid acceptor used for the removal of sulfur oxides from a flue gas stream as disclosed in United States Patents 3,776,854 and 3,832,445. Preferablyl the par-ticulate matter is spherical and has a diameter within the range - of 0.15 to 1.25 cm. ~he words "catalyst" and "particle" are used interchangeably in many instances herein when referring ~o -~ various elements of-the apparatus. ^The use of either word is llU~l~S
not intended to limit the ~pplication or function of these elements in a manner which unduly limits the invention. Catalyst used in the apparatus will preferably comprise an inorganic oxide support, such as alumina or silica, with a catalytically effective amount of a metal or metal oxide. The metal may be one or more chosen from the following group: nickel, cohalt, iron, platinum, tin, palladium, manganese or magnesium.
The outer vessel is preferably made of a suitable metal such as carbon or stainless steel, but may be formed from other materials including fi~er reinforcel plastics if the conditions of temperature, pressure, etc., allow their use.
The two particle or catalyst retention screens are pre-ferably fabricated using wedge-shape wire having a cross-section which decreases in the direction that is away from the particle side of the screen. This results in a self cleaning surface such that as any particles, or pieces thereof, pass through the openings between the screens they may fall free of the screen on the other side. Preferably, the wedge-shaped wires are aligned vertically to minimize catalyst attrition as the , catalyst moves downward against the screen. The outer particle ¦ retention screen may be either cylindrical to provide an annular fluid distribution volume or it may be a scalloped screen as shown in FIGURE 4.
¦ 25 The contact apparatus will be provided with a plurality of particle inlet -conduits which pass through the upper section of the~outer vessel and communicate with the top of the annular j particle retention volume. About 6-10 inlet conduits are :,. :: . ' . . .
S
normally adequate to give proper distribution of the particu-late material. The `retention screens preferably have an imper-forate section at the top to provide a seal which prevents any portion of the fluid stream from passing over the particle bed through possible void spaces. The screens may be capped as shown in FIGURE 1 or they ma~ be extended upward to the inner surface of the vessel. The inlet conduits will normally be connected to a valve for controlling the rate of particle ad-dition or directly to a hopper vessel used to distribute the particles Alternatively the inlet conduits may be connected to the outlet conduits of vessels (reactors) located a~ove as in a stacked design.
In a preferred embodiment the appara~us comprises a -plurality of particle collection scoops which are arranged around the bottom of the centerpipe in a circular pattern, such that the tips of adjacent scoops come together or in close proxi-mity (within 15 cm) of each other to form an annular catalyst collection area which is uniformly disposed about the center-pipe. The width of this zone, which is the same as the distance between the centerpipe and the upper edge of the respective scoop preferably should be less than 30 centimeters. Preferably the distance for the upper edge is less than 10 centimeters and is less than 5 centimeters for the lower edge when arcuate scoops are used. An average distance is specified since the Z5 straight ed~e scoops, such as shown in FIGURE 3, will result in a varyiny distance. Preferably, the uppèr and lower edge of the scoop panels are arcuate and conform to the curvature of thc centerpipe to present a uniform distance between the s~oop , il~ll9S
and the centerpipe. Other edge shapes not shown may also be employed if desired.
The individual scoops are hollowform. That is, they are not solid but have a void interior space which conforms to their outer shape. Preferably, the upper and lower panels and side walls which enclose the scoops are imperforate. These elements of the scoops may be relatively porous, however, as to provide for drainage or vapor circulation. ~his may be desired in some cases to prevent coking or the entrapment of liquids in the particle withdrawal conduits. The cross-sectional area of the interior o~ each scoop is larger at the upper end which face~
the centerpipe than at the lower end which is attached to the particle withdrawal outlet. The scoops are in this regard funnel-li~e particle collectors. To aid in the collection of the particles the lower edge of the scoop ~the upper horizontal edge of the lower panel) is located closer to the centerpipe than the upper edge as illustrated in FIGURES 2 and 3.
The particle collection scoops, or catalyst collection scoops if the apparatus is used as a reactor, are inclined at an angle of from about 5-60 above horizontal. This is measured as the angle"a" of FIGURE 2. A preferred range for this angle is from 15-45, with 30 being particularly preferred.
It is preferred that the upper and lower panels of the scoop are parallel and therefore have the same angle. This is not a necessity and the scoops may taper vertically also. The scoops - may be surr~unded by the same particulate material which is moved through the apparatus, or inert spacers such as ceramic - ~ spheres may be placed in the bottom of the vessel. Several t , 11C~1195 suppor~s may be placed around and under the scoops to pre- .
vent their movemen-t and distortion during the operation of the apparatus.
.
'.' ' , ' " . ' ', - ' - ~ ~ ~ '
Claims (4)
1. A radial flow moving bed contact apparatus which comprises:
(a) a vertically oriented vessel having an internal volume located within a cylindrical side wall having an inner surface, the outer vessel being divided into upper and lower sections;
(b) a first vertically oriented particle retaining screen located within the outer vessel a distance radially in-ward from the inner surface of the outer vessel and defining a fluid distribution volume between the first particle retain-ing screen and the outer vessel;
(c) a second vertically oriented particle retaining screen located within the first particle retaining screen a distance radially inward from the first particle retaining screen and defining an annular particle retention volume having an upper and a lower end and located between the first and the second particle retaining screens and also defining a cylindrical fluid collection volume located within the second particle re-taining screen;
(d) a plurality of particle inlet conduits located in the upper section of the outer vessel and communicating with the upper end of the annular particle retention volume;
(e) a fluid inlet means communicating with the fluid distribution volume;
(f) a fluid outlet means communicating with the cylin-drical fluid collection volume; and, (g) a particle withdrawal means located between the first and the second particle retention screens at the lower end of the annular particle retention volume, the particle withdrawal means comprising:
(i) a plurality of tubular particle withdrawal conduits distributed in a circular pattern encircling the second particle retention screen, each particle withdrawal conduit having an unsealed upper end which communicates with the annular particle retention volume; and, (ii) a plurality of particle collection scoops, each scoop having an open upper first end which faces the second particle retention screen and a lower second end which is attached to the upper end of a particle withdrawal conduit, with one particle collection scoop being positioned over each of the particle withdrawal conduits, and with each particle collection scoop having a greater cross-sectional area at the upper first end than at the lower second end and reposing at an angle of from about 5-60° above horizontal.
(a) a vertically oriented vessel having an internal volume located within a cylindrical side wall having an inner surface, the outer vessel being divided into upper and lower sections;
(b) a first vertically oriented particle retaining screen located within the outer vessel a distance radially in-ward from the inner surface of the outer vessel and defining a fluid distribution volume between the first particle retain-ing screen and the outer vessel;
(c) a second vertically oriented particle retaining screen located within the first particle retaining screen a distance radially inward from the first particle retaining screen and defining an annular particle retention volume having an upper and a lower end and located between the first and the second particle retaining screens and also defining a cylindrical fluid collection volume located within the second particle re-taining screen;
(d) a plurality of particle inlet conduits located in the upper section of the outer vessel and communicating with the upper end of the annular particle retention volume;
(e) a fluid inlet means communicating with the fluid distribution volume;
(f) a fluid outlet means communicating with the cylin-drical fluid collection volume; and, (g) a particle withdrawal means located between the first and the second particle retention screens at the lower end of the annular particle retention volume, the particle withdrawal means comprising:
(i) a plurality of tubular particle withdrawal conduits distributed in a circular pattern encircling the second particle retention screen, each particle withdrawal conduit having an unsealed upper end which communicates with the annular particle retention volume; and, (ii) a plurality of particle collection scoops, each scoop having an open upper first end which faces the second particle retention screen and a lower second end which is attached to the upper end of a particle withdrawal conduit, with one particle collection scoop being positioned over each of the particle withdrawal conduits, and with each particle collection scoop having a greater cross-sectional area at the upper first end than at the lower second end and reposing at an angle of from about 5-60° above horizontal.
2. The apparatus of Claim 1 wherein the first particle retaining screen is cylindrical and the fluid distribution volume is annular.
3. The apparatus of Claim 2 wherein the upper first end of the particle collection scoop has an upper arcuate edge which is substantially uniformly spaced from the second catalyst retention screen to provide an annular vertical particle passageway.
4. The apparatus of Claim 3 wherein the particle collec-tion scoop has an angle above horizontal of from 15-45°.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA307,313A CA1101195A (en) | 1978-07-13 | 1978-07-13 | Moving bed radial flow solids-fluid contacting apparatus |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA307,313A CA1101195A (en) | 1978-07-13 | 1978-07-13 | Moving bed radial flow solids-fluid contacting apparatus |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1101195A true CA1101195A (en) | 1981-05-19 |
Family
ID=4111897
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA307,313A Expired CA1101195A (en) | 1978-07-13 | 1978-07-13 | Moving bed radial flow solids-fluid contacting apparatus |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1101195A (en) |
-
1978
- 1978-07-13 CA CA307,313A patent/CA1101195A/en not_active Expired
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