KR20110081211A - Stripping process and apparatus with multi-sloped baffles - Google Patents

Abstract

The present invention provides a method for stripping a gas from a catalytic material comprising a baffle having a second face extending between the baffles toward the downcomer channel to diffuse the catalyst on adjacent baffles for better contact with the stripping gas. An apparatus and method are provided.

Description

STRIPPING PROCESS AND APPARATUS WITH MULTI-SLOPED BAFFLES}

The present invention relates to an apparatus and a method for fluidly contacting a catalyst with a hydrocarbon. More specifically, the present invention relates to apparatus and methods for stripping hydrocarbons entrained or adsorbed from catalyst particles.

Various processes contact the finely divided particulate matter with the hydrocarbon-containing feed under conditions such that the fluid maintains the particles in a fluid state that transports the solid particles to different stages of the process. Fluid catalytic cracking (FCC) is a representative example of the process of contacting a hydrocarbon in a reaction zone with a catalyst consisting of finely divided particulate matter. Inert diluents, such as hydrocarbon feeds and steam, flow the catalyst and generally transport the catalyst in a riser while the catalyst promotes the decomposition reaction. As the decomposition reaction proceeds, a substantial amount of hydrocarbon called coke is deposited on the catalyst. High temperature regeneration inside the regeneration zone burns coke from the catalyst by contact with an oxygen-containing stream which again acts as the flow medium. The coke-containing catalyst, referred to herein as spent catalyst, is continuously removed from the reaction zone and replaced with a catalyst that is substantially free of coke exiting the regeneration zone.

Most of the hydrocarbon vapors in contact with the catalyst in the reaction zone are separated from the solid particles by impact and / or centrifugation methods inside the reaction zone. However, catalyst particles used in FCC processes have a large surface area because a very large number of pores are present in the particles. Thus, the catalytic material retains hydrocarbons within its pores, on the outer surface of the catalyst and in the spaces between the individual catalyst particles. Although the amount of hydrocarbons retained on each individual catalyst particle is very small, due to the high catalyst circulation rate and the large amount of catalysts commonly used in modern FCC units, significant amounts of hydrocarbons are withdrawn from the reaction zone along with the catalysts.

Therefore, it is common practice to remove or strip hydrocarbons from the spent catalyst before passing the catalyst through the regeneration zone. Improved stripping brings economic benefits to FCC processes by reducing "delta coke". Delta coke is weight percent coke on spent catalyst minus weight percent coke on regenerated catalyst. Reducing delta coke in the FCC process can lower the regenerator temperature. As a result, the more product, the relatively lower temperature regeneration catalyst is required to supply a fixed heat load to the reaction zone. Thus, the reaction zone can operate at higher catalyst-to-feed or catalyst-to-oil (C / O) ratios. The higher the C / O ratio, the higher the conversion, which increases the production of valuable products. Thus, the stripping improvement improves the conversion. In addition, stripping hydrocarbons from the catalyst also allows the recovery of hydrocarbons as a product.

The most common method of stripping a catalyst involves passing a stripping gas, typically steam, in a flow direction of the catalyst countercurrent to the flow direction. This steam stripping operation with varying degrees of efficiency removes hydrocarbon vapors entrained with and adsorbed on the catalyst. The contact of the catalyst with the stripping medium can be made in a simple open vessel, as evidenced by US 4,481,103.

The efficiency of catalyst stripping is increased by cascading the catalyst from side to side using vertically spaced baffles as the catalyst moves under the stripping apparatus and is countercurrently contacted with the stripping medium. Moving the catalyst horizontally increases the contact between the catalyst and the stripping medium over the active flow surface of the tray to remove more hydrocarbons from the catalyst. In this arrangement, the catalyst is provided in a labyrinthine path through a series of baffles located at different heights. Catalyst and gas contact are augmented by this arrangement without leaving an open vertical path of significant cross-sectional area through the stripping device. Further examples of these stripping devices for FCC units are shown in US 2,440,620, US 2,612,438, US 3,894,932, US 4,414,100 and US 4,364,905. These references show a typical stripping vessel arrangement having a stripping vessel, a series of outer baffles in the form of a truncated conical section that directs the catalyst inwardly into a series of inner baffles. The inner baffle is a concentrically arranged conical or truncated section that diverts the catalyst outward to the outer baffle. The stripping medium enters from below the lower baffles and continues to rise up from the bottom of one baffle to the bottom of the next consecutive baffle. The baffle design generally has a perforated hole above the bottom baffles to distribute the steam across the loop between the baffles to ensure complete annular distribution of the vapor jet nozzle and vapor over the top baffle and to maximize contact between the vapor and the catalyst. It includes. To facilitate fabrication, the outer diameter of the inner baffle is generally made smaller than the inner diameter of the outer baffle. Modifications of the baffle include the addition of a skirt around the trailing edge of the baffle as disclosed in US 2,994,659 and the use of multiple linear baffle sections at different baffle heights as shown in FIG. 3 of US 4,500,423. Changes in the introduction of the stripping medium are shown in US 2,541,801, in which a large amount of flowing gas is introduced at a number of distinct locations. The baffle may also include an upright weir on the edge of the baffle adjacent the downcomer.

Therefore, it is desirable to increase the efficiency of stripping in a baffle style stripping vessel by ensuring that the catalyst is in contact with all the baffles in the stripping vessel.

Summary of the Invention

We observed that the catalyst could bypass the baffle or baffle portion in the FCC stripper vessel. Bypass can occur when the stripping fluid rises along the opposite wall of the stripping vessel while the catalyst deviates toward the middle between the opposite walls of the stripping vessel. Thus, the catalyst does not diffuse on the baffles and contacts fewer stripping fluids to reduce the stripping efficiency. This phenomenon is more pronounced in larger stripping vessels because the horizontal distance across each baffle the catalyst must traverse is greater and the distance between the baffles is greater. The bypass phenomenon can also be encountered when operating at low catalyst fluxes due to insufficient acceleration for cascading the catalyst stream from side to side. To prevent this bypass we invented a baffle with two sides. The second face extends into the downcomer channel between the pair of baffles. The second side directs the drop catalyst toward the adjacent baffle on the other side of the stripping vessel. The bottom face promotes transverse motion relative to adjacent baffles to prevent baffle bypass and increase efficiency. Another advantage obtained by avoiding baffle bypass is to provide a more uniform and higher bed density to the stripping vessel, which provides a suitable pressure differential across the slide valve in the conduit that carries the catalyst particles to the regenerator vessel. Is especially important.

Further objects, embodiments and details of the invention are provided in the following detailed description of the invention.

Brief description of the drawings

1 is a cross-sectional view of an FCC reactor and stripper arrangement in which the present invention may be incorporated.

FIG. 2 is an enlarged view of the stripper section taken in FIG. 1.

3 is a partial cross-sectional view taken along the 3-3 segment of FIG.

Detailed description of the invention

The present invention will be disclosed in connection with an FCC unit. However, other situations may apply. 1 shows an FCC unit including a reactor vessel 10, a reactor riser 20, and a regenerator vessel 50. Regenerator standpipe 12 carries catalyst particles from regenerator vessel 50 to reactor riser 20, which may include vertical conduits at a rate controlled by a slide valve. Until a plurality of feed injection nozzles 14 (only one shown) injects the feed across the flow stream of catalyst particles, fluidizing medium, such as steam, from the nozzles 16 carries the catalyst upwards of the reactor ( 20) to a relatively high density.

Conventional FCC feedstocks or high boiling hydrocarbon feedstocks are suitable feeds. The most common of these conventional feedstocks are "vacuum gas oils" (VGOs), which are hydrocarbon materials having a boiling point in the range of 343-552 [deg.] C. (649-1026 [deg.] F.), generally produced by vacuum fractional distillation of atmospheric pressure residues. These fractions are generally low in coke precursors and heavy metal contamination that can contaminate the catalyst. Heavy hydrocarbon feedstocks to which the present invention may be applied include heavy residues derived from crude oil, heavy bitumen crude oil, shale oil, tar sand extracts, deasphalted residues, products derived from coal liquefaction, atmospheric and vacuum residues. The heavy feedstock of the present invention also includes a mixture of the hydrocarbon streams, which is not exhaustive.

As the resulting mixture of catalyst and feed continues to rise along the reactor riser 20, the catalyst decomposes the feed into lighter hydrocarbons and coke is deposited on the catalyst. Two or more separation arms 22 at the top of reactor riser 20 partially feed gas from the catalyst through port 24 (only one shown) to a mixture of spent catalyst and product gas from the top of reactor riser 20. To the separation section 26 of the stripping vessel 40 to be separated in a tangential direction and in a horizontal direction. The stripping vessel 40 is partially disposed in the reactor vessel 10. The delivery conduit 28 carries hydrocarbon vapor, stripping medium, and entrained catalyst, including stripped hydrocarbons, from the stripping vessel 40 to one or more cyclones 30 in the reactor vessel 10, where the hydrocarbon vapors The spent catalyst is further separated from the stream. Collection space 34 in reactor vessel 10 collects the hydrocarbon vapor stream separated from cyclone 30 and passes it to outlet nozzle 36 and ultimately a fractionation recovery zone (not shown). Deflag 38 discharges the catalyst from cyclone 30 to bed 32 below reactor vessel 10. Hydrocarbons and catalyst absorbed or entrained in bed 32 ultimately pass into stripping vessel 40 via port 42 defined in wall 41 of stripping vessel 40. The catalyst separated in separation section 26 passes directly into bed 27 above the stripping vessel 40. The stripping vessel 40 has a baffle pair comprising a first baffle 44 and a second baffle 46 to facilitate mixing between the stripping gas and the catalyst. Stripping gas, generally steam, enters the bottom of stripping vessel 40 and passes through one or more inlets 47 to one or more distributors (not shown). The stripping gas moves up countercurrently with respect to the catalyst cascade. The stripped spent catalyst leaves the stripping vessel 40 via the waste catalyst conduit 48 through the particle outlet 49 and passes through the regenerator vessel 50 at a rate controlled by the slide valve.

The reactor riser 20 of the FCC process is maintained at high temperature, including temperatures generally above 425 ° C (797 ° F). In one embodiment, the reaction zone has a temperature of 480-590 ° C. (896-1094 ° F.) and a pressure of 69-517 kPa (ga) (10-75 psig), but generally less than 275 kPa (ga) (40 psig). It is maintained under decomposition conditions including the pressure of The catalyst-to-oil ratio can range from 20: 1 up to 20: 1 based on the weight of catalyst and feed hydrocarbons entering the bottom of the riser, but generally ranges from 4: 1 to 10: 1. Although hydrogenation is known in the art, hydrogen is usually not added to the riser. In one embodiment, riser 20 is substantially free of hydrogen added except from the hydrocarbon feed. The steam may pass through reactor riser 20 and reactor vessel 10 and corresponds to 4-7 wt% of the feed. The average residence time of the catalyst in the riser may be less than 5 seconds. The type of catalyst used in the process can be selected from a variety of commercially available catalysts. Catalysts comprising a zeolitic material are preferred, but older amorphous catalysts may be used as needed.

Regenerator vessel 50 may be a combustor-type regenerator capable of using hybrid vortex-fast flow conditions in high efficiency regenerator vessel 50 for fully regenerating spent catalyst. However, other regenerator vessels and other flow conditions may be suitable for the present invention. The waste catalyst conduit 48 feeds the waste catalyst through the waste catalyst inlet chute to the first or lower chamber 52 defined by the outer wall. The spent catalyst from reactor vessel 10 usually contains carbon present in the form of coke in an amount of 0.2 to 2% by weight. The coke consists mainly of carbon, but may contain not only 3 to 12% by weight of hydrocarbons but also sulfur and other materials. Oxygen-containing combustion gas, generally air, enters the first chamber 52 of the regenerator vessel 50 through the conduit and is distributed by the distributor 66. Openings in the dispenser 66 emit combustion gases. When the combustion gas enters the combustion section 58, it is in contact with the waste catalyst flowing from the chute and has a combustion gas tower velocity of at least 1.1 m / s (3.6 ft / s) under high flow flow conditions in the first chamber 52. Raise the catalyst with. In one embodiment, the combustion section 58 has a catalyst density of 48 to 320 kg / m ³ (3 to 20 lb / ft ³ ) and a gas tower speed of 1.1 to 2.2 m / s (3.6 to 7.2 ft / s). . Oxygen in the combustion gas is contacted with the spent catalyst to burn carbonaceous deposits from the catalyst to at least partially regenerate the catalyst and generate flue gas.

In the first chamber 52 the mixture of catalyst and combustion gas rises from the combustion section 58 through the truncated conical transition section 56 to the transport riser section 60 of the first chamber 52. The riser section is preferably defined by an outer wall which defines a tube which is preferably cylindrical and preferably extends upwardly from the first chamber 52. The mixture of catalyst and gas moves at a higher gas tower velocity than in the combustion section 58. The increase in gas velocity is due to the decrease in the cross sectional area of the riser section 60 compared to the cross sectional area of the first chamber 52 below the transition section 56. Thus, gas tower velocity usually exceeds 2.2 m / s (7.2 ft / s). The riser section 60 has a lower catalyst density of less than 80 kg / m ³ (5 lb / ft ³ ).

Regenerator vessel 50 also includes an upper or second chamber 54. The mixture of catalyst particles and flue gas exits the second chamber 54 from the top of the riser section 60. Substantially fully regenerated catalyst may come from the top of the conveying riser section 60, but an arrangement in which the partially regenerated catalyst exits the first chamber 52 is also contemplated. Emissions are through a separator 62 which separates most of the regenerated catalyst from the flue gas. In one embodiment, gas and catalyst flowing over riser section 60 impinge on top elliptical cap 64 of riser section 60 to reverse the flow. The catalyst and gas then exit through the downward outlet inlet of separation device 62. Due to the downward flow reversal and rapid loss of acceleration, the heavy catalyst mostly falls into the high density catalyst bed 68 and the light flue gas and the small amount of catalyst still entrained there rise in the second chamber 54. Cyclone 63, 65 further separates the catalyst from the gas and deposits the catalyst on a high density phase. Flue gas exits the cyclones 63 and 65 and is collected in a space for passage to the outlet nozzle 67 of the regenerator vessel 50 and possibly to the flue gas or power recovery system (not shown). The separated catalyst falling down is collected in the high density catalyst bed 68. The catalyst density of the high density catalyst bed 68 is generally maintained at 640-960 kg / m ³ (40-60 lb / ft ³ ). The flow conduit delivers the flowing gas, generally air, through the flow distributor 70 to the high density catalyst bed 59. In combustor-type regenerators, about 2% or less of the total gas demand in the process enters the high density catalyst bed 68 through the flow distributor 70. In this embodiment, the gas is added fluidly through the standpipe 12 because the gas is added only for flow purposes, not for combustion purposes. The flow gas added through the flow distributor 70 may be combustion gas. When partial combustion occurs in the first chamber 52, a larger amount of combustion gas is supplied to the second chamber 54 through the flow distributor 70. The regenerated catalyst is returned to reactor riser 20 through regenerator conduit 12.

FIG. 2 is a partially enlarged view of the stripping vessel 40 of FIG. 1. Several pairs of first baffle 44 and second baffle 46, respectively, are spaced vertically over at least a portion of stripping vessel 40. The first baffle 44 may be at the top of the plurality of baffles and at the bottom of the plurality of baffles. Increasing the number of baffles usually increases stripper performance. Certain feedstocks and operating conditions, the available length of the stripper or other equipment constraints in the layout configuration can affect the number of baffles that can be included in the stripper. The at least one baffle and preferably the first baffle 44 comprises a top face or first face 44a and the second baffle 46 comprises a first face or top face 46a. The first surfaces 44a and 46a are generally inclined or angled with respect to the vertical line, meaning that they form an angle that is not 180 degrees from the vertical line. Providing slopes in the baffle ensures the movement of the catalyst across the surface of the baffle. Generally, the baffle has an inclination acute angle of 45 ° to 60 ° from the vertical line. The greater the angle of the baffle to the vertical line has the advantage of maximizing the number of baffles that can be placed at a given stripper length and providing a smaller difference in the pressure head between the hole near the top edge and the hole near the bottom edge. The spacing between baffles should provide sufficient flow area for cascaded movement of the catalyst around the first and second baffles 44, 46. Baffles 44 and 46 define serpentine downcomer channels 40 along the length of the stripping vessel. The first surfaces 44a and 46a provide a major baffle surface and are therefore wider than the second surfaces 44b and 46b. Since the baffles 44 and 46 are alternately fixed to the opposing walls of the stripping vessel 40, the movement of the baffles from the upper baffles to the lower requires the catalyst to move across the downcomer channel 72. .

Embodiments of the cyclic baffle configuration are shown in FIGS. 1 and 2. However, the present invention can also be applied to baffle configurations that are not cyclic. The reactor riser 20 extends through the stripping vessel 40. The first baffle 44 is supported by the wall 41 of the stripping vessel 40 and the further baffles are supported by the wall 76 of the reactor riser 20. The fixed edge 84 of the first face 44a of the first baffle 44 is fixed to the wall 41 of the stripping vessel 40 and the first face 46a of the second baffle 46. The fixed edge 86 of is fixed to the wall 76 of the riser. The protruding edge of the first face 44a and the protruding edge of the first face 46a protrude into the downcomer channel 72.

In certain cases, when the diameter of the stripping vessel is large and / or the catalyst flow rate is low, the stripping fluid rises along the opposing walls of the stripping vessel while the catalyst flows below the center of the ring between the opposing walls. Is observed. Thus, the catalyst does not have enough acceleration to diffuse on the baffle and only strikes the projecting end of the baffle. The catalyst is in contact with less stripping fluid and thus the stripping efficiency is reduced. To prevent the catalyst from bypassing the baffle, the baffle has a second face 44b, 46b fixed to the protruding edge of the first face 44a, 46a, respectively, extending into the downcomer channel 72 between adjacent baffles. Include. The second face 44b, 46b moves the descending catalyst across the downcomer channel 72 to a vertical position above the bottom baffle, preferably above the first face 46a, 44a of the bottom baffle 46, 44. Orient. This arrangement significantly suppresses baffle bypass.

In one embodiment, the skirt 78 is from the baffles 44, 46 and optionally at the intersection point 82 between the fixed edges of the second faces 44b, 46b and the protruding edges of the first faces 44a, 46a. Can extend down. The skirt 78 is generally vertical and hangs on the bottom of the baffles 44 and 46. Skirt 78 is provided to increase the pressure drop across the opening. In an embodiment of the annular stripper as shown in FIG. 2, each baffle comprises an annular band. Each side and skirt also includes an annular band.

3 is a partial side view along segment 3-3 of FIG. 3 shows the opening 80 of the baffles 44, 46 for flowing the catalyst on the top side of the baffle. The opening is generally in the first face 44a, 46a, but optionally only in the second face 44b, 46b. The second surfaces 44b and 46b have fixed edges fixed to the protruding edges of the first surfaces 44a and 46a of the second baffles 44 and 46, respectively, and the second surfaces 44b and 46b respectively have protruding edges ( 88, 90). In one embodiment, the anchored edges 88, 90 of the second faces 44b, 46b are not positioned vertically or aligned vertically with the bottom baffle, but above the bottom baffle, and the second faces 44b, The protruding edges 88, 90 of 46b) are located above or vertically arranged above the lower baffle. The vertical protrusion A of the first face 44a of the first baffle 44 and the vertical protrusion B of the first face 46a of the second baffle 46 are shown in FIG. 3. In one embodiment, the second faces 44b, 46b of the second baffles 44, 46 extend toward the vertical projections B, A of the adjacent baffles 46, 44, preferably the second faces ( 44b and 46b extend to the vertical projections A and B of the first surfaces 44a and 46a of the adjacent baffles 46 and 44.

The second surfaces 44b and 46b are angled with respect to the first surfaces 44a and 46a respectively, which means that they define an angle α rather than 180 ° from each other. Preferably, the second surface 44b defines an acute angle β upwards from the vertical line that is greater than the acute angle θ that the first surface 44a defines upwards from the vertical line, and the second surface 46b defines the first surface. An acute angle ω that is larger than the acute angle ε that 46a defines upward from the vertical line is defined upward from the vertical line. In FIG. 3 the vertical line is illustrated by the wall 41 of the stripping vessel 40 for the angle θ and by the wall 76 of the riser for the angle ε and the skirt for the angles β and ω Illustrated at 78. The length and slope of these angles from the vertical line can be optimized to obtain the appropriate flux of the catalyst.

The baffles 44 and 46 may be coated with a refractory material. 3 is a refractory material covering the inner surface of the wall and a portion of the first face 44a of the first baffle 44 and the first face 46a of the second baffle 46 at the top of the stripping vessel 40. It is shown. The opening 80 may be formed by simply drilling a hole through the substrate of the baffles 44 and 46. Baffles are generally formed from alloy steels that withstand high temperature conditions. Such steels are often exposed to corrosion, and the baffles can benefit from the use of inserts or nozzles defining openings, providing resistance to the corrosion conditions imposed by the catalyst circulating over the baffles. In addition, the baffles are always covered with a refractory material that provides additional corrosion resistance.

Indeed referring to FIGS. 1-3, the hydrocarbon feed is contacted with a catalytic cracking catalyst to provide a mixture of converted feeds of the vaporized product of light hydrocarbons and spent catalyst with coke deposited in reactor riser 20. The vapor phase product is separated from the spent catalyst in separation section 26 and reactor vessel 10 to produce a stream of separated catalyst particles containing hydrocarbons by adsorption and / or entrainment. The separated catalyst particle stream passes downward over the plurality of baffles 44, 46 in the stripping vessel 40. Stripping fluid, such as steam, exits the inlet 47 below the baffles 44 and 46. Openings 80 in baffles 44 and 46 introduce stripping fluid into the top surfaces of baffles 44 and 46 to facilitate catalyst flow at the top surfaces of the baffles. At least a portion of the spent catalyst particles travels down from the first line 44a of the first baffle 44 at a first acute angle θ up from the vertical line and then at a second acute angle β up from the vertical line. Move below the second surface 44b). The first acute angle θ and the second acute angle β are different from each other. In one embodiment, the second acute angle β is greater than the first acute angle θ. The spent catalyst particles move below the second face 44b of the first baffle 44 and then move down the downcomer channel 72 defined by the baffles and at a third acute angle ε upwards from the vertical line. It moves below the first face 46a of the baffle 46 and then moves down from the second line 46b of the second baffle 46 at a fourth acute angle ω up from the vertical line. In one embodiment, the third and fourth angles are different from each other. In one embodiment, the fourth angle ω is greater than the third angle ε. In one embodiment, the first angle θ and the third angle ε are the same, and in another embodiment, the second angle β and the fourth angle ω are the same.

The stripping fluid and the stripped hydrocarbon are recovered from the stripping vessel 40 through the conveying conduit 28, the cyclone 30, and the outlet nozzle 36. The stripped spent catalyst is returned to the regenerator vessel 50 via an outlet 49 for passage to the spent catalyst conduit 48. In the regenerator, the catalyst is regenerated by coke combustion, and the regenerated catalyst is sent to the reactor riser 20 through the regenerator conduit 12.

Claims (10)

An apparatus for stripping entrained and / or adsorbed hydrocarbons from catalyst particles,
Stripping containers;
At least one port defined by a stripping vessel for receiving catalyst particles containing entrained or adsorbed hydrocarbons;
A first baffle and a second baffle disposed vertically spaced over at least a portion of the stripping vessel and defining a downcomer channel between the first and second baffles (the first baffle being angled with respect to each other with the vertical line); Inclusive);
A fluid inlet for passing a stripping fluid through a lower surface of said first and second baffles for stripping hydrocarbons from particulate material; And
Particle outlet for recovering stripped particles from the first and second baffles
Stripping device comprising a. The apparatus of claim 1, wherein the second face of the first baffle extends toward the vertical protrusion of the second baffle. The apparatus of claim 1, wherein the second face of the first baffle extends into the vertical protrusion of the second baffle. The device of claim 1, wherein a vertical skirt extends downwardly from the intersection of the first and second surfaces. The apparatus of claim 1, wherein the second face defines a vertical line and an acute angle greater than the first face. The apparatus of claim 1, wherein a reactor riser extends through the stripping vessel, the first baffle is supported by the wall of the stripping vessel and the second baffle is supported by the wall of the reactor riser. The device of claim 6, wherein the fixed edge of the first face of the first baffle is secured to each one of the walls. The apparatus of claim 1, wherein the second face of the first baffle extends into the downcomer channel. A method for stripping entrained and / or adsorbed hydrocarbons from catalyst particles,
Contacting the catalyst particles with a hydrocarbon stream;
Separating the hydrocarbons from the catalyst particles after contact with the hydrocarbon stream to produce a stream of spent catalyst particles containing entrained and / or adsorbed hydrocarbons;
Passing the spent catalyst particles downward over the plurality of baffles;
Moving at least a portion of the spent catalyst particles down a first face of the first baffle at a first acute angle with respect to a vertical line and then down a second face of the first baffle at a second acute angle different from the first acute angle with respect to the vertical line. step;
Recovering the stripping fluid and the stripped hydrocarbon from the baffle; And
Recovering stripped catalyst particles from the baffle
Stripping method comprising a. 10. The waste catalyst particle of claim 9, wherein the spent catalyst particles move below the second face of the first baffle traverse the downcomer channel defined by the baffles and below the first face of the adjacent baffle at a third acute angle with respect to the vertical line. And then move below the second face of the second baffle at a fourth acute angle with respect to a vertical line, wherein the fourth acute angle is different from the third acute angle.

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