JPH0425593A - End-to-end shape fcc stripping equipment having stripping gas inlet and provided with baffle skirt - Google Patents

Abstract

PURPOSE: To enable the good stripping of hydrocarebon occluded from a waste catalyst by combining a tank, a barrier plate, a means supplying and extracting gas, a grid skirt and a gas jet orifice so as to perform specific action.

CONSTITUTION: A catalyst and hydrocarbon rises while flows through a rising pipe. A fluidized mixture flows out of the rising pipe 5 and the greater part of the catalyst is separated from a gas flow within a cyclone 13. This catalyst enters a cyclone 11 along with the steam from a stripper. Fine powdery catalyst particles are accompanied in a splashed state by the steam flow and separated in the cyclone 11 to fall. The vapor stream of hydrocarbon separated from the cyclone 11 through a conduit 12 and the hydrocarbon product in the conduit flows into a product recovery apparatus. The waste catalyst goes downwardly from the lower region of a separation tank 1 to enter a stripping tank 2. The catalyst is stagnated within the stripping tank 2 for a desired time and moved from the bottom part of the stripper 2 by a conduit 4 to be drawn out.

COPYRIGHT: (C)1992,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates generally to hydrocarbon conversion methods and apparatus. More particularly, the present invention relates to an apparatus and method for stripping occluded hydrocarbons from spent catalyst in a fluidized bed cracking process.

[Prior art and problems solved by the invention]

The fluidized bed catalytic cracking (commonly referred to as FCC) process was developed in the 1940's to increase the yield of naphtha boiling range hydrocarbons obtained from crude oil. Fluidized bed cracking processes are now widely used commercially in petroleum refineries;
Light boiling hydrocarbons are produced from heavy feedstocks such as atmospheric distillation residues or vacuum crude oils. This process has been utilized to reduce the average molecular weight of various petroleum-derived feedstocks, resulting in economically valuable light oils being obtained from heavy fractions. Feedstocks for FCC processes are typically petroleum derivative feedstocks, but liquids from tar sands, oil shale or coal liquefied products can also be utilized in FCC processes. Today, various FCC processes are also available for cracking heavy oils and distillation residues. Although the FCC process is often used for distillation residue conversion, the term FCC as used herein also applies to heavy oil cracking.

FCC equipment of various designs are listed in the ``The Oil & Gas Journal''.
) is described in an article on page 102 of the May 15, 1972 edition of J and on page 65 of the October 8, 1973 edition of J.

Another example of an FCC process is U.S. Patent No. 4.364.
．． No. 905 (by Furling et al.); (e) No. 4,
No. 051,013 (by Strother); (e) No. 3,894,932 (by Owen); (e) and No. 4,419,221 (by Castagons Jr., et al.); This can be learned from other FCC patent references discussed in .

The most common design of the FCC process involves contacting a feedstock in a reaction zone with a finely divided solid catalyst that is flown with air through the reaction zone in a fluidized medium. The fluidizing medium includes steam, light oil, and vaporized feedstock components that are converted by contact with the catalyst. The catalyst is described as being in a fluid state because the catalyst behaves as a fluid when it is being moved by a fluid medium. When the catalyst particles come into contact with the feedstock, the catalyst becomes covered with a hydrocarbon-like substance called coke. Coke is a byproduct of cracking reactions and contains carbon, hydrogen, and other materials present in the feedstock, such as sulfur. Coke blocks the cracking sites of the catalyst and deactivates the catalyst. This type of catalyst is usually called a spent catalyst. Therefore, after passing through the reaction zone, the spent catalyst is transferred to a regeneration zone where the coke is combusted and separated from the catalyst. The oxygen-containing gas, typically air, is heated to a sufficient temperature and mixed with a catalyst in a regenerator to oxidize attached coke into carbon monoxide and carbon dioxide. The oxidation removes coke and reactivates the catalyst from the regenerator and back to the reactor, thereby completing continuous operation of the FCC unit.

The bulk hydrocarbon vapors in contact with the catalyst in the reaction zone are separated from solid particles by ballistic and/or centrifugal methods. However, the catalyst particles used in the FCC process have a large surface area because they have a large number of pores. As a result, the catalyst material stores hydrocarbons in its pores and on its surface. Although the amount of hydrocarbons held by individual catalyst particles is extremely small, recent FCC
The amount of catalyst typically used in the process is large and the circulation rate is so high that hydrocarbons are absorbed and removed from the reaction zone by the catalyst.

Therefore, it is common to separate or strip the occluded hydrocarbons from the spent catalyst before passing it to a regeneration zone. Removal of occluded hydrocarbons from spent catalysts is of process and economic importance. First, the stored hydrocarbons entering the regenerator create a high carbon combustion load, which causes the regenerator temperature to become too high. Hydrocarbon products can also be recovered by stripping the hydrocarbons from the catalyst. Avoiding unnecessary combustion of hydrocarbons is especially important when processing heavy (relatively high molecular weight) feedstocks. This is because processing such feedstocks results in more coke deposits on the catalyst during the reaction (compared to processing light feedstocks) and increases the combustion load in the regeneration zone. The higher the combustion load, the higher the temperature, which can upset the catalyst or push the metallurgical design limits of the regenerator.

The most common method of stripping catalyst is to pass a stripping gas (usually steam) in a countercurrent direction to the downwardly flowing catalyst stream. Such steam stripping operations, with varying degrees of efficiency, remove entrained and occluded hydrocarbons from the catalyst. To strip the hydrocarbon gas from the catalytic force, the catalyst need only be brought into contact with the stripping catalyst. This contact can be made with a simple open container as shown in US Pat. No. 4,481,103.

Previously, to increase the efficiency of catalyst stripping,
A series of baffles were installed in the stripping device to cause the catalyst to cascade from side to side as it fell through the device.

Moving the catalyst horizontally increases contact between the catalyst and the stripping medium, and increased contact between the catalyst and the stripping medium results in more separation of hydrocarbons from the catalyst.

It has been known since 1944 to use angled guides to increase contact between catalyst and stripping media, as shown in US Pat. No. 2,440,625.

With such devices, the catalyst is provided with a complex flow path by a series of baffles placed at various heights.

This structure increases catalyst-gas contact and eliminates vertical through-hole passages in the major cross-sections of the stripping device. Similar stripping device examples for FCC devices are shown in U.S. Pat.
, No. 438, No. 3, No. 894.932, No. 4.41 of the same
No. 4,100 and No. 4,364.905. Examples of these include a stripper bath or a centrally located conical or frust shaped baffle that directs the catalyst inward to one of a series of centrally located conical or frust-shaped baffles that diverge the catalyst onto the outer baffle. A typical stripper is shown having a series of baffles with a wlast/conical shaped cross section. The stripping medium enters from below the series of lower baffles and continues to rise from the bottom of one baffle to the bottom of the next baffle. Variations of the baffle include adding a skirt near the trailing edge of the baffle as shown in U.S. Pat. No. 2,994,659, and U.S. Pat.
500,423, at various baffle heights as shown in FIG.
ear) There is one that utilizes the cross section of the baffle plate. A variation of introducing a stripping medium is U.S. Pat. No. 2.541,
No. 801, a large amount of flow gas is introduced from multiple separate locations.

An example of a gas-solid contacting device, disclosed in U.S. Pat. Exhaust can be exhausted from the side. However, this device does not function like the previously described stripping device because there is a checkboard pattern of vertical passages through all trough levels. No. 2,460,151, there is no particular emphasis on trough design or equipment.

Relatively large amounts of stripping media have traditionally been required to achieve good stripping of the catalyst, increased product yield, and associated good operation of the regenerator. With steam being the most common stripping medium, the average steam requirement in the industry is well over 1.5 kg per 1000 kg of catalyst for catalyst stripping.

The costs of adding this fluidizing medium are significant and, in the case of steam, include capital costs and utility costs associated with the steam supply and removal of water from downstream separation equipment. Therefore, all the steam savings required to achieve good catalyst stripping are F
There are substantial economic benefits to the CC process.

It has now been discovered that good catalyst stripping can be achieved with less than half the stripping media previously used by utilizing conventional FCC stripping methods and equipment. These results can be achieved by modifying the stopper grid according to the present invention.

[Means to solve the problem]

The present invention is an FCC stripper that redistributes fluidized media at each grid level to increase penetration of fluidized media across the downwardly flowing catalyst stream. Carefully sized and spaced holes at the bottom of each grid are used to inject the fluidizing medium across the descending column of catalyst. Injecting the fluidizing medium further improves the contact between the fluidizing medium and the catalyst particles, so that the fluidizing medium becomes more efficient in removing hydrocarbons from the catalyst. Increased stripping efficiency reduces the amount of stripping gas required for a given level of hydrocarbon removal, or increases hydrocarbon removal with the addition of a given level of stripping media. Those skilled in the art understand that the former saves utilities and facilities;
It can be seen that the latter increases product yield and also improves regeneration operations.

In one embodiment, the present invention is a stripping device for an FCC unit that removes occluded hydrocarbons from a particulate catalyst by contacting it with a stripping gas. The stripping device has a vertically extending container;
It also has a cross section that is open to the flow of catalyst, which enters the catalyst from the top and exits from the bottom. The container has two or more grids forming a baffle system. The grid has horizontal protruding surfaces that allow the catalyst to move from side to side within the container while moving downwards. The horizontal projecting surface of each grid is smaller than the cross section of the container. The horizontal protruding surface of the grid almost covers the entire cross section. The stripping gas is added below the lowest grid and rises to contact the catalyst.

A gas collection space created by the bottom surface of each grid and one or more sidewalls collects the upward flow and stripping gas.

The sidewalls of each grid include at least one skirt that isolates the gas collection space from the downwardly flowing catalyst. Each skirt has two or more sets of gas inlets or holes in evenly spaced horizontal rows of holes. Each set of holes is sized to produce a gas jet that jets and distributes stripping gas from the gas collection space into the downward flow of catalyst. Each set of holes is of a different size so that the jet length is different and the stripping gas spans the width of the downward flow of the catalyst.

To explain the FCC process in more detail, the FCC
The feed to the equipment is typically an oil such as light oil or vacuum gas oil. Other petroleum derived feedstocks for FCC units are mixtures of heavier hydrocarbons such as diesel boiling range hydrocarbons or dry residue.

Preferably, the feedstock has a boiling point greater than about 232°C, more preferably greater than about 288°C, as measured by a suitable ASTM test method. It is becoming common to use FCC type units, RCC (residual crude cracking) units, or resid cracking units to process heavy feedstocks such as atmospheric dropless resid.

FCC process equipment consists of a reaction zone and a catalyst regeneration zone. In the reaction zone, the feed stream is contacted with a micronized, fluid catalyst at elevated temperatures and medium pressures. Contact between the feedstock and the catalyst takes place in a relatively large fluidized bed. However, the reaction zone in modern FCC equipment usually consists of a vertical conduit or riser as the main reaction section, and the effluent from the conduit enters a large capacity process vessel, which is a separator vessel. The residence time of the catalyst and hydrocarbon in the riser is only a few seconds for the cracking reaction to be nearly complete. The flowing vapor/catalyst stream leaving the riser can enter a solids/steam separator located in the separation tank from the riser or directly into the separation tank without passing through an intermediate separation device. In the absence of an intermediate separator, the flowing vapor/
Falling away from the catalyst flow. One or more additional solids/vapor separation devices are usually located in or on top of a large separation vessel, although most certainly a cyclone seven palator. The reaction products are separated from some of the catalyst carried by the steam stream by the cyclone or cyclones. The steam is then exhausted from the cyclone and separation zone. The spent catalyst falls towards the bottom of the separation tank. The stripper may have a reaction zone (or separator tank) at the bottom, or the spent catalyst can be passed from a reaction riser or a separator tank to the stripper.

After passing through the stripping device, the catalyst is transferred to a separate regeneration zone.

The rate of conversion of the feedstock within the reaction zone is controlled by the regulation of temperature, the activity of the catalyst, and the amount of catalyst retained within the reaction zone (ie, catalyst/oil ratio).

The most common method of regulating the temperature of the reaction zone is by adjusting the rate of circulation of catalyst from the regeneration zone to the reaction zone, which simultaneously changes the catalyst/oil ratio. That is, if it is desired to increase the conversion rate in the reaction zone, the flow rate of catalyst from the regeneration zone to the reaction zone is increased. By doing this.

Even with the same amount of oil charged, there will be more catalyst in the reaction zone.

During normal operation, the temperature of the regeneration zone is significantly higher than the temperature of the reaction zone, so increasing the circulation rate of catalyst from the regeneration zone to the reaction zone will increase the temperature of the reaction zone.

The chemical composition and structure of the feedstock used in the FCC unit affects the amount of coke deposited on the catalyst in the reaction zone. Typically, the molecular weight of the raw material, Conradson Carbon (Conr
adson carbon).

The higher the heptane insolubles and the carbon/hydrogen ratio, the higher the coke concentration on the spent catalyst. Also, high concentrations of bound nitrogen, such as those found in shale-derived oils, result in more coke on the spent catalyst.

When processing heavy feedstocks, such as deasphalted oils or atmospheric residues (commonly referred to as dry residues) from feedstock fractionators, some or all of these factors may be affected. increase

The term "spent catalyst" as used herein refers to the catalyst used in the reaction zone that is transferred to the regeneration zone to remove deposited coke.

This term does not mean that the catalyst particles have lost all their catalytic activity. The term "spent catalyst" shall have the same meaning as "spent catalyst".

Due to the widespread use of vertical tubular conduits, they are usually referred to as "riser pipes"
The reaction zone, referred to as the reaction zone, is maintained at a temperature of about 48°C, generally above about 427°C;
2°C to about 592°C.

It is preferable to maintain the decomposition conditions at a pressure of 69 to 517 kPa (ga), but the pressure is approximately 276 kPa (ga).
(ga) is preferable. Based on the weight of catalyst and feed hydrocarbon entering the bottom of the riser, the catalyst/oil ratio is 20
:1, but about 4:1 or lO:
It is preferable that it is 1. Although hydrogen is not normally added to the riser, hydrogen addition is known in the art. Optionally, the steam can be passed through a riser. The average residence time of the catalyst in the riser is preferably less than about 5 seconds. The type of catalyst used in this process can be selected from a number of commercially available catalysts, with zeolite-based catalysts being preferred. Moreover, it can be used even when older types of amorphous catalysts are required. Further information regarding the operation of FCC reaction zones can be found in U.S. Pat. No. 4,541,922, 4.
No. 541.922 and the above-identified patents.

In some FCC processes, catalyst is continuously recycled from the reaction zone to the regeneration zone and back to the reaction zone. The catalyst thus acts as a carrier that transports heat from zone to zone and at the same time provides the necessary catalytic activity. Catalyst removed from the regeneration zone is referred to as "regenerated" catalyst. As mentioned above, the catalyst charged in the 5 regeneration zone is
The coke is brought into contact with an oxygen-containing gas, such as air or oxygen-enriched air, under conditions that cause it to burn. As a result, the temperature of the catalyst increases and a large amount of hot gas is generated from the regeneration zone as a gas stream called the flue gas stream. The regeneration zone typically operates at a temperature of about 593°C to about 788°C. F
Further information on the operation of CC reactions and regeneration zones can be obtained from US Pat.

The catalyst regeneration zone is preferably about 34 to about 517k
It operates at a pressure of Pa (ga). The spent catalyst charged to the regeneration zone contains about 0.2 to about 5 weight percent coke. Coke predominantly contains carbon and about 5 to about 15 weight percent hydrogen, and sulfur and other elements. Oxidation of coke typically produces carbon dioxide, carbon oxides, and water as combustion products. As is well known to those skilled in the art, there is some structure to the regeneration zone, and regeneration occurs in one or more steps. Further step variations are possible, since the fluidized catalyst can be regenerated as a dilute phase or a concentrated phase within the regeneration zone. The term "dilute phase" shall refer to those in which the catalyst/gas mixture has a density of less than 320 kg/m, and similarly the term "concentrated phase" shall refer to those in which the catalyst gas mixture has a density of 320 kg/m or more. shall be taken as a thing. Typical dilute phase operating conditions include catalyst/gas mixture densities of about 16 to about 16
Often 0 kg/m.

〔Example〕

The present invention will be further described with reference to the drawings, which are for the purpose of illustrating particular embodiments of the invention and are not intended to limit the general scope of the invention as set forth in the claims.

FIG. 1 illustrates one type of reaction zone that can be used to carry out the FCC process. The reaction zone consists of a riser 52, a separated phase 1, and a stripper 2 (or stripping vessel 2). The stripping tank 2 is attached to the bottom of the separation tank 1, and the riser pipe 5 passes through the center of the stripper and enters the separation tank. The catalyst and hydrocarbons above flow up in the riser pipe 5, reference number %7.
indicates the inside of the riser pipe 5. The location where the catalyst and hydrocarbon vapors are introduced into the riser 5 is not shown.

The fluid mixture flows out of riser 5 and the bulk of the catalyst is separated from the gas stream in cyclone 13. This catalyst falls into the lower part of the separation tank 1 above a portion of the stripper.

Reference number 10 indicates the height of the catalyst in the lower part. The steam and some catalyst exit the top of cyclone 13 and enter cyclone 11 along with the steam from the stripper.

Fine powder, that is, minute catalyst particles are entrained in the steam flow, separated by the cyclone 11, and fall downward. A vapor stream consisting of hydrocarbons leaves cyclone 11 via conduit 12. The hydrocarbon product in conduit 12 flows to a suitable product recovery system (not shown) which consists of a fractionation column, commonly referred to as the main column, and a separate separation unit, commonly referred to as a gas concentrator.

Other than the two cyclones shown in FIG. 1, there are various configurations of the vapor/solid separation device inside the separation tank 1.

The waste catalyst flows downward from the lower region of the separation tank 1 and enters the stripping tank 2. The stripping vessel 2 is oriented substantially vertically so that a heavy flow passes the catalyst to the stripper vessel.

The elongated shape creates a vertical distance that allows the catalyst to remain in the stripping vessel for the desired amount of time. The outer wall of the riser 5 and the inside of the vessel 2 create an annular space through which the catalyst flows in the flow indicated by reference numeral 8.

This annular space open to the catalyst flow is furthermore called the cross-sectional area in boat fishing. The catalyst is moved from the bottom of the stripper 2 by conduit 4, which draws it out and sends it to a regeneration zone (not shown) for coke removal.

FIG. 1 shows a series of baffles located in an annular space. The baffle is made up of grid members 18.20 and 14, with each grid having scars 1-19.2.
1 and 15 are attached. The term "grid" is a common term in industry and is therefore referred to herein as a "grid" or "grid member." Term "grid"
or "grid member" is a term relating to the means by which the catalyst is cascaded from side to side as it flows downwardly under the influence of weight within the stripper. Although the grid may be one of a variety of geometric shapes, grids of various shapes are shown in this figure. For example, the grid 14 extends completely horizontally around the stripper and is attached to the interior wall surface around the entire periphery of the stripper. The grid 20 extends completely around the stripper and is attached to the outer wall of the riser along the entire circumference of the riser. grid 18
．． Both 20 and 14 have a frusto/conical shape and extend downward in an annular space. The three grid members drawn in Figure 1 are skirts 19, 21 and 15.
attached to form a baffle. Moreover, it is attached to the lowest edge of the grid and extends downward. The skirt is shaped to match the curvature of the bottom edge of the grid to which it is attached. For example, each skirt in Figures 1 and 2 is cylindrical. As shown in FIG. 3, each grid projects horizontally across the annular space.

FIG. 3 shows the stripper 2 and the riser tube 5 concentric with the outer plate of the stripper 2. FIG.

Reference number 7 indicates the inside of the riser pipe 5. The cross section of FIG. 3 is drawn so that the skirt 15 can be seen. The dotted line indicates the position of the skirt 24. The diameter of the skirt 24 is the same as that of the riser pipe 5.
Note the other skirts attached to the grid 5 related to the riser pipe 5, which are slightly smaller in diameter than the skirt 24 and also attached to the grid related to the outer wall.
and an assembly consisting of a grid member and a skirt related to the riser pipe 5 can be pulled out in an upward direction.

Obviously, the horizontal protrusion area of each grid must be much smaller so as not to cover the entire annulus through which the catalyst flows. The sum of all horizontal protrusions of each grid is typically 40 to 80 percent of the cross section. Collectively, the horizontal projections of the grid substantially cover the cross-sectional area. By substantially covering an annular cross-sectional area, the grid increases the contact between the catalyst and the stripping gas. The grid arrangement allows the catalyst to move end to end, leaving no vertical path for the catalyst or stripping gas to pass unobstructed. Recognizing the common stripper construction in which the inner grids 20 and 27 are attached to the riser pipe before inserting the riser pipe 5 into the stripper, the arrangement of the grids that substantially covers said passages has been designed. In order to insert the riser pipe and the inner grid later, the outer diameter of the inner grid is made slightly smaller than the inner diameter of the outer grid. This creates an annular open space between the grids between the skirts 15 and 24, as shown in FIG. Figure 3 shows a normal range of 2.5 to 5. The gap between Oan is exaggerated. Since the stripping tank usually has a total diameter of 1.5 meters or more, the direct flow area with respect to this gap is quite large.

1 and 2 depict the space under the grid member when no catalyst is filled. This space is 9
．． 22, 23 and 29 for grids 20.27.14 and 26, respectively. These spaces are gas collection spaces and collect the ascending stripping gas in a manner as described below. Gas collection space 23
and 29 are formed by the lower surface of the grid and a pair of side surfaces consisting of a skirt on one side and a container wall on the other side. The gas collection spaces 9 and 22 are formed by the lower side of the grid and a pair of side surfaces consisting of the vessel wall and the outside of the riser pipe 5.

Grid member 14 can be used as an example of a portion of a grid group that includes grids 18 and 26. These are called outer grids. That's 360 around a stripper
It expands and is tightly mounted inside the wall of the stripper tank, so that gas and catalyst cannot pass between the green of the grid member 14 and the inner wall of the stripper. Reference numeral 28 in FIGS. 2 and 4 indicates the attachment point. Since FIG. 4 is a cross-sectional view, the attachment is continuous, ie, spans the perimeter 36 (one degree) of the stripping container.

Grid member 27 can be used as an example of a portion of a grid group that also includes grid 20.

It adheres to the outside of the riser pipe 5 and around the riser pipe 5 36
It extends over 0 degrees. Figures 1 and 2 show skirt 19.21. Is, 24, and 25 are shown. Although the total number of grids shown in FIGS. 1 and 2 was chosen arbitrarily, it should be noted that fewer or more grid members may be needed in practice.

Add stripping gas to the stripping bath from below the lowest grid. Steam is the most commonly used stripping gas.

After the stripping gas contacts the catalyst, it mixes with the hydrocarbon vapors stripped from the catalyst. The term "stripping gas" refers to the gas injected into the riser and the mixture of hydrocarbons and injected gas found high in the stripper. The catalyst is shown in the left-hand part of the annular space 8 in FIG. 2 and is also present in the right-hand part, but is not shown in the drawing.

Arrows are drawn in the right-hand portion of FIG. 2 to indicate the direction of flow of the stripping gas outside the perforations of the skirt having a series of perforations and past the catalyst. Figure 4 shows ring 1
7 is a longitudinal cross-sectional view showing the grid member 26 and the skirt 25 with reference numeral 7 omitted. FIG. The skirt 26 has stripping gas distribution holes, designated by reference numerals 30.31. in FIG. and 32
is shown by. There are numerous holes in each skirt shown in FIGS. 1 and 2, but these have been omitted for the sake of clarity.

It can be seen that the catalyst moves from one end to the other as it descends under the influence of gravity. The gas collection spaces 29, 22, 23, and 9 are relatively catalyst-poor, since the catalyst cannot flow upwards. The angle at which the catalyst falls from the bottom of the skirt, ie, the angle at which the material remains as a mass, is called the rest angle. Slip angle is a related concept and can be defined as the minimum angle at which a material will begin to move from rest on an inclined surface. Each grid member is shown to have a downward slope that is greater than the dip angle. This slope prevents catalyst from pooling on top of the grid in the inclined bank.

Gas distribution holes evenly distribute the stripping gas so that the gas contacts substantially all of the catalyst adjacent each grid and skirt. It therefore contacts all the catalyst in the stripper. Referring again to FIG. 2, the stripping gas enters the distribution pipe 17 via the pipeline 3. Pipeline 3 is shown again in FIGS. 1 and 3. The distribution tube 17 forms a 360 degree ring around the stripper below the grid member. The distribution pipe is
It is penetrated in order to evenly distribute the steam in the annular space 29, which is below the grid 26 and the skirt 25
installed by. However, it is not necessary to use a ring-shaped gas distribution means; any device for distributing steam into the space below the lowest grid and skirt can be used. The stripping gas (steam) flows through holes in skirt 25 (not shown) and then passes through the catalyst as indicated by the right-hand arrow in FIG. steam and grid 26
Hydrocarbons stripped from the catalyst adjacent the skirt 25 flow into the space 22 below the grid member 27 and surrounded by the skirt 24 . The gas is then redistributed through the holes in the skirt 24, past the catalyst adjacent the skirt 24, and into the space 23 below the grid member 14. The gas then passes through the holes in the skirt 15 and through the remainder of the stripper. The hydrocarbon vapors leaving the stripping gas section pass through the catalyst at the bottom of vessel 1, enter the free space of vessel 1, and leave vessel 1 via cyclone 11 together with the hydrocarbon product of the FCC unit.

Figures 5 and 6 show the catalyst sparging means within the cylindrical stripping zone. 6 is a plan cross-sectional view taken along the cross-sectional arrow in FIG. 5. FIG. In this case, the grid members are flat plates and do not have segments to allow the catalyst to flow downwards. The plate is mounted at an angle greater than the sliding angle of the catalyst. Reference numeral 70 designates the cylindrical skin of the stripper; skirts 75 and 73 are attached to grid members 76 and 74. In this embodiment of the invention, the skirts are curved as seen from skirt 75 in FIG. It has a rectangular shape. The dotted line in FIG. 6 indicates the skirt 73.

The stripping gas is supplied to the distribution turf 2 by a pipeline 71, from where it is distributed and flows evenly through holes (not shown) in the skirt 73. In this embodiment of the invention, the distribution turf 2 does not have to be ring-shaped; a straight pipe is sufficient. Gas passes through the catalyst adjacent skirt 73 into space 78 below grid 76 and then through holes (not shown) in skirt 75. Similarly,
The gas passes through the remainder of the stripper before entering a separation tank similar to tank 1 of FIG.

Figures 7 and 8 show another type of catalyst evaporation means within a cylindrical vessel. The outer grid members, such as grid 57, are the same as the outer grid members, such as outer grid 14, shown in FIGS. 1 and 2. As in FIGS. 1 and 2, the outer grid members in FIG. 7 extend horizontally 360 degrees around the stripping bath 50. As shown in FIGS.

The skirt shown in FIG. 7, for example skirt 58, is the same as the skirt shown in FIGS. 1 and 2 attached to the outer grid.

The stripping gas is also conveyed to the stripper by a pipeline 51 and by a distribution ring 52 in the case of FIG. 2 (pipeline 3 and distributor 1).
7) will be distributed in the same way. The central grid members designated by reference numerals 56 and 60 are strippers 50.
located within. Each central grid member is a hollow cone within the base and has a skirt such as skirt 55 attached to its bottom green. Each skirt is a vertical hollow cylinder with a short height dimension. Legs (not shown) extending from each central grid member to the outer grid members bear against the central grid. FIG. 8 shows the cylindrical skin 50 and skirt 59 of the stripper.

The dotted line in FIG. 8 indicates the skirt 5 attached to the grid 57.
8 position is shown. Gas from distributor 52 passes through holes (not shown) in skirt 53 and through a catalyst (not shown) adjacent to skirt 53 and grid 54 to the space below grid 56, indicated by reference number %61. flows into. The gas then passes through holes (not shown) in skirt 55 and rises past a catalyst (not shown) adjacent to skirt 55 and grid 56 to grid 57, indicated by reference numeral 63.
flows into the space below. From there, the gas passes through holes (not shown) in skirt 58 and passes through skirt 5 below grid 60.
It flows into the space 62 surrounded by 9.

The height of the skirt and the number and size of gas distribution holes in the skirt are determined by many factors, such as the geometry of the stripper;
Determined by catalyst throughput, operating pressure, stripping gas flow rate, etc. A person skilled in the art will understand that, without carrying out the invention,
The stripping gas flow rate for a particular device can be determined. Determination of this flow rate relies primarily on experience with the stripping equipment, as there is no rigorous calculation method.

The required stripping gas flow rate when not practicing the invention is the starting point for determining the parameters of the invention. Half of the main flow velocity is regarded as the design flow velocity, and the hole size is determined by this design flow velocity. Those skilled in the chemical and hydrocarbon processing arts can calculate the pressure drop as the gas passes through an orifice or bed of particles. The placement and size of the holes are determined by trial and error. The total pressure drop through the stripper is then calculated. If this pressure drop is unsatisfactory, a different porosity is chosen and the process is repeated. The height of the skirt is determined primarily by the characteristics of the holes, but must not be less than 10 cm.

FIG. 4 shows typical grid member and skirt dimensions. The height of the skirt is 30.48 cm, and there are three rows of holes at three heights, each row forming a horizontal plane and spanning 360 degrees along the skirt. The greater the number of rows of holes, the more completely the stripping gas will be distributed and the more effective the invention will be. However, in the present invention, two rows of holes are effective. The vertical distance between each row of holes is 7.5 crn. There are 24 holes in each row, opening at 15 degrees, so all holes are evenly spaced apart. These holes vary in size to vary the length of the jet produced by each row of holes. As an example of gas distribution holes having various dimensions, hole 30
The diameter of the holes in one row is 1.27 cm, the diameter of the holes in the row with holes 31 is 1.9 cm, and the diameter of the holes in the row with holes 32 is 2.54 cm.

These diameter changes provide better catalyst coverage because the stripping gas covers more of the catalyst stream as the gas jet length is varied. Referring again to FIGS. 1 and 2, the arrows in the bottom layer on the right-hand side of FIG. 2 are marked with numbers corresponding to the holes in FIG. 4 with a dash added. 1.27 Gas passing through a hole flows almost horizontally for a short distance before going upwards. Gas from the large hole, hole 31, flows further horizontally as shown by arrow 3I. Gas from the largest hole flows the longest horizontal distance as indicated by arrow 32. The horizontal distance of gas flow relative to a hole is determined by the hole size, other parameters being the same.

In addition to improving hydrocarbon yields by co-combusting with coke to remove hydrocarbons, the present invention allows for the use of small amounts of stripping steam. For example, in a process that would require about 1.5 kg of steam for 1000 kg of catalyst without the present invention, with the present invention, 0.5 kg of steam would be required for 1000 kg of catalyst.
Experiments have shown that 7 ICg of steam gives satisfactory results.

As an example of the size of a stripper, a relatively small FCC unit with a feed rate of 200,000 bpd (132,48 m/hr) has a nominal diameter of 1
98, 12cm stripper and nominal diameter 76.2cm
It has a riser pipe. Therefore, the width of the radial annular space is 6 (1,96 cm). Referring to Figure 2, the width of the radial annular space below the grid 14 is 22.86 cm.
and the width of the inner grid is 35.56 cm. And it is necessary to use different widths. This is because it is desired that the catalyst move from end to end and maintain a horizontal area with relatively constant flow. This second one is the second
This can be understood by referring to Figures 2 and 3, which show that the catalyst was initially
and 5, and then an outer annular space surrounded by members referenced 2 and 74. It is desirable to increase the size of the holes in the skirt in the upper part of the stripper to accommodate them. The pore size varies from the smallest at the bottom to the largest at the pores. For example, the holes in skirt 21 of FIG. 2 are larger than the holes in skirt 25 of FIG. 2 to accommodate hydrocarbons passing through the holes in skirt 21. It can be seen that virtually no hydrocarbons pass through the holes in the skirt 25, and the amount of hydrocarbons passing through the holes increases with increasing height above the NuTeam distributor.

[Brief explanation of the drawing]

FIG. 1 schematically shows a front view of an FCC process reaction and a separation tank whose lower part is a stripping tank or stripping section. The inside of the tank is indicated by a dotted line. Two partial cross-sections are shown as cutaways. 2 is a partial longitudinal sectional view of the stripping section of FIG. 1. FIG. FIG. 3 is a plan view of the stripper of FIG. 2 taken at section 3--3. FIG. 4 is an enlarged view of one of the grid members of FIG. 5 and 7 are side cross-sectional views of a stripping apparatus having an alternating baffle configuration. 6 and 8 are cross-sectional views corresponding to the stripping apparatus of FIGS. 5 and 7. FIG. The symbols in the figure are as follows. 1... Separation tank 2... Stripping tank 3.4.12... Conduit 5... Rising pipe 7... Inside of rising pipe 8... Annular space 10
... Height of catalyst 11.13 ... Cyclone 17 ... Distribution pipe 14. il1,
20.27...Grid 15, 19.21.24...
・Skirts 9, 22, 23 corresponding to the above grids respectively
．． 29...Space formed by grid 30.31
．． 32... Holes in skirt 15 50... Stripping tank 51... Pipeline 52... Distribution rings 56, 60... Grids 55, 59... Skirts 61 corresponding to each of the above grids... Space under the grid 56 62 Space under the grid 60 63 Space under the grid 57 70 Cylindrical outer plate of the stripper 71 Pipeline 72 Distributor turf 4 , 76...grid

Claims (1)

[Claims] 1. In an FCC stripping apparatus designed for removing occluded hydrocarbons from a continuously circulating steam fluidized particle catalyst by contacting with a stripping gas, (a) Elongated shape, predominantly vertical alignment, cross-section open to descending catalyst flow, source of catalyst particles [
tank [2] having a highest part communicating with [5] and a lowest part communicating with means [5] for drawing out catalyst particles;
(b) Frust/conical shape and initial position (locu
an outer grid [18] having an outer diameter portion fixed to the inside of said container in s), but extending inwardly and downwardly from said initial position with respect to the inner diameter portion; at least one inner grid [20] having a conical shape and an outer diameter portion at least substantially equal in size to the inner diameter of said outer grid [18];
], so that both the inner grid [20] and the outer grid [18] substantially cover the cross section, and means [5] for supporting the inner grid from its outer diameter. ] comprises said outer grid [18] extending inwardly and upwardly toward the
and all said inner grids and said outer grids are juxtaposed vertically in an alternating manner to provide a left and right end-to-side channel for the flow of catalyst to flow down said tank [2]. A set of baffle plates located [18, 20 and 14
]; (c) means [3, 17] for supplying stripping gas to the tank [2] below the lowest grid; and means for extracting the stripping gas from the highest end of the tank [2]; [11, 12]; (d) an outer grid skirt [19] which is cylindrical and has a highest portion fixed to the inner diameter portion of the outer grid [18];
(e) cylindrical in shape; and an inner grid skirt [21] having a highest portion fixed to each outer diameter portion of the inner grid [20];
21], said inner grid [20] and said means for supporting said grid [5] are arranged in an inner gas collection space [
9], said inner grid skirt [21
]; and (f) at least two sets of gas injection holes defined by each skirt [19, 21], each set of holes having uniform hole size, uniform hole spacing and a common vertical height; and each hole in each set has a horizontal centerline protrusion and the channel [8] for catalyst flow.
] having a diameter sufficient to obtain a jet of gas therein, and one set of the at least two sets of holes having a different size than the other set of holes; , so that the gas jets extending from the at least two different sets of holes have different jet lengths [30, 3].
1]. 2. Each grid skirt has at least three sets of holes [30,3
1 and 32], and characterized in that the dimension of the diameter of the largest hole is such that the gas injection reaches at least 2/3 of the length of said channel [8] for catalyst flow. do,
A device according to claim 1. 3. In a stripping device of an FCC unit, in which occluded hydrocarbons are removed from a granular catalyst by contacting with a stripping gas, said stripping device has: (a) an elongated shape, a predominantly vertical arrangement, a descending catalyst flow; (b) a vessel [70] having a cross section open to the air, a highest end communicating with a source of catalyst particles and a lowest end communicating with means for withdrawing the catalyst particles; at least two grids [76, 74] located extending downwardly and inwardly from mutually opposing vertical sides of the vessel, each grid extending inwardly over about half of said cross section; said grids thus substantially covering said cross section and said grids being vertically juxtaposed to provide a flow path from side to side for catalyst flow down said vessel. at least two of the aforementioned grids [76, 74]
(c) means for applying stripping gas to said bath below the lowest part of said grids [71]; (d) vertical skirts [75, 73] at the bottom of each said grid [76, 74]; ], said vertical skirts [75, 73], wherein said grids, said skirts and said vessels form a gas collection space [78] under each grid for receiving stripping gas; ) in at least two sets of gas injection holes [30, 31] in each skirt [75, 73], each set of holes having a uniform hole size, uniform hole spacing and a common vertical height;
Each set of holes has a horizontal centerline protrusion and a limited size to produce a gas jet extending into the flow path, in this case the lowest set of holes in each skirt. FCC stripping device as described above, characterized in that it is combined with at least two sets of gas injection holes [30, 31] as described above, wherein the holes have the largest diameter and thereby produce the longest injection length. 4. At least three sets of holes [30, 31 and 32] are defined by each skirt [75, 73], and the gas injection of the largest hole is at least 2/2 of said channel distance for catalyst flow.
4. The device according to claim 3, further characterized in that it reaches 3.