CN87103951A - Be used for the mixing arrangement that vertical mobile fluid-solid contacts - Google Patents

Abstract

A fluid mixing device for a vertical flow fluid-solid contacting column having a fluid inlet and a fluid outlet at an opposite end thereof. Two or more beds of different granular materials through which a single-phase or two-phase fluid flows during operation. The mixing unit consists of a vertical flow shield and an impingement chamber located in the center of the shield. The impingement chamber creates vortex impingement in the fluid flow path, resulting in improved mixing. Fluid exiting the impingement chamber passes through an outlet that includes a central opening in the shield that communicates with the downstream side of the shield and provides a balanced flow out of the impingement chamber.

Description

Mixing device for vertical flow fluid solid contact

The present invention relates generally to the field of fluid-solid contacting. More specifically, the present invention relates to the problem of fluid mixing between beds of fine particulate material. The scope of the invention is to mix single phase or two phase fluids.

Liquid-solid contacting devices have a wide range of applications. Such devices find widespread use in adsorption columns for hydrocarbon conversion processes and for separation of fluid components. When the fluid-solid contacting device is an adsorption column, the fine particulate material will comprise an adsorbent through which the fluid flows. In the conversion of hydrocarbons, the fluid-solid contacting device is typically a reactor containing a catalyst. Hydrogenation, hydrotreating, hydrocracking, hydrodealkylation, and the like may be accomplished via typical hydrocarbon conversion reactions.

The fluid-solid contacting device employed in the present invention is configured as a vertical elongated cylinder through which a vertical flow of fluid can be maintained. The fine particulate material in such vessels is in a plurality of vertically spaced reaction beds. Fluid enters the vessel through at least one inlet and one outlet at its opposite end. The fluid may flow through the reactor in an upflow or downflow manner. It is also generally known to add or remove fluid from between two beds of fine particles. A quench system is used to cool the fluid flowing between the various beds as the fluid components are changing between beds of particles or during hydrocarbon conversion, which is also the method typically employed in adsorption schemes.

Variations in the composition and properties of the fluid flowing through the fine particle region do not present any problem as long as they occur uniformly. In adsorption systems, these changes are the result of retention or displacement of fluid in the adsorbent. Changes to the temperature and fluid composition in the reaction system are caused by the particulate catalyst material contained in the reaction bed.

Poor initial mixing of the fluids entering the reaction beds, or variations in the flow resistance through the fine particle beds, can result in uneven fluid flow through these reaction beds. Variations in the fluid resistance through the reaction bed can alter the contact time of the fluid in the fine particles, thereby resulting in non-uniformity of the reaction or adsorption through the fluid flow channels of the reaction bed. In severe cases this is known as a fluidisation channel (channelling) in which the fluid flows over a limited portion of the bed into a fine open area with virtually no flow resistance. When channeling occurs, a portion of the fluid passing through the reaction bed will have very little contact with the fine particulate matter of the reaction bed. If the process is one of adsorption, the fluid flowing through the flow-through region will not be absorbed, thereby changing the composition of that portion of the fluid relative to other portions of the fluid flowing through the adsorbent bed. For the catalyst reaction, the catalyst contact time is reduced and the composition of the resulting stream as it leaves the catalyst bed at different locations will also be changed.

In addition to the problems with the fluid composition, the non-uniformity of the fines in the reaction bed can also affect the density and temperature of the fluid passing through the reaction bed. For many separation processes, the retained and displaced components in the fluid have different densities, which can contribute to disruption of the flow pattern of the reaction bed. Uneven contact with the adsorbent particles will exacerbate the problem by causing further changes in the density of the fluid flowing through the bed, and thus further disrupt the flow pattern of the fluid as it passes through the bed.

Within the reaction zone, variations in temperature are often accompanied by catalyst contact non-uniformity due to differences in the endothermic or exothermic characteristics of the system. For uneven contact of the catalyst, the progress of the reaction process will be adversely affected due to overheating or overcooling of the reactants. This problem is most severe in exothermic reactions, where the higher temperatures can further result in undesirable products being produced by the reaction of the feedstock or other fluid components being fed or can cause localized hot spots that can damage the catalyst and/or mechanical components.

Therefore, to reduce the problems associated with the variation of flow through the particulate material bed, methods of fluid remixing between different catalyst or sorbent beds have been incorporated into a wide variety of reaction processes. Means for collecting and remixing a portion of the fluid flowing through the series of particle beds are shown in U.S. patent nos. 3,652,450 and 4,087,252. In these references, the remixing of the streams is carried out in conjunction with the additional mixing of a second stream into the region between the two reaction beds. In these references, the mixing of the fluid flowing between the various reaction beds and the additional fluid is conducted in a number of carefully considered mixing chambers located within the lower boundary of the upper reaction bed or within the upper boundary of the lower reaction bed or between the two.

In U.S. patent No. 3,824,080 to Smith, an internal reactor configuration is disclosed for the flow of a mixture through the fluids between the various reaction beds, independent of the addition of a second fluid in the region. The smith device collects a mixed phase fluid flowing between beds of particles having a horizontal restriction with a central opening for passing fluid between the reaction beds. This central opening has a flow diverter device that directs all vapor flow through the top of the reaction chamber and all liquid flow in through the sides. In the Schmitt invention, the vapor and liquid impinge perpendicularly to each other, thereby acting as remixing. The remixed vapor and liquid flows through the opening of the restriction which contacts another horizontal series of restrictions to provide a uniform flow of fluid through the downstream bed of particles.

U.S. patent No. 3, 598, 541 to hennemus et al (Hennemuth et al) teaches: remixing of the fluid flowing between the individual beds of particulate material is achieved by direct impingement of quench fluid introduced into the mixing zone. Mixing takes place in a central space through which all the fluid passes. The central space includes an annular region defined by two vertical cylinders. Fluid flowing between the reaction beds enters through a plurality of horizontally disposed holes, and quench fluid enters the inner barrel through the horizontally disposed holes. The lower end of the annular mixing zone communicates with the downstream particle zone for passage of the mixing fluid.

It is an object of the invention disclosed herein to improve the mixing of various fluids between the reaction beds of particulate material. It is another object of the present invention to achieve mixing of the fluids flowing between the beds of the reactor independently of the addition of a second fluid to the region between the beds of particles. It is a further object of the present invention to provide a simple means for achieving mixing of the fluids between the reactor beds which is easily performed in a minimum space between the individual particle beds.

Accordingly, one embodiment of the present invention comprises a fluid mixing chamber for a vertical flow fluid-solid contactor having a fluid inlet and a fluid outlet at opposite ends thereof, and two or more vertically spaced discrete beds of particulate material.

In a more specific embodiment, the fluid mixing chamber comprises a vertical flow barrier positioned between two beds of particles having a substantially non-porous outer region and at least one central opening for fluid flow between the regions, a fluid impingement compartment positioned in the center of said barrier, the compartment having a vertical sidewall with at least two identical inlet openings sized to create a fluid jet communicating with the upstream end of said barrier for receiving fluid blocked by the barrier, the vertical sidewall of the compartment being positioned so that projections of the axial centerlines of all inlet openings lie in a common horizontal plane and intersect at a preselected point to cause fluid entering the impingement compartment to be concentrated at a center point equidistant from each inlet opening and within the fluid jet range, at least one fluid outlet from the impingement compartment, the outlet having an area greater than the sum of the areas of the inlet openings, the outlet communicating with the downstream end of the barrier and providing a balanced flow to the downstream region of the barrier, means at the upstream end of the barrier for conveying an equal amount of fluid from the periphery of the barrier to each inlet opening, and means for redistributing the flow from the outlet of the impingement compartment downstream through the bed of particles.

More limited embodiments of the invention include various means for applying, distributing, collecting or discharging fluid into or out of the impingement compartment and specific means or structures for fluid collection barriers between the particle bed and the impingement compartment.

In its broadest aspect, therefore, the present invention is directed to a centrally located mixing element for receiving the entire flow of fluid into the downstream bed. The mixing element functions to provide thorough mixing of the fluid and to move the mixed fluid in equilibrium downstream of the particle bed to promote redistribution of the fluid. The mixing of the fluids is essentially achieved by the structure of the mixing zone. The fluids are directed into each other in equal jets in this region, thereby creating turbulence which promotes vigorous mixing in the mixing region and provides a fluid effluent of uniform composition. Thus, an important component of the present invention is to provide a means for directing the introduction of equal amounts of fluid into each other to increase turbulence during mixing. Other objects, embodiments and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, in view of this basic idea.

FIG. 1 is an elevational view, partially in section, of a vertical flow contact column of the present invention having multiple catalyst beds and mixing apparatus located between each of the particle beds;

FIG. 2 is a perspective view of a mixing device removed from the support of the internal components of the contact column of FIG. 1;

FIG. 3 is a partial elevation view of a downflow reactor with portions partially broken away showing a more limited embodiment of a mixing chamber having a plurality of parallel channels for collecting fluid flowing through a rectangular mixing zone;

FIG. 4 is a plan view showing a channel collection system for the mixing zone shown in FIG. 3;

fig. 5 is a perspective view for illustrating the mixing region in the channel part in fig. 3 and 4.

As mentioned above, the present invention relates to a fluid mixing device between particle beds in a fluid-solid contacting apparatus. The basic elements of the invention comprise a sealed vessel, one or more beds of particulate material provided in vertically spaced apart regions and a mixing chamber between each bed of particulate material. The invention resides itself in the particular arrangement of the mixing chamber and the components therein. A more complete understanding of the interrelationships between the various elements within the mixing chamber and within the vertical flow column can be obtained by reference to the figures.

With particular reference to FIG. 1, the elevation view in section shows a contacting column 1 with a fluid inlet nozzle at the top of the column and a fluid outlet at the bottom of the column. Located within the reaction chamber are zones 2, 12 and 14 at the catalyst level.

Each bed of particles is made up of particles which may be in the form of pellets, cylinders or other extruded shapes. The actual properties of the particles will depend on the action process achieved in the sealed container. Generally, the term particle as used herein shall include adsorbents or catalysts. Above each bed of particles is a layer of support material 3 which serves to hold the particles down and enhance flow distribution throughout the reaction bed. Such support materials (which are often used, but not the base material) are typically made of ceramic pellets or other inert substances having a regular shape. Support material 4 is also often used to underlie the particle bed to prevent migration of catalyst particles through a perforated template or shield member 5 which serves to define the lower boundary of the particle bed. The support material at the bottom of the catalyst bed is identical in shape and construction to the support material above the reactor bed.

Located between each reaction bed is a fluid collection and mixing zone. Immediately below the particle retention plate 5 is a fluid collection zone 6. The fluid collection zone allows for the transport of fluid through the shield 8 into the impact chamber 7. As shown in fig. 1, the collection area may be formed by an empty space to allow the fluid to flow in a horizontal direction. However, as discussed in further detail in connection with fig. 3, 4 and 5, the collection area may be integral with the shield 8 so that the various elements that restrict fluid flow may also direct fluid into the impingement compartment. Thus, the fluid collection apparatus is not limited by a configuration, but contemplates any method of fluid passage to the impingement compartment. In its simplest form of construction, the flow screen 8 will comprise a plate mounted and sealed to the side wall of the contact tower, the plate having a central opening through which the impingement compartment 7 is disposed. However, the shield may take any desired shape to prevent fluid flow at any location other than through the openings of the impingement compartment. The restriction of the screen or baffle to prevent fluid flow is to take into account that the particulate material from the various reaction beds is often unloaded from the bottom of the vessel through the various particle beds being laid down. To accomplish this unloading, it is common to provide vertical conduits in the grid between the individual reaction beds to provide a passage for the particulate material from one bed to the next for discharge from the contacting column. It is within the contemplation of the invention that the shield contains several such conduits. These conduits are typically open but filled with an inert support material as described above. The resistance to fluid flow through these conduits is therefore much greater than that of the impingement compartment and collection system described above, with the end result that the amount of fluid passing through these conduits will be less than 5% of the total amount of fluid flow between the individual reaction beds.

The impingement compartment, which will be described in more detail below, receives the fluid from the collection space 6, after sufficient mixing to allow it to pass through a shield 8, below which is another space 10 through which the fluid is redistributed. Again in the simplest form of construction, this redistribution zone is a simple space between the outlet of the impingement compartment and the top of the catalyst bed downstream thereof. However, it is also possible to include other means such as baffles, flow diverters or vapor-liquid trough plates to further assist in redistribution of the fluid flowing through the top of the downstream catalyst bed. Within the redistribution zone 10 a nozzle and a pipe system 9 are shown for feeding or discharging fluid to the contacting column. The nozzle may be used to selectively add or remove fluids of various compositions during the separation process. For downflow reactors, the particular use of the nozzle is to add a quench medium to cool the reaction medium entering the next catalyst bed. It is within the contemplation of the invention that the nozzle and conduit system shown in fig. 1 is arranged below the shield plate 8, whereas the nozzle and conduit system is arranged above the shield plate 8, and possibly on the uppermost part of the catalyst bed downstream or on the lowermost part of the catalyst bed upstream. The mixed fluid enters the next bed of particulate material from which it can continue through the subsequent remixing zone and the respective beds of particulate material before exiting the contacting column through a suitable outlet.

Figure 2 shows an embodiment of an impact chamber. The impingement compartment is made up of two side walls with two inlet openings 16 and 17, a wire screen outlet 20 at the bottom, an imperforate roof 15 and imperforate two side walls 18 and 19. The impact chamber is not limited to any particular shape. For example, the impact chamber may be formed by a vertical cylinder with inlets on the side and a bottom outlet. But with some general dimensional limitations as will be described in more detail below. The primary function of the impingement compartment is to provide uniform mixing of the fluid passing between the individual beds of particulate material. Such uniform mixing is achieved by the determined orientation and size of the inlet openings 16 and 17. The openings are sized so that the fluid entering through each opening forms a jet or a concentrated flow path. The inlet positions are arranged so that the fluid jets impinge in mutually opposite directions at the centre point of the impingement compartment. Only two inlet openings are shown in fig. 2, but more than two inlet openings may be arranged in a symmetrical fashion, so that their impact forces of the jets in all directions cancel each other out. The vertical positioning of the access opening is also important to the present invention. All inlets should be located at the same height. Such equal heights are necessary to provide a constant velocity impact velocity without an imbalance component. Finally, it is not necessary for the shape to be such that the access opening is not rounded. The essential requirement for the inlet opening is merely to limit its cross-sectional dimension in order to form the desired fluid jet.

Obviously, the number and size of the openings will determine the length of the fluid jet for any given pressure drop across the impingement compartment. However, practical considerations will limit the length of the jet stream, since it is generally desirable to reduce the pressure drop in a vertical flow column. As is well known to those skilled in the art: i.e., pressure drop, is a function of fluid velocity and average fluid density. Various methods for calculating the jet length and the pressure drop across an opening or openings have long been known to those skilled in the art. For the most part the fluid to which the invention is applied has its openings dimensioned such that their velocity is in the range of 4.6 to 15.2 m/s. The size of the mixing chamber must be such that it ensures that the jets of fluid will impinge with sufficient velocity to achieve adequate mixing of the fluids. Therefore, the distance between any entrance opening and the center point of the impingement compartment must not exceed 60% of the calculated length of the jet. Thus, consideration of the pressure drop and jet length will determine the length or diameter of the impingement compartment.

Although any shape of impingement compartment may be used, a square or rectangular impingement compartment with only two access openings is particularly suitable due to its simplicity and applicability to the channel collection apparatus described below. When there are only two circular openings in the impact chamber, the maximum distance between the two openings should not exceed six times, preferably less than three times, the diameter of the inlet opening. Reducing the spacing between the two inlets will promote increased swirl and better mixing. Of course some distance between the two access openings must be maintained. The minimum distance needs to be taken into account in order to have a sufficient discharge opening area and also to maintain the necessary length-to-width ratio for the impact compartment.

In addition, in order to increase the turbulence or mixing, the overall height of the mixing chamber should not exceed four times the vertical dimension of the inlet opening. Likewise, to prevent stagnation zones in rectangular configurations, the width of the impact compartment should also be limited to within four times the horizontal dimension of the access opening. In the case of an impact compartment formed by a vertical cylinder with a circular cross-sectional area, the diameter of the impact compartment can be controlled regardless of the limits on the entrance opening and the spacing or the maximum width.

Referring again to fig. 2, the impingement compartment contains at least one discharge opening 20. The most important limitation of the discharge opening is that its open cross-sectional area exceeds the total cross-sectional area of the inlet opening. This is of course necessary to allow jets of fluid to be formed at the various inlets of the impingement compartment. With respect to velocity, it is generally desirable to design the exit velocity so that it does not exceed 4.6 m/s and preferably is less than 3 m/s. Although any restriction to the shape of the entire outlet is not necessary, the openings may be of the wire type as shown in FIG. 2, or may be perforated plates or wire screens. These restrictions on the outlet are often intended to improve flow distribution, to retain particulate material or to reduce foaming due to turbulent mixing of certain fluids. The location of the discharge opening is furthermore not limited on the side of the impact compartment, and the discharge opening may in fact be multi-open. One or several discharge openings may be provided in any side wall of the impingement compartment communicating with the downstream portion of the mixing chamber, as long as the opening or openings are symmetrical to the centre line of the impingement compartment. The only restriction to the discharge opening or openings is the symmetrical position of the downstream bed to deliver an equilibrium flow of fluid from the impingement compartment into the downstream particle bed. In this case, redistribution of the fluid throughout the bed of particulate material is advantageous.

Although FIG. 1 generally shows an apparatus for use as a downflow reactor, the present invention is not limited to a single direction of flow through the reactor column. In an upflow reactor, the inlet must be in communication with the lower particle bed and the impingement compartment is inverted so that the outlet of the impingement compartment leads to an upper redistribution zone. Thus, the mixing chamber of the present invention can be used in either an upflow or downflow configuration as well.

As noted in the prior art, many intermediate mixing devices employ an additional external fluid as an integral part of the mixing operation. In contrast, the present apparatus does not require any additional fluid to be passed between the individual beds of particulate material to effect mixing of the fluids. Thus, the invention has the advantages that: to provide good mixing of the fluid passing between the individual particle beds without additional addition or removal of fluid. Another advantage of the present invention is that the overall structure of the crash compartment is simple and compact. These features make it possible to cooperate with the mixing chamber of the invention to fit into the space between the existing beds of particles without requiring an enlargement of the internal structure of the contact area.

In addition to the impingement compartment, other components of the mixing chamber include the aforementioned distributors, support materials, shield plates, and piping networks. The design of these components depends on a number of factors. Among these factors are: the pressure drop allowed in the apparatus, the composition of the fluid passing between the individual particle beds, and the operating conditions in the contact zone. Furthermore, for the mixed phase system, the amount of vapor or liquid flowing between the individual particle beds will to a large extent determine the type of shielding required, the size of the inlet and outlet openings through the shielding and the appropriate redistribution means. Other considerations that will affect the overall size and configuration of the mixing chamber is an additional chiller. The placement and control of the quench distribution system would require additional space within the mixing zone. Of course, the factors mentioned here do not at all exclude a series of mechanical and process considerations, which should be taken into account in the design of the mixing chamber. However, consideration of such problems is well known to those skilled in the art and need not be described in detail.

The mixing device of the invention is particularly suitable for downflow reactors and is fitted with a screen or a screen consisting of a series of channels. Such reactors are well suited for carrying out hydrogenation, hydrotreating, hydrocracking and hydrodealkylation reactions. When exothermic reactions are completed, such as hydrotreating and hydrocracking, it is common to apply quench streams between the catalyst beds to control the temperature of the various reactants. The action of the mixing zone (independent of the quench stream provided by the present invention) is particularly suitable for such exothermic reactions. The amount and temperature of the quenching agent (which typically contains hydrogen) must be reduced as the catalyst deactivates as it continues to function in the reaction zone. The reduction in cooling requirements for quenching poses a number of problems for those applications in the remixing zone where coolant is provided as part of the mixing action. In such systems, it is often necessary to vary the temperature of the coolant to achieve reduced cooling, while still maintaining a suitable liquid volume of externally applied quench medium within a mixing zone. Since the addition of the quenching agent in the present invention is independent of the impingement compartment, varying the amount of quenching agent will not have much effect on the mixing of the reactants.

However, it is also important to obtain good mixing of the quench agent flow channels and the reactants. It is particularly advantageous to locate the distribution system for the quenching agent upstream of the impingement compartment when it is possible to obtain a suitable mixing of the quenching agent by means of a distribution system for the line downstream of the impingement compartment. The quench agent flow path is located at the front of the impingement chamber and there are two opportunities for mixing the quench medium with the reactants. The first mixing of the quench medium occurs at the point of initial distribution of the quench agent into the reactants, and the second mixing occurs as the quench agent and reactant flow through the impingement chamber.

Attention is now directed to FIGS. 3, 4 and 5, wherein a specialized assembly of quench systems, vertical flow shield and impingement chamber are loaded into a downflow reactor with proper fit. In this embodiment, a general flow scheme as shown in FIG. 1 is provided. Thus, the reactants enter a vertical elongated reactor and flow through several catalyst beds and intermediate mixing chambers. Referring now to fig. 3, a detailed structure of the intermediate mixing section is shown.

In this apparatus, the reactants flow downwardly through the catalyst bed while the quench medium is applied to the nozzles 23 and distributed throughout the lower cross-sectional area of the catalyst bed by the conduit distribution system 24. The reactants continue through the support material 25 which is laid down on the wire screen 21. After passing through the screens, the reactants and quench media are collected in series parallel channels 27, 61 and 62, which are horizontally disposed and open to the upper portion of the catalyst bed. Fluid is delivered from the outer channel 27 through the intermediate channel 61 into the central channel 62 by conduits 28 and 29 which allow fluid to flow between the channels. The central passage 62 is divided into two by the impingement compartment as shown in figure 4. In order to provide equal amounts of fluid to each side of the impingement compartment, four conduits are used to provide equal flows of fluid to each side of the impingement compartment. After exiting the outlet of the impingement compartment, the fluid enters the redistribution zone 40 where the vapor and liquid are redistributed over the entire area of the lower catalyst bed. To promote better distribution of the mixed vapor and liquid flow paths, a vapor liquid redistributor trough plate 51 is placed on top of the lower catalyst bed. Various versions of these trough plates will be apparent to those skilled in the art and include a horizontal trough plate portion 51 and vertical conduits 50 disposed therein. The duct also has a top cover with a V-shaped channel opening at its upper portion for receiving steam and porous side portions adjacent the upper channel plate surface for passage of liquid. Through the vapor liquid redistributor trough plate, the fluid enters another open area 52 where further redistribution may take place. The fluid then flows through a layer of support material 53 and continues through the next catalyst bed 54.

A more complete understanding of the collection channel and the means of the impingement compartment can be obtained from fig. 4, which is a plan view showing the internal structure of these means. The channel has partitions at both ends, which match the contour of the vessel shell. The outer collecting space 27 may be connected to the next inward passage by a single conduit 28. The conduits attached to the channels are designed to meet the minimum pressure drop requirement. The maximum velocity of the fluid through conduits 28 and 29 should not exceed 4.6 m/s and is preferably below 3 m/s. The fluid collected in the intermediate channel 61 flows through the central channel 62, which includes the impingement compartment 30, together with the fluid from the outer channel 27. The fluid is directed into the central passage in a symmetrical manner to provide equal volumes of fluid to both sides of the impingement compartment. Figure 4 also shows vertical conduits 55 which are all used to unload catalyst from the reactor as described above.

Figure 5 shows an impact module disposed in the central passage 62. As can be clearly seen in the figure, the impact compartment is integral with the channels on the three sides 56, 57 and 58. These sides contain a porous member in the region of the impingement compartment which serves as an outlet for the mixed fluid. In this particular embodiment the two facing edges 59 and 63 are provided with an access opening 60 (circular hole shaped) which is at a height below the depth of the channel. This reduced height allows additional fluid to pass through the top of the impingement compartment, which serves to compensate for any imbalance in fluid flow to the inlet. However, it is also possible that the respective end plate provided with several access openings completely blocks the cross-sectional area of the channel.

This embodiment is not meant to limit the manner in which a passageway may be integrated with the crash compartment. The impact module and channel of the present invention may be incorporated into any number of devices. Other possibilities include having the inlet flow passage to the impact chamber flow in a direction perpendicular to the main axis of the passage or using an even number of passages with the impact chamber disposed between two central passages.

The economic value of the internal structure of the apparatus shown in FIG. 3 can be readily understood by those skilled in the internal structure of the reactor. First of all the collection channels for the fluid, which also constitute the screens or baffles, the vertical flow paths for the flow are constricted and hardly any space in the vertical direction is required in the reactor. In addition, the channels are easily manufactured with a support flange portion 42 to mate with a plurality of parallel support columns 26, which are typically used to support the catalyst bed. Furthermore, the impact chamber does not require additional space, and it can be conveniently located in the central passage. It is also advantageous to provide a channel collection system that does not interfere with the quench distribution system at the upper portion of the support column. Thus, the collection channels and impingement modules provide unique benefits to the intermediate mixing zone whether placed in a downflow reactor or, more generally, a vertical flow fluid solids contacting column.

Claims (8)

1. A fluid mixing apparatus for a vertical fluid-solid contact tower having at least one fluid inlet and one fluid outlet at opposite ends thereof, two or more vertically spaced beds of particulate material, said mixing chamber comprising: a) a flow shield for substantially preventing vertical flow of fluid between any two adjacent reactor beds, the flow shield having an imperforate exterior area and at least one central opening for allowing fluid to pass between the reactor beds; b) a fluid impingement chamber centrally located within the shield, having vertical sidewalls containing at least two identical inlet openings, the inlet openings communicating with the upstream end of the shield for receiving fluid blocked by the shield into the impingement chamber, the sidewalls and inlet openings being arranged so that the projections of the axial centerlines of all inlets lie in a common horizontal plane and intersect at a preselected point so that fluid entering the impingement chamber will be concentrated at a center point equidistant from all inlet openings, the inlet openings being sized to produce a fluid jet having a length at least equal to the distance from the inlet opening to the center point; and at least one discharge opening comprising a central opening in the shield having an opening area greater than the sum of the areas of all inlet openings, the central opening communicating with the downstream end of the shield and providing a balanced flow toward the downstream region of the shield; c) means on the upstream side of the shield for transferring equal amounts of fluid from the perimeter of the shield to each inlet opening; d) A means for redistributing the fluid from the impactor chamber outlet across the downstream particle bed. 2. The device of claim 1, wherein the outlet of the impact chamber is formed of a porous plate, a formed wire, or a filter material. 3. The apparatus of claim 1, wherein the impact chamber is substantially rectangular with a plurality of circular inlet openings provided in two opposed vertical side walls and a plurality of outlet openings provided in either of the other two side walls. 4. The device according to claim 1, characterized in that said conveying and redistributing means are formed by the shielding plate and the free area between the upper and lower boundaries of the particle area. 5. The apparatus of claim 1, wherein the inlet opening of the impact chamber is sized to allow an inflow velocity within the range of 4.6 to 15.2 m/s, and the outlet opening of the impact chamber is sized to allow a maximum velocity below 4.6 m/s. 6. The device of claim 3, wherein the distance between two opposing inlet openings is not greater than six times the diameter of the inlet openings. 7. The device of claim 6, wherein the maximum dimension of the impact chamber in a direction perpendicular to the centerline of the entry opening should not exceed three times the diameter of the entry opening. 8. The apparatus of claim 1, wherein said shield comprises a plurality of open parallel channels recessed toward the upstream particle region and interconnected by conduits so that fluid is collected in said channels and conveyed toward the impact chamber.

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