Cyclone trickle valve assembly

Abstract: An improved cyclone trickle valve assembly in a catalytic and thermal reactor (10), includes a cyclone (19) that has a vertical dipleg (21). An annular ring (23) is horizontally disposed in the dipleg (21). A pair of cooperable clamshell doors (24) are positioned within the dipleg and are pivotably supported by the annular ring (23) for mutual opposite swinging movement between a closed position and an open position, thereby substantially preventing gases from progressing upwardly when the doors (24) are in a closed position and permitting solids to progress downwardly when the doors are in an open position.

Description: This invention relates to an improved cyclone separator used in fluid solids contacting zones and especially in dilute phase contacting zones. There are many chemical and petroleum processes in which solid particles of fluidizable size are suspended in a gas under conditions designed to promote catalytic and thermal reactions. One example of such a process is the fluidized catalytic cracking of petroleum. In this process, a petroleum feedstock is contacted with a solid catalyst at temperatures in the range of about 480°C to about 800°C. In the past, the catalyst particles in a fluidized catalytic cracking process were maintained in a reactor in a dense fluidized state or bed. More recently, the trend has been to conduct fluidized catalytic cracking of petroleum without the maintenance of a dense fluidized bed of catalyst particles. Instead, the solid catalyst is suspended as a dilute phase in a fluid which is passed through the reactor vessel at sufficiently high velocities so that the reactants pass rapidly through the hydrocarbon conversion zone. This procedure reduces the residence time of the reactants in the hydrocarbon conversion zone to a predetermined time which is a function of catalyst activity, temperature, nature of the feed and the like. In effect, it permits use of high activity catalysts and higher temperatures than previously practical. In all of these processes, fluid reactors, regenerators and similar vessels must be provided with means for separating the solid particles from the gaseous phase. Typically, this is accomplished by cyclones located in the upper part of the vessel. The solids separate from the gaseous fluid in the cyclones and are returned to the fluid solids contacting zone via a cyclone dipleg. For cyclones to operate efficiently, it is necessary to prevent the ingress of fluidizing gas into the dipleg of the cyclone. Cyclone separators with trickle valves have been used for this purpose. Basically, these consist of an angularly oriented conduit having one end operably connected to the dipleg of the cyclone and a hinged flapper or closure plate at the opposite end for opening and closing the conduit. Examples of these trickle valves can be found in U.S. Patent 2,838,062; U.S. Patent 2,838,065; U.S. Patent 2,901,331; U.S. Patent 3,826,624; U.S. Patent 3,698,874; U.S. Patent 4,074,691; U.S. Patent 4,184,662; U.S. Patent 4,246,231; and U.S. Patent 4,446,107. These references evidence the fact that satisfactory operation of trickle valves has always been a problem. Recent experience, moreover, has shown that achieving satisfactory performance of trickle valves in dilute phase fluid solids contacting zones is even more troublesome. US-A-2,956,582 discloses a valve assembly having swing valve members which are generally clamshell shape, which valve assembly is employed for controlling the flow of fluids through flow lines. Use as a check valve in fluid flow lines is described. It is an object of the present invention to provide an improved cyclone separator for separating solid particles from a gaseous phase in fluid solids contacting zones, particularly dilute phase fluid contacting zones. According to the invention, there is provided a cyclone separator for separating solid particles from a gaseous phase, which cyclone separator includes a vertical dipleg portion having an inner cylindrical wall which houses a trickle valve assembly comprising: an annular ring horizontally disposed in the vertical dipleg portion and joined to the inner wall thereof, the ring having a central opening therein; and a pair of cooperable clamshell doors positioned in the central opening of and pivotably supported by the annular ring for mutual opposite swinging movement between a closed position in which the doors adjoin along a midline and an open position into which the doors swing outwardly with respect to the midline, thereby substantially preventing gases from progressing upwardly through the vertical dipleg portion above the annular ring when the doors are in a closed position and permitting solids to progress downwardly through the vertical dipleg portion when the doors are in an open position, each of the clamshell doors having a semi-circular lip extending radially outwardly from the top end so as to rest on the annular ring when the doors are in a closed position, the semi-circular lips being undercut in an amount and for a distance sufficient to permit the doors to swing outwardly with respect to the midline. In one embodiment, a baffle is located in the dipleg above the annular ring to direct the flow of solids, under conditions of use, away from the annular ring and downwardly toward the clamshell doors. Preferably, the baffle has the shape of a truncated cone. The cylindrical door shells may be counterbalanced so as to permit them to tip at a maximum angle of 15° from the centerline of the dipleg under conditions of use. The invention will be better understood by referring, by way of example, to the accompanying drawings, wherein : Figure 1 is a vertical section of a vessel which includes one form of improved cyclone separator according to the present invention. Figure 2 is a vertical section of a cyclone dipleg showing the valve in a closed position. Figure 3 is a vertical section of the cyclone dipleg showing the valve in an open position. Figure 4 is a top plan view below the baffle of Figure 2. Figures 5 and 6 are fragmentary isometric views illustrating an alternative means for pivotably supporting the clamshell door. For convenience, the following description pertains to a reactor containing a single cyclone separator according to the present invention. However, it will be readily appreciated that fluid solids contacting apparatus, like fluid catalytic cracking reactor units, contain a plurality of cyclones located within the vessel and the present invention is particularly suitable for use in those units and, in particular, in the cyclones located within those units. Referring initially to Figure 1, a fluid solids contacting vessel 10 includes a shell 12 which is provided with an inlet 16 for introducing entrained solids, such as catalyst suspended in a fluidizing gas, into the bottom of vessel 10. A conduit 14 is also provided for introducing a fluid reactant into the bottom of vessel 10. Additional inlets as may be necessary can be provided. In the embodiment shown in Figure 1, a distributor plate 17 is horizontally disposed in the vessel 10 above the inlet conduits 14 and 16 for uniformly distributing the reactants in the vessel. The distributor plate 17, however, is totally optional. It may be left out or other known distributing devices may be employed. Also shown in Figure 1 is a conduit 15 for removal of solids from the vessel. A gas outlet 18 is provided at the top of vessel 10. As can be seen, the gas outlet 18 is operably connected to a cyclone separator 19. The cyclone separator 19 of the present invention includes a conical portion or transition piece 20 and a vertical dipleg portion 21 (hereafter abbreviated "dipleg 21"). As can be seen, the gas outlet 18 is operably connected to the cyclone 19. Additionally, the cyclone 19 has an inlet 22 for the entrained solids. The solids that enter through inlet 22 are separated from the entraining gas and returned to the vessel via dipleg 21. The gaseous material is removed from the vessel via conduit 18. The trickle valve feature of the present invention is located within the dipleg 21 near the lower extremity thereof. Thus, a section of the dipleg 21 extends below the trickle valve. Referring now to Figures 2 and 3, the trickle valve assembly feature of the present invention comprises an annular ring 23 is horizontally disposed within the dipleg 21 and joined to the inner wall of the dipleg 21. As can be seen in the figures, the annular ring 23 is relatively narrow so that the central opening defined by the annular ring has a diameter which is at least 75% of the diameter of the dipleg 21; for example, from about 75% to about 95% of the diameter of the dipleg 21 and, preferably, about 85% of the diameter of the dipleg 21. The trickle valve assembly includes a pair of operable clamshell doors 24 which are pivotably supported by the annular ring 23 for mutual opposite swinging movement between a closed position (see Figure 2), wherein the doors adjoin a midline, and an open position (see Figure 3), wherein the doors swing outwardly with respect to the midline. Thus, when the doors are in a closed position, they prevent gases from progressing upwardly through the dipleg above the annular ring; and, when the doors are in an open position, they permit the solids to progress downwardly through the dipleg. Each door shell 24 has a semi-circular lip 28 that extends radially outwardly from the top of the door shell so as to rest on annular ring 23 when the door is in a closed position. As can be seen in Figures 5 and 6, lip 28 is undercut in the region of the midline in an amount and for a distance sufficient to permit the door shell to swing outwardly with respect to the midline. In one embodiment, the clamshell doors 24 are pivotably mounted by means of roller pins 26. As shown in Figures 2, 3 and 4, there are two roller pins for each door shell. The roller pins are mounted on the annular ring 23 via a roller pin keeper 27. In a preferred embodiment, shown in Figures 5 and 6, the clamshell door 24 is pivotably mounted on ring 23 by a pair of opposed rounded nubs 29 extending downwardly from lip 28 and adapted to be received for pivotable movement in cooperating troughs 30 in annular ring 23. The clamshell doors 24 may be sized and balanced to permit them to tip a maximum of 15° from the centerline of the dipleg 21. Optionally, weights may be attached to each of the clamshell doors 24 in a strategic location, such as on the underside of the door, to provide optimum balancing of the doors thereby optimizing the operating characteristics of the valve assembly. It is preferred that the valve assembly be located within the lower section of the dipleg; for example, from about the midpoint downward. Preferably, the valve assembly will be located within the lower section of the dipleg at a point sufficient to have at least a portion of the dipleg extend below the lowermost extremity of the clamshell doors. Optionally, the trickle valve may be located at the end of the dipleg, in which event a conduit or pipe will be added to the assembly so as to provide some protection of the door shells from the fluidized solids within the reactor. Another feature, as shown in Figures 2 and 3, is the inclusion of a baffle means 128 above ring 23 to direct the flow of solids away from ring 23 and downwardly toward the central region of the clamshell doors 24. Indeed, it is preferred that this baffle means has a shape of a truncated cone.

Claims: A cyclone separator for separating solid particles from a gaseous phase, which cyclone separator (19) includes a vertical dipleg portion (21) having an inner cylindrical wall which houses a trickle valve assembly comprising : an annular ring (23) horizontally disposed in the vertical dipleg portion (21) and joined to the inner wall thereof, the ring having a central opening therein; and a pair of cooperable clamshell doors (24) positioned in the central opening of and pivotably supported by the annular ring (23) for mutual opposite swinging movement between a closed position in which the doors (24) adjoin along a midline and an open position into which the doors (24) swing outwardly with respect to the midline, thereby substantially preventing gases from progressing upwardly through the vertical dipleg portion (21) above the annular ring (23) when the doors (24) are in a closed position and permitting solids to progress downwardly through the vertical dipleg portion (21) when the doors (24) are in an open position, each of the clamshell doors (24) having a semi-circular lip (28) extending radially outwardly from the top end so as to rest on the annular ring when the doors are in a closed position, the semi-circular lips (28) being undercut in an amount and for a distance sufficient to permit the doors (24) to swing outwardly with respect to the midline. A valve assembly according to claim 1, wherein the clamshell doors (24) are pivotably supported by the annular ring (23) by roller pins (26). A valve assembly according to claim 1, wherein each of the clamshell doors (24) is pivotably supported on the annular ring (23) by a pair of rounded nubs (29) extending downwardly from the semicircular lip (28) and wherein the annular ring (23) includes four troughs (30) adapted to receive the nubs (29). A valve assembly according to any preceding claim, wherein the door shells (24) are balanced to permit them to tip a maximum of 15° from the centerline of the vertical dipleg portion (21). A valve assembly according to any preceding claim, including baffle means (128) located above the annular ring to direct the flow of solids, under conditions of use, away from the ring (23) and downwardly toward the central region within the doors (24). A valve assembly according to claim 5, wherein the baffle means (128) extends downwardly and inwardly from the vertical dipleg portion (21). A vessel for conducting reactions with, and/or for treatment of, solids entrained in a fluidized gas, which vessel contains at least one cyclone separator for separating solids from the fluidizing gas, characterized in that at least one of said cyclone separators is as claimed in any one of the preceding claims.

Inventors: TAMMERA ROBERT FRANK, TAMMERA, ROBERT FRANK
Applicants: EXXON RESEARCH ENGINEERING CO, EXXON RESEARCH AND ENGINEERING COMPANY
Application year: 1991
Main classification: B04C5
IPC codes: B04C5, B01J8, F16K15, C10G11