Nozzle for use in fluidized catalytic cracking

Abstract: In fluidized catalytic cracking, enhanced efficiency is produced through the use of a spray nozzle (26) having two transversely elongated discharge orifices (25) for effecting fine atomization of liquid hydrocarbon feed as the latter is sprayed from the nozzle. The orifices preferably are inclined so as t produce a converging spray but can be inclined to produce a diverging spay or a substantially flat spray. Alternative forms of pressurized air atomizing heads are disclosed.

Description: This invention relates generally to atomizing and spraying apparatus and, more particularly, to apparatus for atomizing liquid feed to a fluidized catalytic cracking riser reactor. Apparatus of this general type is shown and described in detail in Dou et al. United States Patent 5,306,418. In general, a liquid hydrocarbon feed is atomized by a gas such as steam and is discharged through a nozzle into the reactor. In the apparatus of the Dou et al patent, the preferred discharge nozzle has a generally hemispherical discharge end which is formed with a single elongated slot-like outlet orifice adapted to produce a flat fan-shaped spray. A goal in atomizing and spraying apparatus is to achieve high efficiency. High efficiency in the context of the present apparatus refers to using as little steam energy as possible to break hydrocarbon feed of a given volume into particles having a large total surface area. Large surface areas are, of course, created by breaking the liquid into very fine particles. Heretofore, this has necessitated introducing the liquid hydrocarbon flow stream into the nozzle apparatus at relatively high pressure, such as on the order of 1035 kN/m 2 (150 psi) to 1380 kN/m 2 (200 psi). This sometimes has required that the refinery use booster pumps and associated equipment in order to achieve the necessary pressurization of the liquid flow stream, which can be costly and add to the complexity of the spraying system. An atomising spray nozzle is disclosed in Haruch et al United States Patent 4349156 having an expansion chamber into which supplies of air and liquid are directed at an angle to each other for efficient mixing and atomising prior to being discharged through a single orifice. The general aim of the present invention is to provide fluidised catalytic cracking apparatus having a new and improved nozzle of comparatively high efficiency for use in the fluidised catalytic cracking of hydrocarbon liquid. According to the present invention this aim is achieved by the apparatus defined in claim 1. A more detailed object of the invention is to achieve the foregoing through the provision of a nozzle having a plurality of slot-like outlets which atomise the liquid into finer particles as the liquid is discharged from the nozzle. A further preferred object is to angle the slot-like outlets relative to one another in such a manner as to produce a converging spray which itself effects post-discharge atomisation of the liquid particles. Another preferred object is to provide a fluidised catalytic cracking nozzle apparatus with improved liquid pre-atomising means which enables high efficiency atomisation and spraying at substantially lower liquid feed pressures than heretofore possible. These and other objects and advantages of the invention will become more apparent from the following detailed description of exemplary embodiments in conjunction with the accompanying drawings wherein:- FIGURE 1 is a cross-sectional view taken axially through catalytic cracking atomising and spraying apparatus equipped wit a new and improved nozzle incorporating the unique features of the present invention; FIG. 2 is an enlarged end view of the nozzle shown in FIG.1; FIG. 3 is an enlarged fragmentary view generally similar to FIG.1 but shows another embodiment of a nozzle according to the invention; FIG. 4 is an end view of the nozzle shown in FIG. 3. FIGS. 5 and 6 are views similar to FIGS. 3 and 4, respectively, but show yet another embodiment of a nozzle. FIG. 7 is a vertical section of a catalytic cracking atomizing and spraying apparatus having an alternative form of pre-atomizing head particularly adapted for high efficiency atomization and spraying of liquid flow streams introduced into the apparatus at relatively lower pressures. FIG. 8 is a vertical section of a catalytic cracking atomizing and spraying apparatus having another alternative form of pre-atomizing head. For purposes of illustration, the invention has been shown in the drawings as incorporated in apparatus 10 for atomizing and spraying liquid. The apparatus is particularly useful for use in a fluidic catalytic cracking process for atomizing a liquid hydrocarbon feed injected into an FCC riser reactor. The aforementioned Dou et al patent contains a detailed disclosure of the use, in an FCC riser reactor, of apparatus of the same general type as the present apparatus. In general, the apparatus 10 includes means for atomizing the liquid feed with a stream of gas which preferably is steam. Herein, the atomizing means are of the same general type as disclosed in aforementioned Haruch et al United States Patent 4,349,156. Such means are shown somewhat schematically in FIG. 1 and comprise an atomizing head having a body 11 defining an internal chamber 12. An elongated impingement pin 13 is located in the chamber 12 with its end positioned approximately at the center of the chamber 12. Pressurized liquid feed preferably at a pressure of between about 1035 kN/m 2 (150 psi) to 1380 kN/m 2 (200 psi), is introduced into the chamber 12 via an inlet port 15 in the body 11, which is disposed in spaced opposing relation with the end of the pin 13. The stream of liquid impinges against an end surface 17 of impingement pin 13 and is mechanically shattered into small droplets. At the same time, a pressurized jet of steam is introduced into the chamber 12 by way of an inlet port 14 and is directed transversely across and about the end of the pin 13, striking the liquid droplets splashing off the pin 13 in perpendicular relation thereto so as to cause the liquid droplets to be further atomized into fine particles. Attached to the body 11 and located downstream of an outlet 16 of the chamber 12 is a nozzle 20 for spraying the atomized liquid feed and the entrained steam into the reactor. Herein, the nozzle 20 includes an elongated and generally cylindrical body 21 having a downstream end 22 which defines a discharge end. The discharge end 22 of the nozzle 20 is generally hemispherical and thus includes a convex outer surface and a concave inner surface. Such surfaces conform generally in shape to the shape of a section of a sphere having a geometric center lying on the longitudinal axis of the body 21 of the nozzle. 20. In accordance with the present invention, the discharge end 22 of the nozzle 20 is formed with a plurality of discharge orifices 25 which are located on opposite sides of the axis of the nozzle 20 and which are elongated in a direction extending transversely of the axis. By virtue of the discharge end 22 of the nozzle 20 having a plurality of outlet orifices 25, the mixture discharged from the nozzle 20 is atomized more finely than is the case of a nozzle having a single discharge orifice of comparable area centered on the axis of the nozzle. As a result of the finer atomization effected by the multiple orifices 25, the efficiency of the apparatus 10 is increased in that a given volume of liquid may be broken into particles having a relatively high surface area even though steam is supplied to the apparatus at a comparatively low volumetric flow rate. In the embodiment of FIGS. 1 and 2, two elongated outlet orifices 25 are formed in the discharge end 22 of the nozzle 20. The orifices 25 are located on opposite sides of and are spaced equidistantly from the axis of the nozzle 20 and, as pointed out above, are elongated in a direction extending transversely of the nozzle 20. FIGS. 1 and 2 represent the most advantageous version of the nozzle 20 and, in this embodiment, the orifices 25 are angled toward one another so as to cause the streams sprayed from the nozzle 20 to converge upon progressing away from the discharge end 22 of the nozzle 20. In this way, the streams impact against one another to effect still further atomization immediately outside the nozzle 20. Each orifice 25 preferably is inclined at an angle up to about ten degrees relative to the axis of the nozzle 20. The discharge orifices 25 may be formed in the discharge end 22 of the nozzle 20 by a milling cutter. Because of the hemispherical shape of the discharge end 22, slotting of the discharge end 22 with a milling cutter inclined at an angle up to about ten degrees causes the upper orifice 25 to appear generally V-shaped and to cause the lower orifice 25 to appear generally as an inverted V when the orifices 25 are viewed from the end of the nozzle 20 as in FIG. 2. Further efficiency may be imparted to the nozzle 20 by providing a sharp edged annular shoulder 26 at the junction between the body 21 and the discharge end 22. The shoulder 26 is created through the provision of a body 21 whose internal diameter is slightly greater than the internal diameter of the discharge end 22. The shoulder 26 produces turbulence in the mixture as the mixture approaches the orifices 25 and effects further atomization of the liquid feed. In the nozzle 20' shown in FIGS. 3 and 4, the orifices 25' are angled such that the streams of atomized liquid discharged through the orifices 25' diverge away from one another upon progressing downstream from the nozzle 20'. This arrangement produces higher efficiency than a nozzle with a single elongated orifice of comparable area but the efficiency is not as great as that achieved with the nozzle 20 of FIGS. 1 and 2. The following table of data resulting from comparative tests demonstrates the increased efficiency obtained from the nozzle 20' with two diverging orifices 25' when compared to an identical nozzle with a single orifice: Nozzle Configuration Eq. Wt. Steam % Liquid Pressure (psi) Steam Pressure (psi) Sauter Mean Diameter Volume Median Diameter kN/m 2 kN/m 2 Single Orifice 3.5 345 (50) 621 (90) 149 198 3.5 690 (100) 621 (90) 143 187 3.5 1035 (150) 621 (90) 141 184 3.5 1380 (200) 621 (90) 137 178 Double Orifices 10° diverging 3.26 345 (50) 621 (90) 133 144 3.26 690 (100) 621 (90) 119 128 3.26 1035 (150) 621 (90) 114 122 3.0 1380 (200) 621 (90) 111 119 Single Orifice 7.0 345 (50) 621 (90) 114 121 7.0 690 (100) 621 (90) 113 121 7.0 1035 (150) 621 (90) 112 120 7.0 1380 (200) 621 (90) 111 118 In the above table, "Eq. Wt. Steam %" represents the percentage by weight of steam supplied to the apparatus 10 with respect to the weight of supplied liquid based upon the flow rate of the liquid. In carrying out the comparative tests at various liquid pressures, the flow rate of liquid to the apparatus 10 was kept constant at all pressures by progressively decreasing the area of the inlet orifice 15 for progressively increasing pressures. By comparing the top four rows of data with the middle four rows, it will be apparent that the nozzle 20' with the two diverging orifices 25' effected atomization of the liquid into significantly smaller particles than a nozzle with a single orifice even though the two nozzles were supplied with substantially equal quantities of steam. The enhanced efficiency of the nozzle 20' is demonstrated further by a comparison of the middle four rows of data with the bottom four rows where it will be seen that the nozzle 20' with two diverging orifices 25' achieved substantially the same particle size as a nozzle with a single orifice even though the single-orifice nozzle was supplied with more than twice the quantity of steam. In the nozzle 20" of FIGS. 5 and 6, the two orifices 25" are not angled but instead extend parallel to one another. As a result, parallel streams of atomized liquid tend to be discharged from the orifices 25". The nozzle 20" is not as efficient as the nozzle 20' but still is more efficient than prior FCC nozzles having a single orifice of comparable area. Referring now to FIG. 7, there is shown a catalytic cracking, atomizing and spraying apparatus 10 a having an alternative form of atomizing head, particularly adapted for use with liquid flow streams introduced into the apparatus at relatively lower pressures. Items similar to those described above have been given similar reference numerals with the distinguishing suffix " a " added. Like the apparatus 10 illustrated in FIG. 1, the atomizing head has a body 11 a which defines an internal chamber 12 a having an elongated impingement pin 13a with an end positioned approximately at the center of the chamber. Pressurized liquid feed is introduced into the chamber 12 a via an inlet 15 a in the body 11 a in opposed relation to the end of the pin 13 a . At the same time, a pressurized jet of steam is introduced into the chamber 12 a from the inlet 14 a and assists in breaking down and atomizing the liquid flow stream. In accordance with a further feature of the invention, in order to enhance atomization of the liquid, even when the liquid flow stream is introduced into the apparatus at relatively low pressures, the atomizing head has an auxiliary gas or steam inlet port 30 in close proximity to the impingement pin 13 a through which pressurized gas or steam may be directed transversely to the stream of pressurized steam introduced into the chamber 12 a from the inlet 14a and in directly opposing relation to the liquid flow stream introduced from the inlet 15 a for further breaking down and atomizing the liquid into extremely fine particles. In the illustrated embodiment, the auxiliary gas or steam inlet port 30, communicates with an axial passageway 31 formed internally within the impingement pin 13 a . The axial passageway 31 extends substantially the length of the impingement pin 13 a , but short the end thereof which defines a substantially flat impingement surface 32. The impingement pin 13 a in this case is supported in the body 11 a by means of an elongated sleeve 34, that extends into the chamber 12 a in surrounding relation to the impingement pin 13 a and substantially the same distance as the impingement pin 13 a . The impingement pin 13 a has an outer annular recessed portion which together with an internal surface of the sleeve 34 define an annular passageway 35 about a portion of the pin 13 a . The impingement pin 13 a is formed with a plurality of axially spaced radial passageways 36 to permit communication of steam from the inlet port 30 through the axial pin passageway 31, through the radial passageway 36, axially along the annular passageway 35 and through a predetermined metering orifice 38 defined between the terminal ends of the sleeve 34 and the impingement pin 13 a . Pressurized steam introduced into the inlet port 30 will exit the metering orifice 38 in an outwardly directed annular pattern or sheath about the impingement surface 32. It has been found that the outer direction of pressurized steam from the metering orifice 38 significantly enhances liquid atomization, even when the liquid is introduced into the atomizing chamber at substantially lowere pressures than heretofore normally required. The apparatus 10a has been found to enable high efficiency atomization of hydrocarbon liquid feed streams when the liquid stream is introduced at pressures as low as 276 to 345kN/m 2 (40 to 50 psi), in contrast to the normally required liquid pressure of 1035 - 1380 kN/m 2 (150-200 psi). It will be understood by one skilled in the art that elongated tubular nozzles with discharge orifices of various forms, including those specifically disclosed herein, may be utilized with the atomizing head of the apparatus 10 a . Referring now to FIG. 8, there is shown a catalytic cracking atomizing and spraying apparatus 10 b having an alternative form of atomizing head, wherein items similar to those described above have been given similar reference numerals with the distinguishing suffix " b " added. The atomizing head of the apparatus 10 b has a hydrocarbon liquid inlet 15 b , and an impingement pin 13 b with a gas or steam metering orifice 38 b substantially similarly to that described in connection with FIG. 7. The annular chamber 35 b about the impingement pin 13 b in this instance is defined by a recess in the internal surface of the sleeve 34 b . Pressurized liquid introduced into the inlet 15 b will impinge against the impingement surface 32b of the pin 13 b so as to be shattered into small droplets. Simultaneously, a pressurized jet of steam emitted from the annular steam orifice 38 b surrounding the impingement surface 32b will strike the liquid droplets splashing off the pin 13 b and forcefully disperse them throughout the mixing and atomizing chamber 12 b of the atomizing head body 11 b . In carrying out this embodiment of the invention, the atomizing head chamber 12 b has a closed upstream end defined by a concave inner surface 40 adapted to redirect the forcefully dispersed liquid droplets in the chamber 12 b in a downstream direction for further interaction with the entering steam and liquid flow streams from the orifice 38 b and inlet 15 b and for ultimate direction through the nozzle 20 b in a form of relatively finely atomized liquid particles. The concave surface 40 in this instance is in the shape of a section of a sphere having a geometric center line on the point of intersection between the longitudinal axis of the cylindrical chamber 12 b of the atomizing head and the longitudinal axis of the impingement pin 13 b and liquid inlet 15 b .

Claims: A fluidised catalytic cracking apparatus comprising a riser through which gases are directed, a hydrocarbon liquid supply, a steam supply, a spray device mounted in the riser, the spray device including a nozzle (20;20';20";20a;20b) having a tubular body (21), the body (21) having a central axis and a discharge end (22) with a convex outer surface and a concave inner surface, the discharge end (22) conforming generally in shape to the shape of a section of a sphere having a geometric centre lying on said axis with the inner concave surface being defined by a diameter of curvature no greater than the diameter of the tubular body (21), the hydrocarbon liquid and steam supplies having respective inlets (15;15a;15b;14;14a;30;30b) for introducing pressurized streams of liquid hydrocarbon and steam into the nozzle (20;20';20";20a;20b) for intermixing and pre-atomising the liquid hydrocarbon while within the nozzle (20;20';20";20a;20b) characterised in that the discharge end (22) is formed with a plurality of discharge orifices (25;25';25") elongated in a direction extending transversely of said axis with half of the plurality of orifices (25;25';25") being located on one side of said axis and the other half of the plurality of orifices (25;25';25") being located on the opposite side of said axis. The fluidised catalytic cracking apparatus according to claim 1 characterised in that the discharge end (22) of the nozzle (20;20';20";20a;20b) is formed with two discharge orifices (25;25';25"). The fluidised catalytic cracking apparatus according to claim 1 or claim 2 characterised in that the orifices (25) are angled such that streams of atomised liquid discharged through the orifices (25) converge toward one another upon progressing away from the discharge end (22) of the nozzle (20). The fluidised catalytic cracking apparatus according to claim 1 or claim 2 characterised in that the orifices (25') are angled such that streams of atomised liquid discharged through the orifices (25') diverge away from one another upon progressing away from the discharge end (22) of the nozzle (20'). The fluidised catalytic cracking apparatus according to claim 1 or claim 2 characterised in that the orifices (25") extend parallel to one another such that streams of atomised liquid discharging through the orifices (25") progress away from the discharge end (22) of the nozzle (20") in substantially parallel relation to each other. The fluidised catalytic cracking apparatus according to any one of the preceding claims characterised in that the inner concave surface of the discharge end (22) is defined by a diameter of curvature less than the diameter of the tubular body (21) with a sharp edged annular shoulder (26) being defined within the nozzle (20;20';20";20a;20b) at the juncture of the tubular body (21) and the discharge end (22). The fluidised catalytic cracking apparatus according to any one of the preceding claims characterised in that the nozzle (20;20';20";20a;20b) defines an internal mixing and atomising chamber (12;12a;12b), an impingement pin (13;13a;13b) defining an impingement surface (17;32;32b) on an end thereof, the hydrocarbon liquid supply inlet (15;15a;15b) being arranged for directing hydrocarbon liquid into the chamber (12;12a;12b) and against the impingement surface (17;32;32b) of the pin (13;13a;13b) and the steam inlet (14;14a;30;30b) being arranged for directing steam into the chamber (12;12a;12b) for intermixing with hydrocarbon liquid upon impingement against the impingement surface (17;32;32b). The fluidised catalytic cracking apparatus according to claim 7 characterised in that the steam inlet (30;30b) is located in close proximity to the impingement pin (13a;13b) for directing the steam in a direction outwardly from the impingement surface (32;32b) for interacting with and atomising hydrocarbon liquid introduced into the chamber (12;12a;12b) against the impingement surface (32;32b). The fluidised catalytic cracking apparatus according to claim 8 characterised in that the nozzle (20a) has a second steam supply inlet (14a) though which pressurized steam may be directed into the chamber (12a) and across the impingement surface (32) of the pin (13a). The fluidised catalytic cracking apparatus according to claim 7 or claim 8 characterised in that the steam inlet (30;30b) communicates with a metering orifice (38;38b) configured to emit an annular stream of steam about the perimeter of the impingement surface (32;32b). The fluidised catalytic cracking apparatus according to claim 10 characterised in that the pin (13a;13b) is formed with an axial passageway (31;31b) communicating with the steam inlet (30;30b) and the pin (13a;13b) has a further passageway (35,36;35b,36b) communicating between the axial passageway (31;31b) and the metering orifice (38;38b). The fluidised catalytic cracking apparatus according to claim 11 characterised in that the further passageway (35,36;35b,36b) includes at least one radial passageway (36;36b) communicating with the axial passageway (31;31b) and an annular passageway (35;35b) communicating between the radial passageway (36;36b) and the metering orifice (38;38b). The fluidised catalytic cracking apparatus according to any one of claims 7 to 12 characterised in that the nozzle (20b) has a closed upstream end (40). The fluidised catalytic cracking apparatus according to claim 13 characterised in that the upstream end (40) is defined by a concave inner surface (40) for directing liquid in the chamber (12b) in a direction towards the discharge orifices of the nozzle (20b). The fluidised catalytic cracking apparatus according to claim 14 characterised in that the concave inner surface (40) is in the shape of a section of a sphere having a geometric centre line on the point of intersection between a longitudinal axis of the chamber (12b) and a longitudinal axis of the pin (13b). The fluidised catalytic cracking apparatus according to claim 7 characterised in that the steam inlet (14;14a) is located in close proximity to the impingement pin (13;13a) for directing the steam in a direction across the impingement surface (17;32) of the pin (13;13a). The fluidised catalytic cracking apparatus according to claim 2 characterised in that the orifices (25;25') are angled relative to the axis of the nozzle (20;20'), for example at an angle up to about ten degrees. The fluidised catalytic cracking apparatus according to claim 17 characterised in that one of the orifices (25;25') appears to be generally of V-shape and the other orifice (25;25') appears to be generally of inverted V-shape when the orifices (25;25') are viewed from the end of the nozzle. The spray device of the fluidised catalytic cracking apparatus (10;10a;10b) according to any one of the preceding claims.

Inventors: HARUCH JAMES, HARUCH, JAMES
Applicants: SPRAYING SYSTEMS CO, SPRAYING SYSTEMS CO.
Application year: 1995
Main classification: C10G11
IPC codes: B05B1, B05B7, C10G11, B01J8