Patent Publication Number: US-2019176120-A1

Title: Catalytic cracking system with pipe formed nozzle body

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application is a divisional of U.S. patent application Ser. No. 15/023,472, filed Mar. 21, 2016, which claims the benefit of U.S. Provisional Patent Application No. 61/880,320, filed Sep. 20, 2013, both of which are incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to liquid spray nozzles, and more particularly, to spray nozzle assemblies particularly adapted for atomizing and spraying a liquid feed to a fluidized catalytic cracking riser reactor. 
     BACKGROUND OF THE INVENTION 
     A spray nozzle assembly of the foregoing type is shown and described in U.S. Pat. No. 5,921,472, the disclosure of which is incorporated by reference. Such spray nozzle assemblies typically include a nozzle body which defines a mixing chamber into which a liquid hydrocarbon and pressurized gas, such as steam, are introduced and within which the liquid hydrocarbon is atomized. To enhance liquid atomization within the mixing chamber, an impingement pin extends into the chamber and defines liquid impingement surface on the center line of the mixing chamber in diametrically opposed relation to the liquid inlet against which a pressurized liquid stream impinges and is transversely dispersed and across which pressurized steam from a gas inlet is directed for further interaction and shearing of the liquid into fine droplets. The atomized liquid within the mixing chamber is directed under the force of the pressurized steam through an elongated tubular barrel, commonly disposed within a wall of the catalytic reactor riser, for discharge from a spray tip at a downstream end thereof within the riser. Notwithstanding passage through the elongated tubular barrel the liquid must discharge as a very fine liquid particle spray for optimum performance. To efficiently breakup and transmit the liquid hydrocarbon, the steam cross flow must be at a high volume and pressure, approximately 110 psi, and the liquid pressure must be kept at approximately the same or greater pressure. 
     In such spray nozzle assemblies, the liquid hydrocarbon flow stream must pass through half the diameter of the mixing chamber before it impacts the impingement pin. Particularly in spray nozzle assemblies with relatively large diameter mixing chambers, such as those having a mixing chamber of four inches and more in diameter, there can be a tendency for the liquid hydrocarbon flow stream introduced into the mixing chamber to only partially impact the impingement surface of the impingement pin. The reason for this is that the liquid flow stream must pass a significant distance through the mixing chamber where it is subjected to a heavy cross flow of steam before impacting the impingement surface. This tends to cause a shift in the liquid flow stream away from the center of the impingement surface, the magnitude of which is dependent upon the velocities of the pressurized steam and liquid flow streams for a particular setup. The shift prevents a portion of the liquid hydrocarbon flow stream from being shattered against the impingement pin, resulting in a significant increase in droplet size for a portion of the spray volume that adversely affects the spray performance. In order to overcome such shift in the liquid flow stream introduced into the mixing chamber, heretofore it has been necessary to increase the liquid pressure even more to overcome the effect of the steam cross flow. This necessitates the need for larger and higher pressure process pumps that are more expensive to operate and more susceptible to breakdowns. On the other hand, operation of such spray nozzles at lower pressures significantly effects spray performance and can create clogging, particularly when spraying heavier crude oils such as resids and petroleum bottoms. 
     SUMMARY AND OBJECTS OF THE INVENTION 
     It is an object of the present invention to provide a liquid hydrocarbon spray nozzle assembly that is adapted for more effective and finer liquid atomization and improved spray performance in catalytic cracking reactors. 
     Another object is to provide a spray nozzle assembly as characterized above that can be efficiently operated at lower liquid pressures, nearly half that of conventional catalytic cracking spray nozzle assemblies, with lesser expensive processing equipment. 
     A further object is to provide a spray nozzle assembly of the foregoing type in which the liquid hydrocarbon flow stream introduced into the mixing chamber of the spray nozzle body is not adversely effected by the pressurized steam prior to engaging an impingement surface that shatters and transversely directs the liquid within a mixing zone. 
     Still another object to provide a spray nozzle assembly of the above kind that reduces the amount of steam necessary for effective liquid atomization. 
     Yet a further object is to provide a spray nozzle assembly of such type that is effective for efficiently atomizing relatively heavy crude oils, such as resids and petroleum bottoms, without clogging or plugging of the spray nozzle components. 
     Another object is to provide such a spray nozzle assembly that has a relatively simple and durable design which lends itself to economical manufacture. 
     Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings, in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic depiction of a spray nozzle assembly in accordance with the present invention mounted within the wall of a riser of a catalytic cracking reactor; 
         FIG. 2  is an enlarged longitudinal section of the spray nozzle assembly shown in  FIG. 1 ; 
         FIG. 3  is an enlarged transverse section taken in the plane of line  3 - 3  in  FIG. 2 ; 
         FIG. 4  is an enlarged perspective of an upstream end of the illustrated spray nozzle assembly; and 
         FIG. 5  is a side view of the liquid injector and associated steam orifice ring subassembly of the illustrated spray nozzle assembly. 
     
    
    
     While the invention is susceptible of various modifications and alternative constructions, a certain illustrative embodiment thereof has been shown in the drawings and will be described below in detail. It should be understood, however, that there is no intention to limit the invention to the specific form disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention. In that regard, while the illustrated spray nozzle assembly is particularly effective for atomizing and spraying liquid hydrocarbons in catalytic cracking systems, it will be understood that the utility of the nozzle assembly is not limited to that usage. 
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now more particularly to the drawings there is shown and illustrative spray nozzle assembly  10  in accordance with the invention mounted in a conventional manner in an insulated wall  11  (shown in phantom) of a riser of a fluidized catalytic reactor. The spray nozzle assembly  10  is supported in a tubular sleeve  12  fixed within the wall  11  at an acute angle to the vertical for discharging atomized liquid hydrocarbon upwardly into the riser. The tubular sleeve  12  in this case has an outwardly extending flange  14  to which a support flange  15  fixed to the spray nozzle assembly  10  may be secured. 
     The illustrated spray nozzle assembly  10 , as best depicted in  FIG. 2 , basically comprises a nozzle body in the form of an elongated tubular member  17  that defines a mixing zone  20  adjacent an upstream end having a pressurized steam inlet  21  and a liquid hydrocarbon inlet  22  disposed on an outer side of the wall  11  of the riser and an elongated barrel extension zone  24  communicating with the mixing zone  20  disposed in and extending downstream through the nozzle support sleeve  12  and riser wall  11 . A spray tip  25  having one or more discharge orifices  26  is supported at a downstream end of the tubular member  17  within the riser for discharging and directing the atomized liquid spray. The tubular member  17  may be one or more lengths of pipe, such as Schedule 80 steel pipe, having an internal diameter of between about 2 to 8 inches. 
     In accordance with the invention, the spray nozzle assembly is operable for atomizing liquid hydrocarbon into a finer liquid particle discharge for more efficient spray performance while operating at significantly lower liquid pressures. To this end, the liquid hydrocarbon inlet  22  is disposed at an upstream end of the nozzle body tubular member  17  and the steam inlet  21  communicates with through a side wall of the tubular member  17 . In the illustrated embodiment, the steam inlet  21  includes a fitting  30  having a mounting clamp  31  for securement to a supply line  32  coupled to a steam or other gas supply and a downstream end with a counter bore section  34  that fits within an opening  35  of the tubular member  17 , which in this case is formed with an inwardly tapered conical side wall for facilitating securement of the fitting  30  to the tubular member  17  by an appropriate annular weldment. The stem inlet fitting  30  has a central flow passageway  36  with a steam inlet passage section  36   a  communicating through the tubular member  17 . 
     The liquid inlet  22 , like the steam inlet  21 , includes a fitting  40  having a mounting flange  41  for securement to a liquid hydrocarbon supply line  42  coupled to a suitable liquid hydrocarbon supply and a downstream cylindrical section  44  for securement to an upstream axial end of the tubular member  17 . The ends of the liquid inlet fitting  40  and the tubular member  17  are chamfered for facilitating securement by a weldment. The liquid inlet fitting  22  includes an orifice member  45  for defining a liquid inlet passage  46  of predetermined diameter through which the feed liquid is accelerated. The orifice member  45  in this instance has a conical entry section for channeling the pressurized liquid flow stream into and through the orifice member passage  46 . 
     In carrying out this embodiment, the liquid inlet  22  includes an elongated closed end liquid injector  50  extending into the mixing zone  20  along a central axis  51  thereof, which has a liquid extension passageway  52  communicating between the orifice member  45  and a plurality of discharge orifices  54  adjacent a downstream end of the extension passageway  52  which transversely direct liquid into the mixing zone  20  in perpendicular relation to the central axis  51 . The liquid injector  50  in this case is a separate tubular member having a closed downstream end fixedly mounted with an upstream end in abutting relation to a downstream end of the liquid orifice member  45 . The liquid injector  50  has an upstream outwardly extending annular flange  55  that is clamped between a shoulder defined by an annular end  38  of the fitting  40  and the downstream end of the orifice member  45 , which is threadedly mounted within the fitting  40 . It will be understood that alternatively the orifice member  45  and the liquid injector  50  could be made as a single part. In this instance, the central extension passageway  52  of the liquid injector  50  has an upstream passage section  52   a  larger in diameter than the orifice member passageway  46  for allowing unimpeded flow of liquid hydrocarbon into the injector  50 , which then is channeled into a smaller downstream passage section  52   b.    
     In further keeping with this embodiment, the liquid injector  50  has a closed downstream terminal end  58  with an “x” configuration of the liquid discharge orifices  54 . The discharge orifices  54  in this case are defined by cylindrical passages that extend radially outwardly in perpendicular relation to the central axis  51  and define a flat internal impingement surface  60  perpendicular to the central axis  51  against which pressurized liquid hydrocarbon communicating through the extension passageway  52  impinges and is transversely directed and spread out into the mixing zone  20 . 
     In further carrying out this embodiment, an annular steam wall  64  and orifice ring  65  are disposed within the tubular member  17  adjacent a downstream end of the liquid injector  50 , which supports the liquid injector  50  and defines a plurality of concentrating steam discharge orifices  66  at the specific locations of each injector discharge orifice  54  for causing steam to directly interact with and atomize the liquid flow streams discharging from the liquid injector  50 . The annular steam wall  64  in this case is a plate like wall member welded within the tubular body member  17  for defining an annular steam chamber  68  about the liquid injector  50  upstream of the liquid discharge orifices  54  into which steam from the steam inlet  21  is directed. The orifice ring  65  in this case is disposed within the annular steam wall  64  and has an axial length of about twice the width of the wall  64  such that a portion extends a length upstream of the annular steam wall  64 . 
     For defining the concentrating steam discharge orifices  66 , a downstream end section of the liquid injector  50  is formed with external flats  70  across the liquid discharge orifices  54  and angled or rounded corners  71  connecting the flats  70 . The orifice ring  65  has a generally rectangular internal opening with opposing sides formed with recesses  74  supporting the corners  71  of the liquid injector  50  and with rounded corners  75  adjacent the liquid injector flats  70  for defining the steam discharge orifices  66  between the flats  70  and rounded corners  75  in aligned relation to liquid discharge orifices  54 . The steam discharge orifices  66  defined by the steam orifice ring  65  and liquid injector flats  70  in this case are aligned with and partially overlap each liquid injector discharge orifice  54 . Preferably, the downstream end of the steam orifice ring  65  is centered over or slightly upstream of the liquid discharge orifices  54 . 
     As can be seen, since the concentrating steam discharge orifices  66  are aligned precisely with the liquid discharge orifices  54  of the liquid injector  50 , they will direct steam over liquid discharge orifices  54  for direct shearing and atomizing the liquid stream at the precise location where the liquid hydrocarbon exits the liquid injector  50 . Since all of the energy of the steam is focused at that location, the liquid can be atomized into very fine liquid particles for transmission to the spray tip  25 . Since the concentrating steam orifices  66  are relatively small, the steam inlet passage  36   a  may be relatively large, such as one half the diameter or greater than the steam chamber, for achieving the desired velocity of steam through the orifices  66 . 
     It has been found that the droplet size of the atomized liquid further can be varied by changing the area of the steam orifices  66 . For effecting smaller atomized liquid droplets, the concentrating steam discharge orifices  66  may be enlarged such as by changing the size of the injector flats  70  in relation to the internal opening of the orifice ring  65 . In addition, auxiliary steam discharge orifices  66   a  may be provided about the outer perimeter of the steam orifice ring  65  by forming the outer perimeter of the ring  65  with flats  80 , as depicted in  FIG. 3 . Preferably, the flats  80  are disposed radially outwardly of the corners  71  of the liquid injector  50  so as to space the auxiliary steam discharge orifices  66   a  circumferentially between the inner steam discharge orifices  66 . 
     The steam orifice ring  65  preferably is welded to the corners  71  of the liquid injector  50  for maintaining proper orientation of the ring  65  with respect to the injector  50 . This further enables easy assembly of the liquid injector  50  and steam orifice ring  65  or a subassembly into the tubular member  17  of the nozzle body and the central opening of the steam chamber wall  64 . The downstream end  58  of the liquid injector  50  and the steam orifice ring  65  can be mounted in the central opening of the steam chamber wall  64  during assembly with a slip fit which will allow the injector  50  and orifice ring  65  assembly to thermally expand or contract without restriction. The end  58  of the liquid injector  50  protruding through the steam orifice ring  65  and chamber wall  64  in this case is rounded for facilitating direction of the atomized liquid downstream into the barrel zone  24  of the nozzle body. 
     In operation, it will be seen that steam directed into the steam inlet  21  will enter the steam chamber  68  defined upstream of the steam chamber wall  64  and will be directed through the four circumferentially spaced concentrating steam discharge orifices  66  at the precise location of the liquid injector discharge orifices  54  for enhanced interaction and atomization of liquid discharging from the liquid injector  50  following impingement upon the internal impingement surface  60  of the liquid injector  50 . The resulting increased atomization efficiency enables the spray nozzle assembly to be operated at liquid pressures as low as 60 psi, or nearly half that the pressure requirements of conventional catalytic cracking spray nozzle assemblies. The focused direction of steam from the orifice ring  65  also reduces the quantity of steam necessary for effective atomization. The more efficient pressurized air atomization of the liquid hydrocarbon further is effective for breaking up even heavier crude oils, such as resids and petroleum bottoms, without plugging or clogging of the nozzle components. Yet the spray nozzle assembly still has a very simple and durable design which lends itself to economical manufacture and reliable usage.