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| CLAIMS What is claimed is: 1. An atomizing nozzle assembly for use in a fluidized bed reactor, said assembly comprising: a nozzle face, said nozzle face comprising a first outlet for a liquid to be atomized and at least one outlet for atomizing gas, such that said atomizing gas flowing from said at least one outlet for atomizing gas atomizes liquid flowing from said first outlet, said first outlet being disposed either even with or downstream from said at least one outlet for atomizing gas, whereby during operation of said nozzle assembly in a fluidized bed reactor said nozzle face remains substantially free of impact by fluidized bed particulates. 2. The atomizing nozzle assembly of claim 1 further comprising: a covering means covering said nozzle face, said covering means having an exit port, wherein said covering means is disposed at a distance from said nozzle face to define a nozzle face plenum there between, said covering means further maintaining said nozzle face substantially free of impact by fluidized bed particles. 3. The atomizing nozzle assembly of claim 1 or claim 2 comprising a plurality of outlets for atomizing gas disposed radially about said first outlet for liquid. 4. The atomizing nozzle assembly of claim 1, 2, or 3 further comprising a base portion, a distal portion, and an atomizer portion, said atomizer portion comprising said nozzle face, said atomizer portion being substantially circumscribed by said distal portion so as to define an annular plenum therebetween, atomizing gas flowing through said annular plenum to said plurality of atomizing gas outlets. 5. The atomizing nozzle assembly of claim 4 as depending from claim 2, said distal portion comprising at least one passageway from said annular plenum to said nozzle face plenum, said passageway providing a path for a stream of supplemental gas to said nozzle face plenum. |
APPARATUS Background
This invention relates to an atomizer nozzle assembly for use in a fluidized bed reactor chamber. More particularly, this invention relates to an atomizer nozzle assembly for use in a fluidized bed reactor chamber wherein fluid flow is configured to minimize erosion of the nozzle by the fluidized bed particles.
The use of atomized reactants in a fluidized bed system is well known. Such reactants are used, for example, in a catalytic process for oxidation of organics, generally as described in U.S Patent No. 4,485,081 and U.S Patent No.
4,804,479.wherein chlorinated organic liquids are reacted with oxygen to generate HCl, CO 2 and water. The HCl then may be used in the manufacture of other chlorinated organics. The chlorinated organic liquid is atomized with an atomizing gas, typically hot air or oxygen, and sprayed into a fluidized bed reactor chamber where it reacts with the fluidized catalyst particles. As is known in the art, an atomizing nozzle is used to atomize the chlorinated organic liquid and dispense the atomized liquid as a spray into the fluidized bed reactor chamber.
An important attribute of atomizing nozzles and their operating conditions is the size of the droplets of atomized fluid produced. Droplet size, measured as the average diameter, is an important parameter for the subsequent operation in which the atomized droplets will be used. Proper functioning of the atomizer nozzle can be critical to the functioning of the operation of the subsequent process in which the fluidized reactant will be used.
Nozzles used in fluidized bed reactors can be subject to damage by premature erosion. Some prior nozzle designs induce a fluid flow which entraps catalyst particles in the region adjacent the nozzle face, causing interparticle collisions that break down the catalyst particles. This process can result in significant attrition levels of the catalyst due to fines generation, which could lead to loss of as much as 80% of the original catalyst over one year of operation, leading to significant expense for replacement catalyst, as well as replacement nozzles. The entrapped particles also can impact the nozzle surfaces, leading to significant degradation in the concave region. As the nozzles erode they become less efficient as atomizers.
SUMMARY OF THE INVENTION
The present invention is directed to an atomizing nozzle assembly suitable for use with a fluidized bed reactor chamber. The atomizing nozzle assembly of this invention does not readily erode in fluidized bed conditions. Advantageously, the atomizing nozzle assembly of the present invention can provide protection of the output region of the nozzle from surrounding fluidized particles during operation of the nozzle in a fluidized bed reactor chamber.
the nozzle assembly of the present invention comprises a nozzle face (43), the face including a liquid outlet (44) and at least one atomizing gas outlet (46), the liquid outlet being disposed substantially even with or downstream of said at least one atomizing gas outlet, whereby during operation of said nozzle in said fluidized bed chamber said nozzle face remains substantially free of impact by fluidized bed particulates. The nozzle assembly further comprises a shield (70) disposed over the nozzle face and spaced therefrom so as to define a plenum (79) therebetween. The plenum defines a region that is substantially free of fluidized bed particulates to protect the nozzle face from erosion. In one embodiment, the liquid outlet is disposed substantially even with or downstream of the at least one atomized gas outlet, such that the liquid to be atomized is dispensed into a flow of atomizing gas.
The atomizing gas can be heated, depending on the properties of the liquid to be atomized and the conditions required for operation of the fluidized bed into which the atomized liquid is dispensed. In a preferred embodiment, the ratio of the area of the plurality of the atomizing gas outlets to the area of the first centrally disposed outlet is optimized to achieve satisfactory atomization with atomizing gases delivered to the nozzle face at a lower velocity. In yet another aspect (cf. FIG. 9), the nozzle assembly of the present invention further includes at least one supplemental air outlet (80) at said nozzle face (43), said supplemental air outlet emitting a gas at a lower velocity than the atomizing gas to prevent entry of fluidized bed particulates into said plenum (79).
It has been found that the nozzle assembly of the present invention provides improved performance in a fluidized bed reactor environment. The use of a nozzle assembly of the present invention allows the velocity of the feed liquid to be reduced by a factor of five, for the same mass flow rate of feed liquid. The diameter of the liquid outlet can be selected to optimize the feed rate of liquid into the atomizing region of the nozzle.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of a system for providing an atomized liquid into a fluidized bed reactor chamber.
FIG. 2 is a partial cross-section view of one embodiment of the atomizing nozzle assembly of the present invention.
FIG. 3 is a bottom perspective view of the embodiment of FIG. 2 with the base portion removed for clarity.
FIG. 4 A is a perspective view of an atomizer portion for directing the flow of atomizing gas in a nozzle assembly of the present invention.
FIG. 4B is a perspective view of a base portion of the nozzle assembly of the present invention. FIG. 5 is a perspective view of an atomizer portion resting atop a base portion, in the same relative positions as in the nozzle assembly of the invention.
FIG. 6 is a top plan view of the components as illustrated in FIG. 5.
FIG. 7 is a top plan view of the components of FIG. 6 with the addition of the distal portion of the nozzle assembly.
FIG. 8 is an exploded view of a second embodiment of the atomizing nozzle assembly of the present invention.
FIG. 9 is a partial cross-section of a second embodiment of the atomizing nozzle of the present invention. FIG. 10 is a top perspective view of the embodiment of FIGS. 8 and 9.
FIG. 11 is a schematic drawing illustrating the flows of liquid and gas through the embodiment of FIGS. 8-10.
DETAILED DESCRIPTION OF THE INVENTION
In the following description, the term "distal" shall refer to the part of a component in the direction of the atomized liquid output, and the term "proximal" shall refer to the part of a component in the direction of the source of atomizing gas and liquid to be atomized, when the components are assembled into a nozzle assembly for atomizing a liquid as described herein.
The present invention relates to an improved atomizer nozzle assembly. The inventive nozzle assembly is particularly suitable for use in a chamber of a fluidized bed reactor. The nozzle assembly includes a nozzle face and is configured so that there is no concave or other region at the nozzle face in which fluidized bed particulates can circulate and impact on each other or on the nozzle surfaces. In a nozzle assembly of the invention comprising at least one liquid outlet and at least one atomizing gas outlet, this is accomplished by positioning the at least one liquid outlet at a position substantially even with or downstream from the at least one atomizing gas outlet such that the liquid is emitted into a stream of fast moving atomizing gas. The nozzle assembly of the present invention is configured to direct atomizing gas angularly into a stream of the liquid to be atomized, the atomizing gas preferably being guided in an annular configuration to the atomizing gas outlets, the atomizing gas outlets being angled toward the liquid outlet. In a preferred embodiment of the present invention, the liquid and atomizing gas outlets define a nozzle face, and the nozzle assembly is provided with a means for covering the outlets of the nozzle face to define a plenum; which covering means can be in the form of a shield. The shield is provided with an exit port to allow for the release of atomized liquid and atomizing gas, while the plenum remains substantially free of particulate matter from the fluidized bed. In a particularly preferred embodiment, at least one supplemental gas outlet is disposed in the plenum such that a supplemental gas flows through the plenum at a lower velocity than the atomizing gas, the flow of supplemental gas serving to further maintain the plenum free of particulate fluidized bed material.
The present invention may be better understood by reference to the Figures, however it is to be understood that the Figures are intended only for purposes of illustration of certain embodiments of the inventive concept, and not by way of limitation. Further, the Figures are not necessarily drawn to scale, but to best illustrate the features of the present invention for the understanding of the reader. FIG. 1 is a schematic representation of a fluidized bed reactor system 10 including a fluidized bed reactor chamber 34 having an atomizing nozzle assembly 40 in which an atomizer portion 42 sprays an atomized liquid into the chamber 34. As illustrated in FIG. 1, a feed system for a fluidized bed reactor includes a coaxial feedpipe 20 having an inner pipe 22 carrying the liquid to be atomized and an outer pipe 24 carrying an atomizing gas, the atomizing gas flowing in the annular space between the inner surface of outer pipe 24 and the outer surface of inner pipe 22. The atomizing gas may be heated as by means known in the art, such heating means omitted from the drawing for the sake of clarity. A distal portion 26 of feedpipe 20 is housed within a supporting pipe 30, which extends through chamber wall 32 of fluidized bed reactor chamber 34. Cooling air 28 flows through the length of supporting pipe 30 to maintain control of the temperature of the atomizing gas in outer pipe 24 before it contacts the liquid to be atomized. In operation, fluidized bed reactor chamber 34 will contain a fluidized bed of catalyst particles circulating at high velocity throughout the chamber 34. Distal portion 26 of feedpipe 20 terminates at terminal end 36 of support pipe 30, which terminal end 36 houses nozzle assembly 40. The nozzle assembly 40 is supported by support pipe 30 such that the output of nozzle assembly 40 is dispensed directly into reaction chamber 34 of the fluidized bed reactor.
In accordance with the invention, nozzle assembly 40 comprises an atomizing portion, the atomizing portion comprising a nozzle face including at least one outlet for a liquid, and at least one and preferably a plurality of outlets for atomizing gas; the outlet for the liquid being located substantially even with or downstream from the outlets for the atomizing gas, the liquid and gas outlets being disposed with respect to one another such that there is no concave region at the nozzle face where particulate matter from the fluidized bed can become entrapped and cause erosion of the nozzle face. The nozzle assembly further comprises a shield for covering the outlets at the nozzle face, the shield comprising an exit port, the shield being disposed at a distance from the nozzle face to define a plenum between the shield and the nozzle face, the plenum defining a region in which particulate matter from the fluidized bed does not come in contact with the nozzle face.
In one embodiment, the first outlet for the liquid is centrally located on the nozzle face, and a plurality of outlets for the atomizing gas is arranged on the outlet face radially about the liquid outlet. The first outlet for the liquid can be disposed substantially even with or downstream of the plurality of outlets for the atomizing gas. The first outlet for the liquid and the plurality of outlets for the atomizing gas are configured with respect to one another such that there is no zone such as a concave region at the nozzle face at which catalyst particles of the fluidized bed can become entrapped.
The liquid can be an organic liquid and the atomizing gas can be an oxidizing gas selected from air, oxygen, and mixtures thereof. In particular, the liquid can be a halogenated organic liquid, the atomizing gas can be an oxidizing gas selected from air, oxygen, and mixtures thereof, and the reaction in the fluidized bed reactor chamber relates to the oxidation of the halogenated organic liquid to produce halide acid, carbon dioxide, and water. The atomizing gas can be heated as is known in the art.
As seen most readily in FIGS. 2-4, atomizing nozzle assembly 40 comprises a base portion 50, a distal portion 60, and an atomizer portion 42 disposed
therebetween. In the illustrated embodiment, base portion 50 is a substantially cylindrical element provided at its distal end with an annular wall 52 extending from shoulder 54 to rim 56, annular wall 52 having threads 58 on its exterior surface.
Distal portion 60 is also substantially cylindrical in shape, and includes an open proximal annular wall 62 having threads 64 on the inner surface thereof, threads 64 on distal portion proximal annular wall 62 being sized and dimensioned to fit in mating relationship with threads 58 on the exterior surface of annular wall 52 of base portion 50, so as to securely yet releasably fasten base portion 50 and distal portion 60, with proximal rim 65 of distal portion 60 seated against shoulder 54 of base portion 50. Distal end 66 of distal portion 60 has an opening 68 formed therein, the opening being larger than and in alignment with the atomized liquid outlet of atomizing portion 42, described below. Distal end 66 of distal portion 60 can be provided at its upper edge with a chamfered surface 69. In the embodiment of FIG. 2, the chamfered surface 69 is spaced apart from opening 68; in the embodiment of FIG. 7 the chamfered surface 69 extends all the way to and defines opening 68 at its upper edge. Such variations in design of the nozzle assembly will be within the knowledge of those skilled in the art.
Further in the illustrated embodiment, atomizer portion 42 also is substantially cylindrical, having at its distal end a nozzle face 43 comprising a centrally disposed first outlet 44 for a liquid, and a plurality of outlets 46 for an atomizing gas disposed radially about centrally disposed first outlet 44. In the illustrated embodiment atomizing gas outlets 46 are in the form of angularly directed slots cut into outer beveled surface 41 of atomizer portion 42. Outer beveled surface 41 of atomizer portion 42 engages interior beveled surface 61 of distal end 66 of distal portion 60, to further securely engage atomizer portion 42 against distal portion 60, and to define the pathways of atomizing gas outlets 46. The gas outlets 46 are angled to direct atomizing gas toward the stream of liquid exiting first outlet 44. Extending through atomizer portion 42 is a central bore 49 that terminates at its distal end at first outlet 44. Bore 49 and outlet 44 are in operative fluid communication with inner pipe 22 carrying the liquid to be atomized. The plurality of outlets 46 is in operative fluid communication with outer pipe 24 carrying the atomizing gas. In the illustrated embodiment, first liquid outlet 44 is surrounded by frusto-conical surface 48 and is disposed downstream of plurality of atomizing gas outlets 46. At the proximal end of atomizer portion 42 is bearing plate 45, having an outer perimeter sized and dimensioned to rest against rim 56 of base portion 50, FIG. 5, and to be circumscribed by threads 64 of distal portion 60, FIG. 2, whereby atomizer portion 42 is held in secure engagement between base portion 50 and distal portion 60. Disposed about the perimeter of bearing plate 45 is a plurality of recesses 47. In the illustrated embodiment the recesses 47 are semicircular in shape; the selection of the size, number and shape of the recesses 47 can be made by one skilled in the art for the particular operating parameters required. Except for bearing plate 45, the outer circumference of atomizer portion 42 is smaller than the inner circumference of distal portion 60, such that when base portion 50, atomizer portion 42, and distal portion 60 are all assembled together to form nozzle assembly 40, an annular plenum 67 is defined between the outer cylindrical wall of atomizer portion 42 and the inner cylindrical wall of distal portion 60.
FIG. 3 illustrates the bearing plate 45 of atomizer portion 42 fitted into distal portion 60 of nozzle assembly 40. It may be seen that bore 49 continues through bearing plate 45 so that liquid to be atomized can travel through atomizer portion 42. Figures 4 A and 4B are perspective views of the disassembled base portion 50 and atomizing portion 42, respectively. FIG. 5 is a perspective view of atomizer portion 42 and base portion 50 as in assembled relation; FIG. 6 is a top plan view of the partial assembly of FIG. 5. FIG. 7 is a top view of the assembled distal portion 60 and atomizing portion 42, and base portion 50; with first outlet 44 centered in frusto- conical surface 48 and surrounded by atomizing gas outlets 46, all being visible through opening 68 of distal portion 60.
In operation, liquid to be atomized flows through inner pipe 22 which extends into base portion 50; the liquid continues through bore 49 in atomizer portion 42 and out through first outlet 44. At the same time, atomizing gas travels at high velocity through outer pipe 24 and into the space defined by the inner walls of base portion 50 and the proximal side of bearing plate 45. The gas then travels through recesses 47, which serve to homogenize turbulence and redirect the atomizing gas into a laminar flow that travels evenly through annular plenum 67 and toward gas outlets 46. The gas outlets 46 are arranged and angled so that the atomizing gas impinges and spreads on frusto-conical surface 48, resulting in a high velocity, high turbulence gas stream that breaks up the liquid stream flowing from outlet 44 at high speed through opening 68 of distal portion 60, causing the liquid stream to disintegrate and the liquid to atomize into a spray of droplets. The atomization process is facilitated by the angular intersection of the atomizing gas flow with the direction of the liquid flow. The spray of atomized droplets of the liquid dispensed as a spray through outlet 44 can travel directly into chamber 34 of the fluidized bed reactor system, such that atomization occurs in an unconfmed region.
In a preferred embodiment, first outlet 44 is even with or downstream from atomizing gas outlets 46; in addition, first outlet 44 is in substantial alignment with end 36 of support pipe 30 in chamber 34. There is therefore no concave region or other zone created near the nozzle face 43 at which fluidized bed material can readily collect. The outer surface of distal end 66, including beveled surface 69, also serves to protect nozzle face 43 from fluidized bed material. The novel design of the present invention uses a reduced liquid velocity while maintaining the drop diameter of the atomized liquid. The flow rate of the atomizing gas can be in the range of about 100-600 kg/hr. The liquid flow rate in the atomizer portion can be in the range of about 400- 1800 kg/hr. The preferred mass ratio of gas to liquid is in the range of about 0.1-0.5; a higher ratio of gas to liquid may allow for reduction in the amount of air used to fluidize the catalyst in the fluidized catalyst bed.
In the illustrated embodiment, the liquid outlet 44 can have a diameter of about 12-13 mm, and the openings of gas outlets 46 of about 9-10 mm 2 . The nozzle face comprising outlets for gas and liquid can be provided with a protective covering means that protects the nozzle face from contact with the high kinetic energy fluidized bed particles. The covering means can be in the form of a shield that spans the diameter of the nozzle assembly. Referring to FIGS. 8 - 10, nozzle assembly 40 comprises a shield 70 in the form of a covering plate 72 having outwardly facing surface 73 and inwardly facing surface 74, with exit port 75 extending therethrough. Circumferential wall 77 allows for secure engagement of shield 70 to distal portion 60 of nozzle assembly 40, such as by means of pin 78 penetrating aligned holes formed in both circumferential wall 77 of shield 70 and distal end 66 of distal portion 60. Inwardly facing surface 74 of covering plate 72 is spaced from nozzle face 43 so as to define a nozzle face plenum 79 therebetween. Exit port 75 is aligned with first outlet 44 to allow atomized liquid to be dispensed directly into the fluidized reactor chamber 34 as atomization takes place. Shield 70 protects the nozzle face 43 from particulate catalyst material while allowing the atomization to take place and allowing the passage of the atomized liquid into the reaction chamber.
In a preferred embodiment, distal portion 60 is provided with a plurality of small passageways 80 extending from annular plenum 67 to nozzle face plenum 79. In the illustrated embodiment, six such passageways are provided, only one of which is shown for the sake of clarity. The outlets of passageways 80 for the supplemental gas can have a diameter of about 2-3 mm, when about six such passageways are used for a plenum 79 having a height of about 3-4 mm. The number, size, and orientation of the passageways can vary in different embodiments depending on the desired operation parameters of the nozzle assembly. The passageways 80 divert a portion of the atomizing air from annular plenum 42 away from atomizing gas outlets 46 and into nozzle face plenum 79. The smaller diameter of passageways 80 reduces the velocity of the atomizing gas, so that the gas enters nozzle face plenum 79 as a lower velocity supplemental gas flow. This supplemental gas flow serves to sweep plenum 79 free of any particulate catalyst materials that might chance to enter through exit port 75, while not interfering with the atomized liquid produced from the nozzle face. The supplemental gas flow can be in the range of about 5-90% of the atomizing gas, more preferably about 20-50% of the atomizing gas, and most preferably about 25- 35% of the atomizing gas.
FIG. 11, which is not drawn to scale, is a schematic cross section of the second embodiment of a nozzle assembly, illustrating the various liquid and gas streams flowing through the embodiment of the nozzle assembly as illustrated in FIGS. 8-10. Incoming liquid to be atomized, indicated by reference letter A, flows through inner pipe 22, and past outlet 44. Atomizing gas flows through atomizing gas pipe 24, through the recesses 47 in bearing plate 47, and into annular plenum 67. A significant portion of the atomizing gas flows through atomizing gas outlets 46 where, as indicated by reference letter B, it is directed to intersect the flow of liquid emitted from outlet 44 at region F, such that high velocity atomizing gas breaks up the stream of liquid into small droplets, thereby producing a spray of atomized liquid indicated by reference letter G, surrounded by a stream of atomizing gas indicated by reference letter H. The remainder of the atomizing gas in annular plenum 67 is directed through passageways 80 as a supplemental gas indicated at reference letter E. This supplemental gas flows from the perimeter of nozzle face plenum 79 toward the center and joins with atomizing gas at region H and flows out through exit port 75. Cooling air 28 from end 36 of support pipe 30 flows out past assembly 40 at region I; this flow can separate the high velocity gas and atomized liquid from the fluidized bed, and can be in the range of about 30-50 m/s. The flow of atomized liquid through region G and high velocity atomizing gas at region H can induce a flow of gas J along the outer surface of covering plate 72 of shield 70, which induced flow can carry particulate catalyst material circulating in reaction chamber 34. Covering plate 72 prevents this particulate material from contacting the nozzle face 43, thereby preventing erosion of the nozzle face and improving the quality of the liquid atomization over the nozzle lifetime.
The foregoing description of preferred embodiment of the present invention is by way of illustration of the inventive concepts herein and not by way of limitation. Those skilled in the art will recognize alternative configurations of the components described and illustrated herein, and alternative means of assembling them, to achieve particular flow patterns as may be desired for each unique application of the inventive nozzle assembly. All such alternative configurations and assembly and their equivalents that embody the spirit of the disclosed invention are intended to be within the scope of the claims appended hereto.
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