CA2187745A1 - V-jet atomizer - Google Patents
V-jet atomizerInfo
- Publication number
- CA2187745A1 CA2187745A1 CA002187745A CA2187745A CA2187745A1 CA 2187745 A1 CA2187745 A1 CA 2187745A1 CA 002187745 A CA002187745 A CA 002187745A CA 2187745 A CA2187745 A CA 2187745A CA 2187745 A1 CA2187745 A1 CA 2187745A1
- Authority
- CA
- Canada
- Prior art keywords
- fluid
- mixture
- passageway
- conical
- atomized
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E20/00—Combustion technologies with mitigation potential
- Y02E20/34—Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery
Landscapes
- Nozzles For Spraying Of Liquid Fuel (AREA)
Abstract
A fluid atomizer and spraying means which is made up of a mixing chamber (16) into which the fluid to be atomized and the atomizing gas are introduced and in which the fluid is admixed with and dispersed in the gas; a generally conical nozzle means extending from the mixing chamber (16) through which the mixed fluid and gas are forced; and a chamber into which the atomized mixed fluid and gas is sprayed. The conical nozzle means is suitably a relatively narrow frusto-conical passageway (28) which contains support-spacer means (34, 36, 38) which is generally parallel to the direction of flow through the passageway (28). At least one such support-spacer means (34, 36, 38) is provided which extends from the end of the passageway (28) proximate to the mixing chamber (16) to the end of the passageway (28) proximate to the chamber into which the mixture is sprayed. The preferred use of this apparatus is in atomizing fuel oil with steam and spraying such atomized mixture into a combustion chamber where it is contacted with combustion air. The amount of effluent NOX is reduced and limited by the use of this configuration by creating alternating fuel-rich and air-rich spatial distribution, and allowing the amount of stoichiometric excess air to be severely limited, while causing the substantially complete combustion of the fuel oil
Description
Wo 95/07761 - PCTNSg~/09768 21 877~5 -V-JET ATOMIZl;R
This invention is directed to the distribution of an atomi2ed fluid in an atomizing gas and to mealls for spraying such. It more particularly refers to a novel 5 dual fluid atomizer apparatus, including a novel spraying nozzle, and the use thereof.
B~CKGROUND OF THE INVENTION
It is well known that there are mally occasions when it is necessary or desirable to form a spray of a liquid 10 in a gas. One such time is in the combustion of a liquid fuel with a gaseous oxidant, for example air, as the means for heating a boiler. Other uses for this type Or operation are in humidification as well as in providing finely divided water droplets for cooling hot gases.
For ease of understanding, since the particular use to which tllis invention will be put will not substantially change the nature of this invention, this invention will be hereinafter described with particular relation to the use of the atomizer design of t~lis invention in connection with the heating means in an oil-fired boiler. This is not to be construed as a limitation on the use to wllich the atomizing means of this invention may be put.
In the field of combusting liquid fuel, it has been found that it is important to effectively control tlle quality of tile sprayed fuel in order to control the potelltial environmental hazards w~lich the effluent from tlle combustion may create. Tlle potential for creating effluent which is detrimental ~o the environment from combustion processes, particularly larse oil-fired steam generators, llas been exacerbated in recent years by a continued reduction in the quality of the liquid fuel being burne~. This has become particularly troublesome where residual fuel is being burned.
SUBSTITUTE SHE~T (RULE 26) WO95/~7761 ? 1 81145 PCTn~S94109768 The problem with t}le residual fuel which is now being fed to the burners of large steam generation facilities is that its heavier fractions have a tendency to form larger, heavier cenosplleric coke particles during combustion. As 5 the Conradson carbon number of the fuel increases, and tlle llydrogen to carbon ratio of the f uel decreases, as is the case with the use of residual fuel, the tendency of the fuel to be less completely combusted increases whereby the problem of coke particulate emissions is aggravated.
As bad as the situation has become over the recent past, it is reasonable ta expect that it will get worse during at least the near term in the future. Thus, it is important that means be found to assist in the utilization of residual fuel to fire steam boilers whereby particulate emissions therefrom are reduced to a manageable level, and whereby more of the energy contained in the residual fuel is used.
Oil f ired boilers are usually e~uipped with burners wllich are specially designed to combust oil with air to generate tlle heat necessary to create the desired steam.
One of the principal components of the burner is the atomizer, that is, the member wilich atomizes the oil to allow it to be readily and efficiently combusted with the air oxidant. The atomizer produces a spray of droplets containing the oil which are then contacted with the air.
One of the detrimental ef1uents produced by ti~e combustion of oil with air is NOX. The quantity of NOX
which is produced is known to be a function of the flame temperature, the local fuel/air stoichiometry and the intimacy of fuel/air mixing. The nature o the oil spray substantially effects the localized fuel/air mixing tllrough droplet dynamics (droplet inertia) and spatial spray distribution. Therefore, the intimacy of mixing of atomizing gas and oil to form the atomized spray, the intimacy of mixing the combustion air with the atomized SUBSTITUTE SHEET (RULE 2~3
This invention is directed to the distribution of an atomi2ed fluid in an atomizing gas and to mealls for spraying such. It more particularly refers to a novel 5 dual fluid atomizer apparatus, including a novel spraying nozzle, and the use thereof.
B~CKGROUND OF THE INVENTION
It is well known that there are mally occasions when it is necessary or desirable to form a spray of a liquid 10 in a gas. One such time is in the combustion of a liquid fuel with a gaseous oxidant, for example air, as the means for heating a boiler. Other uses for this type Or operation are in humidification as well as in providing finely divided water droplets for cooling hot gases.
For ease of understanding, since the particular use to which tllis invention will be put will not substantially change the nature of this invention, this invention will be hereinafter described with particular relation to the use of the atomizer design of t~lis invention in connection with the heating means in an oil-fired boiler. This is not to be construed as a limitation on the use to wllich the atomizing means of this invention may be put.
In the field of combusting liquid fuel, it has been found that it is important to effectively control tlle quality of tile sprayed fuel in order to control the potelltial environmental hazards w~lich the effluent from tlle combustion may create. Tlle potential for creating effluent which is detrimental ~o the environment from combustion processes, particularly larse oil-fired steam generators, llas been exacerbated in recent years by a continued reduction in the quality of the liquid fuel being burne~. This has become particularly troublesome where residual fuel is being burned.
SUBSTITUTE SHE~T (RULE 26) WO95/~7761 ? 1 81145 PCTn~S94109768 The problem with t}le residual fuel which is now being fed to the burners of large steam generation facilities is that its heavier fractions have a tendency to form larger, heavier cenosplleric coke particles during combustion. As 5 the Conradson carbon number of the fuel increases, and tlle llydrogen to carbon ratio of the f uel decreases, as is the case with the use of residual fuel, the tendency of the fuel to be less completely combusted increases whereby the problem of coke particulate emissions is aggravated.
As bad as the situation has become over the recent past, it is reasonable ta expect that it will get worse during at least the near term in the future. Thus, it is important that means be found to assist in the utilization of residual fuel to fire steam boilers whereby particulate emissions therefrom are reduced to a manageable level, and whereby more of the energy contained in the residual fuel is used.
Oil f ired boilers are usually e~uipped with burners wllich are specially designed to combust oil with air to generate tlle heat necessary to create the desired steam.
One of the principal components of the burner is the atomizer, that is, the member wilich atomizes the oil to allow it to be readily and efficiently combusted with the air oxidant. The atomizer produces a spray of droplets containing the oil which are then contacted with the air.
One of the detrimental ef1uents produced by ti~e combustion of oil with air is NOX. The quantity of NOX
which is produced is known to be a function of the flame temperature, the local fuel/air stoichiometry and the intimacy of fuel/air mixing. The nature o the oil spray substantially effects the localized fuel/air mixing tllrough droplet dynamics (droplet inertia) and spatial spray distribution. Therefore, the intimacy of mixing of atomizing gas and oil to form the atomized spray, the intimacy of mixing the combustion air with the atomized SUBSTITUTE SHEET (RULE 2~3
2 1 8 7 7 4 5 PCT~US9.OJ09768 oil droplets, and the nature of the atomization are quite influential on the NOX emissions of the burner.
The quality of the performance of the burner is often directly proportional to t11e performance oE the atomizer.
5 Atomizer performance is commonly measured in five (5) ways: (l) the Sauter Mean Diameter, often abbreviated SMD, of the size distribution of the atomized oil droplets; (2) tlle uniformity of oil mass flux around the periphery of the conically shaped spray of oil; (3) the apex angle of lO the spray cone; (4) the quantity of atomizing fluid, such as air, steam, or a mixture thereof, needed to produce a spray having a given, pre-specified Sauter Mean Diameter;
and (5) the variation of these parameters over a specified range of oil f low rates in a given burner construction .
15 It has been determined in the past that superior atomizer performance, in terms of these parameters: reduces carbonaceous particulate emissions, increases the caloric yield, and therefore expands the range of oils which can be used in this service.
In the past, a wide variety of atomizer designs have been used for this service. These have usually fallen into two general categories: dual fluid atomizers and mechanical atomizers . Dual f luid atomizers derive the energy, which they need to convert the liquid fuel into droplets, by the interaction of the fuel oil with an atomizing fluid, such as air, steam or a mixture thereof.
Mechanical atomizers usually rely on pressure on the liquid fuel, which forces such through a restricted orifice, to disrupt the fuel liquid into droplets.
Dual fluid atomization can usually be accomplished in one of two ways. ~ccording to the internal mixing method, the two f luids are bot~l simultaneously impacted against a suitable plate, such as a back plate of a mixing chamber, from which impact they then fill that mixing chamber with t~le intimate mixture of both f luids . The mixture is then SUBSTIME SHEET (RULE 26) 21 8~745 WO 95/07761 PCrlUS94/09768 .
e~ecte~ through a nozzle, suitably located in the atomizer 6pray plate, into the combustion zone of a f urnace .
I~ccording to another method, the external mixing method, liquid fuel and gas are each independently fed 5 into a common chamber, or several chambers, one for each exit aperture, at intersecting angles to intersperse the two f luids into a mixture. The mixture is then ejected from a suitable nozzle, which nozzle may be an integral part of tlle cllamber housing.
Mechanical atomization may be of the type in which all of the fuel oil, which is to be fed to an atomizing nozzle, is ejected into the combustion zone of a furnace, where it meets with combustion supporting air. The amount of oil fed to the furnace is controlled by controlling the amount of oil fed to the atomizer. This is referred to as a ~Dnce througl~, or Simplex, atomization. In the 80 called return flow type of atomizatioll, the oil flow to the atomizer is maintained at a constant level, but ollly a portion of the oil is fed into the furnace with the rest of it being recycled to tZle fuel oil reservoir. In any oE
these ca6es, in addition to the aerodynamics of the burner, the creation of droplets containing the fuel oil, and the physical properties of tZlese droplets are major determinants witZl respect to the quality of the fuel oil combustion in the furnace.
BROAD DESCRIPTION OF TliIS INVENTION
It is therefore an object of this invention to provide an improved atomizer especially designed to improve the overall efficiency of atomization of a liquid, 30 particularly fuel oil, and therefore to improve tlle overall Qfficiency of mixing the atomized liquid and a gas, for example ~:team, in order to improve the overall efficiency of the combustion of fuel oil in a furnace.
SU~STITUTE SHEET ~RULE 26,Z
Wo95/07761 2 1 8 7 7 4 5 PCT/US9~09768 It is another object of this invention to provide a novel atomizer design, as well a6 a process of atomi~ing a liquid using this novel designed atomizer.
It is a further object of this inventlon to provide ' 5 an improved process of combusting fuel oil, based on an improved atomizer design, in which the size and mass distribution of the less desirable emitted carbonaceous particles are limited whereby enhancing the burn-out of these particles.
It is a still further object of this invention to provide an improved atomizer design which will produce a spray of atomized particles having characteristics that promote mixing thereof with combustion air, particularly in burners wit~1 low primary air flows, or with recirculation f lows at t~1e axis of t~le burner .
It i5 a still further object of this invention to produce desirable fuel/air mixture ratios in a zone near the burner of an oil-fired furnace, and to minimize any exces6 oxygen requirements of the system, thereby ~0 ~iubstantially reducing the NOX emissions produced by the ~ystem .
It is a still further object of this invention to provide a novel atomizer design which is capable of producing a segmented stream oE atomized liquid having disproportionate stoichiometry ill the various spray 6egments .
Other and additional objects of this invention will become apparent from a consideration of this entire specification, including the drawing 1~ereof and the claims
The quality of the performance of the burner is often directly proportional to t11e performance oE the atomizer.
5 Atomizer performance is commonly measured in five (5) ways: (l) the Sauter Mean Diameter, often abbreviated SMD, of the size distribution of the atomized oil droplets; (2) tlle uniformity of oil mass flux around the periphery of the conically shaped spray of oil; (3) the apex angle of lO the spray cone; (4) the quantity of atomizing fluid, such as air, steam, or a mixture thereof, needed to produce a spray having a given, pre-specified Sauter Mean Diameter;
and (5) the variation of these parameters over a specified range of oil f low rates in a given burner construction .
15 It has been determined in the past that superior atomizer performance, in terms of these parameters: reduces carbonaceous particulate emissions, increases the caloric yield, and therefore expands the range of oils which can be used in this service.
In the past, a wide variety of atomizer designs have been used for this service. These have usually fallen into two general categories: dual fluid atomizers and mechanical atomizers . Dual f luid atomizers derive the energy, which they need to convert the liquid fuel into droplets, by the interaction of the fuel oil with an atomizing fluid, such as air, steam or a mixture thereof.
Mechanical atomizers usually rely on pressure on the liquid fuel, which forces such through a restricted orifice, to disrupt the fuel liquid into droplets.
Dual fluid atomization can usually be accomplished in one of two ways. ~ccording to the internal mixing method, the two f luids are bot~l simultaneously impacted against a suitable plate, such as a back plate of a mixing chamber, from which impact they then fill that mixing chamber with t~le intimate mixture of both f luids . The mixture is then SUBSTIME SHEET (RULE 26) 21 8~745 WO 95/07761 PCrlUS94/09768 .
e~ecte~ through a nozzle, suitably located in the atomizer 6pray plate, into the combustion zone of a f urnace .
I~ccording to another method, the external mixing method, liquid fuel and gas are each independently fed 5 into a common chamber, or several chambers, one for each exit aperture, at intersecting angles to intersperse the two f luids into a mixture. The mixture is then ejected from a suitable nozzle, which nozzle may be an integral part of tlle cllamber housing.
Mechanical atomization may be of the type in which all of the fuel oil, which is to be fed to an atomizing nozzle, is ejected into the combustion zone of a furnace, where it meets with combustion supporting air. The amount of oil fed to the furnace is controlled by controlling the amount of oil fed to the atomizer. This is referred to as a ~Dnce througl~, or Simplex, atomization. In the 80 called return flow type of atomizatioll, the oil flow to the atomizer is maintained at a constant level, but ollly a portion of the oil is fed into the furnace with the rest of it being recycled to tZle fuel oil reservoir. In any oE
these ca6es, in addition to the aerodynamics of the burner, the creation of droplets containing the fuel oil, and the physical properties of tZlese droplets are major determinants witZl respect to the quality of the fuel oil combustion in the furnace.
BROAD DESCRIPTION OF TliIS INVENTION
It is therefore an object of this invention to provide an improved atomizer especially designed to improve the overall efficiency of atomization of a liquid, 30 particularly fuel oil, and therefore to improve tlle overall Qfficiency of mixing the atomized liquid and a gas, for example ~:team, in order to improve the overall efficiency of the combustion of fuel oil in a furnace.
SU~STITUTE SHEET ~RULE 26,Z
Wo95/07761 2 1 8 7 7 4 5 PCT/US9~09768 It is another object of this invention to provide a novel atomizer design, as well a6 a process of atomi~ing a liquid using this novel designed atomizer.
It is a further object of this inventlon to provide ' 5 an improved process of combusting fuel oil, based on an improved atomizer design, in which the size and mass distribution of the less desirable emitted carbonaceous particles are limited whereby enhancing the burn-out of these particles.
It is a still further object of this invention to provide an improved atomizer design which will produce a spray of atomized particles having characteristics that promote mixing thereof with combustion air, particularly in burners wit~1 low primary air flows, or with recirculation f lows at t~1e axis of t~le burner .
It i5 a still further object of this invention to produce desirable fuel/air mixture ratios in a zone near the burner of an oil-fired furnace, and to minimize any exces6 oxygen requirements of the system, thereby ~0 ~iubstantially reducing the NOX emissions produced by the ~ystem .
It is a still further object of this invention to provide a novel atomizer design which is capable of producing a segmented stream oE atomized liquid having disproportionate stoichiometry ill the various spray 6egments .
Other and additional objects of this invention will become apparent from a consideration of this entire specification, including the drawing 1~ereof and the claims
3 0 appended hereto .
In accord with and fulfilling these objects, one a6pect o~ this invention comprises an novel atomizer SU8STITUTE SHEET (RULE 26) 2~ 87745 Wo 95/07761 PCT/US9~/09768 design. ~ccording to this design, the atomizer comprises:
a main body, which defines a generally centrally located, circumferel~tially defined open space;
a first conduit means, adapted to communicate through 5 said main body with said open space, to carry fuel oil through said main body and into said open space; and a second conduit means, adapted to communicate through said main body with said open space and to carry atomizing gas through said main body into said open space.
The main body of the atomizer of this invention comprises -one or more side walls, which may be straiyht or curved as desired and required;
a back plate member in closing contact with the side 15 wall(s) defining one end of the main body, and a first end to the opell space; and a front member, which defines a second end to the open space, at the end thereof opposite to the back plate member .
20 The side wall(s), the back plate member, and the front member define and confine an internal mixing chamber. The front member has a generally conical, preferably a right circular frustroconical, slot therein which may be axially aligned with the general center of the mixing chamber.
25 Preferably, the mixing chamber is substantially cylindrical, and there is substantially exact alignment o~
the axes of tilis cylinder and the conical slot.
This conical slot is in the front portion of the atomizer assembly, suitably either wholly within the front 30 member, or partially within the frol~t member and partially within or defined by the side wall (s) of the main body.
Preferably the conical slot is at the juncture between the front member and the side wall (s) of the main body of the atomizer of tllis invention. This slot serves as an exit 35 means and thereby communicates between the internal mixing chamber and an area, for example a furnace combustion chamber, outside the atomizer into whic~ the atomized SUBSTITUTE SHEET (RULE 26) W095/07761 21 g7745 PCr/US94/09768 liquid, for example the fuel, iæ intended to be sprayed.
Where required, means may be provided, suitably disposed through the mixing cl~amber, to operatively support the front member by at least ti1e back plate member of this 5 apparatus.
In a prQferred aspect of this invention, the conical spraying nozzle is segmented. ~hat is, the free passage of atomized material through the cone of the nozzle is interrupted one or more times, by piers suitably disposed lO around its periphery. In addition to their functional use in determining the geometry of the atomized fuel sprayed from the nozzle, these piers may also form the support structure for joining the inner surface of the cone to the outer surface thereof to form the nozzle (channel). In 15 this preferred embodiment of tl~is invention, the conical spraying nozzle may be formed between the front member and t~le side wall (s) of the main body, and the front member may be supportingly joined to the side walls at one or more places around the periphery oE the conical slot.
20 These joining members, or piers, may extend only part way along t}le length of the nozzle. That is they may extend from the front of the conical nozzle in contact with the furnace combustion chamber part way back along the length of t~1e conical channel. In the alternative, these joining 25 menlbers can be located toward tilP r~ar et1d of the conical cllannel starting from the mixing chamber end thereof and e~tending ollly part way alo1lg the ~e11gt~1 of the conical channel. If desired, it is within the spirit and scope of this invention to provide multiple piers along the length 30 of the conical slot. It is preferred, however, to have t11ese pier members extend along the complete length of the col1ical slot from the point where the mixing chamber communicates with tile slot, to the place where the slot communicates with tlle space into which the atomized f luid 35 will be sprayed. Preferably, there are a multiplicity of these joining members, or pier assemblies, spaced about tile periphery of tlle conical slot. The preferred SIJBSI ITUIE SHEET (RULE 26) Wo 95/077C1 2 ~ 8 7 7 4 5 PC~/US94/0976~
configuration is symmetrical, but the pier distribution may be asymmetric if desired.
The novel atomizer described here is adapted to be operatively associated with peripheral apparatus, such as:
means to supply the atomizing gas, means to supply the liquid to be atomized, such as fuel oil, means to pressurize any or all of: the atomizing gas, the liquid to be atomiz~d, and atomized liquid, receptacle means, such as the combustion chamber of a furnace means, into which the mixture of the atomized liquid and the atomizing gas, is sprayed, and where the receptacle means is a furnace combustion chamber, means to introduce all or additional combustion supporting gas, such as air, if needed, into the chamber, or, where the receptacle means is a humidifying chamber, means to introduce into the chamber the gas in need of humidification, suitably air.
sRIEF DESCRIPT~ON OF T~E DRAlqING
This invention will be ~etter understood with reference to the drawing, which is illustrative thereof, and in which:
Fig. 1 is a side sectional view of an atomizer deslgned according to one preferred aspect of this invention, which is provided with mean for adjustment of the exit channel width;
Fig. 2 is a plan view of one of a preferred nozzle design which is adapted to use in this invention;
Fig. 3 is a view of the preferre~ nozzle shown in 3 0 Fig . 2 which has been sectioned along the line 3 - 3 .
This Fig. 3 is a perspective view which looks generally in the direction of the arrows;
SUBSTITUTE SHEET ~RULE 26) _ _ _ _ . . . . .. .. ..... . .
Wo 95/07761 2 1 ~ 7 7~ 5 PCT/US91~09768 Flg. 4 i5 a sidQ view of the preferred nozzle design shown in Fig. 2. 6ectioned along the line 4 - 4 looking in the direction of the arrows;
Figs. 5 - 7 are a typical series of curves depicting 5 various relationships between the design of the atomizer of this invention and the properties of the spray provided thereby. These curves are provided as examples of the operation of this invention. Each specific operation, with its own unique parameters of operation will produce its own unique set of similar curves. In each figure, the specific relationship being depicted is set forth. Fig.
5 shows the relationship between Fuel Flow and supply Pressure; Fig. 6 shows the relationship between Atomizing Mass Ratio and Fuel Flow; and Fig. 7 shows the relationship between Atomizing Spray Quality and Fuel Flow .
DETAILED DESCRIPTION OF THIS INVENTION
Referring now to the drawing, this invention will be described with reference to the atomization of fuel oil, as the liquid to be atomized prior to its combustion, with steam, as the atomizing gaseous fluid. Referring now to Fig. 1, an atomizer according to this invention is shown comprising a generally hollow cylindrically shaped main body 10; a back plate means 12, substantially diametrally disposed across and enclosing one end of the generally hollow main body; and a front plate means 1~, substantially diametrally disposed across and enclosing the other end of the generally hollow main body, to thereby form an enclosed cavity, which serves as a mixing chamber 16 for use in this invention. There is suitably provided passage means 18 and 20 communicating sources of oil to be atomized (not shown) and atomizing steam (not shown) with the mixing chamber 16, preferably through the back plate means 12. These passage means are adapted to allow the introduction into the mixing chamber 16 of the SU~SIITUTE SHEET (RULE 26) WO 95/07761 _ 2 1 g 7 7 ~ ~ PCT/US94/09768 .
liquid 22 to be atomized and the atomizing gas 24. It should be noted that the 6pecif ic arrangement of liquid oil and atomizing steam supply passages is not critical.
In some applications, the6e passages are reversed from the 5 locations depicted here. The front plate means 14 is suitably mounted on the other end of the mixing chamber 16, and may be supported by the back plate means 12, such as by means of a pillar 26 which may pass through the mixing chamber 16.
At a location which may suitably be anywhere in the walls ~uLLu.nlding the mixing chamber 16, but is preferably in, or at least very near to, the front plate means 14 of this atomizer apparatus, there is provided at least one suitable opening 28 which is adapted to allow the atomized 15 mixture to be ejected out of the mixing chamber 16. In a preferred embodiment of this invention, the opening 28 is a conical passageway of a size and shape sufficient to produce a conical spray of atomized vaporous material into the combu6tion chamber. In a preferred aspect of this 20 invention only one such conical shaped passageway is provided for each mixing chamber, but it is possible for there to be two or more.
According to a preferred aspect of this invention, the conical shaped slot passageway or nozzle 28, which is 25 shown in greater detail in figs. 3 and 4, is made up of a pair of spaced apart walls 30 and 32 which define the conical passageway of the nozzle of this invention. These walls are preferably generally concentric and thereby define a conical passageway which has a substantially 30 uniform cross-sectional dimension or thickness. In other words, according to a preferrèd aspect of this invention, the conical nozzle neither diverges nor converges in thickness between the mixing chamber 16 and the area into which the atomized fluid is being sprayed. The width (or 35 thickness) of the conical channel is whatever width is suited to the throughput of atomized fluid and the SUBSTITUTE SHEET (RULE 2~) Wo 95l077 ~ 77~ PCTIUSg4/09768 viscosity thereof. Suitably, the apparatus o~ this invention is equipped with means for adjusting the thickness of the conical channel slot. It has been found that non-limiting channel thicknesses might be about 1/32 5 to 1/2 inch. Thicker or thinner channels are also suited to use in this invention. The angle of the conical nozzle passageway is suitably about 50 to 100. However, larger or smaller angles can be used in special situations.
It iG considered to be within the scope of this 10 invention to provide a conical nozzle means as described above in which the spaced apart walls, which form the conical nozzle, do either converge or diverge, as needed, at the point where the atomized mixture is sprayed out of the nozzle into the combustion chamber or the like. This 15 divergence or convergence is accomplished by providing the walls of the nozzle as cones of differing apex angles, but which preferably have common virtual apices. The angles of convergence or divergence are not particularly critical, but are typically small. Thus, convergent or 20 divergent angles of the walls of the conical channel might be up to about 15, preferably not greater than about 5.
The conical nozzle is preferably made up of two frustro right circular conical surfaces. However, the frustro conical sur~aces do not necessarily have to be 25 circular in cross-section. They may alternatively be elliptical in cross-section, or even irregular in cross-section, if this gives a desirable spray pattern of the atomized f luid.
As will be seen in Figs. 2, 3 and 4, the most 30 preferred aspect of this invention provides internal pier support-spacer means 34, 36 and 38, within the conical channel passageway 28. In the views shown in Figs. 2, 3 and 4, three such support means are shown. Ilowever, this specif ic number of support means is not critical to the 35 practice of this invention. It is possible to use two or '~U8STITUrE SHEET (RULE 26~
WO95107761 2 8774 ~ PCTrUSs4/09768 four or even more such support-spacer means as needed for the particular design of the nozzle being used in the embodiment of this invention which is being practiced.
According to a preferred practice of this invention, these 5 support-spacer pier means should preferably be spaced ~ymmetrically about the conical nozzle passageway. Thus, if there are three such support means, they should preferably be spaced about 120 along the cone axis; if there are four pier means, they should be spaced apart l0 about goo each. However, the spacing may be asymmetric if this will give the spray of atomized f luld that is des ired .
The support-spacer means used in the conical spray channel can extend throughout the length of the channel 15 all the way from the mixing chamber end to the combustion chamber end thereof. 11owever, it is also within the scope of this invention f or~ the spacer-support means to be located only partially along the length of the conical channel. In order to supply specialized support and 20 spacing functions, the spacer-support means may be located anywhere in the conical channel.
1~owever, it has been discovered, and it is an extremely important discovery within the context of this invention, that spacer-support means located at the exit 25 point in the conical nozzle passageway have an important segmentation effect on the geometry of the spray which emerges from the nozzle. The number and the spacing of these exit point spacers has a dramatic effect on the geometry of the atomized spray, on the characteristics of 30 combustion of that spray, and on the particulate, and NOX
emissions produced.
It has been reported elsewhere, see United States patent number 4,790,480, that disrupting a conical spray, from the exit of a nozzle, after it leaves the nozzle and 35 as it is being fed into a combustion chamber, causes SUBSTITUTE SHEET ~RULE 26) Wo95107761 ~ 7~ PCrlUSs4/09768 6ubstantial improvement in the combustion characteristics of the atomized fuel in the combustion chamber. When the conical stream is broken up after it leaves the nozzle, there is substantially improved burn-out accomplished, and 5 the combustion of the fuel oil is substantially more complete thereby reducing the potential adverse efects of the of f gas generated by the combustion .
In that patent, there is described means disposed outside of the nozzle that breaks up the atomized stream lO after it leaves the nozzle. This is to be distinguished from the structure of the instant invention where the stream comprising fuel passing through conical nozzle passageway is broken up within the nozzle, that is before it exits the nozzle and becomes a spray. The spray which 15 is produced according to the practice of this invention is a segmented, substantially conical spray, with non-uniform segments of spray about the entire periphery thereoE.
These segments may have different bulk densities and/or compositions. That is, because of the interposition of 20 the support-spacer pier means in the conical nozzle passageway, the spray which comes out of the nozzle of this invention has a non-uniform bulk density, composition and pattern as a function of the location of the support-spacers. Thus, alternating fuel-rich and air-ric}1 25 segments can be created around the periphery of the spray cone. By constricting this spray inside the nozzle means, the adverse consequences of externally disrupting the spray, which is shown in the '480 patent, are avoided.
The NOX and particulate emissions have been found to 30 be substantially reduced by the practice of this invention and particularly by the use of the special nozzle design which is described herein. During tests of the novel nozzle design of this invention, using heavy fuel oil as the atomized feed, it was found that the excess oxygen 35 requirement, that is the amount of excess oxygen which is required to insure maximum combustion of the fuel oil SUBSTlTUrE SHEET (RULE 26) Wo 95/07761 PCr/U l09768 377~}~ S94 1~1 within the operating parameters of the Gystem, was 6ubstantially decreased. This decrease in the excess oxygen requirement and the alternating fuel-rich and air-rich spatial distribution of the segmented spray causes 5 the NOX emissions to be substantially decreased.
Increased boiler efficiency was also obtained with the decrease in the excess oxygen requirement.
The mixing chamber and the nozzle may be made of any materials which are convenient and which will withstand 10 the rigors of the fluids being contacted therewith and the temperatures and thQ pressures at which these f luids are contacted therewith. Thus, if the fluids are corrosive, the materials of construction should be able to withstand corrosion by these fluids for at least an acceptable 15 service life. Metals and plastics are the usual materials of construction, with steel being especially desirable in most cases. It is considered to be within the scope of this invention to provide suitable coatings on the surfaces of the enclosure for the mixing chamber, the 20 spraying nozzle and the other elements of this apparatus.
Suitably, these coatings may render the underlying construction materials resistant to deterioration by contact with or passage of the contained f luids . For typical oil fired furnace-boiler applications, the 25 atomizer assembly (the main body, nozzle assembly, passageways, and the support shaft if employed) can preferably be constructed of tool steel, such as 1~-13 Rc 53-56 tool steel, or for more corrosive environments and application, AISI 440C pre-heat-treated steel.
With the atomizer design according to this invention specifically adapted for use in atomizing heavy fuel oil with atomizing steam, it has been found that, for a given atomized ruel to atomizing fluid pressure differential, the quality of the spray produced by the practice of this invention will not vary to any appreciable degree as a function of the size of the conical nozzle passageway. It SUBSrITUTE SHEET (RULE 26) _ _ _ WO9S10~761 ~ I 877~$ PCI/US94/09768 has been found that when the fuel oil to atomizing 6team pressure differential was held substantially constant at about 10 pslg., and the gap in the conical nozzle wa6 varied from about o. 078 inch to 0 .100 inch, the SMD
(Sauter Mean Diameter) varied only about 4 ~m from about 66~1m to about 7011m. However, under these conditions, a6 the gap setting was increased from 0 . 078 inch to 0 .100 inch, the exit velocity of the f luid decreased about 25% .
It was also found that the fluid pressures which were required to maintain equivalent fuel flow decreased proportionately to the increase in gap, because the fluids passing through the gap met less resistance to flow at the wider atomizer exit.
It was found that the adjustment of the exit gap width allowed the NOX emissions to be reduced, by providing lower excess oxygen requirements for a wide range of fuel to atomizing fluid pressure differentials.
Thus, variations in fluid Yelocities, small changes in effective spray angle, and the relative penetration of the fuel spray into and about the internal recirculation zone (IRZ) in the combustion chamber, which are associated with variations in the gap size, appear to have a significant impact on the excess oxygen requirement, and the fuel/air mixing rate that is required to support substantially complete fuel combustion with a minimum of NOX emissions.
The internal recirculation zone (IRZ) is a zone formed downstream of the atomizer exit at suf f iciently high levels of combustion air swirl in which combustion products are caused to be circulated back towards the fuel spray exiting the atomizer nozzle.
It has been pointed out above that the front plate means can suitably be supported by means of a center body 26 extending from the back plate means to the front plate.
It has also been pointed out that this is not an essential configuration of the apparatus of this invention, but that the front plate means and nozzle means could be assembled SUBSTITUTE SHEET (~ULE 26) WO 95l07761 ~ ~ 8 7 7 ~ 5 PCT/I~S9~/09768 in a different manner. In initial prototype evaluation, it has been found that it is preferred to utilize a center body support means which is threaded at the nozzle-front plate means end. In this manner, the gap in the conical nozzle passageway can be readily adjusted by bimply turning one surf ace thereof relative to the other about this threading.
Designs of nozzle means according to this invention can be assembled so that the spray is of only one or more portions of a cone. Thus, a full conical 6pray may be used, a partial conical spray may be used, or multiple spray segments, which are each portions of a cone, may be used. As an example of such multiple partial conical areas, a segmented V-jet with two (2) conical exit slots has also demonstrated reductions in NOX emissions of up to about 40% by being able to minimize the excess oxygen requirements of the system, by being able to adjust the stoichiometry of air and fuel about the conical spray, and by producing desirable fuel/air ratios in the zone near the burner. Further, such segmented nozzle sprays have encouraged more thorough combustion and have therefore produced off gases of substantially lower opacity, which are therefore more environmentally acceptable.
In practicing this invention, it has been f ound that the angle at which the atomizing gas and the f luid being atomized, respectively, enter the mixing chamber of the apparatus of this invention is an important consideration in the design of this apparatus from the perspective of efficiency of operation. It has been found to be most prcferred for each of the atomizing gas and the fluid being atomized to impinge upon the back plate means of the mixing chamber and to impact thereon at about a right angle. Of course, this is not an absolute limitation.
The angle may vary from goo to some extent, for example from about 75~ to 105, without substantially jeopardizing the advantageous results which are achieved by the SUBSrlTUTE SHEET (RULE 26J
Wo95/07761 .~ 1 877~ PCr/USs4l09768 practice of this invention. This provides for dynamic mixing of the atomizing gas and the fluid to be atomized, improves atomization, and reduces the consumption of atomizing gas in the operation.
The transport conduits which bring the atomizing gas and the atomized f luid into the mixing chamber may be located in a radial or a tangential manner with respect to the chamber. Where tangential introduction is employed, the two fluids can be introduced in co- or counter-current rotational direction with respect to the external air flow established by the burner flame stabilizer and registers.
By introducing angular momentum to the f luids being introduced into the mixing chamber, it is possible to influence some of the combustion characteristics of the atomized fuel. For example, co-rotating the fluids will decrease the f luid volume f lux in the near portion of the burner zone, and t~lereby reduce fuel rich areas therein.
5uch a design will increase the spray quality uniformity, and it will also positively effect fluid velocities and penetration of the atomized mixture into the near burner zone .
In designing the mixing chamber and conical nozzle assembly of this invention, and in establishing t}le operating conditions for a process usil1g t~lis apparatus, it is possible to introduce variations in size and shape which will affect the residence time in the mixing cllamber. Thus it is possible to optimize this residence time. It i5 preferred that the mixing chamber be directly upstream of the conical nozzle, and that the combustion ci~amber be immediately downstream of the conical nozzle.
sy assembling these elements in very close proximity, it is possible to minimize t~le time lag between atomization in the mixing chamber and combustion in t~1e combustion chamber. The closer these elements are to each other, the less is tlle likelihood that the atomized condition of the fuel will break down prior to combustion thereof.
~UBSTITLITE SHEET (RULE 26) The V-jet atomizer of this invention provides substantially constant spray quality into the combustion 20ne. The droplet size and atomizing mass ratios (6team to oil) are substantially constant over a wide range of fluid input pressures for a given atomizing gas to fluid pressure di$ferential in the range of between about 10 and 30 psig. In a V-jet operation according to this invention at a pressure differential of about 10 psig, a typical operating system can operate at mass ratios of only about 10%. ~3ecause operating in the manner of this invention with the apparatus of this invention still provides excellent atomization even at very low input pressures and flows, this condition allows the operator to be able to turn down the furnace/boiler, that is to reduce boiler load, without having to shut off burners and thereby remove burners f rom service .
The following example is illustrative of the practice of this invention. It is not to be considered as being in any way limiting on the scope of the invention or of the claims appended hereto. In this example, parts and percentages are by weight unless specif ied to be on some other basis.
~a_ple An internal mix V-jet atomizer design was tested using a heavy oil to feed the burners of a 150 klbs/hr utility package boiler . The conventionally boiler f ired low sulfur (<0. 3%) No. 6 fuel oil and used steam as the atomizing fluid. The prototype atomizer tested had an adjustable gap setting feature and an effective spray angle of between 70 and 75. Reference is made to ~ig. 1 of the attached drawings for design details.
The conical spray nozzle-atomizer was tested at three exit gap settings, 0.078", 0.089" and 0.100". As the gap setting was increased from 0.078" to 0.100", the fluid SUBSIITUTE SHEET (RULE 2E~
. , . , .. . .. ... . _ -Wo 9Sl07761 2 1 8 7 7 4 5 pcr/uss4/o9768 exit velocities were significantly decreased, by about 25%. The fluid pressures required to maintain a particular ~uel f low were also reduced as the exit gap width increased. At each of the gap settings, a range of 5 operating parameters was evaluated, including: 1) fuel oil to atomizing steam pressure differential, 2) fuel flow, 3) excess 2 requirement levels, 4) burner register swirl, 5) various flame 6tabilizer designs, and 6) oil gun and stabilizer axial position.
For each of the curved vane swirlers and V-Jet Qxit gap settings (and combinations thereof) ~minP-I, it was noted that the NOX emissions were signif icantly decreased as the fuel oil to steam pressure differential (~P) was increased from 0 to 20 psi. In most cases, as the ~P was 15 increased, and the spray quality thereby improved (reduced droplet sizes), less excess 2 was required to maintain low opacity levela. This reduction in the reguired excess 2 level resulted in a signif icant reduction in NOX
emissions. This effect was particularly apparent under 20 moderate register swirl conditions.
For a given fuel oil to atomi2ing steam pressure differential, the spray quality (as calculated) did not vary signif icantly as a function of gap settings .
However, the mid-range gap setting of 0 . 089", provided 25 lower NOX emissions and lower excess 2 requirements for fuel oil to atomizing steam pressure differentials of 0 and 10 psi. Thus, variations in the fluid exit velocities (and perhaps slight variations in the ef fective spray angle), and variations in the relative penetration of the 30 fuel spray into and about the IRZ, associated with the variation of the gap size, had signif icant impacts on the level of excess 2 required, the local fuel/air ratios, the fuel/air mixing rates, and the resulting NOX
emissions .
A segmented V-jet design was also evaluated during SUBSTITUTE SHEET (RULE 26~
Wo 95107761 2 1 8 7 7 4 5 PCTIUS94/09768 the above test program. This design, which segmented the fuel spray into two portions of a complete cone (highly fuel rich areas), was shown to produce the lowest NOX
emissions of all atomizers tested during the f ield 5 demonstration. That is, lower than all standard, Low-~OX, and other novel atomizer designs. A NOX reduction of approximately 43% (as compared to the original boiler hardware) was documented, with no observed increase in particulate matter emissions.
An additional segmented V-jet with two (2) exit slots, was tested on a face-fired boiler with eight (8) Peabody APR 21 burners. Again, the use of this atomizer design resulted in NOX emission reductions of about 40%
from the baseline conditions, despite significant 15 differences in burner configuration from the previous example .
5U~STITUTE SHEET (RULE 26)
In accord with and fulfilling these objects, one a6pect o~ this invention comprises an novel atomizer SU8STITUTE SHEET (RULE 26) 2~ 87745 Wo 95/07761 PCT/US9~/09768 design. ~ccording to this design, the atomizer comprises:
a main body, which defines a generally centrally located, circumferel~tially defined open space;
a first conduit means, adapted to communicate through 5 said main body with said open space, to carry fuel oil through said main body and into said open space; and a second conduit means, adapted to communicate through said main body with said open space and to carry atomizing gas through said main body into said open space.
The main body of the atomizer of this invention comprises -one or more side walls, which may be straiyht or curved as desired and required;
a back plate member in closing contact with the side 15 wall(s) defining one end of the main body, and a first end to the opell space; and a front member, which defines a second end to the open space, at the end thereof opposite to the back plate member .
20 The side wall(s), the back plate member, and the front member define and confine an internal mixing chamber. The front member has a generally conical, preferably a right circular frustroconical, slot therein which may be axially aligned with the general center of the mixing chamber.
25 Preferably, the mixing chamber is substantially cylindrical, and there is substantially exact alignment o~
the axes of tilis cylinder and the conical slot.
This conical slot is in the front portion of the atomizer assembly, suitably either wholly within the front 30 member, or partially within the frol~t member and partially within or defined by the side wall (s) of the main body.
Preferably the conical slot is at the juncture between the front member and the side wall (s) of the main body of the atomizer of tllis invention. This slot serves as an exit 35 means and thereby communicates between the internal mixing chamber and an area, for example a furnace combustion chamber, outside the atomizer into whic~ the atomized SUBSTITUTE SHEET (RULE 26) W095/07761 21 g7745 PCr/US94/09768 liquid, for example the fuel, iæ intended to be sprayed.
Where required, means may be provided, suitably disposed through the mixing cl~amber, to operatively support the front member by at least ti1e back plate member of this 5 apparatus.
In a prQferred aspect of this invention, the conical spraying nozzle is segmented. ~hat is, the free passage of atomized material through the cone of the nozzle is interrupted one or more times, by piers suitably disposed lO around its periphery. In addition to their functional use in determining the geometry of the atomized fuel sprayed from the nozzle, these piers may also form the support structure for joining the inner surface of the cone to the outer surface thereof to form the nozzle (channel). In 15 this preferred embodiment of tl~is invention, the conical spraying nozzle may be formed between the front member and t~le side wall (s) of the main body, and the front member may be supportingly joined to the side walls at one or more places around the periphery oE the conical slot.
20 These joining members, or piers, may extend only part way along t}le length of the nozzle. That is they may extend from the front of the conical nozzle in contact with the furnace combustion chamber part way back along the length of t~1e conical channel. In the alternative, these joining 25 menlbers can be located toward tilP r~ar et1d of the conical cllannel starting from the mixing chamber end thereof and e~tending ollly part way alo1lg the ~e11gt~1 of the conical channel. If desired, it is within the spirit and scope of this invention to provide multiple piers along the length 30 of the conical slot. It is preferred, however, to have t11ese pier members extend along the complete length of the col1ical slot from the point where the mixing chamber communicates with tile slot, to the place where the slot communicates with tlle space into which the atomized f luid 35 will be sprayed. Preferably, there are a multiplicity of these joining members, or pier assemblies, spaced about tile periphery of tlle conical slot. The preferred SIJBSI ITUIE SHEET (RULE 26) Wo 95/077C1 2 ~ 8 7 7 4 5 PC~/US94/0976~
configuration is symmetrical, but the pier distribution may be asymmetric if desired.
The novel atomizer described here is adapted to be operatively associated with peripheral apparatus, such as:
means to supply the atomizing gas, means to supply the liquid to be atomized, such as fuel oil, means to pressurize any or all of: the atomizing gas, the liquid to be atomiz~d, and atomized liquid, receptacle means, such as the combustion chamber of a furnace means, into which the mixture of the atomized liquid and the atomizing gas, is sprayed, and where the receptacle means is a furnace combustion chamber, means to introduce all or additional combustion supporting gas, such as air, if needed, into the chamber, or, where the receptacle means is a humidifying chamber, means to introduce into the chamber the gas in need of humidification, suitably air.
sRIEF DESCRIPT~ON OF T~E DRAlqING
This invention will be ~etter understood with reference to the drawing, which is illustrative thereof, and in which:
Fig. 1 is a side sectional view of an atomizer deslgned according to one preferred aspect of this invention, which is provided with mean for adjustment of the exit channel width;
Fig. 2 is a plan view of one of a preferred nozzle design which is adapted to use in this invention;
Fig. 3 is a view of the preferre~ nozzle shown in 3 0 Fig . 2 which has been sectioned along the line 3 - 3 .
This Fig. 3 is a perspective view which looks generally in the direction of the arrows;
SUBSTITUTE SHEET ~RULE 26) _ _ _ _ . . . . .. .. ..... . .
Wo 95/07761 2 1 ~ 7 7~ 5 PCT/US91~09768 Flg. 4 i5 a sidQ view of the preferred nozzle design shown in Fig. 2. 6ectioned along the line 4 - 4 looking in the direction of the arrows;
Figs. 5 - 7 are a typical series of curves depicting 5 various relationships between the design of the atomizer of this invention and the properties of the spray provided thereby. These curves are provided as examples of the operation of this invention. Each specific operation, with its own unique parameters of operation will produce its own unique set of similar curves. In each figure, the specific relationship being depicted is set forth. Fig.
5 shows the relationship between Fuel Flow and supply Pressure; Fig. 6 shows the relationship between Atomizing Mass Ratio and Fuel Flow; and Fig. 7 shows the relationship between Atomizing Spray Quality and Fuel Flow .
DETAILED DESCRIPTION OF THIS INVENTION
Referring now to the drawing, this invention will be described with reference to the atomization of fuel oil, as the liquid to be atomized prior to its combustion, with steam, as the atomizing gaseous fluid. Referring now to Fig. 1, an atomizer according to this invention is shown comprising a generally hollow cylindrically shaped main body 10; a back plate means 12, substantially diametrally disposed across and enclosing one end of the generally hollow main body; and a front plate means 1~, substantially diametrally disposed across and enclosing the other end of the generally hollow main body, to thereby form an enclosed cavity, which serves as a mixing chamber 16 for use in this invention. There is suitably provided passage means 18 and 20 communicating sources of oil to be atomized (not shown) and atomizing steam (not shown) with the mixing chamber 16, preferably through the back plate means 12. These passage means are adapted to allow the introduction into the mixing chamber 16 of the SU~SIITUTE SHEET (RULE 26) WO 95/07761 _ 2 1 g 7 7 ~ ~ PCT/US94/09768 .
liquid 22 to be atomized and the atomizing gas 24. It should be noted that the 6pecif ic arrangement of liquid oil and atomizing steam supply passages is not critical.
In some applications, the6e passages are reversed from the 5 locations depicted here. The front plate means 14 is suitably mounted on the other end of the mixing chamber 16, and may be supported by the back plate means 12, such as by means of a pillar 26 which may pass through the mixing chamber 16.
At a location which may suitably be anywhere in the walls ~uLLu.nlding the mixing chamber 16, but is preferably in, or at least very near to, the front plate means 14 of this atomizer apparatus, there is provided at least one suitable opening 28 which is adapted to allow the atomized 15 mixture to be ejected out of the mixing chamber 16. In a preferred embodiment of this invention, the opening 28 is a conical passageway of a size and shape sufficient to produce a conical spray of atomized vaporous material into the combu6tion chamber. In a preferred aspect of this 20 invention only one such conical shaped passageway is provided for each mixing chamber, but it is possible for there to be two or more.
According to a preferred aspect of this invention, the conical shaped slot passageway or nozzle 28, which is 25 shown in greater detail in figs. 3 and 4, is made up of a pair of spaced apart walls 30 and 32 which define the conical passageway of the nozzle of this invention. These walls are preferably generally concentric and thereby define a conical passageway which has a substantially 30 uniform cross-sectional dimension or thickness. In other words, according to a preferrèd aspect of this invention, the conical nozzle neither diverges nor converges in thickness between the mixing chamber 16 and the area into which the atomized fluid is being sprayed. The width (or 35 thickness) of the conical channel is whatever width is suited to the throughput of atomized fluid and the SUBSTITUTE SHEET (RULE 2~) Wo 95l077 ~ 77~ PCTIUSg4/09768 viscosity thereof. Suitably, the apparatus o~ this invention is equipped with means for adjusting the thickness of the conical channel slot. It has been found that non-limiting channel thicknesses might be about 1/32 5 to 1/2 inch. Thicker or thinner channels are also suited to use in this invention. The angle of the conical nozzle passageway is suitably about 50 to 100. However, larger or smaller angles can be used in special situations.
It iG considered to be within the scope of this 10 invention to provide a conical nozzle means as described above in which the spaced apart walls, which form the conical nozzle, do either converge or diverge, as needed, at the point where the atomized mixture is sprayed out of the nozzle into the combustion chamber or the like. This 15 divergence or convergence is accomplished by providing the walls of the nozzle as cones of differing apex angles, but which preferably have common virtual apices. The angles of convergence or divergence are not particularly critical, but are typically small. Thus, convergent or 20 divergent angles of the walls of the conical channel might be up to about 15, preferably not greater than about 5.
The conical nozzle is preferably made up of two frustro right circular conical surfaces. However, the frustro conical sur~aces do not necessarily have to be 25 circular in cross-section. They may alternatively be elliptical in cross-section, or even irregular in cross-section, if this gives a desirable spray pattern of the atomized f luid.
As will be seen in Figs. 2, 3 and 4, the most 30 preferred aspect of this invention provides internal pier support-spacer means 34, 36 and 38, within the conical channel passageway 28. In the views shown in Figs. 2, 3 and 4, three such support means are shown. Ilowever, this specif ic number of support means is not critical to the 35 practice of this invention. It is possible to use two or '~U8STITUrE SHEET (RULE 26~
WO95107761 2 8774 ~ PCTrUSs4/09768 four or even more such support-spacer means as needed for the particular design of the nozzle being used in the embodiment of this invention which is being practiced.
According to a preferred practice of this invention, these 5 support-spacer pier means should preferably be spaced ~ymmetrically about the conical nozzle passageway. Thus, if there are three such support means, they should preferably be spaced about 120 along the cone axis; if there are four pier means, they should be spaced apart l0 about goo each. However, the spacing may be asymmetric if this will give the spray of atomized f luld that is des ired .
The support-spacer means used in the conical spray channel can extend throughout the length of the channel 15 all the way from the mixing chamber end to the combustion chamber end thereof. 11owever, it is also within the scope of this invention f or~ the spacer-support means to be located only partially along the length of the conical channel. In order to supply specialized support and 20 spacing functions, the spacer-support means may be located anywhere in the conical channel.
1~owever, it has been discovered, and it is an extremely important discovery within the context of this invention, that spacer-support means located at the exit 25 point in the conical nozzle passageway have an important segmentation effect on the geometry of the spray which emerges from the nozzle. The number and the spacing of these exit point spacers has a dramatic effect on the geometry of the atomized spray, on the characteristics of 30 combustion of that spray, and on the particulate, and NOX
emissions produced.
It has been reported elsewhere, see United States patent number 4,790,480, that disrupting a conical spray, from the exit of a nozzle, after it leaves the nozzle and 35 as it is being fed into a combustion chamber, causes SUBSTITUTE SHEET ~RULE 26) Wo95107761 ~ 7~ PCrlUSs4/09768 6ubstantial improvement in the combustion characteristics of the atomized fuel in the combustion chamber. When the conical stream is broken up after it leaves the nozzle, there is substantially improved burn-out accomplished, and 5 the combustion of the fuel oil is substantially more complete thereby reducing the potential adverse efects of the of f gas generated by the combustion .
In that patent, there is described means disposed outside of the nozzle that breaks up the atomized stream lO after it leaves the nozzle. This is to be distinguished from the structure of the instant invention where the stream comprising fuel passing through conical nozzle passageway is broken up within the nozzle, that is before it exits the nozzle and becomes a spray. The spray which 15 is produced according to the practice of this invention is a segmented, substantially conical spray, with non-uniform segments of spray about the entire periphery thereoE.
These segments may have different bulk densities and/or compositions. That is, because of the interposition of 20 the support-spacer pier means in the conical nozzle passageway, the spray which comes out of the nozzle of this invention has a non-uniform bulk density, composition and pattern as a function of the location of the support-spacers. Thus, alternating fuel-rich and air-ric}1 25 segments can be created around the periphery of the spray cone. By constricting this spray inside the nozzle means, the adverse consequences of externally disrupting the spray, which is shown in the '480 patent, are avoided.
The NOX and particulate emissions have been found to 30 be substantially reduced by the practice of this invention and particularly by the use of the special nozzle design which is described herein. During tests of the novel nozzle design of this invention, using heavy fuel oil as the atomized feed, it was found that the excess oxygen 35 requirement, that is the amount of excess oxygen which is required to insure maximum combustion of the fuel oil SUBSTlTUrE SHEET (RULE 26) Wo 95/07761 PCr/U l09768 377~}~ S94 1~1 within the operating parameters of the Gystem, was 6ubstantially decreased. This decrease in the excess oxygen requirement and the alternating fuel-rich and air-rich spatial distribution of the segmented spray causes 5 the NOX emissions to be substantially decreased.
Increased boiler efficiency was also obtained with the decrease in the excess oxygen requirement.
The mixing chamber and the nozzle may be made of any materials which are convenient and which will withstand 10 the rigors of the fluids being contacted therewith and the temperatures and thQ pressures at which these f luids are contacted therewith. Thus, if the fluids are corrosive, the materials of construction should be able to withstand corrosion by these fluids for at least an acceptable 15 service life. Metals and plastics are the usual materials of construction, with steel being especially desirable in most cases. It is considered to be within the scope of this invention to provide suitable coatings on the surfaces of the enclosure for the mixing chamber, the 20 spraying nozzle and the other elements of this apparatus.
Suitably, these coatings may render the underlying construction materials resistant to deterioration by contact with or passage of the contained f luids . For typical oil fired furnace-boiler applications, the 25 atomizer assembly (the main body, nozzle assembly, passageways, and the support shaft if employed) can preferably be constructed of tool steel, such as 1~-13 Rc 53-56 tool steel, or for more corrosive environments and application, AISI 440C pre-heat-treated steel.
With the atomizer design according to this invention specifically adapted for use in atomizing heavy fuel oil with atomizing steam, it has been found that, for a given atomized ruel to atomizing fluid pressure differential, the quality of the spray produced by the practice of this invention will not vary to any appreciable degree as a function of the size of the conical nozzle passageway. It SUBSrITUTE SHEET (RULE 26) _ _ _ WO9S10~761 ~ I 877~$ PCI/US94/09768 has been found that when the fuel oil to atomizing 6team pressure differential was held substantially constant at about 10 pslg., and the gap in the conical nozzle wa6 varied from about o. 078 inch to 0 .100 inch, the SMD
(Sauter Mean Diameter) varied only about 4 ~m from about 66~1m to about 7011m. However, under these conditions, a6 the gap setting was increased from 0 . 078 inch to 0 .100 inch, the exit velocity of the f luid decreased about 25% .
It was also found that the fluid pressures which were required to maintain equivalent fuel flow decreased proportionately to the increase in gap, because the fluids passing through the gap met less resistance to flow at the wider atomizer exit.
It was found that the adjustment of the exit gap width allowed the NOX emissions to be reduced, by providing lower excess oxygen requirements for a wide range of fuel to atomizing fluid pressure differentials.
Thus, variations in fluid Yelocities, small changes in effective spray angle, and the relative penetration of the fuel spray into and about the internal recirculation zone (IRZ) in the combustion chamber, which are associated with variations in the gap size, appear to have a significant impact on the excess oxygen requirement, and the fuel/air mixing rate that is required to support substantially complete fuel combustion with a minimum of NOX emissions.
The internal recirculation zone (IRZ) is a zone formed downstream of the atomizer exit at suf f iciently high levels of combustion air swirl in which combustion products are caused to be circulated back towards the fuel spray exiting the atomizer nozzle.
It has been pointed out above that the front plate means can suitably be supported by means of a center body 26 extending from the back plate means to the front plate.
It has also been pointed out that this is not an essential configuration of the apparatus of this invention, but that the front plate means and nozzle means could be assembled SUBSTITUTE SHEET (~ULE 26) WO 95l07761 ~ ~ 8 7 7 ~ 5 PCT/I~S9~/09768 in a different manner. In initial prototype evaluation, it has been found that it is preferred to utilize a center body support means which is threaded at the nozzle-front plate means end. In this manner, the gap in the conical nozzle passageway can be readily adjusted by bimply turning one surf ace thereof relative to the other about this threading.
Designs of nozzle means according to this invention can be assembled so that the spray is of only one or more portions of a cone. Thus, a full conical 6pray may be used, a partial conical spray may be used, or multiple spray segments, which are each portions of a cone, may be used. As an example of such multiple partial conical areas, a segmented V-jet with two (2) conical exit slots has also demonstrated reductions in NOX emissions of up to about 40% by being able to minimize the excess oxygen requirements of the system, by being able to adjust the stoichiometry of air and fuel about the conical spray, and by producing desirable fuel/air ratios in the zone near the burner. Further, such segmented nozzle sprays have encouraged more thorough combustion and have therefore produced off gases of substantially lower opacity, which are therefore more environmentally acceptable.
In practicing this invention, it has been f ound that the angle at which the atomizing gas and the f luid being atomized, respectively, enter the mixing chamber of the apparatus of this invention is an important consideration in the design of this apparatus from the perspective of efficiency of operation. It has been found to be most prcferred for each of the atomizing gas and the fluid being atomized to impinge upon the back plate means of the mixing chamber and to impact thereon at about a right angle. Of course, this is not an absolute limitation.
The angle may vary from goo to some extent, for example from about 75~ to 105, without substantially jeopardizing the advantageous results which are achieved by the SUBSrlTUTE SHEET (RULE 26J
Wo95/07761 .~ 1 877~ PCr/USs4l09768 practice of this invention. This provides for dynamic mixing of the atomizing gas and the fluid to be atomized, improves atomization, and reduces the consumption of atomizing gas in the operation.
The transport conduits which bring the atomizing gas and the atomized f luid into the mixing chamber may be located in a radial or a tangential manner with respect to the chamber. Where tangential introduction is employed, the two fluids can be introduced in co- or counter-current rotational direction with respect to the external air flow established by the burner flame stabilizer and registers.
By introducing angular momentum to the f luids being introduced into the mixing chamber, it is possible to influence some of the combustion characteristics of the atomized fuel. For example, co-rotating the fluids will decrease the f luid volume f lux in the near portion of the burner zone, and t~lereby reduce fuel rich areas therein.
5uch a design will increase the spray quality uniformity, and it will also positively effect fluid velocities and penetration of the atomized mixture into the near burner zone .
In designing the mixing chamber and conical nozzle assembly of this invention, and in establishing t}le operating conditions for a process usil1g t~lis apparatus, it is possible to introduce variations in size and shape which will affect the residence time in the mixing cllamber. Thus it is possible to optimize this residence time. It i5 preferred that the mixing chamber be directly upstream of the conical nozzle, and that the combustion ci~amber be immediately downstream of the conical nozzle.
sy assembling these elements in very close proximity, it is possible to minimize t~le time lag between atomization in the mixing chamber and combustion in t~1e combustion chamber. The closer these elements are to each other, the less is tlle likelihood that the atomized condition of the fuel will break down prior to combustion thereof.
~UBSTITLITE SHEET (RULE 26) The V-jet atomizer of this invention provides substantially constant spray quality into the combustion 20ne. The droplet size and atomizing mass ratios (6team to oil) are substantially constant over a wide range of fluid input pressures for a given atomizing gas to fluid pressure di$ferential in the range of between about 10 and 30 psig. In a V-jet operation according to this invention at a pressure differential of about 10 psig, a typical operating system can operate at mass ratios of only about 10%. ~3ecause operating in the manner of this invention with the apparatus of this invention still provides excellent atomization even at very low input pressures and flows, this condition allows the operator to be able to turn down the furnace/boiler, that is to reduce boiler load, without having to shut off burners and thereby remove burners f rom service .
The following example is illustrative of the practice of this invention. It is not to be considered as being in any way limiting on the scope of the invention or of the claims appended hereto. In this example, parts and percentages are by weight unless specif ied to be on some other basis.
~a_ple An internal mix V-jet atomizer design was tested using a heavy oil to feed the burners of a 150 klbs/hr utility package boiler . The conventionally boiler f ired low sulfur (<0. 3%) No. 6 fuel oil and used steam as the atomizing fluid. The prototype atomizer tested had an adjustable gap setting feature and an effective spray angle of between 70 and 75. Reference is made to ~ig. 1 of the attached drawings for design details.
The conical spray nozzle-atomizer was tested at three exit gap settings, 0.078", 0.089" and 0.100". As the gap setting was increased from 0.078" to 0.100", the fluid SUBSIITUTE SHEET (RULE 2E~
. , . , .. . .. ... . _ -Wo 9Sl07761 2 1 8 7 7 4 5 pcr/uss4/o9768 exit velocities were significantly decreased, by about 25%. The fluid pressures required to maintain a particular ~uel f low were also reduced as the exit gap width increased. At each of the gap settings, a range of 5 operating parameters was evaluated, including: 1) fuel oil to atomizing steam pressure differential, 2) fuel flow, 3) excess 2 requirement levels, 4) burner register swirl, 5) various flame 6tabilizer designs, and 6) oil gun and stabilizer axial position.
For each of the curved vane swirlers and V-Jet Qxit gap settings (and combinations thereof) ~minP-I, it was noted that the NOX emissions were signif icantly decreased as the fuel oil to steam pressure differential (~P) was increased from 0 to 20 psi. In most cases, as the ~P was 15 increased, and the spray quality thereby improved (reduced droplet sizes), less excess 2 was required to maintain low opacity levela. This reduction in the reguired excess 2 level resulted in a signif icant reduction in NOX
emissions. This effect was particularly apparent under 20 moderate register swirl conditions.
For a given fuel oil to atomi2ing steam pressure differential, the spray quality (as calculated) did not vary signif icantly as a function of gap settings .
However, the mid-range gap setting of 0 . 089", provided 25 lower NOX emissions and lower excess 2 requirements for fuel oil to atomizing steam pressure differentials of 0 and 10 psi. Thus, variations in the fluid exit velocities (and perhaps slight variations in the ef fective spray angle), and variations in the relative penetration of the 30 fuel spray into and about the IRZ, associated with the variation of the gap size, had signif icant impacts on the level of excess 2 required, the local fuel/air ratios, the fuel/air mixing rates, and the resulting NOX
emissions .
A segmented V-jet design was also evaluated during SUBSTITUTE SHEET (RULE 26~
Wo 95107761 2 1 8 7 7 4 5 PCTIUS94/09768 the above test program. This design, which segmented the fuel spray into two portions of a complete cone (highly fuel rich areas), was shown to produce the lowest NOX
emissions of all atomizers tested during the f ield 5 demonstration. That is, lower than all standard, Low-~OX, and other novel atomizer designs. A NOX reduction of approximately 43% (as compared to the original boiler hardware) was documented, with no observed increase in particulate matter emissions.
An additional segmented V-jet with two (2) exit slots, was tested on a face-fired boiler with eight (8) Peabody APR 21 burners. Again, the use of this atomizer design resulted in NOX emission reductions of about 40%
from the baseline conditions, despite significant 15 differences in burner configuration from the previous example .
5U~STITUTE SHEET (RULE 26)
Claims (20)
1. In a fluid atomizer comprising:
a substantially hollow main body comprising wall means which together comprise an enclosed mixing chamber;
means to introduce fluid to be atomized and atomizing gas into said mixing chamber;
means to impinge and impact said atomizing gas and said fluid to be atomized with each other in said mixing chamber under conditions sufficient to cause intermixing of said fluid and said gas and to cause atomization of said fluid in said gas to form a mixture of said atomized fluid and said gas;
means to pressurize said mixture in said mixing chamber;
substantially frustro-conically shaped diverging nozzle means communicating said enclosed mixing chamber with space outside said hollow main body;
means to force said pressurized mixture of said gas and said atomized fluid out of said mixing chamber through said nozzle means; and means to divergingly expel said mixture from said nozzle means into said space as a substantially conical spray;
the improved apparatus which comprises:
longitudinally elongated pier means disposed within said nozzle means to define a multiplicity of longitudinal, axially diverging passageways through said nozzle means which progressively widen in an axially diverging direction, wherein said passageways occupy a major portion of said nozzle means and said piers occupy a minor portion of said nozzle means;
means to cause said mixture to pass through said passageways and to axially divergingly emerge from said nozzle means as a multiplicity of mixture-rich regions, corresponding to the locations of said passageways, interspersed with a multiplicity of mixture-lean regions, corresponding to the locations of said piers, which mixture-rich and mixture-lean regions, taken together, comprise a diverging substantially conical spray.
a substantially hollow main body comprising wall means which together comprise an enclosed mixing chamber;
means to introduce fluid to be atomized and atomizing gas into said mixing chamber;
means to impinge and impact said atomizing gas and said fluid to be atomized with each other in said mixing chamber under conditions sufficient to cause intermixing of said fluid and said gas and to cause atomization of said fluid in said gas to form a mixture of said atomized fluid and said gas;
means to pressurize said mixture in said mixing chamber;
substantially frustro-conically shaped diverging nozzle means communicating said enclosed mixing chamber with space outside said hollow main body;
means to force said pressurized mixture of said gas and said atomized fluid out of said mixing chamber through said nozzle means; and means to divergingly expel said mixture from said nozzle means into said space as a substantially conical spray;
the improved apparatus which comprises:
longitudinally elongated pier means disposed within said nozzle means to define a multiplicity of longitudinal, axially diverging passageways through said nozzle means which progressively widen in an axially diverging direction, wherein said passageways occupy a major portion of said nozzle means and said piers occupy a minor portion of said nozzle means;
means to cause said mixture to pass through said passageways and to axially divergingly emerge from said nozzle means as a multiplicity of mixture-rich regions, corresponding to the locations of said passageways, interspersed with a multiplicity of mixture-lean regions, corresponding to the locations of said piers, which mixture-rich and mixture-lean regions, taken together, comprise a diverging substantially conical spray.
2. A fluid atomizer as claimed in claim 1 wherein said passage way means comprises a substantially frustro-conical inside wall, a substantially frustro-conical outside wall of larger effective surface area as said inside wall, and wherein said internal segmentation means comprises at least one support-space pier means disposed in said passageway between said inside and outside walls.
3. A fluid atomizer as claimed in claim 2 including at least two support-spacer pier means disposed symmetrically about said passageway.
4. A fluid atomizer as claimed in claim 1 wherein said internal segmentation means comprises at least one pier member each of which occupies a minor portion of said passageway and is disposed at least at the end of said passageway remote from said mixing chamber.
5. A fluid atomizer as claimed in claim 4 comprising a multiplicity of said pier members which collectively occupy up to about 1/2 of the length of said slot.
6. A fluid atomizer as claimed in claim 4 wherein said pier member extends the entire length of said passageway from the end thereof proximate to said mixing chamber to the end thereof proximate to said spray.
7. A fluid atomizer as claimed in claim 1 wherein said passageway is conical having a vertex angle of about 90°.
8. A fluid atomizer as claimed in claim 1 wherein said passageway is conical having a vertex angle of about 50 to 100°.
9. A fluid atomizer as claimed in claim 1 wherein the walls of said passageway are substantially parallel to each other.
10. A fluid atomizer as claimed in claim 1 wherein the walls of said passageway diverge from each other by up to about 15°.
11. A fluid atomizer as claimed in claim 1 wherein the walls of said passageway are spaced apart by about 1/32 to 1/2 inch.
12. The combination of a fluid atomizer as claimed in claim 1 with a combustion chamber so positioned as to receive said conical spray thereinto; and further including means to provide combustion supporting air to said combustion chamber.
13. The combination as claimed in claim 12 wherein said fluid to be atomized comprises a hydrocarbonaceous fluid.
14. The combination as claimed in claim 12 wherein said atomizing gas comprises steam.
15. The combination as claimed in claim 13 including means to introduce an oxygenated gas into said combustion chamber in an amount sufficient to burn at least most of the combustible components of said hydrocarbonaceous fluid.
16. A fluid atomizer as claimed in claim 1 wherein said substantially frustro-conical passageway is so designed and arranged that said conical spray is not substantially disrupted after it leaves said passageway.
17. A combination as claimed in claim 12 wherein said atomizable fluid comprises a combustible hydrocarbonaceous material, and said atomizing gas comprises steam; and wherein said combination additionally comprises means to introduce an oxygen containing gas into said combustion chamber, in a stoichiometric excess amount with respect to said hydrocarbonaceous material, into intimate association with said conical spray.
18. A combination as claimed in claim 17 wherein the design of said frustro-conical passageway means, the pressure differential between said mixing chamber and said combustion chamber, and stoichiometric excess of said oxygen relative to said hydrocarbonaceous material are all selected in combination such that the amount of NOX emitted as exhaust from said combustion chamber is minimized.
19. A method of combusting fuel oil which comprises:
atomizing liquid fuel oil with an atomizing gas to form a mixture;
pressurizing said mixture;
forcing said mixture of said atomized liquid fuel oil, with said atomizing gas, through diverging frustro-conical nozzle means comprising inner and outer walls, which nozzle means comprises a multiplicity of longitudinally elongated axially diverging passageways each of which is defined by said inner and outer walls, respectively, and two spaced apart axially elongated piers axially disposed within said passageway, wherein said piers occupy a minor portion of said nozzle means and said passageways occupy a major portion of said nozzle means, and wherein said passageways to become wider in said axially divergent direction;
forming such mixture into a multiplicity of streams in said passageways, respectively;
ejecting said multiplicity of streams from said corresponding multiplicity of passageways to form an axially diverging substantially conical spray comprising a multiplicity of mixture-rich regions, corresponding to said passageways, interspersed with a multiplicity of mixture-lean regions, corresponding to the locations of said piers, which mixture-rich and mixture-lean regions, taken together, comprise said diverging substantially conical spray which has a non-uniform bulk density about its periphery, and a non uniform composition of said mixture about its periphery; and mixing said non-uniform axially diverging spray of atomized fuel oil with at least a sufficient amount of air to combust at least a substantial portion of said fuel oil under a combination of conditions conducive to the combustion of said fuel oil with oxygen in said air;
whereby creating combustion products having a lower proportion of nitrogen oxides than would have been created if the same mixture was ejected from the same frustro-conical nozzle without said piers and then burned with the same air.
atomizing liquid fuel oil with an atomizing gas to form a mixture;
pressurizing said mixture;
forcing said mixture of said atomized liquid fuel oil, with said atomizing gas, through diverging frustro-conical nozzle means comprising inner and outer walls, which nozzle means comprises a multiplicity of longitudinally elongated axially diverging passageways each of which is defined by said inner and outer walls, respectively, and two spaced apart axially elongated piers axially disposed within said passageway, wherein said piers occupy a minor portion of said nozzle means and said passageways occupy a major portion of said nozzle means, and wherein said passageways to become wider in said axially divergent direction;
forming such mixture into a multiplicity of streams in said passageways, respectively;
ejecting said multiplicity of streams from said corresponding multiplicity of passageways to form an axially diverging substantially conical spray comprising a multiplicity of mixture-rich regions, corresponding to said passageways, interspersed with a multiplicity of mixture-lean regions, corresponding to the locations of said piers, which mixture-rich and mixture-lean regions, taken together, comprise said diverging substantially conical spray which has a non-uniform bulk density about its periphery, and a non uniform composition of said mixture about its periphery; and mixing said non-uniform axially diverging spray of atomized fuel oil with at least a sufficient amount of air to combust at least a substantial portion of said fuel oil under a combination of conditions conducive to the combustion of said fuel oil with oxygen in said air;
whereby creating combustion products having a lower proportion of nitrogen oxides than would have been created if the same mixture was ejected from the same frustro-conical nozzle without said piers and then burned with the same air.
20. The method as claimed in claim 19, wherein said oil is heavy fuel oil, and the non-uniformity of said conical spray together with the ration of combustion air to fuel oil is sufficient to minimize the production of NOX.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US12082694A | 1994-09-09 | 1994-09-09 | |
| US08/120,826 | 1994-09-09 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2187745A1 true CA2187745A1 (en) | 1995-03-23 |
Family
ID=22392778
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002187745A Abandoned CA2187745A1 (en) | 1994-09-09 | 1994-09-09 | V-jet atomizer |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2187745A1 (en) |
-
1994
- 1994-09-09 CA CA002187745A patent/CA2187745A1/en not_active Abandoned
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