US3920230A

US3920230A - Blast furnace fuel injector lance

Info

Publication number: US3920230A
Application number: US501607A
Authority: US
Inventors: James C Murphy
Original assignee: Republic Steel Corp
Current assignee: Ltv Steel Co Inc
Priority date: 1974-08-29
Filing date: 1974-08-29
Publication date: 1975-11-18
Anticipated expiration: 1992-11-18

Abstract

A lance for introducing atomized liquid fuel through tuyeres into a blast furnace. The lance is a tubular member with an open discharge end adapted to be located in a blow pipe to a tuyere. Apertures are in the tubular member adjacent the discharge end, at least one located to receive an impinging part of the hot blast flowing through the blow pipe and another located to emit the received part of the hot blast along with a portion of the fuel. The construction produces a desired efficiency and flame front that assures ignition of the fuel before it enters the blast furnace.

Description

United States Patent Murphy 5] Nov. 18, 1975 [5 BLAST FURNACE FUEL INJECTOR LANCE 524,192 5/1931 Germany 266/41 [75] Inventor: James C. Murphy, Seven Hills, Ohio [73] Assignee: Republic Steel Corporation, Primary Examiner-Gerald Dost Cleveland Ohio gttorlizeyAgent, or Firm-Watts, Hoffmann, Flsher &

' em e o, [22] Filed: Aug. 29, 1974 p [21] Appl. N0.: 501,607 7 [57] ABSTRACT CCll m; A lance for introducing atomized liquid fuel through Fieid S 110/182 tuyeres into a blast furnace. The lance is a tubular 122/6 member with an open discharge'end adapted to be 10- I v cated in a'blow' pipe to a tuyere.- Apertures are in the [56] References Cited tubular member adjacent the discharge end, at least one located to receive an impinging part of the hot UNITED STATES PATENTS blast flowing through the blow pipe and another 10- 290,343 12/1883 Morgan etal. 266/29 gated to emit the received part of the hot blast along g ng 2 with a portion of the fuel. The construction produces 311' et a a deslred efficiency and flame front that assures lgnl- 3,833,356 9/1974 Luth 266/29 X tion of the fuel before it enters the blast furnace.

FOREIGN PATENTS OR APPLICATIONS 290,861 5/1928 United Kingdom 266/41 8 Claims, 4 Drawing Figures wliglllzm US. Patent Nov. 18,1975 Sheet of2 3,920,230

us QQ/ Q/ 0 O o o n vv Sheet 2 of 2 US. Patent Nov. 18, 1975 BLAST FURNACE FUEL INJECTOR LANCE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a lance for discharging atomized liquid fuel into a hot blast for introduction through tuyeres into a blast furnace.

2. Prior Art Coke has been typically utilized for fueling blast furnaces in the production of iron from iron ore. However, the availability of coke at different iron-producing plants is not uniform and the shipping costs in redistributing coke are undesirable. On the other hand, relatively low-cost fuel oil is readily available. Furthermore, high sulfur content fuel oil can be used in a blast furnace without excess pollution because the sulfur is absorbed by slag produced in the process.

While limited quantities of fuel oil have been introduced through the tuyeres of blast furnaces as supplemental fuel, it has been difficult to use increased amounts effeciently, primarily because of the difficulty in obtaining desired ignition prior to entry into the furnace, a sine qua non for efficient and controlled heating with liquid fuel. For example, conventional oil burners have been able to burn approximately one gallon of liquid fuel oil per minute per tuyere in blast furnace use, whereas approximately three gallons or more per minute per tuyere is desired.

By atomizing the fuel oil in a stream of air or steam and introducing it with a lance to the flow of hot blast at the tuyeres of a furnace, it was found that a much greater quantity of oil could be burnedup to six gallons per minute per tuyere. Yet, substantial problems of lance life and the attainment of a bright, stable, fully developed flame front within the tuyere indicative of full ignition prior to furnace entry remained to impede the commercial adoption of fuel-oil heating.

Excessive wear and burning of the lance tip that supplies the fuel, and an accompanying need for frequent lance replacement, created a particular problem.

If the tip of the lance, which extends into the blow pipe at a tuyere, is burned away, control of the flame is lost. If, as a result, the flame impinges upon and burns through the blow pipe, it becomes necessary to shut down the furnace, an operation so costly as to essentially preclude use of apparatus that reasonably threatens such a risk.

SUMMARY OF THE INVENTION In accordance with the present invention, a lance for introducing atomized liquid fuel to a blast furnace is provided which has adequate life and produces abright, fully developed, stable flame front indicative of efficient ignition within the tuyere, but which does not excessively burn the lance tip. This is accomplished through a particular lance construction in which the lance comprises a tube for carrying a pressurized flow of atomized liquid fuel, with one end adapted to extend into a blow pipe to a tuyere at an angle to the blow pipe axis but otherwise in the general direction of hot blast flow. The discharge end of the tube is open and preferably unobstructed. Open portions of the tube wall are located adjacent the open end, positioned to be within the blow pipe in use. These open portions receive the hot blast to cause additional mixing of the fuel and to improve, i.e., reduce, the size of fuel droplets for ignition. The ignition is enhanced by locating at least one open portion upstream from and diametrically opposed to another open portion in the tube wall and by orienting the tube in use so the upstream open portion receives a velocity component of the hot blast flowing through the blow pipe. The flow component exits through the downstream open portion of the tube wall, carrying with it fuel to provide a pilot flame for assuring continued ignition of the main fuel mixture discharged from the open end of the lance.

As a result of the lance construction, a desirable flame front is created, perhaps best described as having a geometric shape, beginning at the lance tip immediately outside the tube, filling the tuyere opening, and having its greatest brightness at the exit of the tuyere. These characteristics indicate efficient and complete ignition of the fuel by the time the fuel leaves the tuyere, without excessive development of the flame front within the blow pipe. I

A particularly advantageous arrangement of four circular apertures in the tubular wall of a preferred lance embodiment assures proper functioning without regard to the angular orientation of the lance about its longitudinal axis. These apertures are each of a diameter equal to approximately half the diameter of the tube and are displaced longitudinally and circumferentially each from the next in a helical path. Each is displaced circumferentially and approximately a full aperture diameter longitudinally. The closest aperture to the end opening is spaced far enough therefrom that the velocity component of hot blast flow cannot exit in a straight line through the open end. With this construction at least one aperture will always be in a position to at least partially receive a velocity component of the hot blast flow and will be upstream from another aperture positioned to accommodate the exit of the velocity component upstream from the open end.

The above and other features and advantages will become more apparent as the invention becomes better understood from the detailed description that follows, when considered in connection with the accompanying drawings:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view, partially in section and partially in side elevation, illustrating a blast furnace fuel injector lance assembly embodying the present invention;

FIG. 2 is a side elevational view showing the lance itself;

FIG. 3 is a fragmentary view, partly in section, diagrammatically illustrating the injector lance assembly of FIG. 1 in the environment of a blast furnace;

FIG. 4 is a partial top plan view on' an enlarged scale of the injector lance assembly and environment ofFIG. 3.

DETAILED DESCRIPTION A blast furnace fuel injector lance assembly is indicated at 10 in FIG. 1 of the drawings, and comprises a fuel atomizer l2 and a lance 14 embodying the present invention. As best shown in FIG. 2, the lance 14 is tubular in form and has an open discharge end 16 and a plurality of apertures 18 adjacent the discharge end. The lance 14 is secured to the atomizer 12 to receive liquid fuel in a stripping medium, such as air, steam or other gas. The fuel, such as fuel oil or tar, is introduced under pressure to the atomizer through a conduit 20 and the stripping medium is introduced under pressure through a conduit 22.

The manner in which the injector lance assembly is utilized with a blast furnace is best shown in FIGS. 3 and 4. The open discharge end 16 is received in a blow pipe 26 of a blast furnace 28. The blow pipe connects at one end to a tuyere 30 and at the other end to a tuyere stock 32 connected with a bustle pipe 34 that encircles the furnace. The lance 14 of the assembly is supported by and extends through a support pipe 36 carried by the blow pipe. An end coupling 38 on the support pipe receives the front of the atomizer 12, which is locked to the end coupling by a lock bar 40 received in notches of

plates

41, 42 on the coupling.

A plurality, typically eight to ten, of lance assemblies 10 are utilized with a blast furnace. Each lance introduces fuel through a separate tuyere. Liquid fuel and stripping medium is mixed in the atomizer l2 and introduced into the hot blast flow from the bustle pipe in the blow pipe. There it is ignited and carried into the blast furnace, to supply heat necessary to the iron-making process.

With more specific reference now to the lance structure of the assembly 12, the lance 14 is secured at a flared end 44 to a coupling 46. The lance is telescoped within the coupling, the flared end being too large in diameter to pass through the coupling. A tubular spacer 48 with a tapered end 49 fits within the coupling 46 with the tapered end pressed against the flared end of the lance. A threaded pipe nipple 50 is threadably received in the coupling 46, tight against the spacer 48 to seal the spacer against the flared end of the lance 44. This construction facilitates installation and removal of the lance from the coupling.

The pipe nipple 50 connects to a discharge end of a body 52 of the fuel atomizer 12. An entry nozzle 54 is provided at the opposite end of the body 52, for introducing a stripping medium, such as air or steam, into the atomizer and is in direct communication with the conduit 22. The conduit communicates with the body 52 through the side, adjacent the entry nozzle 54, upstream from its discharge orifice. The nozzle 54 discharges into a mixing venturi 56 within the body 52 and the venturi discharges through the pipe nipple 50 and spacer 48 into the lance 14.

As best shown in FIG. 2, the lance 14 is a thinwalled tube of substantial diameter with four apertures 18a, b, c, (1, adjacent the open discharge end 16. The open end 16 is adapted to be located as shown in FIGS. 3 and 4, essentially on the center line of a blow pipe 26 and adjacent the discharge end of the blow pipe. At this location, when fuel from the open end of the lance ignites, it will not impinge directly upon the blow pipe. The lance is arranged at an angle to the longitudinal extent of the blow pipe and the principal flow direction of the hot blast from the bustle pipe through the blow pipe, indicated by the arrow A. This arrangement assures that a velocity component of the hot blast flow can enter an apeture 18 in the side wall of the lance and produce a pilot flame adjacent the discharge end 16 to assure that a desired flame front is produced by the fuel discharged from the lance. In the preferred embodiment the lance forms an angle of approximately 20 to the blow pipe axis and flow direction of the hot blast.

The substantial inside diameter provided for the lance 14 is necessary to achieve a relatively low velocity of the fuel injected into the blow pipe, which decreases the spray penetration of the fuel and produces a relatively wide angle of discharge, necessary for a stable and improved flame front upon ignition. On the is subjected disadvantageously tend to reduce the life of the lance even when it is fabricated from a highly refractory material, such as 347 stainless steel. Fortunately, a specific aperture construction and arrangement as utilized in the preferred embodiment of the lance arrangement shown and described herein has been found to give superior tip life and excellent performance.

The lance tip of the preferred embodiment shown utilizes four circular apertures 18a, b, c, d, the diameters of which are equal to one-half the outside diameter of the lance tube and thus are slightly greater than the inside radius of the tube. As shown, they are successively spaced longitudinally of the lance by a center-tocenter distance equal to twice their diameter. in addition, each is successively displaced one from the next,

circumferentially, by As a result, the apertures lie generally along a helical path such that a straight line path entering one aperture and exiting through another angularly displaced by will extend at an angle approximately equal to the angle at which the tube extends relative to the blow pipe. This accomodates entry and exit through the apertures of a velocity component of the hot blast flow. Also, the hole closest to the open discharge end 16 is spaced therefrom a sufficient distance (which is a function of the diameter of the tube and the wall thickness) so that a straightline flow or velocity component of hot blast entering an aperture 18 at an angle to the longitudinal extent of the lance cannot exit directly through the open end 16 of the lance. In a preferred embodiment with a inch outside tube diameter, the apertures 18a, b, c, d are each 5/l6 inch diameter circular holes on centers longitudinally displaced by inch, the last hole being spaced l-Vz inch from the open end of the tube. The relationship of the aperture diameters to the tube wall thickness is approximately' 6 to l, which assures that the wall depth of the apertures does not obstruct an angular approach or flow of hot blast into and out of the tube. Based on current blast furnace geometry, the hole farthest from the open end of the lance should be no more than 6 inches therefrom, to avoid the impingment of any pilot flame against an adjacent wall of the blow pipe.

The specific construction described is advantageous,

ging from the tar or oil used as fuel. For example, nar- 1 row slots or Vs inch diameter holes tend to clog and result in poor performance.

c. The apertures enhance dispersion and mixing of the fuel into the hot blast.

d. The flow of fuel from the discharge end of the lance is unobstructed by the lance construction.

e. No aperture is directly opposite another in a plane perpendicular to the longitudinal axis of the lance, where it would fail to function efficiently yet weaken the tube tip.

f. The shape, size, location and minimum of four apertures assures that, regardless of the rotational orientation of the lance about its longitudinal axis when it is inserted into a blow pipe, one aperture will be positioned to at least in part catch a velocity component of the hot blast coming at an angle to the lance through the blow pipe, and another aperture will be downstream and diametrically opposite therefrom, to facilitate the exit of the component along with fuel to establish a low velocity pilot flame about the end of the lance. This pilot flame asures ignition of the fuel mixture exiting from the discharge end 16 of the lance.

g. The interrelationship of the size, location and shape of the apertures and diameter of the tube result in a flame front that does not heat the tip of the lance unduly, but rather begins immediately outside the tip and fills the tuyere opening, producing a maximum brightness at the exit of the tuyere. In this manner the temperature at the end of the lance is maintained no more than 2200 F. and typically no more than 1800 F. In short, the construction establishes a level of efficiency in burning the liquid fuel that does not rapidly degrade the lance tip but in which the fuel is ignited by the time it leaves the tuyere,

Somewhat further tip life can be obtained by chrome plating the lance or by alphatizing the lance tip.

By way of example only, a lance 14 of the following construction was used to inject fuel into a blast furnace: a tube of 347 stainless steel, inch outside diameter and 0.049 inch wall thickness, 3 feet-8 inches long, with an open discharge end and four circular holes 5/ 1 6 inch in diameter, with the closest one to the open end being 1- /2 inches therefrom and being spaced successively 90 apart circumferentially and inch apart center to center longitudinally. The lance was connected to a fuel atomizer l2 constructed as shown and described above. Steam and Bunker C fuel oil was introduced to the atomizer l2 and discharged through the lance 14 into a blow pipe of a blast furnace. The steam was introduced to the atomizer at a rate of O. 125 pound steam per pound of Bunker C oil (approximately one pound of steam per gallon of oil). In addition, by way of further example, tar has been used as fuel requiring a steam rate of 0. 1 5 pound steam per pound of tar (or 1.5 pound of steam per gallon of tar). The steam was superheated to 500 F. and supplied at 215 psig. The fuel was ignited at the exit of a blow pipe to the blast exit of a blow pipe to the blast furnace and introduced into the blast furnace through a tuyere at a rate of approximately 3 gallons per minute. A temperature of approximately 1800 F. at the end of the lance was obtained and the useful life of the lance was approximately 8 to 10 weeks with fuel oil. A useful life of approximately 4 to 6 weeks with tar has been obtained. A visual observation of the flame front showed it to be stable, of geo- .metric shape, fully developed, and with a maximum brightness at the exit of the tuyere. Ten such lance assemblies were used with the blast furnace.

While a preferred embodiment of this invention has been disclosed in detail, various modifications or alter- :ations can be made therein without departing from the 6 spirit and scope of the invention set forth in the appended claims. .1 I

I claim:

t l. A lance tip for introducing fuel to a blast furnace, comprising: 7 I 1 a a tube with open unobstructedends through which an atomized fuelcan flow for introduction into a blow pipe to a tuyere of a blast furnace,

said tube having one end portion adapted to extend into the blow pipe at an angle to the blow pipe axis, and

orifice means through said portion of the tube forming two longitudinally and circumferentially displaced passage portions, through which a flow of gas from outside said tube moving at an angle to the tube can pass to disperse fuel and to produce a pilot flame, the locus of said orifice means being along a helical path with a total circumferential displacement of at least 360.

2. A lance tip as defined in claim 1 wherein said ori-' fice means comprises at least four apertures.

3. A lance tip as defined in claim 2 wherein each of said apertures is displaced from the next adjacent one longitudinally of the tube by a distance equal to its dimension longitudinally of the tube.

4. A lance tip as defined in claim 3 wherein the dimension of each of said apertures in the longitudinal direction of the tube is equal to approximately one-half the outside tube diameter.

5. A lance tipas defined in claim 4 wherein the said apertures are circular in shape and the tube wall is no more in thickness than one-sixth of the aperture diameter.

6. A lance tip for introducing fuel through a tuyere of a blast furnace, comprising:

a refractory tube of uniform diameter for introducing an atomized fuel into a blow pipe to a tuyere of a blast furnace,

said tube having an inlet end constructed to be connected to a fuel atomizer and an outlet end extendable into the blow pipe at an angle to the blow pipe axis, said outlet end being open and unrestricted,

a plurality of apertures through that portion of the tube adapted to extend into the blow pipe and adjacent said outlet end, said apertures being essentially circular, equal in size, larger in diameter than the inside radius of said tube, and each peripherally and axially displaced from the next so that any axial plane of the outlet end of the tube intersects portions of two apertures one of which is peripherally displaced from the other and further than the other from the outlet end, all of said apertures being spaced from the outlet end a distance such that any straight path passing through an aperture does not intersect said open end.

7. In combination, a blast furnace, a blast furnace blow pipe that supplies hot blast to a tuyere of the furnace, and a liquid-fuel supplying lance one end portion of which is received in the blow pipe at an acute angle thereto, said lance being comprised of an open ended tube and orifice means through said portion of the tube forming two longitudinally and circumferentially displaced opposite passage portions, through which a flow of hot blast moving through the blow pipe can pass to disperse fuel.

8. In combination, a blast furnace, a blast furnace blow pipe that supplies hot blast to a tuyere of the furnace, and a tube, one end of which is received in the 8 pipe can pass through portions of two said apertures one of which is peripherally and longitudinally displaced from the other, all of said apertures being spaced from the open end of said one end portion a distance such that any straight velocity component of hot blast flow cannot enter an aperture and discharge directly through said open end.

Claims

1. A lance tip for introducing fuel to a blast furnace, comprising: a tube with open unobstructed ends through which an atomized fuel can flow for introduction into a blow pipe to a tuyere of a blast furnace, said tube having one end portion adapted to extend into the blow pipe at an angle to the blow pipe axis, and orifice means through said portion of the tube forming two longitudinally and circumferentially displaced passage portions, through which a flow of gas from outside said tube moving at an angle to the tube can pass to disperse fuel and to produce a pilot flame, the locus of said orifice means being along a helical path with a total circumferential displacement of at least 360*.

2. A lance tip as defined in claim 1 wherein said orifice means comprises at least four apertures.

5. A lance tip as defined in claim 4 wherein the said apertures are circular in shape and the tube wall is no more in thickness than one-sixth of the aperture diameter.

6. A lance tip for introducing fuel through a tuyere of a blast furnace, comprising: a refractory tube of uniform diameter for introducing an atomized fuel into a blow pipe to a tuyere of a blast furnace, said tube having an inlet end constructed to be connected to a fuel atomizer and an outlet end extendable into the blow pipe at an angle to the blow pipe axis, said outlet end being open and unrestricted, a plurality of apertures through that portion of the tube adapted to extend into the blow pipe and adjacent said outlet end, said apertures being essentially circular, equal in size, larger in diameter than the inside radius of said tube, and each peripherally and axially displaced from the next so that any axial plane of the outlet end of the tube intersects portions of two apertures one of which is peripherally displaced from the other and further than the other from the outlet end, all of said apertures being spaced from the outlet end a distance such that any straight path passing through an aperture does not intersect said open end.

8. In combination, a blast furnace, a blast furnace blow pipe that supplies hot blast to a tuyere of the furnace, and a tube, one end of which is received in the blow pipe at an acute angle thereto, for introducing atomized fuel into the blow pipe, said tube being made of a refractory material and uniform diameter, with opposite ends open and unrestricted, a plurality of apertures through said one end portion of the tube, said apertures being essentially circular, equal in size, larger in diameter than the inside radius of said tube, and each peripherally and axially displaced from the next so that a velocity component of hot blast flow through the blow pipe can pass through portions of two said apertures one of which is peripherally and longitudinally displaced from the other, all of said apertures being spaced from the open end of said one end portion a distance such that any straight velocity component of hot blast flow cannot enter an aperture and discharge directly through said open end.