A METHOD TO GENERATE AN OXIDIZING FLAME, A BURNER AND A USE FOR A BURNER

Abstract: The disclosure relates to a method of generating a powerfully oxidizing flame, and a burner therefore, the burner including a central body (9) with a central oxygen nozzle (23) and at least one fuel nozzle (25, 26), a casing (1) surrounding the central body (9), at least one peripheral oxygen nozzle (13) radially outside the fuel nozzle (25, 26), and an oxygen chamber (21) outside the central body (9), all nozzles (23; 25, 26; 13) being at least substantially parallel. The central oxygen nozzle (23) and the peripheral oxygen nozzle (13) are connected to different sources of oxygen, it being possible for the source connected to the central oxygen nozzle (23) to deliver a higher pressure than the other source. Preferably, the central oxygen nozzle (23) is designed as a laval nozzle. When solely oxygen is supplied to the burner, it may be employed as an oxygen lance. Preferably, oxygen is then only supplied to the central oxygen nozzle (23).

Description: AMETHOD TO GENERATEAN OXIDIZING FLAME, ABURNERAND A USE FORABURNER. TECHNICAL FIELD The present invention relates to a method of generating a powerfully oxidizing flame and a burner therefore, the burner including a central body with a central oxygen nozzle and at least one fuel nozzle, a casing which surrounds the central body and which ^ay form the inner wall ' of cooling jacket surrounding the burner, at least one peripheral oxygen nozzle between the central body and the casing and an oxygen chamber outside the central body. The present invention also relates to the use of the burner as an oxygen lance. BACKGROUND ART For generating flames of high temperature, use is made of burners which are supplied with a gaseous, liquid or solid fluidizable fuel and oxygenous gas. Particularly high temperatures are obtained when the oxygenous gas consists of pure oxygen. Burners which are driven with a fuel and an oxygenous gas with a high content of oxygen are normally designated oxy-fuel burners. Oxy-fuel burners are employed in industrial processes in which high temperatures occur, for example in the melting of steel, in the manufacture of aluminium and lead and in cement manufacture. These burners are often employed in electric arc furnaces for, for example, steel melting as a complement to the electric energy so as to increase the output capacity of the furnace. In such instances, they are installed in the roof or side wall of the furnace. In the charging of an arc furnace in steel manufacture, the amount of scrap is often so great that it covers the oxy-fuel burners, in which event problems arise in respect of the space for tb flame of the burner for the combustion process, the efficiency of the burner being thereby reduced. Hence, there is an urgent need for rapidly creating a space in the scrap to allow for the combustion. OBJECTS OF THE PRESENT INVENTION One object of• the present invention is to realize a method of creating, with an oxy-fuel burner, a powerfully oxidizing flame which rapidly creates the necessary space for the flame of the burner. A further object of the present invention is to realize a burner by means which it is possible to create a powerfully oxidizing flame which, in a brief space of time, creates the space necessary for the action an effect of the burner. A further object of the present invention is to realize a burner which gives the powerfully oxidizing flame and may thereafter be employed as a conventional oxy-fuel burner. Yet a further object of the present invention is to realize an oxy-fuel burner which may also be utilized as an oxygen lance. SUMMARY OF THE INVENTION These objects will be attained by means of a burner which includes a central oxygen nozzle, at least one fuel nozzle disposed radially outside the central oxygen nozzle, and at least peripheral oxygen nozzle in greater spaced apart relationship from the central oxygen nozzle than the fuel nozzle. The primary characterizing feature of this burner is that the central oxygen nozzle is designed as a laval nozzle. A further characterizing feature is that the central oxygen nozzle is supplied at a different oxygen pressure than the peripheral oxygen nozzle, separate conduits being connected to the oxygen nozzles. The method according to the present invention is characterized in that the ' ratio between the amount of fuel through the fuel nozzle and the oxygen amount through the peripheral oxygen nozzle are regulated so as to obtain a substantially stoicio etric combustion; and that, for generating the powerfully oxidizing flame, oxygen is caused to flow at great speed through the central oxygen nozzle, the speed of flow of the oxygen through the .central oxygen nozzle being preferably higher than the speed of sound for oxygen. In the employment of the burner as an oxygen lance, there is no flame, in which event only the fuel supply is throttled or both fuel supply and oxygen supply to the peripheral nozzle are throttled. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS The nature of the present invention, its aspects and advantageous embodiments, will be more readily understood from the following brief description of the accompanying drawings and discussion relating thereto. In the accompanying drawings: Fig. 1 illustrates the oxy-fuel burner according to the present invention in section through its longitudinal axis; Fig. 2 illustrates another embodiment of the burner of Fig. 1; and Fig. 3 illustrates yet a further embodiment of the burner according to the present invention in section through the longitudinal axis of the burner. DESCRIPTION OF PREFERRED EMBODIMENT Referring to. the drawings, the burner of Fig. 1 displays a casing 1 which defines a cylindrical oxygen chamber 21. The rear region of the casing 1 is provided with a flange 19, in which a wall 15 defining the oxygen chamber 21 is sealingly mounted by, for example, a number of bolts (not shown). An inlet 17 for oxygen is connected to the oxygen chamber 21. In the forward end of the burner, the casing 1 serves as the inner wall of a cooling jacket 3 surrounding the burner. The cooling jacket 3 is provided with an inlet 5 and an outlet 7 for coolant, which normally is water. The burner further includes a centre body 9 in its forward region, the central body being held in spaced apart relationship from the casing 1 by spacers 11. The forward end of the central body is retracted in relation to the forward end of the casing 1, but may, naturally, also be flush with or ahead of the forward end of the casing. The space between the central body 9 and the casing 1 forms an annular gap which constitutes a first oxygen nozzle 13 through which oxygen may depart from the oxygen chamber 21. Centrally in the centre body 9 there is disposed a second nozzle 23 for oxygen, this nozzle being connected to a conduit 29 which passes through the rear wall 15 of the oxygen chamber 21. The second oxygen nozzle 23 is designed as a laval nozzle. The inlet 19 and the conduit 29 are each connected to their oxygen source, it being possible to obtain, in the conduit 29, a greater pressure than in the oxygen chamber 21. A compartment 27 is disposed at the rear end of the centre body 9, the compartment surrounding the conduit 29 and being defined at its ' forward end by the centre body 9. Concentrically with the second oxygen nozzle 23, there is disposed in the centre body an annular nozzle 25 or a plurality of nozzles 25 arranged about the second oxygen nozzle 23, these preferably being disposed symmetrically in a ring concentrically with the second oxygen nozzle 23. The nozzle 25, 26 connects the chamber 27 with the outside of the burner. A conduit 31 is connected to the compartment 27, this conduit, like the. conduit 29, passing through the oxygen chamber 21 and departing from the burner through the rear defining wall 15. The conduit 31 is connected to a source of fuel, preferably gaseous fuel. The chamber 27 serves as a distribution chamber for the fuel to the fuel nozzle 25, 26. The burner of Fig. 2 is similar to that of Fig. 1. Those parts and details of the burner according to Fig. 2 which are identical with corresponding parts and details in Fig. 1 have been given the same reference numeral. The burner of Fig. 2 displays a casing 2 which defines a cylindrical oxygen chamber 22. The rear region of the casing 2 is provided with a flange 19 in which a wall 15 defining the oxygen chamber 22 is ' -seal ingly mounted. For example, a seal may be disposed between the flange 19 and the wall 15. An inlet 17 for oxygen is connected to the oxygen chamber 22. As opposed to the casing 1 of Fig. 1, the casing 2 lacks the cooling jacket. The casing 2 may, for instance, consist of a ceramic material or an ultra-high-temperature alloy, such as a cemented carbide. The forward bounding definition of the oxygen chamber is a central body 10 disposed in the forward end of the burner. The inlet 17 and the conduit 29 are each connected to their source of oxygen, it being possible in the conduit 29 to achieve a greater pressure than- in the oxygen chamber. The central body 10 sealingly abuts against the inside of the casing 2, and its forward edge is here flush with the forward edge of the casing 2. Centrally within the central body 10, there is disposed an oxygen nozzle 23 which is designed as a laval nozzle and corresponds to the second nozzle of the burner according to Fig. 1. The second oxygen nozzle 23 is, at its end facing away from the forward face of the burner, connected to the conduit 29 for oxygen. About the conduit 29 for oxygen there is disposed a fuel distribution chamber 27, whose forward bounding definition is the central body 10. Concentrically with the second oxygen nozzle 23, there is disposed, in the central body 10, an annular nozzle 25, or a number of nozzles 26 disposed about the second oxygen nozzle 23, these nozzles 26 being preferably arranged symmetrically in a ring which lies concentrically outside the second oxygen ' nozzle 23. The nozzle 25, 26 connects the fuel distribution chamber 27 with the outside of the burner. Thus, the nozzle 25, 26 is a fuel nozzle. A conduit 31 is connected to the chamber 27, this conduit, like the conduit 29 for oxygen, passing through the oxygen chamber 22 and departing therefrom through the rear defining wall 15 of the burner. The conduit 31 is connected to a fuel source, preferably gaseous fuel. The side wall of the fuel chamber is located in spaced apart relationship from the casing 2, such that the forward bounding definition of the oxygen chamber 22 consists of the central body 10. Concentrically outside the fuel nozzle 25, 26, there is provided an odd number of nozzles 14 of which one is shown on the drawing. These are disposed in a ring. The nozzle 14 may also consist of an annular nozzle 14 corresponding to the first oxygen nozzle 13 in Fig. 1. When the first oxygen nozzle 14 and the fuel nozzle 25, 26 consist of a number of nozzles 14 and 26, respectively, arranged concentrically in a ring, these may be cylindrical and straight or cylindrical and helical, in which latter case the helical portion is at most 90 degrees. These nozzles may also be trunco-conical , the base of the truncated cone then facing forwards. The first oxygen nozzles may also be designed as laval nozzles. The burner according to Fig. 3 is very similar to the burner of Fig. 1. The gap which constitutes the peripheral oxygen nozzle 13 in Fig. 1 has, in this figure, been replaced by a make-up piece 16 between the central body 9 and the casing 1. The make-up piece 16 includes a number of nozzles 20 arranged in a ring, these likening the nozzles 14 of Fig. 2, but may also consist of an annular nozzle. The forward edge of the make-up piece is displaced in relation to both the forward edge of the casing 1 and the forward edge of the central body 9. In the illustrated embodiment, the make-up piece 16 is shorter than the central body 9. Naturally, the peripheral oxygen nozzles, like the fuel nozzles, may be odd or even in number. The first and second oxygen nozzle (13, 14; 20, 23, respectively) are designated oxygen nozzles. It is, naturally, possible to use gas mixtures with oxygen instead of pure oxygen. However, in such instance it is appropriate that the oxygen content be at least 50 per cent by volume. In the employment of the burner according to Fig. 1, coolant is supplied to the inlet 5 of the cooling jacket 3, this coolant departing from the jacket 3 through the outlet 7. Oxygen is supplied through the inlet 17 to the oxygen chamber 21, this oxygen departing therefrom through the nozzle 13, and fuel, for example natural gas, is supplied through the conduit 31 where it is dissipated in the chamber 27 and departs therefrom through the nozzle 25, 26. Normally, oxygen is supplied to the oxygen chamber 21 and fuel through the conduit 31 in such volumes and at such proportions that there will be obtained stoiciometric combustion with a suitable flame size. The burner then functions as a conventional oxy-fuel burner. ' When the intention is to employ the burner to generate a powerfully oxidizing flame, the burner is ignited on the supply of oxygen to the nozzle 13 and fuel to the nozzle 25, 26. Thereafter, oxygen is supplied at high pressure to the conduit 29, this oxygen departing from the burner through the second oxygen nozzle 23 which is designed as a laval nozzle. By such means, it is possible to impart to the oxygen departing from the nozzle 23 extremely high speed, for example higher speed than the sonic speed in oxygen. The thus obtained powerfully oxidizing flame may be used for rapidly creating a.space about the burner in those cases when a charge supplied to a furnace covers the burner and prevents, or at least seriously obstructs the normal function of a conventional oxy-fuel burner. When the desired space for the burner has been created, the oxygen supply to the central nozzle 23 for oxygen is cut off. The burner thereafter functions as a conventional oxy-fuel burner. The ratio between the volume of oxygen supplied to the burner through the central nozzle 23 and the peripheral nozzle 13, 14 and 20 may vary within broad limits. In the generation of a powerfully oxidizing flame, the ratio is normally greater than 0.5, preferably greater than 1. The burner will also be employed as a conventional oxygen lance. In such instance, only oxygen is supplied to the burner, preferably solely through the second oxygen nozzle 23 which is designed as- a laval nozzle, or also through the first oxygen nozzle 13 which is also preferably designed as a laval nozzle. In respect of the configuration of the annular first oxygen nozzle - this configuration corresponding to a laval nozzle - this is taken to mean that the cross-sectional area of the nozzle 13, viewed from the oxygen chamber to the nozzle aperture, changes in the same manner as does a laval nozzle. Naturally, the burner according to Figs. 2 and 3 may be employed in the same manner as the burner of Fig. 1. These embodiments of the burner should not be considered as different burners but as a single burner in which corresponding details and parts have been given a different configuration and design.

Claims: WHAT WE CLAIM AND DESIRE TO SECURE BY LETTERS PATENT IS: 1. A method of generating a powerfully oxidizing flame in an oxy-fuel burner which includes a central oxygen nozzle, at least one fuel nozzle disposed outside the oxygen nozzle, and at least " one peripheral oxygen nozzle disposed at greater radial spaced apart relationship from the central oxygen nozzle than the fuel nozzle, characterized in that the ratio between amount of fuel through the fuel nozzle and amount of oxygen through the peripheral ' oxygen nozzle is regulated so as to obtain a substantially stoiciometric combustion; and that oxygen is caused to flow at great speed through the central oxygen nozzle. 2. The method as claimed in Claim 1, characterized in that the speed of the oxygen through the central oxyien nozzle is greater than the sonic speed of oxygen. 3. The method as claimed in Claim 1 or 2, characterized in that the ratio between the amount of oxygen through the central oxygen nozzle and the amount of oxygen through the peripheral oxygen nozzle is at least 0.5. 4. A burner including a central body (9, 10) with a central oxygen nozzle (23), at least one fuel nozzle (25, 26), a casing (1, 2) surrounding the central body (9, 10), at least one peripheral oxygen nozzle (13, 14, 20) radially outside the fuel nozzle (25, 26), and an oxygen chamber (21) outside the central body (9, 10), characterized in that the central oxygen nozzle (23) is designed as a laval nozzle. 5. The burner as claimed in Claim 4, characterized in that the peripheral oxygen nozzle (13, 14, 20) is in communication with the oxygen chamber (21); and that the central oxygen nozzle (23) is connected to a separate conduit (29) for oxygen. 6. The burner as claimed in Claim 4 or 5, characterized in that a fuel chamber (27) surrounding the separate conduit (29) for oxygen is disposed in the oxygen chamber (21), said fuel chamber (27) being in direct communication with the fuel nozzle (25, 26). 7. The burner as claimed any one or more of Claims 4-6, characterized in that the peripheral oxygen nozzle (13, 14, 20) consists of an annular channel (13) between the central body (9) and the casing (1), spacers (11) centring the central body (9). 8. The burner as claimed in any one or more of Claims 4-6, characterized in that the burner includes a number of peripheral oxygen nozzles (14, 20) disposed outside the fuel nozzle (25, 26) and arranged concentrically with the central oxygen nozzle (23); and- that said peripheral oxygen nozzles (14, 20) are designed as laval nozzles. 9. The burner as claimed in Claim 4, characterized in that the peripheral oxygen nozzle (13, 14, 20) is designed as an annular channel (13); and that the width of said annular channel (13) varies along the longitudinal direction of said channel in a manner corresponding to a laval nozzle. 10. The burner as claimed in any one or more of Claims 4-9, characterized in that the fuel nozzle (25, 26) is an annular nozzle (26) which concentricall " surrounds the central oxygen nozzle (23), or consists of a number of nozzles (25) in a ring which concentrically surrounds the central oxygen nozzle (23). 11. Use of a burner which includes a central body (9, 10) with a central oxygen nozzle (23) and at least one fuel nozzle (25, 26), a casing (1, 2) surrounding the central body (9, 10), at least one peripheral oxygen nozzle (13, 14, 20) radially outside said fuel nozzle (25, 26), and an oxygen chamber (21) outside the body (9, 10), fuel supply being wholly throttled, as an oxygen lance.

Inventors: PETERSSON MARTIN, SALTIN LARS, PETERSSON, MARTIN, SALTIN, LARS
Applicants: AGA AB, AGA AKTIEBOLAG
Application year: 1987
Main classification: F23D14
IPC codes: C21B7, F23D14