GB1566503A

GB1566503A - Burner assembly

Info

Publication number: GB1566503A
Application number: GB298977A
Authority: GB
Original assignee: Sumitomo Metal Industries Ltd
Current assignee: Nippon Steel Corp
Priority date: 1976-01-26
Filing date: 1977-01-25
Publication date: 1980-04-30
Also published as: DE2703176A1; JPS5841406B2; JPS5290818A; SU797612A3; DE2703176C2

Description

(54) BURNER ASSEMBLY (71) We. SUMITOMO METAL INDUSTRIES LIMITED, a Japanese Company, of 15, 5-chome, Kitahama, Higashi-ku, Osaka City, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to a burner arrangement for furnaces burning liquid or gaseous fuels, and in particular to a burner arrangement with a structure which, as compared with known arrangements, makes possible a reduction in the formation of nitrogen oxides (NO,).

According to the invention there is provided a burner arrangement consisting of an injector in combination with a refractory tile adapted to form part of a furnace wall, the injector having a body defining a cylindrical air injection passage and extending axially therethrough, a fuel injection pipe, means for supplying air into the air injection passage surrounding said fuel injection pipe, vane means for imparting a swirl motion to the air passing through said air injection passage, said vane means being provided in the interior of said air injection passage, and a straight cylindrical passage in said refractory tile for transmitting the swirling air into a furnace and provided in communication with said air injection passage, said straight passage having a length which is at least four times its diameter and wherein means for acceleratin the air is further provided between said air injection passage and said straight cylindrical passage, said means for accelerating the air being a throttle section effective to reduce the cross-sectional space available for the passage of air by between 20% and 60% as said air moves from said air injection passage into said straight passage, and wherein said fuel injection pipe extends into said straight passage in the refractory tile so that the front end of said pipe is located, short of a front end of said passage where it is adapted to open into a furnace, by a distance equal to 0.1 to 4.0 times the diameter of said passage.

In order that the invention may be more readily understood, the invention will be described with reference to the accompanying drawings in which: Figure 1 is a partially cutaway perspective view of an embodiment of a burner arrangement in accordance with the present invention Figure 2 is a longitudinal sectional view of Figure 1; Figure 3 is a sectional view for explaining the action of combustion in the case where the burner arrangement in accordance with the present invention is used; and Figure 4 is a comparative graph comparing a flame temperature pattern of the burner arrangement in accordance with the present invention with that of a conventional burner arrangement.

An injector adapted to be attached to a furnace indicated at A comprises a fuel injection pipe 1 provided axially of the body constituting a cylindrical air injection pipe 2 for supplying air toward a combustion section. The air injection pipe 2 has a special configuration and structure as described below.

The latter end of pipe 2 has a large diameter pipe section 3 as shown in the drawings, and an annular space, which is formed between the pipe section 3 and the fuel injection pipe 1 extending through the section 3, serving as an air injection passage. Further, the pipe section 3 is provided in its interior with rotatable or stationary vanes 4.

The vanes 4 may be formed with a plurality of moving blades by disposing them radially in parallel; and the blades may be rotated in the direction such as to cross the air passage, for example, at an angle of about 45" to 750 to the flowing air.

The air which is supplied for the larger diameter pipe section 3 at its upstream side in the direction indicated in Figure 2 by the arrow a, is given a swirl motion when it passes through the guide vanes 4, and then it is injected at high velocity toward the furnace A while swirling as indicated by the arrow b. When the angle described above is less than 45 , there is poor ignition of the burner and when it is more than 75 , the velocity produced by the vanes 4 is reduced.

The pipe section 3 is provided with a taper at its outlet to form a throttle section 5 for accelerating air and the ratio at the end diameters of the taper is about 0.4:0.8 with the object of ensuring that the fuel injection rate is greater than the flame transfer rate of fuel. The air injection rate may be varied depending upon the fuel used, but is preferably 20 to 60 m/sec. Moreover, the throttle section 5 is connected at its front end with a straight cylindrical air swirl passage 7 in communication therewith. The air swirl passage 7 has a diameter D which is the same as that of the downstream end of the section 5 and is surrounded by refractory material, since it is formed in a refractory tile 6. Thus the air passes through the air swirl passage 7 while swirling as indicated by the arrow b and is injected into the furnace A.

The length L of the air swirl passage 7 is at least four times its diameter D. The fuel injection pipe extends through the air swirl passage 7 so that the front end of the pipe 1 is located at a distance 0.1 to 4.0 times, preferably 0.5 to 1.0 times, the diameter D, short of the front openings of the passage 7. In this case, the range of less than 0.1 times diameter D may worsen the mixing and the range of more than 4.0 times diameter D may increase the amount of NOX formed.

Since the burner arrangement in accordance with the present invention has the structure described in the foregoing embodiment, the air which is supplied to the air injection pipe 2 as indicated by the arrow a is swirled when passing through .the guide vanes 4 provided in the larger diameter pipe section 3 disposed as described above, and then the Bow rate of the air is increased still more, firstly while swirling as indicated by the arrow b; secondly, when passing through the air throttle section 5; and finally, after passing through the swirl passage 7 the.

air is injected at high speed into the furnace A. Thus, as shown in Figure 3, this swirling air produces a central lower pressure portion in the neighbourhood of its front opening around the axes of the air swirl to form a desirable circulating flow as indicated by the arrow c. The dotted lines in Figure 3 represent pressure distribution lines.

On the other hand, a fuel such as oil or gas which is injected from the front end of the fuel injection pipe 1 into the furnace A at an included angle of 5 to 600, impinges against the circulating flow of high temperature combustion gas within the furnace A whereupon the fuel and air become rapidly mixed.

By way of example, the flame temperature pattern of the burner arrangement in accordance with the present invention is shown in Figure 4, comparing it with a known burner arrangement in the case where, for example, oil is burned. That is to say, in one prior art burner arrangement, the temperature rises within the burner tile at its localized area and NOX is formed while in accordance with the present invention, the combustion begins in the interior of the furnace A after the oil leaves the air swirl passage 7 as described above. Thus it is apparent from Figure 4 that in accordance with the present invention, the maximum flame temperature is lower by about 1000C than that of the known burner arrangement and the area of high temperature is shifted into the interior of the furnace A. By these means the amount of NOX formed by the burner arrangement is achieved.

The values of NOX formed are compared between the burner arrangement in accordance with the present invention and one typical prior art burner, when using oil for combustion for example, and the results are shown in the following table.

Air Ratio of 1:1 1:2 1:4 Burner arrangement of: the present invention type 51 ppm 62 ppm 84 ppm the known type 130 ppm 180 ppm 200 ppm In this table, the furnace temperature is 1250"C and fuel is Minas heavy oil.

From this comparative table, it can be seen that the burner arrangement in accordance with the present invention forms only about 40 Ó NOX formed by the known type burner arrangement.

WHAT WE CLAIM IS: 1. A burner arrangement consisting of an injector in combination with a refractory tile adapted to form part of a furnace wall, the injector having a body defining a cylindrical air injection passage and extending axially therethrough, a fuel injection pipe means for supplying air into the air injection passage surrounding said fuel injection pipe, vane means for imparting a swirl motion to the air passing through said air injection passage, said vane means being provided in the interior of said air injection passage, and a straight cylindrical passage in said refractory tile for transmitting the swirling air into a furnace and provided in communication with said air injection passage, said straight passage having a length which is at least four times its diameter, and wherein means for accelerating the air is further provided between said air injection passage and said straight cylindrical passage, said means for accelerating the air being a throttle section effective to reduce the cross-sectional space available for the passage of air by between 20% and 60% as said air moves from said air injection passage into said straight passage, and wherein said fuel injection pipe extends into straight passage in the refractory tile so that the front end of said pipe is located, short of a front end of said passage where it is adapted to open into a furnace, by a distance equal to 0.1 to 4.0 times the diameter of said passage.

2. The burner arrangement according to claim 1, wherein the injection rate of said air swirled through the open end of the straight passage is larger than the flame transfer rate of fuel.

3. The burner arrangement according to claim 2, wherein the injection rate of said air is 20 to 60 m/sec.

4. The burner arrangement according to claim 1, wherein said air swirling means comprises rotating vanes.

5. The burner arrangement according to claim 1, wherein said vane means are blades provided at an angle of 45" to 750 to the flowing axes of air.

6. The burner arrangement according to claim 1, wherein said fuel injection pipe extends to said passage so that the front end of said pipe is located short of the front end of the passage by a distance equal to 0.5 to 1.0 times the diameter of said passage.

7. A fuel burner arrangement substantially as hereinbefore described and as shown in any of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. In this table, the furnace temperature is 1250"C and fuel is Minas heavy oil. From this comparative table, it can be seen that the burner arrangement in accordance with the present invention forms only about 40 Ó NOX formed by the known type burner arrangement. WHAT WE CLAIM IS:

1. A burner arrangement consisting of an injector in combination with a refractory tile adapted to form part of a furnace wall, the injector having a body defining a cylindrical air injection passage and extending axially therethrough, a fuel injection pipe means for supplying air into the air injection passage surrounding said fuel injection pipe, vane means for imparting a swirl motion to the air passing through said air injection passage, said vane means being provided in the interior of said air injection passage, and a straight cylindrical passage in said refractory tile for transmitting the swirling air into a furnace and provided in communication with said air injection passage, said straight passage having a length which is at least four times its diameter, and wherein means for accelerating the air is further provided between said air injection passage and said straight cylindrical passage, said means for accelerating the air being a throttle section effective to reduce the cross-sectional space available for the passage of air by between 20% and 60% as said air moves from said air injection passage into said straight passage, and wherein said fuel injection pipe extends into straight passage in the refractory tile so that the front end of said pipe is located, short of a front end of said passage where it is adapted to open into a furnace, by a distance equal to 0.1 to 4.0 times the diameter of said passage.