GB1585410A - Burner - Google Patents

Description

(54) BURNER (71) We, ISHIKAWAJIMA-HARIMA JUK OGYO KABUSHIKI KAISHA, a Company organised under the laws of Japan, of No. 2-1, 2chome, Ote-machi, Chiyoda-ku, Tokyo-to, 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, for use, for example, in a boiler for generating electricity or for an industrial boiler. The burner may burn a suitable combination of coal and/or gas and/or liquid fuel.

Nitrogen Oxides (NOX) produced by the combustion with coal, gas, liquid fuel furners cause at present serious atmospheric air pollution problems, but so far, methods and apparatus for completely removing nitrogen oxides from flue gases have enjoyed limited success. Under these circumstances, it is a desired alternative to improve the conditions of combustion in such a way that the production of nitrogen oxides in the combustion zone may be minimized. Therefore, there has been an increasing demand for improved burners which may be not only used in newly constructed boilers and existing boilers at less cost but also may substantially reduce the production of nitrogen oxides.

It is an object of the present invention to provide a burner which not only satisfies the above requirements but also permits the control on the conditions of combustion over a wide range corresponding with the characteristics of the boiler on which the burner is installed.

It is a further object of the present invention to provide a burner whose fuel ignition and extinction process is so easily controlled as to allow the automatic and/or remote operation of the burner.

According to the invention, a burner arrangement includes a combustion air passageway in which is located a first set of adjustable vanes the combustion air passageway being divided downstream of the first set of vanes into a plurality of secondary passageways the burner arrangement further including a second set of adjustable vanes located in one of the secondary passageways.

The various sets of vanes may be controlled remotely and/or automatically. Preferably the sets of vanes have separate control systems, and the secondary passageways are preferably arranged along the axis of the burner.

The invention extends to a boiler incorporating a burner as described in accordance with the invention.

The invention may be carried into practice in various ways and one embodiment will be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a sectional view of a prior art single register single throat type burner; Figure 2 is a sectional view of a prior art double register double throat burner; Figure 3 is a sectional view of a burner in accordance with the present invention; Figure 4a is a view used for the explanation of the flow pattern in a prior art burner; and Figure 4b is a view used for the explanation of the flow pattern in the burner in accordance with the present invention.

Same reference numerals are used to designate similar parts throughout Figures.

Prior to the description of the preferred embodiment of the present invention, the prior art burners will be briefly described with reference to Figures 1 and 2 in order to distinctly and specifically point out their problems.

First referring to Figure 1, the single register-single throat burner installed on a furnace wall I includes a pulverized-coal burner inner tube 9 and a pulverized-coal burner outer tube 14 for feeding pulverized coal 12 as shown in the upper half, a spud type gas burner 17 for feeding a gas fuel 13 as shown in the lower half, and a heavy oil burner 15 with a diffuser 16 for feeding a liquid fuel 11 at the centre of the burner or burner throat 20. Combustion air 2 is forced to swirl by register vanes 5 positioned along the periphery of the burner, and is directed toward the throat 20 in the furnace wall 1 through the space or combustion air passa geway defined by a throat ring 7, a register supporting plate 21 and the pulverized-coal burner outer tube 14 and the space defined by the throat ring 7, the register supporting plate 21 and an interior deflector 10.

One of the advantages of the burner of the type described is that it is simple in construction, only the air register vanes 5 are provided in order to control the pattern of the flow of the air as well as the distribution of the velocity of the air flow but the control range is very limited and consequently the range of the control of the shape of the flame is also very narrow. In practice, the shape of the flame must be controlled to determine the emission of pollutants such as nitrogen oxides, carbon monoxide and particulate matters and upon the effect of the shape of the flame on the performance of the boiler.

Therefore it is desirable that the shape of the flame may be controlled over a wide range.

From the standpoint of this flame shape controllability, the prior art burner of the type shown in Figure 1 is not satisfactory because of its narrow or limited flame shape controllability as described above.

In the double register-double throat burner shown in Figure 2, in addition to the air register vanes 5, additional vanes 6 are provided so that the flows 3 and 4 of combustion air may be controlled independently of each other. However the simultaneous control of two sets 5 and 6 of air register vanes for controlling the combustion air flows 3 and 4 is very troublesome or inconvenient especially on the fuel ignition and extinction process of burners and particularly when a relatively large number of burners are installed. In general, automatic or remote controlled burners are used in the boilers that have been recently constructed or are to be constructed.With the double register-double throat burner of the type described in conjunction with Figure 2, not only are two independent sets of vane drive devices and control wiring systems required whose cost is high, but also these two sets of drive devices must be operated independently during the ignition and extinction processes. In order to overcome these problems, one common drive device may be provided for driving both the air register vanes 5 and 6, but the result would be that two sets 5 and 6 of air register vanes cannot be controlled independently of each other and consequently the range of the control on the shape of the flame will be narrowed.

Thus the arrangement for driving two sets of air register vanes with a common drive device would lose most of the advantages of the double register-double throat burner.

In Figure 3 there is shown one preferred embodiment of the present invention which may substantially overcome the above and other problems encountereda in the prior art burners. The burner shown in Figure 3 is similar in appearance to the prior an burner shown in Figure 1, but is essentially different in construction and function as will be described below so that novel effects hitherto unattainable by the prior art burners may be attained.

The passageway of combustion air 2 from the vanes 5 to the throat 20 is divided into outer and inner passageways by a partition wall plate 22 and an external deflector plate or ring 8, and the register vanes 6 which can be driven independently of the vanes 5 are positioned in the inner passageway defined by the register supporting plate 21 and the partition wall plate 22.

In operation combustion air 2 which is pressurized and supplied from a force draft fan (not shown) or the like is caused to swirl by the vanes 5, and a part of combustion air 3 thus swirled flows toward the throat 20 through an annular passageway defined between the throat ring 7 and the external deflector plate or ring 8. When the remaining part 4 flows into the inner passage defined between the register supporting plate 21 and the partition wall plate 22, it is caused to further swirl by the vanes 6 and flows toward the throat through an annular passage defined between the external deflector plate or ring 8, and the pulverized coal outer tube 14 (shown in the upper half of Figure 3) and an internal deflector plate 10 (shown in the lower half of Figure 3).At the throat 20 combustion air 3 flowing through the outer passageway and combustion air 4 flowing through the inner passageway join.

The liquid fuel 11 such as heavy oil is injected through the heavy oil burner 15; the pulverized coal 12 is injected from the nozzle of the pulverized-coal burner consisting of the inner and outer tubes 9 and 14; and the gas fuel is injected through the spud gas burner 17. These fuels may be fired independently of each other or in any suitable combinations.

The combustion air passageway downstream of the vanes 5 is divided into the outer and inner passageways, and the vanes 6 are positioned in one of the outer and inner passageways. Therefore instead of arranging the vanes 6 in the inner passageway as shown in Figure 3, they may be installed in the outer combustion air passageway. In addition, the passageway downstream of the vanes 5 may be divided into more than two passageways.

With the burner in accordance with the present invention, the flow or flow velocity pattern of the combustion air at the throat 20 may be widely varied so that the shape of the flame and other combustion conditions may be controlled depending upon the content of nitrogen oxides and unburned solids in the exhaust gases and the thermal radiation characteristics of the flame.

In Figures 4a and 4b there are shown, respectively, the flow patterns measured at the section X-X of the prior art burner and the burner in accordance with the present invention for the sake of comparison. As seen from Figure 4a, with the prior art burner, the air flow pattern or the distribution of axial velocities of air flows can be controlled or varied only within a very limited range. That is, when the degree of opening of the vanes 5 is increased, the swirling forces or degree of rotation imparted to the combustion air flows are decreased so that the flame tends to lift or blow off. On the other hand, when the degree of opening of the register vanes 5 is decreased, the tendency of flash-back of the flame increases so that the over-heating of burner tiles and excessive temperature rise of water tubes in the vicinity of the burner tiles will occur.

However with the burner in accordance with the present invention, the flow pattern may be varied over a wide range as shown in Figure 4b by controlling the degree of opening of the register vanes 6 with the register vanes 5 set at 45" as in the prior art burners. Moreover, in the burner in accordance with the present invention, it is not necessary to control the degree of opening of the vanes 5 over a wide range so that the lift of the flame as well as the flash-back may be avoided. Thus, the stable combustion may be proceeded by varying the flow pattern. Furthermore in the burner ignition or extinction process, it suffices only to control the vanes 5 so that the control of the register vanes may be much facilitated and consequently the automatic or remote control of the burner may be also facilitated.

WHAT WE CLAIM IS: 1. A burner arrangement including a combustion air passageway in which is located a first set of adjustable vanes, the combustion air passageway being divided downstream of the first set of vanes into a plurality of secondary passageways, the burner arrangement further including a second set of adjustable vanes located in one of the secondary passageways.

2. A burner arrangement as claimed in Claim 1 including a pulverized solid fuel feed and/or a liquid fuel feed and/or a gas feed.

3. A burner arrangement as claimed in either of Claims 1 and 2 in which at least at the outlet end one of the secondary passageways surrounds the other annularly.

4. A burner arrangement as claimed in any of Claims 1 to 3 in which at least at the inlet ends, the secondary passageways are separated from one another in a direction parallel to the burner axis.

5. A burner arrangement as claimed in any preceding claim in which each set of vanes is provided with separate control means.

6. A burner arrangement as claimed in any preceding Claims in which the vanes are controlled remotely and/or automatically.

7. A burner arrangement substantially as herein specifically described with reference to Figures 3 and 4b of the accompanying drawings.

8. A boiler including a burner as claimed in any preceding Claim.

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

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. In Figures 4a and 4b there are shown, respectively, the flow patterns measured at the section X-X of the prior art burner and the burner in accordance with the present invention for the sake of comparison. As seen from Figure 4a, with the prior art burner, the air flow pattern or the distribution of axial velocities of air flows can be controlled or varied only within a very limited range. That is, when the degree of opening of the vanes 5 is increased, the swirling forces or degree of rotation imparted to the combustion air flows are decreased so that the flame tends to lift or blow off. On the other hand, when the degree of opening of the register vanes 5 is decreased, the tendency of flash-back of the flame increases so that the over-heating of burner tiles and excessive temperature rise of water tubes in the vicinity of the burner tiles will occur. However with the burner in accordance with the present invention, the flow pattern may be varied over a wide range as shown in Figure 4b by controlling the degree of opening of the register vanes 6 with the register vanes 5 set at 45" as in the prior art burners. Moreover, in the burner in accordance with the present invention, it is not necessary to control the degree of opening of the vanes 5 over a wide range so that the lift of the flame as well as the flash-back may be avoided. Thus, the stable combustion may be proceeded by varying the flow pattern. Furthermore in the burner ignition or extinction process, it suffices only to control the vanes 5 so that the control of the register vanes may be much facilitated and consequently the automatic or remote control of the burner may be also facilitated. WHAT WE CLAIM IS:

1. A burner arrangement including a combustion air passageway in which is located a first set of adjustable vanes, the combustion air passageway being divided downstream of the first set of vanes into a plurality of secondary passageways, the burner arrangement further including a second set of adjustable vanes located in one of the secondary passageways.

2. A burner arrangement as claimed in Claim 1 including a pulverized solid fuel feed and/or a liquid fuel feed and/or a gas feed.

3. A burner arrangement as claimed in either of Claims 1 and 2 in which at least at the outlet end one of the secondary passageways surrounds the other annularly.

4. A burner arrangement as claimed in any of Claims 1 to 3 in which at least at the inlet ends, the secondary passageways are separated from one another in a direction parallel to the burner axis.

5. A burner arrangement as claimed in any preceding claim in which each set of vanes is provided with separate control means.

6. A burner arrangement as claimed in any preceding Claims in which the vanes are controlled remotely and/or automatically.

7. A burner arrangement substantially as herein specifically described with reference to Figures 3 and 4b of the accompanying drawings.

8. A boiler including a burner as claimed in any preceding Claim.