OXYGEN-ENRICHED BURNER AND METHOD FOR HEATING USING OXYGEN-ENRICHED BURNER

An object of the present invention is to provide an oxygen-enriched burner which can change any oscillation period and uniformly heat an object to be heated with an excellent heat transfer efficiency when heating the object to be heated while moving the flame with self-induced oscillation, and a method for heating using an oxygen enriched burner, and the present invention provides an oxygen-enriched burner including a center fluid ejection outlet and a peripheral fluid ejection outlet provided around the center fluid ejection outlet, a pair of openings are provided at opposite positions on side walls of a fluid ejection flow path of the center fluid ejection outlet, a pair of the openings are communicated with each other by a communication portion, an interval between a pair of side walls downstream of the openings in the fluid ejection flow path is gradually expanded toward the downstream side, and the communication portion includes a first communication pipe and the second communication pipe each having a first end connected to a pair of the openings, and at least one communication element connected to second ends of the first communication pipe and the second communication pipe and communicating the first communication pipe and the second communication pipe.

FIELD OF THE INVENTION

The present invention relates to an oxygen-enriched burner and a method for heating using an oxygen-enriched burner.

DESCRIPTION OF RELATED ART

A ladle and a tundish, which are furnaces (containers) that receive pig iron (molten metal) used in iron producing process, are preheated using a flame formed by a burner to prevent damage to refractories (refractory bricks, and the like) in the furnace due to rapid heating. The flame of the burner used for such applications is required to have high heat transfer efficiency and to be able to heat uniformly an object to be heated.

As a method for increasing a heat transfer efficiency of the burner, for example, a method for increasing the flame temperature by using an oxygen-enriched air as an oxidizing agent has been adopted. However, in a conventional burner, since the flame has a linear shape, there is a tendency to locally heat one point of the object to be heated, and uniform heating is difficult.

On the other hand, Patent Documents 1 and 2 disclose a method capable of performing uniform heating while moving a flame by using a self-induced oscillating phenomenon of a jet flow and maintaining high heat transfer efficiency. The burners disclosed in Patent Documents 1 and 2 employ a nozzle structure that applies the self-induced oscillating phenomenon in which a jet flow periodically changes without requiring an external driving force. Thereby, since a flame direction can be changed periodically, it becomes possible to perform uniform heating, maintaining high heat transfer efficiency. As a result, the burners disclosed in Patent Documents 1 and 2 can uniformly heat over a wide range as compared with conventional radiant tube burners and the like, and for example, the burners are suitably used for preheating such as the tundish.

PRIOR ART DOCUMENTS

Patent Literature

DISCLOSURE OF THE INVENTION

Problem to be Solved by the Invention

The characteristics of the burners performing the self-induced oscillation disclosed in Patent Documents 1 and 2 can be controlled by the oscillation period of the jet flow. When an ejection velocity of a center fluid ejected from a center fluid ejection outlet of the burner is the same, and the oscillation period is short, fluid mixing is promoted, convection heat transfer is enhanced, and uniform heat transfer distribution can be obtained. On the other hand, when the oscillation period is long, the combustion is slow, and the radiant heat transfer is enhanced, and a long flame can be obtained. In order to control the oscillation period while keeping the ejection velocity constant, the flow of the fluid in a connection pipe provided for generating the self-induced oscillation may be controlled. An arbitrary oscillation period can be obtained by appropriately selecting the length of the connection pipe.

However, in the burners disclosed in Patent Documents 1 and 2, since the oscillation period in the flow rate of the center fluid is fixed, the combustion characteristic cannot be changed. For example, a method of making the connection pipe removable is also conceivable. However, for example, when the oscillation period is controlled using a flexible cable as the connection pipe, it is necessary to increase the cable length in order to increase the oscillation period, which causes a problem that the apparatus becomes complicated. In addition, when the frequency is changed while the burner is operated, the connection pipe needs to be exchanged in the combustion state, which may cause danger in handling the connection pipe in which the fluid has flowed into the inside.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an oxygen-enriched burner which can change any oscillation period with a simple operation and uniformly heat an object to be heated with an excellent heat transfer efficiency when heating the object to be heated while moving the flame with the self-induced oscillation, and a method for heating using an oxygen enriched burner.

Means to Solve the Problem

In order to solve the problems, the present invention provides the following oxygen-enriched burners and methods for heating using an oxygen-enriched burner.

(1) An oxygen-enriched burner which is configured to eject an oxygen-enriched air or a fuel gas from a plurality of fluid ejection outlets provided at the tip surface and burns them,

wherein a plurality of the fluid ejection outlets include a center fluid ejection outlet and a peripheral fluid ejection outlet,

a pair of openings are provided at opposite positions on side walls of a fluid ejection flow path of the center fluid ejection outlet,

a pair of the openings are communicated with a communication portion,

an interval between a pair of the side walls downstream of the opening in the fluid ejection flow path is gradually expanded toward the downstream side,

the peripheral fluid ejection outlet is provided around the center fluid ejection outlet,

the communication portion includes a first communication pipe and a second communication pipe each having a first end connected to a pair of the openings, and at least one communication element connected to a second end of the first communication pipe and the second communication pipe and communicating the first communication pipe and the second communication pipe.

(2) The oxygen-enriched burner according to (1), wherein a plurality of the communication elements are provided in parallel between the first communication pipe and the second communication pipe.

(3) The oxygen-enriched burner according to (2), wherein at least one of an inner diameter and a length of a plurality of the communication elements is different.

(4) The oxygen-enriched burner according to any one of (1) to (3), wherein the first communication pipe, the second communication pipe, and the communication element are detachably connected.

(5) The oxygen-enriched burner according to any one of (1) to (4), wherein the communication portion includes an on-off valve provided between the first communication pipe and the communication element and between the second communication pipe and the communication element.

(6) A method for heating using an oxygen-enriched burner, wherein an object to be heated is heated using the oxygen-enriched burner according to any one of (1) to (5) while causing the fluid ejected from the center fluid ejection outlet to the self-induced oscillation in an expansion direction of the fluid ejection flow path,

(7) The method for heating using an oxygen-enriched burner according to (6), wherein a period of the self-induced oscillation of the fluid ejected from the center fluid ejection outlet is 30 seconds or less.

Effects of the Invention

As explained above, the oxygen-enriched burner according to the present invention is an oxygen-enriched burner which moves a flame by the self-induced oscillation, wherein the communication portion which communicates a pair of the openings provided on the side walls of the fluid ejection flow path of the center fluid ejection outlet includes the communication element which communicates the first communication pipe and the second communication pipe. Thereby, the oxygen-enriched burner according to the present invention can change and control to any oscillation period with a simple operation. Therefore, during the operation of the oxygen-enriched burner, it is possible to change the combustion characteristics with a simple switching operation and to heat the object to be heated uniformly with excellent heat transfer efficiency. Furthermore, by ejecting the oxygen-enriched air from the peripheral fluid ejection outlet toward the fuel gas ejected from the center fluid ejection outlet, the combustion efficiency is improved, and the amount of NOx emissions can be effectively suppressed.

A heating method using an oxygen-enriched burner according to the present invention is a heating method using the oxygen-enriched burner according to the present invention. For this reason, as described above, the oscillation period of the flame due to the self-induced oscillation can be changed by a simple operation as necessary, and the object to be heated can be uniformly heated with excellent heat transfer efficiency.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, an oxygen-enriched burner and a method for heating using an oxygen-enriched burner which is an embodiment according to the present invention will be described with reference to figures as appropriate.

In the drawings used in the following description, in order to make the features easy to understand, the features may be enlarged for the sake of convenience, and the dimensional ratio of each component may be limited to the same as the actual one. In addition, the materials and the like exemplified in the following description are merely examples, and the present invention is not necessarily limited to them, and can be appropriately changed and implemented without changing the gist of the invention.

Hereinafter, the structure and a method for combusting of an oxygen-enriched burner according to the present invention will be described in detail.

FIGS. 1 to 3are diagrams for explaining a structure of an oxygen-enriched burner1(hereinafter sometimes abbreviated as burner1) according to an embodiment of the present invention.FIG. 1is a plan view showing an example of a positional relationship between a center fluid ejection outlet and a peripheral fluid ejection outlet.FIG. 2is a sectional view (cross-sectional view) taken along line A-A shown inFIG. 1.FIG. 3is a conceptual diagram showing oscillation states of an ejection direction of a fluid in the burner1according to one embodiment of the present invention. Moreover,FIGS. 1 to 3are schematic diagrams showing an arrangement relationship and a size of each fluid ejection outlet and opening, and the like, and some of the detailed parts such as a tube wall as a nozzle are omitted.

As shown inFIGS. 1 to 3, the burner1according to the present embodiment ejects at least one of a fuel gas G1and an oxygen-enriched air G2from a plurality of fluid ejection outlets provided at the tip surface of the burner1, and burns them.

Specifically, the burner1of the present embodiment includes a plurality of fluid ejection outlets including a center fluid ejection outlet2, and a peripheral fluid ejection outlet3.

A pair of opening62aand62bare provided at opposing positions on side walls61which form a fluid ejection flow path6that forms the center fluid ejection outlet2. A pair of the openings62aand62bare communicated with each other by a communication portion7.

Further, a distance between a pair of the side walls63aand63bforming the fluid ejection flow path6on the downstream side of the opening62aand62bis gradually expanded toward the downstream side. That is, when the burner1is viewed from above, the fluid ejection flow path6on the downstream side of the opening62a,62bhas a fan shape. Moreover, the peripheral fluid ejection outlet3is arranged around the center fluid ejection outlet2.

In the burner1of the present embodiment, the fuel gas G1or the oxygen-enriched air G2is ejected from the center fluid ejection outlet2and the peripheral fluid ejection outlet3, respectively, but any gas may be ejected from which ejection port.

In the burner1of the present embodiment, the fuel gas G1is ejected from the center fluid ejection outlet2, and the oxygen-enriched air G2is ejected from the peripheral fluid ejection outlet3.

The center fluid ejection outlet2is an opening (nozzle) that ejects the fuel gas G1when the fuel gas G1is supplied to the fluid ejection flow path6. As will be described later, since the cross section of the fluid ejection flow path6in the direction orthogonal to the flow direction of the fluid is substantially rectangular, the shape of the center fluid ejection outlet2is rectangular.

A center fluid supply line (not shown) is connected to an inlet6aof the fluid ejection flow path6. Thereby, the fuel gas G1can be introduced into the fluid ejection flow path6, and the fuel gas G1is ejected from the center fluid ejection outlet2.

As described above, the cross section of the fluid ejection flow path6in the direction orthogonal to the flow direction of the fluid (gas) is substantially rectangular. Side surfaces of the substantial rectangular are formed by a pair of the side walls61and61described above. The side walls61and61are provided with a pair of the openings62aand62bso as to face each other. Further, as shown inFIG. 2, a pair of the openings62aand62bare communicated by a communication portion7.

As described above, the side surfaces of the fluid ejection flow path6located downstream of the opening62aand62bare formed by a pair of the side walls63aand63b.An interval of a pair of the side walls63a,63bis gradually expanded toward the downstream. The cross section of the fluid ejection flow path6along the flow direction of the fluid (gas) located downstream of the openings62aand62bhas a fan shape. That is, the side surfaces of the fluid ejection flow path6positioned downstream of the openings62aand62bare formed by a pair of the side walls63aand63barranged in a substantially V shape.

On the other hand, the fluid ejection flow path6positioned on the upstream side of a pair of the openings62aand62bis formed as a rectangular tube-shaped flow path64in which the opposed side walls61and61extend substantially in parallel. The shape of the cross section along the flow direction of the fluid (gas) is substantially rectangular.

The burner1of the present embodiment has a pair of the openings62aand62barranged opposite to each other on a pair of the side walls61and61forming a fluid ejection flow path6, and a pair of the openings62aand62bare communicated with each other through the communication portion7. Thereby, the so-called flip-flop nozzle self-induced oscillation can be generated in the fuel gas G1ejected from the center fluid ejection outlet2.

That is, as shown inFIGS. 3A and 3B, when the fluid (fuel gas G1) flowing through the flow path64of the fluid ejection flow path6passes between a pair of the openings62aand62band flows between a pair of the side walls63aand63barranged in a fan-shaped cross section, the fluid is ejected from the center fluid ejection outlet2while self-induced oscillation so as to alternately contact one side wall63aand the other side wall63b.InFIG. 1, an arrow R inFIG. 1means a self-induced oscillating direction of the fluid.

The amplitude and frequency of the fluid due to the self-induced oscillation vary according to various conditions such as the dimensions of the opening62aand62b,a air of the side walls63aand63b,and the communication portion7, and the flow velocity of the fluid.

In the oxygen-enriched burner1according to the present embodiment, the fluid ejected from the center fluid ejection outlet2is oscillated at a desired angle and frequency within certain ranges by setting the dimensions and the number of installed communication elements73in the communication portion7. That is, according to the oxygen-enriched burner of the present embodiment, the fluid ejected from the center fluid ejection outlet2can be oscillated at a desired angle and frequency within certain ranges with a simple configuration and a simple operation.

Hereinafter, the communication portion7which is one of the characteristic parts of the oxygen-enriched burner1of the present embodiment will be described.

The communication portion7includes a first communication pipe71and a second communication pipe72each having a first end71a,72aconnected to a pair of the openings62a,62b,and at least one tubular communication element73connected to a second end71b,72bof the first communication pipe71and the second communication pipe72and communicating the first communication pipe71and the second communication pipe72.

That is, the communication portion7includes the first communication pipe71, the second communication pipe72, and a plurality of the communication elements73. The first end71aof the first communication pipe71is connected to the opening62aand the second other end71bis connected to the communication element73. The first end72aof the second communication pipe72is connected to the opening62b,and the second end72bis connected to the communication element73.

InFIG. 2, the communication portion7includes the first communication pipe71, the second communication pipe72, and three communication elements73connected in parallel between the first communication pipe71and the second communication pipe72. That is, as shown inFIG. 2, the first communication pipe71has three second ends71b,71b,71b.Similarly, the second communication pipe72also has three second ends72b,72b,72b.The second ends71b,71b,71bof the first communication pipe71communicate with the second ends72b,72b,72bof the second communication pipe72through three communication elements73(73A,73B,73C). That is, the three communication elements73(73A,73B,73C) are arranged in parallel to the first communication pipe71and the second communication pipe72.

In the oxygen-enriched burner1of the present embodiment, self-induced oscillation is generated by a flip-flop nozzle by communicating a pair of the openings62aand62bwith the communication portion7.

The communication portion7in the oxygen-enriched burner1of the present embodiment further includes an on-off valve74provided between the first communication pipe71and the communication element73, and an on-off valve74provided between the second communication pipe72and the communication element73. That is, the on-off valve74is connected to each of one ends73a,73a,73aand the other ends73b,73b,73bof communication elements73A,73B, and73C.

Since the burner1of the present embodiment includes the on-off valve74, it is possible to select only any communication element among the communication elements73A,73B, and73C. Of course, by operating the on-off valve74, all the communication elements73A,73B,73C can be used simultaneously or all can be stopped.

In the burner1of the present embodiment, the flow rate and flow velocity of the fluid flowing through each communication element can be set to different values by changing the inner diameters and lengths (full lengths) of a plurality of the communication elements73A,73B, and73C. That is, by operating the on-off valve74and selecting an arbitrary communication element, the flow rate and flow velocity of the fluid in the communication portion7can be adjusted, and the self-induced oscillation period can be set to an arbitrary period. The longer the communication element73is, the longer the self-induced oscillation period of the fluid ejected from the center fluid ejection outlet2is. The smaller the inner diameter of the communication element73, the longer the self-induced oscillation period.

The flow rate and flow velocity of the fluid in the communication element73can also be changed by providing a baffle plate or the like in the communication element73.

The relationship between a length len of the communication element, which is made dimensionless by the diameter or the equivalent diameter (when the channel cross section is not circular) D of the fluid ejection flow path6and a cross section S of the communication element73, and a oscillation frequency (Strouhal number) St, which is made dimensionless by the diameter or the equivalent diameter D and the ejection velocity U of the center fluid, is expressed by the expression {len=k·1/St (k: proportional constant)}, and is linear. hat is, the relationship between the length len of the communication element and the frequency St is also expressed by the expression {1/St=D/(t·U) (t: oscillation period)}. However, the diameter or the equivalent diameter D of the fluid ejection flow path6and the ejection velocity U of the center fluid are determined. For this reason, it is possible to change the oscillation period t by using communication elements73having different communication element lengths len.

As shown inFIG. 2, when the cross section of the fluid ejection flow path6in the direction orthogonal to the flow direction of the fluid is rectangular, the interval between the side walls61and61located on the upstream side with respect to a pair of the openings62aand62bcan be the equivalent diameter D.

The oxygen-enriched burner1of the present embodiment includes the communication elements73A,73B, and73C having different specifications, and the oscillation period t can be easily changed by arbitrarily selecting them.

In the oxygen-enriched burner1of the present embodiment, the first communication pipe71and the communication element73may be detachably connected, or the second communication pipe72and the communication element73may be detachably connected. The communication element73may be detachably connected to the on-off valve74. By detachably attaching the communication element73to the first communication pipe71and the second communication pipe72(or the on-off valve74), it is possible to easily replace the communicating element73with a communicating element which can obtain a flow rate and a flow velocity of the fluid according to the characteristics of an object to be heated.

Various methods can be employed to make the communication element73attachable to and detachable from the first communication pipe71and the second communication pipe72(or the on-off valve74). For example, both ends of the communication element73and the first communication pipe71and the second communication pipe72may be sealed with an O-ring. A screwing structure may be provided at both ends of the communication element73and the first communication pipe71and the second communication pipe72.

The opening angle of a pair of the side walls63in the fluid ejection flow path6, that is, the opening angle a (seeFIG. 2) of the center fluid ejection outlet2is not particularly limited, and may be set in consideration of a desired opening angle of the flame. However, from the viewpoint of stably generating oscillation in the ejection direction of the fluid and realizing uniform heating, the angle is preferably 90° or less.

InFIG. 2, the communication portion includes three communication elements73a,73b,and73c,but is not limited thereto. For example, the number of the communication elements73may be one or two, or four or more communication elements73may be provided.

Moreover, in the burner1of the present embodiment, the ejection amount of the center fluid (the fuel gas G1) ejected from the center fluid ejection outlet2and the ejection amount of the peripheral fluid (the oxygen-enriched air G1) ejected from the peripheral fluid ejection outlet3are preferably individually controllable. For example, a flow rate control device may be provided in the line that is connected to each ejection outlet and supplies each fluid.

As shown inFIG. 1, the peripheral fluid ejection outlet3is arranged around the center fluid ejection outlet2so as to surround the center fluid ejection outlet2.

A peripheral fluid supply line (not shown) is connected to the peripheral fluid ejection outlet3. With the introduction of the oxygen-enriched air G2, the peripheral fluid ejection outlet3becomes opening (nozzle) to eject gas.

Here, “the peripheral fluid ejection outlet3is arranged around the center fluid ejection outlet2” in the present embodiment means that the peripheral fluid ejection outlet3is arranged so as to surround the center fluid ejection outlet2, and that the center fluid ejection outlet2and the peripheral fluid ejection outlet3are arranged at adjacent positions.

By arranging the peripheral fluid ejection outlet3around the center fluid ejection outlet2, the oxygen-enriched air G2can be ejected from a position adjacent to the position at which the fuel gas G1is ejected.

In the oxygen-enriched burner of present embodiment, the peripheral fluid ejection outlet3is arranged so as to surround the center fluid ejection outlet2, so that the center fluid ejected from the center fluid ejection outlet2(the fuel gas G1) and the peripheral fluid (the oxygen-enriched air G2) ejected from the peripheral fluid ejection outlet3are effectively mixed. In addition, since the fluid is ejected from the peripheral fluid ejection outlet3to the outer periphery of the flame, the reduction region is spread, and the effect of improving the combustion efficiency when forming the flame is obtained.

The shape of the peripheral fluid ejection outlet3may be a rectangular shape or a circular shape arranged so as to surround the center fluid ejection outlet2. Further, the peripheral fluid ejection outlet3may be configured to surround the center fluid ejection outlet2with a plurality of openings (holes).

Next, a method for combusting the oxygen-enriched burner1of the present embodiment will be described.

In the burner1of the present embodiment, the center fluid ejected from the center fluid ejection outlet2is the fuel gas G1, the peripheral fluid ejected from the peripheral fluid ejection outlet3is the oxygen-enriched air G2, and a flame is formed in an ejection direction of the fuel gas G1.

Examples of the fuel gas G1include natural gas (LNG), but liquid fuel such as heavy oil may be used.

Further, as the oxygen-enriched air G2, for example, a mixed gas of oxygen and air in which the oxygen concentration is increased as much as possible can be exemplified. Instead of the air, for example, nitrogen gas, carbon dioxide gas, exhaust gas, or the like can be used and mixed with oxygen. Moreover, as oxygen used for the mixed gas, industrial pure oxygen may be used.

When combusting the burner1of the present embodiment, the fuel gas G1is ejected from the center fluid ejection outlet2while alternately and periodically changing the ejection direction by the self-induced oscillation (seeFIGS. 3A and 3B). At this time, the oxygen-enriched air G2(peripheral fluid) is ejected toward the fuel gas G2ejected from the center fluid ejection outlet2at a periodically changing angle from the peripheral fluid ejection outlet3so as to wrap the fuel gas G1and contributes to the formation of the flame.

As the oxygen-enriched air G2is ejected toward the fuel gas G1, the combustion efficiency is improved, and the amount of NOx emission can be effectively suppressed. Moreover, the heat transfer efficiency by the flame improves and it becomes possible to heat the object to be heated uniformly.

Moreover, the switching period (oscillation period t) of the ejection direction of the fuel gas G1by the self-induced oscillation is not particularly limited. What is necessary is just to set the switching period suitably in a range which can be heated uniformly with the excellent heat-transfer efficiency also in the position away from the center axis of the burner. As described later, the oscillation period t for obtaining such an effect is preferably set to oscillation period t=30 seconds or less.

The oxygen-enriched burner1of the present embodiment is a burner that oscillates the flame by the self-induced oscillation, and includes the communication portion7. Therefore, the oscillation period t of the fluid ejected from the center fluid ejection outlet2can be arbitrarily changed and controlled. As a result, when the oxygen-enriched burner1is operated, the combustion characteristic can be changed by a simple switching operation, and the object to be heated can be uniformly heated with excellent heat transfer efficiency.

The method for heating according to the present invention is a method for heating an object to be heated, such as a tundish while the oxygen-enriched burner1is used to cause the self-induced oscillation of the fluid ejected from the center fluid ejection outlet2in the expanding direction of the fluid ejection flow path6. Since the method for heating of the present invention is a method for heating an object to be heated using the oxygen-enriched burner1described above, when heating the object to be heated by the flame that oscillates with the self-induced oscillation, the object to be heated can be uniformly heated with excellent heat transfer efficiency while changing the oscillation period t of the self-induced oscillation of the fluid ejected from the center fluid ejection outlet2.

The object to be heated in the method for heating of the present invention is not particularly limited. As one embodiment, a ladle and a tundish (not shown), or the like that receives pig iron used in the steel making process described above can be given.

The method for heating of the present embodiment is a method for heating an object to be heated such as a ladle or a tundish using the burner1, wherein the oscillation period t of the fluid ejected from the center fluid ejection outlet2can be arbitrarily changed and controlled. Thereby, when the burner1is operated, the combustion characteristic can be changed by a simple switching operation, and the object to be heated can be uniformly heated with excellent heat transfer efficiency.

In the method for heating of the present embodiment, the period of the self-induced oscillation (oscillation period t) of the fluid ejected from the center fluid ejection outlet2is not particularly limited and can be set as appropriate in consideration of the characteristics of the object to be heated. Since various objects to be heated can be uniformly heated over a wide area, the oscillation period t=30 seconds or less is preferable.

Note that the object to be heated by the method for heating using the burner1of the present embodiment is not limited to a ladle or a tundish used in the steel making process. For example, in the case of heating various objects to be heated that require high temperature and uniform heating, the present invention can be applied without any limitation.

As explained above, the oxygen-enriched burner of the present embodiment includes the center fluid ejection outlet2and the peripheral fluid ejection outlet3provided around the center fluid ejection outlet2, a pair of the openings62a,62bare provided at opposite positions on the side walls61,61of the fluid ejection flow path6of the center fluid ejection outlet2, a pair of the openings62a,62bare communicated with each other by the communication portion7, the first communication pipe71and the second communication pipe72each having the first end71a,72aconnected to a pair of the openings62a,62b,and at least one communication element73connected to the second ends71b,72bof the first communication pipe71and the second communication pipe72and communicating the first communication pipe71and the second communication pipe72.

Thus, in the oxygen-enriched burner1that oscillates the flame by the self-induced oscillation, the communication portion7that communicates a pair of the openings62aand62bincludes the communication element73that communicates the first communication pipe71and the second communication pipe72. Thereby, it can change and control to arbitrary oscillation periods with a simple structure and a simple operation. Therefore, when the oxygen-enriched burner1is operated, the combustion characteristics can be changed by a simple switching operation, and the object to be heated can be uniformly heated with excellent heat transfer efficiency.

Furthermore, since the center fluid ejection outlet2and the peripheral fluid ejection outlet3are provided, the oxygen-enriched air G2can be ejected toward the fuel gas G1. As a result, the combustion efficiency can be improved, and the amount of NOx emission can be effectively suppressed.

Moreover, the method for heating using an oxygen-enriched burner of the present embodiment is a method for heating using the oxygen-enriched burner1described above. For this reason, similar to the oxygen-enriched burner1, the oscillation period t of the flame caused by the self-induced oscillation can be changed by a simple operation as necessary. Furthermore, the object to be heated can be uniformly heated with excellent heat transfer efficiency.

EXAMPLES

Hereinafter, the oxygen-enriched burner and the method for heating using a burner according to the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Example, and can be appropriately modified and implemented without changing the gist of the invention.

<Burner Specifications and Operating Conditions>

In the Examples, as shown inFIGS. 1 to 3, a self-induced oscillation type oxygen-enriched burner1, which includes the first communication pipe71and the second communication pipe72each having the first end71a,72aconnected to a pair of the openings62a,62b,and three communication element73a,73b,73cconnected to the second ends71b,72bof the first communication pipe71and the second communication pipe72and communicating the first communication pipe71and the second communication pipe72, was prepared. Using the prepared burner1, a combustion test was performed under the following conditions.

In the Examples, the opening angle a of the center fluid ejection outlet2of the burner1shown inFIG. 2was adjusted to 30°.

In the Examples, propane gas was used as the fuel gas G1, and a gas having an oxygen enrichment rate of 40% was used as the oxygen-enriched air G2. The fuel gas G1was flowed to the center fluid ejection outlet2and the oxygen-enriched air G2was flowed to the peripheral fluid ejection outlet3to form a flame.

Burner operation conditions were as follows: the flow rate of the fuel gas G1(propane gas) was 13 Nm3/h, the flow rate of the oxygen-enriched air G2was 170 Nm3/h, and combustion was performed at an oxygen ratio of 1.05. Moreover, the oxygen ratio refers to the proportion of oxygen when the amount of oxygen necessary for complete combustion of the fuel gas was 1.

Further, in the Examples, the burner1was combusted in a test furnace (not shown), and the communication element73was switched during combustion, thereby changing the oscillation period t of the fuel gas G1due to the self-induced oscillation in the center fluid ejection outlet2. After reaching a steady state, measurement was performed for each evaluation items described in the following Examples.

In Example, the possibility of changing the oscillation period t by switching the communication element73described below was also evaluated. At this time, the equivalent diameter D of the fluid ejection flow path6was 10 mm, and the ejection velocity U of the fuel gas ejection G1was adjusted to 40 m/s.

Examples 1 and 2

In Examples 1 and 2, the temperature distribution in the combustion furnace when the oxygen-enriched burner1was combusted by the self-induced oscillation and the communication period73was changed by switching the communication element73was evaluated using thermocouples.FIGS. 4A and 4Bare schematic diagrams showing the positional relationship between the burner1and the thermocouples in the Examples 1 and 2.

In Examples 1 and 2, a plurality of the thermocouples were arranged along the expanding direction of the liquid election flow path6at positions 500 mm forward from the tip surface of the burner1, as shown inFIG. 4B, and 300 mm below the center axis in the height direction of the burner1as shown inFIG. 4B.

In Examples 1 and 2, the evaluation was performed using the communication elements C1and C2having a communication element length len and 1/St (St: frequency) shown in Table 1 below.

As described above, the relationship between the length len of the communication element and 1/St is expressed by the equation {len=k·1/St (k: proportional constant)} and the equation {1/St=D/(t·U) (t: oscillation period)}. Therefore, in the Examples 1 and 2, the diameter or the equivalent diameter D of the fluid ejection flow path6and the ejection velocity U of the center fluid were determined in advance, and the oscillation period t was changed by using communication elements having different communication element lengths len shown in Table 1 below.

In Examples 1 and 2, the temperature when the self-induced oscillation combust was generated and the steady state was reached was measured by each thermocouple in the test apparatus shown inFIGS. 4A and 4B.

The distance from the center axis in the self-induced oscillation direction of the burner1, that is, the gas ejection direction when the self-induced oscillation is not performed is the distance from the center axis of the burner is 0 [mm]. The relationship between the amplitude of the gas ejection direction during the self-induced oscillation and the furnace temperature, that is, the relationship between the position of the thermocouples and the furnace temperature is shown in the graph ofFIG. 5as data representing the temperature distribution in the furnace.

In the graph ofFIG. 5, Example 1 is a measurement result in oscillation period t=0.1 second (see Table 1), and Example 2 is a measurement result in oscillation period t =1 second (see Table 1). As shown inFIG. 5, it can be understood that Example 1 with a short oscillation period t had a flat (uniform) temperature distribution compared to Example 2.

From the evaluation results in Examples 1 and 2, it is confirmed that the oscillation period t could be switched by changing the length of the communication element73, and the temperature distribution could be changed by changing the oscillation period t, that is, the heating characteristics were changed.

It is clear that by using the oxygen-enriched burner according to the Examples, any combust state could be obtained by switching the communication element during the burner operation and changing the oscillation period t.

Examples 3 and 4

In Examples 3 and 4, the change in the flame length in the oxygen-enriched burner that was combusted with the self-induced oscillation, and the change in the heat transfer characteristics associated therewith were evaluated.

FIGS. 6A and 6Bare schematic views showing the positional relationship between the burner1and the thermocouples in the Examples 3 and 4.

As shown inFIG. 6A, a plurality of heatsink members were arranged along the ejection direction of the combust gas from the center fluid ejection outlet2, that is, the flame formation direction at positions 300 mm below the center axis in the height direction of the burner1.

In the Examples 3 and 4, the self-induced oscillation combustion was generated in the test apparatus shown inFIGS. 6A and 6B, and the heat transfer efficiency to the heatsink members in a steady state was measured. At this time, the temperature of the heatsink members was confirmed by measuring the surface temperature using a thermocouple (not shown).

The relationship between the distance from the tip surface of the burner1to the heatsink member and the amount of heat transferred is shown in the graph ofFIG. 7as data representing the amount of heat transferred distribution in the furnace.

In the graph ofFIG. 7, Example 3 is a measurement result in the same oscillation period t=0.1 second (see Table 1) as Example 1, and Example 4 is a measurement result in the same oscillation period t=1 second as in Example 2 (For the length len of the communication element, 1/St, and oscillation period tin Example 3, see communication element C3in Table 1).

As shown inFIG. 7, it can be understood that the slow combustion was promoted in Example 4 having a longer oscillation period t than that in Example 3 than Example 3, the radiant heat transfer was enhanced, and the heat transfer efficiency was higher. In addition, it is revealed that the flame length was longer in Example 4, and a higher amount of heat transferred distribution was obtained even farther from the tip surface of the burner1.

In Example 5, a combustion test with the self-induced oscillation using the burner1was performed under the same conditions as in Example 1, and NOx emission characteristics were evaluated except that the oscillation period t was changed at a plurality of periods (0.1 second, 0.5 second, 1 second, and 5 seconds) shown in the graph ofFIG. 8.

The graph ofFIG. 8shows the relationship between the oscillation period t and the amount of NOx emission in the Example 5.

As shown inFIG. 8, in Example 5, it is confirmed that the NOx emission amount decreased as the oscillation period t increased. This is thought to be because the fuel gas and the oxygen-enriched air were slightly mixed with each other and became a slowly combust state, and the reduction region was formed, so that the amount of NOx emission was suppressed.

From the results of the Examples described above, it is clear that the oscillation period can be changed and controlled arbitrarily with a simple configuration and a simple operation in the oxygen-enriched burner according to the Examples. It is also clear that the combustion characteristics can be changed by a simple switching operation during the burner operation. Furthermore, it is also clear that the object to be heated can be uniformly heated with excellent heat transfer efficiency, and the amount of NOx emission can be effectively suppressed.

INDUSTRIAL APPLICABILITY

The oxygen-enriched burner and the method for heating using an oxygen-enriched burner according to the present invention are preferably used for preheating a tundish used for storing and transporting the molten iron or the molten steel in the steel producing or iron producing processes. Furthermore, The oxygen-enriched burner and the method for heating using an oxygen-enriched burner according to the present invention are very suitable for various applications in which object to be heated is heated using a burner.

EXPLANATION OF REFERENCE NUMERAL

7communication pipe71first communication pipe72second communication pipe71a,72afirst ends of first and second communication pipes71b,72bsecond ends of first and second communication pipes73,73A,73B,73C communication element74on-off valve

D corresponding diameter of center fluid flow path