JP2000039143A - Combustion control method of heat storage type burner device and burner device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize combustion and reduce the generation of NOx, in a heat storage type burner device. SOLUTION: The generation of NOx is restrained by a method wherein primary air is supplied from a primary air supplying pipe 5 around a fuel nozzle 4 while secondary air, low in the oxygen concentration thereof, is supplied through a heat storage body 7 to burn the fuel further. When a temperature in a furnace is low, the rate of the primary air is increased by a control unit 40 but the rate of secondary air is increased by the same unit 40 when the temperature in the furnace is high.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling combustion in a burner device comprising a plurality of regenerative burners which are alternately burned, and a regenerative burner device. More specifically, the present invention relates to a combustion control method for a regenerative burner device capable of further reducing NOx, and to the regenerative burner device.

[0002]

2. Description of the Related Art A regenerative burner device is composed of a plurality of regenerative burners each including a fuel nozzle and a heat storage body disposed near the fuel nozzle. These regenerative burners are alternately burned and burned. The combustion gas in the furnace is exhausted through a heat storage element of a non-heat storage burner, and the heat storage element is heated. Then, the non-burning regenerative burner is burned,
In this case, the combustion air is preheated and supplied through the heated heat storage body, and the preheated air is brought into contact with fuel to burn efficiently.

[0003] However, in such a regenerative burner, the air preheated to a high temperature after passing through the regenerator comes into contact with the fuel and burns, so that the amount of generated NOx tends to increase. Conventionally, in order to reduce this NOx, the flow rate of combustion air blown into the furnace through the heat storage body is adjusted, or the flow of combustion air in the furnace is adjusted to reduce the combustion air and fuel. However, the combustion gas in the furnace is entrained in the flow of the combustion air and brought into contact with the fuel to reduce the amount of NOx generated.

However, the conventional method as described above cannot control the combustion condition of the fuel reliably, and there is a limit in reducing the generation of NOx. For example, in the case where the flow of combustion air blown into the furnace is controlled to contact the fuel over a wide range, or the surrounding combustion gas is involved in the air flow to come into contact with the fuel, the temperature inside the furnace is controlled. If the temperature is low, combustion is not stable, and misfires and the like are likely to occur.

In the conventional method as described above, the range in which the conditions for mixing and contacting the fuel and combustion air can be controlled is narrow, the type of fuel is changed, and the temperature setting in the furnace is changed. In such a case, there is a problem that it is not possible to sufficiently cope with this.

[0006]

SUMMARY OF THE INVENTION The present invention has been made on the basis of the above-mentioned circumstances, and is intended to provide a regenerative burner device capable of further reducing the generation of NOx and reliably controlling combustion conditions. An object of the present invention is to provide a combustion control method and a regenerative burner device.

[0007]

According to a first aspect of the present invention, there is provided a method for supplying primary air to a periphery of a fuel blown into a furnace from a fuel nozzle to perform primary combustion of the fuel and store heat. Secondary air having a lower oxygen concentration than the atmosphere is supplied to the surroundings of the primary air through the body to cause secondary combustion of the fuel, and as the temperature in the furnace increases, the secondary air with respect to the primary air increases. It is characterized in that the supply ratio is increased.

[0008] Therefore, the fuel blown into the furnace is first burned by the primary air, and stable combustion is ensured. And this fuel is further burned by secondary air, but since this secondary air has lower oxygen concentration than the atmosphere,
The generation of NOx can be effectively reduced. Also,
When the temperature in the furnace is low, the ratio of the secondary air to the primary air is low, and the fuel is mainly burned by the primary air, and the combustion is stabilized. In this case, since the temperature inside the furnace is low, the generation of NOx is originally small, so that the generation of NOx can be suppressed even when the combustion is performed mainly with the primary air as described above. Further, when the temperature in the furnace is high, the proportion of the secondary air increases, and the combustion is performed mainly with the secondary air having a low oxygen concentration, so that the generation of NOx can be reduced. In this case, since the temperature in the furnace is high, the combustion is stabilized even when the combustion is performed mainly with the secondary air having a low oxygen concentration as described above.

[0009] The method of the present invention according to claim 2 comprises:
The secondary air is characterized in that the concentration of oxygen is reduced by mixing the combustion gas in the furnace with the atmosphere supplied via the heat storage body. Therefore, the oxygen concentration of the secondary air can be reliably controlled without requiring a special device, and the waste heat of the combustion gas can be introduced again into the furnace, thereby improving the efficiency.

[0010] Further, the method of the present invention according to claim 3 comprises:
The primary air is blown around the fuel nozzle that blows the fuel, and the primary air is always circulated at a minimum flow rate necessary for cooling the fuel nozzle even when the temperature in the furnace is high. It is characterized by the following.
Therefore, the combustion of the fuel by the primary air is stabilized, and the fuel nozzle is always cooled by the primary air. Therefore, even when the temperature in the furnace is high, the fuel nozzle is reliably prevented from burning.

The device according to the present invention described in claim 4 is:
In the regenerative burner device including a plurality of regenerative burners, each regenerative burner is disposed around the fuel nozzle, the regenerator, and the fuel nozzle that blows fuel into the furnace, and is blown from the fuel nozzle. A primary air supply passage that supplies primary air around the fuel, and a secondary air supply passage that is arranged around the primary air supply passage and supplies secondary air through a heat storage body, A mixing passage for mixing the combustion gas into the air supplied to the secondary air supply passage of each of the regenerative burners to form secondary air having an oxygen concentration lower than the air, and a temperature detector for detecting a temperature in the furnace And a control device that receives a signal from the temperature detector and increases the supply ratio of the secondary air to the primary air as the furnace temperature increases.

Therefore, the combustion gas is supplied to and mixed in the secondary air of the regenerative burner burning through the mixing passage, so that the oxygen concentration of the secondary air is reduced. No special device is required to reduce the oxygen concentration in the secondary air, and the structure is simple. Further, since the supply ratio of the secondary air to the primary air is automatically controlled in accordance with the temperature in the furnace, the combustion can be reliably and accurately controlled.

[0013] The device according to the present invention described in claim 5 is:
The mixing passage communicates an air supply passage for supplying air to the heat storage element of the first regenerative burner and an exhaust passage for discharging combustion gas in the furnace via the heat storage element of the second regenerative burner. The combustion gas that has passed through the heat storage element of the second regenerative burner is supplied to and mixed with the air supply passage upstream of the heat storage element of the first regenerative burner device.

Therefore, outside the furnace, the low-temperature combustion gas that has exchanged heat with the regenerator of the second regenerative burner is discharged to the first regenerative burner.
Is mixed with the atmosphere on the upstream side of the regenerator of the regenerative burner, so that the heat resistance of the mixing passage and the valve mechanism is not so much required, the structure is simplified, and the regenerator of the second regenerative burner is It does not affect the action of heat exchange with the combustion gas.

The device according to the present invention described in claim 6 is:
The primary air supply passage is a primary air supply pipe having a double pipe structure surrounding the periphery of the fuel nozzle. Therefore, the fuel nozzle is effectively cooled by the primary air.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. First, an embodiment of the apparatus of the present invention will be described with reference to FIGS. Reference numeral 1 in the figure denotes a furnace wall, on which a plurality of regenerative burners 2a and 2b are provided. Although an actual furnace is provided with a large number of regenerative burners, FIG. 1 shows two regenerative burners 2a and 2b for ease of explanation. These regenerative burners 2a and 2b are divided into a first group of regenerative burners 2a and a second group of regenerative burners 2b, and are burned alternately for each group.

These regenerative burners 2a and 2b are shown in FIG.
It is configured as shown in FIG. That is, reference numeral 3 denotes a housing of the burner.
Is provided. Also, surrounding this fuel nozzle 4,
A double tubular primary air supply pipe 5 is provided. Also,
A burner tile 6 is provided at a front portion of the housing 3, and a plurality of heat storage bodies 7 are provided through the burner tile 7. These heat storage bodies 7 are connected to the fuel nozzles 4.
Are arranged around.

A fuel supply port 8 is provided at the rear end of the fuel nozzle 4, and a primary air supply port 9 is provided at the rear end of the primary air supply pipe 5. The housing 3 is provided with a supply / exhaust port 10.

In such regenerative burners 2a and 2b, when one regenerative burner 2a is burning, the other regenerative burner 2b stops burning, and the combustion gas in the furnace is The gas passes through the heat storage element 7 of the other regenerative burner 2b that is stopped and is exhausted from the supply / discharge port 10, whereby the heat storage element 7 is heated.

Then, the combustion of the other regenerative burner 2a is stopped, and the other regenerative burner 2b is combusted. In this case, the fuel gas supplied from the fuel nozzle 4 is supplied from the primary air supply pipe 5. Combustion by primary air. Further, secondary air is supplied from the supply / exhaust port 10 described above, and the secondary air passes through the heat storage unit 7 and is preheated, and the fuel is further burned by the preheated secondary air.
Such operation is repeated, and these regenerative burner devices 2
z and 2b are alternately burned.

Next, the configuration of a regenerative burner device composed of a plurality of such regenerative burners 2a and 2b will be described with reference to FIG. Fuel supply pipes 20 are connected to the fuel nozzles 4 of the regenerative burners 2a and 2b, respectively. Further, a primary air supply pipe 21 is connected to each of the primary air supply pipes 5, and a primary air control valve 22 is provided in each of the primary air supply pipes 21.

These primary air supply pipes 21 are connected to an air supply source (not shown) for supplying air, that is, the atmosphere. The supply / exhaust port 10 of the housing 3 of each regenerative burner 2a, 2b is connected to a switching valve 26 via a supply / exhaust pipe 25. An exhaust pipe 27 and a secondary air supply pipe 28 are connected to these switching valves 26, respectively. An exhaust control valve 31 is provided in the exhaust pipe 27, and a secondary air control valve 32 is provided in the secondary air supply pipe 28. And
The secondary air supply pipe 28 is connected to the above-described air supply source (not shown), and is configured to supply the atmosphere.

Also, the above-mentioned regenerative burner devices 2a, 2b
Is one secondary air supply pipe 28 and the other exhaust pipe 2
7, the other secondary air supply pipe 28 and one exhaust pipe 27
Are communicated with each other by mixing pipes 35a and 35b. In the middle of the mixing pipes 35a and 35b, mixing valves 37a and 37b and a check valve 36 are provided, respectively.
Are provided respectively.

The furnace wall 1 is provided with a temperature detector 41 for detecting the temperature inside the furnace. The signal from the temperature detector 41 is sent to the control device 40. The control device 40 controls the combustion of the regenerative burner device according to a predetermined program from the signal from the temperature detector 41 and other signals.

The control device 40 is configured as shown in FIG. That is, the control device 40 is provided with a valve opening control unit 42 for controlling the opening of the various valves. The valve opening control unit 42 includes the above-described temperature detector 41. The furnace temperature signal is input from. The valve opening control unit 42 receives a signal from a furnace temperature setting unit 43 for setting the furnace temperature and the like, and a signal from a combustion condition setting unit 44 for setting the type of fuel and other combustion conditions. Is entered.

The valve opening control section 42 performs an operation according to a predetermined program on the basis of the above-mentioned input signal to determine the various valve openings, and transmits this signal to the control valve drive circuit 45. , And to the mixing valve drive circuit 46. These drive circuits output control power and the like for opening and closing the various valves according to this signal. That is, the control valve drive circuit 45 controls the opening and closing of the primary air control valve 22, the exhaust control valve 31, and the secondary air control valve 32. The mixing valve drive circuit 46 controls the opening and closing of the mixing valves 37a and 37b.

Next, the operation of the above-described regenerative burner apparatus will be described. First, a case where the first regenerative burner 2a is burning and the second regenerative burner 2b stops burning will be described. Fuel and primary air are supplied to the first regenerative burner 2a. As described above, the switching valve 26 of the first regenerative burner 2a is switched to the secondary air supply side, and the secondary air is supplied. Further, the switching valve 26 of the second regenerative burner 2b is switched to the exhaust side, and the combustion air in the furnace is exhausted through the regenerator 7, and the combustion gas and the regenerator 7 exchange heat. Then, the heat storage body 7 is heated.

Next, a combustion control method using such a regenerative burner device and a control operation of the control device 40 will be described with reference to FIGS. First, when the temperature in the furnace is low, for example, at the beginning of combustion of the furnace, the opening degree of the primary air control valve 22 and the secondary air control valve 32 is controlled, and as shown in FIG. Supply ratio,
Reduce the secondary air supply ratio. FIG. 5 shows the case where the fuel supply amount is 100%, that is, the supply ratio of the primary air and the secondary air to the fuel supply amount. As shown in FIG. 5, the temperature in the furnace is low, for example, 2
In the case of 50 ° C., the supply amount of the secondary air is set substantially close to zero. Therefore, in this case, the fuel is mainly burned by the primary air.

This primary air is supplied from the atmosphere and has a high oxygen concentration.
Since the fuel gas is blown into the furnace from the primary air supply pipe 5 surrounding the fuel nozzle 4 so as to surround the fuel gas, the fuel burns stably and prevents misfires and the like.

In this case, the primary air having a high oxygen concentration contacts the fuel gas in a narrow range and burns. However, when the temperature in the furnace is low, the amount of generated NOx is originally small. Does not increase.

Next, as the temperature inside the furnace increases,
Accordingly, the supply ratio of the primary air is reduced,
The supply ratio of the secondary air is increased. At the same time, the mixing valve 37 of the mixing pipe 35a is opened, and the combustion gas exhausted through the heat storage element 7 of the second regenerative burner 2b passes through the mixing pipe 35a to the first mixing pipe 35a. It flows into the secondary air supply pipe 28 of the regenerative burner 2a, mixes with the air in this pipe, that is, the atmosphere, and forms the first air as secondary air.
Is supplied to the regenerative burner 2a.

This secondary air is supplied to the first regenerative burner 2a.
After being preheated through the heat accumulator 7 of
Burn the fuel further. In this case, since the secondary air has a combustion gas mixed with the atmosphere and the oxygen concentration thereof has decreased, NOx can be reduced by combustion with the secondary air.

In this case, the amount of generated NOx tends to increase as the temperature in the furnace increases.
In order to offset this tendency, the supply ratio of the primary air is reduced as the temperature in the furnace increases, and the supply ratio of the secondary air having a low oxygen concentration is increased. The supply ratio of the primary air and the secondary air, the ratio of the combustion gas mixed with the secondary air, and the like are determined by the valve opening control unit 42 of the control device 40.
The control valve and the mixing valve are adjusted to automatically and optimally set.

When the temperature in the furnace is sufficiently high, the supply ratio of the secondary air is increased, and the combustion mainly involving the secondary air is performed, so that NOx is reliably reduced. When the furnace temperature is high, stable combustion can be achieved even with such combustion mainly using secondary air having a low oxygen concentration.

In this embodiment, even when the temperature inside the furnace is high and the combustion mainly using the secondary air is performed as described above, the supply amount of the primary air is set to zero. Supply the minimum necessary primary air. The supply of the primary air cools the fuel nozzle 4 and prevents the fuel nozzle 4 from burning out due to the high temperature in the furnace.

Further, in this embodiment, the secondary air supply pipe of the regenerative burner burning the relatively low-temperature combustion gas that has passed through the regenerator 7 of the stopped regenerative burner device and has exchanged heat. 28, the mixing pipes 35a,
The heat resistance of 35b and the mixing valves 37a and 37b is not so required, and the structure of the apparatus is simple. In addition, since the exhaust gas that has passed through the heat storage is mixed with the secondary air, waste heat is effectively used, heat efficiency is improved, and a special device that reduces the oxygen concentration of the secondary air is required. Therefore, the structure of the device is simplified.

When the combustion of the first regenerative burner 2a is stopped and the second regenerative burner 2b is burned, the reverse of the above control is performed. The burners are fired alternately.

The present invention is not limited to the above embodiment. For example, in the case of a furnace with a low maximum temperature, the supply amount of primary air when the furnace temperature is high may be set to zero.
Further, the combustion gas mixed with the secondary air may be directly taken out of the furnace. Furthermore, when the supply of low oxygen concentration air can be obtained from other facilities, furnaces, etc., the combustion gas is taken out from the stopped regenerative burner as described above, and the secondary air of the regenerative burner during combustion is taken out. There is no need to mix.

[0039]

As described above, according to the combustion control method of the present invention, stable combustion of the fuel is ensured by the primary air, and the fuel is further burned by the secondary air having a low oxygen concentration. Is controlled according to the furnace temperature, so that the generation of NOx can be suppressed.

Further, according to the burner device of the present invention, the combustion gas from the non-burning regenerative burner is supplied into the secondary air of the burning regenerative burner and mixed to reduce the oxygen concentration. This does not require a special device for lowering the oxygen concentration of the secondary air, and the structure is simple. Further, since the amount of the secondary air with respect to the primary air is automatically controlled in accordance with the temperature in the furnace, the combustion can be reliably and accurately controlled.

[Brief description of the drawings]

FIG. 1 is a schematic view of an embodiment of a regenerative burner device.

FIG. 2 is a longitudinal sectional view of a regenerative burner.

FIG. 3 is a block diagram of a control device.

FIG. 4 is a diagram showing a supply ratio between primary air and secondary air.

FIG. 5 is a diagram showing supply ratios of primary air and secondary air.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Furnace wall 2 2a, 2b Thermal storage burner 4 Fuel nozzle 5 Primary air supply pipe 7 Thermal storage 26 Switching valve 27 Exhaust piping 28 Secondary air supply piping 35a, 35b Mixing piping 37a, 37b Mixing valve 40 Control device 41 Temperature detector

Continuing from the front page (72) Inventor Shunichi Akiyama 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Inventor Koichi Takashi 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Stock Inside the company (72) Inventor Osamu Oguma 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Japan Pipe Co., Ltd. (72) Inventor Toshio Sasa 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Japan Pipe Co., Ltd. (72) Inventor Keiichi Shiojiri, 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Inventor Yoshihide Okamoto 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. 72) Inventor Makoto Miyata 2-53-1, Shirite, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture F-term in Japan Furness Industrial Co., Ltd. (reference) 3K005 GC03 JA02 3K023 QA03 QB09 QC08

Claims (6)

[Claims] 1. A method for controlling the combustion of a regenerative burner device which alternately burns a plurality of regenerative burners and discharges combustion gas in a furnace through a regenerator of a regenerative burner that is not burning. The primary air is supplied around the fuel blown into the furnace from the fuel nozzle to perform primary combustion of the fuel, and the oxygen concentration is lower than the atmosphere around the primary air through the heat storage body. Secondary storage of fuel is performed by supplying secondary air, and the supply ratio of secondary air to primary air is increased as the temperature in the furnace is increased. Combustion control method. 2. The regenerative burner according to claim 1, wherein said secondary air reduces the oxygen concentration by mixing a combustion gas in a furnace with the atmosphere supplied through said regenerator. Device combustion control method. 3. The primary air is blown around a fuel nozzle that blows the fuel, and the primary air has a minimum flow rate required to cool the fuel nozzle even when the temperature in the furnace is high. The combustion control method for a regenerative burner device according to claim 1, wherein the fuel is constantly circulated. 4. A regenerative burner device for alternatingly burning a plurality of regenerative burners, wherein each of the regenerative burners includes a fuel nozzle that blows fuel into a furnace, a regenerator, and the fuel nozzle. A primary air supply passage that surrounds and supplies primary air around the fuel blown from the fuel nozzle, and a secondary air supply that is arranged around the primary air supply passage and supplies secondary air through a heat storage element A mixing passage for mixing the combustion gas with the air supplied to the secondary air supply passage of each of the regenerative burners to form secondary air having an oxygen concentration lower than the air; A temperature detector for detecting the temperature in the furnace, and a control device for receiving a signal from the temperature detector and increasing a supply ratio of the secondary air to the primary air as the furnace temperature increases. Features Regenerative burner device that. 5. The exhaust passage for exhausting combustion gas in a furnace through an air supply passage for supplying air to a heat storage element of a first regenerative burner and a heat storage element of a second regenerative burner. A combustion gas communicating with the passage and supplying the combustion gas after passing through the regenerator of the second regenerative burner into the air supply passage on the upstream side of the regenerator of the first regenerative burner to be mixed; The regenerative burner device according to claim 4, wherein: 6. The regenerative burner device according to claim 4, wherein the primary air supply passage is a primary air supply pipe having a double pipe structure surrounding the fuel nozzle.