JP3426736B2 - Reflective melting and holding furnace - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection type melting and holding furnace for melting non-ferrous metals and / or holding molten metal. More specifically, the present invention relates to a burner serving as a heating source of a reflection type melting and holding furnace, a heat storage body attached to the burner, a combustion method, and an improvement of a control method.

[0002]

2. Description of the Related Art In a conventional reflection-type melting and holding furnace, as shown in FIG. 12, a general diffusion burner 102 that continuously and continuously burns is used as a heat source, and a furnace for burning the central portion of an aluminum melt is used. It is installed on the body 101. Then, the combustion amount of the burner 102 is controlled by controlling the flow rate adjusting valves 105 and 106 installed in the combustion air supply system 103 and the fuel supply system 104 by a control signal from the combustion load controller 107, and thus the temperature in the furnace and thus the furnace. It is provided to adjust the temperature of the molten aluminum to a predetermined temperature.
On the other hand, an exhaust system 108 for discharging exhaust gas from the melting furnace 101
An exhaust fan 109 and an exhaust damper 110 are provided in the chamber so that the furnace pressure can be kept constant by adjusting the opening degree (opening / closing degree) of the exhaust damper 110 by the furnace pressure controller 111. Incidentally, when the conventional diffusion burner 102 is used, since the combustion in the furnace is small because the combustion is continuous and steady, the pressure in the furnace is detected, and the damper 110 of the exhaust system 108 is controlled so as to maintain this at a constant value. The pressure inside the furnace can be controlled sufficiently by itself.

[0003]

However, in this conventional reflection type melting and holding furnace, since the heating is performed obliquely so as to cover the central portion of the aluminum molten metal, the heat flux is not uniform and the temperature of the aluminum molten metal is not uniform. Unevenness is likely to occur. Also, in a normal diffusion combustion flame that requires excess air, a large amount of scale loss occurs due to residual oxygen in the combustion gas.
Further, since the combustion gas generated by the continuous steady combustion of the diffusion burner 102 is exhausted as it is, there is a problem that the exhaust temperature becomes high and the exhaust heat loss increases.

In order to reduce the waste heat loss, conventionally, heat recovery by a recuperator or the like is generally used. However, since the conventional recuperator cannot be used at a high temperature, it is necessary to mix air into the exhaust gas to recover the heat at a temperature lower than the heat-resistant allowable temperature of the recuperator, and to obtain an exhaust heat recovery rate of 50% or less. There's a problem. Therefore, there is a problem that the dissolution cost becomes high. Therefore, the present inventors considered using the heat storage body to preheat the combustion air to a high temperature close to the exhaust gas temperature to recover the exhaust heat with high efficiency.
Generally, when heat storage combustion is performed, the combustion preheat air temperature becomes high and NOx increases. Further, since the reaction activity is high and sufficient combustion is possible even with a low air ratio, it is possible to burn in a reducing atmosphere, while a large amount of HC,
CO is generated. In order to reduce these harmful exhaust gas components, improvement of the basic structure of the burner has hitherto been finished. For example, in order to reduce NOx in the diffusion burner, a two-stage fuel combustion method as shown in FIG. 13 is adopted. In this two-stage fuel combustion method, the fuel is supplied to the combustion air A flowing in the burner throat 201 in two stages by the primary nozzle 202 and the secondary nozzle 203, and the primary fuel and the entire amount of combustion air are supplied. In addition to forming the primary flame, the secondary flame is formed by the reaction between the secondary fuel and the high temperature combustion gas of the primary flame. Since the oxygen concentration near the secondary fuel nozzle is low, NO of the primary flame is generated by the reduction reaction.
x is reduced.

However, in the burner based on this two-stage fuel combustion method, the injection direction of the secondary fuel forming the main flame is made substantially parallel to the flow of the combustion air, so that the stability of the secondary flame at low temperature is improved. Poorly, the flame is not stable unless the combustion air is preheated to a high temperature of about 1000 ° C or higher. Therefore, in order to improve the stability of the secondary flame at low temperature, if the fuel injection direction is made closer to the direction perpendicular to the flow of combustion air,
Although the flame is stable, local combustion occurs to locally raise the temperature and increase NOx. Therefore, 700-
When used as a heat source for a reflection type melting and holding furnace that operates at a rated temperature in a relatively low temperature range of about 800 ° C, or when the temperature is low, such as when starting up the furnace, the stability of the flame deteriorates, and It is difficult to implement the two-stage fuel combustion method. Further, the suppression of HC and CO generated during reduction combustion was not sufficient.

Further, in the conventional reflection type melting and holding furnace, since dust such as aluminum fume and melting flux is mixed in the exhaust gas, the exhaust damper 1 of the exhaust system 108.
10, recuperator (not shown), exhaust fan 109
These dusts often adhere to the ground and interfere with the operation.

Furthermore, when the flow of heat storage combustion is frequently switched in a short time, the heat storage body is not uniformly heated and becomes hot at a portion closer to the furnace side and cold at a portion opposite to the switching valve side. become. For example, the temperature is 1000 ° C. on the furnace side and 200 ° C. on the valve side. Since the material of the heat storage body having such a large temperature difference is limited to those having high temperature heat resistance and thermal shock resistance, it becomes expensive. Moreover, the ceramic honeycomb heat storage body must be a material that can be manufactured in various shapes. When using a flux, such as in an aluminum melting furnace, the material must also have corrosion resistance. It has been difficult to mold such required quality.

Further, in the conventional furnace pressure control in the reflection type melting furnace, when the alternating combustion is carried out in a short time, the furnace pressure control cannot follow and the rattling of the door (skim door etc.) due to the fluctuation of the furnace pressure occurs. -There is a problem that fluttering occurs and the thermal efficiency is reduced due to the intake of fresh air and the outflow of hot air from the furnace.

Therefore, an object of the present invention is to provide a reflection type melting and holding furnace which produces a small amount of NOx and is capable of high efficiency and uniform heating.

The present invention also has a low N due to the burner structure.
Although aiming at Ox, it is an object of the present invention to provide a reflection-type melting and holding furnace capable of further purifying harmful exhaust gas components such as NOx, CO and HC. In addition, an object of the present invention is to provide a reflection-type melting and holding furnace that improves reliability under high temperature / corrosive environment in heat storage combustion.

A further object of the present invention is to provide a reflection type melting and holding furnace in which fluctuations in furnace pressure are small.

[0012]

To achieve Means for Solving the Problems] Such objects, reflective melting and holding furnace according to claim 1, wherein the injection towards the combustion air preheated to a high temperature by using combustion exhaust gas into the furnace
Establish a secondary combustion chamber at the exit of the combustion air injection
A burner tie with a larger diameter than the combustion air injection port
The burner tile with the expanded diameter
In the expanded portion of the natile, diagonally with respect to the flow of the combustion air
Fuel nozzle (or yes
Is a fuel for injecting fuel around the flow of the combustion air.
At least one pair of heat storage combustion type burner with nozzle)
As a heat source and alternately burn a pair of these burners
A non-stationary flame to uniformly heat the furnace.
, A pressure-electric converter for detecting the pressure in the furnace, and combustion
A sensor that detects the switching of the
Opening and closing of the exhaust system based on the signal from the pressure-electric converter
To bypass the main damper that controls the
And a bypass channel provided in the bypass channel.
Controls opening and closing of the bypass flow path based on combustion switching signal
With a bypass damper, which often occurs
For small fluctuations in the furnace pressure caused by switching the
Corresponding by opening and closing the pass damper, the pressure in the furnace is set value
Opening and closing the main damper when there is a large fluctuation
The reactor pressure fluctuation is absorbed accordingly .

Further, the reflection-type melting and holding furnace according to claim 2 is a regenerative combustion burner that burns using combustion air that has been preheated to a high temperature using fuel exhaust gas, and the combustion air is burned more than the fuel. A nozzle for injecting fuel at a much higher speed and a nozzle for injecting fuel are arranged in parallel, and they are surrounded by a refractory material, and the end face on which the fuel nozzle injection port is formed and the air nozzle injection port are formed. A burner is provided as a heat source in which a step is provided between the burner and the end surface on the fuel nozzle side so as to protrude from the end surface on the air nozzle side.

Here, it is preferable that at least one pair of burners are arranged as a heat source, and they are alternately burned to form a non-stationary flame to uniformly heat the inside of the furnace. Furthermore, the pair of burners are adjacent to each other. It is preferable to install it at a high speed to inject the combustion air at high speed to prevent a short path of flame and combustion gas.

The reflection type melting and holding furnace of the present invention includes a pressure-electric converter for detecting the pressure inside the furnace, a sensor for detecting combustion switching and outputting a combustion switching signal, and a signal from the pressure-electric converter. A main damper for controlling the opening / closing of the exhaust system based on the bypass damper ; a bypass passage bypassing the main damper; and a bypass damper provided in the bypass passage for controlling the opening / closing of the bypass passage based on the combustion switching signal. However , small fluctuations in the furnace pressure that occur with frequent burner switching are handled by opening and closing the bypass damper , and when the furnace pressure fluctuates more than the set value, the main damper is opened and closed. It is designed to absorb fluctuations in furnace pressure.

Further, in the reflection type melting and holding furnace of the present invention, the object to be heated is heated by forming the reducing atmosphere by using the high-temperature preheated air having a theoretical air amount or less.

Further, in the reflection type melting and holding furnace of the present invention, the preheating of the combustion air is performed by the heat storage body that alternately passes the combustion air and the combustion exhaust gas, and the heat storage body is at least in the flow direction of the fluid. It is divided into multiple pieces. Further, the divided heat storage bodies are made of different materials for the inner side of the furnace and the side closer to the flow path switching means, or the structure closer to the inner side of the furnace and different for the side close to the flow path switching means. Is formed by. Further, an exhaust purification catalyst is carried in the catalytic reaction temperature region existing in the plurality of divided heat storage bodies.

Further, the heat storage body is accommodated in a cylindrical casing having a side wall having an openable / closable lid so as to be able to be taken in and out in a direction orthogonal to the flow direction of the combustion gas or the combustion air, and is connected to a burner to open / close the lid. It is set up so that it can be taken in and out freely.

Further, the reflection type melting and holding furnace of the present invention is provided with a dust collector for introducing the combustion exhaust gas passing through the heat storage body.

[0020]

Therefore, in the case of the reflection type melting and holding furnace according to the first aspect of the present invention, a negative pressure is generated in the expanded area of the burner tile due to the flow of the high temperature combustion air, so that strong exhaust gas recirculation in the furnace occurs.
Therefore, even if the combustion is injected perpendicularly to the flow of the high temperature combustion air in order to improve the flame stability at low temperatures, a part of the fuel causes exhaust gas recirculation combustion to suppress the generation of NOx. Further, a part of the fuel injected in the expanded diameter portion of the burner tile rapidly diffuses with a part of the combustion air to form a flame holding region and stabilize the flame, so that the flame is stable even at a low temperature. Further, outside the burner tile, the residual oxygen from the flame-holding region with a high air ratio and the incomplete combustion gas due to the exhaust gas recirculation combustion in the furnace that occurs in the expanded area of the burner tile cause slow combustion. and, at high temperatures it is heated in a combustion gas which is excellent in stability while a low NOx, and at low temperature flame. Moreover,
At least one pair of burners alternates in flames and
Since the burning gas is formed, it becomes a non-stationary flame and a uniform heat
The object to be heated is heated by the soot flux. Furthermore,
Temporarily bypass damper at the same time as burner combustion switching
Is opened and the exhaust gas volume in the furnace is increased.
Reactor pressure changes that occur frequently and cyclically when switching
Motion is suppressed.

In the reflection type melting and holding furnace according to the second aspect, a part of the combustion air flowing along the surface of the step between the end surface from which the combustion air is ejected and the end surface from which the fuel is ejected is
A vortex that flows counter to the flow of combustion air is stably formed in the vicinity of the step on the end face from which the fuel is ejected, and a part of the fuel gas is entrained to form a flame that becomes a pilot fire. In addition, a negative pressure is generated in the step portion and strong exhaust gas recirculation occurs,
Before the combustion air mixes with the fuel gas, the exhaust gas is entrained to reduce the oxygen concentration. Then, on the downstream side of the end surface where the fuel is injected, the fuel is attracted to the flow of the combustion air and admixed with it.

Here, since the volume of the combustion air preheated to a high temperature of about 700 to 800 ° C. or higher expands as compared with that at room temperature, it is appropriate to set the air nozzle to be thin or to be suitable at a low temperature. By adopting a thin nozzle set so as to have a high flow velocity, it is ejected at a considerably high velocity as compared with fuel and air at room temperature.
For example, the high temperature preheated air is jetted at an extremely high flow velocity of 100 m / s or more as compared with the fuel jetted at a flow velocity of 20 to 30 m / s. Therefore, the combustion exhaust gas is entrained by the high-speed flow of the combustion air to reduce the oxygen concentration (partial pressure), while the fuel is also attracted to the flow of the combustion air to be entrained and gradually entrained in the air flow and mixed. . However, the combustion air is much faster than the flow of fuel, and since a large amount of exhaust gas is entrained by the time the fuel reaches the end face where it is injected, the combustion reaction does not occur rapidly and the combustion air The surface layer where the fuel and the fuel come into contact with each other burns, causing slow combustion. Moreover, the stable primary flame can be formed without causing misfire even at a high flow rate. Further, since the flow of the combustion air is fast during the combustion reaction, the combustion reaction is continued while entraining a large amount of exhaust gas, which promotes slower combustion. Therefore, a highly directional flame and combustion gas flow are formed.

Further, when the combustion air is at a low temperature such as when starting up the furnace, the flow rate of the combustion air is slowed to reduce the amount of exhaust gas entrained, but the temperature of the combustion air is low. Therefore, the amount of NOx originally generated is small.
On the contrary, since the oxygen concentration is high, a stable pilot fire is formed between the fuel jet near the injection port of the fuel nozzle and the combustion air jet, and the flame is stabilized.

Further, in the case of the third aspect of the present invention, since the flame and the combustion gas are alternately formed in a short time between at least a pair of burners, a non-stationary flame is formed and the object to be heated is heated with a uniform heat flux. Heating.

Further, in the case of the invention of claim 4, since the flame and the combustion gas have a strong directional flow due to the combustion air injected at a high speed, even if the pair of burners are arranged adjacent to each other, the short circuit occurs. Combustion gas reaches the corner of the furnace by blocking the path and is exhausted after heating.

Further, in the case of the invention of claim 5, since the bypass damper is temporarily opened at the same time as switching the combustion of the burner to increase the exhaust gas amount of the exhaust gas in the furnace, the switching of the burner is periodically performed. Suppresses frequent fluctuations in furnace pressure.

In the sixth aspect of the present invention, the object to be heated is not oxidized because the reduction combustion is carried out and heated at a temperature equal to or lower than the theoretical exhaust gas temperature preheated to a high temperature close to the combustion exhaust gas temperature.

Further, in the case of the invention of claim 7, since it is divided at least in the flow direction, heat storage combustion in which high temperature combustion exhaust gas and low temperature combustion air are alternately flowed in a short time in order to improve thermal efficiency. Therefore, even if a large temperature difference is generated between the portion of the heat storage body that is closer to the inner side of the furnace and the portion that is closer to the switching valve side that is opposite thereto, the difference in thermal expansion between the heat storage bodies is small and cracking can be prevented.

Further, according to the invention of claim 8, when a large temperature difference occurs between the inner side of the furnace and the opposite side thereof, only the heat storing body near the inner side of the furnace employs a heat storage body having heat resistance, and the temperature becomes low. A low-cost heat storage material that does not have heat resistance can be used on the switching valve side.

Further, in the case of the invention of claim 9, a heat storage body having a filter function can be adopted as the heat storage body inside the furnace which firstly comes into contact with the high temperature combustion exhaust gas containing dust and the like. Can be prevented from clogging.

Further, in the case of the invention of claim 10, HC, CO, NOx and the like generated in the reduction combustion can be completely purified.

According to the eleventh aspect of the present invention, the heat storage element can be replaced by simply opening the cover of the casing without disassembling the exhaust system.

In the twelfth aspect of the invention, even if the combustion exhaust gas contains dust, it is separated and collected.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be described in detail below with reference to an embodiment shown in the drawings.

FIG. 1 shows an embodiment in which the present invention is applied to a well type reflection-type melting and holding furnace. The well-type reflection-type melting and holding furnace 30 is a furnace having a molten metal tank exposed to the atmosphere by connecting a heating chamber called a front furnace 31 to the side of a stationary square melting furnace. The forehearth 31 is installed mainly for the purpose of melting recycled aluminum, and scrap is put in to melt the molten aluminum by the heat of the molten metal. The partition between the molten metal tank 32 and the front furnace 31 is blocked by a skimming door 33 that moves up and down, and if necessary, a molten metal pump (not shown) is circulated between them to promote melting.

In the molten metal tank 32, a regenerative combustion type burner system 20 is installed on a furnace wall 35 so as to form a flame / combustion gas substantially parallel to the liquid surface of the molten aluminum 34. still,
In this embodiment, one system of heat storage combustion type burner system 2
Although 0 is set, two or more systems may be equipped.

In the regenerative combustion type burner system 20, combustion air and fuel are ejected onto the wall surface 35 of the molten metal tank 32 substantially parallel to the liquid surface of the molten aluminum 34 to form a flame and a combustion gas flow along the liquid surface. Are arranged as follows. In the case of the present embodiment, one heat storage combustion type burner system 20 is configured with two burners 21 and 22 that burn alternately as one set. In this embodiment, as shown in FIG. 3, the heat storage combustion type burner system 20 has a built-in heat storage body 23 in a burner body 27, and each of the burners 21, 22 and the heat storage bodies 23, 23 is integrated into two sets, which are alternately combined. The combustion exhaust gas can be discharged through the burner and the heat storage body which are in the non-combusted state while being stopped. 2 burners 2
An air supply system 24 for supplying combustion air and an exhaust system 25 for exhausting combustion gas can be selectively connected to the Nos. 1 and 22 by interposing a flow path switching unit 26.
(Or 22) is provided so as to supply combustion air through the heat storage body 23, while exhausting combustion gas from the other burner 22 (or 21) through the heat storage body 23. Combustion air is, for example, a forced air fan
And the combustion exhaust gas is supplied by, for example, the induction fan 2
It is sucked from the inside of the furnace by an exhaust means such as 9 and subjected to necessary processing such as dust collection and then discharged into the atmosphere. Further, although not shown, the fuel supply system is selectively connected to either one of the burners 21 and 22 alternately via a three-way valve or the like to supply the fuel. Reference numeral 36 in the figure is a dust collector such as a cyclone.

As the burners 21 and 22, it is preferable to use low NOx burners shown in FIG. 4, for example. This low NOx burner is a burner that injects a fuel gas in parallel with the flow of combustion air that has been preheated to a high temperature, and an air nozzle that ejects combustion air that has been preheated to a high temperature at a much higher speed than fuel. 1 and a fuel (gas) nozzle 2 are formed so as to penetrate a block 3 of refractory material, and two end surfaces 4, 5 of the block 3 of refractory material are provided with injection ports 6, 7 of each nozzle. Perforated. Here, a pipe 8 forming a flow path for supplying the primary air is embedded around the fuel nozzle 2, and about 1% of the secondary air flows around the fuel nozzle 2.
About 0% of primary air is flowing. Further, in addition to the main injection port 7, an injection port 9 for injecting a part of the fuel toward the surrounding primary air flow path is opened at the tip portion of the fuel nozzle 2, and a part of the fuel is injected as a pilot fuel. The pilot burner is configured to collide with the peripheral wall of the pipe 8 and spread in the flow path of the primary air to obtain a good mixed state. An igniter (not shown) is installed there, and is provided so that a stable primary flame 12 can be formed during combustion. The piping system is composed only of a main piping / air nozzle 1 for flowing most of the combustion air used as secondary air, and a fuel piping (primary air piping 8 and fuel nozzle 2) for flowing fuel and primary air, It is a very compact system. In this embodiment, the pipe 8 for flowing the primary air is provided around the fuel nozzle 2 to form the pilot burner in the vicinity of the injection port, but the invention is not particularly limited to this, and may be separated from the fuel nozzle in some cases. A pilot burner may be installed near the injection port of the fuel nozzle.

Further, the fuel injection port 7 and the air injection port 6 are not formed on the same plane but are provided on different surfaces with steps and the fuel injection port 7 is arranged on the downstream side of the air injection port 6. ing. That is, the fuel injection port 7 is an end surface (hereinafter referred to as a reference surface) 4 of a block of refractory material provided with the air injection port 6.
It is installed on an end surface (hereinafter referred to as a flame holding surface) 5 which is projected from the surface. The stable primary flame 12 and the fuel F are ejected from the fuel ejection port 7 of the flame holding surface 5. Combustion air is ejected from the center of the refractory material block 3 at high speed. At this time, the vortex 11 which flows counter to the flow of the combustion air can be stably formed in the vicinity of the stepped portion of the flame holding surface 5, and is rapidly mixed with a part of the fuel / gas to form the flame holding region. Therefore, it is possible to form a stable pilot fire not to blow out at low temperature, let alone at high temperature. The refractory block 3 for holding the air nozzles 1 and the fuel nozzles 2 in parallel is constituted by a single block integrally molded in the case of the present embodiment, but in some cases, the air nozzles 1 are held. It is also possible to use a combination of a molded portion and a portion that holds the fuel nozzle 2 separately. Further, in the case of the present embodiment, the air nozzle 1 is not composed of piping,
Holes formed in the refractory material block 3 and the refractory material block 3
It is composed of a burner body for interior. Of course, the air nozzle 1 may be constructed by piping.

Further, in the case of adopting the above-mentioned structure, the refractory block 3 has an air nozzle 1 and a fuel nozzle 2 due to a problem in strength.
Requires some distance between and. Therefore, the fuel tends to be difficult to be attracted to the high-speed air flow in the region immediately after the injection. Therefore, it is preferable that the shape of the portion 13 of the fuel injection port 7 near the air nozzle 1 has a curved shape toward the air nozzle 1 side as shown in the drawing. As a result, the fuel easily flows out to the flow side of the combustion air. Therefore, the accompanying mixing capability of fuel is further enhanced, and the generation of free unburned components such as CO and HC can be prevented. Also,
The fuel is well supplied to the vortex 11 in which the combustion air flows backward, and a more stable pilot fire can be formed. This shape is not limited to a curved surface, and any structure that fulfills such a function may be used. For example, it may be a slope.

The air nozzle 1 has a flame holding surface 5 and a reference surface 4.
It is installed at the step of the boundary with. Then, the portion near the flame holding surface 5 has a function of admixing the fuel,
The portion near the reference surface 4 has a function of recirculating exhaust gas. That is, as shown in FIG. 4B, the surface 10 of the step portion between the flame holding surface 5 and the reference surface 4 crosses the center of the injection port 6 so as to divide the injection port 6 of the air nozzle 1 in half. If so arranged, both the admixture mixing function and the recirculation function can be made compatible. On the other hand, although not shown, in the case where the surface 10 of the step portion is circumscribed to the injection port 6 of the air nozzle 1, the area in which the exhaust gas is entrained is wider than in the case shown in FIG. 4B. Therefore, the function of lowering the oxygen concentration of the combustion air is excellent. Further, in the case where the surfaces 10 of the step portions are arranged so as to cross each other so as to wrap most of the injection port 6, the portion where the injected air is restrained to the flame holding surface 5 by the refractory material block 3 is Since there are many, the flow of the combustion air having a stronger directivity is ejected from the flame holding surface 5, and the admixture mixing capability of the combustion gas is excellent.

The low NOx shown in FIG. 4 constructed in this way
According to the burner, when the combustion air is ejected at a high temperature and a high flow rate, the directional combustion air ejected from the flame holding surface 5 at a high flow rate injects fuel that is injected in parallel at a relatively low speed at an early stage. It attracts and accompanies it, and gradually extends to a far distance while being mixed and mixed. However, since the combustion air velocity is much higher than the fuel velocity, for example, 100 m / s or more, which is very high, the entrained fuel is gradually taken in and a large amount of exhaust gas is entrained before reaching the flame stabilizing surface 5. Therefore, the combustion reaction does not occur rapidly, and the combustion reaction proceeds slowly. Further, since the air velocity is high, the combustion reaction is carried out while entraining a large amount of exhaust gas during the combustion reaction, which promotes slower combustion. This is clearer than the experimental results shown in FIG. 5 in which the relationship between the flow velocity of the combustion air and the amount of NOx generated is obtained, but the higher the injection speed of the combustion air, the lower the amount of NOx and The effect became more remarkable as the combustion amount increased (the temperature became higher). Therefore, according to the burner of the present embodiment, a relatively uniform and long heat flux can be formed and low NOx can be formed.
Can be realized. Moreover, since a part of the fuel is attracted to the backflow of the combustion air that occurs in the region near the stepped portion of the flame holding surface 5 and diffused and mixed to form a stable flame that becomes a pilot flame, it is not only at high temperature. That is, a flame is stably formed even at a low temperature. Therefore, the wall surface 3 on which the burners 21 and 22 are installed
It is preferable to apply to a furnace having a long distance to the wall surface facing 5 and a large furnace.

Further, it is preferable to use a low NOx burner as shown in FIG. 6 as the burner. This burner is a burner that injects fuel from the periphery of the flow of combustion air that has been preheated to a high temperature, and the combustion air injection port 4
A burner tile 42 having a burner tile expanded portion 41 having a larger diameter than that is arranged at 0, and a fuel nozzle 43 for injecting fuel from the burner tile expanded portion 41 is provided. In this case, the fuel may be injected from the burner tile expanded portion 41 to the inside of the burner tile 42, that is, to the auxiliary combustion chamber 46, and the injection direction is not particularly limited,
It is preferable to inject toward the flow of combustion air, and more preferably to inject fuel obliquely to the flow of combustion air to cause collision. When the fuel is injected obliquely to the flow of the combustion air, the exhaust gas recirculation combustion in the furnace and the slow combustion outside the burner tile are promoted to further reduce the generation of NOx, as compared with the case where the fuel is injected vertically. Also,
A pilot burner 44 is installed on the upstream side of the burner tile expanded diameter portion 41 so as to inject pilot fuel. In this case, the burner tile expanded portion 4
A stable flame region is formed on the upstream side of 1, and this stabilizes the flame even if it becomes a pilot fire and the temperature of the combustion air becomes low. This pilot burner 44 produces about 1
When supplied at a high temperature of 000 ° C. or higher, it is not necessary to always burn in the vicinity of the burner tile expanded diameter portion 41, and it may be installed further upstream. Further, in the case of the present embodiment, the burner throat 40 is provided with the first fuel nozzle 45 for injecting the primary fuel. This first fuel nozzle 4
No. 5 is not used after the furnace starts up, and when the furnace temperature is low and combustion is difficult to stabilize, that is, when the furnace is started up, the primary fuel is injected so as to be orthogonal to the flow of combustion air. , It mixes and diffuses rapidly for stable combustion. At this time, since the furnace temperature is low, the amount of NOx generated is small and is in a permissible range. Then, when the furnace temperature reaches a predetermined temperature, the second fuel nozzle 4 in the burner tile expanded portion
The fuel is injected only from No. 3 to cause the exhaust gas recirculation combustion and the incomplete combustion gas and the residual oxygen to perform the buffer combustion to reduce the generation of NOx. In addition, in the case of the present embodiment, an example in which the first fuel nozzle 45 and the pilot burner 44 are separately provided is shown, but the present invention is not particularly limited to this, and the first fuel nozzle 45 is particularly provided. Alternatively, only the pilot burner 44 may be provided, or the pilot burner 44 may be provided more upstream than the one shown in FIG. 1 or near the second fuel nozzle 43. Furthermore, the second
As the fuel nozzle 43 of the second burner, the fuel nozzle (2, 8) also used as the pilot burner of the burner shown in FIG. 4 is adopted.
It is possible not to provide a fuel nozzle and a pilot burner other than the fuel nozzle that also serves as the pilot burner. Further, the combustion nozzle 43 may be installed at an arbitrary position when the depth from the furnace inner wall surface of the burner tile expanded portion 41 is constant, but when the depth is different, for example, although not shown, When the burner is installed on a curved surface or when it is installed with an inclination, it is preferable to install it at the deepest place. The same applies to the case where a pilot burner nozzle is used as the combustion nozzle 43. At this time, the exhaust gas in the furnace is easily recirculated into the burner tile expanded diameter portion 41 in the shallow portion, but the exhaust gas in the furnace hardly penetrates in the deep portion and the oxygen concentration does not decrease, so that the ignition stability is excellent. Therefore, if the fuel nozzle 43 or the fuel nozzle that also serves as the pilot burner is arranged at a position where the burner tile expanded diameter portion 41 is deep from the inner wall surface of the furnace, the oxygen concentration does not decrease and the ignition stability is excellent.

According to the low NOx burner configured as described above, as shown in FIG. 6, a part of the fuel injected obliquely and a part of the combustion air preheated to a high temperature by passing through the heat storage body. And are diffusively mixed to form the flame holding region X1 and form a stable flame. Further, the high-temperature combustion air ejected from the air throat at a high velocity strongly attracts the exhaust gas in the furnace into the auxiliary combustion chamber 46 of the burner tile expanded portion 41, and diagonally extends from the corner portion of the burner tile expanded portion 41. Exhaust gas recirculation combustion is caused by mixing with a part of the injected fuel to form an exhaust gas recirculation combustion region X2 in which combustion occurs due to insufficient air. Further, outside the burner tile 42, the flame holding region X
A region X3 is formed which reacts with oxygen remaining in the combustion gas from No. 1 and the incomplete combustion gas generated in the exhaust gas recirculation combustion region X2 in the burner tile expanded diameter portion 41 to cause slow combustion. Further, in this case, by directly injecting the fuel into the burner tile 42, it is possible to suppress the excessive diffusion of gas to the outside of the flame axis direction, so that the amount of unburned gas during combustion is minimized. be able to. For this reason, even in a furnace operated in a medium temperature range of about 700 to 800 ° C. such as a well-type reflection-type melting and holding furnace, the flame is stable and NOx does not increase. In the case of this burner, it is preferable to apply it to a furnace in which the distance between the wall 35 on which the burner is installed and the opposing wall is narrow.

In the case of this burner, the entire amount of fuel is injected and burned from the first fuel nozzle 45 to warm the furnace until the temperature inside the furnace reaches a predetermined temperature. At this time, even if the combustion air has a low temperature, the fuel injected from the first fuel nozzle 45 is immediately mixed with the combustion air and stably burned by the pilot flame provided nearby. Then, when the temperature reaches the predetermined temperature, the fuel injection from the first fuel nozzle is stopped and the fuel is injected from the second fuel nozzle 43. Here, the predetermined temperature is not necessarily the operating temperature of the furnace, but refers to a temperature at which the flame can be maintained only by the fuel injection from the second fuel nozzle 43 and a temperature higher than that. still,
When the pilot burner nozzle is used as the second fuel nozzle 43, the furnace is started by burning the second fuel nozzle from the beginning. The switching between combustion and exhaust is performed, for example, at an interval of 10 seconds to 2 minutes, preferably within about 1 minute, and most preferably at an extremely short interval of about 10 to 40 seconds. In this case, heat exchange is performed with high temperature efficiency. Further, the switching may be performed when the combustion gas discharged via the heat storage body 23 reaches a predetermined temperature, for example, about 200 ° C.

As described above, in the case where at least a pair of burners are alternately burned in this manner, the flame position changes frequently, so that the heat pattern in the combustion chamber can be made more uniform, and uneven heating and heat retention can be reduced. Become.

Here, the combustion air supplied to the burner shown in FIG. 4 or FIG. 6 uses, for example, a heat storage body, and by direct heat exchange in which combustion exhaust gas and combustion air are alternately flowed to the heat storage body, It is preheated to a temperature close to that of combustion exhaust gas, for example, a high temperature of 700 to 800 ° C. or higher.

As the heat storage body 23, there is a honeycomb-shaped ceramic, for example, cordierite or mullite, which has a constant passage cross-sectional area as shown in FIG. The use of other materials is preferred. This honeycomb-shaped ceramic has a large heat capacity and high durability, but relatively low pressure loss.
Moreover, exhaust and air supply are alternately performed without stagnation. Therefore, dust or the like in the exhaust gas is unlikely to adhere to the honeycomb-shaped flow path of the heat storage body 23, and even if it adheres, it is backwashed and is not contaminated. Furthermore, when heat is recovered from the exhaust gas, even if the exhaust gas falls below the acid dew point temperature, the sulfur content in the exhaust gas and its chemically modified substances are captured on the surface of the ceramics, and the duct of the exhaust system 25 downstream is corroded at low temperature. There is nothing to do. The heat storage body 23 is, as shown in FIG.
The burners 21, 22 are accommodated in a casing 38 having a side wall as a lid 39 so as to be able to be taken in and out in a direction orthogonal to the flow path.
And the flow path switching means 26. Therefore, the damaged or clogged heat storage body can be easily taken out and replaced simply by opening the lid 39.

On the other hand, the flux and dust contained in the exhaust gas at the time of melting are introduced into the dust collector 36 and collected therein after passing through the heat storage body 23 and becoming low in temperature. Therefore, the flow path switching means 2 downstream of the dust collector 36
6 does not interfere with dust and the like to the exhaust fan 29 and the like. The dust collector 36 is not limited to a particular system or structure, and may be one that drops dust simply by changing the flow direction.

Further, as shown in FIG. 9A, it is preferable that the heat storage body 23 is divided into multiple layers in the fluid flow direction. This is because when the pair of burners 21 and 22 are alternately burned in a short time in order to improve the heat storage efficiency, the temperature of the heat storage body 23 becomes high at a portion near the furnace side as shown in FIG. 8B. The temperature on the opposite side to the flow path switching means 26 side becomes low. When such a heat storage body 23 is integrally formed, since the flow paths are frequently switched, the temperature difference is large and greatly different, so that the possibility of cracking due to the difference in thermal expansion increases. Therefore, by dividing the heat storage body 23 into multiple layers, the difference in thermal expansion between the blocks is reduced to prevent cracking due to the difference in thermal expansion. As an example, FIG.
(A) shows the heat storage body 23 divided into three parts. At this time, it is desirable to sandwich the cushioning material 37 between the heat storage bodies 23, 23, 23.

Further, the corrosion of the heat storage body 23 progresses remarkably in the high temperature portion near the furnace side and is slow in the low temperature portion near the flow path switching means 26 side. Therefore, manufacturing the entire heat storage body 23 with an expensive corrosion-resistant material causes unnecessary cost increase. Therefore, the heat storage body 23 made of a corrosion-resistant material may be used only in the high temperature portion on the furnace side, and an inexpensive heat storage material may be used in the other portions. Further, as a method of extending the life of the heat storage body 23, it is also possible to increase the wall thickness t of the honeycomb at the high temperature portion. In this case, the thermal shock resistance is expected to decrease, but it can be avoided by using a material having high thermal conductivity. When using a high temperature furnace having a furnace temperature of about 1500 ° C., the first and second heat storage bodies 23, 23 closer to the inner side of the furnace
It is desirable to use a high heat-resistant heat storage material for the part and to make the others inexpensive.

Further, in an environment involving dust such as flux, the use of the honeycomb type heat storage body 23 may cause clogging. Therefore, as a countermeasure against this, as shown in FIG. 9B, a heat-resistant ball-shaped or nugget-shaped heat storage body having high heat resistance is embedded in the first heat storage body 23 as a substitute for a filter so that it can be always replaced. Two
Honeycomb type heat storage bodies may be used for the three layers.

Further, although the heat storage body 23 is installed at the rear of the burner throat in this embodiment, the heat storage body 23 is installed on the furnace side for the purpose of reducing the loss of sensible heat in the furnace as much as possible and utilizing the space of the thickness of the furnace wall. A heat storage body may be installed. In such a case, since there is generally no space in the burner installation space, it may not be possible to insert all the heat storage bodies of the required capacity. In such a case, if the heat storage body is divided, one is installed in the burner tile part and the other is installed in the vicinity of the flow path switching means 26, the loss of high temperature exhaust gas is small and the furnace can be made compact. Further, as described above, in the case of using a combination of heat storage bodies having multiple functions and various structures, it is not always necessary to store them in the same heat storage chamber. The heat storage chamber according to the function and structure is divided and installed, and the exhaust gas and air flow paths are connected in series by a heat insulation duct, so that the degree of freedom in design and construction can be secured.

Further, in the case of reducing and combusting by using the combustion air preheated to a high temperature, even if a burner as shown in FIG. 4 or 6 is used, at least a certain amount of NOx is generated more than in the conventional case. There is a risk. Therefore, the heat storage body 23
It is preferable to use an exhaust purification catalyst supported on a part of the above. For example, when it is desired to purify CO with an oxidation-promoting catalyst, up to about 5% of CO is about 1 in the range of about 150 to 700 ° C.
Can be purified by 00%. On the other hand, the temperature of the heat storage body 23 is high on the furnace side (for example, 1000 ° C.) when alternate combustion is performed in a short time.
However, the temperature becomes low (for example, about 200 ° C.) on the flow path switching means 26 side. Therefore, as shown in FIG. 8, the heat storage body 23 is divided into multiple layers in the flow direction of the fluid, and the catalyst is supported on a block corresponding to a temperature distribution region suitable for the reaction of each catalyst, whereby 100% CO is generated. Can be purified. Further, in the case of purifying CO, an exothermic reaction occurs in the heat storage body 23, but since the heat can be used for preheating the combustion air after switching, no thermal loss occurs. Furthermore, CO
If HC and HC can be purified, combustion in a reducing atmosphere becomes possible, and oxidation of the object to be heated and molten aluminum can be prevented. Similarly, with respect to NOx, a catalyst may be supported in a required temperature range. For example, in the case of purifying only CO or HC, a platinum catalyst is mainly used. The reaction temperature range of this platinum catalyst is 150 ° C to 700 ° C.
If the temperature is higher than the above range, sintering occurs and the catalyst cannot be used. If the temperature is lower than that, catalytic reaction does not occur. Further, when CO and NOx are simultaneously purified, platinum partially added with rhodium is used. The ratio of platinum to rhodium is platinum: rhodium =
About 5: 1 to 20: 1 is preferable, and the temperature range is about 300.
It is preferable to set the temperature to ℃ to 500 ℃. Therefore, while passing the combustion exhaust gas, the temperature of the heat storage body is from 150 ° C to 70 ° C.
CO, HC or NOx can be removed from the exhaust gas by supporting a platinum catalyst on a portion heated to about 0 ° C or by supporting a platinum rhodium catalyst on a portion heated to about 300 ° C to 500 ° C. .

In the reflection type melting and holding furnace of the present embodiment having the above-mentioned structure, the internal pressure of the furnace is controlled by the following furnace pressure control system, and the rattling and fluttering of the furnace body and doors are suppressed. .

The furnace pressure of the melting and holding furnace 30 is controlled by a furnace pressure control system as shown in FIG. 10, for example. The control system includes a pressure-electric converter 51 that detects the pressure inside the furnace, a sensor 53 that detects combustion switching and outputs a combustion switching signal, and the opening / closing of the exhaust system 25 based on the signal from the pressure-electric converter 51. Damper 5 that controls the flow rate
4, a bypass flow passage 55 of the damper 54, and a bypass damper 56 provided in the bypass flow passage 55 to control the opening / closing of the bypass flow passage 55, that is, the flow rate based on the combustion switching signal. The pressure in the furnace is input to the pressure-electric converter 51 from the pressure sensor 52. This control system
When the internal pressure of the furnace fluctuates significantly over the set value, it is dealt with by opening / closing the damper 54 of the main exhaust system 25, but for the fluctuation of the internal pressure of the furnace that is small and frequently occurs with the switching of the burners 21 and 22 for combustion, the bypass passage is used. By opening and closing 55, the bypass damper 56 is temporarily opened at the same time as the combustion of the burners 21 and 22 is switched to increase the exhaust gas amount of the exhaust gas in the furnace. It is designed to suppress fluctuations in the internal pressure of the furnace. By this control, as shown by the broken line in FIG. 11, fluctuations in furnace pressure are suppressed to a small level.

The above-mentioned embodiment is an example of the preferred embodiment of the present invention, but the present invention is not limited to this, and various modifications can be made without departing from the gist of the present invention. For example, in the present embodiment, a case has been mainly described in which high-temperature combustion air is obtained by alternating combustion using a heat storage body connected to or incorporated in a burner, but the present invention is not particularly limited to this, and for example, a combustion air supply system. And the exhaust system by rotating the heat storage body relative to the exhaust system, or by switching the flow direction of the fluid with respect to the heat storage body by using the flow path switching means, etc. The air preheated to a high temperature may be continuously supplied to a single burner for continuous combustion. Further, although the case where the gas fuel is used is mainly described in the present embodiment, the present invention is not particularly limited to this, and it is also possible to use a liquid fuel such as oil.

[0058]

As is apparent from the above description , according to the reflection type melting and holding furnace of claim 1, the fuel injection direction is perpendicular to the flow of the combustion air in order to increase the flame stability at low temperature. Even if they are brought close to each other, the amount of NOx generated is suppressed. That is, the fuel rapidly diffusing in the burner tile and a part of the high temperature combustion air form a flame holding region to stabilize the flame, while the flow of the combustion air strongly attracts the inside of the burner tile. Exhaust gas and a part of the fuel are mixed to cause in-reactor exhaust gas recirculation combustion, and further residual oxygen and incomplete combustion gas due to in-reactor exhaust gas recirculation combustion cause slow combustion outside the burner tile, Stable combustion can be realized with low NOx. The present invention is preferably applied to a furnace having a small furnace or a furnace in which the wall between the wall on which the burner is installed and the wall opposite thereto is narrow. Also forms a non-stationary flame
As the inside of the furnace can be heated uniformly,
Melted or molten metal to be heated
Holding or both can be performed uniformly. Furthermore, the bar
The bypass damper is temporarily opened at the same time as the combustion switching
Release the exhaust gas to increase the exhaust gas volume in the furnace and switch the burner.
Suppress frequent and frequent fluctuations in reactor pressure
Therefore, rattling of the furnace body and door due to fluctuations in furnace pressure
To prevent inflow of fresh air and outflow of hot air in the furnace.
The heat efficiency can be improved.

According to the second aspect of the present invention, a part of the combustion air flowing along the surface of the step between the end surface from which the combustion air is ejected and the end surface from which the fuel is ejected is the end surface from which the fuel is ejected. In the vicinity of the step, a vortex that flows counter to the flow of combustion air is stably formed, and a part of the fuel gas is engulfed to form a flame that serves as a seed flame. When exhaust gas recirculation occurs, the exhaust gas is trapped before the combustion air mixes with the fuel gas to reduce the oxygen concentration.Furthermore, fuel is attracted to the combustion air flow downstream from the end face where the fuel is injected. Since they are entrained and mixed, they form a flame and a combustion gas flow having a strong directivity while causing stable and slow combustion. Therefore, when high-temperature combustion air is used, not only the flame stability is high, but also a highly directional flame and a combustion gas flow can be formed while suppressing the generation of NOx, so that a large space can be formed. It can be burned with a uniform heat flux. Moreover, even when the combustion air is at a low temperature, such as when starting up the furnace, the flow rate of the combustion air slows down, causing the amount of flue gas to be entrained.However, since the temperature of the combustion air is low, The generated NOx is small, and conversely, the oxygen concentration is high, so that a stable pilot fire is formed between the fuel jet and the combustion air jet without being extinguished, and the flame is stabilized. The present invention is preferably applied to a furnace having a large furnace or a furnace in which a wall surface provided with a burner and a wall surface facing the wall surface are wide.

These are low N in the temperature rising process in an iron-based heating furnace operating at a relatively high temperature, for example, 1000 ° C. or higher.
Although it is effective for reducing Ox, it is particularly effective for reducing NOx and stabilizing the flame in a reflection-type melting and holding furnace of non-ferrous metal that is operated at a relatively low temperature, which has been considered difficult in the past.

In the third aspect of the invention, since a non-stationary flame can be formed and the inside of the furnace can be heated uniformly, a uniform heat flux can be obtained and the object to be heated is melted or the molten metal is retained. Or both can be implemented uniformly.

Further, in the case of the invention described in claim 4, since the short path of the combustion gas can be prevented, the sensible heat of the combustion gas can be effectively used for heating the object to be heated, and the thermal economy is improved. improves.

In the fifth aspect of the invention, the bypass damper is temporarily opened at the same time as the combustion switching of the burner to increase the exhaust gas amount of the exhaust gas in the furnace. Since the fluctuations in the furnace pressure that occur in 1) are suppressed, rattling of the furnace body and doors due to fluctuations in the furnace pressure can be prevented, and the inflow of fresh air and the outflow of hot air in the furnace can be eliminated and thermal efficiency can be improved.

Further, in the case of the invention according to claim 6, since heating is possible in a reducing atmosphere, metal loss is reduced.

Further, in the case of the invention described in claim 7, even if a large temperature difference occurs between the inside of the furnace and the side of the flow path switching means, there is no risk of cracks or the like, so it is possible to switch the flow in a short time. And the thermal efficiency is improved.

Further, in the case of the invention described in claims 8 and 9, since it is possible to separately use an appropriate heat storage material or heat storage structure for a portion requiring heat resistance and a portion not requiring heat resistance, the heat storage body can be made inexpensive. In addition, the equipment can be used continuously for a long period of time.

Further, in the case of the invention as defined in claim 10, the exhaust gas purifying catalyst is supported on the heat storage body and is contained in the combustion exhaust gas.
Since O and HC can be trapped, NOx can be reduced even in the case of giving priority to stability of combustion such as in reducing combustion, and without using a low NOx burner having a complicated structure.

Further, in the case of the invention described in claim 11, since the heat storage body can be easily replaced, the furnace can be restarted in a short time even if a trouble occurs in the heat storage body.

According to the twelfth aspect of the invention, even if dust such as aluminum fume or flux is mixed in the exhaust gas in the furnace, it can be separated and collected, so that the life of the heat storage body is extended. Moreover, since the temperature is lowered before it is introduced into the collector, air for dilution is not required, the exhaust volume is reduced, a thin duct is sufficient, and burn prevention is unnecessary, and the dust collector can be downsized.

[Brief description of drawings]

FIG. 1 is a plan sectional view showing a schematic structure of a reflective melting and holding furnace of the present invention.

FIG. 2 is a vertical sectional view of the melting and holding furnace.

FIG. 3 is a schematic diagram showing an embodiment configured as a heat storage alternating combustion burner system.

4A and 4B are principle diagrams illustrating a schematic structure and a combustion state of a low NOx burner, in which FIG. 4A is a vertical sectional view and FIG. 4B is a bottom view.

5 is a graph showing a result of measuring a relationship between a combustion air flow rate and NOx of the low NOx burner shown in FIG.

FIG. 6 is a principle diagram illustrating a schematic structure and a combustion state of a low NOx burner according to another embodiment.

FIG. 7A is a perspective view showing an example of a honeycomb-shaped ceramics heat storage body, and FIG. 7B is a sectional view showing an example of mounting the ceramics heat storage body.

FIG. 8 is an explanatory view showing a temperature distribution state of the heat storage body, (A)
Shows the decomposition state of the heat storage body, and (B) shows the temperature distribution of the heat storage body.

FIG. 9 is an explanatory view showing an example of dividing a heat storage body, where (A) is a case of heat storage bodies having the same structure, and (B) is a case of combining heat storage bodies having different structures.

FIG. 10 is a schematic configuration diagram of a furnace pressure control system.

FIG. 11 is an explanatory diagram showing a fluctuation state of the furnace pressure suppressed by the furnace pressure control system of FIG.

FIG. 12 is a schematic explanatory view of a conventional reflective melting and holding furnace.

FIG. 13 is a principle diagram of a conventional two-stage combustion type low NOx burner.

[Explanation of symbols]

1 Air nozzle for combustion 2 fuel nozzle 3 Blocks of refractory material 4 End face of block with combustion air injection port 5 End face of block with fuel injection port 10 Step surface 11 Vortices formed by backflow of combustion air 12 primary flames 20 Thermal storage combustion burner system 21,22 A pair of burners 23 Heat storage 26 flow path switching means 30 Reflective melting and holding furnace 36 Dust collector 41 Burner tile expansion part 42 burner tiles 43 Fuel Nozzle (Second Fuel Nozzle) 51 Pressure-electric converter 53 Combustion switching signal detection sensor 54 Main damper 55 Bypass Road 56 Bypass damper

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification symbol FI F27D 19/00 F27D 19/00 D (72) Inventor Kazuhisa Mitani 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Corporation (72 ) Inventor Ryoichi Tanaka 2-1553 Shirute, Tsurumi-ku, Yokohama-shi, Kanagawa Japan Furnace Industry Co., Ltd. (72) Inventor Hirota Hirota 3-13-28, Kanayama, Naka-ku, Nagoya, Aichi Prefecture (56) Reference literature JP-A-6-159613 (JP, A) Actual development Sho 52-61546 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) F27B 3/02 F27B 3 / 20 F27B 3/28 F27D 7/00 F27D 17/00 104 F27D 19/00

Claims (12)

(57) [Claims] 1. A combustion air injection port for injecting combustion air, which has been preheated to a high temperature, using combustion exhaust gas into a furnace.
The combustion air injection port so that the auxiliary combustion chamber is defined at the outlet of
With a larger diameter burner tile
Place the tiles and use the burner tile expansion
Make fuel collide obliquely with the flow of combustion air
Fewer heat storage combustion burners with a fuel nozzle for injection
Both are equipped with a pair of heat sources and a pair of these burners.
They are burned alternately to form a non-stationary flame and uniformly heated in the furnace.
A pressure-electric converter that detects the pressure in the furnace while heating
And a switch that detects combustion switching and outputs a combustion switching signal.
And exhaust based on the signal from the sensor and the pressure-electric converter
A main damper that controls opening and closing of the system, and the main damper
A bypass flow path that bypasses the
The bypass flow path is opened based on the combustion switching signal.
With a bypass damper to control closing and before frequent occurrence
For small fluctuations in furnace pressure that occur when switching burners
The bypass damper is opened and closed to respond to the internal pressure of the furnace.
When the value fluctuates significantly above the set value, the main
A reflection-type melting and holding furnace characterized by absorbing fluctuations in furnace pressure in response to opening and closing of the chamber. 2. A regenerative combustion burner that burns using combustion air that has been preheated to a high temperature using fuel exhaust gas, and a nozzle and fuel that inject the combustion air at a much higher speed than the fuel. Is arranged in parallel with the nozzle that ejects
And, surrounding them with a refractory material and providing a step between the end face where the injection port of the fuel nozzle is formed and the end face where the injection port of the air nozzle is formed, the end face on the fuel nozzle side is the end face on the air nozzle side. A reflection-type melting and holding furnace characterized in that it is provided with a burner that is more protruded than the heat source. 3. A furnace according to claim 2, wherein at least a pair of burners is arranged as a heat source, and the pair of burners are alternately burned to form a non-stationary flame to uniformly heat the inside of the furnace. Reflective melting and holding furnace. 4. The reflection-type melting and holding furnace according to claim 3 , wherein a pair of burners are installed at positions adjacent to each other, and combustion air is injected at high speed to prevent a short path of flame and combustion gas. 5. A pressure-electrical transducer for detecting the pressure in the furnace, a sensor for outputting a combustion switching signal by detecting the switching of the combustion, the opening and closing of the exhaust system on the basis of a signal from the pressure-electrical converter a main damper for controlling a bypass flow path which bypasses the main Dan <br/> path, a bypass damper for controlling opening and closing of the bypass passage on the basis of the combustion switching signal provided in the bypass passage And often happens
The variation of the small furnace pressure occurring in association with the switching of the burner corresponds by opening and closing of the bypass damper, the furnace
When the pressure fluctuates significantly beyond the set value, the main
The reflection-type melting and holding furnace according to claim 3 , wherein the fluctuation of the furnace pressure is correspondingly absorbed by opening and closing the damper . 6. The reflection-type melt holding according to claim 1, wherein the object to be heated is heated by forming a reducing atmosphere by using the high temperature preheated air having an amount equal to or less than a theoretical air amount. Furnace. 7. preheating of the combustion air is performed by regenerator passing alternately and combustion exhaust gas and combustion air,
7. The reflection-type melting and holding furnace according to claim 1, wherein the heat storage body is divided into at least a plurality of heat storage bodies in a fluid flow direction. 8. The heat storage body divided into at least a plurality in the flow direction of the fluid is made of different materials for the inner side of the furnace and the side of the flow path switching means. 7. The reflection type melting and holding furnace according to any one of 1 to 6. 9. The heat storage body divided into at least a plurality of portions in the flow direction of the fluid is formed with a different structure for the inside of the furnace and the one for the side of the flow path switching means. 7. The reflection type melting and holding furnace according to any one of 1 to 6. 10. The reflection type according to claim 1, wherein the heat storage body divided into at least a plurality in the flow direction of the fluid carries an exhaust gas purification catalyst in a catalytic reaction temperature region. Melting and holding furnace. Wherein said heat accumulator is connected to the burner is out capable housed in a direction perpendicular to the direction of the combustion gas or the flow of combustion air to the cylindrical casing having an openable lid on a side wall of the lid The reflection-type melting and holding furnace according to any one of claims 6 to 10, wherein the reflection-type melting and holding furnace is installed so as to be opened and closed by opening and closing. 12. A dust collector for introducing the combustion exhaust gas passing through the heat storage body is provided.
The reflective melting and holding furnace according to any one of 1 to 11.