CN1130539C - Reverberatory melting keeping furnace - Google Patents

Abstract

The present invention relates to a reflective fusion keeping furnace. The present invention utilizes a pair of burners as heating sources, that is to say, an opening is arranged on the diameter expansion part of a burner watt barrel, and the diameter of the opening is larger than that of an air ejection port for high temperature preheating. Fuel is ejected along the periphery of air flow for combustion from the diameter expansion part. A high-speed air nozzle for combustion and a fuel nozzle are arranged in mutual parallel. Fire-proof materials surround the nozzles. Steps are arranged among end surfaces forming the ejection port, and the end surface at the side of the fuel nozzle extends forwards. The pair of burners alternately burn, generate flame with unfixed positions, can uniformly heat the inner part of the furnace, decreases NOx, and improves thermal efficiency.

Description

Reflective Melting Holding Furnace

Involved areas

The present invention relates to a reflective melting and holding furnace for melting non-ferrous metals or holding molten metal or simultaneously melting and holding molten metal. More precisely, the present invention relates to the improvement of the burner as the heating source of the reflective melting and holding furnace, its associated regenerator, combustion method and control method.

Background technique

As shown in FIG. 12 described later, in a traditional reflective melting and holding furnace, a continuous and constant combustion diffusion burner 102 is generally used as a heating source. For roasting, the central part of the molten aluminum is set on the furnace body 101 . Moreover, the combustion rate of the burner 102 is controlled by controlling the flow regulating valves 105, 106 provided on the combustion air supply system 103 and the fuel supply system 104 with the control signal from the combustion load controller 107, so that the temperature in the furnace can be adjusted to The temperature of molten aluminum is set and adjusted to the specified temperature. On the other hand, an exhaust fan 109 and an exhaust damper 110 are arranged on the exhaust system 108 of the melting furnace 101, and the pressure in the furnace is adjusted by adjusting the opening degree (opening and closing degree) of the exhaust damper 110 with the furnace pressure controller 111. The setting remains constant. Therefore, in the case of using the traditional diffusion burner 102, because it is continuous and constant combustion, the pressure in the furnace fluctuates very little. The damper 110 is controlled, and the pressure in the furnace can be fully controlled by the controller.

However, in the above-mentioned conventional reflective melting and holding furnace, since the central portion of the molten aluminum is heated obliquely for roasting, the temperature of the molten aluminum is likely to be uneven due to uneven heat flow. In addition, in normal diffusion flame combustion based on the premise of excess air, a large amount of burning loss occurs due to residual oxygen in the combustion gas. In addition, since the combustion gas generated by the diffusion burner 102 during the continuous constant combustion is discharged as it is, there is a problem that the temperature of the exhaust gas increases and the exhaust heat loss increases.

In order to reduce the loss of exhaust heat, conventionally, heat recovery is generally carried out by means of a heat accumulator or the like. However, since the traditional heat accumulator cannot be used at high temperature, due to air mixed into the exhaust gas, heat recovery must be carried out below the heat-resistant allowable temperature of the heat accumulator, and there is a problem that only an exhaust heat recovery rate of less than 50% can be obtained. Therefore, there is a problem of increasing melting cost. For this reason, the inventors of the present invention have considered using a regenerator to preheat the combustion air to a high temperature close to the exhaust gas temperature to perform efficient exhaust heat recovery. Generally, in the case of regenerative combustion, when the combustion preheating air temperature becomes high, NOx will increase. In addition, due to the high reactivity, sufficient combustion can be achieved even with a low air ratio. Although combustion can be carried out in a reducing atmosphere, on the contrary, a large amount of HC and CO are generated during reducing combustion. In order to reduce these harmful exhaust components, the improvement of the basic structure of the conventional burner has been terminated. For example, in order to reduce NOx in the diffusion burner, the fuel two-stage combustion method as shown in Fig. 13 is adopted. This two-stage fuel combustion method is to supply the fuel with the primary nozzle 202 and the secondary nozzle 203 in two stages relative to the combustion air A flowing through the burner throat 201, and use the primary fuel and the full amount of combustion air to form At the same time as the primary flame, the secondary flame is formed by the reaction of the secondary fuel and the high-temperature combustion gas of the primary flame. Due to the low concentration of oxygen near the secondary fuel nozzle, reduction reactions can be used to reduce NOx in the primary flame.

However, in the burner of this fuel two-stage combustion method, since the injection direction of the secondary fuel forming the main flame is approximately parallel to the flow direction of the combustion air, the stability of the secondary flame at low temperature is poor. Preheating the air to a high temperature above 1000°C will make the flame unstable. Therefore, in order to improve the stability of the secondary flame at low temperature, when the injection direction is close to the direction perpendicular to the combustion air flow, the flame is stabilized, but local combustion and local temperature rise are caused, and NOx is increased. However, when a reflective melting and holding furnace is used as a heating source in a relatively low medium temperature range of about 700-800°C, or when the furnace is ignited at a low temperature, the stability of the flame will deteriorate. It is difficult to implement the traditional fuel two-stage combustion method. In addition, HC and CO generated during reducing combustion cannot be sufficiently suppressed.

In addition, in the traditional reflective melting and holding furnace, due to the inclusion of stevensite or flux powder in the exhaust gas, most of the exhaust damper 110 in the exhaust system 108, the heat accumulator (not shown) , Exhaust fan 109 etc. produce the adhesion of these dusts, bring trouble to operation.

In addition, when the flow direction is frequently switched for regenerative combustion in a short period of time, the regenerator cannot be heated evenly, so that the part near the furnace becomes high temperature, and the opposite part near the switching valve becomes low temperature. For example, it is 1000°C on the furnace side and 200°C on the valve side. Due to such a large temperature difference, the material used as the heat storage body can only be limited to expensive materials with high temperature resistance and thermal shock resistance. Furthermore, in the case of using a ceramic honeycomb heat storage body, it must be a material that can be made into various shapes. In addition, for example, when using a flux such as an aluminum melting furnace, a corrosion-resistant material is also required. It is very difficult to obtain materials with such high quality requirements.

In addition, in the furnace pressure control of the traditional reflective melting furnace, in the case of implementing short-time alternate combustion, since the furnace pressure control cannot be tracked, the door (slag retaining door, etc.) Air or hot air in the furnace flows out, resulting in a decrease in thermal efficiency.

Contents of the invention

Therefore, an object of the present invention is to provide a reflective melting and holding furnace capable of reducing the amount of NOx generated, high efficiency, and uniform heating.

In addition, a further object of the present invention is to provide a reflective melting and holding furnace that can not only achieve low NOx through the burner structure, but also purify harmful exhaust components such as NOx, CO, and HC. Another object of the present invention is to provide a reflective melting and holding furnace that improves reliability when performing regenerative combustion under high temperature and corrosive environments. Furthermore, it is an object of the present invention to provide a reflective melting and holding furnace having a small variation in furnace pressure.

In order to achieve the above object, the reflective melting and holding furnace of the present invention uses a regenerative combustion burner as a heating source, and the burner uses combustion air preheated to a high temperature through combustion exhaust for combustion, and is characterized in that the Said burner has nozzles for injecting fuel arranged in parallel and nozzles for injecting said combustion air at a high velocity of at least 100 m/s, and these nozzles are surrounded by refractory materials, while forming the end faces of the injection ports of the fuel nozzles and the end faces of the injection ports of the air nozzles Steps are provided between them, and the end surface on the fuel nozzle side protrudes farther forward than the end surface on the air nozzle side.

In this case, a part of the combustion air flowing along the surface of the stepped portion of the end surface for injecting combustion air and the end surface for injecting fuel stably forms a reverse swirl flow relative to the flow of combustion air in the vicinity of the step near the end surface for injecting fuel, Part of the fuel gas is entrained to form a flame that becomes a kindling seed. In addition, the negative pressure generated at the stepped portion causes strong exhaust gas recirculation, thereby entraining the exhaust gas to lower the oxygen concentration before the combustion air and fuel gas are mixed. Further, in the downstream of the end face where the fuel is injected, the fuel is sucked by the combustion air flow and then mixed.

Here, since the high-temperature combustion air preheated to about 700-800°C or higher expands in volume compared with normal temperature, by setting the air nozzle finely, or using a nozzle set to a flow rate suitable for low temperature The thin nozzle makes it eject at a very high speed compared with normal temperature fuel and air. For example, high-temperature preheated air is sprayed at a very high flow rate of 100 m/s or more compared to fuel sprayed at a flow rate of 20-30 m/s. Therefore, on the one hand, the combustion exhaust gas is entrained by the high-speed combustion air flow, and the oxygen concentration (partial pressure) is lowered; Moreover, since the flow velocity of the combustion air is much higher than the flow velocity of the fuel flow, and until it reaches the fuel injection end face, a large amount of exhaust gas has been involved, so that the combustion reaction caused is not violent, causing the combustion air and fuel on the contact surface The layers are slow-burned. Due to the formation of a stable primary flame, a stable flame that does not go out even at high flow rates can be formed. In addition, in the combustion reaction, because the flow rate of the combustion air is high, a large amount of exhaust gas is entrained while the combustion reaction continues, and the slow combustion is further promoted. This creates a highly directional flame and combustion airflow.

In addition, when the combustion air temperature is low, such as when the furnace is ignited, the amount of exhaust gas involved is reduced due to the low combustion air flow rate. However, due to the low combustion air temperature, the generated NOx is as small as before . On the contrary, due to the high concentration of oxygen, the stable fire formed between the fuel flow and the combustion air flow near the injection port of the fuel nozzle can not be blown out, and a stable flame can be formed.

Therefore, the above-mentioned present invention is due to more ideal configuration at least two burners as a pair of heating sources, so that the flames that are alternately burned to form non-fixed positions can be uniformly heated in the furnace, and then the pair of burners are arranged adjacent to each other In the near position, the combustion air is sprayed at a high speed of at least 100m/s, which can prevent the formation of short-range flames and combustion gases. In this case, since the flame and the combustion gas are alternately formed between at least one pair of burners in a short period of time, the position of the flame is not fixed, and the object to be heated is heated with a uniform heat flow. In addition, since the high-speed injection of combustion air forms a highly directional flame and combustion airflow, even if a pair of burners are arranged adjacent to each other, short distances can be prevented, and the gas can reach all corners of the furnace and be exhausted after heating. .

In addition, the reflective melting and holding furnace of the present invention has: a pressure electric transducer for detecting the pressure in the furnace; a sensor for detecting combustion conversion to output a combustion conversion signal; The main damper that controls the closing, that is, the exhaust flow; the bypass of the damper; the bypass damper that is set on the bypass and controls the opening and closing of the bypass according to the combustion conversion signal, that is, the exhaust flow. The opening and closing of the bypass flow path corresponds to small furnace pressure fluctuations caused by frequent burner switching, and the opening and closing of the main exhaust system corresponds to large fluctuations above the set value, thereby absorbing furnace pressure fluctuations. In this case, since the bypass damper is temporarily opened while the combustion of the burner is switching, the exhaust gas in the furnace is increased, and the frequent periodic changes in the furnace pressure caused by the switching of the burner can be suppressed.

In addition, the reflective melting and holding furnace of the present invention uses high-temperature preheated air below the theoretical air volume (minimum air volume necessary for complete combustion of the fuel in the mixture) to form a reducing atmosphere to heat the object to be heated. In this case, since the reductive combustion is performed by using the high-temperature preheated air which is preheated to a temperature close to the combustion exhaust gas substantially below the theoretical air volume, the object to be heated can be prevented from being oxidized.

In addition, the reflective melting and holding furnace of the present invention preheats the combustion air through the regenerator through which the combustion air and combustion exhaust alternately pass, and at least divides the regenerator into multiple parts along the flow direction of the fluid. In this case, since the division is carried out at least along the flow direction, even in order to improve the thermal efficiency, the heat storage body in the regenerator can be made even through the regenerative combustion in which the high-temperature combustion exhaust gas and the low-temperature combustion air alternately flow in a short period of time. There is a large temperature difference between the part near the furnace and the part on the opposite side near the switching valve, and the difference in thermal expansion of each regenerator is small, thereby preventing cracking. Furthermore, the part of the divided regenerator close to the furnace side and the part close to the flow path conversion side are made of different materials, so that a large temperature difference is generated between the side close to the furnace and the opposite side. In this case, a heat-resistant heat storage body can be used only on the heat storage body close to the furnace side, and a low-cost heat storage body without heat resistance can be used on the side of the low-temperature switching valve. In addition, the part of the regenerator close to the furnace side and the part close to the flow path conversion mechanism are formed with different structures. The heat storage body on the side adopts a heat storage body with a filtering function, which can prevent the heat storage body from being blocked. Furthermore, the heat accumulator which is divided into several parts is equipped with an exhaust gas purification catalytic medium adapted to the temperature range of the catalytic reaction. In this case, HC, CO, NOx, etc. generated in reducing combustion can be completely purified.

In addition, the regenerator is connected to the burner by accommodating the regenerator in a cylindrical casing with an openable and closable cover on the side wall in a manner perpendicular to the flow direction of the combustion gas or combustion air, and is arranged to pass through the cover. It can be taken out or put in freely by opening and closing. In this case, the heat storage body can be exchanged only by opening the casing cover without disassembling the exhaust system.

In addition, the reflective melting and holding furnace of the present invention is provided with a dust collector that introduces the combustion exhaust gas passing through the regenerator. In this case, even if dust is contained in the combustion exhaust gas, it can be separated and collected.

Hereinafter, the effects of the present invention will be further described.

According to the reflective melting and holding furnace of the present invention, since the burner tile cylinder having a larger diameter than the combustion air injection port is provided on the combustion air injection port, the burner tile cylinder is arranged at the same time. The burner of the fuel nozzle that injects fuel from the enlarged diameter portion improves the flame stability at low temperature, and even if the fuel injection direction is nearly perpendicular to the direction of the combustion air flow, the amount of NOx generation can be suppressed. On the one hand, it can make the fuel rapidly diffused in the burner tile cylinder and part of the high-temperature combustion air form a stable flame area to stabilize the flame; on the other hand, the combustion air flow is strongly introduced into the burner tile cylinder and Furnace exhaust gas is mixed with a part of the fuel, causing the furnace exhaust gas to recirculate and burn, and then, due to the residual oxygen outside the burner tile cylinder and the incomplete combustion gas produced by the furnace exhaust gas recirculating combustion, slow combustion occurs , so as to achieve stable combustion under low NOx conditions. Therefore, the present invention is especially suitable for a small furnace, or a furnace having a narrow space between the wall opposite to the wall on which the burner is installed.

In addition, according to the present invention, on the one hand, part of the combustion air flowing along the surface of the stepped portion of the combustion air injection end surface and the fuel injection end surface forms a stable relative combustion air near the step near the fuel injection end surface. The reverse vortex of the flow entrains a part of the fuel gas to form a flame as a kindling seed. On the other hand, a negative pressure is generated in the stepped part to cause a strong exhaust gas recirculation, so that before the combustion air and fuel gas are mixed, due to The exhaust gas is entrained to reduce the oxygen concentration, and further downstream of the fuel injection end surface, the fuel is sucked and mixed by the combustion air, thereby stably causing slow combustion and forming a highly directional flame and combustion airflow. Therefore, in the case of using high-temperature combustion air, not to mention high flame stability, since NOx generation can be suppressed, and a highly directional flame and combustion air flow can be formed, and combustion can be carried out with uniform heat flow in a large space. Moreover, even when the temperature of the combustion air is low, such as when the furnace is ignited, the flow rate of the combustion air is low, and the amount of combustion exhaust gas entrainment appears to be the same due to the low temperature of the combustion air. NOx is less, on the contrary, due to the increase of oxygen concentration, the stable fire between the fuel jet and the combustion air jet will not be blown out, so that the formed flame is stable. Therefore, the present invention is also particularly suitable for larger furnaces, or furnaces with a wide interval between the wall facing the wall on which the burner is installed.

The above are also effective for reducing NOx in the heating process of iron-based heating furnaces that operate at relatively high temperatures, such as 1000°C or higher. However, they are especially effective for non-ferrous metals that have been difficult to form in the past, that is, operating at relatively low temperatures. It is very effective in reducing NOx and stabilizing flames in reflective melting and holding furnaces.

In addition, according to the present invention, a non-fixed flame is formed to uniformly heat the inside of the furnace to obtain a uniform heat flow, and to uniformly melt the object to be heated or maintain its molten state or perform both operations at the same time.

In addition, according to the present invention, generation of short-range combustion gas can be prevented, and sensible heat of combustion gas can be effectively used for heating an object to be heated, thereby improving thermal economy.

In addition, according to the present invention, the bypass damper can be temporarily opened while the combustion of the burner is switched, so that the exhaust gas in the furnace can be increased, and the periodic and frequent furnace pressure caused by the switch of the burner can be reduced. The fluctuation is suppressed, the instability or shaking of the furnace body or door caused by the fluctuation of the furnace pressure is prevented, and the fresh air is not allowed to flow in or the hot air in the furnace is not allowed to flow out, so that the thermal efficiency is improved.

Furthermore, metal losses are reduced due to the possibility of heating in a reducing atmosphere according to the invention.

In addition, according to the present invention, even if there is a large temperature difference between the furnace side and the flow path switching mechanism side, there is no need to worry about cracks, so that the flow can be switched in a short time, and the thermal efficiency can be improved.

In addition, according to the present invention, the heat storage body formed by using appropriate heat storage material or heat storage structure can be used according to the parts that require or do not need heat resistance, so that the cost of the heat storage body can be made cheap and the equipment can be used continuously for a long time. use.

In addition, since according to the present invention, the exhaust gas purifying catalytic medium is provided on the regenerator to collect CO and HC contained in the combustion exhaust gas, so that even when stable combustion such as reduction combustion is given priority, and it is not used It can also reduce NOx in the case of a low NOx burner with a complex structure.

Furthermore, since the heat storage body can be easily replaced according to the present invention, even when the heat storage body breaks down, the furnace can be re-ignited in a short time.

In addition, according to the present invention, even if the dust such as stevensite or flux is mixed in the exhaust gas in the furnace, it can be separated and collected, so that the working life of the heat storage body can be extended. Moreover, since the temperature is lowered before being introduced into the collector, there is no need for dilution air, and because the exhaust volume is reduced, it is sufficient to use thin pipes, and there is no need to prevent burns, etc., which is more conducive to the miniaturization of the dust collector.

Description of drawings.

Fig. 1 is the top sectional view that briefly shows the reflective melting holding furnace structure of the present invention,

Fig. 2 is the longitudinal sectional view of described melting holding furnace,

Fig. 3 is a diagram schematically showing an embodiment of the burner system structure as regenerative alternating combustion,

Fig. 4 is a schematic diagram briefly showing the structure of the low NOx burner and explaining the combustion state, wherein (A) is a longitudinal section view, (B) is a bottom view,

Fig. 5 is a graph showing the measurement results of the relationship between the combustion air flow rate and NOx of the low NOx burner shown in Fig. 10,

Fig. 6 is a schematic diagram briefly showing the structure of the low NOx burner in other embodiments and illustrating the combustion conditions,

7(A) is a perspective view showing an example of a honeycomb ceramic regenerator, and (B) is a sectional view showing an installation example of a ceramic regenerator,

Fig. 8 is an explanatory diagram showing the temperature distribution state of the heat storage body, (A) showing the decomposition state of the heat storage body, (B) showing the temperature distribution state of the heat storage body,

Fig. 9 is an explanatory diagram showing an example of division of heat accumulators, (A) showing the case of heat accumulators of the same structure, (B) showing the occasion of combining heat accumulators of different structures,

Fig. 10 is a diagram simply showing the composition of the pressure control system in the furnace,

Fig. 11 is an explanatory diagram showing the state of furnace pressure fluctuation suppressed by the furnace pressure control system shown in Fig. 10,

Fig. 12 is an explanatory view schematically showing a conventional reflection type melting and holding furnace,

Fig. 13 is a schematic diagram of a conventional two-stage combustion type low NOx burner.

Detailed ways

Hereinafter, the structure of the present invention will be described in detail according 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. This well-type reflective melting and holding furnace 30 is generally a furnace having a molten bath exposed to the atmosphere connected to a heating chamber called a forehearth 31 located on the side of the stationary square melting furnace. The purpose of setting up the forehearth 31 is mainly to melt the secondary aluminum, put the material in, and keep the heat with the melt to melt. The melt tank 32 and the forehearth 31 are separated by the slag gate 33 in the vertical direction, and the melting is promoted by circulating the melt tank 32 and the forehearth 31 with a melt pump (not shown) or the like as necessary.

On the molten tank 32 side, the regenerative combustion type burner system 20 is installed on the furnace wall 35 so that the formed flame gas is substantially parallel to the liquid surface of the molten aluminum 34 . In addition, in this embodiment, one system of regenerative combustion type burner system 20 is installed, however, two or more systems may be installed.

The regenerative combustion type burner system 20 is arranged on the wall surface 35 of the molten aluminum tank 32 so that the ejected combustion air and fuel are approximately parallel to the liquid surface of the molten aluminum 34 and a flame and a gas flow are formed along the liquid surface. In the present embodiment, two burners 21 and 22 that burn alternately are set as a set to form a regenerative combustion type burner system 20 of one system. This regenerative combustion type burner system 20 is shown in Figure 3 in the embodiment, and the regenerator 23 is arranged in the burner housing 27, so that it has been integrated respectively, including burners 21, 22 and heat storage The combination of two bodies 23, 23 will be arranged so that alternate combustion is carried out on the one hand, and the combustion exhaust gas can be discharged by the burner and the regenerator in the stop of the combustion on the other hand. It should be set so that in the two burners 21, 22, the exhaust system 25 that discharges the combustion gas can be selectively connected with the air supply system 24 that supplies the combustion air through the flow path conversion mechanism 26, on the one hand, it can achieve the purpose of passing through the heat storage body. 23 supplies combustion air to one burner 21 (or 22 ), and on the other hand, discharges combustion gas from the other burner 22 (or 21 ) through the heat storage body 23 . For example, a fan 28 is used to push and supply combustion air, and an exhaust mechanism such as an exhaust fan 29 is used to extract the combustion gas from the furnace, and after necessary processing such as dust collection, it is discharged into the atmosphere. The fuel supply system is selectively and alternately connected to one of the burners 21 and 22 by a not-shown, for example, three-way valve to supply fuel. In addition, 36 in the figure is a dust collector such as a cyclone dust collector.

Here, as each burner 21, 22, for example, a low NOx burner shown in FIG. 4 is suitably used. This low NOx burner is a burner that injects fuel gas in parallel with the flow of combustion air preheated to a high temperature, and is configured in such a way that a fuel (gas) nozzle is formed through the refractory block 3 2 and an air nozzle 1 that ejects combustion air preheated to a high temperature at a high speed much higher than the fuel flow rate, and the injection ports of each nozzle are formed on the two end faces 4 and 5 with steps of the refractory block 3 6,7. Also, piping 8 constituting a primary air supply flow path is buried around the fuel nozzle 2 , and primary air, which is about 10% of the secondary air, flows around the fuel nozzle 2 . Furthermore, a primary air flow path is formed on the tip portion of the fuel nozzle 2 toward other surroundings of the main injection port 7, and the injection port 9 that injects a part of the fuel injects a part of the fuel as pilot fuel, so that the fuel is injected into the pipe 8. The surrounding wall impacts and expands into the primary air flow path, thereby forming a pilot burner that obtains a good mixing state. And in order to form a stable primary flame 12 during combustion, an igniter (not shown) is provided there. The piping system consists only of main piping through which most of the combustion air used as secondary air flows, air nozzle 1, and fuel piping (primary air piping 8 and fuel nozzle 2) through which fuel and primary air flow. very compact. In addition, in this embodiment, the piping 8 through which the primary air flows is provided around the fuel nozzle 2, and the pilot burner is formed near the injection port. A pilot burner is provided near the injection port of the fuel nozzle.

In addition, the fuel injection port 7 and the air injection port 6 are not formed on the same plane, but are provided on different surfaces having steps, and the fuel injection port 7 is arranged on the downstream side of the air injection port 6 . That is, the fuel injection port 7 is arranged on the end surface (hereinafter referred to as the flame stabilization surface) 5 protruding from the end surface (hereinafter referred to as the reference surface) 4 of the refractory block on which the air injection port 6 is provided. The stable primary flame 12 and the fuel F are ejected from the fuel ejection port 7 of the flame stabilizing surface 5 . Combustion air is jetted out from the center of the refractory block 3 at high speed. At this time, a reverse swirl 11 against the combustion air flow can be formed in the vicinity of the step portion of the flame stabilization surface 5, and a flame stabilization region where a part of the fuel gas is rapidly mixed can be formed. Therefore, it is possible to form a stable flame that is not easily blown out even at a low temperature, not to mention a high temperature. In the present embodiment, the air nozzle 1 and the fuel nozzle 2 are arranged in parallel and the refractory block 3 that is held constitutes a single integral member. However, the part for holding the air nozzle 1 and the fuel nozzle for holding can also be formed separately according to the occasion. 2 parts, and then use them in combination. In addition, in the present embodiment, the air nozzle 1 is formed by using a burner housing having a hole in the refractory block 3 and a refractory block 3 built therein, without piping. Needless to say, the air nozzle 1 may also be configured by piping.

In addition, in the case of adopting the above-mentioned structure, it is necessary to separate the air nozzle 1 and the fuel nozzle 2 on the refractory block 3 by a certain distance from the viewpoint of strength. Therefore, there is a tendency that the fuel is less likely to be induced by the high-speed air flow in the region where the injection has just occurred. Therefore, as shown in the figure, it is preferable to form the shape of the portion 13 of the fuel injection port 7 close to the air nozzle 1 into a curved shape that is curved toward the side of the air nozzle 1 . According to this, the fuel can be easily flowed out toward the combustion air flow side. Therefore, the concomitant mixing ability of the fuel can be further improved, and the generation of free unburned components such as CO and HC can be prevented. In addition, since the fuel supply to the vortex 11 that generates the backflow of combustion air can also be improved, a more stable ignition can be formed. The above-mentioned shape is not limited to a curved surface, and any structure can satisfy such a function, for example, a slope.

In addition, the air nozzle 1 is arranged on the stepped portion where the flame stabilization surface 5 and the reference surface 4 meet. And the part close to the flame stabilization surface 5 has the function of fuel concomitant mixing, and the part close to the reference plane 4 has the function of exhaust gas recirculation. Exactly as shown in Figure 4 (B), at the surface 10 of the stepped portion of the flame stabilization surface 5 and the reference plane 4, the injection port 6 of the air nozzle 1 is vertically split into two halves with this surface 10. In the case of a halved arrangement in the center of the center, the functions of mixing and recirculation can be obtained at the same time. On the other hand, when the surface 10 of the stepped portion is arranged so as to circumscribe the injection port 6 of the air nozzle 1 (not shown), compared with the situation shown in FIG. Expand, so that the function of reducing the concentration of oxygen in the combustion air becomes better. In addition, when the faces 10 of the stepped portion are crossed and arranged to substantially wrap the injection port 6, since the injected air increases from the refractory block 3 to the restricted portion of the flame stabilization surface 5, the directivity is strong. The combustion air flow is further ejected from the flame stabilization surface 5, so that the concomitant mixing ability of the combustion gas becomes more excellent.

According to the low NOx burner constructed in this way as shown in Figure 4, when the combustion air is ejected at high temperature and high speed, the universal combustion air ejected from the flame stabilization surface 5 at a high speed will be parallel at a relatively low speed. The injected fuel is directed and accompanied early, strongly, and extended far while being gradually drawn into the mix. However, since the combustion air flow rate is much higher than the fuel flow rate, for example, it reaches a very high speed of 100 m/s or more, and because the accompanying fuel is gradually brought in, a large amount of exhaust gas is being involved when it reaches the flame stabilization surface 5 , so that the combustion reaction is not caused sharply, but the combustion reaction proceeds slowly. Furthermore, since the air flow rate is high, and since the combustion reaction proceeds while a large amount of exhaust gas is involved in the combustion reaction, the slow combustion is further promoted. From the experimental results of the relationship between the combustion air flow rate and the NOx generation shown in Figure 5 above, it can be seen more clearly that the higher the injection velocity of the combustion air, the lower the NOx amount, and the effect, that is, the greater the combustion amount. (the degree of becoming a high temperature) is more remarkable. Therefore, according to the burner of this embodiment, a relatively uniform and long heat flow can be formed and NOx can be reduced. Moreover, since a part of the fuel is induced into the counterflow of the combustion air caused by the area near the stepped portion of the flame stabilizing surface 5 and mixed by diffusion, a stable flame that becomes the ignition seed is formed, not to mention at high temperature, even at low temperature. Form a steady flame. Therefore, this embodiment can be applied to a furnace having a relatively long distance between the walls facing the wall 35 on which the burners 21 and 22 are installed, such as a large furnace.

In addition, as a burner, it is preferable to use a low NOx burner as shown in Fig. 6 . This burner is a combustor that injects fuel from the surroundings of the air stream for combustion that is preheated to a high temperature, and a burner tile expansion portion with a larger diameter is arranged on the air injection port 40 for combustion. The burner shoe 42 of 41 is provided with a fuel nozzle 43 for injecting fuel from the enlarged diameter portion 41 of the burner shoe. In this case, as long as the fuel can be injected from the inside of the burner shoe 42 of the burner shoe enlarged diameter portion 41, that is, to the auxiliary combustion chamber 46, the injection direction is not particularly limited, however, it is preferable to face the combustion chamber. The air flow is injected, and more preferably, the fuel is injected obliquely with respect to the combustion air flow, so that a collision occurs. In the case of oblique injection of fuel relative to the combustion air flow, compared with the case of vertical injection, it can promote the exhaust gas recirculation combustion in the furnace and the slow combustion outside the burner tile, and further reduce the amount of NOx generated. In addition, a pilot burner 44 is provided on the upstream side of the burner shoe enlarged diameter portion 41 to inject pilot fuel. In this case, a flame stabilizing region is formed on the upstream side of the burner tile enlarged diameter portion 41 as a kindling seed, and the flame can be stabilized even if the temperature of the combustion air becomes low. When the combustion air is supplied at a high temperature of about 1000°C or higher, the pilot burner 44 may be provided further upstream because it is not necessary to constantly perform combustion in the vicinity of the burner shoe enlarged diameter portion 41 . In addition, in the present embodiment, a first fuel nozzle 45 for injecting primary fuel is provided on the burner throat 40 . Stop using the first fuel nozzle 45 after starting the furnace. When the temperature of the furnace is low and it is difficult to stabilize the combustion, that is, when the furnace is started to work, etc., inject the fuel once in a perpendicular intersection with the air flow for combustion. , so that rapid mixing, diffusion and stable combustion. At this time, due to the low furnace temperature, the NOx produced is also small and within the allowable range. Moreover, when the furnace temperature reaches a predetermined temperature, fuel is injected only from the second fuel nozzle 43 in the enlarged diameter portion of the burner tile, so that the above-mentioned exhaust gas recirculation combustion and slow combustion of the incomplete combustion gas and residual oxygen occur. , so that the generation of NOx is reduced. In addition, this embodiment shows an individual example in which the first fuel nozzle 45 and the pilot burner 44 are provided separately. However, the present invention is not limited thereto, and the first fuel nozzle 45 may not be particularly provided, but only the pilot burner 44 is provided. In addition, the pilot burner 44 is located on the more upstream side of the corresponding components in FIG. Close to the second fuel nozzle 43 . In addition, as the second fuel nozzle 43, the fuel nozzles 2 and 8 used in combination with the pilot burner of the burner shown in FIG. burner. In addition, when the depth of the expanded diameter portion 41 of the burner tile from the inner wall surface of the furnace is constant, the fuel nozzle 43 can also be installed at any position. However, when the depth is not constant, for example, the If the burner is installed on a curved surface or inclined, it is desirable to install it at the deepest point. The same is true in the case of using a pilot burner dual-purpose nozzle as the fuel nozzle 43. At this time, it is easy to cause the recirculation of the furnace exhaust gas toward the inside of the burner tile barrel diameter expansion part 41 if it is installed at a shallow place. The exhaust gas in the furnace is difficult to enter, and the concentration of oxygen does not decrease, so that the ignition stability is excellent. Therefore, if the fuel nozzle 43 or the fuel nozzle used as a pilot burner is arranged In deep places, the ignition stability is excellent because the oxygen concentration is not reduced.

According to the low NOx burner constructed in this way, as shown in Fig. 6, a part of the fuel injected in an oblique direction is mixed and diffused with a part of the combustion air which has been preheated to a high temperature by the regenerator to form a flame stabilization region. X1, forming a stable flame. In addition, in the auxiliary combustion chamber 46 of the burner tile diameter expansion part 41, the exhaust gas in the furnace is strongly attracted by the high-temperature combustion air jetted from the air throat at a high speed, and is drawn from the burner tile diameter expansion part. Part of the fuel injected obliquely at the corner of 41 is mixed to cause exhaust gas recirculation combustion, forming a recirculation combustion area X2 of exhaust gas due to insufficient air. In addition, on the outer surface of the burner tile 42, an incomplete oxygen gas remaining in the combustion gas from the flame stabilization region X1 and the exhaust gas recirculation combustion region X2 in the enlarged diameter portion 41 of the burner tile are formed. The reaction between the combustion gases causes the zone X3 of slow combustion. Also, in this case, since the fuel is injected directly into the burner shoe 42, excess gas diffusion outward in the flame axis is suppressed, and the amount of unburned gas during combustion can be suppressed to a minimum. Therefore, even a furnace that works at a medium temperature range of about 700-800°C like a well-type reflective melting protection furnace can stabilize the flame without increasing NOx. In the case of this burner, it is most suitable for a furnace in which the distance between the walls facing the wall 35 on which the burner is installed is narrow.

In addition, in the case of this burner, all the fuel injected from the first fuel nozzle 45 is burned until the temperature in the furnace reaches a predetermined temperature, thereby warming the furnace. At this time, even if the temperature of the combustion air is low, the fuel injected from the first fuel nozzle 45 can be immediately mixed with the combustion air, and the combustion can be stabilized by the pilot flame provided close to it. Then, when the predetermined temperature is reached, the fuel injection from the first fuel nozzle is stopped, and the fuel injection from the second fuel nozzle 43 is performed. Here, the predetermined temperature is not necessarily the operating temperature of the furnace, but the temperature at which the flame can be maintained only by the injected fuel from the second fuel nozzle 43 or higher. In addition, when a pilot burner double-purpose nozzle is used as the second fuel nozzle 43, the furnace is ignited by burning this second fuel nozzle from the beginning. In addition, the switching between combustion and exhaust is, for example, performed at an interval of 10 seconds to 2 minutes, preferably within about 1 minute, preferably within a very short time interval of about 10 to 40 seconds. In this case, heat exchange is performed at high temperature and high efficiency. In addition, switching may be performed when the combustion gas discharged through the thermal storage body 23 reaches a predetermined temperature, for example, about 200°C.

As mentioned above, in the case where at least one pair of burners are alternately combusted, since the flame position is frequently moved and changed, the heat transfer mode in the combustion chamber can be more uniform, and the occurrence of uneven heating and uneven heat preservation can be reduced. The phenomenon becomes less.

Here, for example, by using a regenerator, by making combustion exhaust gas and combustion air alternately flow over the regenerator, heat exchange is performed directly, and the combustion air supplied by the burner shown in FIG. 4 or FIG. 6 is preheated. To roughly close to the combustion exhaust temperature, for example, a high temperature of 700-800°C or above.

As the regenerator 23, it is preferable to use honeycomb ceramics with a certain flow cross-sectional area, such as cordierite, mullite, or other materials with excellent heat and acid resistance, which have a certain flow cross-sectional area and flow through in a straight line, as shown in Figure 7. . This honeycomb ceramic has a large heat capacity, high durability and low pressure loss. Moreover, exhaust and air supply can be carried out alternately and continuously. Therefore, it is difficult for the dust in the exhaust gas to adhere to the honeycomb flow path of the regenerator 23, and even if it does, it will not be polluted by backwashing. In addition, when recovering heat from the exhaust gas, even if the exhaust gas temperature is lowered below the acid dew point temperature, the ions in the exhaust gas and their chemically changed substances are trapped on the ceramic surface, so the downstream exhaust system will not be damaged. 25 pipes, etc. produce low-temperature corrosion. In addition, the heat accumulator 23 as shown in FIG. 7( b ) is housed in a case 38 with a part of the side wall as a cover 39 so that it can come in and out in a direction perpendicular to the flow path, and is assembled in the burner. 21, 22 and flow path conversion mechanism 26 between. Therefore, a damaged or clogged heat storage body can be easily taken out and replaced only by opening the cover 39 .

In addition, molten powder and dust generated during melting contained in the exhaust gas are brought to a low temperature by the thermal storage body 23 and introduced into the dust collector 36 for collection. Therefore, there is no trouble of dust adhering to the flow path switching mechanism 26 and the exhaust fan 29 located downstream of the dust collector 36 . In addition, the form, structure, etc. of the dust collector 36 are not particularly limited, as long as the dust collector can drop the dust by simply changing the flow direction.

In addition, as shown in FIG. 9(A), it is preferable to divide the heat storage body 23 into a multilayer arrangement along the flow direction of the fluid. This is because, when a pair of burners 21 and 22 are alternately combusted in a short period of time in order to improve heat storage efficiency, that is, as shown in FIG. high temperature, and the opposite side near the side of the flow path switching mechanism 26 is low temperature. When such a thermal storage body 23 is integrated, the temperature difference changes rapidly due to frequent flow path switching, and the possibility of cracks due to thermal expansion difference increases due to the large temperature difference change. Therefore, by dividing the thermal storage body 23 into multiple layers, the difference in thermal expansion per block can be reduced, and cracks due to the difference in thermal expansion can be prevented. As an example, as shown in FIG. 9(A), the heat storage body 23 is divided into three layers. At this time, it is preferable to sandwich the cushioning member 37 between the heat storage bodies 23 , 23 , and 23 .

In addition, corrosion of the heat storage body 23 progresses remarkably at a high-temperature portion near the furnace, while corrosion at a low-temperature portion near the flow path switching mechanism 26 is relatively slow. Therefore, if the entire heat storage body 23 is made of an expensive corrosion-resistant material, the cost will increase unnecessarily. Therefore, only the heat storage body 23 made of a corrosion-resistant material is used in the high temperature part on one side of the furnace, and the cheap heat storage material can be used in other parts. In addition, as a method to prolong the working life of the heat storage body 23, the wall thickness t of the honeycomb body at the high temperature part should be increased as much as possible. In this case, considering that the thermal shock resistance will be reduced, the material with high thermal conductivity should be used to avoid this problem. In addition, when it is suitable for a high-temperature furnace with a furnace temperature of about 1500°C, high heat-resistant heat storage materials can be used only in the parts of the first and second heat storage bodies 23 and 23 on the side close to the furnace, while other parts Use cheap materials.

In addition, when the honeycomb heat storage body 23 is used in an environment accompanied by generation of dust such as molten powder, clogging may occur. Therefore, as a countermeasure, as shown in FIG. 9(B), as a filter body replacing the first heat accumulator 23, a spherical or ore-shaped heat accumulator with high heat resistance can be embedded, so that it can be replaced at ordinary times. It is also possible to use a honeycomb heat storage body on the second and third layers.

In this embodiment, the regenerator 23 is arranged behind the throat of the burner. However, in order to reduce the sensible heat loss in the furnace as much as possible and to utilize the space of the furnace wall thickness, the regenerator can also be arranged in the furnace. side. In this case, generally speaking, since the installation space of the burner is not sufficient, there is a possibility that all the heat storage bodies having the required capacity cannot be inserted. In this case, when the regenerator is divided, a part of it is placed on the burner tile part, and the other part is placed close to the flow path conversion mechanism 26, the loss of high-temperature exhaust gas will be reduced, and the furnace will be compact. change. In addition, as described above, when multiple functions and heat storage bodies of various structures are used in combination, it is not necessary to house them in the same heat storage chamber. The regenerator is divided and installed according to the function, and the degree of freedom in the design and construction can be ensured by connecting the exhaust gas and the air flow path in series with the heat insulating pipe.

In addition, in the case of reduction combustion using combustion air preheated to a high temperature, even if the burner shown in Fig. 4 or Fig. 6 is used, there is a concern that at least some level of NOx will be generated compared with conventional ones. Therefore, it is preferable to use the thermal accumulator 23 having a part of it function as a catalytic medium for exhaust purification. For example, in the case of purifying with a catalytic medium that promotes the oxidation of CO, it is possible to purify 100% of CO contained up to about 5% in the range of about 150-700°C. In addition, when alternate combustion is performed in a short time, the temperature of the regenerator 23 is made high (for example, about 1000° C.) on the side of the furnace, and low (for example, about 200° C.) on the side of the flow path conversion mechanism 26 . ). Therefore, as shown in FIG. 8, by dividing the regenerator 23 into multiple layers along the flow direction of the fluid, and by making the catalytic medium carried on the block adapt to the temperature distribution range of each catalytic medium reaction, 100% CO can be purified. In addition, when performing CO purification, an exothermic reaction occurs in the regenerator 23 , but since the heat can be used for preheating the combustion air after conversion, no heat loss occurs. Furthermore, if purification of CO and HC becomes possible, combustion can be carried out under reducing atmosphere conditions, and oxidation of the object to be heated and molten aluminum can be prevented. In addition, the same applies to NOx, as long as the carried catalyst medium matches the necessary temperature range. For example, when only CO or HC is purified, platinum can be mainly used as a catalytic medium. The reaction temperature range of this platinum catalyst medium is about 150°C-700°C. If it is higher than this temperature, it cannot be used due to sintering. If it is below this temperature range, it will not have a catalytic reaction. In addition, when purifying CO and NOx at the same time, a catalyst medium in which a part of rhodium is added to platinum can be used. The ratio of platinum and rhodium is preferably platinum: rhodium = 5:1-20:1, and the suitable temperature range is 300°C-500°C. Therefore, by passing combustion exhaust gas therethrough, by attaching a platinum catalytic medium to a part of the regenerator heated to 150°C to 700°C, or to attach a platinum rhodium catalytic medium to a portion heated to 300°C to 500°C, Can remove CO or HC and NOx from exhaust gas.

In the reflective melting holding furnace of this embodiment constituted as above, the pressure inside the furnace can be controlled by the following furnace pressure control system, so that instability or shaking of the furnace body and door can be suppressed.

The control of the furnace pressure of the melting holding furnace 30 can be carried out by, for example, a furnace pressure control system shown in FIG. 10 . This control system is composed of the following parts, namely, the pressure electric converter 51 for detecting the pressure in the furnace, the sensor 53 for detecting combustion conversion and outputting the combustion conversion signal, and according to the signal from the pressure electric converter 51, the opening and closing of the exhaust system 25, That is, the damper 54 for flow control, the bypass 55 of the damper 54 is arranged on the bypass 55, and the bypass 55 is opened and closed according to the combustion conversion signal, that is, the bypass damper 56 for flow control is formed. The pressure transducer 51 receives furnace internal pressure information from a pressure sensor 52 . In this control system, when the pressure in the furnace fluctuates greatly and is higher than the set value, the opening and closing of the damper 54 of the main exhaust system 25 is adapted to it. However, with the combustion conversion of the burners 21 and 22, frequent When the pressure in the furnace fluctuates slightly, use the opening and closing of the bypass 55 to adapt to it, and temporarily open the bypass damper 56 while performing the combustion conversion of the burners 21 and 22, so as to increase the exhaust gas volume in the furnace To suppress the periodic and frequent pressure fluctuations in the furnace caused by the switching of the burners 21 and 22. As shown by the dotted line in Fig. 11, the pressure fluctuation in the furnace can be suppressed by this control.

In addition, the above-mentioned embodiment is regarded as an embodiment of the present invention, however, it is not limited thereto, and various modifications can be made without departing from the scope of the concept of the present invention. For example, in this embodiment, the description is mainly made on the case where the high-temperature combustion air is connected to the burner, and even the alternate combustion using the built-in heat storage body is described, but it is not particularly limited thereto. For example, the heat storage body can also be used to The relative combustion air supply system and exhaust system are rotated, or the fluid flow direction relative to the regenerator is converted by using a flow path switching mechanism, and the combustion air preheated to a high temperature is transferred by using the exhaust heat of the high-temperature combustion exhaust It is continuously supplied to a single burner for continuous combustion. In addition, the present embodiment mainly describes the case of using gaseous fuel, but it is not limited thereto. For example, liquid fuel such as oil may also be used.

Claims (11)

1. reverberatory melting keeping furnace, use heat-accumulation combustion type burner as heating source, described burner use is burnt through the combustion air that burning and gas-exhausting is preheated to high temperature, it is characterized in that, described burner has the nozzle for jetting fuel of configured in parallel and the nozzle of the described combustion air of high velocity jet of 100m/s at least, center on these nozzles with refractory material, simultaneously ladder is set forming fuel nozzle jet end face and form between air nozzle jet end face, and the end face that makes fuel nozzle one side stretches out more forward than the end face of air nozzle one side.

2. maintenance stove according to claim 1 is characterized in that, disposes a pair of burner at least as heating source, makes the burning that hockets of this a pair of burner, to form the unfixed flame in position to evenly heating in the stove.

3. maintenance stove according to claim 2 is characterized in that, in the adjacent position, the high speed ejection combustion air with 100m/s at least becomes short distance to prevent flame and burning gases with described a pair of burner configuration.

4. maintenance stove according to claim 2 is characterized in that, described maintenance stove and accessory has: the pressure electric converter that detects furnace pressure; To burning conversion detect, with the sensor of output burning switching signal; According to from the signal of pressure electric converter and to the switching of gas extraction system, be the main air door that extraction flow is controlled; The bypass of described air door; Be arranged in this bypass, according to the burning switching signal and to the switching of this bypass, be the bypass air door that extraction flow is controlled, corresponding with the switching of bypass with the less furnace pressure change of following frequent burning conversion to cause, surpass the bigger change that sets value with the switching and the furnace pressure change of main exhaust system and absorb furnace pressure accordingly and change.

5. maintenance stove according to claim 1 is characterized in that, forms reducing atmosphere with the following high-temperature preheated air of theoretical air requirement heating object is heated.

6. maintenance stove according to claim 1 is characterized in that, carries out the preheating of combustion air with the heat storage that allows combustion air and burning and gas-exhausting alternately pass through, and the flow direction of this heat storage longshore current body is divided into a plurality of parts at least.

7. maintenance stove according to claim 6 is characterized in that, the part of a side in the close stove of the described heat storage that is divided into a plurality of parts and near the part of flow path converter one side respectively with different material formations.

8. maintenance stove according to claim 6 is characterized in that, the part of a side in the close stove of the described heat storage that is divided into a plurality of parts and near the part of flow path converter one side respectively with different structure formations.

9. maintenance stove according to claim 6 is characterized in that, makes on the described heat storage that is divided into a plurality of parts to have the exhaust gas purification catalytic media corresponding with catalytic reaction temperature range.

10. maintenance stove according to claim 6, it is characterized in that, described heat storage is contained in the cartridge type housing that has lid to be opened/closed on sidewall and links to each other with burner, can come in and go out along flow direction, and freely come in and go out by the switching of described lid perpendicular to burning gases or combustion air.

11. maintenance stove according to claim 6 is characterized in that, the dust collection of introducing by the burning and gas-exhausting of heat storage is set.

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