KR102489514B1 - Hot Air Heating System Using Low NOx Burner - Google Patents

Abstract

The present invention relates to an air-heating furnace system capable of suppressing local flames on the front part of an air-heating furnace while stabilizing flames created by a burner since the flames are practically not affected even if the flow and pressure of air for dilution flowing into the air-heating furnace change. According to the present invention, the air-heating furnace system comprises: a cylindrical air-heating furnace having a hot air outlet formed on the front end thereof and discharging hot air and a dilution air inlet formed on a side of a rear portion thereof and introducing air for dilution; a low-NOx burner installed on the rear end of the air-heating furnace; and a flame guide having a cylindrical shape of which the front and rear surfaces are opened to be installed to be extended forward from the front end of the low-NOx burner, wherein a side thereof is formed to face the dilution air inlet of the air-heating furnace to guide the air for dilution introduced through the dilution air inlet forward and backward, and the rear end thereof is arranged to be separated from the rear surface of the air-heating furnace by a prescribed distance. The air for dilution introduced through the dilution air inlet and then guided backward by colliding with the side of the flame guide flows into the internal space of the flame guide through the gap between the rear end of the flame guide and the rear surface of the air-heating furnace to be mixed in flames created by the low-NOx burner.

Description

Hot air heating system using low NOx burner {Hot Air Heating System Using Low NOx Burner}

The present invention relates to a hot stove system, and more particularly, to configure a diffuser having a multi-stage diffusion space at the end of a fuel nozzle to spread and evenly distribute combustion air, and a primary fuel nozzle disposed in the center of the diffuser and a peripheral part By sequentially supplying and burning fuel gas according to the temperature in the hot stove through a plurality of secondary fuel nozzles disposed in the hot stove, the temperature distribution and combustion reaction area in the hot stove become uniform, and the boundary of the flame disappears, making the flame invisible to the naked eye. A hot stove system using a low NOx burner capable of reducing NOx generation by enabling flameless combustion.

In general, nitrogen oxides mean NO and NO ₂ and are usually expressed as NOx (nox), which is generated in large quantities when fossil fuels are burned.

The generation of rust is affected by flame temperature, oxygen concentration and nitrogen content in fuel, but these can be changed by changing operating conditions and combustion methods to reduce rust.

NOx is fuel rust (NOx in fuel), which is produced by oxidation of components that are chemically bound to fuel during combustion, and thermal rust, which is produced by oxidizing nitrogen molecules in the combustion air when nitrogen in the combustion air is oxidized at high temperatures. (NOx at temperature), and Prompt NOx furnace, which is rapidly generated when hydrocarbon-based fossil fuel is oxidized at high temperature in a high-concentration state to generate nitrogen molecules in the combustion air, or when hydrocarbon-based fossil fuel is exposed to a high-temperature region in a high-concentration state. can be distinguished.

Among the rusts, fuel rust, which is rust in fuel, cannot be controlled by combustion technology, so the industry is concentrating on developing burners that can control thermal rust and prompt rust.

NOX is produced by the reaction of oxygen and nitrogen in the air. Oxygen and nitrogen have very low mutual reactivity at room temperature, but react with each other at high temperature (1500 ℃ or higher) to generate NO.

Therefore, since the flame surface area, which is the highest temperature area in most hot stoves, usually reaches a temperature of 1200 to 1750 ° C, this reaction (N ₂ + O ₂ = 2NO) becomes an important source of NO production.

When NO is produced in this way, the decomposition reaction rate is slow, so it does not decompose again into N ₂ and O ₂ , but reacts with oxygen again to produce NO ₂ (2NO + O ₂ = 2NO ₂ ).

This reaction is a reaction in which the rate of reaction slows down as the temperature increases.

Therefore, NO production is active at high temperatures, and when the temperature of the gas gradually decreases, the high-temperature NO is decomposed into N ₂ and O ₂ .

Therefore, in order to reduce the generation of rust, it is desirable to more uniformly supply combustion air over the whole area in the hot stove and at the same time lower the flame temperature of the burner as much as possible.

To this end, Korean Patent Registration No. 10-0784880 (Low NOx burner) is capable of simultaneously reducing the generation of Thermal NOx and Prompt NOx by implementing high-speed flame generation, rapid mixing of fuel and air, and self-recirculation of combustion gas. Korean Patent Registration No. 10-0855719 discloses that rust can be reduced by adjusting the diameter of the fuel diffusion part by installing a fuel diffusion part that is detachable at the tip of the fuel supply pipe and has a larger diameter than the diameter of the fuel supply pipe. made it possible

However, the low NOx type burner of the above registered patents has a problem in that the device is complicated and troublesome.

In addition, Korean Patent Registration No. 10-1022722 (low NOx burner) discloses an air supply pipe supplying air into a hot stove and having an inclined cross section formed at the tip thereof, a fuel supply pipe installed inside the air supply pipe and supplying fuel, the A head located on the outer circumferential surface of the front end of the fuel supply pipe, a plurality of fuel nozzles installed on the outer circumferential surface of the head, and a low NOx burner having an air supply passage for supplying air into the hot stove between the inclined end surface of the air supply pipe and the head, wherein the An air control pipe is installed between the air supply pipe and the fuel supply pipe so that the air supply amount can be adjusted by adjusting the width of the air supply passage.

This registered patent can adjust the amount of combustion air supplied into the hot stove by adjusting the width of the air supply passage, but there is a problem in that the air is not evenly distributed in the air supply pipe, so that the combustion air is not evenly supplied to the positions of each head. .

In addition, in the conventional low-NOx burner, fuel gas is injected from the central injection port and combusted through a process of mixing with combustion air, so that a high combustion temperature is maintained as a large amount of energy is released in a relatively narrow area, and thus the amount of rust is relatively increased. do.

1 is a view showing the configuration of a conventional hot stove system. The combustion system includes a hot stove 1, a burner 2 installed at a rear side of the hot stove 1, and a front end of the burner 2. It includes a mixing cone (3) to be installed.

A dilution air inlet 1b through which air for dilution is introduced is formed at one side of the rear part of the hot air furnace 1, and a hot air outlet 1a through which hot air is discharged is formed at the front end of the hot air furnace 1 to be opened. .

The burner 2 may be configured by applying a general burner or an existing low NOx burner. A combustion air inlet 2a through which combustion air flows is formed on one side of the burner 2, and a fuel nozzle through which fuel gas made of a mixed gas of LNG gas and biogas is introduced and injected into the center of the burner 2 are provided

The mixing cone 3 is formed in the form of a cone in which a plurality of holes are perforated, so that air for dilution introduced through the dilution air inlet 12 of the hot stove 10 passes through the holes of the mixing cone 3 to the burner It is supplied to the front end of (2) and burned.

The conventional combustion system having such a configuration heats the air for dilution to 800° C. or more and discharges it through the hot air outlet 1a.

However, due to fluctuations in the flow rate and pressure of the dilution air introduced through the dilution air inlet 1b of the hot stove 1, the burner flame is affected and the flame shakes toward the mixing cone 3 on the side. Due to incomplete combustion, a large amount of air pollutants such as CO and rust are generated.

In addition, the length of the flame is increased due to incomplete hot air, and the area around the hot air outlet (1a) in front of the hot air furnace (1) is locally heated, and the life of the hot air furnace (1) is greatly shortened, and the local heating causes unburned gas and nitrogen in the air. reacts, rapidly generating rust components, and there is a problem in that fuel consumption increases.

Republic of Korea Patent No. 10-0784880 Republic of Korea Patent No. 10-0855719 Republic of Korea Patent Registration No. 10-1022722

The present invention is to solve the above problems, and an object of the present invention is to stabilize the flame and at the same time stabilize the flame generated from the burner even if there are fluctuations in the flow rate and pressure of air for dilution flowing into the hot stove. It is to provide a combustion system capable of suppressing local flame generation at the front of the furnace, reducing rust by lowering the flame maximum temperature range and rapidly increasing the temperature of air for dilution and mixing it with the flame.

Another object of the present invention is to uniformly distribute the air supplied into the hot stove through the burner, to make the temperature distribution and combustion reaction area in the hot stove even, and to disappear the boundary of the flame, so that the flame is not visible to the naked eye ( An object of the present invention is to provide a hot stove system to which a low NOx burner is applied, which can remarkably reduce the amount of NOx generated by enabling flameless combustion.

In order to achieve the above object, the hot stove system according to the present invention has a hot air outlet for discharging hot air at the front end and a dilution air inlet for introducing air for dilution on the side of the rear portion. as; a low NOx burner installed at the rear end of the hot air furnace; And, the front and rear surfaces are open in the form of a cylinder and are installed to extend forward from the front end of the low NOx burner, and the side faces are formed to face the dilution air inlet of the hot stove, so that the dilution air flowing in through the dilution air inlet. A flame guide which guides the air to the front and rear, and the rear end of which is spaced apart from the rear surface of the hot stove by a predetermined distance, and after being introduced through the dilution air inlet, hits the side of the flame guide to guide it to the rear. Air for dilution may be introduced into the inner space of the flame guide through a gap between the rear end of the flame guide and the rear surface of the hot stove, and mixed with the flame generated by the low NOx burner.

A low NOx burner of a hot stove system according to the present invention includes a cylindrical burner housing having an open front surface, an air inlet into which combustion air flows, and coupled to one end of the hot stove; a diffuser that is coupled to the front end of the burner housing and spreads and sprays combustion air supplied into the burner housing into a front hot stove; The first fuel is installed so that the front end is inserted into the nozzle receiving hole of the diffuser through the center of the burner housing, and primarily injects fuel gas into the diffusion space until the temperature in the hot stove reaches a predetermined temperature. Nozzle; and a plurality of nozzles installed to pass through a periphery of the burner housing at a location spaced apart from the center of the diffuser by a predetermined distance in a radial direction, and injecting fuel gas into the hot stove when the fuel gas injection of the first fuel nozzle is finished. A second fuel nozzle; may be included.

Low NOx burner according to a preferred embodiment of the present invention, the low NOx burner is a cylindrical burner having an open front surface, an air inlet through which air for combustion is introduced, and coupled to one end of a hot stove. housing; It is coupled to the front end of the burner housing, has a nozzle accommodating hole formed at the rear of the center, has a larger diameter than the nozzle accommodating hole in front of the nozzle accommodating hole, and the rear surface communicates with the nozzle accommodating hole and the front surface communicates into the hot air furnace. A diffusion space is provided, and a plurality of inner air supply holes penetrating from the rear end of the nozzle receiving hole to the rear end of the diffusion space are arranged at regular intervals along the circumferential direction, and are arranged radially outside of the diffusion space. a diffuser in which a plurality of external air supply holes communicating with the inside of the burner housing and the hot stove are formed to pass through in the forward and backward directions; The front end is installed to be inserted into the nozzle receiving hole of the diffuser through the center of the burner housing, and the fuel gas is primarily injected into the diffusion space in an axial direction until the temperature in the hot stove reaches a predetermined temperature. a first fuel nozzle; It is installed to pass through a position spaced apart from the center of the diffuser by a predetermined distance in the radial direction through the periphery of the burner housing, and injects fuel gas axially into the hot stove when the fuel gas injection of the first fuel nozzle is finished. of the second fuel nozzle; And, a fuel supply unit connected to the rear ends of the first fuel nozzle and the second fuel nozzle to supply fuel gas to the rear end of the burner housing;
The fuel supply unit is connected to a fuel gas supply source to receive fuel gas, and a flow path control valve for supplying fuel gas to one of a first fuel nozzle and a second fuel nozzle while the flow path is switched by the control unit, and the flow control valve Including a first fuel supply pipe and a second fuel supply pipe respectively connected to the first fuel nozzle and the second fuel nozzle,
The diffusion space of the diffuser may form a multi-stage diffusion space by continuously arranging a plurality of diffusion spaces having a larger inner diameter toward the front.

The second fuel nozzle may be installed at a position further away from the outer air supply hole of the diffuser in a radial direction.

The inner diameter of the second fuel nozzle is preferably smaller than the inner diameter of the first fuel nozzle.

The low NOx burner according to the present invention is arranged at regular intervals along the circumferential direction on the outer circumferential surface of the front end of the first fuel nozzle inserted into the nozzle receiving hole, and extends spirally along the front-back direction or at a certain angle with respect to the axial direction. It may further include a plurality of swirl blades which are twisted to rotate combustion air flowing between the inner circumferential surface of the nozzle receiving hole and the outer circumferential surface of the front end of the first fuel nozzle.

The swirl blade may be integrally formed on an outer surface of a ring-shaped blade head detachably coupled to an outer circumferential surface of an end of the first fuel nozzle.

The inner air supply hole and the outer air supply hole may obliquely extend radially inward from the rear toward the front.

The diffusion space of the diffuser may form a multi-stage diffusion space when a plurality of diffusion spaces having a larger inner diameter are continuously arranged toward the front.

The individual diffusion spaces constituting the multi-stage diffusion space of the diffuser may be formed in a cone shape with an inner diameter gradually increasing from the rear to the front.

According to another aspect of the present invention, a plurality of spiral guide vanes may be installed on the side of the flame guide to guide dilution air introduced through the dilution air inlet toward the rear and circumferential direction of the flame guide.

Further, a plurality of streamlined Coanda blades may be arranged along the circumferential direction on the inner circumferential surface of the rear end of the flame guide to generate a Coanda effect of air for dilution flowing into the inner space of the flame guide.

According to the present invention, the fuel gas is injected through the first fuel nozzle in the center to primarily generate a flame, and the fuel gas is injected through a plurality of second fuel nozzles in the periphery above a certain temperature, so that the combustion area is widely distributed. As the combustion rate decreases, the combustion temperature can be lowered, and the concentration of rust proportional to the combustion temperature can be reduced.

In addition, since combustion air can be uniformly diffused through the multi-stage diffusion space formed at the center of the diffuser and reacted with the fuel gas to generate a flame, the amount of rust generation can be further reduced.

In addition, since the flame generated at the front end of the low NOx burner is surrounded by the flame guide and the dilution air introduced through the dilution air inlet is not directly mixed with the flame and flows into the internal space of the flame guide through the rear end of the flame guide, the dilution air Even if a change in flow rate and pressure occurs, the effect on the flame is minimized, preventing the flame from shaking and preventing local combustion in the hot stove.

In addition, the air for dilution introduced into the inner space of the flame guide through the rear end of the flame guide may contact the flame generated in the low NOx burner to lower the peak temperature of the flame. In particular, since the air for dilution is heated while flowing backward along the side of the flame guide and then supplied to the inside of the flame guide, rust generation can be further reduced.

1 is a cross-sectional view of a hot stove system according to the prior art.
2 is a cross-sectional view of a hot stove system according to an embodiment of the present invention.
3 is a side view showing another embodiment of a flame guide constituting a hot stove system according to the present invention.
4 is a cross-sectional view of main parts of another embodiment of a flame guide constituting a hot stove system according to the present invention.
5 is a perspective view showing an embodiment of a low NOx burner constituting a hot stove system according to the present invention.
6 is a longitudinal sectional view of the low NOx burner shown in FIG. 5;
7 is a cross-sectional view of the low NOx burner shown in FIG. 5;
8 is a front view of a diffuser constituting the low NOx burner shown in FIG. 5;
9 is a longitudinal sectional view showing a modified example of the low NOx burner shown in FIG. 5;
10 is a view showing the principle of flameless operation of a low NOx burner according to an embodiment of the present invention.
11 is a diagram showing a comparison of flame temperature changes of a flameless low NOx burner and a general flame generating low NOx burner according to the present invention.
12a is a graph showing the amount of NOx generated according to the temperature change in the hot air furnace of a general flame-generating low-NOx burner.
Figure 12b is a graph showing the amount of rust (NOx) generation according to the temperature change in the hot stove of the flameless low NOx burner according to the present invention.
13 is a cross-sectional view showing another embodiment of a diffuser constituting a low NOx burner according to the present invention.

A hot stove system according to embodiments of the present invention will be described in detail with reference to the accompanying drawings. Since the present invention can have various changes and various forms, specific embodiments will be illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to a specific form disclosed, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. Like reference numerals have been used for like elements throughout the description of each figure.

In addition, unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and unless explicitly defined in the present application, they should not be interpreted in an ideal or excessively formal meaning. don't

Referring to FIG. 2 , the hot stove system according to an embodiment of the present invention includes a hot air stove 10 for generating and discharging hot air, a low NOx burner 100 installed at the rear end of the hot air stove 10, and a low NOx burner 100. It includes a flame guide 20 for supplying air for dilution to the flame generated by the Nox burner 100 and stabilizing the flame.

In the hot air stove 10, the hot air outlet 11 through which hot air is discharged is formed to be open at the front end, and the dilution air inlet 12 through which air for dilution is introduced is formed to be opened to the side at the rear side of the hot air furnace 10. It is made in the shape of a cylinder.

The low NOx burner 100 is installed at the center of the rear surface of the hot stove 10, and mixes fuel gas and combustion air for combustion. The specific structure and operation of the low NOx burner 100 will be described in more detail later with reference to FIGS. 4 to 12 .

The flame guide 20 is made of highly heat-resistant metal, has a cylindrical shape with open front and rear surfaces, and is installed to extend forward from the front end of the low NOx burner 100 in the internal space of the hot stove 10. The front and rear ends of the flame guide 20 may be fixed to the inner surface of the hot stove 10 by means of a plurality of bar-shaped fixing members 30 .

The flame guide 20 is made of a cylinder having a smaller diameter than the diameter of the hot stove 10 and is disposed so that its side faces the dilution air inlet 12 of the hot stove 10 . In addition, the rear end of the flame guide 20 is spaced apart from the rear surface of the hot stove 10 by a predetermined distance.

Therefore, the air for dilution introduced through the dilution air inlet 12 hits the side of the flame guide 20, and some of it is induced forward and the other part is induced to the rear, and then the rear end of the flame guide 20 and the hot stove ( 10) It flows into the inner space of the flame guide 20 through the gap between the rear surfaces and is mixed with the flame generated by the low NOx burner 100.

As such, the flame generated at the front end of the low NOx burner 100 is surrounded by the flame guide 20 and the air for dilution introduced through the dilution air inlet 12 is not directly mixed with the flame, and the flame guide 20 Since it is introduced into the inner space of the flame guide 20 through the rear end, even if the flow rate and pressure of the dilution air change, the influence of the flame is minimized, the flame shakes, and local combustion in the hot stove 10 can be prevented.

The air for dilution introduced into the inner space of the flame guide 20 through the rear end of the flame guide 20 may contact the flame generated in the low NOx burner 100 to lower the maximum flame temperature. In particular, since the air for dilution is heated while flowing backward along the side of the flame guide 20 and then supplied to the inside of the flame guide 20, the generation of rust can be further reduced.

In order to allow the dilution air flowing in the rear of the flame guide 20 after being introduced through the dilution air inlet 12 to be uniformly introduced over the entire area of the rear end of the flame guide 20, shown in FIG. As described above, a plurality of spiral guide vanes 21 guiding the dilution air introduced through the dilution air inlet 12 to the rear and circumferential direction of the flame guide 20 on the rear side of the flame guide 20 can be installed

A plurality of spiral guide vanes 21 may be arranged at regular intervals along the circumferential direction. The height of the spiral guide vane 21 (radial length of the flame guide) is preferably formed to be about 20 to 30% of the distance between the outer surface of the flame guide 20 and the inner surface of the hot stove 10 in consideration of air flow. Do.

In addition, in order to stabilize the flow of air flowing into the flame guide 20, as shown in FIG. 4, air for dilution flowing into the internal space of the flame guide 20 on the inner circumferential surface of the rear end of the flame guide 20 A plurality of Coanda blades 22 streamlined to generate a Coanda effect of may be arranged along the circumferential direction. The Coanda blade 22 may have an airfoil shape in which a rear portion is convex.

5 to 8, the low NOx burner 100 includes a cylindrical burner housing 110 coupled to one end of the hot air furnace 10 and a front end of the burner housing 110. The diffuser 120, the first fuel nozzle 130 coupled to the center of the rear portion of the diffuser 120 through the central portion of the burner housing 110, and the diffuser 120 through the periphery of the burner housing 110. It includes a plurality of second fuel nozzles 140 coupled to the periphery, and a swirl member 150 coupled to the outer circumferential surface of the front end of the first fuel nozzle 130 to swirl air for combustion.

The burner housing 110 has a cylindrical shape with an open front end and is attached to the outside of the rear end of the hot stove 10 . At one side of the burner housing 110, an air inlet 112 through which combustion air is introduced into the internal space is formed to be open. The air inlet 112 is connected to an air supply device (not shown) to supply room temperature or preheated air for combustion to the internal space of the burner housing 110 .

At the rear end of the burner housing 110, a fuel supply unit 160 is installed that is connected to the rear ends of the first fuel nozzle 130 and the second fuel nozzle 140 to supply fuel gas. The fuel gas may use landfill gas (LFG, Land Fill Gas) or a mixed gas in which LFG and biogas are mixed. In addition, as a fuel gas, LNG or a mixed gas obtained by mixing LNG and biogas may be used. The fuel supply unit 160 is connected to a fuel gas supply source to receive fuel gas, and the fuel gas is supplied to the first fuel nozzle 130 and the second fuel nozzle 140 as the flow path is switched by a control unit (not shown) of the combustion system. The first fuel supply pipe 162 and the second fuel supply pipe 162 connecting the flow control valve 161 to the first fuel nozzle 130 and the second fuel nozzle 140, respectively. A fuel supply pipe 163 may be included.

The diffuser 120 forms a flame ignition area in the front center so that fuel gas and combustion air react to facilitate the formation of flame, and has a function of guiding the flame generated as the fuel gas and combustion air are combusted forward. do.

The diffuser 120 may be made of high-temperature refractory cement. A nozzle accommodating hole 121 into which the front end of the first fuel nozzle 130 is inserted is formed at the rear of the center of the diffuser 120, and a plurality of diffusers having larger inner diameters are formed in front of the nozzle accommodating hole 121. A multi-stage diffusion space 122 in which spaces 122a and 122b are continuously arranged is formed to open forward. In addition, a plurality of inner air supply holes 123 penetrating from the rear end of the nozzle accommodating hole 121 to the rear end of the multi-stage diffusion space 122 may be arranged at regular intervals along the circumferential direction. In addition, a plurality of external air supply holes 124 communicating with the inside of the burner housing 110 and the hot air furnace 10 are formed radially outside the multi-stage diffusion space 122 to pass through in the forward and backward directions.

Therefore, part of the air introduced into the burner housing 110 through the air inlet 112 of the burner housing 110 is transferred to the space between the inner circumferential surface of the nozzle receiving hole 121 and the outer circumferential surface of the first fuel nozzle 130 and the above The air is supplied to the inside of the multistage diffusion space 122 through the inner air supply hole 123, and the remaining part of the air is supplied to the inside of the hot stove 10 through the outer air supply hole 124.

The individual diffusion spaces 122a and 122b constituting the multi-stage diffusion space 122 of the diffuser 120 may each have a constant diameter, but as shown in FIGS. 6 and 7, each individual diffusion space ( 122a, 122b) may have a cone shape with an inner diameter gradually increasing from the rear to the front.

As described above, when the multi-stage diffusion space 122 of the diffuser 120 has a cone shape, combustion air supplied to the inside of the multi-stage diffusion space 122 through the swirl member 150 and the inner air supply hole 123 Uniform diffusion can be achieved by flowing forward while turning smoothly.

In addition, the inner air supply hole 123 and the outer air supply hole 124 may extend parallel to the axial direction, but as shown in FIG. 9, the inner air supply hole 123 and the outer air supply hole 124 are It may have a structure that obliquely extends radially inward from the rear toward the front.

In addition, the diffuser 120 has a plurality of holes 125 for accommodating an ignition device 171 such as a pilot burner installed through the burner housing 110 and a flame detection device 172 such as an ultraviolet detector in a multi-stage diffusion space. (122) and may be formed in communication.

The first fuel nozzle 130 is made of metal having excellent heat resistance, and is installed so that the front end is inserted into the nozzle receiving hole 121 of the diffuser 120 through the center of the rear surface of the burner housing 110 . The first fuel nozzle 130 generates a flame by primarily injecting fuel gas into the multi-stage diffusion space 122 of the diffuser 120 until the temperature in the hot stove 10 reaches a predetermined temperature. .

The outer diameter of the front end of the first fuel nozzle 130 is smaller than the inner diameter of the nozzle receiving hole 121 so that combustion air flows between the outer circumferential surface of the front end of the first fuel nozzle 130 and the inner circumferential surface of the nozzle receiving hole 121. space is created.

As the combustion air flowing through the space between the inner circumferential surface of the nozzle accommodating hole 121 and the outer circumferential surface of the front end of the first fuel nozzle 130 is introduced into the multi-stage diffusion space 122, the fuel gas and combustion air are further supplied. In order to ensure uniform mixing, a swirl member 150 is installed between the inner circumferential surface of the nozzle receiving hole 121 and the outer circumferential surface of the front end of the first fuel nozzle 130 .

The swirl member 150 includes a ring-shaped blade head 151 detachably coupled to the outer circumferential surface of the front end of the first fuel nozzle 130, and a plurality of swirls integrally formed on the outer surface of the blade head 151. A blade 152 may be included. The swirl blade 152 spirally extends along the front-back direction or is formed to be twisted at a certain angle with respect to the axial direction, and the combustion flows between the inner circumferential surface of the nozzle receiving hole 121 and the outer circumferential surface of the front end of the first fuel nozzle 130. It functions to spread the air uniformly while turning it.

At this time, in order to stabilize the air flow by generating a Coanda effect in which combustion air guided along the swirl blade 152 flows along the surface of the swirl blade 152, the swirl blade 152 has a rear portion It may have a convex airfoil shape. That is, each of the plurality of swirl blades 152 may have an airfoil shape in which a leading edge is formed at the rear end and a trailing edge is formed at the front end.

When the swirl blade 152 is formed on the ring-shaped blade head 151 that can be attached to and detached from the outer circumferential surface of the first fuel nozzle 130, the first fuel nozzle 130 itself is not processed, and a separate swirl member ( 150), the swirl member 150 can be attached and detached from the first fuel nozzle 130 as needed, so it is very easy to manufacture and use.

The second fuel nozzle 140 is installed to penetrate the periphery of the diffuser 120 through the periphery of the burner housing 110, that is, a position spaced apart from the center of the diffuser 120 by a predetermined distance in the radial direction, so that the first fuel nozzle When the fuel gas supply in 130 is finished, the fuel gas is injected into the hot stove 10 . The second fuel nozzle 140 is preferably disposed further away from the outer air supply hole 124 of the diffuser 120 in the radial direction. In addition, the second fuel nozzle 140 preferably has a diameter smaller than that of the first fuel nozzle 130 so as to inject a jet of fuel gas into the hot stove 10 .

In this embodiment, two second fuel nozzles 140 are installed close to the edges of both sides of the diffuser 120, so that the oxygen concentration in the hot stove 10 is low (approximately 3% or less) and the concentration of the incombustible diluent is high. By injecting fuel gas directly into the combustion gas recirculation zone as a high-speed jet, flameless operation is possible. Flameless operation is an operation state in which the temperature distribution and combustion reaction area in the hot stove 10 become uniform and the flame boundary disappears, making the flame invisible to the naked eye. Phosphorus flames are not visible.

Referring to FIG. 10, since the fuel gas injected as a high-speed jet by the second fuel nozzles 140 on both sides is mixed with combustion air and recirculation combustion gas at a temperature lower than the ignition point of the fuel gas, the fuel gas and combustion air forms a reaction zone and is sufficiently mixed before flame is generated. The fuel gas injected from the second fuel nozzle 140 consumes oxygen in the hot stove 10 while reacting with oxygen (concentration less than 3%) of the recirculated combustion gas.

Under these flameless operating conditions, NOx (nox) generation is significantly reduced (see the graphs of FIGS. 11 and 12a and 12b), which is due to the mixture of the reactant and non-flammable diluent, the flame is small, the combustion temperature is low, and the combustion area is because it expands In addition, since the fuel gas is not concentrated in the center but dispersed in multiple locations around the periphery, there is no flame front, which is a major area for NOx formation, and the reaction rate of nitrogen can be relatively reduced by lowering the concentration of oxygen in the flame.

A hot stove system having such a configuration operates as follows.

Combustion air introduced through the air inlet 112 of the burner housing 110 of the low NOx burner 100 passes between the inner circumferential surface of the nozzle receiving hole 121 at the center of the diffuser 120 and the outer circumferential surface of the first fuel nozzle 130. It is supplied to the inside of the multi-stage diffusion space 122 through the space and the inner air supply hole 123. At this time, the combustion air introduced into the space between the inner circumferential surface of the nozzle receiving hole 121 and the outer circumferential surface of the first fuel nozzle 130 turns while passing through the swirl blade 152, and a swirling flow is generated inside the multi-stage diffusion space 122. Thus, it can be uniformly mixed with the fuel gas supplied through the first fuel nozzle 130. In addition, the multi-stage diffusion space 122 has a larger diameter when the individual diffusion spaces 122a and 122b are disposed in the front, so that the combustion air flows forward and diffuses more smoothly, so that the mixture with the fuel gas is uniform. As this is done, flames may be generated, which has a beneficial effect on reducing rust.

At this time, a flame is generated while a predetermined amount of combustion air is injected through the external air supply hole 124 of the diffuser 120 .

As fuel gas is supplied through the first fuel nozzle 130 and combustion air is supplied through the diffuser 120, a flame is generated. (For example, 500 ~ 700 ℃), the control unit switches the flow control valve 161 of the fuel supply unit 160 to cut off the supply of fuel gas to the first fuel nozzle 130, and a plurality of second fuel A flow path is controlled to supply fuel gas to the nozzle 140 . The temperature at which the fuel gas is supplied through the second fuel nozzle 140 is a temperature slightly lower than the ignition temperature of the fuel gas, which is before the fuel gas creates a flame, that is, before the fuel gas reacts with the combustion air. This is to sufficiently mix oxygen (O ₂ ) in the combustion gas inside, air for combustion, and fuel gas.

The fuel gas supplied through the plurality of second fuel nozzles 140 is sprayed to the combustion gas recirculation zone in the periphery of the hot stove 10 to perform a flameless operation. At this time, in the course of combustion of the fuel gas injected through the second fuel nozzle 140, residual oxygen in the combustion gas circulating around the hot stove 10 reacts and consumes oxygen, so flameless combustion can proceed. there is. The amount of rust generated can be remarkably reduced by the flameless operation as described above.

On the other hand, in the process of flame operation and non-flame operation (fine flames exist even if there is no flame) through the low NOx burner 100, air for dilution is passed through the dilution air inlet 12 of the hot stove 10 is introduced into the hot stove 10.

The air for dilution introduced through the dilution air inlet 12 hits the side of the flame guide 20 and then diverges forward and backward. It is introduced into the flame guide 20 through the space between the end and the rear surface of the hot stove 10 and comes into contact with the flame generated at the front end of the low NOx burner 100 to help combustion.

As described above, in the low NOx burner 100 constituting the hot stove system of the present invention, fuel gas is injected through the first fuel nozzle 130 in the center to primarily generate a flame, and at a certain temperature or higher, the peripheral area As the fuel gas is injected through the plurality of second fuel nozzles 140 and the combustion area is widely distributed, the combustion speed is reduced, thereby lowering the combustion temperature and reducing the concentration of rust proportional to the combustion temperature.

In addition, since combustion air can be uniformly diffused through the multi-stage diffusion space 122 formed in the center of the diffuser 120 and reacted with the fuel gas to generate flame, the amount of rust can be further reduced.

13 shows a diffuser 120 of a low NOx burner 100 according to another embodiment of the present invention. It further includes a mesh member 180 made of a cylindrical mesh to be attached.

The mesh member 180 is made of a cylindrical mesh made of a heat-resistant metal material, and additionally generates a vortex in the swirling flow of the combustion air flowing into the multi-stage diffusion space 122 to further increase the combustion air. In addition to enabling uniform mixing, it acts to further reduce the occurrence of rust by absorbing thermal energy.

The mesh member 180 may have a mesh structure in which hollow tubes are woven horizontally and vertically, and may be configured to absorb heat energy more effectively by filling the hollow tube with a phase change material that absorbs heat and changes phase.

Although the detailed description of the present invention described above has been described with reference to preferred embodiments of the present invention, those skilled in the art or those having ordinary knowledge in the art will find the spirit of the present invention described in the claims to be described later. And it will be understood that the present invention can be variously modified and changed without departing from the technical scope.

10: hot air furnace 11: hot air outlet
12: dilution air inlet 20: flame guide
21: spiral guide vane 22: Coanda blade
30: fixing member 100: low NOx burner
110: burner housing 112: air inlet
120: diffuser 121: nozzle receiving hole
122: multi-stage diffusion space 123: inner air supply hole
124: external air supply hole 130: first fuel nozzle
140: second fuel nozzle 150: swirl member
160: fuel supply unit 171: ignition device
172: flame detection device 180: mesh member

Claims (12)

A tubular hot air furnace having a hot air outlet through which hot air is discharged at the front end and a dilution air inlet through which air for dilution flows into the rear side of the hot air furnace;
a low NOx burner installed at the rear end of the hot air furnace;
The front and rear surfaces are open in the form of a cylinder and are installed to extend forward from the front end of the low NOx burner, and the side faces the dilution air inlet of the hot stove, so that dilution air flows in through the dilution air inlet. A flame guide which guides the front and rear, and the rear end is disposed to be spaced apart from the rear surface of the hot stove by a predetermined distance;
Including,
Air for dilution introduced through the dilution air inlet and then hit the side surface of the flame guide and is induced rearward is introduced into the internal space of the flame guide through the gap between the rear end of the flame guide and the rear surface of the hot air furnace, and is generated in a low NOx burner. mixed with the flame that becomes
The low NOx burner,
a barrel-shaped burner housing having an open front surface, an air inlet into which combustion air flows, and coupled to one end of the hot stove;
It is coupled to the front end of the burner housing, has a nozzle accommodating hole formed at the rear of the center, has a larger diameter than the nozzle accommodating hole in front of the nozzle accommodating hole, and the rear surface communicates with the nozzle accommodating hole and the front surface communicates into the hot air furnace. A diffusion space is provided, and a plurality of inner air supply holes penetrating from the rear end of the nozzle receiving hole to the rear end of the diffusion space are arranged at regular intervals along the circumferential direction, and are arranged radially outside of the diffusion space. a diffuser in which a plurality of external air supply holes communicating with the inside of the burner housing and the hot stove are formed to pass through in the forward and backward directions;
It extends forward through the center of the burner housing, and the front end is installed to be inserted into the nozzle receiving hole of the diffuser to axially feed the fuel gas into the diffusion space until the temperature in the hot stove reaches a predetermined temperature. A first fuel nozzle that primarily injects;
It extends forward through the periphery of the burner housing and is installed to pass through a position spaced apart from the center of the diffuser by a predetermined distance in the radial direction, and when the fuel gas injection of the first fuel nozzle is completed, the fuel gas is axially directed into the hot stove. A plurality of second fuel nozzles for injecting; and,
a fuel supply unit connected to the rear ends of the first fuel nozzle and the second fuel nozzle to supply fuel gas to the rear end of the burner housing;
including,
The fuel supply unit is connected to a fuel gas supply source to receive fuel gas, and a flow path control valve for supplying fuel gas to one of a first fuel nozzle and a second fuel nozzle while the flow path is switched by the control unit, and the flow control valve Including a first fuel supply pipe and a second fuel supply pipe connected to the first fuel nozzle and the second fuel nozzle, respectively,
The diffusion space of the diffuser forms a multi-stage diffusion space by continuously arranging a plurality of diffusion spaces having larger inner diameters toward the front. delete The hot stove system of claim 1, wherein the second fuel nozzle is installed at a position more distant from the outer air supply hole of the diffuser in a radial direction. The hot stove system according to claim 3, wherein an inner diameter of the second fuel nozzle is smaller than an inner diameter of the first fuel nozzle. The method of claim 1, wherein the low NOx burner,
Arranged at regular intervals along the circumferential direction on the outer circumferential surface of the front end of the first fuel nozzle inserted into the nozzle accommodating hole, extending spirally along the front-back direction or twisted at a certain angle with respect to the axial direction, the inner circumferential surface of the nozzle accommodating hole and a plurality of swirl blades for swirling combustion air flowing between the outer circumferential surface of the front end of the first fuel nozzle;
A hot stove system further comprising a. The hot stove system of claim 5, wherein the swirl blade is integrally formed on an outer surface of a ring-shaped blade head detachably coupled to an outer circumferential surface of an end of the first fuel nozzle. The hot stove system of claim 1, wherein the inner air supply hole and the outer air supply hole obliquely extend inward in a radial direction from the rear toward the front. delete The hot stove system of claim 1, wherein the individual diffusion spaces constituting the multi-stage diffusion space of the diffuser have a cone shape with inner diameters gradually increasing from the rear to the front. The hot stove system of claim 1, wherein a mesh member made of a cylindrical mesh made of metal is attached to an inner circumferential surface of the diffusion space of the diffuser. The hot stove system according to claim 1, wherein a plurality of spiral guide vanes are installed on the side of the flame guide to guide the dilution air introduced through the dilution air inlet toward the rear and circumferential direction of the flame guide. The method of claim 1, wherein a plurality of Coanda blades in the form of an airfoil with a convex rear portion are formed on the inner circumferential surface of the rear end of the flame guide to generate a Coanda effect of air for dilution flowing into the internal space of the flame guide. Arranged along the hot stove system.

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