WO1987002756A1

WO1987002756A1 - Radiant tube burner

Info

Publication number: WO1987002756A1
Application number: PCT/JP1986/000550
Authority: WO
Inventors: Yasushi Yoshida; Nobuyoshi Oomori; Kaneaki Hyodo; Kenji Atarashiya; Norihisa Shiraishi; Toshiyuki Hashime
Original assignee: Nihon Nensho System Kabushiki Kaisha; Mitsubishi Jukogyo Kabushiki Kaisha; Kawasaki Seitetsu Kabushiki Kaisha
Priority date: 1985-10-31
Filing date: 1986-10-30
Publication date: 1987-05-07
Also published as: EP0243506A1; AU6594086A; DE3674198D1; AU573109B2; EP0243506A4; EP0243506B1

Abstract

A radiant tube burner generating only a reduced amount of NOx, composed of an axially movable gas burner element disposed in a combustion tube concentrically therewith and having a flame dispersing nozzle at the tip thereof, a primary air swirling vane fixed to said tip and adapted to form a swirling flame, and an air regulating damper fitted into a primary air supply tube connected to the combustion tube and adapted to regulate the ratio of the primary air to the secondary air, whereby mild two-step combustion can be carried out in the radiant tube.

Description

Description Name of Invention

Radiant tube tube

Technical field

According to the present invention, a nozzle of a gas parner is concentrically directed to a combustion cylinder provided in a radiant tube, and fuel gas ejected from the gas parner is supplied through a rectangular space between the gas parner and the combustion cylinder. The present invention relates to a radiant tube parner in which primary twisting is performed by primary air, and secondary combustion is performed by secondary air supplied through an annular space between the combustion tube and the radiant tube. It relates to a radiant tube parner to be used in heat treatment furnaces that can reduce the amount of NOx contained in the flue gas discharged from the tube.

Background art

Conventionally, in a radiant tube parner of the type described above, in order to suppress the generation of NOx, for example, a damper is provided at an inlet of the primary air supplied into the combustion cylinder, thereby forming a primary air and a secondary air. An adjustable ratio has been proposed. (Japanese Journal Review 52-21036)

However, it was found that simply adjusting the ratio of primary air to secondary air did not sufficiently reduce the generation of NOx.

According to Japanese Patent Publication No. 52-29007, in order to suppress the generation of NOx in other known radiant tube parners, a flame formed by burning a parner is provided by providing a steam pipe inside the fuel gas nozzle. It has been proposed to lower the flame temperature by blowing steam into it.

Thus, compared to the case of steam injection and the case of spraying water, spraying water has a higher effect of lowering the flame temperature and a higher effect of reducing NOx. However, there is a drawback that the spray particle size becomes large, so it is predicted that the radiant tube will be adversely affected and the flame will be unstable. Was considered.

Disclosure of the invention

An object of the present invention is to achieve good and stable combustion by performing high-load combustion in a swirling flow of primary air, and to achieve a low NOx by performing a soft two-stage firing in a radiant tube. In providing bupanah! ). In order to achieve this object, according to the present invention, a nozzle configured as a flame dispersion type nozzle is configured to be movable in the axial direction, and a swirl vane is provided on the outer periphery thereof. It is equipped with an air adjustment damper for adjusting the ratio of the secondary air.

Another object of the present invention is to perform good and stable twisting by performing high-load combustion in a swirling flow of the primary air, to perform soft two-stage combustion in a radiant tube, and to spray mist into the combustion flame. An object of the present invention is to provide a radiant tube burner that can achieve low NOx by lowering the flame temperature by adding water. ,

In order to achieve this object, according to the present invention, the central port of a nozzle configured as a flame dispersion type nozzle is a water spray nozzle, and the nozzle is pressurized via an additive water transfer pipe provided inside a gas parner. It is connected to an atomizing water generator that can supply gas and additive water.

Further, as another advantageous means according to the present invention, an atomizing water generator is provided with a cylinder having a conical hole to be connected to the additive water transfer pipe, a pressurized gas to be fitted into the cylinder, and additive water. It is composed of a concave disk having a blow groove, and a housing containing these cylinders and a disk.

Still another object of the present invention is to perform good and stable combustion by performing high-load combustion with a swirling flow of primary air, perform soft two-stage natural combustion in a radiant tube, and perform combustion in a combustion flame. The purpose of the present invention is to provide a radiant tube parner that can achieve low NOx by adding flame atomization water to lower the flame temperature and blowing twisted exhaust gas as atomizing medium into the center of twisting gas. . To achieve the above object, according to the present invention, the central port of a nozzle configured as a flame dispersion type nozzle is a water spray nozzle, and the nozzle is supplied via an additive water transfer pipe provided inside a gas parner. It is connected to an atomized water generator that can supply compressed gas, low-pressure gas and added water.

Further, as another advantageous means according to the invention, a water outflow nozzle is installed at the center of the flame dispersion type nozzle in order to spray water from the additive water transfer pipe by the injection energy of the low pressure fuel gas.

Further, as still another advantageous means according to the present invention, in order to spray water from the re-supplying water transfer pipe by means of low-pressure combustion exhaust gas injection energy, the exhaust gas introduction cylinder and the water outflow nozzle are provided with a flame dispersion type nozzle. Installed in the center.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is an axial sectional view showing an embodiment of a radiant tube parner according to the present invention. 2 and 3 are a front view and a cross-sectional view of a flame dispersion type nozzle in this burner. 4 and 5 are a longitudinal sectional view and a front view of the same primary air swirling vane as before. FIG. 6 is a diagram showing the NOx reduction effect of the radiant tube parner of the present invention in relation to the maximum temperature of the radiant tube and the amount of generated NOx. FIG. 7 is an axial sectional view showing a second embodiment of the radiant tube parner according to the present invention. Fig. 8 is a vertical cross-sectional view of the flame dispersion type nozzle in this wrench. 9 and 10 are an exploded perspective view and an assembled sectional view of a main part of the same atomized water generator as before. Figure 11 is an illustration of atomized water generation. FIG. 12 is an axial sectional view showing a third embodiment of the radiant tube parner according to the present invention. FIG. 13 is a longitudinal sectional view of a flame dispersion type nozzle in the present wrench. Fig. 14 is a drawing showing only a main part of a fourth embodiment of a radiant tube parner according to the present invention, which employs a low pressure fuel gas conversion system, in a cross-sectional view. FIG. 15 is a drawing showing a cross section of only a main part of a fifth embodiment of a radiant tube parner according to the present invention which employs an atomization method using low-pressure twisting flue gas. FIG. 16 is a diagram showing the relationship between the amount of added water and the NOx reduction rate in the radiant tube burner of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

In FIG. 1 showing a first embodiment of the present invention, a gas parner 1 is provided with a flame-dispersing nozzle 3a (FIGS. 2 and 3) which protrudes into a firing tube 2 provided concentrically around the parner 1. 3), and a gas connection pipe 4 is connected to the rear end of the burner 1. The rear of the combustion liner 2, the primary air supply tube concentrically surrounding the same manner the PANA 1 5: is continued: Iteori, that has four rectangular primary air inlet 6 over the circumference _σ Kono 'inlet 6 The flow cross-sectional area can be changed via the operating rod 8 and the nut 9 by the short cylindrical air adjusting damper 7 slidably fitted on the supply cylinder 5. As shown in FIGS. 4 and 5, a primary air swirling blade 10 having an angle of 15 to 60 ° is fixed on a tip end of the burner 1 via a holding cylinder 11. A radiant tube 12 extends concentrically around the natural firing cylinder 2 and the primary air supply cylinder 5, and an air supply connection pipe 13 is connected to a rear area where the inflow port 6 is located. The primary air supply tube 5 and the radiant tube 12 are closed at the rear end by an end wall 14, and the gas parner 1 extends 'backwardly' through the end wall 14,. The reference numeral 15 denotes a pilot wrench, and the gas wrench 1 penetrates the end wall 14 so as to be movable in the axial direction within the combustion cylinder 2 together with the pit mouth wrench 15. It is supported in the combustion cylinder 2 via the swirl vanes 10 so that the position can be changed.

The setting position L of the flame dispersing nozzle 3a can be changed within a range of 100 to 500 mm, and the position setting is performed by a bolt 16 attached to the end wall 14.

Next, the operation of the radiant tube parner according to the first embodiment of the present invention will be described. In FIG. 1, the twist gas supplied to the gas parner 1 via the connection pipe 4 is supplied from the flame dispersion type nozzle 3a. The jet is dispersed into the combustion cylinder 2 at an injection angle of up to 60 ° within an ejection speed of 10 to 100 m / sec. Jetted fuel gas is stirred with primary air Ci is pivoted Runin vital swirl vane 10 through the inflow port ^{6, 500 X 10 4 kcal /} m 3 1,000 from ^{^{-h X 10 4 kcal / m 3}} - The primary reduction firing is performed under a high load in the range of h, and this primary firing gas is axially 10 m / sec to 30 m / sec

New paper It gushes at a flow rate in the range. The secondary air C ₂ (90 to 50%) distributed to the primary air d (10 to 50%) at a fixed ratio by the air conditioning damper 7 is supplied between the combustion tube 2 and the radiant tube 12. The annular passage is jetted at a lower speed than the primary combustion gas while cooling the combustion cylinder. The difference in kinetic energy secondary air C ₂ and the primary combustion gas having respectively, two 'next air C ₂ flows along the inner side of the radiant tube 12, gas is without localized heating at the interface of the primary combustion gas The generation of NOx is controlled by the secondary twisting.

Next, in the actual 7-inch (17.5 cm) radiant tube parner according to the first embodiment of the present invention, what was generally burned at 110,000 kcal / h was burned at 145,000 kcal / h. By changing the setting position of the flame dispersion type nozzle 3a and the ratio between the secondary air and the secondary air, the NOx can be reduced to 80 to 50 ppm, and the residual in the exhaust gas can be reduced. %, Good combustion without any unburned matter such as soot and carbon monoxide is performed without incomplete twisting, and turndown can be reduced to 1/10 or less. Even when the fuel gas is set to 100% and the fuel gas is set to 10%, stable twisting is performed without blowing out.

Moreover, even with respect to the tube temperature, which is an important condition of the radiant tube burner, the difference between the maximum temperature and the minimum temperature in the circumferential direction can be uniformed within 10 ° C due to the turning of the flame. The difference between the maximum temperature and the minimum temperature in the furnace can be kept within 150 ° C in the direction, and the maximum tube temperature is 1,050 ° C or less, so the radiant tube has a long service life. It became possible to make it a value.

The NOx reduction effect of the radiant tube parner according to the present invention described above is shown by the relationship between the radiant tube maximum temperature and the amount of NOx generated in FIG. As is clear from the above, the radiant tube parner according to the present invention has an NOx reduction effect of about 30% as compared with the conventional radiant tube parner.

Next, in FIG. 7 showing a second embodiment of the present invention, the same parts as those in FIG. 1 are denoted by the same reference numerals. 7 and 8, the gas burner 1 has a flame dispersing nozzle 3a protruding into a combustion cylinder 2 provided concentrically around the burner 1, and a gas A connecting pipe 4 is connected, and a primary air supply pipe 5 for concentrically sealing the burner is continuously formed behind the combustion tube 2, and four primary air supply pipes are provided around the primary air supply pipe 5. A primary air inlet 6 is drilled. Further, a primary air swirl vane 10 having an angle of 15 to 60 ° is fixed on a tip end of the gas parner 1 through a holding cylinder (not shown), and the combustion cylinder 2 and the primary air supply pipe 5 A radiant tube 12 is provided on the outer periphery, and the primary air supply pipe and the radiant tube are each closed at an end wall via a flange 14, and the gas panner 1 extends through the end wall. '

At the center of the flame dispersing nozzle 3a screwed at the tip of the gas parner 1, as shown in FIG. 8, a water spray nozzle 18 communicating with the additive water transfer pipe 17 in the parner and the surrounding area. A plurality of gas outlets 19 communicating with the gas connection pipe 4 are provided at the bottom. In addition, an air supply pipe 13 is connected to the rear of the radial tube 12, and supply pipes 20 and 21 for pressurized gas and added water are connected to the rear end of the added water transfer pipe. A water generator 22 is attached.

As shown in FIGS. 9 and 10, the atomized water generator 22 has a disk 24 having a circular recess 23 and a conical hole 25 at the center which gradually decreases from a diameter corresponding to the recess. In addition, the same cylinder 26 as the disk is coaxially fitted and integrally formed, and this is incorporated into a housing 27. In this case, the disk 24 is pressed by a plug 28. The cylinder 26 is connected to the additive water transfer pipe 17, and an atomized water generation chamber 29 is formed by fitting the disk and the cylinder. On the end face of the disk 24, which is closer to the cylinder 26, there are provided blowing grooves 30, 31 for introducing the pressurized gas and the hydration fluid tangential to the recess 23 in a direction perpendicular to the central axis. These grooves are connected to the pressurized gas supply pipe 20 and the added water supply pipe 21, respectively. Next, the operation of the radiant tube parner according to the second embodiment of the present invention will be described. In FIG. 7, the fuel gas supplied to the gas parner 1 via the connection pipe 4 is supplied from the flame dispersion type nozzle 3a.噴 When the gas is jetted into the firing cylinder 2, the gas flows in through the inlet 6, and is stirred with the primary air Ci swirled by the primary air swirling blades 10 to perform reduced primary combustion under high load. The fuel is ejected from the combustion cylinder 2, which is exactly the same as the first embodiment described above.

On the other hand, the secondary air C ₂ distributed at a constant ratio to the primary air Ci by the air adjusting damper 7 as shown in FIG. 1 forms the annular passage between the combustion tube 2 and the radiant tube 12 as described above. It flows along the inside of the tube while cooling the combustion tube, and sequentially burns secondary without heating locally at the boundary of the primary combustion gas. The atomized water obtained by the atomized water generator 22 as shown in FIG. 10 and FIG. 11 is supplied to the water spray nozzle at the center of the flame dispersion type nozzle 3a in the flame of the secondary burning. The NOx is suppressed by lowering the temperature of the flame by jetting it out of 18; in this case, the foam of the atomized water that is jetted out depends on the gas pressure in the foam and the twisting cylinder. The thickness of the foam is extremely thin, for example, Ο.ΐμπι or more, and the ruptured foam fragments become very fine. The water particles deprive the flame of latent heat of vaporization and lower the flame temperature, thereby significantly reducing NOx emissions.

Next, in FIGS. 12 and 13 showing a third embodiment of the present invention, the same parts as those in FIGS. 7 and 8 are denoted by the same reference numerals. The difference from the example is that the nozzle is configured as a flame-dispersed nozzle 3b.In the second embodiment, atomized water is added to the combustion flame, whereas in the present embodiment, the atomized water is centered on the fuel gas. The combustion exhaust gas is blown as a medium.

The operation of the radiant tube parner according to the third embodiment of the present invention is the same as that of the second embodiment, except that the nozzle is the flame dispersion type nozzle 3b, and therefore, the description is omitted. I do. Next, a modified embodiment of the third embodiment of the present invention relates to an atomization system using a fuel gas having a low pressure, and as shown in FIG. 14, a combustion cylinder provided concentrically around a gas burner 1. A water outflow nozzle 32 is provided at the center of the flame dispersion type nozzle 3b protruding into 2, and a gas swirl vane 33 is provided in an annular space formed by the water outflow nozzle and the exhaust gas nozzle. The angle of the gas swirl vane is set in the range of 15 to 40 °. '

Next, as shown in FIG. 14, a gas tube 4 is used to change the gas gun tube 4 from the gas gun tube 4, as shown in FIG. The fuel gas G introduced into the tank 1 is picked up in the direction of the arrow, and is turned into a high-speed swirling flow by the gas swirling vanes 33. On the other hand, the added water transfer pipe 17 ( (Fig. 13 and Fig. 13) The water introduced into the water is picked up in the direction of the arrow and flows out of the water outflow nozzle 32. In this case, the fuel W is discharged from the water outflow nozzle by the injection energy of the fuel gas. Spray.

As described above, since water is sprayed by the fuel gas, the spray water and the twisting gas are well mixed, and the effect of adding water is increased, thereby making it possible to significantly reduce the generation of NOx. '

Next, a modification of the third embodiment of the present invention relates to an atomization method using low-pressure exhaust gas. As shown in FIGS. 14 and 15, water is discharged to the center of the flame-dispersed nozzle 3b. An exhaust gas introduction tube 34 for spraying water from a nozzle 32, and an addition water transfer pipe 17 provided at a center-center portion of the introduction tube, an annular space formed by the water outflow nozzle and the exhaust gas nozzle. Is equipped with exhaust gas swirl vanes 35, and the blade angle is set in the range of 15 to 40 °.

Next, as shown in FIG. 15, in a radiant tube parner which is a modification of the third embodiment of the present invention which employs an atomization method using low-pressure combustion exhaust gas, the exhaust gas G ′ is formed by exhaust gas swirling blades 35 as shown in FIG. A high-speed swirling flow causes the water W flowing out of the water outflow nozzle 32 to be sprayed, and the sprayed water is mixed with the fuel gas G from the flame-dispersing nozzle 3b by the high-speed swirling flow of exhaust gas (WG), and is mixed with the exhaust gas. Mixing of twisting gas and The fuel gas and the spray water are rapidly mixed, and the flame temperature is reduced due to the uniformization of the flame temperature due to the delay in combustion of the fuel gas and the absorption of the latent heat of the spray water vapor, which significantly increases the generation of NOx. It becomes possible to reduce.

In the radiant tube burner which includes the two modifications of the third embodiment, the atomizing method is used in the range of 2 to 6 kg / cm ² under pressure (air, steam, inert gas). And low-pressure gas (twisting gas, flue gas, etc.) in the form of atomization in the range of 300 to l, 000 mmAq.

Next, the NOx reduction rate by adding water with the radiant tube parner according to the present invention including the third and fourth embodiments is shown by the relationship between the amount of added water and the NOx reduction rate in FIG. is there. '

The operating conditions of the radiant tube parner of the present invention described above are

Fuel COG 4,500 kcal / Nm3

Burning amount 145,000 kcal / h

Combustion air temperature 400 ° C

Residue in exhaust gas 02 4%

Radiant tube 7 inch W type

The NOx reduction rate (%) was monitored by gradually increasing the amount of water added.

As is evident from these results, the addition of water to the radiant tube burner according to the present invention has the effect of reducing NOx, and the maximum tube temperature is also reduced. It became possible to do.

Industrial applicability

As described above, the radiant tube burner according to the present invention is a furnace in which it is not appropriate to burn fuel gas in the furnace, that is, a non-oxidizing furnace, a heat treatment using an atmospheric gas, and an indirect heating of a material to be heated. It has a remarkable effect when used in heat treatment furnaces and the like, and can be used in furnaces of the above types in various technical fields such as metal industry, ceramic industry, glass industry, chemical industry, paper fiber industry, food industry, etc. .

Claims

The scope of the claims

1. With the nozzle of the gas burner concentrically facing the combustion cylinder provided in the radiant tube, the primary air that is supplied with the fuel gas ejected from the gas burner through the annular space between the gas parner and the combustion cylinder Primary combustion, and secondary combustion by secondary air supplied through an annular space between the twisting cylinder and the radiant tube,

A gas burner having a flame dispersing nozzle at a tip that can move in the axial direction to be concentrically arranged in the fuel cylinder;

A primary air swirl vane forming a swirl flame fixed on the tip of the parner, and a ratio of primary air to secondary air fitted to a primary air supply cylinder connected to the twisting cylinder is adjusted. A radiant tube parner having an air adjusting damper.

2. The radiant tube according to claim 1, wherein the secondary air (90-50%) is distributed at a constant ratio to the primary air Ci (10-50) by an air conditioning damper. ', Pana.

3. The radiant tube parner according to claim 1, wherein the setting position L of the flame dispersion type nozzle is set in a range of 100 to 500 mm.

4. Primary air supplied through the annular space between the gas parner and the combustion cylinder, with the nozzle of the gas parner concentrically facing the combustion cylinder provided in the radiant tube. Primary combustion, and secondary combustion by secondary air supplied through an annular space between the twisting cylinder and the radiant tube,

The center port of the flame-dispersed nozzle screwed on the tip of the gas parner to be arranged concentrically inside the combustion cylinder is the water spray nozzle,

A radiant tube parner, characterized in that the nozzle is connected to an atomized water generator capable of supplying pressurized gas and added water via an added water transfer pipe provided inside a gas burner. .11

5. A cylinder with a conical hole in which the atomized water generator is to be connected to the additive water transfer pipe, a concave disk with a pressurized gas and additive water blowing groove to be combined therewith, 5. The radiant tube parner according to claim 4, wherein the housing comprises a cylindrical body and a disk.

6. The method according to claim 4, wherein the water outflow nozzle is installed at the center of the flame dispersion type nozzle in order to spray water from the additive water transfer pipe with the injection energy of the low-pressure fuel gas. Radiant tube parna.

7. In order to spray water from the added water transfer pipe by the injection energy of the low pressure combustion exhaust gas, the exhaust gas introduction cylinder and the water outflow nozzle are installed at the center of the flame dispersion type nozzle. Radiant tube according to claim 4.

8. pressurized gas (air, steam, inert gas) ² ~ 6 kg m 2 atomizing system according range of water addition and the low pressure gas (fuel gas, combustion exhaust gas or the like) 300 ~ l, 000 mmAq range of fog The radiant tube burner according to any one of claims 4 to 7, wherein water is added in a chemical manner.