JP3691863B2 - Radiant tube burner and alternating combustion radiant tube burner system using the same - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a radiant tube burner and an alternating combustion type burner system using the same. More specifically, the present invention relates to a radiant tube burner that burns using high-temperature combustion air obtained by alternately passing flue gas and combustion air through a heat storage body, and an alternating combustion type using the same. It relates to a radiant tube burner system.
[0002]
[Prior art]
In recent years, attempts have been made to apply heat storage combustion to radiant tube burners. In the heat storage combustion, combustion air is preheated to a high temperature with combustion exhaust gas using a heat storage body, and the high temperature combustion air is used for combustion. At that time, radiant tube burners are attached to both ends of the radiant tube, and these are alternately burned, and the combustion exhaust gas that has passed through the radiant tube burner is exhausted through the air throat of the burner on the opposite side of the combustion stop. It is considered to construct a type burner system. In this alternate combustion type radiant tube burner system, the air throat of each burner is connected to a heat storage body, used as a passage through which combustion air is supplied during combustion, and used as an exhaust passage for combustion exhaust gas when combustion is stopped . And in each thermal storage body, when combustion exhaust gas passes, the heat | fever is collect | recovered, and when combustion air passes, the combustion air is pre-heated to the high temperature of the temperature of combustion exhaust gas with the stored heat.
[0003]
However, in general, when heat storage combustion is performed, the preheating temperature of the combustion air becomes high, for example, 800 ° C. or higher, and NOx increases. For this reason, the so-called fuel two-stage combustion method (US Pat. No. 4,856,492 and US Pat. No. 4,870,947) in which fuel is injected in two stages with respect to the flow of combustion air to perform combustion, It has been considered to suppress the generation of NOx by adopting a so-called air multi-stage combustion method in which air is injected into a fuel flow in two stages and burned.
[0004]
[Problems to be solved by the invention]
However, in the radiant tube burner, since the fuel nozzle is inserted into the radiant tube made of a heat-resistant alloy having a relatively small diameter of about 90 to 200 mm and the air throat is formed, it is difficult to implement each of the above-described combustion methods. That is, in the fuel two-stage combustion method, it is necessary to provide a secondary fuel nozzle for injecting secondary fuel on the downstream side of the primary combustion, but in the narrow space inside the radiant tube, It is extremely difficult to provide a secondary fuel nozzle inside. In the air multistage combustion method, it is indispensable to adopt a double cylindrical structure in order to secure a flow path for supplying secondary air to the downstream side of the primary combustion zone, but there is only a limited space. In a radiant tube, the arrangement is extremely difficult. For this reason, it is difficult to make full use of the NOx reduction principle of each combustion method described above.
[0005]
Also, in order to carry out the fuel two-stage combustion method and the air multi-stage combustion method, primary and secondary fuel supply systems or air supply systems are required, and their control becomes complicated and the burner structure is also required. It has the problem of becoming complicated.
[0006]
Further, in the burner system that performs alternate combustion, due to its structure, fuel remains in the fuel nozzle of the burner that is not combusted. For this reason, if the heat insulation structure of the fuel nozzle is not sufficient, there is a problem of so-called coking in which the residual fuel is heated and carbonized due to the high-temperature combustion exhaust gas exhausted through the air throat.
[0007]
An object of the present invention is to provide a radiant tube burner capable of reducing NOx with a simple structure. Another object of the present invention is to provide an alternating combustion radiant tube burner system that can prevent coking of fuel and is easy to control.
[0008]
[Means for Solving the Problems]
  In order to achieve such an object, the present invention provides a fuel for injecting fuel in a radiant tube burner that burns using high-temperature combustion air obtained by alternately passing combustion exhaust gas and combustion air through a heat storage body. While disposing the nozzle and the air throat for injecting combustion air away from each other in parallel in the end of the radiant tube,A radiant tube and a fuel nozzle are provided in the radiant tube with a nozzle support that closes the radiant tube and has a through hole for the fuel nozzle that is inserted and supported at the tip of the fuel nozzle and a groove inscribed in the inner peripheral wall surface of the radiant tube. The air throat is formed between and the hole formed by the peripheral groove of the nozzle support and the inner peripheral wall surface of the radiant tube is used as the air throat injection port.On all cross sections of the radiant tubeClothThe air jet is unevenly distributed along the inner peripheral wall surface of the radiant tube, and an air jet that generates negative pressure on the inner peripheral wall surface opposite to the inner peripheral wall surface where the air jet flow is unevenly formed is formed.Is a thingThe fuel injected into the radiant tube is mixed with the recirculated combustion gas and gradually involved in the flow of combustion air while causing slow combustion.Further, the radiant tube burner of the present invention has a fuel nozzle for injecting fuel and an air throat for injecting combustion air, spaced apart from each other and arranged in parallel in the end of the radiant tube, and an air throat installed in the radiant tube. A nozzle support that closes the radiant tube is integrally provided at the tip of the tube for fuel, and a through hole for the fuel nozzle is provided in the nozzle support to support by inserting the tip of the fuel nozzle, and the radiant tube is provided at the periphery of the nozzle support A through-hole inscribed in the inner peripheral wall surface of the radiant tube is provided, and the through-hole is used as an air throat injection port. A negative pressure is generated on the inner peripheral wall surface opposite to the inner peripheral wall surface on which the air jet is unevenly distributed. So that cause slow combustion gradually be caught in the flow of combustion air fuel injected into the ant tube while mixing with recirculating combustion gases.Here, the radiant tube burner of the present invention preferably employs a pilot burner combined nozzle provided with a primary air pipe to which primary air necessary for pilot combustion is supplied around the fuel nozzle as a fuel nozzle. Further, it is preferable that the air throat injection port is inscribed in the inner peripheral wall surface of the radiant tube, and the fuel nozzle is in the direction opposite to the air injection port in a range not inscribed in the center of the radiant tube or the inner peripheral wall surface of the radiant tube. It is preferable to be eccentric. Moreover, it is preferable to inject combustion air at a flow rate of 100 m / sec or more.
[0010]
Moreover, it is preferable that the heat storage body used for the radiant tube burner of the present invention is a honeycomb-like ceramic having a constant passage cross-sectional area and linearly passing through the flow path.
[0011]
  Furthermore, the present invention configures an alternating combustion type radiant tube burner system in which these radiant tube burners are installed at both ends of the radiant tube and the exhaust gas is exhausted through the air throat of the non-burning radiant tube burner. are doing. In this alternate combustion type radiant tube burner system, a pilot burner combined nozzle is preferably used as the fuel nozzle. This pilot burner combined nozzle is provided with a primary air flow path for flowing primary air around the fuel nozzle, and pilot combustion is performed in the primary air flow path.Minimum requiredA quantity of primary air is always flowed regardless of the burner operating state, while a sufficient quantity of fuel to maintain the pilot flame is always flowed as pilot fuel and the amount of injected fuel is switched between combustion and when combustion is stopped. The main combustion and the pilot combustion are preferably continued.
[0012]
[Action]
  Therefore, the claims1 and 2 of the present inventionIn a radiant tube burner, combustion air is injected along the tube wall of the radiant tube, and the flow is unevenly distributed without being distributed over the entire cross section of the radiant tube because the air throat opening is unevenly positioned. Become. For this reason, negative pressure is generated on the opposite side of the portion where the combustion air is injected, and strong exhaust gas recirculation occurs. At the same time, the exhaust gas and the fuel gas injected in parallel with the combustion air are attracted and accompanied by the flow of the combustion air, and after mixing with the exhaust gas, the fuel gas is gradually involved in the flow of the combustion air and slowly Causes burning.Moreover, in the present invention, when the tip of the fuel nozzle is inserted into the nozzle support in the radiant tube, the position of the fuel nozzle in the radiant tube is determined, and at the same time, an air throat completely isolated from the fuel nozzle is formed. The And since the through-hole or groove | channel of the periphery of a nozzle support body and a radiant tube partition and form the front-end | tip opening of an air throat, it is inscribed in this radiant tube only by fixing a nozzle support body in a radiant tube. A tip opening of the air throat is formed. In addition, the fuel nozzle support functions as a baffle.
[0013]
That is, combustion air preheated to a high temperature, for example, about 800 ° C. or more, has a volume expanded as compared to that at normal temperature, and is thus ejected at a considerably higher speed than fuel at normal temperature. For example, the high-temperature preheated air is ejected at an extremely high flow rate of 100 m / s or more as compared with the fuel ejected at a flow rate of 20 to 30 m / s. For this reason, the fuel does not spread in the tube but is attracted by the flow of high-speed combustion air, flows along the inner wall of the tube, and gradually gets caught in the combustion air flow. In addition, a part of the combustion exhaust gas that flows back in the radiant tube to the vicinity of the injection port is directly attracted by the flow of the combustion air to reduce the oxygen concentration of the combustion air. It is caught between the jets of combustion air to prevent them from coming into immediate contact. Therefore, a long flame is formed while slowly burning.
[0014]
  And claims3In the described radiant tube burner, since a pilot flame is constantly formed at the base of the combustion jet, a flame is stably formed even when combustion air and fuel are injected in parallel.
[0015]
  Claims4In this invention, exhaust gas is caught between the flow of combustion air and the flow of fuel to prevent contact between the combustion air and the fuel immediately after injection, and the oxygen in the combustion air where the fuel diffuses Reduce concentration.
[0017]
  Claims5In the described invention, since the honeycomb-shaped ceramics are used as the heat storage body, it is possible to eliminate the stagnation of the flow of combustion air or exhaust gas, and the flow in the opposite direction of the exhaust gas and the supply air is generated alternately. The self-cleaning action (backwashing) of this works and can prevent the dust in the exhaust gas from adhering to the heat storage body.
[0018]
  Furthermore, the above-mentioned burner is installed at both ends of the radiant tube and burned alternately.6In this invention, the combustion exhaust gas that has passed through the radiant tube is exhausted through the air throat of the burner during which combustion is stopped and guided to the heat storage body.
[0019]
  Where the claim7In the described burner system, the fuel nozzle of the unburned radiant tube burner forms a pilot flame, so that the fuel nozzle itself is cooled with primary air and fuel and can be heated by the hot flue gas. Absent. Moreover, in order to operate the stopped burner, it is only necessary to switch the flow of combustion air and flow it to the burner throat while increasing the amount of fuel flowing to the fuel nozzle.
[0020]
【Example】
Hereinafter, the configuration of the present invention will be described in detail based on embodiments shown in the drawings.
[0021]
FIG. 1 shows an embodiment of an alternating combustion radiant tube burner system to which the present invention is applied. This alternating combustion type radiant tube burner system 1 is combusted in order to burn the radiant tube 3 and a pair of radiant tube burners 5 and 5 disposed at both ends of the radiant tube 3 and the pair of burners 5 and 5 alternately. It consists of a combustion air supply system, a fuel supply system, and an exhaust system that selectively supply most of the engine air and fuel except for the pilot combustion.
[0022]
In the case of the present embodiment, the radiant tube 3 is exemplified as a U-shaped tube. As shown in FIG. 2, both ends of the radiant tube 3 penetrate the furnace wall 7 and are located outside the furnace. Flange 3a is provided at both ends of the radiant tube 3, and the tube 3 is fixed to the furnace wall 7 via a spacer 7b made of a heat insulating material between the flange 3a and the furnace wall 7. The fixing of the radiant tube 3 to the furnace wall 7 is not shown in the figure, but normally, a heat-insulating material bung attached to the tube is fitted into a large hole formed in the furnace wall 7 on the tube side. The sealing member is airtightly closed.
[0023]
Each of the radiant tube burners 5 and 5 is a type in which a heat storage body 17 is provided, and includes a burner body 9, a fuel nozzle 11 also serving as a pilot burner, an air throat 13, a nozzle support 15 and the like. The nozzle support 15 functions as a baffle and forms a stable flame. The radiant tube burners 5 and 5 arranged at both ends of the radiant tube 3 have the same configuration. Therefore, one radiant tube barNa 5The configuration will be described below.
[0024]
In the case of the present embodiment, the burner body 9 has an L-shaped substantially cylindrical shape, and is attached to the radiant tube 3 using the flange 9c of the upper part bent at a right angle. A hole 9a for inserting a fuel nozzle, for example, a pilot burner combined nozzle 11 is formed in the upper portion of the burner body 9, and the nozzle 11 is attached so as to pass therethrough. The space in the burner body 9 is an air throat 13. A plurality of heat storage bodies 17 are accommodated in the air throat 13. Each heat storage body 17 is arrange | positioned along with the lower part bent downward of the burner body 9. As shown in FIG. This prevents the dust in the combustion exhaust gas from staying in the heat accumulator 17 by making the exhaust direction and the gravity direction coincide with each other. Each of the heat storage bodies 17 and 17 is preferably made of, for example, honeycomb-shaped ceramics such as cordierite or mullite having a constant passage cross-sectional area and linearly passing through the passage. This honeycomb-shaped ceramics has a relatively high pressure loss with a relatively high heat capacity and high durability. Moreover, exhaust and supply of air are performed alternately without any stagnation. For this reason, the dust in the exhaust gas does not easily adhere to the honeycomb-shaped flow paths of the heat storage bodies 17 and 17 and is not contaminated because it is washed back even if it adheres. In addition, when recovering heat from the exhaust gas, even if the exhaust gas falls below the acid dew point temperature, sulfur in the exhaust gas and its chemical change substances are trapped on the surface of the ceramics, causing low temperature corrosion of the ducts in the downstream exhaust system, etc. There is nothing.
[0025]
The burner bodies 9 and 9 of the respective burners 5 and 5 are respectively connected to four-way flow path switching means 41 such as a rotary four-way valve via a duct 10. A flange 9b is formed at the lower end of the burner body 9, and is fixed to the duct 10 with screws or the like.
[0026]
In the case of the present embodiment, a pilot burner combined nozzle 11 is employed as the fuel nozzle. As shown in FIG. 12, the pilot burner combined nozzle 11 includes a fuel nozzle 19, a primary air pipe 22 constituting a primary air throat 21, an ignition plug (not shown), and the like. The fuel nozzle 19 and the primary air pipe 22 are arranged concentrically. Therefore, the structure of the nozzle is simple and can be formed relatively thin. According to the pilot burner combined nozzle 11, primary air of about 10% of combustion air flowing to the air throat 13 as the secondary air flows through the primary air throat 21 around the fuel nozzle 19. In addition to the main injection port 20, an injection port 18 that injects a part of the fuel toward the surrounding primary air throat 21 is opened at the tip portion of the fuel nozzle 19, and the primary air throat 21 using a part of the fuel as a pilot fuel. The premixed gas is obtained by being injected into the interior and mixing well with the primary air. There, an igniter (not shown) is installed, and is provided so that a flame holding source can be formed around the injection port 20 of the fuel nozzle 19.
[0027]
Here, the primary air throat 21 always flows primary air in an amount suitable for pilot combustion irrespective of the operating state of the burner. Further, a sufficient amount of fuel to maintain a pilot flame is always supplied to the fuel nozzle 19 as a pilot fuel, and the amount of injected fuel is switched between combustion and when combustion is stopped, and main combustion and pilot combustion continue. It is configured as follows.
[0028]
A fuel supply source (not shown) is connected to the fuel nozzle 19 of the pilot burner combined nozzle 11 via a fuel supply system 23 as shown in FIG. The fuel supply passage 23 is provided with a control valve 25 that controls the amount of fuel injected from the fuel nozzle 19 and a bypass passage 27 that bypasses the flow rate control valve 25. Are provided with a flow control valve 29 and a shutoff valve 31 through which a sufficient amount of fuel is allowed to pass. Therefore, the fuel supplied from the fuel supply source is supplied to the fuel nozzle 19 via the bypass passage 27 even when the flow control valve 25 is closed. However, in the bypass passage 27, the flow control valve 29 restricts the flow rate of the fuel in the bypass passage 27, and the fuel supplied to the fuel nozzle 11 is reduced to the minimum amount necessary for the fuel nozzle 11 to perform pilot combustion. adjust.
[0029]
The pilot burner combined nozzle 11 is inserted into the radiant tube 3 through the hole 9 a of the burner body 9. Therefore, the space around the pilot burner combined nozzle 11 becomes an air throat 13 of combustion air preheated to a high temperature that flows as secondary air. The tip of the pilot burner combined nozzle 11 reaches a position near the inner surface of the furnace wall 7, which will be described in detail later.Nozzle support15 is supported.
[0030]
Further, a primary air supply source (not shown) is connected to the primary air throat 21 of the pilot burner combined nozzle 11 so that a minimum amount of primary air necessary for the fuel nozzle 19 to perform pilot combustion is always supplied. Yes. As the primary air, cold air that does not pass through the heat storage body is used. The air ratio is determined by combining the primary air and the high-temperature combustion air supplied as the secondary air.
[0031]
The nozzle support body 15 is arrange | positioned in the position corresponding to the surface inside the furnace wall 7 in the radiant tube 3, for example. Normally, the bang portion surrounded by the furnace wall cannot dissipate heat, so that a flame is formed inside the furnace. The nozzle support 15 is composed of a disc portion 15a that functions as a baffle plate, and an air passage tube 15b that extends from the entire periphery of the disc portion 15a toward the pilot burner combined nozzle 11. It is molded integrally. The diameters of the disk portion 15a and the air passage tube 15b are set to substantially the same value as the inner diameter of the radiant tube 3, and the radiant tube is formed at the disk portion 15a by inserting the air passage tube 15b into the radiant tube 3. 3 is closed and an air throat 13 is formed.
[0032]
As shown in FIG. 5, the disk portion 15a is provided with a fuel nozzle through hole 15c formed by a peripheral through hole 15d and a cylindrical flange 15e protruding toward the pilot burner combined nozzle 11 side. . As shown in FIG. 5, the through-hole 15d was drilled over a part of the air passage tube 15b so as to cut out the peripheral portion of the disk portion 15a in a half-moon shape.HoleIt is. This through hole 15 d forms an injection port 33 of the air throat 13 together with the radiant tube 3. That is, the injection port 33 of the main air throat 13 that flows the combustion air preheated to a high temperature as secondary air is provided so as to be inscribed in the inner peripheral wall surface of the radiant tube 3. Thereby, high-temperature combustion air, which will be described later, is jetted and flows along the inner peripheral wall surface of the radiant tube 3 from the jet port 33. It should be noted that the through hole 15d in the present embodiment is not necessarily inscribed in the inner wall surface of the tube, and a sufficient effect can be obtained as long as the through hole 15d is close to a state close thereto.
[0033]
Further, the fuel nozzle through hole 15c of the disc portion 15a is offset to the opposite side to the injection port 33 in a range not inscribed in the tube center or the inner peripheral wall surface of the tube. The diameter of the fuel nozzle through hole 15c is set to be approximately the same as the outer diameter of the tip of the pilot burner combined nozzle 11. Further, the peripheral edge of the fuel nozzle through hole 15c extends toward the burner body 9 to form a flange 15e. The tip of the pilot burner combined nozzle 11 is inserted and supported in the flange 15e. Accordingly, as shown in FIG. 2, the pilot burner combined nozzle 11 is disposed substantially parallel to the radiant tube 3 on the upper side of the space inside the radiant tube 3, and the tip thereof is located away from the air injection port 33.
[0034]
The air throats 13 and 13 of the burners 5 and 5 are connected to a combustion air supply system 40 and an exhaust system 42 via a four-way valve 41, and when one burner 5 is connected to the air supply system 40, the other The burner 5 is connected to the exhaust system 42.
[0035]
Where primary air and secondary air and radiant tube barNa 5FIG. 6 shows the relationship with the operation. In the combustion mode in which the radiant tube burner 5 is operated, the secondary air is pumped in addition to the primary air.Na 5Is supplied with 100% of an amount of combustion air suitable for combustion. In this case, the combustion amount of the radiant tube burner 5 reaches 100%.
[0036]
Meanwhile, radiant tube barNa 5In the exhaust mode where the engine is in a non-actuated combustion stop state, only the primary air is pumped. Therefore, the radiant tube burner 5 is supplied with a small amount of combustion air suitable for pilot combustion by the pilot burner combined nozzle 11 and only forms a pilot flame that hardly affects the combustion. That is, primary air is always supplied to the primary air throat 21 of the fuel nozzle 11 regardless of the operating state of the radiant tube burner 5.
[0037]
One radiant tube burner 5 configured as described above operates as follows.
[0038]
First, when performing pilot combustion, fuel is supplied to the fuel nozzle 19 through the bypass passage 27 while the flow control valve 25 of the fuel supply system 23 is closed. Since the primary air is constantly pumped from the primary air supply source to the primary air throat 21 around the fuel nozzle 19, the pilot fuel and the primary air become a premixed gas having an air ratio suitable for pilot combustion. Then, the mixed gas is ignited by a spark plug and pilot combustion is performed (the state of the upper radiant tube burner 5 shown in FIG. 1).
[0039]
After the supply of secondary air from the air supply source is started in a state where the fuel nozzle 11 is performing pilot combustion, the flow control valve 25 of the fuel supply system 23 is opened and the fuel is allowed to flow to the fuel nozzle 19. That is, when the flow control valve 25 of the fuel supply system 23 is opened, a large amount of fuel is supplied from the fuel supply source to the fuel nozzle 19 of the pilot burner combined nozzle 11.
[0040]
On the other hand, the air supplied as secondary air from the combustion air supply system 40 is preheated while passing through each of the heat accumulators 17, 17, is brought to a high temperature, for example, 800 ° C. or higher, and is introduced into the air throat 13. For this reason, the secondary air expands to increase its flow velocity, and the high-speed air is ejected from the secondary air injection port 33 at a speed of, for example, about 100 m / s and is unevenly distributed near the inner peripheral wall surface of the radiant tube 3. To form a flow. The air injection port 33 is provided so as to be displaced from the inner peripheral wall surface of the radiant tube 3 so as to be inscribed or approached, and is disposed away from the through hole 15c into which the tip of the pilot burner combined nozzle 11 is inserted. . Therefore, as shown in FIG. 7, the high-speed combustion air flow A <b> 2 as the secondary air is formed away from the fuel flow F along the inner peripheral wall surface of the radiant tube 3. Accordingly, a negative pressure is generated on the opposite side of the combustion air flow A2 in the radiant tube 3 so that the combustion exhaust gas G flows backward so as to swirl, and after being mixed with fuel, is further entrained in the combustion air flow A2. The flow of the exhaust gas G envelops the high-speed combustion air flow A2, and flows while being taken into the combustion air. That is, the fuel and the combustion air perform so-called slow combustion that extends into the radiant tube 3 while gradually burning in a state where the combustion exhaust gas is sufficiently involved (state of the lower radiant tube burner 5 shown in FIG. 1). Slow combustion aims to suppress NOx production by lowering the flame temperature and lowering the oxygen concentration.
[0041]
And even if the flow control valve 25 of the fuel supply system 23 is closed and the supply of secondary air from the secondary air supply source is stopped from this combustion state, the pilot burner combined nozzle 11 still has a slight amount.combustionBecause the primary air continues to be supplied, the pilot flame is maintained.
[0042]
In the radiant tube burner 5, when the pilot burner combined nozzle 11 or a simple fuel nozzle is mounted, the nozzle 11 is inserted into the air passage tube 15 b from the hole 9 a of the burner body 9 to support the nozzle at the tip. By inserting the tip of the pilot burner combined nozzle 11 into the flange 15e of the body 15, the tip of the pilot burner combined nozzle 11 is positioned and supported. Further, when the burner body 9 is attached to the radiant tube 3 and the air passage tube 15b is inserted into the radiant tube 3, the pilot burner nozzle 11 is parallel to the radiant tube 3 above the space in the radiant tube 3. Automatically arranged.
[0043]
Further, in the fuel nozzle 11 serving as a pilot burner of the radiant tube burner 5, room temperature air is always supplied as primary air around the fuel nozzle 19, and a small amount of fuel is flowing, so that the inside of the air throat 13 burns. Even if exhaust gas flows, the heat does not cause coking.
[0044]
The other radiant tube burner 5 is also the one radiant tube bar described above.Na 5Is configured and operates in the same manner. Therefore, the other radiant tube barNa 5The description about is omitted. However, for the fuel supply source, primary air supply source and secondary air supply source, one radiant tube barNa 5It is desirable to share the same thing.
[0045]
Here, when the four-way valve 41 is switched to the first position (the illustrated position), one of the radiant tube barsNa 5The secondary air throat 13 is connected to the secondary air supply source and the other radiant tube barNa 5When the secondary air throat 13 is connected to the atmosphere side and the four-way valve 41 is switched to the second position, one radiant tube barNa 5The secondary air throat 13 is connected to the atmosphere side and the other radiant tube barNa 5The secondary air throat 13 is connected to a secondary air supply source.
[0046]
The alternating combustion type radiant tube burner system 1 in which the radiant tube burner 5 operating in this way is installed at both ends of the radiant tube 3 and alternately burns operates as follows. One radiant tube burner 5 is hereinafter referred to as an A burner for convenience of explanation, and the other radiant tube burner 5 is referred to as a B burner..
[0047]
First, the flow control valve 25 of the fuel supply system 23 on the A burner side is opened, the flow control valve 25 of the fuel supply system 23 on the B burner side is closed, and the combustion air supply system 40 is connected to the A burner side. The four-way valve 41 is switched so that the exhaust system 42 is connected.
[0048]
As a result, a large amount of fuel, primary air and secondary air are supplied to the A burner side and burned. On the other hand, only a small amount of fuel and primary air are supplied to the pilot burner combined nozzle 11 of the B burner, and pilot combustion is performed. That is, even if the combustion is stopped, the B burner is supplied with the fuel and the primary air suitable for the pilot combustion and continues the pilot combustion.
[0049]
The flue gas generated by the combustion of the A burner flows toward the B burner while heating the radiant tube 3. Then, the combustion exhaust gas flows into the main air throat 13 from the air injection port 33 of the nozzle support 15 on the B burner side, and is attracted to the exhaust system 42 through the four-way valve 41 to perform a predetermined exhaust treatment. And then discharged into the atmosphere. At this time, the heat of the combustion exhaust gas is recovered by the heat storage bodies 17 and 17 in the burner body 9. Therefore, the temperature of each heat storage body 17 is rising.
[0050]
When a predetermined time T, for example, about 20 to 40 seconds elapses after the A burner starts combustion, the flow control valve 25 of the fuel supply system 23 on the A burner side is closed. Then, the four-way valve 41 is switched so that the A burner side is connected to the exhaust system 42 and the B burner side is connected to the combustion air supply system 40 to scavenge the B burner. Thereafter, the flow control valve 25 of the fuel supply system 23 on the B burner side is opened, and the main fuel is supplied to the B burner side.
[0051]
This is shown in FIG. At time t1, the A burner starts main combustion, and the B burner starts pilot combustion. At time t2 when only time T has elapsed, the A burner that has been performing the main combustion is switched to the pilot combustion, and the B burner that has been performing the pilot combustion starts the main combustion. Thereafter, in the same manner, every time the predetermined time T elapses, the burner that burns and the burner that stops burning are switched, and the burner system 1 performs alternate combustion.
[0052]
The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited to this, and various modifications can be made without departing from the scope of the present invention. For example, in the burner system 1, the switching between the A burner and the B burner is repeated every set time T. However, the present invention is not limited to this, and the temperature of the combustion exhaust gas after passing through each heat storage body 17A, 17B is monitored. And it is good also as a structure which switches, when this temperature reaches about 200 degreeC, for example.
[0053]
Further, the nozzle support 15 is integrally formed with the air passage tube 15b built in the radiant tube 3 and incorporated into the tube 3 when the burner is attached. However, the present invention is not limited to this. For example, FIG. Like the nozzle support 53 of the radiant tube burner 51 shown in FIG. 1, a single disk is punched to form the fuel nozzle through hole 53c and the peripheral groove 53d, and fixed to the inner peripheral surface of the radiant tube 3 by welding or the like. You may do it.
[0054]
Furthermore, in the radiant tube burner 5, each heat storage body 17 and 17 is accommodated side by side on the lower side in the burner body 9, but it is not shown in the air throat 13 as shown in FIG. You may accommodate in the duct 10 which connects the burner body 9 and the four-way valve 41. FIG. When accommodated in the air throat 13, as shown in FIG. 9, the heat storage body 17 is accommodated around the pilot burner combined nozzle 11.
[0055]
Further, the radiant tube burner may be of the type shown in FIG. More specifically, in the radiant tube burner 61, a refractory material sleeve 63 is inserted into the end of the radiant tube 3. The distal end portion of the sleeve 63 is a thick portion 63a. As shown in FIG. 11, the hole of the thick portion 63a, that is, the nozzle through hole 63b is slightly displaced above the center of the radiant tube 3. ing. The tip of the pilot burner combined nozzle 11 is inserted into the hole 63b. Therefore, the tip of the fuel nozzle 11 is positioned and supported by the thick portion 63a.
[0056]
Further, a groove 63c that is partially connected to the air throat 13 and extends in the longitudinal direction is formed at the lower end portion of the outer peripheral surface of the thick portion 63a. The groove 63 c forms an injection port 33 of the air throat 13 between the inner peripheral wall surface of the radiant tube 3.
[0057]
That is, the outlet of the air throat 13 of the radiant tube burner 61 is deviated so as to be inscribed in the inner peripheral wall surface of the radiant tube 3 in the same manner as the radiant tube burner 5 described above. In the present embodiment, the example in which the opening of the air throat 13, that is, the injection port 33 is inscribed in the inner peripheral wall surface of the radiant tube 3 has been mainly described. It is possible to cause exhaust gas recirculation on the opposite side of the jet. The exhaust gas recirculation is stronger when the injection port 33 is inscribed.
[0058]
It should be noted that the tip surface of the sleeve 63 is recessed in a crescent-shaped portion where the groove 63c is formed rather than the portion where the hole 63b is formed. By the shape of the step portion, the injection angle and direction of the secondary air flow can be adjusted to a desired value.
[0059]
In this embodiment, the high-temperature combustion air is connected to the burner or exchanged using an internal heat storage.MutualThe case of obtaining by combustion has been mainly described, but it is not particularly limited to this, for example, by rotating the heat storage body relative to the combustion air supply system and the exhaust system, or using the flow path switching means By switching the flow direction of the fluid to the heat storage body, etc., the exhaust air from the high-temperature combustion exhaust gas is used to continuously supply the combustion air preheated to a high temperature to a single burner for continuous combustion. May be. In this embodiment, the pilot burner combined nozzle is used as the fuel nozzle. However, the present invention is not particularly limited to this. In some cases, the pilot burner is installed near the fuel nozzle injection port separately from the fuel nozzle. May be. Furthermore, although the case where gas fuel is used has been mainly described in the present embodiment, the present invention is not particularly limited to this, and liquid fuel such as oil can be used. Furthermore, even if the combustion air does not necessarily have a high flow rate of about 100 m / s, the present invention is established even if the flow velocity is slower than that.
[0060]
【The invention's effect】
  As explained above,Claims 1 and 2According to the radiant tube burner of the present invention, combustion air is injected along the tube wall of the radiant tube, and the flow is unevenly distributed without being distributed over the entire cross section of the radiant tube, and the combustion air is injected. A strong exhaust gas recirculation occurs by creating a negative pressure on the opposite side of the part. At the same time, the exhaust gas and the fuel gas injected in parallel with the combustion air are attracted and accompanied by the flow of the combustion air, and after mixing with the exhaust gas, the fuel gas is gradually involved in the flow of the combustion air and slowly Causes burning. Accordingly, combustion gradually proceeds in radians and tubes, so that the generation of NOx can be suppressed. Further, since a long flame can be formed along the wall surface of the radiant tube, the tube can be heated with a uniform heat flux, local heating that has occurred in the conventional burner can be prevented, and the life of the radiant tube can be extended.According to the first and second aspects of the present invention, the tip of the fuel nozzle is inserted into the nozzle support in the radiant tube, thereby positioning and supporting the fuel nozzle in the tube and at the tip of the air throat. An opening can be formed. For this reason, manufacture of a radiant tube burner becomes easy. In particular, in the case of the invention described in claim 2, the mounting work of the nozzle support in the radiant tube can be facilitated.
[0061]
In addition, when a pilot burner combined nozzle is used as the fuel nozzle, a stable primary flame can be formed and attracted to the combustion air flow side together with the fuel, so that it is stable even if the combustion air and the fuel are injected separately. Flame formation becomes possible, and the amount of combustion exhaust gas entrained can be increased to lower NOx.
[0062]
Further, in the case of claim 3, exhaust gas is caught between the flow of combustion air and the flow of fuel to prevent contact between the combustion air and fuel immediately after injection and combustion of the portion where the fuel diffuses Since the oxygen concentration of the working air is reduced, the generation of NOx can be further suppressed.
[0063]
Further, in the inventions according to claims 4 and 5, the tip of the fuel nozzle is inserted into the nozzle support in the radiant tube, so that the positioning and support of the fuel nozzle in the tube is realized and the tip opening of the air throat is opened. Can be formed. For this reason, manufacture of a radiant tube burner becomes easy. In particular, in the case of the invention described in claim 4, the mounting work of the nozzle support in the radiant tube can be facilitated.
[0064]
Further, in the case of the invention of claim 6, since the honeycomb-shaped ceramics are used as the heat storage body, it is possible to eliminate the stagnation of the flow of combustion air or exhaust gas, and the flow in opposite directions of the exhaust gas and the supply air alternately. As a result, the self-cleaning action (back washing) of the flow path works, and it is possible to prevent dust in the exhaust gas from adhering to the heat storage body.
[0065]
Moreover, in the burner system of Claim 7, exchange combustion can be implemented using the above-mentioned radiant tube burner apparatus, and the improvement of thermal efficiency can be aimed at.
[0066]
  Further claims7In the described invention, even when the combustion is stopped, the fuel and primary air suitable for pilot combustion or the minimum necessary amount are supplied into the fuel nozzle and the primary air pipe. Since it can be cooled with the primary air in the primary air throat, it can prevent the fuel in the fuel passage from being heated by the heat of the combustion exhaust gas exhausted through the main air throat, resulting in high temperature, and the occurrence of coking Can be prevented.
  Further claims8In the described invention, since the combustion air is injected at a high speed of 100 m / sec or more, the fuel is not spread in the tube but is attracted by the flow of the high-speed combustion air and flows along the inner wall of the tube. Involved in the flow of combustion air to reduce the oxygen concentration and prevent the occurrence of local high temperature areas. Therefore, further low NOx combustion is possible.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an embodiment of an alternating combustion type radiant tube burner system using a radiant tube burner of the present invention.
2 is a cross-sectional view of the radiant tube burner of FIG. 1. FIG.
FIG. 3 is a side view of the radiant tube burner as seen from the direction of arrow III in FIG. 2;
4 is a block diagram showing an example of a fuel supply system of the radiant tube burner of FIG. 2. FIG.
5 is a cross-sectional view of a radiant tube burner as seen from the direction of arrow V in FIG. 2. FIG.
6 is a time chart showing the relationship between the combustion state of the radiant tube burner of FIG. 2 and the amount of air supplied. FIG.
7 is a conceptual diagram showing the combustion principle of the radiant tube burner of FIG. 2. FIG.
8 is a time chart showing the state of alternating combustion of the burner system of FIG. 1 and showing the operational relationship of each radiant tube burner. FIG.
FIG. 9 is a sectional view showing another embodiment of the radiant tube burner of the present invention.
FIG. 10 is a sectional view showing still another embodiment of the radiant tube burner of the present invention.
11 is a cross-sectional view of the radiant tube burner as seen from the direction of arrow XI in FIG.
FIG. 12 is a cross-sectional view showing an example of a pilot burner combined nozzle.
[Explanation of symbols]
1 Alternating combustion type radiant tube burner system
3 Radiant tube
5, 51, 61 Radiant tube burner
7 Furnace wall
11 Pilot burner nozzle (fuel nozzle)
13 Air Throat
15,53 Nozzle support
19 Fuel nozzle
21 Primary air throat
33 Injection port (opening of the tip of the main air throat)

Claims (8)

A fuel nozzle for injecting fuel and an air throat for injecting the combustion air in a radiant tube burner for combustion using high-temperature combustion air obtained by alternately passing combustion exhaust gas and combustion air through a heat storage body Are spaced apart from each other in parallel in the end of the radiant tube, and have a fuel nozzle through hole for inserting and supporting the tip of the fuel nozzle and a groove inscribed on the inner peripheral wall surface of the radiant tube at the periphery. A nozzle support that closes the radiant tube is provided in the radiant tube, the air throat is formed between the radiant tube and the fuel nozzle, and a groove on a peripheral edge of the nozzle support and an inner peripheral wall surface of the radiant tube are provided. the holes formed in the injection port of the air throat, the injection port is the radian Causing a negative pressure in the radiant opposite inner circumferential wall surface of the inner circumference along the wall surface of the inner peripheral wall surface of the air jet uneven distribution is allowed and the air jet is unevenly distributed in the tube without the distribution to all cross-section of the tube The air jet is formed , and the fuel injected into the radiant tube is mixed with the recirculating combustion gas and gradually entrained in the flow of the combustion air while causing slow combustion. Radiant tube burner to do. A fuel nozzle for injecting fuel and an air throat for injecting the combustion air in a radiant tube burner for combustion using high-temperature combustion air obtained by alternately passing combustion exhaust gas and combustion air through a heat storage body And a nozzle support for closing the radiant tube at the tip of an air throat tube built in the radiant tube , and is disposed in parallel in the end of the radiant tube. While providing a through hole for a fuel nozzle that inserts and supports the tip of the nozzle, a through hole that is in contact with the inner peripheral wall surface of the radiant tube is provided at the periphery of the nozzle support, and the through hole serves as an air throat injection port. the radiant tube the ejection port without distributed to all cross-section of the radiant tube Is intended to cause a negative pressure to the inner circumferential wall surface opposite to the circumferential inner wall surface inner periphery along the wall surface is unevenly distributed air jet and the air jet is unevenly distributed, said fuel injected into the radiant tube A radiant tube burner characterized by causing slow combustion while gradually being engulfed in the flow of combustion air while being mixed with recirculated combustion gas. 3. The radiant according to claim 1, wherein the fuel nozzle is a pilot burner nozzle, and a primary air pipe is provided around the fuel nozzle to supply primary air necessary for pilot combustion at a minimum. Tube burner. 3. The radiant tube burner according to claim 1, wherein the fuel nozzle is eccentric in a direction opposite to the air throat injection port within a range not inscribed in the center of the radiant tube or an inner peripheral wall surface of the radiant tube. . 3. The radiant tube burner according to claim 1, wherein the heat storage body is a honeycomb ceramic having a constant passage cross-sectional area and linearly passing through a flow path. An alternating combustion type characterized in that the radiant tube burner according to any one of claims 1 to 5 is installed at both ends of the radiant tube, and exhaust gas is exhausted through an air throat of the radiant tube burner which is not burned. Radiant tube burner system. A primary air flow path for flowing primary air around the fuel nozzle is provided, and the primary air is always flowed through the primary air flow path regardless of the operating state of the burner while the pilot flame is flown. A fuel nozzle is used as a pilot burner combined nozzle that allows the main fuel and pilot combustion to continue, with a sufficient amount of fuel constantly flowing as pilot fuel, and the amount of injected fuel switched between burning and stopping. The alternating combustion radiant tube burner system according to claim 6 . The radiant tube burner system according to any one of claims 1 to 7 , wherein an injection speed of the combustion air is set to 100 m / sec or more.

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