JP7150102B1 - Two-stage combustion device - Google Patents

Abstract

An object of the present invention is to provide a two-stage combustion apparatus using hydrogen gas as a fuel, which can suppress generation of NOx while suppressing combustion vibration. A nozzle through which gaseous fuel containing hydrogen flows, a primary air flow path through which primary air to be mixed with the gaseous fuel ejected from the nozzle is circulated, and secondary air to be mixed with the gaseous fuel mixed with the primary air. and a secondary air flow path through which the gas circulates in the nozzle, wherein the air ratio of the primary air to the gas fuel ejected from the nozzle is lower than the air ratio of the secondary air to the gas fuel ejected from the nozzle. The gas pressure of the fuel is 300 kPa or higher. [Selection drawing] Fig. 1

Description

The present disclosure relates to a staged combustion device using hydrogen gas as fuel.

For example, Patent Literature 1 discloses a gas burner that uses hydrogen gas as fuel. In this patent document 1, in order to suppress the generation of NOx (nitrogen oxide), hydrogen gas and oxygen gas are swirled in the same direction, and the flow velocities of the gases ejected while swirling are approximately the same. In this way, a technique for suppressing excessive mixing of hydrogen gas and oxygen gas by centrifugal force has been disclosed.

Further, Patent Document 2 discloses a main hole at the tip of a gas nozzle for injecting gas at an injection angle of 35° to 45° with respect to the central axis of the gas burner, and a main hole at an injection angle of 45° to 55° with respect to the central axis of the gas burner. A gas burner provided with a secondary hole for injecting gas at an injection angle and suppressing the generation of NOx while suppressing combustion oscillation, and two-stage combustion are also disclosed.

JP 2019-045083 A Japanese Patent No. 4600850

As described above, Patent Document 1 discloses a technique for suppressing the generation of NOx (nitrogen oxides) in a gas burner using hydrogen gas as fuel. Even if such a technique suppresses the problem to some extent, it may not be sufficiently suppressed.

Since hydrogen has a high flame temperature, it has a problem of generating high NOx. Therefore, it is desired to suppress generation of NOx while suppressing combustion vibration even in a gas burner using hydrogen gas as a fuel.

On the other hand, Patent Document 2 discloses a gas burner that suppresses the generation of NOx while suppressing combustion oscillation and two-stage combustion, but does not disclose the use of hydrogen gas as a fuel.

The present disclosure has been made in view of the problems described above, and an object of the present disclosure is to provide a two-stage combustion apparatus that uses hydrogen gas as a fuel and is capable of suppressing NOx generation while suppressing combustion oscillation.

In order to achieve the above object, the two-stage combustion apparatus according to the present disclosure includes a nozzle through which gas fuel containing hydrogen flows; a primary air flow path through which primary air to be mixed with the gas fuel ejected from the nozzle flows; a secondary air flow path through which secondary air to be mixed with the gas fuel mixed with the primary air flows, wherein an air ratio of the primary air to the gas fuel jetted from the nozzle is determined by jetting from the nozzle The gas pressure of the gas fuel flowing through the nozzle is 300 kPa or more, which is lower than the air ratio of the secondary air to the gas fuel.

Advantageous Effects of Invention According to the present disclosure, it is possible to obtain a two-stage combustion apparatus using hydrogen gas as a fuel, which is capable of suppressing NOx generation while suppressing combustion oscillation.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic side cross-sectional view showing a partial cross-section of a two-stage combustion apparatus according to an embodiment of the present invention, and a schematic configuration diagram showing a gas fuel supply system to a gas burner; FIG. 4 is a schematic configuration diagram showing another example of a gas fuel supply system to a gas burner; FIG. 4 is a side cross-sectional view of the gas nozzle (cross-sectional view taken along line AA in FIG. 4); Fig. 3 is a front view of the tip of the gas nozzle as seen from the inside of the furnace; 4 is a graph of test results showing the relationship between gas burner inlet pressure and NOx. It is a system outline figure of a small boiler concerning other embodiments. It is a system outline figure of a medium-sized large boiler concerning other embodiments.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail based on the drawings. However, the relative arrangement of components described as the embodiment or shown in the drawings is not intended to limit the scope of the present invention, but is merely an example of explanation.

<One embodiment>
FIG. 1 shows a schematic side cross-sectional view of a partial cross section of a two-stage combustion apparatus 1A according to one embodiment of the present invention. A gas burner 2 is provided at a burner throat portion 5 on the wall surface of the furnace 3A. The gas burner 2 includes a gas nozzle 7 arranged in a portion of the central axis C of the gas burner 2, a primary air flow path 9 for introducing combustion air to the outer peripheral portion of the gas nozzle 7, and an outer peripheral portion of the primary air flow path 9. It consists of a triple structure of the secondary air flow path 11 provided in.

The gas nozzle 7 and the primary air flow path 9 are provided inside a cylindrical primary sleeve 13 , and the secondary air flow path 11 is formed inside a cylindrical secondary sleeve 15 provided on the outer peripheral side of the primary sleeve 13 . be.

A gas fuel containing hydrogen is jetted into the furnace 3A from a main hole 25 and a secondary hole 27 formed at the tip of the gas nozzle 7. As shown in FIG. A tertiary air flow path (not shown) may be provided on the outer periphery of the secondary air flow path 11 . Thus, the gas burner 2 itself can constitute the two-stage combustion device 1A, and the two-stage combustion device 1A can be made compact. The pulverized coal from the burner 3 is opened in the furnace wall 1 for ejecting into the high-temperature furnace 2, and is directed to the surface of the refractory material 20 to the opening 4 formed in the throat shape of the refractory material 20. An ejection port 23 for ejecting a cooling body such as air is provided.

"Gas fuels containing hydrogen" include those containing hydrogen and other fuels (mixed combustion) and hydrogen only (single-fuel combustion).In addition, hydrogen is the main fuel even if it contains hydrogen and other fuels. (the volume percentage of hydrogen is 50% or more) and other fuels (the volume percentage of hydrogen is less than 50%). "Gaseous fuel containing hydrogen" includes all of these cases.

The primary air F1, which is the central air that flows through the opening 21 that forms the inlet and flows through the primary air flow path 9, is a straight flow. Swirling force is applied to a part of the primary air F1 by the swirler (flame stabilizer) 17 provided, and a stagnation region 19 is formed in a region in the furnace 3A on the downstream side of the swirler 17, and this stagnation region 19 By taking in gas fuel in the , it is possible to keep the flame stable.

An air register 23 is installed at the inlet of the secondary air flow path 11, and a turning force is applied to the secondary air F2 flowing into the secondary air flow path 11 by an air register type turning device.

In addition, a water pipe 6 is installed around the outer periphery of the burner throat 5, which is an opening for the gas burner 2 formed in the wall surface of the furnace 3A, so as to cool the surroundings of the opening. .

The ratio of the primary air F1 to the hydrogen-containing gas fuel ejected from the gas nozzle 7 is lower than the air ratio of the secondary air F2 to the gas fuel ejected from the gas nozzle 7. The ratio of air to fuel is set to be less than one. The air ratio is the ratio of the amount of air when the amount of air required for complete combustion of gas fuel is set to 1.

As shown in FIGS. 3 and 4, the tip of the gas nozzle 7 is provided with four main holes 25 and four secondary holes 27 . The gas fuel flowing through all the main holes is 80 to 90% of the total gas fuel flow rate, and the gas fuel flowing through all the sub holes is 20 to 10% of the total gas fuel flow rate. That is, the secondary holes 27 are formed to have a diameter smaller than that of the main holes 25, and when the total opening area of the plurality of main holes 25 is A1 and the total opening area of the plurality of secondary holes 27 is A2, the ratio A1: A2 is between 80:20 and 90:10.

In this way, the amount of fuel ejected from the secondary holes 27 is made smaller than the amount of fuel ejected from the main holes 25 so that the gas fuel flowing through all the secondary holes is 20 to 10% of the total gas fuel flow rate. Therefore, the fuel ejected from the secondary hole 27 is easily taken into the stagnation region 19 formed on the downstream side of the swirler (flame stabilizer) 17 that gives a swirling force to a part of the primary air, stabilizing the flame. It is possible to suppress the combustion vibration by holding the fuel.

Furthermore, if more than 20% of the fuel is ejected from the sub-holes 27, the swirler (flame stabilizer) 17, which gives a swirling force to a portion of the primary air, may be damaged by burning. The gas fuel is preferably configured to flow 20-10% of the total gas fuel flow rate.

As shown in FIGS. 3 and 4, each main hole 25 at the tip of the gas nozzle 7 is arranged symmetrically with respect to the central axis C of the gas nozzle 7 (which is also the central axis C of the gas burner 2). A plurality (four) of nozzles are arranged around the center axis C and are set within a predetermined ejection angle range. Hereinafter, the elevation angle of the main hole 25 with respect to the central axis C will be referred to as a main hole ejection angle θ1.

A plurality (four) of the secondary holes 27 are arranged symmetrically around the central axis C with the central axis C interposed therebetween, and are set within a predetermined ejection angle range with the central axis C interposed therebetween. Hereinafter, the elevation angle of the secondary hole 27 with respect to the central axis C will be referred to as a secondary hole ejection angle θ2. The secondary hole ejection angle θ2 is configured to eject the gaseous fuel at a larger ejection angle than the main hole ejection angle θ1.

The four main holes 25 and the four secondary holes 27 are arranged alternately and evenly around the central axis C, respectively. That is, the pitch angles α around the central axis C are equal and the intervals are 45 degrees. As described above, the main holes 25 are formed in a plurality at the tip of the gas nozzle 7 so as to be symmetrical about the central axis C with the central axis C interposed therebetween. is evenly jetted to the center of the gas burner 2.

Further, since a plurality of secondary holes 27 are also formed at the tip of the gas nozzle 7 so as to be symmetrical about the central axis C with the central axis C interposed therebetween, the gas fuel ejected from the secondary holes 27 is , is evenly jetted to the center of the gas burner 2.

4, the central position 25a of the opening of the main hole 25 and the central position 27a of the opening of the secondary hole 27 are provided so that the distance from the central axis C of the gas nozzle 7 is the same. Further, the cross-sectional shapes of the main hole 25 and the sub-hole 27 are circular.

Next, a system configuration for supplying gas fuel containing hydrogen to the gas burner 2 will be described with reference to FIG. An inlet valve 31 is provided at the outlet of a hydrogen gas tank 29 in which gas fuel containing hydrogen is stored to control the supply and cutoff of gas fuel from the hydrogen gas tank 29, and a pressure reducing valve 33 is provided on the outlet side of the inlet valve 31. and is decompressed to a predetermined pressure.

Downstream of the pressure reducing valve 33, as shown in FIG. 49 are provided. Gas fuel is supplied to the gas nozzle 7 of the gas burner 2 by opening the burner inlet valve 49 .

Therefore, the ejection pressure of the gas fuel from the main hole 25 and the secondary hole 27 is the gas pressure of the gas fuel flowing through the gas nozzle 7 and is the inlet pressure of the gas burner 2 and is measured by the burner inlet pressure gauge 47 . In the hydrogen gas tank 29, gas fuel containing hydrogen at a high pressure exceeding 300 kPa (for example, 15 MPa) is stored under pressure. is supplied to the gas burner 2.

In addition, when the by-product hydrogen 51 produced in the factory is applied, the supply pressure is as low as 3 to 50 kPa, so as shown in FIG. The gas is supplied to the gas burner 2 after being raised to the above target gas pressure.

FIG. 5 shows a graph of the test results showing the relationship between the inlet pressure of the gas burner 2 of the gas fuel containing hydrogen (the ejection pressure from the main hole 25 and the sub-hole 27) and NOx. Test conditions are as shown in Table 1.

In addition, the test confirmed the inlet pressure of the gas burner 2 under four conditions of 80 KPa (comparison base), 300 KPa, 500 KPa, and 900 KPa. The injection pressure was tested by changing the hole diameters of the main hole 25 and the secondary hole 27 formed at the tip of the gas nozzle 7 while keeping the fuel amount constant without changing the structure of the gas burner 2 . For example, the pore size was changed as shown in Table 2. The injection angles of the main hole 25 and the secondary hole 27 during the combustion test were 40° for the main hole injection angle θ1 and 45° for the secondary hole injection angle θ2.

In general, boiler burners using city gas, LPG, etc. as fuel are applied at a maximum of about 130 KPa, and even when hydrogen is used as fuel, a maximum of about 80 KPa is applied. As shown in the graph of the test results in FIG. 5, it was confirmed that the pressure was reduced to 300 KPa, 500 KPa, and 900 KPa. At 900 KPa, a NOx reduction effect of about 30% was observed. Therefore, 300 KPa or higher, at which the NOx reduction effect was recognized, was set as the set pressure for high pressure. More preferably, it should be set to 500 KPa or higher.

According to the embodiment configured as described above, the two-stage combustion, the gas fuel containing hydrogen, and the gas pressure of the gas fuel containing hydrogen are increased to 300 kPa or more, thereby suppressing combustion oscillation. , the generation of NOx can be suppressed. Next, the effects of this embodiment will be described in detail in (A) to (D) below.

(A) Since the gas fuel containing hydrogen is mixed with the primary air F1 and combusted, and then mixed with the secondary air F2 and combusted, the generation of NOx can be suppressed. That is, it is configured to suppress the generation of NOx by performing two-stage combustion.

If the temperature of the region where the fuel burns is low, the generation of NOx is suppressed. Therefore, since the air ratio of the primary air F1 is lower than that of the secondary air F2, the combustion temperature in the region (first region) where the gas fuel and the primary air F1 are mixed and burned is It is lower than the combustion temperature of the area (second area) where it is mixed with the air F2 and burned. Therefore, the generation of NOx can be suppressed by the two-stage combustion.

(B) By increasing the gas pressure of the gas fuel containing hydrogen to 300 kPa or more, the mixing of the gas fuel and the primary air is promoted, and the gas fuel is burned in the first region, which has a lower temperature than the second region. Relative increase in proportion. In addition, hydrogen is a compressible fluid, and the higher the pressure, the more it diffuses at the outlet of the injection hole. With these, low NOx is achieved by increasing the pressure of gas fuel containing hydrogen.

(C) Furthermore, in order to suppress the occurrence of combustion vibration, conventional gas burners are often configured so that the ejection pressure of the gas fuel ejected from the nozzle is less than 300 kPa. For example, in a boiler burner using city gas, LPG, etc. as fuel, a maximum of about 130 KPa is applied, and even when using hydrogen as a fuel, the maximum is about 80 KPa.

According to the knowledge of the inventors of the present application, it has been found that combustion oscillation is suppressed even if the injection pressure is increased to 300 kPa or higher if the gas fuel contains hydrogen.

That is, in general, combustion oscillation is generated by a combination of a burner and a furnace such as a boiler. Combustion oscillation occurs because the combustion sound of gas fuel in the burner resonates in the furnace, but this phenomenon is caused by changes in the amount of air or fuel in the gas burner due to the sound pressure, causing heat generation fluctuations, which lead to sound pressure fluctuations. and changes in a chain reaction.

Since these fluctuations form a feedback loop, combustion oscillation will not occur if some factor forming the loop is removed. Since the main cause of heat generation fluctuations is poor ignition, if the flame stabilization of the gas burner is strengthened, even if sound pressure fluctuations from inside the furnace are received, it will not lead to large heat generation fluctuations, so combustion oscillations will not occur.

Hydrogen has a higher combustion speed and better combustibility than city gas and LPG, so it is thought that flame stability, that is, combustion stability, is enhanced and the potential for combustion oscillation can be reduced compared to city gas and LPG. Therefore, even if the gas pressure of gaseous fuel containing hydrogen is increased to 300 kPa or more, combustion oscillation is less likely to occur, so it is possible to suppress the generation of NOx while suppressing the combustion oscillation.

(D) Furthermore, by increasing the gas pressure of the gas fuel containing hydrogen flowing through the gas nozzle 7 to 300 kPa or more, the gas fuel containing a larger amount of hydrogen can be burned without increasing the diameter of the pipe or the gas burner. be able to.

That is, hydrogen has a smaller calorific value than city gas or LPG and requires a larger volume. Furthermore, it also has the advantage of enabling miniaturization.

In the above-described embodiment, the gas burner 2 includes a gas nozzle 7 through which gas fuel containing hydrogen flows, a primary air flow path 9 through which primary air to be mixed with the gas fuel flows, and a gas fuel mixed with the primary air. The gas burner 2 itself constitutes the two-stage combustion device 1A, but the secondary air flow path 11 in the gas burner 2 alone does not allow for the size of the gas burner 2 and the furnace 3A. Depending on the situation, a sufficient amount of secondary air may not be secured, so in order to secure the secondary air amount, additional secondary air is jetted from the gas burner 2 to the upper wall surface of the furnace 3A into the furnace 3A. Additional secondary air jets (additional secondary air after-air ports) (not shown) may be provided.

<Other embodiments>
In another embodiment, the main hole 25 is set in the range of 50 degrees to 90 degrees across the central axis C of the gas nozzle 7, and the main hole ejection angle is 25 degrees or more and 45 degrees or less with respect to the central axis C of the gas nozzle 7. It is configured to eject gas fuel at an angle θ1.

The secondary hole 27 is set in the range of 70 degrees to 110 degrees across the central axis C of the gas nozzle 7, and the gas is injected at the secondary hole ejection angle θ2 of 35 degrees or more and 55 degrees or less with respect to the central axis C of the gas nozzle 7. It is configured to eject fuel. As already explained, the main hole ejection angle θ1 is smaller than the secondary hole ejection angle θ2.

According to the configuration of the other embodiment described above, when the main hole ejection angle θ1 exceeds 45 degrees, the potential for combustion oscillation due to pressure fluctuations in the furnace 3A increases. Further, when the main hole ejection angle θ1 is less than 25 degrees, the flame becomes excessively long, which affects the heat absorption characteristics of the boiler. Therefore, by setting the main hole ejection angle θ1 from 25 degrees to 45 degrees, it is possible to stabilize the flame and lengthen the flame at the same time. can be reduced to achieve low NOx.

Furthermore, since hydrogen has a higher burning speed than city gas or LPG and a relatively short flame, the main hole injection angle θ1 is set to 25 degrees to 35 degrees compared to city gas or LPG gas fuel. Even if the angle is set as narrow as 100 degrees, there is no problem in affecting the heat absorption characteristics of the boiler.

As for the secondary hole 27, when the secondary hole ejection angle θ2 is less than 35 degrees, the flame holding effect is weakened and the vibration potential is increased. Further, when the secondary hole injection angle θ2 exceeds 55 degrees, the flame stabilization in the vicinity of the swirler 17 becomes too strong, so the burnout potential of the swirler 17 increases, and there is concern about an increase in NOx. Therefore, the proper range of the secondary hole ejection angle θ2 is 35 degrees to 55 degrees.

Furthermore, hydrogen has a faster combustion speed and better flame stability than city gas or LPG, so the secondary hole ejection angle θ2 is reduced from 35 degrees to 45 degrees compared to city gas or LPG gas fuel. Even if the angle is set to such a narrow angle, there is no problem in affecting the combustion oscillation.

Therefore, by increasing the ejection pressure of the hydrogen-containing gaseous fuel to 300 KPa or more, setting the main hole ejection angle θ1 from 25 degrees to 45 degrees, and the secondary hole ejection angle θ2 from 35 degrees to 55 degrees, Vibration can be suppressed and the amount of NOx generated can be reduced.

Furthermore, it is preferable to set the ejection angle to the narrow angle side so that the main hole ejection angle θ1 is set to 25 degrees to 35 degrees and the secondary hole ejection angle θ2 is set to 35 degrees to 45 degrees. By setting the injection angle to the narrow angle side in this way, a further reduction in NOx can be achieved.

<Still another embodiment>
In the above-described embodiment and other embodiments, the gas burner 2 has a gas nozzle 7 through which gas fuel containing hydrogen flows, a primary air flow path 9 through which primary air to be mixed with the gas fuel flows, and the primary air is mixed. and a secondary air flow path 11 mixed with the gas fuel, the air ratio of the primary air is lower than the air ratio of the secondary air, and the gas pressure of the gas fuel flowing through the nozzle is 300 kPa or more. Configuration. That is, the gas burner 2 itself constitutes the two-stage combustion apparatus 1A.

In contrast, as shown in FIGS. 6 and 7, still another embodiment includes gas nozzles 61 and 91 through which gas fuel 60 containing hydrogen flows and primary air flow paths 63 and 93 through which primary air F1 flows. and gas burners 65, 95 provided on the walls 73, 90 above the furnaces 3B, 3C from the gas burners 65, 95, and the secondary air F2 from the secondary air flow paths 67, 97 is supplied to the furnaces 3B, 3C. and a secondary air after-air port (secondary air jet port) 69, 99 that jets out to the air ratio of the primary air is lower than the air ratio of the secondary air, and the gas fuel flowing through the gas nozzles 61, 91 The gas pressure of 300 kPa or more constitutes the two-stage combustion devices 1B and 1C.

FIG. 6 is a system schematic diagram of a small boiler. A gas burner 65 is installed at the bottom of the boiler furnace 3B, and gas fuel and primary air F1 are ejected upward. A secondary air after-air port 69 is provided on the wall surface 73 of the furnace 3B above the gas burner 65, and the secondary air F2 is jetted into the furnace 3B. Steam is generated from the boiler, and the discharged exhaust gas passes through the economizer 75 and is discharged to the outside from the chimney 77 .

Gas fuel containing hydrogen is supplied to the gas nozzle 61 of the gas burner 65 . This hydrogen-containing gas fuel supply system is the same as the gas fuel supply system described with reference to FIGS. The primary air F1 and secondary air F2 to the primary air flow path 63 and the secondary air flow path 67 are adjusted to a predetermined air ratio through the flow control valves 81 and 83 by the forced draft fan 79. adjusted to be supplied.

FIG. 7 is a schematic diagram of the system of a middle- and large-sized boiler. A gas burner 95 is installed on the wall surface 90 of the furnace 3C of the boiler, and gas fuel and primary air F1 are jetted into the furnace 3C. A secondary air after-air port 99 is provided on the wall surface 90 of the furnace 3C above the gas burner 95, and the secondary air F2 is jetted into the furnace 3C. Steam is generated from the boiler, and exhaust gas is discharged from the stack 107 through the economizer 105 and the induced draft fan 106 .

Gas fuel containing hydrogen is supplied to the gas nozzle 91 of the gas burner 95 . This hydrogen-containing gas fuel supply system is the same as the gas fuel supply system described with reference to FIGS. In addition, the primary air F1 and secondary air F2 to the primary air flow path 93 and the secondary air flow path 97 are adjusted to a predetermined air ratio through the flow control valves 111 and 113 by the forced draft fan 109. adjusted to be supplied.

In the embodiments shown in FIGS. 6 and 7 above, the gas burners 65, 95 and the secondary air after-air ports 69, 99 provided on the wall surfaces 73, 90 of the furnaces 3B, 3C are provided, and the two-stage combustion apparatus 1B and 1C can be configured. The two-stage combustion devices 1B and 1C also have the same effects as the two-stage combustion device 1A already described in one embodiment.

In addition, it is possible to appropriately replace the components in the above-described embodiments with well-known components without departing from the scope of the present disclosure, and they may be combined with the above-described embodiments as appropriate.

The contents described in each of the above embodiments are understood as follows, for example.

(1) A two-stage combustion device according to one aspect includes a nozzle (gas nozzle 7 according to one embodiment, gas nozzles 61 and 91 according to another embodiment) through which gas fuel containing hydrogen flows, and A primary air flow path (primary air flow path 9 according to one embodiment, primary air flow paths 63 and 93 according to still another embodiment) through which primary air to be mixed with the gas fuel flows, and the primary air is mixed A secondary air flow path (secondary air flow path 11 according to one embodiment, secondary air flow paths 67 and 97 according to still another embodiment) through which secondary air to be mixed with the gas fuel thus obtained flows; wherein the air ratio of the primary air to the gas fuel ejected from the nozzle is lower than the air ratio of the secondary air to the gas fuel ejected from the nozzle, and the gas fuel flowing through the nozzle The gas pressure is 300 kPa or more.

According to the two-stage combustion apparatus according to the present disclosure, the hydrogen-containing gas fuel is mixed with the primary air and combusted, and then mixed with the secondary air and combusted, so NOx generation can be suppressed. That is, it is configured to suppress the generation of NOx by performing two-stage combustion.

If the temperature of the region where the fuel burns is low, the generation of NOx is suppressed. Since the air ratio of the primary air is lower than that of the secondary air, the combustion temperature in the region (first region) where the gas fuel and primary air are mixed and burned is It is often lower than the combustion temperature of the region (second region) in which the fuel is first combusted. Then, by setting the gas pressure of the gas fuel containing hydrogen flowing through the nozzle to 300 kPa or more, the mixing of the gas fuel and the primary air is promoted, and the gas fuel is supplied in the first region having a lower temperature than the second region. Relatively increases the burning rate. This can suppress the generation of NOx.

In addition, hydrogen is a compressible fluid, and the higher the pressure, the more it diffuses at the outlet of the injection hole. achieved.

Further, conventionally, in order to suppress the occurrence of combustion oscillation, the ejection pressure of the gaseous fuel ejected from the nozzle is often configured to be less than 300 kPa. For example, in a boiler burner using city gas or LPG (liquefied petroleum gas) as fuel, the applied pressure is about 130 KPa at maximum, and even when hydrogen is used as fuel, it is about 80 KPa at maximum.

According to the knowledge of the inventors of the present application, it has been found that combustion oscillation is suppressed even if the injection pressure is increased to 300 kPa or higher if the gas fuel contains hydrogen.

That is, according to the two-stage combustion device according to the present disclosure, hydrogen has a faster burning speed and better combustibility than city gas or LPG, so flame stability, that is, combustion stability is enhanced, and combustion oscillation is reduced. Potential is considered to be lower than city gas and LPG. Therefore, even if the gas pressure of gaseous fuel containing hydrogen is increased to 300 kPa or more, combustion oscillation is less likely to occur, so it is possible to suppress the generation of NOx while suppressing the combustion oscillation.

In addition, by increasing the gas pressure of the gas fuel containing hydrogen flowing through the nozzle to 300 kPa or more, it is possible to burn a larger amount of gas fuel containing hydrogen without increasing the diameter of the pipe or the gas burner.

Hydrogen has a smaller calorific value than city gas or LPG and requires a larger volume. Furthermore, it also has the advantage of enabling miniaturization.

(2) A two-stage combustion device according to another aspect is the two-stage combustion device according to (1), wherein the nozzle includes at least one main hole (main hole 25 according to one embodiment) and the at least one secondary hole (secondary hole 27 in one embodiment) having a smaller hole diameter than the primary hole.

According to the configuration (2), the amount of fuel jetted from the secondary holes is made smaller than the amount of fuel jetted from the main holes, and an appropriate amount of flame-stabilizing fuel jetted from the secondary holes is supplied to the primary air. Combustion oscillation is achieved by stabilizing the flame in the vicinity of the swirler by making it easier to be taken into the low-velocity stagnation area suitable for flame stabilization formed on the downstream side of the swirler (flame stabilizer) that gives a swirling force to a part. can be suppressed.

(3) A two-stage combustion device according to still another aspect is the two-stage combustion device according to (2), wherein the main hole is aligned with the central axis of the nozzle (the central axis C of the gas nozzle according to one embodiment). ), the gas fuel is ejected at an ejection angle of 25 degrees or more and 45 degrees or less (main hole ejection angle θ1 described in another embodiment), and the secondary hole is aligned with the central axis of the nozzle On the other hand, it is configured to eject the gas fuel at an ejection angle of 35 degrees or more and 55 degrees or less (secondary hole ejection angle θ2 described in another embodiment), and the ejection angle of the main hole is equal to the ejection angle of the secondary hole less than

According to the configuration (3), by making the ejection angle of the gas fuel from the main hole (the elevation angle with respect to the central axis C of the nozzle) smaller than 45 degrees, slow combustion is promoted by lengthening the flame. can be done. If the temperature exceeds 45 degrees, the potential for combustion oscillation due to pressure fluctuations in the furnace increases. If the ejection angle of the main hole is less than 25 degrees, the flame becomes excessively long, which affects the heat absorption characteristics of the boiler. Therefore, by setting the ejection angle of the main hole to 25 degrees or more and 45 degrees or less, it is possible to stabilize the flame and lengthen the flame at the same time. can be reduced and low NOx can be achieved.

As for the secondary holes, the amount of NOx generated can be reduced by reducing the ejection angle of the secondary holes to less than 55 degrees. If the injection angle of the secondary hole exceeds 55 degrees, the flame holding in the vicinity of the swirler of the burner becomes too strong, the burnout potential increases, and there is concern about an increase in NOx. If the ejection angle of the secondary holes is less than 35 degrees, the flame holding effect will be weak and the vibration potential will increase. Therefore, by setting the ejection angle of the secondary hole to 35 degrees or more and 55 degrees or less, it is possible to suppress the combustion oscillation and reduce the amount of NOx generated.

(4) A two-stage combustion device according to still another aspect is the two-stage combustion device according to (3), wherein the main hole ejects at an angle of 25 degrees or more and 35 degrees or less with respect to the central axis of the nozzle. the secondary hole is configured to eject the gas fuel at an angle of 35 degrees or more and 45 degrees or less with respect to the central axis of the nozzle; The ejection angle of the holes is smaller than the ejection angle of the secondary holes.

According to such configuration (4), hydrogen has a higher combustion speed than city gas or LPG, and has a relatively short flame. Even if the angle is set as narrow as 25 degrees to 35 degrees, there is no problem with the heat absorption characteristics of the boiler.

As for the secondary holes, hydrogen has a faster combustion rate and better flame stability than city gas or LPG, so the injection angle from the secondary holes is 35 degrees to 45 degrees compared to configuration (3). Even if it is set to a narrow angle as shown in , there is no problem in affecting combustion oscillation, and further reduction in NOx can be achieved.

(5) A two-stage combustion device according to still another aspect is the two-stage combustion device according to any one of (2) to (4), wherein the at least one main hole is the central axis of the nozzle. are formed at the tip of the nozzle so as to be symmetrical with respect to the center axis of the nozzle.

According to the configuration (5), the hydrogen-containing gaseous fuel ejected from the main hole can be evenly ejected toward the center of the nozzle, so that the slow combustion due to the long flame can be smoothly handled.

(6) A two-stage combustion device according to still another aspect is the two-stage combustion device according to any one of (2) to (5), wherein the at least one secondary hole is aligned with the central axis of the nozzle. are formed at the tip of the nozzle so as to be symmetrical with respect to the center axis of the nozzle.

According to the configuration (6), the hydrogen-containing gas fuel ejected from the secondary holes can be ejected evenly toward the center of the nozzle, so that the flame holding area around the swirler can be uniformly formed. , the potential of combustion oscillation can be reduced.

(7) A two-stage combustion device according to still another aspect is the two-stage combustion device according to any one of (2) to (6), wherein the total opening area of the plurality of main holes is A1, and the plurality of The ratio A1:A2 is between 80:20 and 90:10, where A2 is the total opening area of the secondary holes.

According to such a configuration (7), the fuel ejected from the secondary hole is likely to be taken into the stagnation region formed on the downstream side of the swirler (flame stabilizer) that imparts swirling force to a portion of the primary air. The swirler (flame stabilizer) provides a swirling force to a portion of the primary air when more than 20% of the fuel is ejected from the sub-hole, while stabilizing the flame and suppressing combustion oscillation. Since there is a risk of burnout, such a risk can be prevented.

(8) A two-stage combustion apparatus according to still another aspect is the two-stage combustion apparatus according to any one of (1) to (7), wherein the gas burner ( Gas burners 65, 95 according to still other embodiments), and a secondary air outlet (further secondary air after-airports 69, 99) according to other embodiments.

According to such configuration (8), a two-stage combustion apparatus can be configured by including a gas burner provided with a nozzle and a primary air flow path, and a secondary air ejection port.

(9) Further, a two-stage combustion device according to another aspect is the two-stage combustion device according to any one of (1) to (7), wherein the primary air flow path is provided on the outer peripheral portion of the nozzle. and a gas burner (gas burner 2 according to one embodiment) provided with the secondary air flow path on the outer periphery of the primary air flow path.

According to such configuration (9), the two-stage combustion apparatus can be configured by the gas burner itself, and the two-stage combustion apparatus can be compactly configured.

1A, 1B, 1C Two-stage combustion devices 2, 65, 95 Gas burners 3A, 3B, 3C Furnace 5 Burner throat 6 Water pipes 7, 61, 91 Gas nozzles (nozzles)
9, 63, 93 Primary air flow path 11, 67, 97 Secondary air flow path 13 Primary sleeve 15 Secondary sleeve 17 Swirler (flame stabilizer)
19 Stagnation region 21 Opening 23 Air register 25 Main hole 27 Secondary hole 29 Hydrogen gas tank 31 Inlet valve 33 Pressure reducing valve 35 Flow meter 37 Thermometer 39, 45 Shutoff valve 41 Pressure gauge 43 Flow control valve 47 Burner inlet pressure gauge 49 Burner inlet Valve 51 By-product hydrogen 53 Booster 69, 99 Secondary air after-air port (secondary air ejection port)
C Central axis of gas burner and gas nozzle F1 Primary air F2 Secondary air θ1 Main hole ejection angle θ2 Secondary hole ejection angle

Claims (9)

a nozzle through which gas fuel containing hydrogen flows;
a primary air flow path through which primary air to be mixed with the gas fuel ejected from the nozzle flows;
a secondary air flow path through which secondary air to be mixed with the gas fuel mixed with the primary air and burned ,
an air ratio of the primary air to the gas fuel ejected from the nozzle is lower than an air ratio of the secondary air to the gas fuel ejected from the nozzle;
The two-stage combustion device, wherein the gas pressure of the gas fuel flowing through the nozzle is 300 kPa or more. 2. The two-stage combustion device of claim 1, wherein the nozzle includes at least one primary hole and at least one secondary hole having a smaller hole diameter than the primary hole. The main hole is configured to eject the gas fuel at an ejection angle of 25 degrees or more and 45 degrees or less with respect to the central axis of the nozzle,
The secondary hole is configured to eject the gas fuel at an ejection angle of 35 degrees or more and 55 degrees or less with respect to the central axis of the nozzle,
3. The two-stage combustion device according to claim 2, wherein the ejection angle of said main hole is smaller than the ejection angle of said secondary hole. The main hole is configured to eject the gas fuel at an ejection angle of 25 degrees or more and 35 degrees or less with respect to the central axis of the nozzle,
The secondary hole is configured to eject the gas fuel at an ejection angle of 35 degrees or more and 45 degrees or less with respect to the central axis of the nozzle,
4. The two-stage combustion device according to claim 3, wherein the ejection angle of the main hole is smaller than the ejection angle of the secondary hole. 5. A plurality of said at least one main holes are formed at the tip of said nozzle so as to be symmetrical with each other around the central axis of said nozzle with said central axis of said nozzle interposed therebetween. A two-stage combustion device according to any one of claims 1 to 3. 6. A plurality of said at least one secondary holes are formed at the tip of said nozzle so as to be symmetrical with each other around the central axis of said nozzle with said central axis of said nozzle interposed therebetween. A two-stage combustion device according to any one of claims 1 to 3. The ratio A1:A2 is between 80:20 and 90:10, where A1 is the total opening area of the plurality of main holes and A2 is the total opening area of the plurality of secondary holes. 7. The two-stage combustion device according to any one of 6. a gas burner provided with the nozzle and the primary air flow path; and a secondary air ejection port provided on a wall surface of the furnace above the gas burner for ejecting the secondary air from the secondary air flow path into the furnace. 8. A staged combustion apparatus according to any one of claims 1 to 7, comprising: 8. The gas burner according to any one of claims 1 to 7, wherein the gas burner is provided with the primary air flow path on the outer circumference of the nozzle, and the secondary air flow path on the outer circumference of the primary air flow path. Staged combustion device.

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