JPH11350973A - Additional combustion method using gas turbine exhaust gas and additional combustion burner which uses said additional combustion method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable additional carburation of gas turbine exhaust gas, increase of turndown ratio by stabilizing combustion, combustion without using a large amount of fresh air, and elimination of long straight ducts. SOLUTION: In this additional combustion method using gas turbine exhaust gas, an additional combustion fuel F is combusted by using oxygen which remains in an exhaust gas E of the gas turbine for reheating the gas turbine exhaust gas E. Further, fuel supply is divided into a primary and a secondary. To the primary fuel F1 , fresh air A of the amount that burns up the total amount of the primary fuel F1 is injected to the primary fuel F1 to generate a primary flame 2. In addition, after injection of the primary fuel F1 , in the area surrounding the primary flame 2 in the downstream of the primary fuel injection, the secondary fuel F2 is injected, while the gas turbine exhaust gas E is blown generally in parallel with the primary flame 2 around the secondary fuel F2 , which generates a secondary flame 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refired combustion method for increasing the heat of GT exhaust gas by combustion utilizing oxygen remaining in gas turbine exhaust gas (hereinafter abbreviated as GT exhaust gas), and a method thereof. Reburning burner to be used.

[0002]

2. Description of the Related Art Since GT exhaust gas after working in a gas turbine still has sufficient heat as a heat source for a boiler, the entire amount is supplied to an exhaust heat boiler without being discarded and used as a heat source. Have been. At this time, since oxygen is left in the GT exhaust gas, additional heating is performed using the oxygen, and the GT exhaust gas itself is reheated to increase the amount of steam generated as the GT exhaust gas having a higher calorific value. I have. The use of duct burners is the mainstream for reheating GT exhaust gas. In this duct burner, a fuel supply pipe is arranged in a duct for guiding GT exhaust gas to a waste heat boiler so as to be orthogonal to the flow of GT exhaust gas, and refired from a plurality of fuel injection holes toward the downstream side of the flow of GT exhaust gas. It is provided to inject fuel. In this reburning burner, fuel is injected from the injection hole of the fuel supply pipe and reburning is performed using remaining oxygen in the GT exhaust gas, so that the flow of the GT exhaust gas is adjusted and uniformized. Requires a straight pipe section.

[0003]

However, in the above-described duct burner, a considerable length of a straight pipe portion is required to sufficiently suppress the drift of GT exhaust gas in the duct. As a result, there is a problem that the arrangement of facilities such as a gas turbine and a waste heat boiler is significantly restricted. In addition, when a sufficient straight pipe portion cannot be obtained, the mixing of the reburning fuel and the GT exhaust gas is partially insufficient, so that a favorable combustion state cannot be obtained and a desired increase in heat may not be achieved.

[0004] Further, since the duct burner merely injects fuel into the flow of GT exhaust gas, combustion tends to be unstable, and in general, a GT exhaust gas having an oxygen concentration of about 12 to 16% (WET) is used. However, only reburning combustion whose oxygen concentration is reduced to about 9% can be performed, and the combustion amount cannot be increased without replenishment of fresh air (air that has never been used for combustion). For this reason, the amount of heat obtained by the additional combustion becomes insufficient, and a sufficient increase in the heat of the GT exhaust gas cannot be obtained. Therefore, there is a problem that it cannot cope with a case where a large amount of steam is required.

[0005] Further, in this duct burner, since the amount of GT exhaust gas is overwhelmingly large and the oxygen concentration is low, the stability of combustion is originally poor even if the air ratio becomes extremely excessive.
If the amount of combustion is reduced (that is, turned down), the combustion becomes more unstable, so the turndown ratio must be set to a small value of about 3 to 5: 1.

Further, recently, a chain cycle is often adopted in which a surplus of steam generated in a waste heat boiler is heated and returned to the gas turbine side to increase the rotation speed of the gas turbine. However, when the chain cycle is used, the oxygen concentration of the GT exhaust gas often drops to about 8% (WET), and the amount of water is large. For this reason,
It is difficult to perform reburning combustion using only the residual oxygen in the GT exhaust gas, and it is necessary to mix a large amount of fresh air to increase the oxygen concentration before reburning combustion.
The advantage of reburning combustion using residual oxygen in exhaust gas is reduced. That is, it is difficult to realize reheating for increasing the heat of the GT exhaust gas with a small amount of refired fuel.

Further, in order to ensure the amount of steam generated in the exhaust heat boiler even when the gas turbine is stopped, it is necessary to use a normal diffusion combustion method using only fresh air without using GT exhaust gas in a reheating burner. (Fresh mode combustion) must be performed. However, flowing fresh air in place of GT exhaust gas in a duct burner requires an unnecessarily large amount of fresh air, so that a large amount of energy is consumed to supply the fresh air and overall efficiency is deteriorated.

Accordingly, an object of the present invention is to provide a reburning combustion method utilizing GT exhaust gas which can realize a compact combustion facility, and a reburning burner utilizing the method. Further, the present invention provides a G gas capable of further increasing the heat of GT exhaust gas.
An object of the present invention is to provide a reburning combustion method using T exhaust gas and a reburning burner using the method. Another object of the present invention is to provide a reburning combustion method using GT exhaust gas, which can increase the turndown ratio, and a reburning burner using the method. Still another object of the present invention is to provide a reburning combustion method using GT exhaust gas, which can reburn combustion without using a large amount of combustion air, and a reburn burner using the same.

[0009]

In order to achieve the above object, the invention according to claim 1 is to reheat the GT exhaust gas by burning the reburn fuel by using oxygen remaining in the GT exhaust gas. In the method, the supplementary fuel is supplied in two stages of the primary fuel and the secondary fuel, and the combustion air is supplied at an appropriate air ratio to the primary fuel in the first stage to form a primary flame. On the other hand, in the second stage, secondary fuel is injected around the primary flame, GT exhaust gas is injected around the jet of the secondary fuel, and the secondary fuel is completely burned using residual oxygen in the GT exhaust gas. Like that.

Therefore, in the first stage, the primary fuel is completely burned under an appropriate air ratio. Then, the secondary fuel supplied in the second stage is completely burned by utilizing residual oxygen in a large amount of GT exhaust gas injected from around the secondary fuel. At this time, although the primary fuel burns at an appropriate air ratio, a large amount of NOx is generated. However, the NOx is reduced by contact with the secondary fuel, so that the NOx generated in the primary combustion is reduced. On the other hand,
The secondary fuel is completely combusted under a super-excess air ratio utilizing a low concentration of oxygen remaining in a large amount of GT exhaust gas.
The generation amount of x is small. Further, since complete combustion is performed in each of the first-stage and second-stage combustion, the generation of CO can also be suppressed. And, as a whole, NOx
The GT exhaust gas is reheated by using the calorific value obtained while suppressing the generation amount of the gas.

In addition, since fresh air is supplied to the primary fuel at an appropriate air ratio that causes complete combustion, the primary flame that stably burns functions as a flame holding source, and the second stage GT exhaust gas having a low oxygen concentration. The secondary fuel is stably and completely burned even if is supplied in an overwhelming amount due to an overwhelming amount of air, and the combustion stability is not impaired even if the turndown width is increased.

Also, when increasing the amount of generated heat by increasing the injection amount of the refired fuel, the primary flame using fresh air becomes a flame holding source, so that stable combustion using GT exhaust gas becomes possible. In addition, the reburning combustion that lowers the oxygen concentration of the GT exhaust gas is realized.

Further, the remaining reburned fuel (secondary fuel) and the entire amount of GT exhaust gas are ejected from around the primary flame formed by well mixed fresh air and part of the reburned fuel (primary fuel). So that their mixture is G
Even if it is affected by the drift of the T exhaust gas, the secondary combustion does not become unstable.

According to a second aspect of the present invention, there is provided a reburning combustion method for reheating the GT exhaust gas by burning the reburned fuel by utilizing oxygen remaining in the GT exhaust gas. After the supplementary fuel and the combustion air having a stoichiometric amount less than the theoretical air amount are supplied to the supplementary combustion area located on the upstream side and incompletely combusted, a part of the GT exhaust gas is removed from the small combustion area. Into the flame from around the incomplete combustion flame and supplement the insufficient oxygen with the residual oxygen in the flame to burn the unburned portion and complete combustion as a whole, while starting from the small combustion zone to the combustion space The remaining part of the GT exhaust gas is injected into the combustion space almost in parallel with the flame injected into the combustion space, and the remaining GT
The exhaust gas is reheated.

Therefore, incomplete combustion occurs with fresh air less than the stoichiometric air amount and the total amount of refired fuel.
Although the generation of x is small, it involves the generation of unburned components, but a portion of the GT exhaust gas is supplied downstream, and the insufficient oxygen is supplemented by the remaining oxygen in the exhaust gas. Completely burn. And the remaining GT around this flame
Since the exhaust gas is injected in the axial direction, the rest of the GT exhaust gas is heated and heated by mixing with the combustion gas.

Further, since fresh air having less than the theoretical amount of air in the small combustion region and oxygen in the shortage thereof are supplemented by residual oxygen in a part of the GT exhaust gas, the reburned fuel is completely burned.
Reburning combustion that enables stable combustion without being influenced by the oxygen concentration and amount of T exhaust gas, can increase the turndown ratio, and lowers the oxygen concentration of GT exhaust gas to a much lower concentration (for example, about 3%). , And the amount of reheating can be increased to increase the heat of the GT exhaust gas.

Further, since the combustion air is used in addition to the GT exhaust gas, the oxygen concentration can be increased as compared with the case where combustion is performed using only the GT exhaust gas, and there is no problem even if the oxygen concentration of the GT exhaust gas is low. Combustion can be easily performed even when using a GT exhaust gas having a lower oxygen concentration than usual, for example, a GT exhaust gas in a chain cycle.

On the other hand, a reburning burner utilizing GT exhaust gas according to claim 3 is a fuel supply system for supplying reburned fuel in two stages of a primary fuel and a secondary fuel, and an appropriate air ratio to the primary fuel. A combustion air supply system for supplying combustion air to the burner throat, a primary fuel nozzle for injecting primary fuel in the burner throat, and a secondary fuel around the primary flame downstream of the primary fuel nozzle. A secondary fuel nozzle for injecting gas, and an exhaust gas nozzle for injecting gas turbine exhaust gas substantially parallel to the primary flame from around the secondary fuel nozzle into the combustion chamber of the reheating boiler, so that the secondary fuel is contained in the gas turbine exhaust gas. Complete combustion is carried out using the residual oxygen, and the gas turbine exhaust gas is reheated together with the primary flame.

Therefore, diffusion combustion of the secondary fuel injected around the stable flame which completely burns with the amount of fresh air having an appropriate air ratio with respect to the primary fuel and the residual oxygen in the GT exhaust gas is performed. Stabilize. That is, the additional combustion described in claim 1 is realized.

In addition, since the exhaust gas nozzle is arranged around the primary flame with the injection axis directed substantially parallel to the primary flame, the flame holding of the primary flame can be performed without providing a primary combustion cylinder for holding the primary flame. Can be secured. Therefore, the turndown ratio can be increased by stabilizing the combustion.

Further, since the GT exhaust gas is injected from the exhaust gas nozzle around the primary flame formed by the primary fuel and fresh air having an appropriate air ratio in parallel with the flame, the GT exhaust gas is rectified to some extent. As a result, the influence of the drift is eliminated, and the mixing of the combustion gas and the GT exhaust gas is also good.

According to a fourth aspect of the present invention, there is provided a reburning burner utilizing GT exhaust gas, wherein a primary combustion cylinder which forms a combustion space into which gas turbine exhaust gas is introduced and forms a small combustion zone upstream thereof is arranged. A main body, a fuel nozzle for injecting additional combustion fuel into the primary combustion cylinder, a combustion air supply system for injecting combustion air less than the theoretical air amount to the additional combustion fuel, and a peripheral wall of the primary combustion cylinder. A primary exhaust gas nozzle for introducing the gas turbine exhaust gas into the primary combustion cylinder, and a secondary exhaust gas nozzle for injecting the remainder of the gas turbine exhaust gas substantially parallel to the flame into the combustion space. Partial combustion is performed by using less than the amount of combustion air and a part of the gas turbine exhaust gas, and the heat of the combustion gas reheats the remaining gas turbine exhaust gas.

Therefore, in the primary combustion cylinder, first, after burning with fresh air less than the stoichiometric air amount and the whole amount of the reburning fuel, a part of the GT exhaust gas is supplied downstream thereof and the remaining oxygen in the GT exhaust gas is insufficient. The oxygen is supplemented, and the unburned components are burned to perform partial combustion in which the whole is completely burned. Then, the remaining GT exhaust gas around the flame injected from the primary combustion cylinder into the combustion space is injected into the combustion space in parallel with the flame and heated. That is, the additional combustion described in claim 2 is realized.

Moreover, since the primary exhaust gas nozzle injects part of the GT exhaust gas toward the flow of the flame and the combustion gas in the primary combustion cylinder, the GT exhaust gas and the unburned components in the flame are rapidly mixed. Completely burned. In addition, since the flame formed using fresh air less than the theoretical air amount and part of the gas turbine exhaust gas is held by the primary combustion cylinder,
Combustion is stable and the turndown ratio can be increased.

Further, in the primary combustion cylinder, a flame is formed by partial combustion of fresh air in which the refired fuel is less than the theoretical air amount and residual oxygen contained in a part of the GT exhaust gas, and the flame injected from the primary combustion cylinder Since the remaining GT exhaust gas is injected from the secondary exhaust gas nozzle on the periphery thereof, the GT exhaust gas can be rectified to some extent and injected, and the GT exhaust gas after injection and the combustion gas from the primary combustion cylinder can be mixed. Good mixing can be achieved.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail based on an example of an embodiment shown in the drawings. FIG. 1 shows an embodiment of a reburning burner using GT exhaust gas according to the present invention, and the principle of a reburning combustion method using GT exhaust gas will be described based on the reburning burner. The reburning burner 1 using the GT exhaust gas reheats the GT exhaust gas by burning the reburn fuel using oxygen remaining in the GT exhaust gas, and reheats the GT exhaust gas itself with the primary fuel F1 and the secondary fuel F1. A fuel supply system 12 for supplying the fuel in two stages of F2; a combustion air supply system 15 for supplying an amount of combustion air A having an appropriate air ratio to the primary fuel F1 to the burner throat 5; A primary fuel nozzle 10 that injects the primary fuel F1, a secondary fuel nozzle 11 that injects the secondary fuel F2 around the primary flame 2 downstream of the primary fuel nozzle 10, and a secondary fuel nozzle 11 that surrounds the secondary fuel nozzle 11. GT substantially parallel to the primary flame 2 into the combustion chamber 18 formed in the combustion chamber or duct of the reheating boiler.
An exhaust gas nozzle 7 for injecting exhaust gas E is provided, and the secondary fuel F2 is completely burned using residual oxygen in the GT exhaust gas E. The secondary flame 3 and the primary flame 2 generated at this time
The exhaust gas E is reheated.

The reheating burner 1 is attached to the exhaust heat boiler 9 such that the burner tile front surface 8 is exposed inside the exhaust heat boiler 9, for example. This makes it possible to use the combustion chamber 18 and the like of the exhaust heat boiler 9 without providing a combustion chamber in the post-burning burner 1 itself. Therefore, the structure of the reburning burner 1 can be simplified. For this reason, since it is not necessary to perform the construction according to the life of the refractory material such as the combustion chamber and the primary combustion cylinder, the maintenance cost of the post-fired burner 1 can be reduced.

The primary fuel nozzle 10 has a burner throat 5
And is provided so as to inject the primary fuel F1 into the combustion air A ejected from the burner throat 5. The plurality of injection holes formed at the tip of the primary fuel nozzle 10 are opened so as to extend the injection axis of the primary fuel F1 obliquely forward. Thereby, the primary fuel F
1 is injected outward from the injection hole toward the combustion air A. Further, the primary fuel nozzle 10 is connected to the primary fuel supply pipe 12.
And is connected to the outside of the burner casing 13 to receive the supply of the primary fuel F1.

The secondary fuel nozzle 11 is a primary fuel nozzle 1
An injection hole is provided around the primary flame 2 downstream of 0 so as to inject the secondary fuel F2 toward the primary flame 2. One or more, preferably two to four secondary fuel nozzles 11 are arranged around the burner throat 5 so as to penetrate the burner tile 14. For example, in the case of the present embodiment, four secondary fuel nozzles 11 are arranged concentrically with the burner throat 5 at equal intervals. In this embodiment, the burner throat 5 is connected to the burner tile front surface 8.
The secondary fuel nozzle 11 is disposed around the burner throat 5 by being recessed upstream of the combustion air A. For this reason, the secondary fuel nozzle 11 injects the secondary fuel F <b> 2 into the exhaust heat boiler 9 at a position recessed on the upstream side of the combustion air A from the burner tile front surface 8. The injection hole at the tip of the secondary fuel nozzle 11 injects the secondary fuel F2 toward the primary flame 2 and reduces the NOx generated in the primary flame 2 by oxygen remaining in the GT exhaust gas E flowing around after the reduction. It is set slightly inward so as to form the next flame 3. In the present embodiment, the injection hole of the secondary fuel nozzle 11 is formed inward, but the invention is not limited to this, and the injection hole may be formed parallel to the injection axis of the combustion air A or may be formed outward. good. Further, a slight gap 16 is provided between the secondary fuel nozzle 11 and the burner tile 14, and is provided so as to cool the secondary fuel nozzle 11 by flowing a part of the combustion air A, for example, several percent. ing.

Primary fuel nozzle 10 and secondary fuel nozzle 11
Is a header outside the burner casing 13 (not shown)
Connected to a fuel supply source (not shown). Then, the fuel F supplied from the fuel supply source is distributed to the primary fuel nozzles 10 and the secondary fuel nozzles 11 according to a predetermined distribution ratio, and is injected respectively. In the present embodiment, the injection amount of each of the primary fuel F1 and the secondary fuel F2 is set to 50% by volume with respect to the total fuel F.

The burner casing 13 has an air damper 17.
And a combustion air supply system 15 is connected via an air inlet. Then, inside the burner casing 13, the combustion air A flows toward the exhaust heat boiler 9 while cooling it along the secondary fuel nozzle 11 outside the guide cylinder 21. Further, the combustion air A is swirled by the swirler 19 and sent to the burner throat 5. The combustion air A is swirled by a swirler 20 installed around the primary fuel nozzle 10 and injected from the burner throat 5 into the combustion chamber 18 of the exhaust heat boiler 9. Here, the fresh air A supplied from the combustion air supply system 15 is an amount that provides an appropriate air ratio to the primary fuel F1.

Further, a GT exhaust gas box 4 for taking in and rectifying the GT exhaust gas E is provided on the outer peripheral portion of the secondary fuel supply pipe 15. This GT exhaust gas wind box 4 is formed of a refractory material 28 so that the end face on the exhaust heat boiler 9 side is flush with the burner tile front surface 8 to be exposed to the exhaust heat boiler 9 and to take in high-temperature GT exhaust gas E. . This G
The T exhaust gas box 4 has an intake 2 for taking in the GT exhaust gas E.
2 and an exhaust gas nozzle 7 for ejecting the GT exhaust gas E around the primary flame 2. A duct (not shown) to which the GT exhaust gas E is supplied from the gas turbine equipment is connected to the intake port 22.

The exhaust gas nozzle 7 forms the secondary flame 3 by injecting the GT exhaust gas E substantially in parallel with the primary flame 2, and forms a primary flame around the primary flame 2 downstream of the primary fuel nozzle 10. It is installed with the injection axis facing almost parallel to 2. In the present embodiment, the exhaust gas nozzle 7 includes a plurality of through holes that penetrate the refractory material 28 on the outer peripheral portion of the burner throat 5 and communicate the inside of the GT exhaust gas wind box 4 and the exhaust heat boiler 9. The through hole is formed parallel to the injection axis of the burner throat 5 and is formed concentrically around the burner throat 5.

In this embodiment, the burner throat 5 is formed at a position recessed upstream of the burner tile front surface 8 with respect to the combustion air A, so that the exhaust gas nozzle 7 is located downstream of the primary fuel nozzle 10. And the injection axis is oriented around the primary flame 2 almost in parallel with the primary flame 2. For this reason, the GT exhaust gas E is ejected as an axial jet substantially parallel to the primary flame 2 on the side of the primary flame 2, so that the GT exhaust gas E is prevented from directly ejecting toward the primary flame 2 to prevent the primary flame 2. Flame-retardant properties of the product. At the same time, the jet of the GT exhaust gas E whose flow velocity has been increased by the exhaust gas nozzle 7 makes the mixing with the primary and secondary combustion gases better. Accordingly, it is not necessary to provide a primary combustion cylinder for maintaining the flame of the primary flame 2, so that the structure of the reburning burner 1 can be simplified. Moreover,
Since the thermal effects of the flames 2 and 3 are given only to the burner tile 14, the life of the refractory material other than the burner tile 14 can be extended.

According to the reburning burner 1 using GT exhaust gas configured as described above, reburning combustion using GT exhaust gas E can be performed as follows.

This reburning burner uses the fuel F as the primary fuel F1.
And the secondary fuel F2 in two stages.
11, fresh air A is supplied as an oxidizing agent from the burner throat 5 to the first-stage primary fuel F1, and the total amount of GT exhaust gas E as an oxidizing agent is supplied to the second-stage secondary fuel F2. Is supplied from the exhaust gas nozzle 7 to perform two-stage combustion.

In the first-stage primary combustion, the primary flame 2 is formed by injecting the primary fuel F1 and fresh air A in an amount that provides an appropriate air ratio to the primary fuel F1. The appropriate air ratio (m) is usually 1.1 to in the case of gaseous fuel.
1.2, and about 1.1 to 1.3 in the case of oil fuel. In the case of the present embodiment, the distribution of the primary fuel F1 and the secondary fuel F2 is not particularly limited,
For example, 50% by volume of primary fuel F1 and 50% of secondary fuel F2
When the volume% is set, the amount of the fresh air A is set to an air ratio of, for example, m = 0.6 with respect to the total amount of the supplied supplementary fuel F
And In this case, since the air ratio of the fresh air A to the primary fuel F1 is equivalent to the appropriate air ratio m = 1.2, the primary fuel F1 is completely burned by the fresh air A and is stable without generating CO or the like. The primary flame 2 can be formed by combustion.

In the second stage, the secondary fuel F2 is supplied from the secondary fuel nozzle 11 to the primary flame 2 or to the primary flame 2.
Injected in parallel to Thus, reduction combustion is performed around the primary flame 2, so that NOx generated in the primary combustion can be reduced and reduced. And the secondary fuel F
The GT exhaust gas E is ejected from an exhaust gas nozzle 7 further outside the gas exhaust nozzle 2. Thereby, the secondary fuel F2 is completely burned using the low-concentration oxygen contained in the GT exhaust gas E. GT
Since the exhaust gas E is injected almost in parallel with the primary flame 2,
The secondary flame 3 can be formed around the primary flame 2 while maintaining the flame.

In this embodiment, the fresh air A
Is set to m = 0.6 with respect to the total amount of the supplied fuel F, but this is not particularly limited. It is preferable to minimize the amount of fresh air in order to improve the efficiency of reburning combustion. However, if the amount is too small and approaches the theoretical air amount, CO and the like will be generated due to incomplete combustion. As an air ratio to F, for example, m = 0.5
About 0.6 (corresponding to m = 1 to 1.2 in the air ratio to the primary fuel F1), more preferably 0.55 to
0.6 (m = 1.1 to air ratio with respect to primary fuel F1)
(Equivalent to 1.2). A part of the fresh air (usually about several percent) is generally used as cooling air for the secondary fuel nozzle, and substantially all of the fresh air is mixed with the primary fuel F1. Although it cannot be said that the amount is negligible, it does not substantially affect the proper air ratio.

The distribution ratio between the primary fuel F1 and the secondary fuel F2 is set to a ratio other than 50:50, for example, from 70:30 to 30:
Even when the range is 70, the supply amount of the fresh air A is set such that the air ratio of the fresh air A to the primary fuel F1 is about m = 1 to 1.2, preferably m = 1.2. Thereby, the primary fuel F1 can form the primary flame 2 by the fresh air A and completely burn.

According to the reburning burner 1 utilizing the GT exhaust gas, the primary fuel is burned at an appropriate air ratio, so that a large amount of NOx is generated together with the stable combustion, but the NOx is contacted with the secondary fuel. Is reduced, so that NOx generated in the primary combustion is reduced. On the other hand, a large amount of G
Since the low-concentration oxygen remaining in the T exhaust gas is used for complete combustion under a super-excess air ratio, the amount of NOx generated is small. Further, since complete combustion is performed in each of the first-stage and second-stage combustion, the generation of CO can also be suppressed. Thus, the reheat of the GT exhaust gas is achieved by using the calorific value obtained while suppressing the generation amount of NOx as a whole.

Further, since the secondary fuel and the GT exhaust gas substantially parallel to the primary flame are injected around the primary flame that stably and completely burns under an appropriate air ratio, the secondary combustion is performed. The primary flame functions as a flame holding source without providing a primary combustion cylinder that holds the primary flame, and the second stage provides an overwhelmingly large amount of low-oxygen-concentration GT exhaust gas, resulting in a super-excess air state. However, even if the secondary fuel burns stably and completely, and even if the turndown width is increased, the stability of combustion is not impaired. Specifically, the turndown ratio could be improved to about 10: 1 when using gaseous fuel and about 8: 1 when using liquid fuel.

Further, even when the GT exhaust gas from the GT using the chain cycle is used, a stable primary flame 2 can be used.
Fuel F2 using the oxygen of GT exhaust gas due to the presence of
Can be easily burned.

Also, when increasing the amount of heat generated by increasing the injection amount of the refired fuel, the primary flame using fresh air serves as a flame holding source, so that stable combustion using GT exhaust gas becomes possible. In addition, the reburning combustion that lowers the oxygen concentration of the GT exhaust gas is realized. Therefore, the amount of steam generated in the exhaust heat boiler 9 can be increased, and it is possible to easily cope with a case where a large amount of steam is required.

Further, the remaining refired fuel (secondary fuel) and the entire amount of GT exhaust gas are ejected from around the primary flame formed by well mixed fresh air and part of the refired fuel (primary fuel). So that their mixture is G
Even if it is affected by the drift of the T exhaust gas, the secondary combustion does not become unstable. Therefore, GT exhaust gas E
Can be injected into the wind box 4 from the side once to perform a certain degree of rectification, and then injected in parallel with the primary flame 2. A duct (not shown) for the GT exhaust gas E from the gas turbine equipment to the reburning burner 1 Even if the shape is bent, the influence of the drift can be suppressed. For this reason, the degree of freedom in the arrangement of the gas turbine equipment and the reburner 1 can be increased.

When the gas turbine equipment is stopped due to a trouble or the like, it is necessary to supply only fresh air to the reburning burner 1 to perform fresh mode combustion in order to secure the amount of steam generated in the exhaust heat boiler 9. There are cases. In this case, the burner throat 5 injects fresh air A in such an amount that the air ratio becomes, for example, m = 1.15 with respect to the total supplied fuel F, and the total supply amount of the fuel F from each fuel nozzle 10, 11. 50% by volume of fuel F
1, F2 is injected. This fresh mode combustion is performed based on the principle of two-stage fuel combustion similar to the known low NOx burner. For this reason, since primary combustion results in super-excess air combustion, generation of NOx can be suppressed. Then, in the secondary combustion, the complete combustion of the secondary fuel F2 can be performed by using the combustion gas in the primary combustion.
The generation of CO can be suppressed.

When fresh mode combustion is performed using the above-described reburning burner 1, when 13A gas is used as the fuel F, the oxygen content of the combustion gas is set to 5% and N
The content of Ox could be reduced to 60 ppm or less. Similarly, when heavy fuel oil A (N = 0.03% by weight) is used as fuel F, the oxygen content of the combustion gas is set to 4% and NOx
Was reduced to 80 ppm or less.

Therefore, when performing the fresh mode combustion, the air ratio can be suppressed to about m = 1.15, so that the combustion efficiency including the supply of the fresh air can be made better than that of the duct burner.

FIG. 2 shows another embodiment of the present invention. This embodiment shows an example of a post-burning burner 1 that realizes a post-burning combustion method in which GT exhaust gas is injected in two stages.

The post-burning burner 1 includes a burner main body 30 in which a combustion space 27 for introducing the GT exhaust gas E is formed, and a primary combustion cylinder 23 forming a small combustion zone 33 is disposed upstream of the combustion space 27. A fuel nozzle 6 for injecting the reburned fuel F into the cylinder 23, a combustion air supply system 15 for injecting a combustion air A less than the theoretical air amount to the reburned fuel F, and a peripheral wall of the primary combustion cylinder 23. A primary exhaust gas nozzle 24 that is formed to introduce the GT exhaust gas into the primary combustion cylinder 23;
7, a secondary exhaust gas nozzle 26 for injecting the remaining portion of the GT exhaust gas E substantially in parallel with the flame 29, and using a portion of the combustion air A and a part of the GT exhaust gas E less than the theoretical air amount in the primary combustion cylinder 23. The combustion gas and flame 29
Is used to reheat the remaining GT exhaust gas E.

The reburning burner 1 has a combustion space 27 which is installed in the exhaust heat boiler 9 so as to be opened and in which combustion is performed. On the upstream side of the combustion space 27, a primary combustion cylinder 23 forming a small combustion zone 33, and G
An exhaust gas box 4 for rectifying the T exhaust gas E is provided. The primary combustion cylinder 23 is provided with an air throat 31 for injecting fresh air and a fuel nozzle 6 for injecting additional fuel, so that a flame 29 is formed inside. Further, the exhaust gas wind box 4 takes in and rectifies the GT exhaust gas E and sends it out to the combustion space 27. Here, since the surroundings of the flame 29 are protected by the primary combustion cylinder 23, the exhaust gas wind box 4
The flame 29 is not blown off by the GT exhaust gas E introduced into the air.

On the peripheral wall of the primary combustion cylinder 23, the primary exhaust gas E
A primary exhaust gas nozzle 24 including a plurality of through holes is formed for allowing 1 to flow from the exhaust gas wind box 4 to the inside of the primary combustion cylinder 23. Each primary exhaust gas nozzle 24 is formed such that the injection axis faces obliquely forward. Then, the primary exhaust gas E1 enters the inside of the primary combustion cylinder 23 from the exhaust gas wind box 4 through the primary exhaust gas nozzle 24, and is injected toward the flame 29. For this reason, the oxygen in the GT exhaust gas E is supplied to the flame 29, and the insufficient oxygen is compensated for only by the fresh air ejected from the air throat 31, so that the unburned portion is completely burned and the generation of CO is suppressed. I have.

Further, a secondary exhaust gas nozzle 26 is provided around the flame 2 downstream of the primary exhaust gas nozzle 24. In the present embodiment, the secondary exhaust gas nozzle 26 is installed on the front wall 25 of the exhaust gas wind box 4 provided around the front end of the primary combustion cylinder 23, and is disposed concentrically with the primary combustion cylinder 23. Consisting of through holes. This secondary exhaust gas nozzle 26
Represents the flame 2 which is ejected from the primary combustion cylinder 23 through the injection shaft.
9 is formed in parallel. For this reason, the secondary exhaust gas E2 is injected from the secondary exhaust gas nozzle 26 around the flame 29 in parallel thereto. In the present embodiment, the secondary exhaust gas nozzle 26 is formed so that the injection axis is parallel to the injection axis of the fuel F. However, the present invention is not limited to this, and the injection axis is slightly inward with respect to the injection axis of the fuel F. Alternatively, it may be formed so as to face outward.

On the other hand, the fuel nozzle 6 for injecting the reburning fuel F into the primary combustion cylinder 23 has an atomizer. Therefore, the fresh air A and the fuel F can be mixed well. Note that reference numeral 32 in the drawing is a fireproof block.

According to the reburning burner 1 using GT exhaust gas configured as described above, combustion using GT exhaust gas E can be performed as follows.

The reburning burner 1 is supplied with all reburning fuel F and fresh air A which is less than the theoretical air amount to a small burning combustion zone 33 defined by the primary combustion cylinder 23, GT exhaust gas E is introduced into the box 4. For example, additional fuel F and fresh air A in an amount corresponding to an air ratio m = 0.7 are injected into the primary combustion cylinder 23. For this reason, the fresh air A less than the theoretical air amount injected into the primary combustion cylinder 23 and the total amount of the refired fuel F are:
First, incomplete combustion is performed, and a portion of the GT exhaust gas (primary exhaust gas E1) is supplied downstream thereof, and the remaining oxygen in the exhaust gas supplements the insufficient oxygen, and the unburned portion is burned to completely burn as a whole. Perform combustion. The remaining GT around the flame 29 injected from the primary combustion cylinder 23 into the combustion space 27
The exhaust gas (secondary exhaust gas E2) is injected from the secondary exhaust gas nozzle 26 into the combustion space 27 in parallel with the flame 29, and the flame 2
At 9 it is heated and heated by mixing with the combustion gas.

Further, according to the reburning burner 1, fresh mode combustion can be performed. In this case, it is desirable that the fresh air A has an injection amount with an air ratio of m = 1.5 or more. Thus, combustion can be performed while suppressing generation of CO even without injection of GT exhaust gas. When fresh mode combustion is performed by the post-burning burner 1, it is preferable to provide a NOx reduction facility such as steam injection in order to suppress the generation of NOx.

According to the above-described reburning burner 1 utilizing GT exhaust gas, in the primary combustion cylinder 23, the generation of NOx is small due to the partial combustion, and the unburned fuel generated by the incomplete combustion on the upstream side. Is burned by supplementing oxygen by introducing GT exhaust gas downstream, and is completely burned as a whole, so that emission of CO and the like can be suppressed. In particular, when a part of the GT exhaust gas E (primary exhaust gas E1) is injected from the primary exhaust gas nozzle 24 on the peripheral surface of the primary combustion cylinder 23 into the small combustion area 33 in the primary combustion cylinder 23 and is jetted toward the flame 29. Since the GT exhaust gas and the unburned components in the flame 29 are rapidly mixed to compensate for the insufficient oxygen, the generation of CO can be suppressed to, for example, 50 ppm or less.

In the small combustion zone 33, fresh air having less than the theoretical amount of air and insufficient oxygen are supplemented by residual oxygen in a part E1 of the GT exhaust gas to completely burn the reburned fuel. Stable combustion is possible regardless of the oxygen concentration and amount of the gas, and the turndown ratio can be increased and the reburning combustion that reduces the oxygen concentration of GT exhaust gas to a much lower concentration (for example, about 3%) is possible. In addition, the amount of reheating can be increased to increase the heat of the GT exhaust gas. Moreover, since the flame 29 formed by using fresh air less than the theoretical air amount and a part of the exhaust gas of the gas turbine is held by the primary combustion cylinder 23, it is possible to stably burn and increase the turndown ratio. it can. Specifically, the turndown ratio could be improved to about 10: 1 when using gaseous fuel and about 8: 1 when using liquid fuel.

Further, since the GT exhaust gas E is once introduced into the wind box 4 and rectified to some extent around the primary combustion cylinder 23, it can be injected into the primary combustion cylinder 23 and the combustion space 27, respectively. Even if the GT exhaust gas duct from the turbine equipment to the reheating burner is bent and compactly arranged, the influence of the drift can be suppressed.

Further, since the remainder of the GT exhaust gas is injected from the secondary exhaust gas nozzle around the flame injected from the primary combustion cylinder, the GT exhaust gas can be rectified to some extent and injected, and the GT exhaust gas after injection can be injected. With the combustion gas from the primary combustion cylinder.

Further, since the combustion air is used in addition to the GT exhaust gas, the oxygen concentration can be increased as compared with the case where combustion is performed using only the GT exhaust gas, and there is no problem even if the oxygen concentration of the GT exhaust gas is low. Combustion can be easily performed even when using a GT exhaust gas having a lower oxygen concentration than usual, for example, a GT exhaust gas in a chain cycle.

The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the gist of the present invention. For example, in the embodiment shown in FIG. 2, the combustion is performed in the combustion space 27 in the burner main body 30. However, the combustion space 27 is not limited to this, and the front wall 25 and the primary combustion cylinder of the exhaust gas wind box 4 are shortened. 23 may be directly exposed to the waste heat boiler 9. In this case, since the combustion chamber of the secondary flame 3 and the exhaust heat boiler 9 can be used, the burner equipment can be simplified.

Further, in any of the above-described embodiments, G
The reburning burner 1 using the T exhaust gas is directly installed in the exhaust heat boiler 9, but is not limited thereto, and may be provided in a duct from the GT to the exhaust heat boiler 9. In this case, a fire-resistant wall or a water-cooled wall is provided inside the duct on the downstream side of the reburning burner 1. This also allows the amount of combustion to be increased and the GT exhaust E
And the like, and the same effect as the reburning burner 1 of each of the above-described embodiments can be achieved.

In any of the above-described embodiments, the GT exhaust gas reheated by the reburning burner 1 is supplied to the exhaust heat boiler 9.
However, the present invention is not limited to this, and the GT exhaust gas may be used in other facilities. Also in this case, the same effect as the reburning burner 1 of each of the above-described embodiments can be obtained, for example, the amount of combustion can be increased, and the GT exhaust gas E can be reheated by stable combustion to increase the turndown ratio. Can be.

[0066]

As is apparent from the above description, according to the reburning combustion method utilizing GT exhaust gas according to the first aspect of the present invention, the generation of NOx and CO is suppressed while the GT
Enables reheating of exhaust gas. In addition, since the primary flame that stably burns with fresh air at an appropriate air ratio functions as a flame holding source, even if the GT exhaust gas with a low oxygen concentration is supplied in an overwhelmingly large amount, the secondary fuel becomes a super-excess air state. Burns stably, and even if the turndown width is increased, the stability of combustion is not impaired. Moreover, since the combustion is stabilized, the combustion can be easily performed even when using the GT exhaust gas from the GT using the chain cycle, which is extremely difficult to burn in the duct burner.

Also, when increasing the amount of heat generated by increasing the injection amount of the refired fuel, it is possible to perform stable combustion using GT exhaust gas with the primary flame using fresh air as a flame holding source. Achieve reburning combustion to lower the oxygen concentration of exhaust gas. Therefore, it is possible to easily further increase the heat of the GT exhaust gas, and it is possible to easily cope with a case where a large amount of steam is required.

Furthermore, since the GT exhaust gas is ejected from around the primary flame, a straight pipe portion for suppressing the influence of the drift of the GT exhaust gas is not required, and the size can be reduced.

Further, according to the reburning combustion method utilizing GT exhaust gas according to the second aspect of the present invention, fresh air having less than the stoichiometric amount of air in a small combustion zone and oxygen in a shortage thereof are contained in a part of the GT exhaust gas. Since the supplementary fuel is completely burned by partial combustion by supplementing with the residual oxygen, it is possible to reheat the GT exhaust gas while suppressing the generation of NOx and CO. In addition, since the flame formed in the small combustion area is protected from the jet of the GT exhaust gas and stably burns, it can be reheated irrespective of the oxygen concentration and amount of the GT exhaust gas, and the turndown ratio must be increased. Can be. Therefore, it is possible to perform reburning combustion in which the oxygen concentration of the GT exhaust gas is reduced to a much lower concentration (for example, about 3%), and it is possible to increase the amount of reburning to increase the heat of the GT exhaust gas. By injecting part of the GT exhaust gas from around the flame toward the flame, the GT exhaust gas and fuel are sufficiently mixed to supplement the insufficient oxygen in the reburning combustion, The oxygen concentration of the GT exhaust gas after combustion is much lower than that of the conventional reheating combustion method, and can be reduced to, for example, about 3%, and the reheating amount is increased without increasing the amount of fresh air to effectively reduce the amount of heat. It is possible to easily cope with cases where a large amount of steam is required by increasing the heat of the GT exhaust gas.

Further, since the remainder of the GT exhaust gas is injected from around the flame injected from the small combustion region, the GT exhaust gas can be rectified to some extent and injected, and the GT exhaust gas and the combustion gas after injection can be combined with each other. Good mixing can be achieved and the reheating temperature can be made uniform.

Further, since the combustion air is used in addition to the GT exhaust gas, the oxygen concentration can be increased as compared with the case where combustion is performed using only the GT exhaust gas, and there is no problem even if the oxygen concentration of the GT exhaust gas is low. Combustion can be easily performed even when using a GT exhaust gas having a lower oxygen concentration than usual, for example, a GT exhaust gas in a chain cycle.

Further, since the primary exhaust gas is injected into the flame to completely burn the fuel, the stability of the combustion when the GT exhaust gas is reheated can be improved. By stabilizing combustion, the turndown ratio can be increased. Moreover, since the combustion is stabilized, a G-cycle using a chain cycle, which is extremely difficult to burn with a duct burner, is used.
Even when the GT exhaust gas from T is used, combustion can be easily performed.

Further, since the primary exhaust gas is supplied after the flame is formed by the fuel and the fresh air, the GT exhaust gas can be injected into the wind box once to perform a certain degree of rectification, and then injected into the flame. At the same time, the secondary exhaust gas can be injected to the completely burned flame after performing a certain degree of rectification in the wind box, so even if the GT exhaust gas duct from the GT to the reburning burner is bent, it will have an uneven flow. The influence can be suppressed. Therefore, the degree of freedom of the arrangement of the GT and the reburner can be increased. That is,
Since the GT exhaust gas is ejected from around the flame, a straight pipe portion for suppressing the influence of the drift of the GT exhaust gas is not required, and the size can be reduced.

On the other hand, according to the reburning burner utilizing GT exhaust gas according to the third aspect, the reheating method according to the first aspect can be easily realized, and various effects of the reheating method can be obtained. Furthermore, while the generation of NOx and CO is suppressed as a whole, both the primary fuel and the secondary fuel are completely burned, and the reheat of the GT exhaust gas is performed by using the primary flame, which burns most stably with fresh air having an appropriate air ratio, as a flame holding source. Therefore, even if the GT exhaust gas with a low oxygen concentration is supplied in an overwhelmingly large amount and the air becomes an excessive air state, the secondary fuel can stably burn, and even if the turndown width is widened, the combustion is stable. Sex is not spoiled.
In addition, since the primary combustion cylinder included in the reburning burner according to the fourth aspect is not required, the structure can be simple and compact.

In addition, since the GT exhaust gas is ejected from the exhaust gas nozzle so as to surround the primary and secondary flames, the influence of the drift of the GT exhaust gas can be suppressed, so that the flame is stabilized and the combustion is performed. Mixing of gas and GT exhaust gas is also improved. Moreover, since a straight pipe for suppressing the influence of the drift of the GT exhaust gas is not required, the equipment and piping can be made compact.

According to the reburning burner utilizing GT exhaust gas according to the fourth aspect, the reheating method according to the second aspect can be easily realized, and various effects of the reheating method can be obtained. Further, the primary exhaust gas nozzle injects the primary exhaust gas from the outside of the primary combustion cylinder toward the inner flame, thereby sufficiently mixing the GT exhaust gas and the fuel from the duct burner to reduce the oxygen concentration of the GT exhaust gas after the reburn combustion. It is possible to reduce the amount of fresh air to about 3%
Increasing the use efficiency of the T exhaust gas or increasing the reburning amount increases the heat of the GT exhaust gas, and can easily cope with a case where a large amount of steam is required.

Further, since the flame formed by the reburning combustion using the fresh air and part of the GT exhaust gas is held by the primary combustion cylinder, the stability of combustion when reheating the GT exhaust gas is further improved. It can be improved and the turndown ratio can be increased.

Further, since the remainder of the GT exhaust gas is blown from the secondary exhaust gas nozzle around the primary combustion cylinder so as to surround the flame, the influence of the drift of the GT exhaust gas can be suppressed, and the flame can be suppressed. Is stable and the combustion gas and G
Mixing with T exhaust gas is also good. Moreover, since a straight pipe for suppressing the influence of the drift of the GT exhaust gas is not required, the equipment and piping can be made compact.

[Brief description of the drawings]

FIG. 1 is a central longitudinal sectional view showing one embodiment of a reburning burner using a reburning combustion method using GT exhaust gas of the present invention.

FIG. 2 is a central longitudinal sectional view showing another embodiment of a reburning burner using a reburning combustion method using GT exhaust gas of the present invention.

[Explanation of symbols]

 Reference Signs List 1 Reburning burner using GT exhaust gas 2 Primary flame 3 Secondary flame 5 Burner throat 6 Fuel nozzle 7 Exhaust gas nozzle 10 Primary fuel nozzle 11 Secondary fuel nozzle 23 Primary combustion cylinder 24 Primary exhaust gas nozzle 26 Secondary exhaust gas nozzle 29 Flame A Fresh Air (combustion air) E GT exhaust gas E1 Primary exhaust gas E2 Secondary exhaust gas F Fuel F1 Primary fuel F2 Secondary fuel

Claims (4)

[Claims] In a reburning combustion method for reheating the gas turbine exhaust gas by burning the reburned fuel by utilizing oxygen remaining in the gas turbine exhaust gas, the refired fuel is a secondary fuel of a primary fuel and a secondary fuel. The primary flame is formed by supplying combustion air in an amount that provides an appropriate air ratio to the primary fuel in the first stage to form a primary flame, while the secondary stage is provided around the primary flame in the second stage. Gas turbine exhaust gas characterized by injecting the secondary fuel and injecting the gas turbine exhaust gas around a jet of the secondary fuel to completely burn the secondary fuel using residual oxygen in the gas turbine exhaust gas. Use reburning combustion method. 2. A reburning combustion method for reheating the gas turbine exhaust gas by burning the reburned fuel using oxygen remaining in the gas turbine exhaust gas, wherein an upstream side of a combustion space into which the gas turbine exhaust gas is introduced is provided. After the supplementary fuel and the combustion air less than the theoretical air amount for the supplementary fuel are supplied to the disposed small combustion area to cause incomplete combustion, a part of the gas turbine exhaust gas is subjected to the small combustion. While injecting the fuel into the flame from around the incomplete combustion flame toward the flame and supplementing the insufficient oxygen with residual oxygen in the flame to burn the unburned portion to complete combustion as a whole, while the small combustion region Gas, wherein the remaining portion of the gas turbine exhaust gas is injected into the combustion space substantially in parallel with the flame ejected into the combustion space from above, and the heat of the combustion gas reheats the remaining gas turbine exhaust gas. Turbine Refire combustion method using exhaust gas. 3. A fuel supply system for supplying reburned fuel in two stages, a primary fuel and a secondary fuel, and supplying an amount of combustion air having an appropriate air ratio to the primary fuel to a burner throat. A combustion air supply system, a primary fuel nozzle that injects the primary fuel in the burner throat, and a secondary fuel nozzle that injects the secondary fuel around the primary flame downstream of the primary fuel nozzle. An exhaust gas nozzle for injecting gas turbine exhaust gas substantially in parallel with the primary flame from around the secondary fuel nozzle into the combustion chamber of the reheating boiler, and using the residual oxygen in the gas turbine exhaust gas as the secondary fuel. Reburning the gas turbine exhaust gas in combination with the primary flame to reheat the gas turbine exhaust gas. 4. A burner main body in which a combustion space into which a gas turbine exhaust gas is introduced is formed and a primary combustion cylinder forming a small combustion area is arranged upstream of the combustion space, and reburned fuel is injected into the primary combustion cylinder. A fuel nozzle, a combustion air supply system for injecting combustion air having a volume less than a stoichiometric air amount with respect to the refired fuel, and a gas turbine exhaust gas formed on a peripheral wall of the primary combustion cylinder for supplying the gas turbine exhaust gas into the primary combustion cylinder. A primary exhaust gas nozzle, and a secondary exhaust gas nozzle that injects the remainder of the gas turbine exhaust gas substantially parallel to the flame into the combustion space. A reburning burner utilizing gas turbine exhaust gas, wherein partial combustion is performed by using a part of the gas turbine exhaust gas and working air, and the remaining gas turbine exhaust gas is reheated by the heat of the combustion gas.