JPH0282019A - Combustion method in gas turbine combustion unit - Google Patents

Abstract

PURPOSE:To restrict NOx from being generated when started and improve the durability of catalyst by a method wherein fuel is supplied to both preheating part and gaseous phase combustion part when a combustion unit is energized and the fuel is ignited and then a catalyst combustion is performed when a catalyst inlet port temperature reaches such a temperature as one capable of igniting with catalyst. CONSTITUTION:When energized, fuel is supplied from a first fuel nozzle 1, mixture gas having this fuel and air 3 fed from a compressor is ignited at a pre-combustion part 19 with a spark plug 5. At this time, supplied fuel of the first fuel nozzle 1 is controlled to a certain degree so as to restrict a temperature of combustion gas at a pre-combustion part 19, resulting in that production of NOx at the pre-combustion part when energized is quite low. After that, a discharged air temperature from a compressor is also increased as a turbine is operated, and an air temperature at an inlet port of a combustion unit is also increased. With this arrangement, as an inlet gas temperature of a catalyst charging part 15 reaches such a temperature as one where a catalyst combustion may start, fuel of a specified flow rate is injected from a fuel nozzle 17 to a mixing part 21 and then the catalyst combustion is started.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a combustion method in a gas turbine combustor, particularly a gas turbine combustor using catalytic combustion.

(Prior art) Gas turbines are generally used in aircraft engines, power generation systems, etc., but in the combustor used in gas turbine power generation systems, the mixture of fuel and air has traditionally been pumped into the spark plug. It is used to ignite and burn. An example of such a combustor is shown in FIG. In the figure, the fuel injected from the first fuel nozzle 1 is
The mixture is mixed with combustion air 3 shown by an arrow supplied from a compressor (not shown), ignited by the spark plug 5, and combusted. Cooling air 7 and dilution air 9 are added to the combusted gas, that is, the combustion gas, on the downstream side, and after cooling and diluting it to a predetermined turbine inlet temperature, it is injected into the gas turbine through the turbine nozzle 11. Ru. What is indicated by reference numeral 13 is a swirler.

By the way, in a combustor, for example, 2000
If there is a high temperature area that exceeds ℃ or if there is a significant temperature increase, a large amount of nitrogen oxides (
However, in the above-mentioned conventional combustor, there is a high temperature part that exceeds 2000°C during rated operation, so there is a problem that a large amount of NOx is generated during combustion, causing environmental pollution. . For this reason, various combustion methods have recently been studied, and among these, a heterogeneous combustion method using a solid phase catalyst (hereinafter referred to as catalytic combustion method) will be explained.

This catalytic combustion method uses a catalyst to combust a lean air-fuel mixture that would not be combusted in a normal combustor, thus preventing the combustion temperature from reaching a high enough temperature to generate large amounts of NOx. becomes possible. Also,
The turbine inlet temperature can also be kept the same as in conventional systems. FIG. 5 shows an example of a combustor employing this catalytic combustion method. This combustor includes a catalyst filling section 15 as a catalytic combustion section and a second fuel nozzle 17 that supplies fuel for catalytic combustion, and a first fuel nozzle provided upstream of the second fuel nozzle 17 The fuel injected from the second fuel nozzle 1.7 is combusted in the pre-combustion section 19, and when this combustion gas reaches the mixing section 21, the fuel injected from the second fuel nozzle 1.7 is mixed with the combustion gas. Then, this air-fuel mixture is combusted in the catalyst filling section 15. The catalyst filling portion 15 is filled with a combustion catalyst that normally has a honeycomb structure.

However, in such a catalytic combustion method, since most of the fuel is combusted in the catalyst filling section 15, there is a problem in that the catalyst becomes hot, suffers significant thermal deterioration, and decreases durability. Furthermore, it has been difficult to cope with the increase in gas turbine inlet temperature due to the heat resistance of the catalyst.

Therefore, the present applicant has decided to burn only a part of the necessary fuel in the catalyst filling section, further supply fuel downstream of the catalyst, and cause gas phase combustion (non-catalytic combustion) in that part. We have already proposed a catalytic combustion method that not only reduces NOx during rated operation but also maintains the temperature of the catalyst lower than before, improving the durability of the catalyst.

(Problems to be Solved by the Invention) Incidentally, in order for catalytic combustion to occur, it is necessary to increase the temperature of the mixture of fuel and air supplied to the catalyst to some extent. However, since the combustor inlet air temperature is lower when the combustor is started than during rated operation, it is necessary to significantly raise the temperature in the molecular combustion section, resulting in a large amount of NOx being generated.

SUMMARY OF THE INVENTION An object of the present invention is to provide a combustion method in a gas turbine combustor that suppresses the generation of NOx not only during rated operation but also during startup, and improves the durability of the catalyst.

[Structure of the invention]

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention supplies air and fuel in a mixing part to the combustion gas combusted in a pre-combustion part to form a fuel mixture. The fuel mixture is combusted in the catalytic combustion section, the unburnt fuel mixture is mixed with the gas phase in the catalytic combustion section, and the fuel is mixed in the thermal sintering section and combusted in the gas phase. In a combustion method in a gas turbine combustor in which air is supplied to gas in a dilution section,
When the combustor is started, fuel is supplied to both the pre-combustion section and the gas-phase combustion section to cause combustion, and as the turbine operates, the combustor inlet temperature rises and the catalyst inlet temperature reaches a level at which catalytic combustion is possible. Once the temperature was reached, fuel was supplied to the mixing section for catalytic combustion.

(Function) First, fuel is supplied to both the pre-combustion section and the gas-phase combustion section downstream of the catalyst to cause combustion. At this time, there is no need to significantly raise the temperature to the combustion temperature of the catalyst in the pre-combustion section, and therefore the generation of NOx in the pre-combustion section is small.

Thereafter, as the turbine operates, the combustor inlet temperature rises, and when the catalyst inlet temperature reaches a temperature that allows catalytic combustion, fuel is supplied to the mixing section to cause catalytic combustion.

(Embodiment) Hereinafter, an embodiment of the present invention will be described based on FIGS. 1 to 3.

FIG. 1 is a sectional view of a gas turbine combustor. This combustor has an outer cylinder 23 and an inner cylinder 25, between which an annular space 27 is formed into which compressed air from a compressor (not shown) flows. has been done. A plurality of air circulation holes 29 are provided around the inner cylinder 25 over substantially its entire length. The upstream end of the inner cylinder 25 is provided with a first
fuel nozzles 1 are provided, and the first fuel nozzle 1 is a first fuel nozzle 1.
The supplied fuel is adjusted by a flow rate adjustment valve 31 .

The second fuel nozzle 17 that supplies fuel to the mixing section 21 is
The second flow rate regulating valve 33 regulates the supplied fuel.

On the other hand, a catalyst filling section 15 is provided at the downstream end of the inner cylinder 25, and a third fuel nozzle 3 is provided immediately downstream of the catalyst filling section 15.
5 and a spark plug 37 are provided, respectively.

Immediately downstream of this catalyst filling section 15 are three gas phase combustion sections, and the passage diameters of these three gas phase combustion sections are larger than the passage diameter of the inner cylinder 25. The fuel supplied to the third fuel nozzle 35 is adjusted by a third flow rate adjustment valve 41. Furthermore,
A cooling air passage 45 is opened in the combustion gas guide section 43 between the inner cylinder 25 and the turbine nozzle 11 that injects fuel gas to the turbine, and this section becomes a dilution section 47 . The flow rate of the air passing through the cooling air passage 45 is adjusted by four valves.

In a gas turbine combustor having such a configuration, at the time of startup, fuel is first injected from the first fuel nozzle 1, and a mixture of this fuel and air 3 from a compressor (not shown) is pre-combusted by the spark plug 5. In section 19, the mixture is ignited and combusted. The combustion gas temperature at this time does not need to rise to the catalytic combustion temperature since combustion is not performed in the catalyst filling section 15 on the downstream side, and therefore the fuel supplied to the first fuel nozzle 1 is restricted to some extent. . Pre-combustion section 1
Since the temperature rise of the combustion gas at step 9 is suppressed, the generation of NOx in the pre-combustion section at the time of startup is extremely small.

After that, the combustion gas flows into the inner cylinder 25 midway through the air 3.
The fuel is mixed with the gas, and in that state, it passes through the catalyst filling section 15 and reaches the gas phase combustion section 39. In the gas phase combustion section 39, a predetermined amount of fuel is supplied from the third fuel nozzle 35, and the spark plug 3
7 to ignite and burn in the gas phase.

The fuel supplied from the third fuel nozzle 37 in the gas phase combustion section 39 is desirably injected as uniformly as possible to achieve a state close to premixed combustion, and the combustion temperature is 1500°C to 160°C.
It is necessary to adjust the supplied fuel using the third flow rate regulating valve 41 so that the temperature is below 0°C. Thereby, the amount of NOx produced in the gas phase combustion section 39 is suppressed. However, gas-phase combustion is generally difficult or unstable under such conditions, but in this combustor, combustion in one pre-combustion section lowers the temperature of the air-fuel mixture. In addition, the passage diameters of the three gas-phase combustion parts are enlarged compared to the passage diameter of the inner cylinder 25, and the flame-holding effect is produced by the circulation flow generated in this enlarged part, so combustion is stabilized and gas-phase combustion becomes possible.

The combustion gas in the gas phase combustion section 39 is transferred to a dilution section 47 downstream thereof.
In this step, the opening and closing of the valve 49 is adjusted according to the startup schedule of the gas turbine to control the inflow of cooling air, and after setting the cooling air to a predetermined temperature, it is supplied to the turbine, and the turbine is operated.

As the turbine operates, the temperature of the air discharged from the compressor increases, and the temperature of the combustor inlet air also increases. Along with this, the inlet gas temperature of the catalyst filling section 15 also rises, and further, by adjusting the valve 49, this temperature rises to the temperature at which catalytic combustion starts.

When the catalyst inlet gas temperature reaches the temperature at which catalytic combustion starts, a predetermined flow rate of fuel adjusted by the second flow rate adjustment valve 33 is injected from the second fuel nozzle 1-7 into the mixing section 21, thereby Combustion begins. Simultaneously with the fuel supply from the second fuel nozzle 17, the amount of fuel supplied from the third fuel nozzle 35 to the gas phase combustion section 39 is reduced, and the mixing section by the second fuel nozzle 17 is 21
Increase fuel supply to. After that, the distribution of fuel and air to each part is controlled according to the gas turbine's operating schedule.

In this way, when the combustor is started, combustion is first performed in the pre-combustion section 19 and the gas-phase combustion section 39 to operate the turbine, and the combustor inlet temperature is increased as the turbine is operated, thereby reducing the catalyst inlet temperature. Since the temperature is raised to a temperature that allows catalytic combustion, there is no significant rise in the pre-combustion section when the combustor is started, and therefore the amount of NOx produced at this time is extremely small.

In addition, in this example, catalytic combustion and gas phase combustion are combined to enable combustion at a combustion temperature below the high temperature that generates a large amount of NOx, so the amount of NOx generated during rated operation is also small. It has become a thing. therefore,
The amount of NOx produced by the combustor as a whole is also reduced compared to the conventional case. Further, after the catalytic combustion, the catalyst is completely combusted by gas phase combustion in the gas phase combustion section 39 on the downstream side, so that the catalyst is prevented from increasing in temperature and its durability is also prevented from deteriorating.

Next, an experimental example of such a combustion method will be explained in comparison with a conventional example. Here, a simulated combustor in which the ratio of the passage diameter of the inner cylinder 25 to the passage diameter of the gas-phase combustion section 39 as shown in FIG. 1 was 1.5 was used. The fuel is natural gas, the catalyst is a precious metal honeycomb catalyst with a diameter of 100mm and a length of 100mm, and the fuel nozzles that supply the three gas phase combustion sections are as follows:
Nozzles with a diameter of 0.8 mm were provided at eight locations in the circumferential direction.

The experiment was conducted under atmospheric pressure conditions, and two types of data were taken: combustor inlet air flow velocity of 20 ri-s and 3 On+-s in terms of 500°C.

As a result, if the combustor inlet temperature is 20°C, and the temperature at which catalytic combustion starts is 450°C, the combustor inlet temperature can be increased from 20°C to 450°C with only the pre-combustion section as in the conventional combustion method.
When the temperature is raised to ℃, NO at a flow rate of 20 m-s
x production amount is 16 ppm, same 1 at flow rate 30 ff1-s
2111)01.

On the other hand, if the temperature increase in the pre-combustion section is fixed at 100°C and the adiabatic flame temperature in the gas phase combustion section is set to 1.500°C as in the combustion method of this invention, the combustor inlet temperature 2
Even at 0°C, a combustion efficiency of 8% or more was obtained, and the amount of NOx generated at a flow rate of 20 m-s was 3 in the pre-combustion section.
6ppIIl in ppII11 gas phase combustion section, flow rate 30l
In l-s, 2 ppffl in the pre-combustion section, 5 ppffl in the second combustion section
ppm, and the amount of NOX produced in the entire combustor was 9 ppHl and 7 ppm, respectively. This NO
When the combustor inlet air temperature is gradually increased to 350° C., the x production amount gradually decreases as shown in FIG. 2.

When the combustor inlet air temperature reaches 350°C, since the temperature rise in the pre-combustion section is 100°C, the catalyst inlet temperature becomes 450°C, and catalytic combustion starts. After that, when fuel is started to be supplied to the mixing section upstream of the catalyst and at the same time the amount of fuel supplied to the gas phase combustion section is decreased, that is, when the ratio of catalytic combustion is increased, the combustor The total amount of NOx produced decreases.

〔Effect of the invention〕

As explained above, according to the present invention, the combustor is started by combustion in both the pre-combustion section and the gas-phase combustion section,
Then, by increasing the temperature of the air discharged from the compressor, the catalyst inlet temperature was raised to a temperature that enabled catalytic combustion, which suppressed a significant temperature rise in the pre-combustion section when the combustor was started, and now The amount of produced can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a combustor according to an embodiment of the present invention, and FIG. 2 is a correlation diagram between the combustor inlet temperature and the amount of NOx produced in the entire combustor, showing experimental results using the combustion method of the present invention. Figure 3 is an I-scale diagram of the ratio of gas-phase combustion to the combined combustion of gas-phase combustion and catalytic combustion and the amount of NOx produced in the entire combustor, and Figure 4 is a cross-section of a conventional general combustor. FIG. 5 is a sectional view of a conventional combustor using catalytic combustion. 15... Catalyst filling section (catalyst combustion section)

Claims (1)

[Claims] Air and fuel are supplied in the mixing section to the combustion gas combusted in the pre-combustion section to form a fuel mixture, this fuel mixture is combusted in the catalytic combustion section, and the remaining fuel is removed from the catalytic combustion section. The mixture is mixed with fuel in a gas phase combustion section and burned in a gas phase.
In a combustion method in a gas turbine combustor in which air is supplied to the combustion gas from the gas-phase combustion section in a dilution section, when the combustor is started, fuel is supplied to both the pre-combustion section and the gas-phase combustion section. When the combustor inlet temperature rises as the turbine operates, and the catalyst inlet temperature reaches a temperature that allows catalytic combustion, fuel is supplied to the mixing section to cause catalytic combustion. Combustion method in turbine combustor.