JPH09137915A - Exhaust gas mixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase an exhaust gas mixing ratio to a maximum value and enhance the operation ratio of a plant operation efficiency. SOLUTION: This device is provided with a plurality of mixers 303 having an exhaust gas injection part and an opening 306 which discharges the exhaust gas into the combustion air passage 301 at a joining area between a combustion air 301 where a combustion air 302 is supplied and an exhaust gas passage which supplies exhaust gas whose oxygen concentration is lower than the combustion air 302 and is arranged to mix the combustion air with the exhaust gas whose oxygen concentration is lower than the combustion air. In this case, an exhaust gas injection rate control means 307 is provided wholly or partially in the inlet of a plurality of mixers 30 in order to control the exhaust gas injection rate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas mixing apparatus, and more particularly, to an exhaust gas mixing apparatus suitable for use in a boiler apparatus that enhances exhaust gas mixing performance and enables highly efficient boiler operation.

[0002]

2. Description of the Related Art In an exhaust gas mixing system for low NOx combustion of a boiler or an exhaust gas re-combustion system in which exhaust gas of a gas turbine and air supplied by a combustion air blower are mixed and used as boiler combustion air, An airfoil has been conventionally used as a method for efficiently mixing air with a low differential pressure.

A system diagram of air and exhaust gas in the exhaust gas reburn system is shown in FIG. In the figure, the combustion air is supplied by the combustion air blower 1 and is preheated to a predetermined temperature by the air preheater 2, and then the wind of the burner 10 and the two-stage combustion air port 11 is passed through the combustion air ducts 6 and 7. Supplied to boxes 8 and 9.

On the other hand, the combustion gas discharged from the gas turbine 3 is cooled to a predetermined temperature by an exhaust gas cooler 4 and then mixed with combustion air in a mixer 5 downstream of the air preheater 2.

Details of the exhaust gas mixing apparatus will be described with reference to FIGS. 6 and 7. In FIG. 6, the combustion air duct 10
An airfoil 103, the appearance of which is shown in FIG. 7, is installed in the inside 1. The gas turbine exhaust gas 105 is supplied into the airfoil 103 through a gas turbine exhaust gas duct 104 adjacent to the combustion air duct 101. The air is injected into the combustion air duct 101 through the openings 106 provided on the blades and mixed with the combustion air 102.

Gas turbine exhaust gas is usually 13 to 15%
Of oxygen concentration, and when mixed with combustion air (oxygen concentration 21%), a predetermined oxygen concentration is obtained on average. In the exhaust gas re-combustion system, increasing the mixing ratio of the gas turbine exhaust gas improves the plant efficiency because more waste heat of the gas turbine can be recovered.

[0007]

In designing and operating an exhaust gas reburning system, the gas turbine exhaust gas 105 is increased and burned as much as possible so that the air box oxygen concentration is near the boiler stable combustion limit, with the goal of maximum efficiency. Use air 102 as much as possible
Will be reduced.

However, due to the pressure loss in the gas turbine exhaust gas duct 104 and the flow velocity distribution in the combustion air duct 101, the oxygen concentration is not uniform and has a certain distribution. That is, the mixing ratio of the gas turbine exhaust gas and the combustion air is not uniform in the vertical direction of the combustion air duct 101. FIG. 8 shows an example of oxygen concentration distribution at the outlet of a conventional mixing device. In this example, the oxygen concentration in the upper part of the combustion air duct is higher than that in the bottom part. Since such an oxygen concentration distribution is maintained up to the wind box, it is necessary to keep the lowest oxygen concentration in the wind box above the stable combustion limit. FIG. 8 shows an example in which the oxygen concentration at the bottom of the duct is maintained at a combustion stability limit of 16% or higher. As shown in FIG. 8, the oxygen concentration in the upper portion of the duct is 17.5%, which is an excessive oxygen concentration in terms of combustion stability. That is, when the oxygen concentration is the combustion stability limit level 16
The operation efficiency of the plant is lower than that in the ideal state, because the gas turbine exhaust gas mixing ratio is suppressed as compared to the ideal state, which is uniform in%.

The present invention has been made in view of such circumstances, and it is possible to maximize the exhaust gas mixing ratio and improve the operating efficiency of the plant by making the oxygen concentration distribution after mixing the exhaust gas uniform. It is an object of the present invention to provide an exhaust gas mixing device capable of achieving the above.

[0010]

In the exhaust gas mixing apparatus of the present invention, there is provided a joint portion between a combustion air passage to which combustion air is supplied and an exhaust gas passage to supply exhaust gas having an oxygen concentration lower than that of the combustion air. The combustion air passage is provided with a plurality of mixers having an exhaust gas injection portion and an opening for discharging the exhaust gas to the combustion air passage, and the combustion air and the exhaust gas having an oxygen concentration lower than that of the combustion air are mixed. The exhaust gas mixing device is characterized in that exhaust gas injection amount adjusting means for adjusting the exhaust gas injection amount is provided at all or part of the inlets of the plurality of mixers.

In the exhaust gas mixing device of the present invention, the inside of the combustion air passage is formed at the joint between the combustion air passage to which the combustion air is supplied and the exhaust gas passage to supply the exhaust gas having an oxygen concentration lower than that of the combustion air. In the exhaust gas mixing device comprising a plurality of mixers having an exhaust gas injection part and an opening for discharging the exhaust gas to the combustion air passage, and mixing the combustion air and the exhaust gas having a lower oxygen concentration than the combustion air, Exhaust gas injection amount adjusting means for adjusting the exhaust gas injection amount provided at all or part of the inlets of the plurality of mixers, and combustion air amount measuring means for measuring the combustion air amount supplied to the combustion air passage. And an exhaust gas amount measuring means for measuring the amount of exhaust gas supplied to the exhaust gas passage, and a measurement result of the combustion air amount measuring means or the exhaust gas amount measuring means or a combustion air amount measuring hand. And characterized by having a control means for controlling the adjustment amount of the exhaust gas injection amount adjusting means based on the measurement results of the exhaust gas amount measuring means.

In the exhaust gas mixing device of the present invention, the inside of the combustion air passage is formed at the joint between the combustion air passage to which the combustion air is supplied and the exhaust gas passage to supply the exhaust gas having an oxygen concentration lower than that of the combustion air. In the exhaust gas mixing device comprising a plurality of mixers having an exhaust gas injection part and an opening for discharging the exhaust gas to the combustion air passage, and mixing the combustion air and the exhaust gas having a lower oxygen concentration than the combustion air, Exhaust gas injection amount adjusting means for adjusting the exhaust gas injection amount provided in all or part of the inlets of the plurality of mixers, and a plurality of oxygens for measuring the oxygen concentration at the plurality of mixers outlets in the combustion air passage It is characterized by having a concentration measuring means and a control means for controlling the adjustment amount of the exhaust gas injection amount adjusting means based on the measurement results of the plurality of oxygen concentration measuring means.

In the exhaust gas mixing device having the above structure, the oxygen concentration at the outlet of the mixing device is uniformly adjusted or controlled by providing the exhaust gas injection amount adjusting means (damper).
In the exhaust gas re-combustion system, the exhaust gas can be put into the boiler as much as possible, so that the operating efficiency of the plant can be increased to the ideal state.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a configuration of a main part of an example of an embodiment of an exhaust gas mixing apparatus according to the present invention.
1A is a side view, and FIG. 1B is a cross-sectional view taken along the line AA in FIG. In FIG. 1, a plurality of airfoils (mixers) 203 are provided in the height direction inside the combustion air duct 201 at the junction between the combustion air duct 201 and the gas turbine exhaust gas injection duct 204. The airfoil 203 has a plurality of openings 206 on its wings, and a plurality of dampers 2 for adjusting the areas of the plurality of openings 206 are provided inside the airfoil 203.
07 is installed. This damper 207 is shown in FIG.
By adjusting the position in the direction of arrow A at the opening 2
The area of 06 can be adjusted. Therefore, the oxygen concentration distribution at the outlet of the airfoil 203 is adjusted by adjusting the position of each damper so as to give a deviation in the height direction of the combustion air duct 201 based on the measurement result of the oxygen concentration distribution at the outlet of the airfoil 203. It can be adjusted uniformly. For example, when the openings 206 of all the airfoils 203 are fully opened and the oxygen concentration at the outlets of the airfoils 203 has a distribution as shown in FIG. The amount of injection of the gas turbine exhaust gas increases as the foil 203 increases, that is, the opening 206 of the airfoil 203.
The oxygen concentration distribution is uniformly adjusted by providing a deviation in the position of the damper so that the opening area of the above is increased.

Next, FIG. 2 shows another embodiment of the exhaust gas mixing apparatus according to the present invention. In this example, a damper 307 is installed at each inlet of the plurality of airfoils 303, and the opening degree thereof is configured to be controlled by operating means via a drive unit 308 by control means (not shown). Is the same as that of the example of FIG. The deviation of the damper opening from the height direction of the combustion air duct 301 is automatically given according to the operating conditions, and the exhaust gas injection amount is changed in the height direction of the combustion air duct 301 to change the combustion air duct. Since the ratio of the flow rate of the combustion air 302 in the height direction in 301 to the injection flow rate of the exhaust gas 305 can be kept uniform, the oxygen concentration at the outlet of the airfoil 303 can always be kept uniform. Incidentally, 304 is a gas turbine exhaust gas duct, and 306 is an opening of the airfoil 303.

FIG. 3 shows an example of operation / control characteristics for automatically adjusting the damper opening in the configuration of FIG. 2 based on the exhaust gas injection flow rate and the combustion air flow rate. If the deviation of the damper opening to make the oxygen concentration at the outlet of the airfoil (mixer) uniform depends on the amount of exhaust gas injected and the flow rate of combustion air, an appropriate opening is performed based on the test run results for any conditions. By setting the degree, the oxygen concentration at the airfoil outlet can always be kept uniform. In this example, the damper located below the combustion air duct is throttled to reduce the amount of exhaust gas injected and the oxygen concentration below the combustion air duct is increased to increase the combustion air at the airfoil outlet. The operation / control characteristics are set so that the oxygen concentration distribution in the height direction in the duct is maintained uniformly.

In this example, when the combustion air flow rate is low,
Since the influence of the exhaust gas injection flow rate becomes large, the setting deviation of the damper opening becomes large. That is, the damper openings of the middle and lower dampers are further narrowed.

Next, FIG. 4 shows still another embodiment of the exhaust gas mixing apparatus according to the present invention. This example is configured to automatically control the opening degree of the damper based on the measurement signals indicating the oxygen concentration of the plurality of oxygen concentration measuring devices provided at the airfoil outlet.

In the figure, 401 is a combustion air duct, 402 is combustion air, 403 is an airfoil, 40
Reference numeral 4 is a gas turbine exhaust gas duct, and 405 is a gas turbine exhaust gas. An oxygen concentration measuring device 409 is provided at the outlet of each airfoil (mixer) 403, and a damper 407 for adjusting the injection amount of the gas turbine exhaust gas is provided at the inlet of each airfoil in the gas turbine exhaust gas duct 404. It is driven by 408.

Reference numeral 411 denotes a control device, which drives each drive device 4 based on a measurement signal 410 from each oxygen concentration measuring device 409.
08, a control signal is output, the opening degree of each damper 407 is adjusted, and the combustion air duct 401 at the outlet of the airfoil 403 is adjusted.
The oxygen concentration in the inner height direction is controlled to be constant. For example, the damper 4 corresponding to the highest oxygen concentration measurement value
07 is controlled to be fully opened. Other dampers 4
Regarding No. 07, the controller 411 increases the opening degree when the measurement value of the corresponding oxygen concentration measuring instrument 409 is higher than the average value of the measurement values of the total oxygen concentration measuring instrument, and causes the opening degree to occur when it is lower than the average value. The oxygen concentration in the height direction in the combustion air duct 401 at the outlet of the airfoil 403 can be controlled to be constant by controlling by.

[0021]

According to the present invention, the oxygen concentration at the outlet of the mixer for mixing the combustion air and the gas turbine exhaust gas is kept uniform, and the gas turbine exhaust gas can be injected to the maximum extent. The operating efficiency of the plant can be maximized.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a configuration of a main part of an example of an embodiment of an exhaust gas mixing apparatus according to the present invention.

FIG. 2 is a configuration diagram showing another embodiment of an exhaust gas mixing apparatus according to the present invention.

3 is a diagram showing an example of operation / control characteristics for automatically adjusting a damper opening degree based on an exhaust gas injection flow rate and a combustion air flow rate in the exhaust gas mixing apparatus shown in FIG.

FIG. 4 is a configuration diagram showing still another embodiment of the exhaust gas mixing apparatus according to the present invention.

FIG. 5 is a system diagram showing a schematic configuration of an exhaust gas reburn system.

FIG. 6 is a side view and a front view showing a specific configuration of a conventional exhaust gas mixing device.

FIG. 7 is a perspective view showing an external configuration of a mixer of the conventional exhaust gas mixing apparatus shown in FIG.

FIG. 8 is a diagram showing an example of an oxygen concentration distribution at the outlet of a conventional exhaust gas mixing device.

[Explanation of symbols]

 1 Combustion Air Blower 2 Air Reheater 3 Gas Turbine 4 Exhaust Gas Cooler 5 Mixer 6 Combustion Air Duct 7 Two-stage Combustion Air Duct 8 Burner Wind Box 9 Two-stage Combustion Air Port Wind Box 10 Burner 11 Two-stage Combustion air port 12 Furnace 101 Combustion air duct 102 Combustion air 103 Air foil 104 Gas turbine exhaust gas duct 105 Gas turbine exhaust gas 106 Air foil opening 201 Combustion air duct 202 Combustion air 203 Air foil 204 Gas turbine exhaust gas injection duct 205 Gas turbine exhaust gas 206 Airfoil opening 207 Damper 307 Damper 308 Drive device 407 Damper 408 Drive device 409 Oxygen concentration measuring device 411 Control device

Claims (3)

[Claims] 1. An exhaust gas injection part and an exhaust gas in the combustion air passage at a joint between a combustion air passage to which combustion air is supplied and an exhaust gas passage to supply exhaust gas having an oxygen concentration lower than that of the combustion air. An exhaust gas mixing device having a plurality of mixers each having an opening for discharging the air to the combustion air passage, and mixing the combustion air and an exhaust gas having a lower oxygen concentration than the combustion air, all of the plurality of mixers. Alternatively, an exhaust gas injection amount adjusting means for adjusting the exhaust gas injection amount is provided at a part of the inlet portion, which is an exhaust gas mixing device. 2. An exhaust gas injection part and an exhaust gas in the combustion air passage at a joint between a combustion air passage to which combustion air is supplied and an exhaust gas passage to supply exhaust gas having an oxygen concentration lower than that of the combustion air. An exhaust gas mixing device having a plurality of mixers each having an opening for discharging the air to the combustion air passage, and mixing the combustion air and an exhaust gas having a lower oxygen concentration than the combustion air, all of the plurality of mixers. Alternatively, an exhaust gas injection amount adjusting means provided in a part of the inlet portion for adjusting the exhaust gas injection amount, a combustion air amount measuring means for measuring the combustion air amount supplied to the combustion air passage, and the exhaust gas passage Exhaust gas amount measuring means for measuring the amount of exhaust gas supplied to the exhaust gas, and the measurement result of the combustion air amount measuring means or the exhaust gas amount measuring means or the combustion air amount measuring means and the exhaust gas amount measuring means Exhaust gas mixing device, characterized in that a control means for controlling the adjustment amount of the exhaust gas injection amount adjusting means based on the measurement results. 3. An exhaust gas injection part and an exhaust gas in the combustion air passage at a joint between a combustion air passage to which combustion air is supplied and an exhaust gas passage to supply exhaust gas having an oxygen concentration lower than that of the combustion air. An exhaust gas mixing device having a plurality of mixers each having an opening for discharging the air to the combustion air passage, and mixing the combustion air and an exhaust gas having a lower oxygen concentration than the combustion air, all of the plurality of mixers. Or an exhaust gas injection amount adjusting means for adjusting the exhaust gas injection amount provided at a part of the inlet portion, a plurality of oxygen concentration measuring means for measuring the oxygen concentration at the plurality of mixer outlet portions in the combustion air passage, An exhaust gas mixing apparatus comprising: a control unit that controls the adjustment amount of the exhaust gas injection amount adjustment unit based on the measurement results of a plurality of oxygen concentration measurement units.