JPH02136520A - Exhaust gas treatment method for gas turbine - Google Patents

Abstract

PURPOSE:To make improvements in efficiency of a boiler as well as to make low NOx combustion achievable by regulating an amount of oxygen content in exhaust gas out of a gas turbine and feeding it to a combustion part of a boiler unit as combustion gas. CONSTITUTION:In a boiler 1, connecting a burner 2 and a wind box 3 to a wall screen, exhaust gas G out of a gas turbine (unillustrated herein) if fed to the wind box 3 from a pipeline 4, while air A out of a pressure fan 5 is led out of a pipeline 6 via a damper 6d, and it is fed to the burner 2 after being mixed with the gas G at a connecting part with the pipeline 4. A pipeline 7 exhausting the excessive exhaust gas after bypassing the boiler 1 is branched off to the pipeline 4, and a damper 7d is interposingly installed in the midway. Then, there are provided with temperature gauges 4a, 4c, 6a and flowmeters 4b, 4d, 6b, etc., related each to those of exhaust gas, mixed gas and air or the like, and on the basis of each output of these instruments, respective dampers 6d, 7d are controlled by a control box 10.

Description

[Detailed Description of the Invention] <Industrial Application Field> This invention effectively uses the energy contained in the exhaust gas of a gas turbine by effectively utilizing the heat and oxygen contained in the exhaust gas of a gas turbine using existing or newly installed boiler equipment. The present invention relates to a method for treating gas stanibin exhaust gas for recovery.

<Conventional Technology and Its Problems Recently, gas turbines are often used in boilers of power generation facilities where the load fluctuates frequently and in factories where startups and stops are performed intermittently.

However, since gas turbines convert the combustion of pressurized gas into rotation of the turbine, the exhaust gas temperature is approximately 50°C.
The temperature will be as high as 0℃.

For this reason, conventionally this waste heat was collected using a waste heat recovery boiler (Waste Heat Recovery Boiler).
The main method used was to recover steam using a heat boiler (Heat Boiler).

Its structure is as shown in FIG. 5 as an example. (Japanese Unexamined Patent Publication No. 57-204704) Exhaust gas from the gas turbine 1' is discharged from a chimney 9 through a superheater tube 3', an evaporator tube 4', and an economizer 5' of a waste heat boiler. Drum 6'
The steam from is supplied to a p-steam turbine 7' through a superheater 6'.

Therefore, the heat held in the exhaust gas is exchanged with the heat transfer tube group to generate steam, and the exhaust gas contains about 12 to 1
Regarding the use of 5% 02, no special consideration was given other than the use of sensible heat. Therefore, the temperature of the exhaust gas is about 5
Since the temperature was 00°C, high-pressure and high-temperature steam could not be obtained.

Since factories using gas turbines often have in-house power generation equipment, it is desirable to solve the above-mentioned problems by combining gas turbines and high-temperature, high-pressure boiler equipment, including energy saving.

<Purpose of the Invention> This invention takes into consideration the high temperature of gas turbine exhaust gas and the non-adherence of residual acid in the exhaust gas, and improves the efficiency of the boiler by saving energy and effectively utilizing the oxygen contained in it by combining it with a boiler. The purpose of this study is to propose a method for treating gas turbine exhaust gas that produces high-temperature steam and achieves low NOx combustion.

Summary of the Means for Combining the Oxygen Content of the Exhaust Gas of a Gas Turbine> In short, the present invention provides a method for controlling the oxygen content of the exhaust gas of a gas turbine by supplying air to be used as a combustion gas, mixing it with the exhaust gas, and supplying the air to the combustion section of a boiler device.
It is characterized by improving efficiency and recovering retained heat by reducing the amount of boiler exhaust gas by effectively utilizing oxygen contained in exhaust gas.

Furthermore, a gas turbine and exhaust gas are supplied to the fluidized bed furnace, and the retained heat is used to raise the temperature of the fluidized bed and facilitate reverse startup.

Furthermore, air is supplied to adjust the combustible oxygen content, and the gas that has adjusted the temperature of the mixed gas is supplied to the burner of the boiler, thereby increasing the temperature of the combustion gas in the furnace and making it possible to obtain high-temperature, high-pressure steam. It is something.

Furthermore, in the case of a low NOx boiler, the oxygen content can be directly supplied instead of air to a combustion section that is supposed to receive air with a corresponding oxygen content.

<Example 1> Exhaust gas G from a gas turbine (not shown) is connected to a boiler 1 in which a burner 2 and a wind box 3 are connected to a water-cooled wall through a pipe 4.
It is supplied to Wind Box Party B via. In this case, air A is supplied from the forced air blower 5 via the conduit 6 to the connection with the conduit 4, mixed with the exhaust gas G, and then supplied to the burner 2.

The exhaust gas G from the gas turbine is normally at a temperature of about 500° C. and contains 14 to 15% (by volume) of oxygen (02). In addition, it is expected that the content will decrease in the near future due to improved gas turbine efficiency, and the air supplied from the blower 5 will be at 20°C.
0z2i% (volume) (composition of 23.2% in lf amount).

Therefore, when controlling the amount of air supplied, it is possible to supply burner 2 with a mixture of exhaust gas and air at approximately 600°C, which has a temperature of 0.217 cm (the following numerical values are expressed in volume cm). 02 instead of low NOx combustion that does not cause any problems and generates less nitrogen oxides due to conventional recirculated exhaust gas.
Low NOx combustion can be achieved using regulated gas turbine exhaust gas.

When it is determined that the amount of gas turbine exhaust gas is larger than the amount required by the burner section, a damper 7a provided in a pipe 7 branching from the pipe 4 is opened, and a part of the gas is supplied to the boiler outlet exhaust gas pipe 8. Mixed with boiler exhaust gas at 500℃, etc.
When the temperature is set to 0° C., the temperature difference with the economizer 9 is increased to improve heat recovery and improve the efficiency of the boiler.

In addition, when the draft loss of the boiler is small, the boiler inlet (
It is also good to put it in the superheater outlet.

Gas flow rate and temperature signals are sent to the control box 10, respectively.

The pipe line 4 includes a thermometer 4a for exhaust gas, a flowmeter 4b, and a thermometer 4c for mixed gas with air.

Flowmeters 4d are provided, and their signals are sent to the control box 10, respectively. A thermometer t5a is provided in the air supply pipe line 6.

7b, a mixed gas thermometer 8α is provided in the conduit 8, and its signal is sent to the control box 10.

The control box 10 stores the amount of exhaust gas, the amount of air, each temperature, and the relationship between the temperature and amount of mixed gas based on the mixing ratio thereof. Similarly, the relationship between the boiler exhaust gas, the exhaust gas amount temperature of the gas turbine, and the exhaust gas temperature depending on the mixing ratio is stored.

The control box 10 receives the signals from the above-mentioned thermometers and flowmeters, compares them with the stored data, and controls the damper 6d of the pipe line 6 and the damper 7d of the pipe line 7.

Further, the amount of fuel delivered from the pump 11 of the fuel supply system and passing through the pipe 13 is controlled by the control valve 12. The amount of fuel to be delivered is confirmed by a fuel flow meter 11b provided in the pipe line 16.

<Example 2> In plants that use large-capacity boilers, a considerable amount of unburned ash (referred to as EP ash) is discharged, and it is necessary to reduce the volume and recover energy by incinerating the unburned carbon contained, so a fluidized bed is used. A boiler is used.

An example is shown in FIG. The fluidized bed boiler 14 generates steam by immersing heat transfer tubes in a fluidized bed made of a fluidized medium such as sand. At this time, in order to cope with load fluctuations and to speed up the temperature rise of the fluidized medium at startup, etc., the air chamber 16 under the perforated plate 15 is divided into a plurality of air chambers 'I6a, 16b, 16c, and 16ti. A short partition 17 is installed at the bottom to divide the lower part of the layer into a plurality of sections. When starting up, the hot gas generating furnace 18
The hot gas generated by combustion in the burner 18a first heats the fluidized bed above the illustrated air chamber 16d, and the heating medium sequentially ignites the fuel in the fluidized bed corresponding to each air chamber to heat the medium. . When using coal, etc. as fuel, pulverized coal P is added in the layer.
, and take advantage of its good combustibility to cope with load fluctuations.Coarse grain coal C is supplied from above the bed and takes time to burn, so it can cope with steady loads where the response may be slow. ing.

However, in this case, the structure of the fuel quantity boiler 14 for starting the burner 18σ is the same as that shown in FIG.

If necessary, a mixer 22 is provided to receive the air supplied from the pipe line 21, and the mixture is mixed here (~, and mixed gas is mixed in each air chamber 16α~1).
6d. With this device, gas turbine exhaust gas has a temperature of 500°C at startup, so it can be used as is for fluidized bed heating at startup.

Furthermore, when mixing air and exhaust gas appropriately, it can be directly supplied to the air chamber as a combustion gas in accordance with the combustion load.

In addition, when creating a low 02 mixed gas, low NOx in a fluidized bed is used.
It also becomes a gas for combustion. The 02 control for the exhaust gas from the gas turbine allows the control box 23 to mix the exhaust gas and air as in the first embodiment. The gas turbine exhaust gas passing through the Zhangyang pipeline 20 can be made into a mixed gas and used for heating the boiler feed water of the energy saver, as in the first embodiment.

Symbols i9a and 2Cbz are thermometers, and symbols 19b and 20b are flowmeters.

<Embodiment 3> FIG. 4 shows the structure of a low NOx boiler that performs low NOx combustion by adjusting the burner air ratio.

(Special Publication No. 62-25927) In the boiler 25, a main burner 26 that burns at an air ratio of 1 or less is located from the lower stage, and auxiliary burners 27 and 28 that have a lower air ratio are located downstream of the combustion gas, and further downstream thereof. An air supply port 29 is located there.

In this case, the gas turbine exhaust gas pipe 30 is supplied with air through a pipe 66 branching from a pipe 32 having a forced air blower 61 for combustion air, and is supplied with air to a burner which generates a mixed gas and provides an appropriately low air ratio. For example, by supplying a mixed gas with an oxygen content to the burner 27 from the pipe line 64, which will supply an amount of oxygen corresponding to the amount of fuel to be burned, the amount of heat retained in the gas turbine exhaust gas can be recovered and the amount of oxygen contained can be recovered. It can be used effectively.

The fuel supply system and means for controlling the amount of exhaust gas and air to be supplied are similar to those in Embodiment 1.2, so illustrations and explanations are omitted.

<Effects of the Invention> By carrying out this invention, the temperature of the gas turbine exhaust gas, which is low in 02 content and high temperature and unsuitable for burner combustion, was reduced to about 300°C to 350°C by containing 02 appropriately. It is then supplied to the burner to recover the retained thermal energy and serve as a combustion gas, resulting in an energy-saving effect.

It can also be implemented in existing boiler equipment and fluidized bed boilers to save fuel and enable low NOx combustion.

Furthermore, in order to obtain a low NOx boiler by adjusting the air ratio, the gas turbine exhaust gas can be adjusted by 02 and used directly.

[Brief explanation of the drawing]

FIG. 1 is a drawing showing the structure, piping system, and control system of the device according to the first embodiment of the present invention, FIG. 2 is a piping system diagram of the device showing the starting means of a conventional fluidized bed boiler, and FIG. Second
Fig. 4 is a piping system diagram of a sixth embodiment in which the invention is applied to a low NOx boiler, and Fig. 5 is a diagram of a conventional gas turbine and a waste disposal system. It is a structural drawing showing a combination of thermal boilers. 1...Boiler G...Gas turbine exhaust gas 2...Burner 6...Wind box 4...Pipe line 5...Forced blower 6.
7... Pipe line 9... Charcoal vessel 10...
Control box 11...Fuel pump 12...Control valve 14...Fluidized bed boiler 16a, 16b, 16
c, 16d - Air chamber 18... Hot gas generating furnace 22.
...Mixer 26...Control box 25...Low NOx boiler A...Air

Claims (1)

[Scope of Claims] 1. A method for treating gas turbine exhaust gas, which comprises adjusting the oxygen content of exhaust gas from a gas turbine and supplying it as combustion gas to a combustion section of a boiler device. 2. The gas turbine exhaust gas treatment method according to claim 1, wherein the gas turbine exhaust gas and air are mixed, the temperature and oxygen content of the mixed gas are adjusted, and the mixture is supplied to the burner. 3. Supplying exhaust gas from a gas turbine to a fluidized bed, raising the temperature of the fluidized bed, starting a fluidized bed furnace, and after raising the temperature, adjusting the oxygen content of the exhaust gas and supplying it to the fluidized bed as combustion air. 1
The gas turbine exhaust gas treatment method described. 4. Low NO by installing burners in multiple stages on the furnace wall, adjusting the air ratio of the burners, and installing an air supply port in the top stage.
__x Among the burners of the boiler device, gas turbine exhaust gas whose temperature and oxygen content have been adjusted is supplied to a burner that burns at an air ratio that has an oxygen content ratio corresponding to the oxygen content ratio contained in the exhaust gas. 1. The gas turbine exhaust gas treatment method according to 1. 5. The signals from the flowmeters provided in the gas turbine exhaust gas delivery pipe and the air pipe that supplies air to the delivery pipe to adjust the oxygen content are determined based on the gas mixture ratio of the two pipes. It is sent to a control box that stores the relationship between temperature and oxygen content after mixing, and is sent to the delivery pipe and air pipe according to instructions from the control box. The gas turbine exhaust gas treatment method according to any one of claims 1 to 4, further comprising controlling a control damper provided and a control valve that controls the amount of fuel supplied. 6. Sending signals from thermometers provided in the gas turbine exhaust gas delivery pipe and the air pipe to a control box, and controlling the control damper and the control valve that controls the fuel supply amount according to commands from the control box. The gas turbine exhaust gas treatment method according to any one of claims 1 to 5.