JPH05187612A - Burner for exhaust air afterburning type boiler - Google Patents

Abstract

PURPOSE:To make it possible to attain the optimum combustion irrespective of any operating conditions in a burner combustion device for an exhaust gas afterburning type boiler which uses an exhaust gas from a gas turbine and a fresh air selectively as a combustion air. CONSTITUTION:Lean flame burners 22 and 23 are installed to the upper part and lower part of a thick flame burner having two nozzles 21a and 21b. Two fuel gas supply passages 33a and 33b are connected to the thick flame burner 21 while each of fuel gas supply lines 31 and 32 is connected to the leans flame burners 22 and 23 respectively. Combustion air supply lines 24, 25 and 26 are connected to respective burners 21, 22 and 23 where individually controlled burner valves 34, 35, 36a and 36b are installed to each of the fuel gas supply lines 31, 32 and 33a and 33b. At the same time, individually controlled air dampers 28, 29 and 30 are installed to each of the combustion air supply lines 24, 25 and 26 respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas re-combustion type boiler in which exhaust gas from a prime mover such as a gas turbine and fresh air are selectively used as combustion air and a gas body such as natural gas is used as a fuel. It relates to a combustion device.

[0002]

2. Description of the Related Art An outline of a gas fired boiler as an example of a boiler is shown in FIG. Reference numeral 1 is a furnace, and a burner combustion device 2 is provided on the lower wall surface thereof. Fuel gas G and combustion air A are supplied to the burner combustion device 2. In the figure, 3 is a forced draft fan provided in the air supply system, and 4 is a chimney connected to the flue of the boiler.

As shown in FIG. 3, the burner combustor 2 includes one rich diffusion flame burner (hereinafter, referred to as rich flame burner) 5 and two lean premixed flame burners (hereinafter, referred to as rich flame burner) 5 (hereinafter 6, which is referred to as a lean flame burner).

The atmosphere pressurized by the forced draft fan 3 is supplied to each of the burners 5 and 6 as combustion air, and the air flow rate thereof is controlled by an air damper 8 provided in each combustion air passage 7. ..

The fuel gas is supplied from a fuel supply system (not shown) through the fuel supply passage 9, and the fuel flow rate per burner set is controlled by the fuel valve 10 provided in the fuel supply passage 9. The fuel is distributed to the rich flame burner 5 and the lean flame burner 6 which constitute one set of burners by the fuel supply passage 9
An appropriate ratio is set by an orifice 12 provided in a branched fuel supply path 11 that branches off from.

In the burner combustion device 2, the ratio of the combustion air and the fuel supplied to the rich flame burner 5 and the lean flame burner 6 is controlled by the air damper 8 and the orifice 12, and the rich flame burner 5 is used for combustion. The fuel flow rate is increased with respect to the amount of air to form a flame with a high fuel concentration, and the lean flame burner 6 reversely burns fuel against the amount of combustion air (amount different from that of the rich flame burner 5). The flow rate is reduced to form a flame with a low fuel concentration. This enables stable ignition flame, low NO _x combustion, and low excess air ratio operation.

[0007]

By the way, at the present time, a boiler and a gas turbine as described above are combined to use oxygen in the exhaust gas of the gas turbine for combustion and to recover the thermal energy in the exhaust gas. It is intended to improve the power generation efficiency.

In this case, depending on the operating condition, in the burner combustion device 2 on the boiler side, the case of using the exhaust gas of the gas turbine (oxygen concentration: about 10 to 15%) and the fresh air (oxygen concentration: 21%). May be used. However, when the oxygen concentration in the air changes in this way, in the conventional burner combustion device 2, the fuel is distributed to the rich flame burner 5 and the lean flame burner 6 only to the orifices 12, and all the air dampers are used. Since 8 also opens and closes uniquely,
It becomes impossible to perform the combustion that has the original function of the burner combustion device as described above.

[0009]

A burner combustion apparatus according to the present invention for solving the above problems selectively uses exhaust gas from a prime mover and fresh air as combustion air, and uses a gas body as fuel. A burner combustor for an exhaust gas re-burning boiler used, in which a burner unit has a rich diffusion flame burner with a large amount of fuel for combustion air, and a lean premixed flame arranged above and below it with a small amount of fuel for combustion air. Composed of burners and connected to each burner with a combustion air supply system, each combustion air supply system is equipped with a combustion air damper, and each lean premixed flame burner is connected with a fuel gas supply system and diffuses in rich concentration. Two fuel gas supply systems are connected to the flame burner, burner valves are provided in these fuel gas supply systems, and the combustion air damper and burner valve are controlled. Rukoto by, also optimum combustion, characterized in that the so performed at any time during and fresh air used exhaust gas used.

[0010]

According to this burner combustion device, when exhaust gas is used as the combustion air, it is optimal to use the combustion air supply system and the fuel gas supply system of all the burners, as in the conventional burner combustion device. It is possible to control the combustion state.

Further, when fresh air is used as combustion air, the oxygen concentration in the air is higher than when exhaust gas is used, so a smaller amount of air is sufficient to burn the same amount of fuel. Therefore, by closing the burner valve of the fuel gas supply system of one of the lean flame burners and the burner valve of the fuel gas supply system of one of the rich flame burners, and controlling the combustion air damper at the same time, optimal combustion is achieved. You can get the status.

[0012]

FIG. 1 shows the structure of one unit 20 in a burner combustion apparatus according to one embodiment. The burner combustion device is configured by combining a plurality of the units 20.

Reference numeral 21 is a rich flame burner, which has two nozzles 21a and 21b at the top and bottom. Lean flame burners 22 and 23 are arranged on the upper and lower sides of the rich flame burner 21, respectively. Combustion air supply passages 24, 25, 26 are connected to these burners 21, 22, 23 as a combustion air supply system. The main combustion air supply passage 27, where the combustion air supply passages 24, 25, 26 join, is selectively supplied with the exhaust gas of the gas turbine or the atmosphere as fresh air.

Air dampers 28, 29 and 30 are provided in the combustion air supply passages 24, 25 and 26, respectively. These air dampers 28, 29, 30 are independently controlled to open and close. Therefore, the air damper 2
8, 29, 30 by each combustion air supply passage 24, 2
The air flow rates of 5 and 26 are independently controlled.

The lean flame burners 22 and 23 are respectively connected to one fuel gas supply passage 31 and 32 as a fuel gas supply system, and the rich flame burner 21 is provided with each nozzle 21a and 21b.
The two fuel gas supply paths 33a and 33b are connected in correspondence with the above. Each fuel gas supply passage 31, 32, 33a,
33b includes burner valves 3 that are individually controlled to open and close.
4, 35, 36a and 36b are provided. A main fuel gas supply passage 37, into which the fuel gas supply passages 31, 32, 33a, 33b branch, is connected to a fuel gas supply source via a fuel valve 38.

The fuel gas supplied to the main fuel gas supply passage 37 is first controlled by the fuel valve 38 to a fuel flow rate according to the burner output.

Next, when the gas turbine exhaust gas is used as the combustion air, the burner valves 36a, 36b and 34, 3 of the rich flame burner 21 and the lean flame burners 22, 23 are used.
No. 5 fully open, nozzles 2 above and below rich flame burner 21
Combustion is carried out by using all of 1a, 21b and the upper and lower lean flame burners 22, 23. At this time, the combustion air dampers 28, 29, 30 are all used. Damper 28, 2
The opening degrees of 9 and 30 are adjusted by a combustion test so as to achieve an optimum combustion state, and are controlled accordingly.

When fresh air is used as the combustion air, one of the burner valves 36a and 36b of the rich flame burner 21 is fully closed and the other one is fully opened to use one of the nozzles 21a or Combustion is performed only by 21b.
At this time, of the two lean flame burners 22 and 23, the nozzle 21a or 21b of the rich flame burner 21 being used is used.
Lean burner 22 or 23 burner valve 3 closer to
4 or 35 is fully opened, the other burner valve 34 or 35 is fully closed, and one lean flame burner 22 or 2
Only use 3. For example, when the upper nozzle 21a of the rich flame burner 21 is used, the burner valve 34 is fully opened and combustion is performed by the upper lean flame burner 22, the burner valve 35 is fully closed, and the lower lean flame burner 23 is used. Therefore, the combustion by is not performed.

At this time, the combustion air dampers 28, 29,
Among them, the lean-air burner not used, for example, the combustion air damper 30 of the lean-flame burner 23 on the lower side according to the above example is fully closed, and the lean-air burner 22 of the lean-burn burner 22 in use is closed. And the combustion air damper 28 of the rich flame burner 21 is opened. The openings of these dampers 28 and 29 are adjusted by a combustion test so as to achieve an optimum combustion state, and are controlled according to the results.

After all, according to the above combustion apparatus, the rich flame burner 21 and the lean flame burners 22 and 23 are optimal for the amount of oxygen in the air regardless of whether exhaust gas is used or fresh air is used. It is possible to burn with the amount of fuel.

[0021]

EFFECTS OF THE INVENTION According to the burner combustion apparatus for an exhaust gas re-combustion type boiler according to the present invention, the air used when the exhaust gas from a prime mover such as a gas turbine and fresh air are selectively used as combustion air. Since the fuel amount and the air amount are adjusted according to the above, stable combustion with low NO _x and low excess air ratio can be realized.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a burner combustion apparatus according to an embodiment.

FIG. 2 is a schematic diagram of an example of a boiler.

FIG. 3 is a schematic view of a conventional burner combustion device.

[Explanation of symbols]

 1 Furnace 20 Burner Combustor Unit 21 Rich Flame Burner 21a, 21b Nozzle 22, 23 Lean Flame Burner 24, 25, 26 Combustion Air Supply Channel 28, 29, 30 Air Damper 31, 32, 33a, 33b Fuel Gas Supply Channel 34 , 35, 36a, 36b Burner valve

Claims (1)

[Claims] Claim: What is claimed is: 1. A burner combustion apparatus for an exhaust gas re-combustion type boiler, wherein exhaust gas from a prime mover and fresh air are selectively used as combustion air, and a gas body is used as fuel, which burns a burner unit. The rich-diffusion flame burner with a large amount of fuel for the working air, and the burner placed above and below
Composed of a lean premixed flame burner with a small amount of fuel to the combustion air, each combustion air supply system is connected to each burner, and a combustion air damper is installed in each combustion air supply system to provide each lean premixed flame burner. A fuel gas supply system connected to the fuel gas supply system, and two fuel gas supply systems connected to the rich-diffusion flame burner, and burner valves are respectively provided to these fuel gas supply systems to control the combustion air damper and the burner valve. Thus, the burner combustion device is characterized in that optimum combustion can be performed both when exhaust gas is used and when fresh air is used.