JPH06341609A - Boiler device - Google Patents

Abstract

PURPOSE:To reduce the nitrogen oxide or an unburnt portion in the combustion exhaust gas from a boiler device for use in thermal power generation, etc. CONSTITUTION:A main burner 03 is provided at the upper part of a boiler furnace 01 and, at its further upper part, is provided a top part nozzle 31 for delivering a portion of combustion air or recirculating exhaust gas. A combustion gas emission opening 07a is provided at the lower part and a bottom part nozzle 33 for delivering a portion of combustion air is provided near the emission opening. At the intermediate part, an additional air delivering nozzle 06 is provided in a manner similar to the conventional one. Since in this way the combustion takes place downwardly to produce a buoyancy in the direction opposite to the flow of the combustion gas, there is no blow-by of fuel and combustion air, their dispersion and mixing are accelerated and the furnace volume is effectively used in order to enhance the reducing ratio of NOx in the combustion gas. Also, the flame temperature in a main combustion region is lowered to suppress the production of thermal NOx.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steam generating boiler and a chemical industrial furnace used for power generation, factories and the like.

[0002]

2. Description of the Related Art FIG. 3 is a schematic vertical sectional view showing an example of a conventional boiler device. In this figure, (01) is a boiler furnace body, (02) is inside the boiler furnace, (03) is a main burner body, (04) is a main burner fuel nozzle, (05) is an additional air injection nozzle body, and (06) ) Is an additional air injection nozzle, (07) is an exhaust gas flue, (07
a) is a combustion exhaust gas outlet, (08) is a steam superheated tube group,
(09) is an economizer, (10) is a denitrifier, (11)
Is an air heater, (12) is an electrostatic precipitator, (13) is a draft fan, (14) is a chimney, (15) is a forced draft fan, (1
6) is a wind passage, (17) is a combustion ash collection tank, and (18) is a fuel supply pipe.

In this boiler apparatus, a main burner body (03) is provided on a side wall or a corner portion of an upper portion of a boiler furnace body (01), and an additional air injection nozzle body (05) is further provided on a wall surface or a corner portion below the main burner body. It is provided. A combustion ash collection tank (17) is provided below the boiler furnace body (01), and the combustion ash collection tank (17) is provided inside the boiler furnace (0).
Of the combustion ash of the fuel burned in 2), those that fall to the bottom of the furnace are collected and processed. Boiler furnace body (0
1) A combustion exhaust gas outlet (07a) is opened on one of the lower wall surfaces and communicates with the exhaust gas flue (07).

On the other hand, the combustion air sent in by the forced draft fan (15) is heated to a predetermined temperature in the air heater (11), passes through the air passage (16), and is discharged to the main burner body (03). Additional air injection nozzle body (05)
Sent to. Further, the fuel is sent from a fuel supply facility (not shown) to the main burner main body through the fuel supply pipe (18), and the fuel is supplied from the main burner fuel nozzle (04) to a virtual vertical cylinder in the center of the boiler furnace (02). Is tangential to the side of the. The fuel injected into the boiler furnace is ignited by an ignition source (not shown), diffusively mixed with the combustion air, and descends while swirling burning in the boiler furnace (02). The flue gas discharged from the boiler furnace body (01) is steam superheated tube group (08), economizer (0).
9), denitration device (10), air heater (11), and electrostatic precipitator (12), and then a chimney (1
4) Released into the atmosphere.

[0005]

The conventional boiler device shown in FIG. 3 has the following problems to be solved. 1) Since the main burner main body is installed above the boiler main body to perform downward combustion, buoyancy is generated in the boiler furnace in the direction opposite to the combustion gas flow, blow-through of fuel and combustion air is eliminated, and air is diffusely mixed. Although it has the advantage of being promoted, since the combustion rate in the main burner combustion region becomes too high, as shown by the dotted line in FIG. 2, the heat load of the burner part becomes too high, the burner nozzle burns out, and the boiler burns. There is a problem such as the boiler tube metal temperature on the furnace wall becomes high.

2) Due to the buoyancy of the high-temperature gas generated by combustion, a part of the flame in the main combustion region winds up and stays at the top of the furnace (the region above the main burner body), which causes slugging problems. It becomes a factor.

3) As shown by the dotted line in FIG. 2, the gas temperature becomes low at the outlet of the boiler, and the steam superheater tube group radiative heat transfer of the combustion flame in the boiler furnace only by convective heat transfer of the flue. It is difficult to reach the predetermined temperature because the steam cannot be used.

[0008]

In order to solve the above-mentioned conventional problems, the present invention is directed to a vertical rectangular tube-shaped furnace and a combustion exhaust gas which is opened to a side wall at a lower portion of the furnace and communicates with an exhaust gas flue. Exhaust port, a main burner that is arranged in the upper part of the furnace to inject fuel and combustion air, and is arranged between the top part of the furnace and the main burner, and is a vertical cylinder of the virtual center of the furnace. A plurality of top nozzles that inject combustion air or combustion exhaust gas or a mixed gas thereof in a tangential direction to the side surface, and a vertical cylinder that is arranged in the vicinity of the combustion exhaust gas discharge port of the furnace and is virtual in the center of the furnace A plurality of bottom nozzles for injecting combustion air tangentially to the side surface, means for adjusting the horizontal and vertical angles of the top nozzle and the bottom nozzle, and a top nozzle in the furnace. With steam superheat tube group It proposes a boiler apparatus according to claim.

[0009]

[Action]

1) In the present invention, the fuel injected from the main burner provided in the upper part of the furnace burns while diffusing and mixing with the combustion air and descends. Since buoyancy occurs in a high-temperature furnace, there is no blow-through of fuel and combustion air, and diffusion and mixing of both are promoted. Since the blow-through is eliminated, the furnace volume is effectively used, and the rate at which NO _x in the combustion gas generated by the combustion of the fuel is reduced to N ₂ is increased.

2) In the present invention, the flame temperature in the main combustion zone can be lowered by partially injecting the combustion exhaust gas, the combustion air or a mixed gas thereof from the top nozzle provided above the main burner. it can. Therefore, as shown by the solid line in FIG. 2, the heat flux distribution is flattened as compared with the conventional case, and the thermal NO _x (Thermal NO
_x : Generation of NO _x ) generated by decomposition of N _{2 in} air accompanying high temperature combustion is suppressed. Further, the downward momentum of the gas blown from the top nozzle suppresses unnecessary hoisting of the furnace.

3) Since the heat flux in the main combustion region is lower than in the conventional case as described above, a part of the steam superheated tube group can be installed at the top of the boiler furnace. Thereby, the radiant heat transfer of the combustion flame in the boiler furnace can also be used, and the steam temperature can be set to a predetermined value.

4) In the case of the downward combustion system as in the present invention
The main burner to avoid damage from falling slag.
No steam superheater tubes are installed between the bottom of the furnace. Therefore
The effective combustion area in the downward combustion system is the main burner body.
From the combustion gas exhaust port to the boiler furnace body configuration
The apparent effective combustion area in the
Widely set. Therefore, the conventional additional air
NO by_xIn addition to the reduction, also in the vicinity of the combustion exhaust gas outlet
Install a bottom nozzle for charging combustion air _x2 steps
By performing reduction, the unburned fuel level can be suppressed.
One, NO_xCan be further reduced.

[0013]

1 is a schematic vertical sectional view showing an embodiment of the present invention. In this figure, the same parts as those of the conventional one described with reference to FIG. 3 are designated by the same reference numerals to avoid redundancy, and detailed description thereof is omitted.

In this embodiment, the electrostatic precipitator (12)
Exhaust gas recirculation gas is sent from the inlet air passage to the top nozzle body (30) by the exhaust gas recirculation blower (34) via the exhaust gas recirculation air passage (35). The exhaust gas recirculation air passage (35) communicates with the air passage (16) for combustion air, and the combustion air is also supplied to the top nozzle body (30). The amount and distribution of the exhaust gas recirculation gas and the combustion air can be set arbitrarily. The amount of gas supplied to the top nozzle body (30) is in the range of about 5% to 20% of the amount of combustion gas, and this controls the flame temperature in the main combustion region and suppresses the generation of thermal NO _x . Further, the gas injected from the top nozzle body (30) also has a function of preventing the main burner combustion flame from being wound up, and therefore, the blowing angle of the top nozzle (31) in the vertical direction is
Adjust from horizontal to 15 ° downward.

On the other hand, a plurality of bottom nozzle bodies (32) are provided on the wall surface or the corner portion of the boiler furnace body (01) near the combustion gas discharge port (07a) to burn the combustion air for two-stage NO _x reduction. Supply 5% to 15% of the total amount. Here, in order to accelerate the NO _x reduction reaction, the bottom nozzle (3
The blowing angle in the vertical direction of 3) is horizontal to 30.
° Upward and inject in the direction opposite to the combustion gas flow direction.

Also, in this embodiment, the heat flux in the main combustion region is lower than that in the conventional case as shown by the solid line in FIG.
At the top of the boiler furnace (02), a part of the steam superheater tube group (08
A) can be installed.

[0017]

According to the present invention, the following effects can be obtained. That is, by installing a top nozzle for injecting combustion air, combustion exhaust gas, or a mixed gas thereof above the main burner during downward combustion, a steam superheater tube group is installed at the top of the boiler furnace to prevent a decrease in steam temperature. In addition, it is possible to suppress the generation of thermal NO _x generated in the main combustion region. Further, by providing a bottom nozzle for introducing a part of the combustion air in the vicinity of the combustion gas discharge port of the boiler furnace body, NO _x reduction can be efficiently performed.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view showing an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a boiler height and a wall surface reaching heat flux.

FIG. 3 is a schematic vertical sectional view showing an example of a conventional boiler device.

[Explanation of symbols]

(01) Boiler furnace main body (02) Boiler furnace inside (03) Main burner main body (04) Main burner fuel nozzle (05) Additional air injection nozzle main body (06) Additional air injection nozzle (07) Exhaust gas flue (07a) Combustion exhaust gas discharge port (08), (08A) Steam superheated tube group (09) Economizer (10) Denitrifier (11) Air heater (12) Electrostatic precipitator (EP) (13) Induction fan (IDF) ( 14) Chimney (15) Forced draft fan (FDF) (16) Air passage (17) Combustion ash collection tank (18) Fuel supply pipe (30) Top nozzle body (31) Top nozzle (32) Bottom nozzle body (33) ) Bottom nozzle (34) Exhaust gas recirculation blower (GRF) (35) Exhaust gas recirculation air passage

Claims (1)

[Claims] 1. A vertical rectangular tube-shaped furnace, a combustion exhaust gas outlet opening to a side wall at a lower portion of the furnace and communicating with an exhaust gas flue, and a fuel and combustion air arranged at an upper portion of the furnace. A main burner to inject, arranged between the top of the furnace and the main burner, the combustion air or combustion exhaust gas or a mixed gas thereof in a tangential direction to the side surface of a vertical cylinder that is virtually in the center of the furnace. A plurality of top nozzles for injecting, and a plurality of bottom nozzles arranged in the vicinity of the combustion exhaust gas discharge port of the furnace for injecting combustion air in a tangential direction with respect to a side surface of a vertical cylinder virtually in the center of the furnace. And a means for adjusting horizontal and vertical angles of the top nozzle and the bottom nozzle, respectively, and a steam superheated tube group arranged at the top of the furnace.