JP3434337B2 - After air supply device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an after-air supply apparatus, and more particularly to a method for reducing nitrogen oxides (hereinafter referred to as NOx) in exhaust gas without increasing unburned components. The present invention relates to a suitable after-air supply device for a combustion device. 2. Description of the Related Art NOx is one of the serious causes of air pollution, and it has been demanded to remove or reduce NOx from the viewpoint of preventing pollution. For example, N generated from a combustion device such as a boiler
Ox contains fuel NOx, which is generated by oxidizing nitrogen components contained in various fuels during combustion, and hydrocarbons react with nitrogen in air when burning hydrocarbon fuels. Prompt NOx generated through the above reaction and thermal (Therma) generated by combining nitrogen molecules in the air with oxygen at a high temperature.
1) There is NOx, and thermal NOx is particularly regarded as a problem. The generation of thermal NOx involves a high combustion temperature,
The higher the O ₂ concentration in the combustion zone and the longer the residence time of the combustion gas in the high-temperature zone, the more the gas is generated. [0005] Therefore, in order to fundamentally suppress NOx, it is important to suppress the combustion temperature, O ₂ concentration, and residence time. In particular, when the combustion temperature exceeds 1600 ° C, NO
x tends to increase sharply. For this reason, a recent boiler employs a denitrification combustion system to reduce NOx and reduce unburned components. In this denitrification combustion system, incomplete combustion is performed in the main burner to suppress the generation amount of NOx, and low-oxygen combustion is performed in the denitration burner to reduce NOx generated in the main burner by the reducing intermediate product. a combustion method for reducing the harmless N _2. FIG. 6 is a longitudinal sectional view of a boiler employing a denitration combustion system, and FIG. 7 is a side view of FIG. 6 and 7, the boiler 1 comprises a front wall 2, a rear wall 3, side walls 4, 5, a hopper 6, a nose 7, and a furnace outlet 8. Main burners 9, 10 on front wall 2,
A denitration burner 11 and an after-air port 12 are provided in order from bottom to top, and a hopper port 13 is provided at the bottom of the hopper 6, from which recirculated gas is supplied. Then, low NOx in the furnace 14 of the boiler 1
The main burner 9 burns with an air amount substantially equal to the theoretical combustion air amount or an air amount slightly smaller than the theoretical combustion air amount, and the main burner 10 burns 60 to 80% of the theoretical combustion air amount. The denitrification burner 11 burns at 40-60% of the theoretical combustion air amount.
Strong NOx-reducing C, an intermediate product of combustion of hydrocarbons
N, to reduce NOx in the main burners 9, 10 by C _2, NH _3, a combustion method to perform the complete combustion and further supplying combustion air from the after-air port 12. FIG. 8 is an enlarged view of a conventional after-air supply device, and FIGS. 9 and 10 each show an after-air flow pattern in the width direction of the furnace. In FIG. 8 to FIG.
Denotes the same one as in FIGS. 6 and 7, 15 denotes a wind box, 1
6 is a swirl generator, 17 is a swirl air passage, and 18 is a swirl air flow. In such a structure, the after-air in the wind box 15 is adjusted to an arbitrary swirling intensity by a swirling generator 16 in a swirling air passage 17 to form a swirling air flow 18, and passes through the after-air port 12 to the furnace 14. Supplied. As described above, the swirling air flow 18 is generated by the swirl generator 1.
Increasing the degree of swirling by 6 increases the divergence angle of the swirling airflow 18, but reduces the jet velocity in the axial direction. Conversely, if the degree of swirling by the swirl generator 16 is reduced, the spread angle of the swirl air flow 18 becomes smaller, and the jet velocity in the axial direction increases. That is, when the swirling is strong, the swirling air flow 18 spreads in the width direction of the furnace 14 as shown in FIG. 9, but the velocity vector in the axial direction decreases, and the penetration force in the depth direction of the furnace 14 decreases. . On the other hand, when the turning is weak, the velocity vector in the axial direction becomes large as shown in FIG.
Is increased, but the spread of the swirling airflow 18 is reduced. That is, a simple swirling air flow 18
It is not possible to adjust both the spread of the after-air and the penetration force over the entire cross section of the furnace 14 by using only the furnace. Instead of the after-air supply device using only the swirling air flow 18, there is a dual-flow after-air supply device as shown in FIG. FIG. 11 is an enlarged view of a dual flow type after-air supply device, and FIG. 12 shows a flow pattern of the after-air in FIG. In FIGS. 11 and 12, reference numerals 2 to 18 indicate the same components as those in FIG. 19 is a sleeve arranged in the after-air port 12, 20 is a straight air passage, 21 is a straight air flow,
22 is a damper. In such a structure, the swirling air flow 18 outside the sleeve 19 is adjusted to an arbitrary swirling intensity by the swirling generator 16 and guided to the furnace 14 through the after-air port 12. Straight air flow 2 inside sleeve 19
1 is led to the furnace 14 through the straight air passage 20.
The flow rate ratio between the swirling air flow 18 and the straight air flow 21 is arbitrarily adjusted by the resistance difference between the swirling generator 16 and the damper 22. By adjusting the swirling strength of the swirling air flow 18 on the outer periphery of the sleeve 19 and the flow rate ratio of the swirling air flow 18 to the straight air flow 21, the after-air adjusts both the spread and the penetration force in the cross section of the furnace 14. Can be. That is, as shown in the flow pattern of FIG. 12, the swirling air flow 18 causes the furnace 14 to expand in the width direction, and the straight air flow 21 generates a penetration force into the furnace 14. , Both spread and penetration can be adjusted. However, in the prior art after-air supply device shown in FIGS. 8 and 11, since the after-air is an axially symmetric jet of the after-air port 12, the width of the furnace 14 in the width direction is reduced. When the after-air is to be spread, the after-air also spreads in the height direction of the furnace 14, so that the penetration force of the straight air flow 21 into the furnace 14 is reduced accordingly. The present invention is intended to solve the drawbacks of the prior art, and aims at suppressing the spread of the after-air in the furnace height direction and widening the after-air spread in the furnace width direction. To provide a possible after-air supply device. According to the present invention, in order to achieve the above-mentioned object, a sleeve is constituted by a semicircular upper sleeve and a semicircular lower sleeve. The sleeve is provided with a swing mechanism. As described above, the upper and lower sleeves are formed into a semicircular shape, and an axially asymmetric jet is formed by providing the oscillating mechanism, so that the after-air can be spread in the width direction of the furnace. It can be widened, and the spread of after-air in the height direction of the furnace can be narrowed. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view of an after-air supply apparatus according to an embodiment of the present invention, FIG. 2 is a side view of FIG. 1, FIG. 3 is a plan view of FIG. 1, and FIG. FIG. 5 is a diagram showing a flow pattern of after-air in the height direction of the furnace. In FIGS. 1 to 5, reference numerals 2 to 22 indicate the same components as those of the prior art. Reference numerals 23 and 24 denote an upper sleeve and a lower sleeve which are divided into a semicircular shape, 25 denotes a swing mechanism of the upper and lower sleeves 23 and 24, and 26 and 27 denote upper and lower air passages of the upper and lower sleeves 23 and 24. And lower straight air passages 28 and 29 are an upper straight air flow and a lower straight air flow. In such a structure, the swirling air flow 18
After being given an arbitrary turn by the swirl generator 16, the swirl is guided to the furnace 14 through the after-air port 12. The straight air passages in the upper and lower sleeves 23 and 24 are shown in FIG.
The upper and lower sleeves 23, 24 are divided into an upper air passage 26 and a lower air passage 27 as shown in FIG.
2 can be oscillated in the width direction of the furnace 14 at angles of θ and θ ′, respectively, so that the upper straight airflow 28 moves to the left of the center axis of the after-air port 12 and the lower straight airflow Numerals 29 are expanded in the width direction of the furnace 14 to the right side of the center axis of the after-air port 12, respectively. That is, the upper straight air flow 28 and the lower straight air flow 29 are divided and supplied to the upper sleeve 23 and the lower sleeve 24, but by oscillating the upper and lower sleeves 23, 24, The after-air flow pattern in the height direction of the furnace 14 has a smaller divergence angle than that of the prior art as shown in FIG. 5, and the after-air flow pattern in the width direction of the furnace 14 is the same as that of the prior art as shown in FIG. The spread angle in the width direction is larger than that of the object. That is, the after-air from the after-air supply device of the prior art has a flow pattern that is almost circular in both the height direction and the width direction of the furnace 14, but the after-air in the after-air supply device of the embodiment is in the height direction of the furnace 14. Has a narrow divergence angle and spreads in the width direction, so that the flow pattern becomes almost elliptical. Therefore, the after-air in which the spread of the furnace 14 in the height direction is suppressed and the spread of the furnace 14 in the width direction is widened is obtained. According to the present invention, the spread of the furnace in the height direction can be suppressed, and the spread of the furnace in the width direction can be made wider, and NOx and unburned components can also be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view of an after-air supply device according to an embodiment of the present invention. FIG. 2 is a side view of FIG. FIG. 3 is a plan view of FIG. 1; FIG. 4 is a diagram showing a flow pattern of after-air in a width direction of a furnace. FIG. 5 is a view showing a flow pattern of after-air in a height direction of a furnace. FIG. 6 is a vertical sectional view of a boiler employing a denitration combustion method. FIG. 7 is a side view of FIG. 6; FIG. 8 is an enlarged view of a conventional after-air supply device. FIG. 9 is a diagram showing an after-air flow pattern during strong turning. FIG. 10 is a diagram showing a flow pattern of after-air at the time of a weak turn. FIG. 11 is an enlarged view of a conventional dual-flow after-air supply device. FIG. 12 is a diagram showing the flow pattern of FIG. 11 and after-air. [Description of Signs] 12 After air port 17 Swirling air passage 19 Sleeve 20 Straight air passage 23 Upper sleeve 24 Lower sleeve 25 Swing mechanism

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Naoyuki Sei 6-9 Takara-cho, Kure City, Hiroshima Prefecture Inside the Kure Plant, Babkotsuk Hitachi Ltd. (56) References JP-A-59-95308 (JP, A) 57-132907 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F23L 9/02 F23L 1/00 F23C 7/02

Claims (1)

(57) [Claims 1] A sleeve is disposed in an after-air port, a swirling air passage is provided outside the sleeve, and a straight air passage is provided inside the sleeve. Wherein the sleeve is composed of a semicircular upper sleeve and a semicircular lower sleeve, and the upper and lower sleeves are provided with a oscillating mechanism. Feeding device.