JPH0627562B2 - Burner device with edge - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a burner device with an edge, and more particularly to a burner device capable of achieving NOx conversion and stable combustion when solid fuel such as pulverized coal is burned.

(Background of the Invention) Due to recent changes in fuel circumstances, large-scale boilers for business establishments including large-scale boilers for thermal power plants are increasingly using coal as fuel. In this case, the coal is pulverized into, for example, pulverized coal having a passing amount of 200 mesh of about 70% to improve combustibility and controllability.

However, as is well known, N produced as a by-product of combustion
Ox often occurs in high-load combustion burners, and since it is one of the main components of air pollution,
Some basic burner improvements or furnace-wide combustion improvements have been made. A particular problem in the combustion of pulverized coal is that most of NOx due to organic form nitrogen (hereinafter referred to as Fuel N) contained in a large amount (usually 1 to 2 wt%) in pulverized coal is occupied. .

Here, the production reaction of NOx and N ₂ from Fuel N is as shown in the following equations (1) and (2), respectively, and both reactions are competitively performed.

Therefore, in order to give priority to the production of N ₂ and maintain high-load combustion, securing a high-temperature reducing flame is an important point.

A combustion method generally called two-stage combustion is an application of this combustion reaction, in which a high temperature reducing flame is formed by creating an air shortage state in the burner zone of the furnace, and the shortage of air is provided in the wake of the burner, By injecting from a so-called after-air port and completely burning it, combustion is improved in the entire furnace and NOx emission amount is reduced.

However, in the above-mentioned two-stage combustion, unburned coal particles (chairs) are produced in the burner zone where the air is insufficient, and a large empty column is required in the furnace to completely burn these coal particles with after-air. . Therefore, although the above combustion method is a very effective low NOx combustion method in principle, it has a certain limit.

From this, instead of controlling the combustion of the entire boiler,
So-called dual register type burners have been developed in which each burner is configured to perform low NOx combustion based on the above principle.

However, with this type of burner, usually 2
Although the secondary air and the tertiary air are separated by the sleeve and are respectively supplied through the swirling means, the pulverized coal flow, the secondary air flow and the tertiary air flow are easily mixed in the vicinity of the burner throat outlet, It was found that it is difficult to sufficiently maintain the high temperature reducing flame in the early stage of combustion. Further, the conventional type flame holding is due to the so-called pulverized coal wide angle spray type impeller, and it is extremely difficult to concentrate the high temperature reducing flame near the burner central axis with this type of flame holding. It was

On the other hand, coal has the property that its combustibility and exhaust gas characteristics greatly change depending on its properties. In particular, various improvements have been required for stable combustion of flame-retardant coal having a low volatile content.

In the conventional burner device, a flame holding ring (frame cap) 16 is provided at the tip of the primary sleeve, and a flat portion of the flame holding ring is partially formed on the inner air side of the primary air inlet side as shown in FIG. It has a structure in which a plurality of edge portions 16A extended to are provided.

(Problems to be Solved by the Invention) A first drawback of the prior art is that when the burner throat flow velocity increases, the formation of the recirculation region is destroyed, and as a result, the flame becomes unstable. Therefore, there is a drawback that the range of the optimum flow velocity of the burner, that is, the flame stability width is narrowed.

A second drawback of the prior art is that the flame near the burner port always has a certain spatial distance because the shape of the combustion gas recirculation zone is difficult in the immediate vicinity of the burner port. That is, the front edge of the flame was always separated from the solid surface, and the flame was blown off depending on the change in conditions.

The third drawback of the conventional technique is that, due to the above-mentioned second drawback, the draft fluctuation in the furnace is large, and combustion oscillation may occur when the fuel is gas or oil combustion.

An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to provide an edge burner device that can obtain a stable flame under a wide range of combustion conditions.

(Means for Solving Problems) In short, the present invention inserts a flame holding ring (frame cap or bluff body) having a specific turbulent flow edge into the burner opening, and stabilizes the flame by the turbulent vortex generated in the wake. At the same time, the fuel is supplied to the turbulent flow portion at the same time, which makes it possible to cope with high fuel ratio coal, which is particularly flame-retardant.

That is, the present invention relates to a burner device that conveys fuel together with primary air to a primary sleeve and supplies combustion air from a secondary sleeve that is concentrically provided outside the primary sleeve.
Providing a turbulence edge that gives turbulence to the pulverized coal flow at the next air port,
In addition, a taper portion is provided on the side of the turbulent flow edge so that the flow expands.

(Embodiment) FIG. 1 is a sectional view of a burner device showing an embodiment of the present invention, FIG. 2 is its A view, and FIG. 3 is an enlarged view showing a B portion of FIG. . This burner device has a primary sleeve 17 into which an oil gun 11 is inserted in a central axis thereof, a flame holding ring 16 having a substantially L-shaped cross section provided at a tip thereof, and a space provided on an inner circumference of the flame holding ring 16. A plurality of turbulent edges 16A, a secondary sleeve 9 concentrically provided outside the primary sleeve 17, a secondary guide sleeve 9A provided at the tip thereof, and the guide sleeve. Provided 2
Secondary air intake 5, slide damper 4, venturi 12 provided on the inner wall of the primary sleeve 17, secondary vane 6 provided in the secondary sleeve 9, and furnace wall 3
And an air register 8 provided in a secondary air passage formed between the secondary sleeves 9. The wind box 1 is composed of a wind box wall 2 and a boiler wall 3, and one or more burners are installed in the wind box 1. In addition, 7 is a secondary air port, 10 is a tertiary air port, 1
2 is a heavy oil nozzle, 13 is primary air and pulverized coal, and 15 is a primary air port.

In FIG. 2, eight turbulence edges 1 are provided in the primary air port 15.
The state where 6A is provided is shown. 3 and 4 show taper portions 18 provided on both sides of the turbulent flow edge 16A.

In such a configuration, the combustion air is pressurized by the forced draft fan, heated by exchanging heat with the exhaust gas by the air heater, adjusted in the amount of air by the damper, and then guided by the duct to wind box 1. Is supplied to. A part of the combustion air supplied to the wind box 1 enters the secondary sleeve from the secondary air inlet 5 adjusted by the secondary slide damper 4, and becomes a swirling flow by the secondary vane 6 to generate the secondary air. It is supplied from the mouth 7 into the furnace. The remaining combustion air becomes a swirling flow in the tertiary air register 8,
It is supplied from the tertiary air port 10 into the furnace.

On the other hand, the pulverized coal pulverized by the mill and conveyed by the primary air is supplied to the burner as the pulverized coal gas flow 13 by the primary air, is squeezed by the venturi 14 to rectify the flow, and then the primary air is supplied. It is supplied from the mouth 15 into the furnace. When the pulverized coal boiler is activated, oil is supplied from the oil spray nozzle 12 into the furnace through the supply pipe 11.

According to the above embodiment, the turbulent flow edge 1 is formed on the inner circumference of the flame holding ring.
By providing 6A, a small turbulent vortex is generated in the vicinity of the burner port, which rapidly increases the combustion speed and can extremely stabilize the flame.

That is, as shown in FIG. 3 and FIG. 4, the pulverized coal flow 13 is once narrowed by the turbulent flow edge 16A and then rapidly expands. A vortex A19 and a wake vortex B20 are generated, which increases the combustion speed and stabilizes the flame. The taper portion 18 rapidly expands the flow of the pulverized coal flow 13 and promotes the occurrence of turbulence.

FIG. 5 is an explanatory view showing another specific example of the part B in FIG. 2, and here, it has a structure in which a slit 22 is provided between the turbulent flow edges 21.

FIG. 6 shows the DD cross section of FIG. 5, and in order to promote the rapid deceleration at the slit opening 22 and the generation of the slit vortex 25, the tapered portion 18 is provided as in FIG. ing. The pulverized coal flowing out of the slit portion 22 immediately decelerates and forms a slit vortex 25, which further promotes the generation of turbulent flows 19 and 20 downstream of the turbulent flow edge 21.

By creating small turbulent vortices in the wake of the turbulent edge in this manner, combustion can be extremely stabilized. This type of turbulent edge 21 is extremely effective for flame-retardant high fuel ratio coal with low volatile content and high ash content.

FIG. 7 shows another embodiment of part B of FIG. The turbulent flow edge 24 has tapered portions 18 at both ends as in FIGS. 3 and 5, and is provided with a plurality of round openings 23 as shown. This cross-sectional shape is an enlarged cross-section on the wake side as in FIG. According to this embodiment, because of the small opening 23, the flow is decelerated quickly, the fuel is rapidly supplied to the wake side of the turbulent edge 24, and flame stabilization is achieved.

(Effect of the Invention) According to the present invention, turbulence is increased by the above-mentioned turbulent flow edge, and a stable flame can be formed from this portion. It should be noted that this is flame holding only by the primary air,
Since the effect of the swirling of the tertiary air port has no influence, according to the present invention, the operating range of the optimum flow velocity of the burner is significantly expanded. Further, since the flame is formed from the turbulent flow edge portion by the turbulent flow edge, the flame front edge is fixed, and the flame is less likely to be blown off. Further, since the leading edge of the flame is fixed as described above, the fluctuation of draft in the furnace is reduced, and quiet combustion can be performed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a burner device showing an embodiment of the present invention, FIG. 2 is a view as seen from A of FIG. 1, and FIG. 3 is B of FIG.
FIG. 4 is a detailed view of a portion, FIG. 4 is a cross-sectional view taken along the line CC of FIG. 3, and FIG. 5 is a detailed view showing another embodiment of the portion B of FIG. 5 is a cross-sectional view taken along the line DD in FIG. 5, FIG. 7 is a detailed view showing still another embodiment of a portion B in FIG. 2, and FIG. 8 is a conventional burner device. It is a partially enlarged view of a flame holding ring. 1 ... wind box, 2 ... wind box wall, 3 ... furnace wall, 4 ... secondary slide damper, 5 ... secondary air intake, 6 ... secondary vane, 7 ... secondary air inlet , 8 …… 3rd air register, 9
...... Secondary sleeve, 9A ...... Secondary guide sleeve, 10
…… Tertiary air port, 12 …… Heavy oil nozzle, 13 …… Primary air + pulverized coal, 14 …… Venturi, 15 …… Primary air port, 16 …… Flame holding ring, 16A, 21, 24 …… Turbulent edge, 17 ... primary sleeve, 18 ... taper part, 1
9 ... Wake vortex A, 20 ... Wake vortex B, 22 ... Slit opening, 23 ... Round opening, 25 ... Slit vortex.

Claims (3)

[Claims] 1. A burner device for feeding fuel together with primary air to a primary sleeve, and supplying combustion air from a secondary sleeve concentrically provided outside the primary sleeve, to a pulverized coal flow at a primary air port. A burner device with an edge, characterized in that a turbulent flow edge for giving a turbulent flow is provided, and a taper portion for expanding the flow is provided on a side portion of the turbulent flow edge. 2. A burner device with an edge according to claim 1, wherein one or more slits are provided in the turbulent flow edge. 3. A burner device with an edge according to claim 1, wherein one or more small holes are provided in the turbulent flow edge.