JPS6365209A - Burner - Google Patents

Abstract

PURPOSE:To prevent clinker attached on a flame holding ring by providing the flame holding ring with an air flow passage which causes part of a secondary air branch to flow along the inner face of the flame holding ring. CONSTITUTION:After a pulverized coal flow 3 is throttled once by a venturi 4, it is supplied from a primary exhaust opening 5. At the tip of this primary exhaust opening a flame holding ring 13 is provided. On the flame holding ring 13 pulverized coal of a size less than 30mum which is carried by the air flow is supplied and the combustion is started. The holding ring 13 is provided with many air slits 20 arranged circumferentially. Because in front of and at the rear of the flame holding ring 13, there is developed a pressure difference due to the air movement of a secondary air, part of the secondary air flow in filmy form along the inner circumference of the flame holding ring 13 as shown by the arrow mark. Consequently a part of the secondary air in filmy form exists between the pulverized coal flame formed above the flame holding ring 13 and the flame holding ring 13 so that it is possible to prevent the adhesion of fused ash (clinker) contained in the pulverized coal flame on the flame holding ring 13.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a combustion device, and particularly to a flame-holding ring provided in a pulverized coal burner for the purpose of flame-holding.

[Conventional technology]

The flame-holding ring used in the primary nozzle of a pulverized coal burner is designed to trap primary air and pulverized coal onto the flame-holding ring for stable ignition and early ignition of the pulverized coal. As is well known, the properties of coal vary widely, including the flammability and the softening temperature of ash, and it is extremely difficult to burn all types of coal in the same burner. Even in the prior art, classification is centered on flammability, and the actual situation is that the applicable range varies when put into practical use.

In particular, regarding the softening point of ash, taking into account slagging and clinker adhesion to the furnace and heat transfer surfaces, the furnace outlet temperature is usually operated at a temperature approximately 100°C lower than the softening point of ash.

[Problem that the invention seeks to solve]

In conventional flame-holding rings, especially when burning dragonfly with a low softening temperature, clinker adhesion may occur and change the flame-holding properties.

An object of the present invention is to prevent clinker from adhering to the flame-holding ring even for coal whose ash has a low softening point.

[Means for solving problems]

In order to prevent clinker from adhering to the flame-holding ring mentioned above, a part of the secondary air is flowed in a film form onto the inner peripheral surface of the flame-holding ring to eliminate the presence of ash between the flame and the flame-holding ring. This can be achieved by

[For production]

In other words, the differential pressure generated before and after the flame-holding ring is used to create a film-like airflow along the inner circumferential surface of the flame-holding ring, which prevents ash from adhering to the flame-holding ring and clinker from adhering to it. .

[Embodiments of the invention]

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a sectional view of a pulverized coal burner to which the present invention is applied. Combustion air is pressurized by a pressurized machine and then heated by an air preheater.
After being heated to a temperature of 00°C, it is passed through a duct and supplied to the wind box 9. On the other hand, the coal is sent to the mill through the bunker coal feeder, pulverized, conveyed by primary air, and supplied to the burner as a pulverized coal stream 3. A starting oil gun 1 is inserted into the shaft of the burner, and oil is sprayed from an oil spout 2. The oil burner is used to burn up to about % of the normal load, after which the mill is started and the process shifts to pulverized coal combustion.

The pulverized coal flow 3 is once squeezed by a venturi 4 and then supplied from a primary port 5 . A flame holding ring 13 is provided at the tip of the primary port 5 to stabilize the ignition of the burner.

Ultrafine powder of micrometers or less is mainly supplied onto the flame stabilizing ring 13 on the primary air flow, and combustion is started. on the other hand,
Combustion air is supplied into the wind box 9, which is composed of the wind box wall 8 and the boiler wall lO, and a part of it enters from the secondary air intake lower adjusted by the secondary slide damper 6, and is supplied to the secondary vane. 11
After turning into a swirling flow, it is supplied into the furnace through the secondary port 12. The remaining combustion air is taken in as a swirling flow through the tertiary air register 15 and supplied into the furnace through the tertiary air register 16.

FIG. 2 shows the view A-M of FIG. 1, and the flame holding ring 13 and the tertiary guide cone 14 can be seen.

The pulverized coal starts burning on the flame holding ring 13, and the flame temperature there is about 1200 to 1400°C. In other words, if the ash has a low melting point with a softening point of about 1,200 to 1,300°C, a portion of the ash becomes molten and adheres to the inner surface of the flame-holding ring as a heclinker. Generally speaking, the softening point of the ash of overseas charcoal is 1500 to 160.
0 degrees Celsius, such problems such as clinker adhesion do not occur, but in the case of domestic ash, the ash softening point is 1150 to 1
The temperature is as low as 300'C, and adhesion of clinker onto the flame-holding ring 13 becomes a problem.

3 and 4 are diagrams showing one of the clinker adhesion prevention means according to the present invention, in which a large number of air slinters 20 as shown in the figures are provided in the flame stabilizing ring 13 in the circumferential direction. As a matter of course, a pressure difference in degrees Celsius occurs before and after the flame-holding ring 130 due to the flow of secondary air. Flows like a film.

Therefore, a portion of the film-like secondary air CI) exists between the pulverized coal flame formed on the flame stabilizing ring 13 and the flame stabilizing ring 13. In other words, it is possible to prevent the bath-melted ash contained in the pulverized coal flame from adhering to the flame-holding ring 13.

Another embodiment of the invention is shown in FIG. In this example, a case is shown in which a plurality of air holes 21 are used instead of the air suction 20. In this way, it is possible to completely prevent ash adhesion by covering the tip of the flame-holding ring 13, where ash adhesion is likely to occur, with a portion of the secondary air by utilizing the differential pressure generated before and after the flame-holding ring 130. It is.

〔Effect of the invention〕

The first effect of the present invention is flame stabilization.

That is, by preventing ash from adhering to the flame stabilizing ring, the flame can be stabilized.

The second effect of the present invention is to keep the combustion state stable over time during boiler operation. This is extremely effective not only in reducing unburned matter but also in reducing NOx. In other words, it improves the reliability of the burner.

The third effect of the present invention is that the flame-holding ring 13 is sufficiently cooled by the air blown out in a film, so that the life of the flame-holding ring 13 can be extended.

[Brief explanation of drawings]

FIG. 1 is a cutaway diagram of a pulverized coal burner according to an embodiment of the present invention;
2 is a parent diagram of A in FIG. 1, FIG. 3 is an enlarged view of part B in FIG. 1, FIG. 4 is a parent diagram of C in FIG. 3, and FIG. It is an enlarged view of the main part. 3...pulverized coal flow, 5...linear term mouth, 7
...Secondary air intake, 9...Wind box, 1
2...Second order port, 13...Flame holding ring, 16...Tertiary port, addition...Air slit, 21... Air hole.

Claims (1)

[Claims] A pulverized coal burner that transports pulverized coal using primary air and supplies it to the burner, and also supplies secondary air and tertiary air to burn the pulverized coal, and a flame holding ring is provided at the primary air nozzle. A combustion device characterized in that the flame stabilizing ring is provided with an air circulation part so that a part of the secondary air is branched and flows along the inner surface of the flame stabilizing ring.