JPH0344968Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a burner device for burning pulverized coal, and particularly to a device that can perform a wide range of load control even when using high fuel ratio coal.

<Prior art and its problems> For example, in boilers for thermal power plants, conversion from petroleum fuel to coal fuel is actively being carried out due to changes in fuel conditions. In this case, the power generation load of the power station varies considerably due to fluctuations in the power demand of the power station, such as seasonal differences between summer and winter, and differences between weekdays and holidays. Recently, as the amount of power generated by nuclear power generation has increased, it has become necessary to use nuclear power generation as a base load and to vary the load of large boilers for thermal power plants, which have conventionally been operated at a constant load as a base load.

Figure 2 shows a conventional pulverized coal combustion system. Fuel is supplied from the coal bunker 41 to the pulverizer 45 via the coal feeder 43. Inside the pulverizer 45,
The fuel is pulverized and dried, classified, and transferred by hot air from the primary air fan 51. The pulverized coal is supplied to the furnace from the pulverized coal pipe 46 through the pulverized coal burner 48, and is mixed and burned with combustion air sent from the air passage 47 and the air box 50. In the figure, reference numerals 32 and 33 indicate primary and secondary air preheating, and 40 indicates a blower.

In the above device, as shown in Figure 3, the fuel coal is supplied to the pulverizer in proportion to its load factor, while the primary air amount is determined by the amount of pulverized coal accumulated in the pulverized coal pipe. In order to prevent flashback from the burner, the coal pulverizer is controlled to maintain 70% of the maximum load air supply even when the load factor of the coal pulverizer is below 50%.

On the other hand, the pulverized coal supplied into the furnace from the burner has a high ambient temperature in a high load zone and a low ambient temperature in a low load zone due to the influence of radiant heat from within the furnace. In addition, the ignition temperature and
The time required to reach the ignition temperature (ignition time) varies. FIG. 4 specifically shows these points.

In the high load range, the ambient temperature is high and the powder coal concentration is high, so the ignition time is about 0.05 at an ignition temperature of about 500°C with the same volatile content, for example 30%.
However, in the low load range, the ignition time is about 0.15 seconds, which is about three times as long. Here, the ambient temperature in the high load area is approximately 1200°C and the powder coal concentration is 0.55, and the ambient temperature in the low load area is approximately 1000°C and the powder coal concentration is 0.3. As a result of the longer ignition time in the low load range, it becomes difficult to hold the flame, resulting in so-called blow-off combustion, resulting in a longer flame and unstable combustion, making it difficult to further reduce the minimum load. For this reason, it sometimes becomes difficult to realize the load required for the boiler. Although it has been found that increasing the concentration of pulverized coal is more effective in _reducing NO
0.7 is the limit.

<Object of the present invention> The present invention is configured to solve the above-mentioned problems, and an object of the present invention is to provide a burner device that can increase the turndown ratio.

<Summary of the present invention> In short, the present invention improves flame stability by attaching a cyclone separator to the base of the pulverized coal burner, injecting pulverized coal, and increasing the pulverized coal concentration on the outer periphery and lowering it on the injection axis side. This device is designed to improve combustibility and expand the load control range of the burner.

<Example> An example of the present invention will be described below with reference to FIG.

Reference numeral 5 in the figure is an outer cylinder constituting the burner body, and an inner cylinder 20 is disposed within this outer cylinder so as to be approximately equal to the central axis. 19 is a cyclone separator connected to the base of this outer cylinder, that is, to the upstream side of the pulverized coal flow. Reference numeral 21 denotes a control sleeve disposed within the cyclone separator and inserted through the end of the inner cylinder 20, and is movable in the axial direction of the inner cylinder 20 via a rod 23 by a drive device 22 such as hydraulic pressure or pneumatic pressure. It is structured like this. 24 is a bellows for maintaining airtightness of the connection between the control sleeve and the inner cylinder. The pulverized coal supply pipe 25 (FIG. B) is connected to the cyclone separator 19 in a tangential direction.

In the apparatus configured as above, the pulverized coal C in the pulverized coal pipe 25 flows in from the tangential direction of the cyclone separator 19, thereby forming a swirling flow within the separator. As a result, the air-transported pulverized coal moves toward the inner circumferential wall of the separator, and a considerable amount of pulverized coal flows into the passage 10a between the inner cylinder 20 and the outer cylinder 5. On the other hand, the amount of pulverized coal flowing into the control sleeve 21 is relatively reduced, and the concentration of pulverized coal in the passage 10b is reduced. In other words, a jet stream with a low concentration of pulverized coal is injected into the furnace from the center of the burner, and a jet stream with a high concentration is injected from the surrounding area. In other words, even if the pulverized coal concentration decreases in terms of the overall amount to the burner, the pulverized coal concentration is jetted in a layered manner due to classification, so the ignitability of the high concentration area is high, and the low concentration area is the same as the low concentration area. Since the burner is surrounded by flame, the atmospheric temperature becomes high and the ignitability improves even at low concentrations, resulting in a significant improvement in the ignitability of the burner as a whole.

In addition, the amount of pulverized coal is distributed to the passages 10a and 10b by connecting the control sleeve 21 to the inner cylinder 20.
This is done by moving it in the axial direction. By the way, by moving the control sleeve 21 to the furnace side, the classification rate decreases, and by moving it to the opposite side, the space between the opening of the control sleeve 21 and the rear wall of the cyclone separator, that is, the pulverized coal inflow space to the control sleeve, decreases. It decreases and the classification rate improves relatively.

In the figure, 1 is a furnace, 2 is a wind box, 3 is tertiary air, 4 is secondary air, 11 is an ignition torch, 12 is a burner throat, 16 is a secondary air swirling vane, 1
7 is a tertiary register, and 18 is a secondary register.

<Effects> By implementing the present invention, even when the amount of pulverized coal supplied to the burner is small, a portion with a high concentration of pulverized coal is formed in a part of the pulverized coal injection part, so ignitability is good; By increasing the atmospheric temperature in areas with low pulverized coal concentration, the ignitability and combustibility of the burner as a whole improves, and a high turndown ratio can be obtained, which expands the load control range of combustion equipment such as boilers. I can do it.

[Brief explanation of the drawing]

Fig. 1A is a vertical sectional view of a burner showing an embodiment of the present invention, Fig. 1B is a sectional view taken along line A-A of A, Fig. 2 is a system diagram showing a pulverized coal supply system, and Fig. 3 is a pulverized coal supply system diagram. Fig. 4 is a diagram showing the relationship between the ignition temperature, the ignition time, and the volatile content in the coal. 1...Furnace, 5...Outer cylinder, 10a, 10b...
Pulverized coal passage, 19...Cyclone separator, 2
0...Inner cylinder, 21...Control sleeve.

Claims (1)

[Claims for Utility Model Registration] 1. In a device that injects and burns pulverized coal transported by air current, a cyclone separator is attached to the base of the injection cylinder that constitutes the burner body, and the pulverized coal concentration near the inner peripheral surface of the injection cylinder is A pulverized coal combustion burner configured to inject pulverized coal at a concentration higher than that on the central axis side of the injection cylinder. 2. In the pulverized coal combustion burner described in claim 1 of the utility model registration claim, the injection cylinder is composed of an outer cylinder and an inner cylinder disposed within the outer cylinder, and one end of the inner cylinder is disposed within the cyclone separator. The control sleeve is placed in an open position, and a control sleeve is inserted through the end of the inner cylinder so that it can move in the axial direction of the inner cylinder.