JP3137711B2 - Combustion air supply device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion apparatus, and more particularly, to a combustion apparatus comprising a duct, a wind box and a burner. The combustion air flowing from the duct is guided to the wind box and then supplied to the burner. It relates to a supply device.

[0002]

2. Description of the Related Art Recent burners require low-pollution combustion burning with low NOx and low dust, high-efficiency combustion burning with low unburned components, and wide-range operation combustion burning stably from low load to high load. . For this reason, especially for a commercial boiler having a large-capacity burner, the optimal design of the combustor is made as much as possible.

One of them is a wind box. The wind box is used to temporarily reduce the combustion air guided to the burner by the duct, and to make the amount of air flowing into the burner uniform in the circumferential direction.

FIGS. 6 and 7 show a typical structure of a wind box.
FIG . In FIG. 6 , combustion air is sucked from the atmosphere by a forced air blower, heated to about 300 ° C. by a heat exchanger, and then sent to a wind box 6 via a duct 5. Here, the kinetic energy of the combustion air in the duct 5 is 11 mmAq in terms of pressure since the wind speed in the duct is 15 m / s.
It is. Normally, the burner differential pressure (wind box static pressure-furnace static pressure) is 8
Since it is about 0 mmAq, a large imbalance occurs in the inflow speed into the burner 1 as it is.

On the other hand, the wind speed of the combustion air is set to 8 m /
s, the kinetic energy becomes 3.2 mmAq
Thus, the imbalance of the inflow speed into the burner 1 is greatly improved. In the figure, 2 is a furnace, 3 is a furnace wall,
4 is a flame and 7 is a fuel pipe.

FIGS. 7 and 8 show examples in which a plurality of burners 1 are built in one wind box 6. In this case, the principle is the same.

[0007]

As described above, the wind box is designed to uniformly supply the combustion air to the burner. However, as is clear from the principle, the wind box occupies a large space. If you do not have it, you will not use it. In other words, when the burners are mounted in multiple stages and multiple rows as in a commercial boiler and the interval between the burners is limited, the only option is to make the wind box thicker. However, thickening the wind box increases the weight and occupied area of the boiler, so the steel frame supporting the boiler increases,
Construction costs increase significantly.

In order to solve this problem, for example, as shown in FIG. 9 , a rectifying plate 16 is provided between a wind box and a burner so as to make uniform supply to the burner without increasing the size of the wind box. However, since the pressure loss is small in the rectifying plate 16, it is not possible to cope with the case where the opening degree of the swirling blade 8 of the burner changes from the set condition.

According to the present invention, without increasing the size of the boiler,
An object of the present invention is to provide a combustion air supply device capable of uniformly supplying combustion air to a burner.

[0010]

In order to achieve the above object , a cylindrical resistor is provided inside a wind box to surround the burner.
So that the center axis of the resistor is aligned with the center axis of the burner.
Eccentric to the downstream side in the combustion air flow direction as viewed from the duct side
It should be done.

[0011]

The combustion air flowing into the wind box from the duct is uniformly dispersed in the wind box by the cylindrical resistor. Moreover,
Since the resistor is eccentric downstream from the duct side,
In the wind box, the flow rates on the upstream side and the downstream side are almost the same. As a result, the combustion air is uniformly supplied to the burner.

[0012]

1 and 2 show an embodiment of the present invention. The burner 1 is for pulverized coal combustion and has a fuel consumption of 5 t / h. The throat diameter of the burner 1 is 1,000 mm, and a cylindrical resistor 10 surrounds the burner 1. The diameter of the resistor 10 is 1,600 mm, and the center of the burner 1 is 100 mm.
It is attached only by shifting. Resistor 10 is 6m thick
m, a perforated plate having an aperture ratio of 30%. The combustion air flows through the duct 5 at a wind speed of 15 m / s, but is equally distributed by the perforated plate and reaches the throat through the swirling vanes 8. The angle of the swirling vanes 8 is adjusted by the handle 9 so that optimal combustion is performed.

FIG. 3 shows the results of measuring the static pressure at nine points in the circumferential direction from the starting point by providing a hole for measuring the static pressure on the inlet side of the swirling blade 8 to confirm the operation of the present invention. The horizontal axis is the angle from the starting point 11. A indicates the case where the resistor is not inserted, and B indicates the case where the resistor is inserted. In the case of b, once the static pressure has reached a minimum,
He is recovering gradually. This phenomenon can be explained by Bernoulli's equation which states that the sum of the kinetic energy of the fluid and the static pressure is constant. That is, the velocity becomes 0 at the starting point where the air from the duct collides directly in front, and the kinetic energy is directly converted to static pressure. After that, the combustion air is divided into left and right. At that time, the flow velocity becomes maximum and the static pressure becomes minimum. Further, as the combustion air goes downstream, a part of the combustion air enters the burner 1 through the swirling vanes 8, so that the flow rate decreases, and the flow velocity gradually decreases. As a result, the static pressure gradually increases.

[0014] In contrast, the static pressure does not change because there is no decrease in the flow rate in the case of the resistor 10 is provided b.

The amount of air flowing into the burner 1 is distributed in proportion to the measured static pressure distribution because the static pressure on the furnace 2 side is constant. Therefore, according to the present invention, it can be seen that the combustion air flowing into the burner 1 becomes almost uniform even in a small wind box.

The relationship between the amount of eccentricity and the inflow speed between the respective swirling blades 8 at that time is shown in FIG. It is shown in FIG. The horizontal axis in FIG. 4 shows the eccentricity obtained by dividing the amount of eccentricity by the diameter of the perforated plate, and the vertical axis shows the fluctuation rate calculated from each inflow velocity. From this, it can be seen that there is an optimum value when the perforated plate is shifted to the side opposite to the duct 5. The eccentricity is -20% because the variation rate when no perforated plate is installed is 40%.
(Eccentric to the duct side) from + 40% is effective.

FIG. 5 shows a structure in which a shielding plate 15 is provided at a portion serving as a starting point to prevent an increase in the flow rate at this portion. As a result, the flow rate imbalance is 10
%.

[0018]

[0019]

[0020]

As described above, according to the present invention,
Place a cylindrical resistor between the burner and the wind box, and
Since the resistor is disposed eccentrically so that the center of the resistor is different from the center axis of the burner, combustion air can be uniformly supplied to the burner without increasing the size of the wind box, that is, without increasing the size of the boiler.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a wind box according to an embodiment of the present invention.

FIG. 2 is a front view of a wind box according to the embodiment of the present invention.

FIG. 3 is a graph showing static pressure distribution characteristics in a circumferential direction of a burner.

FIG. 4 is a characteristic diagram showing a relationship between an eccentric amount and a speed variation rate.

FIG. 5 is a front view of a wind box to which a shielding plate is added.

FIG. 6 is a side sectional view of a conventional wind box.

FIG. 7 is a front view of a conventional wind box having a plurality of burners.
is there.

FIG. 8 is a plan view of a conventional wind box having a plurality of burners.
is there.

FIG. 9 is a front view of a conventional wind box to which a current plate is attached.
You.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Burner 2 Furnace 3 Furnace wall 4 Flame 5 Duct 6 Wind box 7 Fuel pipe 8 Swirl blade 9 Swirl adjustment handle 10 Resistor 11 Starting point

Claims (2)

(57) [Claims] 1. A combustion device comprising a duct, a wind box, and a burner .
In a combustion air supply device for supplying air to a burner,
A cylindrical resistor inside the wind box surrounds the burner.
So that the center axis of the resistor is aligned with the center axis of the burner.
It is eccentric to the downstream side in the flow direction of the combustion air as viewed from the duct side.
And combustion air supply device, characterized in that it is. 2. The combustion air supply device according to claim 1 ,
Wherein the resistor comprises a perforated plate .