JPS62252808A - Fluidized bed combustion device - Google Patents

Abstract

PURPOSE:To prevent fluid medium from contacting a water tube wall and reduce the abrasion of the water tube wall by a method wherein small holes which eject gas are provided near the top of the fluid medium loading section of a panel which forms the water tube wall. CONSTITUTION:A panel 11 near the top of the fluidized bed 3 loading section of a water tube wall 8 is provided with small holes 14 bored orthogonally to the surface of the panel 11, and other small holes 15, whose center lines are slanted toward water tubes 10. Gas is ejected through these small holes 14, 15 whereby the collision of fluid medium 23 against the water tube wall 8 may be prevented or the speed of the fluid medium 23 which has higher speed may be weakened. Accordingly, the damages of the water tube wall 8 due to abrasion can be remarkably reduced.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a fluidized bed boiler, etc., in which the furnace wall of the fluidized bed is formed by a water pipe wall consisting of a wood pipe and a plate section provided between adjacent water pipes. Regarding combustion equipment.

[Prior art and its problems]

Fluidized bed boilers can use a variety of fuels, and can even burn low calorific value fuels (incinerated materials) such as municipal waste. Further, desulfurization within the bed can be effectively performed by introducing a desulfurizing agent such as limestone or dolomite into the fluidized bed. In addition, if heat transfer tubes are buried in a fluidized bed, the amount of heat transfer (heat transfer coefficient) in the layer of the heat transfer tubes is about 5 to 10 times greater than the amount of heat transfer from only gas in a conventional boiler. Fluidized bed boilers have been attracting a lot of attention in recent years as energy conservation has progressed.

A fluidized bed boiler burns coal, which is usually pulverized to 1 to 1 ounces, in a fluidized bed at a relatively low temperature range of 800 to 900°C. Further, as the fluid medium, it is also possible to use limestone, which has a desulfurizing effect, together with coal as a fuel. In this case, as mentioned above, coal combustion and desulfurization are easily carried out in the fluidized bed. Also, the combustion of coal is 800 to 900
Since the combustion is performed at a relatively low temperature of 0.degree. C., the amount of NOx produced is lower than that of conventional pulverized coal-fired boilers.

Hereinafter, the fluidized bed combustion apparatus will be explained using a fluidized bed boiler as an example with reference to FIG. FIG. 5 is a schematic diagram showing the main combustion furnace of the fluidized bed boiler. In addition, the fluidized bed boiler is comprised of various devices (not shown) such as a mixing hopper, a fuel storage hopper, a desulfurization agent storage hopper, and an ash collection device. In FIG. 5, the main combustion furnace 1 is partitioned by an air distribution plate 2 into a fluidized bed 3 containing coal, desulfurization agent, and combustion ash, and an air chamber 4, and a heat transfer tube 5 is buried in the fluidized bed 3. . Coal and desulfurization agent are
The fuel supply pipe 6 supplies combustion air from the bottom of the main combustion furnace 1 into the fluidized bed 3, and the air supply pipe 7 supplies combustion air to the air chamber 4,
It is supplied to the fluidized bed 3 via the air distribution plate 2. Coal, which is a fuel, gradually becomes smaller in particle size as it burns in the fluidized bed 3, and when it falls below a certain grain boundary, it is sent to the main combustion furnace 1 along with the exhaust gas.
is discharged from the furnace. On the other hand, the heat generated by the combustion of coal is mainly absorbed by the heat transfer tubes 5 installed in the fluidized bed 3 and generates steam. The desulfurization agent, coal ash, etc. scattered from the main combustion furnace 1 to the exhaust gas outlet pipe 9 are collected by an ash collection device (
(not shown) and further stored in a mixing hopper. This collected ash is then recirculated to the combustion furnace 1 via the fuel supply pipe 6 together with coal from a coal storage hopper (not shown) and desulfurization agent from a desulfurization agent storage hopper.

On the other hand, the exhaust gas purified by the ash collection device is released into the atmosphere.

Here, the furnace wall of the combustion furnace 1 is constituted by a water tube wall 8. As shown in FIG. 6, the water pipe wall is formed by wood pipes 10 and plate portions 11 between adjacent wood pipes 10.

By the way, in such a fluidized bed boiler, the inner surface of the water tube wall 8, which is the furnace wall constituting the main combustion furnace 1, is at a high temperature (80
0 to 900°C) and intensely fluidized fluid medium 2
3, there is a problem that it is easily abraded due to the abrasive action of this fluidized material. FIG. 7 schematically shows the wear region 12 of the water pipe wall 8 described above.

No significant thinning due to wear is observed directly above the air distribution plate 2, but significant thinning occurs near the top of the flowing IPJ3.

FIG. 7 shows the occurrence of wear on the water tube wall 8 in relation to the movement of the fluidized bed 3. That is, the diameter of the air bubbles 13 in the fluidized bed 3 is smaller than that of the fluidized bed 3 directly above the air distribution plate 2.
It is approximately the same diameter as the coal inside, and the fluidized bed 3 and bubbles 13
The bubbles 13 show almost the same behavior, but the bubbles 13 coalesce and grow as they move upward from the air distribution plate 2. Due to this rising and coalescing motion of the bubbles 13, the fluidized bed 3 moves rapidly around the bubbles 13, as schematically shown in the figure. In particular, the bubbles 13 burst explosively at the top of the fluidized bed 3, and although the apparent density is lower in this area than in the middle, the velocity of the fluidized medium 23 is high (therefore, the water tube wall 8 is worn out). It is assumed that the amount increases near the top of the fluidized bed.In other words, the flow velocity of the fluidized medium 23 is different in terms of parameters that affect the wear and thinning of the material.For this reason, as shown in Fig. 8. It is estimated that wear 12 of the water pipe wall 8 occurs in the area shown in FIG.

As described above, in the above-mentioned conventional technology, in the combustion boiler configured with the water tube wall 8, no consideration is given to the occurrence of abrasion of the water tube wall 8, so that due to the water tube 10 being worn,
There was a risk that heat exchange media such as water would leak and the system would become inoperable.

An object of the present invention is to provide a fluidized bed combustion apparatus that can significantly reduce wear on water tube walls.

[Means and effects for solving the problem] The present invention provides a small hole for ejecting gas near the top of the fluidized medium filling portion of the plate portion forming the water pipe wall, so that gas can be ejected from the small hole. Flowing! The gas ejected into the II layer prevents the rapidly flowing fluid medium from coming into contact with the water pipe wall.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 4. 1 and 2 are schematic sectional views of the main combustion furnace of the fluidized bed boiler, and FIGS. 3 and 4 are sectional views of the water tube walls, respectively. The present invention provides a small hole 14.1 of approximately φ3nvn in the plate portion 11 near the top of the fluidized bed 3 filling portion of the water tube wall 8.
5 (Fig. 4), this small hole consists of a small hole 14 made perpendicular to the surface of the plate part 11, and a small hole 15 whose center line is inclined in the direction of the water pipe 10 in the horizontal direction. I was able to wear two types. These small holes 14.15 are arranged with a vertical interval of 75+m so that adjacent left and right and upper and lower positions are alternately located, respectively.
The stage was provided all around the water pipe jM8. Also, this position is the lowest one of the small holes 14 and 15.

It is located approximately 500-degrees below the top of the fluidized bed 3 when it is at rest. Further, on the outside of the plate portion 11, this small hole 14.
A wind box 16 having a size that covers the water pipe wall 8 is installed over the entire circumference of the water pipe wall 8.

This wind box 16 is connected to a gas supply pipe 17. The air supply pipe 17 includes an air supply pipe 18 connected to the air supply pipe 7 and an air amount adjustment valve 1 provided therein.
9, and an exhaust gas supply pipe 20 connected to the outlet side of an ash collector (not shown), a fan 21 provided thereon, and an exhaust gas flow rate adjustment valve 22.

Note that the small hole 14. ．． The vertical position where 15 can be drilled varies depending on operating conditions, furnace capacity, etc.
From the top of the fluidized bed 3 when the fluidized bed 3 is at rest at the minimum,
The height to the top of the fluidized bed 3 during operation is required. Further, the vertical distance between the small holes 14 and 15 varies depending on the operating conditions, but a practical range is about 25 to 150 nn.

Next, the action will be explained. Small holes 14.15 are provided in the plate portion 11, which is a part of the water pipe wall 8 that is subject to significant wear due to the fluidized medium 23, and gas is jetted out from these small holes 14.15 during operation, so that the water pipe of the fluidized medium 23 Collision with the wall 8 can be prevented. Alternatively, the speed of the fast fluid medium 23 can be reduced. Therefore, wear and tear on the water pipe wall 8, which is a problem of wear, can be significantly reduced.

- In addition, when air is ejected from the small holes 14 and 15, the excess air ratio changes and the combustion state may change significantly, but in this case, the air flow control valve 19 and the exhaust gas flow control valve 22 to an appropriate mixing ratio. Since part of the exhaust gas after dust removal is used as blowout gas, it is possible to prevent the temperature inside the furnace from decreasing.

〔Effect of the invention〕

According to the present invention, by providing a small hole for ejecting gas near the top of the fluidized medium filling portion of the plate portion forming the water pipe wall, the gas ejected from the small hole into the fluidized bed can cause Since it is possible to prevent the rapidly flowing fluid medium from coming into contact with the water tube wall, wear on the water tube wall can be significantly reduced and the life of the device can be extended. Furthermore, combustion efficiency and desulfurization efficiency can be improved by sucking air above the fluidized bed.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing an embodiment of a combustion furnace of a fluidized bed boiler according to the present invention, Fig. 2 is a sectional view taken along the line ■-■ in Fig. 1, and Fig. 3 shows a water tube wall according to the present invention. Main part side view, Figure 4 is the 3rd
5 is a schematic diagram showing a conventional fluidized bed boiler, FIG. 6 is a sectional view taken along the line VI-VI in FIG. 5,
Fig. 7 is a diagram for explaining the wear generation mechanism, Fig. 8 is a schematic diagram showing the wear generation part, and Fig. 9 corresponds to Fig. 8, and shows the distance between the wear area of the water pipe wall and the air distribution plate. FIG. 8...Water pipe wall, 10...Water pipe, 11...Plate part, 1
4.15... Small hole, 23... Fluid medium.

Claims (1)

[Claims] In a fluidized bed combustion apparatus in which the furnace wall of the fluidized bed is formed by a water tube wall consisting of a water tube and a plate section provided between adjacent water tubes, gas is ejected near the top of the fluidized medium filling section of the plate section. A fluidized bed combustion device characterized by having small holes.