JPH08178212A - Structure of furnace wall of fluidized-bed boiler - Google Patents

Abstract

PURPOSE: To suppress wear of a water-cooled wall which is due to falling particulates by providing a flow-straightening means for particulates close to the upper end of a refractory material with which the water-cooled wall is lined in part. CONSTITUTION: Coal burns at high temperatures while combustion air fluidizes it together with a bed material comprising such as ash or limestone, throughout a furnace. Particulates of the bed material etc., flying about from the furnace, are returned to the furnace and circulate. Water-cooled wall 2, forming the side wall of the furnace and lined in part with a refractory material 21, keeps the temperature inside the furnace at prescribed points so as to reduce NOX, etc. Each of flow-straightening plates 23 is formed in a rectangle and is fixed by welding or the like to the water- cooled wall 2, specifically at a boundary between the wall part 2b and a water tube 2a, in a manner of being held at right angles to the water-cooled wall 2 and with the lower end in contact with the upper end of the refractory material 21. The flow- straightening plate 23 suppresses the fall of particulates by flowing down on the periphery of the water tube 2a. Particulates which impinge upon the upper end of the refractory material 21 move away from the periphery of the water tube 2a and guided down into the furnace. Falling particulates that hit the water tube 2a decrease and wear of the water-cooled wall 2 is suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a furnace wall structure of a fluidized bed boiler.

[0002]

2. Description of the Related Art A circulating fluidized bed boiler is one of the boilers that efficiently burns solid fuel. As shown in FIG. 4, the circulating fluidized bed boiler fluidizes a fuel such as coal in a furnace 4 formed of a water cooling wall by a combustion air from an air dispersion plate 3 together with a bed material such as ash or limestone. It is used to generate steam, etc. that is burned to be supplied to a steam turbine for power generation, etc., solid materials such as bed material and unburned matter scattered from the furnace 4 are captured by the cyclone 5, and this is dispersed in the furnace 4. It is to be put back on the plate 3. In this fluidized bed boiler 1, a refractory material 21 is lined in a part of the side wall (water cooling wall) 2, for example, in a part where the flow (combustion) is intense (downward of the furnace), and the temperature in the furnace 4 is kept at a predetermined temperature (about 850 ~ 900 ° C, for example 900
By maintaining the temperature at (° C), NOx and SOx are reduced. This is because the sulfur content is reacted with the limestone charged into the furnace 4 for desulfurization treatment, and therefore the inside of the furnace 4 needs to be maintained at the optimum temperature for causing the desulfurization reaction.
The optimum temperature range in which the desulfurization reaction and NOx can be reduced is, for example, about 850 to 900 ° C.

[0003]

In the circulating fluidized bed boiler described above, when the fuel and the bed material are fluidized, the particles descend near the water cooling wall along the wall. When the particles descend in this manner, the refractory material 21 is lined on the water cooling wall 2 as shown in FIG. The part flows along the peripheral surface of the water pipe 2a of the water cooling wall 2 at the upper end of the refractory material 21. At this time, particles collide with the peripheral surface of the water pipe 2a of the water cooling wall 2 at an angle, and thus wear occurs. Therefore, the wear-resistant material is sprayed in the vicinity of the upper end of the refractory material 21 of the water cooling wall 2 (the portion where the particles collide), but even if the spraying is performed in this way, the particles flow along the peripheral surface of the water pipe 2a,
The thermal spray material or the water pipe 2a may be worn. That is, even if the wear resistant material is sprayed, there are cases where repair of the sprayed material and addition of the refractory material 21 are required during the periodic inspection. If this is repeated frequently, the casting area of the refractory material 21 also changes greatly, and the performance also changes.

Therefore, the present invention has been made in view of such circumstances, and an object thereof is to provide a furnace wall structure of a fluidized bed boiler which suppresses wear of a water cooling wall.

[0005]

According to the furnace wall structure of a fluidized bed boiler of the present invention, the side wall of a furnace for combusting fuel while fluidizing it with combustion air together with the bed material is formed by a water cooling wall, and one of the water cooling walls is formed. In a furnace wall structure of a fluidized bed boiler in which a refractory material is lined in the part, in the vicinity of the upper end portion of the refractory material of the water cooling wall, a particle rectifying means for suppressing descending particles from flowing along the peripheral surface of the water pipe is provided. is there. The particle rectifying means is preferably a rectifying plate provided at a right angle to the water cooling wall, or a rectifying plate provided on the water pipe of the water cooling wall at a predetermined interval in the circumferential direction.

[0006]

By providing particle rectifying means, for example, a rectifying plate, on the water cooling wall, when particles such as bed material descend, even if they collide with the upper end of the refractory material, they do not descend along the peripheral surface of the water pipe of the water cooling wall. Therefore, the wear of the water cooling wall due to the descending particles is suppressed.

[0007]

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

FIG. 4 is a block diagram showing an example of a circulating fluidized bed boiler. In FIG. 4, reference numeral 1 denotes a circulating fluidized bed boiler. As shown in FIG. 5, the circulating fluidized bed boiler 1 is formed with a water cooling wall 2 formed of STB or the like into a rectangular cross section, and a furnace 4 in which an air dispersion plate 3 is provided below the inside of the furnace 4, and a furnace 4 of the furnace 4. Cyclone 5 connected to the rear of the upper end,
The heat transfer part 6 recovers part of the heat of the exhaust gas from the cyclone 5, and the circulation path (J-valve) 7 that returns the particles separated by the cyclone 5 onto the dispersion plate 3 of the furnace 4. ing.

At the bottom of the furnace 4, a forced draft fan (FDF) is installed.
8, air line 1 with air preheater 9 and control valve 10
1 is connected. The air line 11 has a control valve 12 and an auxiliary air line 13 connected to the J-valve 7.
Are connected so that circulating particles are not boring in the J-valve 7. In addition, the air line 11 has a control valve 1
Secondary air line 1 which has 4 and is connected to the central part of the furnace 4.
5 is connected, and combustion air is supplied to the furnace 4 from the two systems of the air line 11 and the secondary air line 15 to suppress NOx. Below the furnace 4, a fuel line 16 for supplying fuel such as coal onto the air dispersion plate 3 is connected, and coal from this fuel line 16 is converted into bed material (from ash or limestone by combustion air from the air line 11). Bed material) and is combusted at a high temperature while being fluidized in the entire furnace 4, and part of this combustion heat is recovered by the water cooling wall 2,
Particles such as bed material scattered from the furnace 4 are returned to the furnace 4 through the cyclone 5 and the J-valve 7 and circulate. The exhaust gas from the cyclone 5 is cooled through the heat transfer section 6 and then flows into the exhaust gas line 17, further cooled by the air preheater 9 and dedusted by the dust collector (for example, bag filter) 18, and then attracted draft The chimney 20 is opened to the atmosphere via the machine (IDF) 19.

FIG. 1 shows a part of the water cooling wall 2 which is a side wall of the furnace 4 (for example, a part where the flow (combustion) is intense (below the furnace 4)).
The refractory material 21 is lined as shown in FIG. That is, a part of the inside of the water cooling wall 2 is covered with the refractory material 21, and the refractory material 21 travels to form a step. Thus, by covering a part of the water cooling wall 2 with the refractory material 21, the temperature inside the furnace 4 is maintained at a predetermined temperature (about 850 to 900 ° C, for example 900 ° C) to reduce NOx and SOx. ing.

In the vicinity of the upper end of the refractory material 21 of the water cooling wall 2, it is possible to prevent the descending particles from flowing along the peripheral surface of the water pipe 2a.
That is, there is provided a flow straightening plate 23 which is a particle straightening means 22 for guiding the particles so as to descend without going along the peripheral surface of the water pipe 2a. The straightening vane 23 is formed in a rectangular shape, is perpendicular to the water cooling wall 2, and is welded at the time of the wall portion 2b of the water cooling wall 2 and the water pipe 2a so that the lower end surface contacts the upper end surface of the refractory material 21. It is fixed by etc. Although only two straightening vanes 23 are fixed to the water cooling wall 2 for easy understanding in FIG. 1, the straightening vanes 23 are fixed to the water pipes 2a of the wall portions 2b of all the water cooling walls 2. The size and shape of the current plate 23 may be arbitrarily determined as long as it can prevent the descending particles from flowing along the peripheral surface of the water pipe 2a. For example, the shape of the current plate 23 is triangular, polygonal, or semicircular. You may.

As described above, by providing the straightening plate 23 near the upper end of the refractory material 21 of the water cooling wall 2, particles such as bed material descend in the vicinity of the water cooling wall 2 and collide with the upper end surface of the refractory material 21. Even with the straightening vane 23, the water pipe 2a of the water cooling wall 2
Is suppressed along the peripheral surface of. That is, since the particles that have collided with the upper end surface of the refractory material 21 are guided so as to fall into the furnace 4 without following the peripheral surface of the water pipe 2a, the descending particles collide with the water pipe 2a of the water cooling wall 2 at an angle. And the wear of the water cooling wall 2 is suppressed.

2 and 3 are views showing another embodiment of the straightening vanes. In this embodiment, a plurality of straightening vanes 25 are provided on the water pipe 2a of the water cooling wall 2 as shown in FIGS. Is. The current plate 25 is formed in a rectangular shape, and is fixed to the circumferential surface of the water pipe 2a of the water cooling wall 2 along the radially outer side by welding or the like so that the lower end surface contacts the upper end surface of the refractory material 21. . In the illustrated example, three rectifying plates 25 are fixed to the water pipe 2a at predetermined intervals in the circumferential direction.

As described above, by providing three straightening vanes 25 near the upper end of the refractory material 21 of the water pipe 2a of the water cooling wall 2,
Even if particles such as a bed material descend in the vicinity of the water cooling wall 2 and collide with the upper end surface of the refractory material 21, the flow straightening plate 25 prevents the water cooling wall 2 from following the circumferential surface of the water pipe 2a. That is, the particles that have collided with the upper end surface of the refractory material 21 are guided so as to descend into the furnace 4 without following the peripheral surface of the water pipe 2 a, so that the descending particles may collide with the water pipe 2 a of the water cooling wall 2. The amount of water cooling is reduced and wear of the water cooling wall 2 is suppressed.

Therefore, by providing the current plate 23, 25 on the water cooling wall 2, it is possible to suppress the wear of the water cooling wall 2 due to the descending particles, reduce the frequency of maintenance, and lead to cost reduction. Further, since the flow straightening plates 23, 25 are simply fixed to the water cooling wall 2 by welding or the like, the structure and the manufacturing are simple, and the place where the refractory material 21 is applied can be arbitrarily selected, and the refractory material can be applied to the existing boiler such as modification. Is possible.

[0016]

In summary, according to the present invention, the excellent effect that the wear of the water cooling wall due to the descending of particles can be suppressed is exhibited.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention.

FIG. 2 is a perspective view showing another embodiment of the present invention.

3 is a view taken along the line AA in FIG.

FIG. 4 is a configuration diagram showing an example of a circulating fluidized bed boiler.

FIG. 5 is a schematic perspective view showing an example of a water cooling wall.

FIG. 6 is a perspective view showing a conventional example.

[Explanation of symbols]

 2 water cooling wall 2a water tube 4 furnace 21 refractory material 22 particle rectifying means

Claims (3)

[Claims] 1. A furnace wall structure of a fluidized bed boiler in which a side wall of a furnace for combusting a fuel with combustion air while fluidizing it with a bed material is formed by a water cooling wall, and a refractory material is lined in a part of the water cooling wall, A furnace wall structure for a fluidized bed boiler, comprising particle rectifying means for suppressing descending particles from flowing along the peripheral surface of a water pipe near the upper end of the refractory material of the water cooling wall. 2. The furnace wall structure for a fluidized bed boiler according to claim 1, wherein the particle rectifying means is a rectifying plate provided at a right angle to the water cooling wall. 3. The furnace wall structure for a fluidized bed boiler according to claim 1, wherein the particle rectifying means is a rectifying plate provided on the water pipe of the water cooling wall at a predetermined interval in a circumferential direction thereof.