JPH0972502A - Furnace wall structure for fluidized-bed boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the wear and thickness decrease of a water tube at a water cooled wall. SOLUTION: The water cooled wall 21 of a furnace is constituted by many tubes 22 arranged at a predetermined interval in the longitudinal and lateral directions of a boiler and extended substantially perpendicularly toward the upward or downward direction and fins 23 for connecting the adjacent tubes 22. The each tube 22 has a large-diameter part 22a at the upper part, a small- diameter part 22c at the lower part, and a tapered swaged part 22c reducing in the diameter toward the downward direction between the part 22a and the part 22b. The upper end of a refractory material 24 lined on the inside of the wall 21 is disposed near the lower end of the part 22b, and a gradient gradually reducing in thickness toward the upper end is provided at the upper end of the material 24.

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, and more particularly to a furnace wall structure of a fluidized bed boiler capable of preventing wear of a water pipe of a water cooling wall due to descent of particles.

[0002]

2. Description of the Related Art A circulating fluidized bed boiler is known as one of the boilers for efficiently burning solid fuel such as coal.

Such a circulating fluidized bed boiler, as shown in FIG. 4, combusts fuel while fluidizing a bed material 2 made of ash, limestone or the like at the upper part of an air dispersion plate 1 installed in the lower part of the inside thereof, and burning gas. In order to disperse particles such as the bed material 2 and unburned solid content from the rectangular box-shaped furnace 4 for generating 3 and the combustion gas 3 generated and sent in the furnace 4,
A cyclone 6 connected to the rear of the upper end of the furnace 4 via a duct 5, a heat transfer section 8 capable of recovering heat energy from the combustion gas 3 fed from the cyclone 6 via a duct 7, and a cyclone. A circulation path 10 for returning the particles, which have been separated by 6 and descended through the J valve 9 connected to the lower part of the cyclone 6, onto the air dispersion plate 1 of the furnace 4.

Below the furnace 4, a fuel supply line 11 for supplying solid fuel such as coal onto the air dispersion plate 1 in the furnace 4.
Is connected to the bottom surface of the furnace 4, an air supply line 12 is connected to supply the air dispersed by the air dispersion plate 1 upward to fluidize the bed material 2 in the furnace 4, and the J valve 9
An air supply line 13 for feeding particles when returning the particles descending from the cyclone 6 to above the air dispersion plate 1 of the furnace 4 is connected to the lower part of the.

Reference numeral 14 in the drawing denotes exhaust gas discharged from the heat transfer section 8.

In the circulating fluidized bed boiler described above, the air supplied from the air supply line 12 to the lower part of the furnace 4 is dispersed by the air dispersion plate 1 and introduced into the air dispersion plate 1, and the furnace 4
The bed material 2 inside is fluidized.

The solid fuel supplied from the fuel supply line 11 into the furnace 4 flows with the bed material 2 and at the same time, the air that fluidizes the bed material 2 and the solid fuel is burned as combustion air to produce combustion gas. 3 is generated.

Thus, the combustion gas 3 heats the fluid flowing through the water cooling wall of the furnace 4 while rising, and is introduced into the cyclone 6 from the duct 5, where the bed material 2 and unburned solid fuel are mixed in the cyclone 6. The particles are separated and then introduced into the heat transfer section 8 from the duct 7 to heat or superheat the fluid while descending the heat transfer section 8 and discharged as exhaust gas 14 from the lower part of the heat transfer section 8 and sent to the downstream device. To be

On the other hand, the steam generated in the water cooling wall of the furnace 4 and the heat transfer section 8 is sent to a steam turbine to drive the steam turbine, and the steam turbine drives a generator to generate electric power.

The water cooling wall forming the peripheral wall of the furnace 4 is
As shown in FIG. 5, the water cooling wall 15 is provided with a large number of water pipes 16 arranged at predetermined intervals in the boiler front-rear direction and the width direction and extending substantially vertically in the up-down direction, and fins 17 connecting adjacent water pipes 16 to each other. With this configuration, each surface of the water cooling wall 15 is formed on the panel.

Further, when the fluidized bed material 2 and particles such as unburned solids fall below the predetermined height position of the water cooling wall 15 inside the furnace 4 of the furnace 4, they collide with the water pipe 16 and the water pipe 16 A wear-resistant refractory material 18 is lined in order to prevent the outer circumference from being worn and thinning.

Further, the refractory material 18 has a constant thickness from the lower side to the vicinity of the upper end position so as to completely cover the water pipes 16 and the fins 17 from the inside of the furnace as shown in FIGS. 6 and 7, but near the upper end, the water cooling wall 15 is provided. Particles falling along the line are refractory materials 18
In order not to hit the water pipe 16 of the water-cooling wall 15 at the upper end, the inclination angle θ with respect to the horizon is set to about 75 degrees and is gradually thinned upward.

During operation of the circulating fluidized bed boiler, the bed material 2 and particles containing unburned solids are fluidized in the furnace 4 shown in FIG.
Fall along 5.

However, since the refractory material 18 is lined inside the water-cooled wall 15 at the portion where the fluidization of the particles inside the furnace is intense,
At this portion, the water pipe 16 is not worn and the wall thickness is not reduced.

However, since the upper end of the refractory material 18 is inclined so that the thickness thereof gradually becomes thinner as described above, the refractory material 18 is provided on the outer peripheral portion of the water pipe 16 as shown in FIG. A semicircular arc-shaped recess 19 is formed at the upper end of the so as to face downward.

Therefore, the water pipe 1 is located above the refractory material 18.
The particles that have fallen along the fins 17 between 6 fall along the boundary line between the refractory material 18 and the water pipe 16 as shown by the arrow in FIG. The water pipe 16 is worn at this portion, and the water pipe 16 is thinned.

In order to prevent this friction, the boundary line between the refractory material 18 and the water pipe 16 and the boundary line between the water pipe 16 and the fin 17 connected to the boundary line up to a predetermined height position in the recess 19 of the refractory material 18 are shown. As shown in FIG. 7, the wear-resistant metal 20 such as chrome carbide is sprayed to a thickness of about 250 μm.

The water pipe 16 at the upper end of the refractory material 18
In order to prevent the wear of the water cooling wall 15 as shown in FIG.
It is also practiced to bend the vicinity of the upper end of the refractory material 18 to the outside of the furnace and position the lining portion of the refractory material 18 of the water cooling wall 15 to the outside of the furnace rather than the portion of the water cooling wall 15 not lining the refractory material 18.

[0019]

However, the wear-resistant metal 20 sprayed as shown in FIG. 7 deteriorates and wears along with the operation of the boiler, so that the wear of the water pipe 16 near the boundary with respect to the refractory material 18 is prevented. It is not possible.

Further, as shown in FIG. 8, when the lower part of the water cooling wall 15 is bent toward the outside of the furnace, the structure of the water cooling wall 15 becomes complicated and the cost increases.

In view of the above-mentioned circumstances, the present invention is intended to prevent wear of the water pipe and prolong the life of the boiler without increasing the cost.

[0022]

According to the present invention, a plurality of water pipes extending in the vertical direction are arranged at predetermined intervals in the horizontal direction on the peripheral wall of a furnace in which fuel is combusted while being fluidized by air together with a bed material. In the furnace wall structure of the fluidized bed boiler, in which adjacent water pipes are formed by water cooling walls in which fins are connected by fins, and a refractory material is lined over the required range below the water cooling walls, the water pipes are arranged from the middle part in the height direction. From the large diameter portion connected to the lower end of the large-diameter portion, the tapered sedge portion connected to the lower end of the large-diameter portion so that the diameter becomes smaller toward the lower side. It is formed by a small-diameter portion having a small diameter, the upper end position of the refractory material is near the lower end of the sedge portion, and the upper end portion of the refractory material is inclined so that the thickness becomes smaller as it goes upward.

Further, in the present invention, the width of the fin connecting the large diameter portions of the adjacent water pipes can be made smaller than the width of the conventional fin connecting the adjacent water pipes, and the inclination of the upper end portion of the refractory material can be further reduced. The angle can be about 75 degrees with respect to the horizon.

Therefore, in the present invention, the particles falling along the water cooling wall smoothly fall downward and become hard to flow to the recess side formed in the water pipe portion of the inclined portion at the upper end of the refractory material, so that the water pipe is worn out. It is possible to prevent thinning.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 to 3 show an example of an embodiment of the present invention. The water cooling wall 21 forming the peripheral wall of the furnace 4 shown in FIG.
As in the conventional case, with a configuration including a large number of water pipes 22 arranged at predetermined intervals in the boiler front-rear direction and the width direction and extending substantially vertically in the up-down direction, and fins 23 connecting adjacent water pipes 22 to each other, Each surface of the water cooling wall 21 is formed in a panel shape.

The water pipe 22 is connected to the large-diameter portion 22a extending upward from the middle portion in the height direction and the lower end of the large-diameter portion 22a, and is tapered so that the diameter gradually decreases downward. It is composed of an inverted truncated cone short tubular sedge portion 22b and a small diameter portion 22c connected to the lower end of the sedge portion 22b and extending downward and having a diameter smaller than that of the large diameter portion 22a. A wear-resistant refractory material 24 is lined inside the furnace 4 so that the upper end edge is near the lower end of the sedge portion 22b of the water pipe 22.

As in the conventional case, the refractory material 24 has a constant thickness from the lower end to the vicinity of the upper end as shown in the figure so as to completely cover the water pipes 22 and the fins 23 from the inside of the furnace. For the same reason as in the above case, the inclination angle with respect to the horizontal line is about 75 degrees, and it is configured to be gradually thinned upward. Further, at the upper end of the refractory material 24, a semicircular arc-shaped depression 25 is formed on the outer peripheral portion of the water pipe 22 toward the lower side, and the interval between the sedge portions 22b of the adjacent water pipes 22 gradually decreases as it goes downward. Has spread to.

The diameter D1 of the large diameter portion 22a of the water pipe 22 is equal to the diameter D2 of the conventional water pipe 16 shown in FIGS. 6, 7 and 8 (D1 = D2), but the arrangement interval L1 of the water pipe 22 is shown in FIG. It is smaller than the arrangement interval L2 of the conventional water pipe 16 (L1 <L2). Therefore, in the portion of the water cooling wall 21 where the refractory material 24 is not lined, the large diameter portion 22a of the water pipe 22 is
The space (width of the fins 23) W1 between them is narrower than the space (width of the fins 17) W2 between the conventional water pipes 16 shown in FIG.

Next, the operation of the embodiment of the present invention will be described.

During operation of the circulating fluidized bed boiler, the bed material 2 and particles containing unburned solids are fluidized in the furnace 4 shown in FIG. 4, and the particles in the vicinity of the water cooling wall 21 are fluidized.
Fall along 1. At this time, since the refractory material 24 is lined inside the water-cooling wall 21 inside the furnace where the fluidization of the particles is strong, the water pipe 22 is not worn or thinned at this portion.

On the other hand, above the refractory material 24, the particles fall by gravity due to gravity along the fins 23 between the water pipes 22 substantially right below.

However, since the space between the water pipes 22 is small and the width W1 of the fins 23 is small, the flow rate of particles flowing therethrough per unit time is reduced, and the adjacent edge portions 22b are also formed.
In between, the interval gradually expands downward. Therefore, the amount of particles flowing from the fin 23 side into the depression 25 side of the refractory material 24 and flowing along the boundary line between the water pipe 22 and the refractory material 24 is reduced, and as a result, wear and thickness reduction of the water pipe 22 are less likely to occur. Boiler has a long life.

Further, the diameter of the water pipe 22 changes in the middle, but since it has a straight shape, the cost does not increase.

It should be noted that the present invention is not limited to the above-described embodiments, and it goes without saying that various changes can be made without departing from the gist of the present invention.

[0036]

According to the furnace wall structure of the fluidized bed boiler of the present invention, wear and thinning of the water pipe of the water cooling wall are reduced, so that the life of the boiler is extended and the cost is not increased. Various excellent effects can be obtained.

[Brief description of drawings]

FIG. 1 is an enlarged front view of an example of an embodiment of a furnace wall structure of a fluidized bed boiler of the present invention.

FIG. 2 is a view taken along the line II-II in FIG.

FIG. 3 is a perspective view of a water cooling wall used in the furnace wall structure of the fluidized bed boiler of the present invention.

FIG. 4 is a side sectional view of a general example of a circulating fluidized bed boiler.

FIG. 5 is a perspective view of a water cooling wall used in a circulating fluidized bed boiler.

FIG. 6 is an enlarged front view of an example of a conventional water cooling wall used in a circulating fluidized bed boiler.

7 is a view in the direction of arrows VII-VII in FIG. 6;

FIG. 8 is an enlarged side view of another example of the conventional water cooling wall used in the circulating fluidized bed boiler.

[Explanation of symbols]

 2 Bed material 4 Furnace 21 Water cooling wall 22 Water pipe 22a Large diameter part 22b Sedge part 22c Small diameter part 23 Fin 24 Refractory material θ Inclination angle (angle) W1, W2 Interval (width)

Claims (3)

[Claims] 1. A plurality of water pipes extending in the up-down direction are horizontally arranged at predetermined intervals on a peripheral wall of a furnace in which fuel is combusted while being fluidized with air by a bed material, and adjacent water pipes are fins. In the furnace wall structure of the fluidized bed boiler formed by water cooling walls connected by, the refractory material is lined in the lower required range of the water cooling wall, the water pipe,
A large-diameter portion arranged above the midway portion in the height direction, a tapered sedge portion connected to the lower end of the large-diameter portion so that the diameter becomes smaller as it goes downward, and connected to the lower end of the sedge portion. It is formed by a small diameter portion having a diameter smaller than the large diameter portion, the upper end position of the refractory material is near the lower end of the sedge portion, and the upper end portion of the refractory material is inclined so that the thickness becomes thinner as it goes upward. A furnace wall structure of a fluidized bed boiler characterized by the above. 2. The furnace wall structure for a fluidized bed boiler according to claim 1, wherein the width of the fin connecting the large diameter portions of the adjacent water pipes is smaller than the width of the conventional fin connecting the adjacent water pipes. 3. The furnace wall structure for a fluidized bed boiler according to claim 1, wherein the angle of inclination of the upper end of the refractory material is about 75 degrees with respect to the horizontal line.