JP5549213B2 - Furnace wall structure of fluidized bed boiler - Google Patents

Description

  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 that prevents the water-cooled wall water pipe from being worn by the descending of flowing particles.

  A circulating fluidized bed boiler is known as one of the boilers that efficiently burns solid fuel such as coal. As shown in FIGS. 6 to 8, such a circulating fluidized bed boiler moves the bed material 2 made of ash, limestone, or the like with an arrow 2 a (FIG. 7) by the air blown from the air dispersing device 1 installed at the lower part inside. ), A furnace 4 composed of a rectangular water-cooled wall 15 that is made to combust fuel supplied from the fuel supply port 3 while being fluidized, and combustion discharged from a duct 5 connected to the rear upper end of the furnace 4 A cyclone 7 that separates particles such as the bed material 2 and unburned solids contained in the combustion gas 6 by introducing the gas 6, and a combustion gas 6 from which the particles are separated by the cyclone 7 are introduced by a duct 8 and heated. A rear heat transfer section 10 having a plurality of heat exchangers composed of heat transfer tubes 9 for recovering energy, a loop seal 11 for storing particles that are separated by the cyclone 7 and descending, and the particles of the loop seal 11 are again used for And a circulation path 12 for returning to the upper air distribution device 1 of the furnace 4.

  In addition, air is supplied to the lower part of the air dispersion device 1 of the furnace 4 through an air supply line 13 so that the air is dispersed and ejected from the air dispersion device 1 into the furnace 4. The air is supplied to the lower portion of the air supply line 14, and the particles descending from the cyclone 7 are fluidized by the air and returned to the air dispersion device 1 of the furnace 4 through the circulation path 12. 9 ′ is a heat transfer tube provided in the upper part of the furnace 4, and 16 is a gas-liquid separation tank.

  In the above circulating fluidized bed boiler, when air is supplied to the lower part of the air dispersion device 1 of the furnace 4 through the air supply line 13, the air is dispersed by the air dispersion device 1 and supplied into the furnace 4 to flow through the bed material 2. Make it. In this state, when fuel is supplied from the fuel supply port 3 into the furnace 4, the fuel is combusted while being fluidized by the fluidizing air from the air supply line 13 together with the bed material 2, thereby generating combustion gas 6.

  The combustion gas 6 is heated and heated in the water pipe of the water cooling wall 15 constituting the furnace 4 and then guided to the cyclone 7 by the duct 5. In the cyclone 7, the bed material 2 and unburned solid fuel are mixed. Particles are separated. The combustion gas 6 from which the particles have been separated is introduced from the duct 8 to the rear heat transfer section 10, and heats or superheats the fluid flowing through the heat transfer pipe 9 while descending the rear heat transfer section 10, and lowers the rear heat transfer section 10. Is discharged as exhaust gas. On the other hand, steam generated by the water pipe of the water cooling wall 15 of the furnace 4 or the heat transfer pipe 9 of the rear heat transfer section 10 is sent to a steam turbine (not shown). The particles separated by the cyclone 7 are stored in the loop seal 11, and the particles of the loop seal 11 are fluidized by the air from the air supply line 14 and again on the air dispersion device 1 of the furnace 4 through the circulation path 12. Returned to

  As shown in FIGS. 9 and 10, the rectangular water-cooling wall 15 composed of the front and rear and left and right furnace walls constituting the furnace 4 is arranged at predetermined intervals in the front-rear direction and the width direction of the boiler. Are formed in a panel shape by a large number of water pipes 17 extending almost vertically and fins 18 connecting adjacent water pipes 17 to each other.

Then, when particles such as fluidized bed material 2 and unburned solids fall inside the lower part of the water cooling wall 15, they collide with the water pipe 17 to wear and reduce the thickness of the peripheral surface of the water pipe 17. A hard castable refractory 19 having excellent wear resistance is lined to prevent this. In order to form such a hard castable refractory 19, first, a formwork is installed inside the water-cooled wall 15 with a space between them, and alumina (Al ₂ O ₃ ), silicon ( The powder aggregate obtained by finely grinding SiO ₂ ) is fluidized by adding water, and this fluidized product is poured between the water-cooled wall 15 having the stud fixed to the inner surface and the above-mentioned formwork, using a vibration method or the like. After being compacted, it is formed by drying and further heating and baking.

  The bed material 2 flowing in the furnace 4 is blown up so as to ascend the center of the furnace 4 as indicated by an arrow 2a in FIG. 7, and then the water-cooling in which the upward flow of the flow air is weaker than that of the center. Since the liquid falls toward the outside near the wall 15, the flow rate of the particles falling along the water cooling wall 15 tends to increase. Further, the amount (concentration) of particles falling along the water cooling wall 15 increases toward the bottom. Further, since the four corners of the water cooling wall 15 having a rectangular shape are portions where the upward flow of the flowing air is further weakened, the amount of particles falling at the four corners of the water cooling wall 15 is the largest. .

  Thus, since the water cooling wall 15 at the lower position L from the air dispersion device 1 of the furnace 4 to the predetermined height position is subjected to very severe wear action due to particles, the lower position L has wear resistance. An excellent hard castable refractory 19 is provided to prevent the water pipe 17 in the water cooling wall 15 from being worn. In the case of the furnace 4 in which the combustion chamber length from the air dispersion device 1 to the top of the furnace shown in FIG. 6 is about 30 meters, for example, the length of the lower position L where the castable refractory 19 is installed is the length of the combustion chamber. About 20%, that is, about 6 to 7 meters.

  As described above, there is a problem that the water pipe 17 is worn and thinned by the particles due to the fluidized particles falling along the water cooling wall 15, but as described above, the most amount of particles falling inside the water cooling wall 15. Since the castable refractory 19 is lined and protected at the inner lower part where there are many, there is no problem that the water pipe 17 is worn and thinned in this part.

  However, as shown in FIGS. 10 and 11, the particles that have fallen along the fins 18 between the water pipes 17 collide with the upper end of the castable refractory 19 and then flow down to the inside of the castable refractory 19. When such a flow tendency occurs, the particles concentrate and form a flow along the path, and therefore, at the boundary portion where the water pipe 17 is exposed from the upper end portion of the castable refractory 19. There is a problem that the water pipe 17 is worn to form the worn portion 20, and the water pipe 17 is thinned. And in the water cooling wall 15 which has a rectangular shape, since the fall amount of the particle | grains in four corners is the largest, the thickness reduction by abrasion of the water pipe 17 in four corners is the most intense.

  When the water pipe 17 is thinned in this way, repair work such as cutting out the thinned part and replacing it with a new water-cooled wall is necessary. However, conventionally, the thinning of the water pipe 17 due to the particles is severe. For this reason, repair in a short period is necessary, and the repair cost increases, and there is a problem that the period for stopping the operation of the circulating fluidized bed boiler for repair increases.

  In order to prevent such a problem of wear of the water pipe 17, conventionally, a wear resistant metal is sprayed between the boundary line between the castable refractory 19 and the water pipe 17 and between the boundary line and a predetermined height position. To be done. However, even if the wear resistant metal is sprayed, the wear rate of the water pipe 17 in the vicinity of the boundary line can be reduced, but the wear resistant metal deteriorates with the operation of the boiler and the local wear of the water pipe 17 is reduced. In order to proceed, regular inspections and repairs were necessary.

  In addition, as a prior art document for preventing wear of the water pipe as described above, a free fall space is formed by providing a bending member projecting outward from the extended line of the fin at the upper end portion of the castable refractory. There is what has been made (see Patent Document 1).

JP 09-126404 A

  In Patent Document 1, particles that fall along the fins fall away from the fins due to the free fall space, but the particles fall to the upper end of the castable refractory while maintaining the falling speed. Therefore, particles that fall on the upper end of the castable refractory still flow along the boundary between the castable refractory and the water pipe as in the conventional case, and for this reason, the water pipe is removed from the upper end of the castable refractory. It has not yet been possible to effectively prevent the problem that the water pipe is worn at the exposed boundary.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a furnace wall structure of a fluidized bed boiler that can effectively prevent wear of water-cooled wall water pipes and prolong the life of the boiler. It is.

In the present invention, the furnace wall of the furnace for burning the fuel while fluidizing the fuel together with the bed material by air is formed by a water cooling wall formed by a plurality of water pipes extending vertically and fins connecting adjacent water pipes. And in the furnace wall structure of a fluidized bed boiler in which a castable refractory is lined at the inner lower part of the water cooling wall,
Wherein the top of castable refractory, wear buffer structure made of plastic refractories castable refractories less thickness is provided integrally,
The wear buffer structure includes an upper thin portion formed of a plastic refractory along the inner surface shape of the water pipe and the fin, and a plastic refractory so as to project from the lower end of the upper thin portion toward the castable refractory. A furnace wall structure of a fluidized bed boiler, characterized in that it has an overhanging inclined portion formed by inclining, and an embedded buffer stud that is buried in the upper thin portion and the overhanging inclined portion and fixed to a water pipe , It is related to.

In the furnace wall structure of the fluidized bed boiler, the wear cushioning structure preferably has an exposed buffer stud having exposed on the upper thin portion formed by plastic refractory in water pipes.

Further, in the furnace wall structure of the fluidized bed boiler, an upper thin portion formed of a plastic refractory along the inner surface shape of the water pipe and the fin, and the lower thin portion of the upper thin portion protrudes from the lower end toward the inside of the furnace. An upper wear buffer structure having an overhanging inclined portion formed by inclining with a plastic refractory, and having an embedded buffer stud buried in the upper thin wall portion and the overhanging inclined portion and fixed to a water pipe. It is preferable that at least one stage is provided at an upper portion of the structure with an interval.

Further, in the furnace wall structure of the fluidized bed boiler, the upper wear cushioning structure preferably has an exposed buffer stud having exposed on the upper thin portion formed by plastic refractory in water pipes.

  According to the furnace wall structure of the fluidized bed boiler of the present invention, the wear buffer structure having the plastic refractory having a thickness equal to or less than the castable refractory is integrally provided on the upper part of the castable refractory. The particles falling downwardly collide with the wear buffering structure. At this time, the plastic refractory constituting the wear buffering structure is smaller in hardness than the castable refractory, so the plastic refractory gradually As the plastic refractory wears in this way, the boundary where the water pipe is exposed from the plastic refractory gradually moves downward, so that the particles concentrate on one part of the water pipe. Excellent effect that the water pipe can be effectively prevented from being worn locally by providing a small wear buffer structure. It can achieve.

  Further, when the plastic refractory is worn, the plastic refractory can be easily repaired by placing the plastic refractory on the worn portion.

  In addition, an upper wear buffering structure that has a plastic refractory and protrudes from the inner surface of the water-cooled wall is provided at least on the upper part of the wear buffering structure that is integrally provided on the castable refractory. Therefore, the particles falling along the inner surface of the water-cooled wall are buffered by the upper wear buffer structure, decelerated and dropped to the wear buffer structure on the castable refractory, and the particles are deflected to the inside of the furnace by the upper wear buffer structure. As a result, the amount of particles falling onto the wear buffering structure on the castable refractory is reduced, so that the wear of the wear buffering structure on the castable refractory that is subjected to the most severe wear can be reduced.

It is the perspective view which looked at a part of furnace wall structure of the fluidized-bed boiler which implements this invention from the inside of a furnace. It is sectional drawing which shows an example of the wear buffer structure provided on the castable refractory. It is the cutting | disconnection top view which looked at FIG. 2 from the III-III direction. It is the top view which looked at FIG. 2 from the IV-IV direction. It is sectional drawing which shows an example of the upper abrasion buffer structure provided in the upper part of the abrasion buffer structure. It is a side view which shows an example of a circulating fluidized bed boiler. It is the front view which looked at FIG. 6 from the VII-VII direction. It is the top view which looked at FIG. 6 from the VIII-VIII direction. It is a perspective view of the conventional water cooling wall. FIG. 10 is a side sectional view of FIG. 9. It is the front view which showed the state which a water pipe wears in the boundary part which a water pipe exposes from the upper end part of a castable refractory.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  1 and 2 show an embodiment as a basis of the invention. In the figure, the same reference numerals as those in FIGS. 6 to 11 denote the same components.

  In the embodiment shown in FIGS. 1 and 2, a plastic refractory 21 having a thickness equal to or less than that of the castable refractory 19 is formed on the upper portion of the hard castable refractory 19 formed on the inner side of the lower portion of the water cooling wall 15 in the same manner as in the prior art. The wear buffer structure 22 having the above is integrally provided. The plastic refractory 21 is arbitrarily shaped by adhering a clay-like product prepared by adding water to refractory aggregate, clay and viscous material to the inner surface of the water-cooled wall 15 using an air rammer, a mallet or the like. Can be formed.

  The wear buffer structure 22 includes the plastic refractory 21 and a plurality of buried buffer studs 23 fixed in a radial direction with respect to the water pipe 17 so as to be buried in the plastic refractory 21. 2 to 4, the plastic refractory 21 has an upper thin portion 24 formed so as to be thin along the inner surface shape of the water pipe 17, and a lower side from the lower end of the upper thin portion 24. And a projecting inclined portion 26 having an inclined surface 25 that gently slopes so as to project toward the inside of the furnace.

  A plurality of exposed buffer studs 27 fixed in the radial direction with respect to the water pipe 17 are provided at the upper position of the plastic refractory 21 in FIGS.

  In order to form the wear buffer structure 22, the buried buffer stud 23 and the exposed buffer stud 27 are fixed in advance to the inner surface of the water pipe 17 above the castable refractory 19. Then, the clay-like product for forming the plastic refractory 21 is crimped to the inner surface of the water pipe 17 and the fin 18 of the water-cooled wall 15 so that the buried buffer stud 23 is buried, and as described above, The upper thin portion 24 is formed along the inner surface shape of the water pipe 17, and the overhanging inclination is provided so that the inclined surface 25 is gently inclined so as to protrude downward from the lower end of the upper thin portion 24 toward the inside of the furnace. A portion 26 is formed. Thus, after drying the plastic refractory material formed with the clay-like product, the plastic refractory 21 is formed by heating and hardening.

  The above-mentioned wear buffering structure 22 may be provided on the entire inner periphery of the water-cooling wall 15 having a rectangular shape, and the water-cooling wall that has been found to be most severe in thickness reduction due to wear due to a large amount of particles falling. The wear buffering structure 22 may be provided only at the four corners.

  When the height of the furnace 4 in FIG. 6 is around 30 meters and the height of the castable refractory 19 is around 6 to 7 meters, the height dimension in the vertical direction of the wear buffering structure 22 provided on the castable refractory 19 is shown. Can be about 25-50 centimeters.

  In the furnace wall structure of the fluidized bed boiler shown in FIGS. 1 and 2, a wear buffer structure 22 having a plastic refractory 21 having a thickness equal to or less than the castable refractory 19 is integrally provided on the upper part of the castable refractory 19. Therefore, the particles flowing in the furnace 4 and falling along the inner surface of the water-cooled wall 15 first collide with the exposed buffer stud 27 and are buffered to reduce the speed. After colliding with the upper end 24a and further decelerating, it falls toward the inside of the furnace along the gently inclined slope 25 of the overhanging slope 26.

  At this time, since the plastic refractory 21 constituting the wear buffering structure 22 has a lower bending strength than the castable refractory 19, the plastic refractory 21 gradually starts from the upper end 24 a of the upper thin portion 24 where the particles collide. Will wear out.

  Based on past results, the present inventors have obtained that plastic refractories are subject to wear with respect to general castable refractory materials. This is because the strength of the castable refractory and the plastic refractory when the bending strength test is performed at a temperature of 1000 ° C. is 14.7 MPa for the castable refractory and about 8.0 MPa for the plastic refractory. It is estimated from the fact that it is about half the strength. Such a difference in strength is considered to be related to the fact that plastic refractories contain bubbles and have a lower density than castable refractories.

  Therefore, as described above, when the upper end 24a of the upper thin portion 24 is worn, the boundary portion where the water pipe 17 is exposed gradually moves downward from the upper end 24a of the upper thin portion 24. The water pipe 17 does not flow down at one place, and therefore, the provision of the small wear buffering structure 22 can effectively prevent the problem that the water pipe 17 is locally worn.

  Further, as described above, when the upper end 24a of the upper thin portion 24 is worn, the embedded buffer stud 23 is exposed, so that the exposed embedded buffer stud 23 buffers the falling particles. Thus, wear of the upper end 24a of the upper thin portion 24 is suppressed.

  As described above, for example, when the upper end 24a of the upper thin portion 24 of the plastic refractory 21 is worn, it can be easily repaired by placing the plastic refractory on the worn portion.

FIGS. 1 and 5 show another embodiment of the present invention. In this embodiment, the inner surface of the water-cooled wall 15 is provided on the upper part of the wear buffering structure 22 on the castable refractory 19 with a gap H. A two-stage upper wear buffering structure 28b is provided so as to protrude to the inside of the furnace, and a first-stage upper wear buffering structure 28a is provided at the upper part of the second stage upper wear buffering structure 28b with an interval H therebetween. The case where it provided so that it might protrude inside is shown. The number of stages in which the upper wear buffering structure is installed can be an arbitrary number of stages of one or more.

  Similar to the wear buffer structure 22 formed on the castable refractory 19, the upper wear buffer structures 28 a and 28 b described above include a plastic refractory 21, an embedded buffer stud 23 embedded in the plastic refractory 21, and The exposed buffer stud 27 is constituted.

  Further, the upper wear buffering structures 28a and 28b can be formed to have an overhanging height and a vertical height dimension similar to those of the wear buffering structure 22, and the upper wear buffering structures 28a and 28b. The size of the mutual interval H can be arbitrarily selected. Here, in the case where the height of the furnace 4 in FIG. 6 is about 30 meters and the height of the castable refractory 19 is about 6 to 7 meters, the upper wear buffer has an interval H of about 1 meter, for example. Structures 28a, 28b can be provided.

  The upper wear buffering structures 28a and 28b may be formed annularly on the entire inner peripheral surface of the water cooling wall 15, or the amount of particles falling at the four corners of the rectangular water cooling wall 15 is the largest. Therefore, the upper wear buffering structures 28 a and 28 b may be provided only at the four corners of the water cooling wall 15.

  According to the embodiment shown in FIGS. 1 and 3, the upper wear that has the plastic refractory 21 on the upper part of the wear buffering structure 22 integrally provided on the castable refractory 19 and protrudes from the inner surface of the water-cooled wall 15. Since the buffer structures 28a and 28b are provided with at least one step at a distance H, the particles falling along the inner surface of the water cooling wall 15 are buffered and decelerated by the upper wear buffer structures 28a and 28b to be castable refractories. The amount of particles falling to the wear buffer structure 22 on the castable refractory 19 is reduced by dropping to the wear buffer structure 22 on the castable refractory 19 by falling to the inside of the furnace by the upper wear buffer structures 28a and 28b. Thus, there is an effect that the wear of the wear buffering structure 22 on the castable refractory 19 that receives the most severe wear can be reduced.

  1 and 3, even when the upper end 24a of the upper thin portion 24 of the plastic refractory 21 constituting the upper wear buffer structure 28a, 28b is worn, the plastic refractory is applied to the worn portion. It can be easily repaired by arranging.

  It should be noted that the furnace wall structure of the fluidized bed boiler of the present invention is not limited to the above-described embodiments, and it is needless to say that various modifications can be made without departing from the scope of the present invention.

2 Bed Material 4 Furnace 15 Water Cooling Wall 17 Water Pipe 18 Fin 19 Castable Refractory 21 Plastic Refractory 22 Wear Buffer Structure 23 Buried Buffer Stud 24 Upper Thin Wall 25 Inclined Surface 26 Overhang Slope 27 Exposed Buffer Stud 28a, 28b Upper Wear Buffer Structure

Claims (4)

A furnace wall of a furnace that burns fuel while fluidizing the fuel together with the bed material by air is formed by a water cooling wall formed by a plurality of water pipes extending in the vertical direction and fins connecting between adjacent water pipes, and In the furnace wall structure of a fluidized bed boiler in which a castable refractory is lined at the inner bottom of the water cooling wall,
The upper part of the castable refractory is integrally provided with a wear buffering structure made of a plastic refractory having a thickness equal to or less than the castable refractory,
The wear buffer structure includes an upper thin portion formed of a plastic refractory along the inner surface shape of the water pipe and the fin, and a plastic refractory so as to project from the lower end of the upper thin portion toward the castable refractory. A furnace wall structure of a fluidized bed boiler, characterized in that it has an overhanging inclined portion formed by inclining, and an embedded buffer stud buried in the overhanging inclined portion and fixed to a water pipe.   2. The furnace wall structure of a fluidized bed boiler according to claim 1, wherein the wear buffer structure includes an exposed buffer stud that is exposed to an upper portion of an upper thin portion formed of a plastic refractory and provided in a water pipe.   An upper thin part formed of plastic refractory along the inner surface shape of the water pipe and the fin, and an overhang inclination formed by inclining with the plastic refractory so as to protrude from the lower end of the upper thin part toward the lower part toward the inside of the furnace. And an upper wear buffering structure having an embedded buffer stud that is buried in the upper thin wall part and the overhanging inclined part and fixed to the water pipe, at least one stage at an interval above the wear buffering structure. The furnace wall structure of a fluidized bed boiler according to claim 1, wherein the furnace wall structure is provided.   The furnace wall structure of a fluidized bed boiler according to claim 3, wherein the upper wear buffering structure has an exposed buffer stud that is exposed to an upper part of an upper thin part formed of a plastic refractory and is provided in a water pipe.

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