JP2011127818A - Furnace wall structure of fluidized bed boiler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To elongate the service life of a boiler by effectively preventing wear of water pipes. <P>SOLUTION: In this furnace wall structure of the fluidized bed boiler, a furnace wall of a furnace burning fuel while fluidizing the fuel together with a bed material by air is formed of a water wall 15 constituted of the plurality of water pipes 17 extended vertically and fins 18 interconnecting the adjacent water pipes 17, and a castable refractory 19 is lined in a furnace interior side lower part of the water wall 15. At least one stage of bed material diffusion refractories 22A, 22B formed to project to the furnace interior side of the water wall 15 is provided at the upper part of the castable refractory 19, at clearances H. <P>COPYRIGHT: (C)2011,JPO&INPIT

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. 2 to 4, such a circulating fluidized bed boiler moves the bed material 2 made of ash, limestone, or the like by an arrow 2 a (FIG. As shown in 3), the gas is discharged from a furnace 4 composed of a rectangular water cooling wall 15 which is made to burn while supplying fuel supplied from the fuel supply port 3 and a duct 5 connected to the rear upper end of the furnace 4. A combustion gas 6 is introduced to separate particles such as bed material 2 and unburned solids contained in the combustion gas 6, and a combustion gas 6 from which particles are separated by the cyclone 7 is introduced by a duct 8. A rear heat transfer section 10 having a plurality of heat exchangers composed of heat transfer tubes 9 for recovering heat energy, a loop seal 11 for storing particles that are separated by the cyclone 7 and descending, and particles of the loop seal 11 are again collected. in front And a circulation path 12 for returning to the upper air distribution device 1 of the furnace 4.

  Note that air is directly supplied to 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. Air is supplied to the lower part by an air supply line 14, and 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 in the furnace 4, and 16 is a pressure vessel.

  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. 5 and 6, the rectangular water cooling walls 15 made up of the front and rear and left and right furnace walls constituting the furnace 4 are arranged at predetermined intervals in the front and 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 on the inner side of the lower furnace of the water cooling wall 15, they collide with the water pipe 17 to wear the peripheral surface of the water pipe 17 and reduce the thickness. 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 mold is installed at an interval inside the furnace of the water-cooled wall 15, and alumina (Al ₂ O ₃ ), silicon is maintained so as to maintain fluidity. (SiO ₂ ) and the like finely pulverized powder aggregate is fluidized by adding water, the fluidized product is poured between the mold and the water-cooled wall 15 to be compacted by a vibration method or the like, and then dried, Further, it is formed by heating and hardening.

  The bed material 2 flowing in the furnace 4 is blown up so as to rise in the center of the furnace 4 as indicated by an arrow 2a in FIG. 3, and then water cooling with a weak upward flow of flowing air as compared with 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 having a combustion chamber length from the air dispersion device 1 to the top of the furnace of, for example, 30 meters, the length of the lower position L where the castable refractory 19 is installed is about 20% of the length of the combustion chamber. That is, it is around 6 to 7 meters.

  As described above, there is a problem that the fluidized particles fall along the water cooling wall 15 and the water pipe 17 is worn and thinned by the particles. As described above, the most particles inside the furnace of the water cooling wall 15 Since the castable refractory 19 is lined and protected in the lower part inside the furnace where the amount of dropping is large, there is no problem that the water pipe 17 is worn and thinned in this part.

  However, as shown in FIGS. 6 and 7, the particles falling along the fins 18 between the water pipes 17 collide with the upper end of the castable refractory 19 and then flow down into the furnace of the castable refractory 19. When such a flow tendency occurs, the particles concentrate and form a flow along the path. Therefore, the boundary portion where the water pipe 17 is exposed from the upper end portion of the castable refractory 19. In this case, there is a problem that the water pipe 17 is worn to form the worn portion 20 and the water pipe 17 is thinned.

  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 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, In addition, in the furnace wall structure of a fluidized bed boiler in which a castable refractory is lined on the inner lower part of the water-cooled wall, the bed material diffusion formed so as to protrude to the inner side of the water-cooled wall on the castable refractory The present invention relates to a furnace wall structure of a fluidized bed boiler, characterized in that at least one refractory is provided at an interval.

  According to the furnace wall structure of the fluidized bed boiler of the present invention, since at least one bed material diffusion refractory material is provided at an upper portion of the castable refractory material, particles falling along the water-cooled wall are removed from the furnace furnace. Therefore, the wear of the water pipe at the boundary portion where the water pipe is exposed from the upper end portion of the castable refractory that is particularly heavily worn can be remarkably reduced.

It is sectional drawing which shows an example of the furnace wall structure of the fluidized bed boiler which implements this invention. It is a side view which shows an example of a circulating fluidized bed boiler. It is the front 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 a perspective view of the conventional water cooling wall. FIG. 6 is a side sectional view of FIG. 5. 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.

  FIG. 1 shows an embodiment of the present invention. In the figure, the same reference numerals as those in FIGS. 2 to 7 denote the same components.

  In the embodiment of FIG. 1, a second-stage bed material diffusion refractory 22 </ b> B is provided on the upper part of the castable refractory 19 provided on the inner side of the lower furnace of the water-cooled wall 15, with a gap H therebetween, A case is shown in which a first-stage bed material diffusion refractory 22A is provided on the upper portion of the second-stage bed material diffusion refractory 22B with an interval H therebetween so as to protrude inside the furnace.

  The bed material diffusion refractories 22 </ b> A and 22 </ b> B can be formed by a hard castable having excellent wear resistance like the lowermost castable refractory 19, and fall between the water pipes 17 along the fins 18. After the particles collide with the upper ends of the bed material diffusion refractories 22A and 22B and the bed material is diffused, the particles are dropped toward the inside of the furnace as indicated by arrows.

  The number of installation stages of the bed material diffusion refractories 22A and 22B, the protruding height of the bed material diffusion refractories 22A and 22B inside the furnace, and the distance H between the bed material diffusion refractories 22A and 22B shown in FIG. It can be selected arbitrarily.

  The bed material diffusion refractories 22A and 22B may be annularly formed 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. Since the water pipe 17 of the part is most worn, the bed material diffusion refractories 22A and 22B may be provided only at the four corners of the water cooling wall 15.

  Next, the operation of the embodiment shown in FIG. 1 will be described with reference to FIG.

  The particles 2a indicated by the arrows that flow so as to rise in the center of the furnace 4 flow toward the outside where the upward flow of the flowing air is weak and fall along the water cooling wall 15, but at this time Then, the particles are diffused by dropping to the upper end of the first-stage bed material diffusion refractory 22A, and thereafter fall toward the inside of the furnace 4 as indicated by arrows.

  Particles diffused by the action of the first-stage bed material diffusion refractory 22A are directed to the second-stage bed material diffusion refractory 22B, but the particles are placed on the upper end of the second-stage bed material diffusion refractory 22B. It is further diffused by the collision, and then falls toward the inside of the furnace 4 as indicated by an arrow. As described above, the particles falling along the water cooling wall 15 are diffused by the bed material diffusion refractories 22A and 22B, and further, the particles are deflected by the bed material diffusion refractories 22A and 22B toward the inside of the furnace 4. Therefore, the particles falling on the castable refractory 19 are decelerated and the amount of particles is reduced.

  Here, it is conceivable that the water pipe 17 is worn by particles falling at the boundary portion where the water pipe 17 is exposed from the upper ends of the bed material diffusion refractories 22A and 22B. The amount (concentration) of particles toward the upper water-cooled wall 15 provided with 22B is significantly smaller than the amount (concentration) of particles at the lower position L where the castable refractory 19 is provided. The problem that the water pipe 17 is worn by particles at the boundary between the objects 22A and 22B can be kept low.

  As described above, since the particles falling on the castable refractory 19 are diffused and the amount of particles falling on the castable refractory 19 is reduced, the water pipe 17 is formed from the upper end of the castable refractory 19 which has been generated conventionally. The problem that the water pipe 17 is worn at the exposed boundary portion can be remarkably reduced, so that the lifetime of the boiler can be extended.

  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 22A, 22B Bed material diffusion refractory H Interval

Claims (1)

  A furnace wall of a furnace for burning 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. In a furnace bed structure of a fluidized bed boiler in which a castable refractory is lined on the inner lower part of the wall furnace, a bed material diffusion refractory formed so as to protrude to the inner side of the water-cooled wall furnace on the upper part of the castable refractory, A furnace wall structure for a fluidized bed boiler, comprising at least one stage at an interval.

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