JP2006317083A - Method of computing optimum shape of cylindrical fluidized bed type incinerator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily predict distortion generated to a weld part of a cylindrical body and a support plate and to obtain the optimum shape of the cylindrical body and support plate having sufficient strength in a cylindrical fluidized bed type incinerator constituted by welding an air distributor to the inner surface of an incinerator body shell interposing the cylindrical body and the support plate. <P>SOLUTION: The cylindrical fluidized bed type incinerator 20 is constituted by welding the air distributor 6 to the inner surface of the incinerator body shell 9 interposing the cylindrical body 11 and the support plate 12. In this case, optimum values of the thickness tc of the support plate 12, the ratio h/D of a diameter D to height h of the cylindrical body 11, and the thickness tb of the cylindrical body 11 at the working temperature T of the cylindrical fluidized type incinerator 20 are computed based on generated distortion E expressed in an approximate expression using numerical analysis such as two-dimensional numerical analysis from the relationship among the thickness tc of the support plate 12, the ratio h/D of the diameter D to height h of the cylindrical body 11, the thickness tb of the cylindrical body 11 and the working temperature T of the cylindrical fluidized bed type incinerator 20. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  In the present invention, the generated strain generated in the welded portion of the cylindrical body and the support plate in the cylindrical fluidized bed incinerator in which the air dispersion plate is welded to the inner surface of the furnace body iron shell through the cylindrical body and the support plate is provided. The present invention relates to an optimum shape calculation method for a cylindrical fluidized bed incinerator that predicts the optimum shape of a cylindrical body and a support plate.

  Conventionally, fluidized bed incinerators have been used to incinerate combustible organic waste such as municipal waste and sludge. A general fluidized bed incinerator 20 includes a vertical cylindrical furnace body 1 as shown in FIG. FIG. 7 is a schematic cross-sectional view of an air dispersion plate mounting structure in a conventional general cylindrical fluidized bed incinerator. An exhaust gas outlet 3 is provided at the top of the furnace body 1. In addition, an air dispersion plate 6 for forming a fluidized bed 5 and a wind box 7 therebelow are provided in the lower part 4 of the furnace. The air box 7 is provided with an air suction port 8 that is used for both combustion and fluidization. Further, a combustion chamber is formed above the wind box 7, and the furnace body 1 in this portion is formed by an outer furnace body iron skin 9 and an inner refractory (not shown). In the cylindrical fluidized bed incinerator 20, the incinerated waste is removed from the incinerator inlet while circulating the fluidized bed 5 such as sand heated to high temperature by combustion heat during incineration. Put in and incinerate.

  By the way, in the cylindrical fluidized bed incinerator 20, the air dispersion plate 6 is firmly welded to the inner surface of the furnace body iron skin 9 in order to take a structure in which a heavy object is placed to support the fluidized bed 5 such as sand. Is provided. Therefore, when the cylindrical fluidized bed incinerator 20 is started and stopped, the temperature rise / fall speed difference between the furnace body iron skin 9 and the air dispersion plate 6 becomes large, and as a result, the furnace body iron skin 9 and the air dispersion are dispersed. A large thermal stress is generated in the vicinity of the welded portion of the plate 6. As a result, in the cylindrical fluidized bed incinerator 20 shown in FIG. 5, when the high temperature gas is introduced into the wind box below the air dispersion plate 6, the air dispersion plate 6 and the surroundings of the wind box 7 below the air dispersion plate 6 are illustrated. As shown by the two-dot chain line in FIG. As a result of repeated starting and stopping over a long period of time, there is a concern that a crack or the like may occur in the vicinity of the weld where a large thermal stress occurs.

  Therefore, in order to solve this problem, in Patent Document 1, as shown in FIG. 1, an air dispersion plate 6 is welded to the lower part of the cylindrical body 11, and the upper part of the cylindrical body 11 is incinerated with a cylindrical fluidized bed type. A technique for reducing the generated stress by welding to the inner surface of the furnace body iron skin 9 of the furnace 20 is disclosed. In Patent Document 1, as a result of analysis by the finite element method, when the diameter D of the cylindrical body 11 is 1150 mm and the height h of the cylindrical body 11 is variously changed, the ratio h / D is 0.05 to 0. It is shown that the reaction force and bending stress can be sufficiently reduced when the range is defined within the range of 1. (see paragraph [0015] of Patent Document 1).

Japanese Patent Laid-Open No. 2002-5419

  However, the relationship between the ratio of the diameter and height of the cylindrical body 11 shown in Patent Document 1 and the strain or stress generated in the air dispersion plate 6 is also applied to other parts other than the diameter of the cylindrical body and the height of the cylindrical body. This is a result of the shape included, and when the use conditions (cylinder diameter, use temperature, etc.) are different, a structure having sufficient strength is not necessarily determined.

  In addition, in order to consider the shape including other parts, when modeling the shape using a numerical analysis such as a finite element method to predict the distortion, a large amount of calculation time is required.

  It is an object of the present invention to occur in a welded portion between a cylindrical body and a support plate in a cylindrical fluidized bed incinerator in which an air dispersion plate is welded to the inner surface of a furnace body iron core via a cylindrical body and a support plate. An object of the present invention is to provide a method for calculating the optimum shape of a cylindrical fluidized bed incinerator that easily predicts strain and obtains the optimum shape of a cylindrical body and a support plate having sufficient strength.

Means and effects for solving the problems

  The method for calculating the optimum shape of a cylindrical fluidized bed incinerator according to the present invention is a cylindrical fluidized bed incinerator in which an air dispersion plate is welded to the inner surface of the furnace main body through a cylindrical body and a support plate. The cylindrical body and the support plate using the thickness of the support plate, the ratio of the diameter and height of the cylindrical body, the thickness of the cylindrical body, and the operating temperature of the cylindrical fluidized bed incinerator The generation | occurrence | production distortion which generate | occur | produces in the welding part of this is estimated, and the optimal shape of the said cylindrical body and the said support plate is calculated | required.

  According to this, in the cylindrical fluidized bed incinerator in which the air dispersion plate is welded to the inner surface of the furnace main body through the cylindrical body and the support plate, the thickness of the support plate that has a great influence on the generated strain And the generated strain generated in the welded part of the cylindrical body and the support plate is predicted based on the ratio of the diameter and height of the cylindrical body and the thickness of the cylindrical body where the operating temperature has a large effect on the generated strain. The shapes of the cylindrical body and the support plate that are excellent in thermal fatigue life can be easily obtained. As a result, it is expected that there is no concern about the problem of cracks occurring in the welded portion between the cylindrical body and the support plate even if repeated operation of starting and stopping of the cylindrical fluidized bed incinerator is performed over a long period of time.

  Further, the optimum shape calculation method of the cylindrical fluidized bed incinerator according to the present invention includes the thickness of the support plate, the ratio of the diameter and height of the cylindrical body, the thickness of the cylindrical body, and the cylindrical shape. The thickness of the support plate, the diameter and the height of the cylindrical body at the operating temperature of the cylindrical fluidized bed incinerator based on the generated strain expressed by an approximate expression from the relationship of the operating temperature of the fluidized bed incinerator And the optimum value of the thickness of the cylindrical body may be calculated.

  According to this, using numerical analysis such as two-dimensional numerical analysis, the generated strain and the thickness of the support plate, the ratio of the diameter and height of the cylindrical body, the thickness of the cylindrical body, the cylindrical fluidized bed incinerator By modeling the relationship between the service temperatures, the strain generated at the service temperature of the cylindrical fluidized bed incinerator can be easily predicted, and the optimal support plate thickness, cylindrical diameter-to-height ratio, cylinder The body thickness can be determined.

  Hereinafter, the effect of the optimal shape calculation method of the cylindrical fluidized bed incinerator according to the present invention will be described in more detail based on the configuration of the cylindrical fluidized bed incinerator.

  As shown in FIG. 1, a cylindrical fluidized-bed incinerator 20 to which an optimum shape calculation method for a cylindrical fluidized-bed incinerator according to the present invention is provided includes a vertical cylindrical furnace body 1. The furnace top 2 is provided with an exhaust gas outlet 3, the furnace lower part 4 is provided with an air dispersion plate 6 for forming a fluidized bed 5 and a wind box 7 therebelow, and the wind box 7 is used for combustion and fluidization. An air blowing port 8 that also serves as a gasifier is provided. A heat insulating material 10 is provided on the air dispersion plate 6. Further, a combustion chamber is formed above the wind box 7, and the furnace body 1 in this portion is composed of an outer furnace body iron skin 9 and an inner refractory (not shown). In addition, the furnace body 1 constituting the combustion chamber is provided with an incinerator inlet (not shown) and a secondary combustion air inlet (not shown). Further, as shown in FIG. 2, the furnace main body iron skin 9 constituting the wind box 7 is connected to the furnace main body iron skin 9 constituting the furnace main body 1 by a rib 13 which is a flange portion.

  The air dispersion plate 6 is attached by welding to the furnace body iron skin 9 with the cylindrical body 11 interposed. That is, the air dispersion plate 6 is fixed to the inside of the lower portion of the cylindrical body 11 by welding, and the upper outer side is fixed to the support plate 12 facing outward by welding. Further, the support plate 12 is provided with its outer periphery welded and fixed to the inside of the furnace body iron skin 9.

  In the mounting structure of the air dispersion plate 6 of the cylindrical fluidized-bed incinerator 20 having the above-described configuration, when the cylindrical fluidized-bed incinerator 20 is started, air blowing is performed to heat and heat the fluidized bed 5 such as sand. When hot gas is blown from the inlet 8, the cylindrical body 11 and the support plate 12 are expanded by the circumferential stress accompanying the expansion of the air dispersion plate 6, and a further outer furnace is provided via the cylindrical body 11 and the support plate 12. It is transmitted to the main body skin 9. However, the load itself transmitted from the cylindrical body 11 and the support plate 12 to the outer furnace body core 9 is relieved because the cylindrical body 11 and the support plate 12 are deformed and transmitted.

  Here, the effect of each member of the cylindrical fluidized bed incinerator 20 on the generated strain generated in the welded portion of the cylindrical body 11 and the support plate 12 is investigated by conducting a finite element method analysis using a quality engineering technique. did. As shown in FIG. 3, the members of the cylindrical fluidized bed incinerator 20 are supported from the thickness ta of the furnace body iron skin 9, the thickness tb of the cylindrical body 11, the thickness tc of the support plate 12, and the ribs 13. The length La up to the plate 12, the ratio h / D of the diameter D and the height h of the cylindrical body, and the distance Lc between the furnace body iron skin 9 and the cylindrical body 11 were used. FIG. 4 shows the degree of influence on the generated strain when the shape of each member is changed, and FIG. 5 shows the generated strain of each member when the operating temperature T of the cylindrical fluidized bed incinerator 20 is changed. The degree of influence was shown. In FIG. 4, a member having a large inclination is a member having a large influence on the generated strain, and in FIG. 5, a member having a large inclination is a member having a large influence on the generated strain due to a change in operating temperature. 4 and 5, the “outer iron thickness” is the thickness ta of the furnace main body iron 9, the “outer cylinder thickness” is the thickness tb of the cylindrical body 11, and the “tube plate support plate thickness” is the support. The thickness tc of the plate 12, the “outer iron skin length” is the length La from the rib 13 to the support plate 12, the “outer cylinder length” is the height h of the cylindrical body 11, and the “support plate length” is the furnace It means the distance Lc between the main body skin 9 and the cylindrical body 11.

  As shown in FIG. 4, the member having a great influence on the generated strain is a member surrounded by a circle, that is, a cylindrical body having a thickness tc of the support plate 12 that is “tube plate support plate thickness” and an “outer tube length”. It can be seen that the height is 11 h. Further, as shown in FIG. 5, the member having a great influence on the generated strain due to the change in the use temperature T is a member surrounded by a circle, that is, the thickness tb of the cylindrical body 11 having the “outer cylinder thickness”. Recognize. Accordingly, only the thickness tc of the support plate 12, the ratio h / D of the diameter D and the height h of the cylindrical body 11, the thickness tb of the cylindrical body, and the operating temperature T of the cylindrical fluidized bed incinerator 20 are limited. Using numerical analysis such as the element method, the relationship with the generated distortion can be modeled. Then, by simply predicting the generated strain, it is optimal for the allowable strain determined from the assumed operating temperature T of the cylindrical fluidized bed incinerator 20 and the guaranteed lifetime of the equipment of the cylindrical fluidized bed incinerator 20. The thickness tc of the support plate 12, the ratio h / D of the diameter D to the height h of the cylindrical body 11, and the thickness tb of the cylindrical body can be obtained.

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

  An optimum shape calculation method for a cylindrical fluidized bed incinerator according to an embodiment of the present invention will be described. The configuration of the cylindrical fluidized bed incinerator to which the optimum shape calculation method for the cylindrical fluidized bed incinerator according to the embodiment of the present invention is applied is the cylindrical fluidized bed incinerator of FIGS. The configuration is the same as that of No. 20, and the description thereof is omitted.

  As an optimal shape calculation method for the cylindrical fluidized bed incinerator according to the embodiment of the present invention, specifically, for example, in the cylindrical fluidized bed incinerator 20 with a sludge treatment amount of 120 tons / day, each member is replaced with SUS304. When the working temperature of the cylindrical fluidized bed incinerator 20 is T = 900 ° C. (constant) and the thickness of the cylindrical body tb is 6 mm (constant), the welded portion of the cylindrical body 11 and the support plate 12 is The generated distortion E is determined. FIG. 6 shows the generated strain E obtained by simple two-dimensional numerical analysis, the ratio of the diameter D to the height h of the cylindrical body 11 (cylinder length in the drawing) h / D, and the thickness tc of the support plate 12. Shows the relationship. From FIG. 6, the generated strain E can be expressed by the following approximate expression (Expression 1).

E = A (h / D−0.08) ² −0.005 (Formula 1)
Here, A = 0.003 × tc + 0.12

  Therefore, the generated strain E can be easily calculated by this approximate expression (Expression 1). And with respect to the allowable strain determined from the guaranteed life of the equipment of the cylindrical fluidized bed incinerator 20 when the operating temperature T of the cylindrical fluidized bed incinerator 20 is 900 ° C. and the thickness tb of the cylindrical body 11 is 6 mm. Thus, the allowable shape of each member (ratio h / D of diameter D and height h of cylindrical body 11 and thickness tc of support plate 12) is determined.

  As described above, according to the method for calculating the optimum shape of the cylindrical fluidized bed incinerator according to this embodiment, the air dispersion plate 6 is interposed on the inner surface of the furnace body iron skin 9 with the cylindrical body 11 and the support plate 12 interposed therebetween. In the cylindrical fluidized bed incinerator 20 formed by welding, the thickness tc of the support plate 12 and the diameter D of the cylindrical body 11 have a great influence on the generated strain E generated in the welded portion of the cylindrical body 11 and the support plate 12. The air dispersion plate 6 and the cylindrical body 11 are based on the ratio h / D of the height h and the thickness tb of the cylindrical body in which the use temperature T of the cylindrical fluidized bed incinerator 20 has a great influence on the generated strain E. Since the generated strain E generated in the welded portion is predicted, the shapes of the cylindrical body 11 and the support plate 12 having excellent thermal fatigue life can be easily obtained. As a result, even if repeated starting and stopping operations of the cylindrical fluidized bed incinerator 20 are performed over a long period of time, it is expected that there is no concern about the problem of cracks occurring in the welded portion of the cylindrical body 11 and the support plate 12. The

  Further, by using numerical analysis such as two-dimensional numerical analysis, the generated strain E generated in the welded portion of the cylindrical body 11 and the support plate 12, the thickness tc of the support plate 12, the diameter D and the height h of the cylindrical body 11 are as follows. By modeling the relationship between the ratio h / D, the thickness tb of the cylindrical body 11, and the use temperature T of the cylindrical fluidized bed incinerator 20, the generated strain E at the use temperature T of the cylindrical fluidized bed incinerator 20 is modeled. Can be easily predicted, and the optimum thickness tc of the support plate 12, the ratio h / D of the diameter D and the height h of the cylindrical body 11, and the thickness tb of the cylindrical body 11 can be obtained.

  As mentioned above, although preferred embodiment of this invention was described, this invention can be changed in the range which does not exceed the meaning.

  In the above-described embodiment, the generated temperature E generated in the welded portion between the cylindrical body 11 and the support plate 12 is fixed with the operating temperature T of the cylindrical fluidized bed incinerator 20 and the thickness tb of the cylindrical body 11 being constant. Although the relationship between the diameter D of the body 11 and the ratio h / D of the height h and the thickness tc of the support plate 12 is obtained using numerical analysis such as two-dimensional numerical analysis, it is not limited thereto. The operating temperature T of the cylindrical fluidized bed incinerator 20 and the thickness tb of the cylindrical body 11 may be changed. In such a case, the generated strain E and the operating temperature T of the cylindrical fluidized bed incinerator 20 are separately provided. The relationship between the thickness tb of the cylindrical body 11, the ratio h / D of the diameter D and height h of the cylindrical body 11, and the thickness tc of the support plate 12 is obtained using numerical analysis such as two-dimensional numerical analysis.

It is a cross-sectional schematic diagram of the attachment structure of the air dispersion plate in the cylindrical fluidized bed type incinerator according to the present invention. It is the cross-sectional schematic diagram which showed the structure of the rib in the cylindrical fluidized bed type incinerator which concerns on this invention. It is the partial cross section schematic diagram which showed each member in the cylindrical fluidized-bed-type incinerator based on this invention which investigated the influence which it has on generation | occurrence | production distortion. It shows the degree of influence on the generated strain when each member of the cylindrical fluidized bed incinerator is changed by finite element method analysis. It shows the degree of influence on the generated strain of each member of the cylindrical fluidized bed incinerator when the operating temperature of the cylindrical fluidized bed incinerator is changed by the finite element method analysis. It is the figure which showed the relationship between the generation | occurrence | production distortion E in the optimal shape calculation method of the cylindrical fluidized-bed-type incinerator which concerns on this embodiment, the ratio of the diameter D of the cylindrical body 11, and the height h, and the thickness tc of the support plate 12. is there. It is a cross-sectional schematic diagram of the attachment structure of the air dispersion plate in the conventional general cylindrical fluidized bed type incinerator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Furnace main body 6 Air dispersion plate 9 Furnace main body iron core 11 Cylindrical body 12 Support plate 13 Rib 20 Cylindrical fluidized bed type incinerator

Claims (2)

  Thickness of the support plate in a cylindrical fluidized bed incinerator in which an air dispersion plate is welded to the inner surface of the furnace main body through a cylindrical body and a support plate, and the ratio of the diameter and height of the cylindrical body Predicting the generated strain in the welded portion of the cylindrical body and the support plate using the thickness of the cylindrical body and the operating temperature of the cylindrical fluidized bed incinerator, and the cylindrical body and the An optimum shape calculation method for a cylindrical fluidized bed incinerator characterized by obtaining an optimum shape of a support plate. The generated strain expressed by an approximate expression from the relationship between the thickness of the support plate, the ratio of the diameter and height of the cylindrical body, the thickness of the cylindrical body, and the operating temperature of the cylindrical fluidized bed incinerator Based on the above, the thickness of the support plate at the use temperature of the cylindrical fluidized bed incinerator, the ratio of the diameter and height of the cylindrical body, and the optimum value of the thickness of the cylindrical body are calculated. The optimal shape calculation method of the cylindrical fluidized bed type incinerator according to claim 1.

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