Pressure fluidized bed firing boiler

Abstract: A support structure for a fluidized bed firing boiler disposed within a cylindrical pressure vessel and operated while the inside of a fluidized bed furnace is kept pressurized, is improved. A supporting object of a main body of the pressure fluidized bed firing boiler disposed within the pressure vessel is divided into a suspended section (3,4) supported from a support beam (5) disposed at an upper portion within the pressure vessel; and a bottom-support section (6) supported from a support beam (7) disposed at a lower portion within the pressure vessel. Also, a metallic expansion joint (9) is provided at an engaging portion between the suspended section and the bottom-support section. In addition, favorable structures of the pressure fluidized bed firing boiler in the event that the cylindrical pressure vessel is of vertical type and in the event that it is of horizontal type are proposed.

Description: BACKGROUND OF THE INVENTION: Field of the Invention: The present invention relates to a structure of a pressure fluidized bed firing boiler disposed within a pressure vessel, for example, a support structure of a pressure fluidized bed firing boiler or a reinforcement structure of the above-referred pressure vessel, and more particularly to an improved structure of a pressure fluidized bed firing boiler which contributes to smallsizing and reduction in weight thereof. Description of the Prior Art: In a structure for supporting a pressure fluidized bed firing boiler disposed within a pressure vessel, heretofore, a system of suspending an entire load of a supporting object of the boiler main body from a support beam provided at the above within the pressure vessel has been employed. However, in the case where such a system of suspending an entire load of a supporting object of the boiler main body from a support beam at the above is employed, if a large-capacity fluidized bed firing boiler becomes the object, the support beam structure at the above within the pressure vessel would be large-sized and also a load acting upon a shell plate of the pressure vessel would become large, and hence there exists a problem that a strong shell plate reinforcement structure is necessitated. Also, in order to resolve such problem, one can conceive another system in which an entire load of a supporting object of a boiler main body is supported from a support beam provided under the pressure vessel, but according to this system, in a large-capacity fluidized bed firing boiler, especially a compression load acting upon its peripheral wall pipes becomes maximum, and hence there occurs a problem that the load exceeds a buckling strength. An atmospheric fluidized bed steam generator with a bottom supported furnace wall structure and a top supported gas pass structure is known from US-A-4 641 608. A gas tight fabric expansion joint joins the two structures, however, in this known atmospheric fluidized bed steam generator a convection heating surface is located in the gas pass of the bottom supported furnace wall structure below the elevation of the expansion joint whereby the gas temperature is reduced before it reaches the joint thereby making it possible to use a low temperature expansion joint. Furthermore, in such atmospheric fluidized bed furnace also the pressure difference between the in- and outsides of the boiler and thus a stress on the expansion joint is very small. SUMMARY OF THE INVENTION: It is the object of the present invention to eliminate the shortcoming of the above described support structure for a pressure fluidized bed firing boiler in the prior art so that the support structure can be small-sized, and to achieve reduction of a compression load caused by a boiler main body. According to the present invention this object is solved by a support structure for a pressure fluidized bed firing boiler disposed within a cylindrical pressure vessel and operated while the inside of a fluidized bed furnace is kept pressurized, wherein said support structure of the pressure fluidized bed firing boiler disposed within the pressure vessel is divided into a suspended section supported from a support beam disposed at an upper portion within the pressure vessel and a bottom-support section supported from a support beam disposed at a lower portion within the pressure vessel, a metallic expansion joint is provided at an engaging portion between said suspended section and said bottom-support section, said suspended section is formed of a fluidized bed peripheral wall and intralayer tubes, said bottom-support section is formed of fluidized material and a furnace bottom portion, refractory heat-insulating material is provided on the side surface within the fluidized bed of said metallic expansion joint, the bottom portion of the suspended section is provided with a fluidized bed peripheral wall inlet tube header, and said expansion joint made of metal is provided between said inlet tube header and said support beam. According to the above-mentioned measure, owing to the fact that a supporting object of a main body of a pressure fluidized bed firing boiler is divided into a suspended section and a bottom support section, even support for a large-capacity fluidized bed firing boiler can be dealt with, without greatly increasing a structural strength of a support beam and the like. In addition, a difference in a coefficient of thermal expansion between these suspended section and bottom support section can be easily absorbed by a metallic expansion joint. The above-mentioned and other objects, features and advantages of the present invention will become more apparent by reference to the following description of preferred embodiments of the invention taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS: In the accompanying drawings: Fig. 1 is a cross-section front view showing a structure for supporting a pressure fluidized bed firing boiler of horizontal type according to one preferred embodiment of the present invention; Fig. 2 is a schematic perspective view showing a part of the structure shown in Fig. 1; Fig. 3 is a partial cross-section view taken along line III-III in Fig. 2 as viewed in the direction of arrows; Fig. 4 is a schematic cross-section side view showing a whole of a pressure fluidized bed firing boiler of horizontal type; DESCRIPTION OF THE PREFERRED EMBODIMENTS: Now one preferred embodiment of the present invention will be described in greater detail with reference to the accompanying drawings. Fig. 4 is a schematic cross-section side view showing a whole of a pressure fluidized bed firing boiler according to the preferred embodiment, in which a fluidized bed firing boiler 2 is disposed within a pressure vessel 1. Fig. 1 is a cross-section front view showing details of the structure for supporting this fluidized bed firing boiler 2 according to the present invention, Fig. 2 is a schematic perspective view of a part of the structure shown in Fig. 1, and Fig. 3 is a partial cross-section view taken along line III-III in Fig. 2. In these figures, a fluidized bed peripheral wall 3 and intralayer tubes 4 forming constituent members of the fluidized bed firing boiler 2 disposed within the pressure vessel 1, are suspended from a support beam 5 provided at an upper portion within the pressure vessel 1. Also, upon stoppage of the fluidized bed firing boiler, a load of fluidized material (solid) 6 within the fluidized bed furnace is supported from the bottom by a support beam 7 provided at a lower portion within the pressure vessel 1. Accordingly, a load supporting object of the fluidized bed firing boiler 2 is divided into the suspended fluidized bed peripheral wall 3 and the intralayer tubes 4 (suspended section) and the fluidized material 6 supported at the bottom (bottom-supported section). Furthermore, provision is made such that a difference in a coefficient of thermal expansion upon operation between the suspended section 4 and 5 and the bottom-supported section 6 may be absorbed by an expansion joint 9 provided between a fluidized bed peripheral wall inlet tube header 8 and the lower support beam 7. This expansion joint 9 is made of metal because it is subjected to a surface load caused by a pressure difference between the inside of the fluidized bed and the inside of the pressure vessel. It is to be noted that in the illustrated embodiment, as shown in Fig. 3, on the side surface within the fluidized bed of the expansion joint 9 is provided refractory heat-insulating material 10 in order to prevent deterioration and damage of the expansion joint 9 caused by the fluidized material (solid) 6 at a high temperature. As described above, according to the illustrated embodiment, in a support structure of a fluidized bed firing boiler disposed within a pressure vessel, since the suspended section and the bottom-supported section are separately supported, even a large-capacity fluidized bed firing boiler can be dealt with without greatly improving the support structure such as support beams. In addition, only a tensile load is applied to the fluidized bed peripheral wall tubes, the countermeasure against the compression load in the case of bottom-supporting the peripheral wall tubes (the countermeasure for preventing buckling of the peripheral wall tubes such as enhancement of rigidity of the tubes or increase of a number of stages of peripheral wall back stays) becomes unnecessary. Furthermore, at the engaging point between the suspended section and the bottom-supported section, a difference in a coefficient of thermal expansion therebetween, upon operation of the fluidized bed firing boiler, can be easily absorbed by providing the metallic expansion joint.

Claims: A support structure for a pressure fluidized bed firing boiler (2) disposed within a cylindrical pressure vessel (1) and operated while the inside of a fluidized bed furnace is kept pressurized, wherein said support structure of the pressure fluidized bed firing boiler (2) disposed within the pressure vessel (1) is divided into a suspended section supported from a support beam (5) disposed at an upper portion within the pressure vessel (1) and a bottom-support section supported from a support beam (7) disposed at a lower portion within the pressure vessel (1); a metallic expansion joint (9) is provided at an engaging portion between said suspended section and said bottom-support section; said suspended section is formed of a fluidized bed peripheral wall (3) and intralayer tubes (4); said bottom-support section is formed of fluidized material (6) and a furnace bottom portion; refractory heat-insulating material is provided on the side surface within the fluidized bed of said metallic expansion joint (9); the bottom portion of the suspended section is provided with a fluidized bed peripheral wall inlet tube header (8); and said expansion joint (9) made of metal is provided between said inlet tube header (8) and said support beam (7).

Inventors: HAMASAKI KATSUJI C O MITSUBISH, OTSUBO KOICHIRO C O NAGASAKI S, YOKOYAMA TOMOMITSU C O MITSUBI, HAMASAKI, KATSUJI, C/O MITSUBISHI JUKOGYO K.K., OTSUBO, KOICHIRO, C/O NAGASAKI SHIPYARD ENG. WORKS, YOKOYAMA, TOMOMITSU, C/O MITSUBISHI JUKOGYO K.K.
Applicants: MITSUBISHI HEAVY IND LTD, MITSUBISHI JUKOGYO KABUSHIKI KAISHA
Application year: 1990
Main classification: F22B31
IPC codes: F22B37, F22B31