Patent Publication Number: US-2013233212-A1

Title: Burner, reaction furnace such as gasification furnace including the burner, and power plant including the reaction furnace

Description:
TECHNICAL FIELD 
     The present invention relates to a burner, a reaction furnace such as a gasification furnace including the burner, and a power plant including the reaction furnace, and more particularly, to a burner installed in a reaction furnace such as a gasification furnace. 
     BACKGROUND ART 
     A reaction furnace such as a gasification furnace provided in a power plant includes a pressure vessel  11  and a reaction furnace body  12  provided in the pressure vessel  11  as illustrated in  FIGS. 2 and 4 . The reaction furnace includes a space portion  13 , which is called an annulus, between the pressure vessel  11  and the reaction furnace body  12 , and maintains a high-pressure state within a reaction furnace  10 . The reaction furnace  10  has a proximal end at a side wall of the reaction furnace body  12 , and is provided with a burner  20  which extends toward the pressure vessel  11  from the side wall of the reaction furnace body  12  and penetrates the pressure vessel  11 . 
     The burner  20  includes a fuel tube  22  through which a fuel such as dust coal is guided by nitrogen or the like serving as a carrier gas; an oxidizer tube  23  which covers the outer periphery of the fuel tube  22  and through which an oxidizer such as air is guided from an oxidizer connecting flange portion  23   c  into the space formed with the outer periphery of the fuel tube  22 ; and a guide cylinder  24  provided on the outer periphery of the oxidizer tube  23 . 
     During operation of a power plant (not illustrated), thermal stretching occurs in each of the reaction furnace body  12  and the pressure vessel  11 . Accordingly, a difference in thermal stretching is generated between the reaction furnace body  12  and the pressure vessel  11  due to a difference in temperature or material. This causes the burner  20  to warp as illustrated in  FIG. 4 . 
     When the burner  20  warps as illustrated in  FIG. 4 , a stress is generated and concentrated at a proximal end of the oxidizer tube  23  or at a furnace outer fixed portion (hereinafter referred to as “fixed portion”), which may cause deformation or breakage of the burner  20 . To alleviate such a stress generated in the guide cylinder  24  or the oxidizer tube  23 , it is possible to employ a method for preventing deformation or breakage of the fixed portion by use of expansions  25  or the like for the guide cylinder  24  and the oxidizer tube  23  of the burner  20  ( FIGS. 2 and 4  illustrate that the expansions  25  are provided only to the guide cylinder  24 ) (for example, PTLs 1 and 2). 
     However, heretofore, a reaction furnace system such as a gasification furnace, for example, an integrated coal gasification combined cycle power plant, has a structure in which part of gas generated in the reaction furnace body  12  is guided to the space portion  13  of the reaction furnace  10 . As disclosed in PTL 1, when the expansions  25  are used for the guide cylinder  24  and the oxidizer tube  23 , the expansions  25  which are thin members may corrode and rupture due to corrosive gas contained in the generated gas. Particularly, in the case of the oxidizer tube  23 , an oxidizer such as air leaks. For this reason, the use of displacement absorbing members such as the expansions  25  for the oxidizer tube  23  is impractical. 
     To alleviate the stress generated in the fixed portion of the oxidizer tube  23  in view of an adverse effect such as corrosion, there is employed a method for preventing deformation or breakage by increasing the overall length of the oxidizer tube  23  and reducing an angular displacement to thereby reduce the stress generated in the fixed portion at both ends to be equal to or smaller than an allowable value as disclosed in PTL 1. Therefore, the length of the burner  20  (length indicated by “A” in  FIG. 2 ) is the length (burner selected length in  FIG. 2 ) corresponding to the stress generated in the oxidizer tube  23 . 
     CITATION LIST 
     Patent Literature 
     {PTL 1} 
     Japanese Unexamined Patent Application, Publication No. 2003-336809 
     {PTL 2} 
     Japanese Unexamined Patent Application, Publication No. Hei07-133904 
     {PTL 3} 
     Japanese Unexamined Patent Application, Publication No. Hei10-300022 
     {PTL 4} 
     Japanese Unexamined Patent Application, Publication No. Hei10-281414 
     SUMMARY OF INVENTION 
     Technical Problem 
     However, when the length of the burner  20  is determined as the length corresponding to the stress generated in the fixed portion of the oxidizer tube  23 , there is a problem that the weight of the burner  20  increases and the maintainability during maintenance by pulling out the burner  20  deteriorates. In addition, there is a situation where the layout of peripheral devices and pipes of the burner  20  is limited. 
     As illustrated in  FIG. 5 , a seal structure in which a gland packing  31  is provided in a sleeve  32  is employed in the vicinity of a conventional seal box  15 . Accordingly, the sleeve  32 , i.e., the side of the reaction furnace  12 , and an oxidizer tube  3  are structured to be relatively movable in the axial direction through the gland packing  31  (for example, PTLs 3 and 4). 
     Thus, if thermal stretching occurs in the oxidizer tube  3  due to a flow of an high-temperature oxidizer therethrough, the oxidizer tube  3  stretches and projects toward the inside of the reaction furnace  12  and the burning position of the burner greatly varies, which makes it difficult to achieve stable burning. 
     The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a burner capable of weight reduction by reducing the burner length, improving the maintainability and layout of peripheral devices, and capable of stable burning without changing the burning position even when thermal stretching occurs in the burner, a reaction furnace such as a gasification furnace including the burner, and a power plant including the reaction furnace. 
     Solution to Problem 
     To solve the above-mentioned problem, a burner of the present invention provides the following solutions. 
     That is, a burner according to the present invention includes: a fuel tube; an oxidizer tube through which an oxidizer is guided to a space formed with a side wall of the fuel tube, the oxidizer tube being substantially concentric to the fuel tube and covering an outer periphery of the fuel tube; a protective cylinder that covers an outer periphery of the oxidizer tube; and a displacement absorbing member provided to at least a part in an extending direction of the protective cylinder and the oxidizer tube. The fuel tube, the oxidizer tube, and the protective cylinder have a proximal end fixed to a side wall of an inner vessel of a gasification furnace filled with non-oxidizing gas in a space between the inner vessel and an outer vessel covering the inner vessel, and penetrate the outer vessel and extend from the side wall of the inner vessel toward an outside. An overall length is determined depending on a stress generated in the fuel tube. The oxidizer tube is positioned with respect to the side wall of the inner vessel to prevent a length of a distal end of each of the oxidizer tube and the fuel tube projecting to an inside of the gasification furnace from changing. 
     An adverse effect of corrosion due to generated gas can be avoided by filling non-oxidizing gas in the space between the inner vessel and the outer vessel of the gasification furnace including the inner vessel and the outer vessel. Additionally, the displacement absorbing member such as a flexible tube susceptible to corrosion can also be used for the oxidizer tube of the burner. For this reason, the displacement absorbing member is provided to at least a part in the extending direction of the oxidizer tube of the burner having a proximal end fixed to the side wall of the inner vessel of the gasification furnace. As a result, the displacement absorbing member can absorb a bending stress, which is generated in the oxidizer tube, out of the bending stress generated in the oxidizer tube and the fuel tube due to warping of the burner when a difference in thermal stretching occurs between the inner vessel and the outer vessel due to a difference in temperature and material of the inner vessel and the outer vessel. For example, air is used as the oxidizer. 
     As described above, the burner length can be determined based on the length of the fuel tube depending on the stress generated in the fuel tube. In this case, the fuel tube having a minimum tube diameter among tubes constituting the burner and the protective cylinder has a small generated bending stress as compared with other tubes with the same length and bending amount. In other words, in the case of allowing the generated stress at the same level, the same bending amount can be dealt with a length smaller than that of other tubes having a larger tube diameter. Thus, the burner length can be reduced as compared with the conventional case in which the burner length is determined based on the bending stress generated in the oxidizer tube having a tube diameter larger than that of the fuel tube. Accordingly, the weight of the burner can be reduced and the maintainability of the burner can be improved. 
     Note that a bendable flexible tube, bellows stretchable in the extending direction of the oxidizer tube, or the like can be used as the displacement absorbing member. 
     The oxidizer tube is positioned with respect to the side wall of the inner vessel so as to prevent the length of the distal end of the oxidizer tube projecting to the inside of the reaction furnace from changing. The thermal stretching in the axial direction of the oxidizer tube, which occurs in the space between the positioning portion (fixed portion) of the inner side wall and the furnace outer fixed portion is absorbed by the above-mentioned displacement absorbing member. Since the length from the positioning portion (fixed portion) of the inner side wall to the furnace inner distal end of the oxidizer tube is small, the amount of thermal stretching in the furnace inside axial direction at this portion is extremely small and negligible in terms of combustion. Consequently, the adverse effect of thermal stretching of the oxidizer tube is eliminated, and the burner can be stably burned at a predetermined position. 
     Further, a reaction furnace such as a gasification furnace according to the present invention includes the burner described above. 
     A burner capable of reducing a burner length is used. This enables reduction in a space around the burner installed in a reaction furnace such as a gasification furnace and improvement in maintainability. 
     Further, a power plant according to the present invention includes the reaction furnace described above. 
     A reaction furnace capable of reducing a space in the vicinity the burner is used. This makes it possible to reduce the space of the power plant and improve the maintainability. 
     Advantageous Effects of Invention 
     According to the invention described above, an adverse effect of corrosion due to generated gas can be avoided by filling non-oxidizing gas in a space between an inner vessel and an outer vessel of a reaction furnace including the inner vessel and the outer vessel, and a displacement absorbing member such as a flexible tube, which is a thin member susceptible to corrosion and rupture, can be used for an oxidizer tube of the burner. For this reason, the displacement absorbing member is provided to at least a part in the extending direction of the oxidizer tube of the burner having a proximal end fixed to the side wall of the inner vessel of the gasification furnace. As a result, the displacement absorbing member can absorb a bending stress generated in the oxidizer tube due to warping of the oxidizer tube when a difference in thermal stretching occurs between the inner vessel and the outer vessel due to a difference in temperature and material of the inner vessel and the outer vessel. The burner length is determined based on the length of the fuel tube depending on the stress generated in the fuel tube. In this case, the fuel tube having a minimum tube diameter among tubes constituting the burner and the protective cylinder has a small generated bending stress as compared with other tubes with the same length and bending amount. In other words, in the case of allowing the generated stress at the same level, the same bending amount can be dealt with a length smaller than that of other tubes having a larger tube diameter. Thus, the burner length can be reduced as compared with the conventional case in which the burner length is determined based on the bending stress generated in the oxidizer tube having a tube diameter larger than that of the fuel tube. Accordingly, the weight of the burner can be reduced and the maintainability of the burner can be improved. 
     Further, the oxidizer tube is positioned with respect to the side wall of the inner vessel. The thermal stretching in the axial direction of the oxidizer tube, which occurs in the space between the positioning portion (fixed portion) of the inner side wall and the furnace outer fixed portion is absorbed by the above-mentioned displacement absorbing member. Since the length from the positioning portion (fixed portion) of the inner side wall to the furnace inner distal end of the oxidizer tube is small, the amount of thermal stretching in the furnace inside axial direction at this portion is extremely small and negligible in terms of combustion. Consequently, the adverse effect of thermal stretching of the oxidizer tube is eliminated, and the burner can be stably burned at a predetermined position. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic block diagram at the time of installing a burner provided in a coal gasification furnace of an integrated coal gasification combined cycle power plant according to an embodiment of the present invention. 
         FIG. 2  is a schematic block diagram at the time of installing a burner provided in a gasification furnace of a conventional integrated coal gasification combined cycle power plant. 
         FIG. 3  is a detailed view of an oxidizer tube fixed portion according to an embodiment of the present invention. 
         FIG. 4  is a schematic block diagram at the time of operating the integrated coal gasification combined cycle power plant of the burner illustrated in  FIG. 2 . 
         FIG. 5  is a detailed view of a seal portion of a conventional burner. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
       FIG. 1  is a schematic block diagram of a burner provided in a coal gasification furnace of an integrated coal gasification combined cycle power plant according to an embodiment of the present invention. 
     An integrated coal gasification combined cycle power plant (IGCC; Integrated Coal Gasification Combined Cycle) using a carbon-containing fuel (for example, coal) as a fuel mainly includes a coal gasification furnace (reaction furnace)  10 , a gas turbine (not illustrated), a heat recovery steam boiler (not illustrated), and a stream turbine (not illustrated). 
     At an upstream side of the coal gasification furnace  10 , a coal supply facility (not illustrated) for supplying dust coal to the coal gasification furnace  10  is provided. This coal supply facility includes a grinder (not illustrated) which grinds material coal into dust coal having a size of several μm to several hundred μm. The dust coal ground by the grinder is transported to the coal gasification furnace  10  together with carrier gas such as nitrogen at a certain flow rate. 
     The coal gasification furnace  10  includes a reaction furnace (inner vessel)  12  serving as a water wall, a pressure vessel (outer vessel)  11  covering the reaction furnace  12 , and a space portion  13 , which is called an annulus, between the reaction furnace  12  and the pressure vessel  11 . The space portion  13  is filled with non-oxidizing gas such as nitrogen gas. 
     At the side wall of the reaction furnace  12  of the coal gasification furnace  10 , the burner  1  is fixed so as to be orthogonal to the side wall. The burner  1  is fixed to a reaction furnace-side opening  12   a,  which is opened in the side wall of the reaction furnace  12 , through the seal box  15 . The seal box  15  is made of SUS and refractory material, for example. The burner  1  penetrates the substantially central portion of the seal box  15 . 
     The burner  1  having one end fixed to a side wall of the reaction furnace  12  through the seal box  15  extends so as to be orthogonal to the side wall of the reaction furnace  12 , and penetrates a pressure-vessel-side opening  11   a  of the pressure vessel  11  which is provided so as to be opposed to the reaction furnace-side opening  12   a  of the reaction furnace  12 . 
     As illustrated in  FIG. 3 , the oxidizer tube  3  is positioned by a fixed portion  30  with respect to the reaction furnace  12 . The fixed portion  30  includes a sleeve  30   a  and an oxidizer tube flange portion  30   b.  A proximal end of the sleeve  30   a  is joined and fixed to the side of the seal box  15 . Specifically, the sleeve  30   a  is fixed to the side of the inner vessel  12 . The oxidizer tube  3  on the side of the outer vessel  11  (right side in the figure) is provided with the oxidizer tube flange portion  30   b  having a disc shape. The sleeve  30   a  and the oxidizer tube flange portion  30   b  are connectable in a face-to-face manner. The fixed portion  30  is fastened and fixed with a fixture  30   c  such as a bolt. 
     The oxidizer tube  3  is provided with oxidizer tube expansions  7 . 
     The pressure-vessel-side opening  11   a  serves as a flange and is fixed with a support cylinder  16 , which allows the burner  1  to be supported on the pressure-vessel-side opening  11   a  serving as a flange, and a bolt (not illustrated). Both ends of the support cylinder  16  serve as flange portions  16   a  and  16   b,  respectively. 
     The burner  1  includes a fuel tube  2 , an oxidizer tube  3  which is substantially concentric to the fuel tube  2  and covers the outer periphery of the fuel tube  2 , and a guide cylinder (protective tube)  4  which is substantially concentric to the fuel tube  2  and the oxidizer tube  3  and covers the outer periphery of the oxidizer tube  3 . 
     The fuel tube  2  is a tube through which finely-powdered fuel such as dust coal transported therein by nitrogen or the like is guided. The fuel tube  2  has one end extending in the reaction furnace body  12  through the seal box  15  as illustrated in  FIG. 1 . The other end of the fuel tube  2  is connected to a fine powder fuel transporting pipe (not illustrated) for transporting a fuel such as dust coal from a grinder. 
     The length (burner selected length in  FIG. 1 ) in the extending direction of the fuel tube  2  is determined depending on a stress generated in the fuel tube  2 , for example, a stress generated in a penetrating portion (not illustrated) of the fuel tube  2  penetrating the seal box  15 , or in a penetrating portion (not illustrated) of the fuel tube  2  penetrating a flange portion  3   a  described later. Accordingly, the length in the extending direction of the fuel tube  2  is substantially equal to the length of the burner  1  (overall length). 
     The fuel tube  2  includes a plurality of supports  6  extending from the outer wall toward the outside. The plurality of supports  6  is provided radially in the circumferential direction of the fuel tube  2  and at different locations in the axial direction of the fuel tube  2 . Extending ends of the supports  6  radially extending are located in the vicinity of the inner wall of the oxidizer tube  3  and are not fixed to the inner wall of the oxidizer tube  3 . The plurality of supports  6  is provided on the outer wall of the fuel tube  2 , thereby supporting the fuel tube  2  from the inside of the oxidizer tube  3 . 
     The oxidizer tube  3  covers the outer periphery of the fuel tube  2  and has an outer dimension greater than that of the fuel tube  2 . An oxidizer introducing flange portion  3   c  is provided on the side wall of the oxidizer tube  3 . An oxidizer such as air is introduced into the oxidizer tube  3  from the oxidizer introducing flange portion  3   c  in the space between the inner wall of the oxidizer tube  3  and the outer wall of the fuel tube  2 . 
     As illustrated in  FIG. 1 , one end of the oxidizer tube  3  penetrates the seal box  15  and extends in the reaction furnace  12 . A flange portion  3   a  is provided in the vicinity of an end opposite to the end of the oxidizer tube  3  which is connected to the seal box  15 . Further, the oxidizer tube  3  is provided with a flange portion  3   b  at the side of the coal gasification furnace  10  relative to the flange portion  3   a.  The flange portion  3   b  is connectable to a flange portion  4   a  which is provided to a guide cylinder  4  described later. 
     An oxidizer tube expansion (displacement absorbing member)  7  is provided to a part (at least a part in the extending direction; at two positions in  FIG. 1 ) in the axial direction of the oxidizer tube  3  which is exposed to the inside of the support cylinder  16  and the inside of the space portion  13 . Each oxidizer tube expansion  7  is a tube which is bendable and stretchable in the axial direction. 
     The guide cylinder  4  covers the outer periphery of each of the combustion tube  2  and the oxidizer tube  3 , and has an outer dimension greater than that of the oxidizer tube  3 . The guide cylinder  4  includes the oxidizer tube  3  and the fuel tube  2 . A non-oxidizing gas introducing tube for guiding non-oxidizing gas to a space portion (not illustrated) between the inner wall of the guide cylinder  4  and the outer wall of the oxidizer tube  3 , and a flange portion  4   c  are provided at an outer wall between the flange portion  4   a  and a flange portion  4   b  of the guide cylinder  4 . 
     The non-oxidizing gas guided from the flange portion  4   c  is nitrogen gas, for example. One end of the guide cylinder  4  is supported by the seal box  15 , and the other end of the guide cylinder  4  is supported by the flange portion  4   b.    
     The guide cylinder  4  is provided with the flange portion  4   a,  which is connected to the flange portion  3   b  provided to the above-mentioned oxidizer tube  3 , at an end opposite to one end fixed to the seal box  15 . The guide cylinder  4  is also provided with the flange portion  4   b  at the side of the coal gasification furnace  10  relative to the flange portion  4   a.  The flange portion  4   b  is connectable to the flange portion  16   b  of the support cylinder  16 . 
     The guide cylinder  4  has a function of blocking the space portion  13  and the space in the vicinity of the oxidizer tube  3 , and protecting the oxidizer tube  3  from generated gas or char, part of which is flown in only occasionally. A non-oxidizing gas (for example, nitrogen) is supplied from the non-oxidizing gas introducing tube and the flange portion  4   c  to the space between the inside of the guide cylinder  4  and the outside of the oxidizer tube  3  to keep a nitrogen atmosphere. 
     The guide cylinder  4  is provided with guide cylinder expansions  5  at a part (at two locations in  FIG. 1 ) in the axial direction exposed to the inside of the support cylinder  16  and the inside of the space portion  13 . Like the oxidizer tube expansions  7 , each guide cylinder expansion  5  is a tube which is bendable and stretchable in the axial direction. 
     Next, a state where a stress is applied to the burner  1  when the power plant is operated will be described with reference to  FIG. 1 . 
     The operation of the power plant (not illustrated) causes thermal stretching in each of the reaction furnace body  12  and the pressure vessel  11  of the coal gasification furnace (reaction furnace)  10 . The thermal stretching occurring in the reaction furnace body  12  and the pressure vessel  11  causes a difference (thermal stretching difference) due to a difference in material or temperature of the reaction furnace body  12  and the pressure vessel  11 . Accordingly, in the burner  1  which is inserted into the reaction furnace body  12  from the outside of the pressure vessel  11 , a side (hereinafter referred to as “proximal end”) which is fixed to the reaction furnace body  12  through the seal box  15 , for example, is displaced downward along with the operation start. 
     However, the oxidizer tube expansions  7  are also provided to the oxidizer tube  3 , in addition to the guide cylinder expansions  5  provided to the guide cylinder  4 , so each oxidizer tube expansion  7  warps downward when the proximal end of the burner  1  is to be displaced downward. This alleviates a bending stress generated at the proximal end of the oxidizer tube  3 , the flange portion  3   b  of the oxidizer tube  3 , and the fixed portion of the oxidizer tube  3 . 
     While the bending stress generated in the oxidizer tube  3  is alleviated by each oxidizer tube expansion  7 , a bending stress is generated in the fuel tube  2  due to the downward displacement of the burner  1 . In this case, the fuel tube  2  has a tube diameter smaller than that of the oxidizer tube  3  and the guide cylinder  4  which constitute the burner  1 . The generated bending stress is smaller than that of other tubes with the same length and bending amount. In other words, in the case of allowing the generated stress at the same level, the same bending amount can be dealt with with a length smaller than that of other tubes having a larger tube diameter. Thus, the length (length indicated by “A” in  FIG. 1 ) of the burner  1  can be determined depending on the burner selected length of the fuel tube  2  which is determined depending on the bending stress generated in the fuel tube  2 , and the burner length can be reduced as compared with the conventional case in which the burner length is selected based on the oxidizer tube  3 . 
     Note that the space portion  13  of the coal gasification furnace (reaction furnace)  10  is filled with the non-oxidizing gas guided from the non-oxidizing gas introducing tube  4   c,  thereby preventing part of the generated gas having corrosive properties from flowing from the inside of the reaction furnace body  12 . Therefore, there is no possibility of causing corrosion of the oxidizer tube  3  and the oxidizer tube expansions  7  due to the generated gas having corrosive properties. 
     As illustrated in  FIG. 3 , the oxidizer tube  3  is positioned by the fixed portion  30  with respect to the reaction furnace body  12 . The positioning is performed such that a burner distal end  3   d  of each of the oxidizer tube  3  and the fuel tube  2  is positioned so as to prevent the length projecting to the inside of the reaction furnace from changing. The thermal stretching in the axial direction of the oxidizer tube  3  which occurs between the positioning portion  30  (fixed portion) of the inner side wall and the furnace outer fixed portion is absorbed by the above-mentioned oxidizer tube expansions  7 . Since the length from the positioning portion  30  (fixed portion) of the inner side wall to the furnace inner distal end of the oxidizer tube  3  is small, the amount of thermal stretching in the furnace inner axial direction at this portion is extremely small and negligible in term of combustion. 
     As described above, the burner  1  according to this embodiment, the coal gasification furnace (reaction furnace)  10  including the burner  1 , and the power plant including the coal gasification furnace  10  provide the following operation and effect. 
     The space portion  13  formed between the reaction furnace body  12  and the pressure vessel  11  of the coal gasification furnace (reaction furnace)  10  including the reaction furnace body (inner vessel)  12  and the pressure vessel (outer vessel)  11  is filled with nitrogen gas which is non-oxidizing gas. An oxidizer tube expansion (displacement absorbing member)  7  is provided to a part (at least a part) in the extending direction of the oxidizer tube  3  of the burner  1  having a proximal end fixed at the side wall of the reaction furnace body  12  of the coal gasification furnace (reaction furnace)  10 . As a result, the oxidizer tube expansions  7  can absorb the bending stress, which is generated in the oxidizer tube  3 , out of the bending stress generated in the oxidizer tube  3  and the fuel tube  2  due to warping of the burner  1  when a thermal stretching difference occurs between the reaction furnace body  12  and the pressure vessel  11  due to a difference in temperature or material thereof. The length (length indicated by “A” in  FIG. 1 ) of the burner  1  is determined based on the burner selected length of the fuel tube  2  which is determined depending on the bending stress generated in the fuel tube  2 . Among the fuel tube  2 , the oxidizer tube  3 , and the guide cylinder (protective tube)  4  which constitute the burner  1 , the fuel tube  2  having a minimum tube diameter has a small generated bending stress. Accordingly, the length of the burner  1  can be reduced as compared with the conventional case in which the length of the burner  1  is determined based on the bending stress generated in the oxidizer tube  3  having a tube diameter greater than that of the fuel tube  2 . Therefore, the weight of the burner  1  can be reduced and the maintainability can be improved. 
     The burner  1  capable of reducing the overall length is used. This reduces the space around the burner  1  which is installed in the coal gasification furnace (reaction furnace)  10 . 
     The coal gasification furnace (reaction furnace)  10  capable of reducing the space around the burner  1  is used. This reduces the space of the power plant. 
     The oxidizer tube  3  is fixed by the positioning portion  30  at the inner side wall. The thermal stretching in the axial direction of the oxidizer tube  3 , which occurs between the positioning portion  30  (fixed portion) at the inner side wall and the furnace outer fixed portion is absorbed by the oxidizer tube expansions  7  attached to the oxidizer tube  3 . Since the length from the positioning portion  30  (fixed portion) of the inner side wall to the furnace inner distal end of the oxidizer tube  3  is small, the amount of thermal stretching in the furnace inner axial direction at this portion is extremely small and negligible in terms of combustion. This suppresses a change in position of the burner distal end  3   d  of the oxidizer tube  3  due to great thermal stretching. As a result, the position of the burner distal end  3   d  hardly changes from the predetermined position, thereby enabling stable burner combustion. The oxidizer tube  3  is provided with the oxidizer tube expansions  7 . Thus, the oxidizer tube expansions  7  can absorb the thermal stretching of the oxidizer tube  3  at the side of outer vessel  11  from the fixed portion  30 . 
     This embodiment illustrates the case where the oxidizer tube expansions  7  and the guide cylinder expansions  5  are provided as the displacement absorbing member, but the present invention is not limited thereto. Any expansion such as bellows stretchable in the extending direction of the oxidizer tube  3  and the guide cylinder  4  may also be used. 
     Examples of the finely-powdered fuel such as dust coal to be introduced into the fuel tube  2  include char, oil, and gas. 
     REFERENCE SIGNS LIST 
     
         
           1  BURNER 
           2  FUEL TUBE 
           3  OXIDIZER TUBE 
           3   d  BURNER DISTAL END 
           4  GUIDE CYLINDER (PROTECTIVE CYLINDER) 
           4   c  INERT GAS INTRODUCING TUBE AND FLANGE 
           7  OXIDIZER TUBE EXPANSION (DISPLACEMENT ABSORBING MEMBER) 
           10  COAL GASIFICATION FURNACE (REACTION FURNACE) 
           11  PRESSURE VESSEL (OUTER VESSEL) 
           12  REACTION FURNACE BODY (INNER VESSEL) 
           13  SPACE (ANNULUS) PORTION 
         A BURNER LENGTH (OVERALL LENGTH)