Patent Publication Number: US-10775042-B2

Title: Combustion burner and method for maintaining combustion burner

Description:
FIELD 
     The present invention relates to a combustion burner applied to a boiler for generating steam for power generation, factories, or the like. 
     BACKGROUND 
     For example, a conventional pulverized coal fired boiler has a furnace that is formed in a hollow shape and installed in an up-and-down direction, and a plurality of combustion burners are arranged in a furnace wall along a circumferential direction, the combustion burners being arranged in a multiple-stage manner in the vertical direction. The combustion burner supplies thereto a fuel-air mixture of pulverized coal (fuel) in which coal is pulverized and primary air (air) and, at the same time, supplies thereto hot combustion air, wherein the fuel-air mixture and the hot combustion air are blown into the furnace to form flames thus combusting the fuel-air mixture in the furnace. Furthermore, the furnace has a flue gas duct connected with the upper portion thereof, the flue gas duct is provided with a superheater, a reheater, a fuel economizer, and the like that are used for recovering the heat of flue gas, and heat exchange is performed between the flue gas and water that are generated by combusting the fuel-air mixture in the furnace thus generating steam. 
     Here, in the combustion burner of the pulverized coal fired boiler, the fuel is composed of a solid material and hence, the fuel is brought into contact with a member arranged in an area through which the fuel circulates. Consequently, there exists the possibility of generating abrasion in a passage of the fuel, or the like. In this regard, Patent Literature 1 discloses a straightening vane arranged in the inside or the passage, the straightening vane being formed of a high-chrome steel material, or configured to apply thereto the lining of a hard material, such as ceramics or cermet. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese Patent Application Laid-open No. 2005-265354 
     SUMMARY 
     Technical Problem 
     The combustion burner is provided with an abrasion-resistant member thus improving durability thereof. The combustion burner is provided with the abrasion-resistant member to improve the durability thereof thus reducing the frequency of maintenances, such as the replacement or repair of components; however, the replacement or repair of the components is required in some cases. In this case, there exists the case that the maintenance takes time and effort because of the abrasion-resistant member provided to the combustion burner. 
     The present invention has been made to overcome such drawbacks, and it is an object of the present invention to provide a combustion burner and a method for maintaining the combustion burner that are capable of maintaining high durability of the combustion burner and achieving easy maintenance of the combustion burner. 
     Solution to Problem 
     To achieve the object, a combustion burner of the present invention includes a fuel nozzle configured to blow in fuel gas that is a mixture of solid fuel and air; a combustion air nozzle configured to blow in air from outside of the fuel nozzle; at least one flame stabilizer having a wide width part whose width increases in a direction toward a distal end of the fuel nozzle, the flame stabilizer being arranged on the axial center side at the distal end of the fuel nozzle; and a straightening vane having a plate shape, the straightening vane being arranged on an extension of the flame stabilizer on the upstream side in a flow direction of the fuel gas. An abrasion-resistant member is arranged on the wide width part of the flame stabilizer. An abrasion-resistant member is arranged on at least a part of the straightening vane. 
     The combustion burner is provided with the respective abrasion-resistant members arranged on a part of the flame stabilizer, the width of the part being increased along with the extension of the flame stabilizer to the distal end of the combustion burner, and at least a part of the straightening vane thus protecting the part that is easily worn, and improving the durability of the combustion burner. Furthermore, the abrasion-resistant member is selectively arranged thus decreasing time and efforts for arranging the abrasion-resistant member at the time of maintenance, and easily maintaining the combustion burner. Consequently, it is possible to maintain high durability, and achieve easy maintenance. 
     The straightening vane is preferably arranged in a spaced-apart manner from the flame stabilizer in the flow direction of the fuel gas. The flame stabilizer and the straightening vane are formed in a separated manner from each other thus separately replacing each part of the flame stabilizer and the straightening vane. Consequently, it is possible to achieve easy maintenance. 
     The flame stabilizer preferably has an end surface located on the upstream side in the flow direction of the fuel gas, the end surface being orthogonal to the flow direction of the fuel gas. Consequently, the end surface of the flame stabilizer can be hardly scraped away by the solid contents in the combustion gas thus suppressing the occurrence of abrasion of the flame stabilizer. 
     It is preferable that the straightening vane has a surface parallel to the flow direction of the fuel gas, and the abrasion-resistant member is arranged in at least an area of the surface, the area being not greater than 50% of the overall length of the straightening vane from an end surface of the straightening vane located on the upstream side of the straightening vane in the flow direction of the fuel gas. Consequently, the abrasion-resistant member can be selectively arranged on the part that is easily worn thus decreasing the necessity of an abrasion-resistant treatment. Furthermore, it is possible to achieve easy maintenance. 
     The abrasion-resistant, member is preferably arranged on an end surface of the straightening vane located on the upstream side in the flow direction of the fuel gas. Consequently, a part with which the solid contents in the combustion gas are easily brought into contact can be protected thus improving abrasion resistance. 
     The straightening vane preferably has an end surface located on the upstream side in the flow direction of the fuel gas, the end surface being orthogonal to the flow direction of the fuel gas. Consequently, the end surface of the straightening vane can be hardly scraped away by the solid contents in the combustion gas thus suppressing the occurrence of abrasion of the flame stabilizer. 
     It is preferable that the fuel nozzle has a projection portion at a position facing the straightening vane, and the straightening vane has a recessed portion covering a periphery of the projection portion, the straightening vane being held with the projection portion arranged in the recessed portion. Consequently, the projection portion can be protected with the straightening vane thus suppressing the occurrence of replacement of the projection portion fixed to the fuel nozzle side at the time of maintenance. Furthermore, it is possible to improve maintainability. 
     The abrasion-resistant, member is preferably made of high-chrome steel. Consequently, a quantity of work when arranging the abrasion-resistant member in the straightening vane or the flame stabilizer can be reduced thus improving maintainability. 
     The abrasion-resistant member preferably has a structure such that ceramics is embedded in a metal member. Consequently, a quantity of work when arranging the abrasion-resistant member in the straightening vane or the flame stabilizer can be reduced thus improving maintainability. 
     At least one of the flame stabilizer and the straightening vane preferably has a permanent magnet arranged in an exposed manner to the fuel nozzle. Consequently, the magnetic force of the permanent magnet is checked from the outside of the combustion burner thus detecting the abrasion state of the permanent magnet, and determining the abrasion state of the straightening vane or the flame stabilizer from the abrasion state of the permanent magnet. The abrasion state of the permanent magnet can easily be detected thus achieving appropriate maintenance. 
     The flame stabilizer preferably has at least one group of at least two first flame stabilizing members arranged parallel with each other along a horizontal direction in a predetermined spaced apart manner in a vertical direction, and at least two second flame stabilizing members arranged parallel with each other along the vertical direction in a predetermined spaced apart manner in the horizontal direction. Consequently, flames can securely be formed from the inside of the fuel nozzle thus achieving excellent maintainability and abrasion resistance of the combustion burner. 
     To achieve the object, a method of the present invention is for maintaining a combustion burner that includes a fuel nozzle configured to blow in fuel gas that is a mixture of solid fuel and air, a combustion air nozzle configured to blow in air from outside of the fuel nozzle, at least one flame stabilizer having a wide width part whose width increases in a direction toward a distal end of the fuel nozzle, the flame stabilizer being arranged on the axial center side at the distal end of the fuel nozzle, and a straightening vane having a plate shape, the straightening vane being arranged on an extension of the flame stabilizer on the upstream side in a flow direction of the fuel gas. The method includes the steps of replacing the flame stabilizer with another flame stabilizer having the wide width part on which an abrasion-resistant member arranged; and replacing the straightening vane with another straightening vane on which an abrasion-resistant member is arranged on at least a part of the other straightening vane. 
     When maintaining a combustion burner, a flame stabilizer is replaced with another flame stabilizer whose flame stabilizing member has an abrasion-resistant member on a part of the flame stabilizing member, the width of the part being increased along with the extension of the flame stabilizing member to the distal end of the combustion burner, and a flow straightener is replaced with another flow straightener whose straightening vane has an abrasion-resistant member on at least a part thereof thus protecting the portion of the combustion burner that is easily worn, and improving the durability of the combustion burner. Furthermore, the abrasion-resistant member is selectively arranged thus decreasing time and efforts for arranging the abrasion-resistant member at the time of maintenance, and easily maintaining the combustion burner. Consequently, it is possible to maintain high durability, and achieve easy maintenance. 
     Advantageous Effects of Invention 
     According to the present invention, the respective abrasion-resistant, members are arranged on a part of the flame stabilizing member, the width of the part being increased along with the extension of the flame stabilizing member to the distal end of the combustion burner, and at least a part of the straightening vane thus protecting the part that is easily worn, and improving the durability of the combustion burner. Furthermore, the abrasion-resistant member is selectively arranged thus decreasing time and efforts for arranging the abrasion-resistant member at the time of maintenance, and easily maintaining the combustion burner. Consequently, it is possible to maintain high durability, and achieve easy maintenance. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic structural view illustrating a pulverized coal fired boiler to which a combustion burner according to the present embodiment is applied. 
         FIG. 2  is a plan view illustrating the combustion burner in the pulverized coal fired boiler according to the present embodiment. 
         FIG. 3  is a front view illustrating the combustion burner according to the present embodiment. 
         FIG. 4  is a sectional view taken along line A-A in  FIG. 3 , the sectional view illustrating the combustion burner according to the present embodiment. 
         FIG. 5  is a sectional view taken along line B-B in  FIG. 4 , the sectional view illustrating the combustion burner according to the present embodiment. 
         FIG. 6  is a schematic view illustrating a schematic structure of a flame stabilizing member and a straightening vane. 
         FIG. 7  is a schematic view illustrating a schematic structure of a modification of the flame stabilizing member and the straightening vane. 
         FIG. 8  is a schematic view illustrating a schematic structure of a combustion burner according to another embodiment. 
         FIG. 9  is an enlarged schematic view illustrating a connection portion between the straightening vane and the combustion nozzle of the combustion burner illustrated in 
         FIG. 8 . 
         FIG. 10  is a sectional view illustrating a combustion burner of still another embodiment. 
         FIG. 11  is a sectional view taken along line C-C in  FIG. 10 , the sectional view illustrating the combustion burner of the still another embodiment. 
         FIG. 12  is a schematic view illustrating a schematic structure of a flame stabilizing member and a straightening vane of the combustion burner illustrated in  FIG. 10 . 
         FIG. 13  is a schematic view illustrating a schematic structure of a modification of the straightening vane illustrated in  FIG. 12 . 
         FIG. 14  is a schematic view illustrating a schematic structure of a combustion burner of still another embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, with reference to attached drawings, a preferred embodiment of a combustion burner according to the present invention are specifically explained. Here, the present invention is not limited to the embodiment, and when a plurality of embodiments are conceivable, the constitution of the embodiments combined with each other is included in the present invention. 
       FIG. 1  is a schematic structural view illustrating a pulverized coal fired boiler to which a combustion burner according to the present embodiment is applied.  FIG. 2  is a plan view illustrating the combustion burner in the pulverized coal fired boiler according to the present embodiment.  FIG. 3  is a front view illustrating the combustion burner according to the present embodiment.  FIG. 4  is a sectional view taken along line A-A in  FIG. 3 , the sectional view illustrating the combustion burner according to the present embodiment.  FIG. 5  is a sectional view taken along line B-B in  FIG. 4 , the sectional view illustrating the combustion burner according to the present embodiment.  FIG. 6  is a schematic view illustrating a schematic structure of a flame stabilizing member and a straightening vane. 
     The pulverized coal fired boiler to which the combustion burner according to the present embodiment is applied uses pulverized coal obtained by pulverizing coals, as a solid fuel, and burns the pulverized coal with the use of the combustion burner, the pulverized coal fired boiler being capable of recovering heat generated by the burning of the pulverized coal. 
     In the present embodiment, as illustrated in  FIG. 1 , a pulverized coal fired boiler  10  that is a conventional boiler has a furnace  11 , a combustion device  12 , and a flue gas duct  13 . The furnace  11  is formed in a quadrilateral cylindrical hollow shape, and arranged along the perpendicular direction, and the combustion device  12  is arranged in the lower part of the furnace wall that constitutes the furnace  11 . 
     The combustion device  12  has a plurality of combustion burners  21 ,  22 ,  23 ,  24 ,  25  attached to the furnace wall. In the combustion burners  21 ,  22 ,  23 ,  24 ,  25  according to the present embodiment, four combustion burners are arranged along the circumferential direction at equally spaced intervals as one set, and five sets of four combustion burners are arranged along the perpendicular direction; that is, five sets of four combustion burners are arranged in five stages. 
     Furthermore, the respective combustion burners  21 ,  22 ,  23 ,  24 ,  25  are connected with coal pulverizers (mills)  31 ,  32 ,  33 ,  34 ,  35  by way of pulverized coal feed pipes  26 ,  27 ,  28 ,  25 ,  30 . Each of the coal pulverizers  31 ,  32 ,  33 ,  34 ,  35  has, although not illustrated in the drawings, a crushing table arranged in a housing thereof in such a manner that the crushing table is rotatably supported about a rotational axis thereof along the perpendicular direction, and each of a plurality of crushing rollers that face the upper surface of the crushing table is rotatably supported in an interlocking manner with the rotation of the crushing table. Accordingly, when the coals are supplied between the crushing rollers and the crushing table, each of the coals is here crushed to a predetermined size, and the pulverized coal classified by transportation air (air) is supplied from the pulverized coal feed pipes  26 ,  27 ,  28 ,  25 ,  30  to the combustion burners  21 ,  22 ,  23 ,  24 ,  25 , respectively. 
     Furthermore, the furnace  11  includes thereon a wind box  36  in the fixing positions of the combustion burners  21 ,  22 ,  23 ,  24 ,  25 , the wind box  36  connects therewith one end of an air duct  37 , and the air duct  37  attaches an air blower  38  to the other end thereof. In addition, the furnace  11  includes thereon an additional air nozzle  39  in a position above the fixing positions of the combustion burners  21 ,  22 ,  23 ,  24 ,  25 , and the additional air nozzle  39  connects thereto the end of a branch air duct  40  branched from the air duct  37 . Consequently, combustion air (fuel-gas combustion air, secondary air) sent from the air blower  38  can be supplied from the air duct  37  to the wind box  36 , and supplied from the wind box  36  to each of the combustion burners  21 ,  22 ,  23 ,  24 ,  25  and, at the same time, combustion air (additional air) sent from the air blower  38  can be supplied from the branch air duct  40  to the additional air nozzle  39 . 
     Hence, in the combustion device  12 , each of the combustion burners  21 ,  22 ,  23 ,  24 ,  25  is capable of blowing a fine powder fuel-air mixture (fuel gas) of the pulverized coal and air into the furnace  11  and, at the same time, blowing combustion-gas combustion air (secondary air) into the furnace  11 , and an igniter (not illustrated in the drawings) ignites the fine powder fuel-air mixture thus forming flames. 
     Generally, at the time of starting a boiler, each of the combustion burners  21 ,  22 ,  23 ,  24 ,  25  injects oil fuel into the furnace  11  thus forming flames. Alternatively, after forming the flames with an oil-fired burner for start-up, during normal operation, combustion air is supplied from the oil-fired burner. 
     The furnace  11  connects the flue gas duct  13  to the upper portion thereof, and the flue gas duct  13  is provided with, as a convection heating part, superheaters (booster heaters)  41 ,  42  for recovering the heat of flue gas, reheaters  43 ,  44 , and fuel economizers (economizers)  45 ,  46 ,  47 , and heat exchange is performed between the flue gas generated in the burning of the fine powder fuel-air mixture in the furnace  11  and water. 
     The flue gas duct  13  connects a flue gas pipe  48  where flue gas heat-exchanged is discharged, to the downstream side thereof. Provided between the flue gas pipe  48  and the air ducts  37  is an air heater  49  to perform heat-exchange between the air flowing through the air duct  37 , and the flue gas flowing through the flue gas pipe  48  thus heating the combustion air supplied to the combustion burners  21 ,  22 ,  23 ,  24 ,  25 . 
     Accordingly, when the coal pulverizers  31 ,  32 ,  33 ,  34 ,  35  are operated, the pulverized coal generated and the transportation air are supplied to the combustion burners  21 ,  22 ,  23 ,  24 ,  25  through the respective pulverized coal feed pipes  26 ,  27 ,  28 ,  29 ,  30 . Furthermore, the combustion air heated is supplied from the air duct  37  to each of the combustion burners  21 ,  22 ,  23 ,  24 ,  25  by way of the wind box  36  and, at the same time, supplied from the branch air duct  40  to the additional air nozzle  39 . Then, the combustion burners  21 ,  22 ,  23 ,  24 ,  25  blow the fine powder fuel-air mixture of the pulverized coal and the transportation air into the furnace  11 , and blow the combustion air into the furnace  11 , and the fine powder fuel-air mixture is ignited thus forming flames. Furthermore, the additional air nozzle  39  blows the additional air into the furnace  11  thus performing combustion control. In the furnace  11 , when the fine powder fuel-air mixture and the combustion air are burnt to form the flames, and the flames form in the lower part in the inside of the furnace  11 , the combustion gas (flue gas) upwardly moves in the inside of the furnace  11  so as to be discharged to the flue gas duct  13 . 
     That is, the combustion burners  21 ,  22 ,  23 ,  24 ,  25  blow the pulverized coal fuel-air mixture and the combustion air (combustion-gas combustion air/secondary air) into a combustion region in the furnace  11 , and the pulverized coal fuel-air mixture is ignited thus forming a flame swirl flow in the combustion region. Furthermore, the flame swirl flow upwardly moves while swirling, and reaches to a reduced zone. The additional air nozzle  39  blows the additional air into above the reduced zone in the furnace  11 . In the furnace  11 , the amount of supply of air is set less than the theoretical quantity of air with respect to the amount of supply of pulverized coal thus holding a reducing atmosphere in the inside of the furnace  11 . Furthermore, NOx generated by burning the pulverized coal is reduced in the furnace  11  and thereafter, the supplementary air (additional air) is supplied thus completing the oxidation combustion of the pulverized coal, and lowering a generation amount of NOx due to the burning of the pulverized coal. 
     Here, although the combustion device  12  is explained in detail, the combustion burners  21 ,  22 ,  23 ,  24 ,  25  that constitute the combustion device  12  have respective constitutions substantially identical with each other and hence, only the combustion burner  21  located at the uppermost position is explained. 
     The combustion burner  21  is, as illustrated in  FIG. 2 , constituted of combustion burners  21   a ,  21   b ,  21   c ,  21   d  arranged on respective four wall surfaces of the furnace  11 . The combustion burners  21   a ,  21   b ,  21   c ,  21   d  connect thereto respective branch pipes  26   a ,  26   b ,  26   c ,  26   d  branched from the pulverized coal feed pipe  26 , and connect thereto respective branch pipes  37   a ,  37   b ,  37   c ,  37   d  branched from the air duct  37 . 
     Accordingly, each of the combustion burners  21   a ,  21   b ,  21   c ,  21   d  arranged on the respective wall surfaces of the furnace  11  blows the fine powder fuel-air mixture of the transportation air and the pulverized coal into the furnace  11 , and blows the combustion air from the outside of the fine powder fuel-air mixture into the furnace  11 . Furthermore, the fine powder fuel-air mixtures supplied from the respective combustion burners  21   a ,  21   b ,  21   c ,  21   d  are ignited thus forming four flames F 1 , F 2 , F 3 , F 4 , and each of the flames F 1 , F 2 , F 3 , F 4  becomes the flame swirl flow that swirls in the counterclockwise direction as viewed from above the furnace  11  (in  FIG. 2 ). 
     In the combustion burner  21  ( 21   a ,  21   b ,  21   c ,  21   d ) constituted as above, as illustrated in  FIG. 3 ,  FIG. 4 , and  FIG. 5 , a fuel nozzle  51 , a combustion air nozzle  52 , and secondary air nozzles  53  are arranged in order from the center side of the combustion burner  21  and, at the same time, a flame stabilizer  54  and a flow straightener  55  are arranged. The fuel nozzle  51  is capable of blowing fuel gas (fine powder fuel-air mixture, primary air) such that the pulverized coal (solid fuel) and the transportation air (primary air) are mixed with each other, into the furnace  11 . The combustion air nozzle  52  that is arranged on the outside of the fuel nozzle  51  is capable of blowing the combustion air (combustion air, secondary air) from the outer periphery side of the fuel gas injected from the fuel nozzle  51 , into the furnace  11 . One of the secondary air nozzles  53  is arranged in a position on the outside of the combustion air nozzle  52  and on the upper side of the combustion air nozzle  52  in the perpendicular direction, and the other one of the secondary air nozzles  53  is arranged in a position on the outside of the combustion air nozzle  52  and on the lower side of the combustion air nozzle  52  in the perpendicular direction. In this case, the perpendicular direction also includes a direction inclined from the perpendicular direction by a minute angle. The secondary air nozzle  53  is not arranged in a position on the outside of the combustion air nozzle  52  and adjacent to the combustion air nozzle  52  in the horizontal direction. The secondary air nozzle  53  is capable of blowing the secondary air (auxiliary air (AUX)) from the outer periphery side of the combustion-gas combustion air injected from the combustion air nozzle  52 , into the furnace  11 . Furthermore, the secondary air nozzle  53  may be arranged in a position on the outside of the combustion air nozzle  52  and adjacent to the combustion air nozzle  52  in the horizontal direction. Furthermore, when the secondary air nozzle  53  is arranged in a position on the outside of the combustion air nozzle  52  and adjacent to the combustion air nozzle  52  in the horizontal direction, it is unnecessary to arrange the secondary air nozzle  53  in a position adjacent to the combustion air nozzle  52  in the perpendicular direction. The secondary air nozzle  53  may be arranged on each of four outside surfaces of the combustion air nozzle  52 . The secondary air nozzle  53  may include therein a damper opening adjustment mechanism or the like so that the amount of secondary air to be injected can be adjusted. 
     The combustion burner  21  has the fuel nozzle  51 , the combustion air nozzle  52 , an angle adjustment part  80 , and a duct part  82  connected to the angle adjustment part  80  in a slidable manner. The angle adjustment part  80  is located on the distal end of the fuel nozzle  51  of the combustion burner  21  and the combustion air nozzle  52 , and supported in a movable manner in a direction set with respect to the duct part  82 . The direction in which the angle adjustment part  80  can be moved is not limited particularly, and the angle adjustment part  80  may be supported in a movable manner in the axial direction of the furnace  11  (in the perpendicular direction), or supported in a movable manner in the sectional direction of the furnace  11  (in the horizontal direction). The combustion burner  21  adjusts the direction of the angle adjustment part  80  thus adjusting the direction in which the fine powder fuel-air mixture of the pulverized coal and the transportation air is blown into the furnace  11 . Furthermore, the angle adjustment part  80  has a proximal portion  84  to be moved with respect to the duct part  82 , the proximal portion  84  including a fulcrum, and a distal end portion  86  located on the distal end side of the proximal portion  84 , the distal end portion  86  constituting the end portion of the angle adjustment part  80  that is located close to the furnace  11 . The distal end portion  86  is fixed to the proximal portion  84  with a fastener jig, such as a screw. Here, the distal end portion  86  may be fixed to the proximal portion  84  by welding. 
     The duct part  82 , which is connected with the angle adjustment part  80 , forms therein respective passages corresponding to the fuel nozzle  51 , the combustion air nozzle  52 , and the secondary air nozzle  53 , and supplies the fuel gas such that pulverized coal and air are mixed with each other, and the combustion-gas combustion air to each part of the angle adjustment part  80 . The duct part  82  is formed in an elongated tubular shape. The combustion burner  21  may include an angle adjustment part also in the secondary air nozzle  53  so that the angle of the secondary air nozzle  53  with respect to the axial direction of the duct part  82  can be adjusted in an integral manner with the fuel nozzle  51 , and the combustion air nozzle  52 . Furthermore, the combustion burner  21  may be constituted so that the secondary air nozzle  53  is fixed against movement, and the angle of the secondary air nozzle  53  with respect to the axial direction of the duct part  82  is not capable of being changed. Furthermore, in the present embodiment, although the angle adjustment part  80  is provided, it may be possible to adopt the constitution in which the distal end portion  86  configured to inject the fuel gas and the combustion-gas combustion air is fixed so as not to be moved with respect to the duct part  82 . 
     The fuel nozzle  51  includes a straight pipe located on the distal end side thereof; that is, the straight pipe corresponds to the angle adjustment part  80 , and the sectional area (opening area) of the straight pipe in a direction orthogonal to the direction in which the fine powder fuel-air mixture is blown into the furnace  11  is made constant. The combustion air nozzle  52  includes a distal end portion corresponding to the angle adjustment part  80 , and the distal end portion is formed in a shape such that the distal end portion is shrunk in the direction toward the distal end of the combustion air nozzle  52 ; that is, the sectional area (opening area) of the distal end portion in a direction orthogonal to the direction in which the fine powder fuel-air mixture is blown into the furnace  11  is decreased in the direction toward the distal end of the combustion air nozzle  52 . That is, the combustion air nozzle  52  is formed in a shape such that an area surrounded by the outside surfaces of the combustion air nozzle  52  is decreased along with the extension of the combustion air nozzle  52  from the downstream side to the upstream side in the flow direction of the fuel gas. The secondary air nozzle  53  includes a distal end portion corresponding to the angle adjustment part  80 , and the distal end portion is formed in a shape such that the distal end portion is shrunk in the direction toward the distal end of the secondary air nozzle  53 ; that is, the sectional area (opening area) of the distal end portion in a direction orthogonal to the direction in which the fine powder fuel-air mixture is blown into the furnace  11  is decreased in the direction toward the distal end of the secondary air nozzle  53 . 
     Here, the shape of the opening of each of the fuel nozzle  51  and the combustion air nozzle  52  is not limited to a square shape, and a rectangular shape or a circular shape may be adopted. In this case, a shape whose corner portion is rounded may be adopted. A tubular structure whose corner portion is rounded, or a cylindrical structure is adopted thus improving the strength of the nozzle. 
     The flame stabilizer  54  is arranged in the fuel nozzle  51 , on the downstream side in the direction in which the fuel gas is blown into the furnace  11 , and on the axial center side of the fuel nozzle  51  thus functioning as a device for igniting the fuel gas, and as a device for flame stabilizing. The flame stabilizer  54  is fixed to the distal end portion  86  of the angle adjustment part  80 . The flame stabilizer  54  is constituted so that first flame stabilizing members  61 ,  62  each of which is formed along the horizontal direction, and second flame stabilizing members  63 ,  64 ,  65 ,  66  each of which is formed along the vertical direction (up-and-down direction) are arranged in a crossed manner; that is, the flame stabilizer  54  is formed of what is called a double cross split structure. Each of the first flame stabilizing members  61 ,  62  and the second flame stabilizing members  63 ,  64 ,  65 ,  66  has a wide width part whose width is increased in the direction toward the downstream side in the flow direction of the fuel gas. Each of the first flame stabilizing members  61 ,  62  and the second flame stabilizing members  63 ,  64 ,  65 ,  66  in the present embodiment is formed in an isosceles triangle shape as viewed in a sectional view, increased in width in the direction toward the downstream side in the flow direction of the fuel gas, and has a front end that constitutes a planar surface orthogonal to the flow direction of the fuel gas. 
     The flow straightener  55  is arranged in the inside of the fuel nozzle  51 , and arranged closer to the upstream side than the flame stabilizer  54  in the flow direction of the fuel gas. Furthermore, the flow straightener  55  is fixed to the proximal portion  84  of the angle adjustment part  80 . The flow straightener  55  is arranged in a spaced apart manner from the flame stabilizer  54  in the flow direction of the fuel gas. The flow straightener  55  straightens the flow of the fuel gas that flows in the inside of the fuel nozzle  51 . The flow straightener  55  has first straightening vanes  71 ,  72  each of which is formed along the horizontal direction, and second straightening vanes  73 ,  74 ,  75 ,  76  each of which is formed along the vertical direction (up-and-down direction). 
     Each of the first straightening vanes  71 ,  72  and the second straightening vanes  73 ,  74 ,  75 ,  76  is basically formed in a plate-like shape being constant in thickness. The first straightening vanes  71 ,  72  and the second straightening vanes  73 ,  74 ,  75 ,  76  are arranged in a crossed manner. The first straightening vane  71  is arranged in a position overlapping with an extension of the first flame stabilizing member  61  in the flow direction of the fuel gas. In the same manner as above, the first straightening vane  72  is arranged in a position overlapping with an extension of the first flame stabilizing member  62  in the flow direction of the fuel gas. In the same manner as above, the second straightening vane  73  is arranged in a position overlapping with an extension of the second flame stabilizing member  63  in the flow direction of the fuel gas. In the same manner as above, the second straightening vane  74  is arranged in a position overlapping with an extension of the second flame stabilizing member  64  in the flow direction of the fuel gas. In the same manner as above, the second straightening vane  75  is arranged in a position overlapping with an extension of the second flame stabilizing member  65  in the flow direction of the fuel gas. In the same manner as above, the second straightening vane  76  is arranged in a position overlapping with an extension of the second flame stabilizing member  66  in the flow direction of the fuel gas. 
     Next, in conjunction with  FIG. 6 , the structure of each of the flame stabilizer  54  and the flow straightener  55  is explained. Although the first flame stabilizing member  61  of the flame stabilizer  54  and the first straightening vane  71  of the flow straightener  55  are explained in conjunction with  FIG. 6 , each of the other flame stabilizing members and each of the other straightening vanes are also similar in structures to the first flame stabilizing member  61  and the first straightening vane  71 , respectively. As illustrated in  FIG. 6 , each of the first flame stabilizing member  61  and the first straightening vane  71  has an abrasion-resistant member arranged on the surface thereof. The first flame stabilizing member  61  has a base material  92 , and abrasion-resistant members  94  arranged on the respective surfaces of the base material  92 . The base material  92  is formed in an isosceles triangle shape, and has surfaces  93 , the legs of the isosceles triangle shape, which are arranged in symmetry. The abrasion-resistant member  94  is arranged in an extending manner over the surface  93 . The first straightening vane  71  has a base material  102 , and abrasion-resistant members  104  arranged on the respective surfaces of the base material  102 . The base material  102  is a plate member whose end portion  105  located on the upstream side in the flow direction of the fuel gas is formed in a triangle shape; that is, the end portion  105  is formed in a convex shape toward the upstream side in the flow direction of the fuel gas. That is, the end portion  105  is formed in a shape such that the width of the end portion  105  is decreased in the direction toward the upstream side in the flow direction of the fuel gas. The abrasion-resistant member  104  is arranged on a surface  103  of the base material  102  along the flow direction of the fuel gas, in an extending manner over the surface  103 ; that is, the abrasion-resistant member  104  is arranged on the surface  103  that is a surface having a largest area, in an extending manner over the surface  103 . Furthermore, an abrasion-resistant member  106  is arranged in an extending manner over the end portion  105 . 
     Each of the base materials  92 ,  102  can be, for example, formed of metal essentially composed of iron, such as stainless steel (SUS). The abrasion-resistant members  94 ,  104  are higher in abrasion resistances than the respective base materials  92 ,  102 , and ceramics, a high-chrome steel material, and a composite material in which ceramics is embedded with metal can be used for the abrasion-resistant members  94 ,  104 . When each of the abrasion-resistant members  94 ,  104  is, for example, made of ceramics, a plate made of ceramics is attached and fixed to the surface of each of the base materials  92 ,  102  thus arranging the abrasion resistant members  94 ,  104  on the respective surfaces of the base materials  92 ,  102 . Furthermore, when each of the abrasion-resistant members  94 ,  104  is, for example, made of high-chrome steel, a high-chrome steel plate is fixed to each of the base materials  92 ,  102  by electrodepositing or welding thus arranging the abrasion-resistant members  94 ,  104  on the respective surfaces of the base materials  92 ,  102 . 
     Each of the fuel nozzle  51  and the combustion air nozzle  52  has an elongated tubular structure, the fuel nozzle  51  has a rectangular-shaped opening, and the combustion air nozzle  52  has a rectangular ring-shaped opening. That is, the fuel nozzle  51  and the combustion air nozzle  52  constitute a double pipe structure. The respective secondary air nozzles  53  are arranged on the upper side and the lower side of the fuel nozzle  51  and the combustion air nozzle  52  in the vertical direction. As a result, the combustion air nozzle  52  is arranged on the outside of the opening of the fuel nozzle  51 , and the secondary air nozzle  53  is arranged on the outside of the combustion air nozzle  52 . 
     These nozzles  51 ,  52 ,  53  have the respective openings arranged coplanar with each other. Furthermore, the flame stabilizer  54  is supported by the inner wall surface of the fuel nozzle  51 , or a plate (not illustrated in the drawings) from the upstream side of a passage through which the fuel gas flows. Furthermore, the fuel nozzle  51  is provided with the first flame stabilizing members  61 ,  62  and the second flame stabilizing members  63 ,  64 ,  65 ,  66  as the flame stabilizer  54 , and the first straightening vanes  71 ,  72  and the second straightening vanes  73 ,  74 ,  75 ,  76  as the flow straightener  55  and hence, the passage of the fuel gas is divided into 15 areas. Furthermore, the flame stabilizer  54  is formed in a wedge shape such that the width of the flame stabilizer  54  is increased in the direction toward the front end portion of the flame stabilizer  54 , and the front end surface of the flame stabilizer  54  is coplanar with the opening of each of the nozzles  51 ,  52 ,  53 . Furthermore, the flow straightener  55  is formed in a plate shape, and extends in a direction along the angle adjustment part  80 . 
     Accordingly, in the combustion burner  21 , the fuel gas that is a mixture of pulverized coal and air is blown into the furnace  11  from the fuel nozzle  51  and, at the same time, the combustion-gas combustion air is blown into the furnace  11  from the combustion air nozzle  52  on the outside of the fuel nozzle  51 , and the secondary air is blown into the furnace  11  from the secondary air nozzle  53  on the outside of the combustion air nozzle  52 . The fuel gas that flows through the fuel nozzle  51  is straightened in a flow direction along the angle of the angle adjustment part  80  by the flow straightener  55 . The fuel gas that is straightened by the flow straightener  55  and blown into the furnace  11  is branched by the flame stabilizer  54  in the opening of the fuel nozzle  51 , and ignited thus burning the fuel gas and generating combustion gas. Furthermore, the combustion-gas combustion air is blown into the furnace  11  from the outer periphery of the fuel gas thus accelerating the combustion of the fuel gas. Furthermore, the secondary air is blown into the outer periphery of combustion flames, and the ratio of the combustion-gas combustion air to the secondary air is adjusted thus obtaining the optimum combustion. 
     Furthermore, in the combustion burner  21 , the flame stabilizer  54  is formed in a split shape and hence, the fuel gas is branched by the flame stabilizer  54  in the opening of the fuel nozzle  51 . In this case, the flame stabilizer  54  is arranged in a central area of the opening of the fuel nozzle  51 , and ignition of the fuel gas and flame stabilization of the fuel gas are performed in the central area. Consequently, internal flame stabilization (flame stabilization in the central area of the opening of the fuel nozzle  51 ) of combustion flames is achieved. 
     Accordingly, the outer peripheral portion of the combustion flames assumes low temperature as compared with a constitution where external flame stabilization of the combustion flames is performed, and oxygen consumption in the inside of flames causes a low oxygen state thus lowering the temperature of the outer peripheral portion of the combustion flames under a high oxygen atmosphere by the combustion-gas combustion air, and reducing a generation amount of NOx in the outer peripheral portion of the combustion flames. 
     Here, in the combustion burner  21 , the constitution that performs the internal flame stabilization is adopted and hence, it is preferable that each of the fuel gas and the combustion air (combustion-gas combustion air, and secondary air) be supplied as a rectilinear flow. That is, it is preferable that each of the fuel nozzle  51 , the combustion air nozzle  52 , and the secondary air nozzle  53  have a structure such that each of the fuel gas, the combustion-gas combustion air, and the secondary air supplied as a rectilinear flow in the burner axial direction without swirling the fuel gas, the combustion-gas combustion air, and the secondary air. Each of the fuel gas, the combustion-gas combustion air, and the secondary air is injected as a rectilinear flow to form the combustion flames and hence, in the constitution that performs the internal flame stabilization of the combustion flames, gas circulation in the combustion flames is suppressed. Consequently, the outer peripheral portion of the combustion flames is maintained in a low temperature state, and the generation amount of NOx due to the mixing of the fuel gas with the combustion-gas combustion air is reduced. As mentioned above, the combustion burner  21  reduces the flow velocity on a fuel-gas-flow inner side, and causes the flow velocity on a fuel-gas-flow outer side to be substantially equivalent to the flow velocity of a fuel gas flow from the combustion air nozzle  52  thus achieving an appropriate flow capable of suppressing the ignition in the outer periphery of the fuel gas flow. Consequently, it is possible to improve the internal flame stabilization performance so as to cause ignition to start from the inner side of the fuel gas relatively earlier than the outside of the fuel gas, and it is possible to suppress a high-temperature high-oxygen area in the boundary between the fuel gas and the combustion-gas combustion air thus reducing NOx. 
     The combustion burner  21  provides the respective abrasion-resistant members  104  to the flame stabilizer  54  and the flow straightener  55  that are arranged in the inside of the fuel nozzle  51  thus reducing the abrasion of the surfaces of the flame stabilizer  54  and the flow straightener  55  when the solid contents in the combustion gas are brought into contact with the flame stabilizer  54  and the flow straightener  55 . Furthermore, the abrasion-resistant member  94  is provided to the surface  93  of the first flame stabilizing member  61 , and the abrasion-resistant members  104 ,  106  are selectively arranged on the surface  103  and the end portion  105  of the first straightening vane  71 , respectively, thus arranging the abrasion-resistant members selectively on the portions where the abrasion is easily generated. To be, more specific, the abrasion-resistant member  94  is capable of suppressing the abrasion of the surface  93  with which the solid contents are easily brought into contact due to the wedge shape of the base materials  92 . The abrasion-resistant member  104  is capable of suppressing the abrasion of the surface  103  with which the solid contents are easily brought into contact when the angle of the angle adjustment part  80  is inclined toward the duct part  82 . The abrasion-resistant member  106 , which is arranged on the end portion  105 , is capable of suppressing the abrasion of the end portion  105  with which the solid contents are easily brought into contact. 
     Furthermore, the combustion burner  21  according to the present embodiment includes the flame stabilizer  54  and the flow straightener  55  in a spaced apart manner thus separately maintaining the flame stabilizer  54  and the flow straightener  55 . That is, the flame stabilizer  54  can be replaced independently, and the flow straightener  55  can also be replaced independently. As one example, in the combustion burner  21 , in a state that the flow straightener  55  is arranged in the inside of the combustion burner  21 , only the distal end portion of the combustion burner  21  is cut out, and detached by using a fixture thus replacing only the flame stabilizer  54 . Furthermore, in a state that the flame stabilizer  54  is arranged in the inside of the combustion burner  21 , the welded portion of the flow straightener  54  is cut out thus replacing only the flow straightener  54 . Consequently, a part to be replaced can be replaced selectively, and the number of parts to be replaced at the time of maintenance can be reduced thus improving maintainability. The number of the parts to be replaced can be reduced thus reducing the total weight of the parts to be replaced. Furthermore, in the combustion burner  21 , the distal end portion  86  is formed separately from the proximal portion  84  and hence, the flame stabilizer  54  and the flow straightener  55  are formed separately from each other thus also integrally replacing the distal end portion  86  and the flame stabilizer  54  fixed to the distal end portion  86 . Consequently, only the distal end portion  86  can be replaced thus achieving easy maintenance. 
     Here, the combustion burner  21  may constitute the structure according to the present embodiment at the time of manufacturing, and may constitute the structure according to the present embodiment at the time of maintenance. For example, when maintaining a combustion burner in which a flame stabilizer and a flow straightener differ in shape from the flame stabilizer  54  and the flow straightener  55  according to the present embodiment, respectively, the flame stabilizer may be replaced with the flame stabilizer  54  whose flame stabilizing member has the abrasion-resistant member on the wide width part thereof, and the flow straightener may be replaced with the flow straightener  55  whose straightening vane has the abrasion-resistant member on at least a part thereof. Here, also when maintaining the combustion burner  21  according to the present embodiment, the flame stabilizer is replaced with the flame stabilizer  54  whose flame stabilizing member has the abrasion-resistant member on the wide width part thereof, and the flow straightener is replaced with the flow straightener  55  whose straightening vane has the abrasion-resistant member on at least a part thereof. 
     In this manner, when maintaining a combustion burner, a flame stabilizer is replaced with another flame stabilizer whose flame stabilizing member has an abrasion-resistant member on the wide width part thereof, and a flow straightener is replaced with another flow straightener whose straightening vane has an abrasion-resistant member on at least a part thereof thus protecting the portion of the combustion burner that is easily worn, and improving the durability of the combustion burner. Furthermore, the abrasion-resistant member is selectively arranged thus decreasing time and efforts for arranging the abrasion-resistant member at the time of maintenance, and easily maintaining the combustion burner. Consequently, it is possible to maintain high durability, and achieve easy maintenance. 
     Furthermore, the combustion burner  21  includes the flame stabilizer  54  and the flow straightener  55  in a spaced apart manner thus reducing the arrangement area of the flow straightener  55  compared with a case Where the flame stabilizer  54  and the flow straightener  55  are integrally formed with each other. Consequently, it is possible to reduce the area in which the abrasion-resistant member is arranged. 
     Here, although the flame stabilizer according to the present embodiment has a triangular sectional shape, the present invention is not limited to this example, and a rectangular sectional shape may be applicable. Furthermore, in the above-mentioned embodiment, although the combustion burner  21  has a quadrangular sectional shape, a circular sectional shape, or other polygonal sectional shapes may be applicable. 
       FIG. 7  is a schematic view illustrating a schematic structure of a modification of the flame stabilizing member and the straightening vane. A first flame stabilizing member  61   a  and a first straightening vane  71   a  that are illustrated in  FIG. 7  have abrasion-resistant members on the respective surfaces thereof. The first flame stabilizing member  61   a  is formed in a trapezoidal shape in which a downstream-side surface and an upstream-side surface in the flow direction of the fuel gas constitute an upper base and a lower base, respectively. That is, the first flame stabilizing member  61   a  is formed in a shape in which a part of the vertex side of an isosceles triangle is cut off along a surface parallel to the base of the isosceles triangle (a planar surface orthogonal to the flow direction of the fuel gas). In the first flame stabilizing member  61   a , the abrasion-resistant member is formed on a surface  93   a , and the abrasion-resistant member is not formed on a surface  95 . Here, the abrasion-resistant member may be formed on the surface  95 . 
     In the first straightening vane  71   a , an end portion  105   a  that constitutes the rear end of the base material  102  (the end portion on the upstream side in the flow direction of the flue gas) is a planar surface orthogonal to the flow direction of the fuel gas. The first straightening vane  71   a  has an abrasion-resistant member  106   a  on the end portion  105   a  thereof. The abrasion-resistant member  106   a  is formed in a rod-like shape, and can be attached to the base material  102 . 
     In the first flame stabilizing member  61   a , the end portion located on the flow straightener  55  side constitutes a planar surface orthogonal to the flow direction of the fuel gas, thus changing the direction of the solid contents brought into contact with the first flame stabilizing member  61   a , and reducing the solid contents to be brought into contact with the other portions. Consequently, it is possible to reduce the solid contents to be brought into contact with the flame stabilizer  54 , and improve the abrasion resistance of the flame stabilizer  54 . 
     Furthermore, in the first straightening vane  71   a , the end portion located on the flow straightener  55  side constitutes a planar surface orthogonal to the flow direction of the fuel gas thus preventing the solid contents from being brought into rubbing contact with the surface of the end portion, and reducing the abrasion of the end portion. Furthermore, in the first straightening vane  71   a , the end portion  105   a  constitutes a planar surface thus decelerating the solid contents brought into contact with the end portion  105   a  at the end portion  105   a  and thereafter, moving the solid contents along the flow direction of the fuel gas. That is, in the first straightening vane  71   a , the end portion  105   a  constitutes the planar surface thus changing the direction of movement of the solid contents brought into contact with the end portion  105   a  of the first straightening vane  71   a , and preventing the solid contents from moving towards other portions arranged in respective positions facing the first straightening vane  71   a . Namely, the first straightening vane  71   a  changes the direction of movement of the solid contents brought into contact with the end portion  105   a  while maintaining the speed of the solid contents thus preventing the solid contents from being brought into contact with the other portions of the first straightening vane  71   a  after the contact of the solid contents with the end portion  105   a . Consequently, it is possible to decrease the contact of the solid contents brought into contact with the end portion  105   a , with the other portions of the first straightening vane  71   a . Consequently, it is possible to reduce the solid contents to be brought into contact with the flame stabilizer  54 , and improve the abrasion resistance of the flame stabilizer  54 . 
     Furthermore, in  FIG. 7 , although the first flame stabilizing member  61   a  and the first straightening vane  71   a  are included, it is unnecessary to include the first straightening vane  71   a , and a structure provided with only the first flame stabilizing member  61   a  may be adopted. The first straightening vane  71   a  is not arranged thus reducing the number of components to be maintained. 
       FIG. 8  is a schematic view illustrating a schematic structure of a combustion burner according to another embodiment.  FIG. 9  is an enlarged schematic view illustrating a connection portion between a straightening vane and a combustion nozzle of the combustion burn illustrated in  FIG. 8 . The combustion burner  21   a  illustrated in  FIG. 8  and  FIG. 9  has a first flame stabilizing member  61   b , and a first straightening vane  71   b . The first flame stabilizing member  61   b  is similar in structure to the first flame stabilizing member  61 . The first straightening vane  71   b  is fixed to the fuel nozzle  51  at the end portion thereof in the horizontal direction (in a direction orthogonal to the flow direction of the fuel gas). The first straightening vane  71   b  and the fuel nozzle  51  are connected with each other by way of a support mechanism  120 . The first straightening vane  71   b  has a base material  102   b , and respective abrasion-resistant members  104   b  arranged on both sides of the base material  102   b . The base material  102   b  is sandwiched between two abrasion-resistant members  104   b . In the first straightening vane  71   b , in the horizontal direction, two abrasion-resistant members  104   b  project to the fuel nozzle  51  side from the base material  102   b . Consequently, the first straightening vane  71   b  forms a recessed portion  122  surrounded by the base material  102   b  and two abrasion-resistant members  104   b  in the horizontal end portion thereof. The fuel nozzle  51  has a projection portion  124  arranged in a position corresponding to the recessed portion  122 . 
     The support mechanism  120  includes the projection portion  124  in the recessed portion  122  located between two abrasion-resistant members  104   b  and hence, the first straightening vane  71   b  is supported with respect to the fuel nozzle  51 . The first straightening vane  71   b  is fixed to the fuel nozzle  51  by welding, screwing, or the like. 
     The combustion burner  21   a  is constituted in such a manner that the support mechanism  120  has a structure such that the projection portion  124  of the fuel nozzle  51  is sandwiched between the abrasion-resistant members  104   b  thus covering the projection portion  124  of the fuel nozzle  51  with the abrasion-resistant members  104   b . Consequently, it is possible to bring the combustion burner  21   a  into a state in which the projection portion  124  is not exposed in the inside of the fuel nozzle  51 , and it is possible to suppress the deterioration of the projection portion  124 . Consequently, the deterioration of the projection portion  124  can be prevented thus using the projection portion  124  as it is when replacing the abrasion-resistant members  104   b , and achieving easy maintenance. Furthermore, the combustion burner  21   a  is brought into a state in which the projection portion  124  is not exposed and hence, the process for protecting the projection portion  124  against abrasion becomes unnecessary. Consequently, it is possible to decrease an area subject to an abrasion-resistant treatment, and it is possible to achieve easy maintenance. 
       FIG. 10  is a sectional view illustrating a combustion burner of still another embodiment.  FIG. 11  is a sectional view taken along line C-C in  FIG. 10 , the sectional view illustrating the combustion burner of the still another embodiment.  FIG. 12  is a schematic view illustrating a schematic structure of a flame stabilizing member and a straightening vane of the combustion burner illustrated in  FIG. 10 . Although  FIG. 12  illustrates only a first flame stabilizing member  61   c  of the flame stabilizer  54  and a first straightening vane  71   c  of a flow straightener  55 , the other flame stabilizing member and the other straightening vane are also similar in structure to the first flame stabilizing member  61   c  and the first straightening vane  71   c , respectively. The combustion burner  21   b  illustrated in  FIG. 10  to  FIG. 12  has a flame stabilizer  54   a , and a flow straightener  55   a . The combustion burn  21   b  is similar in structure to the combustion burner  21  except for the flame stabilizer  54   a  and the flow straightener  55   a . Furthermore, the flame stabilizer  54   a  and the flow straightener  55   a  are also explained mainly in terms of the constitution that makes the flame stabilizer  54   a  and the flow straightener  55   a  different from the flame stabilizer  54  and flow straightener  55 , respectively. 
     In the combustion burner  21   b , the flame stabilizer  54   a  and the flow straightener  55   a  are integrally formed with each other. The flame stabilizer  54   a  is constituted so that first flame stabilizing members  61   c ,  62   c  each of which is formed along the horizontal direction, and second flame stabilizing members  63   c ,  64   c ,  65   c ,  66   c  each of which is formed along the vertical direction (up-and-down direction) are arranged in a crossed manner. Each of the first flame stabilizing members  61   c ,  62   c  and the second flame stabilizing members  63   c ,  64   c ,  65   c ,  66   c  is formed in a wedge shape whose width is increased in the direction toward the downstream side in the flow direction of the fuel gas. 
     The flow straightener  55   a  has first straightening vanes  71   c ,  72   c  each of which is formed along the horizontal direction, and second straightening vanes  73   c ,  74   c ,  75   c ,  75   c  each of which is formed along the vertical direction (up-and-down direction). The first straightening vanes  71   c ,  72   c  and the second straightening vanes  73   c ,  74   c ,  75   c ,  76   c  are, at the respective end portions thereof located on the downstream side in the flow direction of the flue gas, fixed to the first flame stabilizing members  61   c ,  62   c  and the second flame stabilizing members  63   c ,  64   c ,  65   c ,  66   c  that are arranged on the respective extensions thereof, respectively. 
     The respective structures of the flame stabilizer  54   a  and the flow straightener  55   a  are explained. As illustrated in  FIG. 10  to  FIG. 12 , the straightening vane of the flow straightener  55   a , the first straightening vane  71   c  in  FIG. 12 , has an abrasion-resistant member  104   c  on a part located on the upstream side in each surface thereof that is parallel to the flow direction of the fuel gas. That is, the first straightening vane  71   c  has a surface  107 , which is a part of the surface of a base material  102   c , located on the downstream side (flame stabilizer  54   a  side) in the surface thereof that is parallel to the flow direction of the fuel gas, the surface  107  being an exposed area. The base material  102   c  has a stepped portion between the surface  107  and a surface  103   c , a step height between the surface  107  and the surface of the abrasion-resistant member  104   c  becomes small, and the surface  107  and the surface of the abrasion-resistant member  104   c  are preferably coplanar with each other. Consequently, it is possible to further enhance the advantageous effect of the straightening vane straightening the flow of the fuel gas. 
     In the first straightening vane  71   c , when the length (overall length) of the first straightening vane  71   c  in the flow direction of the fuel gas is indicated by a symbol L 1 , and the length of the abrasion-resistant member  104   c  (the length from the end portion on the upstream side to the end portion on the downstream side in the area where the abrasion-resistant member  104   c  is arranged) is indicated by a symbol L 2 , it is preferable that the ratio of L 2  to L 1  be such that L 2 /L 1 ≤50%. For example, it is preferable that the ratio of L 2  to L 1  be such that L 2 /L 1 =⅓. Furthermore, the abrasion-resistant member  104   c  attaches a plate  150  formed in a panel-like shape to the base material  102   c . The plate  150  is a hardfacing plate, which is a plate formed of metal higher in abrasion resistance than the base material, such as high-chrome steel or the like, by buttered welding. In this manner, the plate  150  is used thus covering a larger area with one plate, and fixing the abrasion-resistant member  104 C to the base material  102 C in a shorter time, compared with the case where the plate-like member made of ceramics is used. 
     In the combustion burner  21   b , the abrasion-resistant member is arranged on a part of the straightening vane on the upstream side in the flow direction of the fuel gas; that is, the abrasion-resistant member is not arranged on the downstream side in the flow direction of the fuel gas thus reducing an area where a countermeasure against abrasion is to be taken. The area where the countermeasure against abrasion is to be taken is reduced thus reducing the treatments of the countermeasure against abrasion to be applied to the straightening vane, also when replacing the straightening vanes at the time of maintenance. Consequently, works at the time of maintenance can be reduced thus achieving easy maintenance. Furthermore, the straightening vane is hardly worn on the downstream side thereof compared with the upstream side thereof. Consequently, even when a structure such that the abrasion-resistant member is not arranged on the downstream side of the straightening vane is adopted, it is possible to suppress the lowering of the abrasion resistance of the straightening vane as a whole, and it is possible to use the combustion burner  21   b  for a long time. 
     In the present embodiment, although the structure such that the flame stabilizer  54   a  and the flow straightener  55   a  are connected with each other is adopted, as described in the above-mentioned embodiment, the flame stabilizer  54   a  and the flow straightener  55   a  may be arranged in a spaced apart manner. The flame stabilizer  54   a  and the flow straightener  55   a  are arranged in a spaced apart manner thus acquiring the above-mentioned advantageous effect. 
       FIG. 13  is a schematic view illustrating a schematic structure of a modification of the straightening vane illustrated in  FIG. 12 . A straightening vane  171  illustrated in  FIG. 13  has the base material  102  and an abrasion-resistant member  173 . The abrasion-resistant member  173  has a structure such that a ceramic portion  175  is embedded around a metal portion  176  formed in a projection shape. The abrasion-resistant member  173  is manufactured as a structure such that the metal portion  176  is formed in a projection shape by casting or the like. The ceramic portion  175  is embedded on the surface of the structure having the metal portion  176  thus manufacturing the abrasion-resistant member  173 . In this manner, the structure such that ceramics and metal, such as high-chrome steel, exist together with each other in the abrasion-resistant member  173  is adopted thus improving the abrasion resistance of the abrasion-resistant member  173 . 
       FIG. 14  is a schematic view illustrating a schematic structure of a combustion burner of still another embodiment. A first straightening vane  71   d  illustrated in  FIG. 14  is provided with a permanent magnet  180  extending over the whole area thereof in the thickness direction. Furthermore, a first flame stabilizing member  61   d  is provided with a permanent magnet  181  extending over the whole area thereof in the thickness direction. In the combustion burner illustrated in  FIG. 14 , the first straightening vane  71   d  and the first flame stabilizing member Sid are provided with the permanent magnets  180 ,  181  extending over the respective whole areas thereof in the thickness direction and hence, the first straightening vane  71   d  and the first flame stabilizing member  61   d  assume respective states in which the permanent magnets  180 ,  181  are worn by the solid contents in the combustion gas. 
     In the combustion burner illustrated in  FIG. 14 , a magnetic force detector  182  is arranged on the outside of the combustion air nozzle  52  or the secondary air nozzle  53  to detect the magnetic force of the permanent magnet  180 , or  181  thus detecting the magnetic force that varies by the abrasion of the permanent magnet  180 , or  181 . Consequently, the combustion burner is provided with the permanent magnets  180 ,  181  thus detecting the abrasions of the permanent magnets  180 ,  181  in the area in which the flame stabilizer and the straightening vane are arranged, from the outside of the fuel nozzle  51 . Furthermore, the correlative relations between the abrasions of the permanent magnets  180 ,  181  and the respective abrasions of the first straightening vane  71   d  and the first flame stabilizing member  61   d  are acquired in advance thus detecting the abrasion states of the first straightening vane  71   d  and the first flame stabilizing members  61   d . In this manner, the abrasion state is detectable from the outside of the fuel nozzle  51  thus determining the necessity of maintenance, and performing the maintenance at an appropriate timing. The maintenance can be performed at an appropriate timing thus suppressing the occurrence of unnecessary maintenance, and achieving a simple maintenance work. For example, to consider a case where an abrasion loss is detected, when the abrasion loss is not less than a predetermined value; to be more specific, when the thickness of a straightening vane or a flame stabilizing member is insufficient to withstand until a next periodical inspection, the component whose abrasion loss is measured is replaced, and when the abrasion loss is less than a predetermined value, the component whose abrasion loss is measured is not replaced and hence, it is possible to efficiently perform the replacement of the component. Furthermore, the magnetic force detector  182  is not always necessary to be arranged in the combustion burner, and can also be arranged at the time of inspection Or the like to measure the magnetic force. 
     Here, it is preferable to arrange the permanent magnets  181 ,  182  in respective less-wearing portions of the first straightening vane  71   d  and the first flame stabilizing members  61   d ; for example, in a portion located on the first flame stabilizing member  61   d  side of the first straightening vane  71   d , or in an inclined face of the first straightening vane  71   d.    
     Here, in the combustion burner  21  according to the present embodiment, although the end portion on the downstream side of the flame stabilizer  54  is located at the end portion on the downstream side of the fuel nozzle  51  in the flow direction of the fuel gas; that is, although the end portion on the downstream side of the flame stabilizer  54  is located at a position overlapping with the opening of the combustion burner  21 , the present invention is not limited to this example. In the combustion burner  21 , the flame stabilizer  54  may be arranged on the distal end side of the fuel nozzle  51 . Here, the distal end of the combustion burner  21  includes a flame-stabilizable area that is not damaged by radiation from the furnace in the inside of the nozzle portion of the fuel nozzle  51 , in addition to the distal end surface of the fuel nozzle  51 . When the combustion burner  21  is, as described in the present embodiment, provided with the angle adjustment part  80 , it is preferable to arrange the flame stabilizer  54  in the inside of the angle adjustment part  80 . 
     Furthermore, although the combustion burner  21  according to the present embodiment has the respective abrasion-resistant members on two surfaces of the flame stabilizing member that face each other, and on two surfaces of the straightening vane that face each other, the abrasion-resistant member may be arranged only in one surface. For example, when the combustion burner  21  has a structure in which the angle adjustment part  80  is not arranged, and the combustion burner  21  is arranged in such a manner that the combustion burner  21  is inclined with respect to the duct part  82 , the abrasion-resistant member may be arranged on a surface inclined to make an angle smaller than 180° with respect to the axis of the duct part  82 . 
     Although the explanation has been made with respect to an example that uses pulverized coal as a combustion fuel, the present invention is not limited to this example that uses pulverized coal (solid fuel), and the combustion fuel may be a fuel including solid contents; that is, the combustion fuel may be a fuel, such as biomass, residues, or petroleum cokes, or two or more kinds of these fuels may be used for multi-fuel combustion. 
     Furthermore, in each of the embodiments mentioned above, although the combustion device  12  is constituted so that four combustion burners  21  ( 22 ,  23 ,  24 ,  25 ) are arranged on the respective four wall surfaces of the furnace  11 , and five sets of four combustion burners ( 21 ,  22 ,  23 ,  24 ,  25 ) are arranged in five stages along the vertical direction, the present invention is not limited to this constitution. That is, it is unnecessary to arrange the combustion burner on the wall surface, and the combustion burner may be arranged at the corner of the furnace. Furthermore, the combustion device may be not only a swirl combustion-type combustion device but also a front combustion-type combustion device in which one combustion device is arranged on one wall surface, or an opposed firing-type combustion device in which two combustion devices are arranged on respective two wall surfaces to face each other in an opposed manner. 
     REFERENCE SIGNS LIST 
       10  Pulverized coal fired boiler 
       11  Furnace 
       21 ,  22 ,  23 ,  24 ,  25  combustion burner 
       51  Fuel nozzle 
       52  Combustion air nozzle 
       53  Secondary air nozzle 
       54  Flame stabilizer 
       61 ,  62  First flame stabilizing member 
       63 ,  64 ,  65 ,  66  Second flame stabilizing member 
       71 ,  72  First straightening vane 
       73 ,  74 ,  75 ,  76  Second straightening vane 
       80  Angle adjustment part 
       82  Duct part