Patent Publication Number: US-2011053102-A1

Title: Solid fuel burner, combustion apparatus using solid fuel burner, and method of operating the combustion apparatus

Description:
TECHNICAL FIELD 
     The present invention relates to a solid fuel burner suitable for pulverizing a solid fuel, carrying by gas flow, performing suspension burning, and a combustion apparatus using the solid fuel burner and a method of operating the same. 
     BACKGROUND ART 
     In combustion apparatuses (boilers, etc.), the steam temperature and pressure are increased and a reheating cycle is used for high efficiency. Normally, water supplied to a boiler passes through a heat transfer tube installed along a furnace wall surface and vaporizes, and passes through a superheater, becomes main steam and drives a steam turbine, and then becomes reheating steam and passes through a reheater, and is reheated and drives the steam turbine again, passes through a condenser and becomes water, and is supplied to the furnace again. 
     Thus, when the s team passes through a complicated fluid channel, it is important to obtain a prescribed heat-transfer amount at each heat-transfer portion. To obtain the prescribed heat-transfer amount, the temperature and flow rate of combustion gas at each heat transfer portion have to be controlled. 
     As a method of controlling the temperature and flow rate of the combustion gas, there is a conventional method in which a temperature distribution inside a furnace is controlled by vertically changing the ejection direction of fuel from the burner (Prior art document 1). There is also known a method in which on the downstream portion of a furnace, the combustion gas passage is divided, and the heat-transfer amount of the heat transfer portion installed in each combustion gas passage is adjusted by controlling the combustion gas amount flowing in each passage by using a means such as a damper. 
     PRIOR ART DOCUMENT 
     U.S. Pat. No. 6,439,136 (FIG. 3) 
     SUMMARY OF THE INVENTION 
     Problems to be solved by the Invention 
     In the conventional techniques described above, the direction of the fuel nozzle has to be mechanically changed when changing the ejection direction of fuel from the burner. Therefore, there was a problem of an increase in size of a drive mechanism. Especially, when a solid fuel is used as a fuel, wearing of a member for mechanically changing the direction of the fuel nozzle and ash adhesion must be taken into consideration to mechanically change the direction of the fuel nozzle. Moreover, the portion facing the furnace have to be provided with a drive mechanism to change the fuel ejection direction from the fuel nozzle, and thermal deformation of the drive mechanism must be taken into consideration as well. 
     Ash adhesion in the combustion gas in the combustion gas passage for supplying fuel to the fuel nozzle must be taken into consideration sufficiently when the gas passage is divided and the combustion gas amount flowing in each gas passage is changed. Further, partitions are provided, and accordingly, the passages are narrowed, so that installation of the heat transfer portions must be sufficiently considered. 
     An object of the present invention is to provide a solid fuel burner which can keep constantly the combustion gas temperature at a furnace outlet, the temperatures of a heat transfer tube installed on a furnace wall surface and a heat transfer tube provided in a flue on the downstream side thereof, and the temperature of a fluid flowing in the heat transfer tubes by changing a flame forming position inside the furnace by controlling the direction of the fuel to be ejected to the furnace from the solid fuel burner vertically or horizontally by an air flow rate flowing in the air nozzle with a comparatively simple structure, and a combustion apparatus using the solid fuel burner and a method of operating the same. 
     Means for Solving the Problems 
     To achieve the object of the present invention, according to the present invention, a solid fuel burner includes: a fuel nozzle which ejects a mixture fluid of a solid fuel and its conveying gas, and at least one air nozzle which is disposed on the outer side of the fuel nozzle and ejects combustion air, wherein at least one air nozzle is formed to be annular on the outer periphery of the fuel nozzle, and the internal air passage is divided into a plurality of regions in the circumferential direction of the nozzle by an obstacle, and the solid fuel burner has means of regulating a flow rate for regulating a flow rate in at least one of the plurality of regions. 
     By dividing the air nozzle into a plurality of regions and changing the air flow rates in the respective regions, deviations of flow rate and momentum can be generated, in the flow ejected from the air nozzle, in the circumferential direction of the fuel nozzle. 
     For example, when the air volume flowing in the air nozzle on the lower side of the fuel nozzle is increased, the flow rate and flow velocity of air increase and the momentum increases at the nozzle outlet. At this time, ejected air involves ambient gasses and a negative pressure is generated in the region on the lower side of the fuel nozzle. Therefore, in the pressure distribution in the circumferential direction around the fuel nozzle, the negative pressure increases in the region on the lower side of the fuel nozzle. Accordingly, depending on the pressure distribution, a downward force is applied to the fuel ejected from the fuel nozzle into the furnace, and the fuel flows while being deflected downward, and a flame is formed at a lower portion inside the furnace than usual. 
     Therefore, the temperature distribution inside the furnace is biased to the lower side, the amount of heat absorption in the furnace increases, and the heat absorption in a heat transfer tube provided in a flue on the downstream side of the furnace can be reduced. 
     On the contrary, when the air flow rate in the air nozzle on the upper side of the fuel nozzle is increased, a flame is formed inside the furnace at an upper portion than usual and the temperature distribution inside the furnace is biased to the upper side than usual, and the amount of heat absorption in the furnace is reduced and the heat absorption in the heat transfer tube provided on the downstream portion of the furnace can be increased. 
     When the air nozzle is divided into a plurality of regions in the circumferential direction of the fuel nozzle as described above, an obstacle connected to the partition walls have to be provided in the radial direction of the air nozzle to connect the inner peripheral side partition wall and the outer peripheral side partition wall. However, in the solid fuel burner, the distance between the inner peripheral side partition wall and the outer peripheral side partition wall of the air nozzle may change during the operation of a combustion apparatus (boiler, etc.) due to an influence of thermal expansion, etc. For example, normally, the outer peripheral side partition wall of the passage on the outermost peripheral side of the solid fuel burner is formed of a partition wall or a water wall of a furnace body constituting a furnace. 
     On the other hand, the inner peripheral side partition wall of the passage on the outermost peripheral side of the solid fuel burner is connected to a wind box to which the fuel nozzle or the burner is connected. The partition wall or water wall of the furnace body constituting the furnace is different in temperature from that of the fuel nozzle and the wind box during the operation of the combustion apparatus (boiler, etc.), so that they are different in ratio of thermal expansion. Therefore, in the solid fuel burner, the relative positions of the partition wall or water wall of the furnace body on the outer peripheral side of the air nozzle or the partition wall connected thereto (the partition wall of the furnace body side) and the partition wall (the partition wall of the fuel nozzle side) connected to the fuel nozzle or the wind box on the inner peripheral side change according to temperature. Therefore, it is difficult to divide the passage in the circumferential direction by providing an obstacle in the radial direction connecting the partition wall of the inner peripheral side and the partition wall of the outer peripheral side constituting the air nozzle. 
     Therefore, in the present invention, as a method of dividing the inside of the air nozzle into a plurality of regions in the circumferential direction (the direction crossing the gas flow), the structure shown as any of the following (A) to (C) was used. 
     (A) A structure has an obstacle which divides the inside of an air nozzle formed annularly into a plurality of regions in the circumferential direction, and the obstacle is connected to the partition wall of the inner peripheral side of the air nozzle, and is not connected to the partition wall of the outer peripheral side. The structure has means of regulating a flow rate for regulating the flow rate in at least one of the plurality of regions of the air nozzle, and a flow rate deviation is generated in the circumferential direction of the fuel nozzle in the flow ejected from the air nozzle. 
     In this case, a part of the air passes through the clearance between the obstacle and the partition wall of the outer peripheral side, however, most of the air remains in the same region. In the pressure distribution in the circumferential direction around the fuel nozzle caused by involving ambient gasses in the air flow ejected from the air nozzle into the furnace, a deviation is generated according to the flow rate deviation. Therefore, the fuel ejected from the fuel nozzle flows while deflecting to the side with a larger air volume ejected from the air nozzle. 
     (B) A structure has an obstacle which divides the inside of the air nozzle formed annularly into a plurality of regions in the circumferential direction, and the obstacle is connected to the partition wall of the outer peripheral side of the air nozzle, and is not connected to the partition wall of the inner peripheral side. The structure has means of regulating a flow rate for regulating the flow rate in at least one of the plurality of regions of the air nozzle, and a flow rate deviation is generated in the circumferential direction of the fuel nozzle in the flow ejected from the air nozzle. 
     In this case, a part of the air passes through the clearance between the obstacle and the partition wall of the inner peripheral side, however, most of the air remains in the same region. Therefore, like the method (A), the fuel ejected from the fuel nozzle flows while deflecting to the side with a larger air volume ejected from the air nozzle. 
     (C) A structure has an obstacle which divides the inside of the air nozzle formed annularly into a plurality of regions in the circumferential direction, and the obstacle includes an obstacle which is connected to the partition wall of the outer peripheral side of the air nozzle and is not connected to the partition wall of the inner peripheral side, and an obstacle which is connected to the partition wall of the inner peripheral side of the air nozzle and is not connected to the partition wall of the outer peripheral side. The structure has means of regulating a flow rate for regulating the flow rate in at least one of the plurality of regions of the air nozzle, and a flow rate deviation is generated in the circumferential direction of the fuel nozzle in the flow ejected from the air nozzle. 
     In this case, a part of the air passes through the clearance between the obstacle and the partition wall of the inner or outer peripheral side, however, most of the air remains in the same region. Therefore, like the methods (A) and (B), the fuel ejected from the fuel nozzle flows while deflecting to the side with a larger air volume ejected from the air nozzle. 
     The obstacles described in (A) to (C) above which divides the inside of the air nozzle into a plurality of regions in the circumferential direction are not limited to a configuration in which combustion air passes through the clearance between the obstacles and the air nozzle wall surface shown in  FIG. 8  to  FIG. 10 , but may have a configuration in which the obstacle forms a closed space opened only at an inlet and an outlet in the combustion air flow direction, and combustion air is made to flow inside the closed space from the burner upstream side to the furnace side (The air nozzles for the combustion air may be called as divided air nozzles). A specific example of that is the tertiary air nozzles  12  and  13  formed by connecting and unifying two obstacles connected to the inner peripheral wall of the air nozzle shown in  FIG. 3  and  FIG. 4 , and these are an embodiment of the air nozzle described in (A) above. Further, divided air nozzles formed by connecting and unifying two obstacles connected to the outer peripheral wall of the air nozzle described in (B) are also included in the scope of the present invention. 
     By regulating the air flow rate flowing in at least one air nozzle of the divided air nozzles disposed on the outer side of the fuel nozzle by means of regulating a flow volume, a flow rate deviation is generated in the circumferential direction of the fuel nozzle in the flows ejected from the divided air nozzles. Therefore, the fuel ejected from the fuel nozzle flows while deflecting to the side with a larger air volume ejected from the air nozzle. 
     By disposing the divided air nozzles positioned on the outer side of the fuel nozzle on the upper and lower sides of the fuel nozzle and regulating the flow rates and jet flow velocities of air ejected from the respective upper and lower air nozzles to the inside of the furnace, the momentum obtained as a product of the air flow rate and the jet flow velocity becomes different in the vertical direction of the burner outlet, and the air flow rates ejected from the upper and lower air nozzles of the burner can be individually controlled in the vertical direction inside the furnace at the burner outlet. Therefore, the temperature distribution inside the furnace differs in the vertical direction of the burner outlet, and the heat absorption in the furnace and the heat absorption in a heat transfer tube provided in a flue on the downstream side of the furnace change. 
     Thus, by the divided air nozzles provided on the upper and lower sides of the fuel nozzle, the controllability of the air flow rate in the burner is enhanced. 
     Further, by combination use of the divided air nozzles shown in  FIG. 3  and  FIG. 4  and an air nozzle to which two obstacles are not connected each other (not the divided ones) shown in  FIG. 8  to  FIG. 10 , deviations in air flow rate and momentum can be encouraged. 
     Moreover, the configuration may be such that, in addition to the annular air nozzle, an air nozzle is disposed on the outer side of the annular nozzle and an obstacle which divides the inside of the annular air nozzle into a plurality of regions in the circumferential direction is disposed, and means of regulating a flow rate for regulating the air volume to be ejected from the air nozzle on the outer side of the annular nozzle is provided. 
     Also, the solid fuel burner of the present invention may also be configured so that the fuel nozzle outlet is shaped into a wide-width nozzle which is relatively short in one direction and is relatively long in the opposite direction at the fuel nozzle outlet (The length in one radial direction of the section in a direction crossing the passage of the fuel nozzle is longer than that in the other radial direction of the two directions orthogonal to each other), and an inner peripheral partition wall constituting at least one passage of the air nozzle also differs in length in the two directions orthogonal to each other, and the outer peripheral partition wall does not differ in length in the two directions orthogonal to each other. 
     By shaping the fuel nozzle outlet into the wide-width nozzle shape, the fuel ejected from the fuel nozzle easily scatters in the long side direction. For example, when the long side direction is orthogonal to the gas flow direction in the combustion apparatus (furnace), by scattering the fuel inside the furnace, the space inside the furnace can be effectively utilized and the fuel retention time in the furnace can be made longer than conventional method. Therefore, the discharge amount of nitrogen oxide (NOx) can be reduced, and unburned fuel can also be reduced. 
     Further, by adopting the configuration in which the fuel nozzle outlet is formed into a wide-width nozzle shape, and the inner peripheral partition wall constituting at least one air passage in the air nozzle differs in length in the long side direction and the short side direction, and the outer peripheral partition wall does not differ in length in the two directions orthogonal to each other, the thickness in one of the two directions orthogonal to each other of the section in a direction crossing the passage of the air nozzle increases. Therefore, when an air flow rate deviation is generated at the thicker portion, due to the large air flow rate, according to the deviation in air flow rate ejected from the air nozzle into the furnace, the fuel jet flow from the fuel nozzle can be easily guided. 
     In particular, in a combustion apparatus (furnace) in which combustion gas flows in the vertical direction, the outlet of the fuel nozzle of the solid fuel burner is formed into a shape with a longer side set in the horizontal direction, that is, a wide-width nozzle shape, and the thickness of the air nozzle described above is increased in the vertical direction, and a deviation in fuel flow rate is generated in the vertical direction, accordingly, the direction of the fuel jet flow from the solid fuel burner can be changed in the vertical direction. At this time, the retention time of combustion gas flowing in the combustion apparatus (furnace) changes, so that the heat transfer amount in the combustion apparatus changes, and the temperature of the combustion gas at the outlet can be changed. 
     Further, the solid fuel burner of the present invention is preferably provided with a ring for stabilizing flame as an obstacle for obstructing a flow of a mixture fluid flowing in the fuel nozzle or a flow of air flowing in the air nozzle, at the tip end of the outer peripheral side partition wall of the fuel nozzle or the tip end of the inner peripheral side partition wall of the air nozzle which includes the fuel nozzle. 
     By providing a ring for stabilizing flame which becomes an obstacle for flows of fuel and air ejected from respective nozzles on the partition wall between the fuel nozzle and the air nozzle, a negative pressure region is formed on the downstream of the ring for stabilizing flame by a pressure of the fluid flowing around thereof. In this negative pressure region, a circulation flow in a direction (from the downstream to the upstream) opposite to the direction ejected from each nozzle is formed. 
     A high-temperature gas generated by combustion is returned from the downstream to the circulation flow, retained, and quickens ignition of fuel particles flowing around. The fuel jet flow ignited by the circulation flow flows while deflecting in the vertical direction due to air flow rate differences among the individual regions of the air nozzle, so that the forming position of flame can be changed. In particular, flame ignition is stably performed near the circulation flow at the fuel nozzle outlet and only the ignition forming direction can be changed, so that the temperature distribution in the furnace, the heat absorption in the furnace, and the heat absorption in a heat transfer tube provided in a flue on the downstream side of the furnace can be easily controlled. 
     The solid fuel burner of the present invention is preferably provided with the guide member that deflects the flow to the outer peripheral side (in the direction away from the fuel nozzle) on the outermost peripheral air nozzle outlet. 
     As a method of reducing nitrogen oxide (NOx) which is generated when burning the solid fuel, a method in which mixture of the fuel and air near the burner is suppressed and the fuel is burned under a condition with air shortage near the burner is available. In a burner using this method, when the air flow rate in the air nozzle is reduced, air is accompanied by the fuel jet flow and flows to the central axis side, and mixture with the fuel may be quickened. However, by providing a guide member for guiding the air ejection direction toward the outer peripheral side on the tip end of the air nozzle, the air direction ejected from the air nozzle is fixed to the outer peripheral side. Therefore, even when the air flow rate is particularly reduced, the mixture of the fuel and air near the burner can be suppressed. 
     The guide member preferably has a projection area in the burner axial direction occupying not less than 90% of the sectional area in the direction across the passage at the smallest portion (throat portion) of the air nozzle. By providing the projection area not less than 90%, the flow direction is guided to the outer periphery by the guide member. 
     Further, a flow velocity component radially outward of the fuel nozzle is induced in the air ejected from the air nozzle by the guide member. The flow of air ejected from the air nozzle into the furnace comes to easily involve ambient gasses radially outward, so that the gas pressure in the region between the air nozzle and the fuel nozzle becomes lower than the case where the guide member is not provided. Therefore, when a flow rate deviation in the circumferential direction of the fuel nozzle is generated in the air ejected from the air nozzle, the deflection of the fuel ejected from the fuel nozzle increases. 
     According to the requirements of the present invention, by regulating the air flow rates in the air nozzle, the forming position of flame can be controlled in the vertical direction or the horizontal direction inside the furnace at the fuel nozzle outlet. At this time, the air flow rates in the air nozzle of the solid fuel burner are preferably individually controlled in the vertical direction based on the combustion gas temperature at the furnace outlet, the temperature of a heat transfer tube installed on the furnace wall surface, the temperature of a fluid flowing in the heat transfer tube, the temperatures of the heat transfer tubes provided inside the furnace and a flue on the downstream side of the furnace or the temperatures of fluids flowing in the heat transfer tubes. 
     EFFECT OF THE INVENTION 
     According to the solid fuel burner of the present invention, the forming position of flame in a furnace can be controlled in the horizontal direction or the horizontal direction of the solid fuel burner by the air flow rate in the air nozzle, and the retention time of combustion gas flowing in the combustion apparatus (furnace) changes, so that the heat transfer amount in the combustion apparatus changes, and the temperature of the combustion gas at the outlet can be changed. 
     Further, according to a combustion apparatus (furnace) including the solid fuel burner and a method of operating the combustion apparatus of the present invention, the combustion gas temperature at the furnace outlet, the temperature of a heat transfer tube installed on the furnace wall surface, the temperature of a fluid flowing in the heat transfer tube, or the temperatures of heat transfer tubes provided inside the furnace and in a flue (refer to  FIG. 14 ) on the downstream side of the furnace and the temperature of a fluid flowing in the heat transfer tube are kept constant, so that the forming position of flame can be changed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view showing a section of a solid fuel burner of a first embodiment of the present invention. 
         FIG. 2  is a schematic view showing the section of the solid fuel burner of the first embodiment of the present invention. 
         FIG. 3  is a sectional view taken along an arrow line A-A of the solid fuel burner of  FIG. 1 . 
         FIG. 4  is a sectional view taken along an arrow line B-B of the solid fuel burner of  FIG. 1 . 
         FIG. 5  is a sectional view taken along an arrow line C-C of the solid fuel burner of  FIG. 1 . 
         FIG. 6  is a view showing gas temperature behavior at a furnace outlet in a combustion apparatus including the solid fuel burner of the first embodiment of the present invention. 
         FIG. 7  is a schematic view showing a section of a solid fuel burner of a second embodiment of the present invention. 
         FIG. 8  is a sectional view taken along an arrow line C-C of the solid fuel burner of  FIG. 7 . 
         FIG. 9  is a sectional view taken along an arrow line C-C of another example of the solid fuel burner of  FIG. 7 . 
         FIG. 10  is a sectional view taken along an arrow line C-C of another example of the solid fuel burner of  FIG. 7 . 
         FIG. 11  is schematic view showing a section of a solid fuel burner of a third embodiment of the present invention. 
         FIG. 12  is a sectional view taken along an arrow line C-C of the solid fuel burner of  FIG. 11 . 
         FIG. 13  is a sectional view taken along an arrow line C-C of another example of the solid fuel burner of  FIG. 11 . 
         FIG. 14  is a schematic view of a combustion apparatus in which a solid fuel burner is provided on a furnace wall showing an embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of the present invention will be described with reference to the drawings. 
     First Embodiment 
     A first embodiment of the present invention will be described with reference to  FIG. 1  to  FIG. 5 . 
       FIG. 1  is a schematic view showing a section of a solid fuel burner of a first embodiment of the present invention.  FIG. 2  is a schematic view showing the status of forming flame when a deviation is generated in an air flow rate ejected from an air nozzle into a furnace with respect to the solid fuel burner.  FIG. 3  is a sectional view taken along an arrow line (sectional view taken along an arrow line A-A of  FIG. 1 ) at the furnace partition wall portion of the solid fuel burner shown in  FIG. 1 ,  FIG. 4  is a sectional view taken along an arrow line (sectional view taken along an arrow line B-B of  FIG. 1 ) at the wind box portion of the solid fuel burner shown in  FIG. 1 , and  FIG. 5  is a sectional view taken along an arrow line (sectional view taken along an arrow line C-C of arrows of  FIG. 1 ) at the wind box portion of the solid fuel burner shown in  FIG. 1 . 
     In  FIG. 1 , a fuel nozzle  10  which supplies and conveys a mixture fluid of primary air and solid fuel in the solid fuel burner  1  is connected to a conveying tube on the upstream side, not shown, and on the outer periphery of the fuel nozzle  10 , an annular secondary air nozzle  11  which ejects secondary air is provided. On the outer periphery of the secondary air nozzle  11 , tertiary air nozzles  12  and  13  which eject tertiary air are provided. On the outer periphery of the tertiary air nozzles  12  and  13 , quaternary air nozzles  14  to  17  which eject quaternary air are provided. The tertiary air nozzles  12  and  13  of the present embodiment are divided air nozzles provided on the upper and lower sides across the fuel nozzle  10 . The quaternary air nozzles  14  to  17  are outermost peripheral air nozzles forming a passage on the outermost periphery in the solid fuel burner  1  of the present embodiment. 
     Here, the layout of the nozzles  10  to  17  and the configuration of the partition walls to be provided for the nozzles  10  to  17  will be described based on  FIG. 3 . 
     The partition wall  18  constituting the fuel nozzle  10  commonly serves as an inner peripheral wall of the secondary air nozzle  11  provided annularly on the outer periphery of the fuel nozzle  10 . Also, the outer peripheral wall  19  of the secondary air nozzle  11  commonly serves as inner peripheral walls of the tertiary air nozzles  12  and  13  and the quaternary air nozzles  16  and  17 . The upper tertiary air nozzle  12  and the lower tertiary air nozzle  13  are disposed so as to sandwich the fuel nozzle  10 , a cylindrical partition wall  19  and a bent-plate-shaped peripheral wall obstacle  20  constitute the upper tertiary air nozzle  12 , and the cylindrical partition wall  19  and a bent-plate-shaped obstacle  21  constitute the lower tertiary air nozzle  13 . The quaternary air nozzles  14  to  17  are divided into respective regions by the peripheral wall obstacles  20  and  21 , however, the partition wall  19  on the outer peripheral side and the partition wall  19  on the inner peripheral side are separated from each other. The quaternary air nozzle  14  is provided on the outer peripheral upper side of the tertiary air nozzle  12 , the quaternary air nozzle  15  is provided on the outer peripheral lower side of the tertiary air nozzle  13 , the quaternary air nozzle  16  is provided on the outer side of the partition wall  19  of the tertiary air nozzle and the obstacles  20  and  21  on the left side as viewed from the furnace side, and the quaternary air nozzle  17  is provided on the outer side of the partition wall  19  of the tertiary air nozzle and the peripheral wall obstacles  20  and  21  on the right side as viewed from the furnace side. 
     Next, a configuration and a combustion state of the burner will be described based on  FIG. 1 . 
     An oil gun  24  is provided to penetrate through the central portion of the fuel (pulverized coal) nozzle  10 , and is used for assisting combustion when starting up the burner and during low-load combustion. For preventing backfire of the solid fuel, a restriction  25  is provided in the fuel nozzle  10 . At the tip end of the partition wall  18  between the fuel nozzle  10  and the secondary air nozzle  11 , a ring for stabilizing flame  26  is provided, and the ring for stabilizing flame  26  has a function to expand circulation flows  33  generated by mixing a mixture fluid of the fuel and primary air with secondary air inside the furnace near the tip end portion of the fuel (pulverized coal) nozzle  10 . 
     An opening portion in which the burner  1  on the furnace wall  28  is installed, is a burner throat portion  29 , and the burner throat portion  29  commonly serves as outer peripheral partition walls of the quaternary air nozzles  14  to  17 . On the wall surface except for the burner throat portion  29  of the furnace wall  28 , a water tube  30  is provided. 
     On the tip end of the partition wall  19  between the secondary air nozzle  11  and the tertiary air nozzles  12  and  13 , a guide member (guide sleeve)  32  which guides secondary air and tertiary air in the direction away from the fuel nozzle  10  is provided, and on the tip ends of the peripheral wall obstacles  20  and  21  between the tertiary air nozzles  12  and  13  and the quaternary air nozzles  14  and  15 , guide members (guide sleeves)  34  and  35  which guide tertiary air and quaternary air in the direction away from the fuel nozzle  10  are provided respectively. 
     Air flowing in these combustion air nozzles  11  to  17  is supplied from a wind box  39  surrounding the burner  1 . 
     In the fuel (pulverized coal) nozzle  10 , a flow  37  of a mixture fluid of the solid fuel and the primary air flows, and in the secondary air nozzle  11 , a flow  41  of the secondary air flows. Moreover, the upstream sides of the tertiary air nozzles  12  and  13  and the quaternary air nozzles  14  to  17  form the same air passage, and an air flow  42  to be used as the tertiary air and the quaternary air is regulated by flow regulators (dampers)  38   a ,  38   b ,  43 , and  44 . 
     Further, the flow rate of the secondary air flow  41  flowing in the secondary air nozzle  11  is regulated by the flow regulator (damper)  40 , and in the air flow  42  to be used as tertiary air and quaternary air, the total flow rate of which is regulated by the flow regulator (damper)  38 , air in the tertiary air nozzles  12  and  13  to be used as tertiary air is respectively regulated by the flow regulators (dampers)  43  and  44 . 
     A flow  46  of a mixture fluid (fuel jet flow) of the solid fuel and primary air ejected from the fuel nozzle  10  into the furnace, a flow  48  of secondary air ejected from the secondary air nozzle  11  into the furnace, flows  49  and  50  of tertiary air and quaternary air (in  FIG. 1 , the tertiary air and the quaternary air in the furnace are not discriminated but are shown as an upper flow  49  and a lower flow  50 ) ejected from the tertiary air nozzles  12  and  13  and the quaternary air nozzles  14  to  17  into the furnace, are formed. Further, in the furnace, an outer peripheral portion of flame (fuel jet flow)  51  is formed. 
     In combustion of the solid fuel in the solid fuel burner  1 , air in the region on the downstream side of the partition wall  18  separating the fuel nozzle  10  and the secondary air nozzle  11  is involved in flows ejected from the respective nozzles  10  and  11 . Therefore, in the region on the downstream side of the partition wall  18 , the pressure is reduced, and circulation flows  33  as flows from the downstream side to the upstream side are formed. 
     When the ring for stabilizing flame  26  is provided on the tip end portion of the partition wall  18 , the flow  46  of the fuel mixture fluid and the flow  48  of the secondary air in the furnace are separated and the circulation flows  33  expand. A high-temperature gas is retained in the circulation flows  33 , so that ignition of fuel particles is promoted and the flame stability is improved. 
     Further, a flame is formed near the outlet of the fuel nozzle  10  and the oxygen consumption is advanced, and accordingly, a reducing flame region with a lower oxygen concentration expands in the flame. In this reducing flame, nitrogen contained in the solid fuel is emitted as a reducing substance such as ammonia or cyan, and acts as a reducing agent for reducing the nitrogen oxide (NOx) to nitrogen. Therefore, the NOx evolution amount can be reduced. 
     Further, the ignition is quickened, so that the combustion reaction of the solid fuel is advanced and the unburned fuel in the fuel ash (hereinafter, referred to as unburned amount) is also reduced. By providing guide members  32 ,  34 , and  35  for guiding air to be ejected from the respective air nozzles toward the outer periphery at the outlets of the tertiary air nozzles  12  and  13  and the quaternary air nozzles  14  to  17 , the flow  46  of the fuel mixture fluid, the flow  48  of the secondary air, and the flows  49  and  50  of the tertiary air and the quaternary air flow in the furnace are made to flow separately from each other, so that mixture of the fuel, the tertiary air, and the quaternary air near the burner is delayed and the reducing flame region expands. 
     Next, features of the present embodiment will be described with reference to  FIG. 1  and  FIG. 2 . 
       FIG. 1  is the case where air is made to flow so that the velocities of jet flows from the tertiary air nozzles  12  and  13  become equal to each other, and  FIG. 2  is in the case where the flow regulating damper  43  of the tertiary air nozzle  12  installed on the upper side of the burner  1  is operated so that a smaller amount of air flows in the tertiary air nozzle than in other nozzles. 
     As shown in  FIG. 2 , when the air volume on the lower side of the burner  1  is increased, in the jet flows from the tertiary air nozzles  12  and  13 , the air flow rate and jet flow velocity from the upper air nozzle  12  are reduced, and the air flow rate and jet flow velocity from the lower air nozzle  13  are increased. The momentum obtained as a product of the flow rate and the jet flow velocity also becomes larger on the lower side of the burner  1  than on the upper side of the burner  1 . The jet flows of the tertiary air involve ambient gasses at the outlet of the burner  1 , so that a negative pressure is generated. When the air volume of the air nozzle  13  on the lower side of the burner  1  is increased as shown in  FIG. 2 , in the pressure distribution around the tertiary air nozzles  12  and  13 , the negative pressure increases more in the lower tertiary air nozzle  13 , and a pressure differs in the vertical direction at the outer peripheral portion of the secondary air nozzle  11 . On the lower side with the higher negative pressure, the secondary air  48  easily deflects downward and flows. Therefore, at the outer peripheral portion of the fuel nozzle  10 , the secondary air  48  also deflects downward from the burner  1  and flows, so that the negative pressure increases downward in the furnace. Therefore, the fuel jet flow (flame)  51  also deflects downward. 
     That is, the fuel jet flow  51  is formed in the furnace as a downward flow due to a deviation between the air flow rates in the tertiary air nozzles  12  and  13 . Further, the fuel flows downward, and accordingly, the flame to be formed from the circulation flows  33  on the downstream of the ring for stabilizing flame  26  is also formed downward. Therefore, the temperature distribution in the furnace is biased to the lower side, and the amount of heat absorption in the furnace can be increased and the amount of heat absorption in the heat transfer tube provided on the downstream portion of the furnace can be reduced. 
     In addition, contrary to  FIG. 2 , when the damper for regulating flow  44  of the tertiary air nozzle  13  installed on the lower side of the burner  1  is operated and the air flow rate on the upper side is relatively increased, the flame is formed inside the furnace at an upper portion than usual, and the temperature distribution in the furnace is biased to the upper side, and the amount of heat absorption in the furnace can be reduced and the amount of heat absorption in the heat transfer tube provided in the flue of a downstream side of the furnace can be increased. 
     According to this embodiment, the position for forming the flame  51  can be controlled in the vertical direction by generating a deviation between air flow rates in the tertiary air nozzles  12  and  13 . Therefore, based on the combustion gas temperature at the furnace outlet, the temperature of a heat transfer tube installed on the furnace wall surface, the temperature of the fluid flowing in the heat transfer tube, or the temperatures of heat transfer tubes provided in the furnace and a flue on the downstream side thereof and the temperatures of fluids flowing in the heat transfer tubes, the air flow rates in the tertiary air nozzles  12  and  13  of the solid fuel burner  1  can be individually controlled in the vertical direction. 
     In the solid fuel burner  1  of the present embodiment, at the tip end of the outer peripheral side partition wall  18  of the fuel nozzle  10 , a ring for stabilizing flame  26  which obstructs the flow of the mixture fluid  37  flowing in the fuel nozzle  10  and the flow of air flowing in the secondary air nozzle  11  is provided. Further, guide members  32 ,  34  and  35  which deflect flows to the outer peripheral side (the direction away from the fuel nozzle  10 ) are provided at the outlets of the tertiary air nozzles  12  and  13  and the quaternary air nozzles  14  to  17 . 
     By providing the ring for stabilizing flame  26 , the circulation flows  33  are formed inside the furnace, and a high-temperature gas is retained in the circulation flows  33 , and by igniting the fuel, the flame can be stably ignited and formed on the downstream side of the ring for stabilizing flame  26  at the outlet of the fuel nozzle  10 . Therefore, regardless of the flow rates of air ejected from the tertiary air nozzles  12  and  13 , the ignition position can be fixed. Therefore, even when a deviation is generated between air flow rates ejected from the tertiary air nozzles  12  and  13 , only the forming direction (angle) of the flame  51  can be changed. The start position of forming the flame  51  does not change and only the angle of the flame  51  changes, so that the temperature distribution or the amount of heat absorption in the furnace and that in a heat transfer tube provided on the downstream portion of the furnace are easily controlled. 
     Further, the guide members  32 ,  34 , and  35  are provided, so that the direction of the air ejected from the air nozzles  11  to  17  can be always set toward the outer peripheral side of the burner  1 . Therefore, particularly, even when the flow rate is reduced, mixing the fuel and air near the burner  1  inside the furnace can be suppressed. Therefore, mixing fuel and air near the burner  1  inside the furnace can be suppressed and NOx can be reduced. 
     As dampers for regulating air flow rate, the respective dampers  40 ,  43 , and  44  corresponding to the secondary air nozzle  11  and the tertiary air nozzles  12  and  13  are shown in the present embodiment, however, as shown in  FIG. 5 , dampers for regulating the flow rate which regulate the air volume in the tertiary air nozzles  12  and  13  and the quaternary air nozzles  14  to  17  may be provided as flow regulating dampers  38   a  and  38   b  respectively provided for the upper and lower quaternary air nozzles  14  and  15  and flow regulating dampers  56   a  and  56   b  provided for the left and right quaternary air nozzles  16  and  17 . 
     In this case, by the flow regulating dampers  38   a ,  38   b ,  56   a  and  56   b , a deviation between the air flow rate in the tertiary air nozzles  12  and  13  and the quaternary air nozzles  14  to  17  can be generated each other.  FIG. 6  shows gas temperature changes at the furnace outlet respectively when a deviation in the flow rate is generated in the vertical direction of the burner  1  by operating the flow regulating dampers  38   a  and  38   b  which regulate the air volume in the quaternary air nozzles  14  and  15  of the solid fuel burner  1  of the first embodiment, and when a deviation in the flow rate is generated in the vertical direction of the burner  1  by operating the flow regulating dampers  43  and  44  of the tertiary air nozzles  12  and  13 . 
     As shown in  FIG. 6 , the gas temperature at the furnace outlet changes by the deviation in the air flow rate in the vertical direction of the air nozzles of the burner  1 . The gas temperature change at the furnace outlet shows an increase or a decrease in heat absorption in the furnace. For example, a decrease of a gas temperature means an increase in heat absorption in the furnace and facilitation of cooling of combustion gas. 
     The results shown in  FIG. 6  show that the quaternary air nozzles  14  to  17  have passages connected to each other, so that the same effect can be obtained although the effect of flow rate regulation by the dampers  38  and  56  is smaller than that by the dampers  43  and  44  of the tertiary air nozzles  12  and  13 . 
     As described above, when the air nozzles  12  to  17  are divided in the circumferential direction into a plurality of regions, the partition walls  19  and  29  and the peripheral wall obstacles  20  and  21 , etc., must be provided. Normally, in the solid fuel burner  1 , similar to the quaternary air nozzles  14  to  17  shown in  FIG. 3 , the outer peripheral side partition wall  29  of the passage on the outermost periphery is a furnace body partition wall  28  or a water wall  30  constituting the furnace. On the other hand, the inner peripheral side partition wall  19  and the peripheral wall obstacles  20  and  21  are connected to the wind box  39  to which the fuel nozzle  10  and the burner  1  are connected. The fuel nozzle  10  and the wind box  39  are different in thermal expansion rate caused by operation of the combustion apparatus (boiler) from that of the furnace body partition wall  28  or the water wall  30 . Therefore, in the solid fuel burner  1 , the relative positions of the outer peripheral side partition wall  29  of the passage on the outermost periphery and the inner peripheral side partition wall  19  and peripheral wall obstacles  20  and  21  change according to the temperature, so that they must be installed independently each other. Therefore, it is difficult to connect the inner peripheral side partition wall  19  and peripheral wall obstacles  20  and  21  to the outer peripheral side partition wall  29 . Therefore, in the present embodiment, the quaternary air nozzles  14  to  17  are divided into four regions by the obstacles  20  and  21  connected to only the tertiary air nozzles  12  and  13 , so that the effect of flow rate regulation is obtained. 
     Second Embodiment 
       FIG. 7  is a schematic view showing a section of a solid fuel burner of a second embodiment of the present invention. In addition,  FIG. 8  is a sectional view taken along an arrow line C-C of the solid fuel burner shown in  FIG. 7 . 
     The second embodiment is different from the first embodiment shown in  FIG. 1  to  FIG. 5  in that the divided tertiary air nozzles  12  and  13  of the first embodiment are not provided and the outermost peripheral nozzle regions  14  to  17  are divided in the circumferential direction in  FIG. 7  and  FIG. 8 . 
     The outermost peripheral air nozzle is divided by obstacles  53  and  54  into the regions  14  to  17  in which air corresponding to the tertiary air flows in this burner  1 . The regions  14  to  17  to be connected to the wind box  39  include the upper region  14 , the lower region  15 , the left region  16  and the right region  17  as viewed from the furnace side, and can individually regulate air flow rates by dampers for regulating the flow rate  38   a  and  38   b  provided in the upper and lower regions  14  and  15  and dampers for regulating the flow rate  56   a  and  56   b  provided in the left and right regions  16  and  17 , respectively. 
     The obstacles  53  and  54  are connected to the partition wall  19  on the inner peripheral side of the outermost peripheral air nozzle, and are not connected to the partition wall  29  on the outer peripheral side (burner throat portion which is an opening portion of the furnace wall  28  in which the burner  1  is installed). By providing the obstacles  53  and  54 , movement of combustion air among the regions  14  to  17  is obstructed. Therefore, by the flow rate regulator (dampers)  38   a ,  38   b ,  56   a  and  56   b , the air volume ejected from the regions  14  to  17  into the furnace can be regulated by the flow rate regulator (dampers)  38   a ,  38   b ,  56   a  and  56   b.    
     Specifically, the air flow rate and air jet flow velocity flowing in the upper region  14  are reduced by squeezing the damper  38   a . Accordingly, the air flow rate and air jet flow velocities in other regions  15  to  17  increase. Therefore, as the air momentum obtained as a product of the air flow rate and the air jet flow velocity, downward momentum increases with respect to the circumferential direction of the fuel nozzle  10 . The air jet flow ejected from the outermost peripheral air nozzle into the furnace involves ambient gasses at the outermost peripheral air nozzle outlet, so that a negative pressure is generated. The momentum in the outermost peripheral air nozzle is increased downward, and accordingly the negative pressure on the lower side is increased at the outermost air nozzle outlet. Therefore, the flow  48  of the secondary air in the furnace, flowing near the outermost peripheral air nozzle, flows while deflecting downward in the furnace. Further, the negative pressure on the lower side portion in the circulation flow  33  is also increased due to the flow  48  of the secondary air, so that the fuel jet flow  46  flowing near the circulation flow  33  also deflects downward. 
     That is, due to a deviation of air flow rates in the regions  14  to  17  of the outermost air nozzle, the fuel jet flow  46  is formed as a downward flow in the furnace. Further, the fuel flows downward, and accordingly, the flame  51  is also formed downward. Therefore, the temperature distribution in the furnace is biased to the lower side, and the amount of heat absorption in the furnace can be increased and the heat absorption in a heat transfer tube provided in the flue on the downstream side of the furnace can be reduced. 
     Further, in the present embodiment, obstacles  53  and  54  that divide the combustion air nozzle of the solid fuel burner  1  in the circumferential direction into a plurality of regions are provided as described above. Normally, the outer peripheral side partition wall  29  of the solid fuel burner  1  is composed of a furnace partition wall  28  or the water wall  35  which constitutes the furnace, and the inner peripheral side partition wall  19  of the regions  14  to  17  of the outermost peripheral air nozzle is connected to the wind box  39  to which the fuel nozzle  10  and the burner  1  are connected. The outer peripheral side partition wall  29  and the inner peripheral side partition wall  19  are different in thermal expansion caused by operation of the combustion apparatus (boiler). Therefore, the relative positions of the outer peripheral side partition wall  29  and the inner peripheral side partition wall  19  in the solid fuel burner  1  change according to temperature, so that both of them must be installed independently. Therefore, it is difficult to connect the inner peripheral side partition wall  19  and the outer peripheral side partition wall  29 . 
     In the present embodiment, the outermost peripheral air nozzle is divided into a plurality of regions, however, the obstacles  53  and  54  are not connected to the outer peripheral side partition wall  29 . Therefore, a deviation in the flow rate can be generated in the circumferential direction of the fuel nozzle  10  without influences from fluctuation of the relative positions of the outer peripheral side partition wall  29  and the inner peripheral side partition wall  19  due to the thermal expansion difference. Also, in the description given above, the direction of forming flame in the vertical direction inside the furnace is described, however, it is also possible that the direction of forming flame is deflected to the left or right by generating a deviation in the flow rate of the combustion air flowing in the regions  16  and  17  for forming flame in the horizontal direction in the furnace. 
     In the second embodiment shown in  FIG. 7  and  FIG. 8 , the obstacles  53  and  54  are connected from the inner peripheral side partition wall  19 , however, it is also possible that, as shown in  FIG. 9 , the obstacles  53  and  54  are connected to the outer peripheral side partition wall  29  and separated from the inner peripheral side partition wall  19 . Alternatively, as shown in  FIG. 10 , it is also possible that the obstacles  53  and  54  are connected to only the inner peripheral side partition wall  19 , the obstacles  60  and  61  are connected to only the outer peripheral side partition wall  29 , and obstacles  53 ,  54 ,  60 , and  61  respectively connected to both of the inner peripheral side and the outer peripheral side are provided doubly. By providing obstacles doubly, air movement among the regions  14  to  17  is further reduced. 
     Moreover, in the present embodiment, the secondary air nozzle  11  is provided on the outer peripheral portion of the fuel nozzle  10 , however, even when the secondary air nozzle  11  is not provided and the fuel nozzle  10  is in contact with the regions  14  to  17  of the outermost peripheral air nozzle, the deflection effect of the position for forming flame by the above-described air flow rate deviation is similarly obtained. 
     Third Embodiment 
       FIG. 11  is a schematic view showing a section of a solid fuel burner of a third embodiment of the present invention.  FIG. 12  is a sectional view taken along an arrow line C-C of  FIG. 11 . 
     The difference of the embodiment shown in  FIG. 11  and  FIG. 12 , from the second embodiment shown in  FIG. 7  and  FIG. 8  is that, for example, the fuel nozzle  10  and the secondary air nozzle  11  are relatively short in diameter in the vertical direction and relatively long in diameter in the horizontal direction orthogonal thereto, that is, wide-width nozzles. In the present embodiment, an example of the fuel nozzle  10  and the secondary air nozzle  11  whose longer side is formed in the horizontal direction is shown. Moreover, the outer peripheral partition wall  29  of the respective regions  14  to  17  of the outermost peripheral air nozzle has a circular shape whose length in the vertical direction and the horizontal direction is equal. 
     The fuel nozzle  10  and the secondary air nozzle  11  become so-called planiform, so that the thickness of the outermost peripheral air nozzle in the sectional direction across the passages of respective regions  14  to  17  is thicker in one of two directions orthogonal to each other. Therefore, when a deviation in the flow rate is generated at the thicker portion, due to larger flow rate, the fuel jet flow ejected from the fuel nozzle  10  into the furnace can be easily guided by a deviation among flow rates ejected from the regions  14  to  17  of the outermost peripheral air nozzle. 
     In the third embodiment of the present invention shown in  FIG. 11  and  FIG. 12 , the air nozzles are provided as the secondary air nozzle  11  and the regions  14  to  17  of the outermost peripheral air nozzle, however, as shown  FIG. 13 , on the inner sides of the regions  14  to  17  of the outermost peripheral air nozzle, tertiary air nozzles  12  and  13  served as the divided air nozzles may be provided. In this case, as shown in  FIG. 13 , the peripheral wall obstacles  20  and  21  of the divided tertiary air nozzles  12  and  13  may also be used as obstacles which divide the regions  14  to  17  of the outermost peripheral air nozzle. 
     Fourth Embodiment 
       FIG. 14  is a schematic view of a combustion apparatus including a solid fuel burner according to the first embodiment of the present invention provided on the furnace wall. 
     The solid fuel burner  1  includes a fuel nozzle  10  and air nozzles  12  and  13 . In the present embodiment, for describing a deviation of the air amount in the vertical direction, the air nozzles  12  and  13  are provided on the upper and lower sides, however, any of the burners  1  of the first to third embodiments described above is applicable. 
     The fuel nozzle  10  is connected to the solid fuel pulverizer  66 , a carrier air fan  67 , and a fuel hopper  68  through a fuel carrying tube for carrying fuel  65  on the upstream thereof. Moreover, the air nozzles  12  and  13  are connected to an air fan  70  via valves for regulating flow volume  71  and  72 . 
     Generally, a plurality of the above-described solid fuel burners  1  are connected to the furnace  74 , however, in the present embodiment, an example to which one solid fuel burner  1  is connected is described. 
     The partition wall  28  constituting the furnace  74  is composed of a water tube and absorbs combustion heat. Further, heat transfer surfaces  76  hung down from the ceiling inside the furnace  74  and a heat transfer surface  76  disposed in a flue on the downstream side of the furnace  74  are provided. Moreover, for measuring the amount of heat absorption on the water tube  30  (refer to  FIG. 1 ) on the wall surface of the furnace  74  or on the heat transfer surface  76 , a plurality of thermometers (not shown) for measuring the temperatures of water and steam or the temperatures of materials constituting the water tube  30  or the heat transfer tube are respectively provided at appropriate positions. 
     A control processor  73  is provided shown in  FIG. 14 , which controls valves for regulating flow amount  71  and  72  based on a steam temperature at the water tube outlet and a steam temperature at the outlet of the heat transfer surfaces  76 . In the embodiment shown in  FIG. 14 , air from the air nozzles  12  and  13  formed to sandwich the fuel nozzle  10  in the vertical direction is ejected while being respectively inclined to the opposite direction to the fuel nozzle  10 . 
     When the air flow rate in the lower side air nozzle  13  is increased, the jet flow velocity also increases. The momentum obtained as a product of the flow rate and the jet flow velocity is also increased in the axial direction, and also inside the furnace  74 , the downward momentum increases. The air jet flow involves ambient gasses at the outlet of the fuel nozzle  10 , so that a negative pressure is generated, and due to the negative pressure, the fuel jet flow flowing near the air jet flow also deflects downward and flows. 
     That is, due to a deviation between air flow rates ejected from the air nozzles  12  and  13 , a fuel jet flow ejected from the fuel nozzle  10  is formed as a downward flow at the outlet of the burner  1  of the furnace. Further due to the downward flow of the fuel, the flame to be formed inside the furnace  74  from the solid fuel burner  1  is also formed downward. Therefore, the temperature distribution inside the furnace  74  is biased to the lower side, and the amount of heat absorption in the furnace  74  can be increased and the amount of heat absorption by the heat transfer surface  76  provided in the flue on the downstream side of the furnace  74  can be reduced. 
     When the air flow rate of the upper side air nozzle  12  is increased, the flame to be formed at the outlet of the burner  1  is formed to be at an upper portion than usual, the temperature distribution inside the furnace  74  is biased to the upper side, and the heat absorption in the furnace  74  can be reduced and the amount of heat absorption by the heat transfer surface  76  provided in the flue on the downstream side of the furnace  74  can be increased. 
     Gas temperature changes at the furnace outlet when the burner structure shown in the first embodiment of the present invention described above are applied to the furnace  74  shown in  FIG. 14  are as shown in  FIG. 6 . As shown in  FIG. 6 , in a combustion apparatus including the solid fuel burner  1  of the present invention provided on the furnace wall, due to the air flow rate deviation in the vertical direction of the burner  1 , the gas temperature at the outlet of the furnace  74  changes. A gas temperature change at the outlet of the furnace  74  shows an increase/decrease in heat absorption inside the furnace  74 . For example, a gas temperature decrease means that the amount of heat absorption in the furnace  74  increases and cooling of the combustion gas is advanced. 
     According to the present embodiment, by changing the flame forming position by controlling the valves for regulating flow volume  71  and  72  via the control processor  73 , the amount of heat absorption on each heat transfer surface  76  can be changed. As for the steam temperature flowing on the wall of the furnace  74  and the heat transfer surface  76 , a predetermined design temperature is set for protecting materials of a turbine installed on the downstream side and a heat transfer surface on the upstream side, and the steam temperature can be kept in the design temperature range by changing the amount of heat absorption. 
     In particular, when ash adhering to the heat transfer surface  76  is removed, the amount of heat absorption may be temporarily increased. In this case, the steam temperature fluctuates, however, the steam temperature fluctuation can be suppressed by changing the position for forming flame as described above. Further, steam temperature fluctuation due to a load change or a change in the kind of fuel can also be suppressed. 
     INDUSTRIAL APPLICABILITY 
     The present invention provides a solid fuel burner which can easily change a heat absorption position inside a combustion apparatus, and is highly applicable to a furnace of a boiler, etc., with high combustion efficiency. 
     DESCRIPTION OF THE REFERENCE NUMERALS 
       
     
       
         
           
               
               
               
               
             
               
                   
               
             
            
               
                  1 
                 Solid fuel burner 
                 10 
                 Fuel nozzle 
               
               
                 12, 13 
                 Tertiary air nozzle 
               
               
                 14 to 17 
                 Quaternary air nozzle (outermost peripheral nozzle 
               
               
                   
                 region) 
               
               
                 18, 19 
                 Partition wall 
                 20, 21 
                 Peripheral wall obstacle 
               
               
                 24 
                 Oil gun 
                 25 
                 Restriction 
               
               
                 26 
                 Obstacle (ring for stabilizing flame) 
               
               
                 28 
                 Furnace wall (furnace body partition wall) 
               
               
                 29 
                 Burner throat portion (outer peripheral side partition wall 
               
               
                   
                 of outermost peripheral passage) 
               
               
                 30 
                 Water wall (water tube) 
               
               
                 32, 34, 35 
                 Guide member (guide sleeve) 
               
               
                 33 
                 Circulation flow 
               
               
                 37 
                 Flow of mixture fluid of solid fuel and primary air 
               
               
                 38, 40, 43, 44 
                 Flow rate regulator (damper) 
               
               
                 39 
                 Wind box 
                 41 
                 Flow of secondary air 
               
               
                 42 
                 Air flow to be used as tertiary air and quaternary air 
               
               
                 46 
                 Flow of mixture fluid (fuel jet flow) in furnace 
               
               
                 48 
                 Flow of secondary air in furnace 
               
               
                 49, 50 
                 Flows of tertiary air and quaternary air in furnace 
               
               
                 51 
                 Outer peripheral portion of flame (fuel jet flow) in furnace 
               
               
                 53, 54 
                 Obstacle 
                 56 
                 Flow rate regulator (damper) 
               
               
                 65 
                 Tube for carrying fuel 
               
               
                 66 
                 Solid fuel pulverizer 
               
               
                 67 
                 Carrier air fan 
                 68 
                 Fuel hopper 
               
               
                 70 
                 Air fan 
               
               
                 71, 72 
                 valves for regulating flow volume 
               
               
                 73 
                 Control processor 
                 74 
                 Furnace 
               
               
                 76 
                 Heat transfer surface