Patent Application
20110053102
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.
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.
U.S. Pat. No. 6,439,136 (FIG. 3)
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.
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
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
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.
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
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
A first embodiment of the present invention will be described with reference to
In
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
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
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) 38a, 38b, 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
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
As shown in
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
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
In this case, by the flow regulating dampers 38a, 38b, 56a and 56b, 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.
As shown in
The results shown in
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
The second embodiment is different from the first embodiment shown in
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 38a and 38b provided in the upper and lower regions 14 and 15 and dampers for regulating the flow rate 56a and 56b 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) 38a, 38b, 56a and 56b, the air volume ejected from the regions 14 to 17 into the furnace can be regulated by the flow rate regulator (dampers) 38a, 38b, 56a and 56b.
Specifically, the air flow rate and air jet flow velocity flowing in the upper region 14 are reduced by squeezing the damper 38a. 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
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.
The difference of the embodiment shown in
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
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
A control processor 73 is provided shown in
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
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.
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-102048 | Apr 2008 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2009/001573 | 4/3/2009 | WO | 00 | 9/23/2010 |
