JP6057784B2 - boiler - Google Patents

Description

  The present invention relates to a boiler that generates steam by burning solid fuel and air.

  Conventional coal-fired boilers have a hollow furnace that is installed in a vertical direction, and a plurality of combustion burners are arranged on the furnace wall along the circumferential direction and arranged in multiple stages in the vertical direction. ing. The combustion burner is supplied with a mixture of pulverized coal (fuel) obtained by pulverizing coal and primary air (carrier air), and also supplied with high-temperature secondary air. The mixture and secondary air are supplied to the combustion burner. Is blown into the furnace to form a flame that can be burned in the furnace. This furnace has a flue connected to the top, and this flue is provided with a superheater, reheater, economizer, etc. for recovering the heat of exhaust gas, and it was generated by combustion in the furnace. Heat exchange is performed between the exhaust gas and water, and steam can be generated.

  In such a coal fired boiler, a two-stage combustion method is generally adopted. That is, a plurality of combustion burners are provided on the furnace wall, and by this combustion burner, an air-fuel mixture of pulverized coal and primary air can be supplied into the furnace, and high-temperature secondary air can be supplied into the furnace. Further, an additional air nozzle is provided above the combustion burner, and high temperature additional air can be supplied into the furnace by the additional air nozzle. Accordingly, the combustion burner can form a flame by blowing a pulverized fuel mixture in which pulverized coal and carrier air are mixed into the furnace and blowing combustion air into the furnace and igniting at this time. Further, the additional air nozzle can blow the additional air into the furnace and perform combustion control.

  At this time, in the furnace, the supply amount of the secondary air is set so as to be less than the theoretical air amount with respect to the supply amount of the pulverized coal, so that the inside is maintained in a reducing atmosphere and is generated by the combustion of the pulverized coal. NOx is reduced, and then additional air is additionally supplied to complete oxidative combustion of the pulverized coal, thereby reducing the amount of NOx generated by the combustion of the pulverized coal.

  Examples of such conventional boilers include those described in Patent Documents 1 and 2 below.

JP 2009-068801 A JP 2011-058737 A

  In the above-described conventional boiler, the pulverized fuel mixture is blown into the furnace from the combustion burner and the combustion air is blown into the furnace. At this time, a flame is formed by ignition, and the NOx is maintained in a reducing atmosphere. Is reduced. However, since additional air is then blown into the furnace from the additional air nozzle, the pulverized coal is oxidized and burned on the inside to reduce the amount of NOx generated, but a high oxygen concentration region is formed in the outer periphery, and here There is a problem that NOx is generated.

  The present invention solves the above-described problems, and an object thereof is to provide a boiler that can suppress the generation of harmful substances.

  In order to achieve the above object, a boiler according to the present invention has a hollow furnace that is installed along a vertical direction, and a fuel gas mixed with solid fuel and combustion air is blown into the furnace. A combustion burner capable of forming a flame swirl flow, and a first air injection device capable of forming an air upward flow by blowing additional air toward the lower side of the flame swirl flow in the furnace. To do.

  Accordingly, the combustion burner blows fuel gas into the furnace to form a flame swirl flow, and the generated combustion gas rises while swirling from the combustion region and moves to the reduction region, while the first air injection device moves to the furnace. An additional air is blown toward the lower side of the flame swirl flow to form an air upflow, and the center of the flame swirl flow rises and moves to the reduction region. At this time, the fuel gas is set so that the air amount is less than the theoretical air amount with respect to the solid fuel, so that a reduction region is formed following the combustion region, and is generated by the combustion of the solid fuel. After the harmful substances are reduced, the oxidative combustion of the pulverized coal is completed by the additional air rising to the center, and the generation of high oxygen concentration regions is suppressed, thereby suppressing the amount of harmful substances generated by the combustion of solid fuel can do.

  The boiler according to the present invention is characterized in that the combustion burner and the first air injection device are spaced apart from each other by a predetermined distance in the vertical direction.

  Accordingly, when the combustion burner and the first air injection device are separated from each other by a predetermined distance in the vertical direction, the flame swirl flow formed by blowing the fuel gas from the combustion burner is injected from the first air injection device. It is possible to prevent the additional air from mixing, and to raise the additional air appropriately.

  In the boiler according to the present invention, the combustion burner can inject fuel gas from a plurality of positions in the circumferential direction of the furnace, and the fuel gas injection position by the combustion burner in the furnace and the addition by the first air injection device The air blowing position is set at a different position in the circumferential direction.

  Therefore, since the position of the fuel gas blown from the combustion burner and the position of the additional air blown from the first air injection device are different in the circumferential direction, the flame swirl formed by blowing the fuel gas from the combustion burner, It becomes difficult to mix the additional air injected from the first air injection device, and the additional air can be appropriately raised.

  In the boiler of the present invention, a plurality of the combustion burners are provided at a predetermined interval in the circumferential direction of the furnace, and the first air injection device includes a plurality of air nozzles provided at a predetermined interval in the circumferential direction of the furnace. The burner and the air nozzle are arranged so as to be shifted by a predetermined distance in the circumferential direction.

  Therefore, since the combustion burner and the air nozzle are displaced by a predetermined distance in the circumferential direction, mixing of the flame swirl and the additional air can be suppressed, and the additional air can be appropriately raised.

  In the boiler according to the present invention, the furnace has a rectangular cross-sectional shape, the combustion burner is disposed at a corner portion of the furnace, and the air nozzle is disposed at a flat portion of the furnace.

  Therefore, by arranging the combustion burner and the air nozzle at appropriate positions with respect to the furnace, it is possible to form a flame swirl flow and an air upward flow without complicating the structure.

  The boiler according to the present invention is characterized in that a second air injection device capable of blowing additional air upward of the flame swirl flow in the furnace is provided.

  Therefore, harmful substances generated by the combustion of the solid fuel in the reduction region are reduced, and thereafter, the oxidative combustion of the solid fuel is completed by the additional air rising to the center and the additional air injected from the second air injection device. At this time, by setting the amount of air injected from each air injection device to an appropriate amount, the generation of a local high oxygen concentration region can be suppressed, and the amount of harmful substances generated by the combustion of solid fuel can be suppressed. .

  In the boiler according to the present invention, the second air injection devices are arranged in multiple stages in the vertical direction.

  Therefore, by dispersing the second air injection device in the vertical direction and injecting additional air, the generation of a local high oxygen concentration region is suppressed, and the amount of harmful substances generated by the combustion of the solid fuel is suppressed. it can.

  In the boiler according to the present invention, the second air injection devices are arranged in multiple upper and lower stages, the upper air nozzles can inject additional air obliquely upward, and the lower air nozzles obliquely downward. It is characterized by being able to inject additional air.

  Therefore, by injecting additional air upward and downward from the upper and lower air nozzles, the generation of local high oxygen concentration regions can be suppressed, and the amount of harmful substances generated by the combustion of solid fuel can be suppressed. .

  According to the boiler of the present invention, a combustion burner capable of forming a flame swirl flow by blowing a fuel gas mixed with solid fuel and combustion air into the furnace, and additional air below the flame swirl flow in the furnace. Since the first air injection device capable of forming an air upward flow by blowing toward the air is provided, the generation of the high oxygen concentration region can be suppressed and the generation amount of harmful substances due to the combustion of the solid fuel can be suppressed.

FIG. 1 is a schematic configuration diagram illustrating a coal fired boiler according to a first embodiment of the present invention. FIG. 2 is a plan view of a combustion burner in the coal fired boiler according to the first embodiment. FIG. 3 is a plan view of the first air injection device in the coal fired boiler according to the first embodiment. FIG. 4 is a schematic diagram illustrating an oxygen concentration state of the coal fired boiler according to the first embodiment. FIG. 5 is a schematic plan view illustrating an oxygen concentration state of the coal fired boiler according to the first embodiment. FIG. 6 is a plan view of a combustion burner and a first air injection device in a coal fired boiler according to a second embodiment of the present invention. FIG. 7 is a schematic diagram of a combustion burner and a first air injection device in a coal fired boiler according to a third embodiment of the present invention. FIG. 8 is a schematic view of a second air injection device in the coal fired boiler according to the fourth embodiment of the present invention. FIG. 9 is a schematic view of a second air injection device in the coal fired boiler according to the fifth embodiment of the present invention.

  Exemplary embodiments of a boiler according to the present invention will be described below in detail with reference to the accompanying drawings. In addition, this invention is not limited by this Example, Moreover, when there exists multiple Example, what comprises combining each Example is also included.

  1 is a schematic configuration diagram illustrating a coal burning boiler according to a first embodiment of the present invention, FIG. 2 is a plan view of a combustion burner in the coal burning boiler according to the first embodiment, and FIG. 3 is a coal burning boiler according to the first embodiment. FIG. 4 is a schematic view showing the oxygen concentration state of the coal-fired boiler of the first embodiment, and FIG. 5 is a schematic plan view showing the oxygen concentration state of the coal-fired boiler of the first embodiment. It is.

  The boiler of Example 1 uses pulverized coal obtained by pulverizing coal (bituminous coal, subbituminous coal, etc.) as pulverized fuel (solid fuel), burns this pulverized coal with a combustion burner, and recovers heat generated by this combustion. This is a pulverized coal fired boiler.

  In the first embodiment, as shown in FIG. 1, the coal fired boiler 10 is a conventional boiler, and includes a furnace 11 and a combustion device 12. The furnace 11 has a rectangular hollow shape and is installed along the vertical direction. The furnace wall constituting the furnace 11 is constituted by a heat transfer tube.

  The combustion device 12 is provided in a lower part of a furnace wall (heat transfer tube) constituting the furnace 11. This combustion apparatus 12 has a plurality of combustion burners 21, 22, 23, 24, 25 mounted on the furnace wall. In this embodiment, the combustion burners 21, 22, 23, 24, and 25 are arranged as four sets at equal intervals along the circumferential direction, and 5 sets along the vertical direction. Five stages are arranged. The shape of the furnace, the number of combustion burners in one stage, and the number of stages are not limited to this embodiment.

  Each combustion burner 21, 22, 23, 24, 25 is connected to a pulverized coal machine (mill) 31, 32, 33, 34, 35 via a pulverized coal supply pipe 26, 27, 28, 29, 30. ing. Although not shown, the pulverized coal machines 31, 32, 33, 34, and 35 are supported in a housing so that the pulverization table can be driven to rotate with a rotation axis along the vertical direction, and face the upper side of the pulverization table. A plurality of crushing rollers are configured to be rotatably supported in conjunction with the rotation of the crushing table. Accordingly, when coal is introduced between a plurality of crushing rollers and a crushing table, the pulverized coal supplied to the pulverized coal supply pipe 26 is pulverized to a predetermined size and classified by transporting air (primary air). 27, 28, 29, 30 can be supplied to the combustion burners 21, 22, 23, 24, 25.

  In the furnace 11, a wind box 36 is provided at the mounting position of each combustion burner 21, 22, 23, 24, 25, and one end of an air duct 37 is connected to the wind box 36. The duct 37 has a blower 38 attached to the other end. Therefore, the combustion air (secondary air) sent by the blower 38 is supplied from the air duct 37 to the wind box 36 and supplied from the wind box 36 to the combustion burners 21, 22, 23, 24, 25. it can.

  Further, the furnace 11 is provided with a first air injection device 39 located below the mounting positions of the combustion burners 21, 22, 23, 24, 25, and an air duct 37 is provided in the first air injection device 39. The end of the first branch air duct 40 branched from is connected. Further, the furnace 11 is provided with a second air injection device 41 above the mounting positions of the combustion burners 21, 22, 23, 24, and 25, and branched to the second air injection device 41 from the air duct 37. The end of the second branch air duct 42 is connected. Therefore, the combustion air (secondary air) sent by the blower 38 can be supplied from the first branch air duct 40 to the first air injection device 39 and from the second branch air duct 42 to the second air injection device. 41 can be supplied.

  Here, although the combustion apparatus 12 is demonstrated in detail, since each combustion burner 21, 22, 23, 24, 25 which comprises this combustion apparatus 12 has comprised the substantially the same structure, it is located in the uppermost stage. Only the combustion burner 21 will be described.

  As shown in FIG. 2, the combustion burner 21 includes combustion burners 21 a, 21 b, 21 c, and 21 d provided at four corners in the furnace 11. Each combustion burner 21a, 21b, 21c, 21d is connected to each branch pipe 26a, 26b, 26c, 26d branched from the pulverized coal supply pipe 26, and each branch pipe 37a, 37b, 37c branched from the air duct 37. , 37d are connected.

  Therefore, each combustion burner 21a, 21b, 21c, 21d at each corner of the furnace 11 blows into the furnace 11 a pulverized fuel mixture in which pulverized coal and carrier air are mixed, and the pulverized fuel mixture. Inject combustion air into the outside. Then, by igniting the pulverized fuel mixture from each combustion burner 21a, 21b, 21c, 21d, four flames F1, F2, F3, F4 can be formed, and this flame F1, F2, F3, F4. Is a flame swirl flow swirling counterclockwise as viewed from above the furnace 11 (in FIG. 2).

  Next, the air injection devices 39 and 41 will be described in detail. Since the air injection devices 39 and 41 have substantially the same configuration, only the first air injection device 39 will be described.

  As shown in FIG. 3, the first air injection device 39 includes additional air nozzles 39 a, 39 b, 39 c, and 39 d provided at positions shifted from the four corners in the furnace 11 by a predetermined distance from the plane. . Each additional air nozzle 39a, 39b, 39c, 39d is connected to each branch pipe 40a, 40b, 40c, 40d branched from the first branch air duct 40.

  Therefore, the additional air nozzles 39 a, 39 b, 39 c, 39 d in the respective flat portions of the furnace 11 blow combustion air into the furnace 11. Then, the combustion air A1, A2, A3, A4 from each additional air nozzle 39a, 39b, 39c, 39d gathers in the center of the furnace 11 as additional air, and rises in the center of the flame swirl flow. Become.

  As described above, the combustion burners 21, 22, 23, 24, and 25 form a flame swirl flow by blowing a pulverized fuel mixture (fuel gas), which is a mixture of pulverized coal and carrier air, into the furnace 11. can do. Moreover, the 1st air injection apparatus 39 can form an air upward flow by blowing in toward the downward direction of the flame swirl | vortex flow in the furnace 11 by using combustion air as additional air. Moreover, the 2nd air injection apparatus 41 can be injected toward the upper direction of the flame swirl | vortex flow in the furnace 11 by making combustion air into additional air.

  In this case, the combustion burners 21, 22, 23, 24, 25 and the first air injection device 39 are arranged apart from each other by a predetermined distance in the vertical direction. In addition, the blowing position of the pulverized fuel mixture by the combustion burners 21, 22, 23, 24, 25 (21a, 21b, 21c, 21d) in the furnace 11 and the first air injection device 39 (additional air nozzles 39a, 39b, 39c). , 39d) are set at different positions in the circumferential direction. In other words, a plurality of combustion burners 21, 22, 23, 24, 25 (21a, 21b, 21c, 21d) are provided at predetermined intervals in the circumferential direction of the furnace 11, and the first air injection device 39 includes additional air nozzles 39a, A plurality of 39b, 39c, and 39d are provided at predetermined intervals in the circumferential direction of the furnace 11, and the combustion burners 21a, 21b, 21c, and 21d and the additional air nozzles 39a, 39b, 39c, and 39d are arranged at a predetermined distance in the circumferential direction. Has been. Specifically, the furnace 11 has a rectangular cross-sectional shape, the combustion burners 21a, 21b, 21c, and 21d are arranged at the corners of the furnace 11, and the additional air nozzles 39a, 39b, 39c, and 39d are flat portions of the furnace 11. Is arranged.

  In addition, each combustion burner 21, 22, 23, 24, 25 which constitutes the combustion apparatus 12 of the present embodiment has an oil nozzle capable of injecting oil fuel at the center and a fine fuel mixture outside the oil nozzle. A fuel nozzle capable of injection, a secondary air nozzle capable of injecting secondary air to the outside of the fuel nozzle, and a tertiary air nozzle capable of injecting tertiary air to the outside of the secondary air nozzle. Yes. Therefore, when the boiler is started, each combustion burner 21, 22, 23, 24, 25 injects oil fuel into the furnace 11 to form a flame, and thereafter, the pulverized fuel mixture, secondary air, and tertiary air are supplied. It is injected into the furnace 11 to form a flame.

  As shown in FIG. 1, a furnace 11 has a flue 50 connected to an upper portion thereof, and superheaters (superheaters) 51 and 52 for collecting heat of exhaust gas as a convection heat transfer section in the flue 50. Further, reheaters 53 and 54 and economizers 55, 56 and 57 are provided, and heat exchange is performed between the exhaust gas generated by combustion in the furnace 11 and water.

  The flue 50 is connected to an exhaust gas pipe 58 from which exhaust gas subjected to heat exchange is discharged downstream. The exhaust gas pipe 58 is provided with an air heater 59 between the air duct 37 and performs heat exchange between the air flowing through the air duct 37 and the exhaust gas flowing through the exhaust gas pipe 58, and the combustion burners 21, 22, 23, The temperature of the combustion air supplied to 24 and 25 can be raised.

  Although not shown, the exhaust gas pipe 58 is provided with a denitration device, an electrostatic precipitator, an induction blower, and a desulfurization device, and a chimney is provided at the downstream end.

  When the pulverized coal machines 31, 32, 33, 34, and 35 are driven in the coal-fired boiler 10 configured as described above, the generated pulverized coal together with the air for conveyance is pulverized coal supply pipes 26, 27, 28, and 29. , 30 to the combustion burners 21, 22, 23, 24, 25. Also, heated combustion air is supplied from the air duct 37 to the combustion burners 21, 22, 23, 24, 25 via the wind box 36. Further, the air is supplied from the first branch air duct 40 to the first air injection device 39 and is supplied from the second branch air duct 42 to the second air injection device 41.

  Then, the combustion burners 21, 22, 23, 24, and 25 blow a pulverized fuel mixture mixture of pulverized coal and carrier air into the furnace 11 and blow combustion air into the combustion region B of the furnace 11, By igniting, a flame swirl can be formed in this combustion region B. The first air injection device 39 blows additional air into the additional air region A below the flame swirl flow in the furnace 11, and the second air injection device 41 blows additional air into the flame swirl flow and reduction region C in the furnace 11. The combustion is controlled by blowing above. In the furnace 11, when the pulverized fuel mixture and the combustion air are combusted to generate a flame swirl, and a flame swirl is generated in the combustion region B, the combustion gas (exhaust gas) rises while swirling in the furnace 11. To the reduction region C.

  At this time, in the furnace 11, the combustion burners 21, 22, 23, 24, and 25 are set so that the supply amount of air is less than the theoretical air amount with respect to the supply amount of pulverized coal. The reduction region C above B is maintained in a reducing atmosphere. Therefore, NOx generated by the combustion of pulverized coal is reduced in this reduction region C. On the other hand, the additional air blown into the additional air region A of the furnace 11 from the first air injection device 39 rises from the lower part of the flame swirl flow through the center (combustion region B) and reaches the reduction region B. Further, the second air injection device 41 blows additional air above the reduction region C in the furnace 11. Then, in the reduction region C, the exhaust gas and additional air react to complete the oxidative combustion of the pulverized coal, and the amount of NOx generated by the combustion of the pulverized coal is reduced.

  The ratio of the combustion air injected together with the pulverized coal from the combustion burners 21, 22, 23, 24, 25 and the additional air injected from the air injection devices 39, 41 is the amount of NOx generated in the combustion region B And the amount of CO generated. When the ratio of combustion air decreases (the amount of additional air increases), the NOx generation amount decreases and the CO generation amount increases. On the other hand, when the proportion of combustion air increases (the amount of additional air decreases), the amount of NOx generated increases and the amount of CO generated decreases. Therefore, it is necessary to determine the ratio of combustion air and additional air so that the NOx generation amount and the CO generation amount are less than the reference values. The combustion air may be 70% and the additional air ratio may be 30%. preferable. Moreover, it is preferable that the ratio of the additional air injected from the 1st air injection apparatus 39 and the additional air injected from the 2nd air injection apparatus 41 is substantially the same, and shall be 15%.

  The water supplied from a water supply pump (not shown) is preheated by the economizers 55, 56, and 57, then supplied to a steam drum (not shown) and supplied to each water pipe (not shown) on the furnace wall. It is heated to become saturated steam and fed into a steam drum (not shown). Further, saturated steam of a steam drum (not shown) is introduced into the superheaters 51 and 52 and is superheated by the combustion gas. The superheated steam generated by the superheaters 51 and 52 is supplied to a power plant (not shown) such as a turbine. Further, the steam taken out in the middle of the expansion process in the turbine is introduced into the reheaters 53 and 54, overheated again, and returned to the turbine. In addition, although the furnace 11 was demonstrated as a drum type | mold (steam drum), it is not limited to this structure.

  Thereafter, the exhaust gas that has passed through the economizers 55, 56, and 57 of the flue 50 is subjected to removal of harmful substances such as NOx by a catalyst in a denitration device (not shown) in the exhaust gas pipe 58, and the particulate matter is collected by an electric dust collector. Is removed, and after the sulfur content is removed by the desulfurizer, it is discharged from the chimney into the atmosphere.

  Here, the oxygen concentration change in the furnace 11 will be described. As shown in FIGS. 4 and 5, the region S <b> 1 in which the fine fuel mixture is blown from the combustion burners 21, 22, 23, 24, and 25 and a flame swirl is formed is burned using oxygen. The oxygen concentration is low. The region S2 into which additional air is blown from the first air injection device 39 has a high oxygen concentration, and the region S3 in the center of the furnace 11 where the additional air rises also has a relatively high oxygen concentration. The region S4 where additional air is blown from the second air injection nozzle 41 has a high oxygen concentration. And area | region S5 of the furnace 11 upper part has comparatively high oxygen concentration similarly to area | region S3. That is, the oxygen concentration in the furnace 11 is S1 <S5 <S3 <S2 = S4.

  Since the combustion region B of the furnace 11 is formed by the flame swirl flow, it becomes a low oxygen region S1 on the outer peripheral side, and the central region S3 does not burn because there is almost no pulverized coal, The additional air from the air rises here and continues to the reduction region C. That is, the reduction region C is also formed at the center of the combustion region B. Therefore, the NOx generated by the combustion of the pulverized coal after burning in the combustion zone B is reduced in the reduction zone C by the additional air rising in the center and the additional air supplied upward, and the second air injection By reducing the amount of additional air injected from the device 41, there is almost no local high oxygen concentration region, and generation of NOx can be suppressed.

  Thus, in the boiler according to the first embodiment, a flame swirl flow can be formed by blowing the furnace 11 installed in the vertical direction in a hollow shape and the pulverized fuel mixture into the furnace 11. Combustion burners 21, 22, 23, 24, and 25, and a first air injection device 39 that can form an upward air flow by blowing additional air downward of the flame swirl flow in the furnace 11. .

  Accordingly, the combustion burners 21, 22, 23, 24, and 25 blow the differential fuel mixture into the furnace 11 to form a flame swirl, and the generated combustion gas is swung up from the combustion region B and reduced. While moving to the region C, the first air injection device 39 blows additional air toward the additional air region A below the flame swirl flow in the furnace 11 to form an air upward flow, and the center portion of the flame swirl flow And move to the reduction region C. At this time, the differential fuel mixture is set so that the amount of air is less than the theoretical amount of air with respect to the pulverized coal, so that the reduction region C is formed following the combustion region B. Here, the pulverized coal Hazardous substances generated by the combustion are reduced, and then the oxidative combustion of the pulverized coal is completed by the additional air rising to the center, and the generation of the high oxygen concentration region is suppressed, thereby generating NOx due to the combustion of the pulverized coal The amount can be suppressed.

  In the boiler according to the first embodiment, the combustion burners 21, 22, 23, 24, and 25 and the first air injection device 39 are arranged apart from each other by a predetermined distance in the vertical direction. Therefore, the additional air injected from the first air injector 39 is prevented from mixing with the flame swirl formed by the differential fuel mixture being blown from the combustion burners 21, 22, 23, 24, 25. The additional air can be raised appropriately.

  In the boiler of the first embodiment, the differential fuel mixture can be blown from a plurality of positions in the circumferential direction of the furnace 11 by the combustion burners 21, 22, 23, 24, 25, and the combustion burners 21, 22, 23, The positions for blowing the differential fuel mixture by 24 and 25 and the positions for blowing additional air by the first air injection device 39 are set at different positions in the circumferential direction. Therefore, it becomes difficult for the additional air injected from the first air injection device 39 to be mixed with the flame swirl formed by the fuel gas being blown from the combustion burners 21, 22, 23, 24, 25, and the additional air is appropriately Can be raised.

  In the boiler according to the first embodiment, a plurality of combustion burners 21, 22, 23, 24, and 25 are provided at predetermined intervals in the circumferential direction of the furnace 11, and the additional air nozzles 39a, 39b, 39c, and 39d of the first air injection device 39 are provided in the furnace. A plurality of combustion burners 21, 22, 23, 24, and 25 and additional air nozzles 39a, 39b, 39c, and 39d are arranged at a predetermined distance in the circumferential direction. Therefore, mixing of the flame swirl flow and the additional air can be suppressed, and the additional air can be appropriately raised.

  In the boiler according to the first embodiment, the furnace 11 has a rectangular cross-sectional shape, the combustion burners 21, 22, 23, 24, and 25 are disposed at the corners of the furnace 11, and the additional air nozzles 39a, 39b, 39c, and 39d are disposed in the furnace 11. It is arranged on the flat part. Therefore, by arranging the combustion burners 21, 22, 23, 24, 25 and the additional air nozzles 39a, 39b, 39c, 39d with respect to the furnace 11, the flame swirl flow can be achieved without complicating the structure. An air upflow can be formed.

  In the boiler according to the first embodiment, a second air injection device 41 capable of blowing additional air toward the upper side of the flame swirl flow in the furnace 11 is provided. Therefore, NOx generated by the combustion of the pulverized coal in the reduction region C is reduced, and thereafter, the oxidative combustion of the pulverized coal is completed by the additional air rising to the center and the additional air injected from the second air injection device 41. . At this time, by setting the amount of air injected from the air injection devices 39 and 41 to an appropriate amount, the generation of a local high oxygen concentration region is suppressed, and the generation amount of NOx due to the combustion of pulverized coal can be suppressed. it can.

  FIG. 6 is a plan view of a combustion burner and a first air injection device in a coal fired boiler according to a second embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the member which has the function similar to the Example mentioned above, and detailed description is abbreviate | omitted.

  In the second embodiment, as shown in FIG. 6, the coal fired boiler is configured by providing a furnace with a combustion burner 61 and a first air injection device 62 as a combustion device. That is, the first air injection device 62 is arranged in the furnace 11 below the mounting position of the combustion burner 61.

  The combustion burner 61 is composed of combustion burners 61a, 61b, 61c, 61d provided on four plane portions in the furnace 11. Each combustion burner 61a, 61b, 61c, 61d is connected to each branch pipe 26a, 26b, 26c, 26d branched from the pulverized coal supply pipe 26, and each branch pipe 37a, 37b, 37c branched from the air duct 37. , 37d are connected.

  Therefore, each combustion burner 61a, 61b, 61c, 61d in each plane part of the furnace 11 blows into the furnace 11 a pulverized fuel mixture in which pulverized coal and transport air are mixed, and the pulverized fuel mixture. Inject combustion air into the outside. Then, by igniting the pulverized fuel mixture from each combustion burner 61a, 61b, 61c, 61d, four flames F1, F2, F3, F4 can be formed, and this flame F1, F2, F3, F4. Is a flame swirl flow swirling counterclockwise as viewed from above the furnace 11 (in FIG. 6).

  The first air injection device 62 is composed of additional air nozzles 62a, 62b, 62c, 62d provided on four planes in the furnace 11 at positions shifted from the combustion burners 61a, 61b, 61c, 61d by a predetermined distance in the circumferential direction. Has been. Each additional air nozzle 62a, 62b, 62c, 62d is connected to each branch pipe 40a, 40b, 40c, 40d branched from the first branch air duct 40.

  Therefore, each additional air nozzle 62 a, 62 b, 2 c, 62 d on each flat surface portion of the furnace 11 blows combustion air into the furnace 11. Then, the combustion air A1, A2, A3, A4 from each additional air nozzle 62a, 62b, 62c, 62d gathers in the center of the furnace 11 as additional air, and rises in the center of the flame swirl flow. Become.

  As described above, the combustion burner 61 can form a flame swirl flow by blowing the pulverized fuel mixture toward the furnace 11. Moreover, the 1st air injection apparatus 62 can form an air upward flow by blowing in toward the downward direction of the flame swirl | vortex flow in the furnace 11 by making combustion air into additional air.

  In this case, the combustion burners 61a, 61b, 61c, 61d and the additional air nozzles 62a, 62b, 62c, 62d of the first air injection device 62 are arranged apart from each other by a predetermined distance in the vertical direction and in the circumferential direction. They are spaced apart by a predetermined interval. Specifically, the furnace 11 has a rectangular cross-sectional shape, and the combustion burners 61 a, 61 b, 61 c, 61 d and the additional air nozzles 62 a, 62 b, 62 c, 62 d are disposed adjacent to the plane portion of the furnace 11.

  In addition, since the effect | action in the coal burning boiler of Example 2 is substantially the same as Example 1, description here is abbreviate | omitted.

  As described above, in the boiler according to the second embodiment, the combustion burners 61a, 61b, 61c, and 61d and the additional air nozzles 62a, 62b, 62c, and 62d of the first air injection device 62 are arranged at predetermined intervals in the vertical direction and the circumferential direction. It is spaced apart and arranged adjacent to the flat portion of the furnace 11.

  Therefore, the combustion burners 61a, 61b, 61c, 61d and the additional air nozzles 62a, 62b, 62c, 62d may be mounted on the flat portion of the furnace 11, and the structure can be simplified.

  FIG. 7 is a schematic diagram of a combustion burner and a first air injection device in a coal fired boiler according to a third embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the member which has the function similar to the Example mentioned above, and detailed description is abbreviate | omitted.

  In Example 3, as shown in FIG. 7, the coal fired boiler is configured by providing combustion furnaces 71, 72, 73, 74, and 75 as combustion devices and a first air injection device 76 in a furnace 11. . That is, the first air injection device 76 is disposed in the furnace 11 below the mounting position of the combustion burners 71, 72, 73, 74, 75.

  Combustion burners 71, 72, 73, 74, and 75 are arranged along the vertical direction, and pulverized coal supply pipes 26, 27, 28, 29, and 30 are connected to each other, and are pulverized by carrier air (primary air). Charcoal can be supplied. In the furnace 11, wind boxes 36a, 36b, 36c, 36d, and 36e are provided at the mounting positions of the combustion burners 71, 72, 73, 74, and 75. The wind boxes 36a, 36b, 36c, 36d, One end of an air duct 37 is connected to 36e, and combustion air (secondary air) can be supplied.

  The first air injection device 76 is disposed below the mounting position of the combustion burner 75, has an additional air nozzle 76a, is connected to the end of the first branch air duct 40 branched from the air duct 37, and burns. Additional air can be supplied as working air.

  In addition, since the effect | action in the coal burning boiler of Example 3 is substantially the same as Example 1, description here is abbreviate | omitted.

  Thus, in the boiler of Example 3, each combustion burner 71, 72, 73, 74, 75 is arrange | positioned independently, and the 1st air injection apparatus 76 is independently arrange | positioned under it. Accordingly, the amount of combustion air to each combustion burner 71, 72, 73, 74, 75 and the first air injection device 76 can be individually adjusted.

  FIG. 8 is a schematic view of a second air injection device in the coal fired boiler according to the fourth embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the member which has the function similar to the Example mentioned above, and detailed description is abbreviate | omitted.

  In the fourth embodiment, as shown in FIG. 8, the second air injection device 81 is provided above the mounting position of the combustion burner (not shown) in the furnace 11, and the additional air nozzles 81a, 81b, 81c are vertically arranged. It is arranged in multiple stages (three stages in this embodiment) in the direction. A plurality of the additional air nozzles 81a, 81b, 81c are arranged at a predetermined interval in the circumferential direction of the furnace 11, and the end portions of the second branch air ducts 42 branched from the air duct are connected to each other.

  Accordingly, the combustion air (secondary air) is supplied from the second branch air duct 42 to each additional air nozzle 81a, 81b, 81c of the second air injection device 81, and in a region above the reduction region in the furnace 11. Additional air can be blown. Therefore, in the reduction region, exhaust gas and additional air react to complete oxidative combustion of pulverized coal, thereby reducing the amount of NOx generated by the combustion of pulverized coal.

  As described above, in the boiler according to the fourth embodiment, the additional air nozzles 81a, 81b, and 81c are arranged in multiple stages in the vertical direction as the second air injection device 81.

  Accordingly, additional air is injected from the additional air nozzles 81a, 81b, 81c of the second air injection device 81 in a wide vertical region, and the generation of a local high oxygen concentration region is suppressed. The amount of NOx generated by the combustion of charcoal can be suppressed.

  FIG. 9 is a schematic view of a second air injection device in the coal fired boiler according to the fifth embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the member which has the function similar to the Example mentioned above, and detailed description is abbreviate | omitted.

  In Example 5, as shown in FIG. 9, the second air injection device 91 is provided above the mounting position of the combustion burner (not shown) in the furnace 11, and the additional air nozzles 91a, 91b are arranged in the vertical direction. They are arranged in multiple stages (in this embodiment, two stages). In the additional air nozzles 91a and 91b, the additional air nozzle 91a on the upper stage side can inject additional air obliquely upward, and the additional air nozzle 91b on the lower stage side can inject additional air obliquely downward. It is. A plurality of additional air nozzles 91a and 91b are arranged at predetermined intervals in the circumferential direction of the furnace 11, and end portions of the second branched air ducts 42 branched from the air duct are connected to each other.

  Accordingly, the combustion air (secondary air) is supplied from the second branch air duct 42 to the additional air nozzles 91 a and 91 b of the second air injection device 91, and is added to the area above the reduction area in the furnace 11. Can be infused. Therefore, in the reduction region, exhaust gas and additional air react to complete oxidative combustion of pulverized coal, thereby reducing the amount of NOx generated by the combustion of pulverized coal.

  Thus, in the boiler according to the fifth embodiment, as the second air injection device 91, the additional air nozzles 91a and 91b are arranged in multiple stages in the vertical direction, and the additional air nozzle 91a on the upper stage side is added obliquely upward. Air can be injected, and the additional air nozzle 91b on the lower stage side can inject additional air obliquely downward.

  Therefore, additional air is dispersed from the additional air nozzles 91a and 91b of the second air injection device 91 in a wide vertical region, and the generation of a local high oxygen concentration region is suppressed. The amount of NOx generated by combustion can be suppressed.

  In the above-described embodiment, the positions of the combustion burners 21, 22, 23, 24, and 25 in the circumferential direction of the furnace 11 and the circumferential position of the first air injection device 39 in the furnace 11 are shifted by a predetermined distance. The shifting method is not limited to the embodiment. Further, the combustion burners 21, 22, 23, 24, 25 and the first air injection device 39 may be at the same position in the circumferential direction as long as they are separated from each other by a predetermined distance in the vertical direction.

  Moreover, in the Example mentioned above, although the boiler of this invention was used as the coal fired boiler, the boiler which uses biomass or petroleum coke as a fuel may be sufficient.

DESCRIPTION OF SYMBOLS 10 Coal-fired boiler 11 Furnace 12 Combustion device 21, 22, 23, 24, 25, 61, 71, 72, 73, 74, 75 Combustion burner 26, 27, 28, 29, 30 Pulverized coal supply pipe 31, 32, 33 , 34, 35 Pulverized coal machine 36 Wind box 37 Air duct 39, 62, 76 First air injection device 41, 81, 91 Second air injection device

Claims (7)

A furnace that is hollow and installed along the vertical direction;
A plurality of combustion burners capable of forming a flame swirl flow by blowing fuel gas, which is disposed in the circumferential direction of the furnace at a predetermined interval and mixed with solid fuel and combustion air, into the furnace;
A first air injection device capable of forming an air upward flow by blowing additional air downward of the flame swirl flow in the furnace;
Have
In the first air injection device, a plurality of air nozzles are provided at a predetermined interval in the circumferential direction on a flat portion of the furnace,
The plurality of air nozzles are provided between the plurality of circumferentially adjacent combustion burners, approaching one of the combustion burners and spaced apart from the other combustion burner, and air toward the center of the furnace Infuse,
A boiler characterized by that.   The boiler according to claim 1, wherein the combustion burner and the first air injection device are spaced apart from each other by a predetermined distance in the vertical direction.   The combustion burner can inject fuel gas from a plurality of positions in the circumferential direction of the furnace, and a position in which the fuel gas is injected by the combustion burner in the furnace and a position in which additional air is injected by the first air injection device The boiler according to claim 1 or 2, wherein the boiler is set at a position having a different direction. 4. The furnace according to claim 1, wherein the furnace has a rectangular cross-sectional shape, the combustion burner is disposed at a corner portion of the furnace, and the air nozzle is disposed at a flat portion of the furnace . The boiler according to one . The boiler according to any one of claims 1 to 4, wherein a second air injection device capable of blowing additional air upward of a flame swirl flow in the furnace is provided.
The boiler according to claim 5 , wherein the second air injection devices are arranged in multiple stages in the vertical direction. The second air injection device is arranged in multiple upper and lower stages, the upper air nozzle can inject additional air obliquely upward, and the lower air nozzle can inject additional air obliquely downward. The boiler according to claim 6 , wherein the boiler is provided.

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