JP6284345B2 - boiler - Google Patents

Description

  The present invention relates to a boiler that generates steam by mixing and burning solid fuel and air, and a combustion burner used in the boiler.

  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, in-furnace denitration technology is generally employed. That is, a plurality of combustion burners are provided on the furnace wall, and an additional air nozzle is provided above the combustion burner. Accordingly, the combustion burner forms 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. The additional air nozzle blows additional air into the furnace to 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 the oxidative combustion of the pulverized coal, thereby reducing the amount of NOx generated by the combustion of the pulverized coal.

By the way, in such a furnace, in a region in a combustion atmosphere or a reducing atmosphere, since it is a low oxygen region and a high temperature region, hydrogen sulfide (H ₂ S), which is a corrosive component, is easily generated. Corrosion may occur on the inner surface of the wall. Therefore, as a solution to such a problem, for example, there is one described in the following patent document.

  The combustion apparatus of the pulverized coal burning boiler described in the following Patent Document 1 is provided with a nozzle for introducing a part of combustion air or combustion gas between adjacent burners. The boiler structure described in the following Patent Document 2 is provided with an air input part that forms a region having a higher air concentration than the surroundings in the vicinity of the flame affected part of the furnace wall where the flame formed for each burner approaches or contacts. is there.

Japanese Patent Laid-Open No. 07-119923 JP 2009-174751 A

  However, in the above-mentioned furnace, the region where corrosion is likely to occur due to hydrogen sulfide on the inner surface of the furnace wall is a region where the temperature is low with low oxygen. Therefore, as in the combustion apparatus of the pulverized coal-fired boiler of Patent Document 1, even if combustion air or combustion gas is input to the flame from the burner, the furnace wall surface in the NOx reduction region generated above it It is difficult to prevent corrosion. In addition, the region where corrosion is likely to occur due to hydrogen sulfide is a region of a predetermined area where the flame approaches, and even if an air input unit is provided in the vicinity of the flame affected part of the furnace wall surface as in the boiler structure of Patent Document 2. It is difficult to prevent a predetermined area from corrosion.

  The present invention solves the above-described problems, and an object of the present invention is to provide a boiler and a combustion burner that improve durability by preventing corrosion of a furnace wall.

  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, an additional air nozzle for blowing additional air into the furnace above the combustion burner, and a protective gas on the furnace wall side from the blowing direction of the fuel gas by the combustion burner And a protective gas nozzle to be blown.

  Therefore, the combustion burner blows fuel gas into the furnace to form a flame swirl, and the generated combustion gas rises while swirling from the combustion region. The fuel gas is set so that the amount of air is less than the theoretical amount of air with respect to the solid fuel, so that a reduction region is formed above the combustion region. Here, harmful substances generated by the combustion of the solid fuel are generated. Reduced. Thereafter, the additional air nozzle blows the additional air into the furnace, whereby the oxidative combustion of the solid fuel is completed. At this time, by blowing protective gas along the inner wall surface of the furnace in the combustion area from the protective gas nozzle, direct contact between the combustion gas and the inner wall surface of the furnace is suppressed, and corrosion of the furnace wall is prevented and durable. Can be improved.

  In the boiler according to the present invention, the combustion burner includes a fuel nozzle capable of injecting fuel gas, and a secondary air nozzle capable of injecting secondary air from the outside of the fuel nozzle. It arrange | positions only at the one side part in a secondary air nozzle, and can inject protective gas toward the outer side of the said flame swirl | flow, It is characterized by the above-mentioned.

  Therefore, by composing the combustion burner and the protective gas nozzle integrally, it is possible to reduce the size and cost of the apparatus.

  In the boiler according to the present invention, the combustion burner and the protective gas nozzle are arranged at corners of the furnace and inject protective gas along one inner wall surface.

  Therefore, when the combustion burner and the protective gas nozzle are arranged at the corner of the furnace, the protective gas nozzle injects protective gas along one inner wall surface, so that it is properly protected between the flame swirl and the inner wall surface of the furnace. Gas can be supplied.

  In the boiler according to the present invention, the combustion burner and the protective gas nozzle are arranged on a furnace wall of the furnace and inject protective gas along one inner wall surface.

  Therefore, when the combustion burner and the protective gas nozzle are arranged on the furnace wall of the furnace, the protective gas nozzle injects protective gas along one inner wall surface, so that a proper protection is provided between the flame swirl and the inner wall surface of the furnace. Gas can be supplied.

  In the boiler of the present invention, the amount of combustion air blown from the combustion burner and the amount of additional air blown from the additional air nozzle are set according to the form of the boiler, and the amount of protective gas blown from the protective gas nozzle is the amount of additional air It is characterized in that a part of is used.

  Therefore, by securing the protective gas from part of the additional air, it is possible to maintain stable boiler efficiency without changing the amount of air supplied to the furnace.

  The boiler according to the present invention is characterized in that at least a part of the exhaust gas discharged from the furnace is used as the protective gas.

  Therefore, the protective gas nozzle can suppress an increase in the temperature of the inner wall surface of the furnace by supplying the exhaust gas as the protective gas to the furnace.

  The combustion burner of the present invention includes a fuel nozzle capable of injecting a fuel gas in which solid fuel and combustion air are mixed, a secondary air nozzle disposed outside the fuel nozzle and capable of injecting secondary air, And a protective gas nozzle that is disposed only on one side of the secondary air nozzle and is capable of injecting protective gas.

  Therefore, by integrally configuring the fuel nozzle, the secondary air nozzle, and the protective gas nozzle, it is possible to reduce the size and cost of the apparatus.

  According to the boiler and the combustion burner of the present invention, since the protective gas nozzle for injecting the protective gas to the furnace wall side from the direction in which the fuel gas is injected by the combustion burner is provided, the direct contact between the combustion gas and the inner wall surface of the furnace by the protective gas Is suppressed, and corrosion of the furnace wall can be prevented and durability can be improved.

Drawing 1 is a schematic structure figure showing a coal burning boiler of a 1st embodiment. FIG. 2 is a plan view of a combustion burner in a coal fired boiler. 3 is a cross-sectional view taken along the line III-III of FIG. 2 showing a cross section of the combustion burner. FIG. 4 is a plan view showing a combustion region in a coal fired boiler. FIG. 5 is a plan view illustrating a combustion region in the coal fired boiler according to the second embodiment. FIG. 6 is a plan view illustrating a combustion region in the coal fired boiler according to the third embodiment. FIG. 7 is a schematic configuration diagram illustrating a coal fired boiler according to a fourth embodiment.

  Exemplary embodiments of a boiler and a combustion burner 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 embodiment, and when there are two or more embodiments, what comprises combining each embodiment is also included.

[First Embodiment]
1 is a schematic configuration diagram showing a coal burning boiler according to the first embodiment, FIG. 2 is a plan view of a combustion burner in the coal burning boiler, and FIG. 3 is a sectional view taken along the line III-III in FIG. 2 showing a section of the combustion burner. FIG. 4 is a plan view showing a combustion region in a coal fired boiler.

  The boiler according to the first embodiment uses pulverized coal obtained by pulverizing coal (bituminous coal, subbituminous coal, etc.) as pulverized fuel (solid fuel), burns the pulverized coal with a combustion burner, and recovers heat generated by the combustion. It is a pulverized coal fired boiler that can.

  In this 1st Embodiment, as shown in FIG. 1, the coal burning boiler 10 is a conventional boiler, Comprising: The furnace 11 and the combustion apparatus 12 are provided. 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. And the combustion apparatus 12 is arrange | positioned as 5 sets along the vertical direction, ie, 5 steps | paragraphs, as one set in which the four combustion burners were arrange | positioned at equal intervals along the circumferential direction. The combustion burners 21, 22, 23, 24 and 25 are a CCF (Circular Corner Filling) combustion system, and the shape of the furnace 11, the number of combustion burners in one stage, and the number of stages are limited to this embodiment. It is not a thing.

  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. . 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 a mounting position of each combustion burner 21, 22, 23, 24, 25, and one end portion of an air duct 37 is connected to the wind box 36. Is equipped with a blower 38 at 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.

  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).

  As shown in FIG. 1, the furnace 11 is provided with an additional combustion air supply device 41 at the upper stage of the combustion device 12. The additional combustion air supply device 41 has a plurality of additional combustion air nozzles 42 and 43 attached to the furnace wall. The additional combustion air nozzles 42, 43 are arranged in a set of four at regular intervals along the circumferential direction, and two sets, that is, two stages, are arranged along the vertical direction. That is, the additional combustion air supply device 41 (additional combustion air nozzles 42, 43) is disposed above the mounting position of the combustion burner 21 in the furnace 11. The additional combustion air supply device 41 blows in additional combustion air (Over Fire Air) into the furnace 11. That is, the additional combustion air nozzles 42 and 43 are composed of a plurality of additional combustion air nozzles provided at four corners in the furnace 11, similarly to the combustion burners 21, 22, 23, 24 and 25. An additional combustion air swirl similar to the flame swirl is formed. The additional air nozzles 42 and 43 are connected to end portions of the first branch air duct 44 branched from the air duct 37.

  Therefore, the combustion air sent by the blower 38 can be supplied from the first branch air duct 44 to the additional combustion air supply device 41. The additional combustion air nozzles 42 and 43 can blow additional combustion air above the pulverized fuel mixture blown by the combustion burners 21, 22, 23, 24 and 25.

  The furnace 11 is provided with an additional air supply device 51 above the combustion device 12. The additional air supply device 51 has a plurality of additional air nozzles 52 mounted on the furnace wall. One set of the additional air nozzles 52 arranged at equal intervals along the circumferential direction, that is, one stage is arranged. In other words, the additional air supply device 51 (additional air nozzle 52) is disposed above the mounting position of the combustion burner 21 in the furnace 11 by a predetermined distance. The additional air supply device 51 blows additional air (Additional Air) into the furnace 11. That is, the additional air nozzle 52 is composed of a plurality of additional air nozzles provided at four corners in the furnace 11, similar to the combustion burners 21, 22, 23, 24, 25, and is similar to the flame swirl flow. An additional air swirl is formed. The additional air nozzle 52 is connected to the end of a second branch air duct 53 branched from the air duct 37.

  Therefore, the combustion air sent by the blower 38 can be supplied from the second branch air duct 53 to the additional air supply device 51. Further, the additional air nozzle 52 has additional air upward by a predetermined distance between the pulverized fuel mixture blown by the combustion burners 21, 22, 23, 24 and 25 and the additional combustion air blown by the additional combustion air nozzles 42 and 43. Can be infused.

  In the furnace 11, a protective gas supply device 61 is provided in the combustion device 12. The protective gas supply device 61 has a plurality of protective gas nozzles 62, 63, 64 mounted on the furnace wall. The protective gas nozzles 62, 63, 64 are arranged in three sets, that is, in three stages, with four nozzles arranged at equal intervals along the circumferential direction. That is, the protective gas supply device 61 (protective gas nozzles 62, 63, 64) is disposed at the same position as the combustion burner 21 in the furnace 11. The protective gas supply device 61 blows air as a protective gas (Wall Protection Air) into the furnace 11. The protective gas nozzles 62, 63, 64 are connected to the ends of the third branch air duct 65 branched from the air duct 37.

  In the present embodiment, the combustion device 12 and the protective gas supply device 61 are integrally configured. The combustion burners 21, 22, 23, 24, and 25 form a flame swirl flow by blowing a pulverized fuel mixture into the furnace 11. The protective gas nozzles 62, 63, 64 blow air (protective gas) into the furnace wall side from the blowing direction of the pulverized fuel mixture by the combustion burners 21, 22, 23, 24, 25. The protective gas nozzles 62, 63, 64 have substantially the same configuration.

  That is, as shown in FIGS. 2 and 3, the combustion burner 21 is composed of combustion burners 21 a, 21 b, 21 c, and 21 d provided at four corners in the furnace 11. Similarly, the protective gas nozzle 62 includes protective gas nozzles 62a, 62b, 62c, and 62d provided at four corners of the furnace 11. Here, the combustion burner 21a includes a fuel nozzle 81 for injecting a fine fuel mixture, and a secondary air nozzle 82 having a cross-sectional ring shape and capable of blowing secondary air from the outside of the fuel nozzle 81, The protective gas nozzle 62 a is disposed only on one side of the secondary air nozzle 82.

  The protective gas nozzles 62a, 62b, 62c, 62d are connected to the branch pipes 65a, 65b, 65c, 65d branched from the third branch air duct 65. And each protective gas nozzle 62a, 62b, 62c, 62d can blow in air horizontally along the inner wall surface of the furnace 11. Therefore, the combustion air sent by the blower 38 can be supplied from the third branch air duct 65 to the protective gas supply device 61. The protective gas nozzles 62, 63, 64 (62a, 62b, 62c, 62d) can blow air to the outside of the pulverized fuel mixture blown by the combustion burners 21, 22, 23, 24, 25. In this case, the amount of air blown by the protective gas nozzles 62 (62a, 62b, 62c, 62d), 63, 64 is about 1% to 5% in terms of the total air amount ratio, and the nozzle flow rate is 20 m / s to 100 m / s. It is.

  In this embodiment, the protective gas supply device 61 is such that the protective gas nozzles 62, 63, 64 blow air between the inner wall surface of the furnace 11 and the flames from the combustion burners 21, 22, 23, 24, 25. It is. Therefore, as shown in FIG. 2, the combustion burners 21 a, 21 b, 21 c, and 21 d can form a flame swirl flow by blowing a fine fuel mixture into the furnace 11 to form flames F 1, F 2, F 3, and F 4. is there. On the other hand, the protective gas nozzles 62a, 62b, 62c, and 62d can form airflows A1, A2, A3, and A4 by blowing air to the outside of the flames F1, F2, F3, and F4.

  In the present embodiment, the combustion device 12 and the protective gas supply device 61 are integrally configured so that the protective gas nozzles 62, 63, and 64 are attached to the combustion burners 21, 22, and 23, so that the combustion burner 21, 22, 23 and the protective gas nozzles 62, 63, 64 are configured as a combustion burner. Here, although the protective gas nozzles 62, 63, 64 are provided on the upper three combustion burners 21, 22, 23, it is not limited to this configuration. Depending on the form of the boiler 10, the protective gas nozzle 62 may be provided only in the upper combustion burner 21, or the protective gas nozzles may be provided in all the combustion burners 21, 22, 23, 24, 25.

  The primary air amount (transport air amount) supplied to the furnace 11, the secondary air amount, the additional fuel air amount, the additional air amount, and the air amount as the protective gas amount are set in accordance with the form of the boiler. ing. That is, the amount of primary air and the amount of secondary air blown by the combustion burners 21, 22, 23, 24, and 25 according to the form of the boiler, the amount of additional fuel air blown by the additional combustion air nozzles 42 and 43, and the additional air nozzle An additional air amount to be blown by 52 is set, and a part of the additional air amount is used as the protective gas amount to be blown by the protective gas nozzle 62.

  As described above, the combustion burners 21, 22, 23, 24, and 25 are flames by blowing pulverized fuel mixture (fuel gas) mixed with pulverized coal and carrier air and secondary air into the furnace 11. A swirling flow can be formed. Further, the additional combustion air nozzles 42, 43 can blow additional combustion air into the furnace 11 at the upper stage of the combustion burners 21, 22, 23, 24, 25. Further, the additional air nozzle 52 can blow additional air into the furnace 11 above the combustion burners 21, 22, 23, 24, 25.

  Further, the protective gas nozzles 62, 63, 64 can blow the air as the protective gas horizontally along the inner wall surface of the furnace 11 at the same position as the combustion burners 21, 22, 23, 24, 25. Then, as shown in FIG. 4, the protective gas nozzles 62a, 62b, 62c, 62d are connected to the flames F1, F2, F3, F4 from the combustion burners 21a, 21b, 21C, 21d and the furnace walls 11A, 11B, 11C, Air flow A1, A2, A3, A4 is formed between the inner wall surface of 11D. Therefore, direct contact of the flames F1, F2, F3, and F4 with the inner wall surface of the furnace 11 is suppressed by the air flows A1, A2, A3, and A4, and in particular, the horizontal intermediate regions 11a, 11b, and 11c on the inner wall surface. , 11d is prevented from being heated.

  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. An injectable fuel nozzle and a secondary air nozzle capable of injecting secondary air outside the fuel nozzle are provided. 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 then the fine fuel mixture and secondary air are introduced into the furnace 11. A flame is formed by spraying.

  As shown in FIG. 1, the furnace 11 has a flue 70 connected to the upper portion thereof, and a superheater (superheater) 71 for recovering the heat of exhaust gas as a convection heat transfer section to the flue 70. , 72, reheaters (reheaters) 73, 74, and economizers 75, 76, 77 are provided, and heat exchange is performed between the exhaust gas generated by combustion in the furnace 11 and water. .

  The flue 70 is connected to an exhaust gas pipe 78 from which exhaust gas subjected to heat exchange is discharged downstream. The exhaust gas pipe 78 is provided with an air heater 79 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 78, and the combustion burners 21, 22, 23, The temperature of the combustion air supplied to 24 and 25 can be raised.

  And although the exhaust gas pipe 78 is not shown in figure, a denitration apparatus, an electrostatic precipitator, an induction blower, and a desulfurization apparatus are provided, and the chimney is provided in the downstream end part.

  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. The heated combustion air is supplied to the additional combustion air nozzles 42, 43, the additional air nozzle 52, and the protective gas nozzle 62 through the branched air ducts 44, 53, 65 branched from the air duct 37.

  Then, the combustion burners 21, 22, 23, 24, 25 blow the pulverized fuel mixture mixture of pulverized coal and carrier air and the secondary air into the furnace 11, and ignite at this time to enter the combustion region A. A flame swirl can be formed. At this time, the additional combustion air nozzles 42 and 43 can appropriately form the combustion region A by blowing the additional combustion air into the furnace 11. In the furnace 11, when the pulverized fuel mixture, the secondary air, and the additional combustion air are burned to generate a flame swirl, and a flame swirl is generated in the combustion region A, the combustion gas (exhaust gas) swirls in the furnace 11. It rises while reaching the reduction region B.

  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 B above A is maintained in a reducing atmosphere. Therefore, NOx generated by the combustion of pulverized coal is reduced in this reduction region B.

  The additional air nozzle 52 blows additional air above the reduction region B of the furnace 11. Then, in the combustion completion region C, the exhaust gas reacts with the additional air, whereby the oxidative combustion of the pulverized coal is completed, and the amount of NOx generated by the combustion of the pulverized coal is reduced.

By the way, in the combustion region A and the reduction region B of the furnace 11, since it becomes a low-oxygen atmosphere and a high-temperature atmosphere, hydrogen sulfide (H ₂ S), which is a corrosive component, easily occurs, and the inner surface of the furnace wall corrodes. May occur. Therefore, in the present embodiment, in the furnace 11, the protective gas nozzles 62, 63, 64 blow air along the inner wall surface in the combustion region A. Since this air is blown outward from the flame swirl flow along the furnace wall, the flame does not directly contact the inner wall surface of the furnace 11, and the occurrence of corrosion is suppressed by lowering the temperature of the furnace wall.

  Further, since air is blown between the inner wall surface of the furnace 11 and the flame swirl flow from the protective gas nozzles 62, 63, 64, this region becomes a high oxygen region, and generation of hydrogen sulfide is suppressed. Wall corrosion is suppressed. Furthermore, since the furnace 11 has a high oxygen atmosphere in the vicinity of the wall surface of the combustion region A and the reduction region B and is suppressed to a low temperature atmosphere, it can suppress the melting of fly ash and prevent slagging. it can.

  The protective gas nozzles 62, 63, 64 may disturb the reduction region B when the air rises in the reduction region B. However, the air from the protective gas nozzles 62, 63, 64 is outside the flame swirl flow. Therefore, this air hardly affects the NOx reduction action.

  The water supplied from a water supply pump (not shown) is preheated by the economizers 75, 76, and 77, 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 71 and 72 and is superheated by the combustion gas. The superheated steam generated by the superheaters 71 and 72 is supplied to a power plant (not shown) (for example, a turbine). Further, the steam taken out in the middle of the expansion process in the turbine is introduced into the reheaters 73 and 74, 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 75, 76, and 77 of the flue 70 is subjected to removal of harmful substances such as NOx by a catalyst in a denitration device (not shown) in the exhaust gas pipe 78, 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.

  As described above, in the boiler according to the first embodiment, a flame swirl flow is formed by blowing the pulverized fuel mixture into the furnace 11 and the furnace 11 installed along the vertical direction in a hollow shape. Possible combustion burners 21, 22, 23, 24, 25, an additional air nozzle 52 for blowing additional air into the furnace 11 above the combustion burners 21, 22, 23, 24, 25, and combustion burners 21, 22 , 23, 24, 25 are provided with protective gas nozzles 62, 63, 64 for blowing air (protective gas) to the furnace wall side from the blowing direction of the pulverized fuel mixture.

  Accordingly, the combustion burners 21, 22, 23, 24, and 25 blow and ignite the fine fuel mixture into the furnace 11 to form a flame swirl flow, and the generated combustion gas rises while swirling from the combustion region A. . The pulverized fuel mixture is set so that the amount of air is less than the theoretical amount of air with respect to the pulverized coal fuel, so that a reduction region B is formed above the combustion region A. Here, the combustion of the pulverized coal fuel NOx generated by the above is reduced. Thereafter, the additional air nozzle 52 blows the additional air into the furnace 11 to complete the oxidative combustion of the pulverized coal. At this time, in the combustion region A from the protective gas nozzle 62, air is blown in the horizontal direction along the inner wall surface of the furnace 11, so that direct contact between the combustion gas and the inner wall surface of the furnace 11 is suppressed. Corrosion can be prevented and durability can be improved.

  In the boiler according to the first embodiment, as the combustion burners 21, 22, and 23, a fuel nozzle 81 capable of blowing fuel gas and a secondary air nozzle 82 capable of blowing secondary air from the outside of the fuel nozzle 81 are provided, The protective gas nozzles 62, 63, and 64 are arranged only on one side of the secondary air nozzle 82 so that air can be blown toward the outside of the flame swirl flow. Therefore, by composing the combustion burners 21, 22, 23 and the protective gas nozzles 62, 63, 64 integrally, the apparatus can be reduced in size and cost.

  In the boiler of the first embodiment, the combustion burners 21, 22, 23, 24, 25 are arranged at the corners of the furnace 11, and the protective gas nozzles 62, 63, 64 are arranged at the same positions as the combustion burners 21, 22, 23, Air is jetted along one inner wall surface. Therefore, when the combustion burners 21, 22, 23 and the protective gas nozzles 62, 63, 64 are arranged at the corners of the furnace 11, the protective gas nozzles 62, 63, 64 inject air along one inner wall surface. Air can be appropriately supplied between the flame swirl flow and the inner wall surface of the furnace 11.

  In the boiler of the first embodiment, the amount of combustion air blown from the combustion burners 21, 22, 23, 24, and 25 and the amount of additional air blown from the additional air nozzle 52 are set according to the form of the boiler, and the protective gas nozzle 62, The amount of air blown from 63, 64 is used from a part of the additional amount of air. Therefore, by securing the air from a part of the additional air, it is possible to maintain stable boiler efficiency without changing the amount of air supplied to the furnace 11.

  Moreover, in the combustion burner of 1st Embodiment, the fuel nozzle 81, the secondary air nozzle 82, and the protective gas nozzle 62 are comprised integrally. Therefore, it is possible to reduce the size and cost of the apparatus.

[Second Embodiment]
FIG. 5 is a plan view illustrating a combustion region in the coal fired boiler according to the second embodiment. In addition, the same code | symbol is attached | subjected to the member which has the same function as embodiment mentioned above, and detailed description is abbreviate | omitted.

  In 2nd Embodiment, as shown in FIG. 5, the coal fired boiler has the furnace 11 and the combustion apparatus 101. As shown in FIG. The combustion apparatus 101 is provided in the lower part of the furnace wall (heat-transfer tube) that constitutes the furnace 11. This combustion apparatus 101 has a plurality of combustion burners 102 mounted on the furnace wall. Although not shown, four combustion apparatuses 101 are arranged along the circumferential direction in the same manner as the combustion apparatus 12 (FIG. 1) of the first embodiment. A set of combustion burners arranged at equal intervals is set as 5 sets along the vertical direction, that is, 5 stages. The combustion burner 102 is a CUF (Circular Ultra Filling) combustion method, and the shape of the furnace 11, the number of combustion burners in one stage, and the number of stages are not limited to this embodiment.

  The combustion burner 101 is composed of combustion burners 102 a, 102 b, 102 c and 102 d provided on four furnace walls in the furnace 11. Each combustion burner 102 a, 102 b, 102 c, 102 d is arranged close to one corner (on the pulverized fuel mixture injection direction side) with respect to the horizontal direction of the furnace wall of the furnace 11. The combustion burners 102a, 102b, 102c, and 102d are connected to the branch pipes 26a, 26b, 26c, and 26d branched from the pulverized coal supply pipe 26, and the branch pipes 37a, 37b, and 37c branched from the air duct 37. , 37d are connected.

  Therefore, each combustion burner 102a, 102b, 102c, 102d 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 102a, 102b, 102c, 102d, 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.

  Although not shown, the furnace 11 is provided with an additional combustion air supply device at the upper stage of the combustion device 101 and an additional air supply device above the combustion device 12 as in the first embodiment. Yes. Since the additional combustion air supply device and the additional air supply device are the same as the additional combustion air supply device 41 and the additional air supply device 51 of the first embodiment, detailed description thereof is omitted.

  The furnace 11 is provided with a protective gas supply device 103 at the same position as the combustion device 101. This protective gas supply device 103 has a plurality of protective gas nozzles 104 mounted on the furnace wall. One set of the protective gas nozzles 104 arranged at equal intervals along the circumferential direction, that is, one stage is arranged. The protective gas supply device 103 blows air as a protective gas (Wall Protection Air) into the furnace 11.

  The protective gas nozzle 103 includes protective gas nozzles 104a, 104b, 104c, and 104d provided on four furnace walls in the furnace 11. Each of the protective gas nozzles 104a, 104b, 104c, and 104d is disposed close to one corner (on the pulverized fuel mixture blowing direction side) with respect to the horizontal direction of the furnace wall of the furnace 11. In this case, each of the protective gas nozzles 104a, 104b, 104c, and 104d is configured integrally with the combustion burners 102a, 102b, 102c, and 102d. Here, the combustion burners 102a, 102b, 102c, and 102d have a fuel nozzle and a secondary air nozzle 82, similarly to the combustion burner 21a of the first embodiment, and the protective gas nozzles 104a, 104b, 104c, and 104d are It is arranged only on one side of the secondary air nozzle. Each of the protective gas nozzles 104a, 104b, 104c, and 104d is connected to each of the branch pipes 63a, 63b, 63c, and 63d branched from the third branch air duct 65. Accordingly, each of the protective gas nozzles 104a, 104b, 104c, and 104d can blow air horizontally along the inner wall surface of the furnace 11 outside the pulverized fuel mixture blown by the combustion burners 102a, 102b, 102c, and 102d. . In this case, the amount of air blown by the protective gas nozzle 104 (104a, 104b, 104c, 104d) is about 1% to 5% in terms of the total air amount ratio, and the nozzle flow velocity is 20 m / s to 100 m / s.

  Therefore, the combustion burners 102a, 102b, 102c, and 102d form a flame swirl flow by blowing finely pulverized fuel mixture (fuel gas) and secondary air into the furnace 11. The protective gas nozzles 104 a, 104 b, 104 c, and 104 d blow the air as the protective gas horizontally along the inner wall surface of the furnace 11 outside the combustion burners 102 a, 102 b, 102 c, and 102 d. Then, the protective gas nozzles 104 a, 104 b, 104 c, 104 d are connected to the air flow A 1, A 2, A 3 between the flames F 1, F 2, F 3, F 4 from the combustion burners 102 a, 102 b, 102 c, 102 d and the inner wall surface of the furnace 11. , A4. Therefore, the flames F1, F2, F3, and F4 are not in direct contact with the inner wall surface of the furnace 11 due to the air flows A1, A2, A3, and A4, and the occurrence of corrosion is suppressed by lowering the temperature of the furnace wall.

  Further, since air is blown between the inner wall surface of the furnace 11 and the flame swirl flow from the protective gas nozzles 104a, 104b, 104c, 104d, this region becomes a high oxygen region, and generation of hydrogen sulfide is suppressed. Corrosion of the furnace wall is suppressed. Furthermore, since the vicinity of the wall surface of the reduction region B is a high-oxygen atmosphere and a low-temperature atmosphere, the furnace 11 can suppress the melting of fly ash and prevent slagging.

  Thus, in the boiler according to the second embodiment, the protective gas nozzles 104a, 104b for blowing air (protective gas) horizontally along the inner wall surface of the furnace 11 at the same position as the combustion burners 102a, 102b, 102c, 102d, 104c and 104d are provided, the combustion burners 102a, 102b, 102c and 102d and the protective gas nozzles 104a, 104b, 104c and 104d are arranged on the furnace wall, and the protective gas nozzles 104a, 104b, 104c and 104d are protected along one inner wall surface. Gas is being injected.

  Therefore, by blowing air from the protective gas nozzles 104a, 104b, 104c, and 104d along the inner wall surface of the furnace 11, direct contact between the combustion gas and the inner wall surface of the furnace 11 is suppressed, and corrosion of the furnace wall is prevented. And durability can be improved. Further, when the combustion burners 102 a, 102 b, 102 c and 102 d and the protective gas nozzles 104 a, 104 b, 104 c and 104 d are arranged on the furnace wall of the furnace 11, the protective gas nozzles 104 a, 104 b, 104 c and 104 d extend along the inner wall surface of the furnace 11. Therefore, air can be appropriately supplied between the flame swirl flow and the inner wall surface of the furnace 11.

[Third Embodiment]
FIG. 5 is a plan view illustrating a combustion region in the coal fired boiler according to the third embodiment. In addition, the same code | symbol is attached | subjected to the member which has the same function as embodiment mentioned above, and detailed description is abbreviate | omitted.

  In 3rd Embodiment, as shown in FIG. 6, the coal fired boiler has the furnace 11 and the combustion apparatus 101. As shown in FIG. The combustion apparatus 101 is provided in the lower part of the furnace wall (heat-transfer tube) that constitutes the furnace 11. This combustion apparatus 101 has a plurality of combustion burners 102 mounted on the furnace wall, and although not shown, is a CUF combustion system as in the second embodiment.

  The combustion burner 102 is composed of combustion burners 102a, 102b, 102c, and 102d provided on four furnace walls in the furnace 11, and the branch pipes 26a, 26b, 26c, and 26d branched from the pulverized coal supply pipe 26 are connected to each other. In addition, the branch pipes 37a, 37b, 37c, and 37d branched from the air duct 37 are connected.

  In the furnace 11, a protective gas supply device 111 is provided between the combustion device 101 and the additional air supply device. The protective gas supply device 111 has a plurality of protective gas nozzles 112 mounted on the furnace wall. The four protective gas nozzles 112 are arranged at equal intervals along the circumferential direction. The protective gas supply device 111 blows air as a protective gas (Wall Protection Air) into the furnace 11.

  The protective gas nozzle 112 is composed of protective gas nozzles 112 a, 112 b, 112 c, 112 d provided on four furnace walls in the furnace 11. Each of the protective gas nozzles 112 a, 112 b, 112 c, 112 d is arranged close to one corner (on the pulverized fuel mixture injection direction side) with respect to the horizontal direction of the furnace wall of the furnace 11. In this case, each of the protective gas nozzles 112a, 112b, 112c, and 112d is in the same position as the combustion burners 102a, 102b, 102c, and 102d in the furnace 11, and a fine fuel mixture is blown in by the combustion burners 102a, 102b, 102c, and 102d. Arranged on the direction side. Each of the protective gas nozzles 112a, 112b, 112c, and 112d is connected to each of the branch pipes 65a, 65b, 65c, and 65d branched from the third branch air duct 65. Accordingly, each of the protective gas nozzles 112a, 112b, 112c, and 112d blows air horizontally along the inner wall surface of the furnace 11 outside the pulverized fuel mixture blown by the combustion burners 21, 22, 23, 24, and 25. Can do.

  In this embodiment, in the protective gas supply device 111, the protective gas nozzles 112a, 112b, 112c, 112d blow air between the inner wall surface of the furnace 11 and the flames from the combustion burners 102a, 102b, 102c, 102d, The air flow A1, A2, A3, A4 is formed. Each of the protective gas nozzles 112a, 112b, 112c, and 112d is connected to each of the branch pipes 65a, 65b, 65c, and 65d branched from the third branch air duct 65. Each protective gas nozzle 112 a, 112 b, 112 c, 112 d can blow air horizontally along the inner wall surface of the furnace 11. In this case, the amount of air blown by the protective gas nozzle 112 (112a, 112b, 112c, 112d) is about 1% to 5% in terms of the total air amount ratio, and the nozzle flow velocity is 20 m / s to 100 m / s.

  Therefore, the combustion burners 102a, 102b, 102c, and 102d form a flame swirl flow by blowing finely pulverized fuel mixture (fuel gas) and secondary air into the furnace 11. The protective gas nozzles 112 a, 112 b, 112 c, and 112 d blow the air as the protective gas horizontally along the inner wall surface of the furnace 11 outside the combustion burners 102 a, 102 b, 102 c, and 102 d. Then, the protective gas nozzles 112 a, 112 b, 112 c, 112 d are connected to the air flow A 1, A 2, A 3 between the flames F 1, F 2, F 3, F 4 from the combustion burners 102 a, 102 b, 102 c, 102 d and the inner wall surface of the furnace 11. , A4. Therefore, the flames F1, F2, F3, and F4 are not in direct contact with the inner wall surface of the furnace 11 due to the air flows A1, A2, A3, and A4, and the occurrence of corrosion is suppressed by lowering the temperature of the furnace wall.

  Further, since air is blown between the inner wall surface of the furnace 11 and the flame swirl flow from the protective gas nozzles 112a, 112b, 112c, and 112d, this region becomes a high oxygen region, and generation of hydrogen sulfide is suppressed. Corrosion of the furnace wall is suppressed. Furthermore, since the vicinity of the wall surface of the reduction region B is a high-oxygen atmosphere and a low-temperature atmosphere, the furnace 11 can suppress the melting of fly ash and prevent slagging.

  As described above, in the boiler according to the third embodiment, the protective gas nozzles 112a, 112b for blowing air (protective gas) horizontally along the inner wall surface of the furnace 11 at the same position as the combustion burners 102a, 102b, 102c, 102d, 112c, 112d are provided, the combustion burners 102a, 102b, 102c, 102d are disposed on the furnace wall, and the protective gas nozzles 112a, 112b, 112c, 112d are disposed outside the combustion burners 102a, 102b, 102c, 102d and the inner wall surface of the furnace 11 Air is sprayed along.

  Accordingly, by blowing air from the protective gas nozzles 112a, 112b, 112c, and 112d along the inner wall surface of the furnace 11, direct contact between the combustion gas and the inner wall surface of the furnace 11 is suppressed, and corrosion of the furnace wall is prevented. And durability can be improved. Further, when the combustion burners 102 a, 102 b, 102 c, 102 d and the protective gas nozzles 112 a, 112 b, 112 c, 112 d are arranged on the furnace wall of the furnace 11, the protective gas nozzles 112 a, 112 b, 112 c, 112 d extend along the inner wall surface of the furnace 11. Therefore, air can be appropriately supplied between the flame swirl flow and the inner wall surface of the furnace 11.

[Fourth Embodiment]
FIG. 7 is a schematic configuration diagram illustrating a coal fired boiler according to a fourth embodiment. In addition, the same code | symbol is attached | subjected to the member which has the same function as embodiment mentioned above, and detailed description is abbreviate | omitted.

  In 4th Embodiment, as shown in FIG. 7, the coal fired boiler 10 has the furnace 11 and the combustion apparatus 12. As shown in FIG. The combustion device 12 has a plurality of combustion burners 21, 22, 23, 24, 25 mounted on the furnace wall. Each combustion burner 21, 22, 23, 24, 25 is connected to a pulverized coal machine 31, 32, 33, 34, 35 via a pulverized coal supply pipe 26, 27, 28, 29, 30. In the furnace 11, a wind box 36 is provided at a mounting position of each combustion burner 21, 22, 23, 24, 25, and an air duct 37 is connected to the wind box 36.

  Further, the furnace 11 is provided with an additional combustion air supply device 41 at the upper stage of the combustion device 12. The additional combustion air supply device 41 has a plurality of additional combustion air nozzles 42 and 43 attached to the furnace wall. The additional combustion air nozzles 42 and 43 are connected to the ends of the first branch air duct 44 branched from the air duct 37. Further, the furnace 11 is provided with an additional air supply device 51 above the combustion device 12. The additional air supply device 51 has a plurality of additional air nozzles 52 mounted on the furnace wall. The additional air nozzle 52 is connected to an end of a second branch air duct 53 branched from the air duct 37.

  The furnace 11 is provided with a protective gas supply device 61 at the same position as the combustion device 12. The protective gas supply device 61 has a plurality of protective gas nozzles 62, 63, 64 mounted on the furnace wall. In the present embodiment, the protective gas nozzles 62, 63, 64 use at least a part of the exhaust gas discharged from the furnace 11 as a protective gas. The protective gas nozzles 62, 63, 64 are connected to the end of a third branch air duct 66 branched from the exhaust system 80 that continues to the exhaust gas pipe 78. In this case, the amount of air blown by the protective gas nozzles 62, 63, 64 is about 1% to 5% in terms of the total air amount ratio, and the nozzle flow rate is 20 m / s to 100 m / s.

  Therefore, the combustion burners 21, 22, 23, 24, and 25 blow fine powder fuel mixture and secondary air into the furnace 11 and ignite at this time to form a flame swirl flow in the combustion region A. At this time, the additional combustion air nozzles 42 and 43 appropriately form the combustion region A by blowing the additional combustion air into the furnace 11. In the furnace 11, when the pulverized fuel mixture, the secondary air, and the additional combustion air are burned to generate a flame swirl, and a flame swirl is generated in the combustion region A, the combustion gas (exhaust gas) swirls in the furnace 11. It rises while reaching the reduction region B.

  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 B above A is maintained in a reducing atmosphere. Therefore, NOx generated by the combustion of pulverized coal is reduced in this reduction region B.

  The additional air nozzle 52 blows additional air above the reduction region B of the furnace 11. Then, in the combustion completion region C, the exhaust gas reacts with the additional air to complete the oxidative combustion of the pulverized coal, and the amount of NOx generated by the combustion of the pulverized coal is reduced.

  Further, in the furnace 11, the protective gas nozzles 62, 63, 64 inject exhaust gas along the inner wall surface in the combustion region A. Since this exhaust gas is blown outside from the flame swirl flow, the flame does not directly contact the inner wall surface of the furnace 11, and the occurrence of corrosion is suppressed by lowering the temperature of the furnace wall.

  As described above, in the boiler according to the fourth embodiment, the combustion burners 21, 22, 23, 24, and 25 that blow the pulverized fuel mixture into the furnace 11, and the combustion burners 21, 22, 23, 24, and 25 Additional combustion air nozzles 42 and 43 for blowing additional combustion air into the furnace 11 at the upper stage, and additional blowing of additional air into the furnace 11 above the combustion burners 21, 22, 23, 24 and 25 An air nozzle 52, and protective gas nozzles 62, 63, 64 for blowing exhaust gas (protective gas) horizontally between the combustion burners 21, 22, 23, 24, 25 and the additional air nozzle 52 along the inner wall surface of the furnace 11; Is provided.

  Accordingly, the exhaust gas is blown horizontally along the inner wall surface of the furnace 11 from the protective gas nozzles 62, 63, 64, so that direct contact between the combustion gas and the inner wall surface of the furnace 11 is suppressed, and corrosion of the furnace wall is prevented. And durability can be improved. Further, the protective gas nozzles 62, 63, 64 can suppress an increase in the temperature of the inner wall surface of the furnace 11 by supplying exhaust gas as the protective gas to the furnace 11.

  In the fourth embodiment, the protective gas nozzle 62 is configured to blow the exhaust gas discharged from the furnace 11 along the inner wall surface of the furnace 11, but the present invention is not limited to this configuration. For example, the protective gas nozzle 62 may be configured to blow an air-fuel mixture obtained by mixing exhaust gas discharged from the furnace 11 and combustion air from the air duct 37 along the inner wall surface of the furnace 11.

  In the above-described fourth embodiment, the form of the combustion burner is the CCF combustion system of the first embodiment, but it may be the CUF combustion system of the second and third embodiments.

  In the embodiment described above, the boiler of the present invention is a coal-fired boiler. However, the fuel may be a boiler using biomass or petroleum coke, or may be applied to an oil-fired boiler.

DESCRIPTION OF SYMBOLS 10 Coal-fired boiler 11 Furnace 12, 101 Combustion device 21, 22, 23, 24, 25, 102 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 41 Additional combustion air supply device 42, 43 Additional combustion air nozzle 44 First branch air duct 51 Additional air supply device 52 Additional air nozzle 53 Second branch air duct 61, 103, 111 Protective gas supply device 62, 63, 64, 104, 112 Protective gas nozzle 65, 66 Third branch air duct

Claims (6)

A furnace that is hollow and installed along the vertical direction;
Combustion burners arranged in multiple stages along the vertical direction capable of forming a flame swirl flow by blowing a fuel gas mixed with solid fuel and combustion air into the furnace,
An additional air nozzle that blows additional air into the furnace above the combustion burner;
The additional air is disposed on one side of the combustion burner corresponding to only the uppermost combustion burner among the combustion burners arranged in a plurality of stages, and the additional air is introduced to the furnace wall side from the blowing direction of the fuel gas by the combustion burner . A protective gas nozzle that blows part of it as protective gas ;
The boiler characterized by having.   The combustion burner has a fuel nozzle capable of injecting fuel gas, and a secondary air nozzle capable of injecting secondary air from the outside of the fuel nozzle, and the protective gas nozzle is one side of the secondary air nozzle. 2. The boiler according to claim 1, wherein the boiler is disposed only in a section and can blow protective gas toward the outside of the flame swirl flow.   The boiler according to claim 1 or 2, wherein the combustion burner and the protective gas nozzle are arranged at corners of the furnace and inject protective gas along one inner wall surface.   The boiler according to claim 1 or 2, wherein the combustion burner and the protective gas nozzle are disposed on a furnace wall of the furnace and inject protective gas along one inner wall surface.   An amount of combustion air blown from the combustion burner and an additional air amount blown from the additional air nozzle are set according to the form of the boiler, and a part of the additional air amount is used as the protective gas amount blown from the protective gas nozzle. The boiler as described in any one of Claims 1-4 characterized by the above-mentioned.   The boiler according to any one of claims 1 to 5, wherein at least a part of the exhaust gas discharged from the furnace is used as the protective gas.

Images