JP2017146077A - Boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accelerate mixture of fuel and air in a furnace to improve combustion efficiency, in a boiler.SOLUTION: A boiler includes: a furnace 11 formed into a hollow shape and installed along a vertical direction; and a combustor 12 in which a plurality of combustion burners 21, 22, 23 arranged in multistage manner along the vertical direction of the furnace 11, the combustion burners configured to jet into the furnace 11 toward a horizontal revolving direction pulverized coal mixture obtained by mixing solid fuel and combustion air. The lower-stage ones of the plurality of combustion burners 21, 22, 23 arranged in a multiple manner are configured to jet pulverized coal mixture toward a center O side of the furnace 11.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a boiler for generating steam by burning fuel and air.

  A conventional boiler has a furnace that is hollow and is installed in a vertical direction, and a plurality of combustion burners are arranged on the furnace wall in the circumferential direction and the vertical direction. In this furnace, a flue is connected to the upper part, and a heat exchanger for collecting the heat of the exhaust gas to generate steam is disposed in the flue.

  As such a boiler, there exists a thing described in the following patent document 1, for example. The combustion apparatus described in Patent Document 1 includes a set of four combustion burners arranged at predetermined intervals along the circumferential direction, arranged in a plurality of stages along the vertical direction, and is ejected from each combustion burner. A flame swirl is formed in the furnace by the fuel and air.

Japanese Patent Laid-Open No. 11-141806

  In the conventional boiler, as described above, each combustion burner constituting the combustion device ignites by injecting fuel and air to form a flame swirl flow in the furnace. However, since each combustion burner arranged over each stage of the furnace injects fuel and air in the same direction, a flame swirl flow having the same diameter is formed along the vertical direction in the furnace. Therefore, the fuel concentration is high around the flame swirl, and the fuel concentration is low in the center, which may result in insufficient fuel and air mixing in the entire furnace.

  The present invention solves the above-described problems, and an object of the present invention is to provide a boiler that promotes mixing of fuel and air in a furnace to improve combustion efficiency.

  In order to achieve the above object, a boiler according to the present invention includes a furnace having a hollow shape and installed in a vertical direction, and a fuel gas in which solid fuel and combustion air are mixed in the furnace, in a horizontal swirl direction. A plurality of combustion burners ejected toward the furnace, arranged in a plurality of stages along the vertical direction of the furnace, the plurality of combustion burners arranged in a plurality of stages, the lower the stage, the center of the furnace The fuel gas is ejected toward the side.

  Therefore, when a fuel gas in which solid fuel and combustion air are mixed is ejected from a plurality of combustion burners into the furnace, a flame swirl is formed by swirling the fuel gas in the furnace. At this time, the plurality of combustion burners eject fuel gas toward the center side of the furnace toward the lower stage. Therefore, in the furnace, solid fuel is collected on the center side by forming a small-sized flame swirl flow at the lower side, and solid fuel is collected on the outer peripheral side by forming a large-sized flame swirl flow at the upper side. Therefore, the mixing of the solid fuel and air in the furnace can be promoted to improve the combustion efficiency.

  In the boiler according to the present invention, the angle of the fuel gas injection axis in the plurality of combustion burners with respect to a reference line connecting the plurality of combustion burners and the center of the furnace is set to be smaller as the lower stage. It is a feature.

  Therefore, the plurality of combustion burners can form a flame swirl that gradually increases from the lower side to the upper side by setting the angle of the fuel gas injection axis to be lower at the lower stage, so that the solid in the furnace Mixing of fuel and air can be facilitated.

  In the boiler according to the present invention, the plurality of combustion burners are arranged at predetermined intervals in the circumferential direction on the wall portion of the furnace, and are arranged in at least three stages along the vertical direction of the furnace. It is said.

  Therefore, it is possible to easily form a flame swirl that gradually increases from the bottom to the top, and to promote mixing of solid fuel and air in the furnace.

  In the boiler according to the present invention, the plurality of combustion burners arranged in a plurality of stages is characterized in that the lower the stage, the smaller the air ratio in the fuel gas is set.

  Therefore, the furnace can form a small-diameter flame swirl flow in a reducing atmosphere by ejecting a fuel gas having a low air ratio downward, and an oxidizing atmosphere by ejecting a fuel gas having a high air ratio upward. Can form a large-diameter flame swirl flow, promote the mixing of solid fuel and air in the furnace, suppress the generation of hydrogen sulfide due to air shortage above the furnace, It is possible to suppress the corrosion of the furnace wall.

  In the boiler according to the present invention, an air ejection direction adjusting device capable of adjusting a fuel gas ejection direction by the plurality of combustion burners in a horizontal direction is provided.

  Therefore, the magnitude of the flame swirl at the vertical position can be adjusted, and the optimum flame swirl can be formed according to changes in operating conditions. And air mixing can be promoted.

  According to the boiler of the present invention, since the plurality of combustion burners arranged in a plurality of stages are configured to eject the fuel gas toward the center of the furnace toward the lower stage, mixing of solid fuel and air in the furnace To improve combustion efficiency.

Drawing 1 is a schematic structure figure showing the boiler of a 1st embodiment. FIG. 2 is a plan view showing the arrangement configuration of the combustion burners. FIG. 3 is a plan view of the boiler representing the flame swirl flow. FIG. 4 is a front view of the boiler representing the flame swirl. FIG. 5 is a plan view illustrating an arrangement configuration of fuel burners in the boiler according to the second embodiment.

  Hereinafter, preferred embodiments of a boiler according to the present invention will be described 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]
FIG. 1 is a schematic configuration diagram illustrating a boiler according to the first embodiment, and FIG. 2 is a plan view illustrating an arrangement configuration of combustion burners.

  The boiler according to the first embodiment is a boiler that can use pulverized coal obtained by pulverizing coal as pulverized fuel (solid fuel), burn the pulverized coal with a combustion burner, and recover the heat generated by the combustion. .

  In the first embodiment, as shown in FIG. 1, the boiler 10 includes a furnace 11, a combustion device 12, and a flue 13. 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 mounted on the furnace wall. In the present embodiment, four combustion burners 21, 22, and 23 are arranged at equal intervals along the circumferential direction as one set, and three sets along the vertical direction, that is, three stages are arranged. ing. However, 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 of the combustion burners 21, 22, 23 is connected to a pulverizer (pulverized coal machine / mill) 27, 28, 29 via pulverized coal supply pipes 24, 25, 26. In the furnace 11, a wind box 31 is provided at a mounting position of each combustion burner 21, 22, 23, and one end portion of an air duct 32 is connected to the wind box 31, and the other end portion of the air duct 32. A blower 33 is connected to the fan. Further, the furnace 11 is provided with an additional air nozzle 34 located above the mounting position of the combustion burners 21, 22, and 23, and an additional air duct 35 branched from the air duct 32 is connected thereto.

  The flue 13 is connected to the upper part of the furnace 11. The flue 13 has superheaters (superheaters) 41, 42, 43 as heat exchangers for recovering the heat of combustion gas, reheaters (reheaters) 44, 45, economizers 46, economizers, 47 is provided, and heat exchange is performed between the combustion gas generated by the combustion in the furnace 11 and water. Further, the flue 13 is connected to a gas duct 48 through which the combustion gas that has exchanged heat is discharged downstream. This gas duct 48 is provided with an air heater 49 between the air duct 32, performs heat exchange between the air flowing through the air duct 32 and the exhaust gas flowing through the gas duct 48, and the combustion burners 21, 22, 23 and the additional air. The temperature of the combustion air supplied to the nozzle 34 can be raised.

  Here, although the combustion apparatus 12 is demonstrated in detail, since the combustion burners 21, 22, and 23 which comprise this combustion apparatus 12 have comprised the substantially the same structure, respectively, the combustion burner 21 is demonstrated as a representative. .

  As shown in FIG. 2, the combustion burner 21 includes combustion burners 21a, 21b, 21c, and 21d provided at four corners of the furnace 11, respectively. Each combustion burner 21a, 21b, 21c, 21d is connected to each branch pipe 24a, 24b, 24c, 24d branched from the pulverized coal supply pipe 24, and each branch pipe 32a, 32b, 32c branched from the air duct 32. , 32d (wind box 31) are connected. In addition, although each combustion burner 21a, 21b, 21c, 21d is arrange | positioned in the four corners in the furnace 11, each combustion burner 21a, 21b, 21c, 21d may be arrange | positioned in the four wall parts in the furnace 11.

  Therefore, each combustion burner 21a, 21b, 21c, 21d blows a pulverized coal mixture (fuel gas), which is a mixture of pulverized coal and carrier air, into the furnace 11, and outside the periphery of the pulverized coal mixture. Combustion air (fuel gas combustion air / secondary air) is blown in. And by igniting this pulverized coal mixture, four flames F1, F2, F3, and F4 can be formed, and these flames F1, F2, F3, and F4 are viewed from vertically above the furnace 11 ( In FIG. 2, the flame swirl flow C swirls counterclockwise as the center O of the furnace 11.

  By the way, the combustion apparatus 12 of the present embodiment is configured such that a plurality of combustion burners 21, 22, and 23 arranged in a plurality of stages eject fuel gas toward the center O side of the furnace 11 toward the lower stage.

  FIG. 3 is a plan view of a boiler representing a flame swirl flow, and FIG. 4 is a front view of the boiler representing a flame swirl flow.

  As shown in FIGS. 3 and 4, in the combustion apparatus 12, the upper combustion burner 21 includes four combustion burners 21 a, 21 b, 21 c, and 21 d provided at each corner in the furnace 11. Each combustion burner 21a, 21b, 21c, 21d has an injection axis G1 on the furnace wall side by a predetermined angle θ1 with respect to a reference line G0 connecting the outlet of the combustion burners 21a, 21b, 21c, 21d and the center O of the furnace 11. Facing. Therefore, a large-diameter flame swirl flow C1 can be formed by blowing pulverized coal mixture and combustion air into the furnace 11 by the combustion burners 21a, 21b, 21c, and 21d.

  The middle-stage combustion burner 22 includes four combustion burners 22 a, 22 b, 22 c, and 22 d provided at each corner of the furnace 11. Each combustion burner 22a, 22b, 22c, 22d has a predetermined angle θ2 on the furnace wall side with respect to a reference line G0 where the injection axis G2 connects the outlet of the combustion burners 22a, 22b, 22c, 22d and the center O of the furnace 11. Facing. Therefore, the flame swirl flow C2 can be formed by blowing the pulverized coal mixture and the combustion air into the furnace 11 by the combustion burners 22a, 22b, 22c, and 22d.

  Further, the lower combustion burner 23 includes four combustion burners 23 a, 23 b, 23 c, and 23 d provided at each corner of the furnace 11. Each combustion burner 23a, 23b, 23c, 23d has a predetermined angle θ3 on the furnace wall side with respect to a reference line G0 where the injection axis G1 connects the outlet of the combustion burners 23a, 23b, 23c, 23d and the center O of the furnace 11. Facing. Therefore, the small-diameter flame swirl flow C1 can be formed by blowing the pulverized coal mixture and the combustion air into the furnace 11 by the combustion burners 21a, 21b, 21c, and 21d.

  Therefore, the combustion apparatus 12 can form a flame swirl flow C (C1, C2, C3) whose diameter gradually increases from the bottom to the top in the furnace 11.

  Further, in the combustion device 12, the air ratio in the pulverized coal mixture and the combustion air is set to be smaller as the plurality of combustion burners 21, 22, and 23 arranged in a plurality of stages become lower. The upper combustion burner 21 (burners 21a, 21b, 21c, 21d) has an air ratio set in the range of 1.0 to 1.05, and the middle combustion burner 22 (burners 22a, 22b, 22c, 22d) The air ratio is set in the range of 0.7 to 0.8, and the lower combustion burner 23 (burners 23a, 23b, 23c, and 23d) is set in the range of 0.5 to 0.6. Here, the air ratio is the ratio of the actual air amount (oxidizer amount) to the theoretical air amount (theoretical oxidizer amount) necessary for completely burning the pulverized coal (coal) supplied to the furnace 11. is there.

  In the boiler 10 of this embodiment configured as described above, as shown in FIGS. 1 to 4, when the crushers 27, 28, and 29 are driven, the supplied coal is crushed and the generated pulverized coal is conveyed. The combustion air is supplied to the combustion burners 21, 22, and 23 through pulverized coal supply pipes 24, 25, and 26 by working air. The combustion air heated by the air heater 49 is supplied to the wind box 31 by the air duct 32 and is supplied to the additional air nozzle 34 by the additional air duct 35.

  Then, the combustion burners 21, 22, and 23 blow a pulverized coal mixture in which pulverized coal and carrier air are mixed and combustion air into the furnace 11 and ignite at this time to form a flame swirl flow C. Further, the additional air nozzle 34 blows additional air above the flame swirl flow C in the furnace 11. In the furnace 11, the pulverized coal mixture and the combustion air are combusted to generate a flame swirl, and the combustion gas (exhaust gas) rises while swirling.

  At this time, the upper combustion burner 21 blows the pulverized coal mixture and the combustion air into the furnace 11 to form a large-diameter flame swirl flow C1, and the middle combustion burner 22 is finely divided into the furnace 11. A flame swirl flow C2 is formed by blowing the coal mixture and the combustion air, and the lower combustion burner 23 blows the pulverized coal mixture and the combustion air into the furnace 11 so that the small-diameter flame swirl flow C3. Form.

  That is, a flame swirl flow C (C1, C2, C3) whose diameter gradually increases from the bottom toward the top is formed in the furnace 11, and the plurality of combustion burners 21, 22, 23 are finer as the lower stage. The air ratio in the charcoal mixture and the combustion air is set small.

  Therefore, the furnace 11 collects pulverized coal on the center O side by forming a small-diameter flame swirl flow C3 in the lower part, and forms a large-diameter flame swirl flow C1 in the upper part to form the outer periphery of the pulverized coal. Mixing of pulverized coal and air is promoted by the flame swirl flow C that gradually increases from the bottom to the top.

  In addition, the furnace 11 becomes a reducing atmosphere by ejecting a pulverized coal mixture and combustion air having a low air ratio downward, and by ejecting a pulverized coal mixture and combustion air having a high air ratio upward, It becomes an oxidizing atmosphere. Therefore, the NOx generated by the combustion of the pulverized coal is maintained in the reducing atmosphere below the furnace 11 and reduced in the furnace 11, and then the oxidative combustion of the pulverized coal is completed in the upper oxidizing atmosphere due to the rise of the combustion gas, The amount of NOx generated by the combustion of pulverized coal is reduced. Moreover, since the furnace 11 becomes an oxidizing atmosphere (air-excess atmosphere) at the upper side, generation of hydrogen sulfide due to air shortage is suppressed, and corrosion of the furnace wall due to hydrogen sulfide is suppressed.

  Then, the water supplied from a water supply pump (not shown) is preheated by the economizers 46 and 47, then supplied to a steam drum (not shown) and heated while being supplied to each water pipe (not shown) on the furnace wall. Then, it becomes saturated steam and is sent to a steam drum (not shown). Further, saturated steam of a steam drum (not shown) is introduced into the superheaters 41, 42, and 43 and is heated by the combustion gas. The superheated steam generated by the superheaters 41, 42, 43 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 44 and 45, overheated again, and returned to the turbine.

  Thereafter, the exhaust gas that has passed through the economizers 46 and 47 of the flue 13 is subjected to a gas duct 48 to remove harmful substances such as NOx by a catalyst by a denitration device (not shown), particulate matter is removed by an electric dust collector, and desulfurization. After the sulfur content is removed by the device, it is discharged into the atmosphere from the chimney.

  Thus, in the boiler of 1st Embodiment, the pulverized coal mixture which mixed the pulverized coal and the combustion air in the furnace 11 which makes hollow shape, and is installed along a perpendicular direction in the furnace 11 is used. A plurality of combustion burners 21, 22, 23 ejected in the horizontal turning direction are provided with a combustion device 12 arranged in a plurality of stages along the vertical direction of the furnace 11, and a plurality of combustion burners 21 arranged in a plurality of stages , 22, and 23, the lower stage is configured to eject the pulverized coal mixture toward the center O side of the furnace 11.

  Accordingly, the furnace 11 collects the pulverized coal on the center O side by forming the small-diameter flame swirl flow C3 at the lower side, and forms the large-diameter flame swirl flow C1 at the upper side to form the outer periphery of the pulverized coal. The pulverized coal is scattered in the vertical direction and the horizontal direction in the entire furnace 11, and the mixing of the pulverized coal and air in the furnace 11 is promoted to improve the combustion efficiency. it can.

  In the boiler of the first embodiment, the plurality of combustion burners 21, 22, 23 are pulverized coal mixtures and combustion air in the combustion burners 21, 22, 23 with respect to a reference line G 0 from the injection port to the center O of the furnace 11. The angles θ1, θ2, and θ3 of the injection axes G1, G2, and G3 are set to be smaller as the lower level. Accordingly, flame swirl flows C1, C2, and C3 that gradually increase from the bottom to the top of the furnace 11 can be formed, and mixing of pulverized coal and air in the furnace 11 can be promoted.

  In the boiler according to the first embodiment, the plurality of combustion burners 21, 22, and 23 arranged in a plurality of stages are set such that the lower the stage, the smaller the air ratio in the pulverized coal mixture and the combustion air. Accordingly, the furnace 11 can form a small-diameter flame swirl flow C3 in a reducing atmosphere by ejecting a pulverized coal mixture and combustion air having a low air ratio downward, and a pulverized coal having a high air ratio upward. By jetting the air-fuel mixture and combustion air, a large-diameter flame swirl flow C1 can be formed in an oxidizing atmosphere, and the mixing of pulverized coal and air in the furnace 11 can be promoted, and the furnace 11, generation of hydrogen sulfide due to air shortage above is suppressed, and corrosion of the furnace wall by hydrogen sulfide can be suppressed.

[Second Embodiment]
FIG. 5 is a plan view illustrating an arrangement configuration of fuel burners in the boiler according to the second embodiment. The basic configuration of the boiler of the present embodiment is substantially the same as that of the first embodiment described above, and a member having the same function as that of the first embodiment described above with reference to FIG. Are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the second embodiment, as shown in FIG. 5, there is provided an ejection direction adjusting device 51 that can adjust the ejection direction of the pulverized coal mixture and combustion air by the combustion burner 21 (22, 23) in the horizontal direction. . In this case, the ejection direction adjusting device 51 is provided independently for each combustion burner 21a, 21b, 21c, 21d, and can individually adjust the ejection direction of the pulverized coal mixture and the combustion air.

  For example, in the rated operation of the boiler 10, as shown in FIG. 2, the upper combustion burner 21 forms a large-diameter flame swirl flow C1 by blowing a pulverized coal mixture and combustion air into the furnace 11. The middle combustion burner 22 blows the pulverized coal mixture and combustion air into the furnace 11 to form a flame swirl C2, and the lower combustion burner 23 combusts the pulverized coal mixture and combustion in the furnace 11. By blowing the working air, a small-diameter flame swirl flow C3 is formed. That is, a flame swirl flow C (C1, C2, C3) having a diameter gradually increasing from the bottom to the top is formed in the furnace 11. Further, the plurality of combustion burners 21, 22, and 23 are set such that the air ratio in the pulverized coal mixture and the combustion air is set lower in the lower stage.

  And if the operation state of the boiler 10 fluctuates, there is a possibility that combustion of pulverized coal may become insufficient. At this time, the ejection direction adjusting device 51 adjusts the ejection direction of the pulverized coal mixture and the combustion air in each combustion burner 21a, 21b, 21c, 21d to the optimum position. The optimum position is, for example, a position where the unburned amount becomes the minimum value.

  Thus, in the boiler of 2nd Embodiment, the injection direction adjustment apparatus 51 which can adjust the injection direction of the pulverized coal mixture and combustion air by the some combustion burners 21, 22, and 23 to a horizontal direction is provided. Yes. Therefore, the magnitude of the flame swirl flow C1, C2, C3 at the vertical position can be adjusted, and the flame swirl flow C1, C2, C3 of the optimum size can be formed according to the change of the operating conditions. The mixing of pulverized coal and air in the furnace 11 can always be promoted.

  In the above-described embodiment, the three-stage combustion burners 21, 22, and 23 are set in the furnace 11, and the diameter of the flame swirl flow C is gradually increased upward. However, the present invention is not limited to this configuration. Absent. For example, a plurality of combustion burners may be set in the furnace, and a plurality of lower stages may have the same diameter, a plurality of middle stages may have the same diameter, or a plurality of upper stages may have the same diameter.

  In the above-described embodiment, the three-stage combustion burners 21, 22, and 23 are set for the furnace 11, but the number may be two or four or more. Further, the number of pulverizers 27, 28, 29 is not limited to the embodiment.

  In the above-described embodiment, the boiler of the present invention is a coal-fired boiler, but the solid fuel may be a boiler using biomass, petroleum coke, petroleum residue, or the like in addition to coal.

DESCRIPTION OF SYMBOLS 10 Boiler 11 Furnace 12 Combustion device 13 Flue 21, 22, 23 Combustion burner 24, 25, 26 Pulverized coal supply pipe 27, 28, 29 Crusher 31 Wind box 32 Air duct 34 Additional air nozzle 41, 42, 43 Superheater (Heat exchanger)
44, 45 Reheater (heat exchanger)
46, 47 economizer (heat exchanger)
51 Ejection direction adjusting device C, C1, C2, C3 Flame swirl flow G0 Reference line G1, G2, G3 Injection axis

Claims (5)

A furnace that is hollow and installed along the vertical direction;
A combustion apparatus in which a plurality of combustion burners for jetting a fuel gas mixed with solid fuel and combustion air into the furnace in a horizontal swirl direction is arranged in a plurality of stages along the vertical direction of the furnace;
With
The plurality of combustion burners arranged in a plurality of stages ejects fuel gas toward the center side of the furnace toward the lower stage,
A boiler characterized by that.   2. The plurality of combustion burners, wherein an angle of a fuel gas injection axis in the plurality of combustion burners with respect to a reference line that connects the plurality of combustion burners and the center of the furnace is set to be smaller as a lower stage. The boiler described in 1.   The plurality of combustion burners are arranged at predetermined intervals in a circumferential direction on a wall portion of the furnace, and are arranged in at least three stages along a vertical direction of the furnace. The boiler according to claim 2.   The boiler according to any one of claims 1 to 3, wherein the plurality of combustion burners arranged in a plurality of stages sets an air ratio in the fuel gas to a lower level.   The boiler according to any one of claims 1 to 4, wherein an air ejection direction adjusting device capable of adjusting a fuel gas ejection direction by the plurality of combustion burners in a horizontal direction is provided.

Images