JP4882422B2 - Gas turbine combustor and combustion method of combustion apparatus - Google Patents

Description

  The present invention relates to a combustion apparatus, a gas turbine combustor, and a combustion method of the combustion apparatus.

  In a combustion apparatus that burns fuel, reduction of nitrogen oxides (NOx) is required. As a technique for using liquefied natural gas (LNG) as a gas turbine fuel and reducing NOx, there is a premixed combustion burner technique in which the fuel-air ratio is reduced by premixing fuel and air. However, when this technology is applied with a fuel having a low self-ignition temperature such as hydrogen, backfire may occur in the premixing flow path, and the combustor may be burned.

  Therefore, in the combustor of Patent Document 1, a plurality of burners in which fuel nozzles and air nozzles are arranged in a radial direction so that a coaxial jet that wraps around the fuel with air is supplied from the air nozzles to the combustion chamber. It is a group of annular burners. And, by reducing the amount of fuel supplied to the annular burner group located radially inside the combustor from the amount of fuel supplied to the annular burner group located radially outside, the fuel is slowly burned on the downstream side of the combustion chamber, NOx is decreased.

JP 2005-30667 A

  There is a limit to reducing NOx by reducing the amount of fuel in one part. That is, if the amount of fuel supplied to the combustor burner is reduced overall, the flame may blow out, and at least one annular burner group must maintain an average fuel concentration at which the flame is held stable. There is a limit to low NOx due to the limit of concentration reduction. Therefore, in order to further reduce the NOx discharged from the combustor, it is desired to improve the combustion stability in a range where the fuel concentration is low.

  Accordingly, an object of the present invention is to improve combustion stability in a range where the fuel concentration is low and to further reduce NOx in the exhausted combustion gas.

  In order to solve the above-mentioned problem, a plurality of jets included in the first burner so that the fuel flow from at least one first burner of the plurality of burners and the flame from the second burner intersect each other. The first plane including the outlet ejection position intersects with the second plane including the ejection positions of the plurality of ejection openings of the second burner.

  According to the present invention, it is possible to improve the combustion stability in a range where the fuel concentration is low and to further reduce the NOx of the exhausted combustion gas.

  There are various types of combustion devices. First, the NOx reduction and flame stability of various combustion technologies will be described. A gas turbine combustor, which is one of combustion apparatuses, uses various fuels. When liquid fuel such as light oil or heavy fuel oil A is used, it is common to adopt a diffusion combustion system in which fuel is atomized and supplied to a combustor and air is supplied from a flow path different from the fuel. In this case, water or steam is injected into the combustor to lower the flame temperature, thereby reducing NOx. On the other hand, in the case of gas turbines that use liquefied natural gas (LNG), there are many that employ a combustion method that combines a premixed combustion burner that premixes fuel and air for combustion and a pilot burner for diffusion combustion. .

  Here, the relationship between the flame temperature and the fuel concentration (fuel / air ratio) will be described. FIG. 9 is a graph showing the relationship between the fuel concentration and the theoretical flame temperature, where the horizontal axis represents the fuel concentration, which is the ratio of fuel to air, and the vertical axis represents the theoretical flame temperature. Flame temperature varies with fuel concentration. The flame temperature tends to increase as the fuel concentration increases in the fuel lean region, reaches a maximum near the stoichiometric mixture ratio, and decreases in the fuel rich region where the fuel concentration increases. In the case of diffusion combustion, since there is a region where the fuel and air have a stoichiometric mixture ratio in the vicinity of the flame surface, the NOx concentration becomes high. On the other hand, in the premixed combustion, fuel and air are uniformly burned, so that low temperature uniform combustion with a low local flame temperature is possible, and low NOx combustion is possible. Accordingly, since the flame temperature decreases as the fuel concentration is decreased in the fuel lean region, a lower NOx can be expected.

  However, premixed combustion has a narrower stable combustion range than diffusion combustion. FIG. 10 is a diagram showing the relationship between the flame temperature and the CO emission concentration. The horizontal axis shows the flame temperature and the vertical axis shows the CO emission concentration. The increase in the amount of unburned matter accompanying the decrease in the flame temperature is remarkable, and the lower limit of combustion at which the flame blows off becomes higher than that in diffusion combustion. Therefore, in many of the natural gas-fired combustors as described above, in order to reduce NOx, the flame is stabilized by combining a pilot burner by diffusion combustion and a premixed burner. For this reason, it is necessary to reduce NOx discharged from the pilot burner by diffusion combustion.

  On the other hand, when a fuel with good combustibility such as hydrogen or a mixed fuel containing it is used for the gas turbine, in the premixed combustion, there is a possibility that the flame is backlit in the premixed flow path for mixing the fuel and air. Becomes higher. As described above, it is difficult to improve both NOx reduction and flame stabilization, and a technique for improving both is desired.

  FIG. 1 shows a schematic configuration of a gas turbine using a high calorie gas fuel such as liquefied natural gas and a partially enlarged view of a combustor head in the present embodiment. FIG. 2 is a view when the burner is viewed from the combustion chamber. The gas turbine includes a compressor 2 that compresses air 101 from the outside, a combustor 3 that combusts fuel and air, a turbine 4 that is rotationally driven by combustion gas from the combustor 3, and a generator 6 that is driven by the turbine 4. And a starting motor 5 for driving the gas turbine.

  The combustor 3 includes a combustion chamber 8 for mixing and burning fuel and air, an outer cylinder 10 of a pressure vessel that partitions the outer space, an inner cylinder 9 that forms the combustion chamber 8 inside, and a fuel nozzle 220 for fuel. And a fuel nozzle 220 for injecting fuel into the combustion chamber 8, and an air nozzle 210 located downstream thereof for injecting combustion air 102 a into the combustion chamber 8. The fuel nozzle 220 and the air nozzle 210 are arranged as coaxial nozzles with their respective central axes arranged coaxially or nearly coaxially so as to form a coaxial jet in which air is wrapped around the fuel.

In this embodiment, the burner is formed by a plurality of fuel nozzles 220, an air nozzle 210 provided on the downstream side of the fuel nozzle 220, and a plate-like member 203 having the plurality of air nozzles 210. The jet nozzle 204 of the air nozzle 210 faces the combustion chamber 8, and the fuel flow of fuel and air injected from the jet nozzle 204 burns inside the combustion chamber 8 to form a flame. The plate-like member 203 of each burner is fixed to the burner holder 230. Here, as shown in FIG. 2, an example in which six outer peripheral burners are arranged outside the pilot burner 201 is shown. A pilot burner 201 is fixed to the center of the combustor in the radial direction, and outer peripheral burners 202a to 202f are fixed to the outside thereof by a burner holder 230 via respective plate members 203. A fuel nozzle 220 is disposed upstream of the air nozzle 210.

  Next, the operation method of this plant is demonstrated. At startup, the gas turbine is driven by external power such as a starter motor 5. Combustion air 102 a from the compressor 2 that compresses the air 101 from the outside and the fuel 51 are supplied to the pilot burner 201 and ignited by the combustor 3. Thereafter, the combustion gas 110 is supplied to the turbine 4. As the fuel flow rate to the pilot burner 201 increases, the turbine 4 speeds up, and when the starter motor 5 is detached, the gas turbine enters a self-sustaining operation and reaches the no-load rated speed. After the gas turbine reaches the no-load rated speed, the inlet gas temperature of the turbine 4 rises due to the addition of the generator 6 and the increase in the flow rate of the fuel 51 to the pilot burner 201, and the load further rises. Thereafter, the flow rate of fuel supplied to the outer peripheral burners 202a and 202b, 202c and 202d and the outer peripheral burner is increased. Eventually, flames are formed in all the outer peripheral burners, and continuous load operation in the operation load range by all burner combustion becomes possible.

  In this embodiment, the plurality of jet nozzles of the first burner are arranged such that the fuel flow from at least one of the plurality of burners intersects with the flame from the second burner. The first plane including the ejection positions of the second and the second plane including the ejection positions of the plurality of ejection ports of the second burner intersect. Therefore, when the fuel flow ejected from the first burner and the flame from the second burner intersect, the fuel flow and the flame interfere with each other, and the fuel flow from the first burner A flame from can be used. Therefore, even if the first burner becomes unstable combustion, it can receive energy from the second burner that is burning stably, so the possibility of the flame from the first burner blowing off is suppressed. Combustion stability is improved.

  In addition, the first plane including the ejection positions of the plurality of ejection openings of the first burner and the second plane including the ejection positions of the plurality of ejection openings of the second burner are allowed to intersect each other. It is possible to incline the jetting positions of the plurality of jet outlets of the burner toward the fuel chamber side so as to approach the flame from the second burner. By configuring in this way, the first burner receives more heat from the flame from the second burner than when the first plane and the second plane are not intersected, so the temperature of the first plane Rises. Therefore, the combustion speed of the fuel flow from the first burner is increased, and the stability of the flame by the first burner is improved. Therefore, the fuel concentration of the fuel flow from the first burner can be made more lean.

  That is, the first plane and the second burner including the ejection positions of the plurality of jet outlets of the first burner so that the fuel flow from the first burner and the flame from the second burner intersect each other. By crossing the second plane including the ejection positions of the plurality of jet outlets of the first flame, the flame of the first burner can be positively held using the flame from the second burner as a heat source. The lean burn of the first burner (combustion with an average fuel concentration lower than the average fuel concentration holding the flame) is possible. Therefore, the lower limit of the fuel concentration of combustion stability that can hold the flame stably can be further lowered, so that the combustion stability in the low fuel concentration range is improved and the combustion gas discharged from the combustor is further reduced in NOx. Is possible.

  In addition, in order to cross | intersect the 1st plane containing the ejection position of the several jet nozzle which a 1st burner has, and the 2nd plane containing the ejection position of the several jet nozzle which a 2nd burner has, it is an air nozzle. It is also possible to incline the plate-like member having 210 with respect to the central axis of the combustion chamber.

  Furthermore, in this embodiment, the fuel concentration of the second burner is set higher than the fuel concentration at which the flame can be maintained by the burner alone. Therefore, at least the flame from the second burner can be prevented from being blown out, and heat can be stably supplied to the fuel flow from the first burner.

  Further, in this embodiment, an inward angle is provided in the perpendicular line from the plane including the outlet of the outer peripheral burner and the combustor axis, and the jet of fuel and air ejected from the outer peripheral burner collides with the flame from the pilot burner 201. Configure as follows. Since the flame ejected from the pilot burner 201 and the jet flow ejected from the outer peripheral burner collide, the jet flow from the outer peripheral burner uses the flame from the pilot burner 201, and even if the outer peripheral burner becomes unstable combustion, it burns stably. Can receive energy from the pilot burner. Therefore, the possibility that the flame of the outer peripheral burner blows out can be reduced, and the combustion stability is improved.

  Moreover, the perpendicular from the plane including the jet nozzles of all the outer peripheral burners has an inward angle α with respect to the axial center of the combustor. For this reason, the plane including the jet port of the outer peripheral burner is approached by the flame from the pilot burner 201, so that the temperature in the vicinity of the plane rises. For this reason, the temperature of the jet from the outer peripheral burner also increases, and the combustion speed increases. Therefore, the combustion stability in a range where the fuel concentration is low can be improved, and the NOx of the exhausted combustion gas can be further reduced.

  In addition, since the inward angle α is provided, when the tip of the fuel nozzle 220 is disposed at the inlet of the air nozzle 210, the length of the fuel nozzle 220 becomes longer toward the outside in the radial direction of the combustor. Although depending on the inward angle, if the inward angle is too large, the space of the fuel nozzle 220 cannot be taken and the burner cannot be configured. Therefore, the inward angle α is preferably 45 ° or less.

FIG. 3 shows the average fuel concentration of the fuel that each burner jets into the combustor. In the downstream of the burner at the combustor head, the average fuel concentration when assuming that the fuel and air ejected from each burner are instantaneously mixed is schematically shown by a dotted line. In this embodiment, the average fuel concentration (F / A) _202a to (F / A) _202f of the outer peripheral burner is made thinner than the average fuel concentration (F / A) ₂₀₁ of the pilot burner. Here, the average fuel concentration (F / A) ₂₀₁ of the pilot burner only needs to be higher than the concentration at which the flame can be held by the burner alone. Here, the average fuel concentration at which the flame can be held by the burner alone is referred to as flame holding limit concentration. On the other hand, the lean average fuel concentration represents a concentration lower than the flame holding limit concentration. In addition, the average fuel concentration of all the peripheral burners is uniform. In this way, the vertical line from the plane including the outlet of the outer peripheral burner and the combustor axis are provided with inward angles, and the jet of fuel and air ejected from the outer peripheral burner collides with the flame from the pilot burner 201. In this case, the average fuel concentration of the fuel and air ejected from the outer peripheral burner is made thinner than the average fuel concentration of the flame ejected from the pilot burner, so that the average fuel concentration of the outer peripheral burner can be further diluted than before. And low NOx combustion due to fuel dilution can be realized.

  FIG. 4 is a view showing the burner side from the combustor downstream, and FIG. 5 is a partially enlarged view of the combustor head. Among the outer peripheral burners, the planes including the plurality of jet nozzles of the first outer peripheral burner and the second outer peripheral burner intersect with each other, and the fuel flow ejected from the adjacent first outer peripheral burner is generated from the second outer peripheral burner. It is configured to collide with the flame.

  In this case, it is possible to improve the flame stability of the fuel flow from the first outer peripheral burner by making the flame and fuel flow ejected from the two outer peripheral burners collide with each other and using the flame from the second outer peripheral burner. it can. Here, adjacent peripheral burners 202a and 202b, 202c and 202d, 202e and 202f are paired. The outer peripheral burners 202a and 202b are inclined to the combustion chamber side between the burners 202a and 202b with reference to a line ab passing through the center in the radial direction of the combustor. Line ab is a line connecting the midpoint of the line connecting the burner centers and the radial center of the combustor. Then, as shown in FIG. 5, with respect to the perpendicular a′b ′ extending in the combustor axial direction with respect to the line ab, it is inward with respect to the perpendicular from the plane including the plurality of outlets of the outer peripheral burners 202a and 202b. The angle β is provided. Also in this case, the length of the fuel nozzle 220 becomes longer as it goes outward with respect to the combustor axis as in the case where the inward angle α is provided. For this reason, it is desirable that the inward angle β between the pair of outer peripheral burners is also 45 ° or less.

  As described above, even between the adjacent outer peripheral burners, the plurality of outlets of the first outer peripheral burner are inclined to the combustion chamber side so that the planes including the outlets of the two adjacent outer peripheral burners intersect each other. Can be brought closer to the flame from the second outer peripheral burner, and more heat can be applied to the first outer peripheral burner to raise the temperature. Therefore, the combustion speed of the flame formed in the first outer peripheral burner is increased, the combustion stability of the flame is improved, and the average fuel concentration of the fuel flow from the first outer peripheral burner can be further diluted.

  FIG. 6 shows the average fuel concentration of the fuel jetted into the combustion chamber by two adjacent outer peripheral burners. The way of indicating the average fuel concentration is the same as in FIG. Of the two outer burners with inward angles, the average fuel concentration ejected from the second outer burner is set to a flame holding limit concentration or more that can be held by the burner alone, and the average fuel concentration ejected from the first outer burner is It is thinner than the second peripheral burner. In FIG. 6, the average fuel concentration of the outer peripheral burner 202a is set to an average fuel concentration capable of holding the flame alone, the outer peripheral burner 202b is thinner than 202a, and the flame formed in the burner 202a is used to hold the flame 202b. is there. With this configuration, half of the six outer peripheral burners can be lower than the flame holding limit concentration, and the NOx emission amount of the entire outer peripheral burner can be suppressed.

  FIG. 7 shows the burner from the combustion chamber. FIG. 7 shows two outer peripheries so that the planes including the ejection positions of the plurality of jet outlets of the two outer burners intersect with each other and the flame from the pilot burner 201 collides with the jet of fuel and air from the outer burner. A plane including the ejection positions of the plurality of ejection ports of the burner is also intersected with a plane including the ejection positions of the plurality of ejection ports of the pilot burner 201. In FIGS. 4 and 5, flame stability is improved by using a flame of a pair of outer peripheral burners to improve combustion stability. Further, in FIG. 7, an inward angle α is provided so that a perpendicular line from a plane including the ejection positions of the plurality of ejection ports of the outer peripheral burner is inclined with respect to the combustor axis. Therefore, the flame of the pilot burner 201 can be used for the flame held by the pair of outer peripheral burners. FIG. 8 shows a cross section A′-A ′ and a cross section BB in FIG. 7. As in the cross section A′-A ′, an inward angle β is provided with reference to the center line between the pair of outer peripheral burners. In addition to the inward angle β provided in the pair of outer peripheral burners, an inward angle α is provided with respect to the combustor axis so that a part of the jet of the outer peripheral burner collides with the flame of the pilot burner 201. In this way, by inclining the plane including the ejection positions of the plurality of jet outlets that are the burner surfaces, the flame of the pilot burner 201 and the jet of the outer peripheral burner interfere with each other, and the combustion in the range where the fuel concentration is low as the entire combustor Stability can be increased.

  Further, the plane including the ejection positions of the plurality of outlets of the first outer peripheral burner approaches the flame from the second outer peripheral burner and also approaches the flame from the pilot burner. The plane including the ejection position of the ejection port can receive more heat. Therefore, the combustion speed of the fuel flow from the first outer peripheral burner is increased, and the combustion stability can be improved.

And it is also possible to set the average fuel concentration of those burners so that it may differ. Specifically, the pilot burner 201 has a single limit flame holding concentration that can be held by the burner alone, and the outer peripheral burner sets the average fuel concentration to be leaner than the pilot burner 201. For example, the average fuel concentration F / A _202a of the average fuel concentration F / A _202a and 202b of the outer peripheral burner 202a in the pair, and when comparing the average fuel concentration F / A ₂₀₁ of the pilot burner _{201, F / A 201> F} / Set as A _202a > F / A _202a . By setting the average fuel concentration in this way, only the pilot burner 201 is set to the single limit flame holding concentration, and the outer peripheral burner can lower the average fuel concentration than the pilot burner 201. Further, in the outer peripheral burner, half of the outer peripheral burners can lower the average fuel concentration than the remaining outer peripheral burners.

  On the other hand, in the combustor of Patent Document 1, in the annular burner group located on the radially outer side, the average fuel concentration is uniform in the circumferential direction. However, in this embodiment, since the inward angle is provided between adjacent burners in the outer peripheral burner, the flame holding performance of the outer peripheral burner is improved. Furthermore, since the average fuel concentration of the outer peripheral burners is set to be different, the average fuel concentration of the entire outer peripheral burner can be reduced. Therefore, it is possible to further reduce NOx discharged from the gas turbine.

  In this embodiment, the average fuel concentration of the pilot burner 201 is set to be the highest, but in some cases, the average fuel concentration of the other outer peripheral burners can be set to be the highest. That is, the average fuel concentration may be made different so that the average fuel concentration is lowered in the pilot burner 201 and the entire outer peripheral burner.

  The embodiment in which six outer peripheral burners provided outside the pilot burner have been described has been described above, but the same effect can be obtained when an odd number of outer peripheral burners such as five or seven are disposed. When an odd number of outer peripheral burners are arranged, one outer peripheral burner that cannot be paired remains. However, an inward angle is provided on the pilot burner 201 side, or an average fuel concentration that can be held independently is set to an axial center of the combustor. The fuel may be ejected in parallel with the fuel. Further, the inward angles α and β provided in the outer peripheral burner do not necessarily have to be set to the same angle with respect to all the outer peripheral burners.

1 is a partially enlarged view of a combustor head showing Example 1. FIG. 1 is a burner arrangement diagram for Example 1. FIG. FIG. 3 is a schematic diagram showing an average fuel concentration in Example 1. 6 is a burner arrangement diagram showing Example 2. FIG. FIG. 6 is a cross-sectional view of the burner taken along AA showing Example 2. 6 is a schematic diagram showing an average fuel concentration in Example 2. FIG. 6 is a front view of a burner showing Example 3. FIG. 7 is a partial A′A ′ sectional view and a BB sectional view of a burner showing Example 3. FIG. It is a figure which shows the relationship between the mass ratio of fuel and air, and theoretical flame temperature. It is a schematic diagram which shows the relationship between flame temperature and CO discharge | emission density | concentration.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 2 ... Compressor, 3 ... Combustor, 4 ... Turbine, 5 ... Motor for starting, 6 ... Generator, 8 ... Combustion chamber, 9 ... Inner cylinder, 10 ... Outer cylinder, 11 ... Fuel distributor, 51 ... Fuel, DESCRIPTION OF SYMBOLS 101 ... Air, 102 ... Compressor discharge air, 102a ... Combustion air, 110 ... Combustion gas, 201 ... Pilot burner, 202a-202f ... Outer periphery burner, 203 ... Plate-shaped member, 204 ... Jet outlet, 210 ... Air nozzle, 220 ... Fuel nozzle, 230 ... Burner holder.

Claims (6)

A fuel chamber for mixing and burning fuel and air, a fuel nozzle for supplying fuel to the combustion chamber, and an air nozzle for supplying air located downstream of the fuel nozzle are provided. And a plurality of coaxial nozzles arranged so that the central axis of the air nozzle is coaxial or close to the coaxial, and configured to eject a fuel flow in which air is wrapped around the fuel from an outlet of the air nozzle. A gas turbine combustor in which a burner is disposed as a pilot burner in the radial center of the combustion chamber, and a plurality of outer peripheral burners including a plurality of the coaxial nozzles on the outer peripheral side of the pilot burner,
An inward angle is provided in the perpendicular line from the plane including the jetting position of the jet outlet of the outer peripheral burner and the combustor axis so that the jet of fuel and air jetted from the outer burner collides with the flame from the pilot burner. The average fuel concentration of the pilot burner is higher than the flame holding limit concentration capable of holding a flame with the pilot burner alone, and the average fuel concentration of the outer peripheral burner is less than the flame holding limit concentration. Gas turbine combustor. 2. The gas turbine combustor according to claim 1, wherein among the outer peripheral burners, adjacent planes including a plurality of jetting positions of a plurality of outlets of the first outer peripheral burner and the second outer peripheral burner are adjacent to each other. A gas turbine combustor characterized in that a fuel flow ejected from a first outer peripheral burner collides with a flame from a second outer peripheral burner. 3. The gas turbine combustor according to claim 2 , wherein an average fuel concentration of the second outer peripheral burner is equal to or higher than a flame holding limit concentration, and an average fuel concentration from the first outer peripheral burner is set to be higher than that of the second burner. A gas turbine combustor characterized by being lean. The gas turbine combustor according to claim 3 , wherein the jets of a plurality of outlets of the two outer burners are arranged so that the flame from the pilot burner and the jet of fuel and air jetted from the outer burner collide with each other. A gas turbine combustor characterized in that it intersects with a plane including a position and a plane including the ejection positions of a plurality of ejection ports of the pilot burner. 5. The gas turbine combustor according to claim 4 , wherein an average fuel concentration of the two outer peripheral burners is made different from an average fuel concentration of the pilot burner. A combustion chamber for mixing and burning fuel and air, a fuel nozzle for supplying fuel, and an air nozzle for supplying air located downstream of the fuel nozzle are provided, the fuel nozzle and the air nozzle Is disposed in a coaxial or near-coaxial state, and a pilot having a plurality of coaxial nozzles configured to eject a fuel flow in which air wraps fuel from the air nozzle is piloted in the radial center of the combustion chamber. A combustion method for a combustion apparatus in which a plurality of outer peripheral burners provided with a plurality of the coaxial nozzles on the outer peripheral side of the pilot burner are disposed as a burner,
An inward angle is provided in the perpendicular line from the plane including the jetting position of the jet outlet of the outer peripheral burner and the combustor axis so that the jet of fuel and air jetted from the outer burner collides with the flame from the pilot burner. And the average fuel concentration of the pilot burner is higher than a flame holding limit concentration capable of holding a flame by the pilot burner alone, and the average fuel concentration of the outer peripheral burner is less than the flame holding limit concentration. A combustion method for a combustion apparatus.

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