JP4881341B2 - Burner and boiler - Google Patents

Description

  The present invention relates to a burner and a boiler.

  In order to prevent air pollution, exhaust gas regulations are becoming stricter year by year, and the exhaust gas regulations include NOx emission regulations.

  As one of NOx generated during combustion, there is thermal NOx generated by nitrogen gas in combustion air. Thermal NOx is produced by oxidizing the N2 component in the combustion air in a high temperature atmosphere, and has a high temperature dependence, and the amount of production increases rapidly as the combustion temperature increases.

  When the fuel is kerosene or A heavy oil with a low nitrogen content, most of the NOx discharged is said to be thermal NOx, and further, NOx discharged from natural gas is thermal NOx. Therefore, combustion methods for lowering the combustion temperature in boilers have been studied.

  There are once-through boilers as simple boilers, small boilers and the like (hereinafter referred to as simple boilers). As a structure of a once-through boiler employed in a simple boiler, there is a structure shown in Patent Document 1, and a large number of heating tubes are arranged around the combustion chamber in parallel with the axis of the combustion chamber. The furnace wall formed in this manner, the fuel injection nozzle provided in the upper part of the combustion chamber, the combustion air supply nozzle having a circular or rectangular cross section disposed around the fuel injection nozzle, and the combustion air supply nozzle below Some have a short cylindrical cone guide disposed concentrically with the fuel injection nozzle, and generate heat by exchanging heat between the combustion gas and the heating pipe.

  In the simplified boiler described above, the combustion air is injected into the cone guide at high speed during combustion, so that the combustion gas in the combustion chamber is drawn into the cone guide and a recirculation flow is formed. By forming the recirculation flow of the combustion gas, the oxygen concentration in the combustion air is reduced, the combustion speed of the fuel is suppressed, and the combustion temperature is kept low.

  The furnace wall is formed with an exhaust port for exhausting combustion gas, and the combustion air supply nozzle is inclined so as to be separated from the exhaust port. This is to prevent the so-called short path in which the combustion gas is exhausted from the exhaust port without sufficiently exchanging heat with the heating tube.

  In Patent Document 1, although the combustion gas is self-recirculated and the structure in which the combustion air supply nozzle is inclined so as to be separated from the exhaust port, the CO reduction effect is obtained, the NOx reduction effect is relatively The result is less.

  In addition, since high-speed combustion gas is ejected from the combustion air supply nozzle, the combustion air supply nozzle may cause low-frequency vibration.

JP 2006-57996 A

  In view of such circumstances, the present invention is intended to further reduce NOx and to suppress low-frequency vibration of the combustion air supply nozzle.

  According to the present invention, a fuel injection nozzle provided on an axial center line of the combustion chamber at a ceiling portion of a cylindrical combustion chamber, a primary air introduction passage formed concentrically around the fuel injection nozzle, and 2 A secondary air nozzle provided at a lower end of the secondary air introduction path and a predetermined number of radial air at an equal angular pitch, the secondary air nozzle having a rectangular shape with a long cross section in the radial direction It relates to a certain burner.

  Further, the present invention relates to a burner having a rectangular ratio of 1.5 to 5 in the cross section, and the combustion chamber has a secondary wall in which an exhaust port is formed in a part of a wall surface and the secondary air nozzle is ejected. It relates to a burner for directing air away from the exhaust port, and is related to a burner inclined in a direction away from the exhaust port, and one of the wall surfaces constituting the burner is centered inside the secondary air nozzle. The vane is divided into a side and an outer side, and the vane relates to a burner inclined so as to keep the circulating secondary air away from the internal exhaust port, and the vane relates to a burner provided when the rectangular ratio is 2 or more. is there.

  The present invention also provides a cylindrical combustion chamber, a heat transfer wall surrounding the combustion chamber, a lower header provided at the lower end of the heat transfer wall, and an upper portion provided at the upper end of the heat transfer wall. A header and a burner provided on the ceiling of the combustion chamber, the burner being formed concentrically around the fuel injection nozzle provided on the axis of the combustion chamber and the fuel injection nozzle A secondary air nozzle provided at a lower end of the secondary air introduction path and a predetermined number of radial air at an equiangular pitch, and the secondary air nozzle. Relates to a boiler whose cross section is a rectangle that is long in the radial direction.

  According to the present invention, the fuel injection nozzle provided on the axial center line of the combustion chamber at the ceiling of the cylindrical combustion chamber, and the primary air introduction passage formed concentrically around the fuel injection nozzle. And a secondary air nozzle provided at a lower end of the secondary air introduction path and a predetermined number of radial air nozzles at an equiangular pitch, the secondary air nozzle having a long cross section in the radial direction. Because of the rectangular shape, the secondary air contributes to the combustion sequentially from the center side, the combustion speed is suppressed, the increase of the combustion temperature is suppressed, NOx is reduced, and the low frequency noise is reduced.

  According to the present invention, the combustion chamber has an exhaust port formed in a part of a wall surface, and the secondary air nozzle directs the secondary air to be ejected away from the exhaust port. Is inclined in a direction away from the exhaust port, a short path of combustion air to the exhaust port can be prevented, and heat recovery of the combustion air is improved.

  In the present invention, the interior of the secondary air nozzle is divided into the center side and the outside, and the vane is inclined so as to keep the circulating secondary air away from the internal exhaust port, and the vane has a rectangular ratio of 2 Since it is provided in the above case, even when the rectangular ratio is increased, the function of directing the secondary air of the secondary air nozzle away from the exhaust port is not impaired, and further NOx reduction is achieved. Can be planned.

  According to the invention, the cylindrical combustion chamber, the heat transfer wall surrounding the combustion chamber, the lower header provided at the lower end of the heat transfer wall, and the upper end of the heat transfer wall are provided. An upper header and a burner provided on the ceiling of the combustion chamber, the burner being provided with a fuel injection nozzle provided on the axial center line of the combustion chamber, and a concentric shape centering on the fuel injection nozzle A secondary air nozzle provided at a lower end of the secondary air introduction path and a predetermined number of radial air at an equiangular pitch at the lower end of the secondary air introduction path. Since the air nozzle has a rectangular shape with a long cross section in the radial direction, secondary air contributes to combustion sequentially from the center side, suppressing the combustion speed, suppressing an increase in combustion temperature, reducing NOx, and Excellent effect of reducing low-frequency noise.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  1 and 2 show a boiler 1 according to the present invention, in which 2 denotes a cylindrical combustion chamber, and an inner heat transfer wall 3, an outer side so as to surround the periphery of the combustion chamber 2. A heat transfer wall 4 is provided.

  The inner heat transfer wall 3 is formed by airtightly connecting a required number of inner row heating tubes 5 with inner fins 6, and the outer heat transfer wall 4 is airtightly connected with a required number of outer row heating tubes 7 by outer fins 8. A gas flow path 9 is formed between the inner heat transfer wall 3 and the outer heat transfer wall 4. A part of the inner fin 6 is cut off in the inner heat transfer wall 3 to form an internal exhaust port 10, and the combustion chamber 2 and the gas flow path 9 are communicated with each other through the internal exhaust port 10.

  A ring-shaped lower header 11 is provided at the lower ends of the inner heat transfer wall 3 and the outer heat transfer wall 4, and a ring-shaped upper tube at the upper ends of the inner heat transfer wall 3 and the outer heat transfer wall 4. A gathering 12 is provided.

  The lower ends of the inner row heating tube 5 and the outer row heating tube 7 communicate with the lower header 11, and the upper ends of the inner row heating tube 5 and the outer row heating tube 7 communicate with the upper header 12, respectively. The lower header 11 is connected to a water supply source (not shown), and the upper header 12 is connected to a header (not shown) which is a steam reservoir.

  The bottom 13 of the combustion chamber 2 is formed of a refractory material, and a burner 15 is supported at the center of the ceiling 14 of the combustion chamber 2. The outer heat transfer wall 4, the outer surfaces of the lower header 11 and the upper header 12 are covered with a heat insulating material 16, and the heat insulating material 16 is further covered with a casing 17.

  A portion of the burner 15 protruding above the ceiling portion 14 is accommodated in a wind box 18, and the wind box 18 is connected to a blower 21 through a duct 19. The duct 19 is provided with a damper 22, and the combustion air blown by the blower 21 is adjusted in air volume by the damper 22 and supplied to the burner 15.

  An exhaust pipe 23 is connected to a position opposite to the internal exhaust port 10 at the lower end of the outer heat transfer wall 4, and exhaust gas is discharged from the exhaust pipe 23.

  Hereinafter, the burner 15 will be described with reference to FIGS.

  At the center of the ceiling portion 14, a throat 25 is formed, and a secondary air introduction cylinder 26 is attached to the ceiling portion 14 via a flange 27 concentrically with the throat 25. The upper end of the secondary air introduction cylinder 26 is opened, and a primary air introduction cylinder 28 is provided concentrically with the secondary air introduction cylinder 26 at the lower end. A flame holding plate is provided at the lower end of the primary air introduction cylinder 28. 40 is provided, and the upper end of the primary air introduction tube 28 is open.

  The lower end of the secondary air introduction cylinder 26 is closed by a bottom plate 29, and the required number of secondary air nozzles 30 radially around the primary air introduction cylinder 28 at an equal angular pitch (6 in the drawing). Pieces). Further, a cylindrical cone guide 31 is provided below the secondary air nozzle 30 concentrically with the secondary air introduction cylinder 26. In addition, the number of the said secondary air nozzle 30 is the range of 4-12, and is suitably selected according to the scale of the said boiler 1, etc.

  The wind box 18 is provided on the upper surface of the ceiling portion 14 concentrically with the secondary air introduction cylinder 26, and the top plate 32 of the wind box 18 is secondary with the secondary air introduction cylinder 26 concentrically. An air guide cylinder 33 is provided vertically. The secondary air guide cylinder 33 overlaps with the upper end portion of the secondary air introduction cylinder 26, and a cylindrical secondary air flow is interposed between the secondary air introduction cylinder 26 and the secondary air guide cylinder 33. A path 34 is formed.

  A fuel injection nozzle 35 is provided through the top plate 32. The fuel injection nozzle 35 is located on the center line of the secondary air introduction cylinder 26, and the lower end extends to the lower end of the secondary air introduction cylinder 26 or near the lower end. An inner lid 36 is provided at a required position of the fuel injection nozzle 35. With the fuel injection nozzle 35 fixed to the top plate 32, the inner lid 36 covers the upper end of the primary air introduction cylinder 28. It is designed to block.

  A space defined by the primary air introduction cylinder 28 and the inner lid 36 forms a primary air introduction path 37, and the interior of the secondary air introduction cylinder 26 and the periphery of the primary air introduction cylinder 28 are formed. The space forms a secondary air introduction path 38.

  In particular, the secondary air introduction cylinder 26 and the primary air introduction cylinder 28 form a double cylinder structure, the outside of the primary air introduction cylinder 28 is the secondary air introduction path 38 and the inside is the primary air. An air introduction path 37 is formed.

  A primary air intake port 39 is formed in the circumferential surface of the primary air introduction cylinder 28 at a required interval in the circumferential direction, and a part of the secondary air flowing through the secondary air introduction path 38 is used as primary air. The primary air intake 39 is diverted to the primary air introduction path 37.

  The cross section of the secondary air nozzle 30 is rectangular, the center line in the longitudinal direction of the rectangle coincides with the radial direction of the secondary air introduction cylinder 26, and the rectangular ratio (= vertical length / horizontal length) is> 1.5.

  One of the wall surface forming the secondary air nozzle 30, the outer peripheral side, and the inner peripheral side is inclined, and the secondary air injected from the secondary air nozzle 30 is supplied to the internal exhaust port 10. Orient it away from it. The angle of the inclined wall surface is an arbitrary angle excluding 0 ° of 20 ° or less with respect to the vertical.

  For example, if the arrow in FIG. 4 is the direction of the internal exhaust port 10, the secondary air nozzle 30a is inclined so that the outer peripheral wall surface is separated from the internal exhaust port 10, and the secondary air nozzle 30b The inner wall surface is inclined so as to be separated from the internal exhaust port 10.

  The operation will be described below.

  When the blower 21 is driven and the combustion air is blown, the combustion air is supplied from the duct 19 to the wind box 18 and passes through the secondary air flow path 34 to the upper end of the secondary air introduction cylinder 26. And then flows into the secondary air introduction passage 38 as secondary air, is diverted from the secondary air nozzle 30 and is ejected downward. Further, a part of the secondary air, for example 5%, is taken as primary air from the primary air intake port 39 into the primary air introduction passage 37 and ejected downward from the periphery of the flame holding plate 40. .

  The fuel ejected from the lower end of the fuel injection nozzle 35 is mixed with primary air and ignited, and further mixed with secondary air and burned. Further, since the secondary air jet flow from the secondary air nozzle 30 is partitioned from the periphery by the cone guide 31, the surrounding combustion gas is guided from the upper end of the cone guide 31, and the secondary air Mix with air. The induction of the surrounding combustion gas is called self-recirculation, which reduces the oxygen concentration in the secondary air and suppresses the combustion rate of the fuel. That is, an increase in combustion temperature is suppressed.

  Further, since the cross section of the secondary air nozzle 30 has a rectangular shape that is long in the radial direction, the secondary air ejected from the secondary air nozzle 30 does not touch the fuel at a time, but gradually from the center side. Contact. Accordingly, the secondary air does not contribute to combustion at a time, but the combustion speed is suppressed. That is, the rise in the combustion temperature is also suppressed by the secondary air ejection form from the secondary air nozzle 30. By suppressing the increase in combustion temperature, the generation of NOx is also suppressed.

  The combustion gas is directed in a direction away from the internal exhaust port 10 due to the inclination of the wall surface of the secondary air nozzle 30 and is prevented from short-passing to the internal exhaust port 10. The combustion gas in the combustion chamber 2 flows into the gas flow path 9 from the internal exhaust port 10 and is further exhausted from the exhaust pipe 23. The inner row heating pipe 5 exchanges heat with the combustion gas in the combustion chamber 2 and the combustion gas flowing through the gas flow path 9, and the outer row heating pipe 7 is a combustion gas flowing through the gas flow path 9. Exchange heat with.

  The water supplied to the inner row heating pipe 5 and the outer row heating pipe 7 evaporates while rising, and the steam is led to the header (not shown) through the upper header 12.

  The effect of reducing NOx and low-frequency vibration when the secondary air nozzle 30 is rectangular will be described with reference to FIGS.

  FIG. 7 schematically shows the shape and arrangement of the secondary air nozzle 30, and is a view corresponding to the arrow BB in FIG.

  The secondary air nozzle 30 is disposed at a position divided into six equal circumferences, and FIG. 7A shows a conventional secondary air nozzle 30 having a square cross-sectional shape. FIG. 7B shows the secondary air nozzle 30 of the present invention, the cross-sectional shape is rectangular, and the rectangular ratio is 2. In addition, both of the conventional and the present invention direct the secondary air that is inclined so that one wall surface of the nozzle is inclined and away from the internal exhaust port 10 (see FIG. 2).

  FIG. 8 shows the NOx concentration in the exhaust gas. Curve A shows a rectangular ratio = 1, curve B shows a rectangular ratio = 2, and the sectional shape of the secondary air nozzle 30 is rectangular. It can be seen that the NOx concentration is reduced. In the figure, curve C shows a rectangular ratio = 1.5. When the rectangular ratio = 1.5, the NOx concentration is lower than when the rectangular ratio = 1, but lower than the rectangular ratio = 2. It can be seen that the effect is small, and the reduction in NOx concentration tends to increase as the rectangular ratio increases.

  FIG. 9 shows the effect of reducing the NOx concentration in the exhaust gas when the number of nozzles and the rectangular ratio are changed. In the figure, the curve A is rectangular ratio = 1 and the number of secondary air nozzles 30 is 6. B is rectangular ratio = 2, the number of secondary air nozzles 30 is 6, curve C is rectangular ratio = 2, the number of secondary air nozzles 30 is 8, and the number of secondary air nozzles 30 is 8 Shows that the NOx concentration is lower than when the rectangular ratio = 1, but the effect of reducing the number of nozzles with the rectangular ratio = 2 is less than that of 6, and compared with FIG. It shows a tendency that the influence on the reduction of the NOx concentration is not great.

  FIG. 10 shows noise in the burner combustion state. Curve A shows a rectangle ratio = 1, curve B shows a rectangle ratio = 2, and when the rectangle ratio = 2, low frequency noise is generated. You can see that it is decreasing. The cause of the reduction in low-frequency noise is that the cross-sectional shape of the secondary air nozzle 30 is symmetrical only in one direction and is difficult to resonate.

  5 and 6 show another embodiment. In the other embodiment, a vane 41 that divides a flow path into an inner side and an outer side is provided inside the secondary air nozzle 30.

  The vane 41 is inclined in the same direction as the inclined wall surface of the secondary air nozzle 30, and is preferably provided in parallel with the inclined wall surface. Accordingly, the vane 41 directs the secondary air to be ejected away from the internal exhaust port 10.

  When the rectangular ratio of the secondary air nozzle 30 is increased, the guide action of the wall surface decreases as the distance from the inclined wall surface increases, and the secondary air flowing through the portion separated from the inclined wall surface is affected by the inclined surface. Without going straight.

  The vane 41 has a function of effectively directing the secondary air away from the internal exhaust port 10 even when the rectangular ratio of the secondary air nozzle 30 is increased. The condition for providing the vane 41 is preferably a rectangular ratio of 2 or more. The rectangular ratio is preferably about 5 at maximum from the relationship with the cross-sectional area of the flow path.

  FIG. 11 shows the effect of reducing the NOx concentration when the rectangular ratio of the secondary air nozzle 30 is 2 and the vane is provided and when the vane is not provided.

  In FIG. 11, a curve A indicates a case where there is no vane, and a curve B indicates a case where there is a vane. By providing the vane 41, the NOx concentration is greatly reduced, and it can be seen that the vane 41 exhibits a great effect in reducing the NOx concentration.

  FIG. 12 shows the effect of reducing the CO concentration when the rectangular ratio of the secondary air nozzle 30 is 2 and the vane is provided and when the vane is not provided.

  In FIG. 12, curve A shows a case where there is no vane and curve B shows a case where there is a vane. By providing the vane 41, the CO concentration is greatly reduced, and it can be seen that the vane 41 is also effective in reducing the CO concentration.

  FIG. 13 shows the CO concentration when the number of nozzles is 6 and the rectangular ratio is 1 and no vane is provided and when the number of nozzles is 6 and the rectangular ratio is 2 and vanes are provided. It can be seen that the CO concentration is lower when the vane 41 is provided.

  The rectangular ratio is not limited to 1.5, 2 or 3, and the number of secondary air nozzles 30 is not limited to 6 or 8, and may be changed as appropriate depending on the scale of the boiler 1 and the like. It is what is done.

  In addition, the secondary air nozzle 30 is configured to direct the secondary air away from the internal exhaust port 10, and one of the wall surfaces is inclined, but the entire secondary air nozzle 30, that is, the center line It is good also as a structure which inclined.

  As the fuel, either oil or gas can be used.

It is sectional drawing of the boiler which concerns on embodiment of this invention. It is an AA arrow line view of FIG. It is sectional drawing of the burner of the said boiler. It is a BB arrow line view of FIG. It is sectional drawing which shows a part of burner in other embodiment. It is CC arrow line view of FIG. The shape arrangement | positioning of a secondary air nozzle is shown typically, (A) is the conventional secondary air nozzle, (B) has shown the secondary air nozzle of this invention. It is a graph which shows the NOx density | concentration in exhaust gas by the difference in the shape of a secondary air nozzle. It is a graph which shows the NOx density | concentration in waste gas by the difference in the shape and number of secondary air nozzles. It is a graph which shows the low frequency vibration by the difference in the shape and number of secondary air nozzles. It is a graph which shows the NOx density | concentration in waste gas when not providing with the vane in the secondary air nozzle. It is a graph which shows the CO density | concentration in waste gas when not providing with the vane in the secondary air nozzle. It is a graph which shows the CO density | concentration in waste gas when not providing with the vane in the secondary air nozzle.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Boiler 2 Combustion chamber 3 Inner heat transfer wall 4 Outer heat transfer wall 10 Internal exhaust port 15 Burner 18 Wind box 26 Secondary air introduction cylinder 28 Primary air introduction cylinder 30 Secondary air nozzle 31 Cone guide 35 Fuel injection nozzle 37 1 Secondary air introduction path 38 Secondary air introduction path 41 Vane

Claims (7)

  A fuel injection nozzle provided on the axial center line of the combustion chamber on the ceiling of the cylindrical combustion chamber, and a primary air introduction passage and a secondary air introduction passage formed concentrically around the fuel injection nozzle And a secondary air nozzle provided in a predetermined number radially at an equiangular pitch at the lower end of the secondary air introduction path, wherein the secondary air nozzle has a rectangular shape with a long cross section in the radial direction. And burner.   The burner according to claim 1, wherein the rectangular ratio of the cross section is 1.5-5.   The burner according to claim 1 or 2, wherein the combustion chamber has an exhaust port formed in a part of a wall surface, and the secondary air nozzle directs the secondary air to be ejected away from the exhaust port.   The burner according to claim 3, wherein one of the wall surfaces constituting the burner is inclined in a direction away from the exhaust port.   The burner according to claim 3 or 4, wherein the inside of the secondary air nozzle is divided into a center side and an outside, and the vane is inclined so as to keep the circulating secondary air away from the internal exhaust port.   The burner according to claim 5, wherein the vane is provided when the rectangular ratio is 2 or more.   A cylindrical combustion chamber, a heat transfer wall surrounding the periphery of the combustion chamber, a lower header provided at the lower end of the heat transfer wall, an upper header provided at the upper end of the heat transfer wall, and A burner provided on the ceiling of the combustion chamber, the burner being a fuel injection nozzle provided on the axis of the combustion chamber, and primary air formed concentrically around the fuel injection nozzle An introduction passage, a secondary air introduction passage, and a secondary air nozzle provided radially at an equal angular pitch at the lower end of the secondary air introduction passage, the secondary air nozzle having a radial cross section Boiler characterized by a long rectangular shape.

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