WO2017126240A1 - アフタエアポート及びこれを備えた燃焼装置 - Google Patents
アフタエアポート及びこれを備えた燃焼装置 Download PDFInfo
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- WO2017126240A1 WO2017126240A1 PCT/JP2016/085996 JP2016085996W WO2017126240A1 WO 2017126240 A1 WO2017126240 A1 WO 2017126240A1 JP 2016085996 W JP2016085996 W JP 2016085996W WO 2017126240 A1 WO2017126240 A1 WO 2017126240A1
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- air
- air nozzle
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN A CARRIER GAS OR AIR
- F23C99/00—Subject-matter not provided for in other groups of this subclass
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23L—SUPPLYING AIR OR NON-COMBUSTIBLE LIQUIDS OR GASES TO COMBUSTION APPARATUS IN GENERAL ; VALVES OR DAMPERS SPECIALLY ADAPTED FOR CONTROLLING AIR SUPPLY OR DRAUGHT IN COMBUSTION APPARATUS; INDUCING DRAUGHT IN COMBUSTION APPARATUS; TOPS FOR CHIMNEYS OR VENTILATING SHAFTS; TERMINALS FOR FLUES
- F23L9/00—Passages or apertures for delivering secondary air for completing combustion of fuel
- F23L9/02—Passages or apertures for delivering secondary air for completing combustion of fuel by discharging the air above the fire
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- the present invention relates to an after-air port and a combustion apparatus such as a boiler equipped with an after-air port, and more particularly to an after-air port capable of two-stage combustion with high combustion efficiency and a combustion apparatus equipped with the same.
- Solid fuel such as a boiler, to which a so-called two-stage combustion method is applied, in which fuel is burned with a burner under conditions of air shortage and the remaining air necessary for complete combustion is supplied from an after-air port (hereinafter also referred to as AAP)
- a combustion apparatus furnace
- the flow rate distribution of the combustion gas including unburned components rising to the after-airport portion changes depending on the arrangement of the burner and the method of supplying fuel and air from the burner.
- FIG. 5 shows a front view of the furnace wall (FIG. 5A) in which the burner 6 and the after-air port 7 are arranged on the wall surface of the furnace 31 to which the two-stage combustion method is applied, a combustion gas jet, and a two-stage combustion air jet.
- FIG. 5B A furnace side cross-sectional view (FIG. 5B) and a cross-sectional view taken along line AA in FIG. 5B (FIG. 5C) are shown.
- the flow distribution of the combustion gas jet 21 including the burner 6 and the AAP 7 on the opposing wall surfaces of the furnace 31 and including unburned fuel from the burner 6 rising to the AAP 7 portion of the furnace wall surface Accordingly, by appropriately setting the flow rate distribution and jet direction of the after-air jet 22 in the furnace 31 and maintaining the straightness and spreadability of the after-air jet 22 stably, the unburned portion of the fuel is effectively obtained. Can be reduced to achieve high combustion performance.
- Patent Document 1 discloses the AAP of FIG. 6 shown in a schematic front view as seen from the inside of a furnace used in a combustion apparatus for solid fuel such as coal.
- the direction of the after air blown into the furnace from the after air port in which the primary after air nozzle 5 is arranged in the center is divided into three or more parts in the horizontal direction, and the direction of each of the divided air is divided into the straight flow and the straight flow of the center.
- An after-air port provided with air dividing members (secondary after-air guide vanes) 15 that prevent the directions of the divided air from being in the same direction as the horizontally dispersed flow on both sides is disclosed.
- the flow path in the AAP is divided into an after-air straight flow and an after-air horizontal dispersed flow using a simple dividing member (plate), and the horizontal spread and direction of the after-air and the adjustment of the flow distribution are adjusted. It is possible.
- the straight air flow and horizontal dispersion flow of the after air can be optimized by adjusting the total after air flow rate and adjusting the straight flow / horizontal dispersion flow ratio.
- the technical problem of the present invention is to maintain the penetration force of the after-air jet in the furnace depth direction.
- the after-airport of the invention is: An after-air port that ejects air for two-stage combustion into the furnace, An inner primary after air nozzle for supplying an inner primary after air that ejects a straight flow at the center of the opening, and an outer primary after air nozzle for supplying an outer primary after air that ejects a straight flow outside the inner primary after air nozzle are provided.
- a secondary after air nozzle for supplying secondary after air is provided on the left and right outside of the outer primary after air nozzle,
- One or more secondary after air guide vanes having an inclination angle with respect to the center axis of the after air port are provided at the outlet of the secondary after air nozzle so that the secondary after air can be deflected and supplied in the horizontal direction.
- At least an inner primary after air supply amount adjusting member in the inner primary after air nozzle or an outer primary after air supply amount adjusting member in the outer primary after air nozzle is provided.
- the invention according to claim 2 is the after-airport according to claim 1,
- the inner primary after air nozzle is a vertically long nozzle whose opening shape is surrounded by a member that partitions the inner primary after air nozzle and the outer primary after air nozzle, and a peripheral wall of the after air port opening (throat portion),
- the outer primary after air nozzle has an opening shape that defines a member that partitions the inner primary after air nozzle and the outer primary after air nozzle, an after air port opening (throat portion) peripheral wall, the outer primary after air nozzle, and the secondary It is a vertically long nozzle surrounded by a member that divides the after air nozzle.
- the invention according to claim 3 is the after-airport according to claim 1 or 2, Ratio when the cross-sectional areas perpendicular to the fluid flow direction of the inner primary after-air nozzle and the outer primary after-air nozzle are Si and So, respectively: Si / (Si + So) is 0.5 ⁇ Si / (Si + So) ⁇ 0 .7 It is characterized by being.
- a combustion apparatus having an after-airport for two-stage combustion in which a burner that burns fuel with an air amount equal to or less than the theoretical air amount is disposed in a furnace, and an after-air port for two-stage combustion that supplies air to a furnace downstream from the installation position of the burner is disposed,
- An inner primary after air nozzle for supplying the inner primary after air for straight flow ejection and an outer primary after air nozzle for supplying the outer primary after air for straight flow ejection are provided outside the inner primary after air nozzle at the center in the opening of the after air port,
- a secondary after air nozzle for supplying secondary after air is provided on the left and right outside of the outer primary after air nozzle,
- One or more secondary after air guide vanes having an inclination angle with respect to the center axis of the after air port are provided at the outlet of the secondary after air nozzle so that the secondary after air can be deflected and supplied in the horizontal direction.
- the Invention of Claim 5 is a combustion apparatus provided with the after-airport for two-stage combustion of Claim 4,
- the inner primary after air nozzle is a vertically long nozzle whose opening shape is surrounded by a member that partitions the inner primary after air nozzle and the outer primary after air nozzle, and a peripheral wall of the after air port opening (throat portion),
- the outer primary after air nozzle has an opening shape that defines a member that partitions the inner primary after air nozzle and the outer primary after air nozzle, an after air port opening (throat portion) peripheral wall, the outer primary after air nozzle, and the secondary It is a vertically long nozzle surrounded by a member that divides the after air nozzle.
- a sixth aspect of the present invention provides a combustion apparatus comprising the after-air port for two-stage combustion according to the fourth or fifth aspect, Ratio when the cross-sectional areas perpendicular to the fluid flow direction of the inner primary after-air nozzle and the outer primary after-air nozzle are Si and So, respectively: Si / (Si + So) is 0.5 ⁇ Si / (Si + So) ⁇ 0 .7 It is characterized by being.
- the after-air flow rate of the entire after-air port (the sum of the after-air flow rates of the inner primary after-air nozzle, the outer primary after-air nozzle, and the secondary after-air nozzle)
- the flow rate of the horizontal dispersed flow (secondary after air) due to the suppression of unburned components near the front and rear walls of the furnace, that is, maintain the after air flow rate of the secondary after air nozzle.
- the after air flow of the outer primary after air nozzle is relatively reduced while the after air of the inner primary after air nozzle is reduced. Maintain or increase the flow rate to maintain the primary after-air flow rate It is possible to Mel adjustment. Thereby, the penetration force of the after-air jet in the furnace depth direction can be maintained high, and the mixing performance of the combustion gas flow rising from below and the primary after-air can be maintained.
- the primary after-air flow rate to be ejected from the outer primary after-air nozzle is reduced, ash is deposited on the upper surface of the inner primary after-air nozzle, particularly in the vicinity of the bottom of the after-opening portion of the after-air port opening.
- ash is deposited on the upper surface of the inner primary after-air nozzle, particularly in the vicinity of the bottom of the after-opening portion of the after-air port opening.
- the outer primary after-air nozzle In operation, while maintaining the after-air flow rate of the above-mentioned secondary after-air nozzle, in the phase of reducing the flow rate of primary after-air (straight forward flow) that combines the inner primary after-air nozzle and the outer primary after-air nozzle, the outer primary after-air nozzle Instead of relatively greatly reducing the after-air flow rate, it is also possible to maintain or increase the after-air flow rate of the outer primary after-air nozzle by relatively reducing the after-air flow rate of the inner primary after-air nozzle.
- the former operation reducing the after air flow rate of the outer primary after air nozzle relatively greatly while the after air flow rate of the inner primary after air nozzle is reduced. Maintain or increase). This is because the effect of increasing the separation effect of the primary after-air and secondary after-air jets can be easily obtained as described later.
- the after-air flow rate of the inner primary after-air nozzle is reduced to a small amount or zero, a vortex is generated in the wake part of the inner primary after-air nozzle opening, and the primary after-air (straight flow) that combines the inner primary after-air nozzle and the outer primary after-air nozzle This is because the penetrating power as a whole is not preferable.
- the ratio of the channel cross-sectional area: Si / (Si + So) is set to 0.5 ⁇ Si / (Si + So) ⁇ 0.7. Therefore, it is possible to achieve a penetration force equivalent to the design value at a burner air ratio of 0.85 or less, which is a normally assumed condition, and to reduce the NOx reduction effect in the two-stage combustion method and Si / (Si + So). It is possible to prevent the problem of an increase in pressure loss.
- FIG. 1 (A) The front view (FIG. 1 (A)) which looked at the after airport of one Example of this invention from the furnace side, AA sectional view taken on the line AA of FIG. 1 (A) (FIG. 1 (B)), an inner primary after It is a figure (Drawing 1 (C)) showing an outline of arrangement of an air nozzle, an outside primary after air nozzle, and a secondary after air nozzle.
- FIG. 2 is an explanatory view of another example of the arrangement of the inner primary after air nozzle, the outer primary after air nozzle, and the secondary after air nozzle.
- FIG. 2A shows the inner primary after air nozzle in an L shape.
- FIG. 2B shows an example in which the inner primary after-air nozzle and the outer primary after-air nozzle are arranged next to each other
- FIG. 2C shows the outer primary after-air nozzle in the inner primary after-air nozzle
- FIG. 2D is an explanatory diagram of an example in which the outer primary after air nozzle is disposed along both side edges of the inner primary after air nozzle. It is a furnace sectional view in the state where the front and back wall surfaces of the furnace of the present invention were cut. When the burner air ratio is 0.8, the AAP jet center height relative to the primary after air nozzle cross-sectional area relative value with respect to the burner air ratio of 0.90, 0.85, 0.80, and 0.75. It is an example of a result of calculating a value.
- FIG. 5A A front view of the furnace wall (FIG. 5A) to which the two-stage combustion method is applied, a furnace sectional side view (FIG. 5B) showing a combustion gas jet and a two-stage combustion air jet, and A in FIG. 5B
- FIG. 6 is a cross-sectional view taken along line A-A (FIG. 5C). It is the example of a front view seen from the furnace side of AAP of patent documents 1.
- FIG. 1 is an explanatory view of an after-airport of the present invention
- FIG. 1 (A) is a front view seen from the furnace side
- FIG. 1 (B) is a cross-sectional view taken along line AA in FIG.
- FIG. 1C is a diagram schematically illustrating the arrangement of the inner primary after-air nozzle, the outer primary after-air nozzle, and the secondary after-air nozzle.
- the alternate long and short dash line extending in the vertical direction on the paper is the center line
- the central black dot is the central axis of the AAP extending in the front and back (back and front) direction (the depth direction of the AAP opening).
- the extending dotted arrow represents the left-right width direction of the AAP opening.
- FIG. 2 is an explanatory view of another example of the arrangement of the inner primary after air nozzle, the outer primary after air nozzle, and the secondary after air nozzle.
- FIG. 2A shows the inner primary after air nozzle in an L shape.
- FIG. 2B shows an example in which the inner primary after-air nozzle and the outer primary after-air nozzle are arranged next to each other, and
- FIG. 2C shows the outer primary after-air nozzle in the inner primary after-air nozzle.
- FIG. 2D is an explanatory diagram of an example in which the outer primary after air nozzle is disposed along both side edges of the inner primary after air nozzle.
- the central portion, the inner side, and the outer side in the opening refer to a relative positional relationship with the center line or the central axis as a reference / base point. 2A and 2B, it can be said that the outer primary after air nozzle is provided outside the inner primary after air nozzle provided at the center in the opening.
- the left and right outer sides of the relationship between the outer primary after-air nozzle and the secondary after-air nozzle refers to a one-dimensional positional relationship only in the left-right width direction with the above-mentioned center line as a reference. Accordingly, in any of the cases of FIGS. 1C, 2A, 2B, 2C, and 2D, the secondary after-air is supplied to the left and right outer sides of the outer primary after-air nozzle. Secondary after-air nozzles are provided.
- the horizontal dispersion type AAP structure of this embodiment shown in FIG. 1 is arranged inside an after-airport opening widened portion 18 of an after-airport opening (throat portion) 17 provided on the furnace wall.
- each of the throat portion 17 and the after-airport opening widening portion 18 represents a circular shape of the outer peripheral portion viewed from the front of the furnace side, but each shape is not particularly limited to a circular shape. . Each may be rectangular or polygonal, or may have different shapes.
- the after-air port shown in FIG. 1 the after-air in the after-air wind box 30 (the wind box 30 represents the entire space surrounded by the wind box casing 32 and the furnace wall) is divided into a primary after air 1 and a secondary after air 11.
- the primary after air 1 is supplied to the furnace 31 via the inner primary after air nozzle 501 and the outer primary after air nozzle 502, and the secondary after air 11 is supplied via the secondary after air nozzle 14, respectively.
- an inner primary after air nozzle inlet current reducing member 501a and an outer primary after air nozzle inlet current reducing member 502a whose sectional area is gradually reduced in the air flow direction are installed. Therefore, the pressure loss at the inlets of the inner primary after air nozzle 501 and the outer primary after air nozzle 502 is suppressed.
- An inner primary after air flow adjustment damper (adjustment member for the inner primary after air supply amount) 301 and an outer primary after air flow adjustment that can change the flow resistance are provided at the inlet of the inner primary after air nozzle 501 and the inlet of the outer primary after air nozzle 502.
- a damper (outer primary after-air supply amount adjusting member) 302 is installed to enable optimal adjustment of the after-air flow rate supplied through the inner primary after-air nozzle 501 and the outer primary after-air nozzle 502.
- the primary after-air rectifier 4 is disposed on the downstream side of the inner primary after-air flow adjustment damper 301.
- a secondary after-air flow rate adjustment damper 12 capable of changing the flow path resistance is disposed at the inlet of the secondary after-air nozzle 14.
- a secondary after-air rectifier 13 is disposed downstream of the secondary after-air flow rate adjustment damper 12.
- An air dividing member (secondary after air guide vane) 15 is disposed at the outlet of the secondary after air nozzle 14.
- the air dividing member 15 of the embodiment is composed of one or more blade-like members having an inclination angle with respect to the center axis of the after-air port so that the secondary after-air 11 can be supplied while being deflected in the horizontal direction.
- the members on the bottom side of the inner primary after air nozzle 501 and the outer primary after air nozzle 502 are shared by the throat portion 17, which is effective for cost reduction. Furthermore, since the flow rate of the blown air in the vicinity of the bottom of the after-opening portion 18 of the after-airport opening that is easy to deposit and adhere to combustion ash is maintained, ash accumulation and adhesion can be suppressed, and the after-air jet can be formed stably and highly efficient. Effective for maintaining combustion.
- the opening shape of the inner primary after air nozzle 501 is composed of a member 506 that partitions the inner primary after air nozzle 501 and the outer primary after air nozzle 502, and an after air port opening (throat portion) peripheral wall 507. It is a vertically long nozzle surrounded.
- the outer primary after-air nozzle 502 has an opening shape of a member 506 that partitions the inner primary after-air nozzle 501 and the outer primary after-air nozzle 502, an after-air port opening (throat portion) peripheral wall 507, and the outer primary after-air nozzle 502 and the second primary after-air nozzle 502.
- This is a vertically long nozzle surrounded by a member 508 that partitions the next after-air nozzle 14.
- Three vertically long nozzles are arranged in the horizontal direction, and the cross-sectional area of the central inner primary after-air nozzle 501 is larger than the total cross-sectional area of the outer primary after-air nozzles 502 on the left and right sides.
- the primary after-air nozzle 501 + 502 is divided by a simple partition plate 506, which is effective for cost reduction.
- the central flow channel (501) is maintained in a vertically long shape as when all the flow channels are used. Therefore, the resistance of the combustion gas rising from the burner part does not increase, and the penetration power of the primary after air does not decrease, and high-efficiency combustion can be maintained.
- the present embodiment is considered advantageous from the viewpoint of making such a region as small as possible and the simplification of the structure (number of members and number of processing).
- the primary after-air jet is a straight flow having a high penetrating force
- the primary after-air jet has an action of attracting the adjacent secondary after-air jet, but the influence can be suppressed. Therefore, since the secondary after-air, which is originally spread in the horizontal direction of the furnace, is hardly disturbed and widely dispersed, it is well mixed with the unburned gas rising from below. This achieves a reduction in unburned content. If the burner air ratio is set to a low value or the like, and the flow rate of the after-air that is ejected from the entire after-air port is large and the penetration force required for the design can be ensured by the primary after-air jet flow from the inner primary after-air nozzle 501, the penetration force is reduced. The excess after-air flow rate can be distributed to the outer primary after-air nozzle 502 or the secondary after-air nozzle 14.
- the possibility of ash accumulation and clinker adhesion growth increases locally, but a small amount of after air is discharged from the outer primary after air nozzle 502. This can be suppressed by ejecting.
- this is raised near the furnace wall or between adjacent after-air ports. It can be mixed with the unburned gas to increase the effect of reducing the unburned content.
- FIG. 3 shows a sectional view of the furnace with the front and rear walls of the furnace 31 cut.
- the height H from the central axis of the AAP 7 is the height at the measurement position of the gas jet trajectory S of the AAP 7. Even if the gas jet from the AAP 7 is introduced horizontally from the furnace wall, it is pushed by the combustion gas rising from the burner side and curves upward as it reaches the depth direction of the furnace 31. In the case of a jet with a strong after-air penetration force, the degree of curvature is weak and the arrival height H of the jet is low.
- the flow of the after air in the furnace exhibits a characteristic as an intersecting jet of the combustion gas upward flow from the burner portion and the after air supplied to intersect with the main upward flow.
- FIG. 4 shows an AAP jet flow with respect to the relative value of the primary after-air nozzle cross-sectional area with respect to the burner air ratio of 0.90, 0.85, 0.80, and 0.75 when the burner air ratio is 0.8. It is an example of the result of having calculated the center height relative value.
- the burner air ratio may be changed from about 0.75 on the low side to about 0.85 to 0.9 on the high side.
- AAP jet center height relative to primary after air nozzle cross-sectional area relative value for burner air ratio 0.90, 0.85, 0.80, 0.75 when the burner air ratio 0.8 is the design point The value is calculated using equation (1) and the result is shown in FIG. A broken line, a one-dot chain line, a two-dot chain line, and a solid line show calculation results for burner air ratios of 0.90, 0.85, 0.80, and 0.75, respectively.
- An increase in the height of the center of the AAP jet means that the AAP jet is pushed by the combustion gas rising from the burner side, so that the upward curve is increased and the penetrating force is reduced. That is, if the AAP jet center height is 1.0 or more, the penetration force is less than the design, and if it is 1.0 or less, the penetration force is more than the design.
- the AAP cross-sectional area (relative value) can be reduced to about 0.7 It is desirable to determine the cross-sectional area of the primary after air nozzle channel.
- the cross-sectional area of the inner primary after-air nozzle channel is determined so that the AAP cross-sectional area (relative value) can be reduced to about 0.5. desirable.
- the burner air ratio is designed at 0.80 and the burner air ratio is adjusted to 0.8 or less, the penetration force can be secured without reducing the AAP cross-sectional area. That is, practically, unless Si / (Si + So) is 0.7 or less, a burner air ratio of 0.85 or less, which is a normally assumed condition, cannot be achieved and a penetration force equivalent to the design value cannot be realized.
- Si / (Si + So) is made smaller than 0.5, even if the burner air ratio is set larger than 0.900, a penetration force exceeding the design value can be obtained. From a point of view, it becomes less practical. First, setting the burner air ratio to be larger than 0.90 is rare because the NOx reduction effect in the two-stage combustion system becomes poor. Further, as Si / (Si + So) is decreased, the flow velocity is increased and the pressure loss is increased. Therefore, in the present invention, 0.5 is set as the lower limit (recommended value).
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Abstract
Description
火炉内に二段燃焼用空気を噴出させるアフタエアポートであって、
開口部内の中央部に直進流を噴出させる内側一次アフタエア供給用の内側一次アフタエアノズルと、該内側一次アフタエアノズルの外側に直進流を噴出させる外側一次アフタエア供給用の外側一次アフタエアノズルを設け、
外側一次アフタエアノズルの左右外側に二次アフタエア供給用の二次アフタエアノズルを設け、
該二次アフタエアノズルの出口部に二次アフタエアを水平方向左右に偏向して供給可能なように、アフタエアポート中心軸に対して傾斜角度を有する1つ以上の二次アフタエア案内羽根を設け、
少なくとも前記内側一次アフタエアノズルにおける内側一次アフタエア供給量の調整部材または前記外側一次アフタエアノズルにおける外側一次アフタエア供給量の調整部材を設けたこと
を特徴とする。
前記内側一次アフタエアノズルは、その開口形状が、該内側一次アフタエアノズルと前記外側一次アフタエアノズルとを区画する部材と、アフタエアポート開口部(スロート部)周壁とで囲まれた縦長のノズルであり、
前記外側一次アフタエアノズルは、その開口形状が、前記内側一次アフタエアノズルと該外側一次アフタエアノズルとを区画する部材と、アフタエアポート開口部(スロート部)周壁と、該外側一次アフタエアノズルと前記二次アフタエアノズルとを区画する部材とで囲まれた縦長のノズル
であることを特徴とする。
前記内側一次アフタエアノズルと前記外側一次アフタエアノズルの流体流れ方向に垂直な流路断面積を夫々Si,Soとしたときの比率:Si/(Si+So)が
0.5≦Si/(Si+So)≦0.7
であることを特徴とする。
理論空気量以下の空気量で燃料を燃焼させるバーナを火炉内に配置し、該バーナの設置位置より下流側の火炉に空気を供給する二段燃焼用のアフタエアポートを配置した燃焼装置において、
アフタエアポート開口部内の中央部に直進流噴出用の内側一次アフタエア供給用の内側一次アフタエアノズルと該内側一次アフタエアノズルの外側に直進流噴出用の外側一次アフタエア供給用の外側一次アフタエアノズルを設け、
外側一次アフタエアノズルの左右外側に二次アフタエア供給用の二次アフタエアノズルを設け、
該二次アフタエアノズルの出口部に二次アフタエアを水平方向左右に偏向して供給可能なように、アフタエアポート中心軸に対して傾斜角度を有する1つ以上の二次アフタエア案内羽根を設け、
少なくとも前記内側一次アフタエアノズルにおける内側一次アフタエア供給量の調整部材または前記外側一次アフタエアノズルにおける外側一次アフタエア供給量の調整部材を設けたこと
を特徴とする。
前記内側一次アフタエアノズルは、その開口形状が、該内側一次アフタエアノズルと前記外側一次アフタエアノズルとを区画する部材と、アフタエアポート開口部(スロート部)周壁とで囲まれた縦長のノズルであり、
前記外側一次アフタエアノズルは、その開口形状が、前記内側一次アフタエアノズルと該外側一次アフタエアノズルとを区画する部材と、アフタエアポート開口部(スロート部)周壁と、該外側一次アフタエアノズルと前記二次アフタエアノズルとを区画する部材とで囲まれた縦長のノズル
であることを特徴とする。
前記内側一次アフタエアノズルと前記外側一次アフタエアノズルの流体流れ方向に垂直な流路断面積を夫々Si,Soとしたときの比率:Si/(Si+So)が
0.5≦Si/(Si+So)≦0.7
であることを特徴とする。
なお、運用上、上述の二次アフタエアノズルのアフタエア流量を維持しつつ、内側一次アフタエアノズル、外側一次アフタエアノズルを合わせた一次アフタエア(直進流)の流量を低減する局面において、外側一次アフタエアノズルのアフタエア流量を相対的に大きく低減する代わりに内側一次アフタエアノズルのアフタエア流量を相対的に大きく低減して、外側一次アフタエアノズルのアフタエア流量を維持ないし増加させることも可能である。
これは、その方が、後述するように一次アフタエアと二次アフタエアの噴流の分離効果が高まる効果が得られやすいことが挙げられる。
加えて内側一次アフタエアノズルのアフタエア流量を少量ないしゼロにすると、内側一次アフタエアノズル開口の後流部に渦が発生して、内側一次アフタエアノズル、外側一次アフタエアノズルを合わせた一次アフタエア(直進流)全体としての貫通力が低下して好ましくないためである。
ここで、図1(C)において、紙面上下方向に伸びる一点鎖線が中心線、中央の黒点が、紙面前後(裏表)方向(AAP開口の奥行方向)に伸びるAAPの中心軸、紙面左右方向に伸びる点線矢印が、AAP開口の左右幅方向を表す。
本発明において、開口部内の中央部、内側、外側とは、上記中心線または中心軸を基準・基点とした相対的な位置関係を指す。
よって、図2(A)、図2(B)のケースについても、開口部内の中央部に設けた内側一次アフタエアノズルの外側に外側一次アフタエアノズルが設けられているといえる。
従って、図1(C)、図2(A)、図2(B)、図2(C)、図2(D)のいずれの場合においても、外側一次アフタエアノズルの左右外側に二次アフタエア供給用の二次アフタエアノズルが設けられていることになる。
図1に示す本実施例の水平分散型AAP構造は火炉壁に設けたアフタエアポート開口部(スロート部)17のアフタエアポート開口部広がり部18の内側に配置される。
図1に示すアフタエアポートにおいて、アフタエア用風箱30(風箱30は風箱ケーシング32と火炉壁に囲まれた空間全体を表す。)内のアフタエアは一次アフタエア1と二次アフタエア11に分けられ、一次アフタエア1は内側一次アフタエアノズル501及び外側一次アフタエアノズル502を経由して、二次アフタエア11は二次アフタエアノズル14を経由して、それぞれ火炉31に供給される。
外側一次アフタエアノズル502は、その開口形状が、内側一次アフタエアノズル501と外側一次アフタエアノズル502とを区画する部材506と、アフタエアポート開口部(スロート部)周壁507と、外側一次アフタエアノズル502と二次アフタエアノズル14とを区画する部材508とで囲まれた縦長のノズルである。
3つの縦長ノズルが水平方向に並べて配置されており、中央の内側一次アフタエアノズル501の断面積を左右両側の外側一次アフタエアノズル502の合計断面積より大きくしている。
外側一次アフタエアノズル502から噴出させる一次アフタエア流量を絞っていき、停止させたような際には、内側一次アフタエアノズル501の上面や、特にアフタエアポート開口部広がり部18底部近傍等に、灰の堆積やクリンカの付着成長の可能性がある。図1の例と比べて本実施形態は、そのような領域を極力小さくする観点及び構造の簡略化(部材点数・加工数)から有利と考えられる。
このことは、一次アフタエアと二次アフタエアの噴流の分離効果が高まる利点がある。
バーナ空気比が低めに設定される等、アフタエアポート全体から噴出させるアフタエア流量が多く、内側一次アフタエアノズル501からの一次アフタエア噴流で設計上必要な貫通力が確保できる場合には、当該貫通力を上回る分のアフタエア流量を外側一次アフタエアノズル502または二次アフタエアノズル14に配分することができる。
また、外側一次アフタエアノズル502から少量のアフタエアを噴出させつつ、二次アフタエアノズル14へのアフタエア流量を増加させる運用を行えば、これを火炉壁近傍や隣接するアフタエアポートとの間を上昇してくる未燃ガスと混合させて、未燃分の低減効果を高めることができる。
内側一次アフタエアノズル501と外側一次アフタエアノズル502の流体流れ方向に垂直な流路断面積を夫々Si,Soとしたとき、
比率:Si/(Si+So)が
0.5≦Si/(Si+So)≦0.7
の範囲にあることが望ましい。
このことについて、以下に説明する。
H=Cx(X/D)x(Aa/Ab/D2)-0.85)(1/0.34) …(1)
ここで、X:火炉奥行距離(m)
H:火炉奥行Xにおけるアフタエア噴流中心の高さ(m)
C:係数(-)
D:アフタエアポートの代表径(m)
Va:アフタエア流速(m/s)
Vb:バーナからAAP領域への上昇流速(m/s)
二段燃焼を行うボイラにおけるバーナ域の一般的な空気比(バーナ空気比=バーナから供給される空気量/理論空気量)0.8を設計点にした場合、燃焼性能や火炉壁腐食抑制などの調整のために、バーナ空気比低側0.75程度から高側0.85~0.9程度まで変化させることがある。
破線、一点鎖線、二点鎖線、実線が、それぞれバーナ空気比0.90,0.85,0.80,0.75に対する計算結果を示す。内側一次アフタエアノズルのAAP断面積(相対値)=Si/(Si+So)に相当する1.0を設計値とし、AAP噴流中心高さ(相対値)は1.0が設計値である。
腐食抑制などのためにバーナ空気比を0.85まで高める必要がある場合で、設計の貫通力を求められる場合は、AAP断面積(相対値)を0.7程度まで小さく出来るように、内側一次アフタエアノズル流路の断面積を決定するのが望ましい。同様に、バーナ空気比を0.90まで高める必要がある場合は、AAP断面積(相対値)を0.5程度まで小さく出来るように、内側一次アフタエアノズル流路の断面積を決定するのが望ましい。バーナ空気比を0.80で設計した場合で、バーナ空気比を0.8以下に調整する場合には、AAP断面積を小さくすることなく貫通力を確保することができる。
すなわち、実用上、Si/(Si+So)を0.7以下にしないと、通常想定される条件であるバーナ空気比0.85以下で、設計値と同等の貫通力を実現できない。
まず、バーナ空気比を0.90よりも大きく設定することは、二段燃焼方式におけるNOx低減効果が乏しくなってくるのでほとんど無い。また、Si/(Si+So)を小さくするに従い、流速が高まり、圧力損失が上昇してくる。よって、本発明においては0.5を下限(推奨値)とする。
6 バーナ
7 アフタエアポート(AAP)
11 二次アフタエア
12 二次アフタエア流量調整ダンパ
13 二次アフタエア整流器
14 二次アフタエアノズル
15 二次アフタエア案内羽根
15a 固定部材
17 アフタエアポート開口部(スロート部)
18 アフタエアポート開口部広がり部
30 アフタエア用風箱
31 火炉
32 アフタエア用風箱ケーシング
301 内側一次アフタエア流量調整ダンパ(内側一次アフタエア供給量の調整部材)
302 外側一次アフタエア流量調整ダンパ(外側一次アフタエア供給量の調整部材)
401 内側一次アフタエア整流器
501 内側一次アフタエアノズル
501a 内側一次アフタエアノズル入口縮流部材
502 外側一次アフタエアノズル
502a 外側一次アフタエアノズル入口縮流部材
Claims (6)
- 火炉内に二段燃焼用空気を噴出させるアフタエアポートであって、
開口部内の中央部に直進流を噴出させる内側一次アフタエア供給用の内側一次アフタエアノズルと、該内側一次アフタエアノズルの外側に直進流を噴出させる外側一次アフタエア供給用の外側一次アフタエアノズルを設け、
外側一次アフタエアノズルの左右外側に二次アフタエア供給用の二次アフタエアノズルを設け、
該二次アフタエアノズルの出口部に二次アフタエアを水平方向左右に偏向して供給可能なように、アフタエアポート中心軸に対して傾斜角度を有する1つ以上の二次アフタエア案内羽根を設け、
少なくとも前記内側一次アフタエアノズルにおける内側一次アフタエア供給量の調整部材または前記外側一次アフタエアノズルにおける外側一次アフタエア供給量の調整部材を設けたこと
を特徴とするアフタエアポート。 - 前記内側一次アフタエアノズルは、その開口形状が、該内側一次アフタエアノズルと前記外側一次アフタエアノズルとを区画する部材と、アフタエアポート開口部(スロート部)周壁とで囲まれた縦長のノズルであり、
前記外側一次アフタエアノズルは、その開口形状が、前記内側一次アフタエアノズルと該外側一次アフタエアノズルとを区画する部材と、アフタエアポート開口部(スロート部)周壁と、該外側一次アフタエアノズルと前記二次アフタエアノズルとを区画する部材とで囲まれた縦長のノズル
であることを特徴とする請求項1に記載のアフタエアポート。 - 前記内側一次アフタエアノズルと前記外側一次アフタエアノズルの流体流れ方向に垂直な流路断面積を夫々Si,Soとしたときの比率:Si/(Si+So)が
0.5≦Si/(Si+So)≦0.7
であることを特徴とする請求項1または2に記載のアフタエアポート。 - 理論空気量以下の空気量で燃料を燃焼させるバーナを火炉内に配置し、該バーナの設置位置より下流側の火炉に空気を供給する二段燃焼用のアフタエアポートを配置した燃焼装置において、
アフタエアポート開口部内の中央部に直進流噴出用の内側一次アフタエア供給用の内側一次アフタエアノズルと該内側一次アフタエアノズルの外側に直進流噴出用の外側一次アフタエア供給用の外側一次アフタエアノズルを設け、
外側一次アフタエアノズルの左右外側に二次アフタエア供給用の二次アフタエアノズルを設け、
該二次アフタエアノズルの出口部に二次アフタエアを水平方向左右に偏向して供給可能なように、アフタエアポート中心軸に対して傾斜角度を有する1つ以上の二次アフタエア案内羽根を設け、
少なくとも前記内側一次アフタエアノズルにおける内側一次アフタエア供給量の調整部材または前記外側一次アフタエアノズルにおける外側一次アフタエア供給量の調整部材を設けたこと
を特徴とするアフタエアポートを備えた燃焼装置。 - 前記内側一次アフタエアノズルは、その開口形状が、該内側一次アフタエアノズルと前記外側一次アフタエアノズルとを区画する部材と、アフタエアポート開口部(スロート部)周壁とで囲まれた縦長のノズルであり、
前記外側一次アフタエアノズルは、その開口形状が、前記内側一次アフタエアノズルと該外側一次アフタエアノズルとを区画する部材と、アフタエアポート開口部(スロート部)周壁と、該外側一次アフタエアノズルと前記二次アフタエアノズルとを区画する部材とで囲まれた縦長のノズル
であることを特徴とする請求項4に記載のアフタエアポートを備えた燃焼装置。 - 前記内側一次アフタエアノズルと前記外側一次アフタエアノズルの流体流れ方向に垂直な流路断面積を夫々Si,Soとしたときの比率:Si/(Si+So)が
0.5≦Si/(Si+So)≦0.7
であることを特徴とする請求項4または5に記載のアフタエアポートを備えた燃焼装置。
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WO2020166305A1 (ja) * | 2019-02-13 | 2020-08-20 | 三菱日立パワーシステムズ株式会社 | アフタエアポート及びこれを備えた燃焼装置 |
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