JP3662599B2 - Water tube boiler - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to water tube boilers such as once-through boilers, natural circulation water tube boilers, forced circulation water tube boilers, and the like that have reduced NOx and CO emission concentrations.
[0002]
[Prior art]
In recent years, due to environmental pollution problems, boilers are required to further reduce the concentration of harmful combustion exhaust, particularly NOx and CO.
Various countermeasures for reducing the emission concentration of such harmful combustion exhaust have been proposed.
As one of the reduction measures, the water tube is placed as close as possible to the burner, the water tube group is positioned in the combustion flame, and the generation of thermal NOx is suppressed as much as possible by cooling the flame simultaneously with heat exchange. A technique for realizing load combustion is known from US Pat. No. 5,020,479.
[0003]
The term “combustion flame” used in this document refers to a high-temperature gas that is currently undergoing a combustion reaction. In this high-temperature gas, a combustible premixed gas that has not been combusted and combustion are used. Generated burned gas. A flame may be rephrased as a combustion gas.
[0004]
However, although this conventional measure can reduce the NOx emission concentration, there is a problem that the CO emission concentration is slightly increased. One reason for this is that for CO, the cooling of the combustion flame, which is done to reduce NOx, has a quenching effect, whereby the combustion reaction is frozen and some of the unreacted material remains at an equilibrium concentration at high temperatures. In other words, it is thought that it may be due to discharge outside the system as CO or the like.
In order to solve this problem, the temperature of the flame is controlled to 1000 ° C. or more and 1500 ° C. or less in the vicinity of the flame generated by high-load combustion or in contact with the flame, and then on the downstream side of the cold object. Japanese Laid-Open Patent Application No. 60-78247 proposes a technique for oxidizing residual CO in a flame in an adiabatic space to convert it into CO2.
[0005]
[Problems to be solved by the invention]
However, this technique has been made for the purpose of reducing CO emissions, and is not aimed at suppressing the production of NOx. For this reason, depending on the position where the heat insulation space is provided, the heat insulation space temperature of the combustion flame becomes high, and NOx (thermal NOx) is generated.
Furthermore, when the combustion flame has a high flow velocity, it is possible to achieve the transformation from the required CO to CO2 by ensuring the length of the heat insulation space in the direction of the combustion flame flow, but this leads to a decrease in thermal efficiency, There is a problem that miniaturization of the can body cannot be realized.
[0006]
Furthermore, in general, a boiler or the like needs to adjust the combustion amount of the burner means (combustion equipment) according to the required amount of heat. For this reason, depending on the adjustment of the combustion amount of the burner means, Position will be different.
That is, the arrangement of the burner means, the heat insulation space on the can body side, and the water pipe are determined so that the amount of NOx and CO produced is reduced during combustion at the normal output or rated output. Therefore, the combustion flame is not effectively quenched by the water pipe at the time of combustion at a low load, so that the amount of NOx generated increases, while the water pipe at the front of the burner means is overheated at the time of excessive combustion. .
[0007]
The burner means can sufficiently cool the pre-mixed gas, fuel, and air injection holes by these gas injections, but the other parts are exposed to the high-temperature gas as described above. In addition, a device for heat resistance is necessary.
[0008]
In addition, it is necessary to configure a good combustion reaction region in the narrow space as described above, and it is also necessary to devise the burner means side, and the structure for that is complicated.
[0009]
[Means for Solving the Problems]
The present invention has been made in view of the above problems, and is disposed substantially parallel to each other and spaced along the flow direction of the combustion flame, and includes a pair of water pipe walls including a plurality of water pipes. A premixed planar burner which is arranged on one side of the combustion / heat exchange zone defined by the water pipe wall and forms a plurality of flames to adjust the combustion amount to high and low, and the other combustion / heat exchange zone A plurality of exhaust gas outlet means provided on the side of the combustion / heat exchange section so as to intersect with the combustion flame from the premixed planar burner means at a predetermined interval substantially parallel to each other. A water pipe group comprising a plurality of water pipes corresponding to the boundary portions of the flames from the burner means so as to form a gap between the water pipes constituting the water pipe wall. Place a small group of the premixed type A water pipe boiler characterized in that each flame from a flat burner is configured to circulate through the gap when the combustion amount is high and when the combustion amount is low.
[0010]
[Action]
According to the water tube boiler of the present invention, regardless of the amount of combustion, the combustion flame of the burner means surely flows from the gap of the water tube toward the gap on the downstream side, and from both sides of the combustion flame. NOx generation is suppressed by cooling with water pipes.
[0011]
【Example】
FIG. 1 is a schematic configuration diagram showing a cross section of a can body of an embodiment in which the present invention is applied to a multi-tube once-through boiler which is a kind of water tube boiler.
In the drawing, the can body (1) of the multi-tube once-through boiler is a vertical water pipe wall (hereinafter referred to as the longitudinal direction of the can body) (hereinafter referred to as the longitudinal direction of the can body) ejected from the burner means (2). (Referred to simply as the pipe wall) and (3), (3) and the pipe walls (3), (3) so as to intersect the combustion flame between the pipe walls (3), (3) with a predetermined distance therebetween. A number of substantially vertical water pipes (4) (4) (which constitutes a group of water pipes) and one of the premixed comparatively arranged at one side opening between the pipe walls (3) and (3). Composed of burner means (2) for forming a flat flame and combustion exhaust gas outlet means (hereinafter simply referred to as exhaust gas outlet) (5) formed at the other side opening between the pipe walls (3) and (3) Is done. Tube walls (3) and (3) define a combustion and heat exchange zone (N). The exhaust gas outlet (5) may be provided at the end of the combustion / heat exchange zone (N) opposite to the burner. For example, a part of the tube wall may be removed and opened.
[0012]
The burner means (2) uses a well-known corrugated type premixed planar combustion burner, and further uses a well-known flame dividing means or the like (2 in the illustrated embodiment to improve flame holding). Of the main flame).
The burner means (2) may be a ceramic plate burner having a large number of small holes for ejecting premixed gas or a vaporized combustion oil in addition to the corrugated type premixed planar combustion burner. In addition to the burner, various burners can be used. In short, as long as it forms a main flame extending in a plurality of directions, it is not limited to one burner means, but may be a plurality of burner means.
[0013]
In this embodiment, the pipe walls (3) and (3) are each provided with a plurality of water pipes (6) arranged side by side in the flow direction of the combustion flame at appropriate intervals, and each water pipe (6) (6) The gap is closed by a flat fin-like member (7) (7) extending along the axial direction of these water pipes (6), (6).
These tube walls (3), (3) are arranged at appropriate intervals so as to be substantially parallel to each other, and the cover bodies (8), (3) are disposed outside the tube walls (3), (3). (8) is attached, and heat insulation spaces (9) and (9) are formed between the pipe walls (3) and (3). In addition, the heat insulating spaces (9) and (9) may be filled with an appropriate heat insulating material such as glass wool in some cases.
[0014]
The water pipe (4) (4)... Includes three water pipe rows X, Y, and Z arranged in the flow direction of the combustion flame. In the following description, subscripts 1, 2, 3,... Are added to the column names X, Y, Z in the direction away from the burner means (2), and pipe numbers (X1), (X2),. ..., (Y1), (Y2), ..., (Z1), (Z2), ..., and the water pipes (6), (6), ... that make up the pipe walls (3), (3) Each pipe number (A1), (A2),..., (B1), (B2),.
[0015]
It said tube wall (3), (3) water pipes constituting the (6) (6) ‥‥ and tube wall (3), (3) water pipe disposed between (4) (4) upper and lower ends of ‥‥ is These are connected in communication with an upper header and a lower header (both not shown). These headers are airtightly joined to the upper and lower ends of the pipe walls (3) and (3), and together with the pipe walls (3) and (3), the upper and lower and left and right sides of the combustion / heat exchange zone (N) The four sides are airtightly divided so that the combustion flame and the burned gas do not leak outside the can body. Of the remaining two openings, one is attached with the burner means (2), and the other opening is connected with an exhaust pipe (not shown). In a steam boiler, the entire lower header and the water pipe (6) (6) ..., (4) (4) ... are always filled with water during normal operation, and the water pipe (6) (6) ... , (4) (4) ... The upper and upper headers are filled with steam.
[0016]
The plurality of water pipes (4), (4) arranged between the pipe walls (3), (3) are arranged in parallel with the three rows X, Y, Z in the flow direction of the combustion flame as described above. It is. The two water pipes (X1) and (Z1) that are closest to the burner means (2) and face each other constitute a small group (hereinafter referred to as a close water pipe group) (G) that is substantially in close contact with each other. The tube walls (3) and (3) are arranged approximately at the center.
The water pipes after this close water pipe group (G) are arranged in a staggered arrangement in the adjacent water pipes including the water pipes (6), (6) of the pipe walls (3), (3). Also, each water pipe (6) (6) ..., (4) (4) ..., the flow path of the combustion flame, is set so that the mutual distance is equal to or less than the outer diameter of each water pipe (6). These intervals may be the same or different from each other as long as they are within the above-described conditions.
[0017]
The above-mentioned burner means (2), the close water pipe group (G) located immediately before the burner means (2), and the water pipes (A1), (B1) on the foremost side constituting the pipe walls (3), (3) The positional relationship of is set as follows.
First, the close water pipe group (G) is arranged so as to form a gap between the water pipes (A1) and (B1) constituting the pipe walls (3) and (3) on both sides thereof. The burner means (2) is provided so that the main flame enters the gaps regardless of the amount of combustion.
[0018]
Furthermore, the positional relationship between the burner means (2), the close water pipe group (G), and the water pipes (A1) (B1) (X1) (Z1) depends on the main flame (the high temperature region of the combustion gas) from the burner means (2). ) Is in contact with the water pipes (A1) (B1) (X1) (Z1) on both sides of the premixed gas ejection direction, that is, the combustion flame from the burner means is directed to the water pipe facing the burner means (2). The positional relationship is that the temperature is lowered by cooling by heat transfer.
Therefore, when the combustion flame passes through the gap between the close water pipe group (G) and the pipe walls (3), (3), the water pipes (A1) (X1) (Z1) (B1) on both sides Therefore, thermal NOx generation can be prevented.
[0019]
Furthermore, the combustion flame that has passed through the gap between the water pipes (X1), (Y1), (Z1) and the water pipes (A1), (B1) is also in the gap space between the water pipes on the downstream side of these water pipes. While continuing a combustion reaction as mentioned above, it distribute | circulates between the said tube walls toward an exhaust gas exit, and heat-transfer to each water pipe is performed in the meantime. Also in this case, the combustion flame conducts heat between the downstream water pipes while continuing the combustion reaction, and the temperature is lowered, so that generation of thermal NOx can be prevented.
In addition, since the main flame is provided so as to enter the gaps regardless of the amount of combustion of the burner means (2), low NOx and low CO can always be achieved regardless of the operating conditions of the boiler. .
[0020]
Next, a second embodiment according to the present invention will be described with reference to FIG.
In this second embodiment, the close water pipe group of the first embodiment is expanded to the region on the downstream side in the flow direction of the combustion flame. Specifically, the pipe wall (3), (3) The water pipes (G1) that are in close contact with each other are constructed by the water pipes (X1), (Y1), and (Z1) closest to the burner means (2).
[0021]
The close water pipe group (G1) has a triangular shape formed by three water pipes (X1), (Y1), and (Z1), and in this state, a substantially central position between the pipe walls (3) and (3). It is arranged in. The arrangement of the water pipes on the downstream side of the close water pipe group (G1) is arranged in the same manner as in the first embodiment.
[0022]
With this arrangement, when vibrations and noises are generated with combustion in the first embodiment, they can be reduced.
That is, in each water pipe gap, the flow rate of the combustion flame (combustion gas) is higher in the gap closer to the burner means (2), and on the downstream side of the water pipe, the opposite side of the main flow of the combustion flame (combustion gas) A swirling vortex (Karman vortex) is generated. Such vortices may affect each other and generate significant vibrations and noises.However, as described above, the close water pipe group (G1) immediately before the burner means (2) is placed downstream of the combustion flame flow direction. The vortex generated on both sides of the wake of the water pipe (X1) (Z1) is isolated from each other by the water pipe (Y1) by removing the influence of each other. Generation of vibration and noise can be effectively suppressed.
[0023]
In the first and second embodiments described above, according to the number of flames formed in the burner means (2), the water pipe located immediately before the flame of the burner means (2) is replaced with an appropriate water pipe small group (close water pipe). Group), the heat load of the water pipe immediately before the burner means (2) can be adjusted.
[0024]
In the above description, the pipe walls (3), (3) constituting the boiler can body are arranged in parallel to each other, and the interval with respect to the flow direction of the combustion flame is the same. In this case, the interval between the tube walls may be partially different, or the interval between the tube walls may be sequentially increased or reduced.
FIG. 3 shows an embodiment applied to a boiler in which the interval between tube walls is partially different.
[0025]
In this third embodiment, the interval between the tube walls (3 '), (3') is narrowed on the burner means (2) side, and the water pipes constituting the tube walls (3 ', 3') Among them, the interval between the pipe wall parts (hereinafter referred to as the front pipe wall) formed by the water pipes (A1) to (A3) and (B1) to (B3) on the burner means (2) side It is narrower than the interval (hereinafter referred to as the rear tube wall). Therefore, only one central row (Y row) of the water tube rows is located between the front tube walls, and three rows (X to Z rows) are located between the rear tube walls as in the above embodiments. . Incidentally, the front tube walls formed by the water pipes (A1) to (A3) and (B1) to (B3) are also substantially parallel to each other like the rear tube wall.
[0026]
The two water pipes arranged in the middle between the front pipe walls are closely arranged, and the two water pipes (Y1) (Y2) and the water pipes (A1) to (A3) constituting the front pipe wall are arranged. ), (B1) to (B3) are arranged in a substantially zigzag pattern. In addition, water pipes (X1) (X2) ..., (Z1) (Z2) ... are located in the wake of the gap formed between the front pipe wall and the close water pipe group (G2). become.
[0027]
With the above configuration, also in the third embodiment, the combustion flame from the burner means (2) is in close contact with the front tube wall (G2) regardless of the amount of combustion as in the above embodiments. It surely enters the gap between the two and passes through the gap of the water pipe group between the rear pipe walls toward the exhaust gas outlet (5). The combustion flame conducts heat transfer with each water pipe (4) (4) (6) (6) ... while continuing to burn as it circulates between the pipe walls.
[0028]
Here, when the combustion amount of the burner means (2) is small, that is, when the boiler is in a low load operation state, the combustion flame from the burner means (2) is short, and the high temperature region of this combustion flame is mainly the front part. Cooled by heat transfer between the tube wall and the close water tube group (G2), the temperature drops. Therefore, when the combustion flame passes through the gap between the front tube wall and the close water tube group (G2), the water tubes (A1) to (A3), (Y1) to (Y2), ( B1) to (B3) are rapidly cooled and the temperature is lowered, so that generation of thermal NOx can be prevented. The combustion flame that has passed through the gap between the front pipe wall and the close water pipe group continues the combustion reaction as described above even in the gap space between the water pipes on the downstream side of these water pipes, while the above-mentioned pipe wall. The air flows toward the exhaust gas outlet (5), and heat is transferred to each water pipe during that time. Also in this case, the combustion flame conducts heat between the downstream water pipes while continuing the combustion reaction, and the temperature is lowered, so that generation of thermal NOx can be prevented.
[0029]
On the other hand, when the combustion amount of the burner means (2) is large, that is, when the boiler is in a high load operation state, the combustion flame from the burner means (2) is long, and the high temperature region of this combustion flame is mainly the rear pipe wall. And cooled by heat transfer with the water tube group in between. Therefore, when the combustion flame passes through the gap between the front tube wall and the close water tube group (G2), the water tubes (A1) to (A3), (Y1) to (Y2), ( When a part of the combustion flame is cooled by B1) to (B3) and passes through the gap between the rear pipe wall and the water pipe group therebetween, the pipes (A4) (A5) to (X1) (X2) to It is cooled rapidly by (Y3) (Y4) ~, (Z1) (Z2) ~, (B4) (B5) ~, and the temperature drops. Then, in the gap space between the water pipes on the downstream side of these water pipes, the combustion reaction is continued to flow between the rear pipe walls toward the exhaust gas outlet (5), and in the meantime, heat is transferred to each water pipe. . Also in this case, the combustion flame conducts heat between the downstream water pipes while continuing the combustion reaction, and the temperature is lowered, so that generation of thermal NOx can be prevented.
[0030]
Therefore, also in the third embodiment, the high temperature region of the combustion flame can be reliably cooled regardless of the combustion amount of the burner means (2), that is, the operating condition of the boiler, as in the above embodiments. Therefore, low NOx and low CO can always be achieved.
[0031]
In addition, in this third embodiment, the close water pipe group (G2) consisting of the water pipes (Y1) (Y2) is compared with the close water pipe group (G1) of the second embodiment (in the direction of combustion flame flow). Since the value of (length) / (width with respect to the combustion flame flow direction) is large, the vibration / noise reduction effect is further improved.
[0032]
In the above description, the single burner means obtained by appropriately dividing the flame into one boiler can body is composed of a plurality of units in the present invention, and a flame is formed for each unit. The burner means may be used.
[0033]
Furthermore, in the description of each of the above embodiments, a plurality of water pipe groups arranged between the pipe walls (3) and (3) are arranged in three rows between the pipe walls, but the number of rows is not limited to this. In addition, the present invention can also be applied to the cans arranged in a tandem row forming even rows.
[0034]
In addition, although the small group of water pipes is a close water pipe group in which the water pipes are substantially in close contact with each other in each of the above embodiments, the small group of water pipes in this invention does not necessarily need to be closely arranged in this manner. What is necessary is just to partition from the water pipe row | line (or water pipe group) which a water pipe comprises.
[0035]
Further, the pipe walls (3) and (3) in the first to third embodiments described above are arranged with a plurality of water pipes arranged in tandem at appropriate intervals, and the gaps between the water pipes are made of flat fin-like members. In the present invention, the structure of the tube wall may be a structure in which the water tubes are arranged in close contact with each other.
[0036]
In the above first to third embodiments, an example in which a multi-tube type once-through boiler that generates steam has been described. However, the present invention may generate hot water. The boiler type is not limited to the once-through boiler, but can be applied to all water pipe boilers such as a natural circulation water pipe boiler and a forced circulation water pipe boiler.
[0037]
【The invention's effect】
According to the water tube boiler according to the present invention, regardless of the amount of combustion, the combustion flame of the burner means surely flows from the gap of the water tube toward the gap on the wake side, and the water tubes from both sides of the combustion flame. Therefore, the production of NOx can be suppressed in any combustion range.
As a result, the combustion range having a high NOx reduction effect can be dramatically expanded as compared with the conventional case.
[Brief description of the drawings]
FIG. 1 is a plan view showing a can structure in a water tube boiler according to the present invention.
FIG. 2 is an enlarged plan view of an essential part showing a second embodiment.
FIG. 3 is an enlarged plan view of an essential part showing a third embodiment.
[Explanation of symbols]
(2) Burner means
(3) Pipe wall (water pipe wall)
(4) Water pipe
(5) Exhaust gas outlet (combustion exhaust gas outlet means)
(6) Water pipe
(G) Close water pipe group (small group of water pipes)
(G1) Close water pipe group (small group of water pipes)
(G2) Close water pipe group (small group of water pipes)
(N) Combustion / heat exchange zone

Claims (1)

A pair of water pipe walls (3), (3) arranged in parallel with each other and spaced along the flow direction of the combustion flame and including a plurality of water pipes (6) (6). A premixed planar burner (2), which is arranged on one side of the combustion / heat exchange zone (N) defined by the water pipe walls (3) and (3), forms multiple flames and adjusts the combustion amount to high and low. ), The flue gas outlet means (5) provided on the other side of the combustion / heat exchange zone (N), and the premixed planar burner means (2) substantially parallel to each other at a predetermined interval. A water pipe group comprising a plurality of water pipes (4), (4),... Provided in almost the entire area of the combustion / heat exchange zone (N) so as to intersect with the combustion flame, the water pipe wall (3) , (3) a small group of water pipes (G), (G1) consisting of a plurality of water pipes corresponding to the boundary portion of each flame from the burner means (2) so as to form a gap with the water pipes constituting (3) ), (G2) Water tube boiler, characterized by being configured so that each flame from engagement formula plan burner (2) is circulated in said gap at high combustion amount and at low combustion amount.

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