JP2933060B2 - Square multi-tube type once-through boiler - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a square multitubular once-through boiler provided with a can body of a type in which a combustion flame and a combustion gas flow in a crosswise direction with respect to a group of water tubes arranged in tandem.

[0002]

BACKGROUND OF THE INVENTION Recently, environmental pollution problems and the like, hazardous combustion emissions even boiler, in particular NO _X, further reduction such as CO are required. Measures to reduce such harmful combustion exhaust include a method of recirculating exhaust gas, a method of injecting water into the premixed air, a primary combustion with excess fuel, and a mixture of secondary air in the subsequent stream. A so-called two-stage combustion method in which secondary combustion is performed, a method in which CO is oxidized in an adiabatic space between a heat exchanger, and the like after a combustion gas temperature is adjusted by a cold body near a burner are known. .

[0003]

However, simply applying these reduction measures to a conventional boiler can increases the size and complexity of the boiler and increases the cost. Further, if an attempt is made to increase the capacity of the boiler by using the premixed combustion burner for high-load combustion, there is a problem that the burner has a flame holding property and that the amount of emission of harmful exhaust gas increases.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and has a structure in which a number of vertical water tubes are arranged in a line and adjacent vertical water tubes are connected to each other by fin-shaped members. A water pipe wall is formed, and the two water pipe walls are arranged so as to face each other at an interval, and an all-primary-air premixed combustion burner having an air ratio of 1 or more is provided in the longitudinal direction of the pair of water pipe walls. Provided at one end, forming a gas passage of the premixed combustion burner between the water pipe wall from one end in the longitudinal direction to the other end,
A large number of vertical water pipes are arranged over substantially the entire area of the gas passage at a predetermined interval from adjacent vertical water pipes, and the distance between the vertical water pipe and the premixed combustion burner immediately adjacent to the premixed combustion burner is determined. The length of the vertical water pipe is set to be equal to or less than approximately three times the diameter of the vertical water pipe, and the gap between the vertical water pipes of the vertical water pipe is set to be equal to or less than the diameter. Of the flame is passed through the gap between the water pipe walls and the vertical water pipes between the water pipe walls, and the gap between the vertical water pipes between the water pipe walls to form a vortex, and between the water pipe walls. Are formed into a plurality of water pipe groups having different heat transfer surface densities, and the plurality of water pipe groups have heat transfer surface densities from the upstream side to the downstream side in the flow direction of the flame and the combustion gas. Are arranged in order from small to large It is characterized.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and has a structure in which a number of vertical water tubes are arranged in a line and adjacent vertical water tubes are connected to each other by fin-shaped members. A water pipe wall is formed, and the two water pipe walls are arranged so as to face each other with an interval therebetween, and an all-primary air premixed combustion burner having an air ratio of 1 or more is provided in the longitudinal direction of the pair of water pipe walls. Provided at one end, forming a gas passage of the premixed combustion burner between the water pipe wall from one end in the longitudinal direction to the other end,
A large number of vertical water pipes are arranged over substantially the entire area of the gas passage at a predetermined interval from adjacent vertical water pipes, and the distance between the vertical water pipe and the premixed combustion burner immediately adjacent to the premixed combustion burner is determined. The length of the vertical water pipe is set to be equal to or less than approximately three times the diameter of the vertical water pipe, and the gap between the vertical water pipes of the vertical water pipe is set to be equal to or less than the diameter. Of the flame flows through the gap between the water pipe walls and the vertical water pipes between the water pipe walls, and the gap between the vertical water pipes between the water pipe walls to form a vortex, and between the water pipe walls. Are composed of a plurality of water pipe groups having different heat transfer surface densities, and the plurality of water pipe groups have heat transfer surface densities from the upstream side to the downstream side in the flow direction of the flame and the combustion gas. Are arranged in order from small to large It is characterized.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. 1 to 5 show an embodiment of a rectangular multi-tube once-through boiler according to the present invention. FIG. 1 is an explanatory side view partially in section, and FIG. 2 is an arrangement of a vertical water pipe in a can body. FIG. 3 is an enlarged side view of a cross section of a part of the economizer in this multi-tube once-through boiler, FIG. 4 is a side view of FIG. 3, and FIG. 5 is a square multi-tube once-through boiler. It is a perspective explanatory view showing the whole boiler.

In the drawings, reference numeral 1 denotes a thin boiler main body, which is formed by surrounding a can body A with a casing 2 via a heat insulating material. The can body A has a large number of vertical water pipes 10.
Are arranged substantially in parallel in tandem to form a narrow, vertically long, substantially rectangular prismatic can body as shown in the figure as a whole, which will be described in detail below. That is, the water pipe wall 12 constituting the outer shell of the can body A is configured by arranging straight vertical water pipes 10 at equal intervals, and connecting the adjacent vertical water pipes 10 with the fin-shaped members 11, 11,.... The vertical water pipe 1
It is in a state in which the gap between the zeros is closed, and is configured as one rectangular wall member. Then, two water pipe walls 12 configured as described above are opposed to each other while maintaining a required interval, and are arranged so as to be substantially parallel to each other. Each vertical water pipe 1
The upper and lower ends of 0, 10...
Reference).

At one end of the pair of water pipe walls 12, 12 in the longitudinal direction (vertical direction, ie, the horizontal direction in FIG. 2), a combustion burner 3 described later is provided, and at the other end, a gas outlet is provided. 7 are provided. As a result, the pair of water pipe walls 12, 12 and the upper and lower headers 15, 16 form a gas passage 8 through which the combustion flame and the combustion gas from the combustion burner 3 pass substantially linearly. A number of vertical water pipes 10, 10... Are inserted in the gas passage 8 at intervals allowing the flow of the combustion flame and the combustion gas from the combustion burner 3.

As shown in FIG. 2, the distance between the vertical water pipes 10 is set to be substantially equal to or less than the diameter d of the vertical water pipes 10. That is, the vertical water pipe 1 in the water pipe walls 12
0, each water pipe row a inserted in the gas passage 8,
The gaps between the vertical water pipes 10 of B, C,..., The gaps of each row of water pipe rows A, B, C,.
0 and the gap between adjacent ones of the vertical water pipes 10 inserted in the gas passage 8 is substantially equal to the diameter d of the vertical water pipes 10,
Set it below. These gaps may be all the same or different from each other, as long as they are within the aforementioned conditions. Each of the vertical water pipes 10 is inserted over substantially the entire area of the gas passage 8 while maintaining the interval. In this way, the upper and lower ends of each vertical water pipe 10 inserted substantially over the entire area in the gas passage 8 are connected to the two water pipe walls 12.
Are connected to the upper and lower headers 15, 16, respectively.

The vertical water pipes 10 inserted in the gas passages 8 are arranged in a staggered arrangement with the vertical water pipes 10, 10... I have. Further, the vertical water pipes 10, 10 facing the combustion burner 3 in the gas passage 8 are disposed relatively close to the combustion burner 3, as shown in FIG. The space between the vertical water pipe 10 facing this, that is, the vertical water pipes 10, 10 of the first vertical water pipe row A is also extremely small. That is, the gap between the combustion burner 3 and the first vertical water pipe row A located immediately before this is set to a predetermined distance, that is, substantially equal to or less than three times the diameter d of the vertical water pipe 10. . Further, the water pipe row closest to the combustion burner 3 among the water pipe rows of the water pipe wall 12 is also set based on the predetermined distance as described above.

Are formed as two or more vertical water pipe groups having different heat transfer surface densities, and these vertical water pipe groups are used for the flow of the combustion gas. In the direction from the upstream side to the downstream side, the heat transfer surface densities are arranged in ascending order from the smallest. In the illustrated embodiment, three vertical water pipe groups having different heat transfer surface densities are provided. That is, in order from the upstream side, a group of 10 smooth vertical water tubes, a group of horizontal finned water tubes 10 ′,
The vertical water pipes constituting each vertical water pipe group are arranged in two rows along the longitudinal direction between the two water pipe walls 12, and the gas flows from the combustion burner 3 side. A predetermined number of them are arranged at regular intervals toward the outlet 7 side.

The combustion burner 3 is an all-primary air premix burner having an air ratio of 1 or more (preferably 1 to 1.5).
Is used. That is, this type uses a mixture (hereinafter, referred to as a pre-mixture) in which the entire amount of combustion air is mixed with the fuel gas so as to have the above-described air ratio. Such a premix burner includes, for example, a surface combustion burner. Further, in the combustion burner 3 in this embodiment, the lateral width of the can body A is narrow as described above, and the frontage (not shown) for attaching the burner is limited, so that a small high-load combustion burner ( Japanese Patent Application No. 63-13
0982).

A blower 4 for supplying combustion air to the combustion burner 3 is disposed on the top surface S ₁ of the boiler body 1. The blower 4 is of a centrifugal type, its outlet 4a is formed downwardly toward the attachment side of the combustion burners 3, via a Banadakuto 5 disposed on the front surface S ₂ of the boiler main body 1 , And the combustion burner 3. The burner duct 5 supplies the combustion burner 3 with a premixed gas obtained by mixing the combustion air from the blower 4 with the fuel gas, and is substantially equal to or less than the width of the can body A. It is formed with a width. That is, the burner duct 5 has a square tubular shape as shown in the figure, and its upper end is connected to the outlet 4 a of the blower 4.
A fuel gas supply nozzle (not shown) is arranged in the middle of the nozzle, and a premixed air having the above-mentioned air ratio is supplied to the combustion burner 3 from an opening (not shown) formed in a portion which comes into contact with the can body A. Installed.

In the above configuration, the combustion air is supplied from the blower 4 through the burner duct 5, and along the fuel gas from a fuel gas supply nozzle (not shown) in the middle of the burner duct 5, as a premixed air. It is supplied to the combustion burner 3. At this time, the combustion air and the fuel gas are mixed so that the premixed air has an air ratio of 1 or more (preferably 1 to 1.5) as described above. Combustion burner 3
The premixed gas supplied to the combustion burner 3 is blown out from the combustion burner 3 and becomes a combustion flame at the front of the combustion burner 3, and the space inside each water pipe 10 in the can body A is directed from left to right in FIG. It flows while completely burning. Accordingly, the combustion flame and the combustion gas transfer heat to each water pipe 10.

At this time, since the gap between the combustion burner 3 and the first vertical water pipe row A and between the two water pipe walls 12 is set to be narrow as described above, the flame from the combustion burner 3 is transmitted to each vertical water pipe row. Along the gas passage 8 in the longitudinal direction of the can through the gaps between the vertical water pipes 10 in (a), (b), (c), etc., a combustion reaction occurs also in the gap space. As a result, the combustion flame from the combustion burner 3 comes into contact with each of the vertical water pipe rows B, C,... Successively from the first vertical water pipe row A, and also on both water pipe walls 12, and sequentially conducts heat. For example, the flame temperature
The temperature can be reduced to about 1200 ° C. to 1300 ° C., and generation of thermal NO _X (thermal NO _X ) can be suppressed. Further, the combustion flame is swirled by the vertical water pipes 10 in the gap between the adjacent vertical water pipes 10, 10,..., So that the flame holding property is improved and the unburned gas is rapidly taken into the high-temperature combustion gas flow. In rare cases, complete combustion takes place, especially CO being oxidized to CO ₂ . Also, the combustion gas after the combustion reaction passes in the longitudinal direction of the can body while being in contact with each water pipe row and the water pipe wall, and is kept in a relatively low temperature range. Therefore, thermal dissociation of CO ₂ into CO is suppressed.

Further, the combustion burner 3 burns a pre-mixed air in which the combustion air and the fuel gas are mixed in advance at the above-described air ratio. Already in a uniform mixed state. Therefore, the combustion flame formed toward the front of the combustion burner 3 completes the combustion immediately before the temperature falls to a temperature range in which a heat transfer effect is exerted on the water pipe and a combustion reaction does not occur. Completely combusts without remaining.
On the other hand, the combustion burner 3 is a premix burner,
In the case of a partially premixed burner, etc., in the can body structure in which the water pipe is arranged immediately before the burner as described above, the ejection distance for mixing air into the fuel gas ejected from the combustion burner or the partially premixed gas is large. Shortage. For this reason, it is difficult to mix air into the fuel gas, and it is not possible to completely burn the fuel gas. Further, even if a sufficient amount of combustion air is taken in, in this kind of can body, combustion starts without being sufficiently mixed with the fuel gas, and an incompletely combusted portion remains.
In particular, since the incompletely burned portion is cooled by the flame temperature suppressing action of the water pipe as described above, it is discharged from the can as it is, which causes a problem of lowering thermal efficiency.

In addition, by adopting the can body structure as described above, the flow path of the combustion gas from the combustion burner 3, that is, the gas passage 8 can be formed linearly and relatively long. Therefore, the combustion gas from the combustion burner 3 can be kept in the can body A at a relatively low temperature, and it is not necessary to form a separate combustion chamber. This leads to a reduction in harmful exhaust emissions due to the effect of imparting swirl to the combustion gas, while at the same time making the can body A compact.

For example, with respect to the conventional can body and the rectangular multi-tube once-through boiler according to the embodiment of the present invention, when the outer dimensions and the combustion load are the same, the amount of harmful exhaust gas generated is examined.
_X is reduced from 70-80 ppm to 40 ppm, and for CO,
The can A in the present invention is as low as 50 ppm or less. These NO _x and CO values are equivalent to those obtained by setting the circulation rate to 10% in a boiler equipped with an exhaust gas circulation device. However, in the rectangular multi-tube type once-through boiler according to the present invention, no circulation is performed at all and only in one direction. In such a form, the combustion gas is circulated to reduce the harmful exhaust, and a complicated pipe for exhaust gas circulation is not required, so that the structure becomes extremely simple.

Further, with the above configuration, the flow path of the combustion air and the combustion gas is formed in an upright space defined by a predetermined width. As a result, the width of the entire boiler can be reduced to a width where a flow path can be formed, and can be significantly narrower than that of a multi-tube once-through boiler having a conventional combustion chamber. In addition, according to this configuration, the combustion burner 3 is located at one end face of the can A, so that maintenance, inspection, replacement, and the like can be performed very easily.

In addition, on the rear surface of the can A in this embodiment, a economizer 6 communicating with a gas outlet 7 of the can A is arranged. That is, this economizer 6 is arranged on the side facing the combustion burner 3 via the can body A, and its width is also
The width is substantially equal to the width of the can A, and this configuration is as follows.

That is, as shown in FIGS. 1 to 4, the economizer 6 is provided inside a tubular economizer body 21 having a substantially L-shape.
The heat transfer tubes 20 with fins extending in the horizontal direction are arranged in a lattice. Both ends of these heat transfer tubes 20 are respectively opened through the side surfaces of the economizer body 21. Out of the openings of the heat transfer tubes 20 on one side surface of the economizer body 21, the uppermost four and the lowermost four are respectively a economizer header 22a disposed on the economizer body 21 side surface. , 22b, and the eight central two stages are connected by the same economizer header 22c. On the other hand, the openings of the heat transfer tubes 20 on the other side of the economizer body 21 have eight openings in the upper two stages,
In addition, each of the eight openings in the lower two stages is in communication with the economizer headers 22d and 22e arranged on the side face of the economizer body 21. Therefore, these heat transfer tubes 20
And the above-mentioned economizer headers 22a to 22e, a flow path meandering in the vertical direction is easily formed in the economizer 6 with a simple configuration.
The process is performed from the water inlet pipe 23 and the water outlet pipe 24 provided in the a and 22b.

The combustion gas which has completed the heat transfer in the gas passage 8 flows into the economizer 6 from the exhaust gas outlet 7 of the can A. The combustion gas that has flowed into the economizer 6 flows upward here, and further exchanges heat with the heat transfer tube 20. Here, the water in the economizer 6 is 4
Since the heat is transferred from each of the heat transfer tubes 20 to the four lowermost heat transfer tubes 20 via the economizer headers 22d, 22c, and 22e, the water in the uppermost heat transfer tube 20 has a relatively low temperature. Therefore, heat can be efficiently recovered from the combustion gas having a lowered temperature on the downstream side of the economizer 6, and as a whole, heat recovery is performed with extremely high efficiency. The exhaust gas is exhausted from a cylinder (not shown).

The arrangement and shape of the blower 4 and the burner duct 5 in the rectangular multi-tube once-through boiler of the above embodiment can be changed as shown in FIGS.

[0024]

As described above, according to the present invention, the vertical water pipe group is arranged close to the all-primary air premixed combustion burner having an air ratio of 1 or more and disposed at one end of a pair of water pipe walls. With the simple configuration of the arrangement, the pollution can be reduced and the combustion chamber can be almost eliminated, so that the can can be reduced in size. Further, since the combustion flame from the premixed combustion burner flows not only in the gap between the vertical water pipes between the water pipe walls, but also in the gap between the water pipe wall and the vertical water pipe between the water pipe walls, The combustion flame from the premixed combustion burner is effectively cooled as a whole in the direction crossing the flow of the combustion flame, the temperature of the combustion flame is almost uniformly suppressed, and the effect of reducing NOx is great. Further, CO generated when the combustion flame is cooled by the water pipe wall and the water pipe group is formed by a gap between the water pipe wall and the vertical water pipe between the water pipe walls and a gap between the vertical water pipes between the water pipe walls. Is oxidized by the swirling flow of the combustion flame, thereby reducing CO emissions. Further, even if a premixed combustion burner of high load combustion is used to increase the capacity of the boiler, the flame holding property can be improved by the swirling flow of the combustion flame in the gap, and stable combustion can be realized, and emission of harmful exhaust gas can be achieved. The amount can also be reduced. Therefore,
It is possible to provide an industrially useful boiler that has simultaneously solved the technical problems that are difficult to solve simultaneously, such as low pollution, miniaturization (space saving), and large capacity.

[Brief description of the drawings]

FIG. 1 is an explanatory side view showing a part of an embodiment of the present invention in section.

FIG. 2 is an explanatory plan sectional view for explaining an arrangement of a vertical water pipe in the can body of the embodiment.

FIG. 3 is an enlarged side view illustrating a part of the economizer in the embodiment.

FIG. 4 is a side view of FIG. 3;

FIG. 5 is a perspective explanatory view showing the entire boiler of the embodiment.

FIG. 6 is an explanatory perspective view showing the whole of another boiler.

FIG. 7 is an explanatory perspective view showing the whole of another boiler.

FIG. 8 is a perspective explanatory view showing the whole of another boiler.

[Explanation of symbols]

 A Can body 3 Combustion burner 7 Gas outlet 8 Gas passage 10 Vertical water pipe 11 Fin member 12 Water pipe wall

Continuation of the front page (56) References JP-A-49-95230 (JP, A) JP-A-60-78247 (JP, A) JP-A-54-130701 (JP, A) , U) Shokai Sho 60-55801 (JP, U) Gas Boiler Technical Report No. 15, “Gas Steam Unit System for Multiple Can Installation”, Osaka Gas, October 27, 1988 (58) Field surveyed (Int. Cl. ⁶ , DB name) F22B 21/04

Claims (1)

(57) [Claims] 1. A plurality of vertical water pipes are arranged in a line, and adjacent vertical water pipes are connected to each other by a fin-shaped member to form a water pipe wall. The two water pipe walls are spaced apart from each other. An all-primary pneumatic premixed combustion burner arranged face-to-face and having an air ratio of 1 or more is provided at one longitudinal end of the pair of water pipe walls, and between the water pipe walls from one longitudinal end to the other end. A gas passage of the premixed combustion burner is formed, and a number of vertical water pipes are arranged over substantially the entire area of the gas passage at a predetermined interval from an adjacent vertical water pipe. The distance between a vertical water pipe and the premixed combustion burner is set to be equal to or less than about three times the diameter of the vertical water pipe, and the gap between the vertical water pipes of the vertical water pipe is equal to the diameter. Or less, the flame of the premixed combustion burner And the gap between the vertical water tubes of the water tube walls and the water tube wall, with circulating to the gap between the adjacent vertical water tubes of the water tube walls, a number of vertical of the water tube walls The water tubes are composed of a plurality of water tube groups having different heat transfer surface densities, and the plurality of water tube groups have a heat transfer surface density that decreases from the upstream side to the downstream side in the flow direction of the flame and the combustion gas. Characterized in that they are arranged in the order from the largest to the smallest.