JP2933055B2 - 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]

2. Description of the Related Art Recently, due to environmental pollution problems,
Hazardous combustion emissions even color, in particular NO _X, such as CO
Further reduction is required. Such harmful combustion emissions
As a measure to reduce airborne matter, recycle exhaust gas.
Method, method of injecting water into premixed gas, primary combustion with excess fuel
Then, secondary air is mixed in the subsequent flow to cause secondary combustion
Or a so-called two-stage combustion method, or a cold body near the burner
After adjusting the combustion gas temperature, adiabatic air between the heat exchanger
What oxidizes CO in a space is known.

[0003]

[0004]

[0005]

[0006]

SUMMARY OF THE INVENTION However, these
Only by applying measures to reduce boilers to conventional boiler bodies.
Increases the size and complexity of boilers and raises costs
You. In addition, the premixed combustion burner is designed for high load combustion, and
Burner flame retention problem when trying to increase the capacity of the irra
And increase of harmful emissions
There is a title.

[0007]

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has a premixed combustion burner provided at one end and a gas mixture having a gas outlet at the other end. Combustion flame from the mixed combustion burner, a square multi-tube once-through boiler having a can body provided with a number of vertical water pipes in the gas passage at intervals allowing the flow of combustion gas,
The premixed combustion burner is a primary aerated-type premixed burner set to air ratio of 1 or more, the plurality of vertical water tubes,
The distance from the premixed combustion burner is the diameter d of the vertical water pipe.
A row of water tubes arranged immediately in front of said premixed combustion burner so as to be less than or equal to approximately three times the length of
The water pipes are arranged in a water pipe group consisting of a row of water pipes, b, c,. It is characterized in that was passed through the flame into the gap.

[0009]

According to the present invention, the combustion flame from the premixed combustion burner is passed through the water tube gap between the water tube rows immediately before the premixed combustion burner and the water pipe group consisting of the water pipe rows following the premix combustion burner, and is cooled by the water pipe groups. This reduces the amount of NOx generated. Also, CO generated when cooling the combustion flame with the water pipe group
Is oxidized by the swirling flow of the combustion flame in the water pipe gap of the water pipe group, and the CO emission is reduced. The combustion flame from the premixed combustion burner, since <br/> as a vortex in the water pipe clearance water tube group, improving flame stability is.

[0010]

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 the multi-tube once-through boiler, FIG. 4 is a side view of FIG. 3, and FIG. 5 is a square multi-tube type. It is a perspective explanatory view which shows the whole of a once-through boiler.

In the drawings, reference numeral 1 denotes a thin boiler 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).

A combustion burner 3, which will be described later, is provided 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), and a gas outlet is provided at the other end. 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 interval 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 into the gas passages 8 are arranged in a staggered arrangement with the vertical water pipes 10, 10... Constituting the water pipe walls 12, as shown in the figure. 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.

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 via 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 ejected 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 the gap between the two water pipe walls 12 are set to be narrow as described above, the flame from the combustion burner 3 is transmitted to each vertical water pipe row. Along the longitudinal direction of the can along the gas passage 8 through the gaps between the vertical water pipes 10a, 2b, 3c,..., A combustion reaction also occurs in these gap spaces. 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. Furthermore, the combustion flame is swirled by the vertical water pipes 10 in the gaps between the adjacent vertical water pipes 10, 10. Therefore, 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-mentioned 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 to be relatively long in a straight line. 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.

[0021] For example, a conventional can body with square-tube once-through boiler according to the present invention, external dimensions, examining the generation of hazardous emissions combustion load as the same, NO _X is 70
The amount of CO is reduced from 80 ppm to 40 ppm, and the can body A of the present invention has a low CO of 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 in 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 finished transferring heat 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.

Next, another embodiment of the can body structure according to the present invention will be described with reference to FIGS. First, in the embodiment shown in FIG. 9, a large number of vertical water pipes inserted into the gas passage 8 are configured as two or more vertical water pipe groups having different heat transfer surface densities, and these vertical water pipe groups are used for combustion gas. The heat transfer surface densities are arranged in order from the smallest to the largest in the flow direction from the upstream side to the downstream side in the flow direction. In the illustrated embodiment, three vertical water pipe groups having different heat transfer surface densities are provided. There are things. That is, in order from the upstream side,
A group of smooth vertical water pipes 10, a group of water pipes with horizontal fins 10 ', and a group of erofin water pipes 10 "are arranged. Each vertical water pipe constituting each vertical water pipe group has a longitudinal section between the two water pipe walls (12). In a two-row state along the direction, a predetermined number of tubes are arranged at regular intervals from the combustion burner 3 side to the gas outlet 7 side.

The embodiment shown in FIG.
Has a length up to the middle of the can body A and a narrow horizontal width (width in the horizontal direction in the drawing) on the downstream side. A vertical water pipe group in which straight vertical water pipes 10 are arranged in series is arranged between the two water pipe walls 12. On the downstream side of the water pipe walls 12, heat insulating walls 18 are arranged on both sides, and a vertical water pipe group consisting of two rows of erofin water pipes 10 "is arranged between the water pipe walls 12.

[0029]

As described above, according to the present invention, a group of water pipes is arranged in close proximity to an all-primary-pneumatic premixed combustion burner set to an air ratio of 1 or more, and the flame of the premixed combustion burner is vertically extended.
With a simple configuration of flowing through the gap between the water pipes , low pollution can be realized, and the can body can be reduced in size by eliminating the combustion chamber. Further, even if a high-load combustion premixed combustion burner is used to increase the capacity of the boiler, the flame holding property can be improved, stable combustion can be realized, and the emission of harmful exhaust gas can be reduced. Therefore, it is possible to provide an industrially useful boiler that simultaneously solves difficult technical problems 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.

FIG. 9 is an explanatory plan sectional view illustrating an arrangement of vertical water pipes in another embodiment of the can body structure.

FIG. 10 is an explanatory plan sectional view illustrating an arrangement of a vertical water pipe in another embodiment of the can body structure.

[Explanation of symbols]

 A Can body 3 Combustion burner 7 Exhaust gas outlet 8 Gas passage 10 Vertical water pipe 11 Fin-like member 12 Water pipe wall 15 Upper header 16 Lower header

Continuation of the front page (56) References JP-A-49-95230 (JP, A) JP-A-60-78247 (JP, A) Jiko 8-7082 (JP, Y1) Gas Boiler Technical Report No. 15 Gas Steam Unit System for Can Installation ", Osaka Gas, October 27, 1988 (58) Field surveyed (Int. Cl. ⁶ , DB name) F22B 21/04

Claims (1)

(57) [Claims] An interval in which a combustion flame and a combustion gas from the premixed combustion burner 3 are allowed to flow in a gas passage 8 having a premixed combustion burner 3 at one end and a gas outlet 7 at the other end. Is a square multi-tube once-through boiler having a can body A provided with a number of vertical water pipes 10 in the gas passage 8 with:
The premix combustion burner 3 is an all-primary pneumatic premix burner set to an air ratio of 1 or more.
0 means that the distance from the premixed combustion burner 3 is
The water pipe row A disposed immediately in front of the premixed combustion burner 3 so as to have a length equal to or less than about three times the diameter d of 10 and the water pipe rows B, C,. And the gap between the vertical water pipes 10 of the group of water pipes was set to be approximately equal to or less than the diameter d, and the combustion flame of the premixed combustion burner 3 was passed through the gap . A rectangular multi-tube once-through boiler characterized in that: