JP2583273Y2 - Square multi-tube type once-through boiler - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION This invention relates to a prismatic multi-tube once-through boiler of the type which linearly flows in the cross-line direction of the combustion gas with respect to the vertical water tubes.

[0002]

2. Description of the Related Art Generally, a small multi-tube once-through boiler is manufactured based on a water pipe assembly (can body) having a cylindrical shape. In this, a water pipe is arranged in a ring shape, and the inside thereof is used as a combustion chamber. However, such a can body structure tends to occupy a relatively large space depending on the installation location and arrangement of the boiler, and in recent years, various multi-tube types based on a so-called square can body structure have been used. Once-through boiler proposed
(For example, Japanese Utility Model Laid-Open No. 56-136904)
reference).

[0003]

SUMMARY OF THE INVENTION The conventional rectangular multi-tube once- through boiler , for example, the Japanese Utility Model Application Laid-Open No. 56-136904.
Heat exchange in a boiler as disclosed in the gazette
To be done only by a pair of water tube panels defining a subsequent combustion chamber furnace to the first and second gas passages, the heat transfer surface area is in the <br/> small castings. Further, in this water pipe panel, since the water pipes are arranged in close contact with each other, a fan-shaped area, a so-called dead water area, is formed between the water pipes that come into contact with each other.
Gas flow rate is lower in water area than between water pipe panels
And, Therefore low heat transfer rate to the water tubes, effective area of the actual heat transfer is a more small castings, there is a problem in improving the thermal efficiency.

[0004] In addition to the first gas passage connected to the combustion chamber as described above, the second gas flowing in reverse from the first gas passage is also provided.
Since it is necessary to provide a gas passage, the can body can be downsized , especially
It is difficult to reduce the size in the width direction, which also hinders the improvement of the thermal efficiency of the can itself .

Further, due to recent environmental pollution problems, further reduction of harmful combustion exhaust gas from the boiler, particularly NO _x , CO, etc., has been demanded. No measures have been taken. That is, in this rectangular multi-tube once-through boiler, a combustion chamber and a first gas passage connected to the combustion chamber are provided on the front surface of the burner, and a wide space exists on the front surface of the burner as a whole.
The fuel (including the premixed gas) injected from the burner burns at a high temperature as it is. Therefore, when the combustion Sir
Mar NO _x (thermal NO _x) is generated, also, CO ₂
However, there is a problem that CO is generated by thermal dissociation.

[0006] Generally, the combustion gas flow from the burner is
Since the temperature decreases toward the downstream side due to heat transfer to the water pipe and the volume decreases accordingly, in a boiler having a structure in which the water pipe walls are simply arranged in parallel as described above, the flow velocity of the combustion gas on the downstream side is reduced. And the heat transfer efficiency is significantly reduced.

[0007]

The present invention has been made to solve these problems. A plurality of vertical water pipes 1a are arranged in two rows, and adjacent vertical water pipes 1a in each row are connected to each other. Are connected by a fin-shaped member 6 to form a pair of water pipe walls 1, 1, and upper and lower ends of each of the vertical water pipes 1a, 1a,.
11 and a burner 5 is provided at one end in the longitudinal direction of the pair of water pipe walls 1 and 1, and an exhaust gas outlet 8 is provided at the other end, and the pair of water pipe walls 1 and 1 and the header are provided. 10 and 11 form a gas passage 9 through which the combustion gas from the burner 5 passes substantially linearly. In the gas passage 9, at intervals allowing the flow of the combustion gas,
A large number of vertical water pipes 2a, 3a, 4a are inserted and inserted substantially over the entire area of the gas passage 9, and the upper and lower ends of the large number of vertical water pipes a, 3a, 4a are connected to the upper and lower headers 10, 11, respectively.
And a number of vertical water pipes 2a, 3a, 4a inserted into the gas passage 9 constitute two or more water pipe groups 2, 3, 4 having different heat transfer surface densities. 3,
4 are characterized in that the heat transfer surface densities are arranged in ascending order from low to high in the gas passage 9 from the upstream side to the downstream side in the flow direction of the combustion gas.

[0008]

According to the square multi-tube once-through boiler according to the present invention, a pair of water pipe walls is provided, in which the vertical water pipes are connected by fin-shaped members, and the combustion gas defined by the pair of vertical water pipes is provided. Since a large number of water pipes are inserted in almost the entire area of the gas passage, the combustion gas directly contacts the vertical water pipes and effective heat transfer is performed by convection heat transfer, realizing a small installation space. be able to. Also, in this invention, by inserting a number of vertical water pipes over almost the entire area of a gas passage defined by a pair of water pipe walls connecting the vertical water pipes with fin-shaped members, in the vicinity of the burner, There will be many vertical water pipes including the vertical water pipe on the water pipe wall,
Even when high-load combustion is performed, the convective heat transfer between the vertical water pipes constituting the water pipe wall and the vertical water pipes in the gas passage (heat transfer due to the combustion gas flowing between these vertical water pipes) causes Since the temperature is kept low and the residence time in the high-temperature atmosphere is also shortened, the generation of NOx can be reduced.

[0009] Further, a group of water pipes inserted in the gas passage is provided with a combustion gas.
From the scan of the flow direction upstream side toward the downstream side, by being arranged in the order of large That Is from those made small heating surface density, the heat transfer from the combustion gases to equalize the upstream side to the downstream side.

[0010]

1 and 2 show one embodiment of a rectangular multi-tube once-through boiler according to the present invention. In the drawing, a water pipe wall 1 is formed by forming a substantially straight vertical water pipe 1a at regular intervals.
The vertical water pipes 1a are arranged in rows, and the adjacent vertical water pipes 1a are connected to each other by fin-shaped members 6, thereby closing the vertical water pipes 1a. Two water pipe walls 1 having such a configuration face each other and are arranged so that they are substantially parallel to each other. Thus, the water pipe walls 1 and 1 define the outer shell of the boiler can and also have a function as a heat transfer surface.

The upper and lower ends of each vertical water pipe 1a forming the pair of water pipe walls 1 , 1 are connected to upper and lower headers 10 , 11 , respectively. The upper and lower headers 10 and 11 in this embodiment are independent of each other with respect to the longitudinal direction of the can body. The upper and lower headers are connected to each other by external piping or the like. , Integrated.

A burner 5 such as a premix burner is provided at one longitudinal end of the pair of water pipe walls 1 and 1 , and an exhaust gas outlet 8 is provided at the other end.
Gas passage combustion gases substantially linearly passing from the burner 5 by 1,1 and the upper and lower headers 10 and 11
9 are formed.

In the gas passage 9 , the burner 5
A number of vertical water pipes 2a, 3a, 4a are inserted at intervals allowing the flow of the combustion gas . In this case, the interval between the vertical water pipes is preferably set to be as small as possible in order to improve the contact heat transfer efficiency between the combustion gas and the vertical water pipes. However, if the interval is extremely narrow, each of the vertical water pipes 2a, 3a, 4a is set.
The surrounding gas flow velocity becomes too fast and the pressure loss increases. Conversely, if the gas flow velocity is extremely wide, the gas flow velocity decreases and the contact heat transfer efficiency decreases .
3a, the number of 4a is reduced, in particular to reduce the heat transfer area
Therefore, the amount of heat transfer itself also decreases . For this reason,
The intervals between the vertical water pipes 2a, 3a, 4a are, for example, as shown in FIG.
As shown in FIG. 1, the diameter is preferably equal to or less than the diameter of the vertical water pipes 2a, 3a, 4a .

The plurality of vertical water pipes 2a, 3a,
4a is are then inserted over substantially the entire region of the gas passage 9 to hold the spacing. As a result, vertical water tubes 2a to the vicinity of the burner 5, 3a, 4a is to be inserted, the interval is extremely small with vertical water tube which faces the burner 5 and the burner 5.

The vertical water pipe 2 inserted into the gas passage 9
a, 3a, 4a , the vertical water pipes adjacent to the pair of water pipe walls 1 , 1 are arranged in a staggered arrangement with the vertical water pipes 1a, 1a constituting the water pipe walls 1 , 1 as shown in FIG. It is inserted so that it becomes. With such arrangement, the
A pair of water pipe walls 1, 1 and both headers 10, 11,
Water pipe assembly 20 composed of straight water pipes 2a, 3a, 4a
It is possible to reduce the horizontal width (the width of the right and left shown in FIG. 1) of, reduce the width of each vertical water tubes cross, more vertical water tubes can be inserted.

As described above, almost all areas of the gas passage 9 are covered.
The upper and lower ends of the vertically inserted vertical water pipes 2a, 3a, 4a are connected to the upper and lower headers 10 , 11 similarly to the vertical water pipes 1a, 1a constituting the water pipe walls 1 , 1 , respectively.

According to the can 20 constructed as described above,
The flow path of the combustion gas , that is, the gas passage 9 can be set to be relatively long linearly, and the time required for the combustion gas from the burner 5 to pass through the last vertical water pipe 4a can be set to be relatively long. That is, the combustion gas in the water pipe assembly 20 is
The residence time of the gas becomes relatively long, and the combustion gas flows through the vertical water pipes 1a, 2a in this gas passage 9 as described above.
The temperature is gradually reduced by conducting heat transfer with the a, 3a and 4a .

Accordingly, in the once-through boiler according to the present invention, there is no locally high temperature portion in the entire gas passage 9 and NO _x, particularly thermal NO _x, is more effectively suppressed.
can do. In addition, the combustion gas
For suppressing the temperature low, the generated CO ₂ is thermal dissociation
Never generate again CO by.

The water pipe walls 1 and 1 are formed by arranging substantially straight vertical water pipes 1a in a row at equal intervals and closing the interval between adjacent vertical water pipes 1a with a fin-shaped member 6. From
Unlike the conventional boiler, there is almost no region where the gas flow rate decreases and the heat transfer coefficient decreases, so that the entire surface of the vertical water pipe 1a facing the gas passage 9 can contribute to heat transfer. Also, the thermal efficiency is improved.

Here, a specific example in which a premix burner is used as the burner 5 in the boiler having the above configuration will be described. If this were the premixed burner to burn by supplying premixture of air ratio 1.3, NO _x is reduced by 1/3 to about 1/2 as compared with the conventional, also CO is ten ppm
The result of reducing to below was obtained. This N
The O _x and CO values are equivalent to those of a boiler equipped with an exhaust gas recirculation system with a circulation rate of 10%. However, the boiler of the present invention circulates the combustion gas in one direction without any circulation. In addition, there is an effect of reducing such harmful exhaust, and a complicated piping for exhaust gas circulation is not required, so that the structure becomes extremely simple.

Further explanation in the illustrated embodiment :
Each of the vertical water pipes 2a, 3a, 4a is provided between the water pipe walls 1, 1.
Along the longitudinal direction, in two rows state, the Yes from the burner 5 side are arranged at regular intervals by a predetermined number toward the exhaust gas outlet 8 side, vertical water tubes of each of the upstream side, the straight pipe
2a, finned water pipe 3a, and erofin pipe 4a .

The vertical water pipes 2a, 3a,
4a is a heat transfer surface density (per unit flow path length of combustion gas)
The first to third water pipe groups 2, 3, and 4 have different heat transfer surface areas) , and the first to third water pipe groups 2, 3, and 4 are arranged in the gas passage 9 from the burner 5 side to the exhaust gas outlet 8 side. , The heat transfer surface densities are arranged in ascending order.

[0023] With this configuration, combustion from the burner 5
Gas, the gas passages 9 between the water tube walls 1,1, formed of the first water tube group 2, the second water tube group 3 consisting of fins with vertical water tubes 3a and Erofin tube 4a, consisting of a straight tubular vertical water tubes 2a the It passes while performing heat transfer to the three water pipe group 4 , and flows out of the exhaust gas outlet 8 via an economizer (not shown) or directly from a chimney (not shown).

Here, as described above, the combustion gas has a high temperature and a large volume on the upstream side, but has a low temperature on the downstream side due to heat transfer to the vertical water pipe, and the volume is reduced , and the heat transfer efficiency is also reduced . However, Oite this invention, because that is increasing the heat transfer surface density toward the downstream side, each vertical water tubes 2a, 3
a, the amount of heat transfer in 4a is not be lowered over a vertical water pipe 4a downstream from the upstream side of the vertical water tubes 2a, generally becomes substantially uniform, the temperature of the combustion gases will be gradually reduced.

In this regard, specific experimental results will be described.
Then, the combustion surface load is 600 ~ 1,200 × 10 ⁴ kcal / m ²・ h
When the temperature distribution in the gas passage 9 is measured using the burner of No. 1, the temperature is about 1,200 ° C. at the point A in FIG.
A result of about 370 ° C. was obtained at the point C and C.

[0026] Thus, also in the water tube group 2 comprised a small heat transfer surface density of the upstream side, suppressed to the temperature of the combustion gas is low
Are therefore, NO _x in particular the generation of thermal NO _x is even more
It will be effectively suppressed. Further, in the water tube groups 3 and 4 having a large heat transfer surface density on the downstream side, the temperature of the combustion gas is reduced.
Because There gradually decreased, CO ₂ was oxidized to thermal dissociation
CO is not generated again, and the generation of CO is more effectively suppressed.

Next, FIG. 3 shows another embodiment of the present invention. In the embodiment of the figure, the water tubes walls 1
Is about the middle of the boiler body and narrow on the downstream side. Then, a water tube group 2 in which straight tubular vertical water tubes 2a are arranged in series between the water tube walls 1 and 1 is located.
On the downstream side of the water pipe walls 1, 1 , for example, heat insulating walls 7 are arranged on both sides as in this embodiment, and a water pipe group 4 composed of two rows of erofin pipes 4a is provided between the heat insulating walls 7, 7. Place.

In this once-through boiler as well, as in the previous embodiment (FIGS. 1 and 2), the heat transfer area per unit flow path length is increased from upstream to downstream in the flow direction of the combustion gas. and, therefore, the above-described embodiments similarly improves the heat transfer efficiency, as well as, NO _x, so that can be reduced harmful emissions such as CO.

[0029]

As has been described above devised], square-tube once-through boiler according to this invention, since a configuration in which inserted a number of vertical water tubes I Wataru substantially the entire inside gas passage, the combustion gas because by in direct contact with the water tubes to perform heat transfer by convection heat transfer, along with suppressing the combustion gas temperature, thereby passing while gradually relatively uniformly lowered the <br/> temperature, NO The generation of harmful combustion exhaust such as _x , CO, etc. can be suppressed, and it is extremely effective as a pollution control measure relating to harmful combustion exhaust, which is the most important subject in recent years.

Further , according to the present invention, a pair of water pipe walls is provided.
And the upper and lower headers effectively reduce the combustion gas from the burner.
Is the gas passage formed to pass straight up
Like conventional square multi-can once-through boilers,
There is no need to form gas passages outside the water pipe panel,
Very simple and easy to reduce the width of the tube assembly
be able to.

In the present invention, the water pipe wall has a plurality of walls.
The vertical water pipes are aligned in two rows, and the adjacent
Vertical water pipes connected by fin-shaped members
However, as in the conventional boiler, the gas flow rate is
An area where the heat transfer coefficient decreases, that is, a dead water area is not formed,
The entire surface of the vertical water pipe facing the water passage can contribute to heat transfer.
And the heat transfer area can be effectively secured.
In addition, while the combustion gas is allowed to flow in the gas passage,
At intervals and over substantially the entire area of the gas passage.
Since the number of vertical water pipes is inserted, the heat transfer area
As a result, when compared with the same capacity
Of the installation space can be reduced.
Reduction can be made possible. Therefore, the same
Because many boilers can be installed in the base,
In recent years, a multi-can installation system has been awarded for efficiency.
Can provide a very effective boiler for
You.

Further, two or more water pipe groups having different heat transfer surface densities are provided in the gas passage from the upstream side to the downstream side in the flow direction of the combustion gas in the gas passage . by disposing the order of those large consisting made small density, fuel
The heat transfer from the burning gas can be equalized from the upstream side to the downstream side, so that a local decrease in heat transfer efficiency can be prevented, and stable heat transfer can be performed. For this reason,
Increased efficiency of the boiler itself Hakare, the running costs can also be a Do Ri, extremely effective der As this type of boiler
You.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a schematic cross section of an embodiment of a square multi-tube once-through boiler according to the present invention.

FIG. 2 is an explanatory front view of FIG. 1;

FIG. 3 is an explanatory view showing a schematic cross section showing another embodiment.

[Description of Signs] 2 First water pipe group 2a water pipe (straight pipe) 3 Second water pipe group 3a water pipe (water pipe with fins) 4 Third water pipe group 4a water pipe (erophine pipe) 9 gas passage

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F22B 21/04

Claims (1)

(57) [Scope of request for utility model registration] 1. A plurality of vertical water pipes 1a are arranged in two rows.
And the adjacent vertical water pipes 1a in each row are
And a pair of water tube walls 1, 1 formed by connecting
Each vertical water pipe 1a, 1a, which constitutes a pair of water pipe walls 1, 1
… Connect upper and lower ends to upper and lower headers 10 and 11 respectively
A bar is provided at one end of the pair of water pipe walls 1, 1 in the longitudinal direction.
And an exhaust gas outlet 8 at the other end,
By the pair of water pipe walls 1, 1 and the headers 10, 11,
The combustion gas from the burner 5 passes substantially linearly.
The gas passage 9 is formed, and the combustion gas is
Gas passage 9 at an interval allowing the flow of gas
A large number of vertical water pipes 2a, 3a, 4a
The vertical water pipes a, 3a, 4a
Connect the ends to the upper and lower headers 10 and 11, respectively,
A large number of vertical water pipes 2a, 3a,
4a denotes two or more water tube groups 2, 3, and 4 having different heat transfer surface densities.
And these water pipe groups 2, 3, and 4
Characterized in that the heat transfer surface densities are arranged in ascending order from high to low , from upstream to downstream in the flow direction of the combustion gas.