JP3384975B2 - Water tube boiler - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water pipe boiler of a type in which combustion gas is circulated linearly in a direction crossing a water pipe. 2. Description of the Related Art Generally, small multi-tube, once-through boilers are
It is manufactured based on a cylindrical can body structure. This is because it is considered that it is desirable to arrange the water pipe in an annular shape and make the inside thereof a combustion chamber in order to improve the heat exchange efficiency with the combustion gas. [0003] However, such a can structure tends to occupy a relatively large space depending on the location and arrangement of the boiler. In recent years, various types of so-called square can structures have been used as bases. Has been proposed. In addition, the square can body structure here is,
A structure in which a plurality of water pipes are arranged in series and water pipe rows are opposed to each other, and a combustion chamber is formed between them.Combustion gas from a burner passes in the cross direction between the water pipe rows. ing. In recent years, due to environmental pollution and the like,
Hazardous combustion exhaust from the boiler, in particular NO _X, further reduction such as CO are required. As a countermeasure for reducing such harmful combustion exhaust, by lowering the combustion gas temperature, NO _x , especially thermal NO _x (thermal N _x) can be reduced.
By keeping the suppressing method and the combustion gas temperature the formation of O _X) in a certain temperature range, a method by oxidizing the CO to CO ₂ to prevent the residual CO is known. More specifically, as shown in Japanese Utility Model Publication No. Sho 56-47477, a burner flame is applied to a water-cooled wall or the like,
As disclosed in Japanese Patent Application Laid-Open No. 6046-78247, an excessively rich mixture is burned at the center of a swirling air flow to adjust the combustion temperature. There is a method in which, after the temperature of a combustion gas is adjusted by a cold body near a burner, CO is oxidized in an adiabatic space between the heat exchanger and the like. In addition, thermal NO
_{As a} measure for reducing _X , a type in which exhaust gas is recirculated is known. DISCLOSURE OF THE INVENTION [0005] The present invention reduces the amount of harmful combustion exhaust emissions, that is, suppresses the generation of NOx to reduce its emissions, thereby reducing the amount of CO emissions.
It is an object to provide a water tube boiler in which a can body is miniaturized. SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is formed between a pair of water pipe walls which are opposed to each other at an interval. A combustion gas passage having a combustion chamber between a pair of water pipe walls, and a number of water pipes provided with an interval through which the combustion gas flows in the combustion gas passage. Water pipe group, and the combustion gas from the burner flows in the cross direction with respect to the water pipe group, and the heat transfer surface density of the water pipe group on the upstream side of the combustion gas is cooled by the water pipe group on the upstream side. the is characterized in that the heat transfer surface density of Ru is oxidized CO generated in the upstream side of the combustion gas passage is prevented from occurring thermal NOx by suppressing the combustion gas temperature. According to this means , the combustion gas from the burner is immediately cooled by the water pipe group on the upstream side, and its temperature becomes NO.
x below the temperature at which the generation of x is prevented, the amount of generated NOx is greatly reduced, and the temperature of the combustion gas in the water pipe group on the upstream side is set to the temperature at which CO is oxidized.
O is oxidized, CO emissions are reduced, and harmful combustion exhaust emissions are significantly reduced. FIG. 1 and FIG. 2 show an embodiment of a square multi-tube once-through boiler as a water tube boiler according to the present invention, showing the arrangement of water tubes in a can body. .
In these drawings, 1 is a water pipe wall, 2, 3, and 4 are water pipe groups arranged in two rows between the water pipe walls 1 and 1, and 5 is a burner. The water pipe wall 1 has a substantially straight water pipe 1a.
Are arranged in a line at equal intervals, and each water pipe 1a
The water tubes 1a are connected to each other by the fin-shaped members 6.
In the embodiment shown in the drawing, the distance between the water pipe walls 1 and 1 is substantially parallel to each other on both sides of the can body. It is a combustion gas passage through which the combustion gas flows. The water pipe groups 2, 3 and 4 are arranged in two rows in a predetermined number at substantially equal intervals, and the water pipes 2a, 3a and 4a constituting each of them are respectively a straight pipe and a finned water pipe. , Erofin tube. As the burner 5, for example, a premix burner such as a surface combustion burner can be used. Such a burner is disposed between the ends of the water pipe wall 1 of the water pipe group 2 (upper in the figure). Therefore, the combustion gas from the burner 5 flows from the upper side to the lower side in the figure between the water pipe walls 1 and 1, and in this connection, the water pipe groups 2, 3 and 4 move in the flow direction. Along the line, the heat transfer surface density (heat transfer surface area per unit flow path length of the combustion gas) is arranged from small to large. In FIG. 2, reference numerals 10 and 11 are used.
Indicates upper and lower headers connecting the upper and lower ends of the water tubes 1a, 2a, 3a, 4a, respectively. The upper and lower headers 10 and 11 are independent of each other on the left and right sides with respect to the longitudinal direction of the can body. These upper and lower headers are connected to each other by an external pipe or the like to be integrated. According to the rectangular multi-tube type once-through boiler described above, the combustion gas from the burner 5 divides the water pipes 1 between the water pipe walls 1 and 1 into a group of straight pipes 2 and a group of water pipes 3 with horizontal fins. And passing through the Erofin water pipe group 4 and through the economizer,
Or it flows out of the chimney directly. Although the combustion gas has a high temperature and a large volume on the upstream side as described above, it has a low temperature on the downstream side due to heat transfer to the water pipe, the volume is reduced, and the heat transfer efficiency is reduced. According to such a can body, since the heat transfer surface density is increased toward the downstream side, each water pipe 1a, 2a, 3a, 4
The heat transfer amount at a does not decrease even from the upstream water pipe 2a to the downstream water pipe 4a, and becomes substantially uniform as a whole. Further, by adopting a can body structure as shown in the figure, the combustion gas passage, that is, the flow path of the combustion gas can be set relatively long in a straight line, and the combustion gas from the burner 5 is disposed at the end of the water pipe group 4. The time required to pass through the water pipe 4a can be set relatively long. That is, in such a can body structure, the time for which the combustion gas stays in the boiler can can be made relatively long, and as described above, the combustion gas flows through each water pipe 1 in this flow path.
Heat is transferred to a, 2a, 3a, and 4a, and the temperature gradually decreases. As a result, when a burner having a combustion surface load of 600 to 1200 × 10 ⁴ Kcal / m ² h is used in a can having the above-described structure, about 1200 ° C. at point A and about 5 ° C. at point B in FIG.
A result of about 370 ° C. at 50 ° C. and point C was obtained. Therefore, in the can of the present invention,
Even in the water pipe group having a small heat transfer surface density on the upstream side, the combustion gas temperature is kept low, and in the water pipe group having the high density on the downstream side, the temperature gradually decreases, so that NO _x, especially thermal NO _Since the generation of _X can be prevented and the combustion gas temperature is about 1200 ° C. also on the upstream side, even if CO is generated, it is oxidized to CO ₂ on the upstream side, and the temperature gradually decreases on the downstream side. Therefore, it is also possible to prevent CO _{2 from} being separated again and becoming CO. In the present invention, when the burner 5 is supplied with premixed air having an air ratio of 1.3 and burned, NO
_X was reduced from about 1/3 to 1/2 of that of the conventional one, and CO was reduced to about 10 ppm or less. These NO _x and CO values are equivalent to those obtained when the circulation rate is set to 10% in a boiler equipped with an exhaust gas circulating device.
In such a form that the combustion gas is circulated only in the direction, the harmful combustion exhaust can be reduced, and a complicated pipe for circulating the exhaust gas is not required, so that the structure becomes extremely simple. FIG. 3 shows another embodiment of the rectangular multi-tube type once-through boiler according to the present invention. In the embodiment shown in the figure, each water pipe wall 1 has a length up to the middle of the boiler body and a narrow downstream side. And this water pipe wall 1,
Water tube group 2 in which straight tubular water tubes 2a are arranged in series between
Is located. On the downstream side of the water pipe group 2, for example, heat insulating walls 7 are arranged on both sides as in this embodiment, and between the heat insulating walls 7, a water pipe group 4 composed of two rows of erofin water pipes 4 a is arranged. Also in this once-through boiler, the heat transfer surface area per unit flow path length increases from upstream to downstream in the direction of flow of the combustion gas, as in the above-described embodiment (FIGS. 1 and 2). and which, therefore, such as described above, improvement of heat transfer efficiency due to the can body itself, NO _X, so that can be reduced harmful emissions such as CO. According to the present invention, the heat transfer surface density of the upstream water pipe group provided immediately before the burner in the combustion gas passage is reduced, and the combustion gas temperature is reduced by cooling by the upstream water pipe group. Since the heat transfer surface density is so controlled as to suppress the generation of thermal NOx and oxidize the CO generated on the upstream side of the combustion gas passage, the combustion gas from the burner is immediately cooled by the upstream water tube group. Te, the temperature is less than the temperature at which NOx generation can be prevented, the generation amount of NOx is significantly reduced, the combustion gas temperature at the upstream water tube group of CO occurs because you are the temperature to oxidize CO is oxidized, CO emissions are reduced, and harmful combustion exhaust emissions are significantly reduced. The combustion chamber is formed in a pair of water tube walls are, so that a substantially without achieves the tremendous effect like can provide a miniaturized boiler boiler.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross-sectional view showing one embodiment of a water pipe boiler according to the present invention. FIG. 2 is a front view of the boiler of FIG. 1 as viewed from a burner mounting opening. FIG. 3 is a schematic cross-sectional view showing another embodiment. [Description of Signs] 2 water pipe group 2a water pipe 3 water pipe group 3a water pipe 4 water pipe group 4a water pipe 5 burner

Continuation of the front page (72) Inventor Seiji Tai 7-7, Horie-cho, Matsuyama-shi, Ehime Miura Kogyo Co., Ltd. (56) References JP-A-60-205105 (JP, A) JP-A-62-84258 (JP, A) JP-A-60-78247 (JP, A) JP-A-61-135106 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F22B 21/04

Claims (1)

(57) [Claims 1] A burner is formed between a pair of water pipe walls disposed to face each other with a space therebetween, and a burner is provided at one end side thereof. A combustion chamber is formed between the pair of water pipe walls. A combustion gas passage, and a group of water pipes formed of a large number of water pipes provided with an interval through which the combustion gas flows in the combustion gas passage and provided immediately close to the burner, and the combustion gas from the burner is It is circulated in the cross direction with respect to the water pipe group, and the heat transfer surface density of the water pipe group on the upstream side of the combustion gas is suppressed by the cooling by the water pipe group on the upstream side, thereby suppressing the temperature of the combustion gas and preventing generation of thermal NOx. water tube boiler, characterized in that the heat transfer surface density of Ru is oxidized CO generated in the upstream side of the combustion gas passage while.