JP2003161429A - Structure of secondary combustion chamber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structure of a secondary combustion chamber having the function of efficiently and immediately quenching high temperature exhaust gas after reburning and decomposing dioxin and the like by water spray. <P>SOLUTION: This structure of the secondary combustion chamber 10 cools gas by the water spray in an upper part in the secondary combustion chamber 10 of the exhaust gas generated in a furnace. A diametrally contracted part 16 squeezed more than an inner diameter of the combustion chamber is arranged on the way from a tail end part 13a of a secondary combustion part (a combustion zone 13) to a cooling zone 14 with the water spray. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a secondary combustion chamber for secondary combustion of exhaust gas generated in a refuse incinerator, an ash melting furnace, etc., and more specifically, by recombusting dioxins. The present invention relates to the structure of a secondary combustion chamber that is capable of efficiently cooling high-temperature exhaust gas after decomposition by water injection.

[0002]

2. Description of the Related Art Conventionally, for example, in a surface melting furnace (ash melting furnace) for treating incinerated ash in a waste treatment facility, in order to reduce the content of heavy metals in slag and the generation of NO _{X in} exhaust gas, , Reduction operation is carried out. In this case,
It is necessary to completely combust the reducing exhaust gas at a temperature of 850 ° C. or higher in order to decompose dioxins in the secondary combustion chamber of the melting furnace.

From the above, as shown in FIG. 4, in the surface melting furnace 100, the exhaust gas generated when the fly ash (incineration ash) is melted in the surface melting furnace 100 to be slag-processed is melted by the surface melting. It is guided from the furnace 100 through the high temperature flue 101 to the melting furnace secondary combustion chamber 102, and is secondarily burned in the melting furnace secondary combustion chamber 102 at a temperature of 850 ° C. or higher to decompose dioxins, and this exhaust gas In order to heat the combustion air of the melting furnace burner 103 using the thermal energy of the jacket 106, the jacket 106 is passed through the melting furnace air preheater 105.
The heat is exchanged with the combustion air sent inside. In the figure, reference numeral 108 is an exhaust gas outlet of the melting furnace air preheater,
109 is a blower for combustion air, 110 is a forced blower for supplying combustion air to the melting furnace burner, 112 is a slag conveyor, and a is a slag.

However, at the exhaust gas inlet 105a of the air preheater 105, the exhaust gas temperature is set to 65 so that the inner peripheral surface temperature of the inner cylinder is equal to or lower than the maximum operating temperature of the material forming the inner cylinder.
It is necessary to lower the temperature to around 0 ° C. Therefore, at present, cooling water spraying means 107 or cooling air blowing means 107a is provided in the upper part of the secondary combustion chamber 102 of the melting furnace to blow cooling water or cooling air to lower the exhaust gas temperature.

[0005]

However, when the cooling water is injected in the secondary combustion chamber 102 of the melting furnace, the temperature of the secondary combustion zone A is lowered by the radiative cooling (radiation) accompanying it, so that the temperature is 850 ° C. or higher. The temperature cannot be secured. Therefore, in order to secure the temperature of the secondary combustion zone A of 850 ° C. or higher, the end portion A ′ of the secondary combustion zone A needs to be separated from the water spray position by 3 m or more. From such a thing,
The height dimension of the secondary combustion chamber 102 of the melting furnace becomes high, which causes a problem that the installation space and the construction cost increase.

Further, conventionally, the secondary combustion chamber 102 of the melting furnace is used.
In the cooling water spraying means 107 in the inner upper part, a single nozzle often sprays the gas flow in parallel with the gas flow, and the high-temperature gas comes into direct contact with the spray nozzle. However, there was a problem that maintenance costs a lot.

The present invention solves such a problem and
It is an object of the present invention to provide a structure of a secondary combustion chamber having a function of rapidly and rapidly quenching high temperature exhaust gas after recombusting and decomposing dioxins by water spray.

[0008]

In order to achieve the above object, the structure of the secondary combustion chamber according to the present invention is such that the exhaust gas generated in the furnace is gas-cooled by water spray in the upper part of the secondary combustion chamber. In the structure of the secondary combustion chamber for performing the above, a reduced diameter portion narrower than the inner diameter of the combustion chamber is provided between the end portion of the secondary combustion portion and the cooling zone by water spray. (First invention).

According to the present invention, by forming a reduced diameter portion narrower than the inner diameter of the secondary combustion chamber between the combustion zone of the secondary combustion chamber and the cooling zone by water spray provided in the upper portion thereof. Since the face-to-face ratio between the cooling zone and the combustion zone can be reduced to reduce the influence of radiation between the two, the position where the cooling means is provided can be brought close to the end portion of the secondary combustion section. In other words, the cooling water spray position can be lowered and the combustion temperature in the combustion section of the secondary combustion chamber must be maintained under conditions that allow the decomposition of dioxins to be secured. There is an effect that the size can be reduced. In addition, even if the exhaust gas burned in the combustion zone passes through the reduced diameter part in the process of moving to the cooling zone to increase the flow velocity and increase the amount of cooling water sprayed by the water spray in the cooling zone, it also affects the combustion zone side. Since it is configured so as not to provide the above, it is possible to rapidly cool the high temperature gas and reduce the influence on the preheater.

In the first invention, the cooling zone includes:
It is preferable that a plurality of water spray nozzles are provided at a plurality of positions so as to cross the gas flow and spray at an upper portion of the reduced diameter portion (second invention). In this case, the spray nozzle is installed in a region where the influence of radiation generated by providing the reduced diameter portion is small, and thus the nozzle tip can be prevented from being damaged by radiation. The water spray nozzle preferably has a fan-shaped spray pattern (third invention). If such a water spray nozzle is adopted, it is possible to spray at a wide angle, so that the spray layer can be effectively formed from the position near the peripheral wall part toward the center part at the upper part of the reduced diameter part, and the contact effect with the exhaust gas flow can be obtained. The effect is that it can be raised and rapidly cooled.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, specific embodiments of the structure of the secondary combustion chamber according to the present invention will be described with reference to the drawings.

FIG. 1 shows a schematic view (a) of the structure of a secondary combustion chamber according to the present invention, and a sectional view (b) taken along line AA.

The structure of the secondary combustion chamber of this embodiment will be described with respect to the secondary combustion chamber in the ash melting furnace. The secondary combustion chamber 10 is provided with an exhaust gas inlet 11 for receiving exhaust gas from a high temperature flue connected to an ash melting furnace (not shown) in the lower part, and the exhaust gas fed from the exhaust gas inlet 11 and the air supply pipe 12 from the outside are supplied. Combustion zone 1 of required diameter for mixing and burning with secondary combustion air
3 (simply referred to as a combustion zone 13) and a gas cooling zone 14 (simply referred to as a cooling zone 14) located thereabove. The cooling zone 14 is provided with an outlet 15 for cooled exhaust gas.

Combustion zone 1 in the secondary combustion chamber 10
3 is provided between the cooling zone 14 and the cooling zone 14, so that the influence of the radiation between the cooling zone 14 and the combustion zone 13 on the combustion portion (radiative cooling) can be avoided. . The reduced diameter portion 16 is provided above the terminal end portion 13a of the combustion zone 13, and the face-to-face ratio between the cooling zone 14 and the combustion zone 13 is such that the gas temperature due to radiation at the combustion zone terminal end portion 13a is the temperature at which dioxin decomposition occurs. It is set so that the conditions can be secured.

As the water spraying means 17 in the cooling zone 14, a plurality of water spraying means 17 are provided above the reduced diameter portion 16 (for example, as shown in FIG. 1 (b), the inner circumference is divided into three equal parts). Water spray nozzles 18 are arranged to supply cooling water from the outside to spray the cooling water in a direction intersecting with exhaust gas flowing upward in the cooling zone 14 of the secondary combustion chamber 10. There is. These water spray nozzles 18 adopt a fan-shaped spray to widen the diffusion range of the cooling water to be sprayed, and spray from a plurality of locations toward the center of the combustion chamber to improve the contact efficiency between the exhaust gas and the cooling water. It is designed to be raised. In addition, the end portion 13 of the combustion zone 13
The flow rate of the exhaust gas flowing from a to the cooling zone 14 is increased by the reduced diameter portion 16 provided therebetween. Therefore, if the flow velocity of the exhaust gas flowing into the cooling zone 14 increases, the cooling water sprayed by the water spraying means 17 rises along with the airflow while exchanging heat, and falls from the reduced diameter portion 16 to the combustion zone 13 side. Of course, no drop of water will occur and the combustion temperature will not be lowered.

Further, the water spraying means 17 in the cooling zone 14 is arranged so that the spraying nozzle 18 is arranged above the reduced diameter portion 16, so that the water spraying means 17 is in direct contact with the exhaust gas flow flowing in the secondary combustion chamber 10. No spray nozzle 18
Thus, the degree of corrosion of the supporting part and the supporting part by the exhaust gas is remarkably reduced as compared with the conventional case, the cooling operation is not affected, and the frequency of maintenance can be reduced accordingly.

In the water spraying means 17 provided in the cooling zone 14, the spraying nozzle 18 is of a type capable of performing fan-shaped spraying so that a sprayed water layer can be formed and maintained on the entire plane section of the secondary combustion chamber. As described above, it is effective to cool the exhaust gas by adopting the structure of spraying from a plurality of locations in the direction intersecting with the flow of the exhaust gas.

Further, the combustion zone 13 and the cooling zone 1
In order to avoid the influence of radiation associated with the formation of the water spray layer in the cooling zone 14, the reduced-diameter portion 16 provided between the combustion zone 13 and the cooling zone 14 is fed into the secondary combustion chamber 10. As a requirement suitable for maintaining a combustion temperature of 850 ° C. or higher, which is a requirement for decomposing dioxins present in exhaust gas to be exhausted, and reducing the formation range of the cooling zone 14 in the axial direction of the combustion chamber, In order to keep the height dimension low, it is preferable that the diameter d of the reduced diameter portion 16 is approximately 1 / 2D with respect to the inner diameter D of the secondary combustion chamber 10.

Therefore, the cooling zone 14 and the combustion zone 13
Radiation cooling due to radiation with the end portion 13a of the cooling zone 14 is prevented, and the cooling water spray position in the cooling zone 14 is shifted to a low position without lowering the combustion temperature in the end portion 13a of the combustion zone 13. An example for providing the portion 16 is as follows.

FIG. 2 is a diagram showing a procedure for setting the reduced diameter portion under the condition that the combustion zone and the cooling water spray position in the cooling zone are fixed.

Explaining with reference to this figure, several conditions are set, and the combustion position a is the end b of the combustion zone, the end b of the combustion zone is a reduced diameter portion c, and the reduced diameter portion c is sprayed with cooling water. The respective distances to the nozzle position d were specified, the temperature conditions at the positions a and d were specified, and each part was subjected to trial calculation. The calculation was based on the following radiative heat transfer equation. Incidentally, amount of radiant heat between each _{location, Q ab = Q bc = Q} cd (1) Q 12 = A 1 F 12 (E 1 -E 2) = A 2 F 21 (E 1 -E 2) ( _{2) E 1 = 4.88 (T} 1/100) 4, E 2 = 4.88 (T 2/100) 4 (3)

[Equation 1] However, the symbols are: A: Area D: Diameter of combustion chamber E: Total radiation of black body E = 4.88 (T / 100) ⁴ F: Form factor L: Distance between two surfaces T: Absolute temperature of black body surface Q The amount of radiant heat transfer Note that the form factor F is set to a value corresponding to D / L from the curve representing the form factor of the opposing two parallel planes. The subscripts 1 and 2 refer to the 1st and 2nd surfaces, respectively.

The combustion position a is calculated by the above formula for calculating the amount of radiant heat transfer.
From the end of the combustion zone 13 to the position b of the combustion zone 13 is set to 1000 mm, from the position b to the position c of the reduced diameter portion 16 is set to 400 mm, and from the position c to the position d of the cooling water spray nozzle is set to 750 mm. As shown in FIG. 3, the gas temperature was determined at. The models obtained by this calculation are shown in (a) to (d). In the model of (b), the temperature at the position c is 8 when the reduced diameter portion is not provided.
The temperature becomes 04 ° C, and the required value (850 ° C or higher) cannot be satisfied. In the model (c), the diameter φd of the reduced diameter portion 16 is 1 / 1.5D with respect to the diameter D of the combustion chamber, and in this case, the gas temperature at the position c is 839 ° C. Therefore, the required value cannot be met yet.

Next, in the model (d), the diameter φd of the reduced diameter portion 16 is set to 1 / 3D, and the gas temperature at the position c in this case is 880 ° C., which satisfies the required value. become. However, under this condition, since the diameter of the reduced diameter portion 16 is considerably reduced, a great resistance is caused to the flow of the exhaust gas in that portion, and the cooling rate in the cooling zone may decrease.

Therefore, in the model (a), the reduced diameter portion 16
The caliber φd of was set to 1/2 of the diameter D of the combustion chamber. According to this model, the gas temperature at the position c is 8 in the above calculation.
The temperature is 60 ° C., which satisfies the required value (850 ° C. or higher). Judging from such calculation results, the diameter of reduced diameter φ
It is understood that it is preferable to set d to 1/2 or more of the diameter φD of the combustion chamber.

By the way, in the model (b) described above, assuming that the temperature of the combustion portion of the combustion zone is 900 ° C., the position d (water spray position 650
It was found that the distance between b and c was 2400 mm, which was not practically preferable.

From the above, the position b of the reduced diameter portion 16
It is possible to arbitrarily change the size from the above to the installation position a of the water injection nozzle 18 from the value of the above calculation standard, but if the excess distance is increased, the height dimension of the secondary combustion chamber becomes high and the building is installed at the time of installation. Must be high,
The cost will increase. Also, if the dimensions of the positions c to d are to be shortened, the diameter of the reduced diameter portion must be reduced, so that the cooling efficiency is reduced. Therefore, it can be understood that the values around the numerical value obtained by the model are practical and preferable.

In the above description, the secondary combustion chamber in the ash melting furnace has been described, but the present invention is not limited to this, and can be applied to the secondary combustion chambers in other furnaces.

[Brief description of drawings]

FIG. 1 is a schematic view (a) of a structure of a secondary combustion chamber according to the present invention and a cross-sectional view (b) taken along line AA.

FIG. 2 is a diagram showing a setting procedure of a reduced diameter portion under a condition in which a combustion zone and a cooling water spray position in a cooling zone are fixed.

FIG. 3 is a diagram showing models for setting a reduced diameter portion by setting conditions of a combustion zone, a cooling zone, and a cooling water spray position.

FIG. 4 is a schematic diagram showing a conventional surface melting furnace.

[Explanation of symbols]

10 Secondary combustion chamber 11 Exhaust gas inlet 13 Burning zone 13a End of combustion zone 14 cooling zones 15 Exhaust gas outlet 16 Reduced diameter part 17 Water spray means 18 spray nozzle

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yoshito Fukuma             2-32 Kinrakuji-cho, Amagasaki City, Hyogo Prefecture Stock             In ceremony company Takuma F-term (reference) 3K070 DA09 DA37                 3K078 AA05 BA03 CA02

Claims (3)

[Claims] 1. A structure of a secondary combustion chamber in which gas is cooled by water spray in an upper part of the secondary combustion chamber of exhaust gas generated in a furnace, and from a terminal portion of the secondary combustion unit to a cooling zone by water spray. The structure of the secondary combustion chamber is characterized in that a reduced diameter portion that is narrower than the inner diameter of the combustion chamber is provided. 2. The secondary combustion according to claim 1, wherein in the cooling zone, a plurality of water spray nozzles are arranged at a plurality of positions so as to cross the gas flow and spray at an upper portion of the reduced diameter portion. The structure of the chamber. 3. The structure of the secondary combustion chamber according to claim 2, wherein the water spray nozzle has a fan-shaped spray pattern.