JP2005140383A - Recombustion furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure sufficient residence time by improving the mixture characteristics between exhaust gas and air, and to maintain temperature in a furnace at high temperatures, and measure the oxygen concentration in exhaust gas in the furnace without using forced outer force by a pump, or the like in a recombustion furnace for decomposing and removing bad odor constituents or dioxins in the exhaust gas. <P>SOLUTION: In the recombustion furnace for treating the exhaust gas in a main combustion furnace, the inside of the recombustion furnace is divided into first, second, and third combustion chambers by a first restrictor and a second one provided at the upper portion of the first one. An outer upward inclined hole is opened on a furnace wall surface closer to the exist of the third combustion chamber, and a horizontal outer hole is opened at the upper section of the opening. Both the holes are connected by a connecting pipe, an oxygen concentration sensor is provided at the connecting pipe, and an air supply section for mixing combustion auxiliary air to the exhaust gas, and a burner for burning the exhaust gas are provided at the first combustion chamber. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a reburning furnace that performs thermal decomposition treatment of exhaust gas discharged from a main furnace.

  A zirconia cell type densitometer is generally used as a method for measuring the oxygen concentration in the reburning furnace, but this densitometer can withstand high temperatures, but other parts are not heat resistant. In general, it is not possible to directly attach to the furnace body, and a sampling probe 35 is attached to the furnace body, and the oxygen concentration in the exhaust gas is measured by the sensor 25 installed in the middle of the path of the sampling probe 35. (Fig. 4).

  In this case, the exhaust gas is drawn into the sampling probe 35 by applying an external force from the pump 36 or the like to forcibly generate a pressure difference, but the exhaust gas is at a high temperature of 800 ° C. to 1000 ° C. Since various harmful substances are included above, special materials are required for the pump 36 and other parts, which increases not only the initial cost but also the running cost, and also requires power to drive the pump and the like. At the same time, the use of a pump or the like has a complicated mechanism, which involves a risk of occurrence of mechanical trouble.

  The exhaust gas discharged during the incineration of waste in the primary combustion chamber (main combustion furnace) contains substances such as odor components and dioxins. In a secondary combustion chamber (reburning furnace), it is directly burned to decompose and remove odor components and dioxins.

  By the way, as conditions required for a reburning furnace for the purpose of decomposing and removing the above-mentioned odor components and dioxins, the inside of the furnace is maintained at a temperature of 850 ° C. or more and the exhaust gas stays in the furnace for 2 seconds or more. It is mentioned that.

  In a small furnace such as a cremation furnace, the amount of exhaust gas discharged is relatively small, and it is not constantly discharged. Therefore, in order to realize the above conditions, the exhaust gas and burner flame and combustion 2 It is further required that the mixing characteristics of the secondary air be good. Therefore, in the conventional reburning furnace, mixing characteristics are improved by installing a checker or the like in the furnace to increase the pressure loss of the exhaust gas.

  However, in order for the exhaust gas discharged from the main furnace maintained at a negative pressure to flow into the reburning furnace and pass through the checker, the furnace pressure in the reburning furnace is set to the main combustion furnace in consideration of the pressure loss. Therefore, it is difficult to secure a sufficient residence time and the temperature inside the reburning furnace is increased to a high temperature. There has been a problem that it is difficult to maintain (for example, Patent Document 1).

  In addition, a reburning furnace in a secondary combustion chamber, for example, a cremation facility, functions to decompose exhaust gas containing a large amount of odorous components and dioxins discharged from the cremation furnace by combustion, and fully exhibits its ability. Therefore, it is required to maintain the oxygen concentration at the outlet of the reburning furnace at a certain value or higher.

JP 2000-111022 A

  The present invention has been made in view of the above problems, and it is possible to measure the oxygen concentration of exhaust gas in a furnace without using a forced external force by a pump or the like, and in the exhaust gas To provide a reburning furnace that can maintain sufficient temperature while maintaining sufficient temperature by improving the mixing characteristics of exhaust gas and air in a reburning furnace that decomposes and removes odorous components and dioxins. The purpose is to provide.

In order to achieve the above object, the present invention firstly opens an outer upward inclined hole in the furnace wall, opens a horizontal outward hole at the upper part of the opening, and connects both holes with a communication pipe. A reburning furnace provided with a concentration sensor;
Second, in the reburning furnace for treating the exhaust gas discharged from the main furnace, the inside of the reburning furnace is divided into a first combustion chamber, a second combustion chamber, and a third by a first throttle and a second throttle provided above the first throttle. The combustion chamber is divided into three chambers, the oxygen concentration sensor is provided near the outlet of the third combustion chamber, an air supply unit for mixing the combustion secondary air with the exhaust gas discharged from the main furnace, and a burner for burning the exhaust gas A reburning furnace according to the first invention, wherein the first combustion chamber is provided with
Consists of.

  According to the present invention, the pressure difference generated by the upward flow of the exhaust gas in the furnace can be used for measuring the oxygen concentration of the exhaust gas, and no forced external force such as a pump is required. It is possible to measure the oxygen concentration of the exhaust gas in the furnace without using the above equipment, and to improve the mixing characteristics of exhaust gas and air in a reburning furnace that decomposes and removes odor components and dioxins in the exhaust gas. It is possible to realize a reburning furnace capable of ensuring a sufficient residence time and maintaining the temperature of the reburning furnace outlet at a high temperature.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 shows a longitudinal sectional view of a cremation furnace showing one embodiment of the present invention.

  Reference numeral 1 denotes a main furnace, in which a main furnace burner 2, a main furnace heat insulating door 3, and an in-furnace carriage 5 on which a body that is a combustible is placed are installed, and a ceiling An exhaust gas passage 4 is opened in a part of the wall. A reburning furnace 10 is erected and fixed on the top of the ceiling wall of the main combustion furnace 1, and the inside of the reburning furnace 10 communicates with the inside of the main combustion furnace 1 through the exhaust gas passage 4. ing.

  The reburning furnace 10 is constituted by a hollow cylinder, and the inside thereof is divided into three layers by a first throttle 14 and a second throttle 15, and the first combustion chamber 11, the second combustion chamber 12 and the third combustion are arranged from the bottom to the top. A chamber 13 is formed, and an exhaust gas outlet 16 is formed in the upper part of the third combustion chamber.

  The exhaust gas S generated in the main combustion furnace 1 first flows into the first combustion chamber 11 in the lowermost layer of the reburning furnace 10 through the exhaust gas passage 4.

  The first combustion chamber 11 is provided with a reburning furnace burner 20 and a reburning furnace secondary air nozzle 21, and the exhaust gas 4 is directly exposed to the flame of the reburning furnace burner 20 for combustion. At this time, combustion is promoted by mixing the combustion secondary air supplied from the reburning furnace secondary air nozzle 21 and the exhaust gas S, and thermal decomposition of odor components and dioxins in the exhaust gas is performed.

  The first diaphragm 14 is formed of a plate-shaped disk, and a circular hole 14a is provided at the approximate center thereof. The circular hole 14a has an opening area on the upper surface of the disk smaller than an opening area on the lower surface of the disk, and is formed so that the cross-sectional area gradually decreases in the direction of combustion gas travel.

  By making the shape of the circular aperture 14a in this way, a sudden change in the cross-sectional area is alleviated and the pressure loss in the recombustion furnace due to the restriction can be reduced, so that the pressure difference between the recombustion furnace and the main combustion furnace can be kept small. It becomes. Thereby, since the flow velocity of the exhaust gas S flowing from the main combustion furnace into the reburning furnace is reduced, the residence time of the exhaust gas S in the reburning furnace can be lengthened.

  Further, the flow of the combustion gas in the first combustion chamber 11 is restricted by the first throttle 14, so that the exhaust gas and the combustion secondary air are sufficiently mixed, and the exhaust gas S is free in the reburning furnace. Since it does not pass, the time during which the exhaust gas S stays in the furnace can be lengthened.

  In addition, the combustion gas passing through the first restrictor 14 is diffused when flowing into the second combustion chamber 12 after gathering in the circular opening 14a, thereby further mixing the exhaust gas and the combustion secondary air. It is promoted to create a uniform combustion temperature field in the second combustion chamber 12, and thermal decomposition of odor components and dioxins in the exhaust gas is performed at a sufficiently high temperature.

  The second diaphragm 15 is composed of a plate-shaped disk, and is configured by providing a plurality of apertures in the disk. Since the opening has a role of forcibly diverting the combustion gas, it is desirable that the opening be distributed evenly in the disk. For example, when three openings are opened, each vertex of the equilateral triangle In addition, it is desirable to provide at each vertex of a square when opening four openings, and at each vertex of a regular pentagon when opening five openings.

  In this embodiment, three circular apertures 15a are opened, and each of the circular apertures 15a is opened at each apex of the equilateral triangle. However, depending on the size of the reburning furnace and the amount of exhaust gas, It is desirable to use by adjusting the number.

  The opening 15a has an opening area on the upper surface of the disk smaller than an opening area on the lower surface of the disk, and is formed so that the cross-sectional area gradually decreases in the direction of combustion gas travel.

  If the shape of the circular opening 15a is configured as described above in the same manner as the shape of the circular opening 14a, the rapid change in the cross-sectional area is alleviated and the pressure loss in the reburning furnace due to the throttle can be reduced. It becomes possible to suppress the pressure difference of the main furnace. Thereby, since the flow velocity of the exhaust gas S flowing from the main combustion furnace into the reburning furnace is reduced, the residence time of the exhaust gas S in the reburning furnace can be lengthened.

  Further, the flow of the combustion gas in the second combustion chamber 12 is restricted by the second throttle 15 so that the exhaust gas and the combustion secondary air are sufficiently mixed, and the exhaust gas S is free in the reburning furnace. Since it does not pass, the time during which the exhaust gas S stays in the furnace can be lengthened.

  Further, the combustion gas passing through the second throttle 15 is forcibly divided and divided by the plurality of circular openings 15a, and then diffused in the third combustion chamber 13 and further stirred, Since generation of a local high temperature region can be prevented and a uniform combustion temperature field can be formed in the third combustion chamber, thermal decomposition by complete combustion of odor components and dioxins contained in the exhaust gas S is performed.

  Further, a furnace pressure sensor 22 for measuring the furnace pressure is provided in the first combustion chamber so that the pressure in the reburning furnace can be grasped and controlled. Since the flow rate of the exhaust gas S in the reburning furnace can be controlled by adjusting the pressure in the reburning furnace, for example, when the residence time of the exhaust gas S in the reburning furnace is less than 2 seconds, the above reburning furnace The residence time can be set to 2 seconds or more by lowering the pressure in the reburning furnace by adjusting the supply amount of the combustion secondary air supplied from the secondary air nozzle 21.

  Further, the third combustion chamber is provided with a temperature sensor 24 for measuring the outlet temperature of the reburning furnace, and detects the outlet temperature of the reburning furnace, which is difficult to maintain a high temperature when the amount of exhaust gas is large as in the early cremation. By adjusting the heating power of the burner 20 for the reburning furnace in the first combustion chamber and the supply amount of the combustion secondary air supplied from the secondary air nozzle 21 for the reburning furnace, The combustion temperature in the reburning furnace can be maintained at a desired temperature (for example, 850 ° C. or higher).

  Since the temperature sensor 23 provided in the second combustion chamber can be used in the second half of the cremation in which the amount of inflowing exhaust gas is reduced, the state in the reburning furnace can be grasped in detail, so that the temperature and pressure in the furnace are precise. Management and adjustment can be made possible.

  Further, as shown in FIG. 3, an outer upward inclined hole 26 is opened in the upright furnace wall surface 13 ′ near the outlet of the third combustion chamber 13, and the upper side of the opening is horizontal (perpendicular to the furnace wall surface 13 ′) outward. By opening the hole 27, connecting both the holes 26 and 27 with the communication pipe 28, and providing the oxygen concentration sensor 25 at the connecting portion, the mixed air flow rising along the furnace wall surface 13 'is an opening having a large opening area. Due to the pressure difference between the opening and the small opening, the flow is divided into the communication pipe 28 from the opening of the inclined hole 26, flows into the furnace from the opening of the horizontal outward hole 27 through the communication pipe 28, and is sent by the oxygen concentration sensor 25. The oxygen concentration near the outlet 16 of the third combustion chamber 13 is detected, and the flow rate adjusting valve 30 provided in the blower pipe 29 is operated according to the detected signal, and the secondary air nozzle for the reburning furnace provided at the lower end of the first combustion chamber 11 Supply amount of combustion secondary air supplied from 21 The oxygen concentration of the outlet 16 by adjusting it obtained and maintained above a certain value, it is possible to decompose the odor and dioxins can hold combustion decomposition of exhaust gas containing odorous and dioxins in a large amount.

  A signal from the oxygen concentration sensor 25 operates a control motor 30 ′ of the flow rate adjusting valve 30 by means of a computer-controlled regulator 35, thereby adjusting the flow rate adjusting valve 30.

  In FIG. 1, 31 is a cooling chamber, 32 is a combustion blower, 33 is a branch blower pipe connecting the blower 32 and the cooling chamber 31, and 34 is a cooling suction blower and ejector blower for the cooling chamber 31.

It is a whole explanation longitudinal section showing an embodiment of a cremation furnace concerning the present invention. (A) is the sectional view on the AA line of FIG. 1, (b) is the sectional view on the BB line of FIG. It is explanatory drawing of the connection relation of an oxygen concentration sensor part and a flow control valve. It is an expanded longitudinal cross-sectional view of the conventional oxygen concentration sensor part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Main combustion furnace 10 Recombustion furnace 11 1st combustion chamber 12 2nd combustion chamber 13 3rd combustion chamber 13 'Furnace wall surface 14 1st aperture 14a Opening hole 15 2nd aperture 15a Opening 16 Exhaust gas outlet 20 Reburner burner 21 Reburning Secondary air nozzle for furnace 22 Furnace pressure sensor 24 Temperature sensor 25 Oxygen concentration sensor 26 Outside upward inclined hole 27 Horizontal outward hole 28 Communication pipe

Claims (2)

  A reburning furnace having an outer upward inclined hole formed in a furnace wall surface, a horizontal outward hole formed in an upper portion of the opening, both holes connected by a communication pipe, and an oxygen concentration sensor provided in the pipe. In the reburning furnace that processes the exhaust gas discharged from the main furnace,
By dividing the inside of the reburning furnace into three chambers, a first combustion chamber, a second combustion chamber, and a third combustion chamber, by a first throttle and a second throttle provided above the first throttle,
The oxygen concentration sensor is provided near the outlet of the third combustion chamber,
The reburning furnace according to claim 1, wherein an air supply unit for mixing combustion secondary air with the exhaust gas discharged from the main combustion furnace and a burner for burning the exhaust gas are provided in the first combustion chamber.

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