JP2004283644A - Method and apparatus for cleaning incinerator exhaust gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for cleaning an incinerator exhaust gas which easily adjusts a dry dust collector at a temperature to enough demonstrate its performance by cooling the high temperature exhaust gas, can remove an acidic gas, and miniaturizes an apparatus itself, and the apparatus for the method. <P>SOLUTION: In the method, the high temperature exhaust gas from the incinerator 2, after being cooled, is passed through the dry dust collector 3. The exhaust gas is discharged into two pathways 5 and 8. Most of the exhaust gas is passed through a wet dust collector 6 from one pathway to remove the acidic gas, and after being cooled adiabatically in the dust collector 6, is led to a mixing temperature control device 7. The residual exhaust gas is led from the other pathway to the temperature control device. In the control device, the low temperature exhaust gas discharged from the wet dust collector 6 is heated by the residual high temperature exhaust gas, and the heated exhaust gas is led to the dry dust collector 3. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for removing acid gas and dioxin from exhaust gas of an incinerator for purification.
[0002]
[Prior art]
In the conventional treatment method for removing dioxin, a cooling tower is provided on the secondary side of the incineration path, and in the cooling tower, exhaust gas at about 800 ° C is sprayed with pressurized high-temperature water to reduce the exhaust gas to about 200 ° C. It was a method of rapidly cooling and then passing through a dry dust collector (bag filter) (for example, see Patent Document 1). This method utilizes the fact that pressurized high-temperature water vaporizes more than cold water.
[0003]
[Patent Document 1]
JP 2001-132937 A (page 4, FIG. 1)
[0004]
In addition to the method described above, there is a method in which the exhaust gas is indirectly cooled by a heat exchange method and then passed through a dry dust collector.
[0005]
[Problems to be solved by the invention]
The cooling tower not only plays a role in rapidly reducing the temperature of the exhaust gas to prevent re-synthesis of dioxin, but also reduces the temperature of the exhaust gas from about 200 ° C, which is the temperature at which the dry dust collector can sufficiently exhibit its performance. There is a need for a role to adjust so that it is not too high or too low.
[0006]
However, temperature control in the cooling tower is performed only by adjusting the spray amount of pressurized high-temperature water. Therefore, when the spray amount is inappropriate, for example, when the spray amount is small, the temperature drop is insufficient. On the other hand, when the spray amount is large, the temperature may be too low, the dry dust collector may get wet, and exhaust gas may not pass. Therefore, temperature control was very important.
[0007]
However, the temperature of the exhaust gas discharged from the incinerator varies depending on the type and amount of refuse to be burned. Therefore, it is difficult to cool the constantly changing exhaust gas temperature to a predetermined temperature only by the spray amount of pressurized high-temperature water. The same can be said for the heat exchange method. In other words, the temperature cannot be controlled without controlling the flow rate of the heat target (for example, water) because of indirect cooling, but the flow rate of the heat target cannot be changed drastically structurally. Can not.
[0008]
Further, a structure in which pressurized high-temperature water is sprayed and cooled by utilizing the heat of vaporization requires a large vaporization region, and the size of the cooling tower increases. In the case of the heat exchange method, of course, the size is increased.
[0009]
Furthermore, the dry dust collector (bag filter) is for removing particles such as dioxin, and has a low ability to remove acidic gases (Hcl, SOx, etc.). Therefore, most of the acid gas is discharged to the secondary side of the dry dust collector, which is not preferable from an environmental point of view. In addition, although powder of slaked lime or activated carbon is usually used for the bag filter, the surface reacts with the acidic gas to generate another compound, and the dioxin removal ability is reduced.
[0010]
The present invention has been created in consideration of the above-described circumstances, and the problems to be solved are as follows. First, it is easy to cool the high-temperature exhaust gas and adjust it to a temperature at which the dry dust collector can sufficiently exhibit its performance. Second, the ability to remove acid gases. Third, the device itself can be miniaturized.
[0011]
[Means for Solving the Problems]
The invention according to claim 1 relates to a method for purifying incinerator exhaust gas by passing a high-temperature exhaust gas from an incinerator through a dry dust collector after cooling. Then, the high-temperature exhaust gas is discharged from the incinerator into two paths, most of the high-temperature exhaust gas is passed from one path through a wet dust collector to remove the acid gas, and then adiabatically cooled. The rest of the gas is led from the other path to the mixing temperature controller, where the temperature of the low-temperature exhaust gas discharged from the wet dust collector is raised by the rest of the high-temperature exhaust gas, and the heated exhaust gas is dried by the dry dust collector. It is characterized by leading to.
[0012]
By passing most of the high-temperature exhaust gas through a wet dust collector, the gaseous acid gas can be removed, and adiabatic cooling allows rapid cooling to a temperature at which dioxin is not resynthesized. By mixing the remainder, the temperature can be raised to a usable temperature at which the dry dust collector sufficiently exhibits its performance. The dry dust collector adsorbs and removes dioxin. As described above, dry dust collectors have a low ability to remove acidic gases, but most of the high-temperature exhaust gases pass through wet dust collectors to remove the acidic gases. What is necessary is just to remove the gaseous substance of the acidic gas contained in the rest of the gas, and almost all of the gaseous substance of the acidic gas is removed.
[0013]
An incinerator exhaust gas purifying apparatus according to claim 2 includes a branch pipe for discharging exhaust gas from the incinerator to two paths, a wet dust collector for connecting a primary side to one path of the branch pipe, and a branch pipe. A mixing temperature controller that connects the primary side to both the other path of the pipe and the secondary side of the wet type dust collector and connects the secondary side to the dry type dust collector, and keeps the temperature of the exhaust gas discharged from the mixing temperature regulator constant. A mixing ratio control device for automatically adjusting a ratio of high-temperature exhaust gas from the incinerator to one path and the other path to maintain the temperature.
[0014]
As the mixing ratio control device, dampers are provided in one path and the other path of the branch pipe so as to be openable and closable, and the temperature of exhaust gas emitted from the mixing temperature control device is detected by a temperature sensor, and the detection result is a constant temperature. One that automatically adjusts the opening / closing state of the damper so that
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 and FIG. 2 show a refuse incineration facility incorporating an incinerator exhaust gas cleaning apparatus 1 of the present invention. The refuse incineration facility includes an incinerator 2, the cleaning device 1 of the present invention, a dry dust collector 3, and an exhaust fan FAN.
[0016]
In the incinerator 2, the refuse is completely burned at a high temperature of 800 ° C. or more to prevent the generation of dioxin. The high-temperature exhaust gas leaving the incinerator 2 is sent to the cleaning device 1 of the present invention.
[0017]
In the cleaning device 1, the taken high-temperature exhaust gas is discharged to two paths through the branch pipe 4, and most of the high-temperature exhaust gas is sequentially sent from one path 5 to the wet dust collector 6 and the mixing temperature adjusting device 7. The remainder of the exhaust gas is sent directly from the other path 8 to the mixing temperature controller 7. In the wet dust collector 6, high-temperature exhaust gas of 800 ° C. or more is adiabatically cooled to about 80 ° C. in 0.5 seconds or less while removing acidic gas to produce low-temperature exhaust gas. The mixing temperature adjusting device 7 mixes the rest of the high-temperature exhaust gas with the low-temperature exhaust gas of approximately 80 ° C., and automatically adjusts the mixing ratio by the mixing ratio control device 9 to reduce the exhaust gas to approximately 200 ° C. Then, the exhaust gas of about 200 ° C. is passed through a dry dust collector (bag filter) 3 to remove dioxin and remove the acidic gas contained in the remaining high-temperature exhaust gas, thereby purifying the exhaust gas. Thereafter, the exhaust gas is attracted by the exhaust fan FAN and released to the atmosphere.
[0018]
The equipment constituting the cleaning device 1 will be described in further detail. The wet dust collector 6 (scrubber) may be any known one that removes acid gas. However, in order to prevent hot exhaust gas from becoming water droplets and being entrained with the exhaust gas when it comes into contact with the cleaning liquid. It is desirable to attach a mist removal unit U. As an example of the wet dust collector 6, the cleaning liquid is sprinkled from the shower nozzle 11 at the upper part of the tower 10, and the high-temperature exhaust gas is adiabatically cooled and discharged with the cleaning liquid. Further, the acidic gas of the high-temperature exhaust gas is removed by the cleaning liquid, and the pH of the cleaning liquid accumulated at the bottom of the tower 10 changes. However, the pH of the accumulated liquid is detected by a sensor (not shown) and maintained at a constant pH. The opening and closing of the valve 12 is automatically controlled as described above, and alkali is supplied into the tower 10. Further, the solution is drained from the inside of the tower 10 using the outlet pipe 13 at a constant rate, and the salt concentration of the washing solution is kept constant. Since the wastewater contains harmful substances, it is treated outside the system together with incineration ash. Since water is lost due to exhaust gas emission and harmful substance emission, the amount of liquid accumulated at the bottom is detected by a sensor (not shown), and the valve 14 is automatically opened and closed so as to maintain a constant level. And refill the tower with water.
[0019]
The mixing temperature adjusting device 7 projects the inner cylinder 17 into the center of the primary side cover plate 16 of the cylindrical case 15, and takes in low-temperature exhaust gas from the inner cylinder 17 into the case 15. On the other hand, the intake port 18 for introducing the remaining high-temperature exhaust gas is opened on the primary side of the cylindrical plate 19 of the case 15, and the high-temperature exhaust gas taken in from the intake port 18 turns around the outer side of the inner cylinder 17. Exhaust gas and low-temperature exhaust gas are efficiently mixed and heated to be discharged from the outlet 20. If saturated low-temperature exhaust gas enters through the inner cylinder 17 and comes into direct contact with the case 15, the case 15 is corroded. To prevent this, a swirling flow of the high-temperature exhaust gas is generated along the inside of the case 15. And wraps the low temperature exhaust gas. Note that the secondary side (outlet side) of the case 15 is tapered so that a swirling flow is easily generated.
[0020]
The mixing ratio control device 9 for automatically adjusting the mixing ratio includes a temperature sensor 21 provided on the outlet side of the mixing temperature control device 7 and a damper 22 provided separately on one path 5 and the other path 8 from the branch pipe 4. , 23, and a controller 24. The controller 24 automatically adjusts the opening / closing state of the two dampers 22, 23 based on the detection signal from the temperature sensor 21 so that the temperature of the exhaust gas becomes about 200 ° C. I do. As a guide of the mixing ratio, 85% of the high-temperature exhaust gas passing through one path 5 (toward the wet-type dust collector) and 85% of the high-temperature exhaust gas passing through the other path 7 (toward the mixing temperature controller). The mixing ratio is adjusted near 15% with reference to 15%.
[0021]
The dry dust collector 3 uses slaked lime or activated carbon powder to remove dioxins, and a temperature of about 200 ° C. is a temperature at which its performance can be sufficiently exhibited. In addition, the ability to remove acidic gas is not high, but there is a little.
[0022]
【The invention's effect】
According to the present invention, the role of removing the gaseous acid gas with a wet dust collector and controlling the temperature of the exhaust gas with a mixing temperature controller is clearly divided, and the temperature of the exhaust gas is reduced in the wet dust collector. It is possible to concentrate on removing the acid gas from the gas without worrying about the decrease. On the other hand, the mixing temperature controller can concentrate on the temperature control of the exhaust gas, so that the temperature control of the exhaust gas can be easily performed. Further, the heat is effectively used by using a skillful method of raising the temperature of the exhaust gas cooled to a low temperature by the wet dust collector with the remainder of the high-temperature exhaust gas. Furthermore, since most of the acidic gas contained in the high-temperature exhaust gas can be removed by the wet dust collector and the remaining gas can be removed by the dry dust collector, the load on the dry dust collector, which has a low gas removing ability, can be reduced. As a result, the exhaust gas discharged from the dry dust collector is almost completely free of gas. In addition, since the dry dust collector also removes dioxin, the exhaust gas discharged is clean. Further, the amount of acidic substances adhering to the dry dust collector can be drastically reduced, and the period during which the dry dust collector can exhibit its performance becomes longer.
[0023]
By adiabatically cooling the high-temperature exhaust gas with a wet dust collector, the amount of exhaust gas to be supplied to the mixing temperature adjusting device can be reduced, and the device itself can be downsized.
[Brief description of the drawings]
FIG. 1 is a block diagram of a refuse incineration facility incorporating an incinerator exhaust gas cleaning device.
FIG. 2 is an explanatory diagram of a refuse incineration facility in which an incinerator exhaust gas cleaning device is incorporated.
[Explanation of symbols]
2 incinerator 3 dry dust collector 4 branch pipe 5 one path 6 wet dust collector 7 mixing temperature regulator 8 other path 9 mixing ratio controller

Claims (2)

In a method for purifying incinerator exhaust gas, the high-temperature exhaust gas from the incinerator (2) is cooled and then passed through a dry dust collector (3).
High-temperature exhaust gas is discharged from the incinerator (2) to two paths (5, 8), and most of the high-temperature exhaust gas is passed from one path (5) to the wet dust collector (6) to remove acid gas, and then adiabatically cooled. After that, the mixture is led to the mixing temperature controller (7), and the rest of the high-temperature exhaust gas is led from the other path (8) to the mixing temperature controller (7).
In the mixing temperature adjusting device (7), the low-temperature exhaust gas discharged from the wet dust collector (6) is heated with the remainder of the high-temperature exhaust gas, and the heated exhaust gas is guided to the dry dust collector (3). To clean incinerator exhaust gas. A branch pipe (4) for discharging exhaust gas from the incinerator (2) to two paths (5, 8), and a wet dust collector (6) for connecting the primary side to one path (5) of the branch pipe (4) A mixing temperature control device (1) that connects the primary side to both the other path (8) of the branch pipe (4) and the secondary side of the wet dust collector (6) and connects the secondary side to the dry dust collector (3) ( 7) and the high-temperature exhaust gas from the incinerator (2) in order to maintain the temperature of the exhaust gas discharged from the mixing temperature adjusting device (7) at a constant temperature in one path (5) and the other path (8). And a mixing ratio control device (9) for automatically adjusting the ratio leading to (1).

Images