JP2001259333A - Method for separating/removing dioxins and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply separate and remove dioxins generated by combustion of chloride and the like from combustion exhaust gas at high efficiency. SOLUTION: The combustion exhaust gas G containing suspended carbon and carbide is flowed from the lower to the upper part of a gas-treating column 10 and absorbed water W is circulated from the upper to the lower part of the gas-treating column 10. Consequently, the suspended carbon and carbide contained in the exhaust gas G are transferred into the absorbed water W and removed. The dioxins contained in the exhaust gas G stick to the suspended carbon and carbide contained in the exhaust gas G. Thus the dioxins contained in the exhaust gas G are removed by removing the suspended carbon and carbide contained in the exhaust gas G.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for separating and removing dioxins generated from combustion exhaust gas by removing dioxins generated by combustion of chlorine compounds and the like.

[0002]

2. Description of the Related Art Dioxins are very toxic substances and are chemically stable. Therefore, environmental pollution by dioxins has become a serious social problem.

It is said that the largest source of dioxins is incinerators for municipal waste and other wastes. For this reason,
In terms of legislation, structural standards and maintenance standards for facilities to reduce dioxins emitted from waste incineration facilities have been strengthened. According to this, the combustion temperature in the combustion chamber is set to 800 ° C. or more, and the residence time is set to 2 seconds or more. In addition, installation of an exhaust gas treatment device provided with an advanced dust collector is obligatory.

[0004]

Dioxins, which are a problem in incineration of municipal garbage and other wastes, are generated by combustion of chlorine compounds and the like. It is generally accepted that the decomposition temperature of dioxins is about 700 ° C. or higher, and from this viewpoint, the combustion temperature in the combustion chamber is set to 800 ° C. or higher.

[0005] However, it has been reported that a considerable amount of dioxins is generated even in combustion at a high temperature of 800 ° C or higher, and in fact, this has been confirmed by investigations by the present inventors. For this reason, the importance of the exhaust gas treatment device has become extremely large. As the current exhaust gas treatment technology, a method of adsorbing dioxins on activated carbon fine powder and the like and removing them with a bag filter is common.
In a bag filter, it is necessary to appropriately control the temperature of the exhaust gas, so that the structure and size of the exhaust gas treatment device are complicated and large, which imposes a great economic burden on the introducer.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method and an apparatus for separating and removing dioxins generated by combustion of chlorine compounds and the like from a combustion exhaust gas with high efficiency and easily. is there.

[0007]

Means for Solving the Problems To achieve the above object, the present inventors have studied in detail the generation mechanism of dioxins in the combustion of chlorine compounds and the like. As a result, the following was found.

[0008] Combustion PVC, combustion temperature 800, which is conventionally considered to be no problem in terms of generation of dioxins
Dioxins are found in the exhaust gas at a relatively high concentration of, for example, about 20 ng-TEQ / m ³ N even under the conditions of ° C., a reaction time of 30 seconds, and excess oxygen.

This is due to the presence of suspended C and C compounds in the exhaust gas. That is, dioxins in high-temperature combustion at 800 ° C. are mainly generated in the boundary layer around suspended C and C compounds. More specifically, 80
Even at a high temperature combustion of 0 ° C., the generation rate is higher than the decomposition rate in the boundary layer around floating C and C compounds,
And dioxins around the C compound are hardly decomposed apparently. In addition, these dioxins become very easily adsorbed to the suspended C-based material as the temperature decreases.

[0010] Suspended C and C compounds in the exhaust gas hinder the decomposition of dioxins, while facilitating the separation and removal of the generated dioxins. That is, dioxins alone are extremely difficult to separate and remove from the exhaust gas, but if they exist in the exhaust gas in a state of being adsorbed by the suspended C and C compounds, the suspended C and C compounds are removed from the exhaust gas. By separating and removing, it is possible to relatively easily separate and remove from the exhaust gas.

Regardless of whether or not dioxins are attached, separation and removal of suspended C and C compounds are much easier than separation and removal of dioxins alone. For example, suspended C and C compounds to which dioxins are attached can be removed. By so-called water injection, the combustion exhaust gas containing the fuel is injected into water in a bubble state and passed therethrough, suspended C and C compounds in the combustion exhaust gas are adsorbed and separated into water together with dioxins adhering thereto, and as a result, the combustion Dioxins in the exhaust gas are separated and removed from the combustion exhaust gas with high efficiency.

The method and apparatus for separating and removing dioxins of the present invention have been completed on the basis of such findings. When the combustion exhaust gas contains suspended C and C compounds, the suspended C and C compounds are removed. The greatest feature is that dioxins adhering to suspended C and C compounds are separated and removed from the flue gas by separating and removing the flue gas from the flue gas. The C compound is typically HC.

As a method of separating and removing suspended C and C compounds from the flue gas, the flue gas containing the suspended C and C compounds is cooled, and then injected into the adsorbent in a bubble state and passed therethrough. , Floating C in combustion exhaust gas
And the method of adsorbing the C compound on the adsorbent is simple and preferable. By repeating this operation stepwise, particularly high separation efficiency can be obtained.

With respect to the adsorbed liquid on which the suspended C and C compounds are adsorbed, the suspended C and C compounds in the adsorbed liquid can be easily separated and removed from the adsorbed liquid by passing the adsorbed liquid through a filter. In addition, the treatment of suspended C and C compounds separated and removed from the adsorbed liquid is also simplified. That is, by incinerating the used filter again at a high temperature, the dioxins adhering to the suspended C and the C compound are decomposed.

An apparatus for separating and removing dioxins includes:
While the flue gas is circulated from bottom to top, a treatment tower body for circulating the adsorbent for adsorbing suspended C and C compounds contained in the flue gas from top to bottom, and a plurality of stages inside the treatment tower body The adsorption liquid introduced into the treatment tower main body is temporarily retained in each stage, and the combustion exhaust gas introduced into the treatment tower main body is bubbled into the retained liquid in each stage, from below. A leak shelf type including a plurality of leak shelves provided with a large number of gas-liquid passage holes in each stage so as to pass upwards has excellent separation efficiency and economic efficiency.

In the leak rack type separation / removal apparatus, the adsorbed liquid that has passed through the inside of the processing tower body is passed through a filter to separate and remove suspended C and C compounds in the adsorbed liquid from the adsorbed liquid. By returning the adsorbent to the tower body, the adsorbent can be recycled and used for floating C separated and removed from the adsorbent.
And compound C can be easily treated.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of an apparatus for separating and removing dioxins according to an embodiment of the present invention, and FIG.
FIG. 3 is an enlarged sectional view of a leak shelf used in the separation and removal apparatus.

The apparatus for separating and removing dioxins shown in FIG. 1 is an incinerator for municipal waste and other wastes (800 ° C.).
This is a leakage rack type separation and removal apparatus suitably used for separation and removal of dioxins generated by the above-described high-temperature combustion.

This separation and removal apparatus comprises a vertical gas treatment tower 10 for treating combustion exhaust gas G discharged from an incinerator with adsorbed water W, and a gas cooler 20 provided on the gas inlet side of the gas treatment tower 10. And a suction blower 30 provided on the gas outlet side.
And a liquid feed pump 40 provided on the adsorbed water inlet side of the gas treatment tower 10 and a liquid processing unit 50 provided on the adsorbed water outlet side.

The gas processing tower 10 includes a processing tower main body 11 having a cylindrical shape, and leakage shelves 12, 12,... Horizontally arranged in a plurality of stages inside the processing tower main body 11. Processing tower body 1
A header 13 for introducing flue gas into the treatment tower main body 11 is provided below the lowermost leak shelf 12 at a lower portion of the main body 1. On the other hand, an introduction pipe 14 for spraying treated water as an adsorbent into the treatment tower main body 11 is provided at an upper portion in the treatment tower main body 11 so as to be located above the uppermost leak shelf 12.

The flue gas G introduced into the lower portion of the processing tower body 11 via the header 13 is leaked from the racks 12, 12,.
Flows from bottom to top while passing through the inside of the processing tower body 11 from bottom to top, and is discharged out of the processing tower body 11 from the top. On the other hand, the adsorbed water W introduced into the upper portion of the processing tower main body 11 by the introduction pipe 14 passes through the leak shelves 12, 12,. The gas flows from the top to the bottom in the inside 11, and is discharged out of the processing tower body 11 from the bottom.

The leakage shelves 12, 12,...
The adsorbed water W introduced therein is passed downward while temporarily staying above it. Further, the combustion exhaust gas G introduced into the treatment tower main body 11 is made into a bubble state, injected into the stagnant layer of the adsorbed water W from below, and passed upward. As shown in FIG. 2, each of the leak shelves 12 is provided for the gas-liquid countercurrent passage of the combustion exhaust gas G accompanied by water injection, as shown in FIG.
A large number of gas-liquid passage holes 12a are provided at predetermined pitches. Each gas-liquid passage hole 12a is a through hole in the vertical direction, and a tapered hole whose inner diameter gradually decreases from bottom to top is said to have a large effect of promoting the bubbling of the combustion exhaust gas G.

The gas cooler 20 rapidly cools the high-temperature flue gas G discharged from an incinerator for municipal garbage and other waste to about 180 ° C. before being introduced into the gas treatment tower 10.
The liquid processing unit 50 includes a tank 51 for storing the adsorbed water W discharged from the gas processing tower 10, and a filter 52. The filter 52 adsorbs the suspended C in the adsorbed water W and a compound (such as HC) by passing the adsorbed water W introduced into the tank 51.

Next, the operation method and functions of the dioxin separation and removal apparatus shown in FIG. 1 will be described.

During operation, the suction blower 30 and the liquid feed pump 40 operate. When the suction blower 30 is operated, the flue gas G of, for example, 800 ° C. discharged from the incinerator for city garbage (high-temperature combustion of 800 ° C. or more) is rapidly cooled by the gas cooler 20 to, for example, about 180 ° C. It is introduced into the processing tower 10 from below.

In the incineration of municipal waste and other waste,
It is unavoidable that suspended C and C compounds (such as HC) coexist. As a result, dioxins are generated even in high-temperature combustion at 800 ° C. or higher, and most of the dioxins are attached to suspended C and C compounds (such as HC).

The cooled flue gas G introduced into the gas treatment tower 10 from below is cooled by the leakage shelf 1 in the gas treatment tower 10.
Pass through 2,12 ... sequentially from bottom to top. On the other hand, when the liquid feed pump 40 operates, the adsorbed water W is introduced into the gas treatment tower 10 from above. The adsorbed water W introduced into the gas processing tower 10 from above passes through the leak shelves 12, 12,... In the gas processing tower 10 in order from top to bottom.

In each of the leak shelves 12, the adsorbed water W has a predetermined thickness T and stays thereon. The accumulated water flows downward through a number of gas-liquid passage holes 12a, 12a,..., But the amount T of the accumulated water is supplied from above, and the thickness T of the accumulated water is kept constant. Is done. The combustion exhaust gas G is injected into the stagnant water from below through a number of gas-liquid passage holes 12a. The injected gas becomes fine bubbles. By this water injection, suspended C and C compounds (such as HC) in the injected gas are adsorbed by the retained water. The stagnant water having adsorbed the suspended C and the C compound (such as HC) flows downward sequentially from the large number of gas-liquid passage holes 12a.

The flue gas G introduced into the gas treatment tower 10 passes through the leak shelves 12, 12,... In the gas treatment tower 10 in order from the bottom to the top. (HC etc.) is gradually reduced by transferring it into the adsorbed water W, and finally suspended C and C compounds (HC etc.)
And is discharged from the uppermost part of the gas processing tower 10 to the atmosphere via the suction blower 30.

On the other hand, the adsorbed water W introduced into the gas treatment tower 10 passes through the leak shelves 12, 12,... C and C compounds (HC and the like) are adsorbed in a stepwise manner to increase the amount thereof, and are finally discharged from the lowermost part of the gas processing tower 10 to the liquid processing part 50.

In the liquid treatment section 50, suspended C and C compounds (such as HC) in the adsorbed water W are adsorbed and removed by the filter 52. As a result, the adsorbed water W is regenerated into clean water, and returned into the gas processing tower 10 by the liquid feed pump 40. Thus, the adsorbed water W is circulated. The filter 52 having adsorbed suspended C and C compounds (such as HC) is treated by high-temperature combustion in an incinerator.

If dioxins are eluted in a very small amount in the adsorbed water W recovered in the tank 51, the adsorbed water W is bubbled through a perforated plate of another small apparatus. The dioxins in the adsorbed water W are brought into contact with the gas to transfer the dioxins in the adsorbed water W to the gas side.
Dioxins contained therein can be effectively removed.

As described above, incineration of municipal garbage and other wastes cannot avoid the coexistence of suspended C and C compounds (HC and the like), and as a result, dioxins cannot be burned even at a high temperature of 800 ° C. or more. Is generated, but the dioxins exist in a state where most of the dioxins adhere to suspended C and C compounds (such as HC). The dioxin separation and removal apparatus shown in FIG. 1 efficiently separates and removes suspended C and C compounds (such as HC) in the flue gas G, thereby separating and removing most of the dioxins from the flue gas G. I do. Experiments have confirmed that the removal rate is 95% or more.

The number of leak shelves 12, 12,...
From the viewpoint of separation and removal of C and C compounds (HC and the like), it is better to increase the amount. However, if it is too large, the cost of the gas treatment tower 10 increases, and 5 to 10 stages are preferable.

The gas-liquid passage holes 12a,
12a is preferable to reduce the individual pore diameter D and increase the number of the pores from the viewpoint of separation and removal of suspended C and C compounds (HC and the like). When the amount is too large, an increase in processing cost becomes a problem. In this respect, the hole diameter D is preferably from 3 to 10 mm, and the number is preferably from 0.3 to 0.6 expressed as a ratio of the total hole area to the shelf area.

Since the hole diameter D and the pitch P of the gas-liquid passage holes 12a, 12a... Affect the layer thickness T of the adsorbed water W retained on the leak shelf 12, a predetermined layer thickness T is obtained. As described above, the selection is made within the above range based on the introduced amount of the adsorbed water W. The thickness T of the adsorbed water W is 30 to 50 mm
Is preferred. If this layer thickness T is too small, floating C and C
If the adsorbability of the compound (HC or the like) decreases, and if it is too large, the power of the exhaust gas exhaust fan (suction blower 30) increases and the economic efficiency decreases.

As the filter 52, a commercially available paper filter, non-woven fabric filter, or the like can be used.

[0038]

As described above, the method and apparatus for separating and removing dioxins of the present invention can separate dioxins generated by combustion of chlorine compounds and the like from combustion exhaust gas with high efficiency and easily. Can be removed. This not only reduces the emission of dioxins into the atmosphere, but also has a great effect in preventing environmental pollution due to dioxins, as well as the treatment of exhaust gas attached to incinerators such as municipal waste and industrial waste. It also has a great effect in preventing environmental pollution from the viewpoint of reducing the price of the device, reducing the burden on the introducer and facilitating its introduction.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an apparatus for separating and removing dioxins according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a leak shelf used in the separation and removal device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Gas processing tower 11 Processing tower main body 12 Leak shelf 12a Gas-liquid passage hole 20 Gas cooler 30 Suction blower 40 Liquid feed pump 50 Liquid processing part 52 Filter

Continued on the front page (71) Applicant 597142295 Yujo Marukawa 28, 1379 Tsuji, Itako-cho, Ibaraki-gun 5-1-1 109 Kushimaya, Sumikin Kansai Kogyo Co., Ltd. (72) Inventor Yusuke Saito 5-1-1109 Shimaya Konohana-ku, Osaka-shi, Osaka Sumikin Kansai Kogyo Co., Ltd. No. 5-109, Shimaya, Konohana-ku, Sumikin Kansai Kogyo Co., Ltd. −25 (72) Inventor Yujo Marukawa, 1379-28, Tsuji, Itako-cho, Ibaraki Pref.

Claims (7)

[Claims] 1. A method for separating and removing dioxins generated in combustion exhaust gas, the method comprising separating and removing dioxins generated by combustion of chlorine compounds and the like. A method for separating and removing dioxins, comprising separating and removing dioxins adhering to suspended C and C compounds from combustion exhaust gas by separating and removing C and C compounds from combustion exhaust gas. 2. The combustion exhaust gas containing suspended C and C compounds is injected into the adsorbent in a bubble state and allowed to pass through, and the suspended C and C compounds in the flue gas are adsorbed by the adsorbent, whereby the flue gas in the flue gas is removed. The method for separating and removing dioxins according to claim 1, wherein the suspended C and C compounds are separated and removed from the combustion exhaust gas. 3. The dioxins according to claim 2, wherein the adsorbed liquid adsorbing the suspended C and C compounds is passed through a filter to separate and remove the suspended C and C compounds in the adsorbed liquid from the adsorbed liquid. Separation and removal method. 4. The method for separating and removing dioxins according to claim 1, wherein the C compound is HC. 5. A dioxin separation and removal apparatus for separating and removing dioxins generated by combustion of chlorine compounds or the like from flue gas, wherein the flue gas is passed upward from below, and the flue gas is A treatment tower body through which an adsorbent for adsorbing suspended C and C compounds contained therein is passed from top to bottom, and a plurality of stages arranged in the treatment tower body, and the adsorption introduced into the treatment tower body The liquid is temporarily retained in each stage, and the combustion exhaust gas introduced into the treatment tower main body is bubbled into the retained liquid in each stage and a large number of fluids are passed through each stage. An apparatus for separating and removing dioxins, comprising: a plurality of leak shelves provided with gas-liquid passage holes. 6. An adsorbent filtering means for passing adsorbent passing through the inside of the treatment tower body through a filter to separate and remove suspended C and C compounds in the adsorbent from the adsorbent. Item 6. An apparatus for separating and removing dioxins according to Item 5. 7. The apparatus for separating and removing dioxins according to claim 6, further comprising means for circulating the adsorbed liquid that returns the adsorbed liquid that has passed through the filtering means into the processing tower body.