JPH10165765A - Process and device for treating exhaust gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a treatment process and a treatment device for exhaust gas which can remove a noxious matter, for example, dioxin contained in exhaust gas effectively and at a low cost. SOLUTION: Exhaust gas is introduced into a closed chamber 2 with a fluidized bed of active carbon 3, and the active carbon 3 is brought into contact with exhaust gas, and then the exhaust gas is passed through a filtration means 4 for permeable exhaust gas and non-permeable active carbon and exhausted outside the closed chamber 2 in an exhaust treatment process. A treatment device 1 is provided with the closed chamber 2 with the fluidized bed of active carbon 3, a means 5 for introducing the exhaust gas into the closed chamber 2, the filtration means 4 for permeable exhaust gas and non-permeable active carbon provided in the closed chamber 2 and a means 22 for exhausting the exhaust gas having passed through the filtration means 4 to the outside of the closed chamber.

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 treating exhaust gas, and more particularly, to the present invention at low cost and effectively removing harmful substances, such as dioxin, contained in exhaust gas. The present invention relates to a method and an apparatus for treating exhaust gas which can be performed.

[0002]

2. Description of the Related Art The problem of environmental pollution caused by harmful substances contained in exhaust gas from refuse incinerators and the like,
It is currently a matter of high interest. Therefore, several treatment methods have been implemented to remove harmful substances from exhaust gas.

[0003] There is known a treatment method in which exhaust gas is passed through a so-called bag filter having a filter means using, for example, a filter cloth. However, the bag filter is originally intended for dust removal, and in order to adsorb harmful substances such as dioxin, it is necessary to increase the thickness of the activated carbon filter layer adhering to the filter cloth. As a method of actually increasing the thickness of the filtration layer, a method of extending the time for removing the bag filter is known.However, although the thickness of the activated carbon filter layer is increased, it is not replaced with a fresh activated carbon layer. However, such a method has a limit in the adsorption efficiency of harmful substances, and the method of blowing activated carbon into exhaust gas at the bag filter inlet alone can reduce the amount of dioxin released to the atmosphere within an economical range.
Currently, it cannot be less than 0.5 ng / m ³ N, which is the guideline of the Ministry of Health and Welfare. Although it is possible to increase the capacity of such a bag filter into which activated carbon is blown, or to arrange several devices in series to increase the removal efficiency, the equipment becomes extremely expensive.

[0004] A technique is also known in which the filter cloth itself in the bag filter is replaced with an activated carbon filter. However, in this case, it is difficult to replace the activated carbon automatically when the activated carbon reaches the breakthrough time. There is a problem that is.

Further, there is known a method in which when activated carbon is passed through a container as a moving bed, the activated carbon is brought into contact with exhaust gas to remove harmful substances. However, this method requires that the activated carbon be formed into pellets so that the activated carbon is not released to the outside of the vessel due to the exhaust gas pressure, which leads to an increase in cost; and when activated carbon is formed into pellets, (the surface area where gas and activated carbon come into contact) Since (/ (volume of pellet)) is very small as compared with that of particulate activated carbon, there is also a disadvantage that the apparatus becomes large. Furthermore, when the activated carbon is formed into pellets and used as a moving bed, the height of the reaction layer is increased, so that the exhaust gas easily blows through, and efficient contact between the exhaust gas and the activated carbon cannot be expected.

As described above, it is extremely difficult for conventional incineration plants to achieve a dioxin emission of 0.5 ng / m ³ N or less, which is a guideline of the Ministry of Health and Welfare. At present it is aiming to achieve the target by combining them.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method and an apparatus for treating exhaust gas, which can remove harmful substances, for example, dioxin and the like, contained in the exhaust gas at low cost and effectively. It is in.

[0008]

Means for Solving the Problems As a result of intensive studies, the present inventors were able to solve the above-mentioned conventional problems. That is, the present invention introduces exhaust gas into a closed chamber having a fluidized bed of activated carbon, and after contacting the activated carbon with the exhaust gas, passes the exhaust gas through an exhaust gas permeable and activated carbon impervious filtration means. To discharge the exhaust gas to the outside of the closed chamber.

Another object of the present invention is to provide a method for treating the above-mentioned exhaust gas in which turbulence is caused in the exhaust gas in a closed chamber to bring the exhaust gas into contact with activated carbon.

[0010] Further, the present invention provides the above-mentioned exhaust gas, in which gas is prevented from flowing into and out of the closed chamber, activated carbon having reached the breakthrough time is discharged out of the closed chamber, and new activated carbon is introduced into the closed chamber. Is provided.

Further, the present invention provides a method for treating exhaust gas as described above, wherein activated carbon adhering to the filtration means is removed before new activated carbon is introduced into the closed chamber.

Another object of the present invention is to provide a method for treating exhaust gas as described above, wherein the amount of activated carbon discharged and introduced is controlled so that a desired pressure is obtained in the closed chamber.

Further, the present invention provides a method for treating the above-mentioned exhaust gas, wherein the exhaust gas passes through a dust remover in advance, and dust and harmful substances are preliminarily removed.

Further, the present invention provides a closed chamber provided with a fluidized bed of activated carbon, and means for introducing exhaust gas into the closed chamber.
Disclosed is an exhaust gas treatment apparatus provided with an exhaust gas permeable and activated carbon impermeable filtration means provided in the closed chamber, and a means for discharging the exhaust gas passing through the filtration means to the outside of the closed chamber. Things.

Further, the present invention provides the above-mentioned exhaust gas treatment apparatus, wherein a means for causing turbulent exhaust gas is provided in a closed chamber.

Further, the present invention provides a means for blocking gas from flowing into and out of the closed chamber; a means for discharging activated carbon to the outside of the closed chamber; a means for introducing new activated carbon into the closed chamber; It is an object of the present invention to provide the exhaust gas treating apparatus further comprising a removing means.

Further, the present invention provides the above-mentioned exhaust gas treating apparatus, wherein the filtering means is formed from a filter cloth.

The present invention also provides an exhaust gas treatment apparatus in which a plurality of the above-described apparatuses are connected in series.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be further described below with reference to the drawings. FIG. 1 is a view for explaining an apparatus according to an embodiment of the present invention, and FIG. 2 is a plan view of the apparatus.

1 and 2, an exhaust gas treatment apparatus 1 according to the present invention has two closed chambers 2.
Exhaust gas generated from an incinerator or the like is introduced from the inlet duct 5 to the pipe 6 and into the two closed chambers 2 via the gas distributor 7. The introduction speed of the exhaust gas depends on the scale and shape of the apparatus, but can be, for example, about 0.1 to 2 m / sec.

In the closed chamber, a fluidized bed of activated carbon 3 is located at the bottom. The exhaust gas introduced from the gas disperser 7 comes into contact with the activated carbon, and at this time, the activated carbon, which is a fluidized bed, is blown up in the closed chamber 2 by the exhaust gas, so that the exhaust gas and the activated carbon 3 are sufficiently contacted with each other, so that the harmful effect is obtained efficiently. The substance is adsorbed on the activated carbon. When the introduction speed of the exhaust gas into the closed chamber 2 is high, the activated carbon 3 is vigorously blown up and becomes a jet state, and in this state, the harmful substances are efficiently adsorbed on the activated carbon 3. Here, it is preferable to provide a means for generating a turbulent flow of the introduced exhaust gas, for example, a baffle plate 8 in the closed chamber, because the contact between the exhaust gas and the activated carbon 3 is further improved.

Subsequently, the exhaust gas that has come into contact with the activated carbon passes in the downstream direction through the exhaust gas-permeable and activated-carbon-impermeable filtration means 4. The filtering means 4 only needs to achieve its purpose,
Although the specific form is not particularly limited, for example, a filtering means using a filter cloth is preferable because it is simple and low-cost. FIG. 3 shows a preferred embodiment of the filtering means 4 using a filter cloth. As the filter cloth, for example, the same as a conventional bag filter can be used. As shown in FIG. 3, a filter cloth is wound on a suitable support so that the filter cloth has a cylindrical shape, for example, so that the contact surface area between the exhaust gas and the activated carbon 3 is high. It is preferable to keep it. The activated carbon is held in the closed chamber 2 by such a filtering means 4, and only the exhaust gas is discharged to the outside of the closed chamber 2.

The exhaust gas passing through the filtering means 4 is discharged to the outside of the closed chamber 2 through the outlet duct 22.

The pressure in the closed chamber 2 depends on the shape of the apparatus 1, the form of the filtering means 4, the processing speed, etc.
For example it is possible 60~1000mmH a ₂ O.

The shape of the activated carbon 3 can be a powder, and it is not necessary to form the activated carbon 3 into a specific shape. The specific surface area of the activated carbon is desirably, for example, about 10 to 1000 m ² / g. However, if the use of activated carbon in the form of pellets is desired, the use is not limited.

As is well known, activated carbon decreases its adsorbing function as the amount of adsorbed substance increases (breakthrough time). Therefore, also in the present invention, the fluidized bed of the activated carbon 3 needs to be appropriately replaced. In this case, when the activated carbon that has reached the breakthrough time is to be discharged to the outside of the closed chamber 2, the exhaust gas inlet damper 12 and the exhaust gas outlet damper 13 are closed, the gas in and out of the closed chamber is shut off, and the activated carbon 3 is closed by the valve 14. Via the ejector 15 and the transporter 16. At this time, when the amount of activated carbon adhering to the filter cloth is large by the filter cloth differential pressure gauge 17, air can be blown by, for example, the air supply means 18 to remove the activated carbon from the filter cloth. On the other hand, new activated carbon is transferred from the transporter 9 to the damper 10.
Is supplied to the activated carbon hopper 11 through the exhaust gas inlet damper 12 and the exhaust gas outlet damper 13 in a closed state. According to the embodiment shown in FIGS. 1 and 2, since the two closed chambers 2 are provided, the exchange of the activated carbon can be performed in order, which is advantageous without completely stopping the exhaust gas treatment operation. is there.

During operation of the apparatus 1 of the present invention, if the activated carbon fluidized bed differential pressure gauge 19 indicates that the fluidized bed differential pressure is low, the activated carbon is replenished. It is desirable to discharge the activated carbon to the outside of the apparatus and maintain the pressure inside the apparatus 1 properly. The discharged activated carbon is used as a fuel for a high-temperature firing furnace such as a cement firing furnace, and can completely decompose harmful substances such as dioxin.

When the amount of exhaust gas is large, the above devices are connected in parallel. FIG. 4 is a plan view of a mode in which the devices 1 are connected in parallel. Each device 1 is connected via an outlet duct 22. When it is assumed that a large amount of harmful substances is contained in the exhaust gas, the apparatus 1 may be connected in series and the operation of treating the exhaust gas may be repeated several times.

Further, before introducing the exhaust gas into the apparatus of the present invention, the exhaust gas may be treated with a conventional dust remover to preliminarily remove dust and harmful substances contained therein. It is valid. FIG. 5 is a diagram for explaining a process of treating exhaust gas when a dust remover is used. Exhaust gas is
After passing through a dust remover 20 such as a bag filter and dust and harmful substances are preliminarily removed, the dust and harmful substances are introduced into the apparatus 1 of the present invention, and the harmful substances are removed to such an extent that they hardly affect the environment. Is released from the chimney 21 into the outside air.

According to the embodiment of the present invention as described above, the 0.1.
Dioxin emissions of 1 ng / m ³ N or less can be achieved.

Although the present invention has been described in detail with reference to preferred embodiments, the present invention is not limited to the above. For example, the shape and number of the closed chambers, the form for introducing the exhaust gas into the closed chamber, the shape of the filtering means, the specific means for discharging the exhaust gas passing through the filtering means to the outside of the closed chamber, and the like, the effects of the present invention are exhibited. Needless to say, it can be changed as needed.

[0032]

According to the present invention, there is provided an exhaust gas treatment method and apparatus capable of effectively removing harmful substances, for example, dioxin and the like, contained in the exhaust gas at low cost.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining an apparatus according to an embodiment of the present invention.

FIG. 2 is a plan view of the apparatus of FIG.

FIG. 3 is a diagram showing a preferred embodiment of a filtering means using a filter cloth.

FIG. 4 is a plan view of an embodiment in which the devices of the present invention are connected in parallel.

FIG. 5 is a diagram for explaining the exhaust gas treatment method of the present invention when a dust remover is used.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Exhaust gas processing apparatus of this invention 2 Sealed chamber 3 Activated carbon 4 Filtration means 5 Inlet duct 6 Pipe 7 Gas disperser 8 Baffle plate 9 Transport machine 10 Damper 11 Activated carbon hopper 12 Exhaust gas inlet damper 13 Exhaust gas outlet damper 14 Valve 15 Discharger 16 Transport Machine 17 Filter cloth differential pressure gauge 18 Air supply means 19 Activated carbon fluidized bed differential pressure gauge 20 Deduster 21 Chimney 22 Outlet duct

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification code FI B01J 20/20 (72) Inventor Koichiro Sato 2-4-2 Daisaku, Sakura-shi, Chiba Pref.

Claims (11)

[Claims] An exhaust gas is introduced into a closed chamber provided with a fluidized bed of activated carbon, and the activated carbon is brought into contact with the exhaust gas. Then, the exhaust gas is passed through an exhaust gas permeable and activated carbon impervious filtration means. Exhaust gas to the outside of the closed chamber. 2. The method for treating exhaust gas according to claim 1, wherein the exhaust gas is caused to generate turbulence in a closed chamber to be brought into contact with activated carbon. 3. After shutting gas in and out of the closed chamber and discharging the activated carbon reaching the breakthrough time to the outside of the closed chamber,
3. A new activated carbon is introduced into the closed chamber.
The method for treating exhaust gas described in 1. 4. The method for treating exhaust gas according to claim 3, wherein the activated carbon adhering to the filtering means is removed before introducing new activated carbon into the closed chamber. 5. The exhaust gas treatment method according to claim 3, wherein the amount of activated carbon discharged and introduced is controlled so that a desired pressure is obtained in the closed chamber. 6. The method for treating exhaust gas according to claim 1, wherein the exhaust gas passes through a dust remover in advance, and dust and harmful substances are preliminarily removed. 7. A closed chamber provided with a fluidized bed of activated carbon, means for introducing exhaust gas into the closed chamber, filtration means permeable to exhaust gas and impermeable to activated carbon provided in the closed chamber; Means for discharging exhaust gas passing through the means to the outside of the closed chamber. 8. The exhaust gas treatment apparatus according to claim 7, further comprising means for causing turbulence in the exhaust gas in the closed chamber. 9. A means for blocking gas from flowing into and out of the closed chamber; a means for discharging activated carbon to the outside of the closed chamber; a means for introducing new activated carbon into the closed chamber; and a means for removing activated carbon adhering to the filtering means The exhaust gas treatment device according to claim 7 or 8, further comprising: 10. The exhaust gas treatment apparatus according to claim 7, wherein the filtration means is formed of a filter cloth. 11. An exhaust gas treatment apparatus comprising a plurality of the apparatuses according to claim 7 connected in series.