JP2000140574A - Waste gas treatment apparatus and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently remove acidic gases such as hydrogen chloride and sulfur oxides contained in a waste gas and lessen the consumption of an alkali. SOLUTION: A waste gas discharged out of a kiln 11 is cooled by a waste gas cooling tower 12 and then dust of the waste gas is removed and incinerator fly ashes are recovered by a dust removing apparatus 13 and further acidic gases such as hydrogen chloride, sulfur oxides, and the likes are removed from the resultant waste gas by reaction with an alkali forming a fluidized bed by passing the resultant waste gas through a fluidized bed filter 14. After that, the treated waste gas is released to atmosphere through a chimney 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas treatment apparatus and method, and more particularly, to an exhaust gas from a combustion furnace in which a baking process is performed to generate an acidic gas such as hydrogen chloride or sulfur oxide. The present invention relates to an apparatus and a method for processing by using the method.

[0002]

2. Description of the Related Art In recent years, the amount of waste such as municipal solid waste has increased remarkably, and for the purpose of effective use and recycling of such waste,
Attempts have been made to produce environmentally friendly cement (hereinafter referred to as ecocement) using incinerated ash from municipal solid waste as part of the raw material. Eco-cement is produced by mixing incinerated ash with natural raw materials such as limestone and clays to prepare a cement-mixed raw material and firing it in a rotary kiln or the like.

[0003] Since municipal solid waste incineration ash and the like are used as part of the raw materials, there is a concern that the exhaust gas generated from the rotary kiln may contain acidic gases such as hydrogen chloride and sulfur oxides. The waste gas was treated with an exhaust gas treatment device as described below. That is, the exhaust gas discharged from the kiln 1 is cooled in the exhaust gas cooling tower 2 and then enters the dust remover 3. Dust remover 3
There is a dust collection mechanism in which an alkali filtration layer such as slaked lime is formed on the surface of the filter cloth. This dust collection mechanism collects incineration fly ash in the exhaust gas, Acid gas such as hydrogen chloride or sulfur oxide contained in the filter reacts with the alkali in the filtration layer and is removed. Dust remover 3
Is discharged from the chimney 4 into the atmosphere.

[0004]

However, in the dust collecting mechanism of the dust remover 3, since an alkaline filter layer formed on the surface of the filter cloth is thin, an acidic gas such as hydrogen chloride or sulfur oxide is mixed with an alkaline gas. And the filtration layer contains incinerated fly ash, which reduces the efficiency of removing acidic gases such as hydrogen chloride and sulfur oxides, and requires a large amount of alkali. there were.

The present invention has been made to solve such a problem, and can efficiently remove acidic gases such as hydrogen chloride and sulfur oxide contained in exhaust gas.
It is an object of the present invention to provide an exhaust gas treatment device and method capable of reducing the amount of alkali used.

[0006]

An exhaust gas treatment apparatus according to the present invention comprises a dust remover for collecting incinerated fly ash from exhaust gas generated in a combustion furnace, and an exhaust gas from which the incinerated fly ash is collected by the dust remover. And an alkaline fluidized bed filter for removing acidic gases such as hydrogen chloride and sulfur oxides contained in the exhaust gas. In addition, a filter having a fluidized bed made of a mixture of an alkali and activated carbon can be used as the fluidized bed filter. In addition, a rotary kiln used for cement production or the like can be used as the combustion furnace.

[0007] The exhaust gas treatment method according to the present invention recovers incinerated fly ash from exhaust gas generated in a combustion furnace, and flows the exhaust gas from which the incinerated fly ash has been recovered through a fluidized bed of alkali to remove hydrogen chloride contained in the exhaust gas. This is a method for removing acidic gases such as sulfur and sulfur oxides. In addition, by using a fluidized bed made of a mixture of alkali and activated carbon as a fluidized bed, the exhaust gas from which the incinerated fly ash was collected was passed through the fluidized bed to remove acidic gases such as hydrogen chloride and sulfur oxides, and to form the exhaust gas. The contained dioxin can also be removed.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a configuration of an exhaust gas treatment apparatus according to one embodiment of the present invention. An exhaust gas cooling tower 12 is connected to a kiln 11 such as a rotary kiln used for cement production.
Is connected. Further, a fluidized bed filter 14 is connected to the dust remover 13, and a chimney 15 is connected to an outlet side of the fluidized bed filter 14.

Next, the operation of the exhaust gas processing apparatus according to this embodiment will be described. First, the exhaust gas discharged from the kiln 11 for sintering the cement raw material is cooled in the exhaust gas cooling tower 12 to a temperature at which the exhaust gas can be circulated to the dust remover 13, and then enters the dust remover 13, where the dust is removed. Incinerated fly ash is collected. This dust remover 13 does not have an alkali filtration layer like the dust remover 3 shown in FIG. 4 and is used only for collecting incinerated fly ash. Therefore, various dust removers such as an electric dust collector are used. be able to.

Next, the exhaust gas leaving the dust remover 13 enters a fluidized bed filter 14 as shown in FIGS. The fluidized bed filter 14 has two closed chambers 21,
In each closed chamber, a fluidized bed of alkali 22 such as slaked lime is formed at the bottom, and an exhaust gas permeable and alkali impermeable filtering means 23 is disposed at the top. Dust remover 1
3 from the inlet duct 24 to the pipe 25,
Then, the gas is introduced into the two closed chambers 21 through the gas distributor 26. Although the introduction speed of the exhaust gas depends on the scale and shape of the apparatus, it can be, for example, about 0.1 to 2 m / sec.

The exhaust gas introduced into the closed chamber 21 from the gas distributor 26 comes into contact with the alkali 22, and at this time, the alkali 22 as a fluidized bed is blown up in the closed chamber 21 by the exhaust gas, and Sufficient contact is made, and acid gases such as hydrogen chloride and sulfur oxides contained in the exhaust gas are efficiently removed. When the introduction speed of the exhaust gas into the closed chamber 21 is high, the alkali 22 is vigorously blown up to be in a jet state, but also in this state, the efficient removal of the acidic gas such as hydrogen chloride and sulfur oxide is achieved. . Here, it is preferable to arrange a means for generating a turbulent flow of the exhaust gas to be introduced, for example, a baffle plate 27 in the closed chamber 21 because the contact between the exhaust gas and the alkali 22 is further improved.

The exhaust gas which has come into contact with the alkali 22 passes through a filtering means 23 which is permeable to the exhaust gas and impermeable to activated carbon in the downstream direction. As long as the purpose of the filtering means 23 is achieved, its specific form is not particularly limited. For example, a filtering means using a filter cloth is preferable because it is simple and low-cost. As the filter cloth, for example, the same cloth as a conventional bag filter can be used. Further, it is preferable that a filter cloth is wound around a suitable support to form a cylindrical shape, and a large number of the filter cloths are provided so that the contact surface area with the exhaust gas and the alkali 22 is increased. Such a filtering means 23
Accordingly, the alkali 22 is held in the closed chamber 21, and only the exhaust gas passes through the filtering means 23 and is discharged to the outside of the closed chamber 21 through the outlet duct 39.

The pressure in the closed chamber 21 depends on the shape of the closed chamber 21, the form of the filtering means 23, the processing speed and the like, but may be, for example, 60 to 1000 mmH ₂ O.

The product produced in the fluidized bed by the reaction of an acidic gas such as hydrogen chloride or sulfur oxide with an alkali accumulates in the lower part of the fluidized bed, which is the entrance of the exhaust gas.
The fluidized bed of the alkali 22 needs to be appropriately replaced. In this case, the exhaust gas inlet damper 31 and the exhaust gas outlet damper 3
2 is closed to shut off gas from flowing into and out of the sealed chamber 21, and the alkali 22 is discharged from the discharger 34 and the transporter 3 via the valve 33.
Carry to 5. At this time, when the amount of alkali adhering to the filter cloth is large by the filter cloth differential pressure gauge 36, the alkali can be removed from the filter cloth by, for example, blowing air by the air supply means 37. On the other hand, fresh alkali is supplied from the transporting machine 28 to the alkali hopper 30 via the damper 29, and the exhaust gas inlet damper 31 and the exhaust gas outlet damper 3 are supplied.
2 is closed, and the sealed chamber 2 is
The gas is introduced into the fuel cell 1 while the supply amount is adjusted by the valve 40. In the fluidized bed filter 14 shown in FIGS.
Since the two closed chambers 21 are provided, the exchange of alkalis can be performed alternately, which is advantageous without completely stopping the exhaust gas treatment operation.

If the pressure difference of the fluidized bed is found to be low by the alkali fluidized bed pressure gauge 38 during the operation of the fluidized bed filter 14, the alkali is replenished. It is desirable to discharge the alkali to the outside of the filter and maintain the pressure inside the fluidized bed filter 14 appropriately.
When the amount of exhaust gas is large, the fluidized bed filters described above may be connected in parallel. Further, when it is assumed that the exhaust gas contains a large amount of an acidic gas such as hydrogen chloride or sulfur oxide, a plurality of fluidized bed filters may be connected in series, and the exhaust gas treatment operation may be repeated several times. preferable. As the alkali forming the fluidized bed, various alkalis such as CaO, CaCO ₃ , NaOH, and KOH can be used in addition to slaked lime.

The exhaust gas from which the acidic gases such as hydrogen chloride and sulfur oxide have been removed is discharged from the chimney 15 into the atmosphere.

If a filter having a fluidized bed made of a mixture of alkali and activated carbon is used as the fluidized bed filter 14 and the exhaust gas from which the incinerated fly ash is collected is passed through the fluidized bed filter 14, it is contained in the exhaust gas. Since dioxin is adsorbed on activated carbon in the fluidized bed, dioxin can be removed simultaneously with the removal of acidic gases such as hydrogen chloride and sulfur oxides in exhaust gas.

The present invention is applicable not only to the above-described firing of cement raw materials, but also to the treatment of exhaust gas from kilns accompanied by generation of acid gas such as hydrogen chloride and sulfur oxides, such as incineration of refuse and combustion of plastics. Are suitable.

[0019]

As described above, according to the present invention, after incineration fly ash is recovered from the exhaust gas, the exhaust gas is passed through an alkali fluidized bed filter, whereby hydrogen chloride and sulfur oxides contained in the exhaust gas are removed. Since acidic gases such as hydrogen chloride and sulfur oxides can be efficiently removed, it is possible to reduce the amount of alkali used. In addition, if a fluidized bed made of a mixture of alkali and activated carbon is used as the fluidized bed, the exhaust gas from which the incinerated fly ash is collected is passed through the fluidized bed to remove acid gases such as hydrogen chloride and sulfur oxides and to remove the exhaust gas. It is also possible to remove dioxins contained in.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an exhaust gas treatment apparatus according to one embodiment of the present invention.

FIG. 2 is a side sectional view showing a fluidized bed filter used in the embodiment.

FIG. 3 is a plan view showing a fluidized bed filter used in the embodiment.

FIG. 4 is a block diagram showing a conventional exhaust gas treatment device.

[Explanation of symbols]

 11 Kiln 12 Exhaust gas cooling tower 13 Dust remover 14 Fluid bed filter 15 Chimney 22 Alkaline

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) B01D 53/70 B01D 53/34 134A B01J 20/20 134E F-term (Reference) 4D002 AA02 AA19 AA21 AC05 BA03 BA04 BA13 BA14 CA07 CA09 DA01 DA04 DA06 DA11 DA12 DA16 DA41 EA02 GA02 GB01 GB04 GB06 HA01 HA10 4D020 AA06 AA08 AA10 BA01 BA02 BA30 BB01 CA07 CC05 CC06 CD02 4G066 AA05B AA13B AA17B AA43B AE02B BA42 CA07 CA23 CA31

Claims (5)

[Claims] 1. A dust remover for recovering incinerated fly ash from exhaust gas generated in a combustion furnace, and an exhaust gas from which the incinerated fly ash is recovered by the dust remover is used to circulate hydrogen chloride, sulfur oxide, etc. contained in the exhaust gas. An exhaust gas treatment device comprising: an alkaline fluidized bed filter for removing acidic gas. 2. The exhaust gas treatment apparatus according to claim 1, wherein the fluidized bed filter has a fluidized bed made of a mixture of alkali and activated carbon. 3. The exhaust gas treatment device according to claim 1, wherein the combustion furnace is a rotary kiln. 4. An incineration fly ash is recovered from an exhaust gas generated in a combustion furnace, and the exhaust gas from which the incineration fly ash is recovered is passed through a fluidized bed of an alkali, so that acidic gases such as hydrogen chloride and sulfur oxide contained in the exhaust gas are recovered. An exhaust gas treatment method comprising removing gas. 5. An exhaust gas from which incinerated fly ash has been collected is passed through a fluidized bed made of a mixture of alkali and activated carbon to remove acidic gases such as hydrogen chloride and sulfur oxides and to remove dioxins contained in the exhaust gas. The exhaust gas treatment method according to claim 4, wherein: