JP5016240B2 - Exhaust gas treatment apparatus and exhaust gas treatment method - Google Patents

Description

  The present invention relates to an exhaust gas treatment apparatus and an exhaust gas treatment method for treating exhaust gas in a waste treatment facility, and in particular, removes dust in the exhaust gas, and then decomposes and removes harmful components such as nitrogen oxides in the exhaust gas with a catalyst. The present invention relates to an exhaust gas treatment device and an exhaust gas treatment method.

  Waste treatment facilities that treat waste such as municipal waste and industrial waste are equipped with an exhaust gas treatment device that treats exhaust gas generated by gasification, combustion, melting treatment, etc. of waste, A dust remover that removes dust in the exhaust gas cooled to a predetermined temperature and a catalyst chamber that detoxifies the exhaust gas after dust removal are provided (see, for example, Patent Document 1).

  FIG. 2 shows a general configuration of a conventional exhaust gas treatment apparatus. In FIG. 2, the exhaust gas is introduced into a bag filter 11 which is a dust remover, and the dust in the exhaust gas is removed. The exhaust gas after dust removal is introduced into the catalyst chamber 13 through the catalyst inlet flue 12, and nitrogen oxides and dioxins in the exhaust gas are decomposed and removed in the catalyst chamber 13. Attracted and discharged from the chimney through the flue gas flue 15.

  In such an exhaust gas treatment apparatus, ammonia is required for the decomposition of nitrogen oxides in the catalyst chamber 13, and it is necessary to uniformly mix ammonia gas into the exhaust gas before the exhaust gas enters the catalyst chamber 13. . If ammonia gas is not mixed uniformly, the concentration of ammonia necessary for decomposition of nitrogen oxides in the exhaust gas is generated. Nitrogen oxides are not sufficiently decomposed in light areas, and ammonium chloride and ammonium sulfide are concentrated in dark areas. Etc. occur and the activity of the catalyst is remarkably reduced.

The amount of ammonia gas that is actually required is as small as 0.02 to 0.04% by volume based on the amount of exhaust gas. In order to uniformly mix this small amount of ammonia gas into the exhaust gas, conventionally, as shown in FIG. 2, the ammonia gas from the ammonia gas generator 16 is diluted with the air from the air fan 17, and then the catalyst inlet flue is used. 12 is sprayed from a nozzle 18 provided in the middle of 12 and mixed with exhaust gas.
JP 2006-15179 A

  However, the conventional exhaust gas treatment apparatus shown in FIG. 2 requires an air fan 17 that supplies air for diluting ammonia gas, and the air supply amount of the air fan 17 is limited, and a large amount of air is required. In order to supply air, it is necessary to use a large air fan, which increases the cost.

  Furthermore, since the air supplied from the air fan 17 is at room temperature, when ammonia gas is diluted with this air and mixed in the exhaust gas, the exhaust gas is normally 150 ° C. to 200 ° C., and therefore mixing failure due to density difference occurs during mixing. Likely to happen. In order to reduce this mixing failure, it is necessary to provide a large number of nozzles 18 in the catalyst inlet flue 12 and lengthen the catalyst inlet flue 12 for mixing. This also leads to an increase in the size of the equipment and causes an increase in cost.

  Further, since the nozzle 18 in the catalyst inlet flue 12 for blowing ammonia gas diluted with air at normal temperature is cooled by air, it causes low temperature corrosion due to condensation of acidic gas such as hydrogen chloride gas and sulfur oxide in the exhaust gas. A problem occurs.

  The problem to be solved by the present invention is that it is not necessary to separately use a blower such as an air fan in order to dilute the ammonia necessary for decomposing nitrogen oxides in the exhaust gas in the catalyst chamber, and ammonia is exhausted from the exhaust gas. It is an object to provide an exhaust gas treatment apparatus and an exhaust gas treatment method using the exhaust gas treatment apparatus that can prevent the occurrence of low-temperature corrosion due to condensation of acidic gases such as hydrogen chloride gas and sulfur oxide in the exhaust gas. .

The exhaust gas treatment apparatus of the present invention is an exhaust gas treatment apparatus for a waste treatment facility, and includes a dust remover that removes dust in the exhaust gas, and a catalyst chamber that treats the exhaust gas discharged from the gas discharge part of the dust remover. Providing an exhaust gas circulation line for returning a part of the exhaust gas discharged from the catalyst chamber to the gas discharge part of the dust remover, and circulating the exhaust gas for ammonia necessary for decomposing nitrogen oxides in the exhaust gas in the catalyst chamber In the exhaust gas treatment apparatus configured to inject into the line, a partition plate having a plurality of openings is provided in the gas discharge part of the dust remover, and a tip of the exhaust gas circulation line is branched to remove the exhaust gas into which ammonia has been injected. The air is blown from the openings so as to face the flow of exhaust gas discharged from the gas discharge portion of the vessel .

  In the exhaust gas treatment apparatus of the present invention, the catalyst chamber is preferably provided in a casing that houses the dust remover.

The exhaust gas treatment method of the present invention using the exhaust gas treatment apparatus of the present invention returns a part of the exhaust gas discharged from the catalyst chamber to the gas discharge part of the dust remover through the exhaust gas circulation line and oxidizes nitrogen in the exhaust gas. In the exhaust gas treatment method for injecting ammonia necessary for decomposing substances in the catalyst chamber into the exhaust gas circulation line, a partition plate having a plurality of openings is provided in the gas exhaust part of the dust remover, and the tip of the exhaust gas circulation line is branched Then, the exhaust gas into which ammonia has been injected is blown from the openings so as to face the flow of exhaust gas discharged from the gas discharge portion of the dust remover .

  According to the present invention, a part of the exhaust gas discharged from the catalyst chamber is returned to the gas discharge part of the dust remover by the exhaust gas circulation line, and ammonia is injected in the middle of the exhaust gas circulation line. Without providing a blower, the ammonia can be diluted and uniformly mixed with the exhaust gas, and the apparatus can be made compact. Further, according to the exhaust gas circulation line, a large air volume can be easily obtained compared to a blower such as an air fan, and the apparatus cost can be reduced.

  And the exhaust gas returned by the exhaust gas circulation line is the same component gas as the exhaust gas discharged from the gas discharge part of the dust remover, and has the same temperature, so the mixing property is improved. Further, since the exhaust gas discharged from the gas discharge portion of the dust remover is not cooled, it is possible to prevent the occurrence of low temperature corrosion due to condensation of acidic gas such as hydrogen chloride gas and sulfur oxide in the exhaust gas.

  In addition, the apparatus can be made more compact if the catalyst chamber is provided and integrated in a casing that houses the dust remover.

  Hereinafter, embodiments of the present invention will be described based on examples.

  FIG. 1 shows a configuration of an exhaust gas treatment apparatus of the present invention, where (a) is a longitudinal sectional view and (b) is an AA sectional view of (a).

  As shown in FIG. 1, exhaust gas generated by waste gasification, combustion, melting treatment, etc. in a waste treatment facility is cooled to 150 ° C. to 200 ° C. and then introduced into a bag filter 1 as a dust remover. , Dust in the exhaust gas is removed. In the embodiment, the combustible gas generated in the waste melting furnace is burned in the combustion chamber, the combustion exhaust gas generated by the combustion is sent to the boiler for heat recovery, and further cooled to 150 ° C. to 200 ° C. with the exhaust gas temperature controller. The exhaust gas was introduced into the bag filter 1. The exhaust gas after dust removal is discharged from the gas discharge part 1a of the bag filter 1 and introduced into the catalyst chamber 2 provided in the casing 1b of the bag filter 1, and the nitrogen oxides and dioxins contained in the exhaust gas in the catalyst chamber 2 Is decomposed and removed. Thereafter, the exhaust gas is attracted by the induction blower 3 and discharged from the chimney through the exhaust gas flue 4.

  Here, a pressure control damper 5 is provided in the middle of the flue connecting the gas discharge part 2a of the catalyst chamber 2 and the induction blower 3, and the exhaust blower 3 induces exhaust gas by adjusting the degree of opening and closing thereof. The amount is adjusted. Normally, the gas discharge part 1a of the bag filter 1 is operated at a negative pressure of -3 to -4 kPa. Further, in the casing 1 b of the bag filter 1, there is provided a backwash pulse tube 6 that blows out high-pressure air in a pulse shape when the bag filter 1 is backwashed above the bag filter 1. Is provided with a dust discharge device 7 for discharging the dust in the exhaust gas removed by the bag filter 1 to the outside of the casing 1b.

  In such an exhaust gas treatment apparatus, ammonia is necessary for the decomposition of nitrogen oxides in the catalyst chamber 2 as described above. In the present invention, as shown in FIG. 1, an exhaust gas circulation line 8 branched from the exhaust gas flue 4 leading to the chimney and leading to the gas discharge part 1 a of the bag filter 1 is provided, and ammonia is generated upstream of the exhaust gas circulation line 8. After injecting ammonia gas from the device 9 and diluting the ammonia gas 100 times or more with the exhaust gas flowing through the exhaust gas circulation line 8, the ammonia gas is blown into the gas discharge part 1 a of the bag filter 1.

  Specifically, in the embodiment, a partition plate 10 is provided in the casing 1b of the bag filter 1 to partition the bag filter 1 and the catalyst chamber 2, and the partition plate 10 has a portion corresponding to the gas discharge part 1a of the bag filter 1. A plurality of openings 10a are provided, and the exhaust gas removed by the bag filter 1 is rectified and introduced into the catalyst chamber 2 through the openings 10a. It is preferable that the plurality of openings 10a have an opening area with a pressure loss of about 50 Pa to 100 Pa in order to ensure a uniform air volume. Then, the exhaust gas circulation line 8 is branched from the header pipe 8a at the tip of the exhaust gas circulation line 8, and ammonia gas diluted with the exhaust gas is blown from each opening 10a from each nozzle 8b at the tip of the exhaust gas circulation line 8. It introduce | transduces into the discharge part 1a. That is, the ammonia gas diluted with the exhaust gas is blown from each opening 10a so as to face the flow of the exhaust gas discharged from the gas discharge portion 1a of the bag filter 1. Therefore, the blown ammonia gas once enters the gas discharge part 1a of the bag filter 1, is mixed with the exhaust gas removed by the bag filter 1, and is then discharged from each opening 10a. In this process, the ammonia gas is completely mixed with the exhaust gas removed by the bag filter 1, and a uniform denitration reaction (decomposition of nitrogen oxides) is performed in the catalyst chamber 2.

  Moreover, since a differential pressure of about 3 to 4 kPa is always applied to the exhaust gas circulation line 8 due to the action of the attraction blower, gas can be flowed without separately providing a blower such as an air fan. Note that the amount of exhaust gas introduced into the exhaust gas circulation line 8 may be about 1 to 2% of the total exhaust gas amount, and there is almost no influence of the increase in the amount of gas passing into the catalyst chamber 2 due to this.

  As described above, according to the present invention, ammonia can be diluted and uniformly mixed with exhaust gas without separately providing a blower such as an air fan, and the apparatus can be made compact and the apparatus cost can be reduced. . Moreover, if the catalyst chamber 2 is provided in the casing 1b of the bag filter 1 and integrated as in the embodiment, the apparatus can be made more compact.

  The present invention is not limited to the exhaust gas from the waste melting furnace, but can be used for the treatment of exhaust gas from various waste treatment furnaces such as a waste incinerator, gasification furnace, and pyrolysis furnace.

The structure of the waste gas processing apparatus of this invention is shown, (a) is a longitudinal cross-sectional view, (b) is AA sectional drawing of (a). 1 shows a general configuration of a conventional exhaust gas treatment apparatus.

Explanation of symbols

1 Bag filter (dust remover)
DESCRIPTION OF SYMBOLS 1a Gas filter exhaust part 1b Bag filter casing 2 Catalyst room 2a Catalyst room gas exhaust part 3 Induction fan 4 Exhaust flue 5 Pressure control damper 6 Backwash pulse pipe 7 Dust discharge device 8 Exhaust gas circulation line 8a Header pipe 8b Nozzle 9 Ammonia gas generator 10 Partition plate 10a Opening 11 Bag filter 12 Catalyst inlet flue 13 Catalyst chamber 14 Induction blower 15 Exhaust gas flue 16 Ammonia gas generator 17 Air fan 18 Nozzle

Claims (3)

An exhaust gas treatment apparatus for a waste treatment facility, comprising: a dust remover that removes dust in the exhaust gas; and a catalyst chamber that treats exhaust gas discharged from a gas discharge part of the dust remover, and discharged from the catalyst chamber An exhaust gas circulation line for returning a part of the exhaust gas to the gas discharge part of the dust remover and injecting ammonia necessary for decomposing nitrogen oxides in the exhaust gas in the catalyst chamber into the exhaust gas circulation line In the processing device ,
A partition plate having a plurality of openings is provided in the gas discharge part of the dust remover, the end of the exhaust gas circulation line is branched, and the exhaust gas into which ammonia is injected is discharged from the gas discharge part of the dust remover. An exhaust gas treatment apparatus, wherein the exhaust gas is blown through the openings so as to face each other.   The exhaust gas treatment apparatus according to claim 1, wherein the catalyst chamber is provided in a casing that houses the dust remover. In a waste treatment facility, there is provided an exhaust gas treatment method by an exhaust gas treatment apparatus comprising a dust remover for removing dust in the exhaust gas and a catalyst chamber for treating the exhaust gas discharged from the gas discharge part of the dust remover, wherein the catalyst A part of the exhaust gas discharged from the chamber is returned to the gas discharge part of the dust remover through the exhaust gas circulation line, and ammonia necessary for decomposing nitrogen oxides in the exhaust gas in the catalyst chamber is returned to the exhaust gas circulation line. In the exhaust gas treatment method to be injected ,
A partition plate having a plurality of openings is provided in the gas discharge part of the dust remover, the end of the exhaust gas circulation line is branched, and the exhaust gas into which ammonia is injected is discharged from the gas discharge part of the dust remover. The exhaust gas treatment method is characterized in that the air is blown through the openings so as to face each other .

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