JP2010227728A - Method for removing n2o contained in exhaust gas from sewage sludge incinerator - Google Patents

Method for removing n2o contained in exhaust gas from sewage sludge incinerator Download PDF

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JP2010227728A
JP2010227728A JP2007167370A JP2007167370A JP2010227728A JP 2010227728 A JP2010227728 A JP 2010227728A JP 2007167370 A JP2007167370 A JP 2007167370A JP 2007167370 A JP2007167370 A JP 2007167370A JP 2010227728 A JP2010227728 A JP 2010227728A
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exhaust gas
sewage sludge
sludge incinerator
water vapor
catalyst
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Toichiro Sasaki
統一郎 佐々木
Tetsuya Yanase
哲也 柳瀬
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Metawater Co Ltd
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    • B01J29/00—Catalysts comprising molecular sieves
    • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
    • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
    • B01J29/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively
    • B01J29/42—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively containing iron group metals, noble metals or copper
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    • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
    • B01J29/70—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65
    • B01J29/72—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65 containing iron group metals, noble metals or copper
    • B01J29/76—Iron group metals or copper
    • B01J29/7615—Zeolite Beta
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/20—Reductants
    • B01D2251/206—Ammonium compounds
    • B01D2251/2062—Ammonia
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    • B01D—SEPARATION
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    • B01D2251/208—Hydrocarbons
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/20—Metals or compounds thereof
    • B01D2255/207—Transition metals
    • B01D2255/20738—Iron
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/50—Zeolites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/20—Halogens or halogen compounds
    • B01D2257/204—Inorganic halogen compounds
    • B01D2257/2045—Hydrochloric acid
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/30—Sulfur compounds
    • B01D2257/302—Sulfur oxides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/40—Nitrogen compounds
    • B01D2257/402—Dinitrogen oxide
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES 
    • F23J2215/00—Preventing emissions
    • F23J2215/10—Nitrogen; Compounds thereof
    • F23J2215/101—Nitrous oxide (N2O)
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
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    • Y02C20/10—Capture or disposal of greenhouse gases of nitrous oxide (N2O)

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Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for industrially and efficiently removing N<SB>2</SB>O contained in exhaust gas from a sewage sludge incinerator while avoiding decrease in catalytic activity caused by water vapor. <P>SOLUTION: The exhaust gas having high temperature ranging from 800 to 850°C and discharged from the sewage sludge incinerator 1 is treated in an exhaust gas treating system equipped with an exhaust smoke treating column 6 and then is cooled to 60°C or below. This procedure can decrease water vapor content in the exhaust gas to 20 vol.% or below. The exhaust gas is heated again to 300 to 550°C by passing the exhaust gas through a heating unit 9. The exhaust gas is brought into contact with an N<SB>2</SB>O removing catalyst 8 in the presence of a reducing agent to reductively remove N<SB>2</SB>O contained in the exhaust gas. Thus about 90% of N<SB>2</SB>O can be removed by this method. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

本発明は、下水汚泥焼却炉から排出される高温の排ガス中に含まれるＮ２Ｏを除去する方法に関するものである。 The present invention relates to a method for removing N 2 O contained in high-temperature exhaust gas discharged from a sewage sludge incinerator.

下水汚泥焼却炉の排ガス中には、下水汚泥中の有機分に由来するＮ２Ｏ（亜酸化窒素）が数百ｐｐｍのオーダーで含まれている。このＮ２Ｏは、地球温暖化係数が３１０である温室効果ガスの一つである。すなわちＮ２ＯはＣＯ２の３１０倍の地球温暖化効果を持ち、京都議定書においても規制対象とされているガスである。従って地球温暖化を抑制するためには、下水汚泥焼却炉の排ガス中に含まれるＮ２Ｏを大幅に低減する必要がある。 The exhaust gas from the sewage sludge incinerator contains N 2 O (nitrous oxide) derived from organic components in the sewage sludge in the order of several hundred ppm. This N 2 O is one of the greenhouse gases having a global warming potential of 310. That is, N 2 O is a gas that has a global warming effect 310 times that of CO 2 and is also regulated in the Kyoto Protocol. Therefore, in order to suppress global warming, it is necessary to significantly reduce N 2 O contained in the exhaust gas of the sewage sludge incinerator.

そこで一部の下水汚泥焼却炉においてはＮ２Ｏ排出量の低減対策として、「高温焼却」が採用されている。これは焼却炉に重油や都市ガスなどの燃料を追加することにより、焼却温度を従来の８００℃より高い８５０℃以上の温度域にまで高める方法であり、これによってＮ２Ｏの排出量を従来よりも６〜７割削減することができる。しかしこの「高温焼却」を行っても３〜４割のＮ２Ｏは依然として排出されるうえ、従来よりも余分の補助燃料が必要となるからＣＯ２の排出量が増加し、かつ焼却コストもかかるという問題がある。 Therefore, “high temperature incineration” is adopted as a measure for reducing N 2 O emission in some sewage sludge incinerators. This by adding fuel, such as heavy oil or natural gas in the incinerator, incineration temperature is a method of increasing up to 850 ° C. over a temperature range higher than the conventional 800 ° C., whereby N 2 O emissions conventional 60 to 70% can be reduced. However, even if this “high temperature incineration” is performed, 30% to 40% of N 2 O is still discharged, and additional auxiliary fuel is required compared to the conventional method, so that the amount of CO 2 emission increases and the incineration cost also increases. There is a problem that it takes.

そこで特許文献１及び特許文献２に示されるように、ゼオライトにＦｅ成分を担持させたＦｅ‐ゼオライト触媒を用い、各種排ガス中のＮ２Ｏを還元除去する技術が提案されている。この技術は４００℃程度でＦｅ‐ゼオライト触媒の存在下において還元剤（炭化水素やアンモニア）とＮ２Ｏを反応させ、Ｎ２Ｏを還元除去するものであり、その反応式は次の通りである。
Ｎ２Ｏ＋1/4ＣＨ４→Ｎ２＋1/4ＣＯ２＋1/2Ｈ２Ｏ
Ｎ２Ｏ＋2/3ＮＨ３→＋3/4Ｎ２＋Ｈ２Ｏ Therefore, as shown in Patent Document 1 and Patent Document 2, a technique for reducing and removing N 2 O in various exhaust gases using an Fe-zeolite catalyst in which an Fe component is supported on zeolite has been proposed. In this technology, a reducing agent (hydrocarbon or ammonia) is reacted with N 2 O in the presence of an Fe-zeolite catalyst at about 400 ° C. to reduce and remove N 2 O. The reaction formula is as follows: is there.
N 2 O + 1 / 4CH 4 → N 2 +1/4 CO 2 + 1 / 2H 2 O
N 2 O + 2 / 3NH 3 → + 3 / 4N 2 + H 2 O

この触媒を用いれば、上記した「高温焼却」の問題点は解決することができる。しかし下水脱水汚泥は含有率が８０％と大量の水分を含むため、下水汚泥焼却炉の排ガス中にも３５〜５０体積％という高濃度の水蒸気が含まれている。そして上記したＦｅ‐ゼオライト触媒は水分によって触媒活性が大幅に低下するため、特許文献１及び特許文献２に示される触媒を利用したとしても、下水汚泥焼却炉の排ガス中に含まれるＮ２Ｏを工業的に効率良く除去することは困難であった。
特許第３５５０６５３号公報 特許第３６８１７６９号公報 If this catalyst is used, the above-mentioned problem of “high temperature incineration” can be solved. However, since the sewage dewatered sludge contains a large amount of water at a content rate of 80%, the exhaust gas of the sewage sludge incinerator also contains a high concentration of 35-50% by volume of water vapor. And since the catalytic activity of the Fe-zeolite catalyst described above is greatly reduced by moisture, even if the catalysts shown in Patent Document 1 and Patent Document 2 are used, N 2 O contained in the exhaust gas of the sewage sludge incinerator is removed. It was difficult to remove industrially efficiently.
Japanese Patent No. 3550653 Japanese Patent No. 3681769

従って本発明の目的は、上記した従来の問題点を解決し、下水汚泥焼却炉の排ガス中に含まれるＮ２Ｏを、水蒸気による触媒活性の低下を回避しつつ工業的に効率良く除去することができる方法を提供することである。 Therefore, the object of the present invention is to solve the above-mentioned conventional problems and efficiently remove N 2 O contained in the exhaust gas of a sewage sludge incinerator while industrially efficiently avoiding a decrease in catalytic activity due to water vapor. Is to provide a way to do this.

上記の課題を解決するためになされた本発明は、下水汚泥焼却炉の排ガスを、排煙処理塔を備えた排ガス処理設備により６０℃以下に冷却することにより含有水蒸気濃度を低下させたうえ、前記排煙処理塔よりも前段に設置した加熱器に通して３００〜５５０℃に再加熱し、還元剤の存在下でＮ２Ｏ除去触媒と接触させ、排ガス中のＮ２Ｏを還元除去することを特徴とするものである。 The present invention made in order to solve the above problems, the exhaust gas of the sewage sludge incinerator is cooled to 60 ° C. or less by an exhaust gas treatment facility equipped with a flue gas treatment tower, and the contained water vapor concentration is reduced. It is reheated to 300 to 550 ° C. through a heater installed upstream of the flue gas treatment tower, and brought into contact with an N 2 O removal catalyst in the presence of a reducing agent to reduce and remove N 2 O in the exhaust gas. It is characterized by this.

なお、本発明においては請求項２のように、排ガスを６０℃以下に冷却することにより、含有水蒸気濃度を２０体積％以下にまで低下させることが好ましい。また請求項３のように、排煙処理塔を通過して６０℃以下に冷却された排ガスを、Ｎ２Ｏ除去触媒を通過した排ガスの保有熱を利用して予熱したうえ、加熱器に通すことができる。またＮ２Ｏ除去触媒として、ゼオライトにＦｅ成分を担持させたＦｅ‐ゼオライト触媒を使用することを特徴とすることができる。 In the present invention, as in claim 2, it is preferable to reduce the concentration of water vapor to 20% by volume or less by cooling the exhaust gas to 60 ° C. or less. Further, as in claim 3, the exhaust gas that has passed through the flue gas treatment tower and has been cooled to 60 ° C. or less is preheated using the retained heat of the exhaust gas that has passed through the N 2 O removal catalyst, and then passed through a heater. be able to. Further, as the N 2 O removal catalyst, an Fe-zeolite catalyst in which an Fe component is supported on zeolite can be used.

本発明によれば、下水汚泥焼却炉の排ガスを排ガス処理設備により６０℃以下に冷却することにより含有水蒸気濃度を低下させたうえで３００〜５５０℃に再加熱し、還元剤の存在下でＮ２Ｏ除去触媒と接触させる。このためＮ２Ｏ除去触媒の活性を低下させることなく排ガス中のＮ２Ｏを除去することができ、後記する実験データに示すように９０％を越えるＮ２Ｏ除去率を達成することができる。 According to the present invention, the exhaust gas from the sewage sludge incinerator is cooled to 60 ° C. or lower by using an exhaust gas treatment facility, and the water vapor concentration is reduced, and then reheated to 300 to 550 ° C. Contact with 2 O removal catalyst. Therefore it is possible to remove the N 2 O in the exhaust gas without reducing the activity of the N 2 O removal catalyst, it is possible to achieve a N 2 O removal ratio exceeding 90%, as shown in the following experimental data .

また、排煙処理塔において浄化された排ガスをＮ２Ｏ除去触媒に通すので、ＳＯＸやＨＣｌなどによって触媒の寿命が低下することもなく、長期間にわたり安定した操業が可能である。また、「高温焼却」のように焼却温度を高める必要はなく、排ガスの再加熱のために余分の熱源も必要としないので、ＣＯ２の排出量が増加することもない。さらに、Ｎ２Ｏ除去触媒を通過した排ガスは十分に暖められているため、煙突で水蒸気の白煙が生じることもない等の多くの利点がある。 Further, since the exhaust gas purified in the flue gas treatment tower is passed through the N 2 O removal catalyst, the life of the catalyst is not reduced by SO X , HCl, etc., and stable operation is possible for a long period of time. Further, it is not necessary to increase the incineration temperature as in “high temperature incineration”, and an extra heat source is not required for reheating the exhaust gas, so that the amount of CO 2 emission does not increase. Furthermore, since the exhaust gas that has passed through the N 2 O removal catalyst is sufficiently warmed, there are many advantages such as that no white smoke of water vapor is generated in the chimney.

以下に本発明の実施形態を説明する。
図１は下水汚泥焼却設備の一般的なフローを示すもので、下水脱水汚泥は下水汚泥焼却炉１において重油その他の補助燃料を用いて焼却される。前記した「高温焼却」を行わない場合、燃焼温度は通常８００〜８５０℃の範囲である。下水汚泥焼却炉１は例えば流動炉であるが、その種類は特に限定されるものではない。 Embodiments of the present invention will be described below.
FIG. 1 shows a general flow of sewage sludge incineration equipment, and sewage dewatered sludge is incinerated using heavy oil or other auxiliary fuel in a sewage sludge incinerator 1. When the above-described “high temperature incineration” is not performed, the combustion temperature is usually in the range of 800 to 850 ° C. Although the sewage sludge incinerator 1 is a fluidized furnace, for example, the kind is not specifically limited.

この下水汚泥焼却炉１から排出された８００〜８５０℃程度の高温の排ガスは、空気予熱器２に導かれて下水汚泥焼却炉１に供給される空気を予熱し、４００〜５５０℃で白煙防止予熱器３に送られる。白煙防止予熱器３は煙突７から水蒸気の白煙が出ることを防止するために、煙突７から放出される排ガスに加えるための加熱空気を得る装置であり、この白煙防止予熱器３を通過した排ガスは３００℃程度まで降温する。   The high-temperature exhaust gas of about 800 to 850 ° C. discharged from the sewage sludge incinerator 1 preheats the air supplied to the air preheater 2 and supplied to the sewage sludge incinerator 1, and produces white smoke at 400 to 550 ° C. It is sent to the prevention preheater 3. The white smoke prevention preheater 3 is a device for obtaining heated air to be added to the exhaust gas discharged from the chimney 7 in order to prevent the white smoke of water vapor from coming out of the chimney 7. The exhaust gas that has passed passes down to about 300 ° C.

この排ガスは冷却塔４において更に２００℃程度まで冷却されたうえで、バグフィルタ５において含有するダストを除去される。バグフィルタ５を通過して浄化された排ガスは排煙処理塔６に送られ、上方からの降水と接触して排ガス中のＳＯＸやＨＣｌを除去される。排煙処理塔６で水と接触した排ガスは温度が６０℃以下にまで低下しているが、前記の白煙防止予熱器３によって加熱された３００℃前後の空気と混合され、煙突７から大気中に放出される。 The exhaust gas is further cooled to about 200 ° C. in the cooling tower 4, and the dust contained in the bag filter 5 is removed. The exhaust gas purified through the bag filter 5 is sent to the flue gas treatment tower 6 and comes into contact with precipitation from above to remove SO X and HCl in the exhaust gas. The exhaust gas that has come into contact with water in the flue gas treatment tower 6 has a temperature lowered to 60 ° C. or less, but is mixed with the air at around 300 ° C. heated by the white smoke prevention preheater 3, Released into.

このような従来のフロー中にＦｅ‐ゼオライト系のＮ２Ｏ除去触媒を組み込む場合、Ｎ２Ｏ除去触媒は３００〜４００℃の温度が必要であるので、その設置位置は空気予熱器２と白煙防止予熱器３との間、あるいは白煙防止予熱器３と冷却塔４との間の区間になる。この区間における一般的な排ガス組成を表１に示す。 When a Fe-zeolite-based N 2 O removal catalyst is incorporated in such a conventional flow, the N 2 O removal catalyst needs to be at a temperature of 300 to 400 ° C. It becomes a section between the smoke prevention preheater 3 or between the white smoke prevention preheater 3 and the cooling tower 4. Table 1 shows the general exhaust gas composition in this section.

Figure 2010227728
Figure 2010227728

このように、この区間における排ガスは４５体積％という大量の水蒸気を含有しているうえに、ＳＯＸとＨＣｌの濃度が高い。これらは焼却対象物である下水脱水汚泥の含水率が高いことと、下水汚泥に含まれるＳやＣｌに起因するものである。このため、この状態の排ガスをＦｅ‐ゼオライト系のＮ２Ｏ除去触媒に通すと、水蒸気が障害となってＮ２Ｏの除去率が低下し、またＳＯＸやＨＣｌにより触媒寿命が短縮化されることとなる。なお特許文献１にはこの触媒は水蒸気含有率が２０％までのガスに適用できると説明されているが、上記したような水蒸気含有率が４５％のガスには適用不能である。 As described above, the exhaust gas in this section contains a large amount of water vapor of 45% by volume, and the concentration of SO X and HCl is high. These are due to the high moisture content of the sewage dewatered sludge, which is an incinerator, and the S and Cl contained in the sewage sludge. For this reason, if the exhaust gas in this state is passed through a Fe-zeolite-based N 2 O removal catalyst, the N 2 O removal rate is reduced due to water vapor, and the catalyst life is shortened by SO X and HCl. The Rukoto. Patent Document 1 describes that this catalyst can be applied to a gas having a water vapor content of up to 20%, but cannot be applied to a gas having a water vapor content of 45% as described above.

そこで本発明では図２、図３の実施形態に示すように、排煙処理塔６を通過した排ガスを再加熱してＮ２Ｏ除去触媒８と接触させる新規なフローを用いる。これらの実施形態においても、下水汚泥焼却炉１、空気予熱器２、冷却塔４、バグフィルタ５、排煙処理塔６は図１に示した従来例と同様であるが、従来の白煙防止予熱器３に代えて、冷却塔４の前段に加熱器９が設置されている。この加熱器９は排煙処理塔６を出た排ガスを再加熱するためのものである。 Therefore, in the present invention, as shown in the embodiment of FIGS. 2 and 3, a novel flow is used in which the exhaust gas that has passed through the flue gas treatment tower 6 is reheated and brought into contact with the N 2 O removal catalyst 8. Also in these embodiments, the sewage sludge incinerator 1, the air preheater 2, the cooling tower 4, the bag filter 5, and the flue gas treatment tower 6 are the same as the conventional example shown in FIG. Instead of the preheater 3, a heater 9 is installed in front of the cooling tower 4. The heater 9 is for reheating the exhaust gas exiting the smoke treatment tower 6.

図２のフローにおいても、排ガスはバグフィルタ５を備えた排ガス処理設備を通過する間にダストを除去されたうえ、排煙処理塔６で水と接触しＳＯＸやＨＣｌを除去されることは図１のフローと同様である。しかし排ガスはこの排煙処理塔６で６０℃以下にまで冷却されることによって水分を凝結させ、含有水蒸気濃度を２０体積％以下にまで低下させた乾燥状態で加熱器９に送られて、３００〜５００℃程度に加熱される。なお、排煙処理塔６の出口における排ガス組成の一例は、表２に示すとおりである。 Also in the flow of FIG. 2, the exhaust gas is removed of dust while passing through the exhaust gas treatment facility provided with the bag filter 5 and is contacted with water in the smoke treatment tower 6 to remove SO X and HCl. This is the same as the flow of FIG. However, the exhaust gas is cooled to 60 ° C. or less by the flue gas treatment tower 6 to condense moisture, and is sent to the heater 9 in a dry state in which the water vapor concentration is reduced to 20% by volume or less. It is heated to about ~ 500 ° C. An example of the exhaust gas composition at the outlet of the flue gas treatment tower 6 is as shown in Table 2.

Figure 2010227728
Figure 2010227728

Ｎ２Ｏ除去触媒８としては、特許文献１、２に示されるようなＦｅ‐ゼオライト系の触媒が用いられる。これはβ型ゼオライトに鉄や鉄イオンを担持させたものである。加熱器９で３００〜５００℃程度に加熱された排ガスは、還元剤を添加されＮ２Ｏ除去触媒８に送られる。排ガスとの接触効率を高めるために、Ｎ２Ｏ除去触媒８はハニカム状あるいは粉末状としておくことができる。 As the N 2 O removal catalyst 8, Fe-zeolite based catalysts as shown in Patent Documents 1 and 2 are used. This is one in which iron or iron ions are supported on β-type zeolite. The exhaust gas heated to about 300 to 500 ° C. by the heater 9 is added with a reducing agent and sent to the N 2 O removal catalyst 8. In order to increase the contact efficiency with the exhaust gas, the N 2 O removal catalyst 8 can be in the form of a honeycomb or powder.

還元剤としては、メタン、プロパン等の炭化水素や、アンモニアが用いられる。これらの還元剤の添加量は理論量の１〜２倍とすることが好ましく、還元剤の添加量はＮ２Ｏ濃度に比例して調整することがより好ましい。還元剤の添加量が過剰となると、反応しなかった還元剤は煙突７から大気中に放出されることとなるが、入手容易な炭化水素であるＣＨ４は地球温暖化係数２１の温暖化ガスである。またアンモニアは悪臭防止法の対象物質である。このため、過剰量の還元剤の放出はできるだけ避けるべきである。 As the reducing agent, hydrocarbons such as methane and propane, and ammonia are used. The addition amount of these reducing agents is preferably 1 to 2 times the theoretical amount, and the addition amount of the reducing agent is more preferably adjusted in proportion to the N 2 O concentration. When the amount of the reducing agent added is excessive, the reducing agent that has not reacted is released from the chimney 7 into the atmosphere, but CH 4 which is an easily available hydrocarbon is a warming gas with a global warming potential of 21. It is. Ammonia is a target substance of the Odor Control Law. For this reason, excessive amounts of reducing agent release should be avoided as much as possible.

図２のフローによれば、加熱器９で３００〜５００℃程度に加熱された排ガスは還元剤の存在下でＮ２Ｏ除去触媒８と接触し、排ガス中のＮ２Ｏは窒素に還元して除去される。還元反応式は前記のとおりである。本発明においては排ガスの含有水蒸気濃度を２０体積％以下にまで低下させてあり、かつ排ガス温度も３００〜５００℃に昇温されているので、９０％を越えるＮ２Ｏ除去率を達成することができる。しかもこの昇温は排ガスの保有熱を利用して行われるので、余分の燃料を必要とせず、余分のＣＯ２を排出することもない。さらに、排煙処理塔６でＳＯＸやＨＣｌを除去されているので、触媒寿命が低下することもない。なお、排ガスの再加熱温度が３００℃未満ではＮ２Ｏの除去率が低く、５５０℃を越えると触媒寿命が低下するので好ましくない。 According to the flow of FIG. 2, the exhaust gas which has been heated to about 300 to 500 ° C. in the heater 9 is in contact with N 2 O removal catalyst 8 in the presence of a reducing agent, N 2 O in the exhaust gas is reduced to nitrogen Removed. The reduction reaction formula is as described above. In the present invention, the water vapor concentration of the exhaust gas is reduced to 20% by volume or less, and the exhaust gas temperature is also raised to 300 to 500 ° C., so that an N 2 O removal rate exceeding 90% is achieved. Can do. Moreover, since this temperature rise is performed using the retained heat of the exhaust gas, no extra fuel is required and no extra CO 2 is discharged. Furthermore, since SO X and HCl are removed by the flue gas treatment tower 6, the catalyst life is not reduced. If the reheating temperature of the exhaust gas is less than 300 ° C., the removal rate of N 2 O is low, and if it exceeds 550 ° C., the catalyst life is reduced, which is not preferable.

図２のフローではＮ２Ｏ除去触媒８を通過しＮ２Ｏが還元された排ガスは、３００〜５００℃のままで煙突７から放出される。このように排ガス温度は高くなるため、煙突７から水蒸気の白煙が発生することもない。 In the flow of FIG. 2, the exhaust gas that has passed through the N 2 O removal catalyst 8 and reduced N 2 O is discharged from the chimney 7 while remaining at 300 to 500 ° C. Since the exhaust gas temperature becomes high in this way, no white smoke of water vapor is generated from the chimney 7.

しかしこの高温の排ガスを図３のフローに示すように別の加熱器１０に通し、排煙処理塔６を通過して６０℃以下に冷却された排ガスを、加熱器１０で予熱したうえで加熱器９に通すこともできる。図３のフローは図２のフローに加熱器１０を付加したものであり、その他の構成は図２と同一であるから説明を省略する。   However, this high-temperature exhaust gas is passed through another heater 10 as shown in the flow of FIG. It can also be passed through the vessel 9. The flow of FIG. 3 is obtained by adding the heater 10 to the flow of FIG. 2, and the other configuration is the same as that of FIG.

以下に本発明の効果を確認するために行った実験の結果を示す。
まず、特許文献１の実施例１に示された方法で、βゼオライトに２価の鉄イオンを担持させたＮ２Ｏ除去触媒を製造した。得られた触媒は粉末状であり、その０.５ｇを反応管に充填し、表３に示す条件１と条件２のサンプルガスを流し、生成物をガスクロマトグラフで測定して、Ｎ２Ｏの除去率を評価した。ガス流量は何れも１ｓｌｍ（スタンダードリッターパーミニッツ：Ｌ/分）であり、ガス温度はいずれも４５０℃である。なおＮ２がバランスとなっているのは、残部の意味である。 The result of the experiment conducted in order to confirm the effect of this invention is shown below.
First, an N 2 O removal catalyst in which a divalent iron ion was supported on β zeolite was produced by the method shown in Example 1 of Patent Document 1. The resulting catalyst is in powder form, and filling the 0.5g of the reaction tube, flushed with sample gas conditions 1 and 2 shown in Table 3, the product was measured by gas chromatography, of N 2 O The removal rate was evaluated. The gas flow rates are all 1 slm (standard liter per minute: L / min), and the gas temperatures are all 450 ° C. Note that N 2 is balanced in the meaning of the remainder.

Figure 2010227728
Figure 2010227728

上記のように、含有水蒸気濃度が３５体積％の場合にはＮ２Ｏ除去率が３８％であったが、含有水蒸気濃度を１０体積％まで低下させると、Ｎ２Ｏ除去率は９８％にまで上昇した。この実験によって、本発明の効果を確認することができた。 As described above, when the water vapor concentration was 35% by volume, the N 2 O removal rate was 38%. However, when the water vapor concentration was reduced to 10% by volume, the N 2 O removal rate was 98%. Rose to. Through this experiment, the effect of the present invention could be confirmed.

次に排ガス中に含まれるＳＯＸとＨＣｌが触媒に与える影響を確認するため、上記と同様にβゼオライトに２価の鉄イオンを担持させたＮ２Ｏ除去触媒０.５ｇを反応管に充填し、表４に示す条件３と条件４のサンプルガスを流し、Ｎ２Ｏの除去率を評価した。ガス流量は何れも１ｓｌｍ（Ｌ/分）であり、ガス温度はいずれも４００℃である。ただしＮ２Ｏの除去率はガスを流し始めてから、２０時間後に評価した。含有水蒸気濃度は１０体積％である。 Next, in order to confirm the influence of SO X and HCl contained in the exhaust gas on the catalyst, 0.5 g of N 2 O removal catalyst in which divalent iron ions are supported on β zeolite is filled in the reaction tube in the same manner as described above. Then, the sample gases of conditions 3 and 4 shown in Table 4 were flowed to evaluate the N 2 O removal rate. The gas flow rate is 1 slm (L / min) for all, and the gas temperature is 400 ° C. for all. However, the N 2 O removal rate was evaluated 20 hours after the gas flow started. The water vapor concentration is 10% by volume.

Figure 2010227728
Figure 2010227728

この実験により、ガス中にＳＯＸとＨＣｌが含まれる場合にはＮ２Ｏの除去率が２０時間で６８％にまで低下したが、ガス中にＳＯＸとＨＣｌが含まれていない場合にはＮ２Ｏの除去率は８７％であり、触媒寿命が長くなることが確認できた。本発明では排煙処理塔６によりＳＯＸやＨＣｌを除去した排ガスをＮ２Ｏ除去触媒と接触させることができるため、長期間にわたり触媒活性を維持できることとなる。 As a result of this experiment, when SO X and HCl were contained in the gas, the N 2 O removal rate decreased to 68% in 20 hours. However, when SO X and HCl were not contained in the gas, The removal rate of N 2 O was 87%, and it was confirmed that the catalyst life was prolonged. In the present invention, since the exhaust gas from which SO X and HCl have been removed by the flue gas treatment tower 6 can be brought into contact with the N 2 O removal catalyst, the catalytic activity can be maintained over a long period of time.

下水汚泥焼却設備の一般的なフローを示すブロック図である。It is a block diagram which shows the general flow of a sewage sludge incineration equipment. 本発明の第１の実施形態のフローを示すブロック図である。It is a block diagram which shows the flow of the 1st Embodiment of this invention. 本発明の第２の実施形態のフローを示すブロック図である。It is a block diagram which shows the flow of the 2nd Embodiment of this invention.

符号の説明Explanation of symbols

１ 下水汚泥焼却炉
２ 空気予熱器
３ 白煙防止予熱器
４ 冷却塔
５ バグフィルタ
６ 排煙処理塔
７ 煙突
８ Ｎ２Ｏ除去触媒
９ 加熱器
１０ 他の加熱器 1 sewage sludge incinerator second air preheater 3 white smoke prevention preheater 4 cooling tower 5 a bag filter 6 flue gas treatment tower 7 chimney 8 N 2 O removal catalyst 9 heater 10 other heaters

Claims (4)

下水汚泥焼却炉の排ガスを、排煙処理塔を備えた排ガス処理設備により６０℃以下に冷却することにより含有水蒸気濃度を低下させたうえ、前記排煙処理塔よりも前段に設置した加熱器に通して３００〜５５０℃に再加熱し、還元剤の存在下でＮ２Ｏ除去触媒と接触させ、排ガス中のＮ２Ｏを還元除去することを特徴とする下水汚泥焼却炉の排ガス中のＮ２Ｏ除去方法。 The exhaust gas from the sewage sludge incinerator is cooled to 60 ° C. or less by an exhaust gas treatment facility equipped with a flue gas treatment tower, and the concentration of water vapor is reduced. N in the exhaust gas of a sewage sludge incinerator, which is reheated to 300 to 550 ° C. and brought into contact with an N 2 O removal catalyst in the presence of a reducing agent to reduce and remove N 2 O in the exhaust gas. 2 O removal method. 排ガスを６０℃以下に冷却することにより、含有水蒸気濃度を２０体積％以下にまで低下させることを特徴とする請求項１記載の下水汚泥焼却炉の排ガス中のＮ２Ｏ除去方法。 The method for removing N 2 O in exhaust gas of a sewage sludge incinerator, wherein the concentration of water vapor is reduced to 20% by volume or less by cooling the exhaust gas to 60 ° C or lower. 排煙処理塔を通過して６０℃以下に冷却された排ガスを、Ｎ２Ｏ除去触媒を通過した排ガスの保有熱を利用して予熱したうえ、加熱器に通すことを特徴とする請求項１記載の下水汚泥焼却炉の排ガス中のＮ２Ｏ除去方法。 2. The exhaust gas that has passed through the flue gas treatment tower and has been cooled to 60 ° C. or less is preheated using the retained heat of the exhaust gas that has passed through the N 2 O removal catalyst, and then passed through a heater. The method for removing N 2 O in exhaust gas from the described sewage sludge incinerator. Ｎ２Ｏ除去触媒として、ゼオライトにＦｅ成分を担持させたＦｅ‐ゼオライト触媒を使用することを特徴とする請求項１記載の下水汚泥焼却炉の排ガス中のＮ２Ｏ除去方法。 The method for removing N 2 O in exhaust gas from a sewage sludge incinerator, wherein an Fe-zeolite catalyst having an Fe component supported on zeolite is used as the N 2 O removal catalyst.
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WO2024048386A1 (en) * 2022-08-29 2024-03-07 日本ヒューム株式会社 Method for treating high-temperature gas
WO2024099945A1 (en) * 2022-11-11 2024-05-16 Topsoe A/S A process for the removal of nox and dinitrogen oxide in a sulfur oxides containing off-gas

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JP4203926B2 (en) * 1995-06-16 2009-01-07 バブコック日立株式会社 Method and apparatus for removing nitrous oxide, etc. from exhaust gas
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WO2012046774A1 (en) 2010-10-07 2012-04-12 株式会社資生堂 Analysis method, adhesive tape, and pen
WO2024048386A1 (en) * 2022-08-29 2024-03-07 日本ヒューム株式会社 Method for treating high-temperature gas
WO2024099945A1 (en) * 2022-11-11 2024-05-16 Topsoe A/S A process for the removal of nox and dinitrogen oxide in a sulfur oxides containing off-gas

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