JP4169235B2 - N2O emission reduction method from incinerator - Google Patents

Description

【００２５】
【発明の効果】
以上に説明したように、本発明によれば化石燃料を用いることなく排ガスをＮ₂Ｏ除去触媒の反応温度まで昇温することができ、システム全体としての地球温暖化物質の排出量を、従来法よりも低減することができる。また請求項２以下に記載のＮ₂Ｏ除去触媒は、排ガスに適用しても高い活性を発揮させることができる実用性に優れたものであり、排ガス中のＮ₂Ｏを確実に除去することができる利点がある。
【図面の簡単な説明】
【図１】本発明の実施形態を示すフローシートである。
【図２】従来例を示すフローシートである。
【図３】Ｎ₂Ｏ除去を行わない従来例を示すフローシートである。
【符号の説明】
１ 焼却炉、２ 流動空気予熱器、３ 白煙防止空気予熱器、４ 集塵機、５ スクラバ、６ 排ガスファン、７ 第一の熱交換器、８ 加熱炉、９ 触媒反応塔、１０ 煙突、１１ 第二の熱交換器 [0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for reducing N ₂ O emission from an incinerator that incinerates sewage sludge and the like.
[0002]
[Prior art]
The global warming substance, at present mainly but carbon dioxide is a problem, nitrous oxide discharged from an incinerator (N ₂ O) showed a much greater greenhouse effect than carbon dioxide, and half Since the period is as long as 150 years, it is becoming a new problem as a global warming substance. Most of N ₂ O is generated from underground or underwater organisms, but N ₂ O is also contained in the combustion exhaust gas. For example, sewage sludge and coal combustion exhaust gas contain several hundred ppm of N ₂ O. There is a report that it is.
[0003]
For this reason, a technique for decomposing N ₂ O contained in combustion exhaust gas with an N ₂ O removal catalyst such as NiO, Fe ₂ O ₃ , CoO, CuO, zeolite, alumina, or the like has been proposed. However, the reaction temperature of the N ₂ O removal catalyst is usually a high temperature of 500 ° C. or higher, and is easily affected by dust, hydrogen chloride, etc. in the exhaust gas. Therefore, when the N ₂ O removal catalyst is incorporated in the actual equipment, a flow as shown in FIG. 2 is adopted.
[0004]
That is, in this flow, the exhaust gas of the incinerator 1 to remove the dust in the dust collector 4 then passed through a fluidized air preheater 2 and white smoke prevention air preheater 3, further removing the SO _X or hydrogen chloride scrubber 5. Since the exhaust gas that has passed through the scrubber 5 has dropped to about 40 ° C., the exhaust gas fan 6 raises the temperature to about 450 ° C. through the first heat exchanger 7 , and then sends it to the heating furnace 8 to raise the temperature again. The heating furnace 8 raises the temperature of the exhaust gas to a temperature necessary for the reaction (for example, 550 ° C.) using fossil fuel, and decomposes it in contact with the N ₂ O removal catalyst in the catalytic reaction tower 9. Thereafter, the exhaust gas is exhausted by the first heat exchanger 7 and then discharged from the chimney 10.
[0005]
However, in such a conventional flow, since it is necessary to heat the exhaust gas using fossil fuel, carbon dioxide gas is newly generated in the process of reducing emission of N ₂ O, which is a global warming substance, The system as a whole remains questionable about the effect of reducing emissions of global warming substances. Especially will consume a large amount of fossil fuel in a heating furnace 8 so it is preferable to react at a high temperature of at least 500 ° C. In order to sufficiently decompose N ₂ O, by generating carbon dioxide gas is global warming substances End up.
[0006]
In addition, conventionally proposed N ₂ O removal catalysts such as NiO, Fe ₂ O ₃ , CoO, CuO, zeolite, and alumina are poisoned by sulfur oxides, hydrogen chloride, and the like in the exhaust gas, and the activity decreases. For this reason, there has been a problem that the catalyst for removing N ₂ O in the exhaust gas still lacks practicality.
[0007]
[Problems to be solved by the invention]
The present invention solves the above-mentioned conventional problems and aims to reduce emission of global warming substances in the entire system by raising the temperature of the exhaust gas to the reaction temperature of the N ₂ O removal catalyst without using fossil fuel. The main object of the present invention is to provide a method for reducing N ₂ O emission from an incinerator . Another object of the present invention is to provide a superior catalyst utility that can reliably remove N ₂ O in the exhaust gas, to provide a N ₂ O emissions reduction method from incinerators.
[0008]
[Means for Solving the Problems]
The present invention made to solve the above-mentioned problems includes a step of conducting heat release from the exhaust gas by introducing the exhaust gas containing N ₂ O discharged from the incinerator to the first heat exchanger, and a temperature by the heat release. There performed dedusting led to a dust collector the exhaust gas drops, followed and performing SO _X and HCl removal led to scrubber, the exhaust gas dust removal and SO _X and HCl removal is made to the second heat exchanger A step of conducting heat absorption by guiding the exhaust gas whose temperature has risen due to heat absorption by the second heat exchanger to the first heat exchanger and further performing heat absorption; and performing thermal decomposition of N ₂ O to the exhaust gas temperature was raised to 550 ° C. to 650 ° C. by the heat absorbed is guided to the catalytic reaction tower, the second heat exchange gas to N ₂ O is removed by the thermal decomposition A process of conducting heat from the exhaust gas, It is characterized in reducing the N ₂ O emissions from incinerator by Ranaru method.
[0009]
Incidentally, the catalyst to be filled in the catalytic reaction tower is preferably a stannate obtained from Sn or SnCl ₄ · 5H ₂ O is N ₂ O removal catalyst as a raw material. The catalyst to be filled in the catalytic reaction tower is preferably Pt or Pd is N2O removal catalyst supported on TiO _2. As the N2O removal catalyst in which Pt or Pd is supported on TiO ₂ , Pt or Pd and Ti are converted into a molecule by reacting a Pt or Pd salt, an organic compound of Ti and an organic conjugate in a solvent. A product obtained by synthesizing an organometallic precursor containing the precursor and heating it is particularly preferred because of its high activity.
[0010]
According to the method of the present invention, the exhaust gas that has passed through the scrubber is heated by the second heat exchanger, and then returned to the first heat exchanger installed at the incinerator outlet to heat the exhaust gas at the incinerator outlet. Since the temperature is further increased by exchange and N ₂ O is removed through the catalytic reaction tower, it is not necessary to heat the exhaust gas using fossil fuel as in the conventional method shown in FIG. Therefore, N ₂ O can be decomposed without generating excess carbon dioxide gas, and the emission of global warming substances in the entire system can be reduced. In this flow, if a catalyst such as the above-described N ₂ O removal catalyst using stannic acid or an N ₂ O removal catalyst in which Pt or Pd is supported on TiO ₂ is used, sulfur oxide, hydrogen chloride, etc. in the exhaust gas Therefore, it is possible to perform exhaust gas treatment with excellent practicality.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention are shown below.
FIG. 1 is a flow sheet showing a preferred embodiment of the present invention, in which a first heat exchanger 7 is arranged at an outlet portion of an incinerator 1 for burning sewage sludge and coal. The high-temperature exhaust gas at 800 to 900 ° C. discharged from the incinerator 1 first passes through the first heat exchanger 7 and passes through the fluidized air preheater 2 and the white smoke-preventing air preheater in the same manner as in the past. The dust is removed at 4 and the SO _X and hydrogen chloride are removed at the scrubber 5.
[0012]
The exhaust gas which has been cooled to approximately 40 ° C. by passing through the scrubber 5 is heated by the exhaust gas fan 6 to the second sent of the heat exchanger 11, for example 390 ° C., further first heat exchanger of the furnace outlets and the The temperature is further raised until the temperature reaches a temperature suitable for the catalytic reaction (for example, 550 ° C.) by heat exchange with the high-temperature exhaust gas. The exhaust gas heated in this way is passed through the catalytic reaction tower 9 to remove N ₂ O. When passing through the second heat exchanger 11 , the exhaust gas is preheated and discharged from the chimney 10.
[0013]
As described above, in the present invention, the exhaust gas is heated up to a temperature suitable for the reaction of the N ₂ O removal catalyst by the first heat exchanger 7 at the furnace outlet instead of the conventional heating furnace 8 for burning fossil fuel. since the way, it is possible to eliminate the generation of excess carbon dioxide, and since it decompose N ₂ O in the exhaust gas as in the conventional, it is possible to reduce emissions of the entire system global warming substances.
[0014]
Below, preferable embodiment of each component is described in detail. First, the catalyst reaction tower 9 is filled with the N ₂ O removal catalyst. However, in addition to filling the catalyst reaction tower 9 alone, it is possible to install a NOx removal catalyst in the previous stage and fill the N ₂ O removal catalyst in the subsequent stage. Thereby, NOx in the exhaust gas can also be decomposed. In addition, in the N ₂ O removal catalyst in which Pt or Pd is supported on TiO ₂ , dioxins and odors can be removed at the same time. In any case, the temperature of the N ₂ O removal catalyst is preferably 250 to 650 ° C., more preferably 550 to 650 ° C.
[0015]
The SV value of the N ₂ O removal catalyst packed in the catalytic reaction tower 9 is 500 to 20000 h ⁻¹ , more preferably 2000 to 8000 h ⁻¹ . The shape of the N2O removal catalyst is preferably a pellet or a honeycomb. In the case of pellets, the size is about 1 to 20 mm, more preferably about 5 to 10 mm. Moreover, when it is set as a honeycomb, the equivalent diameter of the through-hole is 1-30 mm, More preferably, it is 2-10 mm, and it is preferable that an aperture ratio shall be 50% or more.
[0016]
In the invention of claim 2, a catalyst made of stannic acid (SnO ₂ .nH ₂ O) obtained from Sn or SnCl ₄ .5H ₂ O as a raw material is used as the N ₂ O removal catalyst. The catalyst, as a primary component, SnO ₂ and (IV). In general, SnO ₂ is difficult to obtain with a high surface area. However, stannic acid is a white crystal in which Sn or SnCl ₄ · 5H ₂ O is used as a starting material and dissolved in a solvent, and NH ₄ OH is precipitated as a precipitating agent. The catalyst obtained by calcining at about 300 ° C. has a large specific surface area of 30 to 100 m ² / g. For this reason, high catalytic activity can be exhibited.
[0017]
In the invention of claim 3, it was supported Pt or Pd on TiO ₂ N2O removal catalyst is used. In the present invention, it is preferable to support Pt or Pd as a main component on anatase type TiO ₂ in an amount of about 0.2 to 5% by weight, and this TiO ₂ can be coated on a cordierite honeycomb. In this case, the amount of TiO ₂ with respect to the cordierite honeycomb is preferably 30 to 200 g / L.
[0018]
As a method for supporting Pt or Pd on TiO ₂ , a method can be used in which a solution of a salt of Pt or Pd is coated on TiO ₂ and thermally decomposed to precipitate Pt or Pd. However, in this method, the precipitated particle size of Pt or Pd is increased and the active sites are decreased, so that the catalytic effect may not be sufficiently exhibited. Therefore, as shown in claim 4, an organometallic precursor containing Pt or Pd and Ti in a molecule is synthesized by reacting a salt of Pt or Pd, an organic compound of Ti and an organic conjugate in a solvent. It is preferable to use an N ₂ O removal catalyst obtained by heating this.
[0019]
In this case, an alkoxide derivative of Ti can be used as the organic compound of Ti, and amino acids such as lysine, glycine, and proline can be used as the organic conjugate. Specifically, a soluble salt of Pt or Pd such as chloroplatinic acid or palladium chloride is dissolved in a solvent together with an amino acid and an alkoxide derivative of Ti. Ti ions and Pt or Pd ions are bonded and fixed in the molecule by this organic bond, and when heated, an organometallic precursor in which each component is evenly dispersed at the molecular level is obtained.
[0020]
In this state, Ti ions and Pt or Pd ions are bonded via amino acids, but when heated to around 500 ° C., the amino acids are burned out and the organometallic precursor is decomposed, and Pt or Pd is made into ultrafine particles. Thus, a highly active N ₂ O removal catalyst highly dispersed in Ti can be obtained. This catalyst can also exhibit high catalytic activity against exhaust gas, and is excellent in practicality.
[0021]
The effect of the N ₂ O removal catalyst as described above can be further enhanced by using it in combination with a reducing agent. The reducing agent such as methane, ethane, propane, ethylene, can be a hydrocarbon such as propylene, the injection volume can be less than or equal to 5 times the theoretical molar equivalent necessary for the breakdown of the N ₂ O. In the case of installing a NOx removal catalyst upstream of N ₂ O removal catalyst, it is preferred to inject the reducing agent between the NOx removal catalyst and the N ₂ O removal catalyst.
[0022]
【Example】
Examples of the present invention are shown below.
In general sewage sludge incineration, an N ₂ O decomposition experiment was performed by the conventional flow shown in FIG. 2 and the flow of the present invention shown in FIG. For comparison, the case where the flow without the N ₂ O removal catalyst shown in FIG. 3 was used was also shown. The incinerator of the embodiment has an exhaust gas amount of 13000 m ³ N / h at the flue gas processing tower, has a CO ₂ concentration of 11% and an N ₂ O concentration of 380 ppm, and operates for 24 hours over 330 days a year. It is. Note that the global warming potential is CO ₂ = 1, N ₂ O = 310, and CH ₄ = 21.
[0023]
Table 1 shows the results of measuring CO ₂ and N ₂ O released into the atmosphere by changing the type of catalyst in each flow and converting them into annual emissions. Thus, compared with the case where there is no N ₂ O removal catalyst, the CO ₂ equivalent value of the annual emissions of global warming substances is greatly reduced even by the conventional flow. However, according to the flow of the present invention, fossil fuel is not used, so it can be seen that the annual emission of global warming substances can be further reduced.
[0024]
[Table 1]

[0025]
【The invention's effect】
As described above, according to the present invention, the exhaust gas can be heated up to the reaction temperature of the N ₂ O removal catalyst without using fossil fuel, and the amount of global warming substances discharged as a whole system can be reduced. It can be reduced more than the law. Further, the N ₂ O removal catalyst described in claim 2 and below is excellent in practicality that can exhibit high activity even when applied to exhaust gas, and reliably removes N ₂ O in the exhaust gas. There is an advantage that can be.
[Brief description of the drawings]
FIG. 1 is a flow sheet showing an embodiment of the present invention.
FIG. 2 is a flow sheet showing a conventional example.
3 is a flow sheet showing a conventional example is not performed N ₂ O removal.
[Explanation of symbols]
1 incinerator, 2 fluid air preheater, 3 white smoke prevention air preheater, 4 dust collector, 5 scrubber, 6 exhaust gas fan, 7 1st heat exchanger , 8 heating furnace, 9 catalytic reaction tower, 10 chimney, 11 Second heat exchanger

Claims (4)

N discharged from the incinerator ₂ Introducing exhaust gas containing O to the first heat exchanger and releasing heat from the exhaust gas;
The exhaust gas whose temperature has decreased due to the heat release is led to a dust collector to remove dust, and then led to a scrubber to be SO. _X And removing HCl;
Dust removal and SO _X And a step of conducting heat absorption by introducing the exhaust gas from which HCl has been removed to a second heat exchanger;
A step of conducting heat absorption by introducing the exhaust gas whose temperature has increased by heat absorption in the second heat exchanger to the first heat exchanger; and
The exhaust gas heated to 550 ° C. to 650 ° C. by the continuous heat absorption is led to the catalytic reaction tower, and N ₂ A step of thermally decomposing O;
N by the thermal decomposition ₂ Introducing the exhaust gas from which O has been removed to the second heat exchanger to release heat from the exhaust gas;
N from an incinerator characterized by comprising ₂ O emission reduction method. _{2. The} method for reducing N ₂ O emission from an incinerator according to claim 1, wherein the catalyst charged in the catalytic reaction tower is an N ₂ O removal catalyst using stannic acid obtained from Sn or SnCl ₄ .5H ₂ O as a raw material . _{2. The} method for reducing N ₂ O emission from an incinerator according to claim 1, wherein the catalyst charged in the catalytic reaction tower is an N ₂ O removal catalyst in which Pt or Pd is supported on TiO ₂ . An N2O removal catalyst in which Pt or Pd is supported on TiO ₂ is an organic compound containing Pt or Pd and Ti in the molecule by reacting a Pt or Pd salt, an organic compound of Ti and an organic conjugate in a solvent. The method for reducing N ₂ O emission from an incinerator according to claim 3, which is obtained by synthesizing a metal precursor and heating it .

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