JP2000189756A - Treatment method of combustion exhaust gas - Google Patents

Abstract

(57) [Summary] A combustion exhaust gas improved to adopt a decomposition temperature of 250 ° C. or lower required from the viewpoint of decomposition of chlorinated organic compounds and to prevent precipitation of acidic ammonium sulfate on the catalyst surface. Is provided. SOLUTION: The following conditions (a) to (d) are satisfied. (A) Two types of catalysts, a low oxidation performance catalyst (X) having an SO ₂ oxidation conversion of 1.3% or less and a high oxidation performance catalyst (Y) having a conversion of 3.0% or more, are used. (B) The step of contacting the combustion exhaust gas with each catalyst is performed in any order and at a temperature in the range of 100 to 250 ° C. (C) In the case where the step of contacting with the catalyst (X) is preceded, ammonia is introduced into the flue gas flowing into the step of contacting with the catalyst (X). The concentration is adjusted to be 20 ppm or less. (D) When prior to the contacting step with the catalyst (Y), the catalyst
Introduce ammonia into the flue gas flowing into the contact step with (X)

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for treating flue gas, and more particularly, to a method for treating flue gas for removing chlorinated organic compounds and nitrogen oxides.

[0002]

2. Description of the Related Art Combustion exhaust gas discharged from incinerators for treating municipal garbage and industrial waste contains various harmful components, but is highly toxic dioxin and its precursor, an aromatic chlorine compound. Of particular importance is the removal of chlorinated organic compounds such as nitrogen oxides, which are the causative agents of photochemical smog.

Various methods are known for removing chlorinated organic compounds from combustion exhaust gas. Particularly, the catalytic cracking method is an excellent method for decomposing chlorinated organic compounds at 500 ° C. or lower. is there. By the way, the catalytic decomposition of chlorinated organic compounds is required to be performed at a temperature of 250 ° C. or less because once decomposed dioxin and the like are regenerated at a decomposition temperature of 300 ° C. or more.

On the other hand, as a method for removing nitrogen oxides from combustion exhaust gas, there is known a method for catalytic decomposition in the presence of ammonia as a reducing agent. By the way, normally, since sulfur dioxide is contained in the combustion exhaust gas, when the decomposition temperature is 300 ° C. or lower, there is a problem that ammonium ammonium sulfate generated by the reaction with ammonia precipitates on the catalyst surface and deteriorates the catalyst performance. There is.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a method for treating combustion exhaust gas for removing chlorinated organic compounds and nitrogen oxides, which comprises: Ammonium sulfate produced by the ammonia introduced into the exhaust gas for the decomposition of nitrogen oxides and the sulfur dioxide in the exhaust gas, adopting a decomposition temperature of 250 ° C. or less required from the viewpoint of the decomposition of the fluorinated organic compound It is an object of the present invention to provide a method for treating combustion exhaust gas which is improved so as to prevent the deposition on the catalyst surface.

[0006]

As a result of various studies, the present inventors have found that the above object can be easily achieved if two types of catalysts having specific performance are used under specific conditions. To complete the present invention.

That is, the gist of the present invention is a method for treating a combustion exhaust gas containing a chlorinated organic compound, sulfur dioxide and nitrogen oxide, which satisfies the following conditions (a) to (d). The present invention resides in a method for treating combustion exhaust gas.

(A) The catalyst has the ability to degrade chlorinated organic compounds and the ability to decompose nitrogen oxides in the presence of ammonia, and has an oxidation conversion of sulfur dioxide of 1.
A low oxidation performance catalyst (X) of 3% or less and a high oxidation performance catalyst (Y) having a chlorinated organic compound decomposability and an oxidation conversion of sulfur dioxide of 3.0% or more as defined below. use.

<Oxidation conversion of sulfur dioxide> Pressure: normal pressure, temperature: 250 ° C., SV (space velocity): 18
Under the conditions of 50 Hr ^-1 and a catalyst amount of 450 ml, a gas having a composition of O ₂ 10 vol%, SO ₂ 500 ppm, H ₂ O: 10 vol%, and N ₂ balance amount is supplied to the reaction tube filled with the catalyst. Then, the SO ₃ concentration and the total SO _X concentration at the outlet of the reaction tube are obtained, and the oxidation conversion (%) of sulfur dioxide is calculated by the following equation.

[0010]

## EQU2 ## (Outlet SO ₃ concentration / Outlet total SO _X ) × 10
0

(B) The contacting steps between the combustion exhaust gas and the low-oxidizing catalyst and the high-oxidizing catalyst are performed in an arbitrary order in 10
It is performed in a temperature range of 0 to 250 ° C.

(C) In the case where the step of contacting with the catalyst having low oxidation performance is preceded, ammonia is introduced into the flue gas flowing into the step of contacting with catalyst having low oxidation performance, and the amount of ammonia is introduced. Ammonia concentration is 20p
pm or less.

(D) In the case where the step of contacting with the catalyst having a high oxidation performance is preceded, ammonia is introduced into the combustion exhaust gas flowing into the step of contacting with the catalyst having a low oxidation performance.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the catalyst used in the present invention will be described. In the present invention, as a catalyst,
Low oxidation performance catalyst (X) having a chlorinated organic compound resolution and a nitrogen oxide resolution in the presence of ammonia, and having an oxidation conversion of sulfur dioxide of 1.3% or less as defined below (X)
And a high oxidation performance catalyst (Y) which has the ability to degrade chlorinated organic compounds and has an oxidation conversion of sulfur dioxide of 3.0% or more as defined below.

<Oxidation conversion of sulfur dioxide> Pressure: normal pressure, temperature: 250 ° C., SV (space velocity): 18
Under the conditions of 50 Hr ^-1 and a catalyst amount of 450 ml, a gas having a composition of O ₂ 10 vol%, SO ₂ 500 ppm, H ₂ O: 10 vol%, and N ₂ balance amount is supplied to the reaction tube filled with the catalyst. Then, the SO ₃ concentration and the total SO _X concentration at the outlet of the reaction tube are obtained, and the oxidation conversion (%) of sulfur dioxide is calculated by the following equation.

[0016]

(Equation 3) (Outlet SO ₃ concentration / Outlet total SO _X ) × 10
0

The low oxidizing performance catalyst (X) defined as described above can be used in a case where ammonia and sulfur dioxide (actually, sulfur oxides SO _X and H ₂ O) are present in the exhaust gas.
Although SO ₂ and SO ₃ are physically adsorbed, they have a characteristic that they hardly generate ammonium ammonium sulfate. By the way, usually, a catalyst having a low oxidation conversion of sulfur dioxide is
Decomposition performance of chlorinated organic compounds is low. Therefore, when only the low oxidation performance catalyst (X) is used, a large amount of the catalyst is required for a high removal rate of the chlorinated organic compound, and the efficiency is deteriorated.

Therefore, in the present invention, by using the high oxidation performance catalyst (Y) defined above, that is, a catalyst having a high decomposition performance of chlorinated organic compounds, a relatively small amount of catalyst in total is used. High removal rates of chlorinated organic compounds are achieved by volume. In the case of the high oxidation performance catalyst (Y), when ammonia and sulfur dioxide are present in the exhaust gas, at a temperature of 100 to 250 ° C., acidic ammonium sulfate is generated and adheres to the catalyst surface to cause a decrease in performance. Therefore, as described later, the high oxidation performance catalyst (Y) has an ammonia concentration of 20 ppm in the combustion exhaust gas.
Used under the following conditions:

The oxidation conversion of sulfur dioxide of the low oxidation catalyst (X) is preferably 0.8% or less from the viewpoint of more reliably preventing the formation of ammonium acid sulfate. The oxidative conversion rate is preferably 5% or more, and more preferably 6% or more, from the viewpoint of further increasing the removal rate of the chlorinated organic compound.

The above-mentioned different oxidation conversions of sulfur dioxide can be achieved by using catalysts having different compositions and types, and by changing the amount of the catalyst used. Examples of the active component of the catalyst include oxides of transition metals such as vanadium, copper, iron, chromium, and manganese, noble metals, zeolites, and the like. Of these, vanadium oxide, copper oxide,
Iron oxide and gold are preferred. Further, a catalyst containing vanadium oxide is particularly preferable because it is inexpensive, has a high decomposition rate of a chlorinated organic compound, and can decompose nitrogen oxide in the presence of ammonia.

When the above-mentioned metal active ingredient is used, a method of baking after mixing the aqueous solution of the active ingredient and the carrier well and then molding, or impregnating the molded carrier substrate with the aqueous solution of the active ingredient, followed by firing. To prepare a catalyst. When copper is used, for example, copper nitrate is dissolved in water to prepare an aqueous solution of the active ingredient. The amount of the transition metal oxide contained in the support varies depending on the method of using the catalyst, but is usually 0.1 to 40% by weight, preferably 1 to 30% by weight. From such a range, it is selected so as to achieve a desired oxidation conversion. For example, when the copper oxide (CuO) content is 5.0% or less, the low oxidation performance catalyst (X), 8.5%
In the case described above, a high oxidation performance catalyst (Y) is obtained.

Further, as a raw material of the vanadium oxide,
Although not particularly limited, vanadium pentoxide (V ₂ O ₅ ) or ammonium metavanadate is preferably used. These raw materials are usually used as a raw material liquid by dissolving in an oxalic acid aqueous solution or a monoethanolamine aqueous solution.

The content of the vanadium oxide varies depending on the method of using the catalyst, besides using it alone as an active ingredient, but it is usually 0.1 to 50% by weight, preferably 0.1 to 50% by weight.
40% by weight. Then, the catalyst is selected from such a range so as to achieve a desired oxidation conversion rate, and when the V ₂ O ₅ content is 2.5% by weight or less, the low oxidation performance catalyst (X);
When the content is 5% by weight or more, a high oxidation performance catalyst (Y) can be obtained.

Each of the above catalysts is usually used by being supported on a carrier. Although the carrier is not particularly limited, SO _X
From the viewpoint of treating the contained combustion exhaust gas, titania having excellent acid resistance is preferably used. As titania, TiO
_2- SiO ₂ , TiO ₂ -SiO ₂ -ZrO ₂ , TiO ₂ -W
A composite oxide such as O ₃ —SiO ₂ may be used. The amount of vanadium oxide supported is usually 0.1 to 5 as described above.
0% by weight, preferably 0.1 to 40% by weight.

The shape and size of each of the catalysts are determined by the presence or absence of dust in the combustion exhaust gas, the amount of processing gas,
It is appropriately selected depending on the size of the reactor and the like. Examples of the shape of the catalyst include a honeycomb shape, a column shape, a spherical shape, and a plate shape.

As a method for producing a honeycomb-shaped catalyst supported on a carrier, (a) a carrier component and a catalyst component or a raw material thereof are kneaded together with a forming aid, and then formed into a honeycomb shape by an extrusion molding method or the like. And (b) a method of impregnating and supporting a carrier component such as titania and a catalyst component on a honeycomb-shaped substrate. As an example of the above-mentioned manufacturing method (a), the following method is exemplified.

(1) Ammonium metavanadate and ammonium paratungstate are dissolved in an aqueous solution of about 10% by weight of monoethanolamine.

(2) Dissolve ammonium paramolybdate in water or an aqueous solution of about 10% by weight monoethanolamine.

(3) Powdery titania and the aqueous solution prepared in the above (1) and (2) are kneaded with a kneader.

(4) (i) The kneaded material obtained by further kneading with the addition of a molding aid is extruded, and is extruded at a temperature of 50 to 150 ° C. for 3 to 5 minutes.
After drying for 0 hour, the mixture is calcined at a temperature of 450 to 650 ° C. in an air stream of SV 100 to 2000 Hr ⁻¹ , or (ii) the kneaded material is dried at a temperature of 50 to 150 ° C. for 3 to 50 hours. After baking at a temperature of ° C., a molding aid is added and molded.

As an example of the above-mentioned manufacturing method (b), the following method is exemplified. That is, cylindrical, spherical,
A carrier component is coated on a substrate having a desired shape such as a honeycomb shape or a plate shape, and the aqueous solution prepared in the above (1) or (2) is applied to impregnate the catalyst component.
Baking at a temperature of 650 ° C.

In the case of a catalyst formed on a substrate, silica (SiO ₂ ), alumina (Al ₂ O ₃ ), or the like may be used in addition to titania as a carrier component. At that time, the amount of titania is usually 30% by weight or more, preferably 40 to 97% by weight, based on the total amount of the carrier component and the catalyst component.
The total amount of the carrier component and the catalyst component is usually 5 to 70% by weight, preferably 10 to 50% by weight, based on the total amount of the base material, the carrier component and the catalyst component.

When the raw materials added as in the kneading / forming method are all catalyst components, the catalyst composition is estimated from the added amount on the assumption that the raw material components such as metal salts have changed into the corresponding metal oxides. . When the catalyst is manufactured by the impregnation method, the catalyst is treated with hydrofluoric acid, then melted with ammonium sulfate, and plasma emission spectrometry (ICP-AE) is performed.
S analysis) to determine the catalyst composition.

Next, the method for treating combustion exhaust gas of the present invention will be described. In the present invention, each contacting step between the combustion exhaust gas and the low oxidizing performance catalyst and the high oxidizing performance catalyst is performed in an arbitrary order and in a temperature range of 100 to 250 ° C. The condition at a contact temperature of 250 ° C. or less is a condition defined from the viewpoint of preventing regeneration of decomposed dioxin and the like as described above, and the condition at a contact temperature of 100 ° C. or more hinders the operation of the apparatus. This is a condition specified from the viewpoint of reliably preventing dew condensation. The pressure during the contact treatment is usually -0.0
3 to 9 kg / cm ² , preferably 0.01 to 5 kg / c
m ² . SV is usually 100 to 50,000H
r ⁻¹ , preferably 1000 to 20000 Hr ⁻¹ .

As the combustion exhaust gas to be treated by the treatment method of the present invention, an exhaust gas containing a chlorinated organic compound, usually 0.1 ppm or more of NO _x , usually 0.1 ppm or more of SO _x , such as municipal waste or industrial waste Exhaust gas and the like when a substance or the like is burned. Such flue gas usually contains
2,3,7,8-tetrachlorodibenzodioxin,
Dioxins represented by 2,3,4,7,8-pentachlorodibenzofuran are 10 to 200 ng / Nm
³ (Equivalent value of toxicity) is included. Furthermore, chlorinated organic compounds such as monochlorobenzene, dichlorobenzene or o-chlorophenol or chlorobenzofuran, which are precursors of these dioxins, are also included.

The above combustion exhaust gas is usually introduced into a contact step after passing through a bag filter to remove dust and heavy metals. If necessary, an acidic gas may be removed by treating with an alkali washing tower before treating with a bag filter.

In the present invention, when the step of contacting with the catalyst having a low oxidation performance is preceded, ammonia is introduced into the flue gas flowing into the step of contacting with the catalyst having a low oxidation performance. The amount is adjusted so that the ammonia concentration in the exhaust gas becomes 20 ppm or less.

That is, in the above case, the first step of contacting with the catalyst having a low oxidation performance is performed in the presence of ammonia to decompose nitrogen oxides. At this time, ammonium acid sulfate is hardly generated because the catalyst has low oxidizing property. Therefore, at the same time as the decomposition of the nitrogen oxides, the chlorinated organic compounds are decomposed at a high level corresponding to the capacity of the low oxidation performance catalyst. The amount of ammonia introduced into the combustion exhaust gas is determined so that nitrogen oxides can be highly decomposed under the above conditions.
The amount of consumption of ammonia in the flue gas is determined by the temperature and the amount of the flue gas, the amount of the catalyst used, the gas contact area, and the like. The chlorinated organic compound remaining in the combustion exhaust gas flowing out of the first step is decomposed in the second step, a step of contacting with a high oxidation performance catalyst.
At this time, almost no ammonium ammonium sulfate is generated because the ammonia concentration in the combustion exhaust gas is suppressed to 20 ppm or less.

On the other hand, in the present invention, when the step of contacting with the catalyst having a high oxidizing performance is preceded, ammonia is introduced into the combustion exhaust gas flowing into the step of contacting with the catalyst having a low oxidizing performance.

That is, in the above case, the first step, the step of contacting with the catalyst having a high oxidation performance, decomposes the chlorinated organic compound and does not substantially decompose nitrogen oxides, so that the step To do. When ammonia is introduced into the incinerator for partial decomposition of nitrogen oxides, the amount of ammonia introduced into the incinerator is adjusted so that the ammonia concentration in the combustion exhaust gas becomes 20 ppm or less. Nitrogen oxides in the combustion exhaust gas flowing out of the first step are decomposed in the second step, a step of contacting with a low oxidation performance catalyst. At this time, ammonium acid sulfate is hardly generated because the catalyst has low oxidizing property. Therefore, the amount of ammonia introduced into the combustion exhaust gas (outflow gas from the above-mentioned first step) flowing into the contact step with the low oxidation performance catalyst is:
It is arbitrarily determined so that nitrogen oxides can be highly decomposed.

The size and shape of the reactor in each of the above contacting steps can be arbitrarily selected without departing from the object of the present invention. Further, each catalyst may be charged in a separate reactor or may be charged in the same reactor as different layers.

[0042]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. The catalysts (A) to (E) used in the following examples were prepared as follows.

<Preparation of Catalyst (A)> 129 g of ammonium metavanadate and ammonium paratungstate 1
081 g was dissolved in 6000 g of a 10% by weight aqueous solution of monoethanolamine heated to 80 ° C. to prepare a raw material liquid (1). Separately, 73.6 g of ammonium paramolybdate
Was dissolved in 600 g of water to prepare a raw material liquid (2). The raw material liquid (1), the raw material liquid (2), 7,880 g of titania powder, and 1000 g of a forming aid were kneaded with a double-arm kneader for 2 hours, and the obtained kneaded product was formed into a honeycomb structure having a diameter of 5 mm by an extruder. The obtained molding is dried at a temperature of 130 ° C. overnight (about 10 hours), and then SV100Hr ⁻¹ ,
The mixture was calcined at a temperature of 600 ° C. for 3 hours to obtain a catalyst (A). Table 1 shows the composition of the catalyst (A) and its physical properties.

<Preparation of catalyst (B)> The preparation of catalyst (A) was the same as that of catalyst (A) except that the amount of ammonium metavanadate used was changed to 643 g and the amount of titania powder used was changed to 7480 g. Similarly, a catalyst (B) was prepared. Table 1 shows the composition of the catalyst (B) and the physical properties thereof.

<Preparation of catalyst (C)> The preparation of catalyst (A) was the same as that of catalyst (A) except that the amount of ammonium metavanadate used was changed to 516 g and the amount of titania powder used was changed to 7580 g. Similarly, a catalyst (C) was prepared. Table 1 shows the composition of the catalyst (C) and its physical properties.

<Preparation of Catalyst (D)> In the preparation of the catalyst (A), the raw material liquid (1) was used without using the raw material liquid (2).
An aqueous solution prepared by dissolving 1519 g of copper nitrate in 6000 g of water was used, and the used amount of titania powder was 8500.
Except having changed to g, catalyst (D) was prepared similarly to preparation of catalyst (A). Table 1 shows the composition of the catalyst (D) and the physical properties thereof.

<Preparation of Catalyst (E)> In the preparation of the catalyst (A), the raw material liquid (1) was used without using the raw material liquid (2).
An aqueous solution prepared by dissolving 2852 g of copper nitrate in 6000 g of water was used, and the used amount of titania powder was 8150 g.
Except having changed to g, catalyst (E) was prepared similarly to preparation of catalyst (A). Table 1 shows the composition of the catalyst (E) and its physical properties.

<Measurement of Sulfur Dioxide Oxidation Conversion> A sample of each of the above catalysts (A) to (E) was 450 ml (a honeycomb structure having six holes in each of the vertical and horizontal directions and a height of 300 mm). And filled into a reaction tube made of quartz glass. Next, the reaction tube was placed in a tubular electric furnace, and the temperature of the catalyst was maintained at 250 ° C. while flowing a predetermined amount of nitrogen gas and oxygen gas. Next, H ₂ is adjusted to a predetermined concentration.
O and SO ₂ gas were added. The gas composition is O ₂ 10 dry volume
%, SO ₂ 500 ppm, H ₂ O 10 volume%, N ₂ balance amount, and the gas preparation amount (rate) was 835 NL / Hr.

The above-mentioned gas was passed through the reaction tube for 70 hours.
The O ₃ concentration was measured. Next, the gas at the outlet of the reaction tube was sampled again to measure the total SO _X concentration. S
Sampling of O ₃ was performed by collecting only SO _{3 of} SO _X using a spiral tube type collection tube. Then, the collected SO ₃ is washed out with water, and JIS K
The sample was analyzed by the precipitation titration method of No. 103. Sampling and analysis of total SO _X were performed according to the method of JIS K0103. The oxidation conversion of sulfur dioxide was determined by the following equation.

[0050]

## EQU4 ## (Outlet SO ₃ concentration / Outlet total SO _X ) × 10
0

Example 1 A catalyst having a honeycomb structure of 15 cm × 15 cm × 70 cm was placed in a reaction tower having a vertical inner diameter of 45 cm, a horizontal inner diameter of 45 cm, and a height of 5 m at a ratio of 3 × 3 (total 9) in one stage. Five stages were stacked, the first three stages were filled with the catalyst (A), and the second two stages were filled with the catalyst (B), and an atmospheric pressure fixed bed flow reactor was assembled. And
Using this apparatus, a treatment test of a model exhaust gas from a municipal waste incinerator was performed as follows.

At a temperature of 200 ° C. and an SV of 3000 Hr ⁻¹ , while adding ammonia having an average concentration of 80 ppm,
The above device, was passed through a gas containing NO _x of dioxins mean concentration 0.3ng-TEQ / Nm ³ and the average concentration 20ppm of SO ₂ Mean concentration 100 ppm.
The amount of added ammonia was measured by measuring the ammonia concentration immediately before the catalyst (B) (immediately after the first three stages) and adjusting the value to 20 ppm or less.

The exhaust gas after treatment was analyzed by gas chromatography mass spectrometry in "Manual for Standard Measurement and Analysis of Dioxins in Waste Disposal" (Environmental Improvement Division, Water Environment Department, Ministry of Health and Welfare, Ministry of Health and Welfare, February 1997). I went according to.
The analysis was performed two weeks and four months after passing the gas. Table 2 shows the evaluation results.

Example 2 In Example 1, when assembling a normal-pressure fixed-bed flow reactor, the first two stages were filled with the catalyst (B) and the third three stages were filled with the catalyst (A). Then, the ammonia addition position is set immediately before the catalyst (A) (immediately after the first two stages), and the ammonia addition amount is set to an average N
A treatment test of a model exhaust gas from a municipal waste incinerator in the same manner as in Example 1 except that the molar ratio (NO _x / NH ₃ ) was set to 1 with respect to the O _x concentration, and the analysis was performed one week and three months later. Was done. Table 3 shows the evaluation results.

Example 3 Three glass reactors each having an inner diameter of 5 cm and a length of 60 cm filled with a catalyst having a honeycomb structure of 3 cm × 3 cm × 50 cm were connected in series, and a vertical inner diameter of 80 cm, a horizontal inner diameter of 80 cm and a height of 1. It was installed in a 5 m constant temperature bath. The catalyst (D) was charged into the first two reactors and the catalyst (E) was charged into the second reactor, and a normal pressure fixed bed flow reactor was assembled. Using this apparatus, a treatment test of a model exhaust gas from a municipal waste incinerator was performed as follows.

At a temperature of 200 ° C. and an SV of 1000 Hr ⁻¹ , while adding ammonia having an average concentration of 60 ppm,
Dioxins having an average concentration of 1 ng-TEQ / Nm ³ , SO ₂ having an average concentration of 5 ppm, and an average concentration of 75
A gas containing ppm NO _x was passed. The addition amount of ammonia was measured by measuring the ammonia concentration immediately before the catalyst (E) (immediately after the previous two reactors) and adjusting the value to 20 ppm or less. The exhaust gas after the treatment was analyzed in the same manner as in Example 1. Table 4 shows the evaluation results.

COMPARATIVE EXAMPLE 1 In Example 1, the measurement result of the ammonia concentration immediately after the first three stages was obtained by using a normal pressure fixed bed flow reactor assembled by filling the catalyst (C) into all five stages of the honeycomb structure. A model exhaust gas treatment test was performed in the same manner as in Example 1 except that the amount of added ammonia was not adjusted based on the above. Table 5 shows the evaluation results.

[0058]

[Table 1]

[0059]

[Table 2]

[0060]

[Table 3]

[0061]

[Table 4]

[0062]

[Table 5]

[0063]

According to the present invention described above, deterioration of the catalyst over time can be suppressed by minimizing the amount of acidic ammonium sulfate generated from the sulfur oxide.
Chlorinated organic compounds such as dioxins and nitrogen oxides in flue gas can be removed with high efficiency. Also,
According to the present invention, once decomposed dioxin or the like does not regenerate.

[Procedure amendment]

[Submission date] January 21, 2000 (2000.1.2
1)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0048

[Correction method] Change

[Correction contents]

<Measurement of Sulfur Dioxide Oxidation Conversion> Each of the catalysts (A) to (E) was prepared in a volume of 450 ml (a honeycomb structure having six holes in each of the vertical and horizontal directions and a height of 500 mm). The sample was processed and filled in a quartz glass reaction tube. Next, the reaction tube was placed in a tubular electric furnace, and the temperature of the catalyst was maintained at 250 ° C. while flowing a predetermined amount of nitrogen gas and oxygen gas. Next, H ₂ is adjusted to a predetermined concentration.
O and SO ₂ gas were added. The gas composition is O ₂ 10 dry volume
%, SO ₂ 500 ppm, H ₂ O 10 volume%, N ₂ balance amount, and the gas preparation amount (rate) was 835 NL / Hr.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0062

[Correction method] Change

[Correction contents]

[0062]

[Table 5]

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Kenichi Seino 1 Toho-cho, Yokkaichi-shi, Mie Mitsubishi Chemical Corporation Yokkaichi Office (72) Inventor Masaaki Uchida 13-2 Kitaminato-machi, Wakamatsu-ku, Kitakyushu-shi, Fukuoka (72) Inventor Kiyoshi Nagano 13-2 Kitaminato-machi, Wakamatsu-ku, Kitakyushu-city, Fukuoka Prefecture Inventor Shigeru Sugino 5-72 Shiba, Minato-ku, Tokyo 34-6 Mitsubishi Chemical Engineering Corporation (72) Inventor Akihiro Yamauchi 5-34-6 Shiba, Minato-ku, Tokyo Mitsubishi Chemical Engineering Corporation

Claims (4)

[Claims] 1. A method for treating a combustion exhaust gas containing a chlorinated organic compound, sulfur dioxide and nitrogen oxide, wherein the method satisfies the following conditions (a) to (d): Processing method. (A) a low oxidation performance catalyst (X) having a chlorinated organic compound resolution and a nitrogen oxide resolution in the presence of ammonia and having an oxidation conversion of sulfur dioxide of 1.3% or less as defined below. It has the ability to degrade chlorinated organic compounds and has an oxidation conversion of sulfur dioxide of 3.0% as defined below.
Two kinds of the above-mentioned high oxidation performance catalysts (Y) are used. <Oxidation conversion of sulfur dioxide> Pressure: normal pressure, temperature: 250 ° C, SV (space velocity): 18
Under the conditions of 50 Hr ^-1 and a catalyst amount of 450 ml, a gas having a composition of O ₂ 10 vol%, SO ₂ 500 ppm, H ₂ O: 10 vol%, and N ₂ balance amount is supplied to the reaction tube filled with the catalyst. Then, the SO ₃ concentration and the total SO _X concentration at the outlet of the reaction tube are obtained, and the oxidation conversion (%) of sulfur dioxide is calculated by the following equation. ## EQU1 ## (Outlet SO ₃ concentration / Outlet total SO _X ) × 10
0 (b) The contacting steps between the combustion exhaust gas and the low oxidizing performance catalyst and the high oxidizing performance catalyst are performed in an arbitrary order at 100 to 250 ° C.
The temperature range is as follows. (C) When prior to the contacting step with the low oxidation performance catalyst,
Ammonia is introduced into the flue gas flowing into the contact step with the low oxidation performance catalyst, and the amount is adjusted so that the ammonia concentration in the flue gas flowing out from the step becomes 20 ppm or less. (D) When prior to the contacting step with the high oxidation performance catalyst,
Ammonia is introduced into the combustion exhaust gas flowing into the contact step with the low oxidation performance catalyst. 2. The oxidation conversion rate of the high oxidation performance catalyst is 4.2%.
The processing method according to claim 1, which is as described above. 3. The treatment method according to claim 1, wherein each of the catalysts is a catalyst containing vanadium oxide or copper oxide. 4. The treatment method according to claim 1, wherein each of the catalysts is a catalyst supported on titania.