JPH0788334A - Low temperature denitration method - Google Patents

Abstract

(57) [Summary] [Object] The present invention is to remove and reduce nitrogen oxides from exhaust gas containing nitrogen oxides at 90 ° C to 150 ° C.
To provide an effective denitration method in the low temperature region of. [Constitution] Manganese ore having a product of manganese dioxide (MnO ₂ ) weight fraction and specific surface area of 5 m ² / g or more, or an X-ray diffraction diffraction plane spacing of 2.15 ± 0.05Å, 2.
It has peaks at 39 ± 0.05Å and 3.11 ± 0.05Å, and the peak intensity of 2.39 ± 0.05Å is the strongest among the three peaks, and the intensity ratio of the other two peaks to this peak. Is used as a catalyst, and denitration is performed at a temperature of 90 ° C. or more and 150 ° C. or less. [Effect] An inexpensive denitration catalyst can be provided using manganese ore.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a denitration method for removing or reducing nitrogen oxides in exhaust gas containing nitrogen oxides generated in, for example, ironworks and power plants.

[0002]

2. Description of the Related Art Generally, for removing nitrogen oxides in exhaust gas,
As shown in page 5, line 253, "Catalyst Lecture" Vol. 7 (Catalyst Society), V ₂ as an ammonia reduction denitration catalyst was used.
O ₅ -TiO ₂ catalyst has been used. As a method of utilizing an iron-making raw material, a method of utilizing iron ore as a denitration catalyst as disclosed in JP-A-57-15824 is also considered.

Further, as seen in JP-A-51-62181, manganese dioxide is known to be highly active as a denitration catalyst at low temperatures.

[0004]

[Problems to be solved by the invention] However, "catalyst course"
The method shown in Volume 7 has a problem that the catalyst is very expensive because vanadium is used. Further, in the method disclosed in JP-A-57-15824, the reaction temperature is 300 to 370 ° C., and heating is required for application to low temperature exhaust gas of 150 ° C. or lower, such as steel plant sintering exhaust gas. there were. Further, in the method using manganese dioxide disclosed in JP-A-51-62181,
Similarly, the catalyst is expensive.

The present invention is inexpensive and effective in removing or reducing nitrogen oxides from exhaust gas containing nitrogen oxides.
It is an object of the present invention to provide a low-temperature denitration method capable of effectively removing or reducing in a low temperature range of 0 ° C to 150 ° C.

[0006]

The present invention focuses on a manganese ore containing manganese dioxide which is effective as a low temperature denitration catalyst for solving the above problems, and investigates the denitration activity of various manganese ores and various methods. As a result of the analysis by the present invention, the present invention was achieved.

That is, the first aspect of the present invention relates to nitrogen oxide (N
In the low temperature denitration method of removing or reducing nitrogen oxides using a catalyst with ammonia as a reducing agent, the product of manganese dioxide (MnO ₂ ) weight fraction and specific surface area contained is 5 m ² / g or more. Is a low temperature denitration method in which denitration is performed at a temperature of 90 ° C. or higher and 150 ° C. or lower using the manganese ore of No. 1 as a catalyst.

The second aspect of the present invention is directed to nitrogen oxides (NO
x) A low-temperature denitration method in which ammonia is used as a reducing agent from the exhaust gas contained and a nitrogen oxide is removed or reduced by using a catalyst, and the diffraction plane spacing is 2.15 ± 0.05Å by X-ray diffraction
It has peaks at 2.39 ± 0.05Å and 3.11 ± 0.05Å, and of the three peaks is 2.39 ± 0.05Å
Is the strongest peak intensity, and a low temperature denitration method in which denitration is performed at a temperature of 90 ° C to 150 ° C using a manganese ore having a structure in which the intensity ratio of the other two peaks to this peak is 0.2 or more. is there.

As the manganese ore used here, the one used in the iron making process can be diverted and used without sizing and crushing, but in order to ensure air permeability,
Grinding is desirable.

[0010]

[Function] When various manganese ores containing manganese dioxide were used to evaluate the denitration performance under various temperature conditions, it was found that the denitrification performance was significantly different in the low temperature region even if the ores having almost the same manganese dioxide weight fraction were used.

As a result of investigating the cause, 90 ° C. or higher 15
Under the temperature condition of 0 ° C or less, not only the manganese dioxide weight fraction but also the specific surface area are involved in the denitration performance. Under this temperature condition, the product of the specific surface area and the manganese dioxide weight fraction is highly correlated with the denitration performance. Turned out to be good.

When X-ray diffraction was performed on the manganese ore used for the denitration performance evaluation, it was found that the manganese ore having good denitration performance under the above temperature conditions has a unique diffraction pattern.

Here, the specific surface area was measured by the BET method ("Catalyst Lecture", Vol. 3, p. 204) using nitrogen as an adsorption gas. The weight fraction of manganese dioxide was determined by measuring the amount of active oxygen by the sodium oxalate decomposition potassium permanganate titration method (JIS-M8233 method for determining active oxygen in manganese ore) and using the conversion formula shown in Formula 1 below. The amount of manganese was used.

[0014]

## EQU1 ## (Amount of manganese dioxide) = (active oxygen) × 5.434

In the examples described below, these methods were all used. However, the specific surface area and the manganese dioxide weight fraction in the present invention may be examined by any method as long as the measurement results can obtain substantially the same measurement results without using these methods.

[0016]

EXAMPLES The present invention will be specifically described below with reference to examples.

As Example 1, manganese ore a (specific surface area; 28, specific surface area and manganese dioxide weight fraction were measured)
m ² / g, manganese dioxide weight fraction; 67%), 80-200 ° C., space velocity of about 5000 hr ⁻¹ , NO
x (NO + NO ₂ ); 200 ppm (NO; 195 pp
m, NO ₂ ; 5 ppm), H ₂ O; 10%, O ₂ ; 15
%, N ₂ ; NH ₃ 200 ppm in 75% model gas
A denitration test was conducted by adding the above components, and the correlation between the denitration performance (denitration rate) at each temperature, the specific surface area, and the manganese dioxide weight fraction was investigated.

As shown in Table 1, at 90 ° C. or higher and 150 ° C. or lower, the correlation of the product of the manganese dioxide weight fraction and the specific surface area is more than the correlation of the specific surface area and the manganese dioxide weight fraction with respect to the denitration performance. Better.

If the temperature is lower than 90 ° C., the temperature is too low, so that the denitration performance is extremely deteriorated and the correlation with the denitration performance is deteriorated. Further, when the temperature exceeds 150 ° C, the influence of the specific surface area on the denitration performance becomes small, and the manganese dioxide weight fraction becomes the strongest factor that determines the denitration performance.

[0020]

[Table 1]

As an example, FIG. 1 shows the relationship between the product of the manganese dioxide weight fraction and the specific surface area at 90 ° C. and the denitration rate. Table 2 shows the specific surface area and the manganese dioxide weight fraction of the manganese dioxide used.

As shown in FIG. 1, manganese ores could be classified into three groups with respect to denitration performance. That is, the group A having a product of manganese dioxide weight fraction and specific surface area of 5 m ² / g or more and a denitrification rate of 30% or more, a denitrification rate of manganese dioxide weight fraction and specific surface area of 3 or more and less than 5 m ² / g. Group B of 10% or more and less than 20%, the product of manganese dioxide weight fraction and specific surface area is less than 3 m ² / g, and the denitrification rate is 1
It can be classified into C group of less than 0%.

These relationships are established in the temperature range of 90 ° C to 150 ° C. Therefore, by using the manganese ore belonging to the A group as a catalyst, it is possible to efficiently proceed denitration in the temperature range of 90 ° C. or higher and 150 ° C. or lower.

[0024]

[Table 2]

As Example 2, the manganese ore of Example 1 was subjected to X-ray diffraction to examine the form of manganese contained therein. Since manganese ore is an ore and is composed of many elements such as iron in addition to manganese, the height and position of the diffraction peak do not exactly match the X-ray diffraction pattern of the pure manganese compound. It was found that the three groups shown in Example 1 each had a characteristic X-ray diffraction pattern.

Table 3 shows diffraction surface spacings up to the third in terms of peak intensity among peaks estimated to be manganese compound peaks, and peak intensity when the peak intensity of the strongest diffraction surface spacing among these peaks is 1. The ratio is shown.

[0027]

[Table 3]

That is, as shown in Table 2, in the group A, which has good low-temperature denitration performance, the diffraction surface spacing is 2.15 ± 0.05.
Has peaks at Å, 2.39 ± 0.05 Å, 3.11 ± 0.05 Å, and 2.39 ± 0.0 of the three peaks
The peak intensity of 5Å is the strongest, and the intensity ratio of the other two peaks to this peak is 0.2 or more. This peak is estimated to be α-MnO ₂ .

On the other hand, the group B, which has a low denitration performance, has diffraction surface spacing peaks at two common positions with the group A, but the peak intensity patterns are different, and
There is also a peak at 2.15 ± 0.05 Å in the group, but the peak intensity is small at 0.1 in terms of intensity ratio to the strongest diffraction plane spacing. Although the B group also contains the same type of manganese compound as the A group, it is considered that the main component is another manganese compound (presumed to be β-MnO ₂ ).

The C group, which shows almost no denitration performance, has only one peak in common with the A and B groups, but the peak patterns are also completely different, and the main components are completely different from those of the A and B groups. (Mn ₂ O ₃ and Mn ₃ O ₄ are estimated).

From the above, the diffraction plane spacing is 2.15 ±
0.05Å, 2.39 ± 0.05Å, 3.11 ± 0.0
It has a peak at 5Å and 2.39 out of the three peaks.
The peak intensity of ± 0.05Å is the strongest and the intensity ratio of the other two peaks to this peak is 0.2 or more.
It is possible to efficiently proceed denitration in a temperature range of ℃ or less.

[0032]

When the low temperature denitration method according to the present invention is applied, the following effects are obtained. (1) An inexpensive denitration catalyst can be provided by using manganese ore. (2) When it is used for flue gas denitration in a steelworks, the deteriorated ore can be reused as a manganese source for ironmaking.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a product of a manganese dioxide weight fraction and a specific surface area and a denitration rate.

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[Procedure amendment]

[Submission date] November 2, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0024

[Correction method] Change

[Correction content]

[0024]

[Table 2]

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Claims (2)

[Claims] 1. A low-temperature denitration method for removing or reducing nitrogen oxides by using a catalyst with ammonia as a reducing agent from exhaust gas containing nitrogen oxides (NOx), and the ratio to the weight fraction of manganese dioxide (MnO ₂ ) contained. Surface area product is 5m ²
/ G or more manganese ore as a catalyst, a low temperature denitration method of performing denitration at a temperature of 90 ° C or higher and 150 ° C or lower. 2. A low temperature denitration method in which ammonia is used as a reducing agent from a nitrogen oxide (NOx) -containing exhaust gas and a catalyst is used to remove or reduce the nitrogen oxide, and a diffraction plane interval of 2.15 ± 0. 05Å, 2.39 ± 0.05Å,
It has a peak at 3.11 ± 0.05Å and the peak intensity of 2.39 ± 0.05Å is the strongest among the three peaks, and the intensity ratio of the other two peaks to this peak is 0.2 or more. A low-temperature denitration method in which denitration is performed at a temperature of 90 ° C. or higher and 150 ° C. or lower using a structured manganese ore as a catalyst.