JP2003251145A - Remove for organic chlorine compound, nitrogen oxides and sulfur oxides and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a remover which economically and highly removes dioxins, organic chlorine compounds, nitrogen oxides, and sulfur oxides from exhaust gas. <P>SOLUTION: The remover for the organic chlorine compounds, the nitrogen oxides, and the sulfur oxides can be obtained through heat treatment of soil composed mainly of hydrated iron oxide at ≥200°C and ≤500°C, and a method for producing the same is also provided. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a remover for harmful substances such as dioxins, nitrogen oxides and sulfur oxides discharged from, for example, incinerators of municipal waste and industrial waste, iron and steel electric furnaces and the like. .

[0002]

2. Description of the Related Art Hitherto, as a method for reducing organic chlorine compounds such as dioxins generated in a combustion process, an adsorption method using activated carbon is generally performed. As an adsorption treatment method,
Mainly, the adsorption technology using a packed bed using activated carbon or activated coke as the adsorbent and the blowing technology of the powder adsorbent have been put into practical use. In addition, activated coke is disclosed in JP-A-58-12.
As disclosed in Japanese Patent Laid-Open No. 2042 and Japanese Patent Laid-Open No. 4-219308, it has been put to practical use as a remover for nitrogen oxides and sulfur oxides in exhaust gas.

Further, instead of activated carbon, for example, Japanese Patent Laid-Open No.
A method for suppressing dioxin in a refuse incinerator using an iron oxide catalyst has been developed as disclosed in Japanese Patent Laid-Open No. 1-267507. In this method, an iron oxide catalyst is blown into the combustion chamber or reburning chamber of a refuse incinerator to suppress dioxins. The iron oxide used here is prepared from reagents. For example, goethite powder is a ferrous hydroxide or iron carbonate obtained by reacting with one or more selected from ferrous salts, alkali hydroxides, alkali carbonates and ammonia. It can be obtained by aerating an oxygen-containing gas such as air into the suspension containing the contained precipitate to generate goethite particles. The hematite powder can be obtained by subjecting the goethite powder to heat dehydration in air at a temperature range of 200 to 800 ° C. Further, the magnetite powder is obtained by heating and reducing the hematite powder at 300 to 600 ° C. in a reducing atmosphere.

[0004] Generally, as the nitrogen oxide removal in the flue gas are shown "catalyst Course", Vol. 7 (Catalysis Society) p. 253 to the line 5, V ₂ as an ammonia reduction denitration catalyst
O ₅ -TiO ₂ catalyst has been used.

[0005]

In the case of the adsorption method using activated carbon, there is a problem of the treatment of activated carbon after adsorption of dioxins and the risk of coal dust explosion. Activated carbon that has adsorbed dioxins cannot be buried in landfills as waste. Therefore, high-temperature incineration that can decompose dioxins again is necessary. Even in the case of this high temperature incineration, there is a risk that dioxins will be generated again in the cooling process. Further, it is generally known that dioxins are re-synthesized in a temperature range of 300 ° C to 500 ° C, but if activated carbon powder is blown into this temperature range, there is a problem that there is a risk of coal dust explosion. . Further, a nitrogen oxide and sulfur oxide removing agent of activated coke also includes the above problems.

[0006] Further, as described above, Japanese Patent Laid-Open No. 11-267.
The iron oxide catalyst of Japanese Patent No. 507 does not require large-scale construction, but iron oxide is V ₂ O ₅ -TiO ₂ system or V ₂ O.
Compared with a _5- TiO ₂ —WO ₃ type catalyst, it is more likely to be bound to chlorine and sulfur oxides, and the catalytic activity is likely to decrease. Therefore, it cannot be used for a long time, and it is used for a short time by being blown into the exhaust gas. However, in order to suppress dioxin, it is necessary to constantly blow it into the exhaust gas. Also,
The iron oxide catalyst is expensive because the catalyst is prepared from the reagent through the complicated process as described above. When such an expensive iron oxide catalyst is blown in, the used iron oxide catalyst is collected together with dust and poisoned by chlorine and sulfur oxides in the exhaust gas, making it difficult to reuse the waste iron incinerator. In some cases, it is discarded together with dust. Further, the iron oxide catalyst requires a temperature of 250 ° C. or higher in order to obtain efficient decomposition activity, and if the blowing position is limited to the high temperature part of the exhaust gas or the exhaust gas temperature is lower than 250 ° C. Exhaust gas needs to be heated, and its removal performance is not sufficient.

The method of removing nitrogen oxides shown in Volume 7 of "Catalyst Lecture" uses vanadium, so that the catalyst is very expensive and the reduction decomposition reaction of nitrogen oxides using ammonia as a reducing agent is performed. Therefore, the exhaust gas temperature of 200 to 400 ° C. is required, and it is difficult to apply to the exhaust gas of 200 ° C. or less.

Therefore, an object of the present invention is to provide an inexpensive and high-performance remover for removing harmful substances such as organic chlorine compounds such as dioxins, nitrogen oxides and sulfur oxides.

[0009]

Means for Solving the Problems The gist of the invention is (1) an agent for removing one or more organic chlorine compounds, nitrogen oxides or sulfur oxides, the main component of which is water-containing. A method for producing a scavenger obtained by heat-treating soil that is iron oxide at 200 ° C. or higher and 500 ° C. or lower, (2) one or more scavengers of organic chlorine compounds, nitrogen oxides or sulfur oxides. There is a method for producing a removing agent, which comprises heat-treating a soil whose main component is hydrous iron oxide at 200 ° C. or higher and 500 ° C. or lower.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In order to adsorb and decompose an organic chlorine compound such as dioxins, there are pores for adsorbing, and dioxins are resynthesized in exhaust gas.
A substance that does not burn in the above temperature range is effective in suppressing the re-synthesis of dioxin when used in the temperature range of up to 500 ° C. The present invention has focused on hydrous iron oxide in view of the above characteristics, and has found that when hydrous iron oxide is heated at 200 to 500 ° C., bound water is desorbed and innumerable pores are formed on the surface. In addition, among these, substances obtained by heat-treating soil containing iron oxide hydroxide as the main component are inexpensive because they are natural products, and they are not only organic chlorine compounds such as dioxins but also nitrogen oxides and sulfur oxides. The present invention has been found to have an extremely good and excellent adsorption performance, and further, that combustion does not occur in the temperature range of 300 to 500 ° C., leading to the invention.

[0011] Soil is a material in which inorganic substances produced by decomposition of rocks on the surface of the crust are deposited on the surface of the earth, and most of them contain organic matter decomposed and decomposed. Among them, the soil containing iron oxide hydroxide as a main component is the one in which the iron that had been dissolved in the volcanic crater lake of ancient times generally settled as hydrous iron oxide by chemical or biological action, and the crater lake formed dry soil. , Iron, and various minerals and organic substances are contained, and hydrous iron oxide as the main component is 20 to 60 as iron.
% By mass, and as other components, organic matter as carbon 1
It is characterized by containing 10 to 10 mass%. In addition, the measurement of iron and other components is based on dry soil. Drying is for separating water adsorbed to soil, does not mean to separate bound water, and is usually 105 to 1
Treat at a temperature of 10 ° C for 1 hour or more. Here, the iron oxide hydroxide is a structural formula FeOOH (or Fe ₂ O ₃ .H
₂ O). Further, the heat treatment means that the soil is heated to 200 to 500 ° C. in order to desorb the bound water from the soil.
Any means can be used as long as it can be heated to a certain degree. Industrially, various dryers such as a batch type box dryer, a material transfer type dryer, a material stirring type dryer, a hot air transfer type dryer, and a cylindrical dryer can be used.

The present invention will be described in detail below by comparing soil containing iron oxide hydroxide as a main component with iron oxide hydroxide synthesized from a reagent.

The specific surface area (BET) of the iron oxide hydroxide synthesized from the soil containing iron oxide hydroxide as a main component and the reagent by heat treatment (BET
Method) is shown in FIG. Heat treatment 1 in air atmosphere
I went on time. The soil containing iron oxide hydroxide as the main component used here is a soil called loess collected from the foot of Mt. Aso, and the iron oxide hydroxide synthesized from the reagent reacts with ferrous chloride and sodium hydroxide. It is a goethite obtained by aerating an oxygen-containing gas such as air in the suspension containing iron hydroxide obtained in the above. 20 for both loess and game site
The specific surface area begins to increase at 0 ° C or higher,
While the specific surface area decreases with a temperature rise at a peak of 20 ° C., the specific surface area of loess reaches its maximum near 290 ° C., but the specific surface area does not decrease up to 400 ° C. and decreases at 500 ° C. As described above, since loess is stable in a wide temperature range, it is more advantageous than goethite when used in a high temperature range of 300 ° C. or higher. The increase in specific surface area due to heating of both goethite and loess is thought to be mainly due to the formation of pores due to desorption of bound water of hydrous iron oxide, but since the rate of increase in specific surface area due to heating is higher for loess. The increase in the specific surface area of loess may be attributed to the increase in the specific surface area due to another factor such as carbonization of organic matter. Further, by the above heat treatment, in goethite, goethite (α-FeOOH) changes to hematite (Fe ₂ O ₃ ) only at 200 ° C. or higher, but in loess, hematite and lepidocrochrome at 200 ° C. or higher. The presence of sites (γ-FeOOH) and magnetite (Fe ₃ O ₄ ) was observed by X-ray diffraction.

FIG. 2 shows the pore distribution (pore volume change) of loess and goethite after heat treatment at 300 ° C. for 1 hour. While goethite has a peak at a pore radius of 30 nm,
Loess has a peak near a radius of 2 nm. In order to adsorb low-concentration organic chlorine compounds such as dioxins, it is necessary to have pores that are larger than the adsorbed molecules and several times the size of the adsorbed molecules. If the pore size is smaller than the adsorbed molecule, the molecule cannot be adsorbed in the pore, and conversely, if the pore size is large, the larger the pore, the weaker the adsorption force becomes.
It becomes difficult to adsorb and hold a low concentration of the organic chlorine compound. The most toxic dioxins 2,3,7,8-
T4CDD has a length of about 1.8 nm and a width of about 1.0 n
Since m and thickness are about 0.3 nm, it is considered that loess is more suitable for dioxin adsorption than goethite,
The pore radius is preferably about 1 nm or more and 3 nm or less.

In loess, 200 ° C or higher and 500 ° C or lower,
Preferably, the heat treatment at 250 ° C. or higher and 400 ° C. or lower improves the adsorption performance of organic chlorine compounds such as dioxins. If the temperature is lower than 200 ° C, desorption of bound water is small, pores are not formed, and the specific surface area is not increased. When it exceeds 500 ° C, the formed pores collapse, the pore diameter increases and the specific surface area decreases. Therefore, the improvement in adsorption performance is small. Especially 250
The heat treatment at a temperature of not lower than 400 ° C. and not higher than 400 ° C. is preferable because the specific surface area is significantly increased. Further, the heat treatment time may be any time as long as the bound water can be desorbed, it depends on the heating temperature, and although it is not particularly limited, it is usually about 0.5 to 2 hours. The heating atmosphere does not matter, but the one heat-treated in an atmosphere containing oxygen is
It is preferable in terms of adsorption performance.

Regarding the adsorption performance, since loess is superior to goethite at the same specific surface area, the improvement of adsorption performance is not only the increase of the specific surface area due to the heat treatment of loess, but also the existence of pores with a radius of about 2 nm. It is considered that the presence of carbon and the formation of lepidocrocite (γ-FeOOH) and magnetite (Fe ₃ O ₄ ) by the heat treatment are effective. here,
Loess produced in the Aso region has particularly good removal performance for dioxins, nitrogen oxides and sulfur oxides, but any soil produced through a similar production process is acceptable, and the production site is not particularly limited. The loess that has been subjected to the above treatment has a dramatically improved adsorption performance for not only dioxins but also nitrogen oxides and sulfur oxides. Even a mixture of two or more kinds of dioxins, nitrogen oxides or sulfur oxides in exhaust gas can be simultaneously removed.

[0017]

EXAMPLES The substances shown in Table 1 were used to evaluate the adsorption performance of 1-chloronaphthalene, which is a substance similar to dioxin. Here, in Example 1, 30 loess (dry soil base, 50% by mass as iron, 5% by mass as organic matter as carbon) was used.
What was heat-treated in air at 0 ° C. for 1 hour, Comparative Example 1 was untreated with loess, Comparative Example 2 was heat-treated with goethite in air at 300 ° C. for 1 hour, Comparative Example 3 was The iron ore containing iron oxide hydroxide as a main component was heat-treated in air at 300 ° C. for 1 hour, and Comparative Example 4 is an active coke used for removing dioxin. The iron content in the loess was analyzed by the redox dichromic acid titration method, and the carbon in the organic matter was analyzed by the infrared absorption method. In the experiment, a glass tube was filled with the above removing agent adjusted to 5 to 10 mm and kept at 150 ° C. in a constant temperature bath. A gas in which the concentration of 1-chloronaphthalene was adjusted to 14 ppm using nitrogen as a carrier was passed through a glass tube filled with a removing agent, and the mass change of the removing agent was examined. The remover is 1-
Chloronaphthalene is adsorbed and the mass increases, but when the equilibrium adsorption amount is reached, the mass does not increase any more. This equilibrium adsorption amount was measured for each removing agent. Table 1 shows the equilibrium adsorption amount of each removing agent. Heat treatment of loess has dramatically increased the amount of adsorption. This is an artificially prepared natural product similar to goethite and loess, which is far more than the adsorption amount of iron ore mainly containing hydrous iron oxide or active coke. On the other hand, it can be seen that it exhibits excellent adsorption characteristics.

[0018]

[Table 1]

Using the removing agents of Example 1 and Comparative Examples 1 to 4 described above, an experiment for removing dioxin in exhaust gas from a refuse incinerator was carried out. Exhaust gas of 100 Nm ³ / hr was separated from the exhaust gas after passing through the bag filter of the garbage incinerator, and 0.01 m ^{3 of the} above-mentioned scavenger was charged and introduced into the fixed bed kept at 150 ° C. to obtain the dioxin concentration before and after the fixed bed. From 10
The dioxin removal rate after 0 hours was obtained. Here, the dioxin removal rate is defined by (1-fixed layer outlet dioxin concentration / fixed layer inlet dioxin concentration) × 100 (%). The results are shown in Table 2. From Table 2 as well, 3 loess of Example 1
It can be seen that the one that was heat-treated in the air at 00 ° C. for 1 hour exhibited excellent dioxin removal characteristics.

[0020]

[Table 2]

Adsorption experiments of nitrogen oxides and sulfur oxides were carried out using the removing agents of Example 1 and Comparative Examples 1 to 4 described above. The experiment was carried out by filling the glass tube with the above-mentioned removing agent adjusted to 5 to 10 mm and keeping it in a constant temperature bath at 150 ° C.
I kept it warm. Nitrogen as a carrier 200 ppm by volume of nitric oxide (NO), sulfur dioxide (SO ₂ ) 200
Gas flow rate of 1000, adjusted to ppm and oxygen of 15%
Ncm ³ / min, flow into a glass tube filled with a removing agent, NO, NO ₂ (nitrogen dioxide), SO _{2 at the} glass tube outlet
The change in concentration was examined. By the way, SO ₃ is not measured because it can be ignored because SO ₃ is generated in a very small amount. Here, NO ₂ does not exist in the adjusted gas composition, but since oxygen coexists, a part of NO ₂ is NO ₂
Is oxidized to. NOx (NO + NO ₂ ) was continuously measured by a reduced pressure chemiluminescence method, and SO ₂ was continuously measured by a non-dispersive infrared absorption method. Since both NOx and SO ₂ are removed by adsorption, the glass tube outlet concentration increases with time because the adsorption capacity decreases with time. Therefore, the average removal rate from 0 to 20 hours was used to evaluate the removal performance.
The definition of the average removal rate is shown below. Here, 20 hours
Under the above experimental conditions, the time required to distinguish the difference in adsorption performance was determined experimentally.

Average removal rate (%) = 100 × (A−B) / A (wherein, A = glass tube inlet concentration, B = 20-hour average glass tube outlet concentration) NOx of each remover Table 3 shows the average removal rates of SO ₂ and SO ₂ for 20 hours. When the loess of Example 1 was heat-treated in air at 300 ° C. for 1 hour, both the NOx removal rate and the SO ₂ removal rate were significantly improved as compared with the untreated loess of Comparative Example 1. Further, the SO ₂ removal rate is superior to the goethite of Comparative Example 2 and the iron ore of Comparative Example 3, and the NOx removal rate is superior to the activated coke of Comparative Example 4. Thus, the one obtained by heat-treating the loess of Example 1 in air at 300 ° C. for 1 hour not only has excellent dioxin removal performance but also excellent nitrogen oxide and sulfur oxide removal performance. You can see that

[0023]

[Table 3]

[0024]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, it is possible to utilize organic chlorinated compounds such as dioxins, nitrogen oxides and sulfur oxides by using inexpensive soil containing iron oxide hydroxide, which is a natural product, as a main component. Can be removed economically.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between heat treatment temperature and specific surface area.

FIG. 2 is a graph showing pore distributions of loess and goethite treated at 300 ° C.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B01D 53/86 B01D 53/34 123A 53/94 129A B01J 20/12 53/36 D 20/30 G 23 / 745 102C C07D 319/24 B01J 23/74 301A (72) Inventor Akira Tomoshima 1-1 Hibatamachi, Tobata-ku, Kitakyushu, Kitakyushu, Fukuoka Inside the Nippon Steel Corporation Yawata Works (72) Inventor Junichi Sakuragi Fukuoka 1-1 Hibatacho, Tobata-ku, Kitakyushu, Japan (72) Inventor, Yawata Works (72) Inventor Tsuneo Ikeda 2-2, Hibata-cho, Tobata-ku, Kitakyushu, Fukuoka (72) Invention Person Michio Chiba 1-4-4 Fujimi, Chiyoda-ku, Tokyo Incorporated in Ironworks (72) Inventor Masami Ikemoto 1-4-4 Fujimi, Chiyoda-ku, Tokyo F-term in Incorporated ) 4D002 AA02 AA12 AA21 AC02 AC04 BA04 DA58 GA01 GB11 4D048 AA02 AA06 AA11 BA36X BA41X BB01 4G066 AA66B CA23 CA28 CA31 DA02 FA34 4G069 AA02 AA08 BA16A BA16B BA16C BC66B CA02 CA10 CA12 CA13 CA19 DA05 EA01Y EA02Y

Claims (2)

[Claims] 1. Heat treatment of soil containing one or more kinds of organic chlorine compounds, nitrogen oxides or sulfur oxides, the main component of which is hydrous iron oxide, at 200 ° C. or more and 500 ° C. or less. Removal agent obtained by. 2. A method for producing one or more removing agents for organic chlorine compounds, nitrogen oxides or sulfur oxides, wherein soil containing iron oxide hydroxide as the main component is heated to 200 ° C. or higher.
A method for producing a removing agent, which comprises performing a heat treatment at 0 ° C. or lower.