JP2006143494A - Active carbon for treating organic halogen compound and method for treating organic halogen compound-containing exhaust gas using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide active carbon of which the performance of removing organic halogen compounds is high and the performance of removing sulfur oxide is low, and to provide a method for treating organic halogen compound-containing exhaust gas using the same. <P>SOLUTION: In the active carbon, the volume of fine pores is 0.01 to 0.2 ml/g, the ratio between the volume (A) of the fine pores with a fine pore diameter of 100 to 300 Å and the volume (B) of the fine pores with a fine pore diameter of 20 to 30 Å, A/B, is ≥0.6, and also, the content of ash is ≤7 wt.%. The method for treating exhaust gas uses the same. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an activated carbon for treating an organic halogen compound and a method for treating an exhaust gas containing an organic halogen compound using the activated carbon. More specifically, the activated carbon has a pore volume of 0.01 ml / g or more and 0.2 ml / g or less, and has a pore volume (A) having a pore diameter of 100 to 300 mm and a fine pore diameter of 20 to 30 mm. The activated carbon for removing organic halogen compounds, wherein the ratio A / B of the pore volume (B) is 0.6 or more, and the ash content is 7% by weight or less, and the organic halogen compound-containing exhaust gas using the same It relates to the processing method.

  Conventionally, organic halogen compounds typified by dioxins are contained in exhaust gas generated by incineration of industrial wastes such as municipal waste and sewage sludge. Since these organohalogen compounds are highly toxic, there are concerns about their effects on human health and ecosystems, and removal from exhaust gas is being investigated.

The flue gas generated from municipal waste incinerators, industrial waste incinerators, steel sintering furnaces, etc. contains organic halogen compounds such as dioxins, but these organic halogen compounds are removed. In many cases, activated carbon is used. However, since the removal performance deteriorates when activated carbon is used for a certain period of time, it is regenerated or disposed of. However, when regenerated, it is generally heat-treated at a temperature of 350 ° C. to 900 ° C. So far, as a method for adsorbing dioxins using activated carbon, for example, a method using granular activated carbon having a diameter of 4 to 8 mm and a specific surface area of at least 150 m ² / g (Patent Document 1), a pore diameter of less than 10 mm A method of using granular activated carbon having an improved ignition point by defining a pore volume and a pore volume having a pore diameter of 10 to 20 mm (Patent Document 2), by making the Ca content 0.2% by weight or less A method using activated carbon in which activated carbon is prevented from being powdered (Patent Document 3) has been proposed.
Japanese Patent Laid-Open No. 11-104488 JP 2000-225320 A Japanese Patent Laid-Open No. 2001-170481

  However, harmful substances such as sulfur oxides and nitrogen oxides often coexist in the flue exhaust gas in addition to organic halogen compounds. Among them, sulfur oxides are activated carbon as sulfuric acid when oxygen and water are present. As a result, the pores of the activated carbon are occupied by sulfuric acid, and the adsorption performance of dioxins tends to decrease. Moreover, when such used activated carbon is heated and regenerated, sulfuric acid decomposes while consuming the carbon of the activated carbon, so that the weight of the activated carbon decreases and the mechanical strength of the activated carbon decreases, resulting in increased wear of the activated carbon. . As a result, the consumption of activated carbon is increased, leading to an increase in the cost of regeneration treatment.

  If a separate desulfurization facility is installed in the exhaust gas treatment process or if the sulfur oxide concentration in the exhaust gas is below the environmental standard value, it is not necessary to remove the sulfur oxide with activated carbon. By using activated carbon as described above, dioxins and sulfur oxides are adsorbed simultaneously, so that the lifetime of the activated carbon is remarkably shortened. From such a viewpoint, activated carbon having high removal performance of organic halogen compounds and low removal performance of sulfur oxides is desired. Accordingly, an object of the present invention is to provide an activated carbon having a high organic halogen compound removal performance and a low sulfur oxide removal performance, and a method for treating an organic halogen compound-containing exhaust gas using the activated carbon.

  As a result of intensive studies in order to achieve the above object, the inventors of the present invention have found that the pore volume of activated carbon is increased in order to increase the adsorption performance of organic halogenated compounds in exhaust gas and lower the adsorption performance of sulfur oxides. And ash is an important factor, and it is important to adjust them, and the present invention has been completed. That is, the present invention is activated carbon having a pore volume of 0.01 ml / g or more and 0.2 ml / g or less, having a pore volume (A) having a pore diameter of 100 to 300 mm and a pore diameter of 20 to 30 mm. An activated carbon for removing organic halogen compounds, wherein the pore volume (B) ratio A / B is 0.6 or more and the ash content is 7% by weight or less.

  Another invention of the present invention is a method for treating an exhaust gas containing an organic halogen compound using such activated carbon.

  According to the present invention, it is possible to provide activated carbon having high adsorption performance for halogenated organic compounds including dioxins and low adsorption performance for sulfur oxides. When such activated carbon is used for the treatment of flue gas, it is possible to adsorb and remove halogenated organic compounds and to prevent the wear and strength deterioration of the activated carbon in the regeneration process because of its low sulfur oxide adsorption performance. Costs associated with activated carbon consumption can be reduced.

  The carbonaceous material used as the raw material of the activated carbon of the present invention is not particularly limited as long as it can form activated carbon by activation, and can be widely selected from plant-based and mineral-based materials. Specifically, examples of plant-based carbonaceous materials include fruit shells such as wood, charcoal, and coconut shells, and examples of mineral-based carbonaceous materials include coal, petroleum-based and / or coal-based pitch, coke, and the like. it can. The activated carbon of the present invention can be produced by carbonizing and activating these carbonaceous materials.

  The dry distillation may be heated to 550 to 750 ° C. in a reducing gas atmosphere. It is preferable to raise the temperature from 200 to 400 ° C. in an oxidizing gas atmosphere at 5 to 30 ° C./min, and further to 550 to 750 ° C. in a reducing gas atmosphere at 5 to 30 ° C./min. The activation may be performed at 400 to 1100 ° C. in an oxidizing gas atmosphere such as water vapor, carbon dioxide, air, propane combustion exhaust gas, and mixed gas thereof, but in a gas containing 20% by volume or more of water vapor, 800 to 1000 It is preferred to carry out at ° C.

  The activated carbon for removing organic halogen compounds of the present invention is activated carbon having a pore volume of 0.01 ml / g or more and 0.2 ml / g or less, and a pore volume (A) having a pore diameter of 100 to 300 mm and a fine volume. It is necessary that the ratio A / B of the pore volume (B) having a pore diameter of 20 to 30 mm is 0.6 or more. Preferably it is 0.8 or more and 1.2 or less. When the pore volume is less than 0.01 ml / g, the adsorption performance of the organic halogen compound is not sufficient, and when it exceeds 0.2 ml / g, the strength of the activated carbon is lowered, so that it is not suitable for repeated use. Further, the above A / B needs to be 0.6 or more. If A / B is less than 0.6, the effect tends to be low because it tends to adsorb sulfur oxide together with the organic halogen compound. In order to make the above pore volume A / B a desired value, the production conditions differ depending on the starting material, so it cannot be decided unconditionally. However, an example of using coal as a raw material is that steam at a temperature of 920 ° C. or higher. It can carry out by activating in the gas containing 50 volume% or more.

Further, the activated carbon for removing organic halogen compounds of the present invention is required to have an ash content of 7% by weight or less, and preferably 5% by weight or less. The total content of Mg, Ca and Fe in the activated carbon is preferably 1.0% by weight or less. Adjustment of the ash content of activated carbon and the contents of Mg, Ca, and Fe can be adjusted by selecting a carbonaceous material as a raw material. For example, the ash content in coal and the content of each metal composition can be measured and adjusted to the desired content. The specific surface area of the activated carbon is preferably 100 to 500 m ² / g. The starting material and production method of activated carbon in the present invention are not particularly limited, and any activated carbon satisfying the above pore volume and ash content can be used.

  The activated carbon for treating the organic halogen compound of the present invention may be a granulated carbon obtained by pulverizing a carbonaceous material and granulating it using a binder. For example, a carbonaceous material is finely pulverized to an appropriate particle size, and coal or petroleum such as coal tar and coal tar pitch, cellulose organic substances such as starch, carboxymethyl cellulose, and sugar, and a binder such as phenol resin are added and kneaded. Granulated coal that has been molded, granulated by dry distillation and activation can be used.

Although not limited, in the molding process, the raw material finely pulverized with a Z-type biaxial kneader and the binder are sufficiently kneaded and molded at a pressure of 180 kg / cm ² or more so that the molded product can be made clear. Obtainable. Further, as a molding apparatus, a roll press type, a disk type pelleter type, a ring type pelleter type, an extrusion type or the like can be used. The shapes of the activated carbon and the granulated coal are not particularly limited, and may be appropriately determined according to the purpose such as a columnar shape, a cylindrical shape, a spherical shape, or a disk shape. Practically, it is preferable to use in the form of particles having a particle diameter of 1 to 20 mm, but it is desirable in terms of handling to use a cylinder having a diameter of 2 to 11 mm. When used in a cylindrical shape, height / diameter = 1 to 3 is preferable.

  In the present invention, the organic halogen compound is an organic compound containing a halogen such as chlorine, and dioisin is a representative one. The activated carbon of the present invention is characterized by high organohalogen compound removal performance and low sulfur oxide removal performance. The reason for this cannot always be explained clearly, but the activated carbon of the present invention has pores suitable for adsorption of organic halogen compounds, and the catalytic action is suppressed by optimizing the ash content. Can be considered. EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto. In the present invention, each physical property was measured by the following method.

  Pore volume and specific surface area: The adsorption amount of nitrogen was measured using “BELSORP 28SA” manufactured by Bell Japan Co., Ltd., and the total specific surface area was nitrogen adsorption at a relative pressure of 0.931 corresponding to a pore diameter of 300 mm at a liquid nitrogen temperature. Calculated from the amount. The pore volume at 20 to 30 mm and 100 to 300 mm was calculated from the nitrogen adsorption amount by the Cranston-Inkley method (Cranston-Inkley method), and the specific surface area was calculated by the BET method.

  Ash content: 1-2 g of the activated carbon sample was put in a magnetic crucible, heated in air at 815 ° C. for 6 hours, and then cooled to obtain the weight percentage of the residue.

  Mg, Ca, Fe content: After wet decomposition of the sample, it was measured by ICP emission analysis using “Optima 4300 DV” manufactured by PerkinElmer.

  Strength: Ten 8 mm steel balls together with 5 g of sample are placed in a metal cylindrical container with an inner diameter of 25 mm and a length of 300 mm. Sieving was performed with a standard sieve having an opening of 300 μm, the remaining amount on the sieve was measured, and the ratio to the initial weight was determined.

Adsorption performance of the organic halogen compounds and sulfur oxides: reactor gas mixture sample was loaded 200 ml (chlorobenzene: 800 volume _ppm, SO 2: 800 volume _ppm, O 2: _10% by _volume, H 2 O: 10% by volume, N ₂ : remainder) was passed at a space velocity (SV) of 1000 / hr, and the concentration was calculated from the concentration ratio of chlorobenzene and SO ₂ at the reactor inlet and outlet at 105 ° C. for 4 hours. In the present invention, the activated carbon that can withstand repeated use has a strength of 80% or more and a chlorobenzene / SO ₂ performance ratio of 1.0 or more as criteria.

Examples 1-3
Three different types of coal are used as starting materials, 20 parts by weight of coal tar and 15 parts by weight of coal tar pitch are added to 100 parts by weight of coal, and then kneaded into a cylindrical shape with a diameter of 5 mm and a length of 10 mm using a ring-type pelleter did. After dry distillation at 650 ° C., activation was performed at 850 to 950 ° C. in a mixed gas containing 40% by volume or more of water vapor to obtain three types of activated carbon shown in Table 1 (Examples 1 to 3, respectively). Table 1 shows the results of measuring the Mg, Ca, Fe content, specific surface area, strength, chlorobenzene and SO ₂ adsorption performance of each activated carbon.

Comparative Examples 1-3
Three types of activated carbon were obtained in the same manner as in the Examples except that three different types of coal were used as starting materials (Comparative Examples 1 to 3, respectively). Table 1 shows the results of measuring the Mg, Ca, Fe content, specific surface area, strength, chlorobenzene and SO ₂ adsorption performance of each activated carbon.

From the results of Table 1, Comparative Example 1 having a total pore volume of 0.2 ml / g or more has low strength and is not suitable for repeated use. Comparative Example 2 in which the pore volume ratio A / B is smaller than 0.6 and Comparative Example 3 in which the ash content is higher than 7% are lower in chlorobenzene / SO ₂ than 1.0, and in particular, Comparative Example 2 has low performance. Met. The effects of the present invention are clear from the above results.

Since the activated carbon of the present invention is excellent in the adsorption performance of halogenated organic compounds including dioxins and has a low adsorption performance of sulfur oxides, the flue gas of a flue gas such as a waste incinerator containing sulfur oxides or dioxins is not used. It can be preferably used for processing. Moreover, since the wear and strength deterioration of the activated carbon in the regeneration process can be suppressed, the cost associated with the consumption of the activated carbon can be reduced.

Claims (5)

Activated carbon having a pore volume of 0.01 ml / g or more and 0.2 ml / g or less, and having a pore diameter of 100 to 300 mm and a pore volume of 20 to 30 mm (B ) In which the ratio A / B is 0.6 or more and the ash content is 7% by weight or less. The activated carbon according to claim 1, wherein the total content of Mg, Ca and Fe is 1.0% by weight or less. The activated carbon according to claim 1 or 2, wherein the activated carbon has a specific surface area of 100 to 500 m ² / g. The activated carbon according to claim 1, wherein the activated carbon is cylindrical. The processing method of the organic halogen compound containing waste gas using the activated carbon in any one of Claims 1-4.