JP2000225320A - Hot gas treatment method and activated carbon - Google Patents

Abstract

(57) [Problem] To provide a granular activated carbon having a high ignition point and a high ability to adsorb organic halogen compounds including dioxins. SOLUTION: The pore volume of less than 10 mm in diameter is 0.2ml.
/ G or less, and the pore volume of 10 to 20 ° in diameter is 0.1%.
A method for treating a high-temperature gas, comprising using granular activated carbon having a flow rate of 5 ml / g or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for removing harmful substances contained in exhaust gas by passing a high-temperature combustion exhaust gas generated from an incinerator of municipal solid waste or the like through an adsorption tower filled with a porous carbon material such as activated carbon. A method for treating high-temperature gas to be removed and activated carbon,
Furthermore, it relates to a processing device. More specifically, organic halogen compounds, particularly highly toxic dioxins (polychlorinated dibenzodioxins and polychlorinated dibenzofurans) can be efficiently removed, and high-temperature gas, which has a low risk of fire in management and high safety, can be used. The present invention relates to a processing method and apparatus.

[0002]

2. Description of the Related Art Toxic substances in exhaust gas generated from incineration of municipal solid waste and industrial waste include acid gases such as hydrogen chloride and sulfur oxides, heavy metals such as mercury, and highly toxic dioxins. And controlling dioxin emissions is becoming a global problem. The reaction of generating dioxins in the incineration process is complex and has not been elucidated yet, but the precursor generated by the combustion of waste containing chlorine undergoes a resynthesis reaction in the process of cooling the exhaust gas,
It is thought to produce dioxins. One of the most effective methods for removing generated dioxins is adsorption removal using activated carbon, and treatment with activated carbon has the advantage that many harmful substances such as mercury can be removed in addition to dioxins.

[0003] Exhaust gas treatment methods using activated carbon are roughly divided into two methods: a method in which powdered activated carbon is sprayed into a flue and the activated carbon that has adsorbed harmful substances is collected together with fly ash by a dust collector, and a method in which granular activated carbon is filled. There is a method to adsorb and remove harmful substances by installing a desorbed adsorption tower, but the former method is particularly suitable for slaked lime powder used in ordinary incineration plants to remove acidic gases such as hydrogen chloride and sulfur oxides. Since it is possible to use equipment similar to the above-mentioned spray equipment, there is no need for significant equipment remodeling work, and there are many advantages in equipment. Therefore, the introduction of this method is being promoted in many existing incineration facilities. In the latter method using an adsorption tower, although an adsorption tower is required, the removal rate of dioxins is higher than the blowing method, and the concentration of dioxins can be stably kept at a low level, and the action as a denitration catalyst There is also.

[0004]

As a treatment method using the above-mentioned adsorption tower, for example, JP-A-5-237339, JP-A-5-301022, and JP-A-6-28
Japanese Patent Application Laid-Open No. 1128, Japanese Patent Application Laid-Open No. 7-763 and the like have been proposed, but the type and physical properties of the activated carbon used here are not described. Activated carbon suitable for this adsorption is considered from the molecular size of an organic halogen compound such as dioxins to be adsorbed.
In particular, it has been generally considered that those having many small pores of 10 ° or less are desirable.

[0005] However, when activated carbon having a large number of small diameter pores is used for exhaust gas adsorption treatment,
There is no problem during steady gas processing, but when the operation is stopped or drift occurs in the adsorption tower due to accumulation of dust, etc., the heat of oxidation accumulates and partial hot spots are formed, and oxidation rapidly occurs. There is a risk of proceeding and catching fire. Therefore, measures against ignition of activated carbon used as an adsorbent are the biggest problem in safety management of the adsorption tower. From such a background, there has been a demand for granular activated carbon having a high ignition point and a high ability to adsorb organic halogen compounds including dioxins.

[0006]

Means for Solving the Problems Accordingly, the present inventors have:
As a result of intensive studies to solve the above-mentioned problems, as activated carbon granular to be packed in the adsorption tower, pores with a specific small diameter are necessary to adsorb organic halogen compounds, but finer pores than necessary are necessary. , The ignition point of the activated carbon is lowered due to this, and the danger of ignition in the adsorption tower is increased.Based on this finding, the activated carbon with a specific distribution of pore volume is selected to improve safety. And found that organic halogen compounds containing dioxins can be removed efficiently.

That is, the gist of the present invention is that the volume of pores having a diameter of less than 10 mm is 0.2 ml / g or less,
There is provided a method for treating a high-temperature gas, characterized in that granular activated carbon having a volume of pores of 0 ° or less of 0.15 ml / g or more is used. As a preferred embodiment of the present invention, the above-mentioned treatment method characterized by using activated carbon having a total ash content of 8 wt% or more; wherein the contents of potassium, sodium, and calcium are each 0.2 wt% or less. The above-mentioned processing method, wherein the high-temperature gas is incineration exhaust gas; the above-mentioned processing method, wherein the high-temperature gas contains an organic halogen compound; and the above-mentioned processing method, wherein the temperature of the high-temperature gas is 90 ° C. or higher. No.

In another embodiment of the present invention, a high-temperature gas having a pore volume of less than 10 mm in diameter of 0.2 ml / g or less and a pore volume of 10 to 20 mm in diameter of 0.15 ml / g or more is provided. Activated granular activated carbon for hot gas treatment, wherein the total ash content is preferably 8% by weight or more; the content of potassium, sodium and calcium is 0.2% by weight or less, respectively. The granular activated carbon, wherein the high-temperature gas is incineration exhaust gas; the granular activated carbon, wherein the high-temperature gas contains an organic halogen compound;
The above-mentioned granular activated carbon having a temperature of at least ℃ is mentioned. Further, as another embodiment of the present invention, a high-temperature gas processing apparatus having an adsorption tower filled with the above-mentioned granular activated carbon is mentioned.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The most important feature of the present invention is that the pore volume of less than 10 mm in diameter is 0.1 mm.
The use of granular activated carbon having a pore volume of 2 ml / g or less and a diameter of 10 mm or more and 20 mm or less of 0.15 ml / g or more increases the ignition point of the activated carbon. Not only is the risk reduced, the safety management of the adsorption tower becomes easy, but also organic halogen compounds including dioxins can be efficiently removed. In addition,
Activated carbon usually has a pore volume (total pore volume) of 0.3 to 0.7.
ml / g.

In short, since the exhaust gas component is more easily oxidized than the adsorbent itself such as activated carbon, the adsorbent that adsorbs the exhaust gas component has a lower ignition point than the adsorbent before use. The present inventors have found that the lowering of the ignition point due to the adsorption of the exhaust gas component is greatly affected by the pore distribution of the activated carbon. Therefore, when the exhaust gas was adsorbed on various activated carbons and its ignition point was measured, the activated carbon with many small pores had a low desorption property of the exhaust gas component at the time of temperature rise, so the adsorption amount of the organic halogen compound was small. Nevertheless, the ignition point was found to be greatly reduced. Therefore, it has been found that the activated carbon used in the adsorption tower preferably has a large number of pores of 10 to 20 ° effective for adsorption and a small number of pores of 10 ° or less which causes a decrease in ignition point.

The activated carbon used in the present invention has a pore volume of less than 10 mm in diameter of 0.2 ml / g or less, and a pore of 10 mm or more and 20 mm or less in diameter has a volume of 0.15 ml / g or more, preferably 0.15 ml / g or more. １1 ml / g. Activated carbon that does not satisfy this pore volume cannot satisfy both the safety management surface and the organic halogen compound adsorption surface. The raw material and production method of the activated carbon used in the present invention are not particularly limited, and any activated carbon produced by any raw material or method having the above pore volume can be used in the present invention. . In addition, since activated carbon having the above pore volume is commercially available, these commercially available activated carbons can be used.

As the raw material of the activated carbon used in the present invention, many carbonaceous substances can be considered. However, industrially, it is difficult to activate the raw material, the quality of the raw material, the price, the availability of the raw material in large quantities and stably. Is the selection condition. Manufacturing conditions, product prices, and uses vary depending on the type of raw material. Raw materials include plant-based wood, sawdust, coconut shell, pulp waste liquid,
Fossil fuel-based coal, petroleum heavy oil, or thermally decomposed coal and petroleum-based pitch, synthetic polymer, phenolic resin, furan resin, polyvinyl chloride resin, polyvinylidene chloride resin, plastic waste, waste tires, etc. It is a wide variety. These carbonized materials are activated after carbonization. Activation methods are roughly classified into gas activation and chemical activation. The gas activation method is
While chemical activation is chemical activation, it is also called physical activation, and the carbonized raw material is brought into contact with steam, carbon dioxide, oxygen, and other oxidizing gases at high temperature to produce fine This is a method for producing porous activated carbon, and the method using steam is the mainstream industrially. The chemical activation method is
This is a method in which a raw material is uniformly impregnated with an activating chemical, heated in an inert gas atmosphere, and a fine porous activated carbon is produced by a dehydration and oxidation reaction of the chemical. The chemicals used include zinc chloride, phosphoric acid, sodium phosphate, calcium chloride, potassium sulfide, potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, sodium sulfate, potassium sulfate, calcium carbonate and the like.

As the activated carbon of the present invention, granular activated carbon is used, but the shape may be cylindrical or crushed, and is not particularly limited. The particle size is not particularly limited, but is usually 2 to 30 mmφ, preferably 3 to 3 mm for the columnar shape in consideration of the ventilation resistance in the packed tower.
The diameter is preferably 15 to 15 mm, and in the case of a shape other than the columnar shape, it is usually 3 to 30 mm in the longitudinal direction. By using activated carbon having a high ash content in the present invention, the ignition point of new coal can be further increased. The activated carbon used in the present invention preferably has a total ash content of at least 8 wt%, more preferably 8 to 50 wt%. The ash here refers to, for example, inorganic oxides such as silica and alumina.

Further, in the present invention, the ignition point of fresh coal and adsorbed carbon can be further increased by using activated carbon having a low content of alkali metals and alkaline earth metals. Specifically, the activated carbon used in the present invention preferably has a potassium, sodium, and calcium content of 0.2 wt% or less, and more preferably 0.1 wt% or less. The specific surface area of the activated carbon used in the present invention is not particularly limited,
Preferably, 300~2000m ² / g, and more preferably in the 500 to 1500 ² / g. The high-temperature gas referred to in the present invention is usually a gas of 80 ° C. or higher,
The effect of the present invention is particularly remarkable in a gas of 100 ° C. or more,
Furthermore, it is remarkable in the gas at 100 to 400 ° C. The gas in the present invention is often a gas containing an organic halogen compound, and usually includes gases generated from chemical plants, iron and steel plants, non-ferrous plants, power plants, incinerators and the like. Various shapes and methods of the adsorption tower used in the treatment of the high-temperature gas have been proposed, and the method is not particularly limited. The activated carbon used in the present invention is applicable to any type of adsorption tower such as a fluidized bed, a moving bed, and a fixed bed. In particular, the activated carbon of the present invention is useful for dioxin adsorption.

[0015]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples, but the present invention is not limited to the following Examples unless it exceeds the gist thereof. In the present invention, the amount of the organic halogen compound adsorbed was measured. However, there is a correlation between the concentration of the dioxin and the concentration of the organic halogen compound in the flue gas, and the large amount of the adsorbed organic halogen compound indicates the amount of the adsorbed dioxin. Indicates the amount of

Examples 1 to 4 Three kinds of 4 mmφ columnar activated carbon were produced by a steam activation method using three different types of coal as starting materials, and the properties, adsorption amounts of organic halogen compounds and ignition points were measured. The measurement of the specific surface area and the pore volume was performed by nitrogen adsorption using "Sorpmatic 2100" manufactured by Carlo Elba, and the specific surface area was determined by the BET method using Cranston-I.
The pore volume was calculated by the nkley method. The pore volume of 10 ° or less is calculated from Cranston-Ink from the pore volume calculated from the amount of nitrogen adsorbed at a liquid nitrogen temperature and a relative pressure (P / P0) of 0.931 (corresponding to a pore diameter of 300 °).
It was calculated by subtracting the pore volume of 10 to 300 ° obtained by the Ray method.

The ash content was measured by the following method.
Put 1-2 g of activated carbon sample in a magnetic crucible,
Heat at 5 ° C. for 6 hours. After cooling, the mass of the remaining ash was measured, and the weight percentage with respect to the amount of activated carbon put in the crucible was determined to be the ash content. The potassium, sodium and calcium contents are measured by wet decomposition ICP-AES (JOB
IN YVON JY38S). Exhaust gas adsorption carbon was produced by the following method. The above-mentioned three types of activated carbon in a columnar form were prepared by dioxin concentration of 40 ng-TE.
Q / Nm ³ , organic halogen compound concentration 3000 μg-
Exhaust gas components were adsorbed by hanging for 50 hours in a flue at the outlet of a dust collector of a refuse incineration facility with Cl / Nm ³ and an exhaust gas temperature of 130 ° C. The adsorption amount of the organic halogen compound was measured using TOX-100 manufactured by Dia Instruments Co., Ltd., and quantified in terms of chlorine.

The ignition point of each sample was measured as ignition characteristics. It is determined that the higher the ignition point, the lower the risk of ignition of the activated carbon. The ignition point is measured using a differential thermal analyzer.
It carried out by the following method. 5 mg of the activated carbon sample was put in a sample container made of quartz, and was applied to a differential thermal analyzer.
The temperature was raised at a rate of 10 ° C./min while flowing air at a flow rate of 1 min. When the ignition point is reached, the sample heats up rapidly,
The results are shown with the horizontal axis representing the sample temperature and the vertical axis representing the differential temperature,
The intersection of the extension of the temperature line before the rapid rise and the extension of the temperature line after the sudden rise was determined, and the corresponding sample temperature was defined as the ignition point.

Comparative Examples 1 and 2 As activated carbon, the pore volume with a diameter of 10 to 20 ° was 0.15.
The properties, the amount of organic halogen compound adsorbed, and the ignition point were measured in the same manner as in the Example except that a substance having a concentration of less than ml / g was used. Table 1 shows the results. As is clear from Table 1, the adsorption amount of the organic halogen compound is extremely small as compared with the examples.

Comparative Example 3 The properties and the organic halogen compound were determined in the same manner as in the Example except that the starting material was peat, and the activated carbon had a pore volume of less than 10 mm and a pore volume exceeding 0.2 ml / g. The adsorption amount and ignition point were measured. Table 1 shows the results. As is clear from Table 1, the ignition point, particularly the ignition point of the adsorbed carbon, is considerably lower than that of the example, and the danger of ignition is increased.

COMPARATIVE EXAMPLES 4 AND 5 As the activated carbon, the starting material was coconut shell and the pore volume was less than 10 mm and the pore volume exceeded 0.2 ml / g. The organic halogen compound adsorption amount and ignition point were measured. Table 1 shows the results. As is clear from Table 1, the ignition point, particularly the ignition point of the adsorbed carbon, is considerably lower than that of the example, and the danger of ignition is increased.

[0022]

[Table 1]

As is clear from the above Examples and Comparative Examples, the pore volume with a diameter of less than 10 mm is 0.2 ml / g or less, and the pore volume with a diameter of 10 mm or more and 20 mm or less is 0.1 ml.
By using the granular activated carbon having a concentration of 5 ml / g or more, the ignition point of the adsorbed carbon is increased, and the amount of the organic halogen compound containing dioxins in the combustion exhaust gas is increased. That is, by using the granular activated carbon of the present invention in an adsorption tower, the risk of ignition can be reduced and the life of the activated carbon can be extended.

[0024]

According to the method and apparatus for treating high-temperature gas of the present invention, the risk of ignition in the adsorption tower is reduced, and the safety management of the adsorption tower is facilitated. In addition, dioxin contained in the high-temperature gas is reduced. The present invention provides great industrial benefits because it can efficiently remove organic halogen compounds such as organic compounds.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) C01B 31/10

Claims (13)

[Claims] 1. The volume of pores having a diameter of less than 10 mm is 0.2 ml.
/ G or less, and the pore volume of 10 to 20 ° in diameter is 0.1%.
A method for treating a high-temperature gas, comprising using granular activated carbon having a flow rate of 5 ml / g or more. 2. The method according to claim 1, wherein activated carbon having a total ash content of 8 wt% or more is used. 3. The method according to claim 1, wherein the contents of potassium, sodium, and calcium are each 0.2 wt% or less. 4. The high-temperature gas is incineration exhaust gas.
4. The processing method according to any one of claims 1 to 3. 5. The processing method according to claim 1, wherein said high-temperature gas contains an organic halogen compound. 6. The processing method according to claim 1, wherein the temperature of the high-temperature gas is 90 ° C. or higher. 7. The volume of pores having a diameter of less than 10 mm is 0.2 ml.
/ G or less, and the pore volume of 10 to 20 ° in diameter is 0.1%.
Granular activated carbon for treating high temperature gas of 5 ml / g or more. 8. The granular activated carbon according to claim 7, wherein the total ash content is 8% by weight or more. 9. The granular activated carbon according to claim 7, wherein the contents of potassium, sodium and calcium are each 0.2% by weight or less. 10. The granular activated carbon according to claim 7, wherein said high-temperature gas is incineration exhaust gas. 11. The granular activated carbon according to claim 7, wherein the high-temperature gas contains an organic halogen compound. 12. The granular activated carbon according to claim 7, wherein the temperature of the high-temperature gas is 90 ° C. or higher. 13. An apparatus for treating a high-temperature gas, comprising an adsorption tower filled with the granular activated carbon according to claim 7. Description: