JPH07267619A - Production of granular activated carbon - Google Patents

Abstract

PURPOSE:To obtain granular activated carbon having a combination of high strength, high adsorption power and high catalytic ability by molding a mixture containing activated carbon powder and a binder, then effecting carbonization and activation. CONSTITUTION:One hundred parts by weight of at least one selected from carbons which is prepared by activating granular or powdery carbon with steam, by carbonizing and activating in the presence of steam and pulverizing, by activating with zinc chloride, or a powdery activated carbon prepared by heat- regenerating the granular carbon deactivated after use in flue gas desulfurization, denitrification, or desulfurization and denitrification, and has a specific surface area of 400 to 1,000m<2>/g, 10 to 40 pts.wt. of at least one of binders selected from coal tar pitch or petroleum pitch and at least one selected from coking coal, molding auxiliaries are mixed and molded. Then. the molded product is carbonized at 500-800 deg.C, activated at 900 to 1,100 deg.C in the presence of a oxidative gas such as steam to give granular activated carbon having 500 to 1,200m<2>/g specific surface area and 5-30mm granule size.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing granular activated carbon. The granular activated carbon obtained by the present invention is used as an adsorbent and a catalyst in exhaust gas treatment, gas purification, gas reaction and the like.

[0002]

2. Description of the Related Art Activated carbon is SOx, N contained in exhaust gas such as boiler exhaust gas, sintering furnace exhaust gas, and waste incinerator exhaust gas.
Not only can Ox and hydrogen halide be removed, but it can also remove harmful chlorine compounds such as dioxins, odorous components, and harmful heavy metals such as mercury. Further, since it has an adsorption capacity for many other substances, it is widely used as a catalyst for gas purification, gas reaction, etc., in addition to exhaust gas treatment.

In general, since exhaust gas contains dust and it is necessary to regenerate activated carbon, a moving bed reactor (adsorber) is used when treating a large amount of exhaust gas with activated carbon. For this reason, in addition to desulfurization performance, denitration performance, and other adsorption performance, high-strength granular activated carbon is required to reduce powder consumption. Further, granular activated carbon with a large particle size is required to keep the ventilation pressure loss when passing exhaust gas low.

Generally, granular activated carbon is prepared by mixing a carbon-containing substance such as crushed coal with a binder such as pitch, kneading and molding, and then carbonizing and activating it in the presence of steam, oxygen, carbon dioxide gas and the like. Manufactured. Specific examples of the method for producing activated carbon for desulfurization / denitration include (a) a method in which pulverized coal is air-oxidized in advance, and then this is molded to carbonize / activate, and (b) semi-coke is mixed with coal. Then, a method of molding and carbonizing and activating this (see Japanese Patent Publication No. 62-51885), or (c) a method of blending non-caking coal and caking coal and molding and carbonizing and activating ( Japanese Patent Publication No. 63-17761) has been proposed.

[0005]

However, in the above-mentioned conventional methods (a), (b), and (c), coal is used as a raw material and coal contains volatile components. When carbonized and activated after molding, a gas derived from volatile components is rapidly generated. Due to this rapid gas generation, fine cracks are generated inside, and a part of the gas is confined inside to form cavities, which makes it difficult to obtain granular activated carbon with high strength.

[0006] Further, there is a drawback in that when an attempt is made to obtain granular activated carbon having a large particle diameter, the internal activation becomes insufficient, and only activated carbon having insufficient adsorption ability and catalytic ability can be obtained.

If the activation time is lengthened in order to carry out the activation to the inside, the adsorption ability and the catalytic ability of the obtained granular activated carbon are improved, but not only the productivity is lowered but also the strength of the granular activated carbon is lowered.

Further, as a method for obtaining granular activated carbon activated to the inside, after mixing a carbonate such as dolomite and a sulfate such as potassium sulfate and sodium sulfate with the raw material coal, the mixture is heated to remove the carbonate and sulfate. There is a method of generating an oxidizing gas to promote activation of the inside, but also in this case, there is a disadvantage that high-strength granular activated carbon cannot be obtained due to formation of cracks and air conditioning due to gas generation.

That is, in the conventional method for producing granular activated carbon using coal as a raw material, there is a trade-off relationship that the strength and adsorption capacity and the catalytic ability of the granular activated carbon become higher when one increases and the other becomes lower. It was not possible to obtain granular activated carbon that has both high adsorption capacity and high catalyst capacity.

Therefore, the object of the present invention, high strength and high adsorption capacity,
An object of the present invention is to provide a method for producing granular activated carbon which has a high catalytic ability.

[0011]

The present invention has been made to achieve the above-mentioned object, and after molding a mixture containing powdered activated carbon and a binder to a predetermined size, the molded product is carbonized. -The gist is a method for producing granular activated carbon, which is characterized by activation.

The present invention will be described in detail below.

In the method for producing granular activated carbon of the present invention, powdered activated carbon is used as a raw material. As the powdered activated carbon used as a raw material, (i) those obtained by carbonizing and activating fine-grained or powdered coal in the presence of steam, (ii)
Examples thereof include those obtained by previously forming coal into briquette, carbonizing and activating in the presence of water vapor, and then pulverizing, (iii) those produced by a known zinc chloride activation method, and the like. In the present invention, "activated carbon" is a concept in the broadest sense and includes various substances such as a carbonaceous adsorbent, a carbonaceous catalyst, activated coke, activated char.

The granular activated carbon that has been deactivated by flue gas desulfurization treatment, denitration treatment, or desulfurization / denitration treatment is heated and regenerated, and then the powdered activated carbon separated from the regenerated granular activated carbon is used as the raw material powdered activated carbon. It can also be used. It is also possible to use waste powder activated carbon used in water treatment or the like.

The specific surface area of the raw material powdered activated carbon is about 400 to 1 in order to enhance the adsorption ability and catalytic ability of the granular activated carbon of the product.
000 m ² / g is preferred, about 500-800
It is particularly preferably m ² / g.

In the method for producing granular activated carbon of the present invention, a mixture containing the above-mentioned powdery activated carbon as a raw material and a binder is first prepared. A mixture containing powdered activated carbon and a binder,
It may be prepared by mixing powdered activated carbon and a caking agent, or may be prepared by mixing non-powdered (that is, finely granular) activated carbon and a caking agent and then pulverizing. As the binder, the kind is not limited as long as it can give the raw powdery activated carbon a caking property and can make the powdered activated carbon into a moldable state,
For example, coal tar pitch, petroleum pitch, pulp effluent,
It is preferable to use plastic or the like.

The amount of the binder used is preferably 10 to 40 parts by weight, and more preferably 20 to 3 parts by weight, based on 100 parts by weight of the powdered activated carbon as a raw material.
0 parts by weight is especially preferred.

Further, in order to reduce the amount of the above-mentioned binder used, caking coal or the like can be added to the mixture containing the powdered activated carbon and the binder within a range in which the strength is not lowered by the generated gas. . In this case, although depending on the volatile content of caking coal and the button index, the amount of caking coal is preferably about 10 to 50 parts by weight, and about 20 to 40 parts by weight, based on 100 parts by weight of powdered activated carbon. Particularly preferred. When caking coal is used, the compounding amount of the caking agent can be reduced as described above, and powdery activated carbon 100
5 to 30 parts by weight, particularly preferably 10 to 10 parts by weight
It can be 20 parts by weight.

In addition to the binder, a molding aid (a solvent or a surfactant for improving the compatibility of the binder such as pitch with the powdered activated carbon, a lubricant for smoothing extrusion molding), , A metal compound such as vanadium, iron, copper, or manganese for improving SO ₂ adsorption capacity and NOx decomposing ability may be added.

In the method for producing granular activated carbon of the present invention, a mixture containing powdered activated carbon and a binder is molded into a predetermined size.

The molding is carried out by using various molding means such as extrusion molding, compression molding and rolling granulation. The shape of the obtained molded product can be various shapes depending on the use of the finally obtained granular activated carbon and the like, for example, cylindrical shape, pipe shape (hollow), spherical shape, spheroidal shape (carbonaceous body shape), etc. Is mentioned.

In the method for producing granular activated carbon of the present invention, the molded article obtained above is carbonized and activated to obtain the desired granular activated carbon.

Carbonization is a process of raising the temperature to about 500 to 800 ° C. and removing the volatile components in the raw material and the binder in advance at this carbonization temperature.

When the temperature rise temperature exceeds about 500 ° C./h or the carbonization temperature exceeds 800 ° C., the molded product becomes more prone to shrinkage (shrinkage), and the subsequent activation becomes difficult to proceed.

The activation performed after carbonization is about 900-1.
It is a step of gasifying a part of carbon at a temperature of 100 ° C. to develop pores.

For example, when water vapor is used as the activating gas, carbon monoxide gas is generated by the reaction formula C + H ₂ O → CO + H ₂ to generate pores.

When carbon dioxide gas is used as the activating gas, carbon monoxide gas is generated by the reaction formula C + CO ₂ → 2CO to generate fine pores.

An oxidizing gas such as oxygen gas may be used as the activating gas.

Carbonization and activation are preferably carried out separately in order to obtain granular activated carbon having high strength, high adsorption capacity and high catalytic activity. For example, carbonization is first performed in a firing furnace such as an internal heat type or external heat type rotary kiln, and then activation is performed while injecting an activation gas in another firing furnace such as an internal heat type or external heat type rotary kiln. As the firing furnace, an external heating type upright furnace, a fluidized bed furnace, a moving bed furnace, etc. can be used in addition to the rotary kiln.

However, in order to simplify the process, carbonization and activation can be performed in one firing furnace. As described above, the carbonization temperature is about 500 to 800 ° C and the activation temperature is about 900 to 1.
Since it is 100 ° C. and the activation temperature is higher than the carbonization temperature,
This is because the carbonization temperature of about 500 to 800 ° C. is inevitably passed through in the process of raising the temperature to the activation temperature. In this case, since the heating rate of carbonization and activation cannot be adjusted separately,
Normally, the heating rate of carbonization becomes faster, resulting in shrinkage (contraction).
As a result, it is difficult for the activation to proceed, so that it is possible to obtain granular activated carbon that has high strength but is slightly inferior in adsorption performance and catalytic performance to the case where carbonization and activation are performed separately.

The granular activated carbon which is the object of the present invention obtained after carbonization and activation has a large particle size and its size (the diameter of the top surface or the bottom surface in the case of columnar shape, the diameter in the case of spherical shape).
Is, for example, 5 to 30 mm. In the case of columnar granular activated carbon, the height is 1 to 3 times the size (diameter). The granular activated carbon having a particle size of 5 to 30 mm obtained by the present invention has the following merits. That is, if the size is less than 5 mm, the ventilation pressure loss in the moving bed reactor increases, whereas if it is 5 mm or more, such a problem of ventilation pressure loss can be avoided. If the size exceeds 30 mm, (i) the efficiency of contact with the gas in the packed bed is lowered, and the adsorption or catalytic performance is lowered. (Ii) In the moving bed plant, when the activated carbon falls during the transportation process However, it causes problems such as crashing due to collision, while 3
When it is 0 mm or less, desired adsorption or catalytic performance can be maintained, and the problem of fragmentation due to collision is small. In order to obtain a granular activated carbon having a large particle size of more than 30 mm, it is necessary to make the molded product before carbonization / activation also have a large particle size.
In the case of a molded product having a large particle size, it is not easy to remove volatile substances from the molded product and to activate the inside, and it becomes impossible to obtain granular activated carbon having desired physical properties. Also in this respect, the upper limit of the size of the granular activated carbon (3
0 mm) has critical significance.

The granular activated carbon obtained by the method of the present invention is excellent in strength and has a specific surface area of, for example, about 500 in addition to the merit of having a large particle size as described above.
It is as large as ~ 1200 m ² / g and has a high adsorption ability and a high catalytic ability.

The reason why granular activated carbon having both high strength, high adsorption capacity and high catalytic capacity, which could not be obtained by the conventional method, could be obtained by the method of the present invention is that it is volatilized as a raw material. When powdered activated carbon with a small content and a large specific surface area is used, and a mixture containing this and a binder is molded and then carbonized and activated, the generation of gas derived from volatile matter is suppressed to a minimum, and under mild conditions. This is because carbonization and activation can be sufficiently performed.

[0034]

EXAMPLES Examples of the present invention will be described below.

[Example 1] As raw material activated carbon, Australian coal for thermal power generation (particle size 3 to 2 mm or less, volatile content 29%)
About 30% in the presence of 35% water vapor in an internal heating kiln
A product obtained by heating at 0 ° C./h and carbonizing and activating at 950 ° C. for 1 hour was used. The specific surface area of this powdered activated carbon is 600 m
² / g, volatile matter was 2.1%.

Coal tar pitch as a binder was added to this raw material activated carbon in a ratio of 20 parts by weight to 100 parts by weight of the raw material activated carbon, and the mixture was pulverized to 80 mesh or less. Then, a small amount of water was added and kneaded to obtain powdered activated carbon. And a binder mixture was obtained. This mixture is extruded by an extruder and is about 12 mm.
A columnar molded product having a diameter of 15 mm is prepared, and then this molded product is put into an internal heating kiln and heated from room temperature to 950 ° C. at a heating rate of about 300 ° C./h in the presence of 35% steam. Then, this temperature was maintained for 1 hour to carry out carbonization and activation at the same time. The average diameter of the obtained granular activated carbon was about 10 mm. In addition, specific surface area, crush strength, rotary drum strength, SO
₂ Adsorption capacity and NOx resolution are shown in Table 1. The methods for evaluating these physical properties are as follows.

Specific surface area: Measured by the BET method using N ₂ gas. Crushing strength ... A vertical load was applied to activated carbon with a Kiya type hardness meter, and the strength was measured from the load at the time of breaking. Rotating drum strength: Put 2 kg of activated carbon in a hexagonal column-shaped rotating drum, rotate this drum at a speed of 20 rotations per minute for 7 hours, and then sieve with a 2 mm sieve, and the ratio of remaining on the sieve. The rotating drum strength was measured from SO ₂ adsorption capacity ... N ₂ gas containing SO ₂ 2%, H ₂ O 10%, O ₂ 6% was supplied to a test device in which 5 g of granular activated carbon was placed in a basket and the adsorption temperature was 100 ° C. and the adsorption time was Three
The test was carried out for a period of time to determine the SO ₂ adsorption amount (mg) per 1 g of activated carbon NOx resolution ... NO 300 ppm, NH ₃ 300
N ₂ gas containing ppm, H ₂ O 7%, and O ₂ 5% was fed to a fixed bed reactor at 145 ° C. filled with 1 liter of activated carbon at 600 liters each for 24 hours, and the inlet of the reactor,
The NOx concentration at the outlet was measured to calculate the NO removal rate (%).

From Table 1, the granular activated carbon obtained in this example has a high crushing strength of 30 kg and a rotating drum strength of 93%, as well as a high specific surface area of 800 m ² / g.
The SO ₂ adsorption capacity was 120 mg / g, and the NOx decomposing ability was 78%, indicating high adsorption capacity and high catalytic activity.

Comparative Example 1 The above-mentioned Australian coal was used as it was. Coal tar pitch was mixed in a ratio of 20 parts by weight to 100 parts by weight of coal, and then pulverized to 80 mesh or less. Then, after obtaining a molded product in the same manner as in Example 1, the temperature was raised at about 300 ° C./h in the presence of steam to obtain 950
Carbonization and activation at 1 ° C. for 1 hour gave granular activated carbon. The average diameter of the obtained granular activated carbon was about 10 mm. The physical property values are shown in Table 1. From Table 1, the granular activated carbon of this Comparative Example 1 has a crushing strength of 27 kg and a rotating drum strength of 90%.
The strength was lower than that of Example 1. The specific surface area is also low at 320 m ² / g and the SO ₂ adsorption capacity is 65 mg / g,
The NOx resolution was 41%, which was inferior to that of Example 1.

[Comparative Example 2] Using Australian coal as it is,
Coal tar pitch was mixed with this in a ratio of 20 parts by weight with respect to 100 parts by weight of coal, and then pulverized to 80 mesh or less, and the obtained mixture was molded, and in the presence of steam, about 30 parts by weight was formed.
The temperature was raised at 0 ° C / h, and carbonization and activation were performed at 950 ° C for 1 hour.
Up to this point, the operation was the same as in Comparative Example 1 above, but in Comparative Example 2, further activation was carried out at 950 ° C. for 3 hours in the presence of steam to obtain granular activated carbon. The average diameter of the obtained granular activated carbon was about 9.5 mm. The physical property values are shown in Table 1. From Table 1, the granular activated carbon of this Comparative Example 2 is improved in specific surface area, SO ₂ adsorption capacity and NOx decomposing ability as compared with the granular activated carbon of Comparative Example 1 by performing additional activation treatment.
The value was almost equal to that of the granular activated carbon of
The rotary drum strength was significantly lower than that of the granular activated carbons of Comparative Example 1 and Example 1.

[0041]

[Table 1]

From the above results, in Example 1 using a mixture of powdered activated carbon and a binder, granular activated carbon having both high strength, high adsorption ability and high catalytic ability was obtained, whereas coal In Comparative Examples 1 and 2 using the binder mixture, it was clarified that only one of strength, adsorption ability and catalytic ability was inferior.

In Example 1 above, the SO ₂ adsorption capacity and NOx decomposing ability of the obtained granular activated carbon were measured, and Comparative Example 1
The suitability of the granular activated carbon of Example 1 as a desulfurization adsorbent and a denitration catalyst was clarified in comparison with the granular activated carbon of Example 2. However, in addition to the desulfurization adsorbent and the denitration catalyst, (i) hydrogen chloride,
Hydrogen halide such as hydrogen fluoride, harmful chlorine compounds such as trihalomethane and dioxin, harmful odor components such as ammonia, hydrogen sulfide, mercaptan, aldehydes, organic acids and amines, volatile harmful heavy metals such as mercury, benzene and phenol, etc. Removal of many harmful substances such as aromatic hydrocarbons and polycyclic hydrocarbons such as benzpyrene, (ii) recovery of solvent, (iii) purification of various raw material gases, and (iv) various synthesis in which activated carbon exerts catalytic function Similar effects can be obtained even when used for reactions and the like.

[0044]

As described above, according to the present invention, there is provided a method for producing granular activated carbon which has both high strength, high adsorption ability and high catalytic ability.

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[Procedure amendment]

[Submission date] April 8, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

Further, as a method for obtaining granular activated carbon activated to the inside, after mixing a carbonate such as dolomite and a sulfate such as potassium sulfate and sodium sulfate with the raw material coal, the mixture is heated to remove the carbonate and sulfate. Although by generating an oxidizing gas and a method of promoting internal activation, even in this case, the formation of cracks and air sinuses by gas generation, there is a drawback that granular activated carbon of high strength can not be obtained.

Claims (11)

[Claims] 1. A method for producing granular activated carbon, which comprises molding a mixture containing powdered activated carbon and a binder into a predetermined size, and then carbonizing and activating the molded product. 2. A powdered activated carbon as a raw material, which is obtained by (i) carbonizing and activating fine-grained or powdery coal in the presence of steam, (ii) preforming the coal in the presence of steam. Carbonized / activated, then pulverized, (iii) Zinc chloride activated method, and (iv) Flue gas desulfurization treatment, denitration treatment or desulfurization / denitration treatment, and deactivated. The method according to claim 1, which is at least one selected from powdered activated carbon separated from the regenerated granular activated carbon after heating and regeneration of the granular activated carbon. 3. The powdered activated carbon as a raw material is about 400 to 1000.
The method according to claim 1, which has a specific surface area of m ² / g. 4. The method according to claim 1, wherein the binder is at least one selected from coal tar pitch, petroleum pitch, pulp waste liquor and plastics. 5. The method according to claim 1, wherein the amount of the binder used is 10 to 40 parts by weight based on 100 parts by weight of the powdered activated carbon as a raw material. 6. The method according to claim 1, wherein at least one selected from caking coal, a molding aid and a metal compound is added to the raw material powdered activated carbon and a caking agent. 7. The method according to claim 1, wherein carbonization and activation are performed simultaneously or separately. 8. The method of claim 7, wherein the carbonization is performed at a temperature of about 500-800 ° C. 9. The method according to claim 7, wherein the activation is carried out at about 900 to 1100 ° C. in the presence of an oxidizing gas such as water vapor, carbon dioxide gas, and oxygen gas. 10. The obtained granular activated carbon is about 500-12.
The method according to claim 1, having a specific surface area of 00 m ² / g. 11. The method according to claim 1, wherein the obtained granular activated carbon has a size of 5 to 30 mm.