JP3746509B1 - Spherical activated carbon and its manufacturing method - Google Patents

Abstract

[PROBLEMS] An activated carbon that has high hardness, is hardly subject to wear, and has well-developed macropores, transitional pores, and micropores. When used for water treatment, it has excellent adsorption performance for organic matter and at the time of regeneration. Providing activated carbon with less loss due to wear and its manufacturing method.
[MEANS FOR SOLVING PROBLEMS] Coal is a raw material, kneaded with water corresponding to 16 to 24% by weight thereof, formed into a spherical shape by a granulator, and carbonized and activated to obtain a pore volume of 30 nm or more. A spherical activated carbon having a pore volume ratio of 0.2 to 0.6 ml / g, of which the pore volume with a diameter of 1 μm or less is 60% or more and the angle of repose is 30 ° or less solved the above problems.
[Selection figure] None

Description

  The present invention is activated carbon that has high hardness, is hard to be worn, and has well-developed macropores, transitional pores, and micropores. When used for water treatment, it has excellent organic substance adsorption performance and is regenerated. The present invention relates to an activated carbon with little loss due to wear and its manufacturing method.

  Conventionally, activated carbon is used for purification of raw water for water supply, various industrial waters, and waste water. These activated carbons may be regenerated and used after the adsorption capacity is reduced. However, if the activated carbon is lost due to wear or breakage, the activated carbon cannot be regenerated in a high yield.

By the way, in recent years, the existence of trace harmful substances such as dioxins in water has been clarified one after another, and there is a strong demand for an adsorbent that can effectively adsorb these substances. Although the equilibrium adsorption performance is high, it has few transitional pores and macropores, so it cannot handle adsorption of organic substances with various molecular weights present in the target water, and it takes too much time for adsorption, so it is practically sufficient. Adsorption performance cannot be demonstrated.
On the other hand, molded activated carbon made from coal is rich in macropores, but its shape is generally crushed and pelleted, so its shape has a high rate of pulverization during use or when it is regenerated. The playback rate is not high.

A method for producing activated carbon that pulverizes coal into a spherical shape is also known (Patent Document 1), but the spherical activated carbon molded by the conventional molding method has insufficient hardness, so that macropores and micropores are produced. The activated carbon having a practical adsorption capacity and a high regeneration rate has not been obtained.
Shoko 46-41210

  The pores of activated carbon are divided into pores with a diameter of less than 30 nm that are involved in adsorption and pores with a diameter of 30 nm or more that are not directly involved in adsorption and are related to the transport rate of substances inside activated carbon. If the number of pores having a pore diameter of 30 nm or more is small, the adsorption rate becomes slow and it is difficult to use as an adsorbent in practical use. On the other hand, among the pores with a pore diameter of 30 nm or more, for example, if there are many macropores with a diameter of 1 μm or more, the skeleton of activated carbon becomes weak and the mechanical strength becomes low. If this is done, the playback rate will decrease.

Spherical granules are usually produced by rolling granulation. At this time, the particle growth is performed by the powder particles rotating on the granulator being bonded to each other by water intervening between the particles, and the particle size is increased by a snowman type. A spherical molded article having
However, when the raw material is a non-caking powder such as coconut charcoal, it is difficult to form by this rolling granulation method, and even if a spherical granulated material is obtained using a caking agent, etc. The rate of breakage and powdering increases. In the case of coal powder, spherical activated carbon can be obtained by mixing raw material coal with a binder, adding a small amount of water, rolling and granulating, then carbonizing and activating, but it has high mechanical strength and fineness. Activated carbon suitable for water treatment with a pore size of 30 nm to 1 μm and rich in macropores cannot be obtained.
Accordingly, an object of the present invention is a spherical activated carbon suitable for adsorption of organic matter in water, which has high hardness, is hardly subject to wear, and has well-developed pores each having a pore diameter of 30 nm or more and a pore diameter of less than 30 nm. And providing a method for producing the same.

  In order to obtain activated carbon that can solve the above-mentioned problems, the present inventors first realized that the amount of moisture added to the activated carbon during molding and the generation of fine bubbles during kneading are important. That is, when kneading, by adding an amount of water interposing the raw material particles with a minimum necessary thickness, kneading so as not to entrain fine bubbles, thereby narrowing the macropore distribution in the activation process. It was found that spherical activated carbon rich in pores having a diameter of 30 nm to 1 μm and having high hardness can be prepared. Furthermore, it was found that the raw material and particle size of activated carbon are greatly related to the adsorption capacity and strength of activated carbon. The present invention has been completed through further studies based on these findings.

That is, the present invention
(1)
Using coal as a raw material, the pore volume of 30 nm or more in diameter is 0.2 to 0.6 ml / g, of which the proportion of pore volume of 1 μm or less in diameter is 60% or more, and the BET specific surface area is 800 to 2000 m ² / g Spherical activated carbon with an angle of repose of 30 ° or less,
(2)
(1) spherical activated carbon for water purification,
(3)
Powdered coal made from coal is kneaded with water corresponding to 16 to 24% by weight, formed into a spherical shape by a granulator, and carbonized and activated. Spherical shape with a pore volume of 0.2 to 0.6 ml / g, of which the proportion of pore volume with a diameter of 1 μm or less is 60% or more, the BET specific surface area is 800 to 2000 m ² / g, and the angle of repose is 30 ° or less Production method of activated carbon,
(4)
A method for producing a spherical activated carbon in which the spherical activated carbon described in (1) is steam-regenerated at 700 to 1000 ° C .;
It is.

Examples of the raw material of the activated carbon of the present invention include various coals such as lignite, lignite, bituminous coal, and anthracite, but those having appropriate caking properties are preferable. If the caking property is too high, swelling occurs during carbonization, resulting in activated carbon with many voids. On the other hand, if the caking property is low, a spherical object with sufficient hardness cannot be obtained. A preferred raw material is bituminous coal having moderate caking properties.
In order to form activated carbon into a spherical shape, coal is first pulverized with a pulverizer to form a fine powder. The fine powder should be 100-mesh (0.149 mm) pass, preferably 90% or more of powdered charcoal that passes 200 mesh (0.074 mm), and the average particle size of the powder is usually 0.005-0.12 mm, preferably Is 0.01 to 0.1 mm.
In order to make a ball using this powdered charcoal, it is important to first add a specific amount of water and if necessary a binder to the powdered charcoal and mix uniformly, and knead so as not to entrain fine bubbles. .
Since sphere formation is a spherical shape because the cohesion of pulverized coal is promoted by the surface tension of the existing moisture, sphere formation becomes difficult if the amount of moisture contained during sphere formation is too small. On the other hand, if the amount of water supplied is too large, it may become sticky and cannot be formed, and even if it can be formed, particles with fine bubbles are formed, and these bubbles form pores with a diameter of 1 μm or more when carbonized. Since it has a great influence, the ratio of powdered charcoal to water during kneading is extremely important for the formation of pores having a diameter of 1 μm or more of activated carbon.
That is, the moisture present during kneading in the present invention is 16 to 24% by weight, preferably 16 to 20% by weight, and particularly preferably 17 to 20% by weight of the powdered coal. When rolling granulation, an appropriate amount of water, for example, 1 to 10% by weight, preferably 3 to 7% by weight, can be sprayed onto the kneaded product in order to compensate for the water that evaporates. The moisture content of the molded product is 15 to 20%, preferably 16 to 19%.

The binder is effective for imparting strength to the spheroidal charcoal and for increasing the speed of ball forming. Generally, any material having caking properties in the range of 25 to 600 ° C. may be used. For example, carboxymethyl cellulose, hard pitch, soft pitch, pulp waste liquid (main component is lignin sulfonate), and the like are used. The binder is usually used in the range of 3 to 20% by weight, preferably 5 to 15% by weight of the powdered charcoal.
Next, in order to obtain spherical charcoal from this kneaded product, ball rolling can be performed by combining rolling granulation method or extrusion molding with Malmerizer molding, but rolling granulation method is preferred.

  In the present invention, “spherical” does not necessarily mean that each individual particle is a true sphere or a spherical particle close to it, but a rounded particle having an angle of repose of 30 ° or less, preferably 28 ° or less. It means the shape, and the angle of repose is preferably smaller. In molding, it is necessary to determine the proportion of moisture to be blended and the type of binder, but the blending conditions are appropriately selected depending on the raw material coal.

  The obtained spherical charcoal is dried to a moisture content of about 1 to 3% under mild heat conditions, and then carbonized in a temperature range of 300 to 650 ° C. by a known production facility such as a rotary kiln, followed by rotary kiln. And activated in a temperature range of 750 to 1050 ° C. by a known production facility such as a fluidized furnace and a common furnace. The activated carbon is sieved to obtain a uniform particle size. The obtained activated carbon may be washed with a mineral acid such as hydrochloric acid, nitric acid, sulfuric acid and phosphoric acid by a known method, or may be further washed with water. Further, it may be used as an impregnated activated carbon impregnated with chemicals for various purposes.

The activation method is not particularly limited. For example, activated carbon industry, published by Heavy Chemical Industry News Agency (1974), p.23-p.37, activated by active gases such as water vapor, oxygen, carbon dioxide, and chemicals using phosphoric acid, zinc chloride, etc. Activation etc. are used suitably.
BET specific surface area of activation activated carbon is usually 800~2000m ² / g, preferably 900~1800m ² / g, more preferably from 900~1300m ² / g. When the BET specific surface area is small, the micropores are not sufficiently developed and the adsorption performance is lowered.

The activated activated carbon of the present invention has a pore volume of 30 nm or more and a pore volume of 0.2 to 0.6 ml / g, preferably 0.25 to 0.5 ml / g, more preferably 0.3 to 0.4 ml / g, of which the diameter is 1 μm or less. The pore volume ratio is 60% or more, preferably 75% or more, more preferably 80% or more. The pore volume with a diameter of less than 30 nm is 0.4 to 1.0 ml / g, preferably 0.4 to 0.8 ml / g, more preferably 0.5 to 0.8 ml / g. The activated carbon with a small pore volume of less than 30 nm in diameter has a small adsorption capacity.
The packing density of the activated activated carbon is usually 0.43 to 0.63 g / ml, preferably 0.45 to 0.60 g / ml, more preferably 0.47 to 0.57 g / ml.

In order to maximize the ability to adsorb organic substances in water, reduce pressure loss, and increase the regeneration rate, the average particle diameter of the spherical activated carbon should be 0.6 to 10 mm, and for water treatment, preferably 0.6. -3 mm, more preferably 0.6-1.5 mm. What is necessary is just to sieve the spherical charcoal of the target particle diameter using a sieve.
The BET specific surface area of activated carbon is calculated by the BET method by creating a nitrogen adsorption isotherm of activated carbon at liquid nitrogen temperature.
The pore volume of activated carbon with a diameter of 30 nm or less is calculated by the CI method by creating a nitrogen adsorption isotherm of activated carbon at liquid nitrogen temperature.
The macropore volume of the activated carbon is determined using a mercury intrusion pore volume measuring device (manufactured by Micromeritics, AUTOPORE9220).
The angle of repose was obtained by placing activated carbon in the container shown in FIG. 1, gently rolling the container to stand still, and measuring the angle φ (inclination method).
The used activated carbon can be easily regenerated, for example, by heating for about 10 to 30 minutes while introducing water vapor in a furnace maintained at 700 to 1000 ° C., preferably 800 to 900 ° C. The activated carbon obtained by the present invention has a high hardness and is substantially spherical, so that it is difficult to suffer from loss due to particle abrasion due to the regeneration operation, and obtain activated carbon having almost the same preferable performance as before use by steam regeneration. Can do.
This regenerated activated carbon may be washed with a mineral acid such as hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid or the like by a known method, and may be further washed with water. Further, it may be used as an impregnated activated carbon impregnated with chemicals for various purposes.

  In the water treatment process, the activated carbon of the present invention has high adsorptive power and fast organic adsorption rate, and the loss of activated carbon particles during regeneration is extremely small. There is also little deterioration.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

The dried bituminous coal is pulverized to a mean particle size of 62μm (200 mesh pass 90% by weight) with a pulverizer, 10 parts of water and 100 parts of coal (lignin sulfonic acid) are added to 100 parts by weight of coal using a mixer and kneader. 18 parts of 50% aqueous solution was added and kneaded well.
The kneaded product was put on a rolling granulator and granulated while spraying 5 parts by weight of water to obtain a molded product having an average particle size of 1.7 mm. This was dried at 100 ° C. and carbonized at 300 to 600 ° C. Subsequently, steam activation was performed at 850 ° C. for 2 hours. After the activation, particles passed through 2.36 mm through a sieve and not passed through 0.50 mm were collected to obtain activated carbon No. 1. The activated carbon had a BET specific surface area of 1000 m ² / g, a pore volume of 30 nm or more obtained by mercury intrusion method of 0.37 ml / g, of which the ratio of 1 μm or less was 80%.
The pore volume with a diameter of less than 30 nm was 0.50 ml / g, the average particle diameter of activated carbon was 1.3 mm, the angle of repose was 28 °, and the packing density of activated carbon was 0.520 g / ml.

Activated carbon No. 2 was obtained in the same manner as in Example 1 except that the steam activation time was set to 2.5 hours. The activated carbon had a BET specific surface area of 1200 m ² / g, and the pore volume of 30 nm or more obtained by mercury porosimetry was 0.40 ml / g, of which the ratio of 1 μm or less was 83%. The pore volume with a diameter of less than 30 nm was 0.62 ml / g. The average particle diameter of the activated carbon was 1.3 mm, the angle of repose was 28 °, and the packing density of the activated carbon was 0.468 g / ml.

Activated carbon No. 3 was obtained in the same manner as in Example 1 except that the amount of water used in the coal fine powder kneading was 14 parts by weight (a total of 23 parts by weight when combined with the water of the binder solution). The activated carbon had a BET specific surface area of 1020 m ² / g, a pore volume of 30 nm or more in diameter obtained by mercury intrusion method was 0.44 ml / g, of which the ratio of 1 μm or less was 75% . The pore volume with a diameter of less than 30 nm was 0.51 ml / g. The average particle diameter of the activated carbon was 1.3 mm, the angle of repose was 28 °, and the packing density of the activated carbon was 0.491 g / ml.
[Comparative Example 1]

Activated carbon No. 4 was obtained in the same manner as in Example 1 except that the total amount of water used for 100 parts of coal was 26 parts. The activated carbon had a BET specific surface area of 1050 m ² / g, the pore volume of 30 nm or more obtained by mercury intrusion method was 0.52 ml / g, of which the ratio of 1 μm or less was 33%. The pore volume with a diameter of less than 30 nm was 0.53 ml / g, the average particle size of activated carbon was 1.3 mm, and the angle of repose was 28 °. The packing density of activated carbon was 0.459 g / ml.
[Comparative Example 2]

Activated carbon No. 5 was obtained in the same manner as in Example 1 except that the total amount of water used for 100 parts of coal was 15 parts. The activated carbon had a BET specific surface area of 1080 m ² / g, the pore volume of 30 nm or more obtained by mercury porosimetry was 0.15 ml / g, of which the ratio of 1 μm or less was 75%. The pore volume with a diameter of less than 30 nm was 0.54 ml / g, the average particle diameter of activated carbon was 1.3 mm, and the angle of repose was 28 °. The packing density of activated carbon was 0.600 g / ml.
[Comparative Example 3]

In the same manner as in Example 1, 8 parts of water and 18 parts of a 50% by weight aqueous solution of a binder were added to 100 parts by weight of coal, and the mixture was kneaded and molded with a roll compactor, using a hammer mill and a sieve. Activated carbon No. 6 was obtained as a crushed molded product having an average particle diameter of 1.7 mm. The activated carbon had a BET specific surface area of 1040 m ² / g, a pore volume of 30 nm or more in diameter obtained by mercury intrusion method was 0.42 ml / g, of which the ratio of 1 μm or less was 73%. The pore volume with a diameter of less than 30 nm was 0.51 ml / g, the average particle diameter of activated carbon was 1.3 mm, the angle of repose was 39 °, and the packing density of activated carbon was 0.494 g / ml.
[Comparative Example 4]

The coconut shell carbonized product is pulverized to an average particle size of 62 μm (200 mesh pass 90% by weight) with a pulverizer, and 6 parts of water and a binder (lignin sulfonic acid) are added to 100 parts by weight of the coconut shell carbonized product using a mixer and kneader. ) Was added and kneaded well.
While spraying 5 parts by weight of water on the kneaded product, it was put on a rolling granulator to obtain a molded product having an average particle size of 1.9 mm. When this was carbonized at 300-600 degreeC after drying at 60 degreeC, most particle | grains disintegrated and it turned into powder. Therefore, it was not used as a sample in various tests described later.

Except for the powdered activated carbon of Comparative Example 4, various tests described below were performed on activated carbon Nos. 1 to 6.
Hardness measurement test:
The particle size of the activated carbon was adjusted to 2.36 mm to 0.50 mm with a sieve, and the hardness was measured by the hardness measurement method of JIS K1474. This method is mainly a method for obtaining durability against friction.
MS hardness measurement method:
Put 10 ml of activated carbon that has been sieved in advance in the container shown in Fig. 2 using a sieve with a particle size range together with 10 steel balls with a diameter of 7.94 mm. After rotating for 40 minutes at 25 revolutions per minute, the activated carbon and steel balls are separated and activated carbon Is sieved with a 0.355 mm sieve,
[Mass on sieve] x 100 (%) / [Mass on sieve + Mass under sieve]
I asked for it. This method is a method for obtaining durability against impact and friction.

Organic breakthrough adsorption experiment:
Activated carbon No. 1 to 3 (Examples 1 to 3), Activated carbon No. 4 to 6 (Comparative Examples 1 to 3) 220 ml each was packed in a glass column with a diameter of 50 mm, and an aqueous solution containing dibenzofuran 1000 μg / L at 25 ° C. The water was passed at a rate of 2.16 L / h. In order to prevent clogging of the adsorption layer, water was flushed at a rate of 1 L / min for 15 minutes at a frequency of once a week for backwashing. Measure the concentration of dibenzofuran in the activated carbon treated water and the water before treatment with a fluorescence spectrophotometer, obtain the breakthrough rate by the following formula, plot the result on the horizontal axis and the breakthrough rate on the vertical axis. The number of days until the excess rate reached 5% was compared.
Moreover, the volume of the activated carbon at the end of the test was measured.
These results are summarized in Table 1.

本発明の活性炭1〜3、No.5は、高い硬さを有している。一方、直径30ｎｍ以上の細孔容積の過大なNo.4の活性炭は、硬さが低く、直径30ｎｍ以上の細孔容積の過少なNo.5の活性炭は吸着性能が不充分である。また、No.6の活性炭は破砕状であるため、割れ、欠けが生じ、硬さも低かった。

The activated carbons 1 to 3 and No. 5 of the present invention have high hardness. On the other hand, No. 4 activated carbon having an excessive pore volume with a diameter of 30 nm or more has low hardness, and No. 5 activated carbon having an excessive pore volume with a diameter of 30 nm or more has insufficient adsorption performance. Moreover, since the activated carbon of No. 6 was crushed, it was cracked and chipped, and the hardness was low.

Measurement of yield, physical properties and adsorption performance of regenerated activated carbon After completion of the organic breakthrough adsorption test, each activated carbon is heated for 20 minutes while introducing steam in an electric furnace to obtain a regenerated activated carbon. It was. The yield of regenerated activated carbon (based on the fixed carbon content of activated carbon before regeneration), hardness measured by JIS K1474, MS hardness, average particle size, and adsorption performance were compared. The experimental results are shown in Table 2.

The used activated carbon of the present invention (activated carbon No. 1 to No. 3) regenerated at 850 ° C. has a very low loss of activated carbon, a high regeneration yield, and a high hardness of the recycled product. When the regeneration temperature was 950 ° C., the yield and hardness were slightly reduced, but the adsorption ability was improved.
Activated carbon No. 4 having a pore distribution of 30 nm or more in diameter and having a different pore distribution had a low regeneration yield, and the average particle size of the regenerated product was small. When the regeneration temperature was 950 ° C., the regeneration yield further decreased. Activated carbon No. 5 had a low adsorption capacity even after regeneration. Moreover, activated carbon No. 6 in a pulverized state had low yield due to cracking and chipping of the activated carbon during regeneration, the average particle size of the regenerated product was reduced, and the adsorption performance was also lowered. When the regeneration temperature was 950 ° C., the yield was further lowered.

  The activated carbon of the present invention has a high adsorption capacity and does not cause particle loss. In addition, since the activated carbon having a high regeneration yield and the same performance can be obtained even by regeneration, it is particularly advantageously used for water purification of raw water for tap water, various industrial waters, waste water and the like.

Cross section of repose angle measuring device Side view of MS hardness tester container

Claims (4)

Using coal as a raw material, the pore volume of 30 nm or more in diameter is 0.2 to 0.6 ml / g, of which the proportion of pore volume of 1 μm or less in diameter is 60% or more, and the BET specific surface area is 800 to 2000 m ² / g Spherical activated carbon with an angle of repose of 30 ° or less.   2. The spherical activated carbon according to claim 1, which is used for water purification. Powdered coal made from coal is kneaded with water corresponding to 16 to 24% by weight, formed into a spherical shape by a granulator, and carbonized and activated. A spherical shape with a pore volume of 0.2 to 0.6 ml / g, of which the proportion of pore volume with a diameter of 1 μm or less is 60% or more, the BET specific surface area is 800 to 2000 m ² / g, and the angle of repose is 30 ° or less. Production method of activated carbon. A method for producing spherical activated carbon, wherein the spherical activated carbon according to claim 1 is regenerated by steam at 700 to 1000 ° C.

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