JP2007182358A - Method for producing activated carbon - Google Patents

Abstract

An object of the present invention is to provide an activated carbon manufacturing method capable of achieving smooth operation of a manufacturing apparatus, improvement of worker safety, and prevention of environmental pollution when manufacturing activated carbon.
Two or more activation devices are used, a first activation device is charged with a carbon material and the first activation device is started, and then a second activation device is charged with a carbon material. Start of the activation device, further delay the charging timing of the carbon material from the third activation device to the Nth activation device in order to start the operation of the third to Nth activation devices, respectively, and then finished the operation The inside of the activation device is dried, the carbon material is charged, and the first activation device is operated again.
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Description

  The present invention relates to a method for producing activated carbon.

Activated carbon obtained by carbonizing and activating a carbon material has a large internal surface area and is excellent in adsorbability of gas and liquid, and is a useful material used in various applications. Therefore, various techniques have been developed for producing activated carbon.
For example, in Patent Document 1, a container is pushed by a pusher along a container moving path that connects a raw material supply section, an inlet side replacement chamber, a tunnel furnace, a cooling zone, a water injection chamber, an outlet side replacement chamber, and a reaction mixture discharge section in a closed shape. A circulating device is disclosed. This apparatus is an apparatus that continuously performs a series of steps from charging of raw materials to dehydration, activation reaction, cooling, water injection and discharge of the reaction mixture discharge section while moving the container. In Patent Document 1, a mixture in which a carbon material, an alkali hydroxide and water are mixed is used as a raw material. Accordingly, the activation reaction by the alkali hydroxide proceeds, and a metal alkali and a substance containing it (for example, sodium carbonate) are generated.

However, in the technique disclosed in Patent Document 1, metal alkali generated by the activation reaction adheres to and accumulates on a driving mechanism such as a pusher or a shielding door, thereby preventing smooth operation. As a result, it becomes difficult to maintain the confidentiality of the activated carbon production apparatus, which not only pollutes the surrounding environment, but also causes a problem in worker safety.
JP-A-5-306109

  An object of the present invention is to solve the above problems and to provide a method for producing activated carbon capable of achieving smooth operation of a production apparatus, improvement of worker safety, and prevention of environmental pollution when producing activated carbon. And

  In the present invention, when the activated carbon is produced by activating the carbon material, the two activation devices are used, the carbon material is inserted into the first activation device, and the operation of the first activation device is started. Charging the carbon material into the activation device and starting the operation of the second activation device, then drying the interior of the first activation device that has finished operating, charging the carbon material, and operating the first activation device again. Is a method for producing activated carbon in which the first activation device and the second activation device are operated alternately.

  In addition, when the activated carbon is activated by activating the carbon material, the present invention uses three or more activation devices, and after charging the first activation device with the carbon material and starting the operation of the first activation device, The carbon material is charged into the second activation device, the operation of the second activation device is started, and the charging timing of the carbon material is sequentially delayed from the third activation device to the Nth activation device, and the third to Nth activations, respectively. The first activation device to the Nth activation device are sequentially operated by starting the operation of the device, then drying the inside of the first activation device that has finished the operation, charging the carbon material, and operating the first activation device again. This is a method for producing activated carbon that operates repeatedly.

  In the activated carbon production method of the present invention, each activated carbon production process by the first to N-th activation devices is performed in a raw material charging step and an activation device in which a mixture of a carbon material and an alkali metal compound is charged into the activation device. An activation process that generates activated carbon and metal alkali by heating the mixture, a cooling process that cools the heated mixture, and an alkali deactivation that converts the metal alkali to alkali metal hydroxide by adding moisture to the cooled mixture It is preferable to comprise a step and a discharge step of discharging the obtained activated carbon and alkali metal hydroxide from the activation device. The activation device is preferably a rotary kiln furnace or a fixed bed furnace.

  ADVANTAGE OF THE INVENTION According to this invention, when manufacturing activated carbon, smooth operation of a manufacturing apparatus, the improvement of a worker's safety, and prevention of environmental pollution can be achieved.

The carbon material used as a raw material in the present invention is
(a) Carbonated products such as coconut shells and coal
(b) Carbonized products prepared from petroleum or coal pitch
(c) Oil and coal (coke)
(d) Phenolic resin carbonized products
(e) Carbon black
(f) Fullerene black
(g) Carbon fiber
(h) and carbon nanotubes. These carbon materials can be used in any shape such as granular or fibrous. Further, the carbon materials (a) to (h) may be used alone, or two or more kinds thereof may be mixed and used. Further, preliminary firing may be performed in advance before the activation treatment.

In the case of using a granular carbon material, it is preferable to use particles having a particle size of 10 mm or less because the activation reaction does not proceed uniformly when the particle size exceeds 10 mm. More preferably, the particle size is 1 μm to 1 mm.
When a fibrous carbon material is used, a fiber piece having a diameter of 1 mm or less and a length of 10 mm or less is used in order for the activation reaction to proceed uniformly. More preferably, the diameter is 0.1 mm or less and the length is 1 mm or less. The diameter is more preferably 0.1-100 μm. The aspect ratio of the fiber piece is preferably 1 to 10. Here, the aspect ratio is a value calculated by the following equation (1).

Aspect ratio = fiber length / fiber diameter (1)
Such a carbon material is charged into an activation device and activated, and activated carbon is produced. In the present invention, two or more activation devices are used.
Below, the case where two activation apparatuses are used is demonstrated. Here, in order to distinguish the two activation devices, they are referred to as a first activation device and a second activation device, respectively.

  First, the carbon material is charged into the first activation device, and the first activation device is operated. Thereafter, while the first activation device is operating, the carbon material is charged into the second activation device, and the second activation device is operated. Next, after the activation process is completed in the first activation device and the obtained activated carbon is discharged, the inside is dried, the carbon material is charged into the first activation device again, and the first activation device is operated. Thus, activated carbon can be manufactured semi-continuously by operating a 1st activation device and a 2nd activation device alternately.

Next, a case where three or more activation devices are used will be described. Here, in order to distinguish three or more activation devices, they are referred to as a first activation device, a second activation device, a third activation device, and an Nth activation device, respectively. N is an integer of 3 or more.
First, the carbon material is charged into the first activation device, and the first activation device is operated. Thereafter, while the first activation device is operating, the carbon material is charged into the second activation device, and the second activation device is operated. Further, while the first activation device and the second activation device are operating, the carbon material is charged into the third activation device, and the third activation device is operated. In this way, the charging timing of the carbon material is sequentially delayed, and the third to Nth activation devices are operated. Next, after the activation process is completed in the first activation device and the obtained activated carbon is discharged, the inside is dried, the carbon material is charged into the first activation device again, and the first activation device is operated. Thus, activated carbon can be manufactured semi-continuously by sequentially operating the first to Nth activation devices repeatedly.

As described above, a plurality of activation devices are used in the present invention. The procedure of the activation process in each activation device is the same. The procedure of the activation process will be described.
When the carbon material is charged into the activation device, it is preferably mixed with an alkali metal compound in advance. The alkali metal compound used in the present invention is an alkali metal hydroxide, such as lithium hydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide, rubidium hydroxide and the like. These alkali metal compounds may be used alone or in combination of two or more.

When mixing a solid alkali metal compound with a carbon material, a commercially available pellet may be used. However, considering that the carbon material is a solid, it is desirable that the alkali metal compound is fine in order to mix uniformly, and a particle size of 500 μm or less is preferable.
Further, an aqueous solution in which an alkali metal compound is dissolved in water may be mixed with the carbon material.
If the mixing amount of the alkali metal compound is too small, the progress of the activation treatment is hindered. The greater the amount of the alkali metal compound mixed, the more the activation process proceeds. However, when a large amount of alkali metal compound is mixed, the production cost of activated carbon increases. Therefore, the mixing ratio is preferably 1 to 5 parts by mass with respect to 1 part by mass of the carbon material in consideration of economy. More preferably, it is 2 parts by mass of the alkali metal compound with respect to 1 part by mass of the carbon material.

The activation device is not limited to a specific configuration, and conventionally known devices such as a rotary kiln type furnace and a fixed bed type furnace can be used.
When a rotary kiln furnace is used, if the raw material (that is, a mixture of a carbon material and an alkali metal compound) is excessively charged, the progress of the activation process is hindered, and a homogeneous activated carbon cannot be obtained. Therefore, a small amount of raw material is charged and activated. When the amount of raw material charged is reduced, the productivity per one activation device is lowered. In the present invention, however, a decrease in the production amount of activated carbon is prevented by using a plurality of activation devices.

  Even when a fixed bed furnace is used, if the raw material is excessively charged, the progress of the activation treatment is hindered, and homogeneous activated carbon cannot be obtained. Therefore, in the fixed bed furnace, the raw material is thinly deposited on the dish-shaped raw material placing member. When the raw material loading amount of the raw material placing member is reduced, the productivity per raw material placing member is lowered, but in the present invention, the raw material placing members are arranged in multiple stages, or a plurality of activation devices are used. Prevents the production of activated carbon from decreasing. Moreover, considering the use of the raw material mounting member in a high-temperature alkaline atmosphere, it is preferable to use a material having alkali corrosion resistance such as Inconel or nickel.

  The raw material (that is, a mixture of a carbon material and an alkali metal compound) charged in the activation device is heated in the activation device. The heating means is not limited to a specific configuration, and a conventionally known indirect heating heat source such as a heater using gas or electricity can be used. Direct heating such as induction heating or microwave heating can also be used. In the direct heating, since the raw material mounting member serves as a heating body, the heating rate is higher and the thermal efficiency is higher than indirect heating in which heat is supplied from the outside.

The atmosphere in the activation device is an inert atmosphere. Accordingly, helium gas or argon gas can be used as the atmospheric gas, but it is preferable to use nitrogen gas in consideration of economy.
When the heating rate of the activation device exceeds 100 ° C./min, foaming of the carbon material and the alkali metal compound occurs. On the other hand, if it is less than 1 ° C./min, it takes a long time to raise the temperature, and the productivity of the activated carbon decreases. Therefore, the temperature rising rate is preferably in the range of 1 to 100 ° C./min. More preferably, it is 5-20 degreeC / min.

Even if the heating temperature of the activation device exceeds 900 ° C., the effect of significantly activating the activation reaction is not recognized. On the other hand, at less than 600 ° C., the activation reaction does not proceed sufficiently. Therefore, the heating temperature is preferably in the range of 600 to 900 ° C.
The holding time at a predetermined temperature is not particularly required, but it is preferable to provide a holding time of up to 5 hours in order to promote the activation reaction uniformly and obtain a homogeneous activated carbon.

By heating the raw material in this way, the activation reaction proceeds, the alkali metal compound (ie, alkali metal hydroxide) is reduced, and a metal alkali is generated.
After the activation process is completed, the high temperature raw material is cooled in the activation device. The cooling means is not limited to a specific configuration, and a conventionally known cooling method such as natural cooling or cooling with a cooling gas can be used. When the cooling gas is used, it is preferable to circulate a gas having the same component as the atmosphere gas in the activation device. However, it is not possible to safely discharge from the activation reaction only by cooling the raw material. The reason is that the metal alkali generated by the activation reaction releases hydrogen when it comes into contact with air, which may cause combustion or explosion.

  Then, water is added to the raw material which performed the activation process, and a metal alkali is inactivated. Here, inactivation refers to a process of converting a metal alkali into a stable hydroxide. As a method for adding water, there are methods such as circulating water vapor in the activation device or spraying mist-like water droplets. However, in order to prevent the combustion and explosion of the metal alkali, it is preferable to continue supplying water until the inactivation of the metal alkali is completed, regardless of which method is employed.

In addition, cooling of the raw material which performed the activation process, and inactivation of a metal alkali may each be performed separately, or you may perform both processes simultaneously.
After inactivating the metal alkali in this way, the obtained activated carbon and alkali metal hydroxide are discharged from the activation device. For discharging the activated carbon and the alkali metal hydroxide, a method of inserting a dedicated jig into the activation device and mechanically scraping it, or a method of pouring water into the activation device and causing it to flow out as slurry can be employed.

In addition, the method of pouring water into the activation device and causing the slurry to flow out can be used in combination with the above-described treatment for inactivating the metal alkali. In that case, it is impossible to carry out the deactivation of the metal alkali and the cooling of the raw material subjected to the activation treatment at the same time. That is, after the cooling of the raw material subjected to the activation treatment is completed, water is poured into the activation device.
As described above, various methods can be used for cooling the raw material after the activation treatment, inactivating the metal alkali, and discharging the activated carbon and the alkali metal hydroxide. However, even if any method is adopted, it is inevitable that the inside of the activation device gets wet with moisture.

Therefore, it is necessary to dry the inside of the activation device before charging the raw material again. The means for drying the activation device is not limited to a specific configuration, and it is possible to evaporate water by circulating a high-temperature gas. As the gas, the gas used for cooling the raw material after the activation treatment described above can be used.
On the other hand, activated carbon and alkali metal hydroxide discharged from the activation device are supplied with water to dissolve the alkali metal hydroxide in water regardless of the method of discharge. The water can be filtered water, ion exchange water, distilled water, or the like. However, it is preferable to use ion-exchanged water or distilled water because trace amounts of impurities contained in the filtered water may be adsorbed by the activated carbon and the quality of the activated carbon may deteriorate.

The alkali metal hydroxide can be dissolved at room temperature, but the dissolution time can be shortened by heating to about 80 ° C.
Next, the solid activated carbon and the alkali metal hydroxide aqueous solution are filtered to separate and recover the activated carbon. The activated carbon thus recovered is dried and used for various purposes.
As described above, in the present invention, after the activation process is completed, it is necessary to dry the inside of the activation device before charging the raw material again. Therefore, the activation apparatus repeatedly performs a series of procedures including raw material charging, activation treatment, cooling, alkali deactivation, discharge, and drying in a discontinuous manner (so-called batch treatment). Activated carbon is manufactured semi-continuously by using two or more activation devices.

  Since each activation device performs discontinuous operation, the activation process is stopped when the shielding door of the activation device is opened and the raw material is charged or discharged. Further, during operation of the activation device, the metal alkali generated in the activation process is inactivated, so that it is possible to suppress the metal alkali from being deposited on various parts of the activation device (for example, a drive mechanism such as a shielding door). . As a result, not only can the smooth operation of the activation device be maintained, but also the airtightness during operation can be maintained, so that improvement of worker safety and prevention of environmental pollution can be achieved.

  The mesophase pitch was carbonized at 600 ° C., and 24 kg of the obtained carbon material was pulverized to an average particle size of 30 μm. To this fine carbon powder, 48 kg of potassium hydroxide (average particle size 500 μm) was added and mixed. The obtained mixture was placed on a plate with a thickness of 20 mm, and the plates were further arranged in two stages and charged into the first activation device (that is, a fixed bed furnace). The heater was then energized and heated to 800 ° C. at a rate of temperature rise of 2 ° C./min and held for 1 hour in a nitrogen atmosphere. Then, it stood to cool naturally and when the temperature in an activation device became 150 degreeC, water vapor | steam was supplied in the activation device and the metal alkali was inactivated. Next, water was poured into the activation device, and activated carbon and alkali metal hydroxide were discharged as a slurry. The time required for one cycle operation was 24 hours.

On the other hand, after 4 hours passed from the start of operation of the first activation device, a mixture of carbon fine powder and potassium hydroxide was charged into the second activation device, and operation of the second activation device was started. Since the operating conditions of the second activation device are the same as those of the first activation device, description thereof is omitted.
Moreover, after 4 hours passed from the start of operation of the second activation device, a mixture of carbon fine powder and potassium hydroxide was charged into the third activation device, and operation of the third activation device was started. Similarly, the fourth activation device, the fifth activation device, and the sixth activation device were operated with a delay of 4 hours each.

In this way, each of the first to sixth activation devices is operated for one cycle, ion exchange water is supplied to the activated carbon and alkali metal hydroxide discharged from each activation device, and the alkali metal hydroxide is dissolved. Further, the activated carbon was separated and recovered by filtration. This washing with ion-exchanged water was repeated several times to confirm that the water adhering to the activated carbon surface was neutral (pH = 7), and then the recovered activated carbon was dried. The specific surface area of the obtained activated carbon was an average of 1500 m ² / g, and it was confirmed that it had excellent adsorptivity.

  In addition, during the operation of the first to sixth activation devices, there was no breakdown of equipment, generation of soot, and leakage of dust.

Claims (4)

  When the activated carbon is produced by activating the carbon material, the second activating device is used after starting the operation of the first activating device by using the two activating devices and charging the carbon material into the first activating device. The carbon material is charged and the operation of the second activation device is started, and then the inside of the first activation device that has finished the operation is dried, the carbon material is charged, and the first activation device is reactivated. The method for producing activated carbon, wherein the first activation device and the second activation device are operated alternately by operating.   When the activated carbon is produced by activating the carbon material, three or more activation devices are used, the carbon material is inserted into the first activation device, and the operation of the first activation device is started. The carbon material is charged into the apparatus and the operation of the second activation device is started. Further, the charging timing of the carbon material is sequentially delayed from the third activation device to the Nth activation device, and the third to Nth activations are respectively performed. By starting the operation of the apparatus, and then drying the inside of the first activation apparatus that has finished the operation, charging the carbon material, and operating the first activation apparatus again, the first activation apparatus to the Nth activation apparatus A method for producing activated carbon, wherein the activation device is sequentially operated repeatedly.   Each activated carbon production process by the first to N-th activation devices is a raw material charging step of charging the mixture of the carbon material and the alkali metal compound into the activation device, and heating the mixture in the activation device. An activation step of generating activated carbon and a metal alkali, a cooling step of cooling the heated mixture, an alkali deactivation step of adding water to the cooled mixture to convert the metal alkali into an alkali metal hydroxide, The method for producing activated carbon according to claim 1, further comprising a discharge step of discharging the obtained activated carbon and the alkali metal hydroxide from the activation device.   The said activation apparatus is a rotary kiln type furnace or a fixed bed type furnace, The manufacturing method of the activated carbon of Claim 1, 2, or 3 characterized by the above-mentioned.