JP2012180273A - Hollow activated carbon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide hollow activated carbon having high adsorption efficiency, little pressure drop, and high strength, and to increase the strength in particular to a level at which the hollow activated carbon can be used with repeated regeneration.SOLUTION: A molded raw material including a plurality of through-holes is continuously carbonized, dry-distilled, and activated in the same reaction furnace. To be more specific, the molded raw material including a plurality of through-holes inside is obtained first by extrusion molding an organic powder raw material including lignin such as wood, bamboo, okara, coffee grounds, compost, and paper-making sludge, or by machine-molding a wood chip material such as Japanese cedar, ground cedar, lauan, gum tree, bamboo, ramin, and paulownia (S1). Next, the molded raw material is carbonized and dry-distilled by putting the molded raw material in a heating furnace and heating it while oxygen is cut off (S2). Next, subsequent to the carbonization and dry-distillation process, activation is carried out by further raising the temperature and pouring water into the heating furnace (S3). The hollow activated carbon is obtained by these sequential processes.

Description

  The present invention relates to a novel hollow activated carbon having high adsorption efficiency.

  Activated carbon is used by being filled in a deodorizing apparatus or the like, and is widely used for removing odors from large deodorizing treatment facilities to small household deodorizing equipment.

  Activated carbon is generally in the shape of a column called a pellet, but it is known to have a hollow structure with a through-hole by hollowing out the inside in the axial direction and a cross-shaped rib inside. (For example, Patent Documents 1 and 2). Since these structures can reduce pressure loss, the amount of deodorizing air can be increased.

  In general, in order to produce activated carbon with low pressure loss, in the case of pellet-like activated carbon, a method of increasing the outer diameter can be considered. However, when the outer diameter is increased, the activation gas is difficult to reach the inside, so that the activation time becomes longer and the overall size becomes smaller. If the activation time is shortened to prevent this, the resulting adsorption efficiency decreases. Then, in order to raise adsorption performance, in order to make activation gas reach the inside, the idea of making the inside hollow is born.

  Pelletized activated carbon is currently commercially available and has a maximum diameter of 7 mmφ and is approximately 5 mm to 30 mm in length. However, when the inside is hollowed out in the axial direction, it is activated in the activation process. Since the gas easily reaches the inside, the activation time can be shortened to enhance the adsorption performance.

JP 2002-65824 A JP 2005-52785 A

  In general, typical performance indexes of activated carbon include adsorption efficiency, pressure loss, and strength. In the present invention, the adsorption efficiency means an index evaluated by the amount of adsorption of a specific organic substance (for example, benzene). The pressure loss is expressed by the pressure loss ΔP with respect to the gas linear velocity LV (Line Verosity), and means an index for evaluating the amount of deodorized air. A high pressure loss means that the air volume is reduced when a deodorizing fan having the same capacity is used. The strength means an index representing the physical breaking strength of activated carbon itself, that is, the resistance to breaking.

  All of the conventional hollow activated carbons are produced by solidifying activated carbon powder with a binder, and the pressure loss can be reduced, but the strength is small and brittle. Therefore, it could be used only once, and it could not be replayed and used repeatedly.

  The present invention has been made for the purpose of providing an ideal activated carbon having high adsorption efficiency, low pressure loss, and high strength. In particular, while maintaining the conventional adsorption amount and pressure loss. Therefore, the main technical problem is to sufficiently increase the strength to the extent that it can be repeatedly reproduced and used.

  The hollow activated carbon according to the present invention is made by a method in which activated carbon powder is not solidified with a binder as in the prior art, but is formed into a hollow shape from the raw material stage in advance, and the obtained molding material is activated carbonized later. . In this specification, activated carbon having a structure in which a hollow portion is formed inside is collectively referred to as “hollow activated carbon”, but many embodiments can be considered as described later.

  The hollow activated carbon according to the present invention is characterized by being obtained by continuously carbonizing, carbonizing and activating a molding material having a plurality of through holes in the same reaction furnace. Since this hollow activated carbon is provided with a plurality of through holes, the pressure loss can be reduced. In addition, through holes are provided at the molding raw material stage, and through a series of steps of carbonization, carbonization and activation, the activation time can be shortened and the reduction in the size of the hollow activated carbon can be reduced. The strength can be increased.

  This molding raw material may use a powder raw material as a starting material, and specifically includes oga powder, bamboo powder, okara, coffee grounds, compost, papermaking sludge and the like. Further, in order to increase the strength of the finished product, powder lignin may be added as necessary.

  Moreover, this molding raw material may use a wood chip raw material as a starting material. This wood chip raw material should be broadly understood to indicate all raw materials that can be activated carbon by carbonization, carbonization and activation processes. For example, cedar, firewood, lauan, rubber wood, bamboo, lamin, paulownia, etc. High quality wood is preferred. Those that have already been activated carbonized do not fall under “wood chip material”.

  Specifically, this hollow activated carbon has hydrogen and oxygen atoms by repeating the process of placing the molding raw material in a heating furnace, raising the temperature in a state where oxygen is shut off, and maintaining this state for a certain period of time. The carbonization / dry distillation process for desorbing water and the activation process for generating an aqueous reaction by injecting water after further heating are performed continuously and in the same reactor. Conventionally, the carbonization / dry distillation process and the activation process are usually performed in separate furnaces. In the present invention, these processes can be continuously performed in the same reactor. it can.

  According to the hollow activated carbon according to the present invention, the strength can be increased as compared with the conventional hollow activated carbon while maintaining high adsorption performance and low pressure loss, and it can be regenerated and used repeatedly.

FIG. 1 is a diagram illustrating a process for producing the hollow activated carbon of the present embodiment. 2A to 2C show an example of the shape of the forming raw material 1 obtained after the forming step of Step S1. 2A is a perspective view after the molding step, FIG. 2B is a front view, and FIG. 2C is a cross-sectional view. 3A to 3C show an example in which the pellet shape of FIG. 2 is changed to a prism shape. 3A is a perspective view after the molding step, FIG. 3B is a front view, and FIG. 3C is a cross-sectional view. From these figures, the molding raw material 3 has a substantially prismatic shape as a whole, and a through-hole 4 having a diameter D2 is formed along the axial direction on the substantially square bottom surface of one side S. FIG. 4 is an example of a heat curve in the steps S2 and S3. FIG. 5 is a graph showing the pressure loss of various activated carbons. FIGS. 6A to 6C are views for explaining examples of the hollow activated carbon of the present embodiment, and illustrate other embodiments of the forming raw material.

  FIG. 1 is a diagram illustrating a process for producing the hollow activated carbon of the present embodiment. Although details of each step will be described later, an overall flow will be described here. The production method for producing the hollow activated carbon of the present embodiment is characterized in that it is produced by a method in which the hollow activated carbon is molded in advance from the raw material stage, and the obtained molding material is activated carbonized later.

Step S1 is a molding process. The purpose of performing this step is to previously mold the “raw material before being activated carbonized” used as a starting material in the present invention into a hollow shape. Depending on what raw material is used for the starting material, there are roughly two methods. That is,
(1) When using powder raw material (2) When using wood chip raw material. In addition, even if the starting materials are different, the shape of the raw material after the molding step (this is referred to as “molding raw material” in this specification) is substantially the same. However, the size may be different.

  When the powder raw material of (1) is used, this is a process of extruding and molding powder raw materials such as oga powder, bamboo powder, okara, coffee grounds, compost, and paper sludge into a hollow shape. The temperature condition of the extrusion molding is preferably performed in a temperature range from room temperature to 200 ° C. (2) In the case of a wood chip material, this corresponds to a process in which wood such as cedar and straw is previously machined into a hollow shape using a mold or the like.

  2A to 2C show an example of the shape of the forming raw material 1 obtained after the forming step of Step S1. 2A is a perspective view after the molding step, FIG. 2B is a front view, and FIG. 2C is a cross-sectional view. From these figures, it can be seen that the molding raw material 1 has a substantially cylindrical shape (pellet shape) as a whole, and a through hole 2 having a diameter D2 is formed along the axial direction on the bottom surface having a diameter D1. When the length of the column is L, L is approximately 5 mm to 30 mm. Unlike the conventional manufacturing method, it is not yet activated carbonized at this stage.

  In addition, although it is easy to make a pellet shape for reasons such as ease of manufacturing, other shapes such as a prism can be formed by devising a mold or the like. Therefore, in the examples described later, a hollow activated carbon activated by carbonization after providing a through hole in a prism as shown in FIG. 3 is prototyped and its performance is evaluated.

  3A to 3C show an example in which the pellet shape of FIG. 2 is changed to a prism shape. 3A is a perspective view after the molding step, FIG. 3B is a front view, and FIG. 3C is a cross-sectional view. From these figures, the molding raw material 3 has a substantially prismatic shape as a whole, and a through hole 4 having a diameter D2 is formed along the axial direction on the square bottom surface of one side S. When the length of the column is L, L is approximately 5 mm to 30 mm. Unlike the conventional manufacturing method, it is not yet activated carbonized at this stage.

Step S2 is a carbonization / dry distillation process. The purpose of performing this process is to first subject the raw material to glucose decomposition in order to carbonize the molding raw material obtained in step S1. Thereby, hydrogen (H), oxygen (O) and other impurities are eliminated, and a dense carbon structure is obtained. Strictly speaking, carbonization and dry distillation have different meanings, but both are common in that the temperature is raised every certain time in a state where oxygen (O ₂ ) is shut off, so in this specification, the two are not distinguished. It is expressed as “carbonization / dry distillation process”.

Step S3 is an activation process. The purpose of performing this step is to perform an aqueous reaction by injecting water (H ₂ O) into the molding raw material carbonized and carbonized in step S2. As a result, carbon is released from the dense carbon structure in the form of carbon dioxide (CO ₂ ), and a porous carbon structure is obtained. This process is generally called an activation process.

  Step S4 is a sieving step. The purpose of performing this process is to screen the raw material obtained in step 3 based on criteria such as size and quality.

  By the way, in the conventional manufacturing method using wood chip raw material as a starting material, the starting material (for example, coconut husk and coal) is pulverized, sieved, carbonized and carbonized, and then sieved again. , Activate. Finally, another sieving is performed to complete the product. Thus, since there are many steps and the sieving operation is performed three times, the final product is usually 1/9 to 1/10 of the raw material. On the other hand, in the production method for producing the hollow activated carbon of the present embodiment, the sieving step is only required once, and the yield is extremely high.

  In the production method for producing the hollow activated carbon according to the present embodiment, a sieving step is not necessary between Step S2 and Step S3, and both can be performed continuously in the same reactor. This greatly contributes to greatly simplifying the process.

  Next, a specific heat curve will be described. This heat curve is used when a sample described in an example described later is manufactured.

  FIG. 4 is an example of a heat curve showing the passage of time of the temperature in the heating furnace in the steps S2 and S3. The horizontal axis represents the elapsed time, and the vertical axis represents the furnace temperature. However, this is not a strict one, and in fact, a deviation from the set value depending on the performance of the temperature control device is allowed.

As shown in this figure, with the oxygen (O ₂ ) shut off, the temperature is raised to 300 ° C. over about 3 hours, and then 300 ° C. is maintained for 3 hours. Further, the temperature is raised to 400 ° C. over 1 hour and maintained at 400 ° C. for 3 hours. Further, the temperature is raised to 600 ° C. over 2 hours and maintained for 3 hours. The process so far is the carbonization / dry distillation process described in step S2.

Conventionally, the temperature is once lowered for sieving here, but in the present invention, the temperature is increased as it is and the activation process is started. After the carbonization / dry distillation step, the temperature is further raised to 800 ° C. over 3 hours, and after reaching 800 ° C., the temperature is kept for about 28 hours. Water (H ₂ O) is injected at regular intervals during the activation process. As a result, an aqueous reaction occurs, and a porous structure is obtained.

  In addition, since a heat curve can also consider patterns other than this, FIG. 4 only showed an example of the manufacturing method which manufactures the hollow activated carbon of this embodiment.

(Example)
Table 1 shows the results of examining the finished shape, benzene adsorption amount, strength, and pressure loss for various activated carbon samples having different production conditions. The shape was as follows.
As an example of the present invention,
・ Pellet-shaped activated carbon with through-holes (pellet-shaped hollow charcoal)
・ A prismatic activated carbon with through holes (square hollow charcoal)
As a comparative example,
・ Pellets in activated carbon (pellet charcoal)
・ Pellet charcoal with through-holes with cross-shaped ribs formed inside (ribboned hollow charcoal)
・ Flame (crushed charcoal)

Details of the samples A to L shown in Table 1 are as follows.
[Powder material] (Invention)
A Pellet hollow charcoal with 100% sawdust, bottom outer diameter D1 = 25mmφ, bottom inner diameter = 10mmφ, length L = 25mm B Butter: bamboo powder = 4: 1 (weight ratio), molding The raw material dimensions are the bottom outer diameter D1 = 25mmφ, the bottom inner diameter = 10mmφ, the length L = 25mm pellet-shaped hollow charcoal C 100% powder, the molding raw material dimensions are the bottom outer diameter D1 = 20mmφ, the bottom inner diameter = 8mmφ , Length L = 20 mm pellet-shaped hollow charcoal D Oga powder: bamboo powder = 1: 1 (weight ratio), the dimensions of the molding raw material are bottom outer diameter D1 = 15 mmφ, bottom inner diameter = 6 mmφ, length L = 15 mm Pelleted hollow charcoal

[Raw material] (Invention)
E Cedar wood is processed with a mold, and the molding raw material has a pellet-shaped hollow charcoal with a bottom outer diameter D1 = 25 mmφ, a bottom inner diameter = 10 mmφ, and a length L = 25 mm. Is a pellet-shaped hollow charcoal G having a bottom outer diameter D1 = 12 mmφ, a bottom inner diameter = 4 mmφ, and a length L = 12 mm. Square hollow charcoal with a length L = 16 mm provided with through holes

  Among the above samples, the shapes of samples A to F are generally pelleted hollow charcoal as shown in FIG. 2, and the shape of sample G is generally rectangular hollow charcoal as shown in FIG. 3, each having a through hole having an inner diameter D2. Yes.

[Comparative example] (Conventional example)
The following Comparative Examples H to L are all manufactured by a conventional manufacturing method.
H Coconut husk activated carbon made into thin flakes of about 4 mm to 5 mm I Coal pellet charcoal with a finished shape of about 4 mmφ, no through holes J Coal pellet charcoal with a finished shape of about 7 mmφ, no through holes K Powder of coconut shell activated carbon powder Pelletized hollow charcoal that has been granulated by solidifying with a binder (so-called “macaroni charcoal (product name and registered trademark)”)
L Coconut charcoal powder is solidified with a binder, granulated, and ribbed hollow charcoal (so-called “macaroni cross charcoal (product name and registered trademark)”) provided with through-holes and cross-shaped ribs

(result)

  In addition, "shape" in Table 1 has shown the schematic shape of pellet-shaped hollow charcoal, square hollow charcoal, pellet charcoal, hollow charcoal with a rib, and crushed charcoal. In addition, the “finished shape” in the present invention refers to the size of the final shape after the active carbonization of the molding raw material, and in the comparative example, refers to the size of the shape obtained by sieving the activated carbonized final product. . Further, the benzene adsorption amount is an index representing the adsorption performance, and the larger the value, the higher the adsorption performance. Further, the strength is a measured value measured with a Kiyama-type hardness meter, and indicates that the larger the numerical value, the higher the strength.

FIG. 5 is a graph showing the pressure loss of various activated carbons. The samples were A, D, H, I, J, and L in Table 1. This graph is displayed as a logarithm, the horizontal axis represents the gas linear velocity LV [m / s], and the vertical axis represents the pressure loss ΔP [kPa: H ₂ O / m · Bed]. Table 2 shows pressure loss values at three points where the magnitude of the gas linear velocity LV read from FIG. 5 is 0.1, 0.3, and 1 [m / s].

(Evaluation)
-Adsorption performance-
Regarding the adsorption performance, the Lauan material (Sample F) was good, and the white birch (Sample G) was slightly low. In addition, regarding the powder raw material, when a certain amount of bamboo powder was added, the amount of adsorption slightly increased, but overall there was no significant difference. But it turned out that adsorption performance is higher than the sample K and the sample L which were made by the conventional manufacturing method.

-Strength-
From the comparison of powder raw materials having the same raw material composition ratio, it became clear that the larger the size, the higher the strength. Moreover, it became clear from the comparison of the mixing ratio of oga powder and bamboo powder that the amount of adsorption increases as bamboo powder is added, but the strength decreases. This is probably because oga powder contains lignin that functions as a binder, but bamboo powder contains almost no lignin. In other words, it is understood that lignin is effective for increasing the strength of the powder raw material. In this sense, organic powders containing lignin (including powders mixed with “powder lignin”) can be applied as possible powder raw materials. Specifically, powder lignin is added when necessary for oga powder, bamboo powder, okara, coffee grounds and the like. Other possibilities include compost and papermaking sludge. Samples A, C, D, and G that were experimentally produced had sufficient strength to be recyclable.

-Pressure loss-
According to FIG. 5 and Table 2, it can be seen that the pressure loss tends to increase as the air volume increases, but in particular, sample 1 (100% sawdust), sample 2 (slag flour: bamboo powder = 1: 1) and hollow with ribs. It is read that charcoal (corresponding to samples A, D, and L, respectively) has a very small pressure loss.

-Summary-
From the above experiments, each of the three evaluation criteria of adsorption performance, strength, and pressure loss was expressed numerically, but all of these were average on samples A, C, D, and G. It was.

(Example of hollow activated carbon)
Since it is almost impossible to process the shape after activated carbonization, conventionally, the finished activated carbon was sieved for each shape and size to obtain the desired shape, but this method has a very high yield. It was low. On the other hand, when the raw material itself of wood such as cedar and persimmon is used as a starting material, since the wood before active carbonization is processed, the degree of freedom of processing is very large, and thus various shapes are possible. .

  Drawing 6 is a figure for explaining the example of hollow activated carbon of this embodiment, and has illustrated the embodiment of the forming raw material. That is, as shown in FIG. 6 (a), a pellet-shaped wood piece raw material 5a is provided with a plurality of through holes 6a, and as shown in FIG. 6 (b), a spherical wood piece raw material 5b is provided with a plurality of through holes 6b. As shown in FIG. 6C, a heart-shaped wood piece material 5c provided with a plurality of through-holes 6c is conceivable. In addition, although illustration is omitted, many patterns such as a star shape are conceivable.

  In this way, if the wood chip raw material is arbitrarily processed and the carbonization / dry distillation process is performed therefrom, a hollow activated carbon having an arbitrary shape can be produced. In particular, by providing a plurality of through holes, the pressure loss can be further reduced, and further, the activation time is shortened, so that there is an advantage that the reduction in size is reduced.

  The hollow activated carbon of the present embodiment is an ideal activated carbon having high adsorption efficiency, small pressure loss, and high strength, and has the following industrial applicability.

(1) Use for large-sized deodorizing apparatus with large deodorizing air volume When the activated carbon filled in the existing deodorizing apparatus is replaced with the hollow activated carbon according to the present invention, the air volume is greatly increased without changing the facilities. In the past, when it was necessary to increase the air flow, another unit had to be added.
(2) Use as a deodorizing cartridge to be installed in the air outlet of a deodorizing device for a living room or an air conditioner in the field of home use. (3) Use for a rooftop exhaust fan that enables exhaust gas countermeasures.

  Since the hollow activated carbon of this embodiment has the intensity | strength which can be reproduced | regenerated many times, maintaining the conventional adsorption amount and pressure loss, it can suppress a running cost. Therefore, the industrial applicability when the present invention is implemented is extremely large.

1, 3, 5 Molding raw material 2, 4, 6 Through hole

Claims (5)

A hollow activated carbon obtained by continuously carbonizing, carbonizing and activating a molding material having a plurality of through holes in the same reaction furnace. The hollow activated carbon according to claim 1, wherein the molding raw material is an organic powder raw material containing lignin. The hollow activated carbon according to claim 2, wherein the powder raw material includes at least one selected from wood, bamboo, okara, coffee grounds, compost, and paper sludge. The hollow activated carbon according to claim 1, wherein the molding raw material is made of wood chip raw material. 5. The hollow activated carbon according to claim 4, wherein the wood piece material is composed of at least one selected from cedar, straw, lauan, rubber tree, bamboo, lamin, and paulownia.

Images