JP2004277453A - Granular carbonized material and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently provide a granular carbonized material useful as active carbon, etc., and having good sphericity. <P>SOLUTION: The granular carbonized material is produced as follows. A wood substrate granule and a pitch granule are introduced into a rotating furnace and the pitch granule is melted under rotation. The wood substrate granule is impregnated and coated with the molten pitch. The resultant pitch-impregnated/coated wood substrate granule is integrally carbonized and, as necessary, further subjected to an activation treatment. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【発明の効果】
上述したように、本発明によれば、脆くて粉化し易い木質基材粉粒体の単独炭化物に比べて、ピッチ含浸・被覆炭化物であるので、機械的強度が高く、かつ粒状ならびに球状性の良い粉粒状炭化物を、木質基材粉粒体の単独炭化に比べて著しく高い収率で得られ、しかも中間ペレット化あるいは炭化物の粉砕等の工程を要することなく効率的に製造できる。得られた粉粒状炭化物を賦活することにより、木質基材粉体単独の炭化賦活物と殆ど遜色のない性能の活性炭が、高い収率で得られる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a powdery and granular carbide useful as activated carbon and the like and an efficient production method thereof.
[0002]
[Prior art]
Petroleum-based or coal-based pitch or pitch composed of pyrolysis residue of waste plastic (that is, residue composed mainly of heavy hydrocarbons which is solid at room temperature) is carbonized by subjecting it to a high temperature of, for example, 600 to 1200 ° C. Is widely known. The carbonization yield at this time is as high as about 40 to 60% by mass. However, since these pitches are liquefied by heating to about 300 ° C., it is industrially except for a part that even if it is performed on a laboratory scale, it is industrialized to obtain a carbide by carbonizing alone. Almost not done.
[0003]
Japanese Patent Publication No. 50-18879 discloses a technique of granulating a raw material pitch to produce a spherical activated carbon. However, this technique is intended to prevent the pitch granulated material from being fused in a carbonization / activation step. It has only become practical for the first time by introducing an infusibilizing step (a step of imparting oxygen crosslinking to the granulated product).
[0004]
On the other hand, the woody base powder such as wood flour (Japanese Unexamined Patent Publication (Kokai) No. 61-220727) or coffee bean residue (Japanese Unexamined Patent Publication (Kokai) No. 6-9207), which itself has a low carbonization yield of about 10% by mass, It has been proposed that pitch is added as a binder, molded, and then carbonized. Further, Japanese Patent Application Laid-Open No. 6-9207 discloses that coal, coconut shell, charcoal and the like are used as a carbonaceous material, and are formed using tar and pitch together with a small amount of an anti-caking agent such as alumina, aluminum chloride and copper oxide. A method for producing activated carbon that is carbonized and activated is introduced as a conventional technique.
[0005]
[Problems to be solved by the invention]
However, in these conventional techniques, the pitch used together with the wood base powder is essentially a binder, so that a step of molding before carbonization is required, and in order to obtain finer activated carbon, the carbide is pulverized again. This is an inefficient manufacturing method.
[0006]
Accordingly, a main object of the present invention is to provide a powdery and granular carbide efficiently produced from a wood substrate and pitch, and a method for producing the same.
[0007]
[Means for Solving the Problems]
The powdery and granular carbide of the present invention has been developed to achieve the above-mentioned object, and is characterized in that the woody substrate powder and the coating pitch are integrally carbonized.
[0008]
In addition, the method for producing a particulate carbide according to the present invention is characterized in that the wood base material and the pitch powder are introduced into a rotary furnace, and the pitch powder is melted under rotation to produce the wood base material. The present invention is characterized in that the granules are impregnated and coated, and the obtained pitch-coated wood base granules are integrally carbonized.
[0009]
The method for producing a particulate carbide according to the present invention is characterized in that the wooden substrate powder and the pitch powder are heated from room temperature to 600 to 1200 ° C. in a rotary furnace while rotating, and the pitch is about 300 ° C. Despite passing through the melting temperature range of, the particles are essentially based on the carbonized skeleton of the wood-based granular material without excessive aggregation or blocking of the particles, ie, substantially It is based on the finding that a powdery and granular carbide having good spheroidity composed of mononuclear coated carbonized particles can be obtained. Although this phenomenon has not been fully elucidated yet, the following behavior is considered from the behavior of the pitch under heating for carbonization and the interaction of the wood-based powder with a particle size adjusted according to the use of the product carbide. It is explained as follows.
[0010]
That is, when the wood base material and the pitch material are introduced into a rotary furnace and heated under rotation, the pitch material starts melting at 300 ° C. or higher, but the coexisting wood base Since the wood particles are porous, the initial melt is absorbed and impregnated into the voids of the wood base material or pores near the surface layer, and loses excessive tackiness. This prevents excessive coagulation or blocking of the wood-based base material coated with the pitch. As the temperature continues to rise, the pitch naturally causes a further decrease in viscosity. However, the temperature of about 120 ° C. or more is caused by oxygen present in the wood base material or oxygen in the atmosphere introduced as necessary. Since the pitch becomes infusibilized by oxidation in the region, the increase in the melt adhesive force of the pitch covering the wood-based base particles is offset. Therefore, the pitch-coated wood substrate powder passes in the pitch melting zone of 300 ° C. or higher without causing excessive cohesion or excessive development of viscosity that causes blockage, and 600 to 1200 ° C. or higher. At the same temperature. In addition, even if abnormal cohesion occurs in a small area between adjacent granules, a cohesive failure occurs due to the rotational shear force applied by the rotary furnace. As a comprehensive result of the above-mentioned actions, the present invention is made of a substantially mononuclear coated carbonized particle in which the wood base material and the coating pitch are integrally carbonized, and has a good uniformity of particle size and good spheroidity. It is believed that the particulate carbides of the invention are formed.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the powdery and granular carbides of the present invention will be sequentially described according to the steps in the method for producing the same.
[0012]
(Wood-based powder)
The first raw material of the granular carbide of the present invention is a wood-based granular material.
[0013]
In the present invention, various industrial wastes or household wastes are used as suitable wood-based base particles.
[0014]
Preferable examples include coffee extraction residue, wood sawdust, beer slag, cereal husk (wheat husk, rice husk), wood chips, bamboo, waste paper, waste pulp, sludge, green tea and black tea residue, bran, and the like. Oxygen compounds are included. Among them, coffee extraction residue, sawdust, beer residue, cereal husk (wheat husk, rice husk), green tea and black tea residue have a constant and stable particle size, and are essentially non-uniform in woody base powder. This is extremely suitable as a main raw material in the method for producing a powdery carbide of the present invention, in which carbonization is performed integrally with the coating pitch while preventing agglomeration.
[0015]
The average particle size (50 mass% cumulative particle size based on sieve opening, hereinafter the same applies unless otherwise specified) of the wood-based powder used in the present invention, including the above-mentioned examples, is 5 mm or less, particularly The range is preferably 0.1 to 4 mm, and the same range is preferable as the raw material particle size distribution range.
[0016]
In addition, the wood base powder has a carbonization yield (carbonization yield in a nitrogen atmosphere at 800 ° C. for 0.5 hour, the same applies hereinafter) of 5% or more, particularly preferably 10 to 30%. Can be
[0017]
(Pitch powder)
Preferable examples of the pitch granular material as the second raw material in the method for producing a granular carbide of the present invention include a petroleum or coal pitch or a pitch composed of a pyrolysis residue of waste plastic (as mentioned above). , Which means a residue mainly consisting of heavy hydrocarbons which are solid at room temperature). Particularly, in the present invention, those having a softening point of 150 to 250 ° C are preferably used. It is necessary to be solid at room temperature, but even in the early stage of heating, even if it softens or liquefies, it is absorbed by the porous wood base material particles and its tackiness is effectively suppressed, so Those having an extremely low softening point are also preferably used.
[0018]
The pitch is heavier to an H / C atomic ratio of about 0.5 to 1.5, and preferably has a carbonization yield of 40% or more, particularly 50 to 70%.
[0019]
Since the pitch powder is softened or liquefied relatively early in the heating step for carbonization in the production method of the present invention, the powder is preferably a powder. The average particle size is preferably 0.05-2 mm.
[0020]
A preferred embodiment of the granular carbide of the present invention and a method for producing the same is to operate it in cooperation with a waste plastic treatment process. In other words, as awareness of the importance of environmental measures increases, simply consuming a large amount of waste plastic as fuel not only wastes resources but also generates a large amount of carbon dioxide, which is a greenhouse gas. From this viewpoint, it is more desirable to thermally decompose waste plastic that generates a small amount of carbon dioxide gas, and a preferred embodiment of the pitch powder used in the present invention is a pitch powder made of pyrolysis residue of waste plastic. In particular, the dehydrochlorination process of a vinyl chloride resin at a temperature of about 300 to 400 ° C. gives a pitch having a softening point of about 150 to 250 ° C. in high yield, and gives the pitch granular material of the present invention. However, it is particularly suitable. Further, the powdery and granular carbide (particularly activated carbon after activation) obtained through the production method of the present invention is suitable for use as an absorbent for dioxin, which is a harmful substance that may be generated in a waste incineration process.
[0021]
In the present invention, such a pitch powder is preferably used in a proportion of 10 to 50 parts by weight, particularly 20 to 40 parts by weight, based on 100 parts by weight of the wood base powder.
[0022]
According to the method for producing a powdery and granular carbide of the present invention, the above-mentioned woody base material and the pitch and the granular material are subjected to heating for carbonization in a rotary furnace.
[0023]
In this process, the melting of the pitch granules occurs, and the surface is coated while impregnating the surface layer of the wood base granules.
[0024]
Subsequently, the pitch-coated wood substrate powder is heated in a rotary furnace to 600 to 1200 ° C., preferably 650 to 850 ° C., and kept at this temperature for 10 minutes or more, preferably 0.2 to 0.5 hour. Carbonize.
[0025]
According to a preferred embodiment, the powdery and granular carbide obtained above is further activated. That is, the activation treatment is carried out at an activation temperature of 700 ° C. or higher, preferably 700 to 850 ° C., in the presence of steam, carbon dioxide or diluted oxygen for about 0.5 to 3 hours.
[0026]
By cooling the carbonized (and preferably further activated) treated product, the powdery and granular carbide (and preferably activated carbon) of the present invention is obtained.
[0027]
The above series of processes is performed as a batch process in a rotary furnace having a substantially horizontal rotation axis, or as a continuous process using a continuous flow type rotary furnace having a rotation axis slightly inclined from horizontal (a so-called rotary kiln). Done. In the case of continuous treatment, it is also possible to perform only the activation treatment in a separate furnace.
[0028]
Typical properties of the powdery and granular carbide (preferably activated carbon) of the present invention obtained as described above include an average particle diameter of 0.05 to 5 mm, particularly 0.1 to 4 mm, and a minor axis / major axis ratio ( For example, by microscopic observation, the average value of arbitrarily selected 10 particles is 0.5 or more, and the particles have good sphericalness and bulk density of 0.2 to 0.4 g, which are represented by the absence of corners in the cross-sectional shape of the particles. / Cm ³ , and a BET specific surface area of activated carbon of 500 to 1000 m ² / g.
[0029]
The obtained carbide is suitably used as activated carbon for treating various gases and water, particularly as activated carbon suitable for adsorption and removal of dioxins. It is also suitably used as a soil modifier.
[0030]
〔Example〕
Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.
[0031]
In addition, the typical physical properties of the granular carbide described in the specification of the present application including the following examples were measured by the following methods.
[0032]
(1) For the average grain (direct) diameter powdery granular carbide, a mass-based particle size accumulation diagram is created according to JIS K1474. The average particle diameter is obtained by calculating a sieve opening (mm) by drawing a horizontal line on the horizontal axis from an intersection of a vertical line at a point of 50% on the horizontal axis and the particle size cumulative line in the cumulative particle size diagram, The average particle diameter is used.
[0033]
(2) After the powdery and granular carbide as the bulk density sample is dried in a dryer controlled at 115 ° C. for 3 hours, it is allowed to cool in a desiccator. The dried powdery carbide sample is put into a filling density measuring container (a container shown in FIG. 8 of JIS K 1474-5.7) to a volume of １ ／ of the volume of the container. Gently tap on the rubber plate until the upper surface of the powdery and granular carbide sample reaches a certain height, and further add the same amount of the powdery and particulate carbide sample and gently tap. Repeat the tapping and filling operation, filling the granular carbide sample to the upper end of the container, withdrawing the cylinder at the top of the container, shaving off the raised portion using a stainless steel straight ruler, and leveling the upper surface of the granular carbide sample horizontally. I do. The mass of the granular carbide sample in the container is measured to the order of 0.1 g. Subsequently, the bulk density (L) is calculated by the following equation.
[0034]
(Equation 1)
L = S / M
Here, S is the mass (g) of the powdery carbide sample, and M is the volume (ml) of the packed density measurement container.
[0035]
(3) Specific surface area Using a specific surface area measuring device (for example, “Flow Sorb II 2300” manufactured by MICROMERITICS) by a continuous flow gas adsorption method, the gas adsorption amount of the powdery carbide sample was measured, and the BET equation was used. The specific surface area can be calculated. Specifically, the powdered granular carbide as a sample is filled in a sample tube, and the following operation is performed while flowing a helium gas containing 30% by volume of nitrogen into the sample tube to determine the amount of nitrogen adsorbed on the powdered granular carbide sample. Ask. That is, the sample tube is cooled to -196 ° C, and nitrogen is adsorbed on the powdery carbide sample. Next, the sample tube is returned to room temperature. At this time, the amount of nitrogen desorbed from the powdery and granular carbide sample is measured by a heat conduction type detector, and is set as the amount of adsorbed gas (v).
[0036]
Approximation derived from the equation BET _equation: in v m = 1 / (v · (1-x)) liquid nitrogen temperature using a single point method with nitrogen adsorption of _{v m} by (relative pressure x = 0.3) calculated by the following formula: the specific surface area ^{_{= 4.35 × v m (m 2}} / g) calculating the specific surface of the sample. In each formula of the, v _m is an adsorption amount necessary for forming a single molecular weight to the sample surface (cm 3 / ^g), v is an adsorption amount which is actually measured (cm 3 / ^g), x Is the relative pressure.
[0037]
(4) Caramel decolorization performance In order to evaluate the adsorptive capacity of the powdered carbonaceous material as activated carbon, a caramel test solution (20% of a caramel stock solution obtained by carbonization with a specified concentration of sulfuric acid of saccharose) was added to a 150 mg sample according to JIS K 1474. A 50-fold water-diluted solution was added, and the mixture was shaken with a shaker, followed by filtration. From the absorbance E ′ of the filtrate and the absorbance E of the caramel test solution (both at a wavelength of 430 nm), the caramel decolorizing power (= (1-E / E ′) × 100 (%)).
[0038]
(Example 1)
Pulverization of a pitch-like substance having a softening point of 180 ° C and an H / C atomic ratio of 0.7 obtained by dechlorinating a vinyl chloride resin by raising the temperature to 450 ° C in a nitrogen stream over 5 hours. A product (average particle size: 0.1 mm) was used as a pitch powder.
[0039]
100 g of this pitch powder and 400 g of a dried coffee extraction residue (average particle diameter: 0.4 mm) are horizontally held in a rotating inner cylinder having an inner diameter of 270 mm and a length of 420 mm. And a fixed outer cylinder, which is accommodated in the inner cylinder (air atmosphere) in a batch-type rotary furnace in a substantially hermetically sealed state, and the inner cylinder is rotated at a rate of 3 revolutions / minute. While rotating, the combustion gas was introduced into the space between the outer cylinder and the outer cylinder to heat the inner cylinder.
[0040]
The temperature was raised from room temperature to 300 ° C. for about 10 minutes, and then further to 820 ° C. for 30 minutes, and the temperature was maintained for 30 minutes to carbonize the contents.
[0041]
Subsequently, while maintaining the temperature in the inner cylinder at 820 ° C., steam was introduced at a rate of 5 g / min and an activation treatment was performed for 20 minutes.
[0042]
Thereafter, the heating was stopped, forced cooling was performed, the introduction of steam was stopped at 300 ° C., and after cooling to almost room temperature, the contents were collected to obtain a powdery and granular carbide of the present invention. The appearance of the charcoal was a uniform black charcoal consisting essentially of mononuclear coated charcoal particles, leaving almost the shape of the coffee extraction residue as the raw material.
[0043]
The recovery amount of the powdery and granular carbides was 70 g, and the yield based on the total amount of the pitch and the ground coffee extraction residue was 14% by mass.
[0044]
The measurement results of the physical properties of the obtained powdered carbides are summarized in Table 1 below together with the results of the following Examples and Comparative Examples.
[0045]
(Example 2)
Except for using 162 g of pitch powder and 325 g of coffee extraction residue as raw materials, the same treatment as in Example 1 was performed to obtain 87 g of powdery and granular carbide.
[0046]
Table 1 shows the measurement results of the physical properties. With the increase in the pitch compounding amount, the carbonization yield was improved to 18% by mass, but the coarse particles and fine powder slightly increased.
[0047]
(Comparative Example 1)
Except for using only 500 g of the coffee extraction residue as a raw material, a powdery and granular carbide was obtained in the same manner as in Example 1, but the increase in fine powder was conspicuous. Further, the carbonization yield was 8% by mass, which was a low level as compared with Examples 1 and 2.
[0048]
The results of the above Examples and Comparative Examples are summarized in Table 1 below.
[Table 1]

【The invention's effect】
As described above, according to the present invention, compared to a single carbide of a brittle and easily pulverizable wood-based powder, since it is a pitch impregnated and coated carbide, the mechanical strength is high, and the granular and spherical properties are high. Good powdery and granular carbides can be obtained in a much higher yield than single carbonization of wood-based powders and granules, and can be efficiently produced without the need for intermediate pelletization or carbide pulverization. By activating the obtained powdered and granular carbide, activated carbon having a performance almost equal to that of the carbonization activating substance of the wood base powder alone can be obtained in a high yield.

Claims (6)

A granular carbide obtained by integrally carbonizing a wood base material and a coating pitch. The powdery and granular carbide according to claim 1, having an average particle size of 0.05 to 5 mm. The wood base powder and the pitch powder are introduced into a rotary furnace, and the pitch powder is melted under rotation to impregnate and coat the wood base powder. A method for producing a particulate carbide, comprising integrally carbonizing a coated wood base powder. The method according to claim 3, further comprising activating the carbide to produce a powdery and granular carbide functioning as activated carbon. The method according to claim 3 or 4, wherein the pitch granules comprise petroleum-based or coal-based pitch or a residue obtained by heating a waste plastic. 6. The production method according to claim 5, wherein the pitch granules comprise a residue of thermally dehydrogenated waste vinyl chloride resin.