JP2003238136A - Method of and device for producing carbon material having high specific surface area - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of producing, by one step heat treatment operation under a moderate temperature condition in a short time, a carbon material having a high specific surface area which is conventionally produced by adding a chemical such as zinc chloride or phosphoric acid to a ligneous material, mixing and heat treating, or heat treating the ligneous material to once carbonize and then activating the carbonized material at a high temperature of 900-1,200°C while passing steam or carbon dioxide therethrough for a long time, and also to provide a device therefor. <P>SOLUTION: This production method for the carbon material comprises supplying the ligneous material into one side of a cylindrical vessel and feeding steam into the other side thereof so as to bring the ligneous material and its thermally converted material into contact with steam by a counter-flow operation and heating the material at a temperature of 600-900°C by supplying heat from the outer periphery of the cylindrical vessel. The device therefor is also provided. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for producing a high specific surface area carbon material. Specifically, the present invention provides a novel method and apparatus for producing a high specific surface area carbon material using a wood material as a raw material.

[0002]

Carbon materials having a high specific surface area are used for purification of industrial chemicals and gases, catalysts and catalyst carriers, electrodes and electric double layer capacitor materials, oil additives, etc., as well as indoor air purification and humidity control. It is useful for a wide range of purposes such as purification of clean water, purification of industrial wastewater and rivers. The high specific surface area carbon material referred to here is in the category of what is generally called activated carbon, but it refers to those having a high specific surface area among them, that it has a high adsorption capacity and that the surface has high chemical activity. It has features such as.

The method for producing activated carbon is described in detail in, for example, "Activated Carbon-Basics and Applications" (published by Kodansha) edited by Japan Society for Carbon Materials, but the following method is generally summarized.

As a method of producing activated carbon using a wood raw material, a gas activation method in which the raw material is once heated and carbonized, and then steam, carbon dioxide gas, etc. are circulated at a high temperature of 900 to 1200 ° C. to convert into activated carbon, and wood Chemicals such as zinc chloride and phosphoric acid are added to the raw materials and mixed, and then heat treated at a high temperature of 400 to 900 ° C for carbonization treatment, and then the added chemicals and their decomposition products are removed by washing with water or the like. Both of the chemical activation methods for producing are common.

As a method of producing activated carbon, which has been recently published as a patent, for example, Japanese Patent Application Laid-Open No. 7-15560.
In No. 8, a method of producing a high specific surface area carbon material by treating a raw material so as to contain oxygen in advance at 4% by weight and then heating it in an oxidizing gas atmosphere, in JP-A-6-25992,
As a method for adding and mixing an alkali hydroxide as an activator to a raw material and performing heat treatment, JP-A-7-155587 discloses a method for using a Group 8 metal compound as an activator.

Another example is Japanese Patent Publication No. 6-7200.
3 discloses a method for producing a high specific surface area carbon material by heating wood or the like by microwave irradiation.

[0007]

A known method for producing a carbon material having a high specific surface area using a wood raw material is a gas activation method, for example, by heat-treating an organic material such as wood, coconut shell or coal at a high temperature. It is carbonized once, but it generally takes several hours to several days, and 900 to 12 while flowing a so-called activating gas such as steam or carbon dioxide in the next step.
This is inefficient because it requires a long time of several hours to several days at a high temperature of 00 ° C. In addition, since the equipment is required to have high heat resistance due to the high temperature treatment, the process cost becomes high because a large amount of heat energy is consumed.

On the other hand, in the chemical activation method, for example, sawdust, organic fibers, and the like are used as raw materials, and chemical agents such as zinc chloride and phosphoric acid of approximately equal weight are added and mixed as an aqueous solution.
It is manufactured by heating at ~ 700 ° C, cooling and then washing with water or washing with an alkaline aqueous solution, but the cost of the chemicals used is high and the chemicals volatilize and dissipate during heat treatment. Therefore, it may be necessary to repeat the washing process to remove the added chemicals, thermal decomposition products, etc. from the carbon material, which makes it difficult to completely remove them, and a large amount of water is used. There are many problems such as the need for wastewater treatment.

As a result of basic research on the thermal decomposition process of the wood raw material in order to solve these problems, the present inventors have surprisingly found that the wood raw material is thermally decomposed in a specific temperature range while flowing steam. , Found that a carbon material with a high specific surface area is produced. Further, they have found that when water vapor is diluted with an inert gas such as nitrogen gas and is circulated while controlling the partial pressure, a carbon material having a higher specific surface area is generated more stably.

The present invention has been completed as a result of research on the development of a method and an apparatus for producing a carbon material having a high specific surface area industrially and economically based on these discoveries. (EN) A novel method and apparatus capable of continuously producing a carbon material having a high specific surface area under a reasonable temperature condition that does not require a heat-resistant material and by a short-time treatment.

[0011]

According to a first aspect of the present invention, in a method for producing a carbon material by heating a wood raw material, a cylindrical container is used, the wood raw material is supplied from one side of the cylinder, and steam is supplied from the other side. The wood raw material and its heat conversion product are allowed to flow in countercurrent with steam, and heat is supplied from the outer periphery of the cylindrical container to heat the wood raw material to 600 to 900 ° C. to produce a carbon material. It is a method for producing a high specific surface area carbon material, which is characterized in particular.

According to the second aspect of the present invention, the wood raw material is continuously supplied to the heated cylindrical container, and the volume velocity thereof is 600 ° C.
1 to the internal volume of the container heated to 900 ° C
2. The volume is 0.2 to 10 times per hour, and the amount of steam fed in is a volume converted to a standard state and is 5 to 3000 times the volume of the wood raw material supplied. It is the manufacturing method described.

According to the invention of claim 3, the steam to be fed is diluted with a non-oxidizing gas such as nitrogen gas or carbon dioxide gas,
The water vapor concentration in the mixed gas is 5 to 80 mol%,
The supply rate of the mixed gas is 5 to the supply volume of the wood raw material.
It is 3000 times, It is the method of Claim 1 or 2 characterized by the above-mentioned.

According to a fourth aspect of the present invention, as an apparatus for carrying out the method of the first, second or third aspect, a cylindrical shape whose axial length is 4 to 20 times the diameter is heated from the outer periphery. A container that can be heated from 600 ° C to 900 ° C by a rotary propulsion device for moving the wood raw material and its heat conversion product to the outlet side. Is installed at an angle of 1 to 30 degrees with respect to the horizontal, and on the lower side there is a supply port for wood raw materials and an exhaust port for gas and liquid produced by steam and pyrolysis The device is characterized in that a carbon material manufacturing outlet and a steam inlet are disposed on the other high side sandwiched.

The invention of claim 5 is an embodiment of the device of claim 4, in which the mouth to which the wood raw material is supplied is opened upward to the lower side of the cylindrical container and communicates with the raw material storage tank. It is connected to a container that collects the condensate by opening the outlets for gases and liquids generated by steam and thermal decomposition.
On the other high side, a carbon material manufacturing outlet is opened downward, and a recovery container having a carbon material outlet having a structure that is filled with water to shut off the outside air is connected, and from the heated portion of the cylindrical container. The apparatus is characterized in that the carbon material outlet side and the recovery container have a substantially airtight structure.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Various wood species such as cedar, pine, cypress, Karamatsu, head pine, are used as the wood raw material used in the present invention.
You can use all common trees and trees such as chestnuts and kunugi. The form of the raw material is about 5 cm in the form of chips or granules
If the length is less than the corner and longer than that, the minor axis is preferably about 3 cm or less. A mixture of these materials can be used as a raw material, and if necessary, a granular material or a molded product of the above size can also be used.

For example, a log immediately after felling or a scrap material at the time of sawing can be used as a raw material as it is or after being dried and crushed into chips. Crushed materials such as wood, sawdust, etc. can be used as they are or after being compression-molded into the above-mentioned size as a raw material. Construction waste materials can be similarly used as raw materials. If the size of the raw material exceeds the above range, it takes time to heat and raise the temperature,
This is not preferable because the distribution effect of the air-fuel mixture with water vapor or non-oxidizing gas may not be sufficiently obtained.

The above-mentioned wood raw material is supplied from one end of a cylindrical container equipped with heat, heated, and discharged from the other end. The temperature of the wood raw material rises as it progresses through the heated cylindrical container, and after the water content and other volatile components contained therein evaporate, the wood raw material is thermally decomposed and converted into carbon as it advances to the high temperature part. Since a considerable amount of heat is required as water vaporizes, it is necessary to provide a sufficient heating zone on the inlet side of the cylindrical container.

The temperature of the cylindrical container is 6
The temperature may be in the range of 00 to 900 ° C., and the heat is supplied mainly from the wall surface of the outer circumference of the container, but the heat capacity of the circulating atmospheric gas is utilized even when the heat is supplied through the propulsion device. All supplies are acceptable.

The volumetric velocity of the wood raw material is 600.
The volume is 0.2 to 10 times per hour with respect to the internal volume of the container in the zone heated from 0 ° C to 900 ° C. That is, the residence time in this temperature range may be 6 to 5 hours, but if the rate is higher than this range, a sufficient heat treatment effect cannot be obtained and the specific surface area becomes small, while if the rate is low, it is not economical. .

A rotary blade type propulsion device is generally used to transfer the wood raw material to the outlet side in the container, but any other propulsion device can be used. Further, the operation of the propulsion device may be continuous or intermittent, and the raw material may be transferred within the range of the supply speed.

Water vapor is fed from the outlet side in the direction opposite to the wood raw material, but it is important that they flow countercurrently, and it is preferable that they flow in an extrusion flow. By the flow of this steam, various organic substances generated by thermal decomposition of the wood raw material and polymer substances that form tar are sent to the inlet side of the raw material, and the heat conversion product of the raw material is always in a steam atmosphere in a clean state, Alternatively, the high specific surface area carbon material is formed by heat treatment in an atmosphere of a mixed gas with the specified non-oxidizing gas.

When steam is mixed with the non-oxidizing gas and fed in, the non-oxidizing gas may be nitrogen, argon, carbon dioxide, carbon monoxide, methane, helium, hydrogen or the like. When mixed with a non-oxidizing gas, the water vapor concentration can be selected within the range of 5 to 80 mol%. When such a mixed gas is used, a higher specific surface area of the obtained carbon material can be stably obtained.

When steam or a mixed gas of steam and a non-oxidizing gas is fed, the wood raw material is transferred in the container in a state in which the wood raw material is shielded from the atmosphere, while flowing in the direction opposite to the transfer direction of the wood raw material. . At this time, the flow rate of the steam or the mixed gas with the non-oxidizing gas is the volume converted to the standard state, and the flow rate may be 5 to 3000 times the flow rate of the wood raw material. This flow rate is important, and the specific surface area of the carbon material obtained tends to be small at flow rates outside this range.

As described above, it is industrially and economically valuable that a carbon material having a high specific surface area can be obtained by a heat treatment at a low temperature of 900 ° C. or lower, which has never been used before, for a short time, and by a single heat treatment operation. Is. It is not always clear why the present invention in which steam or a non-oxidizing gas is passed under a specific condition produces such a carbon material having a high specific surface area, and further study is awaited.

The invention device of claim 4 is extremely effective for carrying out the invention of claim 1, 2 or 3. A cylindrical container whose axial length is 4 to 20 times the diameter is heated from the outer periphery and the inside is heated from 600 ° C to 900 ° C.
A sufficient heat transfer area can be secured to raise the temperature. The heat may be fuel oil such as heavy oil or kerosene, combustion heat of city gas or natural gas, or heating by an electric furnace. Depending on the case, the combustion heat of waste oil, waste tires, waste wood, etc. can also be used, and the exhaust gas generated when a wood raw material is heated can be recycled and burned to use the heat.

The container having the above-mentioned shape is also suitable for mounting a rotary propulsion device for moving the wood raw material and its heat conversion product to the outlet side. The propeller is generally a rotary vane type, but it is preferable to use a vane having a diameter close to the inner wall of the container so that the central axis of the cylindrical container and the axis of the propeller are aligned with each other. The distance or pitch that the blade moves in one rotation is
It may be designed and equipped in consideration of the shape of the wood raw material and the transfer speed. In this case, the wood raw material and the atmospheric gas spirally flow countercurrently in the space formed by the rotary blades, the rotary shaft, and the inner peripheral wall of the container, and the contact efficiency between them is high, which is preferable.

The central axis of the cylindrical container is 1 to 3 with respect to the horizontal.
It is important that they are installed at an angle of 0 ° and that there is an outlet for gas, liquid, etc. at the lower end to which the raw material is supplied. When a wood raw material is heated and decomposed, a small amount of a high molecular substance is by-produced and becomes a tar-like liquid when the temperature drops, but it does not flow to the carbon material production side even if it condenses on the inner surface of the cylindrical container. Need to do so. When the tar-like polymer substance adheres to the carbon material in the thermal decomposition process or its intermediate conversion product, it is difficult to obtain a carbon material having a high specific surface area. By providing the above inclination angle, the condensate flows down to the inlet side of the raw material, so that the adhesion can be reliably prevented. If the inclination angle is larger than the above, it is not preferable from the viewpoint of transporting the raw material and the heat conversion material or the space for installing the apparatus.

According to a fifth aspect of the present invention, the cylindrical container has a mouth to which a wood raw material is supplied, which opens upward to a lower side thereof and communicates with a raw material storage tank, and below which vapor and gas or liquid produced by thermal decomposition are generated. Due to the arrangement in which the discharge port is opened and connected to the container for collecting the condensed liquid, the storage and supply of the raw material and the flow of the generated gas or liquid are naturally secured.
The container for collecting the condensate is connected to an air blower for discharging non-condensed raw gas, and is discharged to the atmosphere after being detoxified.

Since a carbon material outlet is opened downward on the high side of the cylindrical container and a recovery container having a carbon material outlet having a structure for blocking water from outside by connecting water downward is connected, The carbon material produced at high temperature is recovered in water and cooled at the same time. As a result, it is possible to form a substantially airtight structure from the heating zone of the cylindrical container to the outlet side of the carbon material and the recovery container, and steam or steam diluted with a non-oxidizing gas can be used at a specified flow rate. It becomes possible to flow countercurrently with the raw material.

Since the carbon material comes into contact with water in the recovery container to generate water vapor, this can be fed into the heating cylindrical container as it is or using the non-oxidizing gas as a carrier. The carbon material collected in water is taken out from the take-out port by an arbitrary method while keeping the water-sealed state. For example, a carbon material can be taken out by installing a discharge machine such as a screw conveyor from the take-out port to the bottom of the collection container or by utilizing a water flow. The carbon material is made into a product by separating the water and then drying if necessary.

FIG. 1 shows an example of a specific configuration of the device according to the present invention.
However, the present invention is not limited to this example.
In FIG. 1, reference numeral 1 denotes a cylindrical container for heat-treating a wood raw material, in which a propelling device 2 is mounted and is rotationally driven by a drive gear 11. The wood raw material that has entered the feed port 14 from the raw material storage tank 9 is transferred to the inside of the cylindrical container by this propulsion device. The cylindrical container is heated in the heating furnace 3 to be heated. The heat-treated carbon material produced is recovered from the production outlet 12 in the water-filled carbon material recovery container 7.

The water vapor fed into the cylindrical container is the water metered by a metering pump or the like from the water supply pipe 6 to the water evaporator 4.
Is heated and vaporized, and is fed from the steam inlet 15. When water vapor is diluted with a non-oxidizing gas such as nitrogen gas and then fed, it can be fed through the nitrogen gas supply pipe 5. Further, the steam generated in the carbon material recovery container 7 can be used. In this case, a non-oxidizing gas such as nitrogen gas may be supplied to the carbon material recovery container 7 as a carrier, and steam may be sent along with it.

The gas and liquid generated by the thermal decomposition of the wood raw material and the supplied steam and the like flow out from the discharge port 13 to the condensate recovery container 8 and the condensate is accumulated in the condensate 8. The non-condensable gas or the like is discharged by the exhaust fan 10, but it is preferable that the soot and mist are detoxified and discharged to the atmosphere.

Next, a specific example in which a carbon material is manufactured by the apparatus having the configuration shown in FIG. 1 will be shown below.

[0036]

[Example 1] The cylindrical container 1 is made of heat-resistant stainless steel and has an inner diameter of 1
40 mm, the length from the raw material supply port 14 to the carbon material outlet 12 is 1400 mm, and the heating furnace 3 has a total length of 1
An electric furnace having three electric furnaces each having a temperature of 000 mm was used. The propeller 2 is a rotary blade type made of heat-resistant stainless steel, and has a blade diameter of 130 mm, a pitch of 120 mm, and a shaft diameter of 4.
8mm drive gear 11 with controlled rotation speed
Driven by. The cylindrical container was installed so that the product outlet side was inclined at an angle of 3 degrees with respect to the horizontal.

As the raw material, crushed cedar wood was sieved with a sieve having 5 mm openings and the passed portion was used. The raw material was stored in the raw material storage tank 9 and continuously supplied to the supply port 14 of the cylindrical container. A predetermined amount of water was supplied by a metering pump to the water evaporator 4 heated to 200 ° C., vaporized, and fed from the product outlet side inlet 15 of the cylindrical container. The flow rate of nitrogen gas was controlled by a mass flow valve, supplied from a pipe 5 to a water evaporator, mixed with water vapor, and then fed. The carbon material of the product dropped from the outlet 12 of the cylindrical container to the water-filled recovery container 7 to be cooled, and was intermittently taken out from the outlet 16 communicating with the lower part thereof.

The supplied water vapor and thermal decomposition products are collected in a condensate recovery container 8 connected to a discharge port 13 below the lower end of the cylindrical container, and exhaust gas is exhausted by an exhaust fan 10. Emitted into the atmosphere. Other than that, the structure of the apparatus is the same as that of FIG.

From the raw material inlet side, the first furnace is set to 400 ° C., the second furnace is set to 700 ° C., and the third furnace is set to 850 ° C., and the propulsion device is set to 2400 mm from the raw material supply port to the carbon material outlet.
The transfer speed was set in time. Water was supplied to the evaporator at 135 g / hr for vaporization, and nitrogen gas was supplied at 90 l / hr for mixing and feeding. The mixed gas volume of water vapor and nitrogen gas is 24% of the supply volume of the wood raw material in the standard state.
The water vapor concentration in the mixed gas is 65%.

From the temperature distribution in the cylindrical container, 600 ° C.
The residence time in the temperature range of 850 ° C. was 53 minutes. The carbon material produced 4 hours after the start of operation was taken out of the recovery container to separate water, and then the specific surface area of the sample dried at 90 ° C. for 2 hours was measured. The specific surface area is based on the BET method of nitrogen gas adsorption, and the equipment is Shimadzu Asap 201.
It was measured by the three-point method using 0. The specific surface area of this sample was 689 m2 / g.

[0041]

[Example 2] Example 1 except that the first furnace was set at 500 ° C
A carbon material was manufactured in the same manner as in. When the specific surface area of the sample produced 4 hours after the start of operation was measured in the same manner, it was 750 m2 / g.

[0042]

[Third Embodiment] The same as in the second embodiment, except that the speed of the propulsion device was set to transfer 1400 mm from the raw material supply port to the carbon material outlet in one hour, and the nitrogen gas flow rate was 180 liters / hour. A carbon material was manufactured. The mixed gas volume of water vapor and nitrogen gas is 32 times the supply volume of the wood raw material in the standard state, and the water vapor concentration in the mixed gas is 48%. From the temperature distribution, the residence time in the temperature range of 600 ° C to 850 ° C was 25 minutes. When the specific surface area of the sample produced 2 hours after the start of operation was measured, it was 621 m2 /
It was g.

[0043]

[Example 4] The speed of the propulsion device was set to a rate of transferring 1400 mm from the raw material supply port to the carbon material discharge port in 1 hour, and nitrogen gas was not flowed and only steam was fed in the same manner as in Example 2. The material was manufactured. In the standard state, the feed rate of water vapor was 15 times the supply volume of the wood raw material, and from the temperature distribution, the residence time in the temperature range of 600 ° C to 850 ° C was 27 minutes. The specific surface area of the sample produced 2 hours after the start of operation was measured and found to be 521 m2 / g.

[0044]

[Example 5] A carbon material amount was produced in the same manner as in Example 2 except that the speed of the propulsion device was set to a rate of transferring 1400 mm from the raw material supply port to the carbon material-made outlet in 4 hours. From the temperature distribution, the residence time in the temperature range of 600 ° C to 850 ° C was 110 minutes. When the specific surface area of the sample produced 6 hours after the start of operation was measured, it was 750 m2 /
It was g.

[0045]

Comparative Example A carbon material was produced in the same manner as in Example 3 except that steam and nitrogen gas were not supplied. From the temperature distribution, the residence time in the temperature range of 600 ° C to 850 ° C is 2
It was 5 minutes. The specific surface area of the sample produced 2 hours after the start of operation was measured and found to be 97 m2 / g.

[0046]

INDUSTRIAL APPLICABILITY According to the present invention, a novel method and apparatus capable of continuously producing a carbon material having a high specific surface area from a wood raw material by a one-step heat treatment operation and a short-time treatment at a temperature of 900 ° C. or less. Will be provided. The obtained carbon material is used for purification of industrial chemicals and gases, catalysts and catalyst carriers, electrodes and electric double layer capacitor materials, resin additives, etc.
It is widely used for indoor air purification, humidity control, clean water purification, industrial wastewater and river water purification.

[Brief description of drawings]

FIG. 1 is a side view of a device according to an embodiment of a device configuration of the present invention. It is drawn in a partial perspective view to show the internal structure.

FIG. 2 is a sub-side view seen from the left side of FIG. 1 and is a partial perspective view.

[Explanation of symbols]

1 cylindrical container 2 propulsion machine 3 heating furnace 4 water evaporator 5 Nitrogen gas supply pipe 6 water supply pipe 7 Carbon material collection container 8 Condensate recovery container 9 Raw material storage tank 10 blower 11 Drive gear 12 Carbon material outlet 13 Generated gas outlet 14 Raw material supply port 15 Steam inlet 16 Carbon material outlet

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takanori Shido             7-11-29 Yonehara, Yonago City, Tottori Prefecture             Room 205 F-term (reference) 4G046 HA02 HB05 HC09 HC10 HC12                       HC18 HC24

Claims (5)

[Claims] 1. A method for producing a carbon material by heating a wood raw material, wherein a wood raw material and a heat conversion product thereof are supplied by supplying a wood raw material from one side of a cylinder using a cylindrical container and feeding steam from the other side. And steam so that they contact each other in countercurrent,
Heat is supplied from the outer circumference of the cylindrical container to produce 600 ~
A method of producing a carbon material by heating to 900 ° C. 2. A wood-based material is continuously supplied to a heated cylindrical container, and its volumetric rate is 0.2 to 1 per hour with respect to the internal volume of the container of a portion heated from 600 ° C. to 900 ° C.
The volume is 0 times the volume, and the amount of steam to be fed is the volume converted to the standard state.
The method according to claim 1, which is 0 times. 3. Water vapor is diluted with a non-oxidizing gas such as nitrogen gas and carbon dioxide gas, the water vapor concentration in the gas mixture is 5 to 80 mol%, and the gas mixture is supplied at a feed rate of wood raw material. The method according to claim 1 or 2, wherein the volume is 5 to 3000 times the volume. 4. A cylindrical shape whose axial length is 4 to 20 times the diameter, and which is heated from the outer periphery to 600 ° C. to 9 ° C.
A container heated to 00 ° C, equipped with a rotary propulsion device for moving the wood raw material and its heat conversion product to the outlet side, and the central axis of the cylindrical container is horizontal. It is installed at an angle of 1 to 30 degrees, and on the lower side there is a supply port for wood raw materials and an exhaust port for gas and liquid produced by steam and thermal decomposition A device with a carbon material outlet and steam inlet on the high side. 5. A cylindrical container has a mouth to which a wood raw material is supplied, which opens upward to a lower side thereof and communicates with a raw material storage tank, and a discharge port for vapor and a gas or liquid produced by thermal decomposition is provided below. It is open and connected to a container that collects the condensate, and the carbon material outlet is open downward on the other high side and has a carbon material outlet that is structured to block water from the outside by filling water downward. The device according to claim 4, wherein the recovery container is connected, and the portion from the heated portion of the cylindrical container to the carbon material outlet side and the recovery container are substantially airtight.