JP5114719B2 - Production method and system of porous carbon material - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and system for producing a plant-based porous carbon material. More specifically, the present invention relates to a method for producing a porous carbon material activated by water vapor and an inert gas, and a system thereof.
[0002]
[Prior art]
Carbon materials are used for filter media, adsorbents, electromagnetic shielding materials, sliding members, friction materials, and the like. In recent years, it is also used as an electrode material for secondary batteries, humidity sensors, electric double layer capacitors, fuel cells and the like. Plant-based wood and wood have countless pores inside, and a method of carbonizing this to produce a porous carbon material has also been proposed.
[0003]
For example, wood ceramics are known in which wood is impregnated with phenol resin, cured, and then carbonized. The inventor of the present invention puts wood into a phenolic resin solution, depressurizes with a vacuum pump for a predetermined time, injects the phenolic resin into the wood, and then hardens it in a formalin atmosphere. A manufacturing method was proposed in which this was sintered at a maximum temperature of about 1100 ° C. and carbonized in an electric furnace where air was shut off (Japanese Patent Laid-Open No. 4-164806).
[0004]
Such carbonized plant materials are characterized in that the inside is porous and the specific surface area showing the surface area per unit weight (m ² / g) is large. In order to obtain this porous material, a manufacturing method called activation is used. As this activation, gas activation, chemical activation, water vapor activation and the like are known. Various methods have been proposed and known for the steam activation method. For example, there is a method of continuously producing powdered activated carbon.
[0005]
Steam is injected into a pyrolysis furnace, oxygen in the air that is separately charged is combusted, and diffused into the furnace as an inert gas to increase the probability of contact with the carbon material. The product gas generated by the reaction is rapidly separated from the reaction surface, but a part thereof is circulated, and the amount of this circulating gas is controlled to control the temperature in the activation reaction vessel (Japanese Patent Laid-Open No. 9-20511). Publication).
[0006]
FIG. 4 shows an example of a conventional carbon material activation system for water vapor activation of a carbon material used by the inventors in the experiment. The electric heating furnace 1 has a core tube 2 having a closed space, and a heater 3 for heating the core tube 2 is provided on the outer periphery of the core tube 2. A heat insulating material 4 is wound around the outer periphery of the heater 3. The heat insulating material 4 is a heat insulating material for preventing the heat generated from the heater 3 from escaping from the core tube 2. In the furnace 5 of the electric heating furnace 1, water (normal temperature) is pressurized by the injection device 10 and injected into the fixed amount by the injection pipe 6.
[0007]
The injected water is steamed at the outlet 7 of the injection pipe 6 by the heat energy in the furnace 5 heated to a predetermined temperature. In the furnace 5, an inert gas (nitrogen gas) is supplied from a gas cylinder 11. By this inert gas, water vapor is diffused uniformly and activates the carbon raw material M. However, in this conventional activation method, the injection device 10 injects into the furnace through the introduction pipe.
[0008]
The introduction tube is heated to the same temperature as the heated furnace. The injected water is suddenly heated in the introduction pipe, suddenly boils and is scattered randomly in the furnace. Since the scattered water is vaporized into chaotic water, less steam contributes to activation. That is, it is difficult to uniformly diffuse the water vapor into the carbon raw material M, and the surface area per unit weight was about 900 (m ² / g) according to the experiment results of the present inventors.
[0009]
Further, since water at room temperature was poured into the heated furnace 5, the thermal shock was so great that the ceramic core tube 2 could be damaged. Further, the gas cylinder 11 filled with an inert gas cannot be used due to its limited capacity for long-term continuous operation. Similarly, the syringe 12 of the injection device 10 also needs to be removed for water replenishment.
[0010]
[Problems to be solved by the invention]
The present invention has been made based on the technical background as described above, and achieves the following object.
An object of the present invention is to provide a method and a system for producing a porous carbon material capable of increasing the specific surface area by increasing pores.
Another object of the present invention is to provide a method and system for producing a porous carbon material that can increase the pores and increase the specific surface area by increasing the efficiency of water vapor diffusion.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the present invention employs the following means.
The method for producing a porous carbon material according to the present invention is a method for producing a porous carbon material. The carbon material is placed in a heating furnace, and a saturated water vapor and an inert gas are mixed to produce a hydration gas. After preheating the hydration gas, the carbon material is activated by supplying the hydration gas into the heating furnace, and the heating furnace is heated to 800 ° C. or more to carbonize the carbon material. intended to produce Te, the mixing temperature with water to make an inert gas and saturated steam are and at 98 ° C. lower than the atmospheric pressure, the preheating temperature of the hydration gas, characterized in that a 200 ° C. or higher And
[0012]
The porous carbon material may be any material provided with micropores, transitional pores, macropores, etc., and specifically refers to activated carbon, carbon black, charcoal, wood ceramics, and the like. The inert gas may be any kind as long as it is an inert gas, but nitrogen gas produced by separating air is inexpensive and easy to handle. Further, the mixing temperature of the inert gas and the water is atmospheric pressure and 98 ° C. or lower, and the preheating temperature of the hydrating gas is preferably 200 ° C. or higher. The amount of the saturated water vapor is preferably proportional to the supply amount of the nitrogen gas.
[0013]
The porous carbon material manufacturing system according to the present invention includes a heating furnace for putting a carbon material inside, an inert gas generating means for removing oxygen from air and separating the inert gas, and the inert gas generating device. Hydrating means for mixing the inert gas and water, and preheating means for preheating and supplying the mixed inert gas and water to the heating furnace. The mixing temperature by the hydration means is 98 ° C. or less, and the preheating temperature of the preheating means is preferably 200 ° C. or more.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of the present invention will be described. FIG. 1 is a diagram showing an embodiment of the present invention, and is a system diagram showing an outline of a porous carbon material production system. The electric heating furnace 20 is a ceramic core tube 21 having a closed space. A heater 23 for heating the inside 22 of the furnace core tube 21 is disposed on the outer periphery of the core tube 21.
[0015]
A heat insulating material 24 is wound around the outer periphery of the heater 23. The heat insulating material 24 is a heat insulating material for preventing heat generated from the heater 23 from escaping from the core tube 21. A pipe line and a valve 25 for discharging the inert gas inside the furnace 22 and the generated gas generated in the furnace 22 are arranged at an upper position of the core tube 21, and the valve 25 is opened. To release these gases.
[0016]
On the other hand, in the present embodiment, the porous carbon material production system includes a hydration gas generation system 30 for supplying a hydration gas mixed with water vapor and an inert gas into the furnace 22. The hydration gas generation system 30 includes an inert gas generator 31 for generating an inert gas, that is, a nitrogen gas, a hydration tank 32 for mixing the inert gas and water, and a mixed inert gas. And a preheater 33 for heating water and water.
[0017]
In the hydration tank 32, water having a saturated vapor pressure level determined by the internal pressure and temperature in the hydration tank 32 is added to become saturated steam. In addition, there is a branch pipe (not shown) with a valve between the hydration tank 32 and the preheater 33, and the hydration gas flowing out to the branch pipe side is cooled by closing the valve 37. The obtained water is measured to measure the amount of water. The amount of moisture fed into the electric heating furnace 20 is determined in proportion to the flow rate of the inert gas (see FIG. 3).
[0018]
The inert gas generator 31 includes an air pump unit 34 that pressurizes air in the air and a nitrogen separator 35 that separates the pressurized air and extracts only nitrogen gas (including rare gas). The principle of the nitrogen separator (Kanebo (PSA type nitrogen gas generator) manufactured by Kanebo Co., Ltd.) 35 used in the present embodiment is that the difference in adsorption rate between oxygen and nitrogen is large, and oxygen is applied within a short time under pressure. A synthetic polymer adsorbent that can preferentially adsorb and separate nitrogen gas is used. The purity of the nitrogen gas is obtained in the range of 99.0 to 99.99%, and when it is less than 1/3 of the apparatus capacity of the amount of gas to be taken out, a gas with a purity of 99.0% is obtained when it is 99.99% or more. It is what
[0019]
The separated nitrogen gas passes through the flow meter 36 and is supplied to the hydration tank 32. The hydration tank 32 is a mixture of water and nitrogen gas. The mixing of water and nitrogen gas wets the inert gas by passing the inert gas through warm water heated to 98 ° C. or lower.
[0020]
The inert gas mixed with water is heated by a preheater 33 of the type heated by a heating wire and mixed with the inert gas to become a hydrated gas. The hydration gas passes through the valve 37 and is supplied to the furnace 22.
[0021]
(Operation of Embodiment 1)
Next, the operation of the embodiment will be described. Carbon material M is charged into the furnace 5. Here, the carbon raw material M refers to a plant-based glassy composite material, wood, a wooden system, or the like. After the carbon raw material M is charged, all the valves such as the valve 37 and the valve 25 are closed, and after deoxygenation (practical vacuum state), the valve 37 is opened and an inert gas is allowed to flow in. After the pressure is increased to about 1 MPa, the valve 25 is opened. Thereafter, the electric heating furnace 20 is operated with the valve 37 and the valve 25 opened until the activation is completed.
[0022]
The inert gas generated by the hydration gas generation system 30 is diffused into warm water having an arbitrary temperature of 98 ° C. or lower. The reason why the temperature of the hot water is set to 98 ° C. or less is to prevent any excess liquid water from being included in the hydration gas. This is because, when gas is blown into boiling water, there is a risk that liquid moisture at plus 100 ° C. is entrained in saturated steam. In other words, it becomes wet steam. This is because even if a filter for removing liquid water is disposed, there is a risk that saturated vapor may condense on the filter.
[0023]
Therefore, the hydration gas supplied to the electric heating furnace 20 is heated and supplied in a gas state, that is, in a heated steam state. Saturated steam (hydratable gas) is preheated to 200 ° C. or higher by the preheater 33. By this preheating, the saturated steam becomes heated steam. The reason for heating to 200 ° C. or higher is to prevent condensation due to cooling in the pipeline and to ensure a pressure of 0.49 Kpa (hydrostatic pressure of 50 mmAq) above a certain level to increase the flow rate. As a result, the hydrating gas can be stably supplied to the electric heating furnace 20. The optimum values for the heating temperature and pressure are determined experimentally and theoretically. The preheated hydration gas was put into the furnace 22 to form a uniform water vapor diffusion together with the inert gas, and a specific surface area of about 1300 (m ² / g) was obtained. Further, the inert gas generator 31 is pressurized by an air pump unit 34 that pressurizes air in the air and sent to the nitrogen separator 35.
[0024]
The nitrogen separator 35 continuously extracts only nitrogen gas from the pressurized air. The separated nitrogen gas is supplied to the hydration tank 32. The hydration tank 32 mixes water and nitrogen gas and sends them to the preheater 33. As described above, since the hydrating gas can be continuously generated and supplied, the operation can be performed without interruption. Further, since the hydrating gas is preheated by the preheater 33 and becomes heated steam, the interior 22 of the furnace core tube 21 also creates a stable atmosphere.
[0025]
Since the valve (inner diameter 6 mm) 37 and the valve (inner diameter 2.5 mm) 25 are operated in a fully opened state, the pressure in the furnace 22 is estimated to be a hydrostatic pressure of around several hundred mmAq. The inside of the furnace 22 is always saturated with an inert gas or a hydration gas. FIG. 2 is data showing the relationship between the activation temperature and the specific surface area when comparing the conventional carbon material activation system shown in FIG. 4 with the porous carbon material production plant of the present invention. It can be seen that the specific surface area has increased dramatically. FIG. 3 is a diagram for determining the water to be added, and shows the relationship between the inert gas and the amount of water. The amount of water increases in proportion to the flow rate of nitrogen gas.
[0026]
The amount of the carbon material M in the furnace 5 adsorbs heating steam adsorption amount V _i to the adsorbent of the adsorption component i is known to be expressed by a function of pressure and temperature by the following equation.
[0027]
V _i = F (p ₁ ...... p _i , ...... p _n , T)
In the adsorption of one-component gas, this equilibrium relationship is represented by a three-dimensional curved surface with the adsorption amount, pressure and temperature as coordinates. Actually, it is often expressed by a quadratic curve group in which one variable is fixed. Adsorption isotherm (horizontal axis is equilibrium pressure, vertical axis is adsorption amount), adsorption isobaric line (horizontal axis is temperature, vertical axis is adsorption amount), and adsorption isotherm (horizontal axis is temperature, vertical axis is equilibrium pressure) It is called. For example, the adsorption isotherm for gas adsorption on activated carbon or zeolite rises rapidly with the equilibrium pressure and then becomes a constant amount, and the adsorption isotherm for adsorption of water vapor on carbon black has a slope that increases as the equilibrium pressure increases. It increases functionally (Toshinaga Kawai, “Research on Adsorption and Separation of Gases” published in October 1976, pages 26-28).
[0028]
According to this theory, the adsorption amount of the water vapor gas is determined by the pressure and temperature in the furnace 5, so this adsorption amount, that is, the increase or decrease of the water vapor gas, is controlled by adjusting the temperature of the hydration tank 32. You may adjust by the method of adjusting heating, the method of introduce | transducing heating hot water after the preheater 33, etc. However, in order to activate the carbon raw material M, it is a problem different from the fact that the theoretical and experimental gas adsorption amounts described above must be supplied into the furnace 5. The treatment for activation and the amount of gas adsorption should be considered separately.
[0029]
【Effect of the invention】
According to the method for producing a porous carbon material of the present invention, a porous carbonized material having a large specific surface area can be obtained, and the porous carbon material production system of the present invention can withstand a continuous operation for a long time. is there.
[Brief description of the drawings]
FIG. 1 is a system diagram showing an outline of a porous carbon material production plant.
FIG. 2 is data showing a relationship between an activation temperature and a specific surface area when a conventional carbon material activation system and a porous carbon material production plant of the present invention are compared.
FIG. 3 is a diagram for obtaining water to be added, and shows a relationship between an inert gas and a water content. It is a front view of FIG.
FIG. 4 is a system diagram showing an outline of a porous carbon material production plant.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Injection apparatus 20 ... Electric heating furnace 21 ... Core tube 22 ... Furnace 23 ... Heater 30 ... Hydration gas generation system 31 ... Inert gas generation device 33 ... Pre-heater 32 ... Hydration tank

Claims (5)

A method for producing a porous carbon material,
Put carbon material in the heating furnace, mix saturated steam and inert gas to make hydration gas, after preheating the hydration gas,
The carbon material is activated by supplying the hydrating gas into the heating furnace, and the heating furnace is heated to 800 ° C. or more to carbonize the carbon material .
Mixed temperature of the water to make the saturated steam and the inert gas is and at 98 ° C. lower than the atmospheric pressure, the preheating temperature of the hydration gas, porous carbon, characterized in that at 200 ° C. or higher Material manufacturing method. In the manufacturing method of the porous carbon material according to claim 1,
The method for producing a porous carbon material, wherein the inert gas is nitrogen gas produced by separating air. In the manufacturing method of the porous carbon material according to claim 2,
The method for producing a porous carbon material, wherein the supply amount of the saturated water vapor is proportional to the supply amount of the nitrogen gas. A heating furnace in which carbon material is placed,
An inert gas generating means for removing oxygen from the air and separating the inert gas;
Hydration means for mixing the inert gas and water from the inert gas generator;
A porous carbon material manufacturing system comprising preheated mixed inert gas and water and preheating means for supplying the heated gas to the heating furnace. In the manufacturing system of the porous carbon material according to claim 4 ,
The mixing temperature by the hydration means is 98 ° C. or less,
The preheating temperature of a preheating means is 200 degreeC or more. The manufacturing system of the porous carbon material characterized by the above-mentioned.

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