JPH04353391A - Electrical heating furnace and manufacture of highly crystalline carbon black - Google Patents

Abstract

PURPOSE:To obtain a highly crystalline carbon black, which permits high temperature rise and is excellent is resistance to oxidization, by a method wherein an electrical heating furnace, employing the carbon black as a heat generating body, is employed while the used carbon black and/or another carbon black is heat-treated. CONSTITUTION:Refractory bricks 1 are piled up so as to form a cavity therein and graphite electrodes 4, to which copper plates 5 connected, are inserted into both ends of said cavity while the cavity is filled with heat generating body or acetylene black to constitute an electrical heating furnace. A graphite crucible 3, filled with material acetylene black necessitating high crystallizing treatment, is buried into said heat generating body in the cavity. Subsequently, a voltage is increased gradually employing a transformer while regulating the value of current and the crucible is heated to a high temperature, then, highly crystalline carbon black is produced in the crucible 3. The resistance to oxidization of said products is improved without spoiling the absorbing amount of hydrochloric acid while no damage can be in respective parts of the heating furnace and the furnace is functioned as a heating furnace sufficiently.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric heating furnace capable of raising the temperature to 2000 DEG C. or higher and a method for producing highly crystalline carbon black with good oxidation resistance using the same.

0002

[Prior Art] As a method of improving the oxidation resistance of carbon black, it is known that carbon black is heat treated at a high temperature of 2000°C or higher in vacuum or in an inert atmosphere to increase the degree of crystallinity. However, conventional heat treatment furnaces have poor workability.

That is, conventional electric resistance furnaces have been made using nichrome, tantalum, silicon carbide, and granular carbon (Kryptor).
, molybdenum, tungsten, graphite, etc. are known. Among these, those that can raise the temperature to 2000° C. or more are those that use tungsten or graphite as a heating element.

However, metal heating elements such as tungsten must be heat treated in a vacuum or in an inert atmosphere to prevent wear due to oxidation. On the other hand, in the case of a Tammann furnace that uses graphite, graphite has little effect as a heat insulating material, so it is necessary to heat treat it in a vacuum or in an inert atmosphere to prevent high-temperature oxidation of graphite, and furthermore, it is necessary to heat treat it in a vacuum or in an inert atmosphere. It was necessary to choose expensive furnace materials.

On the other hand, in methods other than electric resistance furnaces,
Furnaces capable of raising the temperature above include high-frequency furnaces, but because of the complicated structure of the equipment, the equipment tends to be large and expensive.

[0006]

[Problems to be Solved by the Invention] The objects of the present invention are to provide an energized heating furnace that can raise the temperature to 2000°C or more with a very simple structure compared to conventional ones, and to provide a high crystallinity heating furnace using this heating furnace. An object of the present invention is to provide a method for producing carbon black. [0007]

[Means for Solving the Problems] That is, the present invention provides an energized heating furnace in which carbon black is used as a heating element, and an energized heating furnace that uses carbon black as a heating element and/or another energized heating furnace. This is a method for producing highly crystalline carbon black, which is characterized by heat-treating carbon black.

The present invention will be explained in more detail below.

The electric heating furnace of the present invention is characterized in that carbon black is used as the heating element. When carbon black is used as a heating element, 200
It becomes possible to raise the temperature above 0°C. Conventional Kryptor furnaces using granular carbon have low electrical conductivity, making it difficult to raise the temperature above 2000°C.

[0010] Furthermore, carbon black used as a heating element has a high porosity, so it also serves as a heat insulating material, and since heat transfer to the outside is small, there is less combustion in the atmosphere, and damage to the furnace material is reduced. few. In the case of a Tammann furnace that uses graphite as a heating element, the porosity of the filled graphite is low, so combustion due to heat transfer is intense, and furnace materials with high refractory properties had to be used.

The present invention will be explained based on the drawings.
FIG. 1 is a schematic cross-sectional view showing an example of the energized heating furnace of the present invention. 1 is a furnace material such as a chamotte brick, 2 is a heating element made of carbon black, 3 is a crucible made of graphite or the like for putting the object to be heat treated, and 4 and 5 are graphite and copper plates constituting electrodes, respectively.

Carbon black used as a heating element includes acetylene black, furnace black,
Any material such as channel black may be used, but one that exhibits an appropriate electric resistance value as a heating element when filled into an electric furnace is selected. For example, when the furnace volume is large and the distance between the electrodes is long, carbon black with low electrical resistivity as shown in JIS K1469 is used, whereas when the furnace volume is small and the distance between the electrodes is short, carbon black with high electrical resistivity is used. selected. Further, during electrical heating, carbon black with a low bulk density may be blown out due to expansion of internal gas, so it is preferable to use a high bulk density product or a granular product rather than a low bulk density product. Note that the electrical resistance value can also be changed by changing the filling volume and packing density of carbon black. Specifically, it is preferable to fill the electrodes so that the electrical resistance value between the electrodes is 1 to 5Ω. If the electrical resistance value is too low, the current will short-circuit, while if it is too high, it will be difficult to generate heat.

[0013] As an electrode, a conductive metal plate such as a copper plate may be used alone, but since there is a risk of high temperature at the part in contact with carbon black, which is a heat generating element, it is recommended to use it in combination with graphite etc. as shown in Fig. 1. is desirable.

[0014] As the furnace material, it is desirable to use a material with high refractoriness, but since carbon black itself serves as a heat insulating material, for example, an alumina-based material with a refractoriness of about SK36 can also be used. Furthermore, since the gas in the carbon black expands during heating with electricity, it is preferable to provide an appropriate gap for extracting the gas.

The current heating furnace of the present invention can be used not only for high crystallization treatment of carbon black as described below, but also for sintering ceramics, etc., and as various high-temperature reaction devices.

[0016] In order to perform high crystallization treatment of carbon black using the above-mentioned heating furnace, the carbon black that requires high crystallization treatment is filled in the furnace as a heating element and/or in a crucible. Heat treatment is performed. The processing temperature is 20
The temperature is preferably 00°C or higher, and the treatment time is preferably 1 hour or more after reaching a temperature of 2000°C or higher.

The heat treatment atmosphere may be air. When carried out in the atmosphere, carbon black, which serves as a heating element, burns to some extent, but this does not adversely affect the function of the heating furnace. The carbon black used as the heating element becomes a highly crystallized product as it is after heat treatment, but it is preferably filled in a crucible of graphite or the like and heat treated, thereby making it possible to obtain a product with less variation.

[0018]

[Examples] The present invention will now be explained in more detail with reference to Examples. Example 1 Chamotte firebrick (SK36 equivalent) 300x200
x 200mm cavities are created and stacked, graphite bricks with copper plates connected are inserted from both ends of the cavity as electrodes, and acetylene black "Denka Black granules (trade name manufactured by Denki Kagaku Kogyo Co., Ltd.)" is placed in the cavities as a heating element. The cavity was completely filled to form an electric furnace.

In a graphite crucible (internal size 80φ x 80mm), raw material acetylene black that requires high crystallization treatment “Denka Black 50% product (trade name manufactured by Denki Kagaku Kogyo Co., Ltd.)
'' and embedded it in the heating element. The total resistance value between the copper plate electrodes at this time was 2Ω.

Next, using a 10KVA transformer, the voltage was gradually increased from the low voltage side while adjusting the current value, and the temperature was raised until the temperature measured with an optical meter reached 2500°C, and the temperature was raised for 5 hours. Heated.

After the temperature was raised, the copper plates, graphite bricks, refractory bricks, etc. were inspected for damage, but no abnormalities were found, and the furnace functioned satisfactorily as an electric heating furnace. The product in the crucible was taken out and its physical properties were measured by the following method. As a result, the specific surface area is 30
m2/g, hydrochloric acid absorption amount 15.4ml/5g, Lc70Å
, the thermal oxidation temperature is 560°C, the specific surface area of the raw material acetylene black is 65 m2/g, and the amount of hydrochloric acid absorbed is 15.5 ml/5.
g, Lc of 35 Å, and thermal oxidation temperature of 420° C., the oxidation resistance could be improved without impairing the hydrochloric acid absorption amount.

(1) Specific surface area: BE due to nitrogen gas adsorption
It was measured by the T1 point method. (2) Hydrochloric acid absorption amount: Measured according to JIS K1469. (3) Lc (thickness of graphite layer): X using Cu-Kα rays
It was calculated according to the following formula from the (002) diffraction line in the line diffraction method. K = Shape factor (0.9 was used) λ = X-ray wavelength (1.54A) θ = Angle showing the maximum value in the (002) diffraction line absorption band β = Half value in the (002) diffraction line absorption band Width expressed in degrees (4) Thermal oxidation temperature: Temperature when the temperature is raised in an air atmosphere using a thermogravimetric balance and 5% by weight of the total weight is reduced by combustion.

[0023]

[Effect of the invention] According to the present invention, two
An energized heating furnace capable of raising the temperature to 000° C. or higher is obtained. By using the electric heating furnace of the present invention, carbon black can be easily crystallized to a high degree.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an example of an energized heating furnace of the present invention.

[Explanation of symbols]

1...Furnace material 2... Heating element made of carbon black 3... Crucible 4...Graphite electrode 5...Copper plate electrode

Claims (2)

[Claims] 1. An electric heating furnace characterized by using carbon black as a heating element. 2. A highly crystalline carbon characterized by heat-treating carbon black used as a heating element and/or another carbon black in an electric heating furnace using carbon black as a heating element. - Method for producing bomb black.