JPS6054909A - Preparation of carbon material - Google Patents

Abstract

PURPOSE:To obtain a calcined carbon material having improved physical properties and clean surface state without causing problems of dust and oxidation consumption of filler, by calcining molded articles of carbon material in a furnace at a specific rate of heating without filling packing powder tol the periphery of the molded articles of carbon material. CONSTITUTION:The supporting columns 5 are stood in a muffle furnace, and the retention plates 2 made of graphite are attached to them. For example, 18 molded articles of the carbon material 1 molded by a hydraulic press are packed onto the plates. A forming gas such as N2:H2=1:3 is made to flow from the gas inlet 3 to the muffle furnace, made to flow uniformly from the top and bottom by the distribution plate 8, and discharged from the exhaust vent 4. As the gas flows, the molded articles are heated to about 1,200 deg.C at a rate of heating of 10 deg.C per hour, kept at this temperature for about 10hr, and allowed to be cooled. A calcined material having clean surface free from cracks, blister, warpage, etc. is prepared. The calcined material is graphitized at about 3,000 deg.C, to give an improved carbon material.

Description

[Detailed description of the invention] The present invention relates to a method for manufacturing carbon materials.

Carbon materials are usually made by extrusion molding of a mixture made by adding binders such as pitch and tar to aggregates such as coke powder, graphite powder, and oil smoke, and heating and kneading the mixture.The mixture is then crushed, the particle size is adjusted, and the molding powder is press-molded. A molded body formed into a predetermined shape is obtained by means such as isostatic pressing, and then heated in a Matsufuru furnace, tunnel furnace, etc.
000℃, and if necessary, this fired body is further heated to 250℃.
A method of graphitizing at a temperature of 0° C. or higher is used.

Conventionally, the molded body is fired by placing the molded body in a Matsufuru furnace and filling the space between the molded bodies and around the molded body with a filling powder such as coke powder or graphite powder to prevent oxidation and welding of the molded body. and maintenance of properties.

However, this method has the following drawbacks due to the use of powdered powder.

In small and medium-sized furnaces, the filling efficiency of compacts is poor, and the dust generated during the powder filling process poses a risk of causing respiratory problems for workers. To prevent this, expensive dust collection equipment is required. Large furnaces also require equipment such as filling equipment, collection equipment, and separation equipment for this powder.

In addition, in this method, since all the spaces in the molded body are filled with the filler, the amount of heat required for heating and raising the temperature is large. Therefore, a temperature difference tends to occur between the vicinity of the furnace body and the opposite side from the center of the furnace, and in order to prevent this, firing is performed at a significantly reduced temperature increase rate. For this reason, firing requires a very long time, usually 350 to 500 hours. moreover,
When the firing time is long, the gas generated from the molded body is not retained around the molded body but diffuses, making it difficult to fire the molded body in an optimal atmosphere.

Furthermore, since a considerable amount of stuffing powder is used, heat loss is also large and cooling time is also increased.

The stuffing powder is coke powder to keep the atmosphere under reducing conditions.

Graphite powder is used, but because it is exposed to high temperatures for a long time,
The consumption of coke powder and graphite powder due to oxidation is also not small.

Furthermore, in order to use these powders, the fired body is once softened and then carbonized, so the large particles in the powder get stuck on the surface, creating unevenness and making it difficult to clean.

The present invention solves these problems, and by firing the molded body without using fillers, it solves the dust problem, the problem of oxidative consumption of fillers, etc., and makes it possible to fire in a short time. ,
The purpose is to obtain a fired body with excellent physical properties and a clean surface condition by maintaining an optimal atmosphere during firing.

As a result of repeated research on the method for firing carbon material molded bodies, the present inventors have discovered that by creating a non-oxidizing atmosphere in the firing furnace, it is possible to fire the molded bodies without using powder.

The present invention is. When firing a carbon material molded body in a firing furnace, the inside of the firing furnace is maintained in a non-oxidizing atmosphere without filling the periphery of the molded body with powder, and the molding is performed at a temperature increase rate of 10°C or more per hour. The present invention relates to a method for producing a carbon material by heating and firing a body.

The molded body in the present invention is a carbon material molded body formed by molding powder by pressure molding or the like, as described above.

The firing furnace used in the present invention is a firing furnace having a gas flow passage through which a non-oxidizing gas, which will be described later, passes, and includes, for example, a Matsufuru-type atmosphere furnace and a tunnel-type atmosphere furnace. The compacts are carried into these firing furnaces, non-oxidizing gas is sent into the furnace to create a non-oxidizing atmosphere, and the space around the compacts is filled with powder such as coke powder or graphite powder. Fire without burning. The non-oxidizing gas mentioned here includes, for example, nitrogen gas, argon gas, carbon dioxide gas, hydrogen gas, carbon oxide gas, methane gas, ethane gas, propane gas, and mixed gases thereof. It is preferable that a molded body having a large volume is placed on a holding plate with small irregularities and fired. This is because the contacting bottom surface of the molded body remains as it is after firing.

The holding plate is a graphite plate that is heat resistant and can withstand the weight of the molded product.

An alumina plate or the like is often used, and the surface can be polished if necessary.

It is preferable to fire a molded body having a small volume in a firing container such as a stainless steel box with a lid because the concentration of gas generated around the molded body tends to be small.

Molded objects that are rectangular parallelepipeds or cylinders and have a volume of 2000 cm or more.

Ring-shaped items can be placed directly on the holding plate.

Since the actual volume of the compact is small relative to the volume it occupies, it is preferable to place it in a firing container and attach a top lid to retain the generated gas in the container.

In addition, for rectangular parallelepipeds and cylinders with a volume of 2000 cm or less, attach a lid to the firing container and make a hole in the entire surface or a part of the container to adjust the gas concentration inside the container. This is because if the generated gas concentration is too high, the surface will blister, while if it is too low, the specific gravity and strength of the fired product will decrease.

The flow rate of the non-oxidizing gas depends on the volume inside the furnace, the size and opening degree of the firing container (the ratio of the total hole area to the total light area of the firing container excluding the bottom), and the volume ratio of the molded product placed in the firing container. Taking these factors into consideration, selection is made so that the concentration of gas generated around the circumference H of the molded body is optimal.

There is no particular limit to the firing temperature (maximum temperature), but it is usually 900~
The temperature is 1300°C. It is necessary to increase the temperature at a rate of 10°C or more per hour. If the temperature is less than 10°C per hour, the molded product will be deformed (warped). It is preferable to set the temperature to 20° C./hour or higher because the amount of deformation is extremely small.

The heat source of the firing furnace may be electricity, gas, or oil, and the heat cover necessary for firing the molded body is provided by heat conduction from the bottom plate in contact with the molded body, convection of surrounding gas, and radiant heat from the furnace wall.

A tunnel furnace is effective for continuously firing a large amount of compacts.

Examples will be described below.

Example 1 A schematic diagram of the electric furnace used for firing is shown in FIG. In the figures, (a) is a side view, and (b) is a front view. This electric furnace is heated with a SiC heat generating rod, the inner wall is lined with 6-SUS 3108 stainless steel plate 6, and the inner dimension (+ nm ) is 7001W)X800(
Melt in an oven at L) x 500 (H). Six pillars 5 are erected in this Matsufuru furnace, and two bottom plates 2 made of graphite with a flatness and surface roughness of 100 μm in maximum height and a thickness of 10 mm and a holding plate 2 with a thickness of 20 fflII+ are installed. I installed one. On top of that, it was molded using a hydraulic press so that the molding specific gravity was 1.58.
Eighteen carbon molded bodies 1 of 100 (F()m) were packed. The occupied volume ratio of these molded bodies was about 35 cm. In this Matsufuru furnace, a forming gas of N2:I (+=1:3) was charged. was flowed uniformly from above and below through the gas inlet 3 and the dispersion plate 8, and while exhausting from the exhaust port 4, the temperature was raised to 1200'C at a rate of 10°C per hour.
After holding for a period of time, it was allowed to cool. The firing time was 180 hours including the cooling time. The fired body thus obtained has a clean surface and is free from cracks, blisters, warps, etc. Thereafter, the fired body was graphitized at 3000°C, but the physical properties before and after graphitization showed no abnormalities as shown in Table 1.

Comparative Example 1 The bottom of a stainless steel baking container with internal dimensions of 500 x 40 Q x 350 was filled with coke powder to a height of 50 mm, and on top of it were placed the same two carbon molded bodies as in Example 1, and the remaining space of the container was filled with an average of 2111 m Filled with coke powder.

This firing container was placed in the same Matsufuru furnace as in Example 1, and firing was performed under the same conditions as in Example 1, including flowing gas.

When the fired body was taken out, it was found that blistering had occurred over almost the entire surface. This swelling was particularly severe on the surfaces where the molded bodies were adjacent to each other.

Cracks were also seen in some parts. As shown in Table 1, this physical property was poor with low specific gravity and low strength.

Example 2 A firing container 10 made of SiC with an inner dimension of 280 x 280 x 100 + nm as shown in the plan view of Fig. 2 (a) and the side view of Fig. 2 (b) has a flatness of 1 x 9 and a surface roughness of A graphite holding plate 2 with a thickness of 100 μm and a thickness of 10 was laid down, and 16 cylindrical carbon molded bodies with a molding specific gravity of 1.58 were placed on it as shown in Figure 2.
Put it in like this and put the lid on.

It was placed in the same Matsufuru furnace as in Example 1 and fired under the same conditions as in Example 1.

When the fired body was taken out, it was found that the surface was in good condition with no cracks. As shown in Table 1, there were no abnormalities in the physical properties.

Comparative Example 2 Sixteen of the same cylindrical molded bodies were placed in the firing container of Example 2, and fired under the same firing conditions as Example 1 without a lid.

The surface condition of the fired body was good. This physical property is the first
As shown in the table, specific gravity 1 strength showed a small value.

Example 3 Dimensions: 280x280x with 48 φ10 holes on the side
Sixteen cylindrical carbon molded bodies having dimensions of φ60×60 mm were placed in a 100-neck firing container, the lid was closed, and firing was performed under the same conditions as in Example 1. The surface condition of the fired body was good.

This physical property is also the 9th As shown in Table 1, there were no abnormalities.

Comparative Example 3 Sixteen molded bodies identical to those of Example 3 were placed in a firing container with dimensions of 280 x 280 x 100 mm without holes.

The lid was closed and firing was performed under the same conditions as in Example 1.

Blisters were found all over the upper surface of this fired body. As for the physical properties, as shown in Table 1, the specific gravity 9 strength showed a rather small value.

Example 4 Using the same firing furnace as in Example 1, a carbon molded body 1 of the same size was produced.
Eight pieces were packed and fired. As an atmospheric gas, N! Gas-Nx: CO2 = 1:1 mixed gas at 2 times per hour
001! It flowed. Other firing conditions are the same as in Example 1. The surface of the fired product at this time was good.

There were no abnormalities in the physical properties as shown in Table 1.

Example 5 As shown in Fig. 3, dimensions 180 threads IX 300 (4) x
A carbon molded body 1 of 10011) nnn is placed on a graphite holding plate 2 and passed through a tunnel-type atmospheric furnace 12 with a width of 9 widths of 350 (%ll x 180ff). Temperature distribution in the furnace at this time.

10- The feeding rate of the compact was adjusted so that the baking temperature rate was 20°C/hour and the maximum temperature was maintained at 1100°C for 10 hours. The firing time was about 80 hours including the cooling time. The gas to be supplied is a forming gas of N2:H2=1:3, which is supplied from three locations in the tunnel furnace.

To ensure that the molded product does not oxidize and the gas concentration generated from the molded product is optimized, the total flow rate is 8001! / Sent the gas of time. The obtained fired body had a good surface condition, and its physical properties showed no abnormalities as shown in Table 1. When the fired body was graphitized at 3000°C, the physical properties showed good values as shown in Table 1.

Example 6 Sixteen cylindrical carbon molded bodies with dimensions of φ60×φ40×60 mm were placed in a firing container with internal dimensions of 280×280×100 mm as shown in FIG. 2, and the lid was closed.

Firing was performed using the same tunnel furnace as in Example 5 and under the same conditions. The surface condition of the fired body was good.

The physical properties at this time were good as shown in Table 1.

Example 7 In a firing container with internal dimensions of 280 x 280 x 100 m + n, ring-shaped carbon molded bodies with dimensions of 40 x 20 x 10 mm for mechanical seals were placed in 4 stages using holding plates, 42 pieces per stage, 168 pieces in total, and the lid was closed. Using the same tunnel furnace, the heating rate was 50℃/hour, and the maximum temperature was 1100℃.
The temperature distribution in the furnace and the feeding speed of the firing container were adjusted so that the temperature was maintained at ℃ for 4 hours. Baking time is approximately 35 minutes including cooling time.
It was time.

As the atmospheric gas, the same forming gas as in Example 5 was sent from three locations in the tunnel furnace at a total flow rate of 1112001/hour.

The obtained fired body had a good surface condition, and the physical properties at this time were good as shown in Table 1.

Table 1 below shows a comparison of Example 1 and Comparative Example 1. Comparative Example 1 causes blisters and has a low specific gravity and strength. This is because in Comparative Example 1, the concentration of generated gas was higher than the optimum value (13-), resulting in foaming. Also, when comparing Example 2 and Comparative Example 2, Comparative Example 2 has a higher specific gravity.

The strength is small. This is because in Comparative Example 2, the firing can was not covered with a lid, so the concentration of 1 generated gas was lower than the optimum value. Furthermore, when comparing Example 3 and Comparative Example 3, Comparative Example 3 has a higher gas concentration than the optimum gas concentration, so blistering occurs and the specific gravity 1 strength decreases.

Comparing Example 1 and Example 5, Example 5 has lower specific gravity 1 strength. This is because the maximum temperature is lower in Example 5, and the temperature increase rate and atmospheric gas concentration are different. The results are similar when comparing Example 2 and Example 6.

Since this generated gas is a condensable gas, there is no optimal method to measure its concentration, but there are several ways to adjust the gas concentration.

Can be fired in a tunnel furnace or the like without using powder.

In the present invention, no powder is used as described above.

Since a molded body of carbon material can be fired, the generation of dust, which is a disadvantage of the conventional method, is eliminated, and the work environment can be significantly improved without the need for expensive dust collection equipment. Furthermore, in the present invention, since the molded body can be fired at a temperature increase rate that is consistent with the size of the molded body, the firing time is 1/4 to 1/2 compared to the conventional method.
Since it can be shortened to /10, compacts of carbon materials can be fired in large quantities and at low cost.

In addition, according to the present invention, there is no problem of temperature difference caused by conventional large furnaces, so there is little variation among fired products, and since no packing powder is used, the surface condition is clean, and the product can be fired under the optimum concentration of generated gas. Since sintering is possible, a carbon material with unchanged physical properties can be obtained.

As described above, the present invention is suitable as an industrial method for firing carbon materials.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing the method of filling a carbon compact into a Matsufuru furnace, +8) is a side view, (b) is a front view, and Figure 2 is a schematic diagram showing a method of filling a carbon compact into a firing container. ta) is a plan view, (b) is a side view, and FIG. 3 is a schematic diagram showing a state in which a carbon molded body passes through a tunnel furnace. Explanation of symbols 1...Carbon molded body -2...Holding plate 3...Gas inlet 4...Exhaust port 5...Strut 6...Furnace wall 7...Opening/closing door 8...・Gas distribution plate 9... Packing 10... Container for firing 11...
Upper lid 12...Tunnel furnace page) Old (a) (b. ] [-] "-] "-] Procedural amendment writing method) February 16, 1975 1. Indication of case 1982 Patent Application No. 162889 2. Title of invention Method for manufacturing carbon material 3. Make amendments Patent applicant name (445) Hitachi Chemical Co., Ltd. 4. Agent January 31, 1982 (shipment date) 6. Full text of the specification subject to the P amendment 70. J'! Amendment Content

Claims (1)

[Claims] 1. When firing a carbon material molded body in a firing furnace, the inside of the firing furnace is maintained in a non-oxidizing atmosphere without filling the periphery of the molded body with powder, and the temperature is increased at a rate of 10°C or more per hour. A method for producing a carbon material, which comprises heating and firing the molded body.