JP2009196850A - Stabilizing apparatus and stabilizing method of carbonized material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stabilizing apparatus and a stabilizing method of a carbonized material by which the carbonized material is formed into a stabilized material for a short time. <P>SOLUTION: The carbonized material T produced in a carbonization apparatus 1 is stabilized by oxidizing to extinguish spontaneously igniting nature and has an apparatus body 51 constituting a closed space where the carbonized material T is charged, a heating means 56 for heating the carbonized material while keeping the inside of the apparatus body 51 at a prescribed temperature and a stirring means 52 for stirring the carbonized material T in the apparatus body 51. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a carbide stabilization treatment apparatus and a stabilization treatment method for making a carbide having self-heating property stable so that it can be safely transported and stored, and particularly to suppress the self-heating property by stirring the carbide. It relates to what makes a stable substance.

  Organic waste such as stored manure discharged from a barn is considered to be carbonized for effective use. However, there is a problem that the carbide generated from the organic waste itself generates heat and burns while being stored. This is considered that carbide has a self-heating property, generates heat during storage, rises in temperature, and ignites when the temperature exceeds a certain temperature. Therefore, it was necessary to suppress combustion due to this ignition in handling the carbide.

Therefore, JP 2004-267950 A describes that it is effective to oxidize carbides in a low-temperature oxidizing atmosphere. That is, a carbide having a low degree of carbonization contains many active groups that are highly active with respect to an oxidation reaction, and self-heats even at a low temperature of 200 ° C. or lower. However, it is thought that the self-heating of carbide is a reaction different from the combustion reaction and is due to the air oxidation reaction of the active group. At low temperatures, the reaction gradually converges and the active site (active group) gradually disappears. And finally stabilize. Therefore, if the oxidation reaction is completed at a low temperature in advance, it is possible to suppress the subsequent self-heating of the carbide and prevent combustion due to ignition.
JP 2004-267950 A

  By the way, there is a self-heating substance test based on the UN Recommendation on the Transport of Dangerous Goods regarding the handling of carbides. Specifically, as shown in FIG. 8, a basket test (WBT test) using a thermostatic bath is performed. A powdered carbide is put into a mesh basket 101 made of stainless steel having a cube shape of 100 mm square, and the sample 102 is heated in a thermostatic chamber 103 maintained at 140 ° C. The temperature of the sample 102 is measured by the thermocouple 105, and the data logger 106 calculates the temperature from the thermocouple 105 and displays it.

  In this WBT test, when the carbide is heated to 40 ° C. or more by heating at 140 ° C., it is determined to have self-heating properties. On the other hand, it has been obtained as a test result that carbide that does not cause combustion rises to a certain value and then gradually decreases to the temperature of the 140 ° C. atmosphere in the tank. Therefore, it has been confirmed from this basket test that by heating at a certain temperature, the self-heating carbide is stable and can be safely transported and stored.

  However, although it can be seen that it is effective to complete the oxidation reaction at a low temperature in advance, it was not clear how to heat specifically. Moreover, in order to make it industrially realizable, it is required to shorten the reaction time so that a large amount of carbide stabilization treatment can be performed.

  Therefore, an object of the present invention is to provide a carbide stabilization treatment apparatus and a stabilization treatment method for making a carbide a stable substance in a short time in order to solve such a problem.

The carbide stabilization treatment apparatus according to the present invention stabilizes the carbide generated by the carbonization apparatus by oxidization treatment by losing pyrophoricity, and the closed space into which the carbide is charged is formed. The apparatus main body comprises: a heating means for heating the carbide while maintaining the inside of the apparatus main body at a predetermined temperature; and a stirring means for stirring the carbide in the apparatus main body. .
In the carbide stabilization apparatus according to the present invention, the apparatus body is a cylindrical trough, and the stirring means is a screw inserted into the trough, and the carbide is stirred by a rotating screw. It is preferable to move in the trough.

Further, the carbide stabilization apparatus according to the present invention is an air for cooling the carbonized exhaust gas discharged from the carbonizer by the heating means, and the air is heated to a predetermined temperature by heat exchange with the carbonized exhaust gas. The heat exchanger is preferably supplied as heated air heated up to the inside of the apparatus main body.
Further, the carbide stabilization treatment apparatus according to the present invention includes a temperature sensor that measures the temperature of the heated air discharged from the apparatus main body, and a valve provided in a gas pipe that supplies carbonized exhaust gas to the heat exchanger. And a controller that adjusts the opening of the valve based on a detection signal of the temperature sensor.

  On the other hand, the method for stabilizing a carbide according to the present invention is a method of stabilizing by losing pyrophoricity by oxidizing the carbide generated by the carbonization apparatus, in the space where the carbide is introduced. Is maintained at a predetermined temperature, and the carbide in the space is stirred for a predetermined time while being heated at the predetermined temperature.

  Therefore, according to the present invention, the carbide in the space is kept at a predetermined temperature, and the carbide in the space is stirred while being heated at the predetermined temperature, so that the carbide is excessively stored due to heat storage and heat generation in a short time. It becomes possible to make the material stable under the condition of preventing the temperature rise. Moreover, a large amount of processing is possible by heating the inside of the cylindrical trough and moving the carbide while stirring with a screw inserted into the trough. Moreover, since the carbide is heated using the thermal energy of the carbonized exhaust gas emitted from the carbonizer, energy efficiency is good.

Next, an embodiment of a carbide stabilization apparatus and a stabilization process according to the present invention will be described below with reference to the drawings.
Carbide is produced by drying stored manure discharged from a poultry house or the like and then carbonizing them with a carbonization device. The carbide thus obtained can be stored for a long period of time, and can be used as a snow melting agent and a soil conditioner in addition to fertilizer. First, a carbonization apparatus that generates carbide will be described. FIG. 1 is a conceptual diagram showing a multistage screw type carbonization apparatus.

  The carbonization apparatus 1 of the present embodiment is such that the carbide to be carbonized introduced into the hopper 4 is heated and pyrolyzed into carbide by passing through a plurality of screw conveyors 11 to 14 heated in the carbonization furnace 2. It is. In the screw conveyors 11 to 14 arranged in the vertical direction, a cylindrical trough 21 is installed on a wall surface facing the carbonization furnace 2, and a screw 22 is inserted into the trough 21. The screw conveyors 11 to 14 are configured as conveying means for conveying the object to be carbonized in the axial direction by the rotating screw 22.

  The screw 22 has a spiral blade formed in a spiral shape at a predetermined pitch on the rotation shaft thereof, is supported by a bearing through a bearing, and is configured to be rotated by a drive motor (not shown). Therefore, the rotational speed of the screw 22, that is, the conveyance speed of the carbide to be moved in the trough 21, can be adjusted by drive control of a drive motor (not shown). The troughs 21 of the screw conveyors 11 to 14 are connected one above the other by the chute unit 5 so that the conveying direction is alternately switched from top to bottom.

  Moreover, the carbonization apparatus 1 is configured with a heating unit that sends hot air (hot air) from below to a conveyance unit including the screw conveyors 11 to 14. The heating unit is configured by a burner 8 in which a heating chamber 7 is provided in the lower part of the carbonization furnace 2 and a flame is injected there. Thereby, the heat by the flame injected from the burner 8 is sent from the inside of the heating chamber 7 to the inside of the carbonizing chamber 9 of the carbonizing furnace 2, and the other screw conveyors 11 to 13 are also heated while directly heating the lowermost screw conveyor 14. The temperature rises. On the other hand, at the upper part of the carbonization furnace 2, there is provided a recombustion furnace 3 for combusting and heating dry distillation gas that has not been combusted in the carbonization chamber 9, and pyrolyzing the odor.

  In the carbonization apparatus 1, the object to be carbonized is conveyed by rotating the screw 22 of the screw conveyors 11 to 14, and the object to be carbonized is carbonized while moving in the heated trough 21. At that time, combustible dry distillation gas is generated from the carbide. Therefore, in this embodiment, it is comprised so that the screw conveyors 11-13 located in an upper stage may be heated with the flame of the dry distillation gas. That is, the screw conveyors 11 to 14 are configured so as to protrude from the upper surface of the trough 21 to form a gas outlet 23, and dry distillation gas generated inside blows upward to generate a flame.

  Therefore, the carbonized material is first put in a drier (not shown) to remove a certain amount of moisture, and then supplied to the carbonizing apparatus 1. In the carbonization apparatus 1, the to-be-carburized materials thrown in from the hopper 4 are conveyed so that the screw conveyors 11-14 lined up and down may descend in order from the top. In the carbonization furnace 2, in addition to heating by the flame of the burner 8, dry distillation gas generated from the carbonized material in the process of carbonization blows out from the gas outlet 23, becomes flame by the heating temperature in the carbonization furnace 2, and gradually gradually converts the carbonized material into the carbonized furnace 2. Carbonize. And the carbide | carbonized_material T is produced | generated by passing through such screw conveyors 11-14, and is sent to the following process.

  Since the carbide T has a self-heating property as described above, when it is deposited as it is or stored in a bag or the like, there is a possibility that the temperature rises due to heat accumulation or heat generation and may ignite. Carbide (pyrolysis residue of organic waste) contains a large amount of ash and functional groups, so that the temperature rises spontaneously by an oxidation reaction, and when it is stacked and left, it accumulates heat and eventually ignites. Such a temperature increase is due to oxidation, but is not completed because the oxygen concentration is reduced in the carbonization apparatus. However, since the carbide has an opportunity to come into contact with air during movement and bagging, ignition may occur after a long time. In addition, since the amount of stored heat after heat generation is large, it tends to ignite as the deposition thickness increases.

  Therefore, in the present embodiment, a stabilization process is performed in the next step in order to make the carbide generated by the carbonization apparatus 1 a stable substance so that it can be safely transported. This is performed by an apparatus and a method that are configured by paying attention to the fact that they can be stabilized by causing an oxidation reaction to the extent that they do not ignite in the atmosphere and once giving a temperature rise history. Furthermore, it makes it possible to perform the stabilization process in a short time. Specifically, the remaining functional group is oxidized by heating and stirring the carbide at a predetermined time and temperature.

  Here, FIG. 3 is a conceptual diagram showing a stabilization treatment method by stirring the deposited carbide at a high temperature. In this method, the carbide T is put in a container 31 made of stainless steel so as to be deposited, and this is placed in a thermostatic chamber 32 that keeps the internal space at a predetermined temperature. The thermostatic bath 32 is an air circulation type, and dissipates heat generated from the carbide T by the stabilization treatment so that the temperature in the bath is kept constant. Further, an anchor type stirring blade 33 is provided in the container 31 in which the carbide T is put, and the stirring blade 33 is rotated by a motor 35 installed outside the thermostat 32 through a connected rod 34. Is to be given.

  In this experiment, for the container 31 having a diameter of 85 mm and a height of 150 mm, the deposition thickness of the filled carbide T is set to 70 mm, and the processing temperature and processing time in the thermostat 32 are changed. It was. Then, the treated carbide was subjected to the WBT test shown in FIG. 8 to determine the presence or absence of ignition. FIG. 4 is a table showing the results of such an experiment. As shown in the figure, when the treatment temperature and the treatment time are 210 ° C. for 10 minutes (experiment 1), 250 ° C. for 4 minutes (experiment 2). And it is a case (experiment 3) at 250 degreeC for 5 minutes.

  The results of the WBT test on the carbides treated under these conditions are as shown in FIGS. FIG. 5 shows the results of experiment 1, FIG. 6 shows the results of experiment 2, and FIG. 7 shows the results of experiment 3. The graph shows the temperature change of carbides over time. The temperature change in the center, the surface, and the tank is shown for each of the carbides volumed in the container 31.

  First, in Experiment 2, the carbide T was heated at a bath temperature of 250 ° C., and the stirring blade 33 was rotated in this state to stir the carbide T in the container 31 for 4 minutes. After the treatment, the WBT test shown in FIG. 8 was performed in a state where the temperature of the carbide T was lowered. In this case, when the temperature in the tank is raised to 140 ° C., the carbide T, which was initially about 30 ° C., is heated as shown in FIG. 6, and the surface first gradually rises and delays following the temperature in the tank. In this way, the temperature of the central part gradually increased. And when the temperature in the tank was kept at 140 ° C., the surface temperature of the carbide T was stabilized at 140 ° C., but the central part generated heat exceeding the temperature in the tank at about 1 hour 30 minutes after the start of heating. After that, when about 3 hours and 30 minutes passed, a rapid temperature increase occurred, and it ignited and burned. Therefore, the carbide T was not stabilized under the conditions of Experiment 2.

  Next, in Experiment 1, the carbide T was heated to 210 ° C., and the stirring blade 33 was rotated in this state to stir the carbide T in the container 31 for 10 minutes. And the WBT test shown in FIG. 8 was performed in the state which lowered the temperature of the carbide T. In this case, when the temperature in the tank is raised to 140 ° C., the carbide T, which was initially about 30 ° C. as shown in FIG. 5, is heated, and the surface first rises following the temperature in the tank, and is delayed. As a result, the temperature of the central part rose gradually. The surface temperature of the carbide T was stabilized at 140 ° C. following the temperature in the tank, while the central portion started to generate heat exceeding the temperature in the tank when about 4 hours had elapsed from the start of heating. However, although the center temperature was raised to about 165 ° C., thereafter, the temperature was gradually lowered to gradually approach the tank temperature, and heat generation stopped. Therefore, the carbide T was stabilized under the conditions of Experiment 1.

  Further, in Experiment 3, the carbide T was heated to 250 ° C. and the stirring blade 33 was rotated in this state, whereby the carbide T in the container 31 was stirred for 5 minutes. And the WBT test shown in FIG. 8 was performed in the state in which the carbide T lowered in temperature. In this case, when the temperature in the tank is increased to 140 ° C., the carbide T that was initially about 30 ° C. is heated as shown in FIG. 7, and the surface first rises following the temperature in the tank and is delayed. As a result, the temperature of the central part rose gradually. Then, the carbide T rises following the temperature in the tank, and the surface temperature stabilizes at about 140 ° C., while the central portion starts to generate heat exceeding the temperature in the tank when about 3 hours have elapsed from the start of heating. . However, in this case as well, although the center temperature was raised to about 165 ° C., thereafter, the temperature was gradually lowered to gradually approach the bath temperature, and heat generation was stopped. Therefore, the carbide T was stabilized even under the conditions of Experiment 3.

  From the above results, it was found that the remaining functional groups in the carbides were oxidized by the heating and stirring operation, and the deposited carbides could be stabilized at a time. It was also found that the stabilization process using agitation requires controlling the conditions for the processing temperature and processing time in the tank. Therefore, in the present embodiment, a stabilization processing device for stabilizing the carbide generated by the carbonization device 1 of FIG. 1 is proposed next. The stabilization processing apparatus according to the present embodiment proposes a batch processing stirrer shown in FIG. 3 that can continuously process carbides that are continuously generated, because it becomes difficult to process. FIG. 2 is a conceptual diagram showing a secondary side line of the carbonization apparatus 1 including such a stabilization processing apparatus.

In the carbonization apparatus 1 shown in FIG. 1, the chute portion 5 of the lowermost screw conveyor 14 is connected to a cooling device 41. This is because the carbide T emitted from the carbonization furnace is as high as 400 to 500 ° C. and burns when it is exposed to the outside air, so it is necessary to cool it to a certain temperature. In the present embodiment, the carbide T is cooled to about 200 ° C. by the cooling device 41.
The cooling device 41 is configured by a screw conveyor, and is configured as a conveying means in which a rotatable screw 43 is inserted into a cylindrical trough 42 and the carbide T moves in the axial direction by the rotating screw 43. And the trough 42 is installed in the cooling tank 44 through which the cooling water W flows. Therefore, the cooling device 41 is configured to cool the carbide T moving in the trough 42 by heat exchange with the cooling water W.

  Next, such a cooling device 41 is connected to the stabilization processing device 50 by a chute 46 provided with a rotary feeder 45. This stabilization processing device 50 is also constituted by a screw conveyor. A rotatable screw 52 is inserted into a cylindrical trough 51, and is configured as an agitating and conveying machine that feeds the carbide T while stirring the rotating screw 52. The stabilization processing device 50 is configured to heat the carbide T inside by sending heated air into the trough 51. Therefore, a supply port 53 for feeding heated air and an exhaust port 54 for exhausting it are formed at the end of the trough 51.

  The stabilization processing apparatus 50 stirs the carbide T for a predetermined time while heating the carbide T at a predetermined processing temperature, similarly to the processing method shown in FIG. The processing temperature is adjusted by the temperature of the heated air supplied into the trough 51, and the processing time, that is, the transport time of the carbide T passing through the trough 51 is adjusted by the rotational speed of the screw 52 by a drive motor (not shown). It is comprised so that.

  In this embodiment, air A for cooling the carbonized exhaust gas discharged from the carbonization furnace 2 is used as the heated air, which is heated and supplied to the trough 51. Therefore, a heat exchanger 56 is connected to the supply port 53 of the trough 51, and heated air A heated to 200 ° C. to 250 ° C. by heat exchange with the carbonized exhaust gas G is supplied to the trough 51. ing. A gas pipe 59 having a valve 61 is connected to the heat exchanger 56 in order to supply the carbonized exhaust gas G as a heat source.

  On the other hand, an exhaust pipe 57 is connected to the exhaust port 54 of the trough 51, and a temperature sensor 58 for measuring the air temperature after heating the carbide T in the trough 51 is provided there. The temperature sensor 58 is connected to a controller 62 that adjusts the opening degree of the valve 61. Therefore, the stabilization processing apparatus 50 of this embodiment adjusts the opening degree of the valve 61 based on the measurement of the secondary side temperature of the heated air by the temperature sensor 58, and the heating temperature of the carbide T is kept at a predetermined value. It is configured to be.

  The stabilization processing device 50 is connected to the cooling device 65 via the chute 63 so that the carbide T after the stabilization processing is sent. The cooling device 65 is also a screw conveyor, and is a conveying means in which a rotatable screw 67 is inserted into a cylindrical trough 66 and the carbide T is sent in the axial direction by the rotating screw 67. And it is comprised so that the cooling water M may be sprayed in the trough 66, and cooling water is sprayed on the carbide | carbonized_material heated by the stabilization processing apparatus 50, and it is trying to reduce temperature to about 60 degreeC. . At the conveying end of the trough 66, a chute 68 is provided with a rotary feeder 69 from which the carbonized product Ts is recovered.

  The cooling device 65 generates steam by spraying the cooling water onto the carbide T, and therefore, an exhaust pipe 71 that exhausts the steam is connected. The exhaust pipe 71 is connected to the exhaust pipe 57 from the stabilization processing device 50. Is connected through a valve 72. Since the exhaust from the stabilization processing device 50 and the cooling device 65 contains powdered particles from the carbide, the exhaust pipe 57 is connected to a cyclone separator 73 that separates the particles. The cyclone separator 73 has a rotary feeder 74 at a lower end portion, and a fine carbonized product Ts is collected. Moreover, the cyclone separator 73 is connected with an exhaust fan 75 so that the hot air from which the particulate matter has been separated is sent into the heating chamber 7 of the carbonization apparatus 1.

  Next, in the secondary line of the carbonization apparatus 1 configured as described above, the generated carbide T is first sent to the cooling apparatus 41. In the cooling device 41, when the carbide T is conveyed through the trough 42 by the screw 43, the carbide T is cooled by heat exchange with the cooling water W flowing around, and the temperature of 400 to 500 ° C. is lowered to about 200 ° C. Such carbide T is then sent to the stabilization device 50 via the rotary feeder 45.

  In the stabilization processing device 50, the heated air A whose temperature is controlled by the temperature sensor 58 or the like is sent, the inside of the trough 51 is kept at a constant temperature, and the carbide T is sent while being stirred by the screw 52. To go. The time required for such heating and stirring treatment varies depending on the heating temperature and the amount of carbide T, but is, for example, about 10 minutes. The carbide T becomes a stable substance by oxidizing the remaining functional groups by heating and stirring for a predetermined time in the stabilization processing device 50.

  Thereafter, the carbide T is sent to the cooling device 65, and while being sent by the screw 67 rotating in the trough 66, the carbide T is cooled to about 60 ° C. by the sprayed cooling water M, and becomes the carbonized product Ts. Collected. On the other hand, the heated air or the like after the stabilization treatment is separated into powder particles by the cyclone separator 73, the powder particles are also collected as the carbonized product Ts, and the hot air is sent again into the heating chamber 7 of the carbonization apparatus 1.

  Therefore, in this embodiment, since the carbide T is stabilized by the stabilization processing apparatus 50, it becomes possible to make the carbide a material that can be safely transported and stored by suppressing heat generation that leads to ignition thereafter. It was. In this embodiment, since the carbide T is stabilized by passing through the stabilization processing apparatus 50 that has performed temperature management or the like in a short time, a large amount of processing can be performed by continuous operation. . Moreover, in the stabilization processing apparatus 50, since the carbide | carbonized_material T is heated using the thermal energy of the carbonization waste gas which comes out of the carbonization apparatus 1, energy efficiency is good.

  By the way, in the said embodiment, the example for stabilizing by giving an oxidation reaction to the extent which does not ignite a carbide | carbonized_material under air | atmosphere, and once giving a temperature rising history was shown. In particular, a structure to which a stirring operation was added was adopted as a structure for mass processing. This is because the stirring operation is effective for preventing accumulated heat from being accumulated in the central portion of the deposited carbide as in the experimental example shown in FIG. Therefore, in addition to stirring the carbide, a method of preventing heat accumulation by applying vibration to the deposited carbide and allowing it to flow to some extent is also effective as a stabilization treatment method. In addition, since heat accumulates in the center when deposited, a method of processing without depositing is also conceivable. That is, a stabilization process is performed in which carbides are put as particles in a container that generates a swirling airflow of hot air, and an oxidation reaction is performed while rising.

  As mentioned above, although embodiment was described about the stabilization processing apparatus and stabilization processing method of carbide, this invention is not limited to this, A various change is possible in the range which does not deviate from the meaning.

It is the conceptual diagram which showed the multistage screw type carbonization apparatus. It is the conceptual diagram which showed the secondary side process of the carbonization apparatus containing the stabilization processing apparatus. It is the conceptual diagram which showed the method of the stabilization process by stirring the deposited carbide | carbonized_material at high temperature. It is the figure which showed the result of the WBT test in the table | surface about the carbide | carbonized_material obtained by changing conditions in the method of FIG. It is the figure which showed the result of the WBT test in the graph about the carbide | carbonized_material obtained on one condition in the method of FIG. It is the figure which showed the result of the WBT test in the graph about the carbide | carbonized_material obtained on one condition in the method of FIG. It is the figure which showed the result of the WBT test in the graph about the carbide | carbonized_material obtained on one condition in the method of FIG. It is the figure which showed the basket test of the UN recommendation about dangerous goods transportation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Carbonization apparatus 2 Carbonization furnace 11-14 Screw conveyor 41 Cooling apparatus 44 Cooling tank 50 Stabilization processing apparatus 51 Trough 52 Screw 53 Supply port 54 Exhaust port 56 Heat exchanger 58 Temperature sensor 62 Controller 65 Cooling apparatus 73 Cyclone separator 75 Exhaust fan T Carbide G Carbonized exhaust gas

Claims (5)

In a carbide stabilization treatment device that stabilizes by igniting the carbides generated by the carbonization device to lose pyrophoric properties,
An apparatus main body constituting a closed space into which the carbide is charged, heating means for heating the carbide while maintaining the inside of the apparatus main body at a predetermined temperature, and stirring means for stirring the carbide in the apparatus main body A carbide stabilization treatment apparatus characterized by comprising: In the carbide stabilization treatment apparatus according to claim 1,
The apparatus main body is a cylindrical trough, and the stirring means is a screw inserted into the trough, and the carbide is stirred by a rotating screw and moved in the trough. There is provided a stabilization treatment apparatus for carbide. In the carbide stabilization treatment apparatus according to claim 1 or 2,
The heating means is air for cooling the carbonized exhaust gas discharged from the carbonization apparatus, and the air is supplied into the apparatus main body as heated air heated to a predetermined temperature by heat exchange with the carbonized exhaust gas. An apparatus for stabilizing a carbide characterized by being a heat exchanger. In the carbide stabilization treatment apparatus according to claim 3,
A temperature sensor for measuring the temperature of the heated air discharged from the apparatus main body, a valve provided in a gas pipe for supplying carbonized exhaust gas to the heat exchanger, and opening of the valve based on a detection signal of the temperature sensor. And a carbide stabilization processing apparatus characterized by comprising a controller for adjusting the degree. In the method of stabilizing a carbide, the pyrolysis is lost and stabilized by oxidizing the carbide generated by the carbonization device.
A method for stabilizing a carbide characterized in that the inside of the space into which the carbide is charged is kept at a predetermined temperature, and the carbide in the space is stirred for a predetermined time while being heated at the predetermined temperature.

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