JP2019073605A - Method for producing needle coke - Google Patents

Abstract

To provide the method for producing the needle coke with an improved physical property by chemical treatment of a tissue, wherein the needle coke is used as an aggregate of graphite electrode formation used for electrodes in an electric furnace industry.SOLUTION: The method for producing the needle coke comprises: blowing again a calcined coke, that is produced by calcining raw coke produced by a delayed coking method at a temperature of 1200 to 1600°C with steam during a calcination process, converting selectively carbonaceous matter with an undeveloped needle-like tissue remaining in the calcined coke into hydrogen and carbon dioxide by a steam gasification reaction, removing the hydrogen and carbon dioxide, and leaving only a carbonaceous material with a developed needle-like tissue.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method for producing needle coke used as an aggregate for forming a graphite electrode used for an electrode in the electric furnace industry.

  Needle coke exhibits a fibrous oriented structure (needle-like structure), and a carbon hexagonal network surface has a well-developed graphitizable structure along the flow pattern. Needle coke having such characteristics is pulverized according to an appropriate method, and after performing particle mixture adjustment, an appropriate amount of caking agent (binder) is added to form soot, which is subjected to calcination and graphitization treatment Thus, a graphite compact can be obtained.

  A typical example of a graphite molded body manufactured in this way is an artificial graphite electrode used in an electric furnace, but in recent years with the improvement of the productivity of the electric furnace, the conditions for using the electrode become severe, and a large current is secured That the electrode itself has a low electrical resistance, and that the electrode is not broken due to the temperature difference generated in the electrode due to a large current, that is, the thermal shock characteristics are good, ie, the coefficient of thermal expansion (Coefficient of thermal) It is required that the expansion, hereinafter, may be abbreviated as "CTE") is extremely low. In order to lower the CTE of the graphite compact, it is necessary to use needle coke having a low CTE as a raw material.

  Needle coke is a raw material which manufactures a graphite electrode, and there are patent documents 1 and patent documents 2 as a prior art of a manufacturing method of coke for graphite compacts, and there is patent documents 3 as a prior art of a manufacturing method of needle coke.

Patent Document 1 discloses a method for producing a coke for a graphite molded body in which puffing is reduced by introducing steam at the time of calcination of green coke. Patent Document 2 discloses a method for producing a coke for a graphite compact with reduced puffing in which calcined coke is recalcined at 700 ° C. or higher in a steam atmosphere.
In these methods, the temperature at which steam is applied to raw coke and calcined coke is as wide as 1000-1600 ° C. in Patent Document 1 and 800-1400 ° C. in Patent Document 2 and the temperature range is high, so a plurality of It is not a method of gasifying and removing only non-needle-grown carbonaceous matter in calcified coke composed of different carbonaceous matter, but it is also possible to gasify even the carbonaceous matter having needle-like tissue developed to form fines formed Since the structure is a method of reducing puffing, it causes a problem of lowering the yield of needle coke.

Patent Document 3 discloses a method of producing raw coke suitable for producing needle coke by using a modified pitch in which the polar molecular component of coal-based pitch is reduced. It is disclosed that raw coke having a high texture of is suitable for the production of needle coke.
However, the above-described technology is a technology for producing raw coke suitable for producing needle coke by reforming raw coke raw material, and focusing on the crystallinity of carbonaceous matter present in needle coke, the needle coke is produced. It is not a method of degassing the low crystalline carbonaceous matter remaining in or the carbonaceous matter where needle-like structure has not developed and reducing the CTE of needle coke.

Japanese Patent Application Laid-Open No. 61-14111 Japanese Patent Application Laid-Open No. 61-14112 Unexamined-Japanese-Patent No. 2010-265367

  The object of the present invention is to provide a coke for a graphite compact, which is a raw material of a graphite compact such as a graphite electrode, without undergoing costly steps such as denitrification of coal-based heavy oil and desulfurization of petroleum-based heavy oil. An object of the present invention is to provide a method for producing needle coke (calcined coke) having a low coefficient of thermal expansion (CTE) suitable for production.

  In response to the demand for improving the physical properties of needle coke associated with recent technological innovations in the manufacture and use of EAF electrodes, the manufacturing technologies developed and disclosed for the purpose of improving the physical properties of needle coke all have cracks and fineness in needle coke. The present inventors have noted that it is captured only in the physical aspect of the coke structure, that is, the change in pore structure.

In the needle coke, there may be a case where a carbonaceous matter having a high CTE, which has not grown into a needle-like structure, remains, and the presence of this carbonaceous matter makes it difficult to lower the CTE of needle coke. Although known, how to control this carbon quality has not been reported so far.
The present inventors diligently studied about the control of carbonaceous matter which has not grown to this needle-like tissue. As a result, they have found a method in which the carbon content in needle coke, which is composed of a plurality of different carbon contents, is individually chemically controlled.

That is, the present invention is characterized by the following constitution.
[1] A method of producing needle coke by the second step of recalcination by the action of steam after the first step of calcining raw coke at a temperature of 1200 to 1600 ° C. to obtain calcined coke The needle is characterized in that the temperature range of the second step is a temperature range determined by determining the temperature at which the carbonaceous matter in which the needle-like structure remaining in the calcined coke is not gasified is gasified. Method for Producing Coke [2] In the temperature range of the second step, the temperature of calcined coke is controlled so that the temperature rising rate of calcined coke changes continuously according to the weight change rate of calcined coke, Calcined coke is heated and gasified in the presence of water vapor to obtain a thermogravimetric change curve (TG curve), and based on this curve, the carbonaceous matter in which the needle-like structure remaining in the calcined coke is not gas is a gas The temperature to be [3] The method for producing needle coke according to the above [1], wherein the temperature rise rate of the calcined coke is continuous according to the weight change rate of the calcined coke. The method of determining the thermogravimetric change curve (TG curve) by controlling the temperature of calcined coke by changing it
(A) Arbitrary constant temperature rising conditions are determined beforehand, constant temperature rising, TG curve is measured by constant temperature rising thermogravimetric analysis, determined from TG curve or from differential curve (DTG curve) of TG curve Setting a control target value to a value smaller than an absolute value of a DTG value (weight change rate) at an estimated carbonaceous gasification start temperature;
(B) The constant temperature rising temperature is carried out under the same conditions as or the conditions before and after the constant temperature rising condition of the step (A), and the constant temperature rising thermogravimetric analysis is carried out. When the temperature is slower than the target value, the temperature raising rate is the same as the constant speed temperature raising condition, and when the weight change rate of the calcined coke is more rapid than the control target value of the weight change rate Method of producing needle coke according to the above [1] or [2], which comprises the step of obtaining the thermogravimetric change curve (TG curve) by controlling the temperature gently. In the method [1] to [3] in which steam is applied to the burned coke, the steam is blown into the calcining device, or the burned coke and water obtained in the first step are mixed to carry out recalculation. Method for producing needle coke as described

  In the present invention, needle coke means needle coke and calcined coke which are raw materials of a graphite compact such as a graphite electrode.

  In the present invention, thermogravimetry measurement is carried out by heating and gasifying needle coke in the presence of steam, and the gasification temperature of carbonaceous material in which a needle-like structure is not developed is measured in advance to obtain a high temperature gas containing steam. In order to determine the temperature of the re-calcination process to make it act, it is possible to selectively convert the non-needle-structured carbonaceous material into hydrogen and carbon dioxide by steam gasification reaction, remove the needle-like structure It is possible to produce needle coke in which only the developed carbonaceous matter remains.

  That is, chemically controlling the carbonaceous matter in needle coke separately, which is composed of different carbonaceous matters, that is, selecting the high CTE-rich carbonaceous matter which has not developed needle-like structure and remains in needle coke CTE-reduced needle coke can be produced by removing only the low CTE carbonaceous matter that has been degasified and needle-like tissue development.

  Furthermore, after removing the carbonaceous matter from which the needle-like structure has not been developed by the steam gasification reaction, a fine void structure is formed, which becomes a gas escape hole, which is also effective in reducing the puffing.

In the present invention, the temperature range of the calcination temperature when the calcined coke is recalcined in the presence of water vapor is in the vicinity of the gasification start temperature of the carbonaceous matter in which the needle-like structure remaining in the calcined coke is not developed. It is characterized in that it is set to.
As a result, it is possible to gasify and remove only the carbonaceous material in which the acicular structure has not developed, and to produce needle coke in which only the carbonaceous material in which the acicular structure has developed has remained. I can expect it.

TG curve of calcined coke Polarized photomicrograph of calcined coke Polarized light micrograph after removal of non-developed needle-like carbonaceous matter

  The method for producing needle coke according to the present invention comprises a first step of calcinating raw coke at a temperature of 1200 to 1600 ° C. to obtain calcined coke, followed by a second step of allowing a steam to act and recalcining the needle A method of producing coke, wherein the temperature range of the second step is determined by determining the temperature at which the carbonaceous matter without the development of acicular structure remaining in the calcined coke is gasified. It is characterized by

  In the calcined coke, there may be a case where a carbonaceous matter having a high needle-like structure and a high CTE is not left, and the presence of this carbonaceous matter makes it difficult to lower the CTE of needle coke. Is well known. That is, the carbonaceous matter in which the acicular structure is not developed can be removed from the calcined coke, and the CTE of the needle coke can be lowered by using only the carbonaceous matter in which the acicular structure has developed.

  The present invention determines the temperature range of the second step in the second step as a temperature range determined by determining the temperature at which the carbonaceous matter in which the needle-like structure remaining in the calcined coke is not gasified is gasified. The CTE of needle coke can be lowered by causing steam to act on the calcined coke produced in the first step to produce needle coke.

First, the first step will be described.
In the first step, the raw coke is calcined at a temperature of 1200 to 1600 ° C. to produce calcined coke. Here, the first step may be performed by a known device or method.

Next, as a second step, the calcined coke obtained in the first step is allowed to react with steam to produce needle coke.
A feature of the present invention is that the temperature range of the second step is a temperature range determined by determining the temperature at which the carbonaceous material in which the acicular structure remaining in the calcined coke is not developed is gasified. is there.

  As a method of causing steam to act on the calcined coke and recalculating it in the second step, steam is blown into the calcining device, or the calcined coke obtained in the first step is mixed with water to be calcined. There is a way to do it.

  As an apparatus used for a 2nd process, existing calcination apparatuses, such as a rotary kiln and a rotary hearth furnace, can be used, for example, and it is not limited to a specific model. The present invention can be implemented in any calciner as long as the conditions of the steam-containing gas blowing and temperature control in the calcining stage are satisfied.

In the rotary kiln, a steam-containing gas feed nozzle can be inserted from the outlet side of the calcined coke to design a device for feeding steam.
In a rotary hearth furnace, a steam injection nozzle can be installed on a fixed roof portion to carry out the present invention.

  However, the simplest method is the temperature at which the non-acicular carbonaceous matter remaining in the calcined coke is gasified when the calcined coke is recalcined at the highest temperature in the calciner. It is a method of setting in the temperature range determined by obtaining and mixing calcined coke and water at one time and charging it into the calciner.

  In the case of producing needle coke by industrially proven two-stage calcination, in the first-stage calcinator, carbonaceous matter in which needle-like structure remaining in calcined coke is not gasified It is calcined in the temperature range determined by determining the temperature, and remains in the calcined coke by blowing steam in the second-stage calcining device or injecting the mixture of the first-stage calcined coke and water. It is possible to simply apply the present invention by carrying out the steam gas reaction in the temperature range determined by determining the temperature at which the carbonaceous material with which the needle-like structure has not developed is gasified.

  Before entering the calciner, the amount of water mixed with the calcined coke is determined by determining the temperature at which the non-acicular carbonaceous matter remaining in the calcined coke is gasified. Chemical engineering can be easily calculated from the water vapor partial pressure required in the gasification reaction area, the size of the apparatus, and the amount of carbonaceous matter in which the needle structure contained in the calcined coke is not developed.

  The water vapor partial pressure is not particularly limited as long as it is a pressure sufficient to promote water vapor gasification, but from the viewpoint of rapidly advancing water vapor gasification, the water vapor partial pressure is 1 to 60 kPa, more preferably 5 to 50 kPa Is preferred.

  The temperature at which the needle-like structure-remaining carbonaceous matter remaining in the calcined coke necessary for determining the temperature range of the second step is gasified is specifically the calcination in the presence of water vapor The coke is heated and gasified, and the temperature of the calcined coke is controlled so that the temperature rising rate of the calcined coke changes continuously according to the weight change rate of the calcined coke, and a thermogravimetric change curve (TG curve) is determined Based on this curve, it is possible to determine the carbonization gasification start temperature of the non-developed needle-like structure remaining in the calcined coke.

  From the analysis of the TG curve and the DTG curve, not only the gasification start temperature but also the abundance of each carbonaceous component can be determined.

Here, the thermogravimetric change curve (TG curve) shows the relationship between the temperature (° C.) of the calcined coke at the time of temperature rise and the thermogravimetric weight (g), and a differential thermogravimetric curve obtained by differentiating this TG ( Derivative Thermo Gravimetry (hereinafter abbreviated as DTG) shows the relationship between the temperature and the thermal weight change rate (g / sec).
The TG curve and the DTG curve can be measured using a known thermal analyzer capable of thermogravimetric measurement.

When the TG curve is determined, the calcined coke is heated and gasified in the presence of steam, which acts as a carbonaceous gasifying agent contained in the calcined coke.
Hereinafter, a method of obtaining a TG curve for heating and gasifying calcined coke in the presence of steam will be described.

The sample used when obtaining the said TG curve can use the calcination coke before making the water vapor | steam of the production line of the needle coke which is actually working act.
When installing a new needle coke production system instead of improving the existing needle coke production system, make a trial production of calcined coke from green coke according to the operation conditions of the first step, and use it as a sample for TG curve Ask.

In the gasification of calcined coke, an open-type reaction vessel containing calcined coke is installed in a temperature-controllable electric furnace such as a thermogravimetry-simultaneous measuring device, and the temperature in the furnace is allowed to flow through water vapor. The calcined coke is heated and gasified by raising its temperature.
By circulating steam in the electric furnace, steam can be continuously supplied, and it becomes possible to continuously remove gas gasified from carbon and generated tar components, and measurement of gasification amount with high reproducibility is realized. it can.

  The shape of the calcined coke to be introduced into the thermogravimetric simultaneous measurement device is not particularly limited as long as it can be introduced into the measurement container, but is preferably in a uniform state. Also, the shape, weight, size or volume of the calcined coke introduced into the apparatus is not particularly limited as long as it can be introduced into the balance and / or the sample container in the apparatus.

  The measurement of the TG curve heats and gasifies the calcined coke in the presence of steam and controls the temperature of the calcined coke so that the temperature rising rate of the calcined coke changes continuously according to the weight loss rate of the calcined coke. do it.

The method of controlling the temperature of the calcined coke so as to continuously change the temperature rising rate of the calcined coke according to the weight change rate of the calcined coke is to change the temperature rising method stepwise or continuously it can.
As a method of changing stepwise, for example, heating is performed at an early temperature rising rate at the initial stage of measurement, and temperature rising rate is controlled stepwise between 5 to 20 ° C./min around evaluation temperature where weight change is observed Can be mentioned.

Here, if the heating rate is too slow, analysis takes time and it can not be a rapid analysis method. On the other hand, if the heating rate is too fast, the other carbonaceous gasification reaction starts before the target carbonaceous gasification reaction is completed, which makes it difficult to separate the carbonaceous matter.
From the above reasons, the temperature rising rate is preferably 5 to 20 ° C./min.

Steam used for heating and gasifying calcined coke is preferably mixed with an inert gas. The water vapor partial pressure is not particularly limited, but is preferably 0.1 to 60 kPa.
When the water vapor partial pressure becomes high, condensation may occur in the gas flow path and the thermogravimetry simultaneous measurement apparatus. If dew condensation occurs in the apparatus, measurement of the gasification amount becomes difficult.
Furthermore, if the water vapor partial pressure is too small, the gasification reaction rate will be slow, and the amount of gasification in a certain measurement time will be small, which makes measurement difficult, so it is desirable to be as high as possible.

  From the above reasons, the steam partial pressure is preferably a steam partial pressure that does not cause condensation in the entire temperature range to be analyzed and in the apparatus, and is preferably a high steam partial pressure, more preferably 1 to 60 kPa, and a steam partial pressure of 5 to 50 kPa. Is more preferred.

  The mixing of the water vapor into the inert gas may be carried out in any manner. For example, a method of bubbling an inert gas in water at a constant temperature and applying water vapor at a saturated vapor pressure at that temperature, or quantitatively adding water to a gas stream using a syringe pump etc. Methods etc. can be used.

  More preferably, the method of determining the thermogravimetric change curve (TG curve) by continuously changing the temperature rising rate of the calcined coke and controlling the temperature of the calcined coke according to the weight change rate of the calcined coke is as follows: Can be illustrated.

  (A) Arbitrary constant temperature rising conditions are determined beforehand, constant temperature rising, TG curve is measured by constant temperature rising thermogravimetric analysis, determined from TG curve or from differential curve (DTG curve) of TG curve A value smaller than the absolute value of the DTG value (weight change rate) at the estimated carbonaceous gasification start temperature is set as the control target value, and the same as or before or after the constant speed heating condition of step (A) of (B) Under the following conditions, the temperature is raised at a constant temperature and the thermogravimetric analysis is carried out, and when the weight change rate of the calcined coke is slower than the control target value of the weight change rate, the temperature increase rate is In the same step, when the weight change rate of the calcined coke is more rapid than the control target value of the weight change rate, the temperature increase is stopped or the temperature increase rate is controlled slowly to obtain a thermogravimetric change curve (TG curve). It is a method of including.

In order to determine the gasification start temperature of each carbonaceous component contained in calcined coke and the abundance of each carbonaceous component, the temperature and velocity at which gasification occurs (DTG) according to the type of each carbonaceous component contained in calcined coke ) Uses different points. The carbonaceous matter present in the calcined coke differs in gasification temperature and rate (DTG) due to the difference in carbonaceous crystallinity or orientation.
For example, in the case of calcined coke composed of crystalline carbonaceous matter and non-crystalline carbonaceous matter, the gasification reaction proceeds at a lower temperature or at a higher rate in the non-crystalline carbonaceous matter. Furthermore, for example, in the case of calcined coke composed of highly oriented carbonaceous matter and less oriented carbonaceous matter, the gasification reaction proceeds at a lower temperature or at a higher rate in the case of less oriented carbonaceous matter.

  That is, by analyzing the TG curve and the DTG curve at the time of heating and heating, it is possible to separate the carbonaceous gasification reaction different in crystallinity or orientation contained in calcined coke, and the corresponding weight change amount By measuring, the gasification start temperature of each carbonaceous component and the abundance of each carbonaceous material can be analyzed.

In the method of measuring the TG curve in advance in the step (A) by constant temperature rising temperature thermogravimetric analysis, calcined coke is heated to gas at a constant temperature rising rate in the presence of water vapor, and the TG curve is measured. Here, from the above-mentioned reason, it is preferable that a temperature rising rate is 5-20 degrees C / min.
The temperature range of measurement should just be a temperature range which can measure gasification reaction of each carbonaceous substance in calcined coke. Specifically, from the vicinity of the coking temperature during raw coke production, which is the calcined coke raw material, for example, around 450 ° C. on the low temperature side, to the vicinity of 1600 ° C. where the gasification reaction of crystalline carbon (graphite) occurs on the high temperature side. It is sufficient to measure the temperature range of

  The gasification start temperatures of a plurality of carbonaceous materials having different crystallinity or orientation (for example, carbonaceous 1, carbonaceous 2 and carbonaceous 3 in descending order of crystallinity) in calcined coke are often close to each other In many cases, each carbonaceous gasification reaction occurs continuously. In this case, it is difficult to determine the gasification start temperature of carbon 2 and carbon 3 from the analysis of the TG curve obtained by constant temperature rising.

Control of the heating rate to a value smaller than the absolute value of the DTG value (weight change rate) at the gasification start temperature of carbonaceous matter determined from the obtained TG curve or estimated from the derivative curve (DTG curve) of the TG curve The target value can be exemplified by the following method.
By differentiating the TG curve, a DTG curve can be drawn, the DTG value at the gasification start temperature of each carbonaceous matter can be determined, and a value smaller than the absolute value can be set as the control target value of the temperature rise rate.

  In the step (B), when the weight change rate is slower than the control target value, the temperature increase rate is the same as the constant temperature increase condition in the step (A), and the weight change rate of the calcined coke is the above When the temperature is steeper than the control target value of (1), the temperature rise is stopped or the temperature rise rate is controlled gradually, and the TG curve is measured.

Here, although the control target value of the temperature rising rate may be a value determined by trial and error, the derivative of the TG curve measured by constant temperature rising temperature thermogravimetric analysis by the method described in the step (A) It is more preferable to set a control target value to a value smaller than the absolute value of the DTG value (weight change rate) at the carbonaceous gasification start temperature estimated from the curve (DTG curve).
By determining the control target value by constant temperature rising temperature thermogravimetric analysis, analysis of different carbonaceous matters can be more accurately advanced. Then, by bringing the control target value close to the absolute value of the DTG value (weight change rate) at the gasification start temperature, it becomes possible to advance the analysis of the different calcined coke more quickly.

  The onset temperature of each carbonaceous material can be determined from the temperature at which the sample weight reduction starts or the temperature at which the sample weight reduction rate changes, but the temperature at which the sample weight reduction of each carbonaceous material starts Is preferred.

In addition, carbon content contained in calcined coke can be separated and quantified based on the TG curve.
The method of separating and quantifying the carbonaceous matter contained in the calcined coke uses the obtained TG curve to determine the gasification initiation temperature of each carbonaceous matter, and the temperature range divided by the gasification initiation temperature of each carbonaceous matter By measuring the amount of each carbonaceous material in
Moreover, although it is preferable to calculate the abundance of each carbonaceous substance here from the weight change of the sample in the specified temperature range where each carbonaceous substance is gasified, the amount of carbon contained in the generated gas is measured You may go by.

  The amount of each carbonaceous material contained in the calcined coke separately separated and quantified is the amount of water vapor blown into the calciner in the second step, or the calcined coke and water obtained in the first step are mixed and calcined. It can be used as data to determine the amount of water in the method to be carried out.

  As described above, the boundary of weight loss due to gasification reaction of different carbonaceous substances can be clearly measured by using thermogravimetry by temperature control method in which the temperature rising rate is continuously changed according to the weight change rate of calcined coke. The separation of the carbonaceous gasification start temperature can be accurately measured. Then, it is possible to calculate the abundance of each carbonaceous matter, for example, by measuring the weight change amount of the sample in the specified temperature range where each carbonaceous matter gasifies or the carbon amount contained in the gas generated by the gasification.

  Generally, the carbonaceous material having the highest gasification start temperature in calcined coke is a carbonaceous material having a needle-like structure developed, so if the gasification starting temperature and the amount of each carbonaceous material are known, the needle-like It is possible to determine the gasification initiation temperature of the carbonaceous material without tissue development and the gasification initiation temperature of the carbonaceous material with the acicular structure development. Then, the temperature range in between can be made the temperature range of the second step.

  Using the method for obtaining the TG curve, clearly separating the non-needle-formed carbonaceous matter and the needle-like tissue-developed carbonaceous matter from the TG curve of the calcined coke measured in the presence of water vapor It is possible to quantify each carbonaceous gasification start temperature and the amount of each carbonaceous material present.

  Furthermore, to determine more precisely the carbonization gasification start temperature of the non-needle structure and the carbonization gas of the needle structure development, microscopic observation of calcined coke and needle coke From the quantitative image analysis of the photograph, determine the abundance ratio of carbonaceous matter without needle-like tissue development and carbonaceous matter with needlelike tissue evolution, and compare with the abundance ratio of each carbonaceous matter analyzed from TG curve It is also possible to specify the carbonization temperature at which the needle-like tissue has not been developed and the carbonization gas temperature at which the needle-like tissue has developed.

  The novel basic knowledge is that the calcified coke is acicularly shaped by carrying out a steam gasification reaction again in the calciner at a carbonaceous steam gasification temperature at which the acicular structure is not developed. Unstructured carbonaceous matter can be gasified and removed as hydrogen and carbon dioxide, and recalcined and steam gasified needle coke becomes a needled coke of only a carbonaceous matter with acicular structure developed .

  Steam gasification method by temperature range determined by determining the temperature at which the non-needle-grown carbonaceous material remaining in the calcined coke is gasified and the temperature at which the needle-like tissue has developed carbonization is determined Can be applied to the process of producing needle coke, thereby producing needle coke in which the non-needle-structured, non-developed carbonaceous matter has been gasified and removed. That is, needle coke with reduced CTE can be produced.

  Furthermore, after removing the carbonaceous matter from which the needle-like structure has not been developed by the steam gasification reaction, a fine void structure is formed, which becomes a gas escape hole, which is also effective in reducing the puffing. It can be expected.

Hereinafter, the present invention will be described by way of examples.
These examples are described to specifically exemplify the present invention, and various modifications can be made without departing from the scope of the present invention. The present invention is directed to the following description. It is not limited.

(Evaluation sample)
Calcined coke used as an evaluation sample is calcined coke derived from heavy coal oil sourced on the market.

(Thermogravimetric analyzer)
For the thermogravimetric measurement apparatus, a water vapor-operated differential thermal balance (TG-DTA / HUM-1 manufactured by Rigaku Corporation) was used.

Example 1
The evaluation sample was precisely weighed to approximately 10 mg and 0.01 mg and introduced into a thermogravimetric measurement apparatus. Here, 300 ml / min of a mixed gas of steam and nitrogen was flowed as a gasifying agent. The water vapor partial pressure at this time was 20 kPa. If the absolute value of the weight change rate is smaller than the control value of 0.002% / sec under the conditions where the gasifying agent is circulated, the temperature is raised by heating at 10 ° C / min, and the absolute value of the weight change rate is controlled When the value was 0.002% / sec or more, the sample temperature was controlled to stop the temperature rise, and the TG curve was measured. Here, the control value 0.002% / sec of the weight change rate is a value determined in advance by analysis of a DTG curve obtained by isothermal temperature rise analysis.
The obtained TG curve is shown in FIG.

  The evaluation sample showed two stages of weight loss. From the TG curve, the temperature at which the weight loss in each stage starts was taken as the gasification start temperature of each stage. The first stage gasification start temperature was 1013 ° C., and the second stage gasification start temperature was 1113 ° C.

Cross-sectional polarized light microscopy was performed on the evaluation sample, and it was found that there is a large amount of carbonaceous material in which a needle-like tissue is not developed. A representative example of a polarized light micrograph is shown in FIG.
By quantitative image analysis of the polarized light micrograph of FIG. 2, the area ratio of the carbonaceous material in which the needle-like tissue was not developed to the carbonaceous material in which the needle-like tissue was developing was calculated. As a result of analysis, the area ratio of the carbonaceous material without needle tissue development to the carbonaceous material with needle tissue development was 28:72.

  The weight ratio of the evaluation sample at two different gasification temperatures was 34:66. As for the weight ratio in the temperature range divided by the steam gasification temperature, the area ratio of each carbonaceous matter calculated from image analysis showed an almost equal ratio.

  Therefore, the carbonaceous material undergoing gasification reaction at each water vapor gasification temperature of the evaluation sample is a low temperature side (water vapor gasification temperature 1013 ° C.) is a carbonaceous material of which needle structure is not developed, high temperature side (water vapor gasification The temperature of 1111 ° C. can be said to be carbon material in which a needle-like structure has developed.

Example 2
From the results of Example 1, it was found that the temperature necessary for degassing the carbonaceous matter in which the needle-like structure in the evaluation sample is not developed is 1013 ° C. or more and less than 1113 ° C. For this reason, the temperature range for gasifying and removing the carbonaceous matter in which the acicular structure is not developed in the second step was determined around 1100 ° C.

  The evaluation sample was precisely weighed to approximately 10 mg and 0.01 mg and introduced into a thermogravimetric measurement apparatus. Here, 300 ml / min of a mixed gas of steam and nitrogen was flowed as a gasifying agent. The water vapor partial pressure at this time was 20 kPa. Under the conditions where the gasifying agent was circulated, the temperature was increased as in Example 1 at a temperature at which the weight loss increased, while raising the temperature to 1100 ° C. at a temperature rising rate of 20 ° C./min and holding for 30 minutes, The temperature was lowered and a sample was taken out.

  A polarization microscope observation of a cross section is performed on the taken-out sample in the same manner as in Example 1, and by quantitative image analysis, a carbonaceous material in which the acicular structure is not developed and a carbonaceous material in which the acicular structure is developed. The area ratio was calculated. A representative polarized light micrograph is shown in FIG.

As shown in FIG. 3, it can be seen that the carbon material in which the needle-like tissue is not clearly developed has almost disappeared.
Also from the image analysis results, the result of supporting visual observation, that is, the ratio of the area of the carbonaceous material in which the needle-like tissue is not developed to the carbonaceous material in which the needle-like tissue is developed, 0.3: 99.7 is obtained. The

  From the above, by causing calcined coke to react with water vapor at a temperature at which the carbonaceous matter without acicular structure develops a steam gasification reaction, carbon in which acicular structure in calcined coke is not developed It has been found that the quality can be selectively removed.

By using the method of the present invention, the CTE high carbon material without needle structure development remaining in needle coke is selectively gasified and removed, and the CTE low carbon material with needle structure developed. By leaving only CTE, needle coke with reduced CTE can be produced. Furthermore, it is possible to produce needle coke in which only carbonaceous matter with acicular structure has developed can be expected, and yield improvement in needle coke production can be expected.

Claims (4)

  A method of producing needle coke in a second step of calcining raw coke at a temperature of 1200 to 1600 ° C. to obtain calcined coke and then subjecting steam to the action of steam to perform recalculation, Production of needle coke characterized in that the temperature range of the second step is a temperature range determined by determining the temperature at which the non-acicular carbonaceous matter remaining in the calcined coke is gasified. Method   In the temperature range of the second step, the temperature of the calcined coke is controlled so that the temperature rising rate of the calcined coke changes continuously according to the weight change rate of the calcined coke, and calcination is performed in the presence of water vapor The coke is heated and gasified to obtain a thermogravimetric change curve (TG curve), and based on this curve, the temperature at which the non-acicular carbonaceous matter remaining in the calcined coke is gasified is determined. The method for producing needle coke according to claim 1, wherein the temperature range is determined. According to the method of obtaining the thermogravimetric change curve (TG curve) by controlling the temperature of the calcined coke by continuously changing the temperature rising rate of the calcined coke according to the weight change rate of the calcined coke,
(A) Arbitrary constant temperature rising conditions are determined beforehand, constant temperature rising, TG curve is measured by constant temperature rising thermogravimetric analysis, determined from TG curve or from differential curve (DTG curve) of TG curve Setting a control target value to a value smaller than an absolute value of a DTG value (weight change rate) at an estimated carbonaceous gasification start temperature;
(B) The constant temperature rising temperature is carried out under the same conditions as or the conditions before and after the constant temperature rising condition of the step (A) and the constant temperature rising thermogravimetric analysis is carried out, and the weight change rate of the calcined coke is the control of the weight change rate When the temperature is slower than the target value, the temperature raising rate is the same as the constant speed temperature raising condition, and when the weight change rate of the calcined coke is more rapid than the control target value of the weight change rate The method for producing needle coke according to claim 1 or 2, comprising the steps of: controlling the temperature slowly and obtaining a thermogravimetric change curve (TG curve). In the second step, the calcined coke is subjected to steam by blowing steam into the calcining device, or by mixing the calcined coke obtained in the first step with water to carry out recalculation. -Process for producing needle coke according to any one of claims 3 to