JP6017371B2 - Ashless coal manufacturing method and carbon material manufacturing method - Google Patents

Description

  The present invention relates to a method for producing ashless coal for obtaining ashless coal from which ash has been removed from coal, and a method for producing a carbon material for obtaining carbon material from ashless coal.

  As the main raw material for nonferrous metal reducing coke, petroleum coke produced from the residue of a petroleum refining process is generally used. However, because petroleum coke is co-produced with transportation fuels such as gasoline, there are restrictions on the supply of raw materials, and impurities such as sulfur contained in crude oil may adversely affect aluminum purity. There are problems.

  On the other hand, coal coke used for blast furnace ironmaking has properties close to petroleum coke as carbon, and an amount sufficient for use as a main raw material for nonferrous metal reducing coke is on the market. However, since it contains about 10% by mass of coal-derived ash, there is a problem in quality, so it is not used in this application.

  Thus, as a raw material for the carbon material having a low ash content, ashless coal (hyper coal) substantially free of ash content can be cited.

  Patent Document 1 discloses a method for producing ashless coal. In this manufacturing method, a coal raw material in which caking coal is mixed with general coal and a solvent are mixed to prepare a slurry, the obtained slurry is heated to extract a coal component soluble in the solvent, and the coal component is extracted. From the extracted slurry, a solution containing coal components soluble in the solvent and a solid concentrate containing coal components insoluble in the solvent are separated from each other by gravity precipitation, and the solvent is separated from the separated solution. I have ash charcoal.

Ashless charcoal has the characteristics that it does not contain ash and has soft melting properties. Therefore, ashless coal is suitable as a caking additive when producing coke for iron making. Moreover, it is a property preferable as a main raw material of the nonferrous metal reduction coke not to contain ash. However, ashless coal has a property of foaming during carbonization, which is a problem in producing non-ferrous metal reducing coke. That is, when the as-produced ashless coal is carbonized, pores due to low molecular compound gases (water vapor, CO, CO ₂ , hydrocarbons, etc.) generated during carbonization remain as they are, so that dense coke is not generated. Also, since ashless coal expands during carbonization, a large capacity furnace is required.

  Therefore, Patent Document 2 discloses a method for producing a carbon material using ashless coal. In this production method, ashless coal is produced, the ashless coal is heat-treated, and then the ashless coal is carbonized to obtain a carbon material. And it suppresses that ashless coal foams in the case of carbonization processing by making atomic ratio (H / C) of hydrogen and carbon of ashless coal after heat processing into 0.6-0.67. doing.

JP 2009-227718 A JP 2011-1240 A

  However, in the method for producing a carbon material of Patent Document 2, in order to suppress the expansibility of ashless coal, ashless coal is mixed with a solvent to form a slurry, and a high temperature of 400 ° C. or higher in an inert gas. Heat treatment. Therefore, there is a problem that the cost increases because a solvent and a high-pressure vessel are required for the heat treatment, and a large amount of heating energy is consumed.

  An object of the present invention is to provide a method for producing ashless coal and a method for producing a carbon material that can suppress the expansibility of ashless coal at low cost.

The method for producing ashless coal in the present invention includes a slurry preparation step of obtaining a slurry by mixing coal and a solvent, an extraction step of extracting the coal component soluble in the solvent by heating the slurry, and the extraction step From the solution separated in the separation step, the separation step of separating the slurry obtained in step 1 into a solution in which the coal component soluble in the solvent is dissolved and the solid content concentrate in which the coal component insoluble in the solvent is concentrated Ashless coal acquisition step of obtaining ashless coal by evaporating the solvent, and ashless coal heating step of heat-treating the ashless coal obtained in the ashless coal acquisition step, the ashless coal heating In the process, ashless coal is heat-treated at 150 to 200 ° C. for 3 to 15 hours or more in a gas containing oxygen, and the atomic ratio (O / C) of oxygen and carbon is a predetermined value or more from the value before the heat treatment. It is characterized by increasing.

  Moreover, the manufacturing method of the carbon material in this invention is characterized by carbonizing the ashless coal manufactured with said manufacturing method of ashless coal, and making it a carbon material.

  According to the method for producing ashless coal and the method for producing a carbon material of the present invention, the expansibility of ashless coal can be suppressed at a low cost.

It is a schematic diagram of an ashless coal manufacturing facility.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

(Method for producing ashless coal)
As shown in FIG. 1, the ashless coal production facility 100 used in the method for producing ashless coal according to the present embodiment includes, in order from the upstream side of the ashless coal (HPC) production process, a coal hopper 1, a solvent tank 2, A slurry preparation tank 3, a transfer pump 4, a preheater 5, an extraction tank 6, a gravity settling tank 7, a filter unit 8, solvent separators 9 and 10, and a dryer 11 are provided.

  The manufacturing method of ashless coal has a slurry preparation process, an extraction process, a separation process, an ashless coal acquisition process, a by-product coal acquisition process, and an ashless coal heating process. Hereinafter, each step will be described. In addition, there is no restriction | limiting in particular in the coal used as a raw material in this manufacturing method, A bituminous coal with a high extraction rate may be used, and cheaper inferior quality coal (subbituminous coal, lignite) may be used. The ashless coal means ash content of 5% by weight or less, preferably 3% by weight or less.

(Slurry preparation process)
The slurry preparation step is a step of preparing a slurry by mixing coal and a solvent. This slurry preparation process is implemented in the slurry preparation tank 3 in FIG. Coal as a raw material is charged into the slurry preparation tank 3 from the coal hopper 1, and a solvent is charged into the slurry preparation tank 3 from the solvent tank 2. The coal and solvent charged into the slurry preparation tank 3 are mixed by the stirrer 3a to become a slurry composed of coal and solvent.

  The mixing ratio of coal with respect to the solvent is, for example, 10 to 50% by weight on the basis of dry coal, and more preferably 20 to 35% by weight.

(Extraction process)
The extraction step is a step of heating the slurry obtained in the slurry preparation step to extract a coal component soluble in the solvent (dissolve in the solvent). This extraction step is performed in the preheater 5 and the extraction tank 6 in FIG. The slurry prepared in the slurry preparation tank 3 is supplied to the preheater 5 by the transfer pump 4 and heated to a predetermined temperature, then supplied to the extraction tank 6, and held at the predetermined temperature while being stirred by the stirrer 6a. Extraction is performed.

  When extracting coal components that are soluble in the solvent by heating the slurry obtained by mixing coal and solvent, a solvent with a large dissolving power for coal, often an aromatic solvent (hydrogen donating property) Or a non-hydrogen-donating solvent) and coal are mixed and heated to extract organic components in the coal.

  The non-hydrogen donating solvent is a coal derivative which is a solvent mainly composed of a bicyclic aromatic and purified mainly from a coal carbonization product. This non-hydrogen-donating solvent is stable even in a heated state and has excellent affinity with coal. Therefore, the proportion of soluble components (herein, coal components) extracted into the solvent (hereinafter also referred to as extraction rate) In addition, it is a solvent that can be easily recovered by a method such as distillation. Main components of the non-hydrogen donating solvent include bicyclic aromatic naphthalene, methyl naphthalene, dimethyl naphthalene, trimethyl naphthalene and the like, and other non-hydrogen donating solvent components have aliphatic side chains. Naphthalenes, anthracenes, fluorenes, and these include biphenyl and alkylbenzenes having long aliphatic side chains.

  In the above description, the case where a non-hydrogen-donating compound is used as a solvent has been described, but it is needless to say that a hydrogen-donating compound (including coal liquefied oil) typified by tetralin may be used as a solvent. . When a hydrogen donating solvent is used, the yield of ashless coal is improved.

  Further, the boiling point of the solvent is not particularly limited. From the viewpoints of pressure reduction in the extraction step and separation step, extraction rate in the extraction step, solvent recovery rate in the ashless coal acquisition step, etc., for example, a solvent having a boiling point of 180 to 300 ° C., particularly 240 to 280 ° C. Preferably used.

  The heating temperature of the slurry in the extraction step is not particularly limited as long as the solvent-soluble component can be dissolved, and is, for example, 300 to 420 ° C. from the viewpoint of sufficient dissolution of the solvent-soluble component and improvement of the extraction rate. More preferably, it is 360-400 degreeC.

  Also, the heating time (extraction time) is not particularly limited, but is, for example, 10 to 60 minutes from the viewpoint of sufficient dissolution and improvement of the extraction rate. The heating time is the total heating time in the preheater 5 and the extraction tank 6 in FIG.

  The extraction process is performed in the presence of an inert gas such as nitrogen. The pressure in the extraction tank 6 is preferably 1.0 to 2.0 MPa, although it depends on the temperature at the time of extraction and the vapor pressure of the solvent used. When the pressure in the extraction tank 6 is lower than the vapor pressure of the solvent, the solvent volatilizes and is not confined in the liquid phase, so that extraction cannot be performed. In order to confine the solvent in the liquid phase, a pressure higher than the vapor pressure of the solvent is required. On the other hand, if the pressure is too high, the cost of the equipment and the operating cost increase, which is not economical.

(Separation process)
In the separation step, the slurry obtained in the extraction step is subjected to a gravity sedimentation method, a solution in which a coal component soluble in a solvent is dissolved, and a solid content in which a coal component insoluble in a solvent (a solvent insoluble component such as ash) is concentrated. This is a step of separating into a concentrated liquid (solvent insoluble component concentrated liquid). This separation step is performed in the gravity settling tank 7 in FIG. The slurry obtained in the extraction step is separated into a supernatant liquid as a solution and a solid content concentrated liquid by gravity in the gravity settling tank 7. The supernatant liquid in the upper part of the gravity settling tank 7 is discharged to the solvent separator 9 through the filter unit 8 as necessary, and the solid concentrate settled in the lower part of the gravity settling tank 7 is sent to the solvent separator 10. Discharged.

  The gravitational sedimentation method is a method in which a slurry is retained in a tank to settle and separate solvent-insoluble components using gravity. A solvent-insoluble component (for example, ash) having a specific gravity greater than that of a solution in which a coal component soluble in a solvent is dissolved is settled by gravity in the lower portion of the gravity settling tank 7. A continuous separation process is possible by continuously discharging the supernatant from the top and the solid concentrate from the bottom while continuously supplying the slurry into the tank.

  The gravity sedimentation tank 7 is preferably kept warm (or heated) or pressurized in order to prevent reprecipitation of solvent-soluble components eluted from coal. The heat retention (heating) temperature is, for example, 300 to 380 ° C., and the tank internal pressure is, for example, 1.0 to 3.0 MPa.

  As a method for separating the solution containing the coal component dissolved in the solvent from the slurry obtained in the extraction step, there are a filtration method, a centrifugal separation method, and the like in addition to the gravity sedimentation method.

(Ashless coal acquisition process)
The ashless coal acquisition step is a step of obtaining ashless coal (HPC) by evaporating and separating the solvent from the solution (supernatant liquid) separated in the separation step. This ashless charcoal acquisition process is performed by the solvent separator 9 in FIG. The solution separated in the gravity settling tank 7 is filtered by the filter unit 8 and then supplied to the solvent separator 9, and the solvent is evaporated and separated from the supernatant in the solvent separator 9. Here, it is preferable that the solvent is separated from the solution in the presence of an inert gas such as nitrogen. In this embodiment, the solvent is evaporated and separated from the solution in nitrogen gas introduced into the solvent separator 9.

  As a method for separating the solvent from the solution (supernatant liquid), a general distillation method, evaporation method or the like can be used. The solvent separated by the solvent separator 9 is returned to the solvent tank 2 and circulated and used repeatedly. In addition, although it is preferable to circulate and use a solvent, it is not indispensable (the same is true in the by-product charcoal acquisition step described later). By separating the solvent from the supernatant, ashless charcoal (HPC) substantially free of ash can be obtained.

  Ashless coal contains almost no ash, has no moisture, and exhibits a higher calorific value than raw coal. Furthermore, softening meltability (fluidity), which is a particularly important quality as a raw material for coke for iron making, has been greatly improved, and the obtained ashless coal (HPC) is good even if the raw coal does not have softening meltability Soft meltability. Therefore, ashless coal can be used, for example, as a blended coal for coke raw materials. In addition, ashless coal containing almost no ash content has high combustion efficiency and can reduce the generation of coal ash. Therefore, the use of ashless coal as a gas turbine direct injection fuel in a high-efficiency combined power generation system based on gas turbine combustion has attracted attention.

(By-product coal acquisition process)
The byproduct charcoal acquisition step is a step of obtaining byproduct charcoal by evaporating and separating the solvent from the solid concentrate separated in the separation step. This byproduct charcoal acquisition step is performed by the solvent separator 10 in FIG. In addition, a byproduct charcoal acquisition process is not an essential process. The solid content concentrate separated in the gravity sedimentation tank 7 is supplied to the solvent separator 10, and the solvent is evaporated and separated from the solid content concentrate in the solvent separator 10. Here, it is preferable to carry out the evaporation and separation of the solvent from the solid concentrate in the presence of an inert gas such as nitrogen. In the present embodiment, the solvent is evaporated and separated from the solid concentrate in the nitrogen gas introduced into the solvent separator 10.

  As a method for separating the solvent from the solid concentrate, a general distillation method or evaporation method can be used as in the above-described ashless coal acquisition step. The solvent separated by the solvent separator 10 is returned to the solvent tank 2 and circulated and used repeatedly. By separating the solvent, by-product charcoal (also referred to as RC or residual charcoal) in which solvent-insoluble components including ash and the like are concentrated can be obtained from the solid concentrate.

  By-product charcoal contains ash, but has no water and has a sufficient calorific value. By-product coal does not exhibit softening and melting properties, but the oxygen-containing functional groups are eliminated, so that when used as a blended coal, it inhibits the softening and melting properties of other coals contained in this blended coal. It is not a thing. Therefore, this by-product coal can be used as a part of the blended coal of the coke raw material, as in the case of ordinary non-slightly caking coal, and is used for various fuels without using the coke raw coal. It is also possible.

(Ashless coal heating process)
The ashless coal heating step is a step of heat-treating the ashless coal obtained in the ashless coal acquisition step. This ashless charcoal heating process is implemented by the dryer 11 in FIG. In general, ashless coal is highly expansible in the as-manufactured state, so it is necessary to suppress expansibility so as not to foam during carbonization.

  The heat treatment of ashless charcoal is performed in a gas containing oxygen, preferably in air or lean air (air in which oxygen is thin). That is, the heat treatment of the present embodiment is an oxidation treatment that oxidizes ashless coal. The heating method in an oxygen atmosphere is not particularly limited, and can be performed using a known method such as batch heating or a fluidized bed reactor.

  Moreover, in this embodiment, it heat-processes so that the atomic number ratio (O / C) of oxygen and carbon of ashless coal after heat processing may increase more than predetermined value from the value before heat processing. For example, if the O / C atomic ratio before the heat treatment is 0.06, the heat treatment is performed so that the O / C atomic ratio is increased by 0.019 or more from the value before the heat treatment. By heat-treating ashless coal in a gas containing oxygen, the oxidation reaction of ashless coal proceeds and oxygen atoms adhere to the surface of ashless coal. Thereby, the O / C atomic ratio of ashless coal gradually increases. The heating conditions depend on the raw coal type and production conditions of ashless coal, but by adjusting the heating temperature to 150 ° C. or higher and 350 ° C. or lower and the heating time in the range of 30 minutes to 6 hours, O / C atoms The number ratio can be increased by a predetermined value or more from the value before the heat treatment.

  Here, coal is composed of macromolecules having a molecular weight of several hundred to several thousand or more, whereas ashless coal is composed of relatively low molecular weight components having 2 to 3 condensed aromatic rings. It has a broad molecular weight distribution up to about 5 or 6 high molecular weight components. When such ashless coal is oxidized, oxygen atoms attached to the surface of the ashless coal play a role of connecting molecules to each other, and the expansibility of the ashless coal is reduced.

  The O / C atomic ratio of as-produced ashless coal that is not oxidized is different depending on the raw coal type and the production conditions of ashless coal, but is generally in the range of 0.02 to 0.08. The expansion rate (times) is 12 times or more. However, when the ashless coal is oxidized by heat treatment and the O / C atomic ratio is increased by a predetermined value or more from the value before the heat treatment, the expansion rate (times) decreases to about twice. Here, the expansion rate (times) is a ratio of the volume of the carbon material after the carbonization treatment to the volume of the ashless coal before the carbonization treatment.

  Therefore, by oxidizing the ashless coal and attaching oxygen atoms to the surface of the ashless coal, the oxygen atoms that connect the molecules are increased separately from the oxygen atoms originally contained in the ashless coal. And when the amount of oxygen atoms contained in the ashless coal is increased and the atomic ratio of oxygen to carbon (O / C) is increased by a predetermined value or more from the value before the heat treatment, the ashless coal is converted into the carbon material. The expansion rate is about double. Thereby, the expansibility of ashless coal can be suppressed. In addition, no solvent or high-pressure vessel is required for the heat treatment for oxidizing the ashless coal, and the expandability can be suppressed at a lower temperature and in a shorter time than the heat treatment using the solvent as disclosed in Patent Document 2. Because it can, energy consumption can be reduced.

  The heat-treated ashless coal can be dry-distilled into coke, solidified into a carbon material, or mixed with iron ore into another product.

(Method for producing carbon material)
The carbon material manufacturing method according to this embodiment is a carbon material obtained by carbonizing ashless coal manufactured by the above ashless coal manufacturing method.

  The method and conditions for the carbonization treatment are not particularly limited, and can be performed using a known technique. Typically, it is steamed and heated at about 1000 ° C. in an inert atmosphere such as nitrogen or argon to change to carbon. Moreover, what is necessary is just to let a temperature increase rate be about 0.1-5 degreeC / min. This carbonization treatment may be performed under pressure using a hot isostatic pressing apparatus or the like. If necessary, a binder component such as asphalt pitch or tar may be added. Further, the heat-treated ashless coal may be appropriately formed and then subjected to carbonization treatment. There is no restriction | limiting in particular also in the form of the heat processing furnace used for carbonization, A well-known thing can be used. For example, a pot furnace, a lead hammer furnace, a kiln, a rotary kiln, a shaft furnace, or a chamber furnace can be used. However, it is not limited to these, and other things may be used.

  Here, since the expansibility of ashless coal is suppressed by the previous ashless coal heating step, foaming of ashless coal during the carbonization treatment is suppressed. Thereby, a high purity (ashless) carbon material can be manufactured suitably.

  The obtained carbon material can be suitably used as a main raw material for coke for nonferrous metal reduction. It can also be used as a non-ferrous metal reducing agent, a structural carbon material, or a carbon material for electrical materials, or can be used as a raw material for a non-ferrous metal reducing agent, a structural carbon material, or a carbon material for electrical materials. it can. Here, the non-ferrous metal reducing agent refers to a reducing agent used for the reduction of non-ferrous metals such as silicon and titanium, and the structural carbon material is, for example, a carbon heat insulating material or a carbon structural material such as a crucible. The carbon material used as a raw material refers to a carbon material used as a raw material for an electric material made of carbon such as an anode for aluminum electrolytic production or a carbon electrode. Note that these materials are used because, for example, it may be necessary to subject the carbon material to a secondary treatment such as heat treatment.

(Expansion rate evaluation)
Next, the ashless coal was oxidized by heat treatment to evaluate the expansion rate. Specifically, ashless coal is produced using bituminous coal as raw coal, the particle size of this ashless coal is adjusted so that the particle size distribution is 0.25 to 1 mm, and then heat-treated in an air atmosphere in a dryer. And oxidized. At that time, the heating temperature and the heating time were varied. The evaluation results are shown in Table 1. Here, the expansion rate (times) is a ratio of the volume of the carbon material after the carbonization treatment to the volume of the ashless coal before the carbonization treatment. Moreover, VM (%) is a volatile matter (mass%).

  Of the six samples in Table 1, sample No. No. 1 (hereinafter, No. 1) is not heat-treated, and the O / C atomic ratio is 0.06. Sample No. heated at 200 ° C. for 1 hour 2 has an O / C atomic ratio of No. 2. Although it increased by 0.015 with respect to 1, the expansion rate did not decrease. On the other hand, Sample No. 3 heated at 200 ° C. for 3 hours. 3 has an O / C atomic ratio of No. 3. It increased by 0.019 with respect to 1, and the expansion rate decreased to about 2 times. Sample No. Nos. 4 to 6 have an O / C atomic ratio of No. 4. It increased by 0.019 or more with respect to 1, and the expansion rate decreased to about 2 times. Sample No. In 3-6, the raise of the carbonization yield was also recognized.

  From this, when the value of the O / C atom number ratio before the heat treatment is 0.06, the heat treatment is performed at a relatively low temperature of about 200 ° C., and the O / C atom number ratio is changed from the value before the heat treatment. It can be seen that when the amount is increased by 0.019 or more, the expansibility of ashless coal can be suppressed.

(effect)
As described above, according to the method for producing ashless coal according to the present embodiment, the ashless coal is oxidized by heat-treating the ashless coal in a gas containing oxygen, so that oxygen and carbon atoms The number ratio (O / C) is increased by a predetermined value or more from the value before the heat treatment. Coal is composed of macromolecules having a molecular weight of several hundred to several thousand or more, whereas ashless coal is composed of relatively low molecular weight components having 2 to 3 fused aromatic rings, It has a broad molecular weight distribution up to high molecular weight components of about 6 rings. When such ashless coal is oxidized, oxygen atoms attached to the surface of the ashless coal play a role of connecting molecules to each other, and the expansibility of the ashless coal is reduced. Therefore, by oxidizing the ashless coal and attaching oxygen atoms to the surface of the ashless coal, the oxygen atoms that connect the molecules are increased separately from the oxygen atoms originally contained in the ashless coal. And when the amount of oxygen atoms contained in the ashless coal is increased and the atomic ratio of oxygen to carbon (O / C) is increased by a predetermined value or more from the value before the heat treatment, the ashless coal is converted into the carbon material. The expansion rate is about double. Thereby, the expansibility of ashless coal can be suppressed. Moreover, no solvent or high-pressure vessel is required for the heat treatment for oxidizing ashless coal, and the expansibility can be suppressed at a lower temperature and in a shorter time than the heat treatment using a solvent, so that energy consumption can be suppressed. . Thereby, the expansibility of ashless coal can be suppressed cheaply.

  In addition, the heat treatment of ashless coal at 150 ° C. or higher and 350 ° C. or lower for 30 minutes to 6 hours can increase the atomic ratio of oxygen and carbon (O / C) by a predetermined value or more from the value before the heat treatment. it can. Thereby, the expansibility of ashless coal can be controlled suitably.

  Moreover, according to the method for producing a carbon material according to the present embodiment, when the heat-treated ashless coal is carbonized to obtain a carbon material, the expansion of the ashless coal is suppressed. Charcoal foaming is suppressed. Thereby, a high purity (ashless) carbon material can be manufactured suitably.

(Modification of this embodiment)
The embodiment of the present invention has been described above, but only specific examples are illustrated, and the present invention is not particularly limited, and the specific configuration and the like can be appropriately changed in design. Further, the actions and effects described in the embodiments of the invention only list the most preferable actions and effects resulting from the present invention, and the actions and effects according to the present invention are described in the embodiments of the present invention. It is not limited to what was done.

DESCRIPTION OF SYMBOLS 1 Coal hopper 2 Solvent tank 3 Slurry preparation tank 3a Stirrer 4 Transfer pump 5 Preheater 6 Extraction tank 6a Stirrer 7 Gravity settling tank 8 Filter unit 9,10 Solvent separator 11 Dryer 100 Ashless coal production equipment

Claims (3)

A slurry preparation step of obtaining a slurry by mixing coal and a solvent;
Extracting the coal component soluble in the solvent by heating the slurry; and
A separation step of separating the slurry obtained in the extraction step into a solution in which a coal component soluble in a solvent is dissolved and a solid content concentrate in which a coal component insoluble in a solvent is concentrated;
Ashless coal acquisition step of obtaining ashless coal by evaporating and separating the solvent from the solution separated in the separation step;
Ashless coal heating step of heat-treating the ashless coal obtained in the ashless coal acquisition step,
With
In the ashless coal heating step, the ashless coal is heat-treated at 150 to 200 ° C. for 3 to 15 hours or more in a gas containing oxygen, and the atomic ratio (O / C) of oxygen and carbon is determined before the heat treatment. A method for producing ashless coal, wherein the value is increased by a predetermined value or more from the value. 2. The method for producing ashless coal according to claim 1, wherein, in the ashless coal heating step, the atomic ratio (O / C) of oxygen and carbon is increased by 0.019 or more from a value before the heat treatment. .   A method for producing a carbon material, wherein the ashless coal produced by the method for producing ashless coal according to claim 1 or 2 is carbonized to obtain a carbon material.