JP4061351B1 - Production method of ashless coal - Google Patents

Abstract

An ashless coal is produced at high efficiency and at low cost, and a method for producing ashless coal having excellent quality as a raw coal used in iron-making coke.
A method for producing ashless coal used as raw coal for iron-making coke, which is obtained by a slurry preparation step (S1) in which a solvent and coal are mixed to prepare a slurry, and a slurry preparation step (S1). The obtained slurry is extracted at a temperature of 400 to 420 ° C. for 20 minutes or less and then cooled to 370 ° C. or less. The slurry obtained in the extraction step (S2) is divided into a liquid part and a non-liquid part. A separation step (S3) that separates into two, and a modified coal acquisition step (S4) that separates the solvent from the liquid portion separated in the separation step (S3) to obtain ashless coal that is a modified coal. It is characterized by that.
[Selection] Figure 1

Description

  The present invention relates to a method for producing ashless coal, which produces ashless coal used as raw material coal for iron-making coke from coal.

  Conventionally, as coking coal for steelmaking coke such as coke for blast furnaces, high-quality caking coal, mainly blended with weak caking coal or non-caking caking coal, has been used in recent years. Attempts have been made to extract extracted coal that is higher in quality than raw coal by extracting components that are soluble in the solvent.

  For example, bituminous coal, subbituminous coal, lignite, lignite, etc. as raw material coal, mixed with liquefied oil as a solvent to make a slurry, this slurry is hydrogenated and liquefied using a catalyst at high temperature and high pressure, finally A method of separating and extracting the produced SRC (solvent refined coal) and using it for coking coal is disclosed (for example, see Patent Document 1).

  In addition, caking coals are becoming scarce and are expensive, so we pay particular attention to non-minor caking coals and low-grade lignite and sub-bituminous coals, in other words, poor quality coals. Developments and proposals have been made to produce extracted coal having the same characteristics as caking coal using these inferior coals as raw coal and to use it as raw coal for coke.

  For example, after heat-treating low-grade coal such as lignite and sub-bituminous coal in a solvent (medium liquid) having a pressure of 1 to 20 MPa and a temperature of 400 ° C. or less, the solvent and the heat-treated coal are separated to obtain heat-treated coal, which is used for coke. The method of utilizing as a part of raw coal is disclosed (for example, refer to Patent Document 2).

Furthermore, as a method for producing ashless coal from which ash in the coal has been efficiently removed, raw coal is made of N-methyl-2-pyrrolidinone (NMP) solvent alone, or carbon disulfide and N-methyl-2-pyrrolidinone. A method for extracting ashless coal from raw coal by bringing it into contact with a mixed solvent in the presence of chlorine or a fluorine compound is disclosed (for example, see Patent Document 3).
JP-A-8-269459 (paragraphs 0010 to 0032) JP 2003-55668 A (paragraphs 0017 to 0030) JP 2001-26791 A (paragraphs 0009 to 0022)

However, the above-described method for producing extracted coal has the following problems.
In the production method described in Patent Document 1, ash and spent catalyst are concentrated in the obtained SRC, and it cannot be said that the quality is sufficient for use as a raw coal for iron-making coke. In addition, although it has softening meltability (softening fluidity), which is an important quality as a binder for coke raw materials (softening fluidity), it has a solidification characteristic at 400 to 500 ° C. because it is too volatile. It was insufficient, and it was difficult to produce coke having a sufficiently high strength even when SRC was used as a binder. Furthermore, this SRC also requires expensive hydrogen and a catalyst in terms of its production method, and must be performed under conditions of high temperature and high pressure, resulting in a problem that production and equipment costs become enormous and not economical. there were.

  Although the manufacturing method described in Patent Document 2 is lower in cost than the above-described liquefaction method, the obtained heat-treated charcoal is a mixture of an extract and a non-extract with a solvent. The quality important as coking coal could not be said to be sufficient.

  The production method described in Patent Document 3 is a method in which a solvent-soluble component is extracted from coal using a strong polar solvent such as NMP without adding hydrogen, but when a polar solvent is used as a solvent, Since the solvent forms a strong bond with the coal, the recovery of the solvent is not easy, and as a result, there is a problem that the production cost of ashless coal increases.

  The present invention has been made in view of the above problems, and its purpose is to produce ashless coal with high efficiency and low cost, and as a raw coal used for ironmaking coke, it has excellent quality. It is to provide a method for producing charcoal.

  As a result of intensive research on the production method of ashless coal used as raw material coal for iron-making coke, the present inventors have efficiently produced ashless coal and have soft melting properties when blended coal ( It is possible to produce ashless coal that can be used as coking coal for steelmaking coke at high efficiency and at low cost by finding the relationship between temperature and time in the extraction process, which is a quality that does not hinder softening fluidity) It came to invent the manufacturing method of ash coal.

  That is, the method for producing ashless coal according to the present invention is a method for producing ashless coal used as raw material coal for iron-making coke, the slurry preparation step of preparing a slurry by mixing a solvent and coal, The slurry obtained in the slurry preparation step is extracted at a temperature of 400 to 420 ° C. for 20 minutes or less and then cooled to 370 ° C. or less, and the slurry obtained in the extraction step is divided into a liquid part and a non-liquid part. And a modified coal acquisition step of separating the solvent from the liquid portion separated in the separation step to obtain ashless coal which is a modified coal.

  According to such a manufacturing method, in a slurry preparation process, a solvent and coal which is a raw material of ashless coal are mixed, and a slurry is prepared. Moreover, in the extraction process, by treating the slurry obtained in the slurry preparation process under conditions of a predetermined temperature and time, the proportion of coal components extracted into the solvent increases, and this coal component is highly efficient in the solvent. As it is extracted, the resolidification temperature of the resulting ashless coal increases. Further, in the separation step, the slurry obtained in the extraction step is separated into a liquid part that is a solution containing a coal component extracted in a solvent and a non-liquid part that is a slurry containing a coal component insoluble in the solvent. . And in a modified coal acquisition process, a solvent is isolate | separated from the liquid part isolate | separated at the isolation | separation process, and ashless coal is manufactured.

  In the ashless coal production method according to the present invention, in the modified coal acquisition step, in addition to obtaining the ashless coal, the solvent is separated from the non-liquid part separated in the separation step. It is characterized by obtaining some by-product charcoal.

  According to such a production method, in addition to the production of ashless coal in the modified coal acquisition step, the solvent is separated from the non-liquid part separated in the separation step, thereby producing by-product coal.

  In the method for producing ashless coal according to the present invention, in the extraction step, the slurry obtained in the slurry preparation step is extracted by raising the temperature to a temperature of 400 to 420 ° C. and immediately cooling to 370 ° C. or less. It is characterized by that.

  According to such a manufacturing method, in the extraction step, after the slurry obtained in the slurry preparation step is heated to a predetermined temperature and extracted, the temperature is not maintained and immediately cooled to 370 ° C. or less. The proportion of the coal component extracted into the solvent is further increased, and this coal component is extracted into the solvent with higher efficiency.

The method for producing ashless coal according to the present invention is characterized in that the coal is inferior coal.
According to such a production method, ashless coal can be produced at a lower cost by using inexpensive inferior quality coal as the raw material for ashless coal.

  According to the method for producing ashless coal according to the present invention, the ashless coal used for the raw coal of iron-making coke can be produced with high efficiency and at low cost. In addition, when this ashless coal is blended with raw coal, the softening and melting properties of this blended coal can be increased, and the amount of expensive caking coal can be suppressed, so that the raw coal for iron making coke In addition to reducing costs, the strength of coke for iron making can be improved by improving the adhesiveness of the blended coal. Furthermore, in addition to ashless coal, by-product coal can be produced with high efficiency and at low cost.

  Next, a method for producing ashless coal according to the present invention will be described in detail with reference to the drawings. In the drawings to be referred to, FIG. 1 is a flowchart for explaining the steps of the method for producing ashless coal, and FIG. 2 is a schematic diagram showing a solid-liquid separation device for performing a gravity sedimentation method.

≪Production method of ashless coal≫
As shown in FIG. 1, the ashless coal manufacturing method includes a slurry preparation step (S1), an extraction step (S2), a separation step (S3), and a modified coal acquisition step (S4). .
Hereinafter, each step will be described.

<Slurry preparation step (S1)>
The slurry preparation step (S1) is a step of preparing a slurry by mixing a solvent and coal.
As a solvent for dissolving coal, generally, a monocyclic aromatic compound such as benzene, toluene, xylene, or a polar solvent such as N-methylpyrrolidone (NMP) or pyridine is used. A non-hydrogen donating solvent mainly containing a bicyclic aromatic is used.

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. Since this non-hydrogen donating solvent is stable even in a heated state and has excellent affinity with coal, the proportion of coal components extracted into the solvent (hereinafter also referred to as “extraction rate”) is high. It is a solvent that can be easily recovered by methods such as distillation. The recovered solvent can be recycled for improving economic efficiency.
Main components of the non-hydrogen donating solvent include bicyclic aromatic naphthalene, methylnaphthalene, dimethylnaphthalene, trimethylnaphthalene and the like, other naphthalenes having an aliphatic side chain, biphenyl and long chain. Alkylbenzenes with aliphatic side chains are included.

  The non-hydrogen donating solvent preferably has a boiling point of 180 to 330 ° C. When the boiling point is less than 180 ° C., the required pressure in the extraction step (S2) and the separation step (S3) increases, and the loss due to volatilization increases in the step of recovering the solvent, and the solvent recovery rate decreases. . Furthermore, the extraction rate in the extraction step (S2) decreases. On the other hand, when it exceeds 330 ° C., it becomes difficult to separate the solvent from the liquid part and the non-liquid part described later, and the solvent recovery rate decreases.

  As described above, the extraction rate of coal can be increased by heat extraction using a non-hydrogen-donating solvent. In addition, unlike polar solvents, the solvent can be easily recovered, so that it is easy to circulate the solvent. Furthermore, since it is not necessary to use expensive hydrogen, a catalyst, or the like, coal can be solubilized at low cost to obtain ashless coal, and economic efficiency can be improved.

Coal used as the raw material for ashless coal (hereinafter also referred to as “raw coal”) is non-slightly caking coal that has little softening and melting properties, and low-grade coal such as general coal, low-grade coal, lignite, sub-bituminous coal, etc. Is preferably used. By using inexpensive coal such as these, ashless coal can be produced at a lower cost, so that economic efficiency can be further improved. However, the coal used is not limited to these inferior coals, and caking coal may be used as necessary.
In addition, inferior coal here means coal, such as a non-slightly caking coal, a general coal, a low grade coal (brown coal, subbituminous coal, etc.). Further, the low-grade coal is coal that contains 20% or more moisture and is desired to be dehydrated. Examples of such low-grade coal include lignite, lignite, and sub-bituminous coal. For example, lignite coal includes Victoria coal, North Dakota coal, Belga coal, etc., and sub-bituminous coal includes West Banco coal, Binungan coal, Samarangau coal, and the like. The low-grade coal is not limited to those exemplified above, and any coal containing a large amount of moisture and desired to be dehydrated is included in the low-grade coal referred to in the present invention.

  Although the coal density | concentration with respect to a solvent is based also on the kind of raw material coal, the range of 10-50 mass% is preferable on a dry coal basis, and the range of 20-35 mass% is more preferable. When the coal concentration with respect to the solvent is less than 10% by mass, the proportion of the coal component extracted into the solvent decreases with respect to the amount of the solvent, which is not economical. On the other hand, the higher the coal concentration is, the more preferable, but when it exceeds 50% by mass, the viscosity of the prepared slurry becomes high, and it is difficult to separate the liquid part and the non-liquid part in the slurry transfer or separation step (S3). .

<Extraction process (S2)>
The extraction step (S2) is a step of extracting the slurry obtained in the slurry preparation step at a temperature of 400 to 420 ° C. for 20 minutes or less (hereinafter also referred to as “heating”) and then cooling to 370 ° C. or less. .

  The heating temperature of the slurry in the extraction step (S2) is in the range of 400 to 420 ° C. When the heating temperature is less than 400 ° C., it is insufficient to weaken the bonds between the molecules constituting the coal, and when inferior coal is used as the raw coal, the resolidification temperature of the resulting ashless coal is strongly consolidated. It cannot be raised to the same level as the resolidification temperature of charcoal. On the other hand, if it exceeds 420 ° C., the pyrolysis reaction of coal becomes very active, and recombination of the generated pyrolysis radical occurs, so that the extraction rate decreases.

  When the heating temperature is in the range of 400 to 420 ° C., as the extraction time becomes longer, the thermal decomposition reaction proceeds too much, the radical polymerization reaction proceeds, and the extraction rate decreases. However, a relatively high extraction rate is maintained for an extraction time of 20 minutes or less. Further, at a temperature of 370 ° C., the extraction rate becomes maximum when the extraction time is 30 minutes or more, and the extraction rate does not change greatly even after the extraction time of several hours thereafter, but the resolidification temperature of the obtained ashless coal Does not go up. Therefore, in order to increase the resolidification temperature of the obtained ashless coal and improve the extraction rate, it is most preferable to heat to 400 to 420 ° C for 20 minutes or less and then cool to 370 ° C or less. It is.

The lower limit of the temperature for cooling is preferably 350 ° C. When the temperature is lower than 350 ° C., the solvent dissolving power is reduced, and re-precipitation of the extracted coal component occurs, and the yield of ashless coal is reduced.
In the extraction step (S2), as will be described later, for example, the extraction tank may be raised to 400 to 420 ° C. and immediately cooled, and the lower limit of the extraction time cannot be generally determined. From the above viewpoint, the lower limit of the extraction time is preferably set to 1 minute. That is, in this case, the extraction time is preferably in the range of 1 to 20 minutes.

And after heating for 20 minutes or less at the temperature of 400-420 degreeC, it cools immediately to 370 degrees C or less. This is because if the cooling to 370 ° C. or lower takes time, the extraction rate decreases accordingly.
Here, “immediately cool” means to cool by applying a cooling process as quickly as possible. For example, as soon as possible until the slurry moves to a gravity settling tank described later. In other words, it is cooled by a cooling process.

Further, the extraction rate is higher as the heating time (extraction time) at a temperature of 400 to 420 ° C. is shorter. Therefore, in order to further improve the extraction rate, the heating time (extraction time) should be 15 minutes or less. Preferably, it is 10 minutes or less, more preferably 5 minutes or less. Furthermore, it is more preferable to cool to 370 ° C. or less immediately after the temperature is raised to 0 minutes, that is, 400 to 420 ° C. for extraction.
Furthermore, in the temperature range of 400 to 420 ° C, a temperature close to 400 ° C is preferable, and 400 ° C is preferable. This is because the closer to 400 ° C., the higher the extraction rate.
In addition, during extraction in this extraction step (S2), aromatic-rich components mainly having an average boiling point (Tb50: 50% distillation temperature) of 200 to 300 ° C. are generated by thermal decomposition of coal. It can be used as a part of the solvent.

The extraction step (S2) is preferably performed in the presence of an inert gas.
This is because contact with oxygen in the extraction step (S2) is dangerous because it may ignite, and the cost increases when hydrogen is used.
As the inert gas used in the extraction step (S2), inexpensive nitrogen is preferably used, but is not particularly limited. The pressure in the extraction step (S2) 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 is lower than the vapor pressure of the solvent, the solvent is volatilized and is not trapped in the liquid phase and cannot be extracted. 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 step (S3)>
The separation step (S3) is a step of separating the slurry obtained in the extraction step (S2) into a liquid part and a non-liquid part.
Here, the liquid part refers to a solution containing a coal component extracted into a solvent, and the non-liquid part refers to a slurry containing a coal component insoluble in a solvent (coal containing ash, that is, ash coal).

A method for separating the slurry into a liquid part and a non-liquid part in the separation step (S3) is not particularly limited, but it is preferable to use a gravity sedimentation method.
As a method for separating the slurry into a liquid part and a non-liquid part, various filtration methods and centrifugal separation methods are generally known. However, the filtration method requires frequent exchange of filter aids, and the centrifuge method tends to cause clogging with undissolved coal components, making it difficult to implement these methods industrially. Therefore, it is preferable to use a gravity sedimentation method that allows continuous operation of fluid and is suitable for a large amount of processing at low cost. Thereby, from the upper part of the gravity sedimentation tank, the liquid part (hereinafter also referred to as “supernatant liquid”) containing the coal component extracted into the solvent, the coal component insoluble in the solvent from the lower part of the gravity sedimentation tank. The non-liquid part (henceforth a "solid content concentrate") which is the slurry containing this can be obtained.

Hereinafter, an example of the gravity sedimentation method will be described with reference to FIGS. 1 and 2.
As shown in FIG. 2, in the gravity sedimentation method, in the solid-liquid separation device 100, first, coal in a powder that is a raw material of ashless coal and a solvent are mixed in a coal slurry preparation tank 1 to prepare a slurry. (Slurry preparation step (S1)). Next, a predetermined amount of slurry is supplied from the coal slurry preparation tank 1 to the preheater 3 by the pump 2, and the slurry is heated to 400 to 420 ° C. Then, the heated slurry is supplied to the extraction tank (extractor) 4, heated at 400 to 420 ° C. for 20 minutes or less while being stirred by the stirrer 10, and then immediately cooled to 370 ° C. or less by the cooler 7 (extraction) Step (S2)). In addition, it is preferable to provide a cooling mechanism in the extraction tank 4 for immediate cooling. In addition, “20 minutes or less” here means the total heating time in the preheater 3 and the extraction tank 4, and immediately after the preheater 3 starts heating at 400 to 420 ° C. Time until cooling to 370 ° C. or lower. And the slurry which performed this extraction process is supplied to the gravity sedimentation tank 5, and a slurry is isolate | separated into a supernatant liquid and solid content concentrated liquid (separation process (S3)), and settled in the lower part of the gravity sedimentation tank 5. The solid concentrate is discharged to the solid concentrate receiver 6 and the upper supernatant liquid is discharged to the filter unit 8 by a predetermined amount.

Here, in the gravity settling tank 5, in order to prevent reprecipitation of the solute eluted from the raw material coal, it is preferably maintained at 350 to 370 ° C., that is, the temperature cooled after the slurry is heated, Is preferably in the pressure range of 1.0 to 2.0 MPa.
Further, in the gravity settling tank 5, the time for maintaining at the cooled temperature is the time required to separate the slurry into the supernatant liquid and the solid concentrate, and is generally 60 to 120 minutes. It is not particularly limited.
In addition, by increasing the number of gravity sedimentation tanks 5, it is possible to recover components soluble in the solvent accompanying the concentrated solid solution, but for efficient recovery, the gravity sedimentation tank 5 is divided into two stages. It is appropriate to arrange.
And the supernatant liquid discharged | emitted from the gravity sedimentation tank 5 is filtered by the filter unit 8 as needed, and is collect | recovered by the supernatant liquid receiver 9. FIG.

Then, as will be described below, the solvent is separated and recovered from the liquid part and the non-liquid part by using a distillation method or the like, and ash-free coal without ash, which is a modified coal, is obtained from the liquid part (reformed Charcoal acquisition process (S4)). Moreover, by-product coal with which the ash content which is reformed coal was concentrated can be obtained from a non-liquid part as needed.

<Modified coal acquisition process (S4)>
The modified coal acquisition step (S4) is a step in which the solvent is separated from the liquid portion separated in the separation step (S3) to obtain ashless coal that is modified coal (ashless coal acquisition step).

As a method for separating the solvent from the supernatant liquid (liquid part), a general distillation method, an evaporation method (spray drying method, etc.) or the like can be used, and the separated and recovered solvent is the coal slurry preparation tank 1 (see FIG. 2) and can be used repeatedly. By separating and collecting the solvent, ashless coal substantially free of ash can be obtained from the supernatant.
This ashless coal contains almost no ash, has no moisture, and exhibits a higher calorific value than raw coal. Furthermore, the softening and melting property, which is a particularly important quality as a raw material for coke for iron making, has been greatly improved, and performance (fluidity) far superior to that of raw material coal is exhibited. Therefore, this ashless coal can be used as a blended coal for coke raw materials. Moreover, it can also be used as a blended coal by mixing with by-product coal.

  If necessary, in the modified coal acquisition step (S4), in addition to obtaining ashless coal, the solvent is separated from the non-liquid part separated in the separation step (S3), and the modified coal is used. A certain byproduct charcoal may be manufactured (byproduct charcoal acquisition process).

The method for separating the solvent from the solid concentrate (non-liquid part) can use a general distillation method or evaporation method as in the ashless coal acquisition step described above. It can be circulated to the coal slurry preparation tank 1 (see FIG. 2) and repeatedly used. By separating and recovering the solvent, by-product charcoal enriched in ash can be obtained from the solid concentrate.
Although this by-product charcoal contains ash, it has no water and has a sufficient calorific value. Although this is not shown for softening meltability, the oxygen-containing functional group is eliminated, so that when used as a blended coal, the softening meltability of other coals contained in this blended coal is inhibited. is not. Therefore, this by-product coal can be used as a part of the blended coal of coke raw material in the same way as ordinary non-slightly caking coal, and is used for various fuels without being used as coke raw coal. It is also possible.
In addition, only ashless coal without ash from the liquid part is produced for coke coking coal, only the solvent is recovered from the non-liquid part, and the ash-enriched by-product coal may be discarded without being recovered. .

  Although the present invention is as described above, in carrying out the present invention, within the range that does not adversely affect the respective steps, for example, a coal pulverization step of pulverizing raw coal between or before and after the respective steps, Other steps such as a removal step of removing unnecessary substances such as garbage and a drying step of drying the obtained ashless coal may be included.

Next, an example is given and the manufacturing method of ashless coal concerning the present invention is explained concretely.
[Example 1]
In Example 1, when the extraction temperature in the extraction step is 370 ° C., changes in softening meltability (softening fluidity), resolidification temperature, etc., between raw coal and ashless coal obtained from this raw coal (Experimental example 1).
The industrial analysis values and elemental analysis values shown in Table 1 are strong caking coal A, strong caking coal B, and subbituminous coal C as raw coal, and 4 times the amount of solvent (20 kg) with respect to 5 kg of raw coal ( 1-methylnaphthalene (manufactured by Nippon Steel Chemical Co., Ltd.) was mixed to prepare a slurry. This slurry was pressurized with 1.2 MPa of nitrogen and extracted in an autoclave with an internal volume of 30 L at 370 ° C. for 1 hour. This slurry is separated into a supernatant and a solid concentrate in a gravity sedimentation tank maintained at the same temperature and pressure, and the solvent is separated and recovered from the supernatant by distillation. Ashless coal b was obtained from charcoal a and strong caking coal B, and ashless coal c was obtained from subbituminous coal C. These industrial analysis values and elemental analysis values are shown in Table 1.

Next, with regard to the strong caking coals A and B, the subbituminous coal C, and the ashless coals a, b, and c, the Gieseller softening flow test defined in JIS M8801 was performed.
The test results are shown in Table 1. FIG. 3 is a graph showing a Gieseller curve by a Gieseller softening flow test.

As shown in Table 1, the ashless coals a, b, and c do not contain moisture, and the ash content is slight compared to the raw material coal. It can also be seen that the calorific value is higher than that of the raw coal. Although the oxygen concentration in the subbituminous coal C is as high as 15% or more, and the ashless coal c has also decreased to about 10%, a relatively high oxygen concentration is maintained.
Here, as a result of the Gieseller softening flow test, paying attention to the resolidification temperature of the raw coal, the strong coking coals A and B are 496 ° C. and 483 ° C., respectively, whereas the resolidification temperature of the subbituminous coal C is Since sub-bituminous coal C is low at 445 ° C., the softening meltability (softening fluidity) state for firmly fixing the raw coal is important for obtaining the strength of the coke, so the raw material for coke for iron making It cannot be used as charcoal.

Moreover, from the value of the maximum fluidity shown in FIG. 3 and Table 1, with regard to softening and melting properties, the ashless coals a, b, and c obtained from these raw coals are much better than the raw coals. It can be seen that it exhibits softening and melting properties.
However, paying attention to the resolidification temperature of the obtained ashless coal, the ashless coals a and b obtained from the strong coking coals A and B are 508 ° C. and 488 ° C., respectively. Although solidified at a higher temperature than coals A and B, the resolidification temperature of ashless coal c obtained from subbituminous coal C is relatively low at 463 ° C., although it is higher than that of subbituminous coal C, which is the raw coal.
Here, when the ashless coal c is added to the coke raw material coal for iron making and caulked as a blended coal, the ashless coal c is solidified at 463 ° C. during which the strongly caking coal is maintaining fluidity. Therefore, the fluidity of the entire blended coal is hindered, resulting in a reduction in the strength of the resulting coke.

From the above results, when inferior coal such as subbituminous coal is used as the raw coal, even if ashless coal is obtained under the above conditions, this ashless coal is particularly excellent as a raw coal for iron making coke. I understand that there is not.
In addition, when strongly caking coal (or caking coal) is used as raw coal, the resulting ashless coal exhibits softening and melting performance superior to that of raw coal and should be used as raw coal for iron-making coke. However, strong caking coal is expensive, so the cost of raw materials cannot be reduced.

[Example 2]
In Example 2, the relationship between the extraction temperature when subbituminous coal C used in Example 1 was extracted and the resolidification temperature of ashless coal c obtained from the subbituminous coal C was examined (Experimental Example 2). ).
FIG. 4 shows the relationship between the extraction temperature when sub-bituminous coal C is used as the raw coal and the extraction process is performed for an extraction time of 1 hour (60 minutes) and the resolidification temperature of the obtained ashless coal c.
In addition, about the method of obtaining ashless coal, it performed according to the said Example 1 except extraction temperature.

As shown in FIG. 4, the resolidification temperature of the ashless coal c increases with an increase in the extraction temperature when the extraction temperature exceeds about 360 ° C., and the resolidification temperature becomes about 490 ° C. at the extraction temperature of 400 ° C. It was found that the re-solidification temperature of the strong caking coal rose to the same level. And when it exceeded 400 degreeC, the resolidification temperature rose further. Therefore, it turns out that the resolidification temperature of the ashless coal obtained becomes high by raising the temperature which extracts coal to 400 degreeC or more.
From the above results, when inferior quality coal such as subbituminous coal is used as the raw coal, it can be seen that the ashless coal obtained can be used as the raw coal for iron-making coke by setting the extraction temperature to 400 ° C. or higher.

[Example 3]
In Example 3, the relationship between the extraction temperature, the extraction time, and the extraction rate when the subbituminous coal C used in Example 1 was extracted was examined (Experimental Example 3).
The extraction time when sub-bituminous coal C was extracted with an extraction temperature of 370 ° C., 400 ° C., and 420 ° C. with a preheater, held in the extractor for a predetermined time, and rapidly cooled to 360 ° C. The relationship of the extraction rate is shown in FIG. In the experiment at 420 ° C., the time to raise the temperature from 400 ° C. to 420 ° C. with the preheater was 8 minutes. Therefore, FIG. 5 shows the extraction time from 400 ° C. to 420 ° C. as 8 hours with the preheater. Displayed as the time added for minutes.
Moreover, about the method of obtaining ashless coal, it carried out according to the said Example 1 except extraction temperature and extraction time.

Moreover, the extraction rate of coal was calculated | required from the quantity of the separated solid by-product coal.
Specifically, it was determined by the formula (raw coal-by-product coal) / raw coal × 100. The raw coal and by-product coal are based on anhydrous ashless coal.
Here, the extraction time is a temperature holding time from when the temperature is raised to a predetermined temperature until the temperature is maintained and cooled to 370 ° C. or less, and the extraction time 0 is after the temperature is raised to a predetermined temperature, This is the case where the cooling process is performed immediately without holding the temperature.

As shown in FIG. 5, at an extraction temperature of 370 ° C., the maximum extraction rate is obtained in 30 minutes, and the extraction rate of coal does not change greatly even if the extraction time reaches several hours thereafter. It was. On the other hand, at temperatures of 400 ° C. and 420 ° C., the thermal decomposition of coal is in a temperature range in which it rapidly increases, and when the temperature is maintained for a relatively long time, the extraction rate is reduced by the repolymerization reaction of radicals generated by the thermal decomposition of coal. It was found that the decrease was significant, and maintaining the temperature for a long time was uneconomical.
In addition, since it is known that thermal decomposition is severe and the extraction rate decreases at a temperature exceeding 420 ° C., the experiment was omitted here.

Specifically, at an extraction temperature of 400 ° C., there was almost no change at an extraction time of 0 to 20 minutes, and an extraction rate of about 60% or more was obtained, but when the extraction time reached 60 minutes, the extraction rate was 50 %. It was also found that even when the extraction temperature was raised to 420 ° C., a relatively high extraction rate (about 52% or more) was maintained if the extraction time was within 20 minutes.
In general, if the extraction rate is about 52% or more, it can be said that the extraction rate is relatively high.
From the above results, it can be seen that if the extraction temperature is 400 to 420 ° C. and the time to cool to 370 ° C. or less is within 20 minutes, ashless coal can be obtained with high efficiency.

In addition, the resolidification temperature of the ashless coal obtained on 400 degreeC and the extraction conditions for 0 minute was 483 degreeC, and it was 490 degreeC in the extraction conditions for 10 minutes. Moreover, the resolidification temperature of the ashless coal obtained on 420 degreeC and the extraction conditions for 0 minute was 487 degreeC, and it was 486 degreeC in the extraction conditions for 22 minutes. From this, the resolidification temperature of the ashless coal obtained by heating an inferior coal such as sub-bituminous coal at a temperature of 400 to 420 ° C. for 20 minutes or less and then cooling to 370 ° C. or less is that of the above-mentioned strong caking coal. If it is comparable to the resolidification temperature and added to the coking coal for iron making coke, it does not inhibit the fluidity of the strong caking coal contained in the blended coal, and the fluidity of the overall blended coal I can say that.
On the other hand, at an extraction temperature of 370 ° C., only a resolidification temperature of about 460 ° C. can be obtained, so even if the extraction rate is high, as described above, it is not particularly excellent as a raw coal for iron making coke.

As described above, from the results of Examples 1 to 3, when using low-grade coal such as non-slightly caking coal that is inexpensive as a raw material, the conditions for having high resolidification temperature and obtaining ashless coal with high efficiency are as follows: The extraction temperature is raised to 400 to 420 ° C., heated for 20 minutes or less, and then cooled to 370 ° C. or less. Preferably, the time (extraction time) held at 400 to 420 ° C. is 15 minutes or less. More preferably, it was found that 10 minutes or less, and further, the shorter the extraction time, the better.
And it can be said that the ashless coal obtained in this way does not deteriorate the strength of the coke even if it is added to the raw coal of the coke for iron making to form a blended coal.

  In addition, in the said Example 2, 3, although the case where inferior quality coal was used as a raw material was shown, when caking coal (strong caking coal) was used as raw material, the ashless coal obtained was made from inferior quality coal as a raw material. Higher quality than ashless charcoal. Moreover, it becomes a thing of higher quality than caking coal which is raw material coal. Therefore, when producing higher quality ashless coal, caking coal may be used as a raw material, but when importance is attached to cost reduction of coke raw material coal, it is preferable to use inexpensive inferior coal as a raw material.

  As mentioned above, although the best embodiment and the example were shown and explained in detail about the manufacturing method of ashless coal concerning the present invention, the meaning of the present invention is not limited to the contents mentioned above, and the scope of the right is patent It should be interpreted broadly based on the claims. Needless to say, the contents of the present invention can be widely modified and changed based on the above description.

It is a flowchart explaining the process of the manufacturing method of ashless coal. It is a schematic diagram which shows the solid-liquid separator for performing a gravity sedimentation method. 2 is a graph showing a Gieseller curve by a Gieseller softening flow test in Example 1. FIG. It is a graph which shows the relationship between the extraction temperature when the subbituminous coal C in Example 2 is made into raw coal, and the re-solidification temperature of the obtained ashless coal c when extracting in 1 hour of extraction time. When sub-bituminous coal C in Example 3 was extracted with a preheater up to 370 ° C., 400 ° C., and 420 ° C. as the extraction temperature, held for a predetermined time in the extractor, and then rapidly cooled to 360 ° C. and extracted. It is a graph which shows the relationship between extraction time and extraction rate.

Explanation of symbols

S1 Slurry preparation process S2 Extraction process S3 Separation process S4 Modified coal acquisition process 1 Coal slurry preparation tank 2 Pump 3 Preheater 4 Extraction tank 5 Gravity sedimentation tank 6 Solid concentration liquid receiver 7 Cooler 8 Filter unit 9 Supernatant liquid receiver 10 Stirrer 100 Solid-liquid separator

Claims (4)

A method for producing ashless coal used as raw material coke for iron making coke,
A slurry preparation step of preparing a slurry by mixing a solvent and coal;
An extraction step of extracting the slurry obtained in the slurry preparation step at a temperature of 400 to 420 ° C. for 20 minutes or less and then cooling to 370 ° C. or less;
A separation step of separating the slurry obtained in the extraction step into a liquid part and a non-liquid part;
A modified coal acquisition step of obtaining ashless coal that is a modified coal by separating the solvent from the liquid part separated in the separation step;
The manufacturing method of the ashless coal characterized by including.   In the modified coal acquisition step, in addition to obtaining ashless coal, the solvent is separated from the non-liquid part separated in the separation step to obtain by-product coal that is modified coal. Item 2. A method for producing ashless coal according to Item 1.   The said extraction process WHEREIN: After heating and extracting the slurry obtained at the said slurry preparation process to the temperature of 400-420 degreeC, it cools immediately to 370 degrees C or less, It is characterized by the above-mentioned. The manufacturing method of ashless coal as described in 2.   The said coal is inferior quality coal, The manufacturing method of the ashless coal as described in any one of Claim 1 thru | or 3 characterized by the above-mentioned.

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