WO2008044728A1 - Method for production of ashless coal - Google Patents

Abstract

Disclosed is a method for producing an ashless coal for use as a raw material coal for a coke for steelmaking. The method comprises: a slurry preparation step (S1) for mixing a solvent and a coal to prepare a slurry; an extraction step (S2) for extracting the slurry produced in the slurry preparation step (S1) at 400 to 420ºC for 20 minutes or shorter and then cooling the resulting product to 370ºC or lower; a separation step (S3) for separating the slurry produced in the extraction step (S2) into a liquid fraction and a non-liquid fraction; and an improved coal production step (S4) for separating the solvent from the liquid fraction obtained in the separation step (S3) to produce an improved coal, i.e., an ashless coal.

Description

 Specification

 Production method of ashless coal

 Technical field

 TECHNICAL FIELD [0001] The present invention relates to a method for producing ashless coal, which produces ashless coal used as raw material coal for iron making coatas from coal.

 Background art

 [0002] Conventionally, as coking coal for iron-making Kotas such as blast furnace Kotas, coal with weak or non-caking coal, mainly high-quality caking coal, has been used in recent years. Attempts have been made to extract extracted coal that is soluble in solvents from coal and to obtain extracted coal that is of higher quality than raw coal.

 [0003] For example, bituminous coal, subbituminous coal, lignite, lignite, etc. are used as raw coal, mixed with liquefied oil as a solvent to form a slurry, and this slurry is hydrogenated and liquefied using a catalyst at high temperature and pressure, A method of separating and extracting SRC (solvent refined coal) that is finally produced and using it as raw material coal for coatus is disclosed (for example, see Patent Document 1).

 [0004] In addition, caking coal has a tight resource and is expensive, so in particular, non-caking coal, coal such as low-grade lignite and sub-bituminous coal, in other words, poor quality coal. Development and proposals have been made to produce extracted coal with the same characteristics as caking coal using these inferior coals as raw coal and to use it as raw coal for coatas.

 [0005] For example, low-grade coal such as lignite and subbituminous coal is heat treated in a solvent (medium liquid) at a pressure of 1 to 20 MPa and a temperature of 400 ° C or lower, and then the solvent and the heat treated coal are separated to obtain a heat treated coal. A method of using this as a part of the raw coal for coatus is disclosed (for example, see Patent Document 2).

 [0006] Furthermore, as a method for producing ashless coal that efficiently removes ash from the coal, the raw coal is N-methyl-2-pyrrolidinone (NMP) solvent alone, or carbon disulfide and N-methyl 2-. A method for extracting ashless coal from raw coal by contacting with a mixed solvent of pyrrolidinone in the presence of chlorine or a fluorine compound is disclosed (for example, see Patent Document 3).

Yes Patent Document 1: JP-A-8-269459 (paragraphs 0010 to 0032)

 Patent Document 2: Japanese Patent Laid-Open No. 2003-55668 (paragraphs 0017 to 0030)

 Patent Document 3: Japanese Patent Laid-Open No. 2001-26791 (paragraphs 0009 to 0022)

 Disclosure of the invention

 Problems to be solved by the invention

[0007] 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 coatas. In addition, although it has softening meltability (softening fluidity), which is an important quality as a binder (caking filler) for coatus raw materials, it is too volatile, so it has solidification characteristics at 400-500 ° C. However, it was difficult to produce a coatus having a sufficiently high strength even when SRC was used as a binder. Furthermore, this SRC also has a problem that its production method requires expensive hydrogen and a catalyst and must be carried out under high temperature and high pressure conditions, resulting in a huge production and equipment cost and is not economical. there were.

[0008] Although the production 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. However, the quality that is important as a raw coal for coatas is not enough.

 [0009] 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. When using, the solvent forms a strong bond with the coal, so that the recovery of the solvent is not easy. As a result, the production cost of ashless coal increases.

 [0010] The present invention has been made in view of the above problems, and an object of the present invention is to produce ashless coal with high efficiency and low cost, and as an excellent quality as raw coal used in iron-making coatas. It is providing the manufacturing method of ashless coal provided with this.

 Means for solving the problem

[0011] As a result of intensive research on the production method of ashless coal used as the raw material coal for iron-making coatas, the present inventors have produced ashless coal efficiently and at the same time as blended coal. Finding the relationship between temperature and time in the extraction process that achieves quality that does not hinder softening solubility (softening fluidity) As a result, the inventors have invented a method for producing ashless coal that can produce ashless coal that can be used as raw material coal for iron-making coatas with high efficiency and low cost.

[0012] 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 coatas, and is a slurry preparation in which a solvent and coal are mixed to prepare a slurry. Extracting the slurry obtained in the step, 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, and the slurry obtained in the extraction step A separation step of separating into a liquid portion and a non-liquid portion, and a modified coal acquisition step of separating the solvent from the liquid portion separated in the separation step to obtain ashless coal that is a modified coal. It is characterized by this.

 [0013] According to such a manufacturing method, in the slurry preparation step, a solvent and coal, which is a raw material for ashless coal, are mixed to prepare a slurry. Also, in the extraction process, the slurry obtained in the slurry preparation process is processed under the conditions of a predetermined temperature and time, so that the proportion of coal components extracted to 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. Furthermore, in the separation step, the slurry obtained in the extraction step is separated into a liquid part that is a solution containing coal components extracted in a solvent and a non-liquid part that is a slurry containing coal components insoluble in the solvent. The Then, in the modified coal acquisition process, the solvent is separated from the liquid part separated in the separation process, and ashless coal is produced.

[0014] In the method for producing ashless coal according to the present invention, in the modified coal acquisition step, in addition to obtaining ashless coal, the solvent is separated from the non-liquid portion separated in the separation step. It is characterized by obtaining by-product coal that is modified coal.

[0015] According to such a production method, in addition to producing 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. Is done.

[0016] 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 then immediately 370 It is characterized by cooling to below ° C.

[0017] 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 is immediately reduced to 370 ° C or lower. By cooling, the proportion of coal components extracted into the solvent is further increased, and this coal component is extracted into the solvent with higher efficiency.

[0018] The method for producing ashless coal according to the present invention is characterized in that the coal is inferior quality 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.

 The invention's effect

 [0019] According to the method for producing ashless coal according to the present invention, ashless coal used as raw material coal for iron-making coatas can be produced with high efficiency and at low cost. In addition, when this ashless coal is blended with the raw coal, the softening and melting properties of this blended coal can be increased, and the amount of expensive caking coal can be suppressed. In addition to reducing the cost of charcoal, the strength of iron-coated coatas can be improved by improving the adhesion of blended coal. Furthermore, in addition to ashless coal, by-product coal can be produced with high efficiency and at low cost.

 Brief Description of Drawings

 [0020] FIG. 1 is a flowchart for explaining the steps of a method for producing ashless coal.

 FIG. 2 is a schematic diagram showing a solid-liquid separator for performing a gravity sedimentation method.

 FIG. 3 is a graph showing a Gieseller curve by a Gieseller softening flow test in Example 1.

 FIG. 4 is a graph showing the relationship between the extraction temperature when sub-bituminous coal C in Example 2 is used as the raw coal and the extraction process is performed for an extraction time of 1 hour and the resolidification temperature of the obtained ashless coal c.

 [Fig. 5] Sub-bituminous coal C in Example 3 was extracted with a preheater to 370 ° C, 400 ° C and 420 ° C, respectively, and held at the extractor for a predetermined time. 6 is a graph showing the relationship between the extraction time and the extraction rate when extraction processing is performed after rapid cooling.

 Explanation of symbols

[0021] S1 slurry preparation process

 S2 extraction process

 S3 Separation process

 S4 Modified coal acquisition process

1 Coal slurry preparation tank 2 Honfu

 3 Preheater

 4 Extraction tank

 5 Gravity settling tank

 6 Concentrated liquid receiver

 7 Cooler

 8 Fino Letter Unit

 9 Supernatant receiver

 10 Stirrer

 100 Solid-liquid separator

 BEST MODE FOR CARRYING OUT THE INVENTION

 Next, the 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 flow chart 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.

[0023] <Method for producing ashless coal>

 As shown in FIG. 1, the method for producing ashless coal 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 (Sl)>

 The slurry preparation step (S I) is a step of preparing a slurry by mixing a solvent and coal. As the solvent for dissolving coal, generally used are monocyclic aromatic compounds such as benzene, toluene and xylene, polar solvents such as N-methylpyrrolidone (NMP) and pyridine, etc. In non-hydrogen donating solvent mainly composed of 2-ring aromatics.

[0025] 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 when heated, and has an excellent affinity with coal. Therefore, 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 a method such as distillation. The recovered solvent can also be recycled for economic efficiency. The main components of the non-hydrogen-donating solvent include bicyclic aromatic naphthalene, methylnaphthalene, dimethylnaphthalene, trimethylnaphthalene, etc., other naphthalenes having aliphatic side chains, and biphenyls. Includes alkylbenzenes with long aliphatic side chains.

 [0026] The non-hydrogen donating solvent preferably has a boiling point of 180 to 330 ° C. If the boiling point is less than 180 ° C, the required pressure in the extraction step (S2) and separation step (S3) will increase, and the loss due to volatilization will increase in the step of collecting the solvent, resulting in a higher solvent recovery rate. descend. Furthermore, the extraction rate in the extraction step (S2) decreases. On the other hand, when the temperature exceeds 330 ° C., it becomes difficult to separate the solvent from the liquid part and non-liquid part described later, and the solvent recovery rate decreases.

 [0027] As described above, heat extraction using a non-hydrogen-donating solvent can increase the coal extraction rate. In addition, unlike polar solvents, the solvent can be easily recovered, making it easy to circulate the solvent. Furthermore, since it is not necessary to use expensive hydrogen or a catalyst, ashless coal can be obtained by solubilizing coal at an inexpensive cost, and power S can be used to improve economy.

 [0028] Coal used as the raw material for ashless coal (hereinafter also referred to as "raw coal"! /, U) is non-slightly caking coal that has almost no softening and melting property, or lignite coal that is low-grade coal. It is preferable to use poor quality coal such as subbituminous coal. By using inexpensive coal such as these, ashless coal can be produced at a lower cost, thus further improving economic efficiency. However, the coal used is not limited to these inferior coals, and caking coal may be used if necessary.

 Incidentally, the inferior coal here refers to coal such as non-slightly caking coal, steam coal, low-grade coal (brown coal, subbituminous coal, etc.). Low-grade coal is coal that contains 20% or more moisture and is desired to be dewatered. Examples of such low-grade coal include lignite, lignite, and sub-bituminous coal. For example, brown coal includes Victoria coal, North Dakota coal, Belga coal, and sub-bituminous coal includes West Banco coal, Binungan coal, and Samarangau coal. The low-grade coal is not limited to those exemplified above, and any coal containing a large amount of water and desired to be dehydrated is included in the low-grade coal referred to in the present invention.

[0029] The coal concentration relative to the solvent depends on the type of raw coal, but it is 10-50 quality on a dry coal basis. A range of 20% to 35% by mass is more preferable. If the coal concentration relative to the solvent is less than 10% by mass, the proportion of coal components extracted into the solvent will be less than the amount of solvent, which is not economical. On the other hand, the higher the coal concentration, the better. However, if it exceeds 50% by mass, the viscosity of the prepared slurry becomes high, and it becomes difficult to separate the liquid part and the non-liquid part in the slurry transfer and separation step (S3). Cheap.

[0030] <Extraction process (S2)>

 In the extraction step (S2), the slurry obtained in the slurry preparation step is extracted at a temperature of 400 to 420 ° C for 20 minutes or less (hereinafter also referred to as “heating”) and then cooled to 370 ° C or less. In the process

[0031] The heating temperature of the slurry in the extraction step (S2) is in the range of 400 to 420 ° C. If the heating temperature is less than 00 ° C, it will not be sufficient to weaken the bonds between the molecules that make up the coal.If inferior coal is used as the raw coal, the resolidification temperature of the resulting ashless coal will It cannot be increased to the same level as the resolidification temperature of coal. On the other hand, if the temperature exceeds 420 ° C, the thermal decomposition reaction of coal becomes very active, and the generated pyrolytic radicals recombine, resulting in a decrease in the extraction rate.

 [0032] 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 extraction times of 20 minutes or less. At a temperature of 370 ° C, the extraction rate reaches its maximum at an extraction time of 30 minutes or more. After that, even if the extraction time reaches several hours, the extraction rate does not change greatly, but the obtained ash-free coal is recycled. Solidification temperature does not increase. Therefore, to increase the resolidification temperature of the resulting ashless coal and improve the extraction rate, heat it at 400-420 ° C for 20 minutes or less and then cool it to 370 ° C or less. This is the most suitable condition.

[0033] The lower limit of the cooling temperature is preferably 350 ° C! /. If it is lower than 350 ° C, the solvent's dissolving power will decrease, causing re-precipitation of the extracted coal components, resulting in a decrease in the yield of ashless coal. In the extraction step (S2), as will be described later. In addition, for example, the lower limit of the extraction time in which the extraction tank can be raised to 400-420 ° C and cooled immediately cannot be determined in general. From an operational point of view, the lower limit of extraction time should be set to 1 minute. That is, in this case, the extraction time is preferably in the range of !! to 20 minutes.

[0034] Then, after heating at a temperature of 400 to 420 ° C for 20 minutes or less, immediately cool to 370 ° C or less. This is because the extraction rate will decrease if it takes time to cool down to 370 ° C or below. Here, “immediately cool” means to cool by applying a cooling process as quickly as possible. For example, the slurry is cooled by the cooling process as quickly as possible until the slurry moves to the gravity settling tank described later.

 [0035] In addition, 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) is 15 minutes. The following is preferable: 10 minutes or less is more preferable, and 5 minutes or less is more preferable. Furthermore, it is more preferable to cool to 370 ° C or less immediately after extracting for 0 minutes, that is, raising the temperature to 400-420 ° C!

 Furthermore, in the temperature range of 400 to 420 ° C., a temperature close to 400 ° C. is preferably 400 ° C. This is because the closer to 400 ° C, the higher the extraction rate.

 During extraction in this extraction step (S2), the pyrolysis of coal produces aromatic-rich components mainly having an average boiling point (Tb50: 50% distillation temperature) of 200-300 ° C, It can be preferably used as a part of the solvent.

 [0036] 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 use of hydrogen increases the cost.

 The inert gas used in the extraction step (S2) is preferably inexpensive nitrogen, but is not particularly limited. The pressure in the extraction step (S2) is preferably 1.0 to 2. OMPa, 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 evaporates and is not trapped in the liquid phase and cannot be extracted. 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.

[0037] <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 means a solution containing a coal component extracted into a solvent, and the non-liquid part means a slurry containing a coal component insoluble in the solvent (coal containing ash, that is, ash coal).

[0038] The method of separating the slurry into the liquid part and the non-liquid part in the separation step (S3) is not particularly limited! /, But it is preferable to use the 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 replacement of the filter aid, and the centrifuge method makes it difficult to industrially implement these methods as soon as clogging with undissolved coal components occurs. It is. Therefore, it is preferable to use a gravity sedimentation method that allows continuous operation of the fluid and is suitable for a large amount of processing at a low cost. As a result, from the upper part of the gravity sedimentation tank, a liquid part (hereinafter also referred to as “supernatant liquid”) containing a coal component extracted into the solvent, and from the lower part of the gravity sedimentation tank, a coal component that is insoluble in the solvent. The force S is obtained to obtain a non-liquid part (hereinafter also referred to as “solid content concentrate”) which is a slurry containing

 Hereinafter, an example of the gravity sedimentation method will be described with reference to FIGS.

As shown in Fig. 2, in the gravity sedimentation method, in the solid-liquid separator 100, first, coal in a slurry slurry preparation tank 1 is mixed with powdered coal, which is a raw material for ashless coal, and a slurry is prepared. (Slurry preparation step (Sl)). 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 and 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. Cool (extraction step (S2)). It should be noted that a cooling mechanism is preferably provided in the extraction tank 4 for immediate cooling. In addition, “less than 20 minutes” here is the total heating time in the preheater 3 and the extraction tank 4, and after the preheater 3 starts heating at 400 to 420 ° C. This is the time to immediately cool to below 370 ° C. Then, the slurry subjected to this extraction treatment is supplied to the gravity sedimentation tank 5, and the slurry is separated into a supernatant and a solid concentrate (separation step (S3)), and settled in the lower part of the gravity sedimentation tank 5. The discharged solid content concentrate is discharged to the solid content receiver 6 and Drain a predetermined amount of the supernatant liquid to the filter unit 8.

[0040] Here, in order to prevent re-precipitation of the solute eluted from the raw material coal, the gravity settling tank 5 is preferably maintained at 350 to 370 ° C, that is, the temperature cooled after the slurry is heated. Moreover, the pressure is preferably in the pressure range of 1.0 to 2 · OMPa.

 In the gravity settling tank 5, the time for maintaining the cooled temperature is the time required for separating the slurry into a supernatant and a solid concentrate, and is generally 60 to 120 minutes. There is no particular limitation.

 In addition, by increasing the number of gravity sedimentation tanks 5, it is possible to recover components that are soluble in the solvent accompanying the concentrated solid solution. It is appropriate to place it.

 Then, the supernatant liquid from which the internal force of the gravity sedimentation tank 5 is also discharged is filtered by the filter unit 8 and collected in the supernatant liquid receiver 9 as necessary.

[0041] Then, as will be described below, the solvent is separated and recovered from the liquid part and the non-liquid part using a distillation method or the like, and ash-free coal free of ash, which is a modified coal, is obtained from the liquid part. (Modified coal acquisition process (S4)). If necessary, the power S can be used to obtain by-product coal enriched in ash, which is reformed coal, from the non-liquid part.

[0042] <Modified coal acquisition process (S4)>

 The modified coal acquisition step (S4) is a step of separating the solvent from the liquid part separated in the separation step (S3) to obtain ashless coal that is a modified coal (ashless coal acquisition step).

[0043] 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 a coal slurry preparation tank. Can be used repeatedly by circulating to 1 (see Figure 2). 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 has a higher calorific value than raw coal. Furthermore, the softening and melting properties, which are particularly important qualities as raw materials for iron-making coatas, have been greatly improved, and performance (fluidity) far superior to that of raw coal. Therefore, this ashless coal can be used as a blended coal for raw materials of Kotas. In addition, it can be used as a cocoon coal by mixing with by-product coal. [0044] If necessary, in addition to obtaining ashless coal in the modified coal acquisition step (S4), the solvent is separated from the non-liquid portion separated in the separation step (S3). By-product coal, which is a modified coal, may be manufactured! /, (By-product coal acquisition process).

 [0045] As a method for separating the solvent from the solid concentrate (non-liquid part), a general distillation method or evaporation method can be used in the same manner as the ashless coal acquisition step described above, and it is separated and recovered. The solvent can be circulated to the coal slurry preparation tank 1 (see Fig. 2) and used repeatedly. By separating and recovering the solvent, by-product charcoal enriched in ash can be obtained from the solid concentrate.

 Although this by-product coal contains ash, it has no water and has a sufficient calorific value. Although this is not shown for softening and melting properties, the oxygen-containing functional groups are eliminated, so that when used as a blended coal, the softening and melting properties of other coals contained in this blended coal are inhibited. It is not a thing. Therefore, this by-product coal can be used as part of the blended coal of Cotas raw material, as with ordinary non-coking coal, and it can be used for various fuels without being made of Cotas raw coal. It is also possible.

 Only ashless coal without ash from the liquid part is produced for Coats coking coal, only the solvent is recovered from the non-liquid part, and the ash-enriched by-product coal can be discarded without recovery. good.

 [0046] The present invention has the same force as described above. For example, coal that pulverizes raw material coal before or after each step within a range that does not adversely affect each step. Other steps such as a grinding step, a removal step to remove unnecessary materials such as dust, and a drying step to dry the obtained ashless coal may be included!

 Example

 Next, the method for producing ashless coal according to the present invention will be specifically described with reference to examples.

 [Example 1]

 In Example 1, when the extraction temperature in the extraction process is 370 ° C, the softening meltability (softening fluidity), resolidification temperature, etc. of the raw coal and ashless coal obtained from this raw coal The change was examined (Experiment 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 (20 kg) of solvent per 5 kg of raw coal. (1-me Tilnaphthalene (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 by the supernatant liquid distillation method. From coal a, strong caking coal B, ashless coal b was obtained, and from subbituminous coal C, ashless coal c was obtained. These industrial analysis values and elemental analysis values are shown in Table 1.

[0048] Next, the strong-coking coals A and B, subbituminous coal C, and ashless coal a, b, c were subjected to the Gieseler softening flow test defined in JIS M 8801.

 The test results are shown in Table 1. Figure 3 shows the Giesera from the Gieseller softening flow test.

[0049] [Table 1]

As shown in Table 1, ashless coal abc does not contain moisture and has a small ash content compared to raw coal. It can also be seen that the calorific value is higher than that of raw coal. Sub-bituminous coal in C The oxygen concentration is as high as 15% or more, and the ash-free coal is also reduced to about 10%, but it is relatively high! /, Maintaining the oxygen concentration! /.

 Here, as a result of the Gieseller softening flow test, paying attention to the resolidification temperature of raw coal, strong coking coals A and B are 496 ° C and 483 ° C, respectively, while subbituminous coal C Since the solidification temperature is as low as 445 ° C, subbituminous coal C impedes the softening and melting (softening fluidity) state, which is important for obtaining the strength of coatas, to firmly fix the raw coal. For this reason, it cannot be used as the raw coal for iron-making coatas.

[0051] From the maximum fluidity values in Fig. 3 and Table 1, for softening and melting properties, ashless coals a, b, and c obtained from these raw coals are much different from their raw coals. It can be seen that it exhibits a good softening and melting property that exceeds.

 However, paying attention to the resolidification temperature of the obtained ashless coal, the ashless coal a and b obtained from the strong coking coals A and B are 508 ° C and 488 ° C, respectively. Although it is solidified at a higher temperature than those of strong coking coals A and B, the resolidification temperature of ashless coal c obtained from subbituminous coal C is higher than that of raw bituminous coal C! ° C and relatively low! /.

 Here, when ashless coal c is added to the iron-coated Kotas coking coal and coked as a blended coal, strong coking coal is still in fluidity at 463 ° C. This solidifies the fluidity of the entire blended coal, resulting in a decrease in the strength of the resulting coatus.

[0052] 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 used as the raw coal for iron-making coatas. It turns out that it is not particularly excellent.

 When strongly caking coal (or caking coal) is used as the raw coal, the resulting ashless coal has softening and melting performance superior to that of the raw coal, and should be used as the raw coal for iron-making Kotas. Power of strong coking coal is expensive, so raw material costs cannot be reduced.

[0053] [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 this subbituminous coal C was examined (experimental). Example 2).

 Figure 4 shows the relationship between the extraction temperature when sub-bituminous coal C is used as the raw coal and the extraction time is 1 hour (60 minutes), and the resolidification temperature of the resulting ashless coal c.

 The method for obtaining ashless coal was carried out according to Example 1 except for the extraction temperature.

 [0054] As shown in Fig. 4, the resolidification temperature of ashless coal c increases with an increase in extraction temperature when the extraction temperature exceeds about 360 ° C, and resolidification at an extraction temperature of 400 ° C. It was found that the temperature reached about 490 ° C, which was equivalent to the re-solidification temperature of the strong caking coal. When the temperature exceeded 400 ° C, the resolidification temperature further increased. Therefore, it can be seen that the resolidification temperature of the resulting ashless coal increases by increasing the coal extraction temperature to 400 ° C or higher.

 From the above results, when inferior quality coal such as subbituminous coal is used as the raw coal, the ability to use the resulting ashless coal as the raw coal for iron-making coatas by setting the extraction temperature to 400 ° C or higher. S

 [0055] [Example 3]

 In Example 3, the relationship between the extraction temperature, extraction time, and extraction rate when the subbituminous coal C used in Example 1 was extracted was examined (Experimental Example 3).

 When sub-bituminous coal C is extracted with a preheater to 370 ° C, 400 ° C, and 420 ° C as the extraction temperature, held for a specified time in the extractor, and then rapidly cooled to 360 ° C and extracted. Figure 5 shows the relationship between extraction time and extraction rate. In the experiment at 420 ° C, the time and power were raised from 400 ° C to 420 ° C with the preheater. Therefore, Fig. 5 shows the extraction at 400 ° C and at 420 ° C. The time is shown as the time of 8 minutes in the preheater.

 The method for obtaining ashless coal was carried out in accordance with Example 1 except for the extraction temperature and the extraction time.

 [0056] Further, the extraction rate of coal was obtained by determining the quantity of separated solid by-product coal.

 Specifically, it was determined by the formula (raw coal-by-product coal) / raw coal X100. The raw coal and by-product coal are based on anhydrous ashless coal.

Here, the extraction time is the temperature holding time from when the temperature is raised to a predetermined temperature until the temperature is maintained and cooled to 370 ° C or lower, and the extraction time 0 is the temperature raised to the predetermined temperature. After that, keep the temperature This is the case when it is cooled immediately without holding.

[0057] As shown in Fig. 5, at an extraction temperature of 370 ° C, the maximum extraction rate was obtained after 30 minutes of extraction, and the extraction rate of coal changed greatly even after several hours of extraction time. There was nothing to do. 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. It was found that maintaining the temperature for a long period of time when the extraction rate declined was uneconomical.

 It is known that at temperatures above 420 ° C, the extraction rate at which pyrolysis is intense decreases, so the experiment was omitted here.

[0058] Specifically, at an extraction temperature of 400 ° C, an extraction rate of approximately 60% or more was obtained with almost no change when the extraction time was 0 to 20 minutes. When the extraction time reached 60 minutes, the extraction rate Decreased to about 50%. It was also found that even if 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 higher, it can be said that the extraction rate is relatively high. Based on the above results, the extraction temperature is 400 to 420 ° C and the cooling rate is 370 ° C or lower. It can be seen that ashless coal can be obtained with high efficiency if the time force is within ¾0 minutes.

[0059] The resolidification temperature of ashless coal obtained under the extraction conditions of 400 ° C and 0 minutes was 483 ° C, and was 490 ° C under the extraction conditions of 10 minutes. The resolidification temperature of ashless coal obtained at 420 ° C at 0 minutes was 487 ° C, and at 486 ° C at 22 minutes. Because of this, the resolidification temperature of ashless coal obtained by heating undergrade coal such as subbituminous coal at a temperature of 400 to 420 ° C for 20 minutes or less and then cooling to 370 ° C or less is the above-mentioned strong caking. Compared to the resolidification temperature of coal, even if added to the raw coal for iron-making Kotas, it does not hinder the fluidity of the strong caking coal contained in the blended coal, but inhibits the fluidity of the entire blended coal X.

On the other hand, at an extraction temperature of 370 ° C, only a re-solidification 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 coatas. . [0060] As described above, from the results of Examples 1 to 3, ashless coal having a high resolidification temperature and high efficiency can be obtained in the case of using inferior quality coal such as non-slightly caking coal that is inexpensive. The extraction temperature is raised to 400 to 420 ° C as the extraction temperature, heated for 20 minutes or less, and then cooled to 370 ° C or less. Preferably, the time for holding at 400 to 420 ° C is used. It was found that the (extraction time) was 15 minutes or less, more preferably 10 minutes or less, and further, the shorter the extraction time, the better.

 And the ashless coal obtained in this way can be added to the raw coal for iron-making Kotas, so that it does not deteriorate the strength of Kotas!

 [0061] In Examples 2 and 3, the case where inferior coal was used as the raw material was shown. However, when caking coal (strong caking coal) was used as the raw material, the resulting ashless coal was inferior quality coal. Higher quality than ashless coal as raw material. 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. However, when importance is placed on cost reduction of coatus raw coal, it is preferable to use inexpensive inferior coal as a raw material. Les.

 [0062] As above, the method for producing ashless coal according to the present invention has been described in detail with reference to the best mode and examples, but the gist of the present invention is limited to the contents described above. The scope of rights must 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.

Claims

The scope of the claims  [1] A method for producing ashless coal used as raw coal for iron-making coatas,  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, and separating the solvent from the liquid part separated in the separation step to obtain ashless coal that is a modified coal Modified coal acquisition process,  The manufacturing method of the ashless coal characterized by including. [2] 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. The method for producing ashless coal according to item 1 of the scope of the featured claim. [3] In the extraction step, the slurry obtained in the slurry preparation step is extracted by raising the temperature to a temperature of 400-420 ° C and then immediately cooling to 370 ° C or less. The method for producing ashless coal according to paragraph 1 or 2 of the above. [4] The method for producing ashless coal according to claim 1 or 2, wherein the coal is inferior coal.  [5] The method for producing ashless coal according to claim 3, wherein the coal is poor quality coal.